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-models/src/custom.rs

@@ -165,6 +165,18 @@ pub fn normalize_base_url(raw: &str) -> Result<String, CustomProviderError> {
     Ok(url.to_owned())
 }
 
+/// A manually added model id: no whitespace, no controls, bounded length.
+pub fn validate_model_id(id: &str) -> Result<(), CustomProviderError> {
+    let err = |reason: &str| Err(CustomProviderError::Name(reason.to_owned()));
+    if id.is_empty() || id.len() > 128 {
+        return err("model id must be 1 to 128 characters");
+    }
+    if id.chars().any(|c| c.is_whitespace() || c.is_control()) {
+        return err("model id must not contain whitespace");
+    }
+    Ok(())
+}
+
 /// A valid provider name derived from a host.
 pub fn default_name(base_url: &str) -> String {
     let host = base_url

crates/codegen/kigi-models/src/lib.rs

@@ -1756,6 +1756,23 @@ pub struct WireThinkEfforts {
     pub default_effort: Option<String>,
 }
 
+impl WireModel {
+    /// An id-only model, as if the listing served no metadata.
+    pub fn bare(id: String) -> Self {
+        Self {
+            id,
+            context_length: 0,
+            supports_reasoning: false,
+            supports_image_in: false,
+            supports_video_in: false,
+            display_name: None,
+            max_output_tokens: 0,
+            supports_thinking_type: None,
+            think_efforts: None,
+        }
+    }
+}
+
 /// `GET {base}/models` response envelope.
 #[derive(Debug, Clone, serde::Deserialize)]
 pub struct WireModelsResponse {

crates/codegen/kigi-shell/src/agent/config.rs

@@ -812,6 +812,9 @@ pub struct PlatformCredentialConfig {
     /// `"openai"` or `"anthropic"`.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub api: Option<String>,
+    /// A custom provider's login-curated model allowlist; absent = whole listing.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub models: Option<Vec<String>>,
 }
 
 /// Resolve the API key for an API-key registry platform with injected env
@@ -2628,6 +2631,11 @@ pub(crate) fn resolve_model_list(
         }
         resolved = prefetched;
     }
+    crate::agent::custom_providers::synthesize_selected(
+        &mut resolved,
+        &cfg.platforms,
+        platform_keys.custom(),
+    );
     let mut explicit_api_backend_keys = std::collections::HashSet::new();
     for (key, model_override) in &cfg.config_models {
         let had_base = resolved.contains_key(key);
@@ -2656,8 +2664,18 @@ pub(crate) fn resolve_model_list(
         );
         resolved.insert(key.clone(), entry);
     }
+    crate::agent::custom_providers::filter_unselected(
+        &mut resolved,
+        &cfg.platforms,
+        platform_keys.custom(),
+    );
     {
         let default_cw = DEFAULT_CONTEXT_WINDOW;
+        let custom_prefixes: Vec<String> = platform_keys
+            .custom()
+            .iter()
+            .map(|c| format!("{}/", c.provider.name))
+            .collect();
         let donors: std::collections::HashMap<String, (std::num::NonZeroU64, ApiBackend)> =
             resolved
                 .values()
@@ -2680,7 +2698,11 @@ pub(crate) fn resolve_model_list(
                     entry.info.context_window = *donor_cw;
                 }
                 // An explicit `[model.X] api_backend` wins even when it is the default.
+                // A provider-owned entry keeps its declared wire too.
                 if !explicit_api_backend_keys.contains(key.as_str())
+                    && !custom_prefixes
+                        .iter()
+                        .any(|p| key.as_str().starts_with(p.as_str()))
                     && entry.info.api_backend == ApiBackend::default()
                     && *donor_backend != ApiBackend::default()
                 {

crates/codegen/kigi-shell/src/agent/custom_providers/fetch.rs

@@ -13,32 +13,17 @@ pub(crate) fn fetch_models_blocking(
     credentialed: &CredentialedProvider,
 ) -> Result<Vec<ModelEntryConfig>, BackendError> {
     let provider = &credentialed.provider;
-    let url = provider.models_url();
-    tracing::info!(provider = %provider.name, api = provider.api.as_str(), %url, "fetching custom provider models");
-    let client = crate::http::shared_blocking_client();
-    let request = match provider.api {
-        CustomApi::OpenAi => client
-            .get(&url)
-            .header("Authorization", format!("Bearer {}", credentialed.key())),
-        CustomApi::Anthropic => client
-            .get(&url)
-            .header("x-api-key", credentialed.key())
-            .header("anthropic-version", kigi_sampling_types::ANTHROPIC_VERSION),
-    };
-    let response = request.send()?;
-    if !response.status().is_success() {
-        let status = response.status().as_u16();
-        let body = response.text().unwrap_or_default();
-        return Err(BackendError::RequestFailed { status, body });
-    }
-    let body = response.text()?;
-    let listing = match provider.api {
-        CustomApi::OpenAi => kigi_models::parse_openai_listing(&body),
-        CustomApi::Anthropic => kigi_models::parse_anthropic_listing(&body),
-    };
-    let wire = listing.map_err(|e| BackendError::RequestFailed {
+    tracing::info!(provider = %provider.name, api = provider.api.as_str(), url = %provider.models_url(), "fetching custom provider models");
+    let body = listing_body(provider, credentialed.key())?;
+    let wire = parse_listing(provider, &body).map_err(|e| BackendError::RequestFailed {
+        // No error content: serde quotes the offending value, a reflected key risk.
         status: 200,
-        body: format!("{} listing parse failed: {e}", provider.api.as_str()),
+        body: format!(
+            "{} listing parse failed at line {} column {}",
+            provider.api.as_str(),
+            e.line(),
+            e.column()
+        ),
     })?;
     if wire.is_empty() {
         tracing::warn!(provider = %provider.name, "custom provider listed no models");
@@ -46,6 +31,153 @@ pub(crate) fn fetch_models_blocking(
     Ok(wire.into_iter().map(|w| entry(provider, w)).collect())
 }
 
+/// The listing GET with the dialect's key header; status-gated body.
+fn listing_body(provider: &CustomProvider, key: &str) -> Result<String, BackendError> {
+    let url = provider.models_url();
+    let client = crate::http::shared_blocking_client();
+    let send = |bearer_fallback: bool| {
+        let request = match (provider.api, bearer_fallback) {
+            (CustomApi::OpenAi, _) => client
+                .get(&url)
+                .header("Authorization", format!("Bearer {key}")),
+            (CustomApi::Anthropic, false) => client
+                .get(&url)
+                .header("x-api-key", key)
+                .header("anthropic-version", kigi_sampling_types::ANTHROPIC_VERSION),
+            (CustomApi::Anthropic, true) => client
+                .get(&url)
+                .header("Authorization", format!("Bearer {key}"))
+                .header("anthropic-version", kigi_sampling_types::ANTHROPIC_VERSION),
+        };
+        request.send()
+    };
+    let mut response = send(false)?;
+    // Relays may gate the listing on Bearer even for the Messages wire.
+    if response.status().as_u16() == 401 && provider.api == CustomApi::Anthropic {
+        tracing::info!(provider = %provider.name, "listing 401 with x-api-key; retrying Bearer");
+        response = send(true)?;
+    }
+    if !response.status().is_success() {
+        let status = response.status().as_u16();
+        let body = response.text().unwrap_or_default();
+        return Err(BackendError::RequestFailed { status, body });
+    }
+    Ok(response.text()?)
+}
+
+fn parse_listing(
+    provider: &CustomProvider,
+    body: &str,
+) -> Result<Vec<WireModel>, serde_json::Error> {
+    match provider.api {
+        CustomApi::OpenAi => kigi_models::parse_openai_listing(body),
+        CustomApi::Anthropic => kigi_models::parse_anthropic_listing(body),
+    }
+}
+
+/// The login-step listing result; `provider` carries the adopted base URL.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct LoginFetch {
+    pub provider: CustomProvider,
+    pub model_ids: Vec<String>,
+}
+
+/// Login listing fetch; probes `{base}/v1` once on a 404 or unparsable body and adopts it.
+pub fn fetch_listing_for_login(provider: &CustomProvider, key: &str) -> Result<LoginFetch, String> {
+    match list_wire(provider, key) {
+        Ok(model_ids) => Ok(LoginFetch {
+            provider: provider.clone(),
+            model_ids,
+        }),
+        Err(first) => {
+            if !first.retryable() || has_version_tail(&provider.base_url) {
+                return Err(first.into_message());
+            }
+            let probed = CustomProvider::new(
+                &provider.name,
+                provider.api,
+                &format!("{}/v1", provider.base_url),
+            )
+            .map_err(|e| e.to_string())?;
+            tracing::info!(
+                provider = %provider.name,
+                base_url = %probed.base_url,
+                "custom provider listing retrying with a /v1 base"
+            );
+            match list_wire(&probed, key) {
+                Ok(model_ids) => Ok(LoginFetch {
+                    provider: probed,
+                    model_ids,
+                }),
+                Err(second) => Err(format!(
+                    "{}; {} also failed: {}",
+                    first.into_message(),
+                    probed.models_url(),
+                    second.into_message()
+                )),
+            }
+        }
+    }
+}
+
+/// A listing failure; `retryable` marks wrong-base-URL shapes only.
+enum ListFail {
+    Retryable(String),
+    Fatal(String),
+}
+
+impl ListFail {
+    fn retryable(&self) -> bool {
+        matches!(self, Self::Retryable(_))
+    }
+
+    fn into_message(self) -> String {
+        match self {
+            Self::Retryable(m) | Self::Fatal(m) => m,
+        }
+    }
+}
+
+fn list_wire(provider: &CustomProvider, key: &str) -> Result<Vec<String>, ListFail> {
+    let url = provider.models_url();
+    let body = listing_body(provider, key).map_err(|e| match &e {
+        BackendError::RequestFailed { status, .. } => {
+            // No body: a reflected error could echo the key.
+            let msg = format!("{url} answered HTTP {status}");
+            if *status == 404 {
+                ListFail::Retryable(msg)
+            } else {
+                ListFail::Fatal(msg)
+            }
+        }
+        BackendError::Network(_) => ListFail::Fatal(format!("Couldn't reach {url}: {e}")),
+        BackendError::Auth(_) => ListFail::Fatal(e.to_string()),
+    })?;
+    let wire = parse_listing(provider, &body).map_err(|e| {
+        ListFail::Retryable(format!(
+            "{url} did not serve a {} model listing (invalid JSON at line {} column {})",
+            provider.api.as_str(),
+            e.line(),
+            e.column()
+        ))
+    })?;
+    Ok(wire.into_iter().map(|w| w.id).collect())
+}
+
+/// True when the base URL's last path segment is a version like `v1`.
+fn has_version_tail(base_url: &str) -> bool {
+    let Some(tail) = base_url.rsplit('/').next() else {
+        return false;
+    };
+    let digits = tail.strip_prefix('v').unwrap_or("");
+    !digits.is_empty() && digits.chars().all(|c| c.is_ascii_digit())
+}
+
+/// A selected id the listing never served becomes an entry with wire defaults.
+pub(crate) fn manual_entry(provider: &CustomProvider, id: &str) -> ModelEntryConfig {
+    entry(provider, WireModel::bare(id.to_owned()))
+}
+
 fn entry(provider: &CustomProvider, wire: WireModel) -> ModelEntryConfig {
     let mut entry = wire_model_to_entry(
         provider.managed_model_key(&wire.id),
@@ -129,6 +261,133 @@ mod tests {
             .unwrap()
     }
 
+    async fn login_fetch_on_thread(
+        provider: CustomProvider,
+        key: &str,
+    ) -> Result<LoginFetch, String> {
+        let key = key.to_owned();
+        tokio::task::spawn_blocking(move || fetch_listing_for_login(&provider, &key))
+            .await
+            .unwrap()
+    }
+
+    #[test]
+    fn version_tail_detection() {
+        assert!(has_version_tail("https://h.example/v1"));
+        assert!(has_version_tail("https://h.example/api/v2"));
+        assert!(!has_version_tail("https://h.example"));
+        assert!(!has_version_tail("https://h.example/coding"));
+        assert!(!has_version_tail("https://h.example/v"));
+        assert!(!has_version_tail("https://h.example/v1x"));
+    }
+
+    #[tokio::test(flavor = "multi_thread")]
+    async fn login_fetch_returns_the_served_ids() {
+        let server = MockServer::start().await;
+        Mock::given(path("/v1/models"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
+                "data": [{"id": "m1"}, {"id": "m2"}]
+            })))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let base = format!("{}/v1", server.uri());
+        let provider = CustomProvider::new("proxy", CustomApi::OpenAi, &base).unwrap();
+
+        let fetch = login_fetch_on_thread(provider, "sk-k").await.unwrap();
+
+        assert_eq!(fetch.provider.base_url, base);
+        assert_eq!(fetch.model_ids, ["m1", "m2"]);
+    }
+
+    #[tokio::test(flavor = "multi_thread")]
+    async fn login_fetch_probes_v1_on_a_404_and_adopts_the_base() {
+        let server = MockServer::start().await;
+        Mock::given(path("/coding/models"))
+            .respond_with(ResponseTemplate::new(404))
+            .expect(1)
+            .mount(&server)
+            .await;
+        Mock::given(path("/coding/v1/models"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
+                "data": [{"id": "m1"}]
+            })))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let base = format!("{}/coding", server.uri());
+        let provider = CustomProvider::new("proxy", CustomApi::OpenAi, &base).unwrap();
+
+        let fetch = login_fetch_on_thread(provider, "sk-k").await.unwrap();
+
+        assert_eq!(fetch.provider.base_url, format!("{base}/v1"));
+        assert_eq!(fetch.model_ids, ["m1"]);
+    }
+
+    #[tokio::test(flavor = "multi_thread")]
+    async fn login_fetch_probes_v1_when_the_200_body_is_not_a_listing() {
+        // A WAF answers every path with an HTML challenge page at HTTP 200.
+        let server = MockServer::start().await;
+        Mock::given(path("/models"))
+            .respond_with(ResponseTemplate::new(200).set_body_string("<html>challenge</html>"))
+            .expect(1)
+            .mount(&server)
+            .await;
+        Mock::given(path("/v1/models"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
+                "data": [{"id": "m1"}]
+            })))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let provider = CustomProvider::new("proxy", CustomApi::OpenAi, &server.uri()).unwrap();
+
+        let fetch = login_fetch_on_thread(provider, "sk-k").await.unwrap();
+
+        assert_eq!(fetch.provider.base_url, format!("{}/v1", server.uri()));
+        assert_eq!(fetch.model_ids, ["m1"]);
+    }
+
+    #[tokio::test(flavor = "multi_thread")]
+    async fn login_fetch_does_not_probe_auth_failures_or_versioned_bases() {
+        let server = MockServer::start().await;
+        Mock::given(path("/models"))
+            .respond_with(ResponseTemplate::new(401))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let provider = CustomProvider::new("proxy", CustomApi::OpenAi, &server.uri()).unwrap();
+        let err = login_fetch_on_thread(provider, "bad").await.unwrap_err();
+        assert!(err.contains("401"), "{err}");
+
+        let server = MockServer::start().await;
+        Mock::given(path("/v2/models"))
+            .respond_with(ResponseTemplate::new(404))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let base = format!("{}/v2", server.uri());
+        let provider = CustomProvider::new("proxy", CustomApi::OpenAi, &base).unwrap();
+        let err = login_fetch_on_thread(provider, "sk-k").await.unwrap_err();
+        assert!(err.contains("404") && !err.contains("also failed"), "{err}");
+    }
+
+    #[tokio::test(flavor = "multi_thread")]
+    async fn login_fetch_reports_both_hops_when_the_probe_fails_too() {
+        let server = MockServer::start().await;
+        Mock::given(method("GET"))
+            .respond_with(ResponseTemplate::new(404))
+            .expect(2)
+            .mount(&server)
+            .await;
+        let provider = CustomProvider::new("proxy", CustomApi::OpenAi, &server.uri()).unwrap();
+
+        let err = login_fetch_on_thread(provider, "sk-k").await.unwrap_err();
+
+        assert!(err.contains("also failed"), "{err}");
+        assert!(!err.contains("sk-k"), "{err}");
+    }
+
     #[tokio::test(flavor = "multi_thread")]
     async fn openai_listing_becomes_chat_completions_entries() {
         let server = MockServer::start().await;
@@ -204,6 +463,54 @@ mod tests {
         assert_eq!(m.auth_scheme, Some(kigi_sampler::AuthScheme::XApiKey));
     }
 
+    #[tokio::test(flavor = "multi_thread")]
+    async fn anthropic_listing_falls_back_to_bearer_on_a_401() {
+        let server = MockServer::start().await;
+        Mock::given(method("GET"))
+            .and(path("/v1/models"))
+            .and(header("x-api-key", "sk-gw"))
+            .respond_with(ResponseTemplate::new(401))
+            .expect(1)
+            .mount(&server)
+            .await;
+        Mock::given(method("GET"))
+            .and(path("/v1/models"))
+            .and(header("authorization", "Bearer sk-gw"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
+                "data": [{"id": "c1"}], "has_more": false
+            })))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let base = format!("{}/v1", server.uri());
+
+        let models = fetch_on_thread(credentialed("gw", CustomApi::Anthropic, &base, "sk-gw"))
+            .await
+            .unwrap();
+
+        assert_eq!(models.len(), 1);
+        assert_eq!(models[0].id.as_deref(), Some("gw/c1"));
+    }
+
+    #[tokio::test(flavor = "multi_thread")]
+    async fn openai_listing_never_retries_on_a_401() {
+        let server = MockServer::start().await;
+        Mock::given(method("GET"))
+            .and(path("/v1/models"))
+            .respond_with(ResponseTemplate::new(401))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let base = format!("{}/v1", server.uri());
+        let err = fetch_on_thread(credentialed("proxy", CustomApi::OpenAi, &base, "bad"))
+            .await
+            .unwrap_err();
+        assert!(matches!(
+            err,
+            BackendError::RequestFailed { status: 401, .. }
+        ));
+    }
+
     #[tokio::test(flavor = "multi_thread")]
     async fn listing_failures_surface_status_and_parse_errors() {
         let server = MockServer::start().await;

crates/codegen/kigi-shell/src/agent/custom_providers/login.rs

@@ -46,19 +46,32 @@ pub(crate) async fn validate_key(credentialed: &CredentialedProvider) -> Result<
     let provider = &credentialed.provider;
     let url = provider.models_url();
     let client = crate::http::shared_client();
-    let request = match provider.api {
-        CustomApi::OpenAi => client
-            .get(&url)
-            .header("Authorization", format!("Bearer {}", credentialed.key())),
-        CustomApi::Anthropic => client
-            .get(&url)
-            .header("x-api-key", credentialed.key())
-            .header("anthropic-version", kigi_sampling_types::ANTHROPIC_VERSION),
+    let send = |bearer_fallback: bool| {
+        let request = match (provider.api, bearer_fallback) {
+            (CustomApi::OpenAi, _) => client
+                .get(&url)
+                .header("Authorization", format!("Bearer {}", credentialed.key())),
+            (CustomApi::Anthropic, false) => client
+                .get(&url)
+                .header("x-api-key", credentialed.key())
+                .header("anthropic-version", kigi_sampling_types::ANTHROPIC_VERSION),
+            (CustomApi::Anthropic, true) => client
+                .get(&url)
+                .header("Authorization", format!("Bearer {}", credentialed.key()))
+                .header("anthropic-version", kigi_sampling_types::ANTHROPIC_VERSION),
+        };
+        request.send()
     };
-    let response = request
-        .send()
+    let mut response = send(false)
         .await
         .map_err(|e| format!("Couldn't reach {url}: {e}"))?;
+    // Mirrors listing_body: relays may gate the listing on Bearer.
+    if response.status().as_u16() == 401 && provider.api == CustomApi::Anthropic {
+        tracing::info!(provider = %provider.name, "validation 401 with x-api-key; retrying Bearer");
+        response = send(true)
+            .await
+            .map_err(|e| format!("Couldn't reach {url}: {e}"))?;
+    }
     let status = response.status().as_u16();
     match status {
         200..=299 => Ok(()),
@@ -136,6 +149,29 @@ mod tests {
             .unwrap();
     }
 
+    #[tokio::test]
+    async fn validation_falls_back_to_bearer_for_anthropic_relays() {
+        let server = MockServer::start().await;
+        Mock::given(method("GET"))
+            .and(path("/v1/models"))
+            .and(header("x-api-key", "sk-gw"))
+            .respond_with(ResponseTemplate::new(401))
+            .expect(1)
+            .mount(&server)
+            .await;
+        Mock::given(method("GET"))
+            .and(path("/v1/models"))
+            .and(header("authorization", "Bearer sk-gw"))
+            .respond_with(ResponseTemplate::new(200).set_body_string("{}"))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let base = format!("{}/v1", server.uri());
+        validate_key(&credentialed(CustomApi::Anthropic, &base, "sk-gw"))
+            .await
+            .unwrap();
+    }
+
     #[tokio::test]
     async fn validation_names_the_failure_without_the_key() {
         let server = MockServer::start().await;

crates/codegen/kigi-shell/src/agent/custom_providers/mod.rs

@@ -7,11 +7,14 @@ use crate::agent::config::{PlatformCredentialConfig, PlatformsConfig};
 mod fetch;
 mod login;
 mod save;
+mod selection;
 
+pub use fetch::{LoginFetch, fetch_listing_for_login};
 pub(crate) use fetch::{drop_orphans, fetch_models_blocking, stamp_credentials};
 pub(crate) use login::validate_key;
 pub use login::{login_method_id, login_provider_name, picker_api, picker_methods};
 pub use save::save_custom_provider;
+pub(crate) use selection::{filter_unselected, synthesize_selected};
 
 /// Tables setting `base_url` or `api`, valid or not.
 fn declarations(platforms: &PlatformsConfig) -> Vec<(&str, Result<CustomProvider, String>)> {

crates/codegen/kigi-shell/src/agent/custom_providers/save.rs

@@ -4,9 +4,14 @@ use toml::Value as TomlValue;
 use toml::map::Map as TomlMap;
 
 /// Writes `[platforms.<name>]` to config.toml and the key to auth.json.
-pub async fn save_custom_provider(provider: &CustomProvider, api_key: &str) -> Result<()> {
+pub async fn save_custom_provider(
+    provider: &CustomProvider,
+    api_key: &str,
+    models: &[String],
+) -> Result<()> {
     let provider = provider.clone();
     let api_key = api_key.to_owned();
+    let models = models.to_owned();
     let _guard = crate::util::config::SAVE_LOCK.lock().await;
     tokio::task::spawn_blocking(move || {
         save_custom_provider_in(
@@ -14,6 +19,7 @@ pub async fn save_custom_provider(provider: &CustomProvider, api_key: &str) -> R
             &crate::util::kigi_home::kigi_home(),
             &provider,
             &api_key,
+            &models,
         )
     })
     .await
@@ -26,6 +32,7 @@ pub(crate) fn save_custom_provider_in(
     kigi_home: &std::path::Path,
     provider: &CustomProvider,
     api_key: &str,
+    models: &[String],
 ) -> Result<()> {
     let api_key = api_key.trim();
     anyhow::ensure!(!api_key.is_empty(), "API key must not be empty");
@@ -37,7 +44,7 @@ pub(crate) fn save_custom_provider_in(
             config_path.display()
         )
     })?;
-    upsert_definition(&mut root, provider)?;
+    upsert_definition(&mut root, provider, models)?;
     let dest = crate::util::config::config_write_dest(config_path)?;
     crate::util::config::atomic_write_string(&dest, &toml::to_string_pretty(&root)?)
         .with_context(|| format!("writing {}", dest.display()))?;
@@ -47,12 +54,17 @@ pub(crate) fn save_custom_provider_in(
         provider = %provider.name,
         api = provider.api.as_str(),
         base_url = %provider.base_url,
+        models = models.len(),
         "custom provider saved"
     );
     Ok(())
 }
 
-fn upsert_definition(root: &mut TomlValue, provider: &CustomProvider) -> Result<()> {
+fn upsert_definition(
+    root: &mut TomlValue,
+    provider: &CustomProvider,
+    models: &[String],
+) -> Result<()> {
     let top = root
         .as_table_mut()
         .ok_or_else(|| anyhow!("config root is not a table"))?;
@@ -68,6 +80,15 @@ fn upsert_definition(root: &mut TomlValue, provider: &CustomProvider) -> Result<
         .ok_or_else(|| anyhow!("[platforms.{}] is not a table", provider.name))?;
     entry.insert("api".into(), provider.api.as_str().into());
     entry.insert("base_url".into(), provider.base_url.as_str().into());
+    entry.insert(
+        "models".into(),
+        TomlValue::Array(
+            models
+                .iter()
+                .map(|m| TomlValue::String(m.clone()))
+                .collect(),
+        ),
+    );
     Ok(())
 }
 
@@ -91,7 +112,7 @@ mod tests {
         .unwrap();
         let p = provider("proxy", CustomApi::OpenAi, "https://h.example/v1/");
 
-        save_custom_provider_in(&config, dir.path(), &p, "  sk-new  ").unwrap();
+        save_custom_provider_in(&config, dir.path(), &p, "  sk-new  ", &["m1".to_owned()]).unwrap();
 
         let saved: TomlValue = toml::from_str(&std::fs::read_to_string(&config).unwrap()).unwrap();
         assert_eq!(saved["ui"]["theme"].as_str(), Some("kiginight"));
@@ -103,6 +124,10 @@ mod tests {
         assert_eq!(entry["api"].as_str(), Some("openai"));
         assert_eq!(entry["base_url"].as_str(), Some("https://h.example/v1"));
         assert_eq!(entry["api_key"].as_str(), Some("hand-written"));
+        assert_eq!(
+            entry["models"].as_array().unwrap(),
+            &[TomlValue::String("m1".into())]
+        );
         let stored = crate::auth::read_auth_json(&dir.path().join("auth.json")).unwrap();
         assert_eq!(stored["proxy"].key, "sk-new");
     }
@@ -116,6 +141,7 @@ mod tests {
             dir.path(),
             &provider("gw", CustomApi::OpenAi, "https://a.example/v1"),
             "k1",
+            &["a1".to_owned()],
         )
         .unwrap();
         save_custom_provider_in(
@@ -123,6 +149,7 @@ mod tests {
             dir.path(),
             &provider("gw", CustomApi::Anthropic, "https://b.example/v1"),
             "k2",
+            &["b1".to_owned()],
         )
         .unwrap();
 
@@ -132,6 +159,10 @@ mod tests {
             saved["platforms"]["gw"]["base_url"].as_str(),
             Some("https://b.example/v1")
         );
+        assert_eq!(
+            saved["platforms"]["gw"]["models"].as_array().unwrap(),
+            &[TomlValue::String("b1".into())]
+        );
         let stored = crate::auth::read_auth_json(&dir.path().join("auth.json")).unwrap();
         assert_eq!(stored["gw"].key, "k2");
     }
@@ -142,12 +173,12 @@ mod tests {
         let config = dir.path().join("config.toml");
         let p = provider("proxy", CustomApi::OpenAi, "https://h.example/v1");
 
-        assert!(save_custom_provider_in(&config, dir.path(), &p, "  ").is_err());
+        assert!(save_custom_provider_in(&config, dir.path(), &p, "  ", &[]).is_err());
         assert!(!config.exists());
         assert!(!dir.path().join("auth.json").exists());
 
         std::fs::write(&config, "[platforms\nnope").unwrap();
-        let err = save_custom_provider_in(&config, dir.path(), &p, "sk").unwrap_err();
+        let err = save_custom_provider_in(&config, dir.path(), &p, "sk", &[]).unwrap_err();
         assert!(err.to_string().contains("unparseable"), "{err}");
         assert_eq!(
             std::fs::read_to_string(&config).unwrap(),
@@ -162,7 +193,7 @@ mod tests {
         let config = dir.path().join("config.toml");
         std::fs::write(&config, "platforms = \"x\"\n").unwrap();
         let p = provider("proxy", CustomApi::OpenAi, "https://h.example/v1");
-        let err = save_custom_provider_in(&config, dir.path(), &p, "sk").unwrap_err();
+        let err = save_custom_provider_in(&config, dir.path(), &p, "sk", &[]).unwrap_err();
         assert!(err.to_string().contains("not a table"), "{err}");
         assert!(!dir.path().join("auth.json").exists());
     }

crates/codegen/kigi-shell/src/agent/custom_providers/selection.rs

@@ -0,0 +1,233 @@
+//! The `[platforms.<name>] models` allowlist: keep the selected, synthesize the manual.
+
+use indexmap::IndexMap;
+
+use super::CredentialedProvider;
+use crate::agent::config::{ModelEntry, PlatformsConfig};
+
+/// Synthesizes selected ids the listing never served; runs before `[model.*]` overrides.
+pub(crate) fn synthesize_selected(
+    resolved: &mut IndexMap<String, ModelEntry>,
+    platforms: &PlatformsConfig,
+    keyed: &[CredentialedProvider],
+) {
+    for credentialed in keyed {
+        let provider = &credentialed.provider;
+        let Some(list) = platforms
+            .entries
+            .get(&provider.name)
+            .and_then(|e| e.models.as_ref())
+        else {
+            continue;
+        };
+        for id in list.iter().map(|m| m.trim()) {
+            if let Err(e) = kigi_models::custom::validate_model_id(id) {
+                tracing::warn!(provider = %provider.name, %e, "skipping an invalid selected model id");
+                continue;
+            }
+            let key = provider.managed_model_key(id);
+            if resolved.contains_key(&key) {
+                continue;
+            }
+            let entry = super::fetch::manual_entry(provider, id);
+            resolved.insert(key, ModelEntry::from_config_entry(&entry));
+        }
+    }
+}
+
+/// Drops `{name}/*` entries outside the provider's selection; runs after `[model.*]` overrides.
+pub(crate) fn filter_unselected(
+    resolved: &mut IndexMap<String, ModelEntry>,
+    platforms: &PlatformsConfig,
+    keyed: &[CredentialedProvider],
+) {
+    for credentialed in keyed {
+        let provider = &credentialed.provider;
+        let Some(list) = platforms
+            .entries
+            .get(&provider.name)
+            .and_then(|e| e.models.as_ref())
+        else {
+            continue;
+        };
+        let list: Vec<&str> = list.iter().map(|m| m.trim()).collect();
+        let prefix = format!("{}/", provider.name);
+        resolved.retain(|key, entry| {
+            let id = entry.info.id.as_deref().unwrap_or(key.as_str());
+            id.strip_prefix(&prefix)
+                .is_none_or(|bare| list.contains(&bare))
+        });
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use kigi_models::custom::{CustomApi, CustomProvider};
+
+    use crate::agent::models::PlatformApiKeys;
+
+    fn provider(name: &str, base: &str) -> CustomProvider {
+        CustomProvider::new(name, CustomApi::OpenAi, base).unwrap()
+    }
+
+    fn fetched_entry(provider: &CustomProvider, id: &str) -> (String, ModelEntry) {
+        let cfg = super::super::fetch::manual_entry(provider, id);
+        let key = cfg.id.clone().unwrap();
+        (key, ModelEntry::from_config_entry(&cfg))
+    }
+
+    fn keyed(provider: CustomProvider) -> Vec<CredentialedProvider> {
+        vec![CredentialedProvider::for_test(provider, "sk-x")]
+    }
+
+    #[test]
+    fn selection_filters_the_listing_and_synthesizes_the_manual() {
+        let proxy = provider("proxy", "https://p.example/v1");
+        let mut resolved = IndexMap::new();
+        for id in ["m1", "m2"] {
+            let (key, entry) = fetched_entry(&proxy, id);
+            resolved.insert(key, entry);
+        }
+        let platforms: PlatformsConfig = toml::from_str(
+            "[proxy]\nbase_url = \"https://p.example/v1\"\napi = \"openai\"\nmodels = [\"m2\", \"manual-1\"]\n",
+        )
+        .unwrap();
+
+        synthesize_selected(&mut resolved, &platforms, &keyed(proxy.clone()));
+        filter_unselected(&mut resolved, &platforms, &keyed(proxy));
+
+        let ids: Vec<_> = resolved.keys().map(String::as_str).collect();
+        assert_eq!(ids, ["proxy/m2", "proxy/manual-1"]);
+        assert_eq!(resolved["proxy/manual-1"].info.model, "manual-1");
+    }
+
+    #[test]
+    fn a_provider_without_the_models_key_keeps_its_whole_listing() {
+        let proxy = provider("proxy", "https://p.example/v1");
+        let mut resolved = IndexMap::new();
+        let (key, entry) = fetched_entry(&proxy, "m1");
+        resolved.insert(key, entry);
+        let platforms: PlatformsConfig =
+            toml::from_str("[proxy]\nbase_url = \"https://p.example/v1\"\napi = \"openai\"\n")
+                .unwrap();
+
+        synthesize_selected(&mut resolved, &platforms, &keyed(proxy.clone()));
+        filter_unselected(&mut resolved, &platforms, &keyed(proxy));
+
+        assert!(resolved.contains_key("proxy/m1"));
+    }
+
+    #[test]
+    fn an_empty_selection_drops_every_fetched_entry() {
+        let proxy = provider("proxy", "https://p.example/v1");
+        let mut resolved = IndexMap::new();
+        let (key, entry) = fetched_entry(&proxy, "m1");
+        resolved.insert(key, entry);
+        let platforms: PlatformsConfig = toml::from_str(
+            "[proxy]\nbase_url = \"https://p.example/v1\"\napi = \"openai\"\nmodels = []\n",
+        )
+        .unwrap();
+
+        synthesize_selected(&mut resolved, &platforms, &keyed(proxy.clone()));
+        filter_unselected(&mut resolved, &platforms, &keyed(proxy));
+
+        assert!(resolved.is_empty());
+    }
+
+    #[test]
+    fn invalid_selected_ids_are_skipped_with_a_warning() {
+        let proxy = provider("proxy", "https://p.example/v1");
+        let mut resolved = IndexMap::new();
+        let platforms: PlatformsConfig = toml::from_str(
+            "[proxy]\nbase_url = \"https://p.example/v1\"\napi = \"openai\"\nmodels = [\"ok\", \"has space\"]\n",
+        )
+        .unwrap();
+
+        synthesize_selected(&mut resolved, &platforms, &keyed(proxy.clone()));
+        filter_unselected(&mut resolved, &platforms, &keyed(proxy));
+
+        assert!(resolved.contains_key("proxy/ok"));
+        assert_eq!(resolved.len(), 1);
+    }
+
+    #[test]
+    fn selection_applies_through_resolve_model_list_and_gets_the_key() {
+        let raw: toml::Value = toml::from_str(
+            "[platforms.proxy]\nbase_url = \"https://p.example/v1\"\napi = \"openai\"\nmodels = [\"manual-1\"]\n",
+        )
+        .unwrap();
+        let cfg = crate::agent::config::Config::new_from_toml_cfg(&raw).unwrap();
+        let proxy = provider("proxy", "https://p.example/v1");
+        let keys =
+            PlatformApiKeys::test_custom(vec![CredentialedProvider::for_test(proxy, "sk-proxy")]);
+
+        let resolved = crate::agent::config::resolve_model_list(&cfg, None, &keys);
+
+        let entry = resolved
+            .get("proxy/manual-1")
+            .expect("a manual model survives without any fetched catalog");
+        assert_eq!(entry.api_key.as_deref(), Some("sk-proxy"));
+        assert!(entry.has_own_credentials());
+        assert_eq!(entry.info.context_window.get(), 256_000);
+    }
+
+    #[test]
+    fn a_model_override_composes_with_the_synthesized_entry() {
+        let raw: toml::Value = toml::from_str(
+            "[platforms.proxy]\nbase_url = \"https://p.example/v1\"\napi = \"openai\"\nmodels = [\"manual-1\"]\n\n[model.\"proxy/manual-1\"]\ncontext_window = 1000000\n",
+        )
+        .unwrap();
+        let cfg = crate::agent::config::Config::new_from_toml_cfg(&raw).unwrap();
+        let proxy = provider("proxy", "https://p.example/v1");
+        let keys =
+            PlatformApiKeys::test_custom(vec![CredentialedProvider::for_test(proxy, "sk-proxy")]);
+
+        let resolved = crate::agent::config::resolve_model_list(&cfg, None, &keys);
+
+        let entry = &resolved["proxy/manual-1"];
+        assert_eq!(entry.info.context_window.get(), 1_000_000);
+        assert_eq!(entry.info.base_url, "https://p.example/v1");
+        assert_eq!(entry.api_key.as_deref(), Some("sk-proxy"));
+    }
+
+    #[test]
+    fn the_selection_is_authoritative_in_the_provider_namespace() {
+        // A context-only override cannot resurrect a deselected model.
+        let raw: toml::Value = toml::from_str(
+            "[platforms.proxy]\nbase_url = \"https://p.example/v1\"\napi = \"openai\"\nmodels = [\"m2\"]\n\n[model.\"proxy/m1\"]\ncontext_window = 123456\n",
+        )
+        .unwrap();
+        let cfg = crate::agent::config::Config::new_from_toml_cfg(&raw).unwrap();
+        let proxy = provider("proxy", "https://p.example/v1");
+        let (key, entry) = fetched_entry(&proxy, "m1");
+        let prefetched = IndexMap::from([(key, entry)]);
+        let keys =
+            PlatformApiKeys::test_custom(vec![CredentialedProvider::for_test(proxy, "sk-proxy")]);
+
+        let resolved = crate::agent::config::resolve_model_list(&cfg, Some(prefetched), &keys);
+
+        assert!(!resolved.contains_key("proxy/m1"));
+        assert!(resolved.contains_key("proxy/m2"));
+    }
+
+    #[test]
+    fn provider_owned_entries_keep_their_declared_wire_against_donors() {
+        let raw: toml::Value = toml::from_str(
+            "[platforms.proxy]\nbase_url = \"https://p.example/v1\"\napi = \"openai\"\nmodels = [\"shared\"]\n\n[model.donorx]\nmodel = \"shared\"\napi_backend = \"messages\"\ncontext_window = 500000\n",
+        )
+        .unwrap();
+        let cfg = crate::agent::config::Config::new_from_toml_cfg(&raw).unwrap();
+        let proxy = provider("proxy", "https://p.example/v1");
+        let keys =
+            PlatformApiKeys::test_custom(vec![CredentialedProvider::for_test(proxy, "sk-proxy")]);
+
+        let resolved = crate::agent::config::resolve_model_list(&cfg, None, &keys);
+
+        let entry = &resolved["proxy/shared"];
+        assert_eq!(
+            entry.info.api_backend,
+            crate::sampling::ApiBackend::ChatCompletions
+        );
+    }
+}

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

crates/codegen/kigi-tui/src/views/welcome/mod.rs

@@ -462,6 +462,7 @@ pub struct WelcomeRenderParams<'a> {
     pub login_label: Option<&'a str>,
     pub auth_code_input: &'a str,
     pub custom_entry: &'a crate::app::custom_entry::CustomEntryDraft,
+    pub custom_select: Option<&'a crate::app::custom_entry::CustomSelectState>,
     pub clipboard_copied: bool,
     pub show_raw_url: bool,
     pub tip: Option<&'a str>,
@@ -605,6 +606,7 @@ pub fn render_welcome(
                 *mode,
                 params.auth_code_input,
                 params.custom_entry,
+                params.custom_select,
                 params.clipboard_copied,
                 params.show_raw_url,
             );
@@ -1179,6 +1181,7 @@ fn render_welcome_authenticating(
     mode: AuthMode,
     auth_code_input: &str,
     custom_entry: &crate::app::custom_entry::CustomEntryDraft,
+    custom_select: Option<&crate::app::custom_entry::CustomSelectState>,
     clipboard_copied: bool,
     show_raw_url: bool,
 ) -> (Option<Rect>, Option<Rect>) {
@@ -1336,6 +1339,21 @@ fn render_welcome_authenticating(
             (None, None)
         }
 
+        AuthMode::CustomProviderSelect => {
+            if let Some(select) = custom_select {
+                render_custom_select(
+                    content_area,
+                    buf,
+                    theme,
+                    top_pad,
+                    logo_line_count,
+                    select,
+                    auth_code_input,
+                );
+            }
+            (None, None)
+        }
+
         AuthMode::Command => render_browser_status_arm(
             content_area,
             buf,
@@ -2034,6 +2052,182 @@ fn render_entry_box(
     Paragraph::new(hints).render(hint_area, buf);
 }
 
+/// The custom provider model-selection screen: fetched rows + manual input.
+fn render_custom_select(
+    content_area: Rect,
+    buf: &mut Buffer,
+    theme: &Theme,
+    top_pad: u16,
+    logo_line_count: u16,
+    select: &crate::app::custom_entry::CustomSelectState,
+    input: &str,
+) {
+    use crate::app::custom_entry::SelectFetch;
+    let h_pad: u16 = content_area.width / 8;
+    let inner_width = content_area.width.saturating_sub(h_pad * 2).max(1);
+    let instruction = format!(
+        "Select the models to add for {} ({})",
+        select.provider.name, select.provider.base_url
+    );
+    let status: Option<(String, Style)> = match &select.fetch {
+        SelectFetch::InFlight if select.finish_requested => Some((
+            "Fetching models... finishing when the list lands".to_owned(),
+            Style::default().fg(theme.gray),
+        )),
+        SelectFetch::InFlight => Some((
+            "Fetching models...".to_owned(),
+            Style::default().fg(theme.gray),
+        )),
+        SelectFetch::Listed if select.rows.is_empty() => Some((
+            "The provider served no models; add one below".to_owned(),
+            Style::default().fg(theme.warning),
+        )),
+        SelectFetch::Listed => None,
+        SelectFetch::Failed(reason) => Some((
+            format!("Fetch failed: {reason}"),
+            Style::default().fg(theme.warning),
+        )),
+    };
+    // Word-wrap-aware rows; byte math undercounts and clips the failure reason.
+    let rows_of = |text: &str| -> u16 {
+        crate::render::wrapping::word_wrap_line(
+            &Line::from(Span::raw(text.to_owned())),
+            inner_width as usize,
+        )
+        .len() as u16
+    };
+    let msg_height = rows_of(&instruction)
+        + status.as_ref().map_or(0, |(s, _)| rows_of(s))
+        + select.error.as_deref().map_or(0, rows_of);
+    let [
+        _,
+        logo_area,
+        _,
+        msg_area,
+        _,
+        rows_area,
+        _,
+        prompt_area,
+        _,
+        hint_area,
+        _,
+    ] = Layout::vertical([
+        Constraint::Length(top_pad),
+        Constraint::Length(logo_line_count),
+        Constraint::Length(1),
+        // Min: spare rows land here, so a mis-measured wrap never clips.
+        Constraint::Min(msg_height),
+        Constraint::Length(1),
+        Constraint::Min(3),
+        Constraint::Length(1),
+        Constraint::Length(5),
+        Constraint::Length(1),
+        Constraint::Length(1),
+        Constraint::Min(0),
+    ])
+    .areas(content_area);
+
+    render_logo(logo_area, buf, theme, content_area.height);
+
+    let mut lines = vec![
+        Line::from(Span::styled(
+            instruction,
+            Style::default().fg(theme.gray_bright),
+        ))
+        .alignment(Alignment::Center),
+    ];
+    if let Some((text, style)) = status {
+        lines.push(Line::from(Span::styled(text, style)).alignment(Alignment::Center));
+    }
+    if let Some(error) = select.error.as_deref() {
+        lines.push(
+            Line::from(Span::styled(error, Style::default().fg(theme.warning)))
+                .alignment(Alignment::Center),
+        );
+    }
+    Paragraph::new(lines)
+        .wrap(Wrap { trim: false })
+        .block(Block::default().padding(Padding::horizontal(h_pad)))
+        .render(msg_area, buf);
+
+    let visible = rows_area.height as usize;
+    let start = select
+        .highlight
+        .saturating_add(1)
+        .saturating_sub(visible)
+        .min(select.rows.len().saturating_sub(visible));
+    let mut row_lines = Vec::new();
+    for (idx, row) in select.rows.iter().enumerate().skip(start).take(visible) {
+        let highlighted = idx == select.highlight;
+        let check = if row.selected { "[x]" } else { "[ ]" };
+        let suffix = if row.manual { " (manual)" } else { "" };
+        let style = if highlighted {
+            Style::default()
+                .fg(theme.accent_user)
+                .add_modifier(Modifier::BOLD)
+        } else {
+            Style::default().fg(theme.gray_bright)
+        };
+        let marker = if highlighted { "› " } else { "  " };
+        row_lines.push(Line::from(Span::styled(
+            format!("{marker}{check} {}{suffix}", row.id),
+            style,
+        )));
+    }
+    Paragraph::new(row_lines)
+        .block(Block::default().padding(Padding::horizontal(h_pad)))
+        .render(rows_area, buf);
+
+    let [_, prompt_centered, _] = Layout::horizontal([
+        Constraint::Min(0),
+        Constraint::Length(content_area.width),
+        Constraint::Min(0),
+    ])
+    .flex(Flex::Center)
+    .areas(prompt_area);
+    render_auth_input_box(
+        prompt_centered,
+        buf,
+        theme,
+        input,
+        "Type a model id and press enter to add",
+        false,
+    );
+
+    let hints = Line::from(vec![
+        Span::styled(
+            "↑↓",
+            Style::default()
+                .fg(theme.accent_user)
+                .add_modifier(Modifier::BOLD),
+        ),
+        Span::styled("  navigate    ", Style::default().fg(theme.gray)),
+        Span::styled(
+            "space",
+            Style::default()
+                .fg(theme.accent_user)
+                .add_modifier(Modifier::BOLD),
+        ),
+        Span::styled("  toggle    ", Style::default().fg(theme.gray)),
+        Span::styled(
+            "enter",
+            Style::default()
+                .fg(theme.accent_user)
+                .add_modifier(Modifier::BOLD),
+        ),
+        Span::styled("  add model / done    ", Style::default().fg(theme.gray)),
+        Span::styled(
+            "esc",
+            Style::default()
+                .fg(theme.accent_user)
+                .add_modifier(Modifier::BOLD),
+        ),
+        Span::styled("  back", Style::default().fg(theme.gray)),
+    ])
+    .alignment(Alignment::Center);
+    Paragraph::new(hints).render(hint_area, buf);
+}
+
 /// Render the auth token input box (loopback mode).
 fn render_auth_input_box(
     area: Rect,
@@ -2197,6 +2391,7 @@ mod tests {
             login_label: None,
             auth_code_input: "",
             custom_entry: &EMPTY_CUSTOM_ENTRY,
+            custom_select: None,
             clipboard_copied: false,
             show_raw_url: false,
             tip: None,
@@ -2409,12 +2604,87 @@ mod tests {
             AuthMode::CustomProviderEntry(step),
             input,
             draft,
+            None,
             false,
             false,
         );
         buffer_text(&buf)
     }
 
+    fn render_custom_select(
+        select: &crate::app::custom_entry::CustomSelectState,
+        input: &str,
+    ) -> String {
+        let area = Rect::new(0, 0, 100, 40);
+        let mut buf = Buffer::empty(area);
+        render_welcome_authenticating(
+            area,
+            &mut buf,
+            &Theme::current(),
+            logo_line_count(area.height),
+            None,
+            AuthMode::CustomProviderSelect,
+            input,
+            &crate::app::custom_entry::CustomEntryDraft::new(),
+            Some(select),
+            false,
+            false,
+        );
+        buffer_text(&buf)
+    }
+
+    /// The selection screen lists rows, status, and the manual input together.
+    #[test]
+    fn custom_select_arm_lists_rows_status_and_input() {
+        use crate::app::custom_entry::CustomSelectState;
+        use kigi_shell::models::custom::{CustomApi, CustomProvider};
+
+        let provider =
+            CustomProvider::new("gw", CustomApi::OpenAi, "https://h.example/v1").unwrap();
+        let mut select = CustomSelectState::new(provider, "sk".to_owned());
+        let fetching = render_custom_select(&select, "");
+        assert!(fetching.contains("Fetching models"), "{fetching}");
+        assert!(fetching.contains("add model / done"), "{fetching}");
+
+        select.apply_fetch(kigi_shell::agent::custom_providers::LoginFetch {
+            provider: select.provider.clone(),
+            model_ids: vec!["m1".to_owned(), "m2".to_owned()],
+        });
+        select.toggle_highlighted();
+        select.add_manual("claude-opus-5-5[1m]");
+        let listed = render_custom_select(&select, "typed-so-far");
+        assert!(listed.contains("[x] m1"), "{listed}");
+        assert!(listed.contains("[ ] m2"), "{listed}");
+        assert!(listed.contains("claude-opus-5-5[1m] (manual)"), "{listed}");
+        assert!(listed.contains("typed-so-far"), "{listed}");
+
+        select.fail_fetch("boom".to_owned());
+        let failed = render_custom_select(&select, "");
+        assert!(failed.contains("Fetch failed: boom"), "{failed}");
+
+        // A two-hop failure reason must render whole, not clip at the wrap.
+        let reason = "https://h.example/models answered HTTP 404; https://h.example/v1/models also failed: https://h.example/v1/models answered HTTP 500";
+        select.fail_fetch(reason.to_owned());
+        let text = render_custom_select(&select, "");
+        assert!(text.contains("Fetch failed:"), "{text}");
+        assert!(text.contains("HTTP 500"), "{text}");
+    }
+
+    /// An empty selection refuses once the fetch resolved.
+    #[test]
+    fn custom_select_arm_shows_the_finish_refusal() {
+        use crate::app::custom_entry::CustomSelectState;
+        use kigi_shell::models::custom::{CustomApi, CustomProvider};
+
+        let provider =
+            CustomProvider::new("gw", CustomApi::OpenAi, "https://h.example/v1").unwrap();
+        let mut select = CustomSelectState::new(provider, "sk".to_owned());
+        select.fail_fetch("boom".to_owned());
+        assert!(select.try_finish().is_none());
+        let text = render_custom_select(&select, "");
+        assert!(text.contains("Select at least one model"), "{text}");
+    }
+
     /// Only the key step masks its input.
     #[test]
     fn custom_entry_arm_masks_only_the_key() {
@@ -2479,6 +2749,7 @@ mod tests {
             // auth_code_input
             "",
             &crate::app::custom_entry::CustomEntryDraft::new(),
+            None,
             // clipboard_copied
             false,
             // show_raw_url
@@ -3147,6 +3418,7 @@ mod tests {
             // auth_code_input — unused in device mode
             "",
             &crate::app::custom_entry::CustomEntryDraft::new(),
+            None,
             // clipboard_copied
             false,
             // show_raw_url
@@ -3204,6 +3476,7 @@ mod tests {
             AuthMode::Device,
             "",
             &crate::app::custom_entry::CustomEntryDraft::new(),
+            None,
             false,
             // show_raw_url
             true,
@@ -3232,6 +3505,7 @@ mod tests {
             AuthMode::Device,
             "",
             &crate::app::custom_entry::CustomEntryDraft::new(),
+            None,
             false,
             // show_raw_url
             true,
@@ -3271,6 +3545,7 @@ mod tests {
             AuthMode::Device,
             "",
             &crate::app::custom_entry::CustomEntryDraft::new(),
+            None,
             false,
             // show_raw_url
             true,
@@ -3313,6 +3588,7 @@ mod tests {
             // auth_code_input — unused
             "",
             &crate::app::custom_entry::CustomEntryDraft::new(),
+            None,
             // clipboard_copied
             false,
             // show_raw_url