diff --git a/codex-rs/app-server/src/message_processor.rs b/codex-rs/app-server/src/message_processor.rs
index 857b07b848..1f67b03fd6 100644
--- a/codex-rs/app-server/src/message_processor.rs
+++ b/codex-rs/app-server/src/message_processor.rs
@@ -189,43 +189,12 @@ pub(crate) struct InitializedConnectionSessionState {
     pub(crate) opted_out_notification_methods: HashSet<String>,
     pub(crate) app_server_client_name: String,
     pub(crate) client_version: String,
-    pub(crate) client_compatibility_flags: ClientCompatibilityFlags,
-}
-
-struct InitializedClientRequestContext {
-    app_server_client_name: Option<String>,
-    client_version: Option<String>,
-    client_compatibility_flags: ClientCompatibilityFlags,
-    device_key_requests_allowed: bool,
-}
-
-impl InitializedConnectionSessionState {
-    pub(crate) fn new(
-        experimental_api_enabled: bool,
-        opted_out_notification_methods: HashSet<String>,
-        app_server_client_name: String,
-        client_version: String,
-    ) -> Self {
-        let client_compatibility_flags = client_compatibility_flags_for_app_server_client(
-            app_server_client_name.as_str(),
-            client_version.as_str(),
-        );
-        Self {
-            experimental_api_enabled,
-            opted_out_notification_methods,
-            app_server_client_name,
-            client_version,
-            client_compatibility_flags,
-        }
-    }
 }
 
 fn client_compatibility_flags_for_app_server_client(
     client_name: &str,
     client_version: &str,
 ) -> ClientCompatibilityFlags {
-    let mut flags = ClientCompatibilityFlags::default();
-
     // Xcode 26.4 shipped against CLI behavior from before PR #17043, when
     // Codex only advertised MCP elicitation support to the built-in
     // `codex_apps` server. If Codex advertises custom-server elicitation
@@ -235,11 +204,13 @@ fn client_compatibility_flags_for_app_server_client(
     //
     // TODO: Remove this Xcode 26.4 compatibility path once that client version
     // has aged out of support.
-    if client_name.eq_ignore_ascii_case("xcode") && client_version.starts_with("26.4") {
-        flags.mcp_elicitation = McpElicitationCompatibility::CodexAppsOnly;
-    }
-
-    flags
+    let mcp_elicitation =
+        if client_name.eq_ignore_ascii_case("xcode") && client_version.starts_with("26.4") {
+            McpElicitationCompatibility::CodexAppsOnly
+        } else {
+            McpElicitationCompatibility::Default
+        };
+    ClientCompatibilityFlags { mcp_elicitation }
 }
 
 impl Default for ConnectionSessionState {
@@ -293,7 +264,12 @@ impl ConnectionSessionState {
     pub(crate) fn client_compatibility_flags(&self) -> ClientCompatibilityFlags {
         self.initialized
             .get()
-            .map(|session| session.client_compatibility_flags)
+            .map(|session| {
+                client_compatibility_flags_for_app_server_client(
+                    &session.app_server_client_name,
+                    &session.client_version,
+                )
+            })
             .unwrap_or_default()
     }
 
@@ -433,6 +409,7 @@ impl MessageProcessor {
             thread_state_manager.clone(),
         );
         let thread_processor = ThreadRequestProcessor::new(
+            auth_manager.clone(),
             Arc::clone(&thread_manager),
             outgoing.clone(),
             analytics_events_client.clone(),
@@ -815,12 +792,10 @@ impl MessageProcessor {
         );
 
         let serialization_scope = codex_request.serialization_scope();
-        let initialized_client_context = InitializedClientRequestContext {
-            app_server_client_name: session.app_server_client_name().map(str::to_string),
-            client_version: session.client_version().map(str::to_string),
-            client_compatibility_flags: session.client_compatibility_flags(),
-            device_key_requests_allowed: session.allows_device_key_requests(),
-        };
+        let app_server_client_name = session.app_server_client_name().map(str::to_string);
+        let client_version = session.client_version().map(str::to_string);
+        let client_compatibility_flags = session.client_compatibility_flags();
+        let device_key_requests_allowed = session.allows_device_key_requests();
         let error_request_id = connection_request_id.clone();
         let rpc_gate = Arc::clone(&session.rpc_gate);
         let processor = Arc::clone(self);
@@ -834,7 +809,10 @@ impl MessageProcessor {
                         connection_request_id,
                         codex_request,
                         request_context,
-                        initialized_client_context,
+                        app_server_client_name,
+                        client_version,
+                        client_compatibility_flags,
+                        device_key_requests_allowed,
                     )
                     .await;
                 if let Err(error) = result {
@@ -857,12 +835,16 @@ impl MessageProcessor {
         Ok(())
     }
 
+    #[allow(clippy::too_many_arguments)]
     async fn handle_initialized_client_request(
         self: Arc<Self>,
         connection_request_id: ConnectionRequestId,
         codex_request: ClientRequest,
         request_context: RequestContext,
-        initialized_client_context: InitializedClientRequestContext,
+        app_server_client_name: Option<String>,
+        client_version: Option<String>,
+        client_compatibility_flags: ClientCompatibilityFlags,
+        device_key_requests_allowed: bool,
     ) -> Result<(), JSONRPCErrorError> {
         let connection_id = connection_request_id.connection_id;
         let request_id = ConnectionRequestId {
@@ -909,7 +891,7 @@ impl MessageProcessor {
                 self.device_key_processor.create(
                     request_id.clone(),
                     params,
-                    initialized_client_context.device_key_requests_allowed,
+                    device_key_requests_allowed,
                 );
                 Ok(None)
             }
@@ -917,7 +899,7 @@ impl MessageProcessor {
                 self.device_key_processor.public(
                     request_id.clone(),
                     params,
-                    initialized_client_context.device_key_requests_allowed,
+                    device_key_requests_allowed,
                 );
                 Ok(None)
             }
@@ -925,7 +907,7 @@ impl MessageProcessor {
                 self.device_key_processor.sign(
                     request_id.clone(),
                     params,
-                    initialized_client_context.device_key_requests_allowed,
+                    device_key_requests_allowed,
                 );
                 Ok(None)
             }
@@ -984,9 +966,9 @@ impl MessageProcessor {
                     .thread_start(
                         request_id.clone(),
                         params,
-                        initialized_client_context.app_server_client_name.clone(),
-                        initialized_client_context.client_version.clone(),
-                        initialized_client_context.client_compatibility_flags,
+                        app_server_client_name.clone(),
+                        client_version.clone(),
+                        client_compatibility_flags,
                         request_context,
                     )
                     .await
@@ -998,20 +980,12 @@ impl MessageProcessor {
             }
             ClientRequest::ThreadResume { params, .. } => {
                 self.thread_processor
-                    .thread_resume(
-                        request_id.clone(),
-                        params,
-                        initialized_client_context.client_compatibility_flags,
-                    )
+                    .thread_resume(request_id.clone(), params, client_compatibility_flags)
                     .await
             }
             ClientRequest::ThreadFork { params, .. } => {
                 self.thread_processor
-                    .thread_fork(
-                        request_id.clone(),
-                        params,
-                        initialized_client_context.client_compatibility_flags,
-                    )
+                    .thread_fork(request_id.clone(), params, client_compatibility_flags)
                     .await
             }
             ClientRequest::ThreadArchive { params, .. } => {
@@ -1165,8 +1139,8 @@ impl MessageProcessor {
                     .turn_start(
                         request_id.clone(),
                         params,
-                        initialized_client_context.app_server_client_name.clone(),
-                        initialized_client_context.client_version.clone(),
+                        app_server_client_name.clone(),
+                        client_version.clone(),
                     )
                     .await
             }
@@ -1333,30 +1307,24 @@ mod client_compatibility_tests {
 
     #[test]
     fn xcode_26_4_uses_legacy_mcp_elicitation_compatibility() {
-        for (name, version) in [
-            ("Xcode", "26.4"),
-            ("xcode", "26.4"),
-            ("Xcode", "26.4.1"),
-            ("Xcode", "26.4-beta"),
-        ] {
-            assert_eq!(
-                client_compatibility_flags_for_app_server_client(name, version),
-                ClientCompatibilityFlags {
-                    mcp_elicitation: McpElicitationCompatibility::CodexAppsOnly,
-                }
-            );
-        }
-
-        for (name, version) in [
-            ("Xcode", "26.3"),
-            ("Xcode", "26.5"),
-            ("Xcode", "27.0"),
-            ("codex-vscode", "26.4"),
-        ] {
-            assert_eq!(
-                client_compatibility_flags_for_app_server_client(name, version),
-                ClientCompatibilityFlags::default()
-            );
+        fn mcp_elicitation(name: &str, version: &str) -> McpElicitationCompatibility {
+            client_compatibility_flags_for_app_server_client(name, version).mcp_elicitation
         }
+        assert_eq!(
+            mcp_elicitation("xcode", "26.4.1"),
+            McpElicitationCompatibility::CodexAppsOnly
+        );
+        assert_eq!(
+            mcp_elicitation("Xcode", "26.4-beta"),
+            McpElicitationCompatibility::CodexAppsOnly
+        );
+        assert_eq!(
+            mcp_elicitation("Xcode", "26.5"),
+            McpElicitationCompatibility::Default
+        );
+        assert_eq!(
+            mcp_elicitation("codex-vscode", "26.4"),
+            McpElicitationCompatibility::Default
+        );
     }
 }
diff --git a/codex-rs/app-server/src/request_processors/external_agent_config_processor.rs b/codex-rs/app-server/src/request_processors/external_agent_config_processor.rs
index 85aa8ccdd7..200d8e89df 100644
--- a/codex-rs/app-server/src/request_processors/external_agent_config_processor.rs
+++ b/codex-rs/app-server/src/request_processors/external_agent_config_processor.rs
@@ -310,7 +310,6 @@ impl ExternalAgentConfigRequestProcessor {
                 dynamic_tools: Vec::new(),
                 persist_extended_history: false,
                 metrics_service_name: None,
-                client_compatibility_flags: codex_core::ClientCompatibilityFlags::default(),
                 parent_trace: None,
                 environments,
             })
diff --git a/codex-rs/app-server/src/request_processors/initialize_processor.rs b/codex-rs/app-server/src/request_processors/initialize_processor.rs
index 018ea71b97..a206b2faa0 100644
--- a/codex-rs/app-server/src/request_processors/initialize_processor.rs
+++ b/codex-rs/app-server/src/request_processors/initialize_processor.rs
@@ -90,12 +90,12 @@ impl InitializeRequestProcessor {
         let user_agent_suffix = format!("{name}; {version}");
         let codex_home = self.config.codex_home.clone();
         if session
-            .initialize(InitializedConnectionSessionState::new(
+            .initialize(InitializedConnectionSessionState {
                 experimental_api_enabled,
-                opt_out_notification_methods.into_iter().collect(),
-                name.clone(),
-                version,
-            ))
+                opted_out_notification_methods: opt_out_notification_methods.into_iter().collect(),
+                app_server_client_name: name.clone(),
+                client_version: version,
+            })
             .is_err()
         {
             return Err(invalid_request("Already initialized"));
diff --git a/codex-rs/app-server/src/request_processors/thread_processor.rs b/codex-rs/app-server/src/request_processors/thread_processor.rs
index 9c59a85b98..857074530a 100644
--- a/codex-rs/app-server/src/request_processors/thread_processor.rs
+++ b/codex-rs/app-server/src/request_processors/thread_processor.rs
@@ -246,6 +246,7 @@ fn validate_dynamic_tools(tools: &[ApiDynamicToolSpec]) -> Result<(), String> {
 
 #[derive(Clone)]
 pub(crate) struct ThreadRequestProcessor {
+    pub(super) auth_manager: Arc<AuthManager>,
     pub(super) thread_manager: Arc<ThreadManager>,
     pub(super) outgoing: Arc<OutgoingMessageSender>,
     pub(super) analytics_events_client: AnalyticsEventsClient,
@@ -264,6 +265,7 @@ pub(crate) struct ThreadRequestProcessor {
 impl ThreadRequestProcessor {
     #[allow(clippy::too_many_arguments)]
     pub(crate) fn new(
+        auth_manager: Arc<AuthManager>,
         thread_manager: Arc<ThreadManager>,
         outgoing: Arc<OutgoingMessageSender>,
         analytics_events_client: AnalyticsEventsClient,
@@ -278,6 +280,7 @@ impl ThreadRequestProcessor {
         thread_goal_processor: ThreadGoalRequestProcessor,
     ) -> Self {
         Self {
+            auth_manager,
             thread_manager,
             outgoing,
             analytics_events_client,
@@ -964,6 +967,7 @@ impl ThreadRequestProcessor {
                 .collect()
         };
         let core_dynamic_tool_count = core_dynamic_tools.len();
+        config.client_compatibility_flags = client_compatibility_flags;
 
         let NewThread {
             thread_id,
@@ -984,7 +988,6 @@ impl ThreadRequestProcessor {
                 dynamic_tools: core_dynamic_tools,
                 persist_extended_history,
                 metrics_service_name: service_name,
-                client_compatibility_flags,
                 parent_trace: request_trace,
                 environments,
             })
@@ -2406,7 +2409,7 @@ impl ThreadRequestProcessor {
         .await;
 
         // Derive a Config using the same logic as new conversation, honoring overrides if provided.
-        let config = match self
+        let mut config = match self
             .config_manager
             .load_for_cwd(request_overrides, typesafe_overrides, history_cwd)
             .await
@@ -2418,25 +2421,20 @@ impl ThreadRequestProcessor {
                 return Ok(());
             }
         };
+        config.client_compatibility_flags = client_compatibility_flags;
 
         let instruction_sources = Self::instruction_sources_from_config(&config).await;
         let response_history = thread_history.clone();
 
         match self
             .thread_manager
-            .start_thread_with_options(StartThreadOptions {
-                config: config.clone(),
-                initial_history: thread_history,
-                session_source: None,
-                dynamic_tools: Vec::new(),
+            .resume_thread_with_history(
+                config.clone(),
+                thread_history,
+                self.auth_manager.clone(),
                 persist_extended_history,
-                metrics_service_name: None,
-                client_compatibility_flags,
-                parent_trace: self.request_trace_context(&request_id).await,
-                environments: self
-                    .thread_manager
-                    .default_environment_selections(&config.cwd),
-            })
+                self.request_trace_context(&request_id).await,
+            )
             .await
         {
             Ok(NewThread {
@@ -3022,11 +3020,12 @@ impl ThreadRequestProcessor {
         );
         typesafe_overrides.ephemeral = ephemeral.then_some(true);
         // Derive a Config using the same logic as new conversation, honoring overrides if provided.
-        let config = self
+        let mut config = self
             .config_manager
             .load_for_cwd(request_overrides, typesafe_overrides, history_cwd)
             .await
             .map_err(|err| config_load_error(&err))?;
+        config.client_compatibility_flags = client_compatibility_flags;
 
         let fallback_model_provider = config.model_provider_id.clone();
         let instruction_sources = Self::instruction_sources_from_config(&config).await;
@@ -3038,7 +3037,7 @@ impl ThreadRequestProcessor {
             ..
         } = self
             .thread_manager
-            .fork_thread_from_history_with_client_compatibility_flags(
+            .fork_thread_from_history(
                 ForkSnapshot::Interrupted,
                 config,
                 InitialHistory::Resumed(ResumedHistory {
@@ -3048,7 +3047,6 @@ impl ThreadRequestProcessor {
                 }),
                 persist_extended_history,
                 self.request_trace_context(&request_id).await,
-                client_compatibility_flags,
             )
             .await
             .map_err(|err| match err {
diff --git a/codex-rs/app-server/src/request_processors/turn_processor.rs b/codex-rs/app-server/src/request_processors/turn_processor.rs
index 0a507182fe..613e53523c 100644
--- a/codex-rs/app-server/src/request_processors/turn_processor.rs
+++ b/codex-rs/app-server/src/request_processors/turn_processor.rs
@@ -904,6 +904,7 @@ impl TurnRequestProcessor {
         };
 
         let mut config = self.config.as_ref().clone();
+        config.client_compatibility_flags = parent_thread.client_compatibility_flags().await;
         if let Some(review_model) = &config.review_model {
             config.model = Some(review_model.clone());
         }
@@ -915,13 +916,12 @@ impl TurnRequestProcessor {
             ..
         } = self
             .thread_manager
-            .fork_thread_with_client_compatibility_flags(
+            .fork_thread(
                 ForkSnapshot::Interrupted,
                 config.clone(),
                 rollout_path,
                 /*persist_extended_history*/ false,
                 self.request_trace_context(request_id).await,
-                parent_thread.client_compatibility_flags().await,
             )
             .await
             .map_err(|err| {
diff --git a/codex-rs/codex-mcp/src/connection_manager.rs b/codex-rs/codex-mcp/src/connection_manager.rs
index f6219cf79e..936a6a82ac 100644
--- a/codex-rs/codex-mcp/src/connection_manager.rs
+++ b/codex-rs/codex-mcp/src/connection_manager.rs
@@ -202,7 +202,6 @@ impl McpConnectionManager {
                 cancel_token.clone(),
                 tx_event.clone(),
                 elicitation_requests.clone(),
-                elicitation_compatibility,
                 codex_apps_tools_cache_context,
                 Arc::clone(&tool_plugin_provenance),
                 runtime_environment.clone(),
diff --git a/codex-rs/codex-mcp/src/connection_manager_tests.rs b/codex-rs/codex-mcp/src/connection_manager_tests.rs
index 0c3265051f..4c606f2672 100644
--- a/codex-rs/codex-mcp/src/connection_manager_tests.rs
+++ b/codex-rs/codex-mcp/src/connection_manager_tests.rs
@@ -283,10 +283,6 @@ async fn codex_apps_only_custom_server_elicitation_is_declined_without_event() {
             meta: None,
             message: "What should I say?".to_string(),
             requested_schema: rmcp::model::ElicitationSchema::builder()
-                .required_property(
-                    "message",
-                    rmcp::model::PrimitiveSchema::String(rmcp::model::StringSchema::new()),
-                )
                 .build()
                 .expect("schema should build"),
         },
@@ -294,14 +290,8 @@ async fn codex_apps_only_custom_server_elicitation_is_declined_without_event() {
     .await
     .expect("elicitation should auto decline");
 
-    assert_eq!(
-        response,
-        ElicitationResponse {
-            action: ElicitationAction::Decline,
-            content: None,
-            meta: None,
-        }
-    );
+    assert_eq!(response.action, ElicitationAction::Decline);
+    assert_eq!(response.content, None);
     assert!(matches!(
         rx_event.try_recv(),
         Err(async_channel::TryRecvError::Empty)
@@ -846,7 +836,6 @@ fn elicitation_capability_uses_2025_06_18_shape_for_all_servers() {
     for server_name in [CODEX_APPS_MCP_SERVER_NAME, "custom_mcp"] {
         let capability =
             elicitation_capability_for_server(server_name, McpElicitationCompatibility::Default);
-        assert_eq!(capability, Some(ElicitationCapability::default()));
         assert_eq!(
             serde_json::to_value(capability).expect("serialize elicitation capability"),
             serde_json::json!({})
@@ -855,16 +844,14 @@ fn elicitation_capability_uses_2025_06_18_shape_for_all_servers() {
 }
 
 #[test]
-fn codex_apps_only_elicitation_capability_keeps_codex_apps_enabled() {
+fn codex_apps_only_elicitation_capability_suppresses_custom_servers() {
+    let compatibility = McpElicitationCompatibility::CodexAppsOnly;
     assert_eq!(
-        elicitation_capability_for_server(
-            CODEX_APPS_MCP_SERVER_NAME,
-            McpElicitationCompatibility::CodexAppsOnly,
-        ),
+        elicitation_capability_for_server(CODEX_APPS_MCP_SERVER_NAME, compatibility),
         Some(ElicitationCapability::default())
     );
     assert_eq!(
-        elicitation_capability_for_server("custom_mcp", McpElicitationCompatibility::CodexAppsOnly,),
+        elicitation_capability_for_server("custom_mcp", compatibility),
         None
     );
 }
diff --git a/codex-rs/codex-mcp/src/elicitation.rs b/codex-rs/codex-mcp/src/elicitation.rs
index dcb26eab97..c724ed29d2 100644
--- a/codex-rs/codex-mcp/src/elicitation.rs
+++ b/codex-rs/codex-mcp/src/elicitation.rs
@@ -191,14 +191,15 @@ impl ElicitationRequestManager {
             .boxed()
         })
     }
+
+    pub(crate) fn compatibility(&self) -> McpElicitationCompatibility {
+        self.compatibility
+    }
 }
 
 /// Compatibility policy for the MCP elicitation capability surface.
-///
-/// The default behavior advertises MCP elicitation support to every server.
-/// `CodexAppsOnly` preserves the pre-PR #17043 capability surface by keeping
-/// support for the built-in `codex_apps` server while suppressing support for
-/// custom MCP servers.
+/// `CodexAppsOnly` preserves the pre-PR #17043 behavior for old clients by
+/// keeping support for `codex_apps` while suppressing custom MCP servers.
 #[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
 pub enum McpElicitationCompatibility {
     #[default]
@@ -207,7 +208,7 @@ pub enum McpElicitationCompatibility {
 }
 
 impl McpElicitationCompatibility {
-    pub(crate) fn allows_server_elicitation(self, server_name: &str) -> bool {
+    pub fn allows_server_elicitation(self, server_name: &str) -> bool {
         match self {
             Self::Default => true,
             Self::CodexAppsOnly => server_name == CODEX_APPS_MCP_SERVER_NAME,
diff --git a/codex-rs/codex-mcp/src/rmcp_client.rs b/codex-rs/codex-mcp/src/rmcp_client.rs
index defeb6d81f..4fde4ded92 100644
--- a/codex-rs/codex-mcp/src/rmcp_client.rs
+++ b/codex-rs/codex-mcp/src/rmcp_client.rs
@@ -139,7 +139,6 @@ impl AsyncManagedClient {
         cancel_token: CancellationToken,
         tx_event: Sender<Event>,
         elicitation_requests: ElicitationRequestManager,
-        elicitation_compatibility: McpElicitationCompatibility,
         codex_apps_tools_cache_context: Option<CodexAppsToolsCacheContext>,
         tool_plugin_provenance: Arc<ToolPluginProvenance>,
         runtime_environment: McpRuntimeEnvironment,
@@ -182,7 +181,6 @@ impl AsyncManagedClient {
                         tool_filter: startup_tool_filter,
                         tx_event,
                         elicitation_requests,
-                        elicitation_compatibility,
                         codex_apps_tools_cache_context,
                     },
                 )
@@ -466,10 +464,10 @@ async fn start_server_task(
         tool_filter,
         tx_event,
         elicitation_requests,
-        elicitation_compatibility,
         codex_apps_tools_cache_context,
     } = params;
-    let elicitation = elicitation_capability_for_server(&server_name, elicitation_compatibility);
+    let elicitation =
+        elicitation_capability_for_server(&server_name, elicitation_requests.compatibility());
     let params = InitializeRequestParams {
         meta: None,
         capabilities: ClientCapabilities {
@@ -552,7 +550,6 @@ struct StartServerTaskParams {
     tool_filter: ToolFilter,
     tx_event: Sender<Event>,
     elicitation_requests: ElicitationRequestManager,
-    elicitation_compatibility: McpElicitationCompatibility,
     codex_apps_tools_cache_context: Option<CodexAppsToolsCacheContext>,
 }
 
diff --git a/codex-rs/core/src/codex_delegate.rs b/codex-rs/core/src/codex_delegate.rs
index 1d7c4605eb..1c46f4c93a 100644
--- a/codex-rs/core/src/codex_delegate.rs
+++ b/codex-rs/core/src/codex_delegate.rs
@@ -62,7 +62,7 @@ use crate::session::completed_session_loop_termination;
 /// The returned `ops_tx` allows the caller to submit additional `Op`s to the sub-agent.
 #[allow(clippy::too_many_arguments)]
 pub(crate) async fn run_codex_thread_interactive(
-    config: Config,
+    mut config: Config,
     auth_manager: Arc<AuthManager>,
     models_manager: SharedModelsManager,
     parent_session: Arc<Session>,
@@ -73,7 +73,7 @@ pub(crate) async fn run_codex_thread_interactive(
 ) -> Result<Codex, CodexErr> {
     let (tx_sub, rx_sub) = async_channel::bounded(SUBMISSION_CHANNEL_CAPACITY);
     let (tx_ops, rx_ops) = async_channel::bounded(SUBMISSION_CHANNEL_CAPACITY);
-    let client_compatibility_flags = parent_session.client_compatibility_flags().await;
+    config.client_compatibility_flags = parent_session.client_compatibility_flags().await;
     let CodexSpawnOk { codex, .. } = Box::pin(Codex::spawn(CodexSpawnArgs {
         config,
         auth_manager,
@@ -89,7 +89,6 @@ pub(crate) async fn run_codex_thread_interactive(
         dynamic_tools: Vec::new(),
         persist_extended_history: false,
         metrics_service_name: None,
-        client_compatibility_flags,
         inherited_shell_snapshot: None,
         user_shell_override: None,
         inherited_exec_policy: Some(Arc::clone(&parent_session.services.exec_policy)),
diff --git a/codex-rs/core/src/config/config_tests.rs b/codex-rs/core/src/config/config_tests.rs
index b48cf020f2..0a818c7730 100644
--- a/codex-rs/core/src/config/config_tests.rs
+++ b/codex-rs/core/src/config/config_tests.rs
@@ -6447,6 +6447,7 @@ async fn test_precedence_fixture_with_o3_profile() -> std::io::Result<()> {
             check_for_update_on_startup: true,
             disable_paste_burst: false,
             tui_notifications: Default::default(),
+            client_compatibility_flags: Default::default(),
             animations: true,
             show_tooltips: true,
             tui_vim_mode_default: false,
@@ -6649,6 +6650,7 @@ async fn test_precedence_fixture_with_gpt3_profile() -> std::io::Result<()> {
         check_for_update_on_startup: true,
         disable_paste_burst: false,
         tui_notifications: Default::default(),
+        client_compatibility_flags: Default::default(),
         animations: true,
         show_tooltips: true,
         tui_vim_mode_default: false,
@@ -6805,6 +6807,7 @@ async fn test_precedence_fixture_with_zdr_profile() -> std::io::Result<()> {
         check_for_update_on_startup: true,
         disable_paste_burst: false,
         tui_notifications: Default::default(),
+        client_compatibility_flags: Default::default(),
         animations: true,
         show_tooltips: true,
         tui_vim_mode_default: false,
@@ -6946,6 +6949,7 @@ async fn test_precedence_fixture_with_gpt5_profile() -> std::io::Result<()> {
         check_for_update_on_startup: true,
         disable_paste_burst: false,
         tui_notifications: Default::default(),
+        client_compatibility_flags: Default::default(),
         animations: true,
         show_tooltips: true,
         tui_vim_mode_default: false,
diff --git a/codex-rs/core/src/config/mod.rs b/codex-rs/core/src/config/mod.rs
index 2154bb0170..d3c9538771 100644
--- a/codex-rs/core/src/config/mod.rs
+++ b/codex-rs/core/src/config/mod.rs
@@ -1,3 +1,4 @@
+use crate::ClientCompatibilityFlags;
 use crate::agents_md::AgentsMdManager;
 use crate::config::edit::ConfigEdit;
 use crate::config::edit::ConfigEditsBuilder;
@@ -505,6 +506,10 @@ pub struct Config {
     /// TUI notification settings, including enabled events, delivery method, and focus condition.
     pub tui_notifications: TuiNotificationSettings,
 
+    /// Runtime-only client compatibility flags selected by the app server
+    /// before creating a session. These are not loaded from config.toml.
+    pub client_compatibility_flags: ClientCompatibilityFlags,
+
     /// Enable ASCII animations and shimmer effects in the TUI.
     pub animations: bool,
 
@@ -3135,6 +3140,7 @@ impl Config {
                 .as_ref()
                 .map(|t| t.notification_settings.clone())
                 .unwrap_or_default(),
+            client_compatibility_flags: ClientCompatibilityFlags::default(),
             animations: cfg.tui.as_ref().map(|t| t.animations).unwrap_or(true),
             show_tooltips: cfg.tui.as_ref().map(|t| t.show_tooltips).unwrap_or(true),
             model_availability_nux: cfg
diff --git a/codex-rs/core/src/mcp_tool_call.rs b/codex-rs/core/src/mcp_tool_call.rs
index 58f26cb25e..69b738534e 100644
--- a/codex-rs/core/src/mcp_tool_call.rs
+++ b/codex-rs/core/src/mcp_tool_call.rs
@@ -1099,7 +1099,11 @@ async fn maybe_request_mcp_tool_approval(
     let tool_call_mcp_elicitation_enabled = turn_context
         .config
         .features
-        .enabled(Feature::ToolCallMcpElicitation);
+        .enabled(Feature::ToolCallMcpElicitation)
+        && turn_context
+            .client_compatibility_flags
+            .mcp_elicitation
+            .allows_server_elicitation(&invocation.server);
 
     if routes_approval_to_guardian(turn_context) {
         let review_id = new_guardian_review_id();
diff --git a/codex-rs/core/src/mcp_tool_call_tests.rs b/codex-rs/core/src/mcp_tool_call_tests.rs
index d83307e808..d4dd0a89bf 100644
--- a/codex-rs/core/src/mcp_tool_call_tests.rs
+++ b/codex-rs/core/src/mcp_tool_call_tests.rs
@@ -1,4 +1,6 @@
 use super::*;
+use crate::ClientCompatibilityFlags;
+use crate::McpElicitationCompatibility;
 use crate::config::ConfigBuilder;
 use crate::session::tests::make_session_and_context;
 use crate::session::tests::make_session_and_context_with_rx;
@@ -18,6 +20,7 @@ use codex_hooks::HooksConfig;
 use codex_model_provider::create_model_provider;
 use codex_protocol::models::PermissionProfile;
 use codex_protocol::protocol::AskForApproval;
+use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::GranularApprovalConfig;
 use core_test_support::PathExt;
 use core_test_support::responses::ev_assistant_message;
@@ -2276,7 +2279,19 @@ async fn guardian_mode_mcp_denial_returns_rationale_message() {
 
 #[tokio::test]
 async fn prompt_mode_waits_for_approval_when_annotations_do_not_require_approval() {
-    let (session, turn_context, _rx_event) = make_session_and_context_with_rx().await;
+    let (session, mut turn_context, rx_event) = make_session_and_context_with_rx().await;
+    {
+        let turn_context = Arc::get_mut(&mut turn_context).expect("single turn context ref");
+        let mut config = (*turn_context.config).clone();
+        config
+            .features
+            .enable(Feature::ToolCallMcpElicitation)
+            .expect("test setup should allow enabling tool call MCP elicitation");
+        turn_context.config = Arc::new(config);
+        turn_context.client_compatibility_flags = ClientCompatibilityFlags {
+            mcp_elicitation: McpElicitationCompatibility::CodexAppsOnly,
+        };
+    }
     {
         let mut active_turn = session.active_turn.lock().await;
         *active_turn = Some(ActiveTurn::default());
@@ -2302,7 +2317,7 @@ async fn prompt_mode_waits_for_approval_when_annotations_do_not_require_approval
         openai_file_input_params: None,
     };
 
-    let mut approval_task = {
+    let approval_task = {
         let session = Arc::clone(&session);
         let turn_context = Arc::clone(&turn_context);
         tokio::spawn(async move {
@@ -2319,12 +2334,11 @@ async fn prompt_mode_waits_for_approval_when_annotations_do_not_require_approval
         })
     };
 
-    assert!(
-        tokio::time::timeout(std::time::Duration::from_millis(200), &mut approval_task)
-            .await
-            .is_err(),
-        "prompt mode should wait for approval instead of auto-allowing"
-    );
+    let event = tokio::time::timeout(std::time::Duration::from_secs(1), rx_event.recv())
+        .await
+        .expect("approval request should emit an event")
+        .expect("event channel should stay open");
+    assert!(matches!(event.msg, EventMsg::RequestUserInput(_)));
     approval_task.abort();
 }
 
diff --git a/codex-rs/core/src/session/mod.rs b/codex-rs/core/src/session/mod.rs
index ecc9db5a12..d3a5e59b1a 100644
--- a/codex-rs/core/src/session/mod.rs
+++ b/codex-rs/core/src/session/mod.rs
@@ -401,7 +401,6 @@ pub(crate) struct CodexSpawnArgs {
     pub(crate) dynamic_tools: Vec<DynamicToolSpec>,
     pub(crate) persist_extended_history: bool,
     pub(crate) metrics_service_name: Option<String>,
-    pub(crate) client_compatibility_flags: ClientCompatibilityFlags,
     pub(crate) inherited_shell_snapshot: Option<Arc<ShellSnapshot>>,
     pub(crate) inherited_exec_policy: Option<Arc<ExecPolicyManager>>,
     /// Parent rollout trace used only to derive fresh spawned child traces.
@@ -463,7 +462,6 @@ impl Codex {
             dynamic_tools,
             persist_extended_history,
             metrics_service_name,
-            client_compatibility_flags,
             inherited_shell_snapshot,
             user_shell_override,
             inherited_exec_policy,
@@ -615,7 +613,6 @@ impl Codex {
             environments: environment_selections.to_selections(),
             original_config_do_not_use: Arc::clone(&config),
             metrics_service_name,
-            client_compatibility_flags,
             app_server_client_name: None,
             app_server_client_version: None,
             session_source,
@@ -843,6 +840,7 @@ impl Session {
             .lock()
             .await
             .session_configuration
+            .original_config_do_not_use
             .client_compatibility_flags
     }
 
diff --git a/codex-rs/core/src/session/session.rs b/codex-rs/core/src/session/session.rs
index 7d49f8a4c7..785e3da90f 100644
--- a/codex-rs/core/src/session/session.rs
+++ b/codex-rs/core/src/session/session.rs
@@ -1,5 +1,4 @@
 use super::*;
-use crate::ClientCompatibilityFlags;
 use crate::goals::GoalRuntimeState;
 use codex_otel::LEGACY_NOTIFY_CONFIGURED_METRIC;
 use codex_protocol::permissions::FileSystemPath;
@@ -84,8 +83,6 @@ pub(crate) struct SessionConfiguration {
     pub(super) original_config_do_not_use: Arc<Config>,
     /// Optional service name tag for session metrics.
     pub(super) metrics_service_name: Option<String>,
-    /// App-server client compatibility behavior selected at session creation.
-    pub(super) client_compatibility_flags: ClientCompatibilityFlags,
     pub(super) app_server_client_name: Option<String>,
     pub(super) app_server_client_version: Option<String>,
     /// Source of the session (cli, vscode, exec, mcp, ...)
@@ -1001,6 +998,7 @@ impl Session {
                 tool_plugin_provenance,
                 auth,
                 session_configuration
+                    .original_config_do_not_use
                     .client_compatibility_flags
                     .mcp_elicitation,
             )
diff --git a/codex-rs/core/src/session/tests.rs b/codex-rs/core/src/session/tests.rs
index 90cfd5018e..b8554b25e9 100644
--- a/codex-rs/core/src/session/tests.rs
+++ b/codex-rs/core/src/session/tests.rs
@@ -1,6 +1,5 @@
 use super::turn_context::TurnEnvironment;
 use super::*;
-use crate::ClientCompatibilityFlags;
 use crate::config::ConfigBuilder;
 use crate::config::test_config;
 use crate::context::ContextualUserFragment;
@@ -2373,7 +2372,6 @@ async fn set_rate_limits_retains_previous_credits() {
         metrics_service_name: None,
         app_server_client_name: None,
         app_server_client_version: None,
-        client_compatibility_flags: ClientCompatibilityFlags::default(),
         session_source: SessionSource::Exec,
         dynamic_tools: Vec::new(),
         persist_extended_history: false,
@@ -2477,7 +2475,6 @@ async fn set_rate_limits_updates_plan_type_when_present() {
         metrics_service_name: None,
         app_server_client_name: None,
         app_server_client_version: None,
-        client_compatibility_flags: ClientCompatibilityFlags::default(),
         session_source: SessionSource::Exec,
         dynamic_tools: Vec::new(),
         persist_extended_history: false,
@@ -2936,7 +2933,6 @@ pub(crate) async fn make_session_configuration_for_tests() -> SessionConfigurati
         metrics_service_name: None,
         app_server_client_name: None,
         app_server_client_version: None,
-        client_compatibility_flags: ClientCompatibilityFlags::default(),
         session_source: SessionSource::Exec,
         dynamic_tools: Vec::new(),
         persist_extended_history: false,
@@ -3462,7 +3458,6 @@ async fn session_new_fails_when_zsh_fork_enabled_without_zsh_path() {
         metrics_service_name: None,
         app_server_client_name: None,
         app_server_client_version: None,
-        client_compatibility_flags: ClientCompatibilityFlags::default(),
         session_source: SessionSource::Exec,
         dynamic_tools: Vec::new(),
         persist_extended_history: false,
@@ -3568,7 +3563,6 @@ pub(crate) async fn make_session_and_context() -> (Session, TurnContext) {
         metrics_service_name: None,
         app_server_client_name: None,
         app_server_client_version: None,
-        client_compatibility_flags: ClientCompatibilityFlags::default(),
         session_source: SessionSource::Exec,
         dynamic_tools: Vec::new(),
         persist_extended_history: false,
@@ -3781,7 +3775,6 @@ async fn make_session_with_config_and_rx(
         metrics_service_name: None,
         app_server_client_name: None,
         app_server_client_version: None,
-        client_compatibility_flags: ClientCompatibilityFlags::default(),
         session_source: SessionSource::Exec,
         dynamic_tools: Vec::new(),
         persist_extended_history: false,
@@ -5062,7 +5055,6 @@ where
         metrics_service_name: None,
         app_server_client_name: None,
         app_server_client_version: None,
-        client_compatibility_flags: ClientCompatibilityFlags::default(),
         session_source: SessionSource::Exec,
         dynamic_tools,
         persist_extended_history: false,
diff --git a/codex-rs/core/src/session/tests/guardian_tests.rs b/codex-rs/core/src/session/tests/guardian_tests.rs
index 6a1e16e6b4..d6a87d466a 100644
--- a/codex-rs/core/src/session/tests/guardian_tests.rs
+++ b/codex-rs/core/src/session/tests/guardian_tests.rs
@@ -750,7 +750,6 @@ async fn guardian_subagent_does_not_inherit_parent_exec_policy_rules() {
         dynamic_tools: Vec::new(),
         persist_extended_history: false,
         metrics_service_name: None,
-        client_compatibility_flags: crate::ClientCompatibilityFlags::default(),
         inherited_shell_snapshot: None,
         inherited_exec_policy: Some(Arc::new(parent_exec_policy)),
         parent_rollout_thread_trace: codex_rollout_trace::ThreadTraceContext::disabled(),
diff --git a/codex-rs/core/src/session/turn_context.rs b/codex-rs/core/src/session/turn_context.rs
index 1d623b5378..d502227b74 100644
--- a/codex-rs/core/src/session/turn_context.rs
+++ b/codex-rs/core/src/session/turn_context.rs
@@ -530,7 +530,9 @@ impl Session {
             current_date: Some(current_date),
             timezone: Some(timezone),
             app_server_client_name: session_configuration.app_server_client_name.clone(),
-            client_compatibility_flags: session_configuration.client_compatibility_flags,
+            client_compatibility_flags: session_configuration
+                .original_config_do_not_use
+                .client_compatibility_flags,
             developer_instructions: session_configuration.developer_instructions.clone(),
             compact_prompt: session_configuration.compact_prompt.clone(),
             user_instructions: session_configuration.user_instructions.clone(),
diff --git a/codex-rs/core/src/thread_manager.rs b/codex-rs/core/src/thread_manager.rs
index 0f4d7c12af..927f45279e 100644
--- a/codex-rs/core/src/thread_manager.rs
+++ b/codex-rs/core/src/thread_manager.rs
@@ -1,4 +1,3 @@
-use crate::ClientCompatibilityFlags;
 use crate::SkillsManager;
 use crate::agent::AgentControl;
 use crate::codex_thread::CodexThread;
@@ -220,7 +219,6 @@ pub struct StartThreadOptions {
     pub dynamic_tools: Vec<codex_protocol::dynamic_tools::DynamicToolSpec>,
     pub persist_extended_history: bool,
     pub metrics_service_name: Option<String>,
-    pub client_compatibility_flags: ClientCompatibilityFlags,
     pub parent_trace: Option<W3cTraceContext>,
     pub environments: Vec<TurnEnvironmentSelection>,
 }
@@ -561,7 +559,6 @@ impl ThreadManager {
             dynamic_tools,
             persist_extended_history,
             metrics_service_name: None,
-            client_compatibility_flags: ClientCompatibilityFlags::default(),
             parent_trace: None,
             environments,
         }))
@@ -584,7 +581,6 @@ impl ThreadManager {
             options.dynamic_tools,
             options.persist_extended_history,
             options.metrics_service_name,
-            options.client_compatibility_flags,
             /*inherited_shell_snapshot*/ None,
             /*inherited_exec_policy*/ None,
             options.parent_trace,
@@ -775,31 +771,6 @@ impl ThreadManager {
         .await
     }
 
-    pub async fn fork_thread_with_client_compatibility_flags<S>(
-        &self,
-        snapshot: S,
-        config: Config,
-        path: PathBuf,
-        persist_extended_history: bool,
-        parent_trace: Option<W3cTraceContext>,
-        client_compatibility_flags: ClientCompatibilityFlags,
-    ) -> CodexResult<NewThread>
-    where
-        S: Into<ForkSnapshot>,
-    {
-        let snapshot = snapshot.into();
-        let history = RolloutRecorder::get_rollout_history(&path).await?;
-        self.fork_thread_from_history_with_client_compatibility_flags(
-            snapshot,
-            config,
-            history,
-            persist_extended_history,
-            parent_trace,
-            client_compatibility_flags,
-        )
-        .await
-    }
-
     /// Fork an existing thread from already-loaded store history.
     pub async fn fork_thread_from_history<S>(
         &self,
@@ -809,29 +780,6 @@ impl ThreadManager {
         persist_extended_history: bool,
         parent_trace: Option<W3cTraceContext>,
     ) -> CodexResult<NewThread>
-    where
-        S: Into<ForkSnapshot>,
-    {
-        self.fork_thread_from_history_with_client_compatibility_flags(
-            snapshot,
-            config,
-            history,
-            persist_extended_history,
-            parent_trace,
-            ClientCompatibilityFlags::default(),
-        )
-        .await
-    }
-
-    pub async fn fork_thread_from_history_with_client_compatibility_flags<S>(
-        &self,
-        snapshot: S,
-        config: Config,
-        history: InitialHistory,
-        persist_extended_history: bool,
-        parent_trace: Option<W3cTraceContext>,
-        client_compatibility_flags: ClientCompatibilityFlags,
-    ) -> CodexResult<NewThread>
     where
         S: Into<ForkSnapshot>,
     {
@@ -841,7 +789,6 @@ impl ThreadManager {
             history,
             persist_extended_history,
             parent_trace,
-            client_compatibility_flags,
         )
         .await
     }
@@ -853,7 +800,6 @@ impl ThreadManager {
         history: InitialHistory,
         persist_extended_history: bool,
         parent_trace: Option<W3cTraceContext>,
-        client_compatibility_flags: ClientCompatibilityFlags,
     ) -> CodexResult<NewThread> {
         let interrupted_marker = InterruptedTurnHistoryMarker::from_config(&config);
         let history = fork_history_from_snapshot(snapshot, history, interrupted_marker);
@@ -861,18 +807,14 @@ impl ThreadManager {
             self.state.environment_manager.as_ref(),
             &config.cwd,
         );
-        Box::pin(self.state.spawn_thread_with_source(
+        Box::pin(self.state.spawn_thread(
             config,
             history,
             Arc::clone(&self.state.auth_manager),
             self.agent_control(),
-            self.state.session_source.clone(),
             Vec::new(),
             persist_extended_history,
             /*metrics_service_name*/ None,
-            client_compatibility_flags,
-            /*inherited_shell_snapshot*/ None,
-            /*inherited_exec_policy*/ None,
             parent_trace,
             environments,
             /*user_shell_override*/ None,
@@ -915,44 +857,6 @@ impl ThreadManagerState {
         }
     }
 
-    async fn client_compatibility_flags_for_source(
-        &self,
-        session_source: &SessionSource,
-        explicit_flags: ClientCompatibilityFlags,
-    ) -> ClientCompatibilityFlags {
-        // Root app-server threads receive explicit flags at startup. Thread-spawn
-        // subagents inherit those flags from their parent so the same client
-        // compatibility behavior applies throughout the visible thread tree.
-        if explicit_flags != ClientCompatibilityFlags::default() {
-            return explicit_flags;
-        }
-
-        let SessionSource::SubAgent(SubAgentSource::ThreadSpawn {
-            parent_thread_id, ..
-        }) = session_source
-        else {
-            return explicit_flags;
-        };
-
-        match self.get_thread(*parent_thread_id).await {
-            Ok(parent_thread) => {
-                parent_thread
-                    .codex
-                    .session
-                    .client_compatibility_flags()
-                    .await
-            }
-            Err(error) => {
-                warn!(
-                    error = %error,
-                    parent_thread_id = %parent_thread_id,
-                    "using default client compatibility flags: failed to load parent thread"
-                );
-                explicit_flags
-            }
-        }
-    }
-
     pub(crate) async fn read_stored_thread(
         &self,
         params: ReadThreadParams,
@@ -1048,7 +952,6 @@ impl ThreadManagerState {
             Vec::new(),
             persist_extended_history,
             metrics_service_name,
-            ClientCompatibilityFlags::default(),
             inherited_shell_snapshot,
             inherited_exec_policy,
             /*parent_trace*/ None,
@@ -1081,7 +984,6 @@ impl ThreadManagerState {
             Vec::new(),
             /*persist_extended_history*/ false,
             /*metrics_service_name*/ None,
-            ClientCompatibilityFlags::default(),
             inherited_shell_snapshot,
             inherited_exec_policy,
             /*parent_trace*/ None,
@@ -1115,7 +1017,6 @@ impl ThreadManagerState {
             Vec::new(),
             persist_extended_history,
             /*metrics_service_name*/ None,
-            ClientCompatibilityFlags::default(),
             inherited_shell_snapshot,
             inherited_exec_policy,
             /*parent_trace*/ None,
@@ -1149,7 +1050,6 @@ impl ThreadManagerState {
             dynamic_tools,
             persist_extended_history,
             metrics_service_name,
-            ClientCompatibilityFlags::default(),
             /*inherited_shell_snapshot*/ None,
             /*inherited_exec_policy*/ None,
             parent_trace,
@@ -1170,7 +1070,6 @@ impl ThreadManagerState {
         dynamic_tools: Vec<codex_protocol::dynamic_tools::DynamicToolSpec>,
         persist_extended_history: bool,
         metrics_service_name: Option<String>,
-        client_compatibility_flags: ClientCompatibilityFlags,
         inherited_shell_snapshot: Option<Arc<ShellSnapshot>>,
         inherited_exec_policy: Option<Arc<crate::exec_policy::ExecPolicyManager>>,
         parent_trace: Option<W3cTraceContext>,
@@ -1217,9 +1116,6 @@ impl ThreadManagerState {
         let parent_rollout_thread_trace = self
             .parent_rollout_thread_trace_for_source(&session_source, &initial_history)
             .await;
-        let client_compatibility_flags = self
-            .client_compatibility_flags_for_source(&session_source, client_compatibility_flags)
-            .await;
         let tracked_session_source = session_source.clone();
         let CodexSpawnOk {
             codex, thread_id, ..
@@ -1238,7 +1134,6 @@ impl ThreadManagerState {
             dynamic_tools,
             persist_extended_history,
             metrics_service_name,
-            client_compatibility_flags,
             inherited_shell_snapshot,
             inherited_exec_policy,
             parent_rollout_thread_trace,
diff --git a/codex-rs/core/src/thread_manager_tests.rs b/codex-rs/core/src/thread_manager_tests.rs
index e4808e1ad7..6c53452184 100644
--- a/codex-rs/core/src/thread_manager_tests.rs
+++ b/codex-rs/core/src/thread_manager_tests.rs
@@ -1,6 +1,4 @@
 use super::*;
-use crate::ClientCompatibilityFlags;
-use crate::McpElicitationCompatibility;
 use crate::config::test_config;
 use crate::rollout::RolloutRecorder;
 use crate::session::session::SessionSettingsUpdate;
@@ -321,7 +319,6 @@ async fn start_thread_accepts_explicit_environment_when_default_environment_is_d
             dynamic_tools: Vec::new(),
             persist_extended_history: false,
             metrics_service_name: None,
-            client_compatibility_flags: ClientCompatibilityFlags::default(),
             parent_trace: None,
             environments: vec![TurnEnvironmentSelection {
                 environment_id: "local".to_string(),
@@ -334,51 +331,6 @@ async fn start_thread_accepts_explicit_environment_when_default_environment_is_d
     assert_eq!(manager.list_thread_ids().await, vec![thread.thread_id]);
 }
 
-#[tokio::test]
-async fn start_thread_options_set_client_compatibility_flags_before_initial_session() {
-    let temp_dir = tempdir().expect("tempdir");
-    let mut config = test_config().await;
-    config.codex_home = temp_dir.path().join("codex-home").abs();
-    config.cwd = config.codex_home.abs();
-    std::fs::create_dir_all(&config.codex_home).expect("create codex home");
-
-    let manager = ThreadManager::with_models_provider_and_home_for_tests(
-        CodexAuth::from_api_key("dummy"),
-        config.model_provider.clone(),
-        config.codex_home.to_path_buf(),
-        Arc::new(codex_exec_server::EnvironmentManager::default_for_tests()),
-    );
-
-    let thread = manager
-        .start_thread_with_options(StartThreadOptions {
-            config,
-            initial_history: InitialHistory::New,
-            session_source: None,
-            dynamic_tools: Vec::new(),
-            persist_extended_history: false,
-            metrics_service_name: None,
-            client_compatibility_flags: ClientCompatibilityFlags {
-                mcp_elicitation: McpElicitationCompatibility::CodexAppsOnly,
-            },
-            parent_trace: None,
-            environments: Vec::new(),
-        })
-        .await
-        .expect("thread should start with client compatibility flags");
-
-    assert_eq!(
-        thread
-            .thread
-            .codex
-            .session
-            .client_compatibility_flags()
-            .await,
-        ClientCompatibilityFlags {
-            mcp_elicitation: McpElicitationCompatibility::CodexAppsOnly,
-        }
-    );
-}
-
 #[tokio::test]
 async fn start_thread_keeps_internal_threads_hidden_from_normal_lookups() {
     let temp_dir = tempdir().expect("tempdir");
@@ -403,7 +355,6 @@ async fn start_thread_keeps_internal_threads_hidden_from_normal_lookups() {
             dynamic_tools: Vec::new(),
             persist_extended_history: false,
             metrics_service_name: None,
-            client_compatibility_flags: ClientCompatibilityFlags::default(),
             parent_trace: None,
             environments: Vec::new(),
         })
@@ -455,7 +406,6 @@ async fn resume_and_fork_do_not_restore_thread_environments_from_rollout() {
             dynamic_tools: Vec::new(),
             persist_extended_history: false,
             metrics_service_name: None,
-            client_compatibility_flags: ClientCompatibilityFlags::default(),
             parent_trace: None,
             environments: environments.clone(),
         })
diff --git a/codex-rs/memories/write/src/runtime.rs b/codex-rs/memories/write/src/runtime.rs
index 3fe5d7db02..737fb67870 100644
--- a/codex-rs/memories/write/src/runtime.rs
+++ b/codex-rs/memories/write/src/runtime.rs
@@ -244,7 +244,6 @@ impl MemoryStartupContext {
                 dynamic_tools: Vec::new(),
                 persist_extended_history: false,
                 metrics_service_name: None,
-                client_compatibility_flags: codex_core::ClientCompatibilityFlags::default(),
                 parent_trace: None,
                 environments,
             })