linux-sandbox: honor split filesystem policies in bwrap

codex-rs/app-server/src/codex_message_processor.rs

@@ -1506,9 +1506,19 @@ impl CodexMessageProcessor {
         };
 
         let requested_policy = params.sandbox_policy.map(|policy| policy.to_core());
-        let effective_policy = match requested_policy {
+        let (
+            effective_policy,
+            effective_file_system_sandbox_policy,
+            effective_network_sandbox_policy,
+        ) = match requested_policy {
             Some(policy) => match self.config.permissions.sandbox_policy.can_set(&policy) {
-                Ok(()) => policy,
+                Ok(()) => {
+                    let file_system_sandbox_policy =
+                        codex_protocol::protocol::FileSystemSandboxPolicy::from(&policy);
+                    let network_sandbox_policy =
+                        codex_protocol::protocol::NetworkSandboxPolicy::from(&policy);
+                    (policy, file_system_sandbox_policy, network_sandbox_policy)
+                }
                 Err(err) => {
                     let error = JSONRPCErrorError {
                         code: INVALID_REQUEST_ERROR_CODE,
@@ -1519,7 +1529,11 @@ impl CodexMessageProcessor {
                     return;
                 }
             },
-            None => self.config.permissions.sandbox_policy.get().clone(),
+            None => (
+                self.config.permissions.sandbox_policy.get().clone(),
+                self.config.permissions.file_system_sandbox_policy.clone(),
+                self.config.permissions.network_sandbox_policy,
+            ),
         };
 
         let codex_linux_sandbox_exe = self.arg0_paths.codex_linux_sandbox_exe.clone();
@@ -1534,6 +1548,8 @@ impl CodexMessageProcessor {
             match codex_core::exec::process_exec_tool_call(
                 exec_params,
                 &effective_policy,
+                &effective_file_system_sandbox_policy,
+                effective_network_sandbox_policy,
                 sandbox_cwd.as_path(),
                 &codex_linux_sandbox_exe,
                 use_linux_sandbox_bwrap,

codex-rs/core/config.schema.json

@@ -562,6 +562,30 @@
       },
       "type": "object"
     },
+    "FileSystemAccessMode": {
+      "enum": [
+        "none",
+        "read",
+        "write"
+      ],
+      "type": "string"
+    },
+    "FilesystemPermissionToml": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/FileSystemAccessMode"
+        },
+        {
+          "additionalProperties": {
+            "$ref": "#/definitions/FileSystemAccessMode"
+          },
+          "type": "object"
+        }
+      ]
+    },
+    "FilesystemPermissionsToml": {
+      "type": "object"
+    },
     "ForcedLoginMethod": {
       "enum": [
         "chatgpt",
@@ -1089,20 +1113,30 @@
       },
       "type": "object"
     },
-    "PermissionsToml": {
+    "PermissionProfileNetworkToml": {
       "additionalProperties": false,
       "properties": {
-        "network": {
-          "allOf": [
-            {
-              "$ref": "#/definitions/NetworkToml"
-            }
-          ],
-          "description": "Network proxy settings from `[permissions.network]`. User config can enable the proxy; managed requirements may still constrain values."
+        "enabled": {
+          "type": "boolean"
         }
       },
       "type": "object"
     },
+    "PermissionProfileToml": {
+      "additionalProperties": false,
+      "properties": {
+        "filesystem": {
+          "$ref": "#/definitions/FilesystemPermissionsToml"
+        },
+        "network": {
+          "$ref": "#/definitions/PermissionProfileNetworkToml"
+        }
+      },
+      "type": "object"
+    },
+    "PermissionsToml": {
+      "type": "object"
+    },
     "Personality": {
       "enum": [
         "none",
@@ -1663,6 +1697,10 @@
       "description": "Compact prompt used for history compaction.",
       "type": "string"
     },
+    "default_permissions": {
+      "description": "Default named permissions profile to apply from the `[permissions]` table.",
+      "type": "string"
+    },
     "developer_instructions": {
       "default": null,
       "description": "Developer instructions inserted as a `developer` role message.",
@@ -2025,6 +2063,15 @@
       ],
       "description": "Optional verbosity control for GPT-5 models (Responses API `text.verbosity`)."
     },
+    "network": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/NetworkToml"
+        }
+      ],
+      "default": null,
+      "description": "Top-level network proxy settings."
+    },
     "notice": {
       "allOf": [
         {
@@ -2060,7 +2107,7 @@
         }
       ],
       "default": null,
-      "description": "Nested permissions settings."
+      "description": "Named permissions profiles."
     },
     "personality": {
       "allOf": [

codex-rs/core/src/apply_patch.rs

@@ -40,6 +40,7 @@ pub(crate) async fn apply_patch(
         &action,
         turn_context.approval_policy.value(),
         turn_context.sandbox_policy.get(),
+        &turn_context.file_system_sandbox_policy,
         &turn_context.cwd,
         turn_context.windows_sandbox_level,
     ) {

codex-rs/core/src/codex.rs

@@ -222,10 +222,12 @@ use crate::protocol::ErrorEvent;
 use crate::protocol::Event;
 use crate::protocol::EventMsg;
 use crate::protocol::ExecApprovalRequestEvent;
+use crate::protocol::FileSystemSandboxPolicy;
 use crate::protocol::McpServerRefreshConfig;
 use crate::protocol::ModelRerouteEvent;
 use crate::protocol::ModelRerouteReason;
 use crate::protocol::NetworkApprovalContext;
+use crate::protocol::NetworkSandboxPolicy;
 use crate::protocol::Op;
 use crate::protocol::PlanDeltaEvent;
 use crate::protocol::RateLimitSnapshot;
@@ -482,6 +484,8 @@ impl Codex {
             compact_prompt: config.compact_prompt.clone(),
             approval_policy: config.permissions.approval_policy.clone(),
             sandbox_policy: config.permissions.sandbox_policy.clone(),
+            file_system_sandbox_policy: config.permissions.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: config.permissions.network_sandbox_policy,
             windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
             cwd: config.cwd.clone(),
             codex_home: config.codex_home.clone(),
@@ -676,6 +680,8 @@ pub(crate) struct TurnContext {
     pub(crate) personality: Option<Personality>,
     pub(crate) approval_policy: Constrained<AskForApproval>,
     pub(crate) sandbox_policy: Constrained<SandboxPolicy>,
+    pub(crate) file_system_sandbox_policy: FileSystemSandboxPolicy,
+    pub(crate) network_sandbox_policy: NetworkSandboxPolicy,
     pub(crate) network: Option<NetworkProxy>,
     pub(crate) windows_sandbox_level: WindowsSandboxLevel,
     pub(crate) shell_environment_policy: ShellEnvironmentPolicy,
@@ -764,6 +770,8 @@ impl TurnContext {
             personality: self.personality,
             approval_policy: self.approval_policy.clone(),
             sandbox_policy: self.sandbox_policy.clone(),
+            file_system_sandbox_policy: self.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: self.network_sandbox_policy,
             network: self.network.clone(),
             windows_sandbox_level: self.windows_sandbox_level,
             shell_environment_policy: self.shell_environment_policy.clone(),
@@ -867,6 +875,8 @@ pub(crate) struct SessionConfiguration {
     approval_policy: Constrained<AskForApproval>,
     /// How to sandbox commands executed in the system
     sandbox_policy: Constrained<SandboxPolicy>,
+    file_system_sandbox_policy: FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     windows_sandbox_level: WindowsSandboxLevel,
 
     /// Working directory that should be treated as the *root* of the
@@ -933,6 +943,10 @@ impl SessionConfiguration {
         }
         if let Some(sandbox_policy) = updates.sandbox_policy.clone() {
             next_configuration.sandbox_policy.set(sandbox_policy)?;
+            next_configuration.file_system_sandbox_policy =
+                FileSystemSandboxPolicy::from(next_configuration.sandbox_policy.get());
+            next_configuration.network_sandbox_policy =
+                NetworkSandboxPolicy::from(next_configuration.sandbox_policy.get());
         }
         if let Some(windows_sandbox_level) = updates.windows_sandbox_level {
             next_configuration.windows_sandbox_level = windows_sandbox_level;
@@ -1145,6 +1159,8 @@ impl Session {
             personality: session_configuration.personality,
             approval_policy: session_configuration.approval_policy.clone(),
             sandbox_policy: session_configuration.sandbox_policy.clone(),
+            file_system_sandbox_policy: session_configuration.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: session_configuration.network_sandbox_policy,
             network,
             windows_sandbox_level: session_configuration.windows_sandbox_level,
             shell_environment_policy: per_turn_config.permissions.shell_environment_policy.clone(),
@@ -4805,6 +4821,8 @@ async fn spawn_review_thread(
         personality: parent_turn_context.personality,
         approval_policy: parent_turn_context.approval_policy.clone(),
         sandbox_policy: parent_turn_context.sandbox_policy.clone(),
+        file_system_sandbox_policy: parent_turn_context.file_system_sandbox_policy.clone(),
+        network_sandbox_policy: parent_turn_context.network_sandbox_policy,
         network: parent_turn_context.network.clone(),
         windows_sandbox_level: parent_turn_context.windows_sandbox_level,
         shell_environment_policy: parent_turn_context.shell_environment_policy.clone(),
@@ -7832,6 +7850,8 @@ mod tests {
             compact_prompt: config.compact_prompt.clone(),
             approval_policy: config.permissions.approval_policy.clone(),
             sandbox_policy: config.permissions.sandbox_policy.clone(),
+            file_system_sandbox_policy: config.permissions.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: config.permissions.network_sandbox_policy,
             windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
             cwd: config.cwd.clone(),
             codex_home: config.codex_home.clone(),
@@ -7927,6 +7947,8 @@ mod tests {
             compact_prompt: config.compact_prompt.clone(),
             approval_policy: config.permissions.approval_policy.clone(),
             sandbox_policy: config.permissions.sandbox_policy.clone(),
+            file_system_sandbox_policy: config.permissions.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: config.permissions.network_sandbox_policy,
             windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
             cwd: config.cwd.clone(),
             codex_home: config.codex_home.clone(),
@@ -8247,6 +8269,8 @@ mod tests {
             compact_prompt: config.compact_prompt.clone(),
             approval_policy: config.permissions.approval_policy.clone(),
             sandbox_policy: config.permissions.sandbox_policy.clone(),
+            file_system_sandbox_policy: config.permissions.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: config.permissions.network_sandbox_policy,
             windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
             cwd: config.cwd.clone(),
             codex_home: config.codex_home.clone(),
@@ -8306,6 +8330,8 @@ mod tests {
             compact_prompt: config.compact_prompt.clone(),
             approval_policy: config.permissions.approval_policy.clone(),
             sandbox_policy: config.permissions.sandbox_policy.clone(),
+            file_system_sandbox_policy: config.permissions.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: config.permissions.network_sandbox_policy,
             windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
             cwd: config.cwd.clone(),
             codex_home: config.codex_home.clone(),
@@ -8398,6 +8424,8 @@ mod tests {
             compact_prompt: config.compact_prompt.clone(),
             approval_policy: config.permissions.approval_policy.clone(),
             sandbox_policy: config.permissions.sandbox_policy.clone(),
+            file_system_sandbox_policy: config.permissions.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: config.permissions.network_sandbox_policy,
             windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
             cwd: config.cwd.clone(),
             codex_home: config.codex_home.clone(),
@@ -8647,6 +8675,8 @@ mod tests {
             compact_prompt: config.compact_prompt.clone(),
             approval_policy: config.permissions.approval_policy.clone(),
             sandbox_policy: config.permissions.sandbox_policy.clone(),
+            file_system_sandbox_policy: config.permissions.file_system_sandbox_policy.clone(),
+            network_sandbox_policy: config.permissions.network_sandbox_policy,
             windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
             cwd: config.cwd.clone(),
             codex_home: config.codex_home.clone(),
@@ -10072,11 +10102,15 @@ mod tests {
 
         // Now retry the same command WITHOUT escalated permissions; should succeed.
         // Force DangerFullAccess to avoid platform sandbox dependencies in tests.
-        Arc::get_mut(&mut turn_context)
-            .expect("unique turn context Arc")
+        let turn_context_mut = Arc::get_mut(&mut turn_context).expect("unique turn context Arc");
+        turn_context_mut
             .sandbox_policy
             .set(SandboxPolicy::DangerFullAccess)
             .expect("test setup should allow updating sandbox policy");
+        turn_context_mut.file_system_sandbox_policy =
+            FileSystemSandboxPolicy::from(turn_context_mut.sandbox_policy.get());
+        turn_context_mut.network_sandbox_policy =
+            NetworkSandboxPolicy::from(turn_context_mut.sandbox_policy.get());
 
         let resp2 = handler
             .handle(ToolInvocation {

codex-rs/core/src/config/mod.rs

@@ -27,6 +27,7 @@ use crate::config::types::WindowsSandboxModeToml;
 use crate::config::types::WindowsToml;
 use crate::config_loader::CloudRequirementsLoader;
 use crate::config_loader::ConfigLayerStack;
+use crate::config_loader::ConfigLayerStackOrdering;
 use crate::config_loader::ConfigRequirements;
 use crate::config_loader::ConstrainedWithSource;
 use crate::config_loader::LoaderOverrides;
@@ -49,6 +50,10 @@ use crate::model_provider_info::built_in_model_providers;
 use crate::project_doc::DEFAULT_PROJECT_DOC_FILENAME;
 use crate::project_doc::LOCAL_PROJECT_DOC_FILENAME;
 use crate::protocol::AskForApproval;
+#[cfg(test)]
+use crate::protocol::FileSystemAccessMode;
+use crate::protocol::FileSystemSandboxPolicy;
+use crate::protocol::NetworkSandboxPolicy;
 use crate::protocol::ReadOnlyAccess;
 use crate::protocol::SandboxPolicy;
 use crate::unified_exec::DEFAULT_MAX_BACKGROUND_TERMINAL_TIMEOUT_MS;
@@ -86,7 +91,8 @@ use std::path::PathBuf;
 #[cfg(test)]
 use tempfile::tempdir;
 
-use crate::config::permissions::network_proxy_config_from_permissions;
+use crate::config::permissions::compile_permission_profile;
+use crate::config::permissions::network_proxy_config_from_network;
 use crate::config::profile::ConfigProfile;
 use toml::Value as TomlValue;
 use toml_edit::DocumentMut;
@@ -107,7 +113,11 @@ pub use codex_network_proxy::NetworkProxyAuditMetadata;
 pub use managed_features::ManagedFeatures;
 pub use network_proxy_spec::NetworkProxySpec;
 pub use network_proxy_spec::StartedNetworkProxy;
+pub use permissions::FilesystemPermissionToml;
+pub use permissions::FilesystemPermissionsToml;
 pub use permissions::NetworkToml;
+pub use permissions::PermissionProfileNetworkToml;
+pub use permissions::PermissionProfileToml;
 pub use permissions::PermissionsToml;
 pub use service::ConfigService;
 pub use service::ConfigServiceError;
@@ -155,6 +165,12 @@ pub struct Permissions {
     pub approval_policy: Constrained<AskForApproval>,
     /// Effective sandbox policy used for shell/unified exec.
     pub sandbox_policy: Constrained<SandboxPolicy>,
+    /// Effective filesystem sandbox policy, including entries that cannot yet
+    /// be fully represented by the legacy [`SandboxPolicy`] projection.
+    pub file_system_sandbox_policy: FileSystemSandboxPolicy,
+    /// Effective network sandbox policy split out from the legacy
+    /// [`SandboxPolicy`] projection.
+    pub network_sandbox_policy: NetworkSandboxPolicy,
     /// Effective network configuration applied to all spawned processes.
     pub network: Option<NetworkProxySpec>,
     /// Whether the model may request a login shell for shell-based tools.
@@ -1047,10 +1063,18 @@ pub struct ConfigToml {
     /// Sandbox configuration to apply if `sandbox` is `WorkspaceWrite`.
     pub sandbox_workspace_write: Option<SandboxWorkspaceWrite>,
 
-    /// Nested permissions settings.
+    /// Default named permissions profile to apply from the `[permissions]`
+    /// table.
+    pub default_permissions: Option<String>,
+
+    /// Named permissions profiles.
     #[serde(default)]
     pub permissions: Option<PermissionsToml>,
 
+    /// Top-level network proxy settings.
+    #[serde(default)]
+    pub network: Option<NetworkToml>,
+
     /// Optional external command to spawn for end-user notifications.
     #[serde(default)]
     pub notify: Option<Vec<String>>,
@@ -1565,6 +1589,78 @@ impl ConfigToml {
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum PermissionConfigSyntax {
+    Legacy,
+    Profiles,
+}
+
+#[derive(Debug, Deserialize, Default)]
+struct PermissionSelectionToml {
+    default_permissions: Option<String>,
+    sandbox_mode: Option<SandboxMode>,
+}
+
+fn resolve_permission_config_syntax(
+    config_layer_stack: &ConfigLayerStack,
+    cfg: &ConfigToml,
+    sandbox_mode_override: Option<SandboxMode>,
+    profile_sandbox_mode: Option<SandboxMode>,
+) -> Option<PermissionConfigSyntax> {
+    if sandbox_mode_override.is_some() || profile_sandbox_mode.is_some() {
+        return Some(PermissionConfigSyntax::Legacy);
+    }
+
+    let mut selection = None;
+    for layer in
+        config_layer_stack.get_layers(ConfigLayerStackOrdering::LowestPrecedenceFirst, false)
+    {
+        let Ok(layer_selection) = layer.config.clone().try_into::<PermissionSelectionToml>() else {
+            continue;
+        };
+
+        if layer_selection.sandbox_mode.is_some() {
+            selection = Some(PermissionConfigSyntax::Legacy);
+        }
+        if layer_selection.default_permissions.is_some() {
+            selection = Some(PermissionConfigSyntax::Profiles);
+        }
+    }
+
+    selection.or_else(|| {
+        if cfg.default_permissions.is_some() {
+            Some(PermissionConfigSyntax::Profiles)
+        } else if cfg.sandbox_mode.is_some() {
+            Some(PermissionConfigSyntax::Legacy)
+        } else {
+            None
+        }
+    })
+}
+
+fn add_additional_file_system_writes(
+    file_system_sandbox_policy: &mut FileSystemSandboxPolicy,
+    additional_writable_roots: &[AbsolutePathBuf],
+) {
+    for path in additional_writable_roots {
+        let exists = file_system_sandbox_policy.entries.iter().any(|entry| {
+            matches!(
+                &entry.path,
+                crate::protocol::FileSystemPath::Path { path: existing }
+                    if existing == path && entry.access == crate::protocol::FileSystemAccessMode::Write
+            )
+        });
+        if !exists {
+            file_system_sandbox_policy
+                .entries
+                .push(crate::protocol::FileSystemSandboxEntry {
+                    path: crate::protocol::FileSystemPath::Path { path: path.clone() },
+                    access: crate::protocol::FileSystemAccessMode::Write,
+                });
+        }
+    }
+}
+
 /// Optional overrides for user configuration (e.g., from CLI flags).
 #[derive(Default, Debug, Clone)]
 pub struct ConfigOverrides {
@@ -1753,7 +1849,7 @@ impl Config {
             None => ConfigProfile::default(),
         };
         let configured_network_proxy_config =
-            network_proxy_config_from_permissions(cfg.permissions.as_ref());
+            network_proxy_config_from_network(cfg.network.as_ref());
 
         let feature_overrides = FeatureOverrides {
             include_apply_patch_tool: include_apply_patch_tool_override,
@@ -1788,29 +1884,112 @@ impl Config {
         let active_project = cfg
             .get_active_project(&resolved_cwd)
             .unwrap_or(ProjectConfig { trust_level: None });
+        let permission_config_syntax = resolve_permission_config_syntax(
+            &config_layer_stack,
+            &cfg,
+            sandbox_mode,
+            config_profile.sandbox_mode,
+        );
+        let has_permission_profiles = cfg
+            .permissions
+            .as_ref()
+            .is_some_and(|profiles| !profiles.is_empty());
+        let legacy_permissions_network_table =
+            cfg.permissions.as_ref().is_some_and(|permissions| {
+                permissions.entries.get("network").is_some_and(|profile| {
+                    profile.filesystem.is_none() && profile.network.is_none()
+                })
+            });
+        if legacy_permissions_network_table {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                "legacy `[permissions.network]` is no longer supported; move this config to the top-level `[network]` table",
+            ));
+        }
+        if has_permission_profiles
+            && !matches!(
+                permission_config_syntax,
+                Some(PermissionConfigSyntax::Legacy)
+            )
+            && cfg.default_permissions.is_none()
+        {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                "config defines `[permissions]` profiles but does not set `default_permissions`",
+            ));
+        }
         let sandbox_mode_was_explicit = sandbox_mode.is_some()
             || config_profile.sandbox_mode.is_some()
-            || cfg.sandbox_mode.is_some();
+            || cfg.sandbox_mode.is_some()
+            || matches!(
+                permission_config_syntax,
+                Some(PermissionConfigSyntax::Profiles)
+            );
 
         let windows_sandbox_level = match windows_sandbox_mode {
             Some(WindowsSandboxModeToml::Elevated) => WindowsSandboxLevel::Elevated,
             Some(WindowsSandboxModeToml::Unelevated) => WindowsSandboxLevel::RestrictedToken,
             None => WindowsSandboxLevel::from_features(&features),
         };
-        let mut sandbox_policy = cfg.derive_sandbox_policy(
-            sandbox_mode,
-            config_profile.sandbox_mode,
-            windows_sandbox_level,
-            &resolved_cwd,
-            Some(&constrained_sandbox_policy),
-        );
-        if let SandboxPolicy::WorkspaceWrite { writable_roots, .. } = &mut sandbox_policy {
-            for path in additional_writable_roots {
-                if !writable_roots.iter().any(|existing| existing == &path) {
-                    writable_roots.push(path);
+        let profiles_are_active = matches!(
+            permission_config_syntax,
+            Some(PermissionConfigSyntax::Profiles)
+        ) || (permission_config_syntax.is_none()
+            && has_permission_profiles);
+        let (sandbox_policy, file_system_sandbox_policy, network_sandbox_policy) =
+            if profiles_are_active {
+                let permissions = cfg.permissions.as_ref().ok_or_else(|| {
+                    std::io::Error::new(
+                        std::io::ErrorKind::InvalidInput,
+                        "default_permissions requires a `[permissions]` table",
+                    )
+                })?;
+                let default_permissions = cfg.default_permissions.as_deref().ok_or_else(|| {
+                    std::io::Error::new(
+                        std::io::ErrorKind::InvalidInput,
+                        "default_permissions requires a named permissions profile",
+                    )
+                })?;
+                let (mut file_system_sandbox_policy, network_sandbox_policy) =
+                    compile_permission_profile(permissions, default_permissions)?;
+                let mut sandbox_policy = file_system_sandbox_policy
+                    .to_legacy_sandbox_policy(network_sandbox_policy, &resolved_cwd)?;
+                if matches!(sandbox_policy, SandboxPolicy::WorkspaceWrite { .. }) {
+                    add_additional_file_system_writes(
+                        &mut file_system_sandbox_policy,
+                        &additional_writable_roots,
+                    );
+                    sandbox_policy = file_system_sandbox_policy
+                        .to_legacy_sandbox_policy(network_sandbox_policy, &resolved_cwd)?;
                 }
-            }
-        }
+                (
+                    sandbox_policy,
+                    file_system_sandbox_policy,
+                    network_sandbox_policy,
+                )
+            } else {
+                let mut sandbox_policy = cfg.derive_sandbox_policy(
+                    sandbox_mode,
+                    config_profile.sandbox_mode,
+                    windows_sandbox_level,
+                    &resolved_cwd,
+                    Some(&constrained_sandbox_policy),
+                );
+                if let SandboxPolicy::WorkspaceWrite { writable_roots, .. } = &mut sandbox_policy {
+                    for path in &additional_writable_roots {
+                        if !writable_roots.iter().any(|existing| existing == path) {
+                            writable_roots.push(path.clone());
+                        }
+                    }
+                }
+                let file_system_sandbox_policy = FileSystemSandboxPolicy::from(&sandbox_policy);
+                let network_sandbox_policy = NetworkSandboxPolicy::from(&sandbox_policy);
+                (
+                    sandbox_policy,
+                    file_system_sandbox_policy,
+                    network_sandbox_policy,
+                )
+            };
         let approval_policy_was_explicit = approval_policy_override.is_some()
             || config_profile.approval_policy.is_some()
             || cfg.approval_policy.is_some();
@@ -2078,6 +2257,7 @@ impl Config {
             .map(AbsolutePathBuf::to_path_buf)
             .or_else(|| resolve_sqlite_home_env(&resolved_cwd))
             .unwrap_or_else(|| codex_home.to_path_buf());
+        let original_sandbox_policy = sandbox_policy.clone();
 
         apply_requirement_constrained_value(
             "approval_policy",
@@ -2125,6 +2305,19 @@ impl Config {
         } else {
             network.enabled().then_some(network)
         };
+        let effective_sandbox_policy = constrained_sandbox_policy.value.get().clone();
+        let effective_file_system_sandbox_policy =
+            if effective_sandbox_policy == original_sandbox_policy {
+                file_system_sandbox_policy
+            } else {
+                FileSystemSandboxPolicy::from(&effective_sandbox_policy)
+            };
+        let effective_network_sandbox_policy =
+            if effective_sandbox_policy == original_sandbox_policy {
+                network_sandbox_policy
+            } else {
+                NetworkSandboxPolicy::from(&effective_sandbox_policy)
+            };
 
         let config = Self {
             model,
@@ -2139,6 +2332,8 @@ impl Config {
             permissions: Permissions {
                 approval_policy: constrained_approval_policy.value,
                 sandbox_policy: constrained_sandbox_policy.value,
+                file_system_sandbox_policy: effective_file_system_sandbox_policy,
+                network_sandbox_policy: effective_network_sandbox_policy,
                 network,
                 allow_login_shell,
                 shell_environment_policy,
@@ -2701,20 +2896,18 @@ consolidation_model = "gpt-5"
     #[test]
     fn config_toml_deserializes_permissions_network() {
         let toml = r#"
-[permissions.network]
+[network]
 enabled = true
 proxy_url = "http://127.0.0.1:43128"
 enable_socks5 = false
 allow_upstream_proxy = false
 allowed_domains = ["openai.com"]
 "#;
-        let cfg: ConfigToml = toml::from_str(toml)
-            .expect("TOML deserialization should succeed for permissions.network");
+        let cfg: ConfigToml =
+            toml::from_str(toml).expect("TOML deserialization should succeed for [network]");
 
         assert_eq!(
-            cfg.permissions
-                .and_then(|permissions| permissions.network)
-                .expect("permissions.network should deserialize"),
+            cfg.network.expect("[network] should deserialize"),
             NetworkToml {
                 enabled: Some(true),
                 proxy_url: Some("http://127.0.0.1:43128".to_string()),
@@ -2739,13 +2932,11 @@ allowed_domains = ["openai.com"]
     fn permissions_network_enabled_populates_runtime_network_proxy_spec() -> std::io::Result<()> {
         let codex_home = TempDir::new()?;
         let cfg = ConfigToml {
-            permissions: Some(PermissionsToml {
-                network: Some(NetworkToml {
-                    enabled: Some(true),
-                    proxy_url: Some("http://127.0.0.1:43128".to_string()),
-                    enable_socks5: Some(false),
-                    ..Default::default()
-                }),
+            network: Some(NetworkToml {
+                enabled: Some(true),
+                proxy_url: Some("http://127.0.0.1:43128".to_string()),
+                enable_socks5: Some(false),
+                ..Default::default()
             }),
             ..Default::default()
         };
@@ -2770,11 +2961,9 @@ allowed_domains = ["openai.com"]
     fn permissions_network_disabled_by_default_does_not_start_proxy() -> std::io::Result<()> {
         let codex_home = TempDir::new()?;
         let cfg = ConfigToml {
-            permissions: Some(PermissionsToml {
-                network: Some(NetworkToml {
-                    allowed_domains: Some(vec!["openai.com".to_string()]),
-                    ..Default::default()
-                }),
+            network: Some(NetworkToml {
+                allowed_domains: Some(vec!["openai.com".to_string()]),
+                ..Default::default()
             }),
             ..Default::default()
         };
@@ -2788,6 +2977,349 @@ allowed_domains = ["openai.com"]
         Ok(())
     }
 
+    #[test]
+    fn config_toml_deserializes_permission_profiles() {
+        let toml = r#"
+default_permissions = "workspace"
+
+[permissions.workspace.filesystem]
+":minimal" = "read"
+
+[permissions.workspace.filesystem.":project_roots"]
+"." = "write"
+"docs" = "read"
+"#;
+        let cfg: ConfigToml = toml::from_str(toml)
+            .expect("TOML deserialization should succeed for permissions profiles");
+
+        assert_eq!(cfg.default_permissions.as_deref(), Some("workspace"));
+        assert_eq!(
+            cfg.permissions.expect("[permissions] should deserialize"),
+            PermissionsToml {
+                entries: BTreeMap::from([(
+                    "workspace".to_string(),
+                    PermissionProfileToml {
+                        filesystem: Some(FilesystemPermissionsToml {
+                            entries: BTreeMap::from([
+                                (
+                                    ":minimal".to_string(),
+                                    FilesystemPermissionToml::Access(FileSystemAccessMode::Read),
+                                ),
+                                (
+                                    ":project_roots".to_string(),
+                                    FilesystemPermissionToml::Scoped(BTreeMap::from([
+                                        (".".to_string(), FileSystemAccessMode::Write),
+                                        ("docs".to_string(), FileSystemAccessMode::Read),
+                                    ])),
+                                ),
+                            ]),
+                        }),
+                        network: None,
+                    },
+                )]),
+            }
+        );
+    }
+
+    #[test]
+    fn default_permissions_profile_populates_runtime_sandbox_policy() -> std::io::Result<()> {
+        let codex_home = TempDir::new()?;
+        let cwd = TempDir::new()?;
+        std::fs::create_dir_all(cwd.path().join("docs"))?;
+        std::fs::write(cwd.path().join(".git"), "gitdir: nowhere")?;
+
+        let cfg = ConfigToml {
+            default_permissions: Some("workspace".to_string()),
+            permissions: Some(PermissionsToml {
+                entries: BTreeMap::from([(
+                    "workspace".to_string(),
+                    PermissionProfileToml {
+                        filesystem: Some(FilesystemPermissionsToml {
+                            entries: BTreeMap::from([
+                                (
+                                    ":minimal".to_string(),
+                                    FilesystemPermissionToml::Access(FileSystemAccessMode::Read),
+                                ),
+                                (
+                                    ":project_roots".to_string(),
+                                    FilesystemPermissionToml::Scoped(BTreeMap::from([
+                                        (".".to_string(), FileSystemAccessMode::Write),
+                                        ("docs".to_string(), FileSystemAccessMode::Read),
+                                    ])),
+                                ),
+                            ]),
+                        }),
+                        network: None,
+                    },
+                )]),
+            }),
+            ..Default::default()
+        };
+
+        let config = Config::load_from_base_config_with_overrides(
+            cfg,
+            ConfigOverrides {
+                cwd: Some(cwd.path().to_path_buf()),
+                ..Default::default()
+            },
+            codex_home.path().to_path_buf(),
+        )?;
+
+        assert_eq!(
+            config.permissions.file_system_sandbox_policy,
+            FileSystemSandboxPolicy::restricted(vec![
+                crate::protocol::FileSystemSandboxEntry {
+                    path: crate::protocol::FileSystemPath::Special {
+                        value: crate::protocol::FileSystemSpecialPath {
+                            kind: crate::protocol::FileSystemSpecialPathKind::Minimal,
+                            subpath: None,
+                        },
+                    },
+                    access: FileSystemAccessMode::Read,
+                },
+                crate::protocol::FileSystemSandboxEntry {
+                    path: crate::protocol::FileSystemPath::Special {
+                        value: crate::protocol::FileSystemSpecialPath {
+                            kind: crate::protocol::FileSystemSpecialPathKind::ProjectRoots,
+                            subpath: None,
+                        },
+                    },
+                    access: FileSystemAccessMode::Write,
+                },
+                crate::protocol::FileSystemSandboxEntry {
+                    path: crate::protocol::FileSystemPath::Special {
+                        value: crate::protocol::FileSystemSpecialPath {
+                            kind: crate::protocol::FileSystemSpecialPathKind::ProjectRoots,
+                            subpath: Some("docs".into()),
+                        },
+                    },
+                    access: FileSystemAccessMode::Read,
+                },
+            ]),
+        );
+        assert_eq!(
+            config.permissions.sandbox_policy.get(),
+            &SandboxPolicy::WorkspaceWrite {
+                writable_roots: Vec::new(),
+                read_only_access: ReadOnlyAccess::Restricted {
+                    include_platform_defaults: true,
+                    readable_roots: vec![
+                        AbsolutePathBuf::try_from(cwd.path().join("docs"))
+                            .expect("absolute docs path"),
+                    ],
+                },
+                network_access: false,
+                exclude_tmpdir_env_var: true,
+                exclude_slash_tmp: true,
+            }
+        );
+        assert_eq!(
+            config.permissions.network_sandbox_policy,
+            NetworkSandboxPolicy::Restricted
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn permissions_profiles_require_default_permissions() -> std::io::Result<()> {
+        let codex_home = TempDir::new()?;
+        let cwd = TempDir::new()?;
+        std::fs::write(cwd.path().join(".git"), "gitdir: nowhere")?;
+
+        let err = Config::load_from_base_config_with_overrides(
+            ConfigToml {
+                permissions: Some(PermissionsToml {
+                    entries: BTreeMap::from([(
+                        "workspace".to_string(),
+                        PermissionProfileToml {
+                            filesystem: Some(FilesystemPermissionsToml {
+                                entries: BTreeMap::from([(
+                                    ":minimal".to_string(),
+                                    FilesystemPermissionToml::Access(FileSystemAccessMode::Read),
+                                )]),
+                            }),
+                            network: None,
+                        },
+                    )]),
+                }),
+                ..Default::default()
+            },
+            ConfigOverrides {
+                cwd: Some(cwd.path().to_path_buf()),
+                ..Default::default()
+            },
+            codex_home.path().to_path_buf(),
+        )
+        .expect_err("missing default_permissions should be rejected");
+
+        assert_eq!(err.kind(), ErrorKind::InvalidInput);
+        assert_eq!(
+            err.to_string(),
+            "config defines `[permissions]` profiles but does not set `default_permissions`"
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn legacy_permissions_network_requires_migration_to_top_level_network() -> std::io::Result<()> {
+        let codex_home = TempDir::new()?;
+        let cwd = TempDir::new()?;
+        std::fs::write(cwd.path().join(".git"), "gitdir: nowhere")?;
+
+        let cfg: ConfigToml = toml::from_str(
+            r#"
+[permissions.network]
+enabled = true
+proxy_url = "http://127.0.0.1:43128"
+"#,
+        )
+        .expect("legacy permissions.network TOML should deserialize");
+
+        let err = Config::load_from_base_config_with_overrides(
+            cfg,
+            ConfigOverrides {
+                cwd: Some(cwd.path().to_path_buf()),
+                ..Default::default()
+            },
+            codex_home.path().to_path_buf(),
+        )
+        .expect_err("legacy permissions.network should require migration");
+
+        assert_eq!(err.kind(), ErrorKind::InvalidInput);
+        assert_eq!(
+            err.to_string(),
+            "legacy `[permissions.network]` is no longer supported; move this config to the top-level `[network]` table"
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn legacy_permissions_network_requires_migration_even_with_legacy_sandbox_mode()
+    -> std::io::Result<()> {
+        let codex_home = TempDir::new()?;
+        let cwd = TempDir::new()?;
+        std::fs::write(cwd.path().join(".git"), "gitdir: nowhere")?;
+
+        let cfg: ConfigToml = toml::from_str(
+            r#"
+sandbox_mode = "read-only"
+
+[permissions.network]
+enabled = true
+proxy_url = "http://127.0.0.1:43128"
+"#,
+        )
+        .expect("legacy permissions.network TOML should deserialize");
+
+        let err = Config::load_from_base_config_with_overrides(
+            cfg,
+            ConfigOverrides {
+                cwd: Some(cwd.path().to_path_buf()),
+                ..Default::default()
+            },
+            codex_home.path().to_path_buf(),
+        )
+        .expect_err("legacy permissions.network should require migration");
+
+        assert_eq!(err.kind(), ErrorKind::InvalidInput);
+        assert_eq!(
+            err.to_string(),
+            "legacy `[permissions.network]` is no longer supported; move this config to the top-level `[network]` table"
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn permissions_profiles_reject_writes_outside_workspace_root() -> std::io::Result<()> {
+        let codex_home = TempDir::new()?;
+        let cwd = TempDir::new()?;
+        std::fs::write(cwd.path().join(".git"), "gitdir: nowhere")?;
+        let external_write_path = if cfg!(windows) { r"C:\temp" } else { "/tmp" };
+
+        let err = Config::load_from_base_config_with_overrides(
+            ConfigToml {
+                default_permissions: Some("workspace".to_string()),
+                permissions: Some(PermissionsToml {
+                    entries: BTreeMap::from([(
+                        "workspace".to_string(),
+                        PermissionProfileToml {
+                            filesystem: Some(FilesystemPermissionsToml {
+                                entries: BTreeMap::from([(
+                                    external_write_path.to_string(),
+                                    FilesystemPermissionToml::Access(FileSystemAccessMode::Write),
+                                )]),
+                            }),
+                            network: None,
+                        },
+                    )]),
+                }),
+                ..Default::default()
+            },
+            ConfigOverrides {
+                cwd: Some(cwd.path().to_path_buf()),
+                ..Default::default()
+            },
+            codex_home.path().to_path_buf(),
+        )
+        .expect_err("writes outside the workspace root should be rejected");
+
+        assert_eq!(err.kind(), ErrorKind::InvalidInput);
+        assert!(
+            err.to_string()
+                .contains("filesystem writes outside the workspace root"),
+            "{err}"
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn permissions_profiles_allow_network_enablement() -> std::io::Result<()> {
+        let codex_home = TempDir::new()?;
+        let cwd = TempDir::new()?;
+        std::fs::write(cwd.path().join(".git"), "gitdir: nowhere")?;
+
+        let config = Config::load_from_base_config_with_overrides(
+            ConfigToml {
+                default_permissions: Some("workspace".to_string()),
+                permissions: Some(PermissionsToml {
+                    entries: BTreeMap::from([(
+                        "workspace".to_string(),
+                        PermissionProfileToml {
+                            filesystem: Some(FilesystemPermissionsToml {
+                                entries: BTreeMap::from([(
+                                    ":minimal".to_string(),
+                                    FilesystemPermissionToml::Access(FileSystemAccessMode::Read),
+                                )]),
+                            }),
+                            network: Some(PermissionProfileNetworkToml {
+                                enabled: Some(true),
+                            }),
+                        },
+                    )]),
+                }),
+                ..Default::default()
+            },
+            ConfigOverrides {
+                cwd: Some(cwd.path().to_path_buf()),
+                ..Default::default()
+            },
+            codex_home.path().to_path_buf(),
+        )?;
+
+        assert!(
+            config.permissions.network_sandbox_policy.is_enabled(),
+            "expected network sandbox policy to be enabled",
+        );
+        assert!(
+            config
+                .permissions
+                .sandbox_policy
+                .get()
+                .has_full_network_access()
+        );
+        Ok(())
+    }
+
     #[test]
     fn tui_theme_deserializes_from_toml() {
         let cfg = r#"
@@ -5129,6 +5661,10 @@ model_verbosity = "high"
                 permissions: Permissions {
                     approval_policy: Constrained::allow_any(AskForApproval::Never),
                     sandbox_policy: Constrained::allow_any(SandboxPolicy::new_read_only_policy()),
+                    file_system_sandbox_policy: FileSystemSandboxPolicy::from(
+                        &SandboxPolicy::new_read_only_policy(),
+                    ),
+                    network_sandbox_policy: NetworkSandboxPolicy::Restricted,
                     network: None,
                     allow_login_shell: true,
                     shell_environment_policy: ShellEnvironmentPolicy::default(),
@@ -5259,6 +5795,10 @@ model_verbosity = "high"
             permissions: Permissions {
                 approval_policy: Constrained::allow_any(AskForApproval::UnlessTrusted),
                 sandbox_policy: Constrained::allow_any(SandboxPolicy::new_read_only_policy()),
+                file_system_sandbox_policy: FileSystemSandboxPolicy::from(
+                    &SandboxPolicy::new_read_only_policy(),
+                ),
+                network_sandbox_policy: NetworkSandboxPolicy::Restricted,
                 network: None,
                 allow_login_shell: true,
                 shell_environment_policy: ShellEnvironmentPolicy::default(),
@@ -5387,6 +5927,10 @@ model_verbosity = "high"
             permissions: Permissions {
                 approval_policy: Constrained::allow_any(AskForApproval::OnFailure),
                 sandbox_policy: Constrained::allow_any(SandboxPolicy::new_read_only_policy()),
+                file_system_sandbox_policy: FileSystemSandboxPolicy::from(
+                    &SandboxPolicy::new_read_only_policy(),
+                ),
+                network_sandbox_policy: NetworkSandboxPolicy::Restricted,
                 network: None,
                 allow_login_shell: true,
                 shell_environment_policy: ShellEnvironmentPolicy::default(),
@@ -5501,6 +6045,10 @@ model_verbosity = "high"
             permissions: Permissions {
                 approval_policy: Constrained::allow_any(AskForApproval::OnFailure),
                 sandbox_policy: Constrained::allow_any(SandboxPolicy::new_read_only_policy()),
+                file_system_sandbox_policy: FileSystemSandboxPolicy::from(
+                    &SandboxPolicy::new_read_only_policy(),
+                ),
+                network_sandbox_policy: NetworkSandboxPolicy::Restricted,
                 network: None,
                 allow_login_shell: true,
                 shell_environment_policy: ShellEnvironmentPolicy::default(),

codex-rs/core/src/config/permissions.rs

@@ -1,15 +1,63 @@
+use std::collections::BTreeMap;
+use std::io;
+use std::path::Path;
+
 use codex_network_proxy::NetworkMode;
 use codex_network_proxy::NetworkProxyConfig;
+use codex_protocol::protocol::FileSystemAccessMode;
+use codex_protocol::protocol::FileSystemPath;
+use codex_protocol::protocol::FileSystemSandboxEntry;
+use codex_protocol::protocol::FileSystemSandboxPolicy;
+use codex_protocol::protocol::FileSystemSpecialPath;
+use codex_protocol::protocol::FileSystemSpecialPathKind;
+use codex_protocol::protocol::NetworkSandboxPolicy;
+use codex_utils_absolute_path::AbsolutePathBuf;
 use schemars::JsonSchema;
 use serde::Deserialize;
 use serde::Serialize;
 
 #[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq, JsonSchema)]
-#[schemars(deny_unknown_fields)]
 pub struct PermissionsToml {
-    /// Network proxy settings from `[permissions.network]`.
-    /// User config can enable the proxy; managed requirements may still constrain values.
-    pub network: Option<NetworkToml>,
+    #[serde(flatten)]
+    pub entries: BTreeMap<String, PermissionProfileToml>,
+}
+
+impl PermissionsToml {
+    pub fn is_empty(&self) -> bool {
+        self.entries.is_empty()
+    }
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq, JsonSchema)]
+#[schemars(deny_unknown_fields)]
+pub struct PermissionProfileToml {
+    pub filesystem: Option<FilesystemPermissionsToml>,
+    pub network: Option<PermissionProfileNetworkToml>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq, JsonSchema)]
+pub struct FilesystemPermissionsToml {
+    #[serde(flatten)]
+    pub entries: BTreeMap<String, FilesystemPermissionToml>,
+}
+
+impl FilesystemPermissionsToml {
+    pub fn is_empty(&self) -> bool {
+        self.entries.is_empty()
+    }
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema)]
+#[serde(untagged)]
+pub enum FilesystemPermissionToml {
+    Access(FileSystemAccessMode),
+    Scoped(BTreeMap<String, FileSystemAccessMode>),
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq, JsonSchema)]
+#[schemars(deny_unknown_fields)]
+pub struct PermissionProfileNetworkToml {
+    pub enabled: Option<bool>,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq, JsonSchema)]
@@ -102,13 +150,161 @@ impl NetworkToml {
     }
 }
 
-pub(crate) fn network_proxy_config_from_permissions(
-    permissions: Option<&PermissionsToml>,
+pub(crate) fn network_proxy_config_from_network(
+    network: Option<&NetworkToml>,
 ) -> NetworkProxyConfig {
-    permissions
-        .and_then(|permissions| permissions.network.as_ref())
-        .map_or_else(
-            NetworkProxyConfig::default,
-            NetworkToml::to_network_proxy_config,
-        )
+    network.map_or_else(
+        NetworkProxyConfig::default,
+        NetworkToml::to_network_proxy_config,
+    )
+}
+
+pub(crate) fn compile_permission_profile(
+    permissions: &PermissionsToml,
+    profile_name: &str,
+) -> io::Result<(FileSystemSandboxPolicy, NetworkSandboxPolicy)> {
+    let profile = permissions.entries.get(profile_name).ok_or_else(|| {
+        io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!("default_permissions refers to undefined profile `{profile_name}`"),
+        )
+    })?;
+
+    let filesystem = profile.filesystem.as_ref().ok_or_else(|| {
+        io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!(
+                "permissions profile `{profile_name}` must define a `[permissions.{profile_name}.filesystem]` table"
+            ),
+        )
+    })?;
+
+    if filesystem.is_empty() {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!(
+                "permissions profile `{profile_name}` must define at least one filesystem entry"
+            ),
+        ));
+    }
+
+    let mut entries = Vec::new();
+    for (path, permission) in &filesystem.entries {
+        compile_filesystem_permission(path, permission, &mut entries)?;
+    }
+
+    let network_sandbox_policy = compile_network_sandbox_policy(profile.network.as_ref());
+
+    Ok((
+        FileSystemSandboxPolicy::restricted(entries),
+        network_sandbox_policy,
+    ))
+}
+
+fn compile_network_sandbox_policy(
+    network: Option<&PermissionProfileNetworkToml>,
+) -> NetworkSandboxPolicy {
+    let Some(network) = network else {
+        return NetworkSandboxPolicy::Restricted;
+    };
+
+    match network.enabled {
+        Some(true) => NetworkSandboxPolicy::Enabled,
+        _ => NetworkSandboxPolicy::Restricted,
+    }
+}
+
+fn compile_filesystem_permission(
+    path: &str,
+    permission: &FilesystemPermissionToml,
+    entries: &mut Vec<FileSystemSandboxEntry>,
+) -> io::Result<()> {
+    match permission {
+        FilesystemPermissionToml::Access(access) => entries.push(FileSystemSandboxEntry {
+            path: compile_filesystem_path(path)?,
+            access: *access,
+        }),
+        FilesystemPermissionToml::Scoped(scoped_entries) => {
+            for (subpath, access) in scoped_entries {
+                entries.push(FileSystemSandboxEntry {
+                    path: compile_scoped_filesystem_path(path, subpath)?,
+                    access: *access,
+                });
+            }
+        }
+    }
+    Ok(())
+}
+
+fn compile_filesystem_path(path: &str) -> io::Result<FileSystemPath> {
+    if let Some(special) = parse_special_path(path)? {
+        return Ok(FileSystemPath::Special { value: special });
+    }
+
+    let path = parse_absolute_path(path)?;
+    Ok(FileSystemPath::Path { path })
+}
+
+fn compile_scoped_filesystem_path(path: &str, subpath: &str) -> io::Result<FileSystemPath> {
+    if subpath == "." {
+        return compile_filesystem_path(path);
+    }
+
+    let subpath = Path::new(subpath);
+    if subpath.is_absolute() {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!(
+                "filesystem subpath `{}` must be relative",
+                subpath.display()
+            ),
+        ));
+    }
+
+    if let Some(mut special) = parse_special_path(path)? {
+        if !matches!(special.kind, FileSystemSpecialPathKind::ProjectRoots) {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                format!("filesystem path `{path}` does not support nested entries"),
+            ));
+        }
+        special.subpath = Some(subpath.to_path_buf());
+        return Ok(FileSystemPath::Special { value: special });
+    }
+
+    let base = parse_absolute_path(path)?;
+    let path = AbsolutePathBuf::resolve_path_against_base(subpath, base.as_path())?;
+    Ok(FileSystemPath::Path { path })
+}
+
+fn parse_special_path(path: &str) -> io::Result<Option<FileSystemSpecialPath>> {
+    let kind = match path {
+        ":root" => Some(FileSystemSpecialPathKind::Root),
+        ":minimal" => Some(FileSystemSpecialPathKind::Minimal),
+        ":project_roots" => Some(FileSystemSpecialPathKind::ProjectRoots),
+        ":tmpdir" => Some(FileSystemSpecialPathKind::Tmpdir),
+        _ if path.starts_with(':') => {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                format!("unknown filesystem special path `{path}`"),
+            ));
+        }
+        _ => None,
+    };
+
+    Ok(kind.map(|kind| FileSystemSpecialPath {
+        kind,
+        subpath: None,
+    }))
+}
+
+fn parse_absolute_path(path: &str) -> io::Result<AbsolutePathBuf> {
+    let path_ref = Path::new(path);
+    if !path_ref.is_absolute() && path != "~" && !path.starts_with("~/") {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!("filesystem path `{path}` must be absolute, use `~/...`, or start with `:`"),
+        ));
+    }
+    AbsolutePathBuf::from_absolute_path(path_ref)
 }

codex-rs/core/src/exec.rs

@@ -24,11 +24,15 @@ use crate::protocol::Event;
 use crate::protocol::EventMsg;
 use crate::protocol::ExecCommandOutputDeltaEvent;
 use crate::protocol::ExecOutputStream;
+use crate::protocol::FileSystemSandboxKind;
+use crate::protocol::FileSystemSandboxPolicy;
+use crate::protocol::NetworkSandboxPolicy;
 use crate::protocol::SandboxPolicy;
 use crate::sandboxing::CommandSpec;
 use crate::sandboxing::ExecRequest;
 use crate::sandboxing::SandboxManager;
 use crate::sandboxing::SandboxPermissions;
+use crate::sandboxing::should_require_platform_sandbox;
 use crate::spawn::SpawnChildRequest;
 use crate::spawn::StdioPolicy;
 use crate::spawn::spawn_child_async;
@@ -149,9 +153,12 @@ pub struct StdoutStream {
     pub tx_event: Sender<Event>,
 }
 
+#[allow(clippy::too_many_arguments)]
 pub async fn process_exec_tool_call(
     params: ExecParams,
     sandbox_policy: &SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     sandbox_cwd: &Path,
     codex_linux_sandbox_exe: &Option<PathBuf>,
     use_linux_sandbox_bwrap: bool,
@@ -159,22 +166,17 @@ pub async fn process_exec_tool_call(
 ) -> Result<ExecToolCallOutput> {
     let windows_sandbox_level = params.windows_sandbox_level;
     let enforce_managed_network = params.network.is_some();
-    let sandbox_type = match &sandbox_policy {
-        SandboxPolicy::DangerFullAccess | SandboxPolicy::ExternalSandbox { .. } => {
-            if enforce_managed_network {
-                get_platform_sandbox(
-                    windows_sandbox_level
-                        != codex_protocol::config_types::WindowsSandboxLevel::Disabled,
-                )
-                .unwrap_or(SandboxType::None)
-            } else {
-                SandboxType::None
-            }
-        }
-        _ => get_platform_sandbox(
+    let sandbox_type = if should_require_platform_sandbox(
+        file_system_sandbox_policy,
+        network_sandbox_policy,
+        enforce_managed_network,
+    ) {
+        get_platform_sandbox(
             windows_sandbox_level != codex_protocol::config_types::WindowsSandboxLevel::Disabled,
         )
-        .unwrap_or(SandboxType::None),
+        .unwrap_or(SandboxType::None)
+    } else {
+        SandboxType::None
     };
     tracing::debug!("Sandbox type: {sandbox_type:?}");
 
@@ -215,6 +217,8 @@ pub async fn process_exec_tool_call(
         .transform(crate::sandboxing::SandboxTransformRequest {
             spec,
             policy: sandbox_policy,
+            file_system_policy: file_system_sandbox_policy,
+            network_policy: network_sandbox_policy,
             sandbox: sandbox_type,
             enforce_managed_network,
             network: network.as_ref(),
@@ -233,7 +237,6 @@ pub async fn process_exec_tool_call(
 
 pub(crate) async fn execute_exec_env(
     env: ExecRequest,
-    sandbox_policy: &SandboxPolicy,
     stdout_stream: Option<StdoutStream>,
 ) -> Result<ExecToolCallOutput> {
     let ExecRequest {
@@ -245,7 +248,9 @@ pub(crate) async fn execute_exec_env(
         sandbox,
         windows_sandbox_level,
         sandbox_permissions,
-        sandbox_policy: _sandbox_policy_from_env,
+        sandbox_policy,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
         justification,
         arg0,
     } = env;
@@ -263,7 +268,15 @@ pub(crate) async fn execute_exec_env(
     };
 
     let start = Instant::now();
-    let raw_output_result = exec(params, sandbox, sandbox_policy, stdout_stream).await;
+    let raw_output_result = exec(
+        params,
+        sandbox,
+        &sandbox_policy,
+        &file_system_sandbox_policy,
+        network_sandbox_policy,
+        stdout_stream,
+    )
+    .await;
     let duration = start.elapsed();
     finalize_exec_result(raw_output_result, sandbox, duration)
 }
@@ -692,15 +705,16 @@ async fn exec(
     params: ExecParams,
     sandbox: SandboxType,
     sandbox_policy: &SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     stdout_stream: Option<StdoutStream>,
 ) -> Result<RawExecToolCallOutput> {
     #[cfg(target_os = "windows")]
-    if sandbox == SandboxType::WindowsRestrictedToken
-        && !matches!(
-            sandbox_policy,
-            SandboxPolicy::DangerFullAccess | SandboxPolicy::ExternalSandbox { .. }
-        )
-    {
+    if should_use_windows_restricted_token_sandbox(
+        sandbox,
+        sandbox_policy,
+        file_system_sandbox_policy,
+    ) {
         return exec_windows_sandbox(params, sandbox_policy).await;
     }
     let ExecParams {
@@ -729,7 +743,7 @@ async fn exec(
         args: args.into(),
         arg0: arg0_ref,
         cwd,
-        sandbox_policy,
+        network_sandbox_policy,
         // The environment already has attempt-scoped proxy settings from
         // apply_to_env_for_attempt above. Passing network here would reapply
         // non-attempt proxy vars and drop attempt correlation metadata.
@@ -741,6 +755,20 @@ async fn exec(
     consume_truncated_output(child, expiration, stdout_stream).await
 }
 
+#[cfg_attr(not(target_os = "windows"), allow(dead_code))]
+fn should_use_windows_restricted_token_sandbox(
+    sandbox: SandboxType,
+    sandbox_policy: &SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+) -> bool {
+    sandbox == SandboxType::WindowsRestrictedToken
+        && file_system_sandbox_policy.kind == FileSystemSandboxKind::Restricted
+        && !matches!(
+            sandbox_policy,
+            SandboxPolicy::DangerFullAccess | SandboxPolicy::ExternalSandbox { .. }
+        )
+}
+
 /// Consumes the output of a child process, truncating it so it is suitable for
 /// use as the output of a `shell` tool call. Also enforces specified timeout.
 async fn consume_truncated_output(
@@ -1093,6 +1121,38 @@ mod tests {
         assert_eq!(aggregated.truncated_after_lines, None);
     }
 
+    #[test]
+    fn windows_restricted_token_skips_external_sandbox_policies() {
+        let policy = SandboxPolicy::ExternalSandbox {
+            network_access: codex_protocol::protocol::NetworkAccess::Restricted,
+        };
+        let file_system_policy = FileSystemSandboxPolicy::restricted(vec![]);
+
+        assert_eq!(
+            should_use_windows_restricted_token_sandbox(
+                SandboxType::WindowsRestrictedToken,
+                &policy,
+                &file_system_policy,
+            ),
+            false
+        );
+    }
+
+    #[test]
+    fn windows_restricted_token_runs_for_legacy_restricted_policies() {
+        let policy = SandboxPolicy::new_read_only_policy();
+        let file_system_policy = FileSystemSandboxPolicy::restricted(vec![]);
+
+        assert_eq!(
+            should_use_windows_restricted_token_sandbox(
+                SandboxType::WindowsRestrictedToken,
+                &policy,
+                &file_system_policy,
+            ),
+            true
+        );
+    }
+
     #[cfg(unix)]
     #[test]
     fn sandbox_detection_flags_sigsys_exit_code() {
@@ -1135,6 +1195,8 @@ mod tests {
             params,
             SandboxType::None,
             &SandboxPolicy::new_read_only_policy(),
+            &FileSystemSandboxPolicy::from(&SandboxPolicy::new_read_only_policy()),
+            NetworkSandboxPolicy::Restricted,
             None,
         )
         .await?;
@@ -1190,6 +1252,8 @@ mod tests {
         let result = process_exec_tool_call(
             params,
             &SandboxPolicy::DangerFullAccess,
+            &FileSystemSandboxPolicy::from(&SandboxPolicy::DangerFullAccess),
+            NetworkSandboxPolicy::Enabled,
             cwd.as_path(),
             &None,
             false,

codex-rs/core/src/landlock.rs

@@ -1,3 +1,5 @@
+use crate::protocol::FileSystemSandboxPolicy;
+use crate::protocol::NetworkSandboxPolicy;
 use crate::protocol::SandboxPolicy;
 use crate::spawn::SpawnChildRequest;
 use crate::spawn::StdioPolicy;
@@ -13,9 +15,9 @@ use tokio::process::Child;
 /// isolation plus seccomp for network restrictions.
 ///
 /// Unlike macOS Seatbelt where we directly embed the policy text, the Linux
-/// helper accepts a list of `--sandbox-permission`/`-s` flags mirroring the
-/// public CLI. We convert the internal [`SandboxPolicy`] representation into
-/// the equivalent CLI options.
+/// helper is a separate executable. We pass the legacy [`SandboxPolicy`] plus
+/// split filesystem/network policies as JSON so the helper can migrate
+/// incrementally without breaking older call sites.
 #[allow(clippy::too_many_arguments)]
 pub async fn spawn_command_under_linux_sandbox<P>(
     codex_linux_sandbox_exe: P,
@@ -31,9 +33,13 @@ pub async fn spawn_command_under_linux_sandbox<P>(
 where
     P: AsRef<Path>,
 {
-    let args = create_linux_sandbox_command_args(
+    let file_system_sandbox_policy = FileSystemSandboxPolicy::from(sandbox_policy);
+    let network_sandbox_policy = NetworkSandboxPolicy::from(sandbox_policy);
+    let args = create_linux_sandbox_command_args_for_policies(
         command,
         sandbox_policy,
+        &file_system_sandbox_policy,
+        network_sandbox_policy,
         sandbox_policy_cwd,
         use_bwrap_sandbox,
         allow_network_for_proxy(false),
@@ -44,7 +50,7 @@ where
         args,
         arg0,
         cwd: command_cwd,
-        sandbox_policy,
+        network_sandbox_policy,
         network,
         stdio_policy,
         env,
@@ -59,13 +65,55 @@ pub(crate) fn allow_network_for_proxy(enforce_managed_network: bool) -> bool {
     enforce_managed_network
 }
 
-/// Converts the sandbox policy into the CLI invocation for `codex-linux-sandbox`.
+/// Converts the sandbox policies into the CLI invocation for
+/// `codex-linux-sandbox`.
 ///
 /// The helper performs the actual sandboxing (bubblewrap + seccomp) after
 /// parsing these arguments. See `docs/linux_sandbox.md` for the Linux semantics.
-pub(crate) fn create_linux_sandbox_command_args(
+#[allow(clippy::too_many_arguments)]
+pub(crate) fn create_linux_sandbox_command_args_for_policies(
     command: Vec<String>,
     sandbox_policy: &SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
+    sandbox_policy_cwd: &Path,
+    use_bwrap_sandbox: bool,
+    allow_network_for_proxy: bool,
+) -> Vec<String> {
+    #[expect(clippy::expect_used)]
+    let sandbox_policy_json =
+        serde_json::to_string(sandbox_policy).expect("Failed to serialize SandboxPolicy to JSON");
+    #[expect(clippy::expect_used)]
+    let file_system_policy_json = serde_json::to_string(file_system_sandbox_policy)
+        .expect("Failed to serialize FileSystemSandboxPolicy to JSON");
+    #[expect(clippy::expect_used)]
+    let network_policy_json = serde_json::to_string(&network_sandbox_policy)
+        .expect("Failed to serialize NetworkSandboxPolicy to JSON");
+
+    let mut linux_cmd = create_linux_sandbox_command_args(
+        command,
+        sandbox_policy_cwd,
+        use_bwrap_sandbox,
+        allow_network_for_proxy,
+    );
+    linux_cmd.splice(
+        2..2,
+        [
+            "--sandbox-policy".to_string(),
+            sandbox_policy_json,
+            "--file-system-sandbox-policy".to_string(),
+            file_system_policy_json,
+            "--network-sandbox-policy".to_string(),
+            network_policy_json,
+        ],
+    );
+    linux_cmd
+}
+
+/// Converts the sandbox cwd and execution options into the CLI invocation for
+/// `codex-linux-sandbox`.
+pub(crate) fn create_linux_sandbox_command_args(
+    command: Vec<String>,
     sandbox_policy_cwd: &Path,
     use_bwrap_sandbox: bool,
     allow_network_for_proxy: bool,
@@ -76,16 +124,7 @@ pub(crate) fn create_linux_sandbox_command_args(
         .expect("cwd must be valid UTF-8")
         .to_string();
 
-    #[expect(clippy::expect_used)]
-    let sandbox_policy_json =
-        serde_json::to_string(sandbox_policy).expect("Failed to serialize SandboxPolicy to JSON");
-
-    let mut linux_cmd: Vec<String> = vec![
-        "--sandbox-policy-cwd".to_string(),
-        sandbox_policy_cwd,
-        "--sandbox-policy".to_string(),
-        sandbox_policy_json,
-    ];
+    let mut linux_cmd: Vec<String> = vec!["--sandbox-policy-cwd".to_string(), sandbox_policy_cwd];
     if use_bwrap_sandbox {
         linux_cmd.push("--use-bwrap-sandbox".to_string());
     }
@@ -112,16 +151,14 @@ mod tests {
     fn bwrap_flags_are_feature_gated() {
         let command = vec!["/bin/true".to_string()];
         let cwd = Path::new("/tmp");
-        let policy = SandboxPolicy::new_read_only_policy();
 
-        let with_bwrap =
-            create_linux_sandbox_command_args(command.clone(), &policy, cwd, true, false);
+        let with_bwrap = create_linux_sandbox_command_args(command.clone(), cwd, true, false);
         assert_eq!(
             with_bwrap.contains(&"--use-bwrap-sandbox".to_string()),
             true
         );
 
-        let without_bwrap = create_linux_sandbox_command_args(command, &policy, cwd, false, false);
+        let without_bwrap = create_linux_sandbox_command_args(command, cwd, false, false);
         assert_eq!(
             without_bwrap.contains(&"--use-bwrap-sandbox".to_string()),
             false
@@ -132,15 +169,46 @@ mod tests {
     fn proxy_flag_is_included_when_requested() {
         let command = vec!["/bin/true".to_string()];
         let cwd = Path::new("/tmp");
-        let policy = SandboxPolicy::new_read_only_policy();
 
-        let args = create_linux_sandbox_command_args(command, &policy, cwd, true, true);
+        let args = create_linux_sandbox_command_args(command, cwd, true, true);
         assert_eq!(
             args.contains(&"--allow-network-for-proxy".to_string()),
             true
         );
     }
 
+    #[test]
+    fn split_policy_flags_are_included() {
+        let command = vec!["/bin/true".to_string()];
+        let cwd = Path::new("/tmp");
+        let sandbox_policy = SandboxPolicy::new_read_only_policy();
+        let file_system_sandbox_policy = FileSystemSandboxPolicy::from(&sandbox_policy);
+        let network_sandbox_policy = NetworkSandboxPolicy::from(&sandbox_policy);
+
+        let args = create_linux_sandbox_command_args_for_policies(
+            command,
+            &sandbox_policy,
+            &file_system_sandbox_policy,
+            network_sandbox_policy,
+            cwd,
+            true,
+            false,
+        );
+
+        assert_eq!(
+            args.windows(2).any(|window| {
+                window[0] == "--file-system-sandbox-policy" && !window[1].is_empty()
+            }),
+            true
+        );
+        assert_eq!(
+            args.windows(2)
+                .any(|window| window[0] == "--network-sandbox-policy"
+                    && window[1] == "\"restricted\""),
+            true
+        );
+    }
+
     #[test]
     fn proxy_network_requires_managed_requirements() {
         assert_eq!(allow_network_for_proxy(false), false);

codex-rs/core/src/network_proxy_loader.rs

@@ -1,5 +1,4 @@
 use crate::config::NetworkToml;
-use crate::config::PermissionsToml;
 use crate::config::find_codex_home;
 use crate::config_loader::CloudRequirementsLoader;
 use crate::config_loader::ConfigLayerStack;
@@ -121,12 +120,6 @@ fn network_constraints_from_trusted_layers(
         if let Some(network) = parsed.network {
             apply_network_constraints(network, &mut constraints);
         }
-        if let Some(network) = parsed
-            .permissions
-            .and_then(|permissions| permissions.network)
-        {
-            apply_network_constraints(network, &mut constraints);
-        }
     }
     Ok(constraints)
 }
@@ -171,7 +164,6 @@ fn apply_network_constraints(network: NetworkToml, constraints: &mut NetworkProx
 #[derive(Debug, Clone, Default, Deserialize)]
 struct NetworkTablesToml {
     network: Option<NetworkToml>,
-    permissions: Option<PermissionsToml>,
 }
 
 fn network_tables_from_toml(value: &toml::Value) -> Result<NetworkTablesToml> {
@@ -185,12 +177,6 @@ fn apply_network_tables(config: &mut NetworkProxyConfig, parsed: NetworkTablesTo
     if let Some(network) = parsed.network {
         network.apply_to_network_proxy_config(config);
     }
-    if let Some(network) = parsed
-        .permissions
-        .and_then(|permissions| permissions.network)
-    {
-        network.apply_to_network_proxy_config(config);
-    }
 }
 
 fn config_from_layers(
@@ -315,10 +301,10 @@ mod tests {
     use pretty_assertions::assert_eq;
 
     #[test]
-    fn higher_precedence_network_table_beats_lower_permissions_network_table() {
-        let lower_permissions: toml::Value = toml::from_str(
+    fn higher_precedence_network_table_beats_lower_network_table() {
+        let lower_network: toml::Value = toml::from_str(
             r#"
-[permissions.network]
+[network]
 allowed_domains = ["lower.example.com"]
 "#,
         )
@@ -334,7 +320,7 @@ allowed_domains = ["higher.example.com"]
         let mut config = NetworkProxyConfig::default();
         apply_network_tables(
             &mut config,
-            network_tables_from_toml(&lower_permissions).expect("lower layer should deserialize"),
+            network_tables_from_toml(&lower_network).expect("lower layer should deserialize"),
         );
         apply_network_tables(
             &mut config,

codex-rs/core/src/safety.rs

@@ -9,6 +9,7 @@ use crate::exec::SandboxType;
 use crate::util::resolve_path;
 
 use crate::protocol::AskForApproval;
+use crate::protocol::FileSystemSandboxPolicy;
 use crate::protocol::SandboxPolicy;
 use codex_protocol::config_types::WindowsSandboxLevel;
 
@@ -28,6 +29,7 @@ pub fn assess_patch_safety(
     action: &ApplyPatchAction,
     policy: AskForApproval,
     sandbox_policy: &SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
     cwd: &Path,
     windows_sandbox_level: WindowsSandboxLevel,
 ) -> SafetyCheck {
@@ -60,7 +62,7 @@ pub fn assess_patch_safety(
     // Even though the patch appears to be constrained to writable paths, it is
     // possible that paths in the patch are hard links to files outside the
     // writable roots, so we should still run `apply_patch` in a sandbox in that case.
-    if is_write_patch_constrained_to_writable_paths(action, sandbox_policy, cwd)
+    if is_write_patch_constrained_to_writable_paths(action, file_system_sandbox_policy, cwd)
         || matches!(policy, AskForApproval::OnFailure)
     {
         if matches!(
@@ -122,20 +124,9 @@ pub fn get_platform_sandbox(windows_sandbox_enabled: bool) -> Option<SandboxType
 
 fn is_write_patch_constrained_to_writable_paths(
     action: &ApplyPatchAction,
-    sandbox_policy: &SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
     cwd: &Path,
 ) -> bool {
-    // Early‑exit if there are no declared writable roots.
-    let writable_roots = match sandbox_policy {
-        SandboxPolicy::ReadOnly { .. } => {
-            return false;
-        }
-        SandboxPolicy::DangerFullAccess | SandboxPolicy::ExternalSandbox { .. } => {
-            return true;
-        }
-        SandboxPolicy::WorkspaceWrite { .. } => sandbox_policy.get_writable_roots_with_cwd(cwd),
-    };
-
     // Normalize a path by removing `.` and resolving `..` without touching the
     // filesystem (works even if the file does not exist).
     fn normalize(path: &Path) -> Option<PathBuf> {
@@ -152,6 +143,9 @@ fn is_write_patch_constrained_to_writable_paths(
         Some(out)
     }
 
+    let unreadable_roots = file_system_sandbox_policy.get_unreadable_roots_with_cwd(cwd);
+    let writable_roots = file_system_sandbox_policy.get_writable_roots_with_cwd(cwd);
+
     // Determine whether `path` is inside **any** writable root. Both `path`
     // and roots are converted to absolute, normalized forms before the
     // prefix check.
@@ -162,6 +156,17 @@ fn is_write_patch_constrained_to_writable_paths(
             None => return false,
         };
 
+        if unreadable_roots
+            .iter()
+            .any(|root| abs.starts_with(root.as_path()))
+        {
+            return false;
+        }
+
+        if file_system_sandbox_policy.has_full_disk_write_access() {
+            return true;
+        }
+
         writable_roots
             .iter()
             .any(|writable_root| writable_root.is_path_writable(&abs))
@@ -193,6 +198,11 @@ fn is_write_patch_constrained_to_writable_paths(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use codex_protocol::protocol::FileSystemAccessMode;
+    use codex_protocol::protocol::FileSystemPath;
+    use codex_protocol::protocol::FileSystemSandboxEntry;
+    use codex_protocol::protocol::FileSystemSpecialPath;
+    use codex_protocol::protocol::FileSystemSpecialPathKind;
     use codex_protocol::protocol::RejectConfig;
     use codex_utils_absolute_path::AbsolutePathBuf;
     use tempfile::TempDir;
@@ -223,13 +233,13 @@ mod tests {
 
         assert!(is_write_patch_constrained_to_writable_paths(
             &add_inside,
-            &policy_workspace_only,
+            &FileSystemSandboxPolicy::from(&policy_workspace_only),
             &cwd,
         ));
 
         assert!(!is_write_patch_constrained_to_writable_paths(
             &add_outside,
-            &policy_workspace_only,
+            &FileSystemSandboxPolicy::from(&policy_workspace_only),
             &cwd,
         ));
 
@@ -244,7 +254,7 @@ mod tests {
         };
         assert!(is_write_patch_constrained_to_writable_paths(
             &add_outside,
-            &policy_with_parent,
+            &FileSystemSandboxPolicy::from(&policy_with_parent),
             &cwd,
         ));
     }
@@ -264,6 +274,7 @@ mod tests {
                 &add_inside,
                 AskForApproval::OnRequest,
                 &policy,
+                &FileSystemSandboxPolicy::from(&policy),
                 &cwd,
                 WindowsSandboxLevel::Disabled
             ),
@@ -294,6 +305,7 @@ mod tests {
                 &add_outside,
                 AskForApproval::OnRequest,
                 &policy_workspace_only,
+                &FileSystemSandboxPolicy::from(&policy_workspace_only),
                 &cwd,
                 WindowsSandboxLevel::Disabled,
             ),
@@ -308,6 +320,7 @@ mod tests {
                     mcp_elicitations: false,
                 }),
                 &policy_workspace_only,
+                &FileSystemSandboxPolicy::from(&policy_workspace_only),
                 &cwd,
                 WindowsSandboxLevel::Disabled,
             ),
@@ -339,6 +352,7 @@ mod tests {
                     mcp_elicitations: false,
                 }),
                 &policy_workspace_only,
+                &FileSystemSandboxPolicy::from(&policy_workspace_only),
                 &cwd,
                 WindowsSandboxLevel::Disabled,
             ),
@@ -348,4 +362,52 @@ mod tests {
             },
         );
     }
+
+    #[test]
+    fn explicit_unreadable_paths_prevent_auto_approval_for_external_sandbox() {
+        let tmp = TempDir::new().unwrap();
+        let cwd = tmp.path().to_path_buf();
+        let blocked_path = cwd.join("blocked.txt");
+        let action = ApplyPatchAction::new_add_for_test(&blocked_path, "".to_string());
+        let sandbox_policy = SandboxPolicy::ExternalSandbox {
+            network_access: codex_protocol::protocol::NetworkAccess::Restricted,
+        };
+        let file_system_sandbox_policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::Root,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Write,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                        subpath: Some(PathBuf::from("blocked.txt")),
+                    },
+                },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        assert!(!is_write_patch_constrained_to_writable_paths(
+            &action,
+            &file_system_sandbox_policy,
+            &cwd,
+        ));
+        assert_eq!(
+            assess_patch_safety(
+                &action,
+                AskForApproval::OnRequest,
+                &sandbox_policy,
+                &file_system_sandbox_policy,
+                &cwd,
+                WindowsSandboxLevel::Disabled,
+            ),
+            SafetyCheck::AskUser,
+        );
+    }
 }

codex-rs/core/src/sandboxing/mod.rs

@@ -12,12 +12,18 @@ use crate::exec::SandboxType;
 use crate::exec::StdoutStream;
 use crate::exec::execute_exec_env;
 use crate::landlock::allow_network_for_proxy;
-use crate::landlock::create_linux_sandbox_command_args;
+use crate::landlock::create_linux_sandbox_command_args_for_policies;
+use crate::protocol::FileSystemAccessMode;
+use crate::protocol::FileSystemPath;
+use crate::protocol::FileSystemSandboxEntry;
+use crate::protocol::FileSystemSandboxKind;
+use crate::protocol::FileSystemSandboxPolicy;
+use crate::protocol::NetworkSandboxPolicy;
 use crate::protocol::SandboxPolicy;
 #[cfg(target_os = "macos")]
 use crate::seatbelt::MACOS_PATH_TO_SEATBELT_EXECUTABLE;
 #[cfg(target_os = "macos")]
-use crate::seatbelt::create_seatbelt_command_args_with_extensions;
+use crate::seatbelt::create_seatbelt_command_args_for_policies_with_extensions;
 #[cfg(target_os = "macos")]
 use crate::spawn::CODEX_SANDBOX_ENV_VAR;
 use crate::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
@@ -29,6 +35,7 @@ use codex_protocol::models::FileSystemPermissions;
 use codex_protocol::models::MacOsSeatbeltProfileExtensions;
 use codex_protocol::models::PermissionProfile;
 pub use codex_protocol::models::SandboxPermissions;
+use codex_protocol::protocol::NetworkAccess;
 use codex_protocol::protocol::ReadOnlyAccess;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use dunce::canonicalize;
@@ -60,6 +67,8 @@ pub struct ExecRequest {
     pub windows_sandbox_level: WindowsSandboxLevel,
     pub sandbox_permissions: SandboxPermissions,
     pub sandbox_policy: SandboxPolicy,
+    pub file_system_sandbox_policy: FileSystemSandboxPolicy,
+    pub network_sandbox_policy: NetworkSandboxPolicy,
     pub justification: Option<String>,
     pub arg0: Option<String>,
 }
@@ -70,6 +79,8 @@ pub struct ExecRequest {
 pub(crate) struct SandboxTransformRequest<'a> {
     pub spec: CommandSpec,
     pub policy: &'a SandboxPolicy,
+    pub file_system_policy: &'a FileSystemSandboxPolicy,
+    pub network_policy: NetworkSandboxPolicy,
     pub sandbox: SandboxType,
     pub enforce_managed_network: bool,
     // TODO(viyatb): Evaluate switching this to Option<Arc<NetworkProxy>>
@@ -169,6 +180,40 @@ fn additional_permission_roots(
     )
 }
 
+fn merge_file_system_policy_with_additional_permissions(
+    file_system_policy: &FileSystemSandboxPolicy,
+    extra_reads: Vec<AbsolutePathBuf>,
+    extra_writes: Vec<AbsolutePathBuf>,
+) -> FileSystemSandboxPolicy {
+    match file_system_policy.kind {
+        FileSystemSandboxKind::Restricted => {
+            let mut merged_policy = file_system_policy.clone();
+            for path in extra_reads {
+                let entry = FileSystemSandboxEntry {
+                    path: FileSystemPath::Path { path },
+                    access: FileSystemAccessMode::Read,
+                };
+                if !merged_policy.entries.contains(&entry) {
+                    merged_policy.entries.push(entry);
+                }
+            }
+            for path in extra_writes {
+                let entry = FileSystemSandboxEntry {
+                    path: FileSystemPath::Path { path },
+                    access: FileSystemAccessMode::Write,
+                };
+                if !merged_policy.entries.contains(&entry) {
+                    merged_policy.entries.push(entry);
+                }
+            }
+            merged_policy
+        }
+        FileSystemSandboxKind::Unrestricted | FileSystemSandboxKind::ExternalSandbox => {
+            file_system_policy.clone()
+        }
+    }
+}
+
 fn merge_read_only_access_with_additional_reads(
     read_only_access: &ReadOnlyAccess,
     extra_reads: Vec<AbsolutePathBuf>,
@@ -212,9 +257,17 @@ fn sandbox_policy_with_additional_permissions(
     let (extra_reads, extra_writes) = additional_permission_roots(additional_permissions);
 
     let policy = match sandbox_policy {
-        SandboxPolicy::DangerFullAccess | SandboxPolicy::ExternalSandbox { .. } => {
-            sandbox_policy.clone()
-        }
+        SandboxPolicy::DangerFullAccess => SandboxPolicy::DangerFullAccess,
+        SandboxPolicy::ExternalSandbox { network_access } => SandboxPolicy::ExternalSandbox {
+            network_access: if merge_network_access(
+                network_access.is_enabled(),
+                additional_permissions,
+            ) {
+                NetworkAccess::Enabled
+            } else {
+                NetworkAccess::Restricted
+            },
+        },
         SandboxPolicy::WorkspaceWrite {
             writable_roots,
             read_only_access,
@@ -265,6 +318,28 @@ fn sandbox_policy_with_additional_permissions(
     Ok(policy)
 }
 
+pub(crate) fn should_require_platform_sandbox(
+    file_system_policy: &FileSystemSandboxPolicy,
+    network_policy: NetworkSandboxPolicy,
+    has_managed_network_requirements: bool,
+) -> bool {
+    if has_managed_network_requirements {
+        return true;
+    }
+
+    if !network_policy.is_enabled() {
+        return !matches!(
+            file_system_policy.kind,
+            FileSystemSandboxKind::ExternalSandbox
+        );
+    }
+
+    match file_system_policy.kind {
+        FileSystemSandboxKind::Restricted => !file_system_policy.has_full_disk_write_access(),
+        FileSystemSandboxKind::Unrestricted | FileSystemSandboxKind::ExternalSandbox => false,
+    }
+}
+
 #[derive(Default)]
 pub struct SandboxManager;
 
@@ -275,7 +350,8 @@ impl SandboxManager {
 
     pub(crate) fn select_initial(
         &self,
-        policy: &SandboxPolicy,
+        file_system_policy: &FileSystemSandboxPolicy,
+        network_policy: NetworkSandboxPolicy,
         pref: SandboxablePreference,
         windows_sandbox_level: WindowsSandboxLevel,
         has_managed_network_requirements: bool,
@@ -290,22 +366,20 @@ impl SandboxManager {
                 )
                 .unwrap_or(SandboxType::None)
             }
-            SandboxablePreference::Auto => match policy {
-                SandboxPolicy::DangerFullAccess | SandboxPolicy::ExternalSandbox { .. } => {
-                    if has_managed_network_requirements {
-                        crate::safety::get_platform_sandbox(
-                            windows_sandbox_level != WindowsSandboxLevel::Disabled,
-                        )
-                        .unwrap_or(SandboxType::None)
-                    } else {
-                        SandboxType::None
-                    }
+            SandboxablePreference::Auto => {
+                if should_require_platform_sandbox(
+                    file_system_policy,
+                    network_policy,
+                    has_managed_network_requirements,
+                ) {
+                    crate::safety::get_platform_sandbox(
+                        windows_sandbox_level != WindowsSandboxLevel::Disabled,
+                    )
+                    .unwrap_or(SandboxType::None)
+                } else {
+                    SandboxType::None
                 }
-                _ => crate::safety::get_platform_sandbox(
-                    windows_sandbox_level != WindowsSandboxLevel::Disabled,
-                )
-                .unwrap_or(SandboxType::None),
-            },
+            }
         }
     }
 
@@ -316,6 +390,8 @@ impl SandboxManager {
         let SandboxTransformRequest {
             mut spec,
             policy,
+            file_system_policy,
+            network_policy,
             sandbox,
             enforce_managed_network,
             network,
@@ -326,14 +402,34 @@ impl SandboxManager {
             use_linux_sandbox_bwrap,
             windows_sandbox_level,
         } = request;
-        let effective_policy =
-            if let Some(additional_permissions) = spec.additional_permissions.take() {
-                sandbox_policy_with_additional_permissions(policy, &additional_permissions)?
+        let effective_policy = if let Some(additional_permissions) =
+            spec.additional_permissions.take()
+        {
+            let (extra_reads, extra_writes) = additional_permission_roots(&additional_permissions);
+            let effective_policy =
+                sandbox_policy_with_additional_permissions(policy, &additional_permissions)?;
+            let file_system_sandbox_policy = if extra_reads.is_empty() && extra_writes.is_empty() {
+                file_system_policy.clone()
             } else {
-                policy.clone()
+                merge_file_system_policy_with_additional_permissions(
+                    file_system_policy,
+                    extra_reads,
+                    extra_writes,
+                )
             };
+            let network_sandbox_policy = NetworkSandboxPolicy::from(&effective_policy);
+            (
+                effective_policy,
+                file_system_sandbox_policy,
+                network_sandbox_policy,
+            )
+        } else {
+            (policy.clone(), file_system_policy.clone(), network_policy)
+        };
+        let (effective_policy, effective_file_system_policy, effective_network_policy) =
+            effective_policy;
         let mut env = spec.env;
-        if !effective_policy.has_full_network_access() {
+        if !effective_network_policy.is_enabled() {
             env.insert(
                 CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR.to_string(),
                 "1".to_string(),
@@ -350,9 +446,10 @@ impl SandboxManager {
             SandboxType::MacosSeatbelt => {
                 let mut seatbelt_env = HashMap::new();
                 seatbelt_env.insert(CODEX_SANDBOX_ENV_VAR.to_string(), "seatbelt".to_string());
-                let mut args = create_seatbelt_command_args_with_extensions(
+                let mut args = create_seatbelt_command_args_for_policies_with_extensions(
                     command.clone(),
-                    &effective_policy,
+                    &effective_file_system_policy,
+                    effective_network_policy,
                     sandbox_policy_cwd,
                     enforce_managed_network,
                     network,
@@ -369,9 +466,11 @@ impl SandboxManager {
                 let exe = codex_linux_sandbox_exe
                     .ok_or(SandboxTransformError::MissingLinuxSandboxExecutable)?;
                 let allow_proxy_network = allow_network_for_proxy(enforce_managed_network);
-                let mut args = create_linux_sandbox_command_args(
+                let mut args = create_linux_sandbox_command_args_for_policies(
                     command.clone(),
                     &effective_policy,
+                    &effective_file_system_policy,
+                    effective_network_policy,
                     sandbox_policy_cwd,
                     use_linux_sandbox_bwrap,
                     allow_proxy_network,
@@ -407,6 +506,8 @@ impl SandboxManager {
             windows_sandbox_level,
             sandbox_permissions: spec.sandbox_permissions,
             sandbox_policy: effective_policy,
+            file_system_sandbox_policy: effective_file_system_policy,
+            network_sandbox_policy: effective_network_policy,
             justification: spec.justification,
             arg0: arg0_override,
         })
@@ -421,16 +522,25 @@ pub async fn execute_env(
     env: ExecRequest,
     stdout_stream: Option<StdoutStream>,
 ) -> crate::error::Result<ExecToolCallOutput> {
-    let effective_policy = env.sandbox_policy.clone();
-    execute_exec_env(env, &effective_policy, stdout_stream).await
+    execute_exec_env(env, stdout_stream).await
 }
 
 #[cfg(test)]
 mod tests {
     use super::SandboxManager;
+    use super::merge_file_system_policy_with_additional_permissions;
     use super::normalize_additional_permissions;
     use super::sandbox_policy_with_additional_permissions;
+    use super::should_require_platform_sandbox;
     use crate::exec::SandboxType;
+    use crate::protocol::FileSystemAccessMode;
+    use crate::protocol::FileSystemPath;
+    use crate::protocol::FileSystemSandboxEntry;
+    use crate::protocol::FileSystemSandboxPolicy;
+    use crate::protocol::FileSystemSpecialPath;
+    use crate::protocol::FileSystemSpecialPathKind;
+    use crate::protocol::NetworkAccess;
+    use crate::protocol::NetworkSandboxPolicy;
     use crate::protocol::ReadOnlyAccess;
     use crate::protocol::SandboxPolicy;
     use crate::tools::sandboxing::SandboxablePreference;
@@ -441,13 +551,15 @@ mod tests {
     use codex_utils_absolute_path::AbsolutePathBuf;
     use dunce::canonicalize;
     use pretty_assertions::assert_eq;
+    use std::collections::HashMap;
     use tempfile::TempDir;
 
     #[test]
     fn danger_full_access_defaults_to_no_sandbox_without_network_requirements() {
         let manager = SandboxManager::new();
         let sandbox = manager.select_initial(
-            &SandboxPolicy::DangerFullAccess,
+            &FileSystemSandboxPolicy::unrestricted(),
+            NetworkSandboxPolicy::Enabled,
             SandboxablePreference::Auto,
             WindowsSandboxLevel::Disabled,
             false,
@@ -460,7 +572,8 @@ mod tests {
         let manager = SandboxManager::new();
         let expected = crate::safety::get_platform_sandbox(false).unwrap_or(SandboxType::None);
         let sandbox = manager.select_initial(
-            &SandboxPolicy::DangerFullAccess,
+            &FileSystemSandboxPolicy::unrestricted(),
+            NetworkSandboxPolicy::Enabled,
             SandboxablePreference::Auto,
             WindowsSandboxLevel::Disabled,
             true,
@@ -468,6 +581,136 @@ mod tests {
         assert_eq!(sandbox, expected);
     }
 
+    #[test]
+    fn restricted_file_system_uses_platform_sandbox_without_managed_network() {
+        let manager = SandboxManager::new();
+        let expected = crate::safety::get_platform_sandbox(false).unwrap_or(SandboxType::None);
+        let sandbox = manager.select_initial(
+            &FileSystemSandboxPolicy::restricted(vec![FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::Root,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Read,
+            }]),
+            NetworkSandboxPolicy::Enabled,
+            SandboxablePreference::Auto,
+            WindowsSandboxLevel::Disabled,
+            false,
+        );
+        assert_eq!(sandbox, expected);
+    }
+
+    #[test]
+    fn full_access_restricted_policy_skips_platform_sandbox_when_network_is_enabled() {
+        let policy = FileSystemSandboxPolicy::restricted(vec![FileSystemSandboxEntry {
+            path: FileSystemPath::Special {
+                value: FileSystemSpecialPath {
+                    kind: FileSystemSpecialPathKind::Root,
+                    subpath: None,
+                },
+            },
+            access: FileSystemAccessMode::Write,
+        }]);
+
+        assert_eq!(
+            should_require_platform_sandbox(&policy, NetworkSandboxPolicy::Enabled, false),
+            false
+        );
+    }
+
+    #[test]
+    fn root_write_policy_with_carveouts_still_uses_platform_sandbox() {
+        let policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::Root,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Write,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                        subpath: Some("blocked".into()),
+                    },
+                },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        assert_eq!(
+            should_require_platform_sandbox(&policy, NetworkSandboxPolicy::Enabled, false),
+            true
+        );
+    }
+
+    #[test]
+    fn full_access_restricted_policy_still_uses_platform_sandbox_for_restricted_network() {
+        let policy = FileSystemSandboxPolicy::restricted(vec![FileSystemSandboxEntry {
+            path: FileSystemPath::Special {
+                value: FileSystemSpecialPath {
+                    kind: FileSystemSpecialPathKind::Root,
+                    subpath: None,
+                },
+            },
+            access: FileSystemAccessMode::Write,
+        }]);
+
+        assert_eq!(
+            should_require_platform_sandbox(&policy, NetworkSandboxPolicy::Restricted, false),
+            true
+        );
+    }
+
+    #[test]
+    fn transform_preserves_unrestricted_file_system_policy_for_restricted_network() {
+        let manager = SandboxManager::new();
+        let cwd = std::env::current_dir().expect("current dir");
+        let exec_request = manager
+            .transform(super::SandboxTransformRequest {
+                spec: super::CommandSpec {
+                    program: "true".to_string(),
+                    args: Vec::new(),
+                    cwd: cwd.clone(),
+                    env: HashMap::new(),
+                    expiration: crate::exec::ExecExpiration::DefaultTimeout,
+                    sandbox_permissions: super::SandboxPermissions::UseDefault,
+                    additional_permissions: None,
+                    justification: None,
+                },
+                policy: &SandboxPolicy::ExternalSandbox {
+                    network_access: crate::protocol::NetworkAccess::Restricted,
+                },
+                file_system_policy: &FileSystemSandboxPolicy::unrestricted(),
+                network_policy: NetworkSandboxPolicy::Restricted,
+                sandbox: SandboxType::None,
+                enforce_managed_network: false,
+                network: None,
+                sandbox_policy_cwd: cwd.as_path(),
+                #[cfg(target_os = "macos")]
+                macos_seatbelt_profile_extensions: None,
+                codex_linux_sandbox_exe: None,
+                use_linux_sandbox_bwrap: false,
+                windows_sandbox_level: WindowsSandboxLevel::Disabled,
+            })
+            .expect("transform");
+
+        assert_eq!(
+            exec_request.file_system_sandbox_policy,
+            FileSystemSandboxPolicy::unrestricted()
+        );
+        assert_eq!(
+            exec_request.network_sandbox_policy,
+            NetworkSandboxPolicy::Restricted
+        );
+    }
+
     #[test]
     fn normalize_additional_permissions_preserves_network() {
         let temp_dir = TempDir::new().expect("create temp dir");
@@ -541,4 +784,139 @@ mod tests {
             }
         );
     }
+
+    #[test]
+    fn external_sandbox_additional_permissions_can_enable_network() {
+        let temp_dir = TempDir::new().expect("create temp dir");
+        let path = AbsolutePathBuf::from_absolute_path(
+            canonicalize(temp_dir.path()).expect("canonicalize temp dir"),
+        )
+        .expect("absolute temp dir");
+        let policy = sandbox_policy_with_additional_permissions(
+            &SandboxPolicy::ExternalSandbox {
+                network_access: NetworkAccess::Restricted,
+            },
+            &PermissionProfile {
+                network: Some(NetworkPermissions {
+                    enabled: Some(true),
+                }),
+                file_system: Some(FileSystemPermissions {
+                    read: Some(vec![path]),
+                    write: Some(Vec::new()),
+                }),
+                ..Default::default()
+            },
+        )
+        .expect("policy");
+
+        assert_eq!(
+            policy,
+            SandboxPolicy::ExternalSandbox {
+                network_access: NetworkAccess::Enabled,
+            }
+        );
+    }
+
+    #[test]
+    fn transform_additional_permissions_enable_network_for_external_sandbox() {
+        let manager = SandboxManager::new();
+        let cwd = std::env::current_dir().expect("current dir");
+        let temp_dir = TempDir::new().expect("create temp dir");
+        let path = AbsolutePathBuf::from_absolute_path(
+            canonicalize(temp_dir.path()).expect("canonicalize temp dir"),
+        )
+        .expect("absolute temp dir");
+        let exec_request = manager
+            .transform(super::SandboxTransformRequest {
+                spec: super::CommandSpec {
+                    program: "true".to_string(),
+                    args: Vec::new(),
+                    cwd: cwd.clone(),
+                    env: HashMap::new(),
+                    expiration: crate::exec::ExecExpiration::DefaultTimeout,
+                    sandbox_permissions: super::SandboxPermissions::WithAdditionalPermissions,
+                    additional_permissions: Some(PermissionProfile {
+                        network: Some(NetworkPermissions {
+                            enabled: Some(true),
+                        }),
+                        file_system: Some(FileSystemPermissions {
+                            read: Some(vec![path]),
+                            write: Some(Vec::new()),
+                        }),
+                        ..Default::default()
+                    }),
+                    justification: None,
+                },
+                policy: &SandboxPolicy::ExternalSandbox {
+                    network_access: NetworkAccess::Restricted,
+                },
+                file_system_policy: &FileSystemSandboxPolicy::unrestricted(),
+                network_policy: NetworkSandboxPolicy::Restricted,
+                sandbox: SandboxType::None,
+                enforce_managed_network: false,
+                network: None,
+                sandbox_policy_cwd: cwd.as_path(),
+                #[cfg(target_os = "macos")]
+                macos_seatbelt_profile_extensions: None,
+                codex_linux_sandbox_exe: None,
+                use_linux_sandbox_bwrap: false,
+                windows_sandbox_level: WindowsSandboxLevel::Disabled,
+            })
+            .expect("transform");
+
+        assert_eq!(
+            exec_request.sandbox_policy,
+            SandboxPolicy::ExternalSandbox {
+                network_access: NetworkAccess::Enabled,
+            }
+        );
+        assert_eq!(
+            exec_request.network_sandbox_policy,
+            NetworkSandboxPolicy::Enabled
+        );
+    }
+
+    #[test]
+    fn merge_file_system_policy_with_additional_permissions_preserves_unreadable_roots() {
+        let temp_dir = TempDir::new().expect("create temp dir");
+        let cwd = AbsolutePathBuf::from_absolute_path(
+            canonicalize(temp_dir.path()).expect("canonicalize temp dir"),
+        )
+        .expect("absolute temp dir");
+        let allowed_path = cwd.join("allowed").expect("allowed path");
+        let denied_path = cwd.join("denied").expect("denied path");
+        let merged_policy = merge_file_system_policy_with_additional_permissions(
+            &FileSystemSandboxPolicy::restricted(vec![
+                FileSystemSandboxEntry {
+                    path: FileSystemPath::Special {
+                        value: FileSystemSpecialPath {
+                            kind: FileSystemSpecialPathKind::Root,
+                            subpath: None,
+                        },
+                    },
+                    access: FileSystemAccessMode::Read,
+                },
+                FileSystemSandboxEntry {
+                    path: FileSystemPath::Path {
+                        path: denied_path.clone(),
+                    },
+                    access: FileSystemAccessMode::None,
+                },
+            ]),
+            vec![allowed_path.clone()],
+            Vec::new(),
+        );
+
+        assert_eq!(
+            merged_policy.get_unreadable_roots_with_cwd(cwd.as_path()),
+            vec![denied_path]
+        );
+        assert_eq!(
+            merged_policy.entries.contains(&FileSystemSandboxEntry {
+                path: FileSystemPath::Path { path: allowed_path },
+                access: FileSystemAccessMode::Read,
+            }),
+            true
+        );
+    }
 }

codex-rs/core/src/seatbelt.rs

@@ -15,6 +15,8 @@ use tokio::process::Child;
 use tracing::warn;
 use url::Url;
 
+use crate::protocol::FileSystemSandboxPolicy;
+use crate::protocol::NetworkSandboxPolicy;
 use crate::protocol::SandboxPolicy;
 use crate::seatbelt_permissions::MacOsSeatbeltProfileExtensions;
 use crate::seatbelt_permissions::build_seatbelt_extensions;
@@ -51,7 +53,7 @@ pub async fn spawn_command_under_seatbelt(
         args,
         arg0,
         cwd: command_cwd,
-        sandbox_policy,
+        network_sandbox_policy: NetworkSandboxPolicy::from(sandbox_policy),
         network,
         stdio_policy,
         env,
@@ -231,10 +233,23 @@ fn unix_socket_policy(proxy: &ProxyPolicyInputs) -> String {
         .collect()
 }
 
+#[cfg_attr(not(test), allow(dead_code))]
 fn dynamic_network_policy(
     sandbox_policy: &SandboxPolicy,
     enforce_managed_network: bool,
     proxy: &ProxyPolicyInputs,
+) -> String {
+    dynamic_network_policy_for_network(
+        NetworkSandboxPolicy::from(sandbox_policy),
+        enforce_managed_network,
+        proxy,
+    )
+}
+
+fn dynamic_network_policy_for_network(
+    network_policy: NetworkSandboxPolicy,
+    enforce_managed_network: bool,
+    proxy: &ProxyPolicyInputs,
 ) -> String {
     if !proxy.ports.is_empty() {
         let mut policy =
@@ -270,7 +285,7 @@ fn dynamic_network_policy(
         return String::new();
     }
 
-    if sandbox_policy.has_full_network_access() {
+    if network_policy.is_enabled() {
         // No proxy env is configured: retain the existing full-network behavior.
         format!(
             "(allow network-outbound)\n(allow network-inbound)\n{MACOS_SEATBELT_NETWORK_POLICY}"
@@ -287,9 +302,28 @@ pub(crate) fn create_seatbelt_command_args(
     enforce_managed_network: bool,
     network: Option<&NetworkProxy>,
 ) -> Vec<String> {
-    create_seatbelt_command_args_with_extensions(
+    create_seatbelt_command_args_for_policies(
         command,
-        sandbox_policy,
+        &FileSystemSandboxPolicy::from(sandbox_policy),
+        NetworkSandboxPolicy::from(sandbox_policy),
+        sandbox_policy_cwd,
+        enforce_managed_network,
+        network,
+    )
+}
+
+pub(crate) fn create_seatbelt_command_args_for_policies(
+    command: Vec<String>,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
+    sandbox_policy_cwd: &Path,
+    enforce_managed_network: bool,
+    network: Option<&NetworkProxy>,
+) -> Vec<String> {
+    create_seatbelt_command_args_for_policies_with_extensions(
+        command,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
         sandbox_policy_cwd,
         enforce_managed_network,
         network,
@@ -297,6 +331,64 @@ pub(crate) fn create_seatbelt_command_args(
     )
 }
 
+fn root_absolute_path() -> AbsolutePathBuf {
+    match AbsolutePathBuf::from_absolute_path(Path::new("/")) {
+        Ok(path) => path,
+        Err(err) => panic!("root path must be absolute: {err}"),
+    }
+}
+
+#[derive(Debug, Clone)]
+struct SeatbeltAccessRoot {
+    root: AbsolutePathBuf,
+    excluded_subpaths: Vec<AbsolutePathBuf>,
+}
+
+fn build_seatbelt_access_policy(
+    action: &str,
+    param_prefix: &str,
+    roots: Vec<SeatbeltAccessRoot>,
+) -> (String, Vec<(String, PathBuf)>) {
+    let mut policy_components = Vec::new();
+    let mut params = Vec::new();
+
+    for (index, access_root) in roots.into_iter().enumerate() {
+        let root =
+            normalize_path_for_sandbox(access_root.root.as_path()).unwrap_or(access_root.root);
+        let root_param = format!("{param_prefix}_{index}");
+        params.push((root_param.clone(), root.into_path_buf()));
+
+        if access_root.excluded_subpaths.is_empty() {
+            policy_components.push(format!("(subpath (param \"{root_param}\"))"));
+            continue;
+        }
+
+        let mut require_parts = vec![format!("(subpath (param \"{root_param}\"))")];
+        for (excluded_index, excluded_subpath) in
+            access_root.excluded_subpaths.into_iter().enumerate()
+        {
+            let excluded_subpath =
+                normalize_path_for_sandbox(excluded_subpath.as_path()).unwrap_or(excluded_subpath);
+            let excluded_param = format!("{param_prefix}_{index}_RO_{excluded_index}");
+            params.push((excluded_param.clone(), excluded_subpath.into_path_buf()));
+            require_parts.push(format!(
+                "(require-not (subpath (param \"{excluded_param}\")))"
+            ));
+        }
+        policy_components.push(format!("(require-all {} )", require_parts.join(" ")));
+    }
+
+    if policy_components.is_empty() {
+        (String::new(), Vec::new())
+    } else {
+        (
+            format!("(allow {action}\n{}\n)", policy_components.join(" ")),
+            params,
+        )
+    }
+}
+
+#[cfg_attr(not(test), allow(dead_code))]
 pub(crate) fn create_seatbelt_command_args_with_extensions(
     command: Vec<String>,
     sandbox_policy: &SandboxPolicy,
@@ -305,101 +397,132 @@ pub(crate) fn create_seatbelt_command_args_with_extensions(
     network: Option<&NetworkProxy>,
     extensions: Option<&MacOsSeatbeltProfileExtensions>,
 ) -> Vec<String> {
-    let (file_write_policy, file_write_dir_params) = {
-        if sandbox_policy.has_full_disk_write_access() {
-            // Allegedly, this is more permissive than `(allow file-write*)`.
-            (
-                r#"(allow file-write* (regex #"^/"))"#.to_string(),
-                Vec::new(),
-            )
-        } else {
-            let writable_roots = sandbox_policy.get_writable_roots_with_cwd(sandbox_policy_cwd);
+    create_seatbelt_command_args_for_policies_with_extensions(
+        command,
+        &FileSystemSandboxPolicy::from(sandbox_policy),
+        NetworkSandboxPolicy::from(sandbox_policy),
+        sandbox_policy_cwd,
+        enforce_managed_network,
+        network,
+        extensions,
+    )
+}
 
-            let mut writable_folder_policies: Vec<String> = Vec::new();
-            let mut file_write_params = Vec::new();
+pub(crate) fn create_seatbelt_command_args_for_policies_with_extensions(
+    command: Vec<String>,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
+    sandbox_policy_cwd: &Path,
+    enforce_managed_network: bool,
+    network: Option<&NetworkProxy>,
+    extensions: Option<&MacOsSeatbeltProfileExtensions>,
+) -> Vec<String> {
+    create_seatbelt_command_args_from_policies_inner(
+        command,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
+        sandbox_policy_cwd,
+        enforce_managed_network,
+        network,
+        extensions,
+    )
+}
 
-            for (index, wr) in writable_roots.iter().enumerate() {
-                // Canonicalize to avoid mismatches like /var vs /private/var on macOS.
-                let canonical_root = wr
-                    .root
-                    .as_path()
-                    .canonicalize()
-                    .unwrap_or_else(|_| wr.root.to_path_buf());
-                let root_param = format!("WRITABLE_ROOT_{index}");
-                file_write_params.push((root_param.clone(), canonical_root));
-
-                if wr.read_only_subpaths.is_empty() {
-                    writable_folder_policies.push(format!("(subpath (param \"{root_param}\"))"));
-                } else {
-                    // Add parameters for each read-only subpath and generate
-                    // the `(require-not ...)` clauses.
-                    let mut require_parts: Vec<String> = Vec::new();
-                    require_parts.push(format!("(subpath (param \"{root_param}\"))"));
-                    for (subpath_index, ro) in wr.read_only_subpaths.iter().enumerate() {
-                        let canonical_ro = ro
-                            .as_path()
-                            .canonicalize()
-                            .unwrap_or_else(|_| ro.to_path_buf());
-                        let ro_param = format!("WRITABLE_ROOT_{index}_RO_{subpath_index}");
-                        require_parts
-                            .push(format!("(require-not (subpath (param \"{ro_param}\")))"));
-                        file_write_params.push((ro_param, canonical_ro));
-                    }
-                    let policy_component = format!("(require-all {} )", require_parts.join(" "));
-                    writable_folder_policies.push(policy_component);
-                }
-            }
-
-            if writable_folder_policies.is_empty() {
-                ("".to_string(), Vec::new())
+fn create_seatbelt_command_args_from_policies_inner(
+    command: Vec<String>,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
+    sandbox_policy_cwd: &Path,
+    enforce_managed_network: bool,
+    network: Option<&NetworkProxy>,
+    extensions: Option<&MacOsSeatbeltProfileExtensions>,
+) -> Vec<String> {
+    let unreadable_roots =
+        file_system_sandbox_policy.get_unreadable_roots_with_cwd(sandbox_policy_cwd);
+    let (file_write_policy, file_write_dir_params) =
+        if file_system_sandbox_policy.has_full_disk_write_access() {
+            if unreadable_roots.is_empty() {
+                // Allegedly, this is more permissive than `(allow file-write*)`.
+                (
+                    r#"(allow file-write* (regex #"^/"))"#.to_string(),
+                    Vec::new(),
+                )
             } else {
-                let file_write_policy = format!(
-                    "(allow file-write*\n{}\n)",
-                    writable_folder_policies.join(" ")
-                );
-                (file_write_policy, file_write_params)
+                build_seatbelt_access_policy(
+                    "file-write*",
+                    "WRITABLE_ROOT",
+                    vec![SeatbeltAccessRoot {
+                        root: root_absolute_path(),
+                        excluded_subpaths: unreadable_roots.clone(),
+                    }],
+                )
             }
-        }
-    };
-
-    let (file_read_policy, file_read_dir_params) = if sandbox_policy.has_full_disk_read_access() {
-        (
-            "; allow read-only file operations\n(allow file-read*)".to_string(),
-            Vec::new(),
-        )
-    } else {
-        let mut readable_roots_policies: Vec<String> = Vec::new();
-        let mut file_read_params = Vec::new();
-        for (index, root) in sandbox_policy
-            .get_readable_roots_with_cwd(sandbox_policy_cwd)
-            .into_iter()
-            .enumerate()
-        {
-            // Canonicalize to avoid mismatches like /var vs /private/var on macOS.
-            let canonical_root = root
-                .as_path()
-                .canonicalize()
-                .unwrap_or_else(|_| root.to_path_buf());
-            let root_param = format!("READABLE_ROOT_{index}");
-            file_read_params.push((root_param.clone(), canonical_root));
-            readable_roots_policies.push(format!("(subpath (param \"{root_param}\"))"));
-        }
-
-        if readable_roots_policies.is_empty() {
-            ("".to_string(), Vec::new())
         } else {
-            (
-                format!(
-                    "; allow read-only file operations\n(allow file-read*\n{}\n)",
-                    readable_roots_policies.join(" ")
-                ),
-                file_read_params,
+            build_seatbelt_access_policy(
+                "file-write*",
+                "WRITABLE_ROOT",
+                file_system_sandbox_policy
+                    .get_writable_roots_with_cwd(sandbox_policy_cwd)
+                    .into_iter()
+                    .map(|root| SeatbeltAccessRoot {
+                        root: root.root,
+                        excluded_subpaths: root.read_only_subpaths,
+                    })
+                    .collect(),
             )
-        }
-    };
+        };
+
+    let (file_read_policy, file_read_dir_params) =
+        if file_system_sandbox_policy.has_full_disk_read_access() {
+            if unreadable_roots.is_empty() {
+                (
+                    "; allow read-only file operations\n(allow file-read*)".to_string(),
+                    Vec::new(),
+                )
+            } else {
+                let (policy, params) = build_seatbelt_access_policy(
+                    "file-read*",
+                    "READABLE_ROOT",
+                    vec![SeatbeltAccessRoot {
+                        root: root_absolute_path(),
+                        excluded_subpaths: unreadable_roots,
+                    }],
+                );
+                (
+                    format!("; allow read-only file operations\n{policy}"),
+                    params,
+                )
+            }
+        } else {
+            let (policy, params) = build_seatbelt_access_policy(
+                "file-read*",
+                "READABLE_ROOT",
+                file_system_sandbox_policy
+                    .get_readable_roots_with_cwd(sandbox_policy_cwd)
+                    .into_iter()
+                    .map(|root| SeatbeltAccessRoot {
+                        excluded_subpaths: unreadable_roots
+                            .iter()
+                            .filter(|path| path.as_path().starts_with(root.as_path()))
+                            .cloned()
+                            .collect(),
+                        root,
+                    })
+                    .collect(),
+            );
+            if policy.is_empty() {
+                (String::new(), params)
+            } else {
+                (
+                    format!("; allow read-only file operations\n{policy}"),
+                    params,
+                )
+            }
+        };
 
     let proxy = proxy_policy_inputs(network);
-    let network_policy = dynamic_network_policy(sandbox_policy, enforce_managed_network, &proxy);
+    let network_policy =
+        dynamic_network_policy_for_network(network_sandbox_policy, enforce_managed_network, &proxy);
     let seatbelt_extensions = extensions.map_or_else(
         || {
             // Backward-compatibility default when no extension profile is provided.
@@ -408,7 +531,7 @@ pub(crate) fn create_seatbelt_command_args_with_extensions(
         build_seatbelt_extensions,
     );
 
-    let include_platform_defaults = sandbox_policy.include_platform_defaults();
+    let include_platform_defaults = file_system_sandbox_policy.include_platform_defaults();
     let mut policy_sections = vec![
         MACOS_SEATBELT_BASE_POLICY.to_string(),
         file_read_policy,
@@ -475,12 +598,18 @@ mod tests {
     use super::ProxyPolicyInputs;
     use super::UnixDomainSocketPolicy;
     use super::create_seatbelt_command_args;
+    use super::create_seatbelt_command_args_for_policies;
     use super::create_seatbelt_command_args_with_extensions;
     use super::dynamic_network_policy;
     use super::macos_dir_params;
     use super::normalize_path_for_sandbox;
     use super::unix_socket_dir_params;
     use super::unix_socket_policy;
+    use crate::protocol::FileSystemAccessMode;
+    use crate::protocol::FileSystemPath;
+    use crate::protocol::FileSystemSandboxEntry;
+    use crate::protocol::FileSystemSandboxPolicy;
+    use crate::protocol::NetworkSandboxPolicy;
     use crate::protocol::SandboxPolicy;
     use crate::seatbelt::MACOS_PATH_TO_SEATBELT_EXECUTABLE;
     use crate::seatbelt_permissions::MacOsAutomationPermission;
@@ -508,6 +637,15 @@ mod tests {
         AbsolutePathBuf::from_absolute_path(Path::new(path)).expect("absolute path")
     }
 
+    fn seatbelt_policy_arg(args: &[String]) -> &str {
+        let policy_index = args
+            .iter()
+            .position(|arg| arg == "-p")
+            .expect("seatbelt args should include -p");
+        args.get(policy_index + 1)
+            .expect("seatbelt args should include policy text")
+    }
+
     #[test]
     fn base_policy_allows_node_cpu_sysctls() {
         assert!(
@@ -555,6 +693,96 @@ mod tests {
         );
     }
 
+    #[test]
+    fn explicit_unreadable_paths_are_excluded_from_full_disk_read_and_write_access() {
+        let unreadable = absolute_path("/tmp/codex-unreadable");
+        let file_system_policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: crate::protocol::FileSystemSpecialPath {
+                        kind: crate::protocol::FileSystemSpecialPathKind::Root,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Write,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Path { path: unreadable },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        let args = create_seatbelt_command_args_for_policies(
+            vec!["/bin/true".to_string()],
+            &file_system_policy,
+            NetworkSandboxPolicy::Restricted,
+            Path::new("/"),
+            false,
+            None,
+        );
+
+        let policy = seatbelt_policy_arg(&args);
+        assert!(
+            policy.contains("(require-not (subpath (param \"READABLE_ROOT_0_RO_0\")))"),
+            "expected read carveout in policy:\n{policy}"
+        );
+        assert!(
+            policy.contains("(require-not (subpath (param \"WRITABLE_ROOT_0_RO_0\")))"),
+            "expected write carveout in policy:\n{policy}"
+        );
+        assert!(
+            args.iter()
+                .any(|arg| arg == "-DREADABLE_ROOT_0_RO_0=/tmp/codex-unreadable"),
+            "expected read carveout parameter in args: {args:#?}"
+        );
+        assert!(
+            args.iter()
+                .any(|arg| arg == "-DWRITABLE_ROOT_0_RO_0=/tmp/codex-unreadable"),
+            "expected write carveout parameter in args: {args:#?}"
+        );
+    }
+
+    #[test]
+    fn explicit_unreadable_paths_are_excluded_from_readable_roots() {
+        let root = absolute_path("/tmp/codex-readable");
+        let unreadable = absolute_path("/tmp/codex-readable/private");
+        let file_system_policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Path { path: root },
+                access: FileSystemAccessMode::Read,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Path { path: unreadable },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        let args = create_seatbelt_command_args_for_policies(
+            vec!["/bin/true".to_string()],
+            &file_system_policy,
+            NetworkSandboxPolicy::Restricted,
+            Path::new("/"),
+            false,
+            None,
+        );
+
+        let policy = seatbelt_policy_arg(&args);
+        assert!(
+            policy.contains("(require-not (subpath (param \"READABLE_ROOT_0_RO_0\")))"),
+            "expected read carveout in policy:\n{policy}"
+        );
+        assert!(
+            args.iter()
+                .any(|arg| arg == "-DREADABLE_ROOT_0=/tmp/codex-readable"),
+            "expected readable root parameter in args: {args:#?}"
+        );
+        assert!(
+            args.iter()
+                .any(|arg| arg == "-DREADABLE_ROOT_0_RO_0=/tmp/codex-readable/private"),
+            "expected read carveout parameter in args: {args:#?}"
+        );
+    }
+
     #[test]
     fn seatbelt_args_include_macos_permission_extensions() {
         let cwd = std::env::temp_dir();
@@ -933,7 +1161,7 @@ sys.exit(0 if allowed else 13)
 ; allow read-only file operations
 (allow file-read*)
 (allow file-write*
-(require-all (subpath (param "WRITABLE_ROOT_0")) (require-not (subpath (param "WRITABLE_ROOT_0_RO_0"))) (require-not (subpath (param "WRITABLE_ROOT_0_RO_1"))) ) (subpath (param "WRITABLE_ROOT_1")) (subpath (param "WRITABLE_ROOT_2"))
+(subpath (param "WRITABLE_ROOT_0")) (require-all (subpath (param "WRITABLE_ROOT_1")) (require-not (subpath (param "WRITABLE_ROOT_1_RO_0"))) (require-not (subpath (param "WRITABLE_ROOT_1_RO_1"))) ) (subpath (param "WRITABLE_ROOT_2"))
 )
 
 ; macOS permission profile extensions
@@ -946,43 +1174,51 @@ sys.exit(0 if allowed else 13)
 "#,
         );
 
-        let mut expected_args = vec![
-            "-p".to_string(),
-            expected_policy,
+        assert_eq!(seatbelt_policy_arg(&args), expected_policy);
+
+        let expected_definitions = [
             format!(
                 "-DWRITABLE_ROOT_0={}",
-                vulnerable_root_canonical.to_string_lossy()
-            ),
-            format!(
-                "-DWRITABLE_ROOT_0_RO_0={}",
-                dot_git_canonical.to_string_lossy()
-            ),
-            format!(
-                "-DWRITABLE_ROOT_0_RO_1={}",
-                dot_codex_canonical.to_string_lossy()
-            ),
-            format!(
-                "-DWRITABLE_ROOT_1={}",
-                empty_root_canonical.to_string_lossy()
-            ),
-            format!(
-                "-DWRITABLE_ROOT_2={}",
                 cwd.canonicalize()
                     .expect("canonicalize cwd")
                     .to_string_lossy()
             ),
+            format!(
+                "-DWRITABLE_ROOT_1={}",
+                vulnerable_root_canonical.to_string_lossy()
+            ),
+            format!(
+                "-DWRITABLE_ROOT_1_RO_0={}",
+                dot_git_canonical.to_string_lossy()
+            ),
+            format!(
+                "-DWRITABLE_ROOT_1_RO_1={}",
+                dot_codex_canonical.to_string_lossy()
+            ),
+            format!(
+                "-DWRITABLE_ROOT_2={}",
+                empty_root_canonical.to_string_lossy()
+            ),
         ];
+        for expected_definition in expected_definitions {
+            assert!(
+                args.contains(&expected_definition),
+                "expected definition arg `{expected_definition}` in {args:#?}"
+            );
+        }
+        for (key, value) in macos_dir_params() {
+            let expected_definition = format!("-D{key}={}", value.to_string_lossy());
+            assert!(
+                args.contains(&expected_definition),
+                "expected definition arg `{expected_definition}` in {args:#?}"
+            );
+        }
 
-        expected_args.extend(
-            macos_dir_params()
-                .into_iter()
-                .map(|(key, value)| format!("-D{key}={value}", value = value.to_string_lossy())),
-        );
-
-        expected_args.push("--".to_string());
-        expected_args.extend(shell_command);
-
-        assert_eq!(expected_args, args);
+        let command_index = args
+            .iter()
+            .position(|arg| arg == "--")
+            .expect("seatbelt args should include command separator");
+        assert_eq!(args[command_index + 1..], shell_command);
 
         // Verify that .codex/config.toml cannot be modified under the generated
         // Seatbelt policy.

codex-rs/core/src/skills/permissions.rs

@@ -12,6 +12,10 @@ use codex_protocol::models::MacOsSeatbeltProfileExtensions;
 #[cfg(any(unix, test))]
 use codex_protocol::models::PermissionProfile;
 #[cfg(any(unix, test))]
+use codex_protocol::protocol::FileSystemSandboxPolicy;
+#[cfg(any(unix, test))]
+use codex_protocol::protocol::NetworkSandboxPolicy;
+#[cfg(any(unix, test))]
 use codex_utils_absolute_path::AbsolutePathBuf;
 #[cfg(any(unix, test))]
 use dunce::canonicalize as canonicalize_path;
@@ -89,10 +93,14 @@ pub(crate) fn compile_permission_profile(
     let macos_permissions = macos.unwrap_or_default();
     let macos_seatbelt_profile_extensions =
         build_macos_seatbelt_profile_extensions(&macos_permissions);
+    let file_system_sandbox_policy = FileSystemSandboxPolicy::from(&sandbox_policy);
+    let network_sandbox_policy = NetworkSandboxPolicy::from(&sandbox_policy);
 
     Some(Permissions {
         approval_policy: Constrained::allow_any(AskForApproval::Never),
         sandbox_policy: Constrained::allow_any(sandbox_policy),
+        file_system_sandbox_policy,
+        network_sandbox_policy,
         network: None,
         allow_login_shell: true,
         shell_environment_policy: ShellEnvironmentPolicy::default(),
@@ -234,6 +242,8 @@ mod tests {
     use codex_protocol::models::MacOsPreferencesValue;
     use codex_protocol::models::NetworkPermissions;
     use codex_protocol::models::PermissionProfile;
+    use codex_protocol::protocol::FileSystemSandboxPolicy;
+    use codex_protocol::protocol::NetworkSandboxPolicy;
     use codex_utils_absolute_path::AbsolutePathBuf;
     use pretty_assertions::assert_eq;
     use std::fs;
@@ -243,6 +253,25 @@ mod tests {
         AbsolutePathBuf::try_from(path).expect("absolute path")
     }
 
+    fn expected_permissions(sandbox_policy: SandboxPolicy) -> Permissions {
+        Permissions {
+            approval_policy: Constrained::allow_any(AskForApproval::Never),
+            sandbox_policy: Constrained::allow_any(sandbox_policy.clone()),
+            file_system_sandbox_policy: FileSystemSandboxPolicy::from(&sandbox_policy),
+            network_sandbox_policy: NetworkSandboxPolicy::from(&sandbox_policy),
+            network: None,
+            allow_login_shell: true,
+            shell_environment_policy: ShellEnvironmentPolicy::default(),
+            windows_sandbox_mode: None,
+            #[cfg(target_os = "macos")]
+            macos_seatbelt_profile_extensions: Some(
+                crate::seatbelt_permissions::MacOsSeatbeltProfileExtensions::default(),
+            ),
+            #[cfg(not(target_os = "macos"))]
+            macos_seatbelt_profile_extensions: None,
+        }
+    }
+
     #[test]
     fn compile_permission_profile_normalizes_paths() {
         let tempdir = tempfile::tempdir().expect("tempdir");
@@ -269,37 +298,24 @@ mod tests {
 
         assert_eq!(
             profile,
-            Permissions {
-                approval_policy: Constrained::allow_any(AskForApproval::Never),
-                sandbox_policy: Constrained::allow_any(SandboxPolicy::WorkspaceWrite {
-                    writable_roots: vec![
-                        AbsolutePathBuf::try_from(skill_dir.join("output"))
-                            .expect("absolute output path")
+            expected_permissions(SandboxPolicy::WorkspaceWrite {
+                writable_roots: vec![
+                    AbsolutePathBuf::try_from(skill_dir.join("output"))
+                        .expect("absolute output path")
+                ],
+                read_only_access: ReadOnlyAccess::Restricted {
+                    include_platform_defaults: true,
+                    readable_roots: vec![
+                        AbsolutePathBuf::try_from(
+                            dunce::canonicalize(&read_dir).unwrap_or(read_dir)
+                        )
+                        .expect("absolute read path")
                     ],
-                    read_only_access: ReadOnlyAccess::Restricted {
-                        include_platform_defaults: true,
-                        readable_roots: vec![
-                            AbsolutePathBuf::try_from(
-                                dunce::canonicalize(&read_dir).unwrap_or(read_dir)
-                            )
-                            .expect("absolute read path")
-                        ],
-                    },
-                    network_access: true,
-                    exclude_tmpdir_env_var: false,
-                    exclude_slash_tmp: false,
-                }),
-                network: None,
-                allow_login_shell: true,
-                shell_environment_policy: ShellEnvironmentPolicy::default(),
-                windows_sandbox_mode: None,
-                #[cfg(target_os = "macos")]
-                macos_seatbelt_profile_extensions: Some(
-                    crate::seatbelt_permissions::MacOsSeatbeltProfileExtensions::default(),
-                ),
-                #[cfg(not(target_os = "macos"))]
-                macos_seatbelt_profile_extensions: None,
-            }
+                },
+                network_access: true,
+                exclude_tmpdir_env_var: false,
+                exclude_slash_tmp: false,
+            })
         );
     }
 
@@ -330,23 +346,10 @@ mod tests {
 
         assert_eq!(
             profile,
-            Permissions {
-                approval_policy: Constrained::allow_any(AskForApproval::Never),
-                sandbox_policy: Constrained::allow_any(SandboxPolicy::ReadOnly {
-                    access: ReadOnlyAccess::FullAccess,
-                    network_access: true,
-                }),
-                network: None,
-                allow_login_shell: true,
-                shell_environment_policy: ShellEnvironmentPolicy::default(),
-                windows_sandbox_mode: None,
-                #[cfg(target_os = "macos")]
-                macos_seatbelt_profile_extensions: Some(
-                    crate::seatbelt_permissions::MacOsSeatbeltProfileExtensions::default(),
-                ),
-                #[cfg(not(target_os = "macos"))]
-                macos_seatbelt_profile_extensions: None,
-            }
+            expected_permissions(SandboxPolicy::ReadOnly {
+                access: ReadOnlyAccess::FullAccess,
+                network_access: true,
+            })
         );
     }
 
@@ -371,31 +374,18 @@ mod tests {
 
         assert_eq!(
             profile,
-            Permissions {
-                approval_policy: Constrained::allow_any(AskForApproval::Never),
-                sandbox_policy: Constrained::allow_any(SandboxPolicy::ReadOnly {
-                    access: ReadOnlyAccess::Restricted {
-                        include_platform_defaults: true,
-                        readable_roots: vec![
-                            AbsolutePathBuf::try_from(
-                                dunce::canonicalize(&read_dir).unwrap_or(read_dir)
-                            )
-                            .expect("absolute read path")
-                        ],
-                    },
-                    network_access: true,
-                }),
-                network: None,
-                allow_login_shell: true,
-                shell_environment_policy: ShellEnvironmentPolicy::default(),
-                windows_sandbox_mode: None,
-                #[cfg(target_os = "macos")]
-                macos_seatbelt_profile_extensions: Some(
-                    crate::seatbelt_permissions::MacOsSeatbeltProfileExtensions::default(),
-                ),
-                #[cfg(not(target_os = "macos"))]
-                macos_seatbelt_profile_extensions: None,
-            }
+            expected_permissions(SandboxPolicy::ReadOnly {
+                access: ReadOnlyAccess::Restricted {
+                    include_platform_defaults: true,
+                    readable_roots: vec![
+                        AbsolutePathBuf::try_from(
+                            dunce::canonicalize(&read_dir).unwrap_or(read_dir)
+                        )
+                        .expect("absolute read path")
+                    ],
+                },
+                network_access: true,
+            })
         );
     }
 

codex-rs/core/src/spawn.rs

@@ -6,13 +6,13 @@ use tokio::process::Child;
 use tokio::process::Command;
 use tracing::trace;
 
-use crate::protocol::SandboxPolicy;
+use crate::protocol::NetworkSandboxPolicy;
 
 /// Experimental environment variable that will be set to some non-empty value
 /// if both of the following are true:
 ///
 /// 1. The process was spawned by Codex as part of a shell tool call.
-/// 2. SandboxPolicy.has_full_network_access() was false for the tool call.
+/// 2. NetworkSandboxPolicy is restricted for the tool call.
 ///
 /// We may try to have just one environment variable for all sandboxing
 /// attributes, so this may change in the future.
@@ -33,15 +33,15 @@ pub enum StdioPolicy {
 /// ensuring the args and environment variables used to create the `Command`
 /// (and `Child`) honor the configuration.
 ///
-/// For now, we take `SandboxPolicy` as a parameter to spawn_child() because
-/// we need to determine whether to set the
+/// For now, we take `NetworkSandboxPolicy` as a parameter to spawn_child()
+/// because we need to determine whether to set the
 /// `CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR` environment variable.
 pub(crate) struct SpawnChildRequest<'a> {
     pub program: PathBuf,
     pub args: Vec<String>,
     pub arg0: Option<&'a str>,
     pub cwd: PathBuf,
-    pub sandbox_policy: &'a SandboxPolicy,
+    pub network_sandbox_policy: NetworkSandboxPolicy,
     pub network: Option<&'a NetworkProxy>,
     pub stdio_policy: StdioPolicy,
     pub env: HashMap<String, String>,
@@ -53,14 +53,14 @@ pub(crate) async fn spawn_child_async(request: SpawnChildRequest<'_>) -> std::io
         args,
         arg0,
         cwd,
-        sandbox_policy,
+        network_sandbox_policy,
         network,
         stdio_policy,
         mut env,
     } = request;
 
     trace!(
-        "spawn_child_async: {program:?} {args:?} {arg0:?} {cwd:?} {sandbox_policy:?} {stdio_policy:?} {env:?}"
+        "spawn_child_async: {program:?} {args:?} {arg0:?} {cwd:?} {network_sandbox_policy:?} {stdio_policy:?} {env:?}"
     );
 
     let mut cmd = Command::new(&program);
@@ -74,7 +74,7 @@ pub(crate) async fn spawn_child_async(request: SpawnChildRequest<'_>) -> std::io
     cmd.env_clear();
     cmd.envs(env);
 
-    if !sandbox_policy.has_full_network_access() {
+    if !network_sandbox_policy.is_enabled() {
         cmd.env(CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR, "1");
     }
 

codex-rs/core/src/tasks/user_shell.rs

@@ -22,6 +22,8 @@ use crate::protocol::ExecCommandBeginEvent;
 use crate::protocol::ExecCommandEndEvent;
 use crate::protocol::ExecCommandSource;
 use crate::protocol::ExecCommandStatus;
+use crate::protocol::FileSystemSandboxPolicy;
+use crate::protocol::NetworkSandboxPolicy;
 use crate::protocol::SandboxPolicy;
 use crate::protocol::TurnStartedEvent;
 use crate::sandboxing::ExecRequest;
@@ -163,6 +165,8 @@ pub(crate) async fn execute_user_shell_command(
         windows_sandbox_level: turn_context.windows_sandbox_level,
         sandbox_permissions: SandboxPermissions::UseDefault,
         sandbox_policy: sandbox_policy.clone(),
+        file_system_sandbox_policy: FileSystemSandboxPolicy::from(&sandbox_policy),
+        network_sandbox_policy: NetworkSandboxPolicy::from(&sandbox_policy),
         justification: None,
         arg0: None,
     };
@@ -173,7 +177,7 @@ pub(crate) async fn execute_user_shell_command(
         tx_event: session.get_tx_event(),
     });
 
-    let exec_result = execute_exec_env(exec_env, &sandbox_policy, stdout_stream)
+    let exec_result = execute_exec_env(exec_env, stdout_stream)
         .or_cancel(&cancellation_token)
         .await;
 

codex-rs/core/src/tools/handlers/artifact_path_access.rs

@@ -0,0 +1,123 @@
+use codex_protocol::protocol::FileSystemSandboxPolicy;
+use std::path::Path;
+
+pub(super) fn path_is_readable(
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    cwd: &Path,
+    path: &Path,
+) -> bool {
+    if file_system_sandbox_policy
+        .get_unreadable_roots_with_cwd(cwd)
+        .iter()
+        .any(|root| path.starts_with(root.as_path()))
+    {
+        return false;
+    }
+
+    if file_system_sandbox_policy.has_full_disk_read_access() {
+        return true;
+    }
+
+    file_system_sandbox_policy
+        .get_readable_roots_with_cwd(cwd)
+        .iter()
+        .any(|root| path.starts_with(root.as_path()))
+}
+
+pub(super) fn path_is_writable(
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    cwd: &Path,
+    path: &Path,
+) -> bool {
+    if file_system_sandbox_policy
+        .get_unreadable_roots_with_cwd(cwd)
+        .iter()
+        .any(|root| path.starts_with(root.as_path()))
+    {
+        return false;
+    }
+
+    if file_system_sandbox_policy.has_full_disk_write_access() {
+        return true;
+    }
+
+    file_system_sandbox_policy
+        .get_writable_roots_with_cwd(cwd)
+        .iter()
+        .any(|root| root.is_path_writable(path))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::path_is_readable;
+    use super::path_is_writable;
+    use codex_protocol::protocol::FileSystemAccessMode;
+    use codex_protocol::protocol::FileSystemPath;
+    use codex_protocol::protocol::FileSystemSandboxEntry;
+    use codex_protocol::protocol::FileSystemSandboxPolicy;
+    use codex_protocol::protocol::FileSystemSpecialPath;
+    use codex_protocol::protocol::FileSystemSpecialPathKind;
+    use pretty_assertions::assert_eq;
+    use std::path::PathBuf;
+    use tempfile::TempDir;
+
+    #[test]
+    fn unreadable_subpaths_override_root_read_access() {
+        let cwd = TempDir::new().expect("tempdir");
+        let readable = cwd.path().join("readable.txt");
+        let blocked = cwd.path().join("blocked.txt");
+        let policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::Root,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Read,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                        subpath: Some(PathBuf::from("blocked.txt")),
+                    },
+                },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        assert_eq!(path_is_readable(&policy, cwd.path(), &readable), true);
+        assert_eq!(path_is_readable(&policy, cwd.path(), &blocked), false);
+    }
+
+    #[test]
+    fn unreadable_subpaths_override_writable_roots() {
+        let cwd = TempDir::new().expect("tempdir");
+        let allowed = cwd.path().join("allowed.txt");
+        let blocked = cwd.path().join("blocked.txt");
+        let policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Write,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                        subpath: Some(PathBuf::from("blocked.txt")),
+                    },
+                },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        assert_eq!(path_is_writable(&policy, cwd.path(), &allowed), true);
+        assert_eq!(path_is_writable(&policy, cwd.path(), &blocked), false);
+    }
+}

codex-rs/core/src/tools/handlers/mod.rs

@@ -1,5 +1,6 @@
 pub(crate) mod agent_jobs;
 pub mod apply_patch;
+mod artifact_path_access;
 mod dynamic;
 mod grep_files;
 mod js_repl;

codex-rs/core/src/tools/handlers/presentation_artifact.rs

@@ -19,6 +19,7 @@ use crate::path_utils::resolve_symlink_write_paths;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolOutput;
 use crate::tools::context::ToolPayload;
+use crate::tools::handlers::artifact_path_access;
 use crate::tools::handlers::parse_arguments;
 use crate::tools::registry::ToolHandler;
 use crate::tools::registry::ToolKind;
@@ -111,8 +112,16 @@ async fn authorize_path_access(
         PathAccessKind::Write => effective_write_path(&access.path),
     };
     let allowed = match access.kind {
-        PathAccessKind::Read => path_is_readable(turn, &effective_path),
-        PathAccessKind::Write => path_is_writable(turn, &effective_path),
+        PathAccessKind::Read => artifact_path_access::path_is_readable(
+            &turn.file_system_sandbox_policy,
+            &turn.cwd,
+            &effective_path,
+        ),
+        PathAccessKind::Write => artifact_path_access::path_is_writable(
+            &turn.file_system_sandbox_policy,
+            &turn.cwd,
+            &effective_path,
+        ),
     };
     if allowed {
         return Ok(());
@@ -188,28 +197,6 @@ async fn authorize_path_access(
     )))
 }
 
-fn path_is_readable(turn: &TurnContext, path: &Path) -> bool {
-    if turn.sandbox_policy.has_full_disk_read_access() {
-        return true;
-    }
-
-    turn.sandbox_policy
-        .get_readable_roots_with_cwd(&turn.cwd)
-        .iter()
-        .any(|root| path.starts_with(root.as_path()))
-}
-
-fn path_is_writable(turn: &TurnContext, path: &Path) -> bool {
-    if turn.sandbox_policy.has_full_disk_write_access() {
-        return true;
-    }
-
-    turn.sandbox_policy
-        .get_writable_roots_with_cwd(&turn.cwd)
-        .iter()
-        .any(|root| root.is_path_writable(path))
-}
-
 fn effective_read_path(path: &Path) -> PathBuf {
     normalize_for_path_comparison(path).unwrap_or_else(|_| normalize_without_fs(path))
 }

codex-rs/core/src/tools/handlers/spreadsheet_artifact.rs

@@ -20,6 +20,7 @@ use crate::path_utils::resolve_symlink_write_paths;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolOutput;
 use crate::tools::context::ToolPayload;
+use crate::tools::handlers::artifact_path_access;
 use crate::tools::handlers::parse_arguments;
 use crate::tools::registry::ToolHandler;
 use crate::tools::registry::ToolKind;
@@ -100,8 +101,16 @@ async fn authorize_path_access(
         PathAccessKind::Write => effective_write_path(&access.path),
     };
     let allowed = match access.kind {
-        PathAccessKind::Read => path_is_readable(turn, &effective_path),
-        PathAccessKind::Write => path_is_writable(turn, &effective_path),
+        PathAccessKind::Read => artifact_path_access::path_is_readable(
+            &turn.file_system_sandbox_policy,
+            &turn.cwd,
+            &effective_path,
+        ),
+        PathAccessKind::Write => artifact_path_access::path_is_writable(
+            &turn.file_system_sandbox_policy,
+            &turn.cwd,
+            &effective_path,
+        ),
     };
     if allowed {
         return Ok(());
@@ -173,28 +182,6 @@ async fn authorize_path_access(
     )))
 }
 
-fn path_is_readable(turn: &TurnContext, path: &Path) -> bool {
-    if turn.sandbox_policy.has_full_disk_read_access() {
-        return true;
-    }
-
-    turn.sandbox_policy
-        .get_readable_roots_with_cwd(&turn.cwd)
-        .iter()
-        .any(|root| path.starts_with(root.as_path()))
-}
-
-fn path_is_writable(turn: &TurnContext, path: &Path) -> bool {
-    if turn.sandbox_policy.has_full_disk_write_access() {
-        return true;
-    }
-
-    turn.sandbox_policy
-        .get_writable_roots_with_cwd(&turn.cwd)
-        .iter()
-        .any(|root| root.is_path_writable(path))
-}
-
 fn effective_read_path(path: &Path) -> PathBuf {
     normalize_for_path_comparison(path).unwrap_or_else(|_| normalize_without_fs(path))
 }

codex-rs/core/src/tools/js_repl/mod.rs

@@ -852,7 +852,8 @@ impl JsReplManager {
             .network
             .is_some();
         let sandbox_type = sandbox.select_initial(
-            &turn.sandbox_policy,
+            &turn.file_system_sandbox_policy,
+            turn.network_sandbox_policy,
             SandboxablePreference::Auto,
             turn.windows_sandbox_level,
             has_managed_network_requirements,
@@ -861,6 +862,8 @@ impl JsReplManager {
             .transform(crate::sandboxing::SandboxTransformRequest {
                 spec,
                 policy: &turn.sandbox_policy,
+                file_system_policy: &turn.file_system_sandbox_policy,
+                network_policy: turn.network_sandbox_policy,
                 sandbox: sandbox_type,
                 enforce_managed_network: has_managed_network_requirements,
                 network: None,
@@ -1727,6 +1730,16 @@ mod tests {
     use std::path::Path;
     use tempfile::tempdir;
 
+    fn set_danger_full_access(turn: &mut crate::codex::TurnContext) {
+        turn.sandbox_policy
+            .set(SandboxPolicy::DangerFullAccess)
+            .expect("test setup should allow updating sandbox policy");
+        turn.file_system_sandbox_policy =
+            crate::protocol::FileSystemSandboxPolicy::from(turn.sandbox_policy.get());
+        turn.network_sandbox_policy =
+            crate::protocol::NetworkSandboxPolicy::from(turn.sandbox_policy.get());
+    }
+
     #[test]
     fn node_version_parses_v_prefix_and_suffix() {
         let version = NodeVersion::parse("v25.1.0-nightly.2024").unwrap();
@@ -2405,9 +2418,7 @@ mod tests {
         turn.approval_policy
             .set(AskForApproval::Never)
             .expect("test setup should allow updating approval policy");
-        turn.sandbox_policy
-            .set(SandboxPolicy::DangerFullAccess)
-            .expect("test setup should allow updating sandbox policy");
+        set_danger_full_access(&mut turn);
 
         let session = Arc::new(session);
         let turn = Arc::new(turn);
@@ -2459,9 +2470,7 @@ console.log("cell-complete");
         turn.approval_policy
             .set(AskForApproval::Never)
             .expect("test setup should allow updating approval policy");
-        turn.sandbox_policy
-            .set(SandboxPolicy::DangerFullAccess)
-            .expect("test setup should allow updating sandbox policy");
+        set_danger_full_access(&mut turn);
 
         let session = Arc::new(session);
         let turn = Arc::new(turn);
@@ -2517,9 +2526,7 @@ console.log(out.type);
         turn.approval_policy
             .set(AskForApproval::Never)
             .expect("test setup should allow updating approval policy");
-        turn.sandbox_policy
-            .set(SandboxPolicy::DangerFullAccess)
-            .expect("test setup should allow updating sandbox policy");
+        set_danger_full_access(&mut turn);
 
         let session = Arc::new(session);
         let turn = Arc::new(turn);

codex-rs/core/src/tools/orchestrator.rs

@@ -169,7 +169,8 @@ impl ToolOrchestrator {
         let initial_sandbox = match tool.sandbox_mode_for_first_attempt(req) {
             SandboxOverride::BypassSandboxFirstAttempt => crate::exec::SandboxType::None,
             SandboxOverride::NoOverride => self.sandbox.select_initial(
-                &turn_ctx.sandbox_policy,
+                &turn_ctx.file_system_sandbox_policy,
+                turn_ctx.network_sandbox_policy,
                 tool.sandbox_preference(),
                 turn_ctx.windows_sandbox_level,
                 has_managed_network_requirements,
@@ -182,6 +183,8 @@ impl ToolOrchestrator {
         let initial_attempt = SandboxAttempt {
             sandbox: initial_sandbox,
             policy: &turn_ctx.sandbox_policy,
+            file_system_policy: &turn_ctx.file_system_sandbox_policy,
+            network_policy: turn_ctx.network_sandbox_policy,
             enforce_managed_network: has_managed_network_requirements,
             manager: &self.sandbox,
             sandbox_cwd: &turn_ctx.cwd,
@@ -296,6 +299,8 @@ impl ToolOrchestrator {
                 let escalated_attempt = SandboxAttempt {
                     sandbox: crate::exec::SandboxType::None,
                     policy: &turn_ctx.sandbox_policy,
+                    file_system_policy: &turn_ctx.file_system_sandbox_policy,
+                    network_policy: turn_ctx.network_sandbox_policy,
                     enforce_managed_network: has_managed_network_requirements,
                     manager: &self.sandbox,
                     sandbox_cwd: &turn_ctx.cwd,

codex-rs/core/src/tools/runtimes/shell/unix_escalation.rs

@@ -25,7 +25,9 @@ use codex_protocol::config_types::WindowsSandboxLevel;
 use codex_protocol::models::MacOsSeatbeltProfileExtensions;
 use codex_protocol::models::PermissionProfile;
 use codex_protocol::protocol::AskForApproval;
+use codex_protocol::protocol::FileSystemSandboxPolicy;
 use codex_protocol::protocol::NetworkPolicyRuleAction;
+use codex_protocol::protocol::NetworkSandboxPolicy;
 use codex_protocol::protocol::RejectConfig;
 use codex_protocol::protocol::ReviewDecision;
 use codex_protocol::protocol::SandboxPolicy;
@@ -92,6 +94,8 @@ pub(super) async fn try_run_zsh_fork(
         windows_sandbox_level,
         sandbox_permissions,
         sandbox_policy,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
         justification,
         arg0,
     } = sandbox_exec_request;
@@ -107,6 +111,8 @@ pub(super) async fn try_run_zsh_fork(
         command,
         cwd: sandbox_cwd,
         sandbox_policy,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
         sandbox,
         env: sandbox_env,
         network: sandbox_network,
@@ -629,6 +635,8 @@ struct CoreShellCommandExecutor {
     command: Vec<String>,
     cwd: PathBuf,
     sandbox_policy: SandboxPolicy,
+    file_system_sandbox_policy: FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     sandbox: SandboxType,
     env: HashMap<String, String>,
     network: Option<codex_network_proxy::NetworkProxy>,
@@ -669,6 +677,8 @@ impl ShellCommandExecutor for CoreShellCommandExecutor {
                 windows_sandbox_level: self.windows_sandbox_level,
                 sandbox_permissions: self.sandbox_permissions,
                 sandbox_policy: self.sandbox_policy.clone(),
+                file_system_sandbox_policy: self.file_system_sandbox_policy.clone(),
+                network_sandbox_policy: self.network_sandbox_policy,
                 justification: self.justification.clone(),
                 arg0: self.arg0.clone(),
             },
@@ -713,6 +723,8 @@ impl ShellCommandExecutor for CoreShellCommandExecutor {
                 workdir,
                 env,
                 &self.sandbox_policy,
+                &self.file_system_sandbox_policy,
+                self.network_sandbox_policy,
                 None,
                 self.macos_seatbelt_profile_extensions.as_ref(),
             )?,
@@ -723,15 +735,23 @@ impl ShellCommandExecutor for CoreShellCommandExecutor {
                 workdir,
                 env,
                 &self.sandbox_policy,
+                &self.file_system_sandbox_policy,
+                self.network_sandbox_policy,
                 Some(permission_profile),
                 None,
             )?,
             EscalationExecution::Permissions(EscalationPermissions::Permissions(permissions)) => {
+                let file_system_sandbox_policy =
+                    FileSystemSandboxPolicy::from(&permissions.sandbox_policy);
+                let network_sandbox_policy =
+                    NetworkSandboxPolicy::from(&permissions.sandbox_policy);
                 self.prepare_sandboxed_exec(
                     command,
                     workdir,
                     env,
                     &permissions.sandbox_policy,
+                    &file_system_sandbox_policy,
+                    network_sandbox_policy,
                     None,
                     permissions.macos_seatbelt_profile_extensions.as_ref(),
                 )?
@@ -743,12 +763,15 @@ impl ShellCommandExecutor for CoreShellCommandExecutor {
 }
 
 impl CoreShellCommandExecutor {
+    #[allow(clippy::too_many_arguments)]
     fn prepare_sandboxed_exec(
         &self,
         command: Vec<String>,
         workdir: &AbsolutePathBuf,
         env: HashMap<String, String>,
         sandbox_policy: &SandboxPolicy,
+        file_system_sandbox_policy: &FileSystemSandboxPolicy,
+        network_sandbox_policy: NetworkSandboxPolicy,
         additional_permissions: Option<PermissionProfile>,
         #[cfg(target_os = "macos")] macos_seatbelt_profile_extensions: Option<
             &MacOsSeatbeltProfileExtensions,
@@ -762,7 +785,8 @@ impl CoreShellCommandExecutor {
             .ok_or_else(|| anyhow::anyhow!("prepared command must not be empty"))?;
         let sandbox_manager = crate::sandboxing::SandboxManager::new();
         let sandbox = sandbox_manager.select_initial(
-            sandbox_policy,
+            file_system_sandbox_policy,
+            network_sandbox_policy,
             SandboxablePreference::Auto,
             self.windows_sandbox_level,
             self.network.is_some(),
@@ -784,6 +808,8 @@ impl CoreShellCommandExecutor {
                     justification: self.justification.clone(),
                 },
                 policy: sandbox_policy,
+                file_system_policy: file_system_sandbox_policy,
+                network_policy: network_sandbox_policy,
                 sandbox,
                 enforce_managed_network: self.network.is_some(),
                 network: self.network.as_ref(),

codex-rs/core/src/tools/runtimes/shell/unix_escalation_tests.rs

@@ -30,6 +30,10 @@ use codex_protocol::models::FileSystemPermissions;
 use codex_protocol::models::MacOsPreferencesPermission;
 use codex_protocol::models::MacOsSeatbeltProfileExtensions;
 use codex_protocol::models::PermissionProfile;
+#[cfg(target_os = "macos")]
+use codex_protocol::protocol::FileSystemSandboxPolicy;
+#[cfg(target_os = "macos")]
+use codex_protocol::protocol::NetworkSandboxPolicy;
 use codex_shell_escalation::EscalationExecution;
 use codex_shell_escalation::EscalationPermissions;
 use codex_shell_escalation::ExecResult;
@@ -418,6 +422,10 @@ async fn prepare_escalated_exec_turn_default_preserves_macos_seatbelt_extensions
         network: None,
         sandbox: SandboxType::None,
         sandbox_policy: SandboxPolicy::new_read_only_policy(),
+        file_system_sandbox_policy: FileSystemSandboxPolicy::from(
+            &SandboxPolicy::new_read_only_policy(),
+        ),
+        network_sandbox_policy: NetworkSandboxPolicy::Restricted,
         windows_sandbox_level: WindowsSandboxLevel::Disabled,
         sandbox_permissions: SandboxPermissions::UseDefault,
         justification: None,
@@ -468,6 +476,8 @@ async fn prepare_escalated_exec_permissions_preserve_macos_seatbelt_extensions()
         network: None,
         sandbox: SandboxType::None,
         sandbox_policy: SandboxPolicy::DangerFullAccess,
+        file_system_sandbox_policy: FileSystemSandboxPolicy::from(&SandboxPolicy::DangerFullAccess),
+        network_sandbox_policy: NetworkSandboxPolicy::Enabled,
         windows_sandbox_level: WindowsSandboxLevel::Disabled,
         sandbox_permissions: SandboxPermissions::UseDefault,
         justification: None,
@@ -481,6 +491,10 @@ async fn prepare_escalated_exec_permissions_preserve_macos_seatbelt_extensions()
     let permissions = Permissions {
         approval_policy: Constrained::allow_any(AskForApproval::Never),
         sandbox_policy: Constrained::allow_any(SandboxPolicy::new_read_only_policy()),
+        file_system_sandbox_policy: FileSystemSandboxPolicy::from(
+            &SandboxPolicy::new_read_only_policy(),
+        ),
+        network_sandbox_policy: NetworkSandboxPolicy::Restricted,
         network: None,
         allow_login_shell: true,
         shell_environment_policy: ShellEnvironmentPolicy::default(),

codex-rs/core/src/tools/sandboxing.rs

@@ -7,6 +7,8 @@
 use crate::codex::Session;
 use crate::codex::TurnContext;
 use crate::error::CodexErr;
+use crate::protocol::FileSystemSandboxPolicy;
+use crate::protocol::NetworkSandboxPolicy;
 use crate::protocol::SandboxPolicy;
 use crate::sandboxing::CommandSpec;
 use crate::sandboxing::SandboxManager;
@@ -318,6 +320,8 @@ pub(crate) trait ToolRuntime<Req, Out>: Approvable<Req> + Sandboxable {
 pub(crate) struct SandboxAttempt<'a> {
     pub sandbox: crate::exec::SandboxType,
     pub policy: &'a crate::protocol::SandboxPolicy,
+    pub file_system_policy: &'a FileSystemSandboxPolicy,
+    pub network_policy: NetworkSandboxPolicy,
     pub enforce_managed_network: bool,
     pub(crate) manager: &'a SandboxManager,
     pub(crate) sandbox_cwd: &'a Path,
@@ -336,6 +340,8 @@ impl<'a> SandboxAttempt<'a> {
             .transform(crate::sandboxing::SandboxTransformRequest {
                 spec,
                 policy: self.policy,
+                file_system_policy: self.file_system_policy,
+                network_policy: self.network_policy,
                 sandbox: self.sandbox,
                 enforce_managed_network: self.enforce_managed_network,
                 network,

codex-rs/core/src/unified_exec/mod.rs

@@ -201,6 +201,10 @@ mod tests {
         turn.sandbox_policy
             .set(SandboxPolicy::DangerFullAccess)
             .expect("test setup should allow updating sandbox policy");
+        turn.file_system_sandbox_policy =
+            crate::protocol::FileSystemSandboxPolicy::from(turn.sandbox_policy.get());
+        turn.network_sandbox_policy =
+            crate::protocol::NetworkSandboxPolicy::from(turn.sandbox_policy.get());
         (Arc::new(session), Arc::new(turn))
     }
 

codex-rs/core/tests/suite/approvals.rs

@@ -2234,7 +2234,7 @@ async fn denying_network_policy_amendment_persists_policy_and_skips_future_netwo
     let home = Arc::new(TempDir::new()?);
     fs::write(
         home.path().join("config.toml"),
-        r#"[permissions.network]
+        r#"[network]
 enabled = true
 mode = "limited"
 allow_local_binding = true

codex-rs/core/tests/suite/exec.rs

@@ -10,6 +10,8 @@ use codex_core::exec::process_exec_tool_call;
 use codex_core::sandboxing::SandboxPermissions;
 use codex_core::spawn::CODEX_SANDBOX_ENV_VAR;
 use codex_protocol::config_types::WindowsSandboxLevel;
+use codex_protocol::protocol::FileSystemSandboxPolicy;
+use codex_protocol::protocol::NetworkSandboxPolicy;
 use codex_protocol::protocol::SandboxPolicy;
 use tempfile::TempDir;
 
@@ -45,7 +47,17 @@ async fn run_test_cmd(tmp: TempDir, cmd: Vec<&str>) -> Result<ExecToolCallOutput
 
     let policy = SandboxPolicy::new_read_only_policy();
 
-    process_exec_tool_call(params, &policy, tmp.path(), &None, false, None).await
+    process_exec_tool_call(
+        params,
+        &policy,
+        &FileSystemSandboxPolicy::from(&policy),
+        NetworkSandboxPolicy::from(&policy),
+        tmp.path(),
+        &None,
+        false,
+        None,
+    )
+    .await
 }
 
 /// Command succeeds with exit code 0 normally

codex-rs/core/tests/suite/user_shell_cmd.rs

@@ -5,6 +5,7 @@ use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::ExecCommandEndEvent;
 use codex_protocol::protocol::ExecCommandSource;
 use codex_protocol::protocol::ExecOutputStream;
+use codex_protocol::protocol::NetworkSandboxPolicy;
 use codex_protocol::protocol::Op;
 use codex_protocol::protocol::SandboxPolicy;
 use codex_protocol::protocol::TurnAbortReason;
@@ -23,6 +24,7 @@ use core_test_support::test_codex::test_codex;
 use core_test_support::wait_for_event;
 use core_test_support::wait_for_event_match;
 use core_test_support::wait_for_event_with_timeout;
+use pretty_assertions::assert_eq;
 use regex_lite::escape;
 use std::path::PathBuf;
 use tempfile::TempDir;
@@ -328,6 +330,35 @@ async fn user_shell_command_history_is_persisted_and_shared_with_model() -> anyh
     Ok(())
 }
 
+#[tokio::test]
+async fn user_shell_command_does_not_set_network_sandbox_env_var() -> anyhow::Result<()> {
+    let server = responses::start_mock_server().await;
+    let mut builder = core_test_support::test_codex::test_codex().with_config(|config| {
+        config.permissions.network_sandbox_policy = NetworkSandboxPolicy::Restricted;
+    });
+    let test = builder.build(&server).await?;
+
+    #[cfg(windows)]
+    let command = r#"$val = $env:CODEX_SANDBOX_NETWORK_DISABLED; if ([string]::IsNullOrEmpty($val)) { $val = 'not-set' } ; [System.Console]::Write($val)"#.to_string();
+    #[cfg(not(windows))]
+    let command =
+        r#"sh -c "printf '%s' \"${CODEX_SANDBOX_NETWORK_DISABLED:-not-set}\"""#.to_string();
+
+    test.codex
+        .submit(Op::RunUserShellCommand { command })
+        .await?;
+
+    let end_event = wait_for_event_match(&test.codex, |ev| match ev {
+        EventMsg::ExecCommandEnd(event) => Some(event.clone()),
+        _ => None,
+    })
+    .await;
+    assert_eq!(end_event.exit_code, 0);
+    assert_eq!(end_event.stdout.trim(), "not-set");
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 #[cfg(not(target_os = "windows"))] // TODO: unignore on windows
 async fn user_shell_command_output_is_truncated_in_history() -> anyhow::Result<()> {

codex-rs/linux-sandbox/src/bwrap.rs

@@ -15,6 +15,7 @@ use std::path::PathBuf;
 
 use codex_core::error::CodexErr;
 use codex_core::error::Result;
+use codex_protocol::protocol::FileSystemSandboxPolicy;
 use codex_protocol::protocol::SandboxPolicy;
 use codex_protocol::protocol::WritableRoot;
 
@@ -89,7 +90,17 @@ pub(crate) fn create_bwrap_command_args(
     cwd: &Path,
     options: BwrapOptions,
 ) -> Result<Vec<String>> {
-    if sandbox_policy.has_full_disk_write_access() {
+    let file_system_sandbox_policy = FileSystemSandboxPolicy::from(sandbox_policy);
+    create_bwrap_command_args_for_policy(command, &file_system_sandbox_policy, cwd, options)
+}
+
+pub(crate) fn create_bwrap_command_args_for_policy(
+    command: Vec<String>,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    cwd: &Path,
+    options: BwrapOptions,
+) -> Result<Vec<String>> {
+    if file_system_sandbox_policy.has_full_disk_write_access() {
         return if options.network_mode == BwrapNetworkMode::FullAccess {
             Ok(command)
         } else {
@@ -97,7 +108,7 @@ pub(crate) fn create_bwrap_command_args(
         };
     }
 
-    create_bwrap_flags(command, sandbox_policy, cwd, options)
+    create_bwrap_flags(command, file_system_sandbox_policy, cwd, options)
 }
 
 fn create_bwrap_flags_full_filesystem(command: Vec<String>, options: BwrapOptions) -> Vec<String> {
@@ -124,14 +135,14 @@ fn create_bwrap_flags_full_filesystem(command: Vec<String>, options: BwrapOption
 /// Build the bubblewrap flags (everything after `argv[0]`).
 fn create_bwrap_flags(
     command: Vec<String>,
-    sandbox_policy: &SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
     cwd: &Path,
     options: BwrapOptions,
 ) -> Result<Vec<String>> {
     let mut args = Vec::new();
     args.push("--new-session".to_string());
     args.push("--die-with-parent".to_string());
-    args.extend(create_filesystem_args(sandbox_policy, cwd)?);
+    args.extend(create_filesystem_args(file_system_sandbox_policy, cwd)?);
     // Isolate the PID namespace.
     args.push("--unshare-pid".to_string());
     if options.network_mode.should_unshare_network() {
@@ -147,7 +158,7 @@ fn create_bwrap_flags(
     Ok(args)
 }
 
-/// Build the bubblewrap filesystem mounts for a given sandbox policy.
+/// Build the bubblewrap filesystem mounts for a given filesystem policy.
 ///
 /// The mount order is important:
 /// 1. Full-read policies use `--ro-bind / /`; restricted-read policies start
@@ -158,11 +169,14 @@ fn create_bwrap_flags(
 ///    writable subpaths under `/dev` (for example, `/dev/shm`).
 /// 4. `--ro-bind <subpath> <subpath>` re-applies read-only protections under
 ///    those writable roots so protected subpaths win.
-fn create_filesystem_args(sandbox_policy: &SandboxPolicy, cwd: &Path) -> Result<Vec<String>> {
-    let writable_roots = sandbox_policy.get_writable_roots_with_cwd(cwd);
+fn create_filesystem_args(
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    cwd: &Path,
+) -> Result<Vec<String>> {
+    let writable_roots = file_system_sandbox_policy.get_writable_roots_with_cwd(cwd);
     ensure_mount_targets_exist(&writable_roots)?;
 
-    let mut args = if sandbox_policy.has_full_disk_read_access() {
+    let mut args = if file_system_sandbox_policy.has_full_disk_read_access() {
         // Read-only root, then mount a minimal device tree.
         // In bubblewrap (`bubblewrap.c`, `SETUP_MOUNT_DEV`), `--dev /dev`
         // creates the standard minimal nodes: null, zero, full, random,
@@ -185,12 +199,12 @@ fn create_filesystem_args(sandbox_policy: &SandboxPolicy, cwd: &Path) -> Result<
             "/dev".to_string(),
         ];
 
-        let mut readable_roots: BTreeSet<PathBuf> = sandbox_policy
+        let mut readable_roots: BTreeSet<PathBuf> = file_system_sandbox_policy
             .get_readable_roots_with_cwd(cwd)
             .into_iter()
             .map(PathBuf::from)
             .collect();
-        if sandbox_policy.include_platform_defaults() {
+        if file_system_sandbox_policy.include_platform_defaults() {
             readable_roots.extend(
                 LINUX_PLATFORM_DEFAULT_READ_ROOTS
                     .iter()
@@ -380,6 +394,12 @@ fn find_first_non_existent_component(target_path: &Path) -> Option<PathBuf> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use codex_protocol::protocol::FileSystemAccessMode;
+    use codex_protocol::protocol::FileSystemPath;
+    use codex_protocol::protocol::FileSystemSandboxEntry;
+    use codex_protocol::protocol::FileSystemSandboxPolicy;
+    use codex_protocol::protocol::FileSystemSpecialPath;
+    use codex_protocol::protocol::FileSystemSpecialPathKind;
     use codex_protocol::protocol::ReadOnlyAccess;
     use codex_protocol::protocol::SandboxPolicy;
     use codex_utils_absolute_path::AbsolutePathBuf;
@@ -521,4 +541,47 @@ mod tests {
             );
         }
     }
+
+    #[test]
+    fn split_policy_reapplies_unreadable_carveouts_after_writable_binds() {
+        let temp_dir = TempDir::new().expect("temp dir");
+        let writable_root = temp_dir.path().join("workspace");
+        let blocked = writable_root.join("blocked");
+        std::fs::create_dir_all(&blocked).expect("create blocked dir");
+        let writable_root =
+            AbsolutePathBuf::from_absolute_path(&writable_root).expect("absolute writable root");
+        let blocked = AbsolutePathBuf::from_absolute_path(&blocked).expect("absolute blocked dir");
+        let policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Path {
+                    path: writable_root.clone(),
+                },
+                access: FileSystemAccessMode::Write,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Path {
+                    path: blocked.clone(),
+                },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        let args = create_filesystem_args(&policy, temp_dir.path()).expect("filesystem args");
+        let writable_root_str = path_to_string(writable_root.as_path());
+        let blocked_str = path_to_string(blocked.as_path());
+
+        assert!(args.windows(3).any(|window| {
+            window
+                == [
+                    "--bind",
+                    writable_root_str.as_str(),
+                    writable_root_str.as_str(),
+                ]
+        }));
+        assert!(
+            args.windows(3).any(|window| {
+                window == ["--ro-bind", blocked_str.as_str(), blocked_str.as_str()]
+            })
+        );
+    }
 }

codex-rs/linux-sandbox/src/landlock.rs

@@ -8,6 +8,7 @@ use std::path::Path;
 use codex_core::error::CodexErr;
 use codex_core::error::Result;
 use codex_core::error::SandboxErr;
+use codex_protocol::protocol::NetworkSandboxPolicy;
 use codex_protocol::protocol::SandboxPolicy;
 use codex_utils_absolute_path::AbsolutePathBuf;
 
@@ -40,13 +41,14 @@ use seccompiler::apply_filter;
 /// Filesystem restrictions are intentionally handled by bubblewrap.
 pub(crate) fn apply_sandbox_policy_to_current_thread(
     sandbox_policy: &SandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     cwd: &Path,
     apply_landlock_fs: bool,
     allow_network_for_proxy: bool,
     proxy_routed_network: bool,
 ) -> Result<()> {
     let network_seccomp_mode = network_seccomp_mode(
-        sandbox_policy,
+        network_sandbox_policy,
         allow_network_for_proxy,
         proxy_routed_network,
     );
@@ -91,20 +93,20 @@ enum NetworkSeccompMode {
 }
 
 fn should_install_network_seccomp(
-    sandbox_policy: &SandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     allow_network_for_proxy: bool,
 ) -> bool {
     // Managed-network sessions should remain fail-closed even for policies that
     // would normally grant full network access (for example, DangerFullAccess).
-    !sandbox_policy.has_full_network_access() || allow_network_for_proxy
+    !network_sandbox_policy.is_enabled() || allow_network_for_proxy
 }
 
 fn network_seccomp_mode(
-    sandbox_policy: &SandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     allow_network_for_proxy: bool,
     proxy_routed_network: bool,
 ) -> Option<NetworkSeccompMode> {
-    if !should_install_network_seccomp(sandbox_policy, allow_network_for_proxy) {
+    if !should_install_network_seccomp(network_sandbox_policy, allow_network_for_proxy) {
         None
     } else if proxy_routed_network {
         Some(NetworkSeccompMode::ProxyRouted)

codex-rs/linux-sandbox/src/linux_run_main.rs

@@ -8,12 +8,15 @@ use std::path::PathBuf;
 
 use crate::bwrap::BwrapNetworkMode;
 use crate::bwrap::BwrapOptions;
-use crate::bwrap::create_bwrap_command_args;
+use crate::bwrap::create_bwrap_command_args_for_policy;
 use crate::landlock::apply_sandbox_policy_to_current_thread;
 use crate::proxy_routing::activate_proxy_routes_in_netns;
 use crate::proxy_routing::prepare_host_proxy_route_spec;
 use crate::vendored_bwrap::exec_vendored_bwrap;
 use crate::vendored_bwrap::run_vendored_bwrap_main;
+use codex_protocol::protocol::FileSystemSandboxPolicy;
+use codex_protocol::protocol::NetworkSandboxPolicy;
+use codex_protocol::protocol::SandboxPolicy;
 
 #[derive(Debug, Parser)]
 /// CLI surface for the Linux sandbox helper.
@@ -26,8 +29,18 @@ pub struct LandlockCommand {
     #[arg(long = "sandbox-policy-cwd")]
     pub sandbox_policy_cwd: PathBuf,
 
-    #[arg(long = "sandbox-policy")]
-    pub sandbox_policy: codex_protocol::protocol::SandboxPolicy,
+    /// Legacy compatibility policy.
+    ///
+    /// Newer callers pass split filesystem/network policies as well so the
+    /// helper can migrate incrementally without breaking older invocations.
+    #[arg(long = "sandbox-policy", hide = true)]
+    pub sandbox_policy: Option<SandboxPolicy>,
+
+    #[arg(long = "file-system-sandbox-policy", hide = true)]
+    pub file_system_sandbox_policy: Option<FileSystemSandboxPolicy>,
+
+    #[arg(long = "network-sandbox-policy", hide = true)]
+    pub network_sandbox_policy: Option<NetworkSandboxPolicy>,
 
     /// Opt-in: use the bubblewrap-based Linux sandbox pipeline.
     ///
@@ -77,6 +90,8 @@ pub fn run_main() -> ! {
     let LandlockCommand {
         sandbox_policy_cwd,
         sandbox_policy,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
         use_bwrap_sandbox,
         apply_seccomp_then_exec,
         allow_network_for_proxy,
@@ -89,6 +104,16 @@ pub fn run_main() -> ! {
         panic!("No command specified to execute.");
     }
     ensure_inner_stage_mode_is_valid(apply_seccomp_then_exec, use_bwrap_sandbox);
+    let EffectiveSandboxPolicies {
+        sandbox_policy,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
+    } = resolve_sandbox_policies(
+        sandbox_policy_cwd.as_path(),
+        sandbox_policy,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
+    );
 
     // Inner stage: apply seccomp/no_new_privs after bubblewrap has already
     // established the filesystem view.
@@ -104,6 +129,7 @@ pub fn run_main() -> ! {
         let proxy_routing_active = allow_network_for_proxy;
         if let Err(e) = apply_sandbox_policy_to_current_thread(
             &sandbox_policy,
+            network_sandbox_policy,
             &sandbox_policy_cwd,
             false,
             allow_network_for_proxy,
@@ -114,9 +140,10 @@ pub fn run_main() -> ! {
         exec_or_panic(command);
     }
 
-    if sandbox_policy.has_full_disk_write_access() && !allow_network_for_proxy {
+    if file_system_sandbox_policy.has_full_disk_write_access() && !allow_network_for_proxy {
         if let Err(e) = apply_sandbox_policy_to_current_thread(
             &sandbox_policy,
+            network_sandbox_policy,
             &sandbox_policy_cwd,
             false,
             allow_network_for_proxy,
@@ -142,6 +169,8 @@ pub fn run_main() -> ! {
         let inner = build_inner_seccomp_command(
             &sandbox_policy_cwd,
             &sandbox_policy,
+            &file_system_sandbox_policy,
+            network_sandbox_policy,
             use_bwrap_sandbox,
             allow_network_for_proxy,
             proxy_route_spec,
@@ -149,7 +178,8 @@ pub fn run_main() -> ! {
         );
         run_bwrap_with_proc_fallback(
             &sandbox_policy_cwd,
-            &sandbox_policy,
+            &file_system_sandbox_policy,
+            network_sandbox_policy,
             inner,
             !no_proc,
             allow_network_for_proxy,
@@ -159,6 +189,7 @@ pub fn run_main() -> ! {
     // Legacy path: Landlock enforcement only, when bwrap sandboxing is not enabled.
     if let Err(e) = apply_sandbox_policy_to_current_thread(
         &sandbox_policy,
+        network_sandbox_policy,
         &sandbox_policy_cwd,
         true,
         allow_network_for_proxy,
@@ -169,6 +200,53 @@ pub fn run_main() -> ! {
     exec_or_panic(command);
 }
 
+#[derive(Debug, Clone)]
+struct EffectiveSandboxPolicies {
+    sandbox_policy: SandboxPolicy,
+    file_system_sandbox_policy: FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
+}
+
+fn resolve_sandbox_policies(
+    sandbox_policy_cwd: &Path,
+    sandbox_policy: Option<SandboxPolicy>,
+    file_system_sandbox_policy: Option<FileSystemSandboxPolicy>,
+    network_sandbox_policy: Option<NetworkSandboxPolicy>,
+) -> EffectiveSandboxPolicies {
+    match (
+        sandbox_policy,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
+    ) {
+        (Some(sandbox_policy), Some(file_system_sandbox_policy), Some(network_sandbox_policy)) => {
+            EffectiveSandboxPolicies {
+                sandbox_policy,
+                file_system_sandbox_policy,
+                network_sandbox_policy,
+            }
+        }
+        (Some(sandbox_policy), None, None) => EffectiveSandboxPolicies {
+            file_system_sandbox_policy: FileSystemSandboxPolicy::from(&sandbox_policy),
+            network_sandbox_policy: NetworkSandboxPolicy::from(&sandbox_policy),
+            sandbox_policy,
+        },
+        (None, Some(file_system_sandbox_policy), Some(network_sandbox_policy)) => {
+            let sandbox_policy = file_system_sandbox_policy
+                .to_legacy_sandbox_policy(network_sandbox_policy, sandbox_policy_cwd)
+                .unwrap_or_else(|err| {
+                    panic!("failed to derive legacy sandbox policy from split policies: {err}")
+                });
+            EffectiveSandboxPolicies {
+                sandbox_policy,
+                file_system_sandbox_policy,
+                network_sandbox_policy,
+            }
+        }
+        (None, None, None) => panic!("missing sandbox policy configuration"),
+        _ => panic!("file-system and network sandbox policies must be provided together"),
+    }
+}
+
 fn ensure_inner_stage_mode_is_valid(apply_seccomp_then_exec: bool, use_bwrap_sandbox: bool) {
     if apply_seccomp_then_exec && !use_bwrap_sandbox {
         panic!("--apply-seccomp-then-exec requires --use-bwrap-sandbox");
@@ -177,15 +255,21 @@ fn ensure_inner_stage_mode_is_valid(apply_seccomp_then_exec: bool, use_bwrap_san
 
 fn run_bwrap_with_proc_fallback(
     sandbox_policy_cwd: &Path,
-    sandbox_policy: &codex_protocol::protocol::SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     inner: Vec<String>,
     mount_proc: bool,
     allow_network_for_proxy: bool,
 ) -> ! {
-    let network_mode = bwrap_network_mode(sandbox_policy, allow_network_for_proxy);
+    let network_mode = bwrap_network_mode(network_sandbox_policy, allow_network_for_proxy);
     let mut mount_proc = mount_proc;
 
-    if mount_proc && !preflight_proc_mount_support(sandbox_policy_cwd, sandbox_policy, network_mode)
+    if mount_proc
+        && !preflight_proc_mount_support(
+            sandbox_policy_cwd,
+            file_system_sandbox_policy,
+            network_mode,
+        )
     {
         eprintln!("codex-linux-sandbox: bwrap could not mount /proc; retrying with --no-proc");
         mount_proc = false;
@@ -195,17 +279,22 @@ fn run_bwrap_with_proc_fallback(
         mount_proc,
         network_mode,
     };
-    let argv = build_bwrap_argv(inner, sandbox_policy, sandbox_policy_cwd, options);
+    let argv = build_bwrap_argv(
+        inner,
+        file_system_sandbox_policy,
+        sandbox_policy_cwd,
+        options,
+    );
     exec_vendored_bwrap(argv);
 }
 
 fn bwrap_network_mode(
-    sandbox_policy: &codex_protocol::protocol::SandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     allow_network_for_proxy: bool,
 ) -> BwrapNetworkMode {
     if allow_network_for_proxy {
         BwrapNetworkMode::ProxyOnly
-    } else if sandbox_policy.has_full_network_access() {
+    } else if network_sandbox_policy.is_enabled() {
         BwrapNetworkMode::FullAccess
     } else {
         BwrapNetworkMode::Isolated
@@ -214,12 +303,17 @@ fn bwrap_network_mode(
 
 fn build_bwrap_argv(
     inner: Vec<String>,
-    sandbox_policy: &codex_protocol::protocol::SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
     sandbox_policy_cwd: &Path,
     options: BwrapOptions,
 ) -> Vec<String> {
-    let mut args = create_bwrap_command_args(inner, sandbox_policy, sandbox_policy_cwd, options)
-        .unwrap_or_else(|err| panic!("error building bubblewrap command: {err:?}"));
+    let mut args = create_bwrap_command_args_for_policy(
+        inner,
+        file_system_sandbox_policy,
+        sandbox_policy_cwd,
+        options,
+    )
+    .unwrap_or_else(|err| panic!("error building bubblewrap command: {err:?}"));
 
     let command_separator_index = args
         .iter()
@@ -237,24 +331,24 @@ fn build_bwrap_argv(
 
 fn preflight_proc_mount_support(
     sandbox_policy_cwd: &Path,
-    sandbox_policy: &codex_protocol::protocol::SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
     network_mode: BwrapNetworkMode,
 ) -> bool {
     let preflight_argv =
-        build_preflight_bwrap_argv(sandbox_policy_cwd, sandbox_policy, network_mode);
+        build_preflight_bwrap_argv(sandbox_policy_cwd, file_system_sandbox_policy, network_mode);
     let stderr = run_bwrap_in_child_capture_stderr(preflight_argv);
     !is_proc_mount_failure(stderr.as_str())
 }
 
 fn build_preflight_bwrap_argv(
     sandbox_policy_cwd: &Path,
-    sandbox_policy: &codex_protocol::protocol::SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
     network_mode: BwrapNetworkMode,
 ) -> Vec<String> {
     let preflight_command = vec![resolve_true_command()];
     build_bwrap_argv(
         preflight_command,
-        sandbox_policy,
+        file_system_sandbox_policy,
         sandbox_policy_cwd,
         BwrapOptions {
             mount_proc: true,
@@ -361,7 +455,9 @@ fn is_proc_mount_failure(stderr: &str) -> bool {
 /// Build the inner command that applies seccomp after bubblewrap.
 fn build_inner_seccomp_command(
     sandbox_policy_cwd: &Path,
-    sandbox_policy: &codex_protocol::protocol::SandboxPolicy,
+    sandbox_policy: &SandboxPolicy,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
     use_bwrap_sandbox: bool,
     allow_network_for_proxy: bool,
     proxy_route_spec: Option<String>,
@@ -375,6 +471,14 @@ fn build_inner_seccomp_command(
         Ok(json) => json,
         Err(err) => panic!("failed to serialize sandbox policy: {err}"),
     };
+    let file_system_policy_json = match serde_json::to_string(file_system_sandbox_policy) {
+        Ok(json) => json,
+        Err(err) => panic!("failed to serialize filesystem sandbox policy: {err}"),
+    };
+    let network_policy_json = match serde_json::to_string(&network_sandbox_policy) {
+        Ok(json) => json,
+        Err(err) => panic!("failed to serialize network sandbox policy: {err}"),
+    };
 
     let mut inner = vec![
         current_exe.to_string_lossy().to_string(),
@@ -382,6 +486,10 @@ fn build_inner_seccomp_command(
         sandbox_policy_cwd.to_string_lossy().to_string(),
         "--sandbox-policy".to_string(),
         policy_json,
+        "--file-system-sandbox-policy".to_string(),
+        file_system_policy_json,
+        "--network-sandbox-policy".to_string(),
+        network_policy_json,
     ];
     if use_bwrap_sandbox {
         inner.push("--use-bwrap-sandbox".to_string());

codex-rs/linux-sandbox/src/linux_run_main_tests.rs

@@ -1,7 +1,13 @@
 #[cfg(test)]
 use super::*;
 #[cfg(test)]
+use codex_protocol::protocol::FileSystemSandboxPolicy;
+#[cfg(test)]
+use codex_protocol::protocol::NetworkSandboxPolicy;
+#[cfg(test)]
 use codex_protocol::protocol::SandboxPolicy;
+#[cfg(test)]
+use pretty_assertions::assert_eq;
 
 #[test]
 fn detects_proc_mount_invalid_argument_failure() {
@@ -29,9 +35,10 @@ fn ignores_non_proc_mount_errors() {
 
 #[test]
 fn inserts_bwrap_argv0_before_command_separator() {
+    let sandbox_policy = SandboxPolicy::new_read_only_policy();
     let argv = build_bwrap_argv(
         vec!["/bin/true".to_string()],
-        &SandboxPolicy::new_read_only_policy(),
+        &FileSystemSandboxPolicy::from(&sandbox_policy),
         Path::new("/"),
         BwrapOptions {
             mount_proc: true,
@@ -62,9 +69,10 @@ fn inserts_bwrap_argv0_before_command_separator() {
 
 #[test]
 fn inserts_unshare_net_when_network_isolation_requested() {
+    let sandbox_policy = SandboxPolicy::new_read_only_policy();
     let argv = build_bwrap_argv(
         vec!["/bin/true".to_string()],
-        &SandboxPolicy::new_read_only_policy(),
+        &FileSystemSandboxPolicy::from(&sandbox_policy),
         Path::new("/"),
         BwrapOptions {
             mount_proc: true,
@@ -76,9 +84,10 @@ fn inserts_unshare_net_when_network_isolation_requested() {
 
 #[test]
 fn inserts_unshare_net_when_proxy_only_network_mode_requested() {
+    let sandbox_policy = SandboxPolicy::new_read_only_policy();
     let argv = build_bwrap_argv(
         vec!["/bin/true".to_string()],
-        &SandboxPolicy::new_read_only_policy(),
+        &FileSystemSandboxPolicy::from(&sandbox_policy),
         Path::new("/"),
         BwrapOptions {
             mount_proc: true,
@@ -90,22 +99,29 @@ fn inserts_unshare_net_when_proxy_only_network_mode_requested() {
 
 #[test]
 fn proxy_only_mode_takes_precedence_over_full_network_policy() {
-    let mode = bwrap_network_mode(&SandboxPolicy::DangerFullAccess, true);
+    let mode = bwrap_network_mode(NetworkSandboxPolicy::Enabled, true);
     assert_eq!(mode, BwrapNetworkMode::ProxyOnly);
 }
 
 #[test]
 fn managed_proxy_preflight_argv_is_wrapped_for_full_access_policy() {
-    let mode = bwrap_network_mode(&SandboxPolicy::DangerFullAccess, true);
-    let argv = build_preflight_bwrap_argv(Path::new("/"), &SandboxPolicy::DangerFullAccess, mode);
+    let mode = bwrap_network_mode(NetworkSandboxPolicy::Enabled, true);
+    let argv = build_preflight_bwrap_argv(
+        Path::new("/"),
+        &FileSystemSandboxPolicy::from(&SandboxPolicy::DangerFullAccess),
+        mode,
+    );
     assert!(argv.iter().any(|arg| arg == "--"));
 }
 
 #[test]
 fn managed_proxy_inner_command_includes_route_spec() {
+    let sandbox_policy = SandboxPolicy::new_read_only_policy();
     let args = build_inner_seccomp_command(
         Path::new("/tmp"),
-        &SandboxPolicy::new_read_only_policy(),
+        &sandbox_policy,
+        &FileSystemSandboxPolicy::from(&sandbox_policy),
+        NetworkSandboxPolicy::Restricted,
         true,
         true,
         Some("{\"routes\":[]}".to_string()),
@@ -117,10 +133,31 @@ fn managed_proxy_inner_command_includes_route_spec() {
 }
 
 #[test]
-fn non_managed_inner_command_omits_route_spec() {
+fn inner_command_includes_split_policy_flags() {
+    let sandbox_policy = SandboxPolicy::new_read_only_policy();
     let args = build_inner_seccomp_command(
         Path::new("/tmp"),
-        &SandboxPolicy::new_read_only_policy(),
+        &sandbox_policy,
+        &FileSystemSandboxPolicy::from(&sandbox_policy),
+        NetworkSandboxPolicy::Restricted,
+        true,
+        false,
+        None,
+        vec!["/bin/true".to_string()],
+    );
+
+    assert!(args.iter().any(|arg| arg == "--file-system-sandbox-policy"));
+    assert!(args.iter().any(|arg| arg == "--network-sandbox-policy"));
+}
+
+#[test]
+fn non_managed_inner_command_omits_route_spec() {
+    let sandbox_policy = SandboxPolicy::new_read_only_policy();
+    let args = build_inner_seccomp_command(
+        Path::new("/tmp"),
+        &sandbox_policy,
+        &FileSystemSandboxPolicy::from(&sandbox_policy),
+        NetworkSandboxPolicy::Restricted,
         true,
         false,
         None,
@@ -133,9 +170,12 @@ fn non_managed_inner_command_omits_route_spec() {
 #[test]
 fn managed_proxy_inner_command_requires_route_spec() {
     let result = std::panic::catch_unwind(|| {
+        let sandbox_policy = SandboxPolicy::new_read_only_policy();
         build_inner_seccomp_command(
             Path::new("/tmp"),
-            &SandboxPolicy::new_read_only_policy(),
+            &sandbox_policy,
+            &FileSystemSandboxPolicy::from(&sandbox_policy),
+            NetworkSandboxPolicy::Restricted,
             true,
             true,
             None,
@@ -145,6 +185,59 @@ fn managed_proxy_inner_command_requires_route_spec() {
     assert!(result.is_err());
 }
 
+#[test]
+fn resolve_sandbox_policies_derives_split_policies_from_legacy_policy() {
+    let sandbox_policy = SandboxPolicy::new_read_only_policy();
+
+    let resolved =
+        resolve_sandbox_policies(Path::new("/tmp"), Some(sandbox_policy.clone()), None, None);
+
+    assert_eq!(resolved.sandbox_policy, sandbox_policy.clone());
+    assert_eq!(
+        resolved.file_system_sandbox_policy,
+        FileSystemSandboxPolicy::from(&sandbox_policy)
+    );
+    assert_eq!(
+        resolved.network_sandbox_policy,
+        NetworkSandboxPolicy::from(&sandbox_policy)
+    );
+}
+
+#[test]
+fn resolve_sandbox_policies_derives_legacy_policy_from_split_policies() {
+    let sandbox_policy = SandboxPolicy::new_read_only_policy();
+    let file_system_sandbox_policy = FileSystemSandboxPolicy::from(&sandbox_policy);
+    let network_sandbox_policy = NetworkSandboxPolicy::from(&sandbox_policy);
+
+    let resolved = resolve_sandbox_policies(
+        Path::new("/tmp"),
+        None,
+        Some(file_system_sandbox_policy.clone()),
+        Some(network_sandbox_policy),
+    );
+
+    assert_eq!(resolved.sandbox_policy, sandbox_policy);
+    assert_eq!(
+        resolved.file_system_sandbox_policy,
+        file_system_sandbox_policy
+    );
+    assert_eq!(resolved.network_sandbox_policy, network_sandbox_policy);
+}
+
+#[test]
+fn resolve_sandbox_policies_rejects_partial_split_policies() {
+    let result = std::panic::catch_unwind(|| {
+        resolve_sandbox_policies(
+            Path::new("/tmp"),
+            Some(SandboxPolicy::new_read_only_policy()),
+            Some(FileSystemSandboxPolicy::default()),
+            None,
+        )
+    });
+
+    assert!(result.is_err());
+}
+
 #[test]
 fn apply_seccomp_then_exec_without_bwrap_panics() {
     let result = std::panic::catch_unwind(|| ensure_inner_stage_mode_is_valid(true, false));

codex-rs/linux-sandbox/tests/suite/landlock.rs

@@ -9,6 +9,11 @@ use codex_core::exec::process_exec_tool_call;
 use codex_core::exec_env::create_env;
 use codex_core::sandboxing::SandboxPermissions;
 use codex_protocol::config_types::WindowsSandboxLevel;
+use codex_protocol::protocol::FileSystemAccessMode;
+use codex_protocol::protocol::FileSystemPath;
+use codex_protocol::protocol::FileSystemSandboxEntry;
+use codex_protocol::protocol::FileSystemSandboxPolicy;
+use codex_protocol::protocol::NetworkSandboxPolicy;
 use codex_protocol::protocol::SandboxPolicy;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use pretty_assertions::assert_eq;
@@ -69,20 +74,6 @@ async fn run_cmd_result_with_writable_roots(
     use_bwrap_sandbox: bool,
     network_access: bool,
 ) -> Result<codex_core::exec::ExecToolCallOutput> {
-    let cwd = std::env::current_dir().expect("cwd should exist");
-    let sandbox_cwd = cwd.clone();
-    let params = ExecParams {
-        command: cmd.iter().copied().map(str::to_owned).collect(),
-        cwd,
-        expiration: timeout_ms.into(),
-        env: create_env_from_core_vars(),
-        network: None,
-        sandbox_permissions: SandboxPermissions::UseDefault,
-        windows_sandbox_level: WindowsSandboxLevel::Disabled,
-        justification: None,
-        arg0: None,
-    };
-
     let sandbox_policy = SandboxPolicy::WorkspaceWrite {
         writable_roots: writable_roots
             .iter()
@@ -96,12 +87,49 @@ async fn run_cmd_result_with_writable_roots(
         exclude_tmpdir_env_var: true,
         exclude_slash_tmp: true,
     };
+    let file_system_sandbox_policy = FileSystemSandboxPolicy::from(&sandbox_policy);
+    let network_sandbox_policy = NetworkSandboxPolicy::from(&sandbox_policy);
+    run_cmd_result_with_policies(
+        cmd,
+        sandbox_policy,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
+        timeout_ms,
+        use_bwrap_sandbox,
+    )
+    .await
+}
+
+#[expect(clippy::expect_used)]
+async fn run_cmd_result_with_policies(
+    cmd: &[&str],
+    sandbox_policy: SandboxPolicy,
+    file_system_sandbox_policy: FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
+    timeout_ms: u64,
+    use_bwrap_sandbox: bool,
+) -> Result<codex_core::exec::ExecToolCallOutput> {
+    let cwd = std::env::current_dir().expect("cwd should exist");
+    let sandbox_cwd = cwd.clone();
+    let params = ExecParams {
+        command: cmd.iter().copied().map(str::to_owned).collect(),
+        cwd,
+        expiration: timeout_ms.into(),
+        env: create_env_from_core_vars(),
+        network: None,
+        sandbox_permissions: SandboxPermissions::UseDefault,
+        windows_sandbox_level: WindowsSandboxLevel::Disabled,
+        justification: None,
+        arg0: None,
+    };
     let sandbox_program = env!("CARGO_BIN_EXE_codex-linux-sandbox");
     let codex_linux_sandbox_exe = Some(PathBuf::from(sandbox_program));
 
     process_exec_tool_call(
         params,
         &sandbox_policy,
+        &file_system_sandbox_policy,
+        network_sandbox_policy,
         sandbox_cwd.as_path(),
         &codex_linux_sandbox_exe,
         use_bwrap_sandbox,
@@ -333,6 +361,8 @@ async fn assert_network_blocked(cmd: &[&str]) {
     let result = process_exec_tool_call(
         params,
         &sandbox_policy,
+        &FileSystemSandboxPolicy::from(&sandbox_policy),
+        NetworkSandboxPolicy::from(&sandbox_policy),
         sandbox_cwd.as_path(),
         &codex_linux_sandbox_exe,
         false,
@@ -473,6 +503,59 @@ async fn sandbox_blocks_codex_symlink_replacement_attack() {
     assert_ne!(codex_output.exit_code, 0);
 }
 
+#[tokio::test]
+async fn sandbox_blocks_explicit_split_policy_carveouts_under_bwrap() {
+    if should_skip_bwrap_tests().await {
+        eprintln!("skipping bwrap test: bwrap sandbox prerequisites are unavailable");
+        return;
+    }
+
+    let tmpdir = tempfile::tempdir().expect("tempdir");
+    let blocked = tmpdir.path().join("blocked");
+    std::fs::create_dir_all(&blocked).expect("create blocked dir");
+    let blocked_target = blocked.join("secret.txt");
+
+    let sandbox_policy = SandboxPolicy::WorkspaceWrite {
+        writable_roots: vec![AbsolutePathBuf::try_from(tmpdir.path()).expect("absolute tempdir")],
+        read_only_access: Default::default(),
+        network_access: true,
+        exclude_tmpdir_env_var: true,
+        exclude_slash_tmp: true,
+    };
+    let file_system_sandbox_policy = FileSystemSandboxPolicy::restricted(vec![
+        FileSystemSandboxEntry {
+            path: FileSystemPath::Path {
+                path: AbsolutePathBuf::try_from(tmpdir.path()).expect("absolute tempdir"),
+            },
+            access: FileSystemAccessMode::Write,
+        },
+        FileSystemSandboxEntry {
+            path: FileSystemPath::Path {
+                path: AbsolutePathBuf::try_from(blocked.as_path()).expect("absolute blocked dir"),
+            },
+            access: FileSystemAccessMode::None,
+        },
+    ]);
+    let output = expect_denied(
+        run_cmd_result_with_policies(
+            &[
+                "bash",
+                "-lc",
+                &format!("echo denied > {}", blocked_target.to_string_lossy()),
+            ],
+            sandbox_policy,
+            file_system_sandbox_policy,
+            NetworkSandboxPolicy::Enabled,
+            LONG_TIMEOUT_MS,
+            true,
+        )
+        .await,
+        "explicit split-policy carveout should be denied under bubblewrap",
+    );
+
+    assert_ne!(output.exit_code, 0);
+}
+
 #[tokio::test]
 async fn sandbox_blocks_ssh() {
     // Force ssh to attempt a real TCP connection but fail quickly.  `BatchMode`

codex-rs/protocol/src/protocol.rs

@@ -7,6 +7,7 @@ use std::collections::HashMap;
 use std::collections::HashSet;
 use std::ffi::OsStr;
 use std::fmt;
+use std::io;
 use std::path::Path;
 use std::path::PathBuf;
 use std::str::FromStr;
@@ -537,6 +538,425 @@ impl NetworkAccess {
     }
 }
 
+#[derive(
+    Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Display, Default, JsonSchema, TS,
+)]
+#[serde(rename_all = "kebab-case")]
+#[strum(serialize_all = "kebab-case")]
+pub enum NetworkSandboxPolicy {
+    #[default]
+    Restricted,
+    Enabled,
+}
+
+impl NetworkSandboxPolicy {
+    pub fn is_enabled(self) -> bool {
+        matches!(self, NetworkSandboxPolicy::Enabled)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Display, JsonSchema, TS)]
+#[serde(rename_all = "lowercase")]
+#[strum(serialize_all = "lowercase")]
+pub enum FileSystemAccessMode {
+    None,
+    Read,
+    Write,
+}
+
+impl FileSystemAccessMode {
+    pub fn can_read(self) -> bool {
+        !matches!(self, FileSystemAccessMode::None)
+    }
+
+    pub fn can_write(self) -> bool {
+        matches!(self, FileSystemAccessMode::Write)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema, TS)]
+#[serde(rename_all = "snake_case")]
+pub enum FileSystemSpecialPathKind {
+    Root,
+    Minimal,
+    CurrentWorkingDirectory,
+    ProjectRoots,
+    Tmpdir,
+    SlashTmp,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema, TS)]
+#[serde(rename_all = "snake_case")]
+pub struct FileSystemSpecialPath {
+    pub kind: FileSystemSpecialPathKind,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[ts(optional)]
+    pub subpath: Option<PathBuf>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema, TS)]
+#[serde(tag = "type", rename_all = "snake_case")]
+#[ts(tag = "type")]
+pub enum FileSystemPath {
+    Path { path: AbsolutePathBuf },
+    Special { value: FileSystemSpecialPath },
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema, TS)]
+pub struct FileSystemSandboxEntry {
+    pub path: FileSystemPath,
+    pub access: FileSystemAccessMode,
+}
+
+#[derive(
+    Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Display, Default, JsonSchema, TS,
+)]
+#[serde(rename_all = "kebab-case")]
+#[strum(serialize_all = "kebab-case")]
+pub enum FileSystemSandboxKind {
+    #[default]
+    Restricted,
+    Unrestricted,
+    ExternalSandbox,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema, TS)]
+pub struct FileSystemSandboxPolicy {
+    pub kind: FileSystemSandboxKind,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub entries: Vec<FileSystemSandboxEntry>,
+}
+
+impl Default for FileSystemSandboxPolicy {
+    fn default() -> Self {
+        Self {
+            kind: FileSystemSandboxKind::Restricted,
+            entries: vec![FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::Root,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Read,
+            }],
+        }
+    }
+}
+
+impl FileSystemSandboxPolicy {
+    fn has_root_access(&self, predicate: impl Fn(FileSystemAccessMode) -> bool) -> bool {
+        matches!(self.kind, FileSystemSandboxKind::Restricted)
+            && self.entries.iter().any(|entry| {
+                matches!(
+                    &entry.path,
+                    FileSystemPath::Special { value }
+                        if value.kind == FileSystemSpecialPathKind::Root && predicate(entry.access)
+                )
+            })
+    }
+
+    fn has_explicit_deny_entries(&self) -> bool {
+        matches!(self.kind, FileSystemSandboxKind::Restricted)
+            && self
+                .entries
+                .iter()
+                .any(|entry| entry.access == FileSystemAccessMode::None)
+    }
+
+    pub fn unrestricted() -> Self {
+        Self {
+            kind: FileSystemSandboxKind::Unrestricted,
+            entries: Vec::new(),
+        }
+    }
+
+    pub fn external_sandbox() -> Self {
+        Self {
+            kind: FileSystemSandboxKind::ExternalSandbox,
+            entries: Vec::new(),
+        }
+    }
+
+    pub fn restricted(entries: Vec<FileSystemSandboxEntry>) -> Self {
+        Self {
+            kind: FileSystemSandboxKind::Restricted,
+            entries,
+        }
+    }
+
+    /// Returns true when filesystem reads are unrestricted.
+    pub fn has_full_disk_read_access(&self) -> bool {
+        match self.kind {
+            FileSystemSandboxKind::Unrestricted | FileSystemSandboxKind::ExternalSandbox => true,
+            FileSystemSandboxKind::Restricted => {
+                self.has_root_access(FileSystemAccessMode::can_read)
+                    && !self.has_explicit_deny_entries()
+            }
+        }
+    }
+
+    /// Returns true when filesystem writes are unrestricted.
+    pub fn has_full_disk_write_access(&self) -> bool {
+        match self.kind {
+            FileSystemSandboxKind::Unrestricted | FileSystemSandboxKind::ExternalSandbox => true,
+            FileSystemSandboxKind::Restricted => {
+                self.has_root_access(FileSystemAccessMode::can_write)
+                    && !self.has_explicit_deny_entries()
+            }
+        }
+    }
+
+    /// Returns true when platform-default readable roots should be included.
+    pub fn include_platform_defaults(&self) -> bool {
+        !self.has_full_disk_read_access()
+            && matches!(self.kind, FileSystemSandboxKind::Restricted)
+            && self.entries.iter().any(|entry| {
+                matches!(
+                    &entry.path,
+                    FileSystemPath::Special { value }
+                        if value.kind == FileSystemSpecialPathKind::Minimal
+                            && entry.access.can_read()
+                )
+            })
+    }
+
+    /// Returns the explicit readable roots resolved against the provided cwd.
+    pub fn get_readable_roots_with_cwd(&self, cwd: &Path) -> Vec<AbsolutePathBuf> {
+        if self.has_full_disk_read_access() {
+            return Vec::new();
+        }
+
+        let cwd_absolute = AbsolutePathBuf::from_absolute_path(cwd).ok();
+        let mut readable_roots = Vec::new();
+        if self.has_root_access(FileSystemAccessMode::can_read)
+            && let Some(cwd_absolute) = cwd_absolute.as_ref()
+        {
+            readable_roots.push(absolute_root_path_for_cwd(cwd_absolute));
+        }
+
+        dedup_absolute_paths(
+            readable_roots
+                .into_iter()
+                .chain(
+                    self.entries
+                        .iter()
+                        .filter(|entry| entry.access.can_read())
+                        .filter_map(|entry| {
+                            resolve_file_system_path(&entry.path, cwd_absolute.as_ref())
+                        }),
+                )
+                .collect(),
+        )
+    }
+
+    /// Returns the writable roots together with read-only carveouts resolved
+    /// against the provided cwd.
+    pub fn get_writable_roots_with_cwd(&self, cwd: &Path) -> Vec<WritableRoot> {
+        if self.has_full_disk_write_access() {
+            return Vec::new();
+        }
+
+        let cwd_absolute = AbsolutePathBuf::from_absolute_path(cwd).ok();
+        let unreadable_roots = self.get_unreadable_roots_with_cwd(cwd);
+        let mut writable_roots = Vec::new();
+        if self.has_root_access(FileSystemAccessMode::can_write)
+            && let Some(cwd_absolute) = cwd_absolute.as_ref()
+        {
+            writable_roots.push(absolute_root_path_for_cwd(cwd_absolute));
+        }
+
+        dedup_absolute_paths(
+            writable_roots
+                .into_iter()
+                .chain(
+                    self.entries
+                        .iter()
+                        .filter(|entry| entry.access.can_write())
+                        .filter_map(|entry| {
+                            resolve_file_system_path(&entry.path, cwd_absolute.as_ref())
+                        }),
+                )
+                .collect(),
+        )
+        .into_iter()
+        .map(|root| {
+            let mut read_only_subpaths = default_read_only_subpaths_for_writable_root(&root);
+            read_only_subpaths.extend(
+                unreadable_roots
+                    .iter()
+                    .filter(|path| path.as_path().starts_with(root.as_path()))
+                    .cloned(),
+            );
+            WritableRoot {
+                root,
+                read_only_subpaths: dedup_absolute_paths(read_only_subpaths),
+            }
+        })
+        .collect()
+    }
+
+    /// Returns explicit unreadable roots resolved against the provided cwd.
+    pub fn get_unreadable_roots_with_cwd(&self, cwd: &Path) -> Vec<AbsolutePathBuf> {
+        if !matches!(self.kind, FileSystemSandboxKind::Restricted) {
+            return Vec::new();
+        }
+
+        let cwd_absolute = AbsolutePathBuf::from_absolute_path(cwd).ok();
+        dedup_absolute_paths(
+            self.entries
+                .iter()
+                .filter(|entry| entry.access == FileSystemAccessMode::None)
+                .filter_map(|entry| resolve_file_system_path(&entry.path, cwd_absolute.as_ref()))
+                .collect(),
+        )
+    }
+
+    pub fn to_legacy_sandbox_policy(
+        &self,
+        network_policy: NetworkSandboxPolicy,
+        cwd: &Path,
+    ) -> io::Result<SandboxPolicy> {
+        Ok(match self.kind {
+            FileSystemSandboxKind::ExternalSandbox => SandboxPolicy::ExternalSandbox {
+                network_access: if network_policy.is_enabled() {
+                    NetworkAccess::Enabled
+                } else {
+                    NetworkAccess::Restricted
+                },
+            },
+            FileSystemSandboxKind::Unrestricted => {
+                if network_policy.is_enabled() {
+                    SandboxPolicy::DangerFullAccess
+                } else {
+                    SandboxPolicy::ExternalSandbox {
+                        network_access: NetworkAccess::Restricted,
+                    }
+                }
+            }
+            FileSystemSandboxKind::Restricted => {
+                let cwd_absolute = AbsolutePathBuf::from_absolute_path(cwd).ok();
+                let mut include_platform_defaults = false;
+                let mut has_full_disk_read_access = false;
+                let mut has_full_disk_write_access = false;
+                let mut workspace_root_writable = false;
+                let mut writable_roots = Vec::new();
+                let mut readable_roots = Vec::new();
+                let mut tmpdir_writable = false;
+                let mut slash_tmp_writable = false;
+
+                for entry in &self.entries {
+                    match &entry.path {
+                        FileSystemPath::Path { path } => {
+                            if entry.access.can_write() {
+                                if cwd_absolute.as_ref().is_some_and(|cwd| cwd == path) {
+                                    workspace_root_writable = true;
+                                } else {
+                                    writable_roots.push(path.clone());
+                                }
+                            } else if entry.access.can_read() {
+                                readable_roots.push(path.clone());
+                            }
+                        }
+                        FileSystemPath::Special { value } => match value.kind {
+                            FileSystemSpecialPathKind::Root => match entry.access {
+                                FileSystemAccessMode::None => {}
+                                FileSystemAccessMode::Read => has_full_disk_read_access = true,
+                                FileSystemAccessMode::Write => {
+                                    has_full_disk_read_access = true;
+                                    has_full_disk_write_access = true;
+                                }
+                            },
+                            FileSystemSpecialPathKind::Minimal => {
+                                if entry.access.can_read() {
+                                    include_platform_defaults = true;
+                                }
+                            }
+                            FileSystemSpecialPathKind::CurrentWorkingDirectory
+                            | FileSystemSpecialPathKind::ProjectRoots => {
+                                if value.subpath.is_none() && entry.access.can_write() {
+                                    workspace_root_writable = true;
+                                } else if let Some(path) =
+                                    resolve_file_system_special_path(value, cwd_absolute.as_ref())
+                                {
+                                    if entry.access.can_write() {
+                                        writable_roots.push(path);
+                                    } else if entry.access.can_read() {
+                                        readable_roots.push(path);
+                                    }
+                                }
+                            }
+                            FileSystemSpecialPathKind::Tmpdir => {
+                                if entry.access.can_write() {
+                                    tmpdir_writable = true;
+                                } else if entry.access.can_read()
+                                    && let Some(path) = resolve_file_system_special_path(
+                                        value,
+                                        cwd_absolute.as_ref(),
+                                    )
+                                {
+                                    readable_roots.push(path);
+                                }
+                            }
+                            FileSystemSpecialPathKind::SlashTmp => {
+                                if entry.access.can_write() {
+                                    slash_tmp_writable = true;
+                                } else if entry.access.can_read()
+                                    && let Some(path) = resolve_file_system_special_path(
+                                        value,
+                                        cwd_absolute.as_ref(),
+                                    )
+                                {
+                                    readable_roots.push(path);
+                                }
+                            }
+                        },
+                    }
+                }
+
+                if has_full_disk_write_access {
+                    return Ok(if network_policy.is_enabled() {
+                        SandboxPolicy::DangerFullAccess
+                    } else {
+                        SandboxPolicy::ExternalSandbox {
+                            network_access: NetworkAccess::Restricted,
+                        }
+                    });
+                }
+
+                let read_only_access = if has_full_disk_read_access {
+                    ReadOnlyAccess::FullAccess
+                } else {
+                    ReadOnlyAccess::Restricted {
+                        include_platform_defaults,
+                        readable_roots: dedup_absolute_paths(readable_roots),
+                    }
+                };
+
+                if workspace_root_writable {
+                    SandboxPolicy::WorkspaceWrite {
+                        writable_roots: dedup_absolute_paths(writable_roots),
+                        read_only_access,
+                        network_access: network_policy.is_enabled(),
+                        exclude_tmpdir_env_var: !tmpdir_writable,
+                        exclude_slash_tmp: !slash_tmp_writable,
+                    }
+                } else if !writable_roots.is_empty() || tmpdir_writable || slash_tmp_writable {
+                    return Err(io::Error::new(
+                        io::ErrorKind::InvalidInput,
+                        "permissions profile requests filesystem writes outside the workspace root, which is not supported until the runtime enforces FileSystemSandboxPolicy directly",
+                    ));
+                } else {
+                    SandboxPolicy::ReadOnly {
+                        access: read_only_access,
+                        network_access: network_policy.is_enabled(),
+                    }
+                }
+            }
+        })
+    }
+}
+
 fn default_include_platform_defaults() -> bool {
     true
 }
@@ -715,6 +1135,22 @@ impl FromStr for SandboxPolicy {
     }
 }
 
+impl FromStr for FileSystemSandboxPolicy {
+    type Err = serde_json::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        serde_json::from_str(s)
+    }
+}
+
+impl FromStr for NetworkSandboxPolicy {
+    type Err = serde_json::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        serde_json::from_str(s)
+    }
+}
+
 impl SandboxPolicy {
     /// Returns a policy with read-only disk access and no network.
     pub fn new_read_only_policy() -> Self {
@@ -877,45 +1313,11 @@ impl SandboxPolicy {
                 // For each root, compute subpaths that should remain read-only.
                 roots
                     .into_iter()
-                    .map(|writable_root| {
-                        let mut subpaths: Vec<AbsolutePathBuf> = Vec::new();
-                        #[allow(clippy::expect_used)]
-                        let top_level_git = writable_root
-                            .join(".git")
-                            .expect(".git is a valid relative path");
-                        // This applies to typical repos (directory .git), worktrees/submodules
-                        // (file .git with gitdir pointer), and bare repos when the gitdir is the
-                        // writable root itself.
-                        let top_level_git_is_file = top_level_git.as_path().is_file();
-                        let top_level_git_is_dir = top_level_git.as_path().is_dir();
-                        if top_level_git_is_dir || top_level_git_is_file {
-                            if top_level_git_is_file
-                                && is_git_pointer_file(&top_level_git)
-                                && let Some(gitdir) = resolve_gitdir_from_file(&top_level_git)
-                                && !subpaths
-                                    .iter()
-                                    .any(|subpath| subpath.as_path() == gitdir.as_path())
-                            {
-                                subpaths.push(gitdir);
-                            }
-                            subpaths.push(top_level_git);
-                        }
-
-                        // Make .agents/skills and .codex/config.toml and
-                        // related files read-only to the agent, by default.
-                        for subdir in &[".agents", ".codex"] {
-                            #[allow(clippy::expect_used)]
-                            let top_level_codex =
-                                writable_root.join(subdir).expect("valid relative path");
-                            if top_level_codex.as_path().is_dir() {
-                                subpaths.push(top_level_codex);
-                            }
-                        }
-
-                        WritableRoot {
-                            root: writable_root,
-                            read_only_subpaths: subpaths,
-                        }
+                    .map(|writable_root| WritableRoot {
+                        read_only_subpaths: default_read_only_subpaths_for_writable_root(
+                            &writable_root,
+                        ),
+                        root: writable_root,
                     })
                     .collect()
             }
@@ -923,6 +1325,268 @@ impl SandboxPolicy {
     }
 }
 
+impl From<&SandboxPolicy> for NetworkSandboxPolicy {
+    fn from(value: &SandboxPolicy) -> Self {
+        if value.has_full_network_access() {
+            NetworkSandboxPolicy::Enabled
+        } else {
+            NetworkSandboxPolicy::Restricted
+        }
+    }
+}
+
+impl From<&SandboxPolicy> for FileSystemSandboxPolicy {
+    fn from(value: &SandboxPolicy) -> Self {
+        match value {
+            SandboxPolicy::DangerFullAccess => FileSystemSandboxPolicy::unrestricted(),
+            SandboxPolicy::ExternalSandbox { .. } => FileSystemSandboxPolicy::external_sandbox(),
+            SandboxPolicy::ReadOnly { access, .. } => {
+                let mut entries = Vec::new();
+                match access {
+                    ReadOnlyAccess::FullAccess => entries.push(FileSystemSandboxEntry {
+                        path: FileSystemPath::Special {
+                            value: FileSystemSpecialPath {
+                                kind: FileSystemSpecialPathKind::Root,
+                                subpath: None,
+                            },
+                        },
+                        access: FileSystemAccessMode::Read,
+                    }),
+                    ReadOnlyAccess::Restricted {
+                        include_platform_defaults,
+                        readable_roots,
+                    } => {
+                        entries.push(FileSystemSandboxEntry {
+                            path: FileSystemPath::Special {
+                                value: FileSystemSpecialPath {
+                                    kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                                    subpath: None,
+                                },
+                            },
+                            access: FileSystemAccessMode::Read,
+                        });
+                        if *include_platform_defaults {
+                            entries.push(FileSystemSandboxEntry {
+                                path: FileSystemPath::Special {
+                                    value: FileSystemSpecialPath {
+                                        kind: FileSystemSpecialPathKind::Minimal,
+                                        subpath: None,
+                                    },
+                                },
+                                access: FileSystemAccessMode::Read,
+                            });
+                        }
+                        entries.extend(readable_roots.iter().cloned().map(|path| {
+                            FileSystemSandboxEntry {
+                                path: FileSystemPath::Path { path },
+                                access: FileSystemAccessMode::Read,
+                            }
+                        }));
+                    }
+                }
+                FileSystemSandboxPolicy::restricted(entries)
+            }
+            SandboxPolicy::WorkspaceWrite {
+                writable_roots,
+                read_only_access,
+                exclude_tmpdir_env_var,
+                exclude_slash_tmp,
+                ..
+            } => {
+                let mut entries = Vec::new();
+                match read_only_access {
+                    ReadOnlyAccess::FullAccess => entries.push(FileSystemSandboxEntry {
+                        path: FileSystemPath::Special {
+                            value: FileSystemSpecialPath {
+                                kind: FileSystemSpecialPathKind::Root,
+                                subpath: None,
+                            },
+                        },
+                        access: FileSystemAccessMode::Read,
+                    }),
+                    ReadOnlyAccess::Restricted {
+                        include_platform_defaults,
+                        readable_roots,
+                    } => {
+                        if *include_platform_defaults {
+                            entries.push(FileSystemSandboxEntry {
+                                path: FileSystemPath::Special {
+                                    value: FileSystemSpecialPath {
+                                        kind: FileSystemSpecialPathKind::Minimal,
+                                        subpath: None,
+                                    },
+                                },
+                                access: FileSystemAccessMode::Read,
+                            });
+                        }
+                        entries.extend(readable_roots.iter().cloned().map(|path| {
+                            FileSystemSandboxEntry {
+                                path: FileSystemPath::Path { path },
+                                access: FileSystemAccessMode::Read,
+                            }
+                        }));
+                    }
+                }
+
+                entries.push(FileSystemSandboxEntry {
+                    path: FileSystemPath::Special {
+                        value: FileSystemSpecialPath {
+                            kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                            subpath: None,
+                        },
+                    },
+                    access: FileSystemAccessMode::Write,
+                });
+                if !exclude_slash_tmp {
+                    entries.push(FileSystemSandboxEntry {
+                        path: FileSystemPath::Special {
+                            value: FileSystemSpecialPath {
+                                kind: FileSystemSpecialPathKind::SlashTmp,
+                                subpath: None,
+                            },
+                        },
+                        access: FileSystemAccessMode::Write,
+                    });
+                }
+                if !exclude_tmpdir_env_var {
+                    entries.push(FileSystemSandboxEntry {
+                        path: FileSystemPath::Special {
+                            value: FileSystemSpecialPath {
+                                kind: FileSystemSpecialPathKind::Tmpdir,
+                                subpath: None,
+                            },
+                        },
+                        access: FileSystemAccessMode::Write,
+                    });
+                }
+                entries.extend(
+                    writable_roots
+                        .iter()
+                        .cloned()
+                        .map(|path| FileSystemSandboxEntry {
+                            path: FileSystemPath::Path { path },
+                            access: FileSystemAccessMode::Write,
+                        }),
+                );
+                FileSystemSandboxPolicy::restricted(entries)
+            }
+        }
+    }
+}
+
+fn absolute_root_path_for_cwd(cwd: &AbsolutePathBuf) -> AbsolutePathBuf {
+    let root = cwd
+        .as_path()
+        .ancestors()
+        .last()
+        .unwrap_or_else(|| panic!("cwd must have a filesystem root"));
+    AbsolutePathBuf::from_absolute_path(root)
+        .unwrap_or_else(|err| panic!("cwd root must be an absolute path: {err}"))
+}
+
+fn resolve_file_system_path(
+    path: &FileSystemPath,
+    cwd: Option<&AbsolutePathBuf>,
+) -> Option<AbsolutePathBuf> {
+    match path {
+        FileSystemPath::Path { path } => Some(path.clone()),
+        FileSystemPath::Special { value } => resolve_file_system_special_path(value, cwd),
+    }
+}
+
+fn resolve_file_system_special_path(
+    value: &FileSystemSpecialPath,
+    cwd: Option<&AbsolutePathBuf>,
+) -> Option<AbsolutePathBuf> {
+    match value.kind {
+        FileSystemSpecialPathKind::Root | FileSystemSpecialPathKind::Minimal => None,
+        FileSystemSpecialPathKind::CurrentWorkingDirectory
+        | FileSystemSpecialPathKind::ProjectRoots => {
+            let cwd = cwd?;
+            match value.subpath.as_ref() {
+                Some(subpath) => {
+                    AbsolutePathBuf::resolve_path_against_base(subpath, cwd.as_path()).ok()
+                }
+                None => Some(cwd.clone()),
+            }
+        }
+        FileSystemSpecialPathKind::Tmpdir => {
+            let tmpdir = std::env::var_os("TMPDIR")?;
+            if tmpdir.is_empty() {
+                None
+            } else {
+                let tmpdir = AbsolutePathBuf::from_absolute_path(PathBuf::from(tmpdir)).ok()?;
+                match value.subpath.as_ref() {
+                    Some(subpath) => {
+                        AbsolutePathBuf::resolve_path_against_base(subpath, tmpdir.as_path()).ok()
+                    }
+                    None => Some(tmpdir),
+                }
+            }
+        }
+        FileSystemSpecialPathKind::SlashTmp => {
+            #[allow(clippy::expect_used)]
+            let slash_tmp = AbsolutePathBuf::from_absolute_path("/tmp").expect("/tmp is absolute");
+            if !slash_tmp.as_path().is_dir() {
+                return None;
+            }
+            match value.subpath.as_ref() {
+                Some(subpath) => {
+                    AbsolutePathBuf::resolve_path_against_base(subpath, slash_tmp.as_path()).ok()
+                }
+                None => Some(slash_tmp),
+            }
+        }
+    }
+}
+
+fn dedup_absolute_paths(paths: Vec<AbsolutePathBuf>) -> Vec<AbsolutePathBuf> {
+    let mut deduped = Vec::with_capacity(paths.len());
+    let mut seen = HashSet::new();
+    for path in paths {
+        if seen.insert(path.to_path_buf()) {
+            deduped.push(path);
+        }
+    }
+    deduped
+}
+
+fn default_read_only_subpaths_for_writable_root(
+    writable_root: &AbsolutePathBuf,
+) -> Vec<AbsolutePathBuf> {
+    let mut subpaths: Vec<AbsolutePathBuf> = Vec::new();
+    #[allow(clippy::expect_used)]
+    let top_level_git = writable_root
+        .join(".git")
+        .expect(".git is a valid relative path");
+    // This applies to typical repos (directory .git), worktrees/submodules
+    // (file .git with gitdir pointer), and bare repos when the gitdir is the
+    // writable root itself.
+    let top_level_git_is_file = top_level_git.as_path().is_file();
+    let top_level_git_is_dir = top_level_git.as_path().is_dir();
+    if top_level_git_is_dir || top_level_git_is_file {
+        if top_level_git_is_file
+            && is_git_pointer_file(&top_level_git)
+            && let Some(gitdir) = resolve_gitdir_from_file(&top_level_git)
+        {
+            subpaths.push(gitdir);
+        }
+        subpaths.push(top_level_git);
+    }
+
+    // Make .agents/skills and .codex/config.toml and related files read-only
+    // to the agent, by default.
+    for subdir in &[".agents", ".codex"] {
+        #[allow(clippy::expect_used)]
+        let top_level_codex = writable_root.join(subdir).expect("valid relative path");
+        if top_level_codex.as_path().is_dir() {
+            subpaths.push(top_level_codex);
+        }
+    }
+
+    dedup_absolute_paths(subpaths)
+}
+
 fn is_git_pointer_file(path: &AbsolutePathBuf) -> bool {
     path.as_path().is_file() && path.as_path().file_name() == Some(OsStr::new(".git"))
 }
@@ -3121,6 +3785,7 @@ mod tests {
     use pretty_assertions::assert_eq;
     use serde_json::json;
     use tempfile::NamedTempFile;
+    use tempfile::TempDir;
 
     #[test]
     fn external_sandbox_reports_full_access_flags() {
@@ -3201,6 +3866,193 @@ mod tests {
         }
     }
 
+    #[test]
+    fn restricted_file_system_policy_reports_full_access_from_root_entries() {
+        let read_only = FileSystemSandboxPolicy::restricted(vec![FileSystemSandboxEntry {
+            path: FileSystemPath::Special {
+                value: FileSystemSpecialPath {
+                    kind: FileSystemSpecialPathKind::Root,
+                    subpath: None,
+                },
+            },
+            access: FileSystemAccessMode::Read,
+        }]);
+        assert!(read_only.has_full_disk_read_access());
+        assert!(!read_only.has_full_disk_write_access());
+        assert!(!read_only.include_platform_defaults());
+
+        let writable = FileSystemSandboxPolicy::restricted(vec![FileSystemSandboxEntry {
+            path: FileSystemPath::Special {
+                value: FileSystemSpecialPath {
+                    kind: FileSystemSpecialPathKind::Root,
+                    subpath: None,
+                },
+            },
+            access: FileSystemAccessMode::Write,
+        }]);
+        assert!(writable.has_full_disk_read_access());
+        assert!(writable.has_full_disk_write_access());
+    }
+
+    #[test]
+    fn restricted_file_system_policy_treats_root_with_carveouts_as_scoped_access() {
+        let cwd = TempDir::new().expect("tempdir");
+        let cwd_absolute =
+            AbsolutePathBuf::from_absolute_path(cwd.path()).expect("absolute tempdir");
+        let root = absolute_root_path_for_cwd(&cwd_absolute);
+        let blocked = AbsolutePathBuf::resolve_path_against_base("blocked", cwd.path())
+            .expect("resolve blocked");
+        let policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::Root,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Write,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                        subpath: Some(PathBuf::from("blocked")),
+                    },
+                },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        assert!(!policy.has_full_disk_read_access());
+        assert!(!policy.has_full_disk_write_access());
+        assert_eq!(
+            policy.get_readable_roots_with_cwd(cwd.path()),
+            vec![root.clone()]
+        );
+        assert_eq!(
+            policy.get_unreadable_roots_with_cwd(cwd.path()),
+            vec![blocked.clone()]
+        );
+
+        let writable_roots = policy.get_writable_roots_with_cwd(cwd.path());
+        assert_eq!(writable_roots.len(), 1);
+        assert_eq!(writable_roots[0].root, root);
+        assert!(
+            writable_roots[0]
+                .read_only_subpaths
+                .iter()
+                .any(|path| path.as_path() == blocked.as_path())
+        );
+    }
+
+    #[test]
+    fn restricted_file_system_policy_derives_effective_paths() {
+        let cwd = TempDir::new().expect("tempdir");
+        std::fs::create_dir_all(cwd.path().join(".agents")).expect("create .agents");
+        std::fs::create_dir_all(cwd.path().join(".codex")).expect("create .codex");
+        let cwd_absolute =
+            AbsolutePathBuf::from_absolute_path(cwd.path()).expect("absolute tempdir");
+        let secret = AbsolutePathBuf::resolve_path_against_base("secret", cwd.path())
+            .expect("resolve unreadable path");
+        let agents = AbsolutePathBuf::resolve_path_against_base(".agents", cwd.path())
+            .expect("resolve .agents");
+        let codex = AbsolutePathBuf::resolve_path_against_base(".codex", cwd.path())
+            .expect("resolve .codex");
+        let policy = FileSystemSandboxPolicy::restricted(vec![
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::Minimal,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Read,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                        subpath: None,
+                    },
+                },
+                access: FileSystemAccessMode::Write,
+            },
+            FileSystemSandboxEntry {
+                path: FileSystemPath::Special {
+                    value: FileSystemSpecialPath {
+                        kind: FileSystemSpecialPathKind::CurrentWorkingDirectory,
+                        subpath: Some(PathBuf::from("secret")),
+                    },
+                },
+                access: FileSystemAccessMode::None,
+            },
+        ]);
+
+        assert!(!policy.has_full_disk_read_access());
+        assert!(!policy.has_full_disk_write_access());
+        assert!(policy.include_platform_defaults());
+        assert_eq!(
+            policy.get_readable_roots_with_cwd(cwd.path()),
+            vec![cwd_absolute]
+        );
+        assert_eq!(
+            policy.get_unreadable_roots_with_cwd(cwd.path()),
+            vec![secret.clone()]
+        );
+
+        let writable_roots = policy.get_writable_roots_with_cwd(cwd.path());
+        assert_eq!(writable_roots.len(), 1);
+        assert_eq!(writable_roots[0].root.as_path(), cwd.path());
+        assert!(
+            writable_roots[0]
+                .read_only_subpaths
+                .iter()
+                .any(|path| path.as_path() == secret.as_path())
+        );
+        assert!(
+            writable_roots[0]
+                .read_only_subpaths
+                .iter()
+                .any(|path| path.as_path() == agents.as_path())
+        );
+        assert!(
+            writable_roots[0]
+                .read_only_subpaths
+                .iter()
+                .any(|path| path.as_path() == codex.as_path())
+        );
+    }
+
+    #[test]
+    fn file_system_policy_rejects_legacy_bridge_for_non_workspace_writes() {
+        let cwd = if cfg!(windows) {
+            Path::new(r"C:\workspace")
+        } else {
+            Path::new("/tmp/workspace")
+        };
+        let external_write_path = if cfg!(windows) {
+            AbsolutePathBuf::from_absolute_path(r"C:\temp").expect("absolute windows temp path")
+        } else {
+            AbsolutePathBuf::from_absolute_path("/tmp").expect("absolute tmp path")
+        };
+        let policy = FileSystemSandboxPolicy::restricted(vec![FileSystemSandboxEntry {
+            path: FileSystemPath::Path {
+                path: external_write_path,
+            },
+            access: FileSystemAccessMode::Write,
+        }]);
+
+        let err = policy
+            .to_legacy_sandbox_policy(NetworkSandboxPolicy::Restricted, cwd)
+            .expect_err("non-workspace writes should be rejected");
+
+        assert!(
+            err.to_string()
+                .contains("filesystem writes outside the workspace root"),
+            "{err}"
+        );
+    }
+
     #[test]
     fn item_started_event_from_web_search_emits_begin_event() {
         let event = ItemStartedEvent {