extension: move git attribution into an extension

codex-rs/Cargo.lock

@@ -1895,11 +1895,13 @@ dependencies = [
  "codex-core",
  "codex-core-plugins",
  "codex-exec-server",
+ "codex-extension-api",
  "codex-external-agent-migration",
  "codex-external-agent-sessions",
  "codex-features",
  "codex-feedback",
  "codex-file-search",
+ "codex-git-attribution",
  "codex-git-utils",
  "codex-hooks",
  "codex-login",
@@ -2471,6 +2473,7 @@ dependencies = [
  "codex-core-skills",
  "codex-exec-server",
  "codex-execpolicy",
+ "codex-extension-api",
  "codex-features",
  "codex-feedback",
  "codex-git-utils",
@@ -2575,6 +2578,7 @@ dependencies = [
  "codex-config",
  "codex-core",
  "codex-exec-server",
+ "codex-extension-api",
  "codex-features",
  "codex-login",
  "codex-model-provider-info",
@@ -2792,6 +2796,16 @@ dependencies = [
  "syn 2.0.114",
 ]
 
+[[package]]
+name = "codex-extension-api"
+version = "0.0.0"
+dependencies = [
+ "codex-protocol",
+ "codex-tools",
+ "serde_json",
+ "thiserror 2.0.18",
+]
+
 [[package]]
 name = "codex-external-agent-migration"
 version = "0.0.0"
@@ -2870,6 +2884,15 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "codex-git-attribution"
+version = "0.0.0"
+dependencies = [
+ "codex-core",
+ "codex-extension-api",
+ "codex-features",
+]
+
 [[package]]
 name = "codex-git-utils"
 version = "0.0.0"
@@ -3055,6 +3078,7 @@ dependencies = [
  "codex-config",
  "codex-core",
  "codex-exec-server",
+ "codex-extension-api",
  "codex-login",
  "codex-protocol",
  "codex-shell-command",
@@ -4263,6 +4287,7 @@ dependencies = [
  "codex-config",
  "codex-core",
  "codex-exec-server",
+ "codex-extension-api",
  "codex-features",
  "codex-hooks",
  "codex-login",

codex-rs/Cargo.toml

@@ -44,6 +44,8 @@ members = [
     "exec-server",
     "execpolicy",
     "execpolicy-legacy",
+    "ext/extension-api",
+    "ext/git-attribution",
     "external-agent-migration",
     "external-agent-sessions",
     "keyring-store",
@@ -157,6 +159,8 @@ codex-exec = { path = "exec" }
 codex-file-system = { path = "file-system" }
 codex-exec-server = { path = "exec-server" }
 codex-execpolicy = { path = "execpolicy" }
+codex-extension-api = { path = "ext/extension-api" }
+codex-git-attribution = { path = "ext/git-attribution" }
 codex-external-agent-migration = { path = "external-agent-migration" }
 codex-external-agent-sessions = { path = "external-agent-sessions" }
 codex-experimental-api-macros = { path = "codex-experimental-api-macros" }
@@ -464,6 +468,7 @@ unwrap_used = "deny"
 [workspace.metadata.cargo-shear]
 ignored = [
     "codex-agent-graph-store",
+    "codex-extension-api",
     "codex-memories-mcp",
     "icu_provider",
     "openssl-sys",

codex-rs/app-server/Cargo.toml

@@ -37,9 +37,11 @@ codex-config = { workspace = true }
 codex-core = { workspace = true }
 codex-core-plugins = { workspace = true }
 codex-exec-server = { workspace = true }
+codex-extension-api = { workspace = true }
 codex-external-agent-migration = { workspace = true }
 codex-external-agent-sessions = { workspace = true }
 codex-features = { workspace = true }
+codex-git-attribution = { workspace = true }
 codex-git-utils = { workspace = true }
 codex-hooks = { workspace = true }
 codex-otel = { workspace = true }

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

@@ -0,0 +1,13 @@
+use std::sync::Arc;
+
+use codex_core::config::Config;
+use codex_extension_api::ExtensionRegistry;
+use codex_extension_api::ExtensionRegistryBuilder;
+
+pub(crate) fn thread_extensions() -> Arc<ExtensionRegistry<Config>> {
+    Arc::new(
+        ExtensionRegistryBuilder::<Config>::new()
+            .with_extension(codex_git_attribution::extension())
+            .build(),
+    )
+}

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

@@ -82,6 +82,7 @@ mod config_manager_service;
 mod connection_rpc_gate;
 mod dynamic_tools;
 mod error_code;
+mod extensions;
 mod filters;
 mod fs_watch;
 mod fuzzy_file_search;

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

@@ -99,6 +99,7 @@ async fn queue_refresh(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::extensions::thread_extensions;
     use async_trait::async_trait;
     use codex_arg0::Arg0DispatchPaths;
     use codex_config::CloudRequirementsLoader;
@@ -183,6 +184,7 @@ mod tests {
             auth_manager,
             SessionSource::Exec,
             Arc::new(EnvironmentManager::default_for_tests()),
+            thread_extensions(),
             /*analytics_events_client*/ None,
             thread_store,
             Some(state_db.clone()),

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

@@ -7,6 +7,7 @@ use std::sync::atomic::AtomicBool;
 use crate::config_manager::ConfigManager;
 use crate::connection_rpc_gate::ConnectionRpcGate;
 use crate::error_code::invalid_request;
+use crate::extensions::thread_extensions;
 use crate::fs_watch::FsWatchManager;
 use crate::outgoing_message::ConnectionId;
 use crate::outgoing_message::ConnectionRequestId;
@@ -289,6 +290,7 @@ impl MessageProcessor {
             auth_manager.clone(),
             session_source,
             environment_manager,
+            thread_extensions(),
             Some(analytics_events_client.clone()),
             Arc::clone(&thread_store),
             state_db.clone(),

codex-rs/core-api/Cargo.toml

@@ -19,6 +19,7 @@ codex-arg0 = { workspace = true }
 codex-analytics = { workspace = true }
 codex-config = { workspace = true }
 codex-core = { workspace = true }
+codex-extension-api = { workspace = true }
 codex-exec-server = { workspace = true }
 codex-features = { workspace = true }
 codex-login = { workspace = true }

codex-rs/core-api/src/lib.rs

@@ -46,6 +46,7 @@ pub use codex_core::thread_store_from_config;
 pub use codex_exec_server::EnvironmentManager;
 pub use codex_exec_server::EnvironmentManagerArgs;
 pub use codex_exec_server::ExecServerRuntimePaths;
+pub use codex_extension_api::empty_extension_registry;
 pub use codex_features::Feature;
 pub use codex_features::Features;
 pub use codex_login::AuthManager;

codex-rs/core/Cargo.toml

@@ -35,6 +35,7 @@ codex-config = { workspace = true }
 codex-core-plugins = { workspace = true }
 codex-core-skills = { workspace = true }
 codex-exec-server = { workspace = true }
+codex-extension-api = { workspace = true }
 codex-features = { workspace = true }
 codex-feedback = { workspace = true }
 codex-login = { workspace = true }

codex-rs/core/src/codex_delegate.rs

@@ -83,6 +83,7 @@ pub(crate) async fn run_codex_thread_interactive(
         skills_manager: Arc::clone(&parent_session.services.skills_manager),
         plugins_manager: Arc::clone(&parent_session.services.plugins_manager),
         mcp_manager: Arc::clone(&parent_session.services.mcp_manager),
+        extensions: Arc::clone(&parent_session.services.extensions),
         skills_watcher: Arc::clone(&parent_session.services.skills_watcher),
         conversation_history: initial_history.unwrap_or(InitialHistory::New),
         session_source: SessionSource::SubAgent(subagent_source.clone()),

codex-rs/core/src/commit_attribution.rs

@@ -1,33 +0,0 @@
-const DEFAULT_ATTRIBUTION_VALUE: &str = "Codex <noreply@openai.com>";
-
-fn build_commit_message_trailer(config_attribution: Option<&str>) -> Option<String> {
-    let value = resolve_attribution_value(config_attribution)?;
-    Some(format!("Co-authored-by: {value}"))
-}
-
-pub(crate) fn commit_message_trailer_instruction(
-    config_attribution: Option<&str>,
-) -> Option<String> {
-    let trailer = build_commit_message_trailer(config_attribution)?;
-    Some(format!(
-        "When you write or edit a git commit message, ensure the message ends with this trailer exactly once:\n{trailer}\n\nRules:\n- Keep existing trailers and append this trailer at the end if missing.\n- Do not duplicate this trailer if it already exists.\n- Keep one blank line between the commit body and trailer block."
-    ))
-}
-
-fn resolve_attribution_value(config_attribution: Option<&str>) -> Option<String> {
-    match config_attribution {
-        Some(value) => {
-            let trimmed = value.trim();
-            if trimmed.is_empty() {
-                None
-            } else {
-                Some(trimmed.to_string())
-            }
-        }
-        None => Some(DEFAULT_ATTRIBUTION_VALUE.to_string()),
-    }
-}
-
-#[cfg(test)]
-#[path = "commit_attribution_tests.rs"]
-mod tests;

codex-rs/core/src/commit_attribution_tests.rs

@@ -1,43 +0,0 @@
-use super::build_commit_message_trailer;
-use super::commit_message_trailer_instruction;
-use super::resolve_attribution_value;
-
-#[test]
-fn blank_attribution_disables_trailer_prompt() {
-    assert_eq!(build_commit_message_trailer(Some("")), None);
-    assert_eq!(commit_message_trailer_instruction(Some("   ")), None);
-}
-
-#[test]
-fn default_attribution_uses_codex_trailer() {
-    assert_eq!(
-        build_commit_message_trailer(/*config_attribution*/ None).as_deref(),
-        Some("Co-authored-by: Codex <noreply@openai.com>")
-    );
-}
-
-#[test]
-fn resolve_value_handles_default_custom_and_blank() {
-    assert_eq!(
-        resolve_attribution_value(/*config_attribution*/ None),
-        Some("Codex <noreply@openai.com>".to_string())
-    );
-    assert_eq!(
-        resolve_attribution_value(Some("MyAgent <me@example.com>")),
-        Some("MyAgent <me@example.com>".to_string())
-    );
-    assert_eq!(
-        resolve_attribution_value(Some("MyAgent")),
-        Some("MyAgent".to_string())
-    );
-    assert_eq!(resolve_attribution_value(Some("   ")), None);
-}
-
-#[test]
-fn instruction_mentions_trailer_and_omits_generated_with() {
-    let instruction = commit_message_trailer_instruction(Some("AgentX <agent@example.com>"))
-        .expect("instruction expected");
-    assert!(instruction.contains("Co-authored-by: AgentX <agent@example.com>"));
-    assert!(instruction.contains("exactly once"));
-    assert!(!instruction.contains("Generated-with"));
-}

codex-rs/core/src/lib.rs

@@ -22,10 +22,10 @@ mod config_lock;
 pub use codex_thread::CodexThread;
 pub use codex_thread::CodexThreadTurnContextOverrides;
 pub use codex_thread::ThreadConfigSnapshot;
+pub use session::turn_context::TurnContext;
 mod agent;
 mod codex_delegate;
 mod command_canonicalization;
-mod commit_attribution;
 pub mod config;
 pub mod connectors;
 pub mod context;

codex-rs/core/src/prompt_debug.rs

@@ -20,6 +20,7 @@ use crate::session::turn::built_tools;
 use crate::state_db_bridge::StateDbHandle;
 use crate::thread_manager::ThreadManager;
 use crate::thread_manager::thread_store_from_config;
+use codex_extension_api::empty_extension_registry;
 
 /// Build the model-visible `input` list for a single debug turn.
 #[doc(hidden)]
@@ -45,6 +46,7 @@ pub async fn build_prompt_input(
         Arc::clone(&auth_manager),
         SessionSource::Exec,
         Arc::new(EnvironmentManager::new(EnvironmentManagerArgs::new(local_runtime_paths)).await),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store,
         state_db.clone(),

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

@@ -15,7 +15,6 @@ use crate::agent::MailboxReceiver;
 use crate::agent::agent_status_from_event;
 use crate::agent::status::is_final;
 use crate::build_available_skills;
-use crate::commit_attribution::commit_message_trailer_instruction;
 use crate::compact;
 use crate::config::ManagedFeatures;
 use crate::config::resolve_tool_suggest_config_from_layer_stack;
@@ -52,6 +51,7 @@ use codex_config::types::OAuthCredentialsStoreMode;
 use codex_exec_server::Environment;
 use codex_exec_server::EnvironmentManager;
 use codex_exec_server::FileSystemSandboxContext;
+use codex_extension_api::PromptSlot;
 use codex_features::FEATURES;
 use codex_features::Feature;
 use codex_features::unstable_features_warning_event;
@@ -392,6 +392,7 @@ pub(crate) struct CodexSpawnArgs {
     pub(crate) skills_manager: Arc<SkillsManager>,
     pub(crate) plugins_manager: Arc<PluginsManager>,
     pub(crate) mcp_manager: Arc<McpManager>,
+    pub(crate) extensions: Arc<codex_extension_api::ExtensionRegistry<crate::config::Config>>,
     pub(crate) skills_watcher: Arc<SkillsWatcher>,
     pub(crate) conversation_history: InitialHistory,
     pub(crate) session_source: SessionSource,
@@ -455,6 +456,7 @@ impl Codex {
             skills_manager,
             plugins_manager,
             mcp_manager,
+            extensions,
             skills_watcher,
             conversation_history,
             session_source,
@@ -650,6 +652,7 @@ impl Codex {
             skills_manager,
             plugins_manager,
             mcp_manager.clone(),
+            extensions,
             skills_watcher,
             agent_control,
             environment_manager,
@@ -2588,6 +2591,7 @@ impl Session {
     ) -> Vec<ResponseItem> {
         let mut developer_sections = Vec::<String>::with_capacity(8);
         let mut contextual_user_sections = Vec::<String>::with_capacity(2);
+        let mut separate_developer_sections = Vec::<String>::new();
         let (
             reference_context_item,
             previous_turn_settings,
@@ -2725,12 +2729,23 @@ impl Session {
         {
             developer_sections.push(plugin_instructions.render());
         }
-        if turn_context.features.enabled(Feature::CodexGitCommit)
-            && let Some(commit_message_instruction) = commit_message_trailer_instruction(
-                turn_context.config.commit_attribution.as_deref(),
-            )
-        {
-            developer_sections.push(commit_message_instruction);
+        for contributor in self.services.extensions.context_contributors() {
+            for fragment in contributor.contribute(
+                &self.services.session_extension_data,
+                &self.services.thread_extension_data,
+            ) {
+                match fragment.slot() {
+                    PromptSlot::DeveloperPolicy | PromptSlot::DeveloperCapabilities => {
+                        developer_sections.push(fragment.text().to_string());
+                    }
+                    PromptSlot::ContextualUser => {
+                        contextual_user_sections.push(fragment.text().to_string());
+                    }
+                    PromptSlot::SeparateDeveloper => {
+                        separate_developer_sections.push(fragment.text().to_string());
+                    }
+                }
+            }
         }
         if let Some(user_instructions) = turn_context.user_instructions.as_deref() {
             contextual_user_sections.push(
@@ -2764,6 +2779,13 @@ impl Session {
         {
             items.push(developer_message);
         }
+        for section in separate_developer_sections {
+            if let Some(developer_message) =
+                crate::context_manager::updates::build_developer_update_item(vec![section])
+            {
+                items.push(developer_message);
+            }
+        }
         if let Some(usage_hint_text) = multi_agent_v2_usage_hint_text
             && let Some(usage_hint_message) =
                 crate::context_manager::updates::build_developer_update_item(vec![

codex-rs/core/src/session/session.rs

@@ -364,6 +364,7 @@ impl Session {
         skills_manager: Arc<SkillsManager>,
         plugins_manager: Arc<PluginsManager>,
         mcp_manager: Arc<McpManager>,
+        extensions: Arc<codex_extension_api::ExtensionRegistry<crate::config::Config>>,
         skills_watcher: Arc<SkillsWatcher>,
         agent_control: AgentControl,
         environment_manager: Arc<EnvironmentManager>,
@@ -810,6 +811,16 @@ impl Session {
                 SessionId::from(thread_id)
             };
             let agent_control = agent_control.with_session_id(session_id);
+            let session_extension_data = codex_extension_api::ExtensionData::new();
+            let thread_extension_data = codex_extension_api::ExtensionData::new();
+            for contributor in extensions.thread_start_contributors() {
+                contributor.contribute(
+                    config.as_ref(),
+                    &session_extension_data,
+                    &thread_extension_data,
+                );
+            }
+
             let services = SessionServices {
                 // Initialize the MCP connection manager with an uninitialized
                 // instance. It will be replaced with one created via
@@ -845,6 +856,10 @@ impl Session {
                 skills_manager,
                 plugins_manager: Arc::clone(&plugins_manager),
                 mcp_manager: Arc::clone(&mcp_manager),
+                extensions,
+                // TODO(jif): extract session to share between sub-agents
+                session_extension_data,
+                thread_extension_data,
                 skills_watcher,
                 agent_control,
                 network_proxy,

codex-rs/core/src/session/tests.rs

@@ -3724,6 +3724,7 @@ async fn session_new_fails_when_zsh_fork_enabled_without_zsh_path() {
         skills_manager,
         plugins_manager,
         mcp_manager,
+        Arc::new(codex_extension_api::ExtensionRegistryBuilder::new().build()),
         Arc::new(SkillsWatcher::noop()),
         AgentControl::default(),
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
@@ -3871,6 +3872,9 @@ pub(crate) async fn make_session_and_context() -> (Session, TurnContext) {
         skills_manager,
         plugins_manager,
         mcp_manager,
+        extensions: Arc::new(codex_extension_api::ExtensionRegistryBuilder::new().build()),
+        session_extension_data: codex_extension_api::ExtensionData::new(),
+        thread_extension_data: codex_extension_api::ExtensionData::new(),
         skills_watcher,
         agent_control,
         network_proxy: None,
@@ -4060,6 +4064,7 @@ async fn make_session_with_config_and_rx(
         skills_manager,
         plugins_manager,
         mcp_manager,
+        Arc::new(codex_extension_api::ExtensionRegistryBuilder::new().build()),
         Arc::new(SkillsWatcher::noop()),
         AgentControl::default(),
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
@@ -4162,6 +4167,7 @@ async fn make_session_with_history_source_and_agent_control_and_rx(
         skills_manager,
         plugins_manager,
         mcp_manager,
+        Arc::new(codex_extension_api::ExtensionRegistryBuilder::new().build()),
         Arc::new(SkillsWatcher::noop()),
         agent_control,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
@@ -5586,6 +5592,9 @@ where
         skills_manager,
         plugins_manager,
         mcp_manager,
+        extensions: Arc::new(codex_extension_api::ExtensionRegistryBuilder::new().build()),
+        session_extension_data: codex_extension_api::ExtensionData::new(),
+        thread_extension_data: codex_extension_api::ExtensionData::new(),
         skills_watcher,
         agent_control,
         network_proxy: None,
@@ -6132,6 +6141,73 @@ async fn make_multi_agent_v2_usage_hint_test_session(
     (session, turn_context)
 }
 
+struct GitAttributionTestContributor;
+struct GitAttributionTestState;
+
+impl codex_extension_api::ContextContributor for GitAttributionTestContributor {
+    fn contribute(
+        &self,
+        _session_store: &codex_extension_api::ExtensionData,
+        thread_store: &codex_extension_api::ExtensionData,
+    ) -> Vec<codex_extension_api::PromptFragment> {
+        thread_store
+            .get::<GitAttributionTestState>()
+            .is_some()
+            .then(|| {
+                codex_extension_api::PromptFragment::developer_policy(
+                    "git attribution extension enabled",
+                )
+            })
+            .into_iter()
+            .collect()
+    }
+}
+
+fn git_attribution_test_registry()
+-> Arc<codex_extension_api::ExtensionRegistry<crate::config::Config>> {
+    let mut builder = codex_extension_api::ExtensionRegistryBuilder::new();
+    builder.prompt_contributor(Arc::new(GitAttributionTestContributor));
+    Arc::new(builder.build())
+}
+
+#[tokio::test]
+async fn build_initial_context_includes_git_attribution_from_extensions() {
+    let (mut session, turn_context) = make_session_and_context().await;
+    session.services.extensions = git_attribution_test_registry();
+    session
+        .services
+        .thread_extension_data
+        .insert(GitAttributionTestState);
+
+    let initial_context = session.build_initial_context(&turn_context).await;
+    let developer_messages = developer_message_texts(&initial_context);
+
+    assert!(
+        developer_messages
+            .iter()
+            .flatten()
+            .any(|text| *text == "git attribution extension enabled"),
+        "expected git attribution developer text, got {developer_messages:?}"
+    );
+}
+
+#[tokio::test]
+async fn build_initial_context_omits_git_attribution_when_feature_is_disabled() {
+    let (mut session, turn_context) = make_session_and_context().await;
+    session.services.extensions = git_attribution_test_registry();
+
+    let initial_context = session.build_initial_context(&turn_context).await;
+    let developer_messages = developer_message_texts(&initial_context);
+
+    assert!(
+        !developer_messages
+            .iter()
+            .flatten()
+            .any(|text| *text == "git attribution extension enabled"),
+        "did not expect git attribution developer text, got {developer_messages:?}"
+    );
+}
+
 #[tokio::test]
 async fn build_initial_context_adds_multi_agent_v2_root_usage_hint_as_developer_message() {
     let (session, turn_context) =

codex-rs/core/src/session/tests/guardian_tests.rs

@@ -743,6 +743,7 @@ async fn guardian_subagent_does_not_inherit_parent_exec_policy_rules() {
         skills_manager,
         plugins_manager,
         mcp_manager,
+        extensions: codex_extension_api::empty_extension_registry(),
         skills_watcher,
         conversation_history: InitialHistory::New,
         session_source: SessionSource::SubAgent(SubAgentSource::Other(

codex-rs/core/src/session/turn_context.rs

@@ -52,11 +52,11 @@ impl TurnEnvironment {
 
 /// The context needed for a single turn of the thread.
 #[derive(Debug)]
-pub(crate) struct TurnContext {
+pub struct TurnContext {
     pub(crate) sub_id: String,
     pub(crate) trace_id: Option<String>,
     pub(crate) realtime_active: bool,
-    pub(crate) config: Arc<Config>,
+    pub config: Arc<Config>,
     pub(crate) auth_manager: Option<Arc<AuthManager>>,
     pub(crate) model_info: ModelInfo,
     pub(crate) session_telemetry: SessionTelemetry,
@@ -84,7 +84,7 @@ pub(crate) struct TurnContext {
     pub(crate) windows_sandbox_level: WindowsSandboxLevel,
     pub(crate) shell_environment_policy: ShellEnvironmentPolicy,
     pub(crate) tools_config: ToolsConfig,
-    pub(crate) features: ManagedFeatures,
+    pub features: ManagedFeatures,
     pub(crate) ghost_snapshot: GhostSnapshotConfig,
     pub(crate) final_output_json_schema: Option<Value>,
     pub(crate) codex_self_exe: Option<PathBuf>,

codex-rs/core/src/state/service.rs

@@ -18,6 +18,8 @@ use arc_swap::ArcSwap;
 use codex_analytics::AnalyticsEventsClient;
 use codex_core_plugins::PluginsManager;
 use codex_exec_server::EnvironmentManager;
+use codex_extension_api::ExtensionData;
+use codex_extension_api::ExtensionRegistry;
 use codex_hooks::Hooks;
 use codex_login::AuthManager;
 use codex_mcp::McpConnectionManager;
@@ -59,6 +61,9 @@ pub(crate) struct SessionServices {
     pub(crate) skills_manager: Arc<SkillsManager>,
     pub(crate) plugins_manager: Arc<PluginsManager>,
     pub(crate) mcp_manager: Arc<McpManager>,
+    pub(crate) extensions: Arc<ExtensionRegistry<crate::config::Config>>,
+    pub(crate) session_extension_data: ExtensionData,
+    pub(crate) thread_extension_data: ExtensionData,
     pub(crate) skills_watcher: Arc<SkillsWatcher>,
     pub(crate) agent_control: AgentControl,
     pub(crate) network_proxy: Option<StartedNetworkProxy>,

codex-rs/core/src/thread_manager.rs

@@ -22,6 +22,8 @@ use codex_app_server_protocol::ThreadHistoryBuilder;
 use codex_app_server_protocol::TurnStatus;
 use codex_core_plugins::PluginsManager;
 use codex_exec_server::EnvironmentManager;
+use codex_extension_api::ExtensionRegistry;
+use codex_extension_api::empty_extension_registry;
 use codex_login::AuthManager;
 use codex_login::CodexAuth;
 use codex_model_provider::create_model_provider;
@@ -246,6 +248,7 @@ pub(crate) struct ThreadManagerState {
     skills_manager: Arc<SkillsManager>,
     plugins_manager: Arc<PluginsManager>,
     mcp_manager: Arc<McpManager>,
+    extensions: Arc<ExtensionRegistry<Config>>,
     skills_watcher: Arc<SkillsWatcher>,
     thread_store: Arc<dyn ThreadStore>,
     session_source: SessionSource,
@@ -287,6 +290,7 @@ impl ThreadManager {
         auth_manager: Arc<AuthManager>,
         session_source: SessionSource,
         environment_manager: Arc<EnvironmentManager>,
+        extensions: Arc<ExtensionRegistry<Config>>,
         analytics_events_client: Option<AnalyticsEventsClient>,
         thread_store: Arc<dyn ThreadStore>,
         state_db: Option<StateDbHandle>,
@@ -315,6 +319,7 @@ impl ThreadManager {
                 skills_manager,
                 plugins_manager,
                 mcp_manager,
+                extensions,
                 skills_watcher,
                 thread_store,
                 auth_manager,
@@ -416,6 +421,7 @@ impl ThreadManager {
                 skills_manager,
                 plugins_manager,
                 mcp_manager,
+                extensions: empty_extension_registry(),
                 skills_watcher,
                 thread_store,
                 auth_manager,
@@ -1188,6 +1194,7 @@ impl ThreadManagerState {
             skills_manager: Arc::clone(&self.skills_manager),
             plugins_manager: Arc::clone(&self.plugins_manager),
             mcp_manager: Arc::clone(&self.mcp_manager),
+            extensions: Arc::clone(&self.extensions),
             skills_watcher: Arc::clone(&self.skills_watcher),
             conversation_history: initial_history,
             session_source,

codex-rs/core/src/thread_manager_tests.rs

@@ -7,6 +7,7 @@ use crate::session::session::SessionSettingsUpdate;
 use crate::session::tests::make_session_and_context;
 use crate::tasks::InterruptedTurnHistoryMarker;
 use crate::tasks::interrupted_turn_history_marker;
+use codex_extension_api::empty_extension_registry;
 use codex_features::Feature;
 use codex_models_manager::manager::RefreshStrategy;
 use codex_protocol::models::ContentItem;
@@ -397,6 +398,7 @@ async fn resume_and_fork_do_not_restore_thread_environments_from_rollout() {
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, /*state_db*/ None),
         /*state_db*/ None,
@@ -513,6 +515,7 @@ async fn explicit_installation_id_skips_codex_home_file() {
         auth_manager,
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store,
         state_db.clone(),
@@ -550,6 +553,7 @@ async fn resume_active_thread_from_rollout_returns_running_thread() {
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, /*state_db*/ None),
         /*state_db*/ None,
@@ -605,6 +609,7 @@ async fn resume_stopped_thread_from_rollout_spawns_new_thread() {
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, /*state_db*/ None),
         /*state_db*/ None,
@@ -667,6 +672,7 @@ async fn resume_stopped_thread_from_rollout_preserves_thread_source() {
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store,
         state_db.clone(),
@@ -755,6 +761,7 @@ async fn rollout_path_resume_and_fork_read_history_through_thread_store() {
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store.clone(),
         state_db,
@@ -856,6 +863,7 @@ async fn new_uses_active_provider_for_model_refresh() {
         auth_manager,
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, /*state_db*/ None),
         /*state_db*/ None,
@@ -1070,6 +1078,7 @@ async fn interrupted_fork_snapshot_does_not_synthesize_turn_id_for_legacy_histor
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, state_db.clone()),
         state_db.clone(),
@@ -1176,6 +1185,7 @@ async fn interrupted_fork_snapshot_preserves_explicit_turn_id() {
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, state_db.clone()),
         state_db.clone(),
@@ -1271,6 +1281,7 @@ async fn interrupted_fork_snapshot_uses_persisted_mid_turn_history_without_live_
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, state_db.clone()),
         state_db.clone(),
@@ -1412,6 +1423,7 @@ async fn resumed_thread_keeps_paused_goal_paused() -> anyhow::Result<()> {
         auth_manager.clone(),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, state_db.clone()),
         state_db.clone(),

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

@@ -15,6 +15,7 @@ use crate::tools::handlers::multi_agents_v2::SendMessageHandler as SendMessageHa
 use crate::tools::handlers::multi_agents_v2::SpawnAgentHandler as SpawnAgentHandlerV2;
 use crate::tools::handlers::multi_agents_v2::WaitAgentHandler as WaitAgentHandlerV2;
 use crate::turn_diff_tracker::TurnDiffTracker;
+use codex_extension_api::empty_extension_registry;
 use codex_features::Feature;
 use codex_login::AuthManager;
 use codex_login::CodexAuth;
@@ -3163,6 +3164,7 @@ async fn tool_handlers_cascade_close_and_resume_and_keep_explicitly_closed_subtr
         AuthManager::from_auth_for_testing(CodexAuth::from_api_key("dummy")),
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, state_db.clone()),
         state_db.clone(),

codex-rs/core/tests/common/Cargo.toml

@@ -18,6 +18,7 @@ base64 = { workspace = true }
 codex-arg0 = { workspace = true }
 codex-config = { workspace = true }
 codex-core = { workspace = true }
+codex-extension-api = { workspace = true }
 codex-exec-server = { workspace = true }
 codex-features = { workspace = true }
 codex-hooks = { workspace = true }

codex-rs/core/tests/common/test_codex.rs

@@ -23,6 +23,7 @@ use codex_core::thread_store_from_config;
 use codex_exec_server::CreateDirectoryOptions;
 use codex_exec_server::ExecutorFileSystem;
 use codex_exec_server::RemoveOptions;
+use codex_extension_api::empty_extension_registry;
 use codex_features::Feature;
 use codex_login::CodexAuth;
 use codex_model_provider_info::ModelProviderInfo;
@@ -431,6 +432,7 @@ impl TestCodexBuilder {
             codex_core::test_support::auth_manager_from_auth(auth.clone()),
             SessionSource::Exec,
             Arc::clone(&environment_manager),
+            empty_extension_registry(),
             /*analytics_events_client*/ None,
             thread_store,
             state_db.clone(),

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

@@ -7,6 +7,7 @@ use codex_core::ResponseEvent;
 use codex_core::ThreadManager;
 use codex_core::resolve_installation_id;
 use codex_core::thread_store_from_config;
+use codex_extension_api::empty_extension_registry;
 use codex_features::Feature;
 use codex_login::AuthManager;
 use codex_login::CodexAuth;
@@ -1122,6 +1123,7 @@ async fn prefers_apikey_when_config_prefers_apikey_even_with_chatgpt_tokens() {
         auth_manager,
         SessionSource::Exec,
         Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         thread_store_from_config(&config, /*state_db*/ None),
         /*state_db*/ None,

codex-rs/ext/extension-api/BUILD.bazel

@@ -0,0 +1,6 @@
+load("//:defs.bzl", "codex_rust_crate")
+
+codex_rust_crate(
+    name = "extension-api",
+    crate_name = "codex_extension_api",
+)

codex-rs/ext/extension-api/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+edition.workspace = true
+license.workspace = true
+name = "codex-extension-api"
+version.workspace = true
+
+[lib]
+name = "codex_extension_api"
+path = "src/lib.rs"
+
+[lints]
+workspace = true
+
+[dependencies]
+codex-protocol = { workspace = true }
+codex-tools = { workspace = true }
+serde_json = { workspace = true }
+thiserror = { workspace = true }

codex-rs/ext/extension-api/examples/enabled_extensions.rs

@@ -0,0 +1,68 @@
+#[path = "enabled_extensions/shared_state_extension.rs"]
+mod shared_state_extension;
+
+use std::sync::Arc;
+
+use codex_extension_api::ExtensionData;
+use codex_extension_api::ExtensionRegistryBuilder;
+use shared_state_extension::SharedStateExtension;
+use shared_state_extension::recorded_style_contributions;
+use shared_state_extension::recorded_usage_contributions;
+
+fn main() {
+    // 1. Build the extension value owned by the host.
+    let extension = Arc::new(SharedStateExtension);
+
+    // 2. Install it into the registry for the thread-start input type this host exposes.
+    let registry = ExtensionRegistryBuilder::<()>::new()
+        .with_extension(extension)
+        .build();
+
+    // 3. The host decides which stores are shared.
+    let session_store = ExtensionData::new();
+    let first_thread_store = ExtensionData::new();
+    let second_thread_store = ExtensionData::new();
+
+    // 4. Reusing the same session store shares session state across threads.
+    let first_thread_fragments = contribute_prompt(&registry, &session_store, &first_thread_store);
+    contribute_prompt(&registry, &session_store, &first_thread_store);
+    contribute_prompt(&registry, &session_store, &second_thread_store);
+
+    println!("first prompt fragments: {}", first_thread_fragments.len());
+    println!(
+        "session style contributions: {}",
+        recorded_style_contributions(&session_store)
+    );
+    println!(
+        "session usage contributions: {}",
+        recorded_usage_contributions(&session_store)
+    );
+    println!(
+        "first thread style contributions: {}",
+        recorded_style_contributions(&first_thread_store)
+    );
+    println!(
+        "first thread usage contributions: {}",
+        recorded_usage_contributions(&first_thread_store)
+    );
+    println!(
+        "second thread style contributions: {}",
+        recorded_style_contributions(&second_thread_store)
+    );
+    println!(
+        "second thread usage contributions: {}",
+        recorded_usage_contributions(&second_thread_store)
+    );
+}
+
+fn contribute_prompt(
+    registry: &codex_extension_api::ExtensionRegistry<()>,
+    session_store: &ExtensionData,
+    thread_store: &ExtensionData,
+) -> Vec<codex_extension_api::PromptFragment> {
+    registry
+        .context_contributors()
+        .iter()
+        .flat_map(|contributor| contributor.contribute(session_store, thread_store))
+        .collect()
+}

codex-rs/ext/extension-api/examples/enabled_extensions/shared_state_extension.rs

@@ -0,0 +1,100 @@
+use std::sync::Arc;
+use std::sync::atomic::AtomicU64;
+use std::sync::atomic::Ordering;
+
+use codex_extension_api::CodexExtension;
+use codex_extension_api::ContextContributor;
+use codex_extension_api::ExtensionData;
+use codex_extension_api::ExtensionRegistryBuilder;
+use codex_extension_api::PromptFragment;
+
+/// Small tutorial extension that installs two prompt contributors.
+#[derive(Debug, Default)]
+pub struct SharedStateExtension;
+
+impl CodexExtension<()> for SharedStateExtension {
+    fn install(self: Arc<Self>, registry: &mut ExtensionRegistryBuilder<()>) {
+        registry.prompt_contributor(Arc::new(StyleContributor));
+        registry.prompt_contributor(Arc::new(UsageContributor));
+    }
+}
+
+#[derive(Debug)]
+struct StyleContributor;
+
+impl ContextContributor for StyleContributor {
+    fn contribute(
+        &self,
+        session_store: &ExtensionData,
+        thread_store: &ExtensionData,
+    ) -> Vec<PromptFragment> {
+        contribution_counts(session_store).record_style();
+        contribution_counts(thread_store).record_style();
+
+        vec![PromptFragment::developer_policy(
+            "Prefer short answers unless the user asks for detail.",
+        )]
+    }
+}
+
+#[derive(Debug)]
+struct UsageContributor;
+
+impl ContextContributor for UsageContributor {
+    fn contribute(
+        &self,
+        session_store: &ExtensionData,
+        thread_store: &ExtensionData,
+    ) -> Vec<PromptFragment> {
+        contribution_counts(session_store).record_usage();
+        contribution_counts(thread_store).record_usage();
+
+        vec![PromptFragment::developer_capability(
+            "This extension can contribute more than one prompt fragment.",
+        )]
+    }
+}
+
+/// Returns how many style contributions were recorded in `store`.
+pub fn recorded_style_contributions(store: &ExtensionData) -> u64 {
+    store
+        .get::<ContributionCounts>()
+        .map(|counts| counts.style())
+        .unwrap_or_default()
+}
+
+/// Returns how many usage contributions were recorded in `store`.
+pub fn recorded_usage_contributions(store: &ExtensionData) -> u64 {
+    store
+        .get::<ContributionCounts>()
+        .map(|counts| counts.usage())
+        .unwrap_or_default()
+}
+
+#[derive(Debug, Default)]
+struct ContributionCounts {
+    style: AtomicU64,
+    usage: AtomicU64,
+}
+
+impl ContributionCounts {
+    fn record_style(&self) {
+        self.style.fetch_add(1, Ordering::Relaxed);
+    }
+
+    fn record_usage(&self) {
+        self.usage.fetch_add(1, Ordering::Relaxed);
+    }
+
+    fn style(&self) -> u64 {
+        self.style.load(Ordering::Relaxed)
+    }
+
+    fn usage(&self) -> u64 {
+        self.usage.load(Ordering::Relaxed)
+    }
+}
+
+fn contribution_counts(store: &ExtensionData) -> Arc<ContributionCounts> {
+    store.get_or_init::<ContributionCounts>(Default::default)
+}

codex-rs/ext/extension-api/notes.md

@@ -0,0 +1,14 @@
+Everything becomes a good contributor design, which contributors do we need?
+
+git attribution              Context
+memories                     Context + Tool + Output
+guardian                     Context + Request
+goal                         Tool + Runtime
+image generation             Tool + Output
+skills                       Context + Turn
+personality                  Context
+plugins / apps / connectors  Context + Turn
+shell snapshot               Runtime
+web search                   Tool
+AGENTS.md                    Context   (Runtime too only if you want eager refresh/cache behavior)
+future sandboxing            probably Request + Runtime

codex-rs/ext/extension-api/src/contributors.rs

@@ -0,0 +1,65 @@
+use std::future::Future;
+
+use codex_protocol::items::TurnItem;
+
+use crate::ExtensionData;
+
+mod prompt;
+mod tool;
+
+pub use prompt::PromptFragment;
+pub use prompt::PromptSlot;
+pub use tool::ToolCallError;
+pub use tool::ToolContribution;
+pub use tool::ToolHandler;
+
+/// Contributor that receives host-owned thread-start input before later
+/// contributors read from extension stores.
+pub trait ThreadStartContributor<C>: Send + Sync {
+    fn contribute(&self, input: &C, session_store: &ExtensionData, thread_store: &ExtensionData);
+}
+
+/// Extension contribution that adds prompt fragments during prompt assembly.
+pub trait ContextContributor: Send + Sync {
+    fn contribute(
+        &self,
+        session_store: &ExtensionData,
+        thread_store: &ExtensionData,
+    ) -> Vec<PromptFragment>;
+}
+
+/// Extension contribution that exposes native tools owned by a feature.
+pub trait ToolContributor: Send + Sync {
+    /// Returns the native tools visible for the supplied runtime context.
+    fn tools(&self, thread_store: &ExtensionData) -> Vec<ToolContribution>;
+}
+
+/// Future returned by one ordered turn-item contribution.
+pub type TurnItemContributionFuture<'a> =
+    std::pin::Pin<Box<dyn Future<Output = Result<(), String>> + Send + 'a>>;
+
+/// Ordered post-processing contribution for one parsed turn item.
+///
+/// Implementations may mutate the item before it is emitted and may use the
+/// explicitly exposed thread- and turn-lifetime stores when they need durable
+/// extension-private state.
+pub trait TurnItemContributor: Send + Sync {
+    fn contribute<'a>(
+        &'a self,
+        thread_store: &'a ExtensionData,
+        turn_store: &'a ExtensionData,
+        item: &'a mut TurnItem,
+    ) -> TurnItemContributionFuture<'a>;
+}
+
+// TODO: WIP (do not consider)
+/// Extension contribution that can claim approval requests for a runtime context.
+/// (ideally we can replace it by a session lifecycle thing or a request contributor?)
+pub trait ApprovalInterceptorContributor: Send + Sync {
+    /// Returns whether this contributor should intercept approvals in `context`.
+    fn intercepts_approvals(
+        &self,
+        thread_store: &ExtensionData,
+        turn_store: &ExtensionData,
+    ) -> bool;
+}

codex-rs/ext/extension-api/src/contributors/prompt.rs

@@ -0,0 +1,50 @@
+// All this file should be replaced by the existing fragment implementation ofc
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum PromptSlot {
+    DeveloperPolicy,
+    DeveloperCapabilities,
+    ContextualUser,
+    SeparateDeveloper,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PromptFragment {
+    slot: PromptSlot,
+    text: String,
+}
+
+impl PromptFragment {
+    /// Creates a prompt fragment for the given slot.
+    pub fn new(slot: PromptSlot, text: impl Into<String>) -> Self {
+        Self {
+            slot,
+            text: text.into(),
+        }
+    }
+
+    /// Creates a developer-policy prompt fragment.
+    pub fn developer_policy(text: impl Into<String>) -> Self {
+        Self::new(PromptSlot::DeveloperPolicy, text)
+    }
+
+    /// Creates a developer-capabilities prompt fragment.
+    pub fn developer_capability(text: impl Into<String>) -> Self {
+        Self::new(PromptSlot::DeveloperCapabilities, text)
+    }
+
+    /// Creates a separate top-level developer prompt fragment.
+    pub fn separate_developer(text: impl Into<String>) -> Self {
+        Self::new(PromptSlot::SeparateDeveloper, text)
+    }
+
+    /// Returns the target prompt slot.
+    pub fn slot(&self) -> PromptSlot {
+        self.slot
+    }
+
+    /// Returns the model-visible text.
+    pub fn text(&self) -> &str {
+        &self.text
+    }
+}

codex-rs/ext/extension-api/src/contributors/tool.rs

@@ -0,0 +1,68 @@
+use std::future::Future;
+use std::pin::Pin;
+use std::sync::Arc;
+
+use codex_tools::ResponsesApiTool;
+use serde_json::Value;
+use thiserror::Error;
+
+// TMP while we don't have the fully extracted tools
+#[derive(Clone)]
+pub struct ToolContribution {
+    spec: ResponsesApiTool,
+    handler: Arc<dyn ToolHandler>,
+    supports_parallel_tool_calls: bool,
+}
+
+impl ToolContribution {
+    pub fn new(spec: ResponsesApiTool, handler: Arc<dyn ToolHandler>) -> Self {
+        Self {
+            spec,
+            handler,
+            supports_parallel_tool_calls: false,
+        }
+    }
+
+    #[must_use]
+    pub fn allow_parallel_calls(mut self) -> Self {
+        self.supports_parallel_tool_calls = true;
+        self
+    }
+
+    pub fn spec(&self) -> &ResponsesApiTool {
+        &self.spec
+    }
+
+    pub fn supports_parallel_tool_calls(&self) -> bool {
+        self.supports_parallel_tool_calls
+    }
+
+    pub fn handler(&self) -> Arc<dyn ToolHandler> {
+        Arc::clone(&self.handler)
+    }
+}
+
+//////// Just to make it compile ////////////////////////////////
+pub trait ToolHandler: Send + Sync {
+    /// Handles one JSON-encoded invocation for this tool.
+    fn handle<'a>(
+        &'a self,
+        arguments: Value,
+    ) -> Pin<Box<dyn Future<Output = Result<Value, ToolCallError>> + Send + 'a>>;
+}
+
+/// Error returned by a contributed native tool handler.
+#[derive(Clone, Debug, Error, PartialEq, Eq)]
+#[error("{message}")]
+pub struct ToolCallError {
+    message: String,
+}
+
+impl ToolCallError {
+    /// Creates a contributed-tool error with the supplied model-visible text.
+    pub fn new(message: impl Into<String>) -> Self {
+        Self {
+            message: message.into(),
+        }
+    }
+}

codex-rs/ext/extension-api/src/extension.rs

@@ -0,0 +1,12 @@
+use std::sync::Arc;
+
+use crate::ExtensionRegistryBuilder;
+
+/// First-party extension that can install one or more typed runtime contributions.
+///
+/// Implementations should use [`Self::install`] only to register the concrete
+/// providers they own.
+pub trait CodexExtension<C>: Send + Sync {
+    /// Registers this extension's concrete typed contributions.
+    fn install(self: Arc<Self>, registry: &mut ExtensionRegistryBuilder<C>);
+}

codex-rs/ext/extension-api/src/lib.rs

@@ -0,0 +1,21 @@
+mod contributors;
+mod extension;
+mod registry;
+mod state;
+
+pub use contributors::ApprovalInterceptorContributor;
+pub use contributors::ContextContributor;
+pub use contributors::PromptFragment;
+pub use contributors::PromptSlot;
+pub use contributors::ThreadStartContributor;
+pub use contributors::ToolCallError;
+pub use contributors::ToolContribution;
+pub use contributors::ToolContributor;
+pub use contributors::ToolHandler;
+pub use contributors::TurnItemContributionFuture;
+pub use contributors::TurnItemContributor;
+pub use extension::CodexExtension;
+pub use registry::ExtensionRegistry;
+pub use registry::ExtensionRegistryBuilder;
+pub use registry::empty_extension_registry;
+pub use state::ExtensionData;

codex-rs/ext/extension-api/src/registry.rs

@@ -0,0 +1,134 @@
+use std::sync::Arc;
+
+use crate::ApprovalInterceptorContributor;
+use crate::CodexExtension;
+use crate::ContextContributor;
+use crate::ThreadStartContributor;
+use crate::ToolContributor;
+use crate::TurnItemContributor;
+
+/// Mutable registry used while extensions install their typed contributions.
+pub struct ExtensionRegistryBuilder<C> {
+    thread_start_contributors: Vec<Arc<dyn ThreadStartContributor<C>>>,
+    context_contributors: Vec<Arc<dyn ContextContributor>>,
+    tool_contributors: Vec<Arc<dyn ToolContributor>>,
+    turn_item_contributors: Vec<Arc<dyn TurnItemContributor>>,
+    approval_interceptor_contributors: Vec<Arc<dyn ApprovalInterceptorContributor>>,
+}
+
+impl<C> Default for ExtensionRegistryBuilder<C> {
+    fn default() -> Self {
+        Self {
+            thread_start_contributors: Vec::new(),
+            approval_interceptor_contributors: Vec::new(),
+            context_contributors: Vec::new(),
+            tool_contributors: Vec::new(),
+            turn_item_contributors: Vec::new(),
+        }
+    }
+}
+
+impl<C> ExtensionRegistryBuilder<C> {
+    /// Creates an empty registry builder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Installs one extension and returns the builder.
+    #[must_use]
+    pub fn with_extension<E>(mut self, extension: Arc<E>) -> Self
+    where
+        E: CodexExtension<C> + 'static,
+    {
+        self.install_extension(extension);
+        self
+    }
+
+    /// Installs one extension into the registry under construction.
+    pub fn install_extension<E>(&mut self, extension: Arc<E>)
+    where
+        E: CodexExtension<C> + 'static,
+    {
+        extension.install(self);
+    }
+
+    /// Registers one approval interceptor contributor.
+    pub fn approval_interceptor_contributor(
+        &mut self,
+        contributor: Arc<dyn ApprovalInterceptorContributor>,
+    ) {
+        self.approval_interceptor_contributors.push(contributor);
+    }
+
+    /// Registers one thread-start contributor.
+    pub fn thread_start_contributor(&mut self, contributor: Arc<dyn ThreadStartContributor<C>>) {
+        self.thread_start_contributors.push(contributor);
+    }
+
+    /// Registers one prompt contributor.
+    pub fn prompt_contributor(&mut self, contributor: Arc<dyn ContextContributor>) {
+        self.context_contributors.push(contributor);
+    }
+
+    /// Registers one native tool contributor.
+    pub fn tool_contributor(&mut self, contributor: Arc<dyn ToolContributor>) {
+        self.tool_contributors.push(contributor);
+    }
+
+    /// Registers one ordered turn-item contributor.
+    pub fn turn_item_contributor(&mut self, contributor: Arc<dyn TurnItemContributor>) {
+        self.turn_item_contributors.push(contributor);
+    }
+
+    /// Finishes construction and returns the immutable registry.
+    pub fn build(self) -> ExtensionRegistry<C> {
+        ExtensionRegistry {
+            thread_start_contributors: self.thread_start_contributors,
+            approval_interceptor_contributors: self.approval_interceptor_contributors,
+            context_contributors: self.context_contributors,
+            tool_contributors: self.tool_contributors,
+            turn_item_contributors: self.turn_item_contributors,
+        }
+    }
+}
+
+/// Immutable typed registry produced after extensions are installed.
+pub struct ExtensionRegistry<C> {
+    thread_start_contributors: Vec<Arc<dyn ThreadStartContributor<C>>>,
+    context_contributors: Vec<Arc<dyn ContextContributor>>,
+    tool_contributors: Vec<Arc<dyn ToolContributor>>,
+    turn_item_contributors: Vec<Arc<dyn TurnItemContributor>>,
+    approval_interceptor_contributors: Vec<Arc<dyn ApprovalInterceptorContributor>>,
+}
+
+impl<C> ExtensionRegistry<C> {
+    /// Returns the registered thread-start contributors.
+    pub fn thread_start_contributors(&self) -> &[Arc<dyn ThreadStartContributor<C>>] {
+        &self.thread_start_contributors
+    }
+
+    /// Returns the registered approval interceptor contributors.
+    pub fn approval_interceptor_contributors(&self) -> &[Arc<dyn ApprovalInterceptorContributor>] {
+        &self.approval_interceptor_contributors
+    }
+
+    /// Returns the registered prompt contributors.
+    pub fn context_contributors(&self) -> &[Arc<dyn ContextContributor>] {
+        &self.context_contributors
+    }
+
+    /// Returns the registered native tool contributors.
+    pub fn tool_contributors(&self) -> &[Arc<dyn ToolContributor>] {
+        &self.tool_contributors
+    }
+
+    /// Returns the registered ordered turn-item contributors.
+    pub fn turn_item_contributors(&self) -> &[Arc<dyn TurnItemContributor>] {
+        &self.turn_item_contributors
+    }
+}
+
+/// Creates an empty shared registry for hosts that do not install extensions.
+pub fn empty_extension_registry<C>() -> Arc<ExtensionRegistry<C>> {
+    Arc::new(ExtensionRegistryBuilder::new().build())
+}

codex-rs/ext/extension-api/src/state.rs

@@ -0,0 +1,77 @@
+use std::any::Any;
+use std::any::TypeId;
+use std::collections::HashMap;
+use std::sync::Arc;
+use std::sync::Mutex;
+use std::sync::PoisonError;
+
+type ErasedData = Arc<dyn Any + Send + Sync>;
+
+/// Typed extension-owned data attached to one host object.
+#[derive(Default, Debug)]
+pub struct ExtensionData {
+    entries: Mutex<HashMap<TypeId, ErasedData>>,
+}
+
+impl ExtensionData {
+    /// Creates an empty attachment map.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Returns the attached value of type `T`, if one exists.
+    pub fn get<T>(&self) -> Option<Arc<T>>
+    where
+        T: Any + Send + Sync,
+    {
+        let value = self.entries().get(&TypeId::of::<T>())?.clone();
+        Some(downcast_data(value))
+    }
+
+    /// Returns the attached value of type `T`, inserting one from `init` when absent.
+    ///
+    /// The initializer runs while this map is locked, so it should stay cheap;
+    /// heavyweight lazy work belongs inside the attached value itself.
+    pub fn get_or_init<T>(&self, init: impl FnOnce() -> T) -> Arc<T>
+    where
+        T: Any + Send + Sync,
+    {
+        let mut entries = self.entries();
+        let value = entries
+            .entry(TypeId::of::<T>())
+            .or_insert_with(|| Arc::new(init()));
+        downcast_data(Arc::clone(value))
+    }
+
+    /// Stores `value` as the attachment of type `T`, returning any previous value.
+    pub fn insert<T>(&self, value: T) -> Option<Arc<T>>
+    where
+        T: Any + Send + Sync,
+    {
+        self.entries()
+            .insert(TypeId::of::<T>(), Arc::new(value))
+            .map(downcast_data)
+    }
+
+    /// Removes and returns the attached value of type `T`, if one exists.
+    pub fn remove<T>(&self) -> Option<Arc<T>>
+    where
+        T: Any + Send + Sync,
+    {
+        self.entries().remove(&TypeId::of::<T>()).map(downcast_data)
+    }
+
+    fn entries(&self) -> std::sync::MutexGuard<'_, HashMap<TypeId, ErasedData>> {
+        self.entries.lock().unwrap_or_else(PoisonError::into_inner)
+    }
+}
+
+fn downcast_data<T>(value: ErasedData) -> Arc<T>
+where
+    T: Any + Send + Sync,
+{
+    let Ok(value) = value.downcast::<T>() else {
+        unreachable!("typed extension data stored an incompatible value");
+    };
+    value
+}

codex-rs/ext/git-attribution/BUILD.bazel

@@ -0,0 +1,6 @@
+load("//:defs.bzl", "codex_rust_crate")
+
+codex_rust_crate(
+    name = "git-attribution",
+    crate_name = "codex_git_attribution",
+)

codex-rs/ext/git-attribution/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+edition.workspace = true
+license.workspace = true
+name = "codex-git-attribution"
+version.workspace = true
+
+[lib]
+name = "codex_git_attribution"
+path = "src/lib.rs"
+
+[lints]
+workspace = true
+
+[dependencies]
+codex-core = { workspace = true }
+codex-extension-api = { workspace = true }
+codex-features = { workspace = true }

codex-rs/ext/git-attribution/src/lib.rs

@@ -0,0 +1,100 @@
+use std::sync::Arc;
+
+use codex_core::config::Config;
+use codex_extension_api::CodexExtension;
+use codex_extension_api::ContextContributor;
+use codex_extension_api::ExtensionData;
+use codex_extension_api::ExtensionRegistryBuilder;
+use codex_extension_api::PromptFragment;
+use codex_extension_api::ThreadStartContributor;
+use codex_features::Feature;
+
+const DEFAULT_ATTRIBUTION_VALUE: &str = "Codex <noreply@openai.com>";
+
+/// Prompt-only extension that contributes the configured git-attribution instruction.
+#[derive(Clone, Copy, Debug, Default)]
+pub struct GitAttributionExtension;
+
+impl GitAttributionExtension {
+    /// Creates an extension instance.
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl ContextContributor for GitAttributionExtension {
+    fn contribute(
+        &self,
+        _session_store: &ExtensionData,
+        thread_store: &ExtensionData,
+    ) -> Vec<PromptFragment> {
+        let Some(config_store) = thread_store.get::<GitAttributionConfig>() else {
+            return Vec::new();
+        };
+        if !config_store.enabled {
+            return Vec::new();
+        }
+        build_instruction(config_store.prompt.as_deref())
+            .map(PromptFragment::developer_policy)
+            .into_iter()
+            .collect()
+    }
+}
+
+#[derive(Clone, Debug, Default)]
+struct GitAttributionConfig {
+    enabled: bool,
+    prompt: Option<String>,
+}
+
+impl ThreadStartContributor<Config> for GitAttributionExtension {
+    fn contribute(
+        &self,
+        config: &Config,
+        _session_store: &ExtensionData,
+        thread_store: &ExtensionData,
+    ) {
+        thread_store.insert(GitAttributionConfig {
+            enabled: config.features.enabled(Feature::CodexGitCommit),
+            prompt: config.commit_attribution.clone(),
+        });
+    }
+}
+
+impl CodexExtension<Config> for GitAttributionExtension {
+    fn install(self: Arc<Self>, registry: &mut ExtensionRegistryBuilder<Config>) {
+        registry.thread_start_contributor(self.clone());
+        registry.prompt_contributor(self);
+    }
+}
+
+/// Creates a shared git-attribution extension instance.
+pub fn extension() -> Arc<GitAttributionExtension> {
+    Arc::new(GitAttributionExtension::new())
+}
+
+fn build_commit_message_trailer(config_attribution: Option<&str>) -> Option<String> {
+    let value = resolve_attribution_value(config_attribution)?;
+    Some(format!("Co-authored-by: {value}"))
+}
+
+fn build_instruction(config_attribution: Option<&str>) -> Option<String> {
+    let trailer = build_commit_message_trailer(config_attribution)?;
+    Some(format!(
+        "When you write or edit a git commit message, ensure the message ends with this trailer exactly once:\n{trailer}\n\nRules:\n- Keep existing trailers and append this trailer at the end if missing.\n- Do not duplicate this trailer if it already exists.\n- Keep one blank line between the commit body and trailer block."
+    ))
+}
+
+fn resolve_attribution_value(config_attribution: Option<&str>) -> Option<String> {
+    match config_attribution {
+        Some(value) => {
+            let trimmed = value.trim();
+            if trimmed.is_empty() {
+                None
+            } else {
+                Some(trimmed.to_string())
+            }
+        }
+        None => Some(DEFAULT_ATTRIBUTION_VALUE.to_string()),
+    }
+}

codex-rs/mcp-server/Cargo.toml

@@ -22,6 +22,7 @@ codex-arg0 = { workspace = true }
 codex-config = { workspace = true }
 codex-core = { workspace = true }
 codex-exec-server = { workspace = true }
+codex-extension-api = { workspace = true }
 codex-login = { workspace = true }
 codex-protocol = { workspace = true }
 codex-utils-cli = { workspace = true }

codex-rs/mcp-server/src/message_processor.rs

@@ -7,6 +7,7 @@ use codex_core::ThreadManager;
 use codex_core::config::Config;
 use codex_core::thread_store_from_config;
 use codex_exec_server::EnvironmentManager;
+use codex_extension_api::empty_extension_registry;
 use codex_login::AuthManager;
 use codex_login::default_client::USER_AGENT_SUFFIX;
 use codex_login::default_client::get_codex_user_agent;
@@ -68,6 +69,7 @@ impl MessageProcessor {
             auth_manager,
             SessionSource::Mcp,
             environment_manager,
+            empty_extension_registry(),
             /*analytics_events_client*/ None,
             thread_store_from_config(config.as_ref(), state_db.clone()),
             state_db.clone(),

codex-rs/thread-manager-sample/src/main.rs

@@ -54,6 +54,7 @@ use codex_core_api::UserInput;
 use codex_core_api::WebSearchMode;
 use codex_core_api::arg0_dispatch_or_else;
 use codex_core_api::built_in_model_providers;
+use codex_core_api::empty_extension_registry;
 use codex_core_api::find_codex_home;
 use codex_core_api::init_state_db;
 use codex_core_api::item_event_to_server_notification;
@@ -122,6 +123,7 @@ async fn run_main(arg0_paths: Arg0DispatchPaths) -> anyhow::Result<()> {
         auth_manager,
         SessionSource::Exec,
         environment_manager,
+        empty_extension_registry(),
         /*analytics_events_client*/ None,
         Arc::clone(&thread_store),
         state_db,