diff --git a/codex-rs/config/src/lenient.rs b/codex-rs/config/src/lenient.rs
new file mode 100644
index 0000000000..0c60e79677
--- /dev/null
+++ b/codex-rs/config/src/lenient.rs
@@ -0,0 +1,563 @@
+use crate::config_toml::RealtimeTransport;
+use crate::config_toml::RealtimeWsMode;
+use crate::config_toml::RealtimeWsVersion;
+use crate::permissions_toml::NetworkDomainPermissionToml;
+use crate::permissions_toml::NetworkUnixSocketPermissionToml;
+use crate::types::AppToolApproval;
+use crate::types::AuthCredentialsStoreMode;
+use crate::types::NotificationCondition;
+use crate::types::NotificationMethod;
+use crate::types::OAuthCredentialsStoreMode;
+use crate::types::OtelExporterKind;
+use crate::types::OtelHttpProtocol;
+use crate::types::UriBasedFileOpener;
+use crate::types::WindowsSandboxModeToml;
+use codex_protocol::config_types::AltScreenMode;
+use codex_protocol::config_types::ApprovalsReviewer;
+use codex_protocol::config_types::ForcedLoginMethod;
+use codex_protocol::config_types::Personality;
+use codex_protocol::config_types::ReasoningSummary;
+use codex_protocol::config_types::SandboxMode;
+use codex_protocol::config_types::ServiceTier;
+use codex_protocol::config_types::ShellEnvironmentPolicyInherit;
+use codex_protocol::config_types::TrustLevel;
+use codex_protocol::config_types::Verbosity;
+use codex_protocol::config_types::WebSearchContextSize;
+use codex_protocol::config_types::WebSearchMode;
+use codex_protocol::config_types::WebSearchUserLocationType;
+use codex_protocol::openai_models::ReasoningEffort;
+use codex_protocol::protocol::AskForApproval;
+use serde::Deserialize;
+use serde::de::DeserializeOwned;
+use toml::Value as TomlValue;
+use toml::map::Map as TomlMap;
+
+#[derive(Deserialize)]
+#[serde(untagged)]
+enum Lenient<T> {
+    Success(T),
+    Failure,
+}
+
+pub(crate) fn sanitize_config_toml_enums(
+    value: &mut TomlValue,
+    source: impl Into<String>,
+) -> Vec<String> {
+    let source = source.into();
+    let mut warnings = Vec::new();
+    let Some(table) = value.as_table_mut() else {
+        return warnings;
+    };
+
+    sanitize_config_table(table, &source, &mut warnings);
+    warnings
+}
+
+fn sanitize_config_table(
+    table: &mut TomlMap<String, TomlValue>,
+    source: &str,
+    warnings: &mut Vec<String>,
+) {
+    remove_invalid_enum::<AskForApproval>(
+        table,
+        "approval_policy",
+        "approval_policy",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<ApprovalsReviewer>(
+        table,
+        "approvals_reviewer",
+        "approvals_reviewer",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<SandboxMode>(table, "sandbox_mode", "sandbox_mode", source, warnings);
+    remove_invalid_enum::<ReasoningEffort>(
+        table,
+        "model_reasoning_effort",
+        "model_reasoning_effort",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<ReasoningEffort>(
+        table,
+        "plan_mode_reasoning_effort",
+        "plan_mode_reasoning_effort",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<ReasoningSummary>(
+        table,
+        "model_reasoning_summary",
+        "model_reasoning_summary",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<Verbosity>(
+        table,
+        "model_verbosity",
+        "model_verbosity",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<Personality>(table, "personality", "personality", source, warnings);
+    remove_invalid_enum::<ServiceTier>(table, "service_tier", "service_tier", source, warnings);
+    remove_invalid_enum::<ForcedLoginMethod>(
+        table,
+        "forced_login_method",
+        "forced_login_method",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<AuthCredentialsStoreMode>(
+        table,
+        "cli_auth_credentials_store",
+        "cli_auth_credentials_store",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<OAuthCredentialsStoreMode>(
+        table,
+        "mcp_oauth_credentials_store",
+        "mcp_oauth_credentials_store",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<UriBasedFileOpener>(
+        table,
+        "file_opener",
+        "file_opener",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<ThreadStoreProbe>(
+        table,
+        "experimental_thread_store",
+        "experimental_thread_store",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<WebSearchMode>(table, "web_search", "web_search", source, warnings);
+    if let Some(tui) = table.get_mut("tui").and_then(TomlValue::as_table_mut) {
+        remove_invalid_enum::<NotificationMethod>(
+            tui,
+            "notification_method",
+            "tui.notification_method",
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<NotificationCondition>(
+            tui,
+            "notification_condition",
+            "tui.notification_condition",
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<AltScreenMode>(
+            tui,
+            "alternate_screen",
+            "tui.alternate_screen",
+            source,
+            warnings,
+        );
+    }
+
+    if let Some(shell) = table
+        .get_mut("shell_environment_policy")
+        .and_then(TomlValue::as_table_mut)
+    {
+        remove_invalid_enum::<ShellEnvironmentPolicyInherit>(
+            shell,
+            "inherit",
+            "shell_environment_policy.inherit",
+            source,
+            warnings,
+        );
+    }
+
+    if let Some(windows) = table.get_mut("windows").and_then(TomlValue::as_table_mut) {
+        remove_invalid_enum::<WindowsSandboxModeToml>(
+            windows,
+            "sandbox",
+            "windows.sandbox",
+            source,
+            warnings,
+        );
+    }
+
+    if let Some(realtime) = table.get_mut("realtime").and_then(TomlValue::as_table_mut) {
+        remove_invalid_enum::<RealtimeWsVersion>(
+            realtime,
+            "version",
+            "realtime.version",
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<RealtimeWsMode>(realtime, "type", "realtime.type", source, warnings);
+        remove_invalid_enum::<RealtimeTransport>(
+            realtime,
+            "transport",
+            "realtime.transport",
+            source,
+            warnings,
+        );
+    }
+
+    if let Some(web_search_tool) = table
+        .get_mut("tools")
+        .and_then(TomlValue::as_table_mut)
+        .and_then(|tools| tools.get_mut("web_search"))
+        .and_then(TomlValue::as_table_mut)
+    {
+        remove_invalid_enum::<WebSearchContextSize>(
+            web_search_tool,
+            "search_context_size",
+            "tools.web_search.search_context_size",
+            source,
+            warnings,
+        );
+        if let Some(user_location) = web_search_tool
+            .get_mut("user_location")
+            .and_then(TomlValue::as_table_mut)
+        {
+            remove_invalid_enum::<WebSearchUserLocationType>(
+                user_location,
+                "type",
+                "tools.web_search.user_location.type",
+                source,
+                warnings,
+            );
+        }
+    }
+
+    if let Some(projects) = table.get_mut("projects").and_then(TomlValue::as_table_mut) {
+        for (name, project) in projects {
+            if let Some(project) = project.as_table_mut() {
+                remove_invalid_enum::<TrustLevel>(
+                    project,
+                    "trust_level",
+                    &format!("projects.{name}.trust_level"),
+                    source,
+                    warnings,
+                );
+            }
+        }
+    }
+
+    sanitize_profiles(table, source, warnings);
+    sanitize_permissions(table, source, warnings);
+    sanitize_mcp_servers(table, source, warnings);
+    sanitize_plugins(table, source, warnings);
+    sanitize_otel(table, source, warnings);
+}
+
+fn sanitize_profiles(
+    table: &mut TomlMap<String, TomlValue>,
+    source: &str,
+    warnings: &mut Vec<String>,
+) {
+    let Some(profiles) = table.get_mut("profiles").and_then(TomlValue::as_table_mut) else {
+        return;
+    };
+    for (name, profile) in profiles {
+        let Some(profile) = profile.as_table_mut() else {
+            continue;
+        };
+        remove_invalid_enum::<ServiceTier>(
+            profile,
+            "service_tier",
+            &format!("profiles.{name}.service_tier"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<AskForApproval>(
+            profile,
+            "approval_policy",
+            &format!("profiles.{name}.approval_policy"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<ApprovalsReviewer>(
+            profile,
+            "approvals_reviewer",
+            &format!("profiles.{name}.approvals_reviewer"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<SandboxMode>(
+            profile,
+            "sandbox_mode",
+            &format!("profiles.{name}.sandbox_mode"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<ReasoningEffort>(
+            profile,
+            "model_reasoning_effort",
+            &format!("profiles.{name}.model_reasoning_effort"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<ReasoningEffort>(
+            profile,
+            "plan_mode_reasoning_effort",
+            &format!("profiles.{name}.plan_mode_reasoning_effort"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<ReasoningSummary>(
+            profile,
+            "model_reasoning_summary",
+            &format!("profiles.{name}.model_reasoning_summary"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<Verbosity>(
+            profile,
+            "model_verbosity",
+            &format!("profiles.{name}.model_verbosity"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<Personality>(
+            profile,
+            "personality",
+            &format!("profiles.{name}.personality"),
+            source,
+            warnings,
+        );
+        remove_invalid_enum::<WebSearchMode>(
+            profile,
+            "web_search",
+            &format!("profiles.{name}.web_search"),
+            source,
+            warnings,
+        );
+        if let Some(windows) = profile.get_mut("windows").and_then(TomlValue::as_table_mut) {
+            remove_invalid_enum::<WindowsSandboxModeToml>(
+                windows,
+                "sandbox",
+                &format!("profiles.{name}.windows.sandbox"),
+                source,
+                warnings,
+            );
+        }
+    }
+}
+
+fn sanitize_permissions(
+    table: &mut TomlMap<String, TomlValue>,
+    source: &str,
+    warnings: &mut Vec<String>,
+) {
+    let Some(permissions) = table
+        .get_mut("permissions")
+        .and_then(TomlValue::as_table_mut)
+    else {
+        return;
+    };
+    for (profile_name, profile) in permissions {
+        let Some(network) = profile
+            .as_table_mut()
+            .and_then(|profile| profile.get_mut("network"))
+            .and_then(TomlValue::as_table_mut)
+        else {
+            continue;
+        };
+        if let Some(domains) = network.get_mut("domains").and_then(TomlValue::as_table_mut) {
+            remove_invalid_map_enums::<NetworkDomainPermissionToml>(
+                domains,
+                &format!("permissions.{profile_name}.network.domains"),
+                source,
+                warnings,
+            );
+        }
+        if let Some(unix_sockets) = network
+            .get_mut("unix_sockets")
+            .and_then(TomlValue::as_table_mut)
+        {
+            remove_invalid_map_enums::<NetworkUnixSocketPermissionToml>(
+                unix_sockets,
+                &format!("permissions.{profile_name}.network.unix_sockets"),
+                source,
+                warnings,
+            );
+        }
+    }
+}
+
+fn sanitize_mcp_servers(
+    table: &mut TomlMap<String, TomlValue>,
+    source: &str,
+    warnings: &mut Vec<String>,
+) {
+    let Some(mcp_servers) = table
+        .get_mut("mcp_servers")
+        .and_then(TomlValue::as_table_mut)
+    else {
+        return;
+    };
+    for (server_name, server) in mcp_servers {
+        let Some(server) = server.as_table_mut() else {
+            continue;
+        };
+        remove_invalid_enum::<AppToolApproval>(
+            server,
+            "default_tools_approval_mode",
+            &format!("mcp_servers.{server_name}.default_tools_approval_mode"),
+            source,
+            warnings,
+        );
+        if let Some(tools) = server.get_mut("tools").and_then(TomlValue::as_table_mut) {
+            for (tool_name, tool) in tools {
+                if let Some(tool) = tool.as_table_mut() {
+                    remove_invalid_enum::<AppToolApproval>(
+                        tool,
+                        "approval_mode",
+                        &format!("mcp_servers.{server_name}.tools.{tool_name}.approval_mode"),
+                        source,
+                        warnings,
+                    );
+                }
+            }
+        }
+    }
+}
+
+fn sanitize_plugins(
+    table: &mut TomlMap<String, TomlValue>,
+    source: &str,
+    warnings: &mut Vec<String>,
+) {
+    let Some(plugins) = table.get_mut("plugins").and_then(TomlValue::as_table_mut) else {
+        return;
+    };
+    for (plugin_name, plugin) in plugins {
+        let Some(mcp_servers) = plugin
+            .as_table_mut()
+            .and_then(|plugin| plugin.get_mut("mcp_servers"))
+            .and_then(TomlValue::as_table_mut)
+        else {
+            continue;
+        };
+        for (server_name, server) in mcp_servers {
+            let Some(server) = server.as_table_mut() else {
+                continue;
+            };
+            remove_invalid_enum::<AppToolApproval>(
+                server,
+                "default_tools_approval_mode",
+                &format!(
+                    "plugins.{plugin_name}.mcp_servers.{server_name}.default_tools_approval_mode"
+                ),
+                source,
+                warnings,
+            );
+            if let Some(tools) = server.get_mut("tools").and_then(TomlValue::as_table_mut) {
+                for (tool_name, tool) in tools {
+                    if let Some(tool) = tool.as_table_mut() {
+                        remove_invalid_enum::<AppToolApproval>(
+                            tool,
+                            "approval_mode",
+                            &format!(
+                                "plugins.{plugin_name}.mcp_servers.{server_name}.tools.{tool_name}.approval_mode"
+                            ),
+                            source,
+                            warnings,
+                        );
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn sanitize_otel(table: &mut TomlMap<String, TomlValue>, source: &str, warnings: &mut Vec<String>) {
+    let Some(otel) = table.get_mut("otel").and_then(TomlValue::as_table_mut) else {
+        return;
+    };
+    remove_invalid_enum::<OtelHttpProtocol>(otel, "protocol", "otel.protocol", source, warnings);
+    remove_invalid_enum::<OtelExporterKind>(otel, "exporter", "otel.exporter", source, warnings);
+    remove_invalid_enum::<OtelExporterKind>(
+        otel,
+        "trace_exporter",
+        "otel.trace_exporter",
+        source,
+        warnings,
+    );
+    remove_invalid_enum::<OtelExporterKind>(
+        otel,
+        "metrics_exporter",
+        "otel.metrics_exporter",
+        source,
+        warnings,
+    );
+}
+
+fn remove_invalid_map_enums<T>(
+    table: &mut TomlMap<String, TomlValue>,
+    path: &str,
+    source: &str,
+    warnings: &mut Vec<String>,
+) where
+    T: DeserializeOwned,
+{
+    let invalid_keys = table
+        .iter()
+        .filter_map(|(key, value)| invalid_enum::<T>(value).then_some(key.clone()))
+        .collect::<Vec<_>>();
+    for key in invalid_keys {
+        let Some(value) = table.remove(&key) else {
+            continue;
+        };
+        warnings.push(invalid_enum_warning(
+            source,
+            &format!("{path}.{key}"),
+            &value,
+        ));
+    }
+}
+
+fn remove_invalid_enum<T>(
+    table: &mut TomlMap<String, TomlValue>,
+    key: &str,
+    path: &str,
+    source: &str,
+    warnings: &mut Vec<String>,
+) where
+    T: DeserializeOwned,
+{
+    let Some(value) = table.get(key) else {
+        return;
+    };
+    if !invalid_enum::<T>(value) {
+        return;
+    }
+    let Some(value) = table.remove(key) else {
+        return;
+    };
+    warnings.push(invalid_enum_warning(source, path, &value));
+}
+
+fn invalid_enum<T>(value: &TomlValue) -> bool
+where
+    T: DeserializeOwned,
+{
+    match value.clone().try_into::<Lenient<T>>() {
+        Ok(Lenient::Success(_)) => false,
+        Ok(Lenient::Failure) | Err(_) => true,
+    }
+}
+
+fn invalid_enum_warning(source: &str, path: &str, value: &TomlValue) -> String {
+    format!("Ignoring invalid config value in {source} at {path}: {value}")
+}
+
+#[derive(serde::Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+enum ThreadStoreProbe {
+    Local {},
+    Remote {},
+    InMemory {},
+}
diff --git a/codex-rs/config/src/lib.rs b/codex-rs/config/src/lib.rs
index e88c736db0..7cc97a7063 100644
--- a/codex-rs/config/src/lib.rs
+++ b/codex-rs/config/src/lib.rs
@@ -7,6 +7,7 @@ mod fingerprint;
 mod hook_config;
 mod host_name;
 mod key_aliases;
+mod lenient;
 pub mod loader;
 mod marketplace_edit;
 mod mcp_edit;
diff --git a/codex-rs/config/src/loader/mod.rs b/codex-rs/config/src/loader/mod.rs
index f5f8ec44e5..b0a6e5a102 100644
--- a/codex-rs/config/src/loader/mod.rs
+++ b/codex-rs/config/src/loader/mod.rs
@@ -15,6 +15,7 @@ use crate::diagnostics::ConfigError;
 use crate::diagnostics::config_error_from_toml;
 use crate::diagnostics::first_layer_config_error_from_entries as typed_first_layer_config_error_from_entries;
 use crate::diagnostics::io_error_from_config_error;
+use crate::lenient::sanitize_config_toml_enums;
 use crate::merge::merge_toml_values;
 use crate::overrides::build_cli_overrides_layer;
 use crate::project_root_markers::default_project_root_markers;
@@ -173,6 +174,8 @@ pub async fn load_config_layers_state(
         )?)
     };
 
+    let mut startup_warnings = Vec::new();
+
     // Include an entry for the "system" config folder, loading its config.toml,
     // if it exists.
     let system_config_toml_file = system_config_toml_file_with_overrides(&overrides)?;
@@ -186,7 +189,12 @@ pub async fn load_config_layers_state(
             )
         })
         .await?;
-    layers.push(system_layer);
+    push_config_layer_with_enum_warnings(
+        system_layer,
+        &mut layers,
+        &mut startup_warnings,
+        CONFIG_TOML_FILE,
+    );
 
     // Add a layer for $CODEX_HOME/config.toml so folder-derived resources such
     // as rules/ can still be discovered. When user config is ignored, preserve
@@ -210,9 +218,14 @@ pub async fn load_config_layers_state(
         })
         .await?
     };
-    layers.push(user_layer);
+    push_config_layer_with_enum_warnings(
+        user_layer,
+        &mut layers,
+        &mut startup_warnings,
+        CONFIG_TOML_FILE,
+    );
 
-    let mut startup_warnings = None;
+    let checked_stack_warnings = cwd.is_some();
     if let Some(cwd) = cwd {
         let mut merged_so_far = TomlValue::Table(toml::map::Map::new());
         for layer in &layers {
@@ -270,7 +283,7 @@ pub async fn load_config_layers_state(
         )
         .await?;
         layers.extend(project_layers.layers);
-        startup_warnings = Some(project_layers.startup_warnings);
+        startup_warnings.extend(project_layers.startup_warnings);
     }
 
     // Add a layer for runtime overrides from the CLI or UI, if any exist.
@@ -306,10 +319,16 @@ pub async fn load_config_layers_state(
         })?;
         let managed_config =
             resolve_relative_paths_in_config_toml(config.managed_config, managed_parent)?;
-        layers.push(ConfigLayerEntry::new(
+        let managed_layer = ConfigLayerEntry::new(
             ConfigLayerSource::LegacyManagedConfigTomlFromFile { file: config.file },
             managed_config,
-        ));
+        );
+        push_config_layer_with_enum_warnings(
+            managed_layer,
+            &mut layers,
+            &mut startup_warnings,
+            CONFIG_TOML_FILE,
+        );
     }
     if let Some(config) = managed_config_from_mdm {
         // As a general rule, config from MDM should _not_ include relative
@@ -319,11 +338,17 @@ pub async fn load_config_layers_state(
         // value for base_dir, so codex_home is as good a value as any.
         let managed_config =
             resolve_relative_paths_in_config_toml(config.managed_config, codex_home)?;
-        layers.push(ConfigLayerEntry::new_with_raw_toml(
+        let managed_layer = ConfigLayerEntry::new_with_raw_toml(
             ConfigLayerSource::LegacyManagedConfigTomlFromMdm,
             managed_config,
             config.raw_toml,
-        ));
+        );
+        push_config_layer_with_enum_warnings(
+            managed_layer,
+            &mut layers,
+            &mut startup_warnings,
+            CONFIG_TOML_FILE,
+        );
     }
 
     let config_layer_stack = ConfigLayerStack::new(
@@ -332,12 +357,48 @@ pub async fn load_config_layers_state(
         config_requirements_toml.into_toml(),
     )?
     .with_user_and_project_exec_policy_rules_ignored(ignore_user_and_project_exec_policy_rules);
-    Ok(match startup_warnings {
-        Some(startup_warnings) => config_layer_stack.with_startup_warnings(startup_warnings),
-        None => config_layer_stack,
+    Ok(if checked_stack_warnings || !startup_warnings.is_empty() {
+        config_layer_stack.with_startup_warnings(startup_warnings)
+    } else {
+        config_layer_stack
     })
 }
 
+fn push_config_layer_with_enum_warnings(
+    mut layer: ConfigLayerEntry,
+    layers: &mut Vec<ConfigLayerEntry>,
+    startup_warnings: &mut Vec<String>,
+    config_toml_file: &str,
+) {
+    startup_warnings.extend(sanitize_config_toml_enums(
+        &mut layer.config,
+        config_warning_source(&layer.name, config_toml_file),
+    ));
+    layers.push(layer);
+}
+
+fn config_warning_source(layer: &ConfigLayerSource, config_toml_file: &str) -> String {
+    match layer {
+        ConfigLayerSource::System { file } => {
+            format!("system config {}", file.as_path().display())
+        }
+        ConfigLayerSource::User { file } => {
+            format!("user config {}", file.as_path().display())
+        }
+        ConfigLayerSource::Project { dot_codex_folder } => format!(
+            "project config {}",
+            dot_codex_folder.as_path().join(config_toml_file).display()
+        ),
+        ConfigLayerSource::SessionFlags => "session config overrides".to_string(),
+        ConfigLayerSource::LegacyManagedConfigTomlFromFile { file } => {
+            format!("managed config {}", file.as_path().display())
+        }
+        ConfigLayerSource::Mdm { .. } | ConfigLayerSource::LegacyManagedConfigTomlFromMdm => {
+            "managed device config".to_string()
+        }
+    }
+}
+
 fn insert_layer_by_precedence(layers: &mut Vec<ConfigLayerEntry>, layer: ConfigLayerEntry) {
     match layers
         .iter()
@@ -1024,6 +1085,12 @@ async fn load_project_layers(
                 };
                 let mut config = config;
                 let ignored_project_config_keys = sanitize_project_config(&mut config);
+                if disabled_reason.is_none() {
+                    startup_warnings.extend(sanitize_config_toml_enums(
+                        &mut config,
+                        format!("project config {}", config_file.as_path().display()),
+                    ));
+                }
                 let config =
                     resolve_relative_paths_in_config_toml(config, dot_codex_abs.as_path())?;
                 if disabled_reason.is_none() && !ignored_project_config_keys.is_empty() {
diff --git a/codex-rs/core/src/config/config_loader_tests.rs b/codex-rs/core/src/config/config_loader_tests.rs
index 6fcd5f872d..8e7a2ed382 100644
--- a/codex-rs/core/src/config/config_loader_tests.rs
+++ b/codex-rs/core/src/config/config_loader_tests.rs
@@ -118,6 +118,61 @@ async fn returns_config_error_for_invalid_user_config_toml() {
     assert_eq!(config_error, &expected_config_error);
 }
 
+#[tokio::test]
+async fn invalid_enum_values_emit_warnings_without_poisoning_config() -> std::io::Result<()> {
+    let tmp = tempdir().expect("tempdir");
+    let contents = r#"
+model = "gpt-5-codex"
+sandbox_mode = "make-it-so"
+
+[tui]
+notification_method = "loudly"
+"#;
+    let config_path = tmp.path().join(CONFIG_TOML_FILE);
+    std::fs::write(&config_path, contents).expect("write config");
+
+    let cwd = AbsolutePathBuf::try_from(tmp.path()).expect("cwd");
+    let layers = load_config_layers_state(
+        LOCAL_FS.as_ref(),
+        tmp.path(),
+        Some(cwd),
+        &[] as &[(String, TomlValue)],
+        LoaderOverrides::default(),
+        CloudRequirementsLoader::default(),
+        &codex_config::NoopThreadConfigLoader,
+    )
+    .await?;
+
+    let effective_config = layers.effective_config();
+    let expected_config = toml::from_str::<TomlValue>(
+        r#"
+model = "gpt-5-codex"
+
+[tui]
+"#,
+    )
+    .expect("expected config should parse");
+    let expected_startup_warnings = vec![
+        format!(
+            "Ignoring invalid config value in user config {} at sandbox_mode: \"make-it-so\"",
+            config_path.display()
+        ),
+        format!(
+            "Ignoring invalid config value in user config {} at tui.notification_method: \"loudly\"",
+            config_path.display()
+        ),
+    ];
+
+    assert_eq!(
+        (
+            effective_config,
+            layers.startup_warnings().unwrap_or_default().to_vec()
+        ),
+        (expected_config, expected_startup_warnings)
+    );
+    Ok(())
+}
+
 #[tokio::test]
 async fn ignore_user_config_keeps_empty_user_layer() -> std::io::Result<()> {
     let tmp = tempdir().expect("tempdir");