Enable incremental tool declarations by default for GCP (#60848)

## What changed

- Add the stable `incremental_tools_legacy_gcp` feature, enabled by default, to control incremental tool declarations on regular GCP Responses independently of Amazon Bedrock.
- Mark `incremental_tools_legacy` stable and keep it disabled by default for Amazon Bedrock.
- Expose the new flag in the configuration schema.

## Testing

Update integration coverage for GCP defaults and opt-out, independent provider flags, and incremental tool declarations during remote compaction.

GitOrigin-RevId: 7acf085789d44122fd2a5da97932a8b9e93e240e

codex-rs/core/config.schema.json

@@ -1130,6 +1130,9 @@
             "incremental_tools_legacy": {
               "type": "boolean"
             },
+            "incremental_tools_legacy_gcp": {
+              "type": "boolean"
+            },
             "instant_interrupt": {
               "type": "boolean"
             },
@@ -8197,6 +8200,9 @@
         "incremental_tools_legacy": {
           "type": "boolean"
         },
+        "incremental_tools_legacy_gcp": {
+          "type": "boolean"
+        },
         "instant_interrupt": {
           "type": "boolean"
         },

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

@@ -62,11 +62,13 @@ impl StepContext {
         if self.settings.model_info.use_responses_lite {
             Some(Feature::IncrementalTools)
         } else {
-            matches!(
-                self.turn.config.model_provider_id.as_str(),
-                AMAZON_BEDROCK_PROVIDER_ID | AMAZON_BEDROCK_RUNTIME_PROVIDER_ID | GCP_PROVIDER_ID
-            )
-            .then_some(Feature::IncrementalToolsLegacy)
+            match self.turn.config.model_provider_id.as_str() {
+                AMAZON_BEDROCK_PROVIDER_ID | AMAZON_BEDROCK_RUNTIME_PROVIDER_ID => {
+                    Some(Feature::IncrementalToolsLegacy)
+                }
+                GCP_PROVIDER_ID => Some(Feature::IncrementalToolsLegacyGcp),
+                _ => None,
+            }
         }
     }
 

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

@@ -581,6 +581,10 @@ async fn provider_automatic_compaction_uses_v2_responses_endpoint(
                         config.model_provider_id = GCP_PROVIDER_ID.to_string();
                         config.model_provider = provider;
                         config.model_reasoning_summary = Some(ReasoningSummary::Detailed);
+                        config
+                            .features
+                            .enable(Feature::IncrementalToolsLegacyGcp)
+                            .expect("enable incremental tools on Vertex");
                         config
                             .features
                             .enable(Feature::RemoteCompactionV2)
@@ -652,7 +656,7 @@ async fn provider_automatic_compaction_uses_v2_responses_endpoint(
                     request.header("x-openai-internal-codex-responses-lite"),
                     None
                 );
-                assert!(request.inputs_of_type("additional_tools").is_empty());
+                assert!(!request.inputs_of_type("additional_tools").is_empty());
             }
         }
     }

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

@@ -136,8 +136,12 @@ async fn vertex_requests_use_command_auth_with_namespaces_and_tool_search(
             config.base_instructions = Some("Vertex test instructions".to_string());
             config
                 .features
-                .set_enabled(Feature::IncrementalToolsLegacy, incremental_tools)
+                .set_enabled(Feature::IncrementalToolsLegacyGcp, incremental_tools)
                 .expect("configure incremental tools on Vertex");
+            config
+                .features
+                .set_enabled(Feature::IncrementalToolsLegacy, !incremental_tools)
+                .expect("configure independent Bedrock flag");
         })
         .build_with_auto_env(&server)
         .await?;

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

@@ -152,21 +152,25 @@ async fn prediction_fork_keeps_inherited_tools() -> Result<()> {
     Ok(())
 }
 
-#[test_case(true, None, true, OPENAI_PROVIDER_ID; "responses_lite")]
-#[test_case(true, Some(true), true, OPENAI_PROVIDER_ID; "announcements_suppressed")]
-#[test_case(false, None, false, OPENAI_PROVIDER_ID; "responses_api")]
-#[test_case(false, None, false, AMAZON_BEDROCK_PROVIDER_ID; "mantle_provider_id")]
-#[test_case(false, None, true, AMAZON_BEDROCK_PROVIDER_ID; "mantle_provider_id_incremental")]
-#[test_case(false, None, false, AMAZON_BEDROCK_RUNTIME_PROVIDER_ID; "runtime_provider_id")]
-#[test_case(false, None, true, AMAZON_BEDROCK_RUNTIME_PROVIDER_ID; "runtime_provider_id_incremental")]
-#[test_case(false, None, false, GCP_PROVIDER_ID; "gcp_provider_id")]
-#[test_case(false, None, true, GCP_PROVIDER_ID; "gcp_provider_id_incremental")]
+#[test_case(true, None, true, OPENAI_PROVIDER_ID, &[]; "responses_lite")]
+#[test_case(true, Some(true), true, OPENAI_PROVIDER_ID, &[]; "announcements_suppressed")]
+#[test_case(false, None, false, OPENAI_PROVIDER_ID, &[]; "responses_api")]
+#[test_case(false, None, false, AMAZON_BEDROCK_PROVIDER_ID, &[]; "mantle_default")]
+#[test_case(false, None, true, AMAZON_BEDROCK_PROVIDER_ID,
+    &[(Feature::IncrementalToolsLegacy, true), (Feature::IncrementalToolsLegacyGcp, false)]; "mantle_enabled")]
+#[test_case(false, None, false, AMAZON_BEDROCK_RUNTIME_PROVIDER_ID, &[]; "runtime_default")]
+#[test_case(false, None, true, AMAZON_BEDROCK_RUNTIME_PROVIDER_ID,
+    &[(Feature::IncrementalToolsLegacy, true), (Feature::IncrementalToolsLegacyGcp, false)]; "runtime_enabled")]
+#[test_case(false, None, true, GCP_PROVIDER_ID, &[]; "gcp_default")]
+#[test_case(false, None, false, GCP_PROVIDER_ID,
+    &[(Feature::IncrementalToolsLegacyGcp, false), (Feature::IncrementalToolsLegacy, true)]; "gcp_opt_out")]
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn incremental_tools_append_changed_catalog_without_rewriting_history(
     use_responses_lite: bool,
     suppress_model_change_announcements: Option<bool>,
     incremental_tools: bool,
     provider_id: &'static str,
+    feature_overrides: &'static [(Feature, bool)],
 ) -> Result<()> {
     skip_if_no_network!(Ok(()));
     let server = responses::start_mock_server().await;
@@ -214,15 +218,11 @@ async fn incremental_tools_append_changed_catalog_without_rewriting_history(
         })
         .with_config(move |config| {
             config.model_provider_id = provider_id.to_string();
-            if !use_responses_lite && incremental_tools {
+            for &(feature, enabled) in feature_overrides {
                 config
                     .features
-                    .disable(Feature::IncrementalTools)
-                    .expect("disable the Lite flag");
-                config
-                    .features
-                    .enable(Feature::IncrementalToolsLegacy)
-                    .expect("enable incremental tools on regular Responses");
+                    .set_enabled(feature, enabled)
+                    .expect("configure independent provider flags");
             }
             if let Some(suppress) = suppress_model_change_announcements {
                 config

codex-rs/features/src/lib.rs

@@ -310,8 +310,10 @@ pub enum Feature {
     CommandSessionsWorldState,
     /// Track top-level tool definitions in world state and emit incremental context updates.
     IncrementalTools,
-    /// Publish incremental tool declarations on regular Amazon Bedrock and GCP Responses.
+    /// Publish incremental tool declarations on regular Amazon Bedrock Responses.
     IncrementalToolsLegacy,
+    /// Publish incremental tool declarations on regular GCP Responses.
+    IncrementalToolsLegacyGcp,
     /// Suppress the model ID announcement in incremental context after a model switch.
     SuppressModelChangeAnnouncements,
     /// Preserve inherited tool declarations in MCP-disabled prediction forks.
@@ -1821,9 +1823,15 @@ pub const FEATURES: &[FeatureSpec] = &[
     FeatureSpec {
         id: Feature::IncrementalToolsLegacy,
         key: "incremental_tools_legacy",
-        stage: Stage::UnderDevelopment,
+        stage: Stage::Stable,
         default_enabled: false,
     },
+    FeatureSpec {
+        id: Feature::IncrementalToolsLegacyGcp,
+        key: "incremental_tools_legacy_gcp",
+        stage: Stage::Stable,
+        default_enabled: true,
+    },
     FeatureSpec {
         id: Feature::SuppressModelChangeAnnouncements,
         key: "suppress_model_change_announcements",