Enable model upgrade popup even when selected model is no longer in picker (#8802)

With `config.toml`:
```
model = "gpt-5.1-codex"
```
(where `gpt-5.1-codex` has `show_in_picker: false` in
[`model_presets.rs`](https://github.com/openai/codex/blob/main/codex-rs/core/src/models_manager/model_presets.rs);
this happens if the user hasn't used codex in a while so they didn't see
the popup before their model was changed to `show_in_picker: false`)

The upgrade picker used to not show (because `gpt-5.1-codex` was
filtered out of the model list in code). Now, the filtering is done
downstream in tui and app-server, so the model upgrade popup shows:

<img width="1503" height="227" alt="Screenshot 2026-01-06 at 5 04 37 PM"
src="https://github.com/user-attachments/assets/26144cc2-0b3f-4674-ac17-e476781ec548"
/>

codex-rs/tui2/src/app.rs

@@ -2088,17 +2088,20 @@ mod tests {
     use codex_core::AuthManager;
     use codex_core::CodexAuth;
     use codex_core::ConversationManager;
+    use codex_core::config::ConfigBuilder;
     use codex_core::protocol::AskForApproval;
     use codex_core::protocol::Event;
     use codex_core::protocol::EventMsg;
     use codex_core::protocol::SandboxPolicy;
     use codex_core::protocol::SessionConfiguredEvent;
     use codex_protocol::ConversationId;
+    use insta::assert_snapshot;
     use pretty_assertions::assert_eq;
     use ratatui::prelude::Line;
     use std::path::PathBuf;
     use std::sync::Arc;
     use std::sync::atomic::AtomicBool;
+    use tempfile::tempdir;
 
     async fn make_test_app() -> App {
         let (chat_widget, app_event_tx, _rx, _op_rx) = make_chatwidget_manual_with_sender().await;
@@ -2208,6 +2211,24 @@ mod tests {
         codex_core::models_manager::model_presets::all_model_presets().clone()
     }
 
+    fn model_migration_copy_to_plain_text(
+        copy: &crate::model_migration::ModelMigrationCopy,
+    ) -> String {
+        let mut s = String::new();
+        for span in &copy.heading {
+            s.push_str(&span.content);
+        }
+        s.push('\n');
+        s.push('\n');
+        for line in &copy.content {
+            for span in &line.spans {
+                s.push_str(&span.content);
+            }
+            s.push('\n');
+        }
+        s
+    }
+
     #[tokio::test]
     async fn model_migration_prompt_only_shows_for_deprecated_models() {
         let seen = BTreeMap::new();
@@ -2243,6 +2264,59 @@ mod tests {
         ));
     }
 
+    #[tokio::test]
+    async fn model_migration_prompt_shows_for_hidden_model() {
+        let codex_home = tempdir().expect("temp codex home");
+        let config = ConfigBuilder::default()
+            .codex_home(codex_home.path().to_path_buf())
+            .build()
+            .await
+            .expect("config");
+
+        let available_models = all_model_presets();
+        let current = available_models
+            .iter()
+            .find(|preset| preset.model == "gpt-5.1-codex")
+            .cloned()
+            .expect("gpt-5.1-codex preset present");
+        assert!(
+            !current.show_in_picker,
+            "expected gpt-5.1-codex to be hidden from picker for this test"
+        );
+
+        let upgrade = current.upgrade.as_ref().expect("upgrade configured");
+        assert!(
+            should_show_model_migration_prompt(
+                &current.model,
+                &upgrade.id,
+                &config.notices.model_migrations,
+                &available_models,
+            ),
+            "expected migration prompt to be eligible for hidden model"
+        );
+
+        let target = available_models
+            .iter()
+            .find(|preset| preset.model == upgrade.id)
+            .cloned()
+            .expect("upgrade target present");
+        let target_description =
+            (!target.description.is_empty()).then(|| target.description.clone());
+        let can_opt_out = true;
+        let copy = migration_copy_for_models(
+            &current.model,
+            &upgrade.id,
+            target.display_name,
+            target_description,
+            can_opt_out,
+        );
+
+        assert_snapshot!(
+            "model_migration_prompt_shows_for_hidden_model",
+            model_migration_copy_to_plain_text(&copy)
+        );
+    }
+
     #[tokio::test]
     async fn transcript_selection_copy_includes_offscreen_lines() {
         let mut app = make_test_app().await;

codex-rs/tui2/src/chatwidget.rs

@@ -2106,7 +2106,7 @@ impl ChatWidget {
         let models = self.models_manager.try_list_models(&self.config).ok()?;
         models
             .iter()
-            .find(|preset| preset.model == NUDGE_MODEL_SLUG)
+            .find(|preset| preset.show_in_picker && preset.model == NUDGE_MODEL_SLUG)
             .cloned()
     }
 
@@ -2222,6 +2222,14 @@ impl ChatWidget {
                     return;
                 }
             };
+        self.open_model_popup_with_presets(presets);
+    }
+
+    pub(crate) fn open_model_popup_with_presets(&mut self, presets: Vec<ModelPreset>) {
+        let presets: Vec<ModelPreset> = presets
+            .into_iter()
+            .filter(|preset| preset.show_in_picker)
+            .collect();
 
         let current_label = presets
             .iter()

codex-rs/tui2/src/chatwidget/snapshots/codex_tui2__chatwidget__tests__model_picker_filters_hidden_models.snap

@@ -0,0 +1,11 @@
+---
+source: tui2/src/chatwidget/tests.rs
+assertion_line: 1758
+expression: popup
+---
+  Select Model and Effort
+  Access legacy models by running codex -m <model_name> or in your config.toml
+
+› 1. test-visible-model (current)  test-visible-model description
+
+  Press enter to select reasoning effort, or esc to dismiss.

codex-rs/tui2/src/chatwidget/tests.rs

@@ -1731,6 +1731,41 @@ async fn model_selection_popup_snapshot() {
     assert_snapshot!("model_selection_popup", popup);
 }
 
+#[tokio::test]
+async fn model_picker_hides_show_in_picker_false_models_from_cache() {
+    let (mut chat, _rx, _op_rx) = make_chatwidget_manual(Some("test-visible-model")).await;
+    let preset = |slug: &str, show_in_picker: bool| ModelPreset {
+        id: slug.to_string(),
+        model: slug.to_string(),
+        display_name: slug.to_string(),
+        description: format!("{slug} description"),
+        default_reasoning_effort: ReasoningEffortConfig::Medium,
+        supported_reasoning_efforts: vec![ReasoningEffortPreset {
+            effort: ReasoningEffortConfig::Medium,
+            description: "medium".to_string(),
+        }],
+        is_default: false,
+        upgrade: None,
+        show_in_picker,
+        supported_in_api: true,
+    };
+
+    chat.open_model_popup_with_presets(vec![
+        preset("test-visible-model", true),
+        preset("test-hidden-model", false),
+    ]);
+    let popup = render_bottom_popup(&chat, 80);
+    assert_snapshot!("model_picker_filters_hidden_models", popup);
+    assert!(
+        popup.contains("test-visible-model"),
+        "expected visible model to appear in picker:\n{popup}"
+    );
+    assert!(
+        !popup.contains("test-hidden-model"),
+        "expected hidden model to be excluded from picker:\n{popup}"
+    );
+}
+
 #[tokio::test]
 async fn approvals_selection_popup_snapshot() {
     let (mut chat, _rx, _op_rx) = make_chatwidget_manual(None).await;

codex-rs/tui2/src/snapshots/codex_tui2__app__tests__model_migration_prompt_shows_for_hidden_model.snap

@@ -0,0 +1,12 @@
+---
+source: tui2/src/app.rs
+assertion_line: 2314
+expression: model_migration_copy_to_plain_text(&copy)
+---
+Try gpt-5.2-codex
+
+We recommend switching from gpt-5.1-codex to gpt-5.2-codex.
+
+Latest frontier agentic coding model.
+
+You can continue using gpt-5.1-codex if you prefer.