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 7269fdacda..a2ec69ed9d 100644
--- a/codex-rs/app-server/src/request_processors/thread_processor.rs
+++ b/codex-rs/app-server/src/request_processors/thread_processor.rs
@@ -2788,15 +2788,18 @@ impl ThreadRequestProcessor {
             developer_instructions,
             personality,
         );
-        self.load_and_apply_persisted_resume_metadata(
-            &thread_history,
-            &mut request_overrides,
-            &mut typesafe_overrides,
-        )
-        .await;
+        let has_explicit_model_resume_override =
+            has_model_resume_override(request_overrides.as_ref(), &typesafe_overrides);
+        let persisted_metadata = self
+            .load_and_apply_persisted_resume_metadata(
+                &thread_history,
+                &mut request_overrides,
+                &mut typesafe_overrides,
+            )
+            .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
@@ -2808,6 +2811,13 @@ impl ThreadRequestProcessor {
                 return Ok(());
             }
         };
+        if !has_explicit_model_resume_override
+            && persisted_metadata
+                .as_ref()
+                .is_some_and(|metadata| metadata.reasoning_effort.is_none())
+        {
+            config.model_reasoning_effort = None;
+        }
 
         let response_history = thread_history.clone();
 
diff --git a/codex-rs/app-server/tests/suite/v2/thread_resume.rs b/codex-rs/app-server/tests/suite/v2/thread_resume.rs
index efdd2c9eed..352d96409f 100644
--- a/codex-rs/app-server/tests/suite/v2/thread_resume.rs
+++ b/codex-rs/app-server/tests/suite/v2/thread_resume.rs
@@ -59,10 +59,14 @@ use codex_config::types::AuthCredentialsStoreMode;
 use codex_core::ARCHIVED_SESSIONS_SUBDIR;
 use codex_login::REFRESH_TOKEN_URL_OVERRIDE_ENV_VAR;
 use codex_protocol::ThreadId;
+use codex_protocol::config_types::CollaborationMode;
+use codex_protocol::config_types::ModeKind;
 use codex_protocol::config_types::Personality;
+use codex_protocol::config_types::Settings;
 use codex_protocol::mcp::CallToolResult;
 use codex_protocol::models::ContentItem;
 use codex_protocol::models::ResponseItem;
+use codex_protocol::openai_models::ReasoningEffort;
 use codex_protocol::protocol::AgentMessageEvent;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::ImageGenerationEndEvent;
@@ -529,21 +533,30 @@ async fn thread_resume_preserves_persisted_approvals_reviewer() -> Result<()> {
 }
 
 #[tokio::test]
-async fn thread_resume_preserves_acknowledged_approvals_reviewer_update() -> Result<()> {
+async fn thread_resume_preserves_acknowledged_model_effort_and_approvals_reviewer_update()
+-> Result<()> {
     let server = create_mock_responses_server_repeating_assistant("Done").await;
     let codex_home = TempDir::new()?;
     create_config_toml(codex_home.path(), &server.uri())?;
+    let config_path = codex_home.path().join("config.toml");
+    let config_toml = std::fs::read_to_string(&config_path)?;
+    std::fs::write(
+        &config_path,
+        config_toml.replace(
+            "model = \"gpt-5.4\"",
+            "model = \"gpt-5.4\"\nmodel_reasoning_effort = \"high\"",
+        ),
+    )?;
 
     let thread_id = {
         let mut mcp = TestAppServer::builder()
             .with_codex_home(codex_home.path())
-            .without_auto_env()
             .build()
             .await?;
         timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
 
         let start_id = mcp
-            .send_thread_start_request(ThreadStartParams {
+            .send_thread_start_request_with_auto_env(ThreadStartParams {
                 model: Some("gpt-5.4".to_string()),
                 ..Default::default()
             })
@@ -580,6 +593,8 @@ async fn thread_resume_preserves_acknowledged_approvals_reviewer_update() -> Res
         let update_id = mcp
             .send_thread_settings_update_request(ThreadSettingsUpdateParams {
                 thread_id: thread.id.clone(),
+                model: Some("gpt-5.2-codex".to_string()),
+                effort: Some(ReasoningEffort::Ultra),
                 approvals_reviewer: Some(ApprovalsReviewer::AutoReview),
                 ..Default::default()
             })
@@ -601,7 +616,60 @@ async fn thread_resume_preserves_acknowledged_approvals_reviewer_update() -> Res
 
     let mut mcp = TestAppServer::builder()
         .with_codex_home(codex_home.path())
-        .without_auto_env()
+        .build()
+        .await?;
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
+    let resume_id = mcp
+        .send_thread_resume_request(ThreadResumeParams {
+            thread_id: thread_id.clone(),
+            ..Default::default()
+        })
+        .await?;
+    let resume_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(resume_id)),
+    )
+    .await??;
+    let ThreadResumeResponse {
+        model,
+        reasoning_effort,
+        approvals_reviewer,
+        ..
+    } = to_response::<ThreadResumeResponse>(resume_resp)?;
+
+    assert_eq!(model, "gpt-5.2-codex");
+    assert_eq!(reasoning_effort, Some(ReasoningEffort::Ultra));
+    assert_eq!(approvals_reviewer, ApprovalsReviewer::AutoReview);
+
+    let update_id = mcp
+        .send_thread_settings_update_request(ThreadSettingsUpdateParams {
+            thread_id: thread_id.clone(),
+            collaboration_mode: Some(CollaborationMode {
+                mode: ModeKind::Default,
+                settings: Settings {
+                    model: "gpt-5.2-codex".to_string(),
+                    reasoning_effort: None,
+                    developer_instructions: None,
+                },
+            }),
+            ..Default::default()
+        })
+        .await?;
+    let update_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(update_id)),
+    )
+    .await??;
+    let _: ThreadSettingsUpdateResponse = to_response(update_resp)?;
+    timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_notification_message("thread/settings/updated"),
+    )
+    .await??;
+    drop(mcp);
+
+    let mut mcp = TestAppServer::builder()
+        .with_codex_home(codex_home.path())
         .build()
         .await?;
     timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
@@ -617,10 +685,10 @@ async fn thread_resume_preserves_acknowledged_approvals_reviewer_update() -> Res
     )
     .await??;
     let ThreadResumeResponse {
-        approvals_reviewer, ..
+        reasoning_effort, ..
     } = to_response::<ThreadResumeResponse>(resume_resp)?;
 
-    assert_eq!(approvals_reviewer, ApprovalsReviewer::AutoReview);
+    assert_eq!(reasoning_effort, None);
 
     Ok(())
 }
diff --git a/codex-rs/state/src/extract.rs b/codex-rs/state/src/extract.rs
index ac4201de9f..1bf81168d7 100644
--- a/codex-rs/state/src/extract.rs
+++ b/codex-rs/state/src/extract.rs
@@ -37,7 +37,10 @@ pub fn rollout_item_affects_thread_metadata(item: &RolloutItem) -> bool {
     match item {
         RolloutItem::SessionMeta(_) | RolloutItem::TurnContext(_) => true,
         RolloutItem::EventMsg(
-            EventMsg::TokenCount(_) | EventMsg::UserMessage(_) | EventMsg::ThreadGoalUpdated(_),
+            EventMsg::TokenCount(_)
+            | EventMsg::UserMessage(_)
+            | EventMsg::ThreadGoalUpdated(_)
+            | EventMsg::ThreadSettingsApplied(_),
         ) => true,
         RolloutItem::EventMsg(EventMsg::ItemCompleted(event))
             if matches!(event.item, TurnItem::UserMessage(_)) =>
@@ -114,6 +117,16 @@ fn apply_event_msg(metadata: &mut ThreadMetadata, event: &EventMsg) {
                 set_preview_if_empty(metadata, Some(objective.to_string()));
             }
         }
+        EventMsg::ThreadSettingsApplied(event) => {
+            let settings = &event.thread_settings;
+            metadata.model = Some(settings.model.clone());
+            metadata.model_provider = settings.model_provider_id.clone();
+            metadata.reasoning_effort = settings.reasoning_effort.clone();
+            metadata.cwd = settings.cwd.clone().into_path_buf();
+            metadata.sandbox_policy =
+                serde_json::to_string(&settings.permission_profile).unwrap_or_default();
+            metadata.approval_mode = enum_to_string(&settings.approval_policy);
+        }
         _ => {}
     }
 }
@@ -151,10 +164,16 @@ pub(crate) fn enum_to_string<T: Serialize>(value: &T) -> String {
 #[cfg(test)]
 mod tests {
     use super::apply_rollout_item;
+    use super::rollout_item_affects_thread_metadata;
     use crate::model::ThreadMetadata;
     use chrono::DateTime;
     use chrono::Utc;
     use codex_protocol::ThreadId;
+    use codex_protocol::config_types::ApprovalsReviewer;
+    use codex_protocol::config_types::CollaborationMode;
+    use codex_protocol::config_types::ModeKind;
+    use codex_protocol::config_types::ReasoningSummary;
+    use codex_protocol::config_types::Settings;
     use codex_protocol::items::TurnItem;
     use codex_protocol::items::UserMessageItem;
     use codex_protocol::models::ContentItem;
@@ -173,6 +192,8 @@ mod tests {
     use codex_protocol::protocol::ThreadGoalStatus;
     use codex_protocol::protocol::ThreadGoalUpdatedEvent;
     use codex_protocol::protocol::ThreadHistoryMode;
+    use codex_protocol::protocol::ThreadSettingsAppliedEvent;
+    use codex_protocol::protocol::ThreadSettingsSnapshot;
     use codex_protocol::protocol::TurnContextItem;
     use codex_protocol::protocol::USER_MESSAGE_BEGIN;
     use codex_protocol::protocol::UserMessageEvent;
@@ -530,6 +551,54 @@ mod tests {
         assert_eq!(metadata.reasoning_effort, Some(ReasoningEffort::High));
     }
 
+    #[test]
+    fn thread_settings_applied_updates_resume_metadata() {
+        let mut metadata = metadata_for_test();
+        let permission_profile = PermissionProfile::workspace_write();
+        let cwd = std::env::current_dir()
+            .expect("current directory")
+            .join("updated/workspace");
+        let item = RolloutItem::EventMsg(EventMsg::ThreadSettingsApplied(
+            ThreadSettingsAppliedEvent {
+                thread_settings: ThreadSettingsSnapshot {
+                    model: "gpt-5.2-codex".to_string(),
+                    model_provider_id: "updated-provider".to_string(),
+                    service_tier: None,
+                    approval_policy: AskForApproval::Never,
+                    approvals_reviewer: ApprovalsReviewer::User,
+                    permission_profile: permission_profile.clone(),
+                    active_permission_profile: None,
+                    cwd: cwd.clone().try_into().expect("absolute settings cwd"),
+                    reasoning_effort: Some(ReasoningEffort::Ultra),
+                    reasoning_summary: Some(ReasoningSummary::Auto),
+                    personality: None,
+                    collaboration_mode: CollaborationMode {
+                        mode: ModeKind::Default,
+                        settings: Settings {
+                            model: "gpt-5.2-codex".to_string(),
+                            reasoning_effort: Some(ReasoningEffort::Ultra),
+                            developer_instructions: None,
+                        },
+                    },
+                },
+            },
+        ));
+
+        assert!(rollout_item_affects_thread_metadata(&item));
+        apply_rollout_item(&mut metadata, &item, "test-provider");
+
+        assert_eq!(metadata.model.as_deref(), Some("gpt-5.2-codex"));
+        assert_eq!(metadata.model_provider, "updated-provider");
+        assert_eq!(metadata.reasoning_effort, Some(ReasoningEffort::Ultra));
+        assert_eq!(metadata.cwd, cwd);
+        assert_eq!(metadata.approval_mode, "never");
+        assert_eq!(
+            metadata.sandbox_policy,
+            serde_json::to_string(&permission_profile)
+                .expect("permission profile should serialize")
+        );
+    }
+
     #[test]
     fn session_meta_does_not_set_model_or_reasoning_effort() {
         let mut metadata = metadata_for_test();
diff --git a/codex-rs/thread-store/src/in_memory.rs b/codex-rs/thread-store/src/in_memory.rs
index 0d6ea80f2a..76f8727c8b 100644
--- a/codex-rs/thread-store/src/in_memory.rs
+++ b/codex-rs/thread-store/src/in_memory.rs
@@ -773,7 +773,9 @@ fn stored_thread_from_state(
             .and_then(|metadata| metadata.model_provider.clone())
             .unwrap_or_else(|| "test".to_string()),
         model: metadata.and_then(|metadata| metadata.model.clone()),
-        reasoning_effort: metadata.and_then(|metadata| metadata.reasoning_effort.clone()),
+        reasoning_effort: metadata
+            .and_then(|metadata| metadata.reasoning_effort.clone())
+            .flatten(),
         created_at: metadata
             .and_then(|metadata| metadata.created_at)
             .unwrap_or_else(Utc::now),
diff --git a/codex-rs/thread-store/src/local/update_thread_metadata.rs b/codex-rs/thread-store/src/local/update_thread_metadata.rs
index 580df1dc61..a6ea76e7e0 100644
--- a/codex-rs/thread-store/src/local/update_thread_metadata.rs
+++ b/codex-rs/thread-store/src/local/update_thread_metadata.rs
@@ -266,7 +266,7 @@ async fn apply_metadata_update(
                 metadata.model = Some(model);
             }
             if let Some(reasoning_effort) = patch.reasoning_effort {
-                metadata.reasoning_effort = Some(reasoning_effort);
+                metadata.reasoning_effort = reasoning_effort;
             }
             if let Some(created_at) = patch.created_at {
                 metadata.created_at = created_at;
@@ -717,6 +717,7 @@ fn rollout_path_is_archived(store: &LocalThreadStore, path: &Path) -> bool {
 #[cfg(test)]
 mod tests {
     use codex_protocol::models::PermissionProfile;
+    use codex_protocol::openai_models::ReasoningEffort;
     use codex_protocol::protocol::ThreadHistoryMode;
     use pretty_assertions::assert_eq;
     use serde_json::Value;
@@ -1008,7 +1009,7 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn update_thread_metadata_sets_permission_profile() {
+    async fn update_thread_metadata_updates_permission_profile_and_reasoning_effort() {
         let home = TempDir::new().expect("temp dir");
         let config = test_config(home.path());
         let runtime = codex_state::StateRuntime::init(
@@ -1027,6 +1028,7 @@ mod tests {
                 thread_id,
                 patch: ThreadMetadataPatch {
                     permission_profile: Some(PermissionProfile::Disabled),
+                    reasoning_effort: Some(Some(ReasoningEffort::Ultra)),
                     ..Default::default()
                 },
                 include_archived: false,
@@ -1035,6 +1037,19 @@ mod tests {
             .expect("set permission profile");
 
         assert_eq!(thread.permission_profile, PermissionProfile::Disabled);
+        let thread = store
+            .update_thread_metadata(UpdateThreadMetadataParams {
+                thread_id,
+                patch: ThreadMetadataPatch {
+                    reasoning_effort: Some(None),
+                    ..Default::default()
+                },
+                include_archived: false,
+            })
+            .await
+            .expect("clear reasoning effort");
+
+        assert_eq!(thread.reasoning_effort, None);
         let metadata = runtime
             .get_thread(thread_id)
             .await
@@ -1045,6 +1060,7 @@ mod tests {
             metadata.sandbox_policy,
             serde_json::to_string(&permission_profile).expect("serialize profile")
         );
+        assert_eq!(metadata.reasoning_effort, None);
     }
 
     #[tokio::test]
diff --git a/codex-rs/thread-store/src/thread_metadata_sync.rs b/codex-rs/thread-store/src/thread_metadata_sync.rs
index 4b53990828..54ef305c07 100644
--- a/codex-rs/thread-store/src/thread_metadata_sync.rs
+++ b/codex-rs/thread-store/src/thread_metadata_sync.rs
@@ -240,7 +240,7 @@ impl ThreadMetadataSync {
                         update.cwd = Some(turn_ctx.cwd.clone().into_path_buf());
                     }
                     update.model = Some(turn_ctx.model.clone());
-                    update.reasoning_effort = turn_ctx.effort.clone();
+                    update.reasoning_effort = Some(turn_ctx.effort.clone());
                     update.approval_mode = Some(turn_ctx.approval_policy);
                     update.permission_profile = Some(turn_ctx.permission_profile());
                 }
@@ -269,6 +269,16 @@ impl ThreadMetadataSync {
                         }
                     }
                 }
+                RolloutItem::EventMsg(EventMsg::ThreadSettingsApplied(event)) => {
+                    let settings = &event.thread_settings;
+                    self.cwd_seen = true;
+                    update.model = Some(settings.model.clone());
+                    update.model_provider = Some(settings.model_provider_id.clone());
+                    update.reasoning_effort = Some(settings.reasoning_effort.clone());
+                    update.cwd = Some(settings.cwd.clone().into_path_buf());
+                    update.approval_mode = Some(settings.approval_policy);
+                    update.permission_profile = Some(settings.permission_profile.clone());
+                }
                 RolloutItem::SessionMeta(_)
                 | RolloutItem::EventMsg(_)
                 | RolloutItem::ResponseItem(_)
@@ -374,7 +384,15 @@ fn git_info_patch_from_observation(git_info: GitInfo) -> GitInfoPatch {
 mod tests {
     use std::sync::Arc;
 
+    use codex_protocol::config_types::ApprovalsReviewer;
+    use codex_protocol::config_types::CollaborationMode;
+    use codex_protocol::config_types::ModeKind;
+    use codex_protocol::config_types::ReasoningSummary;
+    use codex_protocol::config_types::Settings;
     use codex_protocol::items::UserMessageItem;
+    use codex_protocol::models::PermissionProfile;
+    use codex_protocol::openai_models::ReasoningEffort;
+    use codex_protocol::protocol::AskForApproval;
     use codex_protocol::protocol::CompactedItem;
     use codex_protocol::protocol::ItemCompletedEvent;
     use codex_protocol::protocol::SessionMeta;
@@ -383,6 +401,8 @@ mod tests {
     use codex_protocol::protocol::ThreadGoal;
     use codex_protocol::protocol::ThreadGoalStatus;
     use codex_protocol::protocol::ThreadGoalUpdatedEvent;
+    use codex_protocol::protocol::ThreadSettingsAppliedEvent;
+    use codex_protocol::protocol::ThreadSettingsSnapshot;
     use codex_protocol::protocol::TurnStartedEvent;
     use codex_protocol::protocol::UserMessageEvent;
     use codex_protocol::user_input::UserInput;
@@ -551,6 +571,74 @@ mod tests {
         assert!(update.patch.advance_recency_at.is_some());
     }
 
+    #[test]
+    fn thread_settings_applied_updates_live_metadata() {
+        let thread_id = ThreadId::new();
+        let mut sync = ThreadMetadataSync::for_resume(&resume_params(thread_id, Vec::new()));
+        let permission_profile = PermissionProfile::workspace_write();
+        let cwd = std::env::current_dir()
+            .expect("current directory")
+            .join("updated/workspace");
+
+        let mut item = RolloutItem::EventMsg(EventMsg::ThreadSettingsApplied(
+            ThreadSettingsAppliedEvent {
+                thread_settings: ThreadSettingsSnapshot {
+                    model: "gpt-5.2-codex".to_string(),
+                    model_provider_id: "updated-provider".to_string(),
+                    service_tier: None,
+                    approval_policy: AskForApproval::Never,
+                    approvals_reviewer: ApprovalsReviewer::User,
+                    permission_profile: permission_profile.clone(),
+                    active_permission_profile: None,
+                    cwd: cwd.clone().try_into().expect("absolute settings cwd"),
+                    reasoning_effort: Some(ReasoningEffort::Ultra),
+                    reasoning_summary: Some(ReasoningSummary::Auto),
+                    personality: None,
+                    collaboration_mode: CollaborationMode {
+                        mode: ModeKind::Default,
+                        settings: Settings {
+                            model: "gpt-5.2-codex".to_string(),
+                            reasoning_effort: Some(ReasoningEffort::Ultra),
+                            developer_instructions: None,
+                        },
+                    },
+                },
+            },
+        ));
+
+        let update = sync
+            .observe_appended_items(&[item.clone()])
+            .expect("thread settings metadata update");
+
+        assert_eq!(update.patch.model.as_deref(), Some("gpt-5.2-codex"));
+        assert_eq!(
+            update.patch.model_provider.as_deref(),
+            Some("updated-provider")
+        );
+        assert_eq!(
+            update.patch.reasoning_effort,
+            Some(Some(ReasoningEffort::Ultra))
+        );
+        assert_eq!(update.patch.cwd, Some(cwd));
+        assert_eq!(update.patch.approval_mode, Some(AskForApproval::Never));
+        assert_eq!(update.patch.permission_profile, Some(permission_profile));
+
+        let RolloutItem::EventMsg(EventMsg::ThreadSettingsApplied(event)) = &mut item else {
+            panic!("thread settings applied item");
+        };
+        event.thread_settings.reasoning_effort = None;
+        event
+            .thread_settings
+            .collaboration_mode
+            .settings
+            .reasoning_effort = None;
+
+        let update = sync
+            .observe_appended_items(&[item])
+            .expect("thread settings clear metadata update");
+        assert_eq!(update.patch.reasoning_effort, Some(None));
+    }
+
     #[test]
     fn resume_history_waits_for_append_before_flushing_metadata() {
         let thread_id = ThreadId::new();
diff --git a/codex-rs/thread-store/src/types.rs b/codex-rs/thread-store/src/types.rs
index 4e688eca6f..317170442c 100644
--- a/codex-rs/thread-store/src/types.rs
+++ b/codex-rs/thread-store/src/types.rs
@@ -543,7 +543,12 @@ pub struct ThreadMetadataPatch {
     /// Latest observed model.
     pub model: Option<String>,
     /// Latest observed reasoning effort.
-    pub reasoning_effort: Option<ReasoningEffort>,
+    #[serde(
+        default,
+        skip_serializing_if = "Option::is_none",
+        with = "optional_option"
+    )]
+    pub reasoning_effort: ClearableField<ReasoningEffort>,
     /// Creation timestamp when known.
     pub created_at: Option<DateTime<Utc>>,
     /// Last update timestamp for this metadata observation.
@@ -741,6 +746,7 @@ mod tests {
     fn thread_metadata_patch_round_trips_optional_clears() {
         let patch = ThreadMetadataPatch {
             name: Some(None),
+            reasoning_effort: Some(None),
             thread_source: Some(None),
             agent_nickname: Some(None),
             agent_role: Some(None),
@@ -750,6 +756,7 @@ mod tests {
 
         let value = serde_json::to_value(&patch).expect("serialize patch");
         assert_eq!(value["name"], json!(null));
+        assert_eq!(value["reasoning_effort"], json!(null));
         assert_eq!(value["thread_source"], json!(null));
         assert_eq!(value["agent_nickname"], json!(null));
         assert_eq!(value["agent_role"], json!(null));
@@ -758,6 +765,7 @@ mod tests {
         let decoded: ThreadMetadataPatch =
             serde_json::from_value(value).expect("deserialize patch");
         assert_eq!(decoded.name, Some(None));
+        assert_eq!(decoded.reasoning_effort, Some(None));
         assert_eq!(decoded.thread_source, Some(None));
         assert_eq!(decoded.agent_nickname, Some(None));
         assert_eq!(decoded.agent_role, Some(None));
diff --git a/codex-rs/tui/src/app.rs b/codex-rs/tui/src/app.rs
index 554df264e2..cffd90edb8 100644
--- a/codex-rs/tui/src/app.rs
+++ b/codex-rs/tui/src/app.rs
@@ -925,8 +925,12 @@ impl App {
                 (chat_widget, None)
             }
             SessionSelection::Resume(target_session) => {
+                let model_settings = config_persistence::resume_model_settings_for_overrides(
+                    &config,
+                    &harness_overrides,
+                );
                 let resumed = app_server
-                    .resume_thread(config.clone(), target_session.thread_id)
+                    .resume_thread(config.clone(), target_session.thread_id, model_settings)
                     .await
                     .map_err(|err| session_start_error("resume", &target_session, err))?;
                 let init = crate::chatwidget::ChatWidgetInit {
diff --git a/codex-rs/tui/src/app/config_persistence.rs b/codex-rs/tui/src/app/config_persistence.rs
index 80ed84d01e..6021a5e6a3 100644
--- a/codex-rs/tui/src/app/config_persistence.rs
+++ b/codex-rs/tui/src/app/config_persistence.rs
@@ -5,6 +5,7 @@
 //! loop.
 
 use super::*;
+use codex_config::ConfigLayerSource;
 #[cfg(target_os = "windows")]
 use codex_utils_approval_presets::ApprovalPreset;
 
@@ -25,6 +26,36 @@ async fn build_config_on_runtime_worker(
     }
 }
 
+pub(super) fn resume_model_settings_for_overrides(
+    config: &Config,
+    harness_overrides: &ConfigOverrides,
+) -> crate::app_server_session::ResumeModelSettings {
+    let has_layer_override = config
+        .config_layer_stack
+        .layers_high_to_low()
+        .into_iter()
+        .any(|layer| {
+            matches!(
+                &layer.name,
+                ConfigLayerSource::SessionFlags
+                    | ConfigLayerSource::User {
+                        profile: Some(_),
+                        ..
+                    }
+            ) && ["model", "model_provider", "model_reasoning_effort"]
+                .iter()
+                .any(|key| layer.config.get(*key).is_some())
+        });
+    if harness_overrides.model.is_some()
+        || harness_overrides.model_provider.is_some()
+        || has_layer_override
+    {
+        crate::app_server_session::ResumeModelSettings::OverrideFromCurrentConfig
+    } else {
+        crate::app_server_session::ResumeModelSettings::RestoreFromThread
+    }
+}
+
 impl App {
     pub(super) async fn rebuild_config_for_cwd(&self, cwd: PathBuf) -> Result<Config> {
         let mut overrides = self.harness_overrides.clone();
@@ -734,10 +765,89 @@ impl App {
     }
 
     pub(super) fn on_update_reasoning_effort(&mut self, effort: Option<ReasoningEffortConfig>) {
+        let clear_ephemeral_plan_effort = effort != Some(ReasoningEffortConfig::Ultra)
+            && self.chat_widget.config_ref().plan_mode_reasoning_effort
+                == Some(ReasoningEffortConfig::Ultra)
+            && self.config.plan_mode_reasoning_effort != Some(ReasoningEffortConfig::Ultra);
         // TODO(aibrahim): Remove this and don't use config as a state object.
         // Instead, explicitly pass the stored collaboration mode's effort into new sessions.
         self.config.model_reasoning_effort = effort.clone();
-        self.chat_widget.set_reasoning_effort(effort);
+        self.chat_widget.set_reasoning_effort(effort.clone());
+        if clear_ephemeral_plan_effort {
+            self.chat_widget.set_plan_mode_reasoning_effort(effort);
+        }
+    }
+
+    pub(super) fn on_update_plan_mode_reasoning_effort(
+        &mut self,
+        effort: Option<ReasoningEffortConfig>,
+    ) {
+        let clear_ephemeral_default_effort = effort != Some(ReasoningEffortConfig::Ultra)
+            && self
+                .chat_widget
+                .current_collaboration_mode()
+                .reasoning_effort()
+                == Some(ReasoningEffortConfig::Ultra)
+            && self.config.model_reasoning_effort != Some(ReasoningEffortConfig::Ultra);
+        self.config.plan_mode_reasoning_effort = effort.clone();
+        self.chat_widget
+            .set_plan_mode_reasoning_effort(effort.clone());
+        if clear_ephemeral_default_effort {
+            self.chat_widget.set_reasoning_effort(effort);
+        }
+    }
+
+    pub(super) fn on_apply_advanced_reasoning(
+        &mut self,
+        model: &str,
+        effort: ReasoningEffortConfig,
+    ) -> Option<ReasoningEffortConfig> {
+        let default_effort = self.default_reasoning_effort_for_conversation_model(model);
+        if let Some(default_effort) = default_effort.as_ref() {
+            self.config.model = Some(model.to_string());
+            self.config.model_reasoning_effort = Some(default_effort.clone());
+        }
+        self.chat_widget.set_model(model);
+        self.chat_widget.set_reasoning_effort(Some(effort.clone()));
+        self.chat_widget
+            .set_plan_mode_reasoning_effort(Some(effort));
+        default_effort
+    }
+
+    fn default_reasoning_effort_for_conversation_model(
+        &self,
+        model: &str,
+    ) -> Option<ReasoningEffortConfig> {
+        let configured_effort = self
+            .config
+            .model_reasoning_effort
+            .as_ref()
+            .filter(|effort| **effort != ReasoningEffortConfig::Ultra);
+        let preset = self
+            .model_catalog
+            .try_list_models()
+            .ok()?
+            .into_iter()
+            .find(|preset| preset.model == model)?;
+        let supported = &preset.supported_reasoning_efforts;
+
+        configured_effort
+            .filter(|effort| supported.iter().any(|option| option.effort == **effort))
+            .cloned()
+            .or_else(|| {
+                (preset.default_reasoning_effort != ReasoningEffortConfig::Ultra)
+                    .then_some(preset.default_reasoning_effort)
+            })
+            .or_else(|| {
+                supported
+                    .iter()
+                    .find(|option| option.effort != ReasoningEffortConfig::Ultra)
+                    .map(|option| option.effort.clone())
+            })
+    }
+
+    pub(super) fn resume_model_settings(&self) -> crate::app_server_session::ResumeModelSettings {
+        resume_model_settings_for_overrides(&self.config, &self.harness_overrides)
     }
 
     pub(super) fn on_update_personality(&mut self, personality: Personality) {
@@ -1059,12 +1169,19 @@ fn windows_toml_from_json(value: &serde_json::Value) -> Option<WindowsToml> {
 
 #[cfg(test)]
 mod tests {
+    use std::sync::Arc;
+
     use super::*;
     use crate::app::test_support::app_enabled_in_effective_config;
     use crate::app::test_support::make_test_app;
     use crate::legacy_core::config::edit::ConfigEdit;
     use crate::test_support::PathBufExt;
+    use codex_config::ConfigLayerEntry;
+    use codex_config::ConfigLayerStack;
     use codex_protocol::models::PermissionProfile;
+    use codex_protocol::openai_models::ReasoningEffortPreset;
+    use crossterm::event::KeyCode;
+    use crossterm::event::KeyEvent;
     use pretty_assertions::assert_eq;
     use tempfile::tempdir;
 
@@ -1086,6 +1203,249 @@ mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn conversation_reasoning_uses_compatible_default_for_new_threads() {
+        for (configured_effort, expected_default_effort) in [
+            (ReasoningEffortConfig::Low, ReasoningEffortConfig::Low),
+            (
+                ReasoningEffortConfig::Custom("unsupported".to_string()),
+                ReasoningEffortConfig::Medium,
+            ),
+            (ReasoningEffortConfig::Ultra, ReasoningEffortConfig::Medium),
+        ] {
+            let mut app = make_test_app().await;
+            app.config.model = Some("gpt-5.4".to_string());
+            app.config.model_reasoning_effort = Some(configured_effort.clone());
+            app.chat_widget
+                .set_reasoning_effort(Some(configured_effort));
+
+            let default_effort =
+                app.on_apply_advanced_reasoning("gpt-5.4", ReasoningEffortConfig::Ultra);
+            let new_thread_config = app.fresh_session_config();
+
+            assert_eq!(default_effort, Some(expected_default_effort.clone()));
+            assert_eq!(app.chat_widget.current_model(), "gpt-5.4");
+            assert_eq!(
+                app.chat_widget.current_reasoning_effort(),
+                Some(ReasoningEffortConfig::Ultra)
+            );
+            assert_eq!(
+                (
+                    new_thread_config.model.as_deref(),
+                    new_thread_config.model_reasoning_effort,
+                ),
+                (Some("gpt-5.4"), Some(expected_default_effort))
+            );
+        }
+    }
+
+    #[tokio::test]
+    async fn conversation_reasoning_keeps_previous_default_for_ultra_only_model() {
+        let mut app = make_test_app().await;
+        app.config.model = Some("gpt-5.4".to_string());
+        app.config.model_reasoning_effort = Some(ReasoningEffortConfig::Low);
+        let mut preset = app
+            .model_catalog
+            .try_list_models()
+            .expect("model catalog is infallible")
+            .into_iter()
+            .find(|preset| preset.model == "gpt-5.4")
+            .expect("gpt-5.4 preset");
+        preset.model = "ultra-only".to_string();
+        preset.default_reasoning_effort = ReasoningEffortConfig::Ultra;
+        preset.supported_reasoning_efforts = vec![ReasoningEffortPreset {
+            effort: ReasoningEffortConfig::Ultra,
+            description: "Ultra reasoning".to_string(),
+        }];
+        app.model_catalog = Arc::new(ModelCatalog::new(vec![preset]));
+
+        let default_effort =
+            app.on_apply_advanced_reasoning("ultra-only", ReasoningEffortConfig::Ultra);
+        let new_thread_config = app.fresh_session_config();
+
+        assert_eq!(default_effort, None);
+        assert_eq!(app.chat_widget.current_model(), "ultra-only");
+        assert_eq!(
+            app.chat_widget.current_reasoning_effort(),
+            Some(ReasoningEffortConfig::Ultra)
+        );
+        assert_eq!(
+            (
+                new_thread_config.model.as_deref(),
+                new_thread_config.model_reasoning_effort,
+            ),
+            (Some("gpt-5.4"), Some(ReasoningEffortConfig::Low))
+        );
+    }
+
+    #[tokio::test]
+    async fn conversation_reasoning_updates_active_plan_without_changing_plan_default() {
+        let mut app = make_test_app().await;
+        app.config.model_reasoning_effort = Some(ReasoningEffortConfig::Low);
+        app.config.plan_mode_reasoning_effort = Some(ReasoningEffortConfig::High);
+        app.chat_widget
+            .set_feature_enabled(Feature::CollaborationModes, /*enabled*/ true);
+        app.chat_widget
+            .set_plan_mode_reasoning_effort(Some(ReasoningEffortConfig::High));
+        app.chat_widget
+            .handle_key_event(KeyEvent::from(KeyCode::BackTab));
+
+        let default_effort =
+            app.on_apply_advanced_reasoning("gpt-5.4", ReasoningEffortConfig::Ultra);
+
+        assert_eq!(default_effort, Some(ReasoningEffortConfig::Low));
+        assert_eq!(
+            app.chat_widget.current_reasoning_effort(),
+            Some(ReasoningEffortConfig::Ultra)
+        );
+        app.chat_widget
+            .handle_key_event(KeyEvent::from(KeyCode::BackTab));
+        assert_eq!(
+            app.chat_widget.current_reasoning_effort(),
+            Some(ReasoningEffortConfig::Ultra)
+        );
+        app.chat_widget
+            .handle_key_event(KeyEvent::from(KeyCode::BackTab));
+        assert_eq!(
+            app.chat_widget.current_reasoning_effort(),
+            Some(ReasoningEffortConfig::Ultra)
+        );
+        assert_eq!(
+            (
+                app.config.model_reasoning_effort.clone(),
+                app.config.plan_mode_reasoning_effort.clone(),
+            ),
+            (
+                Some(ReasoningEffortConfig::Low),
+                Some(ReasoningEffortConfig::High),
+            )
+        );
+    }
+
+    #[tokio::test]
+    async fn leaving_conversation_ultra_in_default_clears_the_ephemeral_plan_effort() {
+        let mut app = make_test_app().await;
+        app.config.model_reasoning_effort = Some(ReasoningEffortConfig::Low);
+        app.config.plan_mode_reasoning_effort = Some(ReasoningEffortConfig::High);
+        app.chat_widget
+            .set_feature_enabled(Feature::CollaborationModes, /*enabled*/ true);
+        app.chat_widget
+            .set_plan_mode_reasoning_effort(Some(ReasoningEffortConfig::High));
+
+        app.on_apply_advanced_reasoning("gpt-5.4", ReasoningEffortConfig::Ultra);
+        app.on_update_reasoning_effort(Some(ReasoningEffortConfig::Medium));
+        app.chat_widget
+            .handle_key_event(KeyEvent::from(KeyCode::BackTab));
+
+        assert_eq!(
+            app.chat_widget.current_reasoning_effort(),
+            Some(ReasoningEffortConfig::Medium)
+        );
+        assert_eq!(
+            app.config.plan_mode_reasoning_effort,
+            Some(ReasoningEffortConfig::High)
+        );
+    }
+
+    #[tokio::test]
+    async fn leaving_conversation_ultra_in_plan_clears_the_ephemeral_default_effort() {
+        let mut app = make_test_app().await;
+        app.config.model_reasoning_effort = Some(ReasoningEffortConfig::Low);
+        app.config.plan_mode_reasoning_effort = Some(ReasoningEffortConfig::High);
+        app.chat_widget
+            .set_feature_enabled(Feature::CollaborationModes, /*enabled*/ true);
+        app.chat_widget
+            .set_plan_mode_reasoning_effort(Some(ReasoningEffortConfig::High));
+        app.chat_widget
+            .handle_key_event(KeyEvent::from(KeyCode::BackTab));
+
+        app.on_apply_advanced_reasoning("gpt-5.4", ReasoningEffortConfig::Ultra);
+        app.on_update_plan_mode_reasoning_effort(Some(ReasoningEffortConfig::Medium));
+        app.chat_widget
+            .handle_key_event(KeyEvent::from(KeyCode::BackTab));
+
+        assert_eq!(
+            app.chat_widget.current_reasoning_effort(),
+            Some(ReasoningEffortConfig::Medium)
+        );
+        assert_eq!(
+            app.config.model_reasoning_effort,
+            Some(ReasoningEffortConfig::Low)
+        );
+    }
+
+    #[tokio::test]
+    async fn resume_model_settings_preserves_only_explicit_model_overrides() {
+        let mut app = make_test_app().await;
+
+        assert_eq!(
+            app.resume_model_settings(),
+            crate::app_server_session::ResumeModelSettings::RestoreFromThread
+        );
+        let profile_path = test_path_buf("/tmp/work.config.toml").abs();
+        let profile = "work"
+            .parse::<codex_config::ProfileV2Name>()
+            .expect("valid profile name");
+        for (key, expected) in [
+            (
+                "model",
+                crate::app_server_session::ResumeModelSettings::OverrideFromCurrentConfig,
+            ),
+            (
+                "model_provider",
+                crate::app_server_session::ResumeModelSettings::OverrideFromCurrentConfig,
+            ),
+            (
+                "model_reasoning_effort",
+                crate::app_server_session::ResumeModelSettings::OverrideFromCurrentConfig,
+            ),
+            (
+                "sandbox_mode",
+                crate::app_server_session::ResumeModelSettings::RestoreFromThread,
+            ),
+        ] {
+            let config = TomlValue::Table(toml::map::Map::from_iter([(
+                key.to_string(),
+                TomlValue::String("value".to_string()),
+            )]));
+            app.config.config_layer_stack = ConfigLayerStack::new(
+                vec![ConfigLayerEntry::new(
+                    ConfigLayerSource::SessionFlags,
+                    config.clone(),
+                )],
+                Default::default(),
+                Default::default(),
+            )
+            .expect("session flags layer stack");
+            assert_eq!(app.resume_model_settings(), expected);
+
+            app.config.config_layer_stack = ConfigLayerStack::default().with_user_config_profile(
+                &profile_path,
+                Some(&profile),
+                config,
+            );
+            assert_eq!(app.resume_model_settings(), expected);
+        }
+
+        app.config.config_layer_stack = ConfigLayerStack::default().with_user_config(
+            &profile_path,
+            TomlValue::Table(toml::map::Map::from_iter([(
+                "model_reasoning_effort".to_string(),
+                TomlValue::String("high".to_string()),
+            )])),
+        );
+        assert_eq!(
+            app.resume_model_settings(),
+            crate::app_server_session::ResumeModelSettings::RestoreFromThread
+        );
+
+        app.harness_overrides.model_provider = Some("custom-provider".to_string());
+        assert_eq!(
+            app.resume_model_settings(),
+            crate::app_server_session::ResumeModelSettings::OverrideFromCurrentConfig
+        );
+    }
+
     #[tokio::test]
     async fn refresh_in_memory_config_from_disk_loads_latest_apps_state() -> Result<()> {
         let mut app = make_test_app().await;
diff --git a/codex-rs/tui/src/app/event_dispatch.rs b/codex-rs/tui/src/app/event_dispatch.rs
index 8713537fbc..a5d408d4ca 100644
--- a/codex-rs/tui/src/app/event_dispatch.rs
+++ b/codex-rs/tui/src/app/event_dispatch.rs
@@ -173,7 +173,11 @@ impl App {
                 if let Some(thread_id) = self.chat_widget.thread_id() {
                     self.refresh_in_memory_config_from_disk_best_effort("forking the thread")
                         .await;
-                    match app_server.fork_thread(self.config.clone(), thread_id).await {
+                    let mut fork_config = self.config.clone();
+                    fork_config.model = Some(self.chat_widget.current_model().to_string());
+                    fork_config.model_reasoning_effort =
+                        self.chat_widget.current_reasoning_effort();
+                    match app_server.fork_thread(fork_config, thread_id).await {
                         Ok(forked) => {
                             self.shutdown_current_thread(app_server).await;
                             match self
@@ -1026,6 +1030,42 @@ impl App {
             AppEvent::OpenReasoningPopup { model } => {
                 self.chat_widget.open_reasoning_popup(model);
             }
+            AppEvent::OpenAdvancedReasoningPopup { model } => {
+                self.chat_widget.open_advanced_reasoning_popup(model);
+            }
+            AppEvent::ApplyAdvancedReasoning { model, effort } => {
+                let default_effort =
+                    self.on_apply_advanced_reasoning(model.as_str(), effort.clone());
+                if let Some(mut params) =
+                    self.active_thread_model_setting_update_params(model.clone())
+                {
+                    params.effort = Some(effort.clone());
+                    self.send_thread_settings_update(app_server, params).await;
+                }
+                self.sync_active_thread_service_tier_to_cached_session()
+                    .await;
+
+                if let Some(default_effort) = default_effort.as_ref()
+                    && let Err(err) = crate::config_update::write_config_batch(
+                        app_server.request_handle(),
+                        crate::config_update::build_model_selection_edits(
+                            model.as_str(),
+                            Some(default_effort),
+                        ),
+                    )
+                    .await
+                {
+                    let error = format_config_error(&err);
+                    tracing::error!(error = %error, "failed to persist conversation model");
+                    self.chat_widget
+                        .add_error_message(format!("Failed to save default model: {error}"));
+                } else {
+                    self.chat_widget.add_info_message(
+                        format!("Model changed to {model} {effort} for this conversation"),
+                        /*hint*/ None,
+                    );
+                }
+            }
             AppEvent::OpenPlanReasoningScopePrompt { model, effort } => {
                 self.chat_widget
                     .open_plan_reasoning_scope_prompt(model, effort);
@@ -1803,8 +1843,7 @@ impl App {
                 self.chat_widget.set_rate_limit_switch_prompt_hidden(hidden);
             }
             AppEvent::UpdatePlanModeReasoningEffort(effort) => {
-                self.config.plan_mode_reasoning_effort = effort.clone();
-                self.chat_widget.set_plan_mode_reasoning_effort(effort);
+                self.on_update_plan_mode_reasoning_effort(effort);
                 self.sync_active_thread_plan_mode_reasoning_setting(app_server)
                     .await;
             }
diff --git a/codex-rs/tui/src/app/session_lifecycle.rs b/codex-rs/tui/src/app/session_lifecycle.rs
index b4bbbd231a..5c2e174651 100644
--- a/codex-rs/tui/src/app/session_lifecycle.rs
+++ b/codex-rs/tui/src/app/session_lifecycle.rs
@@ -269,7 +269,7 @@ impl App {
         }
 
         let (session, turns, live_attached) = match app_server
-            .resume_thread(self.config.clone(), thread_id)
+            .resume_thread(self.config.clone(), thread_id, self.resume_model_settings())
             .await
         {
             Ok(started) => (started.session, started.turns, true),
@@ -789,7 +789,11 @@ impl App {
             self.chat_widget.rollout_path().as_deref(),
         );
         match app_server
-            .resume_thread(resume_config.clone(), target_session.thread_id)
+            .resume_thread(
+                resume_config.clone(),
+                target_session.thread_id,
+                self.resume_model_settings(),
+            )
             .await
         {
             Ok(resumed) => {
diff --git a/codex-rs/tui/src/app/tests.rs b/codex-rs/tui/src/app/tests.rs
index d8d63575bb..04c2e8505b 100644
--- a/codex-rs/tui/src/app/tests.rs
+++ b/codex-rs/tui/src/app/tests.rs
@@ -1,5 +1,7 @@
 //! App-level orchestration tests for the TUI.
 
+#[path = "tests/advanced_reasoning_tests.rs"]
+mod advanced_reasoning_tests;
 mod model_catalog;
 mod plugin_catalog;
 mod session_summary;
diff --git a/codex-rs/tui/src/app/tests/advanced_reasoning_tests.rs b/codex-rs/tui/src/app/tests/advanced_reasoning_tests.rs
new file mode 100644
index 0000000000..662a16bfc1
--- /dev/null
+++ b/codex-rs/tui/src/app/tests/advanced_reasoning_tests.rs
@@ -0,0 +1,90 @@
+use super::*;
+use app_test_support::create_fake_rollout;
+use pretty_assertions::assert_eq;
+
+#[tokio::test]
+async fn fork_current_session_preserves_conversation_ultra() -> Result<()> {
+    let mut app = make_test_app().await;
+    let codex_home = tempdir()?;
+    app.config.codex_home = codex_home.path().to_path_buf().abs();
+    app.config.sqlite_home = codex_home.path().to_path_buf();
+    let source_thread_id = ThreadId::from_string(
+        &create_fake_rollout(
+            codex_home.path(),
+            "2025-01-05T12-00-00",
+            "2025-01-05T12:00:00Z",
+            "Saved user message",
+            Some(app.config.model_provider_id.as_str()),
+            /*git_info*/ None,
+        )
+        .expect("create source rollout"),
+    )?;
+    app.chat_widget.handle_thread_session(ThreadSessionState {
+        model: "gpt-5.4".to_string(),
+        reasoning_effort: Some(ReasoningEffortConfig::Ultra),
+        ..test_thread_session(source_thread_id, test_path_buf("/tmp/project"))
+    });
+    let mut tui = crate::tui::test_support::make_test_tui()?;
+    let mut app_server = crate::start_embedded_app_server_for_picker(&app.config).await?;
+
+    let control =
+        Box::pin(app.handle_event(&mut tui, &mut app_server, AppEvent::ForkCurrentSession)).await?;
+
+    assert!(matches!(control, AppRunControl::Continue));
+    assert_ne!(app.chat_widget.thread_id(), Some(source_thread_id));
+    assert_eq!(app.chat_widget.current_model(), "gpt-5.4");
+    assert_eq!(
+        app.chat_widget.current_reasoning_effort(),
+        Some(ReasoningEffortConfig::Ultra)
+    );
+    app_server.shutdown().await?;
+    Ok(())
+}
+
+#[tokio::test]
+async fn switching_from_ultra_thread_restores_configured_plan_effort() {
+    let mut app = make_test_app().await;
+    app.config.plan_mode_reasoning_effort = Some(ReasoningEffortConfig::High);
+    app.chat_widget
+        .set_feature_enabled(Feature::CollaborationModes, /*enabled*/ true);
+    let ultra_session = ThreadSessionState {
+        model: "gpt-5.4".to_string(),
+        reasoning_effort: Some(ReasoningEffortConfig::Ultra),
+        ..test_thread_session(ThreadId::new(), test_path_buf("/tmp/ultra"))
+    };
+    let normal_session = ThreadSessionState {
+        model: "gpt-5.4".to_string(),
+        reasoning_effort: Some(ReasoningEffortConfig::Medium),
+        ..test_thread_session(ThreadId::new(), test_path_buf("/tmp/normal"))
+    };
+
+    app.replay_thread_snapshot(
+        ThreadEventSnapshot {
+            session: Some(ultra_session),
+            turns: Vec::new(),
+            events: Vec::new(),
+            input_state: None,
+        },
+        /*resume_restored_queue*/ false,
+    );
+    app.replay_thread_snapshot(
+        ThreadEventSnapshot {
+            session: Some(normal_session),
+            turns: Vec::new(),
+            events: Vec::new(),
+            input_state: None,
+        },
+        /*resume_restored_queue*/ false,
+    );
+    app.chat_widget
+        .handle_key_event(KeyEvent::from(KeyCode::BackTab));
+
+    assert_eq!(
+        app.chat_widget.active_collaboration_mode_kind(),
+        ModeKind::Plan
+    );
+    assert_eq!(
+        app.chat_widget.current_reasoning_effort(),
+        Some(ReasoningEffortConfig::High)
+    );
+}
diff --git a/codex-rs/tui/src/app/thread_routing.rs b/codex-rs/tui/src/app/thread_routing.rs
index b149fd53f3..a353711072 100644
--- a/codex-rs/tui/src/app/thread_routing.rs
+++ b/codex-rs/tui/src/app/thread_routing.rs
@@ -1201,7 +1201,7 @@ impl App {
         }
 
         match app_server
-            .resume_thread(self.config.clone(), thread_id)
+            .resume_thread(self.config.clone(), thread_id, self.resume_model_settings())
             .await
         {
             Ok(started) => {
@@ -1325,6 +1325,10 @@ impl App {
         let suppress_replay_notices =
             replay_filter::snapshot_has_pending_interactive_request(&snapshot);
         if let Some(session) = snapshot.session {
+            if session.reasoning_effort != Some(ReasoningEffortConfig::Ultra) {
+                self.chat_widget
+                    .set_plan_mode_reasoning_effort(self.config.plan_mode_reasoning_effort.clone());
+            }
             if self.side_threads.contains_key(&session.thread_id) {
                 self.chat_widget.handle_side_thread_session(session);
             } else if suppress_replay_notices {
diff --git a/codex-rs/tui/src/app/thread_settings.rs b/codex-rs/tui/src/app/thread_settings.rs
index 84dcebe1a8..1f96b1750e 100644
--- a/codex-rs/tui/src/app/thread_settings.rs
+++ b/codex-rs/tui/src/app/thread_settings.rs
@@ -153,7 +153,7 @@ impl App {
         }
     }
 
-    async fn send_thread_settings_update(
+    pub(super) async fn send_thread_settings_update(
         &mut self,
         app_server: &mut AppServerSession,
         params: ThreadSettingsUpdateParams,
diff --git a/codex-rs/tui/src/app_event.rs b/codex-rs/tui/src/app_event.rs
index fa2c9f29fc..553a58d8d4 100644
--- a/codex-rs/tui/src/app_event.rs
+++ b/codex-rs/tui/src/app_event.rs
@@ -741,6 +741,17 @@ pub(crate) enum AppEvent {
         model: ModelPreset,
     },
 
+    /// Open the explicit Max/Ultra reasoning selection popup for a model.
+    OpenAdvancedReasoningPopup {
+        model: ModelPreset,
+    },
+
+    /// Apply an advanced reasoning effort to the active conversation without changing defaults.
+    ApplyAdvancedReasoning {
+        model: String,
+        effort: ReasoningEffort,
+    },
+
     /// Open the Plan-mode reasoning scope prompt for the selected model/effort.
     OpenPlanReasoningScopePrompt {
         model: String,
diff --git a/codex-rs/tui/src/app_server_session.rs b/codex-rs/tui/src/app_server_session.rs
index ab29dfd598..1afa758908 100644
--- a/codex-rs/tui/src/app_server_session.rs
+++ b/codex-rs/tui/src/app_server_session.rs
@@ -190,6 +190,15 @@ pub(crate) enum ThreadParamsMode {
     Remote,
 }
 
+/// Determines where model settings come from when resuming a thread.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(crate) enum ResumeModelSettings {
+    /// Sends the current config's model, provider, and reasoning effort as explicit overrides.
+    OverrideFromCurrentConfig,
+    /// Omits those overrides so app-server restores the settings saved with the thread.
+    RestoreFromThread,
+}
+
 impl ThreadParamsMode {
     fn model_provider_from_config(self, config: &Config) -> Option<String> {
         match self {
@@ -484,9 +493,14 @@ impl AppServerSession {
         &mut self,
         config: Config,
         thread_id: ThreadId,
+        model_settings: ResumeModelSettings,
     ) -> Result<AppServerStartedThread> {
         let request_id = self.next_request_id();
-        let session_config = self.session_config_with_effective_service_tier(&config);
+        let session_config = if model_settings == ResumeModelSettings::RestoreFromThread {
+            config.clone()
+        } else {
+            self.session_config_with_effective_service_tier(&config)
+        };
         let response: ThreadResumeResponse = self
             .client
             .request_typed(ClientRequest::ThreadResume {
@@ -496,6 +510,7 @@ impl AppServerSession {
                     thread_id,
                     self.thread_params_mode(),
                     self.remote_cwd_override.as_deref(),
+                    model_settings,
                 ),
             })
             .await
@@ -1437,6 +1452,7 @@ fn thread_resume_params_from_config(
     thread_id: ThreadId,
     thread_params_mode: ThreadParamsMode,
     remote_cwd_override: Option<&std::path::Path>,
+    model_settings: ResumeModelSettings,
 ) -> ThreadResumeParams {
     let permissions = permissions_selection_from_config(&config, thread_params_mode);
     let sandbox = permissions
@@ -1448,10 +1464,26 @@ fn thread_resume_params_from_config(
             )
         })
         .flatten();
+    let mut config_overrides = config_request_overrides_from_config(&config);
+    if model_settings == ResumeModelSettings::RestoreFromThread
+        && let Some(overrides) = config_overrides.as_mut()
+    {
+        overrides.remove("model_reasoning_effort");
+        if overrides.is_empty() {
+            config_overrides = None;
+        }
+    }
+    let (model, model_provider) = match model_settings {
+        ResumeModelSettings::OverrideFromCurrentConfig => (
+            config.model.clone(),
+            thread_params_mode.model_provider_from_config(&config),
+        ),
+        ResumeModelSettings::RestoreFromThread => (None, None),
+    };
     ThreadResumeParams {
         thread_id: thread_id.to_string(),
-        model: config.model.clone(),
-        model_provider: thread_params_mode.model_provider_from_config(&config),
+        model,
+        model_provider,
         service_tier: service_tier_override_from_config(&config),
         cwd: thread_cwd_from_config(&config, thread_params_mode, remote_cwd_override),
         runtime_workspace_roots: Some(config.workspace_roots.clone()),
@@ -1459,7 +1491,7 @@ fn thread_resume_params_from_config(
         approvals_reviewer: approvals_reviewer_override_from_config(&config),
         sandbox,
         permissions,
-        config: config_request_overrides_from_config(&config),
+        config: config_overrides,
         developer_instructions: with_terminal_visualization_instructions(
             &config, /*control_instructions*/ None,
         ),
@@ -1767,6 +1799,7 @@ mod tests {
     use super::*;
     use crate::legacy_core::config::ConfigBuilder;
     use crate::legacy_core::config::ConfigOverrides;
+    use app_test_support::create_fake_rollout;
     use codex_app_server_protocol::ThreadStatus;
     use codex_app_server_protocol::Turn;
     use codex_app_server_protocol::TurnStatus;
@@ -1779,6 +1812,7 @@ mod tests {
     use codex_protocol::models::BUILT_IN_PERMISSION_PROFILE_READ_ONLY;
     use codex_protocol::models::BUILT_IN_PERMISSION_PROFILE_WORKSPACE;
     use codex_protocol::models::ManagedFileSystemPermissions;
+    use codex_protocol::openai_models::ModelServiceTier;
     use codex_protocol::openai_models::ReasoningEffort;
     use codex_protocol::permissions::FileSystemAccessMode;
     use codex_protocol::permissions::FileSystemPath;
@@ -2023,6 +2057,7 @@ mod tests {
             thread_id,
             ThreadParamsMode::Remote,
             /*remote_cwd_override*/ None,
+            ResumeModelSettings::OverrideFromCurrentConfig,
         );
         let fork = thread_fork_params_from_config(
             config,
@@ -2140,6 +2175,7 @@ mod tests {
             thread_id,
             ThreadParamsMode::Remote,
             Some(remote_cwd.as_path()),
+            ResumeModelSettings::OverrideFromCurrentConfig,
         );
         let fork = thread_fork_params_from_config(
             config,
@@ -2191,6 +2227,7 @@ mod tests {
             thread_id,
             ThreadParamsMode::Embedded,
             /*remote_cwd_override*/ None,
+            ResumeModelSettings::OverrideFromCurrentConfig,
         );
         let fork = thread_fork_params_from_config(
             config,
@@ -2217,6 +2254,88 @@ mod tests {
         assert_eq!(fork.config, Some(expected_config));
     }
 
+    #[tokio::test]
+    async fn thread_resume_params_can_restore_persisted_model_settings() {
+        let temp_dir = tempfile::tempdir().expect("tempdir");
+        let mut config = build_config(&temp_dir).await;
+        config.model = Some("configured-model".to_string());
+        config.model_provider_id = "configured-provider".to_string();
+        config.model_reasoning_effort = Some(ReasoningEffort::Ultra);
+        config.model_reasoning_summary = Some(ReasoningSummary::Detailed);
+
+        let params = thread_resume_params_from_config(
+            config,
+            ThreadId::new(),
+            ThreadParamsMode::Embedded,
+            /*remote_cwd_override*/ None,
+            ResumeModelSettings::RestoreFromThread,
+        );
+
+        assert_eq!(params.model, None);
+        assert_eq!(params.model_provider, None);
+        assert_eq!(
+            params.config,
+            Some(HashMap::from([
+                (
+                    "model_reasoning_summary".to_string(),
+                    serde_json::Value::String("detailed".to_string()),
+                ),
+                (
+                    "personality".to_string(),
+                    serde_json::Value::String("pragmatic".to_string()),
+                ),
+                (
+                    "web_search".to_string(),
+                    serde_json::Value::String("cached".to_string()),
+                ),
+            ]))
+        );
+    }
+
+    #[tokio::test]
+    async fn persisted_resume_does_not_forward_implicit_service_tier() -> Result<()> {
+        let codex_home = tempfile::tempdir().expect("tempdir");
+        let mut config = build_config(&codex_home).await;
+        config.model = Some("gpt-5.4".to_string());
+        config.service_tier = None;
+        config
+            .features
+            .enable(Feature::FastMode)
+            .expect("enable fast mode");
+        let thread_id = ThreadId::from_string(
+            &create_fake_rollout(
+                codex_home.path(),
+                "2025-01-05T12-00-00",
+                "2025-01-05T12:00:00Z",
+                "Saved user message",
+                Some(config.model_provider_id.as_str()),
+                /*git_info*/ None,
+            )
+            .expect("create source rollout"),
+        )?;
+        let mut app_server = crate::start_embedded_app_server_for_picker(&config).await?;
+        let mut preset = crate::test_support::TEST_MODEL_PRESETS
+            .iter()
+            .find(|preset| preset.model == "gpt-5.4")
+            .expect("gpt-5.4 test preset")
+            .clone();
+        preset.service_tiers = vec![ModelServiceTier {
+            id: ServiceTier::Fast.request_value().to_string(),
+            name: "fast".to_string(),
+            description: "Fast tier".to_string(),
+        }];
+        preset.default_service_tier = Some(ServiceTier::Fast.request_value().to_string());
+        app_server.available_models = vec![preset];
+
+        let resumed = app_server
+            .resume_thread(config, thread_id, ResumeModelSettings::RestoreFromThread)
+            .await?;
+
+        assert_eq!(resumed.session.service_tier, None);
+        app_server.shutdown().await?;
+        Ok(())
+    }
+
     #[tokio::test]
     async fn config_request_overrides_preserve_implicit_personality_default() {
         let temp_dir = tempfile::tempdir().expect("tempdir");
@@ -2278,6 +2397,7 @@ mod tests {
             thread_id,
             ThreadParamsMode::Embedded,
             /*remote_cwd_override*/ None,
+            ResumeModelSettings::OverrideFromCurrentConfig,
         );
         let control_fork = thread_fork_params_from_config(
             config.clone(),
@@ -2307,6 +2427,7 @@ mod tests {
             thread_id,
             ThreadParamsMode::Embedded,
             /*remote_cwd_override*/ None,
+            ResumeModelSettings::OverrideFromCurrentConfig,
         );
         let treatment_fork = thread_fork_params_from_config(
             config,
diff --git a/codex-rs/tui/src/chatwidget/model_popups.rs b/codex-rs/tui/src/chatwidget/model_popups.rs
index b7d218c5bc..c8ace98397 100644
--- a/codex-rs/tui/src/chatwidget/model_popups.rs
+++ b/codex-rs/tui/src/chatwidget/model_popups.rs
@@ -100,22 +100,39 @@ impl ChatWidget {
                 let description =
                     (!preset.description.is_empty()).then_some(preset.description.clone());
                 let model = preset.model.clone();
-                let should_prompt_plan_mode_scope = self.should_prompt_plan_mode_reasoning_scope(
-                    model.as_str(),
-                    Some(preset.default_reasoning_effort.clone()),
-                );
-                let actions = self.model_selection_actions(
-                    model.clone(),
-                    Some(preset.default_reasoning_effort.clone()),
-                    should_prompt_plan_mode_scope,
-                );
+                let requires_advanced_selection =
+                    Self::is_advanced_reasoning_effort(&preset.default_reasoning_effort)
+                        || preset
+                            .supported_reasoning_efforts
+                            .iter()
+                            .any(|option| Self::is_advanced_reasoning_effort(&option.effort));
+                let actions: Vec<SelectionAction> = if requires_advanced_selection {
+                    let preset_for_action = preset.clone();
+                    vec![Box::new(move |tx| {
+                        tx.send(AppEvent::OpenReasoningPopup {
+                            model: preset_for_action.clone(),
+                        });
+                    })]
+                } else {
+                    let should_prompt_plan_mode_scope = self
+                        .should_prompt_plan_mode_reasoning_scope(
+                            model.as_str(),
+                            Some(preset.default_reasoning_effort.clone()),
+                        );
+                    self.model_selection_actions(
+                        model.clone(),
+                        Some(preset.default_reasoning_effort.clone()),
+                        should_prompt_plan_mode_scope,
+                    )
+                };
                 SelectionItem {
                     name: model.clone(),
                     description,
                     is_current: model.as_str() == current_model,
                     is_default: preset.is_default,
                     actions,
-                    dismiss_on_select: true,
+                    dismiss_on_select: !requires_advanced_selection,
+                    dismiss_parent_on_child_accept: requires_advanced_selection,
                     ..Default::default()
                 }
             })
@@ -225,20 +242,24 @@ impl ChatWidget {
             .as_ref()
             .and_then(|effort| self.ultra_reasoning_concurrency_warning(effort));
         vec![Box::new(move |tx| {
-            if should_prompt_plan_mode_scope {
+            if effort_for_action == Some(ReasoningEffortConfig::Ultra) {
+                tx.send(AppEvent::ApplyAdvancedReasoning {
+                    model: model_for_action.clone(),
+                    effort: ReasoningEffortConfig::Ultra,
+                });
+            } else if should_prompt_plan_mode_scope {
                 tx.send(AppEvent::OpenPlanReasoningScopePrompt {
                     model: model_for_action.clone(),
                     effort: effort_for_action.clone(),
                 });
-                return;
+            } else {
+                tx.send(AppEvent::UpdateModel(model_for_action.clone()));
+                tx.send(AppEvent::UpdateReasoningEffort(effort_for_action.clone()));
+                tx.send(AppEvent::PersistModelSelection {
+                    model: model_for_action.clone(),
+                    effort: effort_for_action.clone(),
+                });
             }
-
-            tx.send(AppEvent::UpdateModel(model_for_action.clone()));
-            tx.send(AppEvent::UpdateReasoningEffort(effort_for_action.clone()));
-            tx.send(AppEvent::PersistModelSelection {
-                model: model_for_action.clone(),
-                effort: effort_for_action.clone(),
-            });
             if let Some(warning) = warning.clone() {
                 tx.send(AppEvent::InsertHistoryCell(Box::new(
                     history_cell::new_warning_event(warning),
@@ -372,10 +393,13 @@ impl ChatWidget {
         });
     }
 
-    /// Open a popup to choose the reasoning effort (stage 2) for the given model.
+    /// Open a popup to choose the standard reasoning effort for the given model.
+    ///
+    /// Max and Ultra require an explicit second step so expensive efforts cannot
+    /// be selected accidentally while moving through the normal effort scale.
     pub(crate) fn open_reasoning_popup(&mut self, preset: ModelPreset) {
-        let default_effort = preset.default_reasoning_effort;
-        let supported = preset.supported_reasoning_efforts;
+        let default_effort = preset.default_reasoning_effort.clone();
+        let supported = &preset.supported_reasoning_efforts;
         let in_plan_mode =
             self.collaboration_modes_enabled() && self.active_mode_kind() == ModeKind::Plan;
 
@@ -400,15 +424,18 @@ impl ChatWidget {
             || preset.model.starts_with("gpt-5.1-codex-max")
             || preset.model.starts_with("gpt-5.2");
 
-        let mut choices: Vec<ReasoningEffortConfig> = supported
+        let mut all_choices: Vec<ReasoningEffortConfig> = supported
             .iter()
             .map(|option| option.effort.clone())
             .collect();
-        if choices.is_empty() {
-            choices.push(default_effort.clone());
+        if all_choices.is_empty() {
+            all_choices.push(default_effort.clone());
         }
+        let (choices, advanced_choices): (Vec<_>, Vec<_>) = all_choices
+            .into_iter()
+            .partition(|effort| !Self::is_advanced_reasoning_effort(effort));
 
-        if choices.len() == 1 {
+        if choices.len() == 1 && advanced_choices.is_empty() {
             let selected_effort = choices.first().cloned();
             let selected_model = preset.model;
             if self
@@ -427,9 +454,7 @@ impl ChatWidget {
 
         let default_choice = choices
             .contains(&default_effort)
-            .then(|| default_effort.clone())
-            .or_else(|| choices.first().cloned())
-            .or(Some(default_effort));
+            .then(|| default_effort.clone());
 
         let model_slug = preset.model.to_string();
         let is_current_model = self.current_model() == preset.model.as_str();
@@ -443,7 +468,7 @@ impl ChatWidget {
                 self.effective_reasoning_effort()
             }
         } else {
-            default_choice.clone()
+            default_choice.clone().or_else(|| choices.first().cloned())
         };
         let selection_choice = highlight_choice.clone().or_else(|| default_choice.clone());
         let initial_selected_idx = choices
@@ -452,7 +477,6 @@ impl ChatWidget {
         let mut items: Vec<SelectionItem> = Vec::new();
         for choice in choices.iter() {
             let effort = choice.clone();
-            let warning = self.ultra_reasoning_concurrency_warning(&effort);
             let mut effort_label = Self::reasoning_effort_label(&effort);
             if Some(choice) == default_choice.as_ref() {
                 effort_label.push_str(" (default)");
@@ -476,32 +500,16 @@ impl ChatWidget {
                 None
             };
 
-            let model_for_action = model_slug.clone();
             let choice_effort = Some(effort);
             let should_prompt_plan_mode_scope = self.should_prompt_plan_mode_reasoning_scope(
                 model_slug.as_str(),
                 choice_effort.clone(),
             );
-            let actions: Vec<SelectionAction> = vec![Box::new(move |tx| {
-                if should_prompt_plan_mode_scope {
-                    tx.send(AppEvent::OpenPlanReasoningScopePrompt {
-                        model: model_for_action.clone(),
-                        effort: choice_effort.clone(),
-                    });
-                } else {
-                    tx.send(AppEvent::UpdateModel(model_for_action.clone()));
-                    tx.send(AppEvent::UpdateReasoningEffort(choice_effort.clone()));
-                    tx.send(AppEvent::PersistModelSelection {
-                        model: model_for_action.clone(),
-                        effort: choice_effort.clone(),
-                    });
-                    if let Some(warning) = warning.clone() {
-                        tx.send(AppEvent::InsertHistoryCell(Box::new(
-                            history_cell::new_warning_event(warning),
-                        )));
-                    }
-                }
-            })];
+            let actions = self.model_selection_actions(
+                model_slug.clone(),
+                choice_effort,
+                should_prompt_plan_mode_scope,
+            );
 
             items.push(SelectionItem {
                 name: effort_label,
@@ -514,6 +522,36 @@ impl ChatWidget {
             });
         }
 
+        if !advanced_choices.is_empty() {
+            let advanced_label = advanced_choices
+                .iter()
+                .map(Self::reasoning_effort_label)
+                .collect::<Vec<_>>()
+                .join(" and ");
+            let verb = if advanced_choices.len() == 1 {
+                "consumes"
+            } else {
+                "consume"
+            };
+            let preset_for_action = preset;
+            let actions: Vec<SelectionAction> = vec![Box::new(move |tx| {
+                tx.send(AppEvent::OpenAdvancedReasoningPopup {
+                    model: preset_for_action.clone(),
+                });
+            })];
+            items.push(SelectionItem {
+                name: "More reasoning…".to_string(),
+                description: Some(format!("{advanced_label} {verb} usage limits faster")),
+                is_current: is_current_model
+                    && highlight_choice
+                        .as_ref()
+                        .is_some_and(Self::is_advanced_reasoning_effort),
+                actions,
+                dismiss_parent_on_child_accept: true,
+                ..Default::default()
+            });
+        }
+
         let mut header = ColumnRenderable::new();
         header.push(Line::from(
             format!("Select Reasoning Level for {model_slug}").bold(),
@@ -528,6 +566,76 @@ impl ChatWidget {
         });
     }
 
+    /// Open the explicit Max/Ultra effort picker for the given model.
+    pub(crate) fn open_advanced_reasoning_popup(&mut self, preset: ModelPreset) {
+        let mut choices = preset
+            .supported_reasoning_efforts
+            .iter()
+            .map(|option| option.effort.clone())
+            .filter(Self::is_advanced_reasoning_effort)
+            .collect::<Vec<_>>();
+        if choices.is_empty()
+            && Self::is_advanced_reasoning_effort(&preset.default_reasoning_effort)
+        {
+            choices.push(preset.default_reasoning_effort.clone());
+        }
+        choices.sort_by_key(|effort| matches!(effort, ReasoningEffortConfig::Ultra));
+        if choices.is_empty() {
+            return;
+        }
+
+        let model_slug = preset.model.to_string();
+        let is_current_model = self.current_model() == preset.model.as_str();
+        let highlight_choice = is_current_model
+            .then(|| self.effective_reasoning_effort())
+            .flatten();
+        let mut items = Vec::new();
+        for effort in choices {
+            let description = match &effort {
+                ReasoningEffortConfig::Max => {
+                    "For difficult problems when quality matters more than speed · higher usage"
+                }
+                ReasoningEffortConfig::Ultra => {
+                    "For demanding work using multiple agents · highest usage"
+                }
+                _ => unreachable!("advanced choices are limited to Max and Ultra"),
+            };
+            let should_prompt_plan_mode_scope = self
+                .should_prompt_plan_mode_reasoning_scope(model_slug.as_str(), Some(effort.clone()));
+            let actions = self.model_selection_actions(
+                model_slug.clone(),
+                Some(effort.clone()),
+                should_prompt_plan_mode_scope,
+            );
+
+            items.push(SelectionItem {
+                name: Self::reasoning_effort_label(&effort),
+                description: Some(description.to_string()),
+                is_current: is_current_model && Some(&effort) == highlight_choice.as_ref(),
+                actions,
+                dismiss_on_select: true,
+                ..Default::default()
+            });
+        }
+
+        let mut header = ColumnRenderable::new();
+        header.push(Line::from("Advanced Reasoning".bold()));
+        header.push(Line::from("⚠ Consumes usage limits faster".cyan()));
+        self.bottom_pane.show_selection_view(SelectionViewParams {
+            header: Box::new(header),
+            footer_hint: Some(standard_popup_hint_line()),
+            items,
+            ..Default::default()
+        });
+    }
+
+    pub(super) fn is_advanced_reasoning_effort(effort: &ReasoningEffortConfig) -> bool {
+        matches!(
+            effort,
+            ReasoningEffortConfig::Max | ReasoningEffortConfig::Ultra
+        )
+    }
+
     pub(super) fn reasoning_effort_label(effort: &ReasoningEffortConfig) -> String {
         match effort {
             ReasoningEffortConfig::None => "None".to_string(),
diff --git a/codex-rs/tui/src/chatwidget/reasoning_shortcuts.rs b/codex-rs/tui/src/chatwidget/reasoning_shortcuts.rs
index b611281d0b..b247ca9e65 100644
--- a/codex-rs/tui/src/chatwidget/reasoning_shortcuts.rs
+++ b/codex-rs/tui/src/chatwidget/reasoning_shortcuts.rs
@@ -10,7 +10,8 @@
 //! current model preset's default, and it walks only efforts advertised by the
 //! active model. Unsupported efforts anchor to the model default, or the first
 //! advertised effort when the default is absent, before stepping through the
-//! advertised order.
+//! advertised order. Raising never silently crosses into Max or Ultra; those
+//! efforts require the explicit advanced-reasoning picker.
 
 use codex_protocol::config_types::ModeKind;
 use codex_protocol::openai_models::ModelPreset;
@@ -109,6 +110,34 @@ impl ChatWidget {
             return true;
         };
 
+        if direction == ReasoningShortcutDirection::Raise
+            && Self::is_advanced_reasoning_effort(&next_effort)
+        {
+            let advanced_label = choices
+                .iter()
+                .filter(|effort| Self::is_advanced_reasoning_effort(effort))
+                .map(Self::reasoning_effort_label)
+                .collect::<Vec<_>>()
+                .join(" and ");
+            let verb = if advanced_label.contains(" and ") {
+                "are"
+            } else {
+                "is"
+            };
+            let model_path = if current_model.starts_with("codex-auto-") {
+                current_model
+            } else {
+                format!("All models → {current_model}")
+            };
+            self.add_info_message(
+                format!(
+                    "{advanced_label} {verb} available under /model → {model_path} → More reasoning…"
+                ),
+                /*hint*/ None,
+            );
+            return true;
+        }
+
         if self.collaboration_modes_enabled() && self.active_mode_kind() == ModeKind::Plan {
             let warning = self.ultra_reasoning_concurrency_warning(&next_effort);
             self.app_event_tx
@@ -136,11 +165,13 @@ impl ChatWidget {
 }
 
 fn reasoning_choices(preset: &ModelPreset) -> Vec<ReasoningEffortConfig> {
-    let mut choices: Vec<ReasoningEffortConfig> = preset
+    let (mut choices, mut advanced_choices): (Vec<_>, Vec<_>) = preset
         .supported_reasoning_efforts
         .iter()
         .map(|option| option.effort.clone())
-        .collect();
+        .partition(|effort| !ChatWidget::is_advanced_reasoning_effort(effort));
+    advanced_choices.sort_by_key(|effort| matches!(effort, ReasoningEffortConfig::Ultra));
+    choices.extend(advanced_choices);
     if choices.is_empty() {
         choices.push(preset.default_reasoning_effort.clone());
     }
diff --git a/codex-rs/tui/src/chatwidget/session_flow.rs b/codex-rs/tui/src/chatwidget/session_flow.rs
index 177700d4f4..782aa7e1d0 100644
--- a/codex-rs/tui/src/chatwidget/session_flow.rs
+++ b/codex-rs/tui/src/chatwidget/session_flow.rs
@@ -83,6 +83,9 @@ impl ChatWidget {
             Some(session.reasoning_effort.clone()),
             /*developer_instructions*/ None,
         );
+        if session.reasoning_effort == Some(ReasoningEffortConfig::Ultra) {
+            self.set_plan_mode_reasoning_effort(Some(ReasoningEffortConfig::Ultra));
+        }
         match session.collaboration_mode.as_deref() {
             Some(collaboration_mode) => {
                 self.set_effective_collaboration_mode(collaboration_mode.clone());
diff --git a/codex-rs/tui/src/chatwidget/settings.rs b/codex-rs/tui/src/chatwidget/settings.rs
index 269606098f..e5688e92f2 100644
--- a/codex-rs/tui/src/chatwidget/settings.rs
+++ b/codex-rs/tui/src/chatwidget/settings.rs
@@ -345,7 +345,6 @@ impl ChatWidget {
         )
     }
 
-    #[allow(dead_code)] // Used in tests
     pub(crate) fn current_collaboration_mode(&self) -> &CollaborationMode {
         &self.current_collaboration_mode
     }
diff --git a/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__advanced_only_reasoning_selection_popup.snap b/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__advanced_only_reasoning_selection_popup.snap
new file mode 100644
index 0000000000..ad57955bcc
--- /dev/null
+++ b/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__advanced_only_reasoning_selection_popup.snap
@@ -0,0 +1,9 @@
+---
+source: tui/src/chatwidget/tests/popups_and_settings.rs
+expression: popup
+---
+  Select Reasoning Level for gpt-5.4
+
+› 1. More reasoning…  Ultra consumes usage limits faster
+
+  Press enter to confirm or esc to go back
diff --git a/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__model_advanced_reasoning_selection_popup.snap b/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__model_advanced_reasoning_selection_popup.snap
new file mode 100644
index 0000000000..926a0b1b71
--- /dev/null
+++ b/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__model_advanced_reasoning_selection_popup.snap
@@ -0,0 +1,12 @@
+---
+source: tui/src/chatwidget/tests/popups_and_settings.rs
+expression: popup
+---
+  Advanced Reasoning
+  ⚠ Consumes usage limits faster
+
+  1. Max              For difficult problems when quality matters more than
+                      speed · higher usage
+› 2. Ultra (current)  For demanding work using multiple agents · highest usage
+
+  Press enter to confirm or esc to go back
diff --git a/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__model_reasoning_selection_popup.snap b/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__model_reasoning_selection_popup.snap
index 6027772004..1b91548f11 100644
--- a/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__model_reasoning_selection_popup.snap
+++ b/codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__model_reasoning_selection_popup.snap
@@ -6,8 +6,8 @@ expression: popup
 
   1. Low               Fast responses with lighter reasoning
   2. Medium (default)  Balances speed and reasoning depth for everyday tasks
-  3. Max               Maximum available reasoning
-› 4. High (current)    Greater reasoning depth for complex problems
-  5. Extra high        Extra high reasoning depth for complex problems
+› 3. High (current)    Greater reasoning depth for complex problems
+  4. Extra high        Extra high reasoning depth for complex problems
+  5. More reasoning…   Max and Ultra consume usage limits faster
 
   Press enter to confirm or esc to go back
diff --git a/codex-rs/tui/src/chatwidget/tests/history_replay.rs b/codex-rs/tui/src/chatwidget/tests/history_replay.rs
index 8126cc89b1..37a3bd8a07 100644
--- a/codex-rs/tui/src/chatwidget/tests/history_replay.rs
+++ b/codex-rs/tui/src/chatwidget/tests/history_replay.rs
@@ -75,6 +75,43 @@ async fn resumed_initial_messages_render_history() {
     );
 }
 
+#[tokio::test]
+async fn restored_conversation_ultra_remains_selected_after_switching_to_plan() {
+    let (mut chat, _rx, _ops) = make_chatwidget_manual(Some("gpt-5.4")).await;
+    chat.set_feature_enabled(Feature::CollaborationModes, /*enabled*/ true);
+    chat.set_plan_mode_reasoning_effort(Some(ReasoningEffortConfig::High));
+
+    chat.handle_thread_session(crate::session_state::ThreadSessionState {
+        thread_id: ThreadId::new(),
+        forked_from_id: None,
+        fork_parent_title: None,
+        thread_name: None,
+        model: "gpt-5.4".to_string(),
+        model_provider_id: "test-provider".to_string(),
+        service_tier: None,
+        approval_policy: AskForApproval::Never,
+        approvals_reviewer: ApprovalsReviewer::User,
+        permission_profile: PermissionProfile::read_only(),
+        active_permission_profile: None,
+        cwd: test_path_buf("/home/user/project").abs(),
+        runtime_workspace_roots: Vec::new(),
+        instruction_source_paths: Vec::new(),
+        reasoning_effort: Some(ReasoningEffortConfig::Ultra),
+        collaboration_mode: None,
+        personality: None,
+        message_history: None,
+        network_proxy: None,
+        rollout_path: None,
+    });
+    chat.handle_key_event(KeyEvent::from(KeyCode::BackTab));
+
+    assert_eq!(chat.active_collaboration_mode_kind(), ModeKind::Plan);
+    assert_eq!(
+        chat.current_reasoning_effort(),
+        Some(ReasoningEffortConfig::Ultra)
+    );
+}
+
 #[tokio::test]
 async fn replayed_user_messages_seed_composer_history() {
     let (mut chat, mut rx, _ops) = make_chatwidget_manual(/*model_override*/ None).await;
diff --git a/codex-rs/tui/src/chatwidget/tests/plan_mode.rs b/codex-rs/tui/src/chatwidget/tests/plan_mode.rs
index 82c4ef50b5..780648c106 100644
--- a/codex-rs/tui/src/chatwidget/tests/plan_mode.rs
+++ b/codex-rs/tui/src/chatwidget/tests/plan_mode.rs
@@ -427,6 +427,52 @@ async fn reasoning_shortcut_in_plan_mode_updates_plan_override_without_prompt_or
     );
 }
 
+#[tokio::test]
+async fn advanced_reasoning_selection_in_plan_mode_uses_expected_scope() {
+    for effort in [ReasoningEffortConfig::Ultra, ReasoningEffortConfig::Max] {
+        let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.4")).await;
+        chat.thread_id = Some(ThreadId::new());
+        chat.set_feature_enabled(Feature::CollaborationModes, /*enabled*/ true);
+        let plan_mask = collaboration_modes::plan_mask(chat.model_catalog.as_ref())
+            .expect("expected plan collaboration mode");
+        chat.set_collaboration_mask(plan_mask);
+        let _ = drain_insert_history(&mut rx);
+
+        let mut preset = get_available_model(&chat, "gpt-5.4");
+        preset.supported_reasoning_efforts = vec![ReasoningEffortPreset {
+            effort: effort.clone(),
+            description: "Advanced reasoning".to_string(),
+        }];
+        chat.open_advanced_reasoning_popup(preset);
+        chat.handle_key_event(KeyEvent::from(KeyCode::Enter));
+
+        let events = std::iter::from_fn(|| rx.try_recv().ok()).collect::<Vec<_>>();
+        if effort == ReasoningEffortConfig::Ultra {
+            assert!(events.iter().any(|event| matches!(
+                event,
+                AppEvent::ApplyAdvancedReasoning {
+                    model,
+                    effort: ReasoningEffortConfig::Ultra,
+                } if model == "gpt-5.4"
+            )));
+            assert!(events.iter().all(|event| !matches!(
+                event,
+                AppEvent::OpenPlanReasoningScopePrompt { .. }
+                    | AppEvent::PersistPlanModeReasoningEffort(_)
+                    | AppEvent::PersistModelSelection { .. }
+            )));
+        } else {
+            assert!(events.iter().any(|event| matches!(
+                event,
+                AppEvent::OpenPlanReasoningScopePrompt {
+                    model,
+                    effort: Some(ReasoningEffortConfig::Max),
+                } if model == "gpt-5.4"
+            )));
+        }
+    }
+}
+
 #[tokio::test]
 async fn plan_mode_reasoning_override_is_marked_current_in_reasoning_popup() {
     let (mut chat, _rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.4")).await;
diff --git a/codex-rs/tui/src/chatwidget/tests/popups_and_settings.rs b/codex-rs/tui/src/chatwidget/tests/popups_and_settings.rs
index a3560dac4f..72daaeeadb 100644
--- a/codex-rs/tui/src/chatwidget/tests/popups_and_settings.rs
+++ b/codex-rs/tui/src/chatwidget/tests/popups_and_settings.rs
@@ -3196,12 +3196,40 @@ async fn model_reasoning_selection_popup_snapshot() {
             description: "Maximum available reasoning".to_string(),
         },
     );
+    preset
+        .supported_reasoning_efforts
+        .push(ReasoningEffortPreset {
+            effort: ReasoningEffortConfig::Ultra,
+            description: "Ultra reasoning".to_string(),
+        });
     chat.open_reasoning_popup(preset);
 
     let popup = render_bottom_popup(&chat, /*width*/ 80);
     assert_chatwidget_snapshot!("model_reasoning_selection_popup", popup);
 }
 
+#[tokio::test]
+async fn model_advanced_reasoning_selection_popup_snapshot() {
+    let (mut chat, _rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.4")).await;
+    chat.set_reasoning_effort(Some(ReasoningEffortConfig::Ultra));
+
+    let mut preset = get_available_model(&chat, "gpt-5.4");
+    preset.supported_reasoning_efforts.extend([
+        ReasoningEffortPreset {
+            effort: ReasoningEffortConfig::Ultra,
+            description: "Ultra reasoning".to_string(),
+        },
+        ReasoningEffortPreset {
+            effort: ReasoningEffortConfig::Max,
+            description: "Maximum available reasoning".to_string(),
+        },
+    ]);
+    chat.open_advanced_reasoning_popup(preset);
+
+    let popup = render_bottom_popup(&chat, /*width*/ 80);
+    assert_chatwidget_snapshot!("model_advanced_reasoning_selection_popup", popup);
+}
+
 #[tokio::test]
 async fn model_reasoning_selection_popup_applies_custom_effort() {
     let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.4")).await;
@@ -3262,11 +3290,21 @@ async fn select_ultra_with_multi_agent_thread_limit(max_threads: usize) -> (bool
     chat.handle_key_event(KeyEvent::from(KeyCode::Down));
     chat.handle_key_event(KeyEvent::from(KeyCode::Enter));
 
+    let advanced_preset = std::iter::from_fn(|| rx.try_recv().ok()).find_map(|event| match event {
+        AppEvent::OpenAdvancedReasoningPopup { model } => Some(model),
+        _ => None,
+    });
+    chat.open_advanced_reasoning_popup(advanced_preset.expect("advanced reasoning popup"));
+    chat.handle_key_event(KeyEvent::from(KeyCode::Enter));
+
     let mut selected_ultra = false;
     let mut warnings = Vec::new();
     while let Ok(event) = rx.try_recv() {
         match event {
-            AppEvent::UpdateReasoningEffort(Some(ReasoningEffortConfig::Ultra)) => {
+            AppEvent::ApplyAdvancedReasoning {
+                effort: ReasoningEffortConfig::Ultra,
+                ..
+            } => {
                 selected_ultra = true;
             }
             AppEvent::InsertHistoryCell(cell) => {
@@ -3299,6 +3337,38 @@ async fn ultra_reasoning_selection_skips_warning_below_threshold() {
     assert_eq!(below_threshold, (true, Vec::new()));
 }
 
+#[tokio::test]
+async fn max_reasoning_selection_persists_model_selection() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.4")).await;
+    chat.set_reasoning_effort(Some(ReasoningEffortConfig::High));
+
+    let mut preset = get_available_model(&chat, "gpt-5.4");
+    preset.supported_reasoning_efforts = vec![ReasoningEffortPreset {
+        effort: ReasoningEffortConfig::Max,
+        description: "Maximum reasoning".to_string(),
+    }];
+    chat.open_advanced_reasoning_popup(preset);
+    chat.handle_key_event(KeyEvent::from(KeyCode::Enter));
+
+    let events = std::iter::from_fn(|| rx.try_recv().ok()).collect::<Vec<_>>();
+    assert!(events.iter().any(|event| matches!(
+        event,
+        AppEvent::UpdateReasoningEffort(Some(ReasoningEffortConfig::Max))
+    )));
+    assert!(events.iter().any(|event| matches!(
+        event,
+        AppEvent::PersistModelSelection {
+            model,
+            effort: Some(ReasoningEffortConfig::Max),
+        } if model == "gpt-5.4"
+    )));
+    assert!(
+        events
+            .iter()
+            .all(|event| !matches!(event, AppEvent::ApplyAdvancedReasoning { .. }))
+    );
+}
+
 #[tokio::test]
 async fn model_reasoning_selection_popup_extra_high_warning_snapshot() {
     let (mut chat, _rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.2")).await;
@@ -3421,6 +3491,96 @@ async fn reasoning_shortcut_is_ignored_with_model_popup_open() {
     );
 }
 
+#[tokio::test]
+async fn reasoning_up_shortcut_does_not_silently_enter_advanced_effort() {
+    for (model, model_path) in [
+        ("gpt-5.4", "All models → gpt-5.4"),
+        ("codex-auto-test", "codex-auto-test"),
+    ] {
+        let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.4")).await;
+        chat.thread_id = Some(ThreadId::new());
+        let mut preset = get_available_model(&chat, "gpt-5.4");
+        preset.id = model.to_string();
+        preset.model = model.to_string();
+        preset.display_name = model.to_string();
+        preset.supported_reasoning_efforts.extend([
+            ReasoningEffortPreset {
+                effort: ReasoningEffortConfig::Max,
+                description: "Maximum reasoning".to_string(),
+            },
+            ReasoningEffortPreset {
+                effort: ReasoningEffortConfig::Ultra,
+                description: "Ultra reasoning".to_string(),
+            },
+        ]);
+        chat.model_catalog = std::sync::Arc::new(ModelCatalog::new(vec![preset]));
+        chat.set_model(model);
+
+        for effort in [ReasoningEffortConfig::XHigh, ReasoningEffortConfig::Max] {
+            chat.set_reasoning_effort(Some(effort));
+            chat.handle_key_event(KeyEvent::new(KeyCode::Char('.'), KeyModifiers::ALT));
+
+            let events = std::iter::from_fn(|| rx.try_recv().ok()).collect::<Vec<_>>();
+            assert!(events.iter().all(|event| !matches!(
+                event,
+                AppEvent::UpdateReasoningEffort(_) | AppEvent::ApplyAdvancedReasoning { .. }
+            )));
+            let messages = events
+                .into_iter()
+                .filter_map(|event| match event {
+                    AppEvent::InsertHistoryCell(cell) => {
+                        Some(lines_to_single_string(&cell.display_lines(/*width*/ 140)))
+                    }
+                    _ => None,
+                })
+                .collect::<Vec<_>>();
+            assert_eq!(
+                messages,
+                vec![format!(
+                    "• Max and Ultra are available under /model → {model_path} → More reasoning…\n"
+                )]
+            );
+        }
+    }
+}
+
+#[tokio::test]
+async fn reasoning_down_shortcut_can_leave_advanced_effort() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.4")).await;
+    chat.thread_id = Some(ThreadId::new());
+    let mut preset = get_available_model(&chat, "gpt-5.4");
+    preset.supported_reasoning_efforts.extend([
+        ReasoningEffortPreset {
+            effort: ReasoningEffortConfig::Ultra,
+            description: "Ultra reasoning".to_string(),
+        },
+        ReasoningEffortPreset {
+            effort: ReasoningEffortConfig::Max,
+            description: "Maximum reasoning".to_string(),
+        },
+    ]);
+    chat.model_catalog = std::sync::Arc::new(ModelCatalog::new(vec![preset]));
+
+    for (current, expected) in [
+        (ReasoningEffortConfig::Ultra, ReasoningEffortConfig::Max),
+        (ReasoningEffortConfig::Max, ReasoningEffortConfig::XHigh),
+    ] {
+        chat.set_reasoning_effort(Some(current));
+        chat.handle_key_event(KeyEvent::new(KeyCode::Char(','), KeyModifiers::ALT));
+
+        let events = std::iter::from_fn(|| rx.try_recv().ok()).collect::<Vec<_>>();
+        assert!(events.iter().any(|event| matches!(
+            event,
+            AppEvent::UpdateReasoningEffort(Some(effort)) if effort == &expected
+        )));
+        assert!(
+            events
+                .iter()
+                .all(|event| !matches!(event, AppEvent::PersistModelSelection { .. }))
+        );
+    }
+}
+
 #[tokio::test]
 async fn reasoning_popup_shows_extra_high_with_space() {
     let (mut chat, _rx, _op_rx) = make_chatwidget_manual(Some("gpt-5.4")).await;
@@ -3488,6 +3648,60 @@ async fn single_reasoning_option_skips_selection() {
     );
 }
 
+#[tokio::test]
+async fn advanced_only_reasoning_option_requires_explicit_selection() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+    let mut preset = get_available_model(&chat, "gpt-5.4");
+    preset.default_reasoning_effort = ReasoningEffortConfig::Ultra;
+    preset.supported_reasoning_efforts = vec![ReasoningEffortPreset {
+        effort: ReasoningEffortConfig::Ultra,
+        description: "Ultra reasoning".to_string(),
+    }];
+    chat.open_reasoning_popup(preset);
+
+    let popup = render_bottom_popup(&chat, /*width*/ 80);
+    assert_chatwidget_snapshot!("advanced_only_reasoning_selection_popup", popup);
+    let events = std::iter::from_fn(|| rx.try_recv().ok()).collect::<Vec<_>>();
+    assert!(events.iter().all(|event| !matches!(
+        event,
+        AppEvent::UpdateReasoningEffort(_)
+            | AppEvent::ApplyAdvancedReasoning { .. }
+            | AppEvent::PersistModelSelection { .. }
+    )));
+}
+
+#[tokio::test]
+async fn auto_model_advertising_advanced_effort_opens_reasoning_picker() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+    let mut preset = get_available_model(&chat, "gpt-5.4");
+    preset.id = "codex-auto-test".to_string();
+    preset.model = "codex-auto-test".to_string();
+    preset.display_name = "codex-auto-test".to_string();
+    preset.default_reasoning_effort = ReasoningEffortConfig::Medium;
+    preset
+        .supported_reasoning_efforts
+        .push(ReasoningEffortPreset {
+            effort: ReasoningEffortConfig::Ultra,
+            description: "Ultra reasoning".to_string(),
+        });
+    chat.open_model_popup_with_presets(vec![preset]);
+
+    chat.handle_key_event(KeyEvent::from(KeyCode::Enter));
+
+    let events = std::iter::from_fn(|| rx.try_recv().ok()).collect::<Vec<_>>();
+    assert!(events.iter().all(|event| !matches!(
+        event,
+        AppEvent::UpdateReasoningEffort(_)
+            | AppEvent::ApplyAdvancedReasoning { .. }
+            | AppEvent::PersistModelSelection { .. }
+    )));
+    assert!(
+        events
+            .iter()
+            .any(|event| matches!(event, AppEvent::OpenReasoningPopup { .. }))
+    );
+}
+
 #[tokio::test]
 async fn feedback_selection_popup_snapshot() {
     let (mut chat, _rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;