diff --git a/codex-rs/core/src/mcp_tool_call.rs b/codex-rs/core/src/mcp_tool_call.rs
index a9a0d6eb5c18..1176a53f3dc1 100644
--- a/codex-rs/core/src/mcp_tool_call.rs
+++ b/codex-rs/core/src/mcp_tool_call.rs
@@ -159,8 +159,12 @@ pub(crate) async fn handle_mcp_tool_call(
                 .unwrap_or_else(|| JsonValue::Object(serde_json::Map::new())),
         };
     }
-    let request_meta =
-        build_mcp_tool_call_request_meta(turn_context.as_ref(), &server, metadata.as_ref());
+    let request_meta = build_mcp_tool_call_request_meta(
+        turn_context.as_ref(),
+        &server,
+        &call_id,
+        metadata.as_ref(),
+    );
     let connector_id = metadata
         .as_ref()
         .and_then(|metadata| metadata.connector_id.clone());
@@ -693,6 +697,7 @@ fn custom_mcp_tool_approval_mode(
 fn build_mcp_tool_call_request_meta(
     turn_context: &TurnContext,
     server: &str,
+    call_id: &str,
     metadata: Option<&McpToolApprovalMetadata>,
 ) -> Option<serde_json::Value> {
     let mut request_meta = serde_json::Map::new();
@@ -704,10 +709,14 @@ fn build_mcp_tool_call_request_meta(
         );
     }
 
-    if server == CODEX_APPS_MCP_SERVER_NAME
-        && let Some(codex_apps_meta) =
-            metadata.and_then(|metadata| metadata.codex_apps_meta.clone())
-    {
+    if server == CODEX_APPS_MCP_SERVER_NAME {
+        let mut codex_apps_meta = metadata
+            .and_then(|metadata| metadata.codex_apps_meta.clone())
+            .unwrap_or_default();
+        codex_apps_meta.insert(
+            "call_id".to_string(),
+            serde_json::Value::String(call_id.to_string()),
+        );
         request_meta.insert(
             MCP_TOOL_CODEX_APPS_META_KEY.to_string(),
             serde_json::Value::Object(codex_apps_meta),
diff --git a/codex-rs/core/src/mcp_tool_call_tests.rs b/codex-rs/core/src/mcp_tool_call_tests.rs
index 522686446b01..f532053f9095 100644
--- a/codex-rs/core/src/mcp_tool_call_tests.rs
+++ b/codex-rs/core/src/mcp_tool_call_tests.rs
@@ -668,9 +668,13 @@ async fn mcp_tool_call_request_meta_includes_turn_metadata_for_custom_server() {
     )
     .expect("turn metadata json");
 
-    let meta =
-        build_mcp_tool_call_request_meta(&turn_context, "custom_server", /*metadata*/ None)
-            .expect("custom servers should receive turn metadata");
+    let meta = build_mcp_tool_call_request_meta(
+        &turn_context,
+        "custom_server",
+        "call-custom",
+        /*metadata*/ None,
+    )
+    .expect("custom servers should receive turn metadata");
 
     assert_eq!(
         meta,
@@ -715,11 +719,13 @@ async fn codex_apps_tool_call_request_meta_includes_turn_metadata_and_codex_apps
         build_mcp_tool_call_request_meta(
             &turn_context,
             CODEX_APPS_MCP_SERVER_NAME,
+            "call_abc123xyz789",
             Some(&metadata),
         ),
         Some(serde_json::json!({
             crate::X_CODEX_TURN_METADATA_HEADER: expected_turn_metadata,
             MCP_TOOL_CODEX_APPS_META_KEY: {
+                "call_id": "call_abc123xyz789",
                 "resource_uri": "connector://calendar/tools/calendar_create_event",
                 "contains_mcp_source": true,
                 "connector_id": "calendar",
@@ -728,6 +734,33 @@ async fn codex_apps_tool_call_request_meta_includes_turn_metadata_and_codex_apps
     );
 }
 
+#[tokio::test]
+async fn codex_apps_tool_call_request_meta_includes_call_id_without_existing_codex_apps_meta() {
+    let (_, turn_context) = make_session_and_context().await;
+    let expected_turn_metadata = serde_json::from_str::<serde_json::Value>(
+        &turn_context
+            .turn_metadata_state
+            .current_header_value()
+            .expect("turn metadata header"),
+    )
+    .expect("turn metadata json");
+
+    assert_eq!(
+        build_mcp_tool_call_request_meta(
+            &turn_context,
+            CODEX_APPS_MCP_SERVER_NAME,
+            "call_abc123xyz789",
+            /*metadata*/ None,
+        ),
+        Some(serde_json::json!({
+            crate::X_CODEX_TURN_METADATA_HEADER: expected_turn_metadata,
+            MCP_TOOL_CODEX_APPS_META_KEY: {
+                "call_id": "call_abc123xyz789",
+            },
+        }))
+    );
+}
+
 #[test]
 fn mcp_tool_call_thread_id_meta_is_added_to_request_meta() {
     assert_eq!(
diff --git a/codex-rs/core/tests/suite/openai_file_mcp.rs b/codex-rs/core/tests/suite/openai_file_mcp.rs
index 2912b5fb0e21..3bfa264d7990 100644
--- a/codex-rs/core/tests/suite/openai_file_mcp.rs
+++ b/codex-rs/core/tests/suite/openai_file_mcp.rs
@@ -222,6 +222,7 @@ async fn codex_apps_file_params_upload_local_paths_before_mcp_tool_call() -> Res
     assert_eq!(
         apps_tool_call.pointer("/params/_meta/_codex_apps"),
         Some(&json!({
+            "call_id": "extract-call-1",
             "resource_uri": DOCUMENT_EXTRACT_TEXT_RESOURCE_URI,
             "contains_mcp_source": true,
             "connector_id": "calendar",
diff --git a/codex-rs/core/tests/suite/search_tool.rs b/codex-rs/core/tests/suite/search_tool.rs
index 1e37d5ae10db..fa2eca9b22d4 100644
--- a/codex-rs/core/tests/suite/search_tool.rs
+++ b/codex-rs/core/tests/suite/search_tool.rs
@@ -555,6 +555,7 @@ async fn tool_search_returns_deferred_tools_without_follow_up_tool_injection() -
             .structured_content,
         Some(json!({
             "_codex_apps": {
+                "call_id": "calendar-call-1",
                 "resource_uri": CALENDAR_CREATE_EVENT_RESOURCE_URI,
                 "contains_mcp_source": true,
                 "connector_id": "calendar",
@@ -586,6 +587,7 @@ async fn tool_search_returns_deferred_tools_without_follow_up_tool_injection() -
     assert_eq!(
         apps_tool_call.pointer("/params/_meta/_codex_apps"),
         Some(&json!({
+            "call_id": "calendar-call-1",
             "resource_uri": CALENDAR_CREATE_EVENT_RESOURCE_URI,
             "contains_mcp_source": true,
             "connector_id": "calendar",