diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index 4acc1ef4e..ba5ee02d6 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -490,7 +490,7 @@ pub(crate) struct TurnContext {
     pub(crate) developer_instructions: Option<String>,
     pub(crate) compact_prompt: Option<String>,
     pub(crate) user_instructions: Option<String>,
-    pub(crate) collaboration_mode_kind: ModeKind,
+    pub(crate) collaboration_mode: CollaborationMode,
     pub(crate) personality: Option<Personality>,
     pub(crate) approval_policy: AskForApproval,
     pub(crate) sandbox_policy: SandboxPolicy,
@@ -692,7 +692,7 @@ impl Session {
             developer_instructions: session_configuration.developer_instructions.clone(),
             compact_prompt: session_configuration.compact_prompt.clone(),
             user_instructions: session_configuration.user_instructions.clone(),
-            collaboration_mode_kind: session_configuration.collaboration_mode.mode,
+            collaboration_mode: session_configuration.collaboration_mode.clone(),
             personality: session_configuration.personality,
             approval_policy: session_configuration.approval_policy.value(),
             sandbox_policy: session_configuration.sandbox_policy.get().clone(),
@@ -1356,16 +1356,14 @@ impl Session {
 
     fn build_collaboration_mode_update_item(
         &self,
-        previous_collaboration_mode: &CollaborationMode,
-        next_collaboration_mode: Option<&CollaborationMode>,
+        previous: Option<&Arc<TurnContext>>,
+        next: &TurnContext,
     ) -> Option<ResponseItem> {
-        if let Some(next_mode) = next_collaboration_mode {
-            if previous_collaboration_mode == next_mode {
-                return None;
-            }
+        let prev = previous?;
+        if prev.collaboration_mode != next.collaboration_mode {
             // If the next mode has empty developer instructions, this returns None and we emit no
             // update, so prior collaboration instructions remain in the prompt history.
-            Some(DeveloperInstructions::from_collaboration_mode(next_mode)?.into())
+            Some(DeveloperInstructions::from_collaboration_mode(&next.collaboration_mode)?.into())
         } else {
             None
         }
@@ -1375,8 +1373,6 @@ impl Session {
         &self,
         previous_context: Option<&Arc<TurnContext>>,
         current_context: &TurnContext,
-        previous_collaboration_mode: &CollaborationMode,
-        next_collaboration_mode: Option<&CollaborationMode>,
     ) -> Vec<ResponseItem> {
         let mut update_items = Vec::new();
         if let Some(env_item) =
@@ -1389,10 +1385,9 @@ impl Session {
         {
             update_items.push(permissions_item);
         }
-        if let Some(collaboration_mode_item) = self.build_collaboration_mode_update_item(
-            previous_collaboration_mode,
-            next_collaboration_mode,
-        ) {
+        if let Some(collaboration_mode_item) =
+            self.build_collaboration_mode_update_item(previous_context, current_context)
+        {
             update_items.push(collaboration_mode_item);
         }
         if let Some(personality_item) =
@@ -2573,18 +2568,6 @@ mod handlers {
         sub_id: String,
         updates: SessionSettingsUpdate,
     ) {
-        let previous_context = sess
-            .new_default_turn_with_sub_id(sess.next_internal_sub_id())
-            .await;
-        let previous_collaboration_mode = sess
-            .state
-            .lock()
-            .await
-            .session_configuration
-            .collaboration_mode
-            .clone();
-        let next_collaboration_mode = updates.collaboration_mode.clone();
-
         if let Err(err) = sess.update_settings(updates).await {
             sess.send_event_raw(Event {
                 id: sub_id,
@@ -2594,24 +2577,6 @@ mod handlers {
                 }),
             })
             .await;
-            return;
-        }
-
-        let initial_context_seeded = sess.state.lock().await.initial_context_seeded;
-        if !initial_context_seeded {
-            return;
-        }
-
-        let current_context = sess.new_default_turn_with_sub_id(sub_id).await;
-        let update_items = sess.build_settings_update_items(
-            Some(&previous_context),
-            &current_context,
-            &previous_collaboration_mode,
-            next_collaboration_mode.as_ref(),
-        );
-        if !update_items.is_empty() {
-            sess.record_conversation_items(&current_context, &update_items)
-                .await;
         }
     }
 
@@ -2671,14 +2636,6 @@ mod handlers {
             _ => unreachable!(),
         };
 
-        let previous_collaboration_mode = sess
-            .state
-            .lock()
-            .await
-            .session_configuration
-            .collaboration_mode
-            .clone();
-        let next_collaboration_mode = updates.collaboration_mode.clone();
         let Ok(current_context) = sess.new_turn_with_sub_id(sub_id, updates).await else {
             // new_turn_with_sub_id already emits the error event.
             return;
@@ -2691,12 +2648,8 @@ mod handlers {
         // Attempt to inject input into current task
         if let Err(items) = sess.inject_input(items).await {
             sess.seed_initial_context_if_needed(&current_context).await;
-            let update_items = sess.build_settings_update_items(
-                previous_context.as_ref(),
-                &current_context,
-                &previous_collaboration_mode,
-                next_collaboration_mode.as_ref(),
-            );
+            let update_items =
+                sess.build_settings_update_items(previous_context.as_ref(), &current_context);
             if !update_items.is_empty() {
                 sess.record_conversation_items(&current_context, &update_items)
                     .await;
@@ -3211,7 +3164,7 @@ async fn spawn_review_thread(
         developer_instructions: None,
         user_instructions: None,
         compact_prompt: parent_turn_context.compact_prompt.clone(),
-        collaboration_mode_kind: parent_turn_context.collaboration_mode_kind,
+        collaboration_mode: parent_turn_context.collaboration_mode.clone(),
         personality: parent_turn_context.personality,
         approval_policy: parent_turn_context.approval_policy,
         sandbox_policy: parent_turn_context.sandbox_policy.clone(),
@@ -3326,7 +3279,7 @@ pub(crate) async fn run_turn(
     let total_usage_tokens = sess.get_total_token_usage().await;
     let event = EventMsg::TurnStarted(TurnStartedEvent {
         model_context_window: turn_context.client.get_model_context_window(),
-        collaboration_mode_kind: turn_context.collaboration_mode_kind,
+        collaboration_mode_kind: turn_context.collaboration_mode.mode,
     });
     sess.send_event(&turn_context, event).await;
     if total_usage_tokens >= auto_compact_limit {
@@ -4239,7 +4192,7 @@ async fn try_run_sampling_request(
     let mut last_agent_message: Option<String> = None;
     let mut active_item: Option<TurnItem> = None;
     let mut should_emit_turn_diff = false;
-    let plan_mode = turn_context.collaboration_mode_kind == ModeKind::Plan;
+    let plan_mode = turn_context.collaboration_mode.mode == ModeKind::Plan;
     let mut plan_mode_state = plan_mode.then(|| PlanModeStreamState::new(&turn_context.sub_id));
     let receiving_span = trace_span!("receiving_stream");
     let outcome: CodexResult<SamplingRequestResult> = loop {
diff --git a/codex-rs/core/src/compact.rs b/codex-rs/core/src/compact.rs
index af9aacc76..7e7445a6f 100644
--- a/codex-rs/core/src/compact.rs
+++ b/codex-rs/core/src/compact.rs
@@ -61,7 +61,7 @@ pub(crate) async fn run_compact_task(
 ) {
     let start_event = EventMsg::TurnStarted(TurnStartedEvent {
         model_context_window: turn_context.client.get_model_context_window(),
-        collaboration_mode_kind: turn_context.collaboration_mode_kind,
+        collaboration_mode_kind: turn_context.collaboration_mode.mode,
     });
     sess.send_event(&turn_context, start_event).await;
     run_compact_task_inner(sess.clone(), turn_context, input).await;
diff --git a/codex-rs/core/src/compact_remote.rs b/codex-rs/core/src/compact_remote.rs
index b45a2769d..9f7a8dfea 100644
--- a/codex-rs/core/src/compact_remote.rs
+++ b/codex-rs/core/src/compact_remote.rs
@@ -22,7 +22,7 @@ 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::TurnStarted(TurnStartedEvent {
         model_context_window: turn_context.client.get_model_context_window(),
-        collaboration_mode_kind: turn_context.collaboration_mode_kind,
+        collaboration_mode_kind: turn_context.collaboration_mode.mode,
     });
     sess.send_event(&turn_context, start_event).await;
 
diff --git a/codex-rs/core/src/stream_events_utils.rs b/codex-rs/core/src/stream_events_utils.rs
index 91f7efdb0..02d982251 100644
--- a/codex-rs/core/src/stream_events_utils.rs
+++ b/codex-rs/core/src/stream_events_utils.rs
@@ -48,7 +48,7 @@ pub(crate) async fn handle_output_item_done(
     previously_active_item: Option<TurnItem>,
 ) -> Result<OutputItemResult> {
     let mut output = OutputItemResult::default();
-    let plan_mode = ctx.turn_context.collaboration_mode_kind == ModeKind::Plan;
+    let plan_mode = ctx.turn_context.collaboration_mode.mode == ModeKind::Plan;
 
     match ToolRouter::build_tool_call(ctx.sess.as_ref(), item.clone()).await {
         // The model emitted a tool call; log it, persist the item immediately, and queue the tool execution.
diff --git a/codex-rs/core/src/tasks/user_shell.rs b/codex-rs/core/src/tasks/user_shell.rs
index 177d12255..fe3688e19 100644
--- a/codex-rs/core/src/tasks/user_shell.rs
+++ b/codex-rs/core/src/tasks/user_shell.rs
@@ -67,7 +67,7 @@ impl SessionTask for UserShellCommandTask {
 
         let event = EventMsg::TurnStarted(TurnStartedEvent {
             model_context_window: turn_context.client.get_model_context_window(),
-            collaboration_mode_kind: turn_context.collaboration_mode_kind,
+            collaboration_mode_kind: turn_context.collaboration_mode.mode,
         });
         let session = session.clone_session();
         session.send_event(turn_context.as_ref(), event).await;
diff --git a/codex-rs/core/src/tools/handlers/plan.rs b/codex-rs/core/src/tools/handlers/plan.rs
index 79e332a77..88e0b0dc2 100644
--- a/codex-rs/core/src/tools/handlers/plan.rs
+++ b/codex-rs/core/src/tools/handlers/plan.rs
@@ -104,7 +104,7 @@ pub(crate) async fn handle_update_plan(
     arguments: String,
     _call_id: String,
 ) -> Result<String, FunctionCallError> {
-    if turn_context.collaboration_mode_kind == ModeKind::Plan {
+    if turn_context.collaboration_mode.mode == ModeKind::Plan {
         return Err(FunctionCallError::RespondToModel(
             "update_plan is a TODO/checklist tool and is not allowed in Plan mode".to_string(),
         ));
diff --git a/codex-rs/core/tests/suite/collaboration_instructions.rs b/codex-rs/core/tests/suite/collaboration_instructions.rs
index 7a311b4bf..9dcecdf38 100644
--- a/codex-rs/core/tests/suite/collaboration_instructions.rs
+++ b/codex-rs/core/tests/suite/collaboration_instructions.rs
@@ -22,9 +22,12 @@ fn sse_completed(id: &str) -> String {
     sse(vec![ev_response_created(id), ev_completed(id)])
 }
 
-fn collab_mode_with_instructions(instructions: Option<&str>) -> CollaborationMode {
+fn collab_mode_with_mode_and_instructions(
+    mode: ModeKind,
+    instructions: Option<&str>,
+) -> CollaborationMode {
     CollaborationMode {
-        mode: ModeKind::Custom,
+        mode,
         settings: Settings {
             model: "gpt-5.1".to_string(),
             reasoning_effort: None,
@@ -33,6 +36,10 @@ fn collab_mode_with_instructions(instructions: Option<&str>) -> CollaborationMod
     }
 }
 
+fn collab_mode_with_instructions(instructions: Option<&str>) -> CollaborationMode {
+    collab_mode_with_mode_and_instructions(ModeKind::Custom, instructions)
+}
+
 fn developer_texts(input: &[Value]) -> Vec<String> {
     input
         .iter()
@@ -171,7 +178,7 @@ async fn collaboration_instructions_added_on_user_turn() -> Result<()> {
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn override_then_user_turn_uses_updated_collaboration_instructions() -> Result<()> {
+async fn override_then_next_turn_uses_updated_collaboration_instructions() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
     let server = start_mock_server().await;
@@ -196,20 +203,12 @@ async fn override_then_user_turn_uses_updated_collaboration_instructions() -> Re
         .await?;
 
     test.codex
-        .submit(Op::UserTurn {
+        .submit(Op::UserInput {
             items: vec![UserInput::Text {
                 text: "hello".into(),
                 text_elements: Vec::new(),
             }],
-            cwd: test.config.cwd.clone(),
-            approval_policy: test.config.approval_policy.value(),
-            sandbox_policy: test.config.sandbox_policy.get().clone(),
-            model: test.session_configured.model.clone(),
-            effort: None,
-            summary: test.config.model_reasoning_summary,
-            collaboration_mode: None,
             final_output_json_schema: None,
-            personality: None,
         })
         .await?;
     wait_for_event(&test.codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
@@ -272,7 +271,7 @@ async fn user_turn_overrides_collaboration_instructions_after_override() -> Resu
     let dev_texts = developer_texts(&input);
     let base_text = collab_xml(base_text);
     let turn_text = collab_xml(turn_text);
-    assert_eq!(count_exact(&dev_texts, &base_text), 1);
+    assert_eq!(count_exact(&dev_texts, &base_text), 0);
     assert_eq!(count_exact(&dev_texts, &turn_text), 1);
 
     Ok(())
@@ -419,6 +418,159 @@ async fn collaboration_mode_update_noop_does_not_append() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn collaboration_mode_update_emits_new_instruction_message_when_mode_changes() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+    let _req1 = mount_sse_once(&server, sse_completed("resp-1")).await;
+    let req2 = mount_sse_once(&server, sse_completed("resp-2")).await;
+
+    let test = test_codex().build(&server).await?;
+    let code_text = "code mode instructions";
+    let plan_text = "plan mode instructions";
+
+    test.codex
+        .submit(Op::OverrideTurnContext {
+            cwd: None,
+            approval_policy: None,
+            sandbox_policy: None,
+            windows_sandbox_level: None,
+            model: None,
+            effort: None,
+            summary: None,
+            collaboration_mode: Some(collab_mode_with_mode_and_instructions(
+                ModeKind::Code,
+                Some(code_text),
+            )),
+            personality: None,
+        })
+        .await?;
+
+    test.codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "hello 1".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await?;
+    wait_for_event(&test.codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
+
+    test.codex
+        .submit(Op::OverrideTurnContext {
+            cwd: None,
+            approval_policy: None,
+            sandbox_policy: None,
+            windows_sandbox_level: None,
+            model: None,
+            effort: None,
+            summary: None,
+            collaboration_mode: Some(collab_mode_with_mode_and_instructions(
+                ModeKind::Plan,
+                Some(plan_text),
+            )),
+            personality: None,
+        })
+        .await?;
+
+    test.codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "hello 2".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await?;
+    wait_for_event(&test.codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
+
+    let input = req2.single_request().input();
+    let dev_texts = developer_texts(&input);
+    let code_text = collab_xml(code_text);
+    let plan_text = collab_xml(plan_text);
+    assert_eq!(count_exact(&dev_texts, &code_text), 1);
+    assert_eq!(count_exact(&dev_texts, &plan_text), 1);
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn collaboration_mode_update_noop_does_not_append_when_mode_is_unchanged() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+    let _req1 = mount_sse_once(&server, sse_completed("resp-1")).await;
+    let req2 = mount_sse_once(&server, sse_completed("resp-2")).await;
+
+    let test = test_codex().build(&server).await?;
+    let collab_text = "mode-stable instructions";
+
+    test.codex
+        .submit(Op::OverrideTurnContext {
+            cwd: None,
+            approval_policy: None,
+            sandbox_policy: None,
+            windows_sandbox_level: None,
+            model: None,
+            effort: None,
+            summary: None,
+            collaboration_mode: Some(collab_mode_with_mode_and_instructions(
+                ModeKind::Code,
+                Some(collab_text),
+            )),
+            personality: None,
+        })
+        .await?;
+
+    test.codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "hello 1".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await?;
+    wait_for_event(&test.codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
+
+    test.codex
+        .submit(Op::OverrideTurnContext {
+            cwd: None,
+            approval_policy: None,
+            sandbox_policy: None,
+            windows_sandbox_level: None,
+            model: None,
+            effort: None,
+            summary: None,
+            collaboration_mode: Some(collab_mode_with_mode_and_instructions(
+                ModeKind::Code,
+                Some(collab_text),
+            )),
+            personality: None,
+        })
+        .await?;
+
+    test.codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "hello 2".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await?;
+    wait_for_event(&test.codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
+
+    let input = req2.single_request().input();
+    let dev_texts = developer_texts(&input);
+    let collab_text = collab_xml(collab_text);
+    assert_eq!(count_exact(&dev_texts, &collab_text), 1);
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn resume_replays_collaboration_instructions() -> Result<()> {
     skip_if_no_network!(Ok(()));
diff --git a/codex-rs/core/tests/suite/override_updates.rs b/codex-rs/core/tests/suite/override_updates.rs
index 14469c964..897bb665d 100644
--- a/codex-rs/core/tests/suite/override_updates.rs
+++ b/codex-rs/core/tests/suite/override_updates.rs
@@ -18,7 +18,6 @@ use core_test_support::skip_if_no_network;
 use core_test_support::test_codex::test_codex;
 use core_test_support::wait_for_event;
 use pretty_assertions::assert_eq;
-use std::collections::HashSet;
 use std::path::Path;
 use std::time::Duration;
 use tempfile::TempDir;
@@ -104,7 +103,7 @@ fn rollout_environment_texts(text: &str) -> Vec<String> {
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn override_turn_context_records_permissions_update() -> Result<()> {
+async fn override_turn_context_without_user_turn_does_not_record_permissions_update() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
     let server = start_mock_server().await;
@@ -138,19 +137,15 @@ async fn override_turn_context_records_permissions_update() -> Result<()> {
         .filter(|text| text.contains("`approval_policy`"))
         .collect();
     assert!(
-        approval_texts
-            .iter()
-            .any(|text| text.contains("`approval_policy` is `never`")),
-        "expected updated approval policy instructions in rollout"
+        approval_texts.is_empty(),
+        "did not expect permissions updates before a new user turn: {approval_texts:?}"
     );
-    let unique: HashSet<&String> = approval_texts.iter().copied().collect();
-    assert_eq!(unique.len(), 2);
 
     Ok(())
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn override_turn_context_records_environment_update() -> Result<()> {
+async fn override_turn_context_without_user_turn_does_not_record_environment_update() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
     let server = start_mock_server().await;
@@ -177,17 +172,16 @@ async fn override_turn_context_records_environment_update() -> Result<()> {
     let rollout_path = test.codex.rollout_path().expect("rollout path");
     let rollout_text = read_rollout_text(&rollout_path).await?;
     let env_texts = rollout_environment_texts(&rollout_text);
-    let new_cwd_text = new_cwd.path().display().to_string();
     assert!(
-        env_texts.iter().any(|text| text.contains(&new_cwd_text)),
-        "expected environment update with new cwd in rollout"
+        env_texts.is_empty(),
+        "did not expect environment updates before a new user turn: {env_texts:?}"
     );
 
     Ok(())
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn override_turn_context_records_collaboration_update() -> Result<()> {
+async fn override_turn_context_without_user_turn_does_not_record_collaboration_update() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
     let server = start_mock_server().await;
@@ -220,7 +214,7 @@ async fn override_turn_context_records_collaboration_update() -> Result<()> {
         .iter()
         .filter(|text| text.as_str() == collab_text.as_str())
         .count();
-    assert_eq!(collab_count, 1);
+    assert_eq!(collab_count, 0);
 
     Ok(())
 }
diff --git a/codex-rs/core/tests/suite/permissions_messages.rs b/codex-rs/core/tests/suite/permissions_messages.rs
index b500689ef..c54203b4f 100644
--- a/codex-rs/core/tests/suite/permissions_messages.rs
+++ b/codex-rs/core/tests/suite/permissions_messages.rs
@@ -136,7 +136,7 @@ async fn permissions_message_added_on_override_change() -> Result<()> {
     let permissions_2 = permissions_texts(input2);
 
     assert_eq!(permissions_1.len(), 1);
-    assert_eq!(permissions_2.len(), 3);
+    assert_eq!(permissions_2.len(), 2);
     let unique = permissions_2.into_iter().collect::<HashSet<String>>();
     assert_eq!(unique.len(), 2);
 
@@ -267,7 +267,7 @@ async fn resume_replays_permissions_messages() -> Result<()> {
     let body3 = req3.single_request().body_json();
     let input = body3["input"].as_array().expect("input array");
     let permissions = permissions_texts(input);
-    assert_eq!(permissions.len(), 4);
+    assert_eq!(permissions.len(), 3);
     let unique = permissions.into_iter().collect::<HashSet<String>>();
     assert_eq!(unique.len(), 2);
 
@@ -337,7 +337,7 @@ async fn resume_and_fork_append_permissions_messages() -> Result<()> {
     let body2 = req2.single_request().body_json();
     let input2 = body2["input"].as_array().expect("input array");
     let permissions_base = permissions_texts(input2);
-    assert_eq!(permissions_base.len(), 3);
+    assert_eq!(permissions_base.len(), 2);
 
     builder = builder.with_config(|config| {
         config.approval_policy = Constrained::allow_any(AskForApproval::UnlessTrusted);
diff --git a/codex-rs/core/tests/suite/personality.rs b/codex-rs/core/tests/suite/personality.rs
index 2b00574d5..85cc25f4c 100644
--- a/codex-rs/core/tests/suite/personality.rs
+++ b/codex-rs/core/tests/suite/personality.rs
@@ -272,6 +272,97 @@ async fn user_turn_personality_some_adds_update_message() -> anyhow::Result<()>
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn user_turn_personality_same_value_does_not_add_update_message() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+    let resp_mock = mount_sse_sequence(
+        &server,
+        vec![sse_completed("resp-1"), sse_completed("resp-2")],
+    )
+    .await;
+    let mut builder = test_codex()
+        .with_model("exp-codex-personality")
+        .with_config(|config| {
+            config.features.disable(Feature::RemoteModels);
+            config.features.enable(Feature::Personality);
+            config.personality = Some(Personality::Pragmatic);
+        });
+    let test = builder.build(&server).await?;
+
+    test.codex
+        .submit(Op::UserTurn {
+            items: vec![UserInput::Text {
+                text: "hello".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+            cwd: test.cwd_path().to_path_buf(),
+            approval_policy: test.config.approval_policy.value(),
+            sandbox_policy: SandboxPolicy::ReadOnly,
+            model: test.session_configured.model.clone(),
+            effort: test.config.model_reasoning_effort,
+            summary: ReasoningSummary::Auto,
+            collaboration_mode: None,
+            personality: None,
+        })
+        .await?;
+
+    wait_for_event(&test.codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
+
+    test.codex
+        .submit(Op::OverrideTurnContext {
+            cwd: None,
+            approval_policy: None,
+            sandbox_policy: None,
+            windows_sandbox_level: None,
+            model: None,
+            effort: None,
+            summary: None,
+            collaboration_mode: None,
+            personality: Some(Personality::Pragmatic),
+        })
+        .await?;
+
+    test.codex
+        .submit(Op::UserTurn {
+            items: vec![UserInput::Text {
+                text: "hello".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+            cwd: test.cwd_path().to_path_buf(),
+            approval_policy: test.config.approval_policy.value(),
+            sandbox_policy: SandboxPolicy::ReadOnly,
+            model: test.session_configured.model.clone(),
+            effort: test.config.model_reasoning_effort,
+            summary: ReasoningSummary::Auto,
+            collaboration_mode: None,
+            personality: None,
+        })
+        .await?;
+
+    wait_for_event(&test.codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
+
+    let requests = resp_mock.requests();
+    assert_eq!(requests.len(), 2, "expected two requests");
+    let request = requests
+        .last()
+        .expect("expected second request after personality override");
+
+    let developer_texts = request.message_input_texts("developer");
+    let personality_text = developer_texts
+        .iter()
+        .find(|text| text.contains("<personality_spec>"));
+    assert!(
+        personality_text.is_none(),
+        "expected no personality preamble for unchanged personality, got {personality_text:?}"
+    );
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn instructions_uses_base_if_feature_disabled() -> anyhow::Result<()> {
     let codex_home = TempDir::new().expect("create temp dir");
diff --git a/codex-rs/core/tests/suite/prompt_caching.rs b/codex-rs/core/tests/suite/prompt_caching.rs
index 579a1856d..6b06726ea 100644
--- a/codex-rs/core/tests/suite/prompt_caching.rs
+++ b/codex-rs/core/tests/suite/prompt_caching.rs
@@ -388,17 +388,14 @@ async fn overrides_turn_context_but_keeps_cached_prefix_and_key_constant() -> an
     });
     let expected_permissions_msg = body1["input"][0].clone();
     let body1_input = body1["input"].as_array().expect("input array");
-    // After overriding the turn context, emit two updated permissions messages.
+    // After overriding the turn context, emit one updated permissions message.
     let expected_permissions_msg_2 = body2["input"][body1_input.len()].clone();
-    let expected_permissions_msg_3 = body2["input"][body1_input.len() + 1].clone();
     assert_ne!(
         expected_permissions_msg_2, expected_permissions_msg,
         "expected updated permissions message after override"
     );
-    assert_eq!(expected_permissions_msg_2, expected_permissions_msg_3);
     let mut expected_body2 = body1_input.to_vec();
     expected_body2.push(expected_permissions_msg_2);
-    expected_body2.push(expected_permissions_msg_3);
     expected_body2.push(expected_user_message_2);
     assert_eq!(body2["input"], serde_json::Value::Array(expected_body2));