feat(login): custom provider logins fetch and select models

After the base URL, name, and key steps, the login now opens a model
selection screen instead of blindly saving. The listing fetch runs
concurrently with a manual-id input — a WAF challenge page or a 404 no
longer passes validation silently: a base without a /vN tail is probed
once as {base}/v1 and the working base is adopted, an anthropic-wire
listing that 401s on x-api-key retries once with Bearer (relays gate
GET /models on Bearer while /messages takes the key header), and a
failed fetch shows its reason while manual add stays usable. The chosen
ids persist as [platforms.<name>] models = [...]; catalog assembly
synthesizes selected ids the listing never served (before [model.*]
overrides so they compose) and filters unselected provider entries
(after overrides, authoritative in the provider namespace). Provider-
owned entries keep their declared wire against donor backend
inheritance, and listing errors quote line/column only — a reflected
body could carry the key.

crates/codegen/kigi-tui/src/app/actions.rs

@@ -574,6 +574,8 @@ pub enum Action {
     BeginCustomProviderEntry(kigi_shell::models::custom::CustomApi),
     /// Enter in a custom provider step.
     SubmitCustomProviderInput(String),
+    /// Enter on an empty manual-model box: finish the model selection.
+    SubmitCustomProviderSelection,
     /// Copy the auth URL to the clipboard during authentication.
     CopyAuthUrl,
     /// Show the raw auth URL with mouse capture disabled for manual copy.
@@ -1623,6 +1625,13 @@ pub enum Effect {
         request_seq: u64,
         provider: kigi_shell::models::custom::CustomProvider,
         key: String,
+        models: Vec<String>,
+    },
+    /// List the provider's models for the login selection screen.
+    FetchCustomProviderModels {
+        request_seq: u64,
+        provider: kigi_shell::models::custom::CustomProvider,
+        key: String,
     },
     /// Fetch MCP server list from the shell (kigi/mcp/list).
     FetchMcpsList {
@@ -2166,6 +2175,11 @@ pub enum TaskResult {
     AuthCodeSubmitted {
         request_seq: u64,
     },
+    /// The login-step model listing came back (or failed).
+    CustomProviderModelsListed {
+        request_seq: u64,
+        result: Result<kigi_shell::agent::custom_providers::LoginFetch, String>,
+    },
     /// MCP server list fetched from shell.
     McpsListLoaded {
         agent_id: AgentId,

crates/codegen/kigi-tui/src/app/app_view.rs

@@ -264,6 +264,8 @@ pub enum AuthMode {
     ApiKeyEntry(PlatformLogin),
     /// Custom provider login, one field per step.
     CustomProviderEntry(crate::app::custom_entry::CustomEntryStep),
+    /// Custom provider login, the model-selection screen.
+    CustomProviderSelect,
 }
 /// API-key platform login target, selected from the welcome picker. Wraps a
 /// non-OAuth registry platform ([`kigi_shell::models::PlatformId`]);
@@ -924,6 +926,8 @@ pub struct AppView {
     pub auth_code_input: String,
     /// Values collected by the custom provider login steps.
     pub custom_entry: crate::app::custom_entry::CustomEntryDraft,
+    /// Model-selection state of a custom provider login; present in that mode.
+    pub custom_select: Option<crate::app::custom_entry::CustomSelectState>,
     /// Monotonically increasing sequence number for auth requests.
     pub next_auth_request_seq: u64,
     /// Every session/chat/worktree/prompt action deferred behind startup gates.
@@ -1128,6 +1132,7 @@ impl AppView {
             auth_start_mode: AuthMode::Pending,
             auth_code_input: String::new(),
             custom_entry: Default::default(),
+            custom_select: None,
             next_auth_request_seq: 1,
             deferred_startup: Default::default(),
             auth_use_oauth: false,
@@ -1663,6 +1668,7 @@ impl AppView {
                     mid_session_login: self.auth_return_view.is_some(),
                     auth_methods: &self.auth_methods,
                     auth_code_input: &mut self.auth_code_input,
+                    custom_select: &mut self.custom_select,
                     prompt: &mut self.welcome_prompt,
                     prompt_focused: &mut self.welcome_prompt_focused,
                     new_worktree_dialog: &mut self.new_worktree_dialog,
@@ -2188,6 +2194,7 @@ struct WelcomeInputCtx<'a> {
     /// the `AuthState::Pending` welcome menu.
     auth_methods: &'a [acp::AuthMethod],
     auth_code_input: &'a mut String,
+    custom_select: &'a mut Option<crate::app::custom_entry::CustomSelectState>,
     prompt: &'a mut PromptWidget,
     prompt_focused: &'a mut bool,
     new_worktree_dialog: &'a mut Option<NewWorktreeDialogState>,
@@ -2712,6 +2719,70 @@ fn handle_welcome_input(ev: &Event, ctx: &mut WelcomeInputCtx<'_>) -> InputOutco
                     return InputOutcome::Changed;
                 }
             }
+            AuthState::Authenticating {
+                mode: AuthMode::CustomProviderSelect,
+                ..
+            } => {
+                // Esc cancels back to the picker, like the entry steps.
+                if key!(Esc).matches(key) {
+                    return InputOutcome::Action(Action::CancelPlatformKeyEntry);
+                }
+                if key!('q', CONTROL).matches(key) || key!('c', CONTROL).matches(key) {
+                    if ctx.mid_session_login {
+                        return InputOutcome::Action(Action::CancelLogin);
+                    }
+                    return InputOutcome::Action(Action::QuitConfirmed);
+                }
+                let Some(select) = ctx.custom_select.as_mut() else {
+                    return InputOutcome::Unchanged;
+                };
+                if key!(Up).matches(key) {
+                    select.move_highlight(-1);
+                    return InputOutcome::Changed;
+                }
+                if key!(Down).matches(key) {
+                    select.move_highlight(1);
+                    return InputOutcome::Changed;
+                }
+                // Model ids hold no spaces, so the spacebar toggles rows.
+                if key!(Char(' ')).matches(key) {
+                    select.toggle_highlighted();
+                    return InputOutcome::Changed;
+                }
+                if crate::input::key::is_paste_key(key)
+                    || crate::input::key::is_inline_paste_key(key)
+                {
+                    if let Some(text) = crate::clipboard::system_clipboard_get() {
+                        let cleaned: String =
+                            text.chars().filter(|c| *c != '\n' && *c != '\r').collect();
+                        ctx.auth_code_input.push_str(&cleaned);
+                        return InputOutcome::Changed;
+                    }
+                    crate::clipboard::log_paste_key_empty_host_clipboard("auth input");
+                    return InputOutcome::Unchanged;
+                }
+                if key!(Enter).matches(key) {
+                    let trimmed = ctx.auth_code_input.trim().to_string();
+                    if trimmed.is_empty() {
+                        return InputOutcome::Action(Action::SubmitCustomProviderSelection);
+                    }
+                    select.add_manual(&trimmed);
+                    if select.error.is_none() {
+                        ctx.auth_code_input.clear();
+                    }
+                    return InputOutcome::Changed;
+                }
+                if key!(Backspace).matches(key) {
+                    ctx.auth_code_input.pop();
+                    return InputOutcome::Changed;
+                }
+                if let crossterm::event::KeyCode::Char(c) = key.code
+                    && crate::input::key::is_text_input_key(key)
+                {
+                    ctx.auth_code_input.push(c);
+                    return InputOutcome::Changed;
+                }
+            }
             AuthState::Authenticating {
                 mode: AuthMode::Loopback,
                 ..
@@ -2775,7 +2846,10 @@ fn handle_welcome_input(ev: &Event, ctx: &mut WelcomeInputCtx<'_>) -> InputOutco
             }
             AuthState::Authenticating {
                 mode:
-                    AuthMode::Loopback | AuthMode::ApiKeyEntry(_) | AuthMode::CustomProviderEntry(_),
+                    AuthMode::Loopback
+                    | AuthMode::ApiKeyEntry(_)
+                    | AuthMode::CustomProviderEntry(_)
+                    | AuthMode::CustomProviderSelect,
                 ..
             } => {
                 let cleaned: String = text.chars().filter(|c| *c != '\n' && *c != '\r').collect();
@@ -3276,6 +3350,7 @@ impl AppView {
                             login_label: self.login_label.as_deref(),
                             auth_code_input: &self.auth_code_input,
                             custom_entry: &self.custom_entry,
+                            custom_select: self.custom_select.as_ref(),
                             clipboard_copied: self.auth_clipboard_copied,
                             show_raw_url: self.auth_show_raw_url,
                             tip,
@@ -4412,6 +4487,7 @@ pub(crate) mod tests {
             auth_start_mode: AuthMode::Pending,
             auth_code_input: String::new(),
             custom_entry: Default::default(),
+            custom_select: None,
             next_auth_request_seq: 1,
             deferred_startup: Default::default(),
             auth_use_oauth: false,
@@ -7632,12 +7708,24 @@ pub(crate) mod tests {
     /// Ctrl+V / Super+V paste the host clipboard into every auth input.
     #[test]
     fn auth_inputs_paste_key_chords_insert_clipboard_text() {
+        let select_state = || {
+            crate::app::custom_entry::CustomSelectState::new(
+                kigi_shell::models::custom::CustomProvider::new(
+                    "gw",
+                    kigi_shell::models::custom::CustomApi::OpenAi,
+                    "https://h.example/v1",
+                )
+                .unwrap(),
+                "sk".to_owned(),
+            )
+        };
         let modes = [
             AuthMode::Loopback,
             AuthMode::ApiKeyEntry(PlatformLogin(kigi_shell::models::PlatformId::MoonshotCn)),
             AuthMode::CustomProviderEntry(crate::app::custom_entry::CustomEntryStep::first(
                 kigi_shell::models::custom::CustomApi::OpenAi,
             )),
+            AuthMode::CustomProviderSelect,
         ];
         for mode in modes {
             for mods in [KeyModifiers::CONTROL, KeyModifiers::SUPER] {
@@ -7648,12 +7736,13 @@ pub(crate) mod tests {
                     auth_url: None,
                     mode,
                 };
-                crate::clipboard::set_clipboard_probe_hook(
-                    crate::clipboard::ClipboardProbeHook {
-                        text: Some("sk-pasted\nkey".to_owned()),
-                        ..Default::default()
-                    },
-                );
+                if matches!(mode, AuthMode::CustomProviderSelect) {
+                    app.custom_select = Some(select_state());
+                }
+                crate::clipboard::set_clipboard_probe_hook(crate::clipboard::ClipboardProbeHook {
+                    text: Some("sk-pasted\nkey".to_owned()),
+                    ..Default::default()
+                });
                 let outcome = app.handle_input(&key_event(KeyCode::Char('v'), mods));
                 crate::clipboard::clear_clipboard_probe_hook();
                 assert!(

crates/codegen/kigi-tui/src/app/custom_entry.rs

@@ -1,7 +1,7 @@
 //! Custom provider login steps: base URL, name, key.
 
 use kigi_shell::models::custom::{
-    CustomApi, CustomProvider, default_name, normalize_base_url, validate_name,
+    CustomApi, CustomProvider, default_name, normalize_base_url, validate_model_id, validate_name,
 };
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -141,6 +141,141 @@ impl CustomEntryDraft {
     }
 }
 
+/// Fetch status of the model-selection screen.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum SelectFetch {
+    InFlight,
+    Listed,
+    Failed(String),
+}
+
+/// One selectable model row; `manual` marks user-typed ids.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SelectRow {
+    pub id: String,
+    pub selected: bool,
+    pub manual: bool,
+}
+
+/// Model selection after the key step: fetched rows plus manual adds.
+#[derive(Clone)]
+pub struct CustomSelectState {
+    /// The fetch may adopt a `/v1` base URL.
+    pub provider: CustomProvider,
+    key: String,
+    pub rows: Vec<SelectRow>,
+    pub highlight: usize,
+    pub fetch: SelectFetch,
+    pub error: Option<String>,
+    /// Enter hit while the listing is in flight; it completes on arrival.
+    pub finish_requested: bool,
+}
+
+impl CustomSelectState {
+    pub fn new(provider: CustomProvider, key: String) -> Self {
+        Self {
+            provider,
+            key,
+            rows: Vec::new(),
+            highlight: 0,
+            fetch: SelectFetch::InFlight,
+            error: None,
+            finish_requested: false,
+        }
+    }
+
+    pub fn take_key(self) -> String {
+        self.key
+    }
+
+    pub fn apply_fetch(&mut self, fetch: kigi_shell::agent::custom_providers::LoginFetch) {
+        self.provider = fetch.provider;
+        for id in fetch.model_ids {
+            if self.rows.iter().any(|r| r.id == id) {
+                continue;
+            }
+            self.rows.push(SelectRow {
+                id,
+                selected: false,
+                manual: false,
+            });
+        }
+        self.fetch = SelectFetch::Listed;
+    }
+
+    pub fn fail_fetch(&mut self, reason: String) {
+        self.fetch = SelectFetch::Failed(reason);
+    }
+
+    pub fn move_highlight(&mut self, delta: isize) {
+        if self.rows.is_empty() {
+            return;
+        }
+        let max = self.rows.len() - 1;
+        self.highlight = self.highlight.saturating_add_signed(delta).min(max);
+    }
+
+    pub fn toggle_highlighted(&mut self) {
+        if let Some(row) = self.rows.get_mut(self.highlight) {
+            row.selected = !row.selected;
+        }
+    }
+
+    /// Adds a typed id selected; an id already listed just gets selected.
+    pub fn add_manual(&mut self, raw: &str) {
+        let id = raw.trim();
+        if let Err(e) = validate_model_id(id) {
+            self.error = Some(e.to_string());
+            return;
+        }
+        if let Some(row) = self.rows.iter_mut().find(|r| r.id == id) {
+            row.selected = true;
+        } else {
+            self.rows.push(SelectRow {
+                id: id.to_owned(),
+                selected: true,
+                manual: true,
+            });
+        }
+        self.error = None;
+    }
+
+    /// The chosen ids, or a refusal when nothing is chosen.
+    pub fn try_finish(&mut self) -> Option<Vec<String>> {
+        // Wait for the listing: it may adopt a probed `/v1` base URL.
+        if self.fetch == SelectFetch::InFlight {
+            self.finish_requested = true;
+            return None;
+        }
+        let ids: Vec<String> = self
+            .rows
+            .iter()
+            .filter(|r| r.selected)
+            .map(|r| r.id.clone())
+            .collect();
+        if ids.is_empty() {
+            self.finish_requested = false;
+            self.error = Some("Select at least one model, or type one and press enter".to_owned());
+            return None;
+        }
+        Some(ids)
+    }
+}
+
+impl std::fmt::Debug for CustomSelectState {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("CustomSelectState")
+            .field("provider", &self.provider)
+            .field("key", &"<set>")
+            .field("rows", &self.rows)
+            .field("highlight", &self.highlight)
+            .field("fetch", &self.fetch)
+            .field("error", &self.error)
+            .field("finish_requested", &self.finish_requested)
+            .finish()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -236,4 +371,69 @@ mod tests {
         assert!(!step(CustomEntryField::BaseUrl).masks_input());
         assert!(!step(CustomEntryField::Name).masks_input());
     }
+
+    fn select_state() -> CustomSelectState {
+        let provider =
+            CustomProvider::new("gw", CustomApi::OpenAi, "https://h.example/v1").unwrap();
+        CustomSelectState::new(provider, "sk-secret".to_owned())
+    }
+
+    #[test]
+    fn select_state_toggles_adds_and_finishes() {
+        let mut state = select_state();
+        assert!(state.try_finish().is_none(), "in flight: finish waits");
+        assert!(state.finish_requested && state.error.is_none());
+        state.finish_requested = false;
+
+        state.apply_fetch(kigi_shell::agent::custom_providers::LoginFetch {
+            provider: state.provider.clone(),
+            model_ids: vec!["m1".to_owned(), "m2".to_owned()],
+        });
+        assert!(state.try_finish().is_none());
+        assert!(state.error.is_some(), "listed: an empty selection refuses");
+        assert_eq!(state.rows.len(), 2);
+
+        state.toggle_highlighted();
+        state.move_highlight(1);
+        state.toggle_highlighted();
+        state.move_highlight(9);
+        assert_eq!(state.highlight, 1, "highlight clamps at the last row");
+
+        state.add_manual(" claude-opus-5-5[1m] ");
+        assert_eq!(state.rows.len(), 3);
+        state.add_manual("m1");
+        assert_eq!(
+            state.rows.len(),
+            3,
+            "a listed id is selected, not duplicated"
+        );
+        state.add_manual("has space");
+        assert!(state.error.is_some());
+        assert_eq!(state.rows.len(), 3);
+
+        let ids = state.try_finish().expect("three selected");
+        assert_eq!(ids, ["m1", "m2", "claude-opus-5-5[1m]"]);
+    }
+
+    #[test]
+    fn select_state_apply_fetch_adopts_the_probed_base_and_dedups() {
+        let mut state = select_state();
+        state.add_manual("m1");
+        let adopted =
+            CustomProvider::new("gw", CustomApi::OpenAi, "https://h.example/coding/v1").unwrap();
+        state.apply_fetch(kigi_shell::agent::custom_providers::LoginFetch {
+            provider: adopted,
+            model_ids: vec!["m1".to_owned(), "m2".to_owned()],
+        });
+        assert_eq!(state.provider.base_url, "https://h.example/coding/v1");
+        assert_eq!(state.rows.len(), 2, "the manual row covers the fetched id");
+        assert!(state.rows[0].manual && state.rows[0].selected);
+        assert!(!state.rows[1].selected);
+    }
+
+    #[test]
+    fn select_state_debug_hides_the_key() {
+        let state = select_state();
+        assert!(!format!("{state:?}").contains("sk-secret"));
+    }
 }

crates/codegen/kigi-tui/src/app/dispatch/auth.rs

@@ -282,6 +282,7 @@ pub(super) fn dispatch_cancel_login(app: &mut AppView) -> Vec<Effect> {
     app.auth_state = AuthState::Done;
     app.auth_show_raw_url = false;
     app.auth_code_input.clear();
+    app.custom_select = None;
     app.auth_in_flight_method = None;
     restore_auth_return_view(app, return_view);
     // The user bailed out of re-auth — drop stashed prompts and strip the
@@ -335,6 +336,7 @@ pub(super) fn dispatch_begin_custom_provider_entry(
     app.next_auth_request_seq += 1;
     app.auth_code_input.clear();
     app.custom_entry.clear();
+    app.custom_select = None;
     app.auth_state = AuthState::Authenticating {
         request_seq,
         handle: None,
@@ -373,18 +375,20 @@ pub(super) fn dispatch_submit_custom_provider_input(
             vec![]
         }
         CustomEntryOutcome::Done { provider, key } => {
-            app.auth_in_flight_method = Some(kigi_shell::agent::custom_providers::login_method_id(
-                &provider.name,
-            ));
+            // Key accepted: open the model selection and fetch concurrently.
             app.custom_entry.clear();
             app.auth_code_input.clear();
+            app.custom_select = Some(crate::app::custom_entry::CustomSelectState::new(
+                provider.clone(),
+                key.clone(),
+            ));
             app.auth_state = AuthState::Authenticating {
                 request_seq,
                 handle: None,
                 auth_url: None,
-                mode: AuthMode::Pending,
+                mode: AuthMode::CustomProviderSelect,
             };
-            vec![Effect::PersistCustomProviderAndAuthenticate {
+            vec![Effect::FetchCustomProviderModels {
                 request_seq,
                 provider,
                 key,
@@ -393,6 +397,81 @@ pub(super) fn dispatch_submit_custom_provider_input(
     }
 }
 
+/// Enter on an empty manual-model box: persist the chosen models, then auth.
+pub(super) fn dispatch_submit_custom_provider_selection(app: &mut AppView) -> Vec<Effect> {
+    let request_seq = match &app.auth_state {
+        AuthState::Authenticating {
+            request_seq,
+            mode: AuthMode::CustomProviderSelect,
+            ..
+        } => *request_seq,
+        _ => return vec![],
+    };
+    complete_custom_provider_selection(app, request_seq)
+}
+
+/// Persists the selection once the listing no longer gates the base URL.
+fn complete_custom_provider_selection(app: &mut AppView, request_seq: u64) -> Vec<Effect> {
+    let Some(state) = app.custom_select.as_mut() else {
+        return vec![];
+    };
+    let Some(models) = state.try_finish() else {
+        return vec![];
+    };
+    let state = app.custom_select.take().expect("checked above");
+    let provider = state.provider.clone();
+    let key = state.take_key();
+    app.auth_in_flight_method = Some(kigi_shell::agent::custom_providers::login_method_id(
+        &provider.name,
+    ));
+    app.auth_code_input.clear();
+    app.auth_state = AuthState::Authenticating {
+        request_seq,
+        handle: None,
+        auth_url: None,
+        mode: AuthMode::Pending,
+    };
+    vec![Effect::PersistCustomProviderAndAuthenticate {
+        request_seq,
+        provider,
+        key,
+        models,
+    }]
+}
+
+/// The login-step model listing came back; fill or flag the selection.
+pub(super) fn handle_custom_provider_models_listed(
+    app: &mut AppView,
+    request_seq: u64,
+    result: Result<kigi_shell::agent::custom_providers::LoginFetch, String>,
+) -> Vec<Effect> {
+    let in_flight = matches!(
+        &app.auth_state,
+        AuthState::Authenticating {
+            request_seq: current_seq,
+            mode: AuthMode::CustomProviderSelect,
+            ..
+        } if *current_seq == request_seq
+    );
+    if !in_flight {
+        return vec![];
+    }
+    match (app.custom_select.as_mut(), result) {
+        (Some(state), Ok(fetch)) => state.apply_fetch(fetch),
+        (Some(state), Err(reason)) => state.fail_fetch(reason),
+        (None, _) => {}
+    }
+    // A finish pressed during the fetch completes now, with the adopted base.
+    if app
+        .custom_select
+        .as_ref()
+        .is_some_and(|s| s.finish_requested)
+    {
+        return complete_custom_provider_selection(app, request_seq);
+    }
+    vec![]
+}
+
 /// Esc in the API-key paste box: back to the login picker (no error line).
 /// Bumps the request seq so any stale in-flight auth result is dropped by
 /// the `AuthComplete`/`AuthFailed` guards.
@@ -400,7 +479,9 @@ pub(super) fn dispatch_cancel_platform_key_entry(app: &mut AppView) -> Vec<Effec
     if !matches!(
         app.auth_state,
         AuthState::Authenticating {
-            mode: AuthMode::ApiKeyEntry(_) | AuthMode::CustomProviderEntry(_),
+            mode: AuthMode::ApiKeyEntry(_)
+                | AuthMode::CustomProviderEntry(_)
+                | AuthMode::CustomProviderSelect,
             ..
         }
     ) {
@@ -409,6 +490,7 @@ pub(super) fn dispatch_cancel_platform_key_entry(app: &mut AppView) -> Vec<Effec
     app.next_auth_request_seq += 1;
     app.auth_code_input.clear();
     app.custom_entry.clear();
+    app.custom_select = None;
     app.auth_state = AuthState::Pending { error: None };
     vec![]
 }

crates/codegen/kigi-tui/src/app/dispatch/router.rs

@@ -3,7 +3,8 @@ use super::auth::{
     dispatch_begin_custom_provider_entry, dispatch_begin_platform_key_entry, dispatch_cancel_login,
     dispatch_cancel_platform_key_entry, dispatch_login, dispatch_login_with, dispatch_logout,
     dispatch_open_login_picker, dispatch_submit_auth_code, dispatch_submit_custom_provider_input,
-    dispatch_submit_platform_api_key, dispatch_switch_account,
+    dispatch_submit_custom_provider_selection, dispatch_submit_platform_api_key,
+    dispatch_switch_account,
 };
 use super::ctx::{
     active_agent_session_id, get_active_agent_mut, navigate_clearing_selection,
@@ -894,6 +895,7 @@ pub(crate) fn dispatch(action: Action, app: &mut AppView) -> Vec<Effect> {
         Action::SubmitCustomProviderInput(input) => {
             dispatch_submit_custom_provider_input(app, input)
         }
+        Action::SubmitCustomProviderSelection => dispatch_submit_custom_provider_selection(app),
         Action::CopyAuthUrl => {
             if let AuthState::Authenticating {
                 auth_url: Some(url),

crates/codegen/kigi-tui/src/app/dispatch/task_result.rs

@@ -509,9 +509,14 @@ pub(super) fn dispatch_task_result(result: TaskResult, app: &mut AppView) -> Vec
             {
                 app.auth_state = AuthState::Pending { error: Some(error) };
                 app.auth_code_input.clear();
+                app.custom_select = None;
             }
             vec![]
         }
+        TaskResult::CustomProviderModelsListed {
+            request_seq,
+            result,
+        } => super::auth::handle_custom_provider_models_listed(app, request_seq, result),
         TaskResult::AuthUrlReady {
             request_seq,
             auth_url,
@@ -798,6 +803,7 @@ pub(super) fn dispatch_task_result(result: TaskResult, app: &mut AppView) -> Vec
             app.login_method_id = None;
             ensure_login_method(app);
             app.auth_clipboard_copied = false;
+            app.custom_select = None;
             let effects = dispatch_exit_session(app);
             app.welcome_prompt_focused = false;
             effects

crates/codegen/kigi-tui/src/app/dispatch/tests/auth.rs

@@ -582,9 +582,9 @@ fn custom_field(app: &AppView) -> crate::app::custom_entry::CustomEntryField {
     }
 }
 
-/// URL, name, key; the last Enter emits one persist effect.
+/// URL, name, key; the last Enter opens the selection screen and fetches.
 #[test]
-fn custom_provider_steps_end_in_one_persist_effect() {
+fn custom_provider_steps_end_in_the_model_selection() {
     use crate::app::custom_entry::CustomEntryField;
     use kigi_shell::models::custom::CustomApi;
 
@@ -619,7 +619,7 @@ fn custom_provider_steps_end_in_one_persist_effect() {
     let effects = dispatch(Action::SubmitCustomProviderInput("sk-gw".into()), &mut app);
     match effects.as_slice() {
         [
-            Effect::PersistCustomProviderAndAuthenticate {
+            Effect::FetchCustomProviderModels {
                 request_seq,
                 provider,
                 key,
@@ -631,21 +631,236 @@ fn custom_provider_steps_end_in_one_persist_effect() {
             assert_eq!(provider.base_url, "https://api.gw.example/v1");
             assert_eq!(key, "sk-gw");
         }
-        other => panic!("expected exactly the persist effect, got {other:?}"),
+        other => panic!("expected exactly the fetch effect, got {other:?}"),
     }
     assert!(matches!(
         app.auth_state,
         AuthState::Authenticating {
             request_seq,
-            mode: AuthMode::Pending,
+            mode: AuthMode::CustomProviderSelect,
             ..
         } if request_seq == seq
     ));
+    assert!(app.custom_select.is_some());
+    assert!(app.auth_code_input.is_empty());
+}
+
+/// The listing fills rows; the selection persists only the chosen models.
+#[test]
+fn custom_provider_selection_persists_the_chosen_models() {
+    use kigi_shell::models::custom::{CustomApi, CustomProvider};
+
+    let mut app = test_app();
+    app.auth_state = AuthState::Pending { error: None };
+    dispatch(
+        Action::BeginCustomProviderEntry(CustomApi::OpenAi),
+        &mut app,
+    );
+    dispatch(
+        Action::SubmitCustomProviderInput("https://h.example".into()),
+        &mut app,
+    );
+    dispatch(Action::SubmitCustomProviderInput("gw".into()), &mut app);
+    dispatch(Action::SubmitCustomProviderInput("sk-gw".into()), &mut app);
+    let seq = match &app.auth_state {
+        AuthState::Authenticating { request_seq, .. } => *request_seq,
+        _ => unreachable!(),
+    };
+
+    // The listing lands: rows appear, the probed base is adopted.
+    let adopted = CustomProvider::new("gw", CustomApi::OpenAi, "https://h.example/v1").unwrap();
+    let listed = kigi_shell::agent::custom_providers::LoginFetch {
+        provider: adopted,
+        model_ids: vec!["m1".to_owned(), "m2".to_owned()],
+    };
+    let effects = dispatch(
+        Action::TaskComplete(TaskResult::CustomProviderModelsListed {
+            request_seq: seq,
+            result: Ok(listed),
+        }),
+        &mut app,
+    );
+    assert!(effects.is_empty());
+    let state = app.custom_select.as_ref().expect("selection lives");
+    assert_eq!(state.provider.base_url, "https://h.example/v1");
+    assert_eq!(state.rows.len(), 2);
+    assert!(!state.rows[0].selected);
+
+    // An empty selection refuses to finish once the listing resolved.
+    assert!(dispatch(Action::SubmitCustomProviderSelection, &mut app).is_empty());
+    assert!(
+        app.custom_select
+            .as_ref()
+            .and_then(|s| s.error.as_deref())
+            .is_some()
+    );
+
+    // A late manual id typed before the fetch survives the fill.
+    let state = app.custom_select.as_mut().expect("selection lives");
+    state.add_manual("claude-opus-5-5[1m]");
+    assert_eq!(state.rows.len(), 3);
+    assert!(state.rows[2].manual && state.rows[2].selected);
+
+    // Select m2 as well, then finish.
+    let state = app.custom_select.as_mut().expect("selection lives");
+    state.highlight = 1;
+    state.toggle_highlighted();
+    let effects = dispatch(Action::SubmitCustomProviderSelection, &mut app);
+    match effects.as_slice() {
+        [
+            Effect::PersistCustomProviderAndAuthenticate {
+                request_seq,
+                provider,
+                key,
+                models,
+            },
+        ] => {
+            assert_eq!(*request_seq, seq);
+            assert_eq!(provider.base_url, "https://h.example/v1");
+            assert_eq!(key, "sk-gw");
+            assert_eq!(models, &["m2".to_owned(), "claude-opus-5-5[1m]".to_owned()]);
+        }
+        other => panic!("expected the persist effect, got {other:?}"),
+    }
+    assert!(app.custom_select.is_none());
+    assert!(matches!(
+        app.auth_state,
+        AuthState::Authenticating {
+            mode: AuthMode::Pending,
+            ..
+        }
+    ));
     assert_eq!(
         app.auth_in_flight_method.as_ref().map(|m| m.0.as_ref()),
         Some("custom:gw")
     );
-    assert!(app.auth_code_input.is_empty());
+}
+
+/// Finishing while the listing is in flight completes when it lands.
+#[test]
+fn custom_provider_selection_finish_waits_for_the_fetch() {
+    use kigi_shell::models::custom::{CustomApi, CustomProvider};
+
+    let mut app = test_app();
+    app.auth_state = AuthState::Pending { error: None };
+    dispatch(
+        Action::BeginCustomProviderEntry(CustomApi::OpenAi),
+        &mut app,
+    );
+    dispatch(
+        Action::SubmitCustomProviderInput("https://h.example".into()),
+        &mut app,
+    );
+    dispatch(Action::SubmitCustomProviderInput("gw".into()), &mut app);
+    dispatch(Action::SubmitCustomProviderInput("sk-gw".into()), &mut app);
+    let seq = match &app.auth_state {
+        AuthState::Authenticating { request_seq, .. } => *request_seq,
+        _ => unreachable!(),
+    };
+
+    let state = app.custom_select.as_mut().expect("selection lives");
+    state.add_manual("m1");
+    // Enter with an empty box while the fetch runs: no persist yet.
+    assert!(dispatch(Action::SubmitCustomProviderSelection, &mut app).is_empty());
+    assert!(app.custom_select.as_ref().expect("lives").finish_requested);
+    assert!(matches!(
+        app.auth_state,
+        AuthState::Authenticating {
+            mode: AuthMode::CustomProviderSelect,
+            ..
+        }
+    ));
+
+    // The listing lands with an adopted /v1 base; the finish fires now.
+    let adopted = CustomProvider::new("gw", CustomApi::OpenAi, "https://h.example/v1").unwrap();
+    let effects = dispatch(
+        Action::TaskComplete(TaskResult::CustomProviderModelsListed {
+            request_seq: seq,
+            result: Ok(kigi_shell::agent::custom_providers::LoginFetch {
+                provider: adopted,
+                model_ids: vec!["m2".to_owned()],
+            }),
+        }),
+        &mut app,
+    );
+    match effects.as_slice() {
+        [
+            Effect::PersistCustomProviderAndAuthenticate {
+                provider, models, ..
+            },
+        ] => {
+            assert_eq!(provider.base_url, "https://h.example/v1");
+            assert_eq!(models, &["m1".to_owned()]);
+        }
+        other => panic!("expected the persist effect, got {other:?}"),
+    }
+    assert!(app.custom_select.is_none());
+}
+
+/// A failed listing keeps the manual input usable and shows the reason.
+#[test]
+fn custom_provider_selection_survives_a_failed_fetch() {
+    use kigi_shell::models::custom::CustomApi;
+
+    let mut app = test_app();
+    app.auth_state = AuthState::Pending { error: None };
+    dispatch(
+        Action::BeginCustomProviderEntry(CustomApi::OpenAi),
+        &mut app,
+    );
+    dispatch(
+        Action::SubmitCustomProviderInput("https://h.example/v1".into()),
+        &mut app,
+    );
+    dispatch(Action::SubmitCustomProviderInput("gw".into()), &mut app);
+    dispatch(Action::SubmitCustomProviderInput("sk-gw".into()), &mut app);
+    let seq = match &app.auth_state {
+        AuthState::Authenticating { request_seq, .. } => *request_seq,
+        _ => unreachable!(),
+    };
+
+    let effects = dispatch(
+        Action::TaskComplete(TaskResult::CustomProviderModelsListed {
+            request_seq: seq,
+            result: Err("https://h.example/v1/models answered HTTP 404".to_owned()),
+        }),
+        &mut app,
+    );
+    assert!(effects.is_empty());
+    let state = app.custom_select.as_ref().expect("selection lives");
+    assert!(matches!(
+        &state.fetch,
+        crate::app::custom_entry::SelectFetch::Failed(reason) if reason.contains("404")
+    ));
+
+    // A stale result for an older request never clobbers the screen.
+    let effects = dispatch(
+        Action::TaskComplete(TaskResult::CustomProviderModelsListed {
+            request_seq: seq + 99,
+            result: Ok(kigi_shell::agent::custom_providers::LoginFetch {
+                provider: state.provider.clone(),
+                model_ids: vec!["stale".to_owned()],
+            }),
+        }),
+        &mut app,
+    );
+    assert!(effects.is_empty());
+    assert!(
+        app.custom_select
+            .as_ref()
+            .expect("selection lives")
+            .rows
+            .is_empty()
+    );
+
+    // Manual add still finishes the flow.
+    let state = app.custom_select.as_mut().expect("selection lives");
+    state.add_manual("m1");
+    let effects = dispatch(Action::SubmitCustomProviderSelection, &mut app);
+    assert!(matches!(
+        effects.as_slice(),
+        [Effect::PersistCustomProviderAndAuthenticate { models, .. }] if models == &["m1".to_owned()]
+    ));
 }
 
 /// A refused field keeps the user on it.

crates/codegen/kigi-tui/src/app/dispatch/tests/mod.rs

@@ -127,6 +127,7 @@ fn test_app() -> AppView {
         auth_start_mode: AuthMode::Pending,
         auth_code_input: String::new(),
         custom_entry: Default::default(),
+        custom_select: None,
         next_auth_request_seq: 1,
         deferred_startup: Default::default(),
         auth_use_oauth: false,

crates/codegen/kigi-tui/src/app/effects/mod.rs

@@ -1915,13 +1915,15 @@ pub(crate) fn execute(
             request_seq,
             provider,
             key,
+            models,
         } => {
             let tx = acp_tx.clone();
             let abort_handle = tasks.spawn(async move {
                 // Persist first so authenticate finds the definition and key.
-                if let Err(e) =
-                    kigi_shell::agent::custom_providers::save_custom_provider(&provider, &key)
-                        .await
+                if let Err(e) = kigi_shell::agent::custom_providers::save_custom_provider(
+                    &provider, &key, &models,
+                )
+                .await
                 {
                     let error = format!("Couldn't save the provider: {e:#}");
                     ulog::error(
@@ -1940,6 +1942,23 @@ pub(crate) fn execute(
             });
             meta.auth_abort_handle = Some((request_seq, abort_handle));
         }
+        Effect::FetchCustomProviderModels {
+            request_seq,
+            provider,
+            key,
+        } => {
+            tasks.spawn(async move {
+                let result = tokio::task::spawn_blocking(move || {
+                    kigi_shell::agent::custom_providers::fetch_listing_for_login(&provider, &key)
+                })
+                .await
+                .unwrap_or_else(|e| Err(format!("listing task failed: {e}")));
+                TaskResult::CustomProviderModelsListed {
+                    request_seq,
+                    result,
+                }
+            });
+        }
         Effect::SubmitAuthCode { request_seq, code } => {
             let tx = acp_tx.clone();
             tasks