diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index b6f7505d1b..fcd827fddc 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -3945,6 +3945,12 @@ impl Session {
         arguments: Option<serde_json::Value>,
         meta: Option<serde_json::Value>,
     ) -> anyhow::Result<CallToolResult> {
+        if server == CODEX_APPS_MCP_SERVER_NAME
+            && let Some((turn_context, _)) = self.active_turn_context_and_cancellation_token().await
+        {
+            self.sync_mcp_request_headers_for_turn(turn_context.as_ref())
+                .await;
+        }
         self.services
             .mcp_connection_manager
             .read()
diff --git a/codex-rs/core/src/codex_tests.rs b/codex-rs/core/src/codex_tests.rs
index f767c05f4e..22e83ee216 100644
--- a/codex-rs/core/src/codex_tests.rs
+++ b/codex-rs/core/src/codex_tests.rs
@@ -26,6 +26,8 @@ use codex_protocol::protocol::ReadOnlyAccess;
 use codex_protocol::protocol::SandboxPolicy;
 use codex_protocol::request_permissions::PermissionGrantScope;
 use codex_protocol::request_permissions::RequestPermissionProfile;
+use codex_protocol::user_input::UserInput;
+use reqwest::header::HeaderValue;
 use tracing::Span;
 
 use crate::protocol::CompactedItem;
@@ -56,6 +58,7 @@ use crate::tools::handlers::UnifiedExecHandler;
 use crate::tools::registry::ToolHandler;
 use crate::tools::router::ToolCallSource;
 use crate::turn_diff_tracker::TurnDiffTracker;
+use async_trait::async_trait;
 use codex_app_server_protocol::AppInfo;
 use codex_execpolicy::Decision;
 use codex_execpolicy::NetworkRuleProtocol;
@@ -78,7 +81,10 @@ use opentelemetry::trace::TracerProvider as _;
 use opentelemetry_sdk::trace::SdkTracerProvider;
 use std::path::Path;
 use std::time::Duration;
+use tokio::sync::Notify;
 use tokio::time::sleep;
+use tokio_util::sync::CancellationToken;
+use tokio_util::task::AbortOnDropHandle;
 use tracing_opentelemetry::OpenTelemetrySpanExt;
 use tracing_subscriber::prelude::*;
 
@@ -2716,6 +2722,99 @@ async fn request_permissions_is_auto_denied_when_granular_policy_blocks_tool_req
     );
 }
 
+struct NoopTask;
+
+#[async_trait]
+impl SessionTask for NoopTask {
+    fn kind(&self) -> TaskKind {
+        TaskKind::Regular
+    }
+
+    fn span_name(&self) -> &'static str {
+        "noop"
+    }
+
+    async fn run(
+        self: Arc<Self>,
+        _ctx: Arc<SessionTaskContext>,
+        _turn_context: Arc<TurnContext>,
+        _input: Vec<UserInput>,
+        _cancellation_token: CancellationToken,
+    ) -> Option<String> {
+        None
+    }
+}
+
+#[tokio::test]
+async fn call_tool_refreshes_codex_apps_request_headers_from_active_turn() {
+    let (session, turn_context) = make_session_and_context().await;
+    let session = Arc::new(session);
+    let turn_context = Arc::new(turn_context);
+
+    session
+        .services
+        .mcp_connection_manager
+        .write()
+        .await
+        .register_test_server_for_request_headers(CODEX_APPS_MCP_SERVER_NAME);
+
+    session
+        .sync_mcp_request_headers_for_turn(turn_context.as_ref())
+        .await;
+    let base_header = turn_context
+        .turn_metadata_state
+        .current_header_value()
+        .expect("base turn metadata header");
+
+    let updated_header = serde_json::json!({
+        "turn_id": turn_context.sub_id,
+        "sandbox": "test",
+        "workspaces": {
+            "/tmp/repo": {
+                "has_changes": true
+            }
+        }
+    })
+    .to_string();
+    turn_context
+        .turn_metadata_state
+        .set_enriched_header_for_tests(Some(updated_header.clone()));
+
+    let mut active_turn = ActiveTurn::default();
+    let handle = tokio::spawn(async {});
+    active_turn.add_task(crate::state::RunningTask {
+        done: Arc::new(Notify::new()),
+        kind: TaskKind::Regular,
+        task: Arc::new(NoopTask),
+        cancellation_token: CancellationToken::new(),
+        handle: Arc::new(AbortOnDropHandle::new(handle)),
+        turn_context: Arc::clone(&turn_context),
+        _timer: None,
+    });
+    *session.active_turn.lock().await = Some(active_turn);
+
+    let _err = session
+        .call_tool(CODEX_APPS_MCP_SERVER_NAME, "echo", None, None)
+        .await
+        .expect_err("test server is not initialized");
+
+    let headers = session
+        .services
+        .mcp_connection_manager
+        .read()
+        .await
+        .request_headers_for_server(CODEX_APPS_MCP_SERVER_NAME)
+        .expect("request headers should be tracked for codex apps");
+    assert_eq!(
+        headers.get(crate::X_CODEX_TURN_METADATA_HEADER),
+        Some(&HeaderValue::from_str(&updated_header).expect("valid enriched header")),
+    );
+    assert_ne!(
+        headers.get(crate::X_CODEX_TURN_METADATA_HEADER),
+        Some(&HeaderValue::from_str(&base_header).expect("valid base header")),
+    );
+}
+
 #[tokio::test]
 async fn submit_with_id_captures_current_span_trace_context() {
     let (session, _turn_context) = make_session_and_context().await;
diff --git a/codex-rs/core/src/mcp_connection_manager.rs b/codex-rs/core/src/mcp_connection_manager.rs
index 7c8a343070..cd80220d71 100644
--- a/codex-rs/core/src/mcp_connection_manager.rs
+++ b/codex-rs/core/src/mcp_connection_manager.rs
@@ -636,6 +636,40 @@ impl McpConnectionManager {
         Self::new_uninitialized(approval_policy)
     }
 
+    #[cfg(test)]
+    pub(crate) fn register_test_server_for_request_headers(&mut self, server_name: &str) {
+        let failed_client = futures::future::ready::<Result<ManagedClient, StartupOutcomeError>>(
+            Err(StartupOutcomeError::Failed {
+                error: "test request headers stub".to_string(),
+            }),
+        )
+        .boxed()
+        .shared();
+        self.clients.insert(
+            server_name.to_string(),
+            AsyncManagedClient {
+                client: failed_client,
+                request_headers: Arc::new(StdMutex::new(None)),
+                startup_snapshot: None,
+                startup_complete: Arc::new(AtomicBool::new(true)),
+                tool_plugin_provenance: Arc::new(ToolPluginProvenance::default()),
+            },
+        );
+    }
+
+    #[cfg(test)]
+    pub(crate) fn request_headers_for_server(
+        &self,
+        server_name: &str,
+    ) -> Option<reqwest::header::HeaderMap> {
+        let client = self.clients.get(server_name)?;
+        client
+            .request_headers
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .clone()
+    }
+
     pub(crate) fn has_servers(&self) -> bool {
         !self.clients.is_empty()
     }
diff --git a/codex-rs/core/src/turn_metadata.rs b/codex-rs/core/src/turn_metadata.rs
index c0298c5221..1056752728 100644
--- a/codex-rs/core/src/turn_metadata.rs
+++ b/codex-rs/core/src/turn_metadata.rs
@@ -217,6 +217,14 @@ impl TurnMetadataState {
         }
     }
 
+    #[cfg(test)]
+    pub(crate) fn set_enriched_header_for_tests(&self, header: Option<String>) {
+        *self
+            .enriched_header
+            .write()
+            .unwrap_or_else(std::sync::PoisonError::into_inner) = header;
+    }
+
     async fn fetch_workspace_git_metadata(&self) -> WorkspaceGitMetadata {
         let (latest_git_commit_hash, associated_remote_urls, has_changes) = tokio::join!(
             get_head_commit_hash(&self.cwd),
diff --git a/codex-rs/core/tests/suite/search_tool.rs b/codex-rs/core/tests/suite/search_tool.rs
index 118f1bd585..62659aa4de 100644
--- a/codex-rs/core/tests/suite/search_tool.rs
+++ b/codex-rs/core/tests/suite/search_tool.rs
@@ -30,6 +30,8 @@ use core_test_support::wait_for_event;
 use pretty_assertions::assert_eq;
 use serde_json::Value;
 use serde_json::json;
+use std::fs;
+use std::process::Command;
 
 const SEARCH_TOOL_DESCRIPTION_SNIPPETS: [&str; 2] = [
     "You have access to all the tools of the following apps/connectors",
@@ -86,6 +88,15 @@ fn tool_search_output_tools(request: &ResponsesRequest, call_id: &str) -> Vec<Va
         .unwrap_or_default()
 }
 
+fn json_rpc_method(request: &wiremock::Request) -> Option<String> {
+    request
+        .body_json::<Value>()
+        .ok()?
+        .get("method")
+        .and_then(Value::as_str)
+        .map(str::to_string)
+}
+
 fn configure_apps(config: &mut Config, apps_base_url: &str) {
     config
         .features
@@ -499,5 +510,195 @@ async fn tool_search_returns_deferred_tools_without_follow_up_tool_injection() -
         "post-tool follow-up should still rely on tool_search_output history, not tool injection: {third_request_tools:?}"
     );
 
+    let mcp_requests = server
+        .received_requests()
+        .await
+        .expect("failed to fetch recorded requests");
+    let tools_list_request = mcp_requests
+        .iter()
+        .find(|request| json_rpc_method(request).as_deref() == Some("tools/list"))
+        .expect("tools/list MCP request");
+    assert!(
+        tools_list_request
+            .headers
+            .get("x-codex-turn-metadata")
+            .is_none(),
+        "tools/list should not include per-turn MCP headers"
+    );
+
+    let tools_call_request = mcp_requests
+        .iter()
+        .find(|request| json_rpc_method(request).as_deref() == Some("tools/call"))
+        .expect("tools/call MCP request");
+    let session_id_header = tools_call_request
+        .headers
+        .get("session_id")
+        .expect("tools/call session_id header");
+    let request_id_header = tools_call_request
+        .headers
+        .get("x-client-request-id")
+        .expect("tools/call x-client-request-id header");
+    let turn_metadata_header = tools_call_request
+        .headers
+        .get("x-codex-turn-metadata")
+        .expect("tools/call turn metadata header");
+    assert_eq!(
+        session_id_header
+            .to_str()
+            .expect("session_id header to be utf8"),
+        request_id_header
+            .to_str()
+            .expect("x-client-request-id header to be utf8")
+    );
+    assert!(
+        turn_metadata_header
+            .to_str()
+            .expect("turn metadata header to be utf8")
+            .contains("\"turn_id\""),
+        "expected turn metadata header to contain serialized turn metadata"
+    );
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn apps_mcp_tool_call_uses_enriched_turn_metadata_header() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+    let apps_server = AppsTestServer::mount_searchable(&server).await?;
+    let call_id = "tool-search-git-metadata";
+    let mock = mount_sse_sequence(
+        &server,
+        vec![
+            sse(vec![
+                ev_response_created("resp-1"),
+                ev_tool_search_call(
+                    call_id,
+                    &json!({
+                        "query": "create calendar event",
+                        "limit": 1,
+                    }),
+                ),
+                ev_completed("resp-1"),
+            ]),
+            sse(vec![
+                ev_response_created("resp-2"),
+                json!({
+                    "type": "response.output_item.done",
+                    "item": {
+                        "type": "function_call",
+                        "call_id": "calendar-call-git-metadata",
+                        "name": SEARCH_CALENDAR_CREATE_TOOL,
+                        "namespace": SEARCH_CALENDAR_NAMESPACE,
+                        "arguments": serde_json::to_string(&json!({
+                            "title": "Lunch",
+                            "starts_at": "2026-03-10T12:00:00Z"
+                        })).expect("serialize calendar args")
+                    }
+                }),
+                ev_completed("resp-2"),
+            ]),
+            sse(vec![
+                ev_response_created("resp-3"),
+                ev_assistant_message("msg-1", "done"),
+                ev_completed("resp-3"),
+            ]),
+        ],
+    )
+    .await;
+
+    let mut builder = configured_builder(apps_server.chatgpt_base_url.clone());
+    let test = builder.build(&server).await?;
+
+    let cwd = test.cwd_path().to_path_buf();
+    assert!(
+        Command::new("git")
+            .arg("init")
+            .current_dir(&cwd)
+            .status()?
+            .success()
+    );
+    assert!(
+        Command::new("git")
+            .args(["config", "user.name", "Codex Test"])
+            .current_dir(&cwd)
+            .status()?
+            .success()
+    );
+    assert!(
+        Command::new("git")
+            .args(["config", "user.email", "codex@example.com"])
+            .current_dir(&cwd)
+            .status()?
+            .success()
+    );
+    assert!(
+        Command::new("git")
+            .args(["remote", "add", "origin", "https://example.test/repo.git"])
+            .current_dir(&cwd)
+            .status()?
+            .success()
+    );
+    for idx in 0..400 {
+        fs::write(
+            cwd.join(format!("file-{idx:04}.txt")),
+            format!("fixture file {idx}\n"),
+        )?;
+    }
+    assert!(
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(&cwd)
+            .status()?
+            .success()
+    );
+    assert!(
+        Command::new("git")
+            .args(["commit", "-m", "init"])
+            .current_dir(&cwd)
+            .status()?
+            .success()
+    );
+
+    test.codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "Find the calendar create tool".to_string(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await?;
+
+    wait_for_event(&test.codex, |event| {
+        matches!(event, EventMsg::TurnComplete(_))
+    })
+    .await;
+
+    let _requests = mock.requests();
+    let mcp_requests = server
+        .received_requests()
+        .await
+        .expect("failed to fetch recorded requests");
+    let tools_call_request = mcp_requests
+        .iter()
+        .find(|request| json_rpc_method(request).as_deref() == Some("tools/call"))
+        .expect("tools/call MCP request");
+    let turn_metadata_header = tools_call_request
+        .headers
+        .get("x-codex-turn-metadata")
+        .expect("tools/call turn metadata header")
+        .to_str()
+        .expect("turn metadata header to be utf8");
+    let parsed: Value = serde_json::from_str(turn_metadata_header)?;
+    assert!(
+        parsed
+            .get("workspaces")
+            .and_then(Value::as_object)
+            .is_some_and(|workspaces| !workspaces.is_empty()),
+        "expected enriched MCP turn metadata header with workspace git metadata, got {parsed:#?}"
+    );
+
     Ok(())
 }