diff --git a/codex-rs/core/src/client.rs b/codex-rs/core/src/client.rs
index bd22ab2e56..3426da78c1 100644
--- a/codex-rs/core/src/client.rs
+++ b/codex-rs/core/src/client.rs
@@ -33,6 +33,7 @@ use http::StatusCode as HttpStatusCode;
 use reqwest::StatusCode;
 use serde_json::Value;
 use std::time::Duration;
+use tokio::sync::RwLock;
 use tokio::sync::mpsc;
 use tracing::warn;
 
@@ -57,8 +58,8 @@ use crate::tools::spec::create_tools_json_for_responses_api;
 pub struct ModelClient {
     config: Arc<Config>,
     auth_manager: Option<Arc<AuthManager>>,
-    model_family: ModelFamily,
-    models_etag: Option<String>,
+    model_family: RwLock<ModelFamily>,
+    models_etag: RwLock<Option<String>>,
     otel_manager: OtelManager,
     provider: ModelProviderInfo,
     conversation_id: ConversationId,
@@ -84,8 +85,8 @@ impl ModelClient {
         Self {
             config,
             auth_manager,
-            model_family,
-            models_etag,
+            model_family: RwLock::new(model_family),
+            models_etag: RwLock::new(models_etag),
             otel_manager,
             provider,
             conversation_id,
@@ -95,8 +96,8 @@ impl ModelClient {
         }
     }
 
-    pub fn get_model_context_window(&self) -> Option<i64> {
-        let model_family = self.get_model_family();
+    pub async fn get_model_context_window(&self) -> Option<i64> {
+        let model_family = self.get_model_family().await;
         let effective_context_window_percent = model_family.effective_context_window_percent;
         model_family
             .context_window
@@ -149,8 +150,8 @@ impl ModelClient {
         }
 
         let auth_manager = self.auth_manager.clone();
-        let model_family = self.get_model_family();
-        let instructions = prompt.get_full_instructions(model_family).into_owned();
+        let model_family = self.get_model_family().await;
+        let instructions = prompt.get_full_instructions(&model_family).into_owned();
         let tools_json = create_tools_json_for_chat_completions_api(&prompt.tools)?;
         let api_prompt = build_api_prompt(prompt, instructions, tools_json);
         let conversation_id = self.conversation_id.to_string();
@@ -170,7 +171,7 @@ impl ModelClient {
 
             let stream_result = client
                 .stream_prompt(
-                    &self.get_model(),
+                    &self.get_model().await,
                     &api_prompt,
                     Some(conversation_id.clone()),
                     Some(session_source.clone()),
@@ -203,8 +204,8 @@ impl ModelClient {
         }
 
         let auth_manager = self.auth_manager.clone();
-        let model_family = self.get_model_family();
-        let instructions = prompt.get_full_instructions(model_family).into_owned();
+        let model_family = self.get_model_family().await;
+        let instructions = prompt.get_full_instructions(&model_family).into_owned();
         let tools_json: Vec<Value> = create_tools_json_for_responses_api(&prompt.tools)?;
 
         let reasoning = if model_family.supports_reasoning_summaries {
@@ -265,11 +266,14 @@ impl ModelClient {
                 store_override: None,
                 conversation_id: Some(conversation_id.clone()),
                 session_source: Some(session_source.clone()),
-                extra_headers: beta_feature_headers(&self.config, self.get_models_etag().clone()),
+                extra_headers: beta_feature_headers(
+                    &self.config,
+                    self.get_models_etag().await.clone(),
+                ),
             };
 
             let stream_result = client
-                .stream_prompt(&self.get_model(), &api_prompt, options)
+                .stream_prompt(&self.get_model().await, &api_prompt, options)
                 .await;
 
             match stream_result {
@@ -300,17 +304,25 @@ impl ModelClient {
     }
 
     /// Returns the currently configured model slug.
-    pub fn get_model(&self) -> String {
-        self.get_model_family().get_model_slug().to_string()
+    pub async fn get_model(&self) -> String {
+        self.get_model_family().await.get_model_slug().to_string()
     }
 
     /// Returns the currently configured model family.
-    pub fn get_model_family(&self) -> &ModelFamily {
-        &self.model_family
+    pub async fn get_model_family(&self) -> ModelFamily {
+        self.model_family.read().await.clone()
     }
 
-    fn get_models_etag(&self) -> &Option<String> {
-        &self.models_etag
+    pub async fn get_models_etag(&self) -> Option<String> {
+        self.models_etag.read().await.clone()
+    }
+
+    pub async fn update_models_etag(&self, etag: Option<String>) {
+        *self.models_etag.write().await = etag;
+    }
+
+    pub async fn update_model_family(&self, model_family: ModelFamily) {
+        *self.model_family.write().await = model_family;
     }
 
     /// Returns the current reasoning effort setting.
@@ -347,10 +359,10 @@ impl ModelClient {
             .with_telemetry(Some(request_telemetry));
 
         let instructions = prompt
-            .get_full_instructions(self.get_model_family())
+            .get_full_instructions(&self.get_model_family().await)
             .into_owned();
         let payload = ApiCompactionInput {
-            model: &self.get_model(),
+            model: &self.get_model().await,
             input: &prompt.input,
             instructions: &instructions,
         };
diff --git a/codex-rs/core/src/client_common.rs b/codex-rs/core/src/client_common.rs
index ca8a142a3a..db1a7333d1 100644
--- a/codex-rs/core/src/client_common.rs
+++ b/codex-rs/core/src/client_common.rs
@@ -48,7 +48,7 @@ pub struct Prompt {
 }
 
 impl Prompt {
-    pub(crate) fn new(
+    pub(crate) async fn new(
         sess: &Session,
         turn_context: &TurnContext,
         router: &ToolRouter,
@@ -57,6 +57,7 @@ impl Prompt {
         let model_supports_parallel = turn_context
             .client
             .get_model_family()
+            .await
             .supports_parallel_tool_calls;
 
         Prompt {
diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index d9e5974cbb..90e6a0b2c1 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -790,7 +790,7 @@ impl Session {
                         }
                     })
                 {
-                    let curr = turn_context.client.get_model();
+                    let curr = turn_context.client.get_model().await;
                     if prev != curr {
                         warn!(
                             "resuming session with different model: previous={prev}, current={curr}"
@@ -1338,7 +1338,7 @@ impl Session {
             if let Some(token_usage) = token_usage {
                 state.update_token_info_from_usage(
                     token_usage,
-                    turn_context.client.get_model_context_window(),
+                    turn_context.client.get_model_context_window().await,
                 );
             }
         }
@@ -1350,6 +1350,7 @@ impl Session {
             .clone_history()
             .await
             .estimate_token_count(turn_context)
+            .await
         else {
             return;
         };
@@ -1370,7 +1371,7 @@ impl Session {
             };
 
             if info.model_context_window.is_none() {
-                info.model_context_window = turn_context.client.get_model_context_window();
+                info.model_context_window = turn_context.client.get_model_context_window().await;
             }
 
             state.set_token_info(Some(info));
@@ -1400,7 +1401,7 @@ impl Session {
     }
 
     pub(crate) async fn set_total_tokens_full(&self, turn_context: &TurnContext) {
-        let context_window = turn_context.client.get_model_context_window();
+        let context_window = turn_context.client.get_model_context_window().await;
         if let Some(context_window) = context_window {
             {
                 let mut state = self.state.lock().await;
@@ -2226,7 +2227,7 @@ fn errors_to_info(errors: &[SkillError]) -> Vec<SkillErrorInfo> {
 ///
 pub(crate) async fn run_task(
     sess: Arc<Session>,
-    mut turn_context: Arc<TurnContext>,
+    turn_context: Arc<TurnContext>,
     input: Vec<UserInput>,
     cancellation_token: CancellationToken,
 ) -> Option<String> {
@@ -2237,6 +2238,7 @@ pub(crate) async fn run_task(
     let auto_compact_limit = turn_context
         .client
         .get_model_family()
+        .await
         .auto_compact_token_limit()
         .unwrap_or(i64::MAX);
     let total_usage_tokens = sess.get_total_token_usage().await;
@@ -2244,7 +2246,7 @@ pub(crate) async fn run_task(
         run_auto_compact(&sess, &turn_context).await;
     }
     let event = EventMsg::TaskStarted(TaskStartedEvent {
-        model_context_window: turn_context.client.get_model_context_window(),
+        model_context_window: turn_context.client.get_model_context_window().await,
     });
     sess.send_event(&turn_context, event).await;
 
@@ -2309,7 +2311,7 @@ pub(crate) async fn run_task(
             .collect::<Vec<String>>();
         match run_turn(
             Arc::clone(&sess),
-            &mut turn_context,
+            &turn_context,
             Arc::clone(&turn_diff_tracker),
             turn_input,
             cancellation_token.child_token(),
@@ -2370,7 +2372,7 @@ pub(crate) async fn run_task(
 
 async fn refresh_models_and_reset_turn_context(
     sess: &Arc<Session>,
-    turn_context: &mut Arc<TurnContext>,
+    turn_context: &Arc<TurnContext>,
 ) {
     let config = {
         let state = sess.state.lock().await;
@@ -2387,15 +2389,15 @@ async fn refresh_models_and_reset_turn_context(
     {
         error!("failed to refresh models after outdated models error: {err}");
     }
-    let session_configuration = sess.state.lock().await.session_configuration.clone();
-    *turn_context = sess
-        .new_turn_from_configuration(
-            turn_context.sub_id.clone(),
-            session_configuration,
-            Some(turn_context.final_output_json_schema.clone()),
-            false,
-        )
+    let model = turn_context.client.get_model().await;
+    let model_family = sess
+        .services
+        .models_manager
+        .construct_model_family(&model, &config)
         .await;
+    let models_etag = sess.services.models_manager.get_models_etag().await;
+    turn_context.client.update_model_family(model_family).await;
+    turn_context.client.update_models_etag(models_etag).await;
 }
 
 async fn run_auto_compact(sess: &Arc<Session>, turn_context: &Arc<TurnContext>) {
@@ -2410,13 +2412,13 @@ async fn run_auto_compact(sess: &Arc<Session>, turn_context: &Arc<TurnContext>)
     skip_all,
     fields(
         turn_id = %turn_context.sub_id,
-        model = %turn_context.client.get_model(),
+        model = %turn_context.client.get_model().await,
         cwd = %turn_context.cwd.display()
     )
 )]
 async fn run_turn(
     sess: Arc<Session>,
-    turn_context: &mut Arc<TurnContext>,
+    turn_context: &Arc<TurnContext>,
     turn_diff_tracker: SharedTurnDiffTracker,
     input: Vec<ResponseItem>,
     cancellation_token: CancellationToken,
@@ -2454,7 +2456,7 @@ async fn run_turn(
             Arc::clone(&sess),
             Arc::clone(turn_context),
             Arc::clone(&turn_diff_tracker),
-            &prompt,
+            &prompt.await,
             cancellation_token.child_token(),
         )
         .await
@@ -2490,7 +2492,7 @@ async fn run_turn(
                     retries += 1;
                     // Refresh models if we got an outdated models error
                     if matches!(e, CodexErr::OutdatedModels) {
-                        refresh_models_and_reset_turn_context(&sess, turn_context).await;
+                        refresh_models_and_reset_turn_context(&sess, &turn_context).await;
                         continue;
                     }
                     let delay = match e {
@@ -2550,7 +2552,7 @@ async fn drain_in_flight(
     skip_all,
     fields(
         turn_id = %turn_context.sub_id,
-        model = %turn_context.client.get_model()
+        model = %turn_context.client.get_model().await,
     )
 )]
 async fn try_run_turn(
@@ -2565,7 +2567,7 @@ async fn try_run_turn(
         cwd: turn_context.cwd.clone(),
         approval_policy: turn_context.approval_policy,
         sandbox_policy: turn_context.sandbox_policy.clone(),
-        model: turn_context.client.get_model(),
+        model: turn_context.client.get_model().await,
         effort: turn_context.client.get_reasoning_effort(),
         summary: turn_context.client.get_reasoning_summary(),
     });
diff --git a/codex-rs/core/src/compact.rs b/codex-rs/core/src/compact.rs
index 3290d1b321..3ccbfb6128 100644
--- a/codex-rs/core/src/compact.rs
+++ b/codex-rs/core/src/compact.rs
@@ -55,7 +55,7 @@ pub(crate) async fn run_compact_task(
     input: Vec<UserInput>,
 ) {
     let start_event = EventMsg::TaskStarted(TaskStartedEvent {
-        model_context_window: turn_context.client.get_model_context_window(),
+        model_context_window: turn_context.client.get_model_context_window().await,
     });
     sess.send_event(&turn_context, start_event).await;
     run_compact_task_inner(sess.clone(), turn_context, input).await;
@@ -83,7 +83,7 @@ async fn run_compact_task_inner(
         cwd: turn_context.cwd.clone(),
         approval_policy: turn_context.approval_policy,
         sandbox_policy: turn_context.sandbox_policy.clone(),
-        model: turn_context.client.get_model(),
+        model: turn_context.client.get_model().await,
         effort: turn_context.client.get_reasoning_effort(),
         summary: turn_context.client.get_reasoning_summary(),
     });
diff --git a/codex-rs/core/src/compact_remote.rs b/codex-rs/core/src/compact_remote.rs
index b855f28d39..3419b2e51f 100644
--- a/codex-rs/core/src/compact_remote.rs
+++ b/codex-rs/core/src/compact_remote.rs
@@ -20,7 +20,7 @@ pub(crate) async fn run_inline_remote_auto_compact_task(
 
 pub(crate) async fn run_remote_compact_task(sess: Arc<Session>, turn_context: Arc<TurnContext>) {
     let start_event = EventMsg::TaskStarted(TaskStartedEvent {
-        model_context_window: turn_context.client.get_model_context_window(),
+        model_context_window: turn_context.client.get_model_context_window().await,
     });
     sess.send_event(&turn_context, start_event).await;
 
diff --git a/codex-rs/core/src/context_manager/history.rs b/codex-rs/core/src/context_manager/history.rs
index c18ad7df8e..841be4bae5 100644
--- a/codex-rs/core/src/context_manager/history.rs
+++ b/codex-rs/core/src/context_manager/history.rs
@@ -79,8 +79,8 @@ impl ContextManager {
 
     // Estimate token usage using byte-based heuristics from the truncation helpers.
     // This is a coarse lower bound, not a tokenizer-accurate count.
-    pub(crate) fn estimate_token_count(&self, turn_context: &TurnContext) -> Option<i64> {
-        let model_family = turn_context.client.get_model_family();
+    pub(crate) async fn estimate_token_count(&self, turn_context: &TurnContext) -> Option<i64> {
+        let model_family = turn_context.client.get_model_family().await;
         let base_tokens =
             i64::try_from(approx_token_count(model_family.base_instructions.as_str()))
                 .unwrap_or(i64::MAX);
diff --git a/codex-rs/core/src/tasks/user_shell.rs b/codex-rs/core/src/tasks/user_shell.rs
index aec09514ca..b053020bdb 100644
--- a/codex-rs/core/src/tasks/user_shell.rs
+++ b/codex-rs/core/src/tasks/user_shell.rs
@@ -59,7 +59,7 @@ impl SessionTask for UserShellCommandTask {
         cancellation_token: CancellationToken,
     ) -> Option<String> {
         let event = EventMsg::TaskStarted(TaskStartedEvent {
-            model_context_window: turn_context.client.get_model_context_window(),
+            model_context_window: turn_context.client.get_model_context_window().await,
         });
         let session = session.clone_session();
         session.send_event(turn_context.as_ref(), event).await;