fix(core): restore thread_source in x-codex-turn-metadata (#29455)

## Description

Restore `thread_source` in `x-codex-turn-metadata`.

Inadvertently removed `thread_source` from `x-codex-turn-metadata` in
https://github.com/openai/codex/pull/27122 - didn't realize it was a
top-level thread app-server API field, not passed in
`responsesapi_client_metadata`.

This also reserves the key so `responsesapi_client_metadata` cannot
override it.

codex-rs/app-server/tests/suite/v2/client_metadata.rs

@@ -63,7 +63,10 @@ async fn turn_start_forwards_client_metadata_to_responses_request_v2() -> Result
     timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
 
     let thread_req = mcp
-        .send_thread_start_request(ThreadStartParams::default())
+        .send_thread_start_request(ThreadStartParams {
+            thread_source: Some(ThreadSource::Feature("automation".to_string())),
+            ..Default::default()
+        })
         .await?;
     let thread_resp: JSONRPCResponse = timeout(
         DEFAULT_READ_TIMEOUT,
@@ -75,7 +78,6 @@ async fn turn_start_forwards_client_metadata_to_responses_request_v2() -> Result
     let client_metadata = HashMap::from([
         ("fiber_run_id".to_string(), "fiber-start-123".to_string()),
         ("origin".to_string(), "gaas".to_string()),
-        ("thread_source".to_string(), "client-supplied".to_string()),
     ]);
     let turn_req = mcp
         .send_turn_start_request(TurnStartParams {
@@ -110,7 +112,7 @@ async fn turn_start_forwards_client_metadata_to_responses_request_v2() -> Result
         .expect("x-codex-turn-metadata header should be present");
     assert_eq!(metadata["fiber_run_id"].as_str(), Some("fiber-start-123"));
     assert_eq!(metadata["origin"].as_str(), Some("gaas"));
-    assert_eq!(metadata["thread_source"].as_str(), Some("client-supplied"));
+    assert_eq!(metadata["thread_source"].as_str(), Some("automation"));
     assert_eq!(metadata["turn_id"].as_str(), Some(turn.id.as_str()));
     assert!(metadata.get("installation_id").is_some());
     assert!(metadata.get("session_id").is_some());
@@ -561,7 +563,10 @@ async fn turn_start_forwards_client_metadata_to_responses_websocket_request_body
     timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
 
     let thread_req = mcp
-        .send_thread_start_request(ThreadStartParams::default())
+        .send_thread_start_request(ThreadStartParams {
+            thread_source: Some(ThreadSource::Feature("automation".to_string())),
+            ..Default::default()
+        })
         .await?;
     let thread_resp: JSONRPCResponse = timeout(
         DEFAULT_READ_TIMEOUT,
@@ -619,6 +624,7 @@ async fn turn_start_forwards_client_metadata_to_responses_websocket_request_body
         .expect("websocket x-codex-turn-metadata client metadata should be present");
     assert_eq!(metadata["fiber_run_id"].as_str(), Some("fiber-start-123"));
     assert_eq!(metadata["origin"].as_str(), Some("gaas"));
+    assert_eq!(metadata["thread_source"].as_str(), Some("automation"));
     assert_eq!(metadata["turn_id"].as_str(), Some(turn.id.as_str()));
     assert!(metadata.get("session_id").is_some());
     assert_eq!(

codex-rs/core/src/responses_metadata.rs

@@ -10,6 +10,7 @@ use codex_protocol::ThreadId;
 use codex_protocol::protocol::InternalSessionSource;
 use codex_protocol::protocol::SessionSource;
 use codex_protocol::protocol::SubAgentSource;
+use codex_protocol::protocol::ThreadSource;
 use codex_utils_string::to_ascii_json_string;
 use http::HeaderMap as ApiHeaderMap;
 use http::HeaderValue;
@@ -34,6 +35,7 @@ pub(crate) const TURN_STARTED_AT_UNIX_MS_KEY: &str = "turn_started_at_unix_ms";
 pub(crate) const FORKED_FROM_THREAD_ID_KEY: &str = "forked_from_thread_id";
 pub(crate) const PARENT_THREAD_ID_KEY: &str = "parent_thread_id";
 pub(crate) const SUBAGENT_KIND_KEY: &str = "subagent_kind";
+pub(crate) const THREAD_SOURCE_KEY: &str = "thread_source";
 pub(crate) const SANDBOX_KEY: &str = "sandbox";
 pub(crate) const WORKSPACES_KEY: &str = "workspaces";
 
@@ -56,6 +58,7 @@ const RESERVED_METADATA_KEYS: &[&str] = &[
     FORKED_FROM_THREAD_ID_KEY,
     PARENT_THREAD_ID_KEY,
     SUBAGENT_KIND_KEY,
+    THREAD_SOURCE_KEY,
     SANDBOX_KEY,
     WORKSPACES_KEY,
 ];
@@ -143,6 +146,7 @@ pub struct CodexResponsesMetadata {
     pub(crate) parent_thread_id: Option<ThreadId>,
     pub(crate) subagent_header: Option<String>,
     pub(crate) subagent_kind: Option<String>,
+    pub(crate) thread_source: Option<ThreadSource>,
     pub(crate) sandbox: Option<String>,
     pub(crate) workspaces: BTreeMap<String, TurnMetadataWorkspace>,
     pub(crate) turn_started_at_unix_ms: Option<i64>,
@@ -167,6 +171,7 @@ impl CodexResponsesMetadata {
             parent_thread_id: None,
             subagent_header: None,
             subagent_kind: None,
+            thread_source: None,
             sandbox: None,
             workspaces: BTreeMap::new(),
             turn_started_at_unix_ms: None,
@@ -268,6 +273,7 @@ impl CodexResponsesMetadata {
             forked_from_thread_id: self.forked_from_thread_id,
             parent_thread_id: self.parent_thread_id,
             subagent_kind: self.subagent_kind.as_deref(),
+            thread_source: self.thread_source.as_ref(),
             sandbox: self.sandbox.as_deref(),
             workspaces: non_empty_workspaces(&self.workspaces),
             turn_started_at_unix_ms: self.turn_started_at_unix_ms,
@@ -354,6 +360,8 @@ struct CodexTurnMetadataPayload<'a> {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     subagent_kind: Option<&'a str>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
+    thread_source: Option<&'a ThreadSource>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
     sandbox: Option<&'a str>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     workspaces: Option<&'a BTreeMap<String, TurnMetadataWorkspace>>,

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

@@ -75,9 +75,12 @@ pub(super) async fn spawn_review_thread(
         .model_reasoning_summary
         .unwrap_or(model_info.default_reasoning_summary);
     let session_source = parent_turn_context.session_source.clone();
-    let forked_from_thread_id = {
+    let (forked_from_thread_id, thread_source) = {
         let state = sess.state.lock().await;
-        state.session_configuration.forked_from_thread_id
+        (
+            state.session_configuration.forked_from_thread_id,
+            state.session_configuration.thread_source.clone(),
+        )
     };
 
     let per_turn_config = Arc::new(per_turn_config);
@@ -88,6 +91,7 @@ pub(super) async fn spawn_review_thread(
         forked_from_thread_id,
         parent_turn_context.parent_thread_id,
         &session_source,
+        thread_source,
         review_turn_id.clone(),
         #[allow(deprecated)]
         parent_turn_context.cwd.clone(),

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

@@ -536,6 +536,7 @@ impl Session {
             session_configuration.forked_from_thread_id,
             session_configuration.parent_thread_id,
             &session_configuration.session_source,
+            session_configuration.thread_source.clone(),
             sub_id.clone(),
             cwd.clone(),
             &session_configuration.permission_profile(),

codex-rs/core/src/turn_metadata.rs

@@ -25,6 +25,7 @@ use codex_protocol::config_types::WindowsSandboxLevel;
 use codex_protocol::models::PermissionProfile;
 use codex_protocol::openai_models::ReasoningEffort as ReasoningEffortConfig;
 use codex_protocol::protocol::SessionSource;
+use codex_protocol::protocol::ThreadSource;
 use codex_utils_absolute_path::AbsolutePathBuf;
 
 const MODEL_KEY: &str = "model";
@@ -91,6 +92,7 @@ pub(crate) struct TurnMetadataState {
     parent_thread_id: Option<ThreadId>,
     subagent_header: Option<String>,
     subagent_kind: Option<String>,
+    thread_source: Option<ThreadSource>,
     turn_id: String,
     sandbox: Option<String>,
     enriched_workspaces: Arc<RwLock<Option<BTreeMap<String, TurnMetadataWorkspace>>>>,
@@ -108,6 +110,7 @@ impl TurnMetadataState {
         forked_from_thread_id: Option<ThreadId>,
         parent_thread_id: Option<ThreadId>,
         session_source: &SessionSource,
+        thread_source: Option<ThreadSource>,
         turn_id: String,
         cwd: AbsolutePathBuf,
         permission_profile: &PermissionProfile,
@@ -132,6 +135,7 @@ impl TurnMetadataState {
             parent_thread_id,
             subagent_header: subagent_header_value(session_source),
             subagent_kind: subagent_metadata_kind(session_source),
+            thread_source,
             turn_id,
             sandbox,
             enriched_workspaces: Arc::new(RwLock::new(None)),
@@ -225,6 +229,7 @@ impl TurnMetadataState {
             parent_thread_id: self.parent_thread_id,
             subagent_header: self.subagent_header.clone(),
             subagent_kind: self.subagent_kind.clone(),
+            thread_source: self.thread_source.clone(),
             sandbox: self.sandbox.clone(),
             workspaces: self.current_workspaces(),
             turn_started_at_unix_ms: self.current_turn_started_at_unix_ms(),

codex-rs/core/src/turn_metadata_tests.rs

@@ -13,6 +13,7 @@ use codex_protocol::models::PermissionProfile;
 use codex_protocol::openai_models::ReasoningEffort as ReasoningEffortConfig;
 use codex_protocol::protocol::SessionSource;
 use codex_protocol::protocol::SubAgentSource;
+use codex_protocol::protocol::ThreadSource;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use core_test_support::PathBufExt;
 use core_test_support::PathExt;
@@ -187,6 +188,7 @@ fn turn_metadata_state_uses_platform_sandbox_tag() {
         /*forked_from_thread_id*/ None,
         /*parent_thread_id*/ None,
         &SessionSource::Exec,
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -229,6 +231,7 @@ fn turn_metadata_state_includes_root_fork_lineage() {
         Some(source_thread_id),
         /*parent_thread_id*/ None,
         &SessionSource::Exec,
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -267,6 +270,7 @@ fn turn_metadata_state_includes_thread_spawn_subagent_parent_without_fork() {
             agent_nickname: None,
             agent_role: None,
         }),
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -305,6 +309,7 @@ fn turn_metadata_state_includes_forked_thread_spawn_subagent_lineage() {
             agent_nickname: None,
             agent_role: None,
         }),
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -349,6 +354,7 @@ fn turn_metadata_state_includes_known_parent_for_non_thread_spawn_subagents_with
             /*forked_from_thread_id*/ None,
             Some(parent_thread_id),
             &SessionSource::SubAgent(subagent_source),
+            /*thread_source*/ None,
             "turn-a".to_string(),
             cwd.clone(),
             &permission_profile,
@@ -380,6 +386,7 @@ fn turn_metadata_state_includes_turn_started_at_unix_ms_after_start() {
         /*forked_from_thread_id*/ None,
         /*parent_thread_id*/ None,
         &SessionSource::Exec,
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -409,6 +416,7 @@ fn turn_metadata_state_includes_model_and_reasoning_effort_only_in_request_meta(
         /*forked_from_thread_id*/ None,
         /*parent_thread_id*/ None,
         &SessionSource::Exec,
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -457,6 +465,7 @@ fn turn_metadata_state_marks_user_input_requested_during_turn_only_for_mcp_reque
         /*forked_from_thread_id*/ None,
         /*parent_thread_id*/ None,
         &SessionSource::Exec,
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -509,6 +518,7 @@ fn turn_metadata_state_ignores_client_reserved_metadata_before_start() {
         /*forked_from_thread_id*/ None,
         /*parent_thread_id*/ None,
         &SessionSource::Exec,
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -562,6 +572,7 @@ fn turn_metadata_state_merges_client_metadata_without_replacing_reserved_fields(
             agent_nickname: None,
             agent_role: None,
         }),
+        Some(ThreadSource::Feature("automation".to_string())),
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -637,7 +648,7 @@ fn turn_metadata_state_merges_client_metadata_without_replacing_reserved_fields(
         Some("55555555-5555-4555-8555-555555555555")
     );
     assert_eq!(json["subagent_kind"].as_str(), Some("thread_spawn"));
-    assert_eq!(json["thread_source"].as_str(), Some("client-supplied"));
+    assert_eq!(json["thread_source"].as_str(), Some("automation"));
     assert_eq!(json["turn_id"].as_str(), Some("turn-a"));
     assert!(json.get("request_kind").is_none());
     assert!(json.get(WINDOW_ID_KEY).is_none());
@@ -650,6 +661,10 @@ fn turn_metadata_state_merges_client_metadata_without_replacing_reserved_fields(
     let model_request_json: Value =
         serde_json::from_str(&model_request_header).expect("model request json");
     assert_eq!(model_request_json["request_kind"].as_str(), Some("turn"));
+    assert_eq!(
+        model_request_json["thread_source"].as_str(),
+        Some("automation")
+    );
     assert_eq!(
         model_request_json[INSTALLATION_ID_KEY].as_str(),
         Some("installation-a")
@@ -679,6 +694,7 @@ fn turn_metadata_state_overlays_compaction_only_on_compaction_requests() {
         /*forked_from_thread_id*/ None,
         /*parent_thread_id*/ None,
         &SessionSource::Exec,
+        /*thread_source*/ None,
         "turn-a".to_string(),
         cwd,
         &permission_profile,
@@ -741,6 +757,7 @@ async fn turn_metadata_state_preserves_lineage_after_git_enrichment() {
             agent_nickname: None,
             agent_role: None,
         }),
+        /*thread_source*/ None,
         "turn-a".to_string(),
         repo_path,
         &permission_profile,