diff --git a/README.md b/README.md
index c2c3706..8a34cd2 100644
--- a/README.md
+++ b/README.md
@@ -155,8 +155,8 @@ Anything that speaks the OpenAI Chat Completions API or the Anthropic Messages
 API works: a gateway, a proxy, Ollama, LM Studio, vLLM. In `kigi`, open `/login`
 (or the welcome login screen) and pick **Custom provider (OpenAI compatible)**
 or **(Anthropic compatible)**, then enter a base URL, a name, and an API key.
-Kigi checks the key against
-`GET {base}/models`, saves the provider, and `/model` lists what the endpoint
+Kigi saves the provider,
+checks the key against `GET {base}/models`, and `/model` lists what the endpoint
 serves as `name/model`.
 
 ```toml
diff --git a/crates/codegen/kigi-models/src/custom.rs b/crates/codegen/kigi-models/src/custom.rs
index ec799b6..e440318 100644
--- a/crates/codegen/kigi-models/src/custom.rs
+++ b/crates/codegen/kigi-models/src/custom.rs
@@ -165,7 +165,7 @@ pub fn normalize_base_url(raw: &str) -> Result<String, CustomProviderError> {
     Ok(url.to_owned())
 }
 
-/// A valid provider name from a base URL's host, for a login default.
+/// A valid provider name derived from a host.
 pub fn default_name(base_url: &str) -> String {
     let host = base_url
         .split("://")
diff --git a/crates/codegen/kigi-shell/src/agent/auth_method.rs b/crates/codegen/kigi-shell/src/agent/auth_method.rs
index 67770fe..9d8e153 100644
--- a/crates/codegen/kigi-shell/src/agent/auth_method.rs
+++ b/crates/codegen/kigi-shell/src/agent/auth_method.rs
@@ -599,7 +599,7 @@ mod tests {
         );
     }
 
-    /// `custom:<name>` is an API-key login; the picker rows are not loginable.
+    /// `custom:<name>` logs in; picker rows cannot.
     #[test]
     fn custom_provider_method_ids_classify_as_api_key() {
         let kind = AuthMethodKind::from_id(&acp::AuthMethodId::new("custom:my-proxy"));
diff --git a/crates/codegen/kigi-shell/src/agent/config.rs b/crates/codegen/kigi-shell/src/agent/config.rs
index 0626a95..0bf220d 100644
--- a/crates/codegen/kigi-shell/src/agent/config.rs
+++ b/crates/codegen/kigi-shell/src/agent/config.rs
@@ -3960,8 +3960,7 @@ pub fn resolve_model_auth_facts(model_id: &str) -> ModelAuthFacts {
         },
     })
 }
-/// Auth facts of a catalog entry the caller already holds. A fetched entry
-/// exists only in the live catalog, never in a disk reload.
+/// Auth facts of a held live-catalog entry.
 pub(crate) fn auth_facts_of(entry: &ModelEntry) -> ModelAuthFacts {
     ModelAuthFacts {
         byok: if entry.has_own_credentials() {
@@ -5286,7 +5285,7 @@ reasoning_effort = "low"
             auth_scheme: Default::default(),
         }
     }
-    /// A fetched entry's scheme and BYOK status come from the entry itself.
+    /// Scheme and BYOK status come from the entry.
     #[test]
     fn auth_facts_come_from_the_held_entry() {
         let mut model = test_model_entry("claude-x", "https://gw.example/v1", None, None, None);
diff --git a/crates/codegen/kigi-shell/src/agent/custom_providers/login.rs b/crates/codegen/kigi-shell/src/agent/custom_providers/login.rs
index 86eaf15..f7b58ba 100644
--- a/crates/codegen/kigi-shell/src/agent/custom_providers/login.rs
+++ b/crates/codegen/kigi-shell/src/agent/custom_providers/login.rs
@@ -9,7 +9,7 @@ const PICKER_PREFIX: &str = "custom-";
 const LOGIN_PREFIX: &str = "custom:";
 const ALL_APIS: [CustomApi; 2] = [CustomApi::OpenAi, CustomApi::Anthropic];
 
-/// The picker row that starts the custom provider flow for one wire.
+/// The picker row for one wire.
 pub fn picker_method(api: CustomApi) -> acp::AuthMethod {
     acp::AuthMethod::Agent(
         acp::AuthMethodAgent::new(
@@ -41,7 +41,7 @@ pub fn login_provider_name(id: &str) -> Option<&str> {
     id.strip_prefix(LOGIN_PREFIX)
 }
 
-/// Probes the listing endpoint with the key; the error text never holds the key.
+/// Probes the listing endpoint; errors never hold the key.
 pub(crate) async fn validate_key(credentialed: &CredentialedProvider) -> Result<(), String> {
     let provider = &credentialed.provider;
     let url = provider.models_url();
diff --git a/crates/codegen/kigi-shell/src/agent/mvp_agent/agent_ops.rs b/crates/codegen/kigi-shell/src/agent/mvp_agent/agent_ops.rs
index 22eebbf..72a72c9 100644
--- a/crates/codegen/kigi-shell/src/agent/mvp_agent/agent_ops.rs
+++ b/crates/codegen/kigi-shell/src/agent/mvp_agent/agent_ops.rs
@@ -553,7 +553,7 @@ impl MvpAgent {
             tracing::warn!(provider = name, %message, "custom provider login failed");
             emit_login_span(
                 false,
-                "custom-provider",
+                method_id.0.as_ref(),
                 None,
                 Some("custom_provider_invalid_or_missing"),
             );
@@ -561,7 +561,7 @@ impl MvpAgent {
         }
         Ok(self.finish_api_key_login(method_id).await)
     }
-    /// Shared tail of an API-key login: reload config, refresh the catalog.
+    /// Shared tail of an API-key login.
     async fn finish_api_key_login(&self, method_id: acp::AuthMethodId) -> AuthenticateResponse {
         // Rebuild the catalog from the on-disk config: the rebuild freshly
         // resolves platform keys (env > auth.json > config), so the key just
diff --git a/crates/codegen/kigi-shell/src/agent/subagent/mod.rs b/crates/codegen/kigi-shell/src/agent/subagent/mod.rs
index fc8b47f..ba97f50 100644
--- a/crates/codegen/kigi-shell/src/agent/subagent/mod.rs
+++ b/crates/codegen/kigi-shell/src/agent/subagent/mod.rs
@@ -879,6 +879,20 @@ fn log_subagent_model_resolution(
         )),
     );
 }
+/// The parent model's auth scheme: its live catalog entry, else a disk lookup.
+fn parent_auth_scheme(
+    available: &indexmap::IndexMap<String, crate::agent::config::ModelEntry>,
+    catalog_id: &acp::ModelId,
+    slug: &str,
+) -> kigi_sampler::AuthScheme {
+    crate::agent::models::entry_for_slug(available, Some(catalog_id.0.as_ref()), slug)
+        .map(|entry| crate::agent::config::auth_facts_of(entry).auth_scheme)
+        .or_else(|| {
+            crate::agent::config::try_resolve_model_credentials(slug, None).map(|r| r.auth_scheme)
+        })
+        .unwrap_or_default()
+}
+
 /// Read the parent session's actual current sampling config.
 ///
 /// Prefers the live state from `ChatStateHandle` (authoritative). Falls back
@@ -897,17 +911,7 @@ async fn read_parent_sampling_config(
                 creds.alpha_test_key.as_deref(),
                 &cfg.base_url,
             );
-            let auth_scheme = crate::agent::models::entry_for_slug(
-                &ctx.available_models,
-                Some(ctx.model_id.0.as_ref()),
-                &cfg.model,
-            )
-            .map(|entry| crate::agent::config::auth_facts_of(entry).auth_scheme)
-            .or_else(|| {
-                crate::agent::config::try_resolve_model_credentials(&cfg.model, None)
-                    .map(|r| r.auth_scheme)
-            })
-            .unwrap_or_default();
+            let auth_scheme = parent_auth_scheme(&ctx.available_models, &ctx.model_id, &cfg.model);
             // Claude Pro/Max OAuth Messages adaptation inherits from the parent
             // model's platform (claude-pro-max → true); every other platform,
             // and BYOK, → false, so the API-key paths stay byte-identical.
@@ -2667,3 +2671,32 @@ pub(crate) fn reconcile_orphaned_subagents(
 }
 #[cfg(test)]
 mod tests;
+
+#[cfg(test)]
+mod parent_auth_scheme_tests {
+    use super::*;
+
+    /// A fetched Messages model exists only in the live catalog.
+    #[test]
+    fn a_fetched_entry_gives_its_own_scheme_to_the_child() {
+        let wire: kigi_models::WireModel =
+            serde_json::from_value(serde_json::json!({ "id": "claude-x" })).unwrap();
+        let cfg = crate::agent::models_fetch::wire_model_to_entry(
+            "gw/claude-x".into(),
+            kigi_models::PlatformWireApi::Messages,
+            kigi_models::PlatformKeyHeader::XApiKey,
+            None,
+            true,
+            wire,
+            "https://gw.example/v1",
+        );
+        let available = indexmap::IndexMap::from([(
+            "gw/claude-x".to_owned(),
+            crate::agent::config::ModelEntry::from_config_entry(&cfg),
+        )]);
+
+        let scheme = parent_auth_scheme(&available, &acp::ModelId::new("gw/claude-x"), "claude-x");
+
+        assert_eq!(scheme, kigi_sampler::AuthScheme::XApiKey);
+    }
+}
diff --git a/crates/codegen/kigi-tui/src/app/actions.rs b/crates/codegen/kigi-tui/src/app/actions.rs
index b2b35e5..dcf908a 100644
--- a/crates/codegen/kigi-tui/src/app/actions.rs
+++ b/crates/codegen/kigi-tui/src/app/actions.rs
@@ -570,9 +570,9 @@ pub enum Action {
     /// under the platform-id scope, then authenticate with the platform's
     /// method id. The key must never be logged.
     SubmitPlatformApiKey(String),
-    /// A custom provider row was picked: start the URL, name, key steps.
+    /// Custom provider row picked: open the URL step.
     BeginCustomProviderEntry(kigi_shell::models::custom::CustomApi),
-    /// Enter in a custom provider step, with the trimmed input.
+    /// Enter in a custom provider step.
     SubmitCustomProviderInput(String),
     /// Copy the auth URL to the clipboard during authentication.
     CopyAuthUrl,
@@ -1618,8 +1618,7 @@ pub enum Effect {
         target: crate::app::app_view::PlatformLogin,
         key: String,
     },
-    /// Save a custom provider (config.toml and auth.json), then send
-    /// AuthenticateRequest with `custom:<name>`. SECURITY: never log the key.
+    /// Saves the provider, then authenticates; never log the key.
     PersistCustomProviderAndAuthenticate {
         request_seq: u64,
         provider: kigi_shell::models::custom::CustomProvider,
diff --git a/crates/codegen/kigi-tui/src/app/app_view.rs b/crates/codegen/kigi-tui/src/app/app_view.rs
index 7bdaaef..b26f2cf 100644
--- a/crates/codegen/kigi-tui/src/app/app_view.rs
+++ b/crates/codegen/kigi-tui/src/app/app_view.rs
@@ -262,7 +262,7 @@ pub enum AuthMode {
     /// Open-platform API-key entry: paste box for a Moonshot key selected
     /// from the welcome login picker. Esc returns to the picker (no quit).
     ApiKeyEntry(PlatformLogin),
-    /// Custom provider login: one field per step; Esc returns to the picker.
+    /// Custom provider login, one field per step.
     CustomProviderEntry(crate::app::custom_entry::CustomEntryStep),
 }
 /// API-key platform login target, selected from the welcome picker. Wraps a
diff --git a/crates/codegen/kigi-tui/src/app/custom_entry.rs b/crates/codegen/kigi-tui/src/app/custom_entry.rs
index 989754a..cbf877d 100644
--- a/crates/codegen/kigi-tui/src/app/custom_entry.rs
+++ b/crates/codegen/kigi-tui/src/app/custom_entry.rs
@@ -1,4 +1,4 @@
-//! The base URL, name, and key steps of the custom provider login.
+//! Custom provider login steps: base URL, name, key.
 
 use kigi_shell::models::custom::{
     CustomApi, CustomProvider, default_name, normalize_base_url, validate_name,
@@ -26,7 +26,7 @@ impl CustomEntryStep {
         }
     }
 
-    /// Only the key is a secret; URL and name show as typed.
+    /// Only the key is masked.
     pub fn masks_input(self) -> bool {
         self.field == CustomEntryField::Key
     }
@@ -43,9 +43,9 @@ impl CustomEntryStep {
 /// What one Enter press did.
 #[derive(Debug, PartialEq, Eq)]
 pub enum CustomEntryOutcome {
-    /// The input stays; `CustomEntryDraft::error` says why, if it does.
+    /// The input stays; the draft error says why.
     Stay,
-    /// Move to the next field with this text in the box.
+    /// Next field, with this text in the box.
     Next {
         field: CustomEntryField,
         prefill: String,
diff --git a/crates/codegen/kigi-tui/src/app/dispatch/auth.rs b/crates/codegen/kigi-tui/src/app/dispatch/auth.rs
index 2d815a1..c6fc8c4 100644
--- a/crates/codegen/kigi-tui/src/app/dispatch/auth.rs
+++ b/crates/codegen/kigi-tui/src/app/dispatch/auth.rs
@@ -326,7 +326,7 @@ pub(super) fn dispatch_begin_platform_key_entry(
     vec![]
 }
 
-/// A custom provider row was selected: open the first step (base URL).
+/// Custom provider row selected: open the URL step.
 pub(super) fn dispatch_begin_custom_provider_entry(
     app: &mut AppView,
     api: kigi_shell::models::custom::CustomApi,
@@ -344,7 +344,7 @@ pub(super) fn dispatch_begin_custom_provider_entry(
     vec![]
 }
 
-/// Enter in a custom provider step: advance, stay with a reason, or save.
+/// Enter in a custom provider step.
 pub(super) fn dispatch_submit_custom_provider_input(
     app: &mut AppView,
     input: String,
diff --git a/crates/codegen/kigi-tui/src/app/dispatch/tests/auth.rs b/crates/codegen/kigi-tui/src/app/dispatch/tests/auth.rs
index 7923f28..8f5b330 100644
--- a/crates/codegen/kigi-tui/src/app/dispatch/tests/auth.rs
+++ b/crates/codegen/kigi-tui/src/app/dispatch/tests/auth.rs
@@ -582,8 +582,7 @@ fn custom_field(app: &AppView) -> crate::app::custom_entry::CustomEntryField {
     }
 }
 
-/// The custom provider flow: URL, then name (prefilled from the host), then
-/// key; the last Enter emits ONE persist+authenticate effect for the provider.
+/// URL, name, key; the last Enter emits one persist effect.
 #[test]
 fn custom_provider_steps_end_in_one_persist_effect() {
     use crate::app::custom_entry::CustomEntryField;
@@ -649,7 +648,7 @@ fn custom_provider_steps_end_in_one_persist_effect() {
     assert!(app.auth_code_input.is_empty());
 }
 
-/// A refused field keeps the user on it and does not emit an effect.
+/// A refused field keeps the user on it.
 #[test]
 fn custom_provider_refusals_stay_on_the_field() {
     use crate::app::custom_entry::CustomEntryField;
@@ -687,7 +686,7 @@ fn custom_provider_refusals_stay_on_the_field() {
     assert!(app.custom_entry.error.is_some());
 }
 
-/// Esc at any step returns to the picker and drops the draft.
+/// Esc returns to the picker and drops the draft.
 #[test]
 fn cancel_custom_provider_entry_returns_to_picker() {
     use kigi_shell::models::custom::CustomApi;
diff --git a/crates/codegen/kigi-tui/src/views/welcome/mod.rs b/crates/codegen/kigi-tui/src/views/welcome/mod.rs
index f312434..3aa0654 100644
--- a/crates/codegen/kigi-tui/src/views/welcome/mod.rs
+++ b/crates/codegen/kigi-tui/src/views/welcome/mod.rs
@@ -1294,7 +1294,7 @@ fn render_welcome_authenticating(
         }
 
         AuthMode::ApiKeyEntry(target) => {
-            // Platform API-key paste box: the key comes from the platform console.
+            // Platform API-key paste box.
             let instruction = format!(
                 "Paste your {} API key (from {})",
                 target.vendor(),
@@ -1938,8 +1938,7 @@ pub(crate) fn render_session_picker(
     )
 }
 
-/// Render the auth token input box (loopback mode).
-/// One text field under the logo: instruction, optional error, input box, hints.
+/// One text field under the logo.
 struct EntryBox<'a> {
     instruction: &'a str,
     error: Option<&'a str>,
@@ -2035,6 +2034,7 @@ fn render_entry_box(
     Paragraph::new(hints).render(hint_area, buf);
 }
 
+/// Render the auth token input box (loopback mode).
 fn render_auth_input_box(
     area: Rect,
     buf: &mut Buffer,
@@ -2393,8 +2393,6 @@ mod tests {
         assert!(!text.contains("Moonshot"), "{text}");
     }
 
-    /// The Moonshot API-key entry arm renders the platform copy, the paste
-    /// box, and the esc-back hint — and no OAuth-URL affordances.
     fn render_custom_entry(
         step: crate::app::custom_entry::CustomEntryStep,
         draft: &crate::app::custom_entry::CustomEntryDraft,
@@ -2417,7 +2415,7 @@ mod tests {
         buffer_text(&buf)
     }
 
-    /// The URL and name steps show typed text; only the key step masks it.
+    /// Only the key step masks its input.
     #[test]
     fn custom_entry_arm_masks_only_the_key() {
         use crate::app::custom_entry::{CustomEntryDraft, CustomEntryField, CustomEntryStep};
@@ -2447,7 +2445,7 @@ mod tests {
         assert!(empty.contains("provider name"), "{empty}");
     }
 
-    /// A refusal shows under the instruction so the user sees what to fix.
+    /// A refusal shows under the instruction.
     #[test]
     fn custom_entry_arm_shows_the_refusal() {
         use crate::app::custom_entry::{CustomEntryDraft, CustomEntryStep};
@@ -2460,6 +2458,8 @@ mod tests {
         assert!(text.contains("must start with http"), "{text}");
     }
 
+    /// The Moonshot API-key entry arm renders the platform copy, the paste
+    /// box, and the esc-back hint — and no OAuth-URL affordances.
     #[test]
     fn api_key_entry_arm_shows_platform_copy_and_paste_box() {
         let area = Rect::new(0, 0, 80, 40);
diff --git a/crates/codegen/kigi-tui/tests/pty_e2e/custom_provider.rs b/crates/codegen/kigi-tui/tests/pty_e2e/custom_provider.rs
index 8d742c1..689197e 100644
--- a/crates/codegen/kigi-tui/tests/pty_e2e/custom_provider.rs
+++ b/crates/codegen/kigi-tui/tests/pty_e2e/custom_provider.rs
@@ -57,10 +57,7 @@ async fn run_turn(content: &ContentController) -> PtyHarness {
     harness
 }
 
-/// A declared OpenAI-compatible provider supplies the catalog and the turn:
-/// the request goes to `/chat/completions` for the fetched model with the
-/// provider's own key. The house key, which is set in this environment on the
-/// same loopback URL as the session's coding endpoint, never rides it.
+/// An OpenAI provider lists models and uses its own key.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 #[ignore]
 async fn custom_openai_provider_lists_models_and_uses_its_own_key() {
@@ -94,8 +91,7 @@ async fn custom_openai_provider_lists_models_and_uses_its_own_key() {
     harness.quit().expect("clean quit");
 }
 
-/// An Anthropic-compatible provider is reached on `/messages` with
-/// `x-api-key` and `anthropic-version`, and no Bearer header.
+/// An Anthropic provider uses `/messages` with `x-api-key`.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 #[ignore]
 async fn custom_anthropic_provider_uses_messages_and_x_api_key() {
@@ -128,8 +124,7 @@ async fn custom_anthropic_provider_uses_messages_and_x_api_key() {
     harness.quit().expect("clean quit");
 }
 
-/// A saved provider is a complete login: with no house key and no session, the
-/// pager starts authenticated and the turn reaches the provider.
+/// A saved provider alone is a complete login.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 #[ignore]
 async fn custom_provider_alone_authenticates_at_startup() {