diff --git a/codex-rs/app-server/src/external_agent_migration/session_importer.rs b/codex-rs/app-server/src/external_agent_migration/session_importer.rs
index 47292d1635..1a3613b434 100644
--- a/codex-rs/app-server/src/external_agent_migration/session_importer.rs
+++ b/codex-rs/app-server/src/external_agent_migration/session_importer.rs
@@ -432,12 +432,23 @@ impl ExternalAgentSessionImporter {
                     format!("failed to load imported session config: {err}"),
                 )
             })?;
-        let models_manager = self.thread_manager.get_models_manager();
+        let originator = codex_login::default_client::originator().value;
+        let models_manager = self.thread_manager.models_manager_for_config(&config);
+        let models_manager = models_manager
+            .for_originator(&originator)
+            .unwrap_or(models_manager);
+        // A pinned model skips discovery. Load its destination cache without fetching or
+        // replacing a provider response that is already in memory.
+        if models_manager.refreshed_model_catalog().is_none() {
+            models_manager
+                .list_models(RefreshStrategy::Offline, config.http_client_factory())
+                .await;
+        }
         let model = models_manager
             .get_default_model(
                 &config.model,
                 /*allow_provider_model_fallback*/ false,
-                RefreshStrategy::Offline,
+                RefreshStrategy::InMemory,
                 config.http_client_factory(),
             )
             .await;
@@ -465,7 +476,7 @@ impl ExternalAgentSessionImporter {
             parent_thread_id: None,
             source: source.clone(),
             thread_source: None,
-            originator: codex_login::default_client::originator().value,
+            originator,
             base_instructions: BaseInstructions {
                 text: config
                     .base_instructions
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 93c52ffe5b..a1e74cb2f8 100644
--- a/codex-rs/app-server/src/request_processors/thread_processor.rs
+++ b/codex-rs/app-server/src/request_processors/thread_processor.rs
@@ -5435,10 +5435,8 @@ impl ThreadRequestProcessor {
                     .items()
                     .any(|item| matches!(item, ResponseItem::AdditionalTools { .. }))
                 && let Some(model) = options.config.model.as_deref()
-                && self
-                    .thread_manager
-                    .get_models_manager()
-                    .get_model_info(model, &options.config.to_models_manager_config())
+                && parent
+                    .model_info(model, &options.config.to_models_manager_config())
                     .await
                     .use_responses_lite
             {
diff --git a/codex-rs/app-server/src/thread_sample.rs b/codex-rs/app-server/src/thread_sample.rs
index 048d9e6c6e..289190f7ae 100644
--- a/codex-rs/app-server/src/thread_sample.rs
+++ b/codex-rs/app-server/src/thread_sample.rs
@@ -182,9 +182,8 @@ impl SampleTask {
         })
         .await
         .map_err(|error| internal_error(error.to_string()))?;
-        let model = manager
-            .get_models_manager()
-            .get_model_info(
+        let model = parent
+            .model_info(
                 options.config.model.as_deref().unwrap_or(&snapshot.model),
                 &options.config.to_models_manager_config(),
             )
diff --git a/codex-rs/app-server/tests/suite/v2/external_agent_config.rs b/codex-rs/app-server/tests/suite/v2/external_agent_config.rs
index 15a45c7567..4b74133e8f 100644
--- a/codex-rs/app-server/tests/suite/v2/external_agent_config.rs
+++ b/codex-rs/app-server/tests/suite/v2/external_agent_config.rs
@@ -1918,7 +1918,39 @@ async fn external_agent_config_import_sends_completion_notification_after_pendin
 async fn external_agent_config_import_creates_session_rollouts() -> Result<()> {
     let server = create_mock_responses_server_repeating_assistant("follow-up answer").await;
     let codex_home = TempDir::new()?;
-    MockResponsesConfig::new(&server.uri()).write(codex_home.path())?;
+    let url = server.uri();
+    let instructions = "Instructions from the destination provider.";
+    let mut model = codex_models_manager::model_info::model_info_from_slug("mock-model");
+    model.visibility = codex_protocol::openai_models::ModelVisibility::List;
+    model.model_messages = Some(codex_protocol::openai_models::ModelMessages {
+        instructions_template: Some(instructions.into()),
+        ..Default::default()
+    });
+    wiremock::Mock::given(wiremock::matchers::method("GET"))
+        .and(wiremock::matchers::path("/v1/models"))
+        .and(wiremock::matchers::header(
+            "originator",
+            "codex_work_desktop",
+        ))
+        .respond_with(
+            wiremock::ResponseTemplate::new(200)
+                .set_body_json(serde_json::json!({"models": [model]})),
+        )
+        // The responses fixture also registers a default empty catalog.
+        .with_priority(1)
+        .mount(&server)
+        .await;
+    MockResponsesConfig::new(&url)
+        .enable_feature(codex_features::Feature::ApiKeyModelDiscovery)
+        .with_extra_config(&format!(
+            r#"[model_providers.destination]
+name = "Destination"
+base_url = "{url}/v1"
+model_catalog_url = "{url}/v1/models"
+http_headers = {{ originator = "unscoped-test" }}
+env_key = "TEST_CATALOG_KEY""#
+        ))
+        .write(codex_home.path())?;
     let project_root = codex_home.path().join("repo");
     let source_created_at_text = "2024-01-02T03:04:05Z";
     let source_updated_at_text = "2024-03-01T04:05:06Z";
@@ -1979,10 +2011,40 @@ async fn external_agent_config_import_creates_session_rollouts() -> Result<()> {
     let mut mcp = TestAppServer::builder()
         .with_codex_home(codex_home.path())
         .without_auto_env()
-        .with_env_overrides(&[("HOME", Some(home_dir.as_str()))])
-        .build_initialized_with_timeout(DEFAULT_TIMEOUT)
+        .with_env_overrides(&[
+            ("HOME", Some(home_dir.as_str())),
+            ("TEST_CATALOG_KEY", Some("test-key")),
+        ])
+        .build()
         .await?;
 
+    mcp.initialize_with_client_info(codex_app_server_protocol::ClientInfo {
+        name: "codex_work_desktop".into(),
+        title: None,
+        version: "0.1.0".into(),
+    })
+    .await?;
+    let id = mcp
+        .send_raw_request(
+            "modelProvider/default/set",
+            Some(serde_json::json!({"providerId": "destination"})),
+        )
+        .await?;
+    let write: codex_app_server_protocol::ConfigWriteResponse = mcp.read_response(id).await?;
+    assert_eq!(write.status, codex_app_server_protocol::WriteStatus::Ok);
+    // Warm the partition the imported chat will use on resume.
+    let id = mcp
+        .send_thread_start_request(codex_app_server_protocol::ThreadStartParams {
+            ephemeral: Some(true),
+            ..Default::default()
+        })
+        .await?;
+    let started: codex_app_server_protocol::ThreadStartResponse = mcp.read_response(id).await?;
+    assert_eq!(
+        started.thread.originator.as_deref(),
+        Some("codex_work_desktop")
+    );
+
     let request_id = mcp
         .send_raw_request(
             "externalAgentConfig/detect",
@@ -2077,7 +2139,7 @@ async fn external_agent_config_import_creates_session_rollouts() -> Result<()> {
             limit: None,
             sort_key: None,
             sort_direction: None,
-            model_providers: None,
+            model_providers: Some(vec!["destination".into()]),
             source_kinds: None,
             archived: None,
             section_id: None,
@@ -2097,6 +2159,18 @@ async fn external_agent_config_import_creates_session_rollouts() -> Result<()> {
         .expect("expected imported thread")
         .clone();
     assert_eq!(imported_thread_id, thread.id.to_string());
+    assert_eq!(thread.model_provider, "destination");
+    let meta =
+        codex_rollout::read_session_meta_line(thread.path.as_deref().expect("imported rollout"))
+            .await?;
+    assert_eq!(meta.meta.originator, "codex_work_desktop");
+    assert_eq!(
+        meta.meta
+            .base_instructions
+            .expect("imported instructions")
+            .text,
+        instructions
+    );
     assert_eq!(thread.preview, control_request);
     assert_eq!(thread.name.as_deref(), Some("Fix auth flow"));
     assert_eq!(thread.created_at, source_created_at);
diff --git a/codex-rs/app-server/tests/suite/v2/thread_fork.rs b/codex-rs/app-server/tests/suite/v2/thread_fork.rs
index 43528e6850..e8111e7fb4 100644
--- a/codex-rs/app-server/tests/suite/v2/thread_fork.rs
+++ b/codex-rs/app-server/tests/suite/v2/thread_fork.rs
@@ -3095,10 +3095,7 @@ async fn fork_option_disables_mcp_servers(
     )?;
     MockResponsesConfig::new(&server.uri())
         .with_model("gpt-5.4")
-        .with_root_config(&format!(
-            "model_catalog_json = {}\nfeatures.incremental_tools = {incremental_tools}",
-            serde_json::to_string(&catalog)?
-        ))
+        .with_root_config(&format!("features.incremental_tools = {incremental_tools}"))
         .with_extra_config(&format!(
             "[mcp_servers.fixture]\nurl = \"{}/mcp\"\nrequired = true\n",
             mcp_server.uri()
@@ -3111,6 +3108,8 @@ async fn fork_option_disables_mcp_servers(
     let parent = app
         .start_thread(ThreadStartParams {
             history_mode: Some(history_mode),
+            // Only the parent catalog advertises the capability used by the prediction fork.
+            config: Some([("model_catalog_json".into(), json!(catalog))].into()),
             ..Default::default()
         })
         .await?;
diff --git a/codex-rs/app-server/tests/suite/v2/thread_sample.rs b/codex-rs/app-server/tests/suite/v2/thread_sample.rs
index bfa40673c5..e3c40aa3e1 100644
--- a/codex-rs/app-server/tests/suite/v2/thread_sample.rs
+++ b/codex-rs/app-server/tests/suite/v2/thread_sample.rs
@@ -1348,6 +1348,95 @@ async fn sample_rejects_invalid_sources_and_prompts() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn sample_uses_the_parent_catalog_after_a_default_provider_switch() -> Result<()> {
+    let alpha = wiremock::MockServer::start().await;
+    let beta = wiremock::MockServer::start().await;
+    let mut model = codex_models_manager::bundled_models_response()?
+        .models
+        .into_iter()
+        .find(|model| model.slug == "gpt-5.5")
+        .expect("bundled reasoning model");
+    for (provider, supports_updates) in [(&alpha, false), (&beta, true)] {
+        model.supports_reasoning_effort_updates = supports_updates;
+        wiremock::Mock::given(wiremock::matchers::method("GET"))
+            .and(wiremock::matchers::path("/v1/models"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(json!({"models": [&model]})))
+            .mount(provider)
+            .await;
+    }
+    let replies = ["parent", "sample"].map(|id| {
+        responses::sse(vec![
+            responses::ev_assistant_message(id, "Ready."),
+            responses::ev_completed(id),
+        ])
+    });
+    let alpha_requests = responses::mount_sse_sequence(&alpha, replies.to_vec()).await;
+    let beta_requests = responses::mount_sse_sequence(&beta, replies.to_vec()).await;
+    let home = TempDir::new()?;
+    let alpha_url = alpha.uri();
+    let beta_url = beta.uri();
+    MockResponsesConfig::new(&alpha_url)
+        .with_model_provider("alpha")
+        .with_provider_name("OpenAI")
+        .with_model(&model.slug)
+        .with_root_config("model_reasoning_effort = 'medium'")
+        .enable_feature(Feature::ApiKeyModelDiscovery)
+        .enable_feature(Feature::ReasoningEffortOverride)
+        .with_provider_config(&format!(
+            "env_key = 'TEST_CATALOG_KEY'\nmodel_catalog_url = '{alpha_url}/v1/models'"
+        ))
+        .with_extra_config(&format!(
+            r#"[model_providers.beta]
+name = "OpenAI"
+base_url = "{beta_url}/v1"
+model_catalog_url = "{beta_url}/v1/models"
+env_key = "TEST_CATALOG_KEY""#
+        ))
+        .write(home.path())?;
+    let mut client = TestAppServer::builder()
+        .with_codex_home(home.path())
+        .with_env_overrides(&[("TEST_CATALOG_KEY", Some("test-key"))])
+        .build_initialized_with_timeout(WAIT)
+        .await?;
+    let alpha_parent = ready_parent(&mut client, ThreadStartParams::default()).await?;
+    let id = client
+        .send_raw_request(
+            "modelProvider/default/set",
+            Some(json!({"providerId": "beta"})),
+        )
+        .await?;
+    let write: codex_app_server_protocol::ConfigWriteResponse = client.read_response(id).await?;
+    assert_eq!(write.status, codex_app_server_protocol::WriteStatus::Ok);
+    let beta_parent = ready_parent(&mut client, ThreadStartParams::default()).await?;
+    for ((thread_id, expected_turn_id), requests, supports_updates) in [
+        (alpha_parent, alpha_requests, false),
+        (beta_parent, beta_requests, true),
+    ] {
+        sample(
+            &mut client,
+            ThreadSampleParams {
+                thread_id,
+                expected_turn_id,
+                prompt: "Predict".into(),
+                effort: Some(ReasoningEffort::High),
+                ..Default::default()
+            },
+        )
+        .await?;
+        let requests = requests.requests();
+        assert_eq!(requests.len(), 2);
+        let updates = requests[1].inputs_of_type("configuration_update");
+        assert_eq!(
+            updates
+                .iter()
+                .any(|item| item["reasoning"]["effort"] == "high"),
+            supports_updates
+        );
+    }
+    Ok(())
+}
+
 #[test_case(false; "unsupported model")]
 #[test_case(true; "unsupported provider")]
 #[tokio::test]
diff --git a/codex-rs/core/src/codex_thread.rs b/codex-rs/core/src/codex_thread.rs
index c512c26feb..9f1fb465d8 100644
--- a/codex-rs/core/src/codex_thread.rs
+++ b/codex-rs/core/src/codex_thread.rs
@@ -25,6 +25,7 @@ use codex_extension_api::ConversationHistorySnapshot;
 use codex_extension_api::ThreadIdleCause;
 use codex_features::Feature;
 use codex_history::RolloutItem;
+use codex_models_manager::ModelsManagerConfig;
 use codex_otel::SessionTelemetry;
 use codex_otel::current_span_w3c_trace_context;
 use codex_protocol::ThreadId;
@@ -41,6 +42,7 @@ use codex_protocol::models::ActivePermissionProfile;
 use codex_protocol::models::PermissionProfile;
 use codex_protocol::models::ProfileWorkspaceRoot;
 use codex_protocol::models::ResponseItem;
+use codex_protocol::openai_models::CatalogModel;
 use codex_protocol::openai_models::ModelInfo;
 use codex_protocol::openai_models::ReasoningEffort;
 use codex_protocol::protocol::AskForApproval;
@@ -1205,6 +1207,15 @@ impl CodexThread {
         self.session.selected_model_info().await
     }
 
+    /// Looks up a named model in the catalog selected for this thread's provider and credentials.
+    pub async fn model_info(&self, model: &str, config: &ModelsManagerConfig) -> CatalogModel {
+        self.session
+            .services
+            .models_manager
+            .get_model_info(model, config)
+            .await
+    }
+
     pub async fn config_snapshot(&self) -> ThreadConfigSnapshot {
         self.session.thread_config_snapshot().await
     }
diff --git a/codex-rs/core/src/lib.rs b/codex-rs/core/src/lib.rs
index dc7d756ac1..4ecc5ee848 100644
--- a/codex-rs/core/src/lib.rs
+++ b/codex-rs/core/src/lib.rs
@@ -42,6 +42,8 @@ mod compact_remote_v2;
 mod compact_retained_tool_outputs;
 mod compact_token_budget;
 mod thread_startup_metadata;
+/// Catalog handle installed in each thread's extension data before startup callbacks.
+pub use codex_models_manager::manager::SharedModelsManager;
 pub use codex_network_proxy::EnvironmentNetworkPolicy;
 pub use codex_network_proxy::NetworkDomainPermission;
 pub use codex_network_proxy::NetworkDomainPermissionEntry;
diff --git a/codex-rs/core/src/session/session.rs b/codex-rs/core/src/session/session.rs
index 017d5124da..9d3687700f 100644
--- a/codex-rs/core/src/session/session.rs
+++ b/codex-rs/core/src/session/session.rs
@@ -1054,6 +1054,7 @@ impl Session {
         thread_extension_init.insert(codex_extension_api::ThreadOriginator(
             session_configuration.originator.clone(),
         ));
+        thread_extension_init.insert(Arc::clone(&models_manager));
         // Publish the already resolved model before extensions make startup decisions.
         // Turn construction refreshes this attachment when the selected model changes.
         thread_extension_init.insert(Arc::unwrap_or_clone(model_info.model));
diff --git a/codex-rs/core/src/thread_manager.rs b/codex-rs/core/src/thread_manager.rs
index 043661be2e..33f4bc47ec 100644
--- a/codex-rs/core/src/thread_manager.rs
+++ b/codex-rs/core/src/thread_manager.rs
@@ -1107,6 +1107,8 @@ impl ThreadManager {
         Arc::clone(&self.state.git_root_discovery)
     }
 
+    /// Returns the startup catalog. Use [`CodexThread::model_info`] for a live chat or
+    /// [`Self::models_manager_for_config`] for a new destination.
     pub fn get_models_manager(&self) -> SharedModelsManager {
         self.state.model_catalog.manager.clone()
     }
diff --git a/codex-rs/core/tests/suite/models_cache_auth.rs b/codex-rs/core/tests/suite/models_cache_auth.rs
index 96e0a83e22..c3323881c6 100644
--- a/codex-rs/core/tests/suite/models_cache_auth.rs
+++ b/codex-rs/core/tests/suite/models_cache_auth.rs
@@ -436,8 +436,10 @@ async fn host_model_info_uses_the_thread_catalog(source: SessionSource) -> Resul
     assert_eq!(selected.comp_hash.as_deref(), Some("thread-revision"));
     assert_eq!(selected.context_window, Some(32_000));
 
+    let model_config = options.config.to_models_manager_config();
     let thread = test.thread_manager.start_thread(options).await?.thread;
     assert_eq!(thread.selected_model_info().await, selected);
+    let other_model = thread.model_info("after-update", &model_config).await.model;
     thread
         .update_thread_settings(ThreadSettingsOverrides {
             model: Some("after-update".into()),
@@ -445,6 +447,7 @@ async fn host_model_info_uses_the_thread_catalog(source: SessionSource) -> Resul
         })
         .await?;
     let next = thread.selected_model_info().await;
+    assert_eq!(next, other_model);
     assert_eq!(next.slug, "after-update");
     assert_eq!(next.comp_hash.as_deref(), Some("thread-revision"));
     Ok(())
diff --git a/codex-rs/ext/guardian-v2/src/async_scorer/extension.rs b/codex-rs/ext/guardian-v2/src/async_scorer/extension.rs
index 32911bb006..7283dacdb3 100644
--- a/codex-rs/ext/guardian-v2/src/async_scorer/extension.rs
+++ b/codex-rs/ext/guardian-v2/src/async_scorer/extension.rs
@@ -68,8 +68,7 @@ impl ThreadLifecycleContributor<Config> for GuardianV2Extension {
                 input.config.config_layer_stack.requirements(),
             );
             let scoring_enabled = policy.scoring_enabled();
-            let sampler_config =
-                super::startup::sampler_config(&input, self.thread_manager.upgrade()).await;
+            let sampler_config = super::startup::sampler_config(&input).await;
 
             if scoring_enabled && guardian_config.transcript.include_images {
                 input
diff --git a/codex-rs/ext/guardian-v2/src/async_scorer/sampler_routing_tests.rs b/codex-rs/ext/guardian-v2/src/async_scorer/sampler_routing_tests.rs
index f352fe388c..76db303827 100644
--- a/codex-rs/ext/guardian-v2/src/async_scorer/sampler_routing_tests.rs
+++ b/codex-rs/ext/guardian-v2/src/async_scorer/sampler_routing_tests.rs
@@ -215,7 +215,7 @@ async fn idle_classifier_retains_the_owning_threads_workspace_binding() -> Resul
         .thread_store
         .get::<codex_model_provider::WorkspaceRoutingContext>()
         .expect("Core seeds the owning thread's routing context before extensions start");
-    let classifier = crate::async_scorer::startup::sampler_config(&input, /*manager*/ None).await;
+    let classifier = crate::async_scorer::startup::sampler_config(&input).await;
     classifier
         .provider
         .responses_api_provider(&owning_context)
diff --git a/codex-rs/ext/guardian-v2/src/async_scorer/startup.rs b/codex-rs/ext/guardian-v2/src/async_scorer/startup.rs
index 3d07088fb5..25fa1119d5 100644
--- a/codex-rs/ext/guardian-v2/src/async_scorer/startup.rs
+++ b/codex-rs/ext/guardian-v2/src/async_scorer/startup.rs
@@ -3,7 +3,7 @@
 
 use std::sync::Arc;
 
-use codex_core::ThreadManager;
+use codex_core::SharedModelsManager;
 use codex_core::config::Config;
 use codex_core::cyber_access_program::ApiKeyCyberAccessPrograms;
 use codex_extension_api::ThreadOriginator;
@@ -107,21 +107,13 @@ pub(super) fn valid_implicit_decisions_key(key: &str) -> bool {
     !key.is_empty() && key.trim() == key && !codex_login::auth::is_fedramp_api_key(key)
 }
 
-pub(super) async fn sampler_config(
-    input: &ThreadStartInput<'_, Config>,
-    manager: Option<Arc<ThreadManager>>,
-) -> LunaSamplerConfig {
+pub(super) async fn sampler_config(input: &ThreadStartInput<'_, Config>) -> LunaSamplerConfig {
     let inherit_parent_cyber_access_program =
         codex_core::RequiredCyberAccessPrograms::for_thread(input.thread_store).is_none();
-    let luna_model = if let Some(thread_manager) = manager {
+    let luna_model = if let Some(catalog) = input.thread_store.get::<SharedModelsManager>() {
         let mut model_config = input.config.to_models_manager_config();
         model_config.model_context_window = None;
-        Some(
-            thread_manager
-                .get_models_manager()
-                .get_model_info(MODEL, &model_config)
-                .await,
-        )
+        Some(catalog.get_model_info(MODEL, &model_config).await)
     } else {
         None
     };
diff --git a/codex-rs/memories/write/src/runtime.rs b/codex-rs/memories/write/src/runtime.rs
index b41804fff6..84fcbd5cdb 100644
--- a/codex-rs/memories/write/src/runtime.rs
+++ b/codex-rs/memories/write/src/runtime.rs
@@ -291,9 +291,8 @@ impl MemoryStartupContext {
     ) -> StageOneRequestContext {
         let config_snapshot = self.thread.config_snapshot().await;
         let model_info = self
-            .thread_manager
-            .get_models_manager()
-            .get_model_info(model_name, &config.to_models_manager_config())
+            .thread
+            .model_info(model_name, &config.to_models_manager_config())
             .await;
         let reasoning_summary = config
             .model_reasoning_summary