diff --git a/AGENTS.md b/AGENTS.md
index bb3b8db..5d2d3cd 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -168,21 +168,36 @@ edges stay deterministic Rust. The harness appends a terminal
   are built generically from advertised methods (`AuthMethodKind::
   ApiKeyPlatform`), so new registry rows appear in the picker with no TUI
   changes.
-- Refreshable-OAuth providers beyond Kimi Code use a GENERIC device-code
-  (RFC-8628) path, NOT Kimi's bespoke wire. A `uses_oauth` platform carrying
-  `oauth: Some(&OAuthConfig)` (client id / auth host / device+token paths /
-  scope / `scope_key` / optional extra device field) drives
-  `auth::oauth_device` (plain kigi UA, no X-Msh headers) + a scope-keyed
-  `AuthManager::new_oauth_provider` + `refresh::GenericDeviceRefresher`
-  (selected by `build_refresher` via `oauth_config_for_scope_key`). Kimi Code
-  keeps `oauth: None` and its bespoke path unchanged. First such provider:
-  `xai-grok` (`scope_key oauth/xai`, base `api.x.ai/v1`, same wire as the
-  API-key `xai` row) — an INTERACTIVE login row advertised right after
-  `kimi-code` (`AuthMethodKind::OAuthPlatform`). Its `authenticate` arm runs
-  the generic device flow under its own scope; the catalog fetch resolves each
-  such platform's OWN session token (`resolve_generic_oauth_tokens`, refreshed
-  on expiry) and routes `platform.oauth().is_some()` → `platform.base_url()`
-  (kimi-code alone → `proxy_url()`). Tokens are NEVER logged.
+- Refreshable-OAuth providers beyond Kimi Code use a GENERIC path, NOT Kimi's
+  bespoke wire. A `uses_oauth` platform carrying `oauth: Some(&OAuthConfig)`
+  (client id / auth host / start+token paths / `token_host` / `scope` /
+  `scope_key` / optional extra device field / `flow` / `token_body`) drives a
+  scope-keyed `AuthManager::new_oauth_provider` +
+  `refresh::GenericDeviceRefresher` (selected by `build_refresher` via
+  `oauth_config_for_scope_key`; the refresher dispatches the refresh body by
+  `token_body`: form → `auth::oauth_device`, JSON → `auth::oauth_pkce`). Kimi
+  Code keeps `oauth: None` and its bespoke path unchanged. The interactive
+  login is dispatched by `OAuthConfig.flow` (in `run_oauth_provider_flow`):
+  - `OAuthFlow::DeviceCode` → `auth::oauth_device` (RFC-8628 device-code, plain
+    kigi UA, no X-Msh headers). Provider: `xai-grok` (`scope_key oauth/xai`,
+    base `api.x.ai/v1`, form token body, same wire as the API-key `xai` row).
+  - `OAuthFlow::PkceLocalhost { redirect_port }` → `auth::oauth_pkce`
+    (authorization-code + PKCE S256, `127.0.0.1:redirect_port/callback` loopback
+    with STRICT `state` validation + manual-paste fallback, JSON token body,
+    authorize host ≠ token host). Provider: `claude-pro-max` (`scope_key
+    oauth/claude-pro-max`, base `api.anthropic.com/v1`, Anthropic Messages +
+    listing wire reached with an OAuth `sk-ant-oat…` Bearer). Its Messages
+    requests take the OAuth adaptation — `anthropic-beta claude-code-…,oauth-…`
+    + `claude-cli` UA + `x-app cli` + the required "You are Claude Code…" system
+    prefix — gated on `SamplerConfig.anthropic_oauth` (claude-pro-max only), so
+    API-key `anthropic`/`minimax` Messages requests stay byte-identical. Its
+    `/v1/models` listing rides the same Bearer + oauth-beta headers.
+  Both are INTERACTIVE login rows advertised right after `kimi-code`
+  (`AuthMethodKind::OAuthPlatform`, in `PlatformId::ALL` order: `xai-grok` then
+  `claude-pro-max`). The catalog fetch resolves each such platform's OWN session
+  token (`resolve_generic_oauth_tokens`, refreshed on expiry) and routes
+  `platform.oauth().is_some()` → `platform.base_url()` (kimi-code alone →
+  `proxy_url()`). Tokens/codes/verifiers are NEVER logged.
 - Model metadata (context window, thinking levels) comes from the provider
   wire when served; metadata-poor listings are enriched from models.dev
   (`kigi-models/src/enrichment.rs` — bundled raw snapshot regenerated by
diff --git a/crates/codegen/kigi-models/src/lib.rs b/crates/codegen/kigi-models/src/lib.rs
index b583b9a..a1a7344 100644
--- a/crates/codegen/kigi-models/src/lib.rs
+++ b/crates/codegen/kigi-models/src/lib.rs
@@ -96,8 +96,35 @@ enum BaseUrlSource {
     },
 }
 
-/// Generic RFC-8628 device-code OAuth configuration carried by a `uses_oauth`
-/// platform whose login is the GENERIC device-code path (xai-grok today).
+/// The interactive login mechanism a `uses_oauth` [`OAuthConfig`] provider
+/// drives. `DeviceCode` is the RFC-8628 device flow (xai-grok); `PkceLocalhost`
+/// is the authorization-code + PKCE (S256) flow with a loopback callback
+/// (Claude Pro/Max). Kimi Code carries neither (its bespoke flow lives in
+/// kigi-shell with `oauth: None`).
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum OAuthFlow {
+    /// RFC-8628 device-code: POST `device_path`, poll `token_path`.
+    DeviceCode,
+    /// Authorization-code + PKCE (S256): browser hits `auth_host`+`device_path`
+    /// (the authorize endpoint); the code returns to a `127.0.0.1:redirect_port`
+    /// loopback listener, then is exchanged at `token_host`+`token_path`.
+    PkceLocalhost { redirect_port: u16 },
+}
+
+/// Body encoding a provider's token endpoint expects for the code-exchange and
+/// refresh POSTs. xAI's `/oauth2/token` is form-encoded; Claude's
+/// `/v1/oauth/token` is JSON.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum OAuthTokenBody {
+    /// `application/x-www-form-urlencoded` (xai-grok device wire).
+    Form,
+    /// `application/json` (Claude PKCE wire).
+    Json,
+}
+
+/// Generic OAuth configuration carried by a `uses_oauth` platform whose login
+/// is the GENERIC device-code path (xai-grok) or the PKCE-localhost path
+/// (claude-pro-max).
 ///
 /// Kimi Code keeps its bespoke device flow (client id, `/api/oauth/*` paths,
 /// X-Msh device headers, `kigi_env::oauth_host()`); its `oauth` field stays
@@ -105,15 +132,22 @@ enum BaseUrlSource {
 /// tokens they mint are NEVER stored in this struct and never logged.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct OAuthConfig {
-    /// OAuth client id sent on every device-authorization / token call.
+    /// OAuth client id sent on every authorize / token call.
     pub client_id: &'static str,
-    /// Authorization-server origin (no trailing slash), e.g. `https://auth.x.ai`.
+    /// Authorization-server origin (no trailing slash), e.g. `https://auth.x.ai`
+    /// (device) or `https://claude.ai` (PKCE authorize host).
     pub auth_host: &'static str,
-    /// Device-authorization path (POST), relative to `auth_host`.
+    /// Start-endpoint path (POST for `DeviceCode` device-authorization; the
+    /// browser authorize path for `PkceLocalhost`), relative to `auth_host`.
     pub device_path: &'static str,
-    /// Token path (POST) — used for BOTH the device grant and refresh.
+    /// Token-endpoint origin (no trailing slash). Equals `auth_host` for the
+    /// device wire; for Claude the token host (`https://platform.claude.com`)
+    /// differs from the authorize host (`https://claude.ai`).
+    pub token_host: &'static str,
+    /// Token path (POST) — used for BOTH the initial grant and refresh,
+    /// relative to `token_host`.
     pub token_path: &'static str,
-    /// OAuth scope string requested at device authorization.
+    /// OAuth scope string requested at authorization.
     pub scope: &'static str,
     /// auth.json map key + keyring entry name for this provider's persisted
     /// session (e.g. `oauth/xai`).
@@ -121,6 +155,10 @@ pub struct OAuthConfig {
     /// A non-standard extra form field sent ONLY on the device-authorization
     /// request (e.g. `("referrer", "kigi")`). `None` = no extra field.
     pub extra_device_field: Option<(&'static str, &'static str)>,
+    /// Interactive login mechanism (device-code vs PKCE-localhost).
+    pub flow: OAuthFlow,
+    /// Body encoding the token endpoint expects (form vs JSON).
+    pub token_body: OAuthTokenBody,
 }
 
 /// xAI / Grok subscription device-code OAuth (ported from Pi
@@ -129,10 +167,36 @@ pub const XAI_OAUTH_CONFIG: OAuthConfig = OAuthConfig {
     client_id: "b1a00492-073a-47ea-816f-4c329264a828",
     auth_host: "https://auth.x.ai",
     device_path: "/oauth2/device/code",
+    token_host: "https://auth.x.ai",
     token_path: "/oauth2/token",
     scope: "openid profile email offline_access grok-cli:access api:access",
     scope_key: "oauth/xai",
     extra_device_field: Some(("referrer", "kigi")),
+    flow: OAuthFlow::DeviceCode,
+    token_body: OAuthTokenBody::Form,
+};
+
+/// Base-URL override for the Claude Pro/Max OAuth channel (dev/test escape
+/// hatch). Production defaults to `https://api.anthropic.com/v1`.
+pub const CLAUDE_OAUTH_BASE_URL_ENV: &str = "KIGI_CLAUDE_OAUTH_BASE_URL";
+
+/// Claude Pro/Max subscription OAuth (authorization-code + PKCE S256, loopback
+/// callback). Authoritative constants from Pi `earendil-works/pi`
+/// `auth/oauth/anthropic.ts`: authorize host `https://claude.ai`, token host
+/// `https://platform.claude.com` (JSON body), public Claude Code client id.
+pub const CLAUDE_OAUTH_CONFIG: OAuthConfig = OAuthConfig {
+    client_id: "9d1c250a-e61b-44d9-88ed-5944d1962f5e",
+    auth_host: "https://claude.ai",
+    device_path: "/oauth/authorize",
+    token_host: "https://platform.claude.com",
+    token_path: "/v1/oauth/token",
+    scope: "org:create_api_key user:profile user:inference user:sessions:claude_code user:mcp_servers user:file_upload",
+    scope_key: "oauth/claude-pro-max",
+    extra_device_field: None,
+    flow: OAuthFlow::PkceLocalhost {
+        redirect_port: 53692,
+    },
+    token_body: OAuthTokenBody::Json,
 };
 
 /// The generic device-code OAuth config for a platform, or `None` for API-key
@@ -1001,6 +1065,42 @@ const MINIMAX_CN_SPEC: PlatformSpec = PlatformSpec {
     restrict_to_enriched: false,
 };
 
+/// Claude Pro/Max subscription via PKCE-localhost OAuth. Reaches
+/// `api.anthropic.com` with an OAuth `sk-ant-oat…` bearer (NOT an API key) —
+/// same Anthropic Messages + listing wire as the API-key `anthropic` row, plus
+/// the OAuth identity headers + "You are Claude Code" system prefix (gated on
+/// this platform's OAuth path in the sampler/fetch, so the API-key rows stay
+/// byte-identical).
+const CLAUDE_PRO_MAX_SPEC: PlatformSpec = PlatformSpec {
+    id: "claude-pro-max",
+    display_name: "Claude Pro/Max",
+    // WITH /v1 so listing → /v1/models and inference → /v1/messages, matching
+    // ANTHROPIC_SPEC's base handling.
+    base_url: BaseUrlSource::EnvOr {
+        env: CLAUDE_OAUTH_BASE_URL_ENV,
+        default: "https://api.anthropic.com/v1",
+    },
+    uses_oauth: true,
+    oauth: Some(&CLAUDE_OAUTH_CONFIG),
+    allowed_model_prefixes: None,
+    // OAuth channel: no API key envs (the PKCE session is the bearer).
+    api_key_envs: &[],
+    vendor: "Anthropic",
+    console_host: None,
+    login_label: Some("Claude Pro/Max (subscription)"),
+    models_dev_id: Some("anthropic"),
+    wire_serves_metadata: false,
+    wire_api: PlatformWireApi::Messages,
+    listing: ListingDialect::Anthropic,
+    // Passthrough is ignored for the Messages backend.
+    chat_compat: PlatformChatCompat::Passthrough,
+    // OAuth uses Authorization: Bearer, NOT x-api-key.
+    key_header: PlatformKeyHeader::Bearer,
+    restrict_to_enriched: false,
+    key_validation_path: None,
+    strip_listing_id_prefix: None,
+};
+
 /// The platform registry. Platforms are compiled-in spec rows; there is no
 /// dynamic provider registration (PRD F2).
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
@@ -1057,12 +1157,15 @@ pub enum PlatformId {
     MinimaxCn,
     /// xAI Grok subscription via device-code OAuth (same wire as `Xai`).
     XaiGrok,
+    /// Claude Pro/Max subscription via PKCE-localhost OAuth (Anthropic Messages
+    /// wire reached with an OAuth bearer instead of an API key).
+    ClaudeProMax,
 }
 
 impl PlatformId {
     /// All platforms, in catalog precedence order: the subscription channel
     /// first so "default model = first list item" favors it when present.
-    pub const ALL: [PlatformId; 26] = [
+    pub const ALL: [PlatformId; 27] = [
         Self::KimiCode,
         Self::MoonshotCn,
         Self::MoonshotAi,
@@ -1089,6 +1192,7 @@ impl PlatformId {
         Self::Minimax,
         Self::MinimaxCn,
         Self::XaiGrok,
+        Self::ClaudeProMax,
     ];
 
     /// The registry row backing this platform (single source of per-platform
@@ -1121,6 +1225,7 @@ impl PlatformId {
             Self::Minimax => &MINIMAX_SPEC,
             Self::MinimaxCn => &MINIMAX_CN_SPEC,
             Self::XaiGrok => &XAI_GROK_SPEC,
+            Self::ClaudeProMax => &CLAUDE_PRO_MAX_SPEC,
         }
     }
 
@@ -1899,7 +2004,7 @@ mod tests {
         let g = PlatformId::XaiGrok;
         assert_eq!(g.as_str(), "xai-grok");
         assert!(g.uses_oauth());
-        // The only two uses_oauth platforms; only xai-grok carries a config.
+        // Kimi Code is uses_oauth yet carries no generic config (bespoke flow).
         assert!(PlatformId::KimiCode.uses_oauth());
         assert_eq!(PlatformId::KimiCode.oauth(), None);
         let cfg = g
@@ -1933,6 +2038,65 @@ mod tests {
         assert_eq!(g.base_url(), "https://mock.grok/v1");
     }
 
+    /// claude-pro-max is the first PKCE-localhost OAuth platform: it carries a
+    /// PKCE `OAuthConfig` (authorize host ≠ token host, JSON token body), reuses
+    /// the Anthropic Messages + listing wire with a Bearer key header (OAuth,
+    /// NOT x-api-key), enriches from models.dev "anthropic", and keys its models
+    /// under `claude-pro-max/`.
+    #[test]
+    fn claude_pro_max_is_a_pkce_oauth_platform() {
+        let c = PlatformId::ClaudeProMax;
+        assert_eq!(c.as_str(), "claude-pro-max");
+        assert!(c.uses_oauth());
+        let cfg = c
+            .oauth()
+            .expect("claude-pro-max carries a PKCE OAuthConfig");
+        assert_eq!(cfg, &CLAUDE_OAUTH_CONFIG);
+        assert_eq!(cfg.client_id, "9d1c250a-e61b-44d9-88ed-5944d1962f5e");
+        // Authorize host ≠ token host (the distinguishing PKCE trait).
+        assert_eq!(cfg.auth_host, "https://claude.ai");
+        assert_eq!(cfg.device_path, "/oauth/authorize");
+        assert_eq!(cfg.token_host, "https://platform.claude.com");
+        assert_eq!(cfg.token_path, "/v1/oauth/token");
+        assert_eq!(
+            cfg.scope,
+            "org:create_api_key user:profile user:inference \
+             user:sessions:claude_code user:mcp_servers user:file_upload"
+        );
+        assert_eq!(cfg.scope_key, "oauth/claude-pro-max");
+        assert_eq!(cfg.extra_device_field, None);
+        assert_eq!(
+            cfg.flow,
+            OAuthFlow::PkceLocalhost {
+                redirect_port: 53692
+            }
+        );
+        assert_eq!(cfg.token_body, OAuthTokenBody::Json);
+        // xai stays the device-code / form contract — unaffected.
+        assert_eq!(XAI_OAUTH_CONFIG.flow, OAuthFlow::DeviceCode);
+        assert_eq!(XAI_OAUTH_CONFIG.token_body, OAuthTokenBody::Form);
+        assert_eq!(XAI_OAUTH_CONFIG.token_host, "https://auth.x.ai");
+        // Scope-key lookup resolves the config (drives the generic refresher).
+        assert_eq!(
+            oauth_config_for_scope_key("oauth/claude-pro-max"),
+            Some(&CLAUDE_OAUTH_CONFIG)
+        );
+        // Anthropic Messages + listing wire, reached with a Bearer OAuth token.
+        assert_eq!(c.models_dev_id(), Some("anthropic"));
+        assert!(!c.restrict_to_enriched());
+        assert_eq!(c.key_header(), PlatformKeyHeader::Bearer);
+        assert_eq!(c.wire_api(), PlatformWireApi::Messages);
+        assert_eq!(c.listing(), ListingDialect::Anthropic);
+        assert_eq!(c.api_key_env_names(), &[] as &[&str]);
+        assert_eq!(
+            c.managed_model_key("claude-opus-4-8"),
+            "claude-pro-max/claude-opus-4-8"
+        );
+        let _guard =
+            kigi_env::EnvVarGuard::set(CLAUDE_OAUTH_BASE_URL_ENV, "https://mock.claude/v1");
+        assert_eq!(c.base_url(), "https://mock.claude/v1");
+    }
+
     /// A variant missing from `ALL` compiles fine (`ALL`'s length is a plain
     /// literal) but is silently unparseable and excluded from model sync.
     /// The exhaustive match below fails compilation when a variant is added,
@@ -1967,9 +2131,10 @@ mod tests {
                 PlatformId::Minimax => 23,
                 PlatformId::MinimaxCn => 24,
                 PlatformId::XaiGrok => 25,
+                PlatformId::ClaudeProMax => 26,
             }
         }
-        const VARIANT_COUNT: usize = 26; // update together with `ordinal`
+        const VARIANT_COUNT: usize = 27; // update together with `ordinal`
         let mut seen: Vec<usize> = PlatformId::ALL.iter().map(|&p| ordinal(p)).collect();
         seen.sort_unstable();
         seen.dedup();
diff --git a/crates/codegen/kigi-sampler/src/actor/state.rs b/crates/codegen/kigi-sampler/src/actor/state.rs
index aacba13..57021c9 100644
--- a/crates/codegen/kigi-sampler/src/actor/state.rs
+++ b/crates/codegen/kigi-sampler/src/actor/state.rs
@@ -89,6 +89,7 @@ mod tests {
             top_p: None,
             api_backend: ApiBackend::ChatCompletions,
             auth_scheme: Default::default(),
+            anthropic_oauth: false,
             chat_compat: Default::default(),
             extra_headers: IndexMap::new(),
             context_window: 8192,
diff --git a/crates/codegen/kigi-sampler/src/client.rs b/crates/codegen/kigi-sampler/src/client.rs
index e477b16..f050e8c 100644
--- a/crates/codegen/kigi-sampler/src/client.rs
+++ b/crates/codegen/kigi-sampler/src/client.rs
@@ -41,6 +41,35 @@ pub use kigi_sampling_types::ApiBackend;
 const AGENT_PRODUCT: &str = "kigi";
 const ANTHROPIC_DEFAULT_MAX_TOKENS: u32 = 128_000;
 
+/// Prepend the required Claude-Code system block to a Messages request's
+/// `system` field (Claude Pro/Max OAuth path). Anthropic inspects the FIRST
+/// system block, so the prefix is inserted as a distinct leading `text` block
+/// while preserving any caller-supplied prompt (string or block form).
+/// Idempotent: a leading block already equal to the prefix is not re-added.
+fn prepend_claude_code_system_prefix(system: &mut Option<messages::SystemParam>) {
+    use messages::{SystemParam, TextBlock};
+    let text_block = |text: String| TextBlock {
+        r#type: "text".to_string(),
+        text,
+        cache_control: None,
+    };
+    let mut blocks = match system.take() {
+        None => Vec::new(),
+        Some(SystemParam::Text(text)) => vec![text_block(text)],
+        Some(SystemParam::Blocks(blocks)) => blocks,
+    };
+    let already_present = blocks
+        .first()
+        .is_some_and(|b| b.text == kigi_sampling_types::CLAUDE_CODE_SYSTEM_PREFIX);
+    if !already_present {
+        blocks.insert(
+            0,
+            text_block(kigi_sampling_types::CLAUDE_CODE_SYSTEM_PREFIX.to_string()),
+        );
+    }
+    *system = Some(SystemParam::Blocks(blocks));
+}
+
 /// Parse the `Retry-After` response header as delta-seconds.
 /// Our inference backends only emit integer seconds (never HTTP-date),
 /// so we only handle that form. HTTP-dates silently return `None` and
@@ -273,6 +302,8 @@ struct ClientDefaults {
     chat_compat: kigi_sampling_types::ChatCompat,
     stream_tool_calls: bool,
     doom_loop_recovery: Option<kigi_sampling_types::DoomLoopRecoveryPolicy>,
+    /// Claude Pro/Max OAuth Messages adaptation (see [`SamplerConfig`]).
+    anthropic_oauth: bool,
 }
 
 // =============================================================================
@@ -398,6 +429,31 @@ impl SamplingClient {
             }
         }
 
+        // Claude Pro/Max OAuth identity headers (claude-pro-max only). The
+        // OAuth `sk-ant-oat…` bearer is Claude-Code-scoped, so Anthropic
+        // rejects the Messages request without the oauth beta + claude-cli
+        // identity. Gated on `anthropic_oauth` so API-key anthropic/minimax
+        // requests carry none of this and stay byte-identical. `Accept` is set
+        // per-request (text/event-stream for streams), so it is NOT added here.
+        if config.anthropic_oauth {
+            headers.insert(
+                HeaderName::from_static("anthropic-version"),
+                HeaderValue::from_static(kigi_sampling_types::ANTHROPIC_VERSION),
+            );
+            headers.insert(
+                HeaderName::from_static("anthropic-beta"),
+                HeaderValue::from_static(kigi_sampling_types::ANTHROPIC_OAUTH_BETA),
+            );
+            headers.insert(
+                HeaderName::from_static("x-app"),
+                HeaderValue::from_static("cli"),
+            );
+            headers.insert(
+                HeaderName::from_static("anthropic-dangerous-direct-browser-access"),
+                HeaderValue::from_static("true"),
+            );
+        }
+
         // Apply all extra headers verbatim. This is the single
         // injection point for proxy-auth headers and any other URL- or
         // environment-specific headers the session decides to set.
@@ -415,12 +471,18 @@ impl SamplingClient {
         // (PRD F3: auth is a plain bearer; kimi-cli sends only User-Agent
         // plus the OAuth device headers, src/kimi_cli/llm.py:317-323).
         {
-            let ua_string = match config.origin_client.as_ref() {
-                Some(origin) => user_agent_string_for(origin),
-                None => user_agent_string_for(&OriginClientInfo {
-                    product: AGENT_PRODUCT.to_string(),
-                    version: Some(agent_version()),
-                }),
+            // Claude Pro/Max OAuth path presents the claude-cli identity;
+            // every other path keeps the kigi User-Agent.
+            let ua_string = if config.anthropic_oauth {
+                kigi_sampling_types::CLAUDE_CODE_USER_AGENT.to_string()
+            } else {
+                match config.origin_client.as_ref() {
+                    Some(origin) => user_agent_string_for(origin),
+                    None => user_agent_string_for(&OriginClientInfo {
+                        product: AGENT_PRODUCT.to_string(),
+                        version: Some(agent_version()),
+                    }),
+                }
             };
             if let Ok(v) = HeaderValue::from_str(&ua_string) {
                 headers.insert(USER_AGENT, v);
@@ -460,6 +522,7 @@ impl SamplingClient {
             chat_compat: config.chat_compat,
             stream_tool_calls: config.stream_tool_calls,
             doom_loop_recovery: config.doom_loop_recovery,
+            anthropic_oauth: config.anthropic_oauth,
         };
 
         Ok(Self {
@@ -1344,6 +1407,15 @@ impl SamplingClient {
 
     /// Apply default configuration to a Messages API request.
     fn apply_message_defaults(&self, request: &mut MessagesRequestWrapper) -> Result<()> {
+        // Claude Pro/Max OAuth adaptation (claude-pro-max only): the OAuth
+        // token is Claude-Code-scoped, so the request MUST lead with the exact
+        // "You are Claude Code…" system block or Anthropic rejects it. Prepend
+        // it as a distinct first system block, preserving any caller prompt.
+        // Gated on `anthropic_oauth` so API-key anthropic/minimax are untouched.
+        if self.defaults.anthropic_oauth {
+            prepend_claude_code_system_prefix(&mut request.inner.system);
+        }
+
         // Apply model default if not specified
         if request.inner.model.is_empty() {
             request.inner.model = self.defaults.model.clone();
@@ -1888,6 +1960,7 @@ mod tests {
             top_p: None,
             api_backend: ApiBackend::ChatCompletions,
             auth_scheme: AuthScheme::Bearer,
+            anthropic_oauth: false,
             chat_compat: Default::default(),
             extra_headers: IndexMap::new(),
             context_window: 8192,
@@ -1942,6 +2015,130 @@ mod tests {
         );
     }
 
+    /// Claude Pro/Max OAuth Messages client (`anthropic_oauth = true`, Bearer,
+    /// Messages) carries the full OAuth identity: Bearer auth, anthropic-version,
+    /// the oauth `anthropic-beta`, `x-app: cli`, the claude-cli User-Agent, and
+    /// the direct-browser-access header.
+    #[test]
+    fn anthropic_oauth_messages_client_sends_oauth_identity_headers() {
+        let mut config = minimal_config();
+        config.api_key = Some("sk-ant-oat-secret".to_string());
+        config.auth_scheme = AuthScheme::Bearer;
+        config.api_backend = ApiBackend::Messages;
+        config.anthropic_oauth = true;
+        let client = SamplingClient::new(config).expect("client builds");
+        let h = &client.default_headers;
+        assert_eq!(
+            h.get(AUTHORIZATION).and_then(|v| v.to_str().ok()),
+            Some("Bearer sk-ant-oat-secret"),
+            "OAuth path rides Authorization: Bearer, never x-api-key"
+        );
+        assert!(
+            h.get("x-api-key").is_none(),
+            "OAuth path must not send x-api-key"
+        );
+        assert_eq!(
+            h.get("anthropic-version").and_then(|v| v.to_str().ok()),
+            Some(kigi_sampling_types::ANTHROPIC_VERSION)
+        );
+        assert_eq!(
+            h.get("anthropic-beta").and_then(|v| v.to_str().ok()),
+            Some(kigi_sampling_types::ANTHROPIC_OAUTH_BETA)
+        );
+        assert_eq!(h.get("x-app").and_then(|v| v.to_str().ok()), Some("cli"));
+        assert_eq!(
+            h.get(USER_AGENT).and_then(|v| v.to_str().ok()),
+            Some(kigi_sampling_types::CLAUDE_CODE_USER_AGENT)
+        );
+        assert_eq!(
+            h.get("anthropic-dangerous-direct-browser-access")
+                .and_then(|v| v.to_str().ok()),
+            Some("true")
+        );
+    }
+
+    /// REGRESSION: an API-key Anthropic Messages client (XApiKey, NOT oauth)
+    /// carries NONE of the OAuth identity — no anthropic-beta, no x-app, and
+    /// the kigi User-Agent — so the API-key path stays byte-identical.
+    #[test]
+    fn api_key_anthropic_messages_client_has_no_oauth_identity() {
+        let mut config = minimal_config();
+        config.auth_scheme = AuthScheme::XApiKey;
+        config.api_backend = ApiBackend::Messages;
+        // anthropic_oauth stays false.
+        let client = SamplingClient::new(config).expect("client builds");
+        let h = &client.default_headers;
+        assert!(
+            h.get("anthropic-beta").is_none(),
+            "API-key anthropic must NOT send the oauth beta"
+        );
+        assert!(
+            h.get("x-app").is_none(),
+            "API-key anthropic must NOT send x-app"
+        );
+        assert!(h.get("anthropic-dangerous-direct-browser-access").is_none());
+        assert!(
+            h.get(USER_AGENT)
+                .and_then(|v| v.to_str().ok())
+                .is_some_and(|ua| ua.starts_with("kigi/")),
+            "API-key anthropic keeps the kigi User-Agent"
+        );
+    }
+
+    /// The system-prompt prefix is prepended as a distinct leading `text`
+    /// block for each `system` shape (absent / string / blocks), preserving the
+    /// caller's prompt, and is idempotent (not stamped twice).
+    #[test]
+    fn claude_code_system_prefix_prepends_and_is_idempotent() {
+        use messages::{SystemParam, TextBlock};
+        let prefix = kigi_sampling_types::CLAUDE_CODE_SYSTEM_PREFIX;
+
+        // Absent system → a single prefix block.
+        let mut none = None;
+        prepend_claude_code_system_prefix(&mut none);
+        match none {
+            Some(SystemParam::Blocks(b)) => {
+                assert_eq!(b.len(), 1);
+                assert_eq!(b[0].text, prefix);
+            }
+            other => panic!("expected one prefix block, got {other:?}"),
+        }
+
+        // String system → [prefix, original].
+        let mut text = Some(SystemParam::Text("do the thing".into()));
+        prepend_claude_code_system_prefix(&mut text);
+        match text {
+            Some(SystemParam::Blocks(b)) => {
+                assert_eq!(b.len(), 2);
+                assert_eq!(b[0].text, prefix);
+                assert_eq!(b[1].text, "do the thing");
+            }
+            other => panic!("expected two blocks, got {other:?}"),
+        }
+
+        // Idempotent: a leading prefix block is not re-added.
+        let mut already = Some(SystemParam::Blocks(vec![
+            TextBlock {
+                r#type: "text".into(),
+                text: prefix.to_string(),
+                cache_control: None,
+            },
+            TextBlock {
+                r#type: "text".into(),
+                text: "tail".into(),
+                cache_control: None,
+            },
+        ]));
+        prepend_claude_code_system_prefix(&mut already);
+        match already {
+            Some(SystemParam::Blocks(b)) => {
+                assert_eq!(b.len(), 2, "prefix must not be duplicated");
+                assert_eq!(b[0].text, prefix);
+            }
+            other => panic!("expected unchanged blocks, got {other:?}"),
+        }
+    }
+
     /// Verify the serialized shape of StreamingChatRequest matches the
     /// expected wire format: all ChatCompletionRequest fields flattened at
     /// top level, plus `stream: true` and `stream_options.include_usage: true`.
diff --git a/crates/codegen/kigi-sampler/src/config.rs b/crates/codegen/kigi-sampler/src/config.rs
index b7175ae..af0dd5c 100644
--- a/crates/codegen/kigi-sampler/src/config.rs
+++ b/crates/codegen/kigi-sampler/src/config.rs
@@ -55,6 +55,13 @@ pub struct SamplerConfig {
     pub api_backend: ApiBackend,
     #[serde(default)]
     pub auth_scheme: AuthScheme,
+    /// Claude Pro/Max OAuth adaptation (claude-pro-max only). When true the
+    /// Messages request carries the OAuth identity headers (`anthropic-beta`
+    /// oauth, `claude-cli` User-Agent, `x-app: cli`) and its system prompt is
+    /// prefixed with the required "You are Claude Code…" line. Gated so the
+    /// API-key `anthropic` + `minimax` Messages requests stay byte-identical.
+    #[serde(default)]
+    pub anthropic_oauth: bool,
     /// Extra request headers applied verbatim. The sampler never inspects
     /// the URL to derive headers; callers (the session) inject proxy auth
     /// and other access headers here before constructing the config.
@@ -144,6 +151,7 @@ impl Default for SamplerConfig {
             top_p: None,
             api_backend: ApiBackend::default(),
             auth_scheme: AuthScheme::default(),
+            anthropic_oauth: false,
             extra_headers: IndexMap::new(),
             context_window: 0,
             force_http1: false,
diff --git a/crates/codegen/kigi-sampler/tests/test_actor.rs b/crates/codegen/kigi-sampler/tests/test_actor.rs
index 319ba43..477a004 100644
--- a/crates/codegen/kigi-sampler/tests/test_actor.rs
+++ b/crates/codegen/kigi-sampler/tests/test_actor.rs
@@ -78,6 +78,7 @@ fn test_config(base_url: String, model: &str) -> SamplerConfig {
         top_p: None,
         api_backend: ApiBackend::ChatCompletions,
         auth_scheme: Default::default(),
+        anthropic_oauth: false,
         chat_compat: Default::default(),
         extra_headers: IndexMap::new(),
         context_window: 128_000,
diff --git a/crates/codegen/kigi-sampling-types/src/types.rs b/crates/codegen/kigi-sampling-types/src/types.rs
index 7aaba35..c656591 100644
--- a/crates/codegen/kigi-sampling-types/src/types.rs
+++ b/crates/codegen/kigi-sampling-types/src/types.rs
@@ -1060,6 +1060,22 @@ pub fn normalize_effort_echo(value: &mut Value) {
 /// wires (Messages inference and the /v1/models listing).
 pub const ANTHROPIC_VERSION: &str = "2023-06-01";
 
+/// `anthropic-beta` value for the Claude-Code OAuth (Pro/Max subscription)
+/// path — required on BOTH the Messages inference request and the `/v1/models`
+/// listing when the bearer is an OAuth `sk-ant-oat…` token. API-key Anthropic
+/// and MiniMax NEVER send this (their requests stay byte-identical).
+pub const ANTHROPIC_OAUTH_BETA: &str = "claude-code-20250219,oauth-2025-04-20";
+
+/// User-Agent kigi presents on the Claude-Code OAuth path (mirrors the
+/// official Claude Code CLI). OAuth-gated: unrelated to the default kigi UA.
+pub const CLAUDE_CODE_USER_AGENT: &str = "claude-cli/2.1.75";
+
+/// System-prompt prefix REQUIRED on the Claude-Code OAuth Messages path: the
+/// OAuth token is Claude-Code-scoped, so Anthropic rejects the request unless
+/// the system prompt's first block is exactly this line. OAuth-gated.
+pub const CLAUDE_CODE_SYSTEM_PREFIX: &str =
+    "You are Claude Code, Anthropic's official CLI for Claude.";
+
 /// ChatCompletions request-body adaptation dialect. Providers disagree on
 /// how thinking rides an OpenAI-compatible body: Kimi wants
 /// `thinking:{type,effort}`, DeepSeek wants
diff --git a/crates/codegen/kigi-shell/src/agent/auth_method.rs b/crates/codegen/kigi-shell/src/agent/auth_method.rs
index c8ec282..f082a72 100644
--- a/crates/codegen/kigi-shell/src/agent/auth_method.rs
+++ b/crates/codegen/kigi-shell/src/agent/auth_method.rs
@@ -595,6 +595,11 @@ mod tests {
         );
         assert_eq!(
             ids[kimi_pos + 2],
+            "claude-pro-max",
+            "claude-pro-max is the next interactive OAuth login, after xai-grok"
+        );
+        assert_eq!(
+            ids[kimi_pos + 3],
             MOONSHOT_CN_METHOD_ID,
             "the api-key rows follow the generic oauth logins"
         );
@@ -628,6 +633,29 @@ mod tests {
         assert_eq!(kind.auth_error_message(), AUTH_ERROR_SESSION_EXPIRED);
     }
 
+    /// claude-pro-max classifies as an interactive OAuth login too (the
+    /// authenticate handler dispatches it to the PKCE-localhost flow by the
+    /// config's `flow`): session-based, needs a browser, never api-key, and
+    /// `oauth_platform()` returns ClaudeProMax.
+    #[test]
+    fn claude_pro_max_is_an_interactive_oauth_login() {
+        let id = acp::AuthMethodId::new("claude-pro-max");
+        let kind = AuthMethodKind::from_id(&id);
+        assert_eq!(
+            kind,
+            AuthMethodKind::OAuthPlatform(kigi_models::PlatformId::ClaudeProMax)
+        );
+        assert!(kind.needs_interactive_login());
+        assert!(kind.is_session_based());
+        assert!(!kind.is_api_key());
+        assert_eq!(
+            kind.oauth_platform(),
+            Some(kigi_models::PlatformId::ClaudeProMax)
+        );
+        // Never an API-key picker target (keeps it out of the paste-box path).
+        assert_eq!(platform_for_method_id(&id), None);
+    }
+
     /// The OAuth platform id must never resolve as an API-key platform
     /// method — `platform_for_method_id`'s `uses_oauth` filter is what keeps
     /// the generic `authenticate` arm from hijacking the device login.
@@ -721,6 +749,7 @@ mod tests {
                 XAI_API_KEY_METHOD_ID,
                 KIMI_CODE_METHOD_ID,
                 "xai-grok",
+                "claude-pro-max",
                 MOONSHOT_CN_METHOD_ID,
                 MOONSHOT_AI_METHOD_ID,
                 "openai",
@@ -770,6 +799,7 @@ mod tests {
                 CACHED_TOKEN_AUTH_METHOD_ID,
                 KIMI_CODE_METHOD_ID,
                 "xai-grok",
+                "claude-pro-max",
                 MOONSHOT_CN_METHOD_ID,
                 MOONSHOT_AI_METHOD_ID,
                 "openai",
@@ -812,6 +842,7 @@ mod tests {
                 CACHED_TOKEN_AUTH_METHOD_ID,
                 KIMI_CODE_METHOD_ID,
                 "xai-grok",
+                "claude-pro-max",
                 MOONSHOT_CN_METHOD_ID,
                 MOONSHOT_AI_METHOD_ID,
                 "openai",
@@ -857,6 +888,7 @@ mod tests {
             vec![
                 KIMI_CODE_METHOD_ID,
                 "xai-grok",
+                "claude-pro-max",
                 MOONSHOT_CN_METHOD_ID,
                 MOONSHOT_AI_METHOD_ID,
                 "openai",
diff --git a/crates/codegen/kigi-shell/src/agent/config.rs b/crates/codegen/kigi-shell/src/agent/config.rs
index 2ef7fdb..c652245 100644
--- a/crates/codegen/kigi-shell/src/agent/config.rs
+++ b/crates/codegen/kigi-shell/src/agent/config.rs
@@ -4079,6 +4079,18 @@ pub fn sampling_config_for_model(
             }
         })
         .unwrap_or_default();
+    // Claude Pro/Max OAuth Messages adaptation: a managed key whose platform is
+    // a generic-OAuth Messages provider (claude-pro-max) drives the OAuth
+    // identity headers + "You are Claude Code" system prefix in the sampler.
+    // Gated here so API-key anthropic/minimax (oauth None) stay byte-identical.
+    let anthropic_oauth = info
+        .id
+        .as_deref()
+        .and_then(kigi_models::parse_managed_model_key)
+        .is_some_and(|(platform, _)| {
+            platform.oauth().is_some()
+                && platform.wire_api() == kigi_models::PlatformWireApi::Messages
+        });
     SamplerConfig {
         api_key: credentials.api_key,
         model: model_name,
@@ -4088,6 +4100,7 @@ pub fn sampling_config_for_model(
         top_p,
         api_backend,
         auth_scheme: credentials.auth_scheme,
+        anthropic_oauth,
         chat_compat,
         extra_headers,
         context_window: info.context_window.get(),
diff --git a/crates/codegen/kigi-shell/src/agent/models_fetch.rs b/crates/codegen/kigi-shell/src/agent/models_fetch.rs
index acdd9de..dacbcfa 100644
--- a/crates/codegen/kigi-shell/src/agent/models_fetch.rs
+++ b/crates/codegen/kigi-shell/src/agent/models_fetch.rs
@@ -345,9 +345,22 @@ fn fetch_one_platform_models(
     };
     tracing::info!(platform = platform.as_str(), url = %url, "fetching platform models");
     let request = match platform.key_header() {
-        kigi_models::PlatformKeyHeader::Bearer => client
-            .get(&url)
-            .header("Authorization", format!("Bearer {}", bearer)),
+        kigi_models::PlatformKeyHeader::Bearer => {
+            let mut req = client
+                .get(&url)
+                .header("Authorization", format!("Bearer {}", bearer));
+            // An Anthropic listing reached with a Bearer key is the OAuth
+            // channel (claude-pro-max): the /v1/models endpoint requires
+            // anthropic-version, and the OAuth bearer needs the oauth beta.
+            // The OpenAI-listing Bearer platforms (xai-grok, api-key OpenAI
+            // rows) add neither, so their requests stay byte-identical.
+            if platform.listing() == kigi_models::ListingDialect::Anthropic {
+                req = req
+                    .header("anthropic-version", kigi_sampling_types::ANTHROPIC_VERSION)
+                    .header("anthropic-beta", kigi_sampling_types::ANTHROPIC_OAUTH_BETA);
+            }
+            req
+        }
         kigi_models::PlatformKeyHeader::XApiKey => client
             .get(&url)
             .header("x-api-key", bearer)
@@ -1106,6 +1119,118 @@ mod tests {
         );
     }
 
+    /// Claude Pro/Max OAuth fetch e2e (mock wire): `GET /v1/models?limit=1000`
+    /// gated on the OAuth `Authorization: Bearer` + the oauth `anthropic-beta`
+    /// (the OAuth listing contract) → anthropic listing → enriched from
+    /// models.dev "anthropic" → keyed `claude-pro-max/<id>` on the Messages
+    /// backend. The token is drawn from the claude-pro-max OAuth-session map,
+    /// NOT an x-api-key.
+    #[tokio::test(flavor = "multi_thread")]
+    #[serial_test::serial]
+    async fn claude_pro_max_oauth_listing_is_bearer_gated_and_keyed() {
+        let platform_server = wiremock::MockServer::start().await;
+        wiremock::Mock::given(wiremock::matchers::method("GET"))
+            .and(wiremock::matchers::path("/models"))
+            .and(wiremock::matchers::query_param("limit", "1000"))
+            // OAuth listing: Bearer token + the oauth beta + anthropic-version.
+            // NO x-api-key header (that is the API-key `anthropic` path).
+            .and(wiremock::matchers::header(
+                "Authorization",
+                "Bearer sk-ant-oat-session",
+            ))
+            // The oauth beta is comma-joined; wiremock's exact `header` matcher
+            // splits on commas, so assert both tokens via the multi-valued form.
+            .and(wiremock::matchers::headers(
+                "anthropic-beta",
+                vec!["claude-code-20250219", "oauth-2025-04-20"],
+            ))
+            .and(wiremock::matchers::header(
+                "anthropic-version",
+                "2023-06-01",
+            ))
+            .respond_with(wiremock::ResponseTemplate::new(200).set_body_json(
+                serde_json::json!({ "data": [
+                    {
+                        "id": "claude-opus-4-8",
+                        "display_name": "Claude Opus 4.8",
+                        "type": "model"
+                    }
+                ], "has_more": false }),
+            ))
+            .expect(1)
+            .mount(&platform_server)
+            .await;
+        let modelsdev_server = wiremock::MockServer::start().await;
+        wiremock::Mock::given(wiremock::matchers::method("GET"))
+            .and(wiremock::matchers::path("/api.json"))
+            .respond_with(wiremock::ResponseTemplate::new(200).set_body_json(
+                serde_json::json!({ "anthropic": { "models": {
+                    "claude-opus-4-8": {
+                        "limit": {"context": 1000000, "output": 128000},
+                        "tool_call": true
+                    }
+                }}}),
+            ))
+            .expect(1)
+            .mount(&modelsdev_server)
+            .await;
+        let cache_dir = tempfile::tempdir().unwrap();
+        let _base = kigi_test_support::EnvGuard::set(
+            kigi_models::CLAUDE_OAUTH_BASE_URL_ENV,
+            platform_server.uri(),
+        );
+        let _mdev = kigi_test_support::EnvGuard::set(
+            crate::agent::enrichment_fetch::MODELS_DEV_URL_ENV,
+            format!("{}/api.json", modelsdev_server.uri()),
+        );
+        let _mdev_cache = kigi_test_support::EnvGuard::set(
+            crate::agent::enrichment_fetch::MODELS_DEV_CACHE_DIR_ENV,
+            cache_dir.path(),
+        );
+
+        let endpoints = crate::agent::config::EndpointsConfig::default();
+        // The listing bearer comes from the claude-pro-max OAuth-session map,
+        // never a Kimi session (auth=None) or an API key (keys empty).
+        let mut oauth_tokens = OAuthSessionTokens::new();
+        oauth_tokens.insert(
+            kigi_models::PlatformId::ClaudeProMax,
+            "sk-ant-oat-session".to_string(),
+        );
+        let keys = crate::agent::models::PlatformApiKeys::default();
+        let result = tokio::task::spawn_blocking(move || {
+            fetch_platform_models_blocking(&endpoints, None, &oauth_tokens, &keys)
+        })
+        .await
+        .unwrap()
+        .expect("claude-pro-max oauth fetch must succeed");
+
+        assert_eq!(result.models.len(), 1);
+        let opus = &result.models[0];
+        assert_eq!(
+            opus.id.as_deref(),
+            Some("claude-pro-max/claude-opus-4-8"),
+            "the entry must key under the claude-pro-max platform"
+        );
+        assert_eq!(
+            opus.api_backend,
+            crate::sampling::ApiBackend::Messages,
+            "claude-pro-max speaks the Messages wire"
+        );
+        assert_eq!(
+            opus.auth_scheme, None,
+            "OAuth Bearer entries carry no XApiKey auth scheme"
+        );
+        assert_eq!(
+            opus.context_window.get(),
+            1_000_000,
+            "enrichment fills the context window from models.dev anthropic"
+        );
+        assert!(
+            !opus.supported_in_api,
+            "subscription (uses_oauth) models require the OAuth session"
+        );
+    }
+
     /// DeepSeek-cycle e2e: bare OpenAI-shape listing + enrichment efforts
     /// (high/max) produce ChatCompletions entries whose sampler config
     /// speaks the DeepSeek thinking dialect.
diff --git a/crates/codegen/kigi-shell/src/agent/subagent/mod.rs b/crates/codegen/kigi-shell/src/agent/subagent/mod.rs
index db5fa31..ecfd3f0 100644
--- a/crates/codegen/kigi-shell/src/agent/subagent/mod.rs
+++ b/crates/codegen/kigi-shell/src/agent/subagent/mod.rs
@@ -880,6 +880,14 @@ async fn read_parent_sampling_config(
             let auth_scheme = crate::agent::config::try_resolve_model_credentials(&cfg.model, None)
                 .map(|r| r.auth_scheme)
                 .unwrap_or_default();
+            // 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.
+            let anthropic_oauth = kigi_models::parse_managed_model_key(ctx.model_id.0.as_ref())
+                .is_some_and(|(platform, _)| {
+                    platform.oauth().is_some()
+                        && platform.wire_api() == kigi_models::PlatformWireApi::Messages
+                });
             let inherited = kigi_sampler::SamplerConfig {
                 api_key: creds.api_key,
                 base_url: cfg.base_url,
@@ -889,6 +897,7 @@ async fn read_parent_sampling_config(
                 top_p: cfg.top_p,
                 api_backend: cfg.api_backend,
                 auth_scheme,
+                anthropic_oauth,
                 chat_compat: cfg.chat_compat,
                 extra_headers,
                 context_window: cfg.context_window.get(),
diff --git a/crates/codegen/kigi-shell/src/auth/device_code.rs b/crates/codegen/kigi-shell/src/auth/device_code.rs
index e093163..1003331 100644
--- a/crates/codegen/kigi-shell/src/auth/device_code.rs
+++ b/crates/codegen/kigi-shell/src/auth/device_code.rs
@@ -198,8 +198,8 @@ async fn complete_device_code_login(
 /// Open `url` in the browser off-thread: `webbrowser::open` is synchronous and
 /// would stall the single-threaded TUI loop. Returns `true` on success so the
 /// caller can decide how to notify the user (eprintln on CLI, nothing on TUI
-/// where the URL is already rendered in the widget).
-async fn open_browser_detached(url: &str) -> bool {
+/// where the URL is already rendered in the widget). Shared with the PKCE flow.
+pub(super) async fn open_browser_detached(url: &str) -> bool {
     // Unit tests drive the full login flow against mock servers — their
     // fixture URLs must never reach a real browser.
     if cfg!(test) {
diff --git a/crates/codegen/kigi-shell/src/auth/flow.rs b/crates/codegen/kigi-shell/src/auth/flow.rs
index e6bb001..e0977c5 100644
--- a/crates/codegen/kigi-shell/src/auth/flow.rs
+++ b/crates/codegen/kigi-shell/src/auth/flow.rs
@@ -67,10 +67,11 @@ pub async fn run_auth_flow(
     run_auth_flow_inner(auth_manager, kimi_code_config, reauth, false, channels).await
 }
 
-/// Login flow for a GENERIC device-code OAuth provider (xai-grok): use a valid
-/// cached session unless re-authing, otherwise run the generic device flow
+/// Login flow for a GENERIC OAuth provider (xai-grok device-code,
+/// claude-pro-max PKCE-localhost): use a valid cached session unless re-authing,
+/// otherwise dispatch by `oauth.flow` to the device-code or PKCE-localhost login
 /// (persisting under the provider's own scope via `auth_manager`). Unlike the
-/// Kimi flow this does not run the silent-refresh dance — the device flow's
+/// Kimi flow this does not run the silent-refresh dance — the login's
 /// `AuthManager::update` persists a fresh token set directly.
 pub async fn run_oauth_provider_flow(
     auth_manager: &Arc<AuthManager>,
@@ -94,8 +95,96 @@ pub async fn run_oauth_provider_flow(
         return Ok((auth, false));
     }
     let mut channels = channels;
-    crate::auth::device_code::run_device_code_login_generic(oauth, auth_manager, &mut channels)
+    match oauth.flow {
+        kigi_models::OAuthFlow::DeviceCode => {
+            crate::auth::device_code::run_device_code_login_generic(
+                oauth,
+                auth_manager,
+                &mut channels,
+            )
+            .await
+        }
+        kigi_models::OAuthFlow::PkceLocalhost { redirect_port } => {
+            run_pkce_localhost_login(oauth, redirect_port, auth_manager, &mut channels).await
+        }
+    }
+}
+
+/// PKCE-localhost login (claude-pro-max): generate PKCE, present the browser
+/// authorize URL (TUI channel or stderr), open the browser, then await the code
+/// from EITHER the `127.0.0.1:{redirect_port}` loopback callback OR a manual
+/// paste (headless fallback). Exchange it at the token endpoint and persist.
+///
+/// SECURITY: the verifier / code / tokens are never logged; the loopback binds
+/// `127.0.0.1` only and validates `state` strictly.
+async fn run_pkce_localhost_login(
+    oauth: &'static kigi_models::OAuthConfig,
+    redirect_port: u16,
+    auth_manager: &Arc<AuthManager>,
+    channels: &mut Option<AuthChannels>,
+) -> anyhow::Result<(KimiAuth, bool)> {
+    use crate::auth::oauth_pkce;
+
+    let pkce = oauth_pkce::generate_pkce();
+    let redirect = oauth_pkce::redirect_uri(redirect_port);
+    let authorize_url = oauth_pkce::build_authorize_url(oauth, &redirect, &pkce);
+
+    let mut chans = channels.take();
+    if let Some(tx) = chans.as_mut().and_then(|c| c.url_tx.take()) {
+        // TUI: push the URL BEFORE opening the browser (never block the UI on a
+        // slow/headless browser launch).
+        let _ = tx.send(AuthUrlInfo {
+            url: authorize_url.clone(),
+            mode: AuthUrlMode::Device,
+        });
+        crate::auth::device_code::open_browser_detached(&authorize_url).await;
+    } else {
+        eprintln!();
+        eprintln!("To sign in to Claude Pro/Max, open this URL in your browser:");
+        eprintln!();
+        eprintln!("  {authorize_url}");
+        eprintln!();
+        if !crate::auth::device_code::open_browser_detached(&authorize_url).await {
+            eprintln!("  (Could not open the browser automatically — open the URL above.)");
+            eprintln!();
+        }
+        eprintln!("Waiting for the sign-in to complete...");
+    }
+
+    let code = await_pkce_code(redirect_port, &pkce, chans.as_mut()).await?;
+    let auth = oauth_pkce::exchange_code(oauth, &code, &pkce, &redirect).await?;
+    let auth = auth_manager
+        .update(auth)
         .await
+        .map_err(|e| anyhow::anyhow!("Failed to save credentials: {e}"))?;
+    Ok((auth, true))
+}
+
+/// Await the authorization code: the loopback callback is primary; when a TUI
+/// channel is present, a pasted code (redirect URL / `code#state` / bare code)
+/// is accepted concurrently as a headless fallback. State is validated in both
+/// arms (strict on the loopback, mismatch-rejecting on the paste).
+async fn await_pkce_code(
+    redirect_port: u16,
+    pkce: &crate::auth::oauth_pkce::PkceCodes,
+    channels: Option<&mut AuthChannels>,
+) -> anyhow::Result<String> {
+    use crate::auth::oauth_pkce;
+    match channels {
+        Some(ch) => {
+            tokio::select! {
+                code = oauth_pkce::await_loopback_code(redirect_port, &pkce.state) => code,
+                pasted = ch.code_rx.recv() => {
+                    let pasted = pasted
+                        .ok_or_else(|| anyhow::anyhow!("auth code channel closed before a code arrived"))?;
+                    let params = oauth_pkce::parse_manual_paste(&pasted)?;
+                    oauth_pkce::validate_pasted_state(&params, &pkce.state)?;
+                    Ok(params.code)
+                }
+            }
+        }
+        None => oauth_pkce::await_loopback_code(redirect_port, &pkce.state).await,
+    }
 }
 
 async fn run_auth_flow_inner(
diff --git a/crates/codegen/kigi-shell/src/auth/mod.rs b/crates/codegen/kigi-shell/src/auth/mod.rs
index 4068984..1f3b4fe 100644
--- a/crates/codegen/kigi-shell/src/auth/mod.rs
+++ b/crates/codegen/kigi-shell/src/auth/mod.rs
@@ -9,6 +9,7 @@ pub(crate) mod kimi_oauth;
 pub(crate) mod manager;
 mod model;
 pub(crate) mod oauth_device;
+pub(crate) mod oauth_pkce;
 pub(crate) mod oauth_registry;
 pub(crate) mod recovery;
 pub(crate) mod refresh;
diff --git a/crates/codegen/kigi-shell/src/auth/oauth_pkce.rs b/crates/codegen/kigi-shell/src/auth/oauth_pkce.rs
new file mode 100644
index 0000000..880a6e9
--- /dev/null
+++ b/crates/codegen/kigi-shell/src/auth/oauth_pkce.rs
@@ -0,0 +1,687 @@
+//! Generic authorization-code + PKCE (S256) OAuth wire with a `127.0.0.1`
+//! loopback callback, driven by a registry [`kigi_models::OAuthConfig`] whose
+//! `flow` is [`OAuthFlow::PkceLocalhost`] (claude-pro-max today).
+//!
+//! Shape (Pi `earendil-works/pi` `auth/oauth/anthropic.ts`):
+//! - `verifier = base64url(32 random bytes)`; `challenge = base64url(SHA-256(
+//!   verifier))`; `state = verifier`.
+//! - Browser opens `{auth_host}{device_path}?client_id&response_type=code&
+//!   scope&redirect_uri&state&code_challenge&code_challenge_method=S256`.
+//! - The code returns to a loopback listener on `127.0.0.1:{redirect_port}`
+//!   answering ONLY `/callback`, with STRICT `state` validation (a mismatch is
+//!   rejected — CSRF guard). A manual paste (redirect URL / `code#state` / bare
+//!   code) is accepted as a headless fallback.
+//! - Code → token exchange and refresh POST `{token_host}{token_path}` as JSON
+//!   (per `token_body`); the refresh token ROTATES.
+//!
+//! SECURITY: the verifier, authorization code, access token, and refresh token
+//! are NEVER logged (only non-secret events: authorize URL requested, callback
+//! received, token issued, token refreshed).
+
+use anyhow::Context;
+use base64::Engine;
+use kigi_models::{OAuthConfig, OAuthTokenBody};
+use serde::Deserialize;
+use sha2::{Digest, Sha256};
+
+use super::kimi_oauth::{RefreshError, TokenResponse};
+use super::model::KimiAuth;
+
+const CODE_GRANT_TYPE: &str = "authorization_code";
+const REFRESH_GRANT_TYPE: &str = "refresh_token";
+/// Refresh retry budget over the retryable statuses / network blips.
+const MAX_REFRESH_RETRIES: u32 = 3;
+/// HTTP statuses worth retrying a refresh for (parity with the device wire).
+const RETRYABLE_REFRESH_STATUSES: [u16; 5] = [429, 500, 502, 503, 504];
+
+/// PKCE secrets for one login attempt. `state == verifier` (Pi's convention:
+/// the state is the verifier, so a returned state binds the callback to this
+/// attempt AND doubles as the CSRF token).
+#[derive(Debug, Clone)]
+pub(crate) struct PkceCodes {
+    /// `code_verifier` — the 43-char base64url secret, sent at token exchange.
+    pub verifier: String,
+    /// `code_challenge = base64url(SHA-256(verifier))`, sent at authorize.
+    pub challenge: String,
+    /// `state` — equal to `verifier`; validated on the callback (CSRF guard).
+    pub state: String,
+}
+
+/// Generate PKCE S256 codes: `verifier = base64url(32 random bytes)`,
+/// `challenge = base64url(SHA-256(verifier))`, `state = verifier`.
+pub(crate) fn generate_pkce() -> PkceCodes {
+    use rand::RngCore;
+    let mut raw = [0u8; 32];
+    rand::rng().fill_bytes(&mut raw);
+    let verifier = base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(raw);
+    let digest = Sha256::digest(verifier.as_bytes());
+    let challenge = base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(digest);
+    PkceCodes {
+        state: verifier.clone(),
+        verifier,
+        challenge,
+    }
+}
+
+/// The loopback redirect URI for a PKCE-localhost provider.
+pub(crate) fn redirect_uri(redirect_port: u16) -> String {
+    format!("http://localhost:{redirect_port}/callback")
+}
+
+/// Build the browser authorize URL:
+/// `{auth_host}{device_path}?client_id&response_type=code&scope&redirect_uri&
+/// state&code_challenge&code_challenge_method=S256`.
+pub(crate) fn build_authorize_url(
+    cfg: &OAuthConfig,
+    redirect_uri: &str,
+    pkce: &PkceCodes,
+) -> String {
+    let base = format!("{}{}", cfg.auth_host.trim_end_matches('/'), cfg.device_path);
+    let query = url::form_urlencoded::Serializer::new(String::new())
+        .append_pair("client_id", cfg.client_id)
+        .append_pair("response_type", "code")
+        .append_pair("scope", cfg.scope)
+        .append_pair("redirect_uri", redirect_uri)
+        .append_pair("state", &pkce.state)
+        .append_pair("code_challenge", &pkce.challenge)
+        .append_pair("code_challenge_method", "S256")
+        .finish();
+    format!("{base}?{query}")
+}
+
+/// `code` + `state` extracted from a callback (loopback query OR manual paste).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) struct CallbackParams {
+    pub code: String,
+    pub state: Option<String>,
+}
+
+/// Parse `code`/`state` from the raw query string of a `/callback?…` request
+/// (e.g. `code=abc&state=xyz`). An `error=` param surfaces as an `Err`.
+pub(crate) fn parse_callback_query(query: &str) -> anyhow::Result<CallbackParams> {
+    let mut code = None;
+    let mut state = None;
+    let mut error = None;
+    for (k, v) in url::form_urlencoded::parse(query.as_bytes()) {
+        match k.as_ref() {
+            "code" => code = Some(v.into_owned()),
+            "state" => state = Some(v.into_owned()),
+            "error" => error = Some(v.into_owned()),
+            _ => {}
+        }
+    }
+    if let Some(error) = error {
+        anyhow::bail!("Authorization server returned an error: {error}");
+    }
+    let code = code.context("callback missing authorization code")?;
+    if code.is_empty() {
+        anyhow::bail!("callback authorization code was empty");
+    }
+    Ok(CallbackParams { code, state })
+}
+
+/// Parse a MANUAL paste (headless fallback). Accepts, in order:
+/// - a full redirect URL (`http://localhost:…/callback?code=…&state=…`),
+/// - a `code#state` pair (Anthropic's console shows this form),
+/// - a bare `code` (state then unknown → `None`, caller validation applies).
+pub(crate) fn parse_manual_paste(input: &str) -> anyhow::Result<CallbackParams> {
+    let trimmed = input.trim();
+    if trimmed.is_empty() {
+        anyhow::bail!("empty paste");
+    }
+    // Full redirect URL.
+    if trimmed.starts_with("http://") || trimmed.starts_with("https://") {
+        let url = url::Url::parse(trimmed).context("pasted value is not a valid URL")?;
+        return parse_callback_query(url.query().unwrap_or_default());
+    }
+    // `code#state`.
+    if let Some((code, state)) = trimmed.split_once('#') {
+        if code.is_empty() {
+            anyhow::bail!("pasted code was empty");
+        }
+        return Ok(CallbackParams {
+            code: code.to_owned(),
+            state: (!state.is_empty()).then(|| state.to_owned()),
+        });
+    }
+    // Bare code.
+    Ok(CallbackParams {
+        code: trimmed.to_owned(),
+        state: None,
+    })
+}
+
+/// STRICT state validation (CSRF guard): the callback `state` MUST be present
+/// AND equal to the expected value. A mismatch (or absence, when a paste has no
+/// state) is rejected — the flow NEVER proceeds on an unverified callback.
+pub(crate) fn validate_state(params: &CallbackParams, expected_state: &str) -> anyhow::Result<()> {
+    match params.state.as_deref() {
+        Some(state) if state == expected_state => Ok(()),
+        Some(_) => anyhow::bail!("OAuth state mismatch — rejecting callback (CSRF guard)"),
+        None => anyhow::bail!("OAuth callback carried no state — rejecting (CSRF guard)"),
+    }
+}
+
+/// State validation for a MANUAL paste (headless fallback): a present state
+/// MUST match (mismatch rejected — CSRF guard), but an ABSENT state is allowed
+/// — a bare-code paste is user-initiated (not a network-reachable callback), so
+/// there is no state to check. The loopback path uses the stricter
+/// [`validate_state`] (an absent state there IS rejected).
+pub(crate) fn validate_pasted_state(
+    params: &CallbackParams,
+    expected_state: &str,
+) -> anyhow::Result<()> {
+    match params.state.as_deref() {
+        Some(state) if state == expected_state => Ok(()),
+        Some(_) => anyhow::bail!("OAuth state mismatch — rejecting pasted code (CSRF guard)"),
+        None => Ok(()),
+    }
+}
+
+/// The token-endpoint URL (`{token_host}{token_path}`).
+fn token_url(cfg: &OAuthConfig) -> String {
+    format!("{}{}", cfg.token_host.trim_end_matches('/'), cfg.token_path)
+}
+
+/// POST the token endpoint with a JSON body, honoring `cfg.token_body`. Claude
+/// is JSON; a `Form`-bodied config would be handled by the device wire, so the
+/// PKCE path asserts JSON (never silently mis-encodes).
+async fn post_token_json(
+    cfg: &OAuthConfig,
+    body: serde_json::Value,
+) -> reqwest::Result<reqwest::Response> {
+    debug_assert!(
+        matches!(cfg.token_body, OAuthTokenBody::Json),
+        "PKCE token exchange expects a JSON token body"
+    );
+    crate::http::shared_client()
+        .post(token_url(cfg))
+        .header("Accept", "application/json")
+        .json(&body)
+        .send()
+        .await
+}
+
+/// Exchange an authorization `code` for a token set (JSON body):
+/// `{grant_type:"authorization_code", code, state, client_id, redirect_uri,
+/// code_verifier}`. Returns the materialized [`KimiAuth`].
+pub(crate) async fn exchange_code(
+    cfg: &OAuthConfig,
+    code: &str,
+    pkce: &PkceCodes,
+    redirect_uri: &str,
+) -> anyhow::Result<KimiAuth> {
+    let body = serde_json::json!({
+        "grant_type": CODE_GRANT_TYPE,
+        "code": code,
+        "state": pkce.state,
+        "client_id": cfg.client_id,
+        "redirect_uri": redirect_uri,
+        "code_verifier": pkce.verifier,
+    });
+    tracing::info!(
+        scope_key = cfg.scope_key,
+        "auth: exchanging code for token (pkce)"
+    );
+    let resp = post_token_json(cfg, body)
+        .await
+        .context("token exchange request failed")?;
+    let status = resp.status();
+    if !status.is_success() {
+        let body = resp.text().await.unwrap_or_default();
+        tracing::warn!(%status, scope_key = cfg.scope_key, "auth: code exchange failed (pkce)");
+        anyhow::bail!("Token exchange failed (HTTP {status}): {body}");
+    }
+    let tokens: TokenResponse = resp.json().await.context("malformed token payload")?;
+    tracing::info!(
+        scope_key = cfg.scope_key,
+        "auth: pkce code exchange succeeded"
+    );
+    Ok(tokens.into_auth())
+}
+
+/// `POST {token_host}{token_path}` with `grant_type=refresh_token` (JSON body).
+/// Claude ROTATES the refresh token, so the caller MUST persist the returned
+/// one. Retries the retryable statuses / network errors with exponential
+/// backoff; 401/403 returns immediately as [`RefreshError::Unauthorized`].
+pub(crate) async fn refresh_token(
+    cfg: &OAuthConfig,
+    refresh_token: &str,
+) -> Result<KimiAuth, RefreshError> {
+    let mut last_error = String::from("no attempt made");
+    for attempt in 0..MAX_REFRESH_RETRIES {
+        if attempt > 0 {
+            let backoff = std::time::Duration::from_secs(1 << (attempt - 1));
+            tracing::warn!(
+                attempt,
+                backoff_secs = backoff.as_secs(),
+                last_error = %last_error,
+                "auth: retrying token refresh (pkce)"
+            );
+            tokio::time::sleep(backoff).await;
+        }
+        tracing::info!(
+            attempt,
+            scope_key = cfg.scope_key,
+            "auth: token refresh attempt (pkce)"
+        );
+        let body = serde_json::json!({
+            "grant_type": REFRESH_GRANT_TYPE,
+            "client_id": cfg.client_id,
+            "refresh_token": refresh_token,
+        });
+        let resp = match post_token_json(cfg, body).await {
+            Ok(resp) => resp,
+            Err(e) => {
+                last_error = format!("network error: {e}");
+                continue;
+            }
+        };
+        let status = resp.status().as_u16();
+        let bytes = resp.bytes().await.unwrap_or_default();
+        if status == 401 || status == 403 {
+            let err: OAuthErrorBody = serde_json::from_slice(&bytes).unwrap_or_default();
+            return Err(RefreshError::Unauthorized {
+                status,
+                description: err
+                    .error_description
+                    .unwrap_or_else(|| "Token refresh unauthorized.".to_owned()),
+            });
+        }
+        if status == 200 {
+            return match serde_json::from_slice::<TokenResponse>(&bytes) {
+                Ok(tokens) => Ok(tokens.into_auth()),
+                Err(e) => Err(RefreshError::Fatal {
+                    status,
+                    description: format!("malformed token payload: {e}"),
+                }),
+            };
+        }
+        let err: OAuthErrorBody = serde_json::from_slice(&bytes).unwrap_or_default();
+        let description = err
+            .error_description
+            .unwrap_or_else(|| format!("Token refresh failed (HTTP {status})."));
+        if RETRYABLE_REFRESH_STATUSES.contains(&status) {
+            last_error = description;
+            continue;
+        }
+        return Err(RefreshError::Fatal {
+            status,
+            description,
+        });
+    }
+    Err(RefreshError::Exhausted { last_error })
+}
+
+#[derive(Deserialize, Default)]
+struct OAuthErrorBody {
+    #[serde(default)]
+    error_description: Option<String>,
+}
+
+/// Bind a loopback HTTP listener on `127.0.0.1:{redirect_port}` and wait for a
+/// single `GET /callback?code=…&state=…`, validating `state` STRICTLY against
+/// `expected_state` (mismatch → rejected). Returns the authorization code.
+///
+/// The listener answers ONLY `/callback`; any other path gets 404. It binds
+/// `127.0.0.1` (never `0.0.0.0`), so no non-loopback host can reach it.
+pub(crate) async fn await_loopback_code(
+    redirect_port: u16,
+    expected_state: &str,
+) -> anyhow::Result<String> {
+    let listener = tokio::net::TcpListener::bind(("127.0.0.1", redirect_port))
+        .await
+        .with_context(|| format!("could not bind loopback 127.0.0.1:{redirect_port}"))?;
+    tracing::info!(port = redirect_port, "auth: pkce loopback listener bound");
+    loop {
+        let (stream, _peer) = listener.accept().await.context("loopback accept failed")?;
+        match handle_loopback_conn(stream, expected_state).await {
+            LoopbackOutcome::Code(code) => return Ok(code),
+            LoopbackOutcome::Rejected(err) => return Err(err),
+            // Not the /callback GET (favicon, health probe): keep listening.
+            LoopbackOutcome::Ignore => continue,
+        }
+    }
+}
+
+enum LoopbackOutcome {
+    Code(String),
+    Rejected(anyhow::Error),
+    Ignore,
+}
+
+/// Read the request line of one loopback connection, answer with a small HTML
+/// page, and classify the outcome. STRICT: a `/callback` with a bad/missing
+/// state is [`LoopbackOutcome::Rejected`] (the browser sees an error page).
+async fn handle_loopback_conn(
+    mut stream: tokio::net::TcpStream,
+    expected_state: &str,
+) -> LoopbackOutcome {
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
+    // Read only enough for the request line — a GET has no body.
+    let mut buf = [0u8; 8192];
+    let n = match stream.read(&mut buf).await {
+        Ok(0) => return LoopbackOutcome::Ignore,
+        Ok(n) => n,
+        Err(_) => return LoopbackOutcome::Ignore,
+    };
+    let head = String::from_utf8_lossy(&buf[..n]);
+    let Some(request_line) = head.lines().next() else {
+        return LoopbackOutcome::Ignore;
+    };
+    // `GET /callback?code=…&state=… HTTP/1.1`
+    let mut parts = request_line.split_whitespace();
+    let (Some(method), Some(target)) = (parts.next(), parts.next()) else {
+        return LoopbackOutcome::Ignore;
+    };
+    if method != "GET" {
+        let _ = write_http(&mut stream, 405, "Method Not Allowed").await;
+        return LoopbackOutcome::Ignore;
+    }
+    let (path, query) = target.split_once('?').unwrap_or((target, ""));
+    if path != "/callback" {
+        let _ = write_http(&mut stream, 404, "Not Found").await;
+        return LoopbackOutcome::Ignore;
+    }
+
+    let result = parse_callback_query(query)
+        .and_then(|params| validate_state(&params, expected_state).map(|()| params.code));
+    match result {
+        Ok(code) => {
+            let _ = write_http(
+                &mut stream,
+                200,
+                "Signed in to Claude Pro/Max. You can close this window and return to kigi.",
+            )
+            .await;
+            let _ = stream.flush().await;
+            LoopbackOutcome::Code(code)
+        }
+        Err(e) => {
+            let _ = write_http(&mut stream, 400, "Login failed — return to kigi and retry.").await;
+            let _ = stream.flush().await;
+            LoopbackOutcome::Rejected(e)
+        }
+    }
+}
+
+/// Write a minimal HTTP/1.1 response with an HTML body.
+async fn write_http(
+    stream: &mut tokio::net::TcpStream,
+    status: u16,
+    message: &str,
+) -> std::io::Result<()> {
+    use tokio::io::AsyncWriteExt;
+    let reason = match status {
+        200 => "OK",
+        400 => "Bad Request",
+        404 => "Not Found",
+        405 => "Method Not Allowed",
+        _ => "Error",
+    };
+    let body = format!("<!doctype html><meta charset=utf-8><p>{message}</p>");
+    let response = format!(
+        "HTTP/1.1 {status} {reason}\r\nContent-Type: text/html; charset=utf-8\r\n\
+         Content-Length: {}\r\nConnection: close\r\n\r\n{body}",
+        body.len()
+    );
+    stream.write_all(response.as_bytes()).await
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use kigi_models::CLAUDE_OAUTH_CONFIG;
+    use wiremock::matchers::{body_string_contains, method, path};
+    use wiremock::{Mock, MockServer, ResponseTemplate};
+
+    /// A config pointed at a mock token host (copies Claude's client_id/scope/
+    /// paths but overrides the token host).
+    fn mock_cfg(token_host: &'static str) -> OAuthConfig {
+        OAuthConfig {
+            token_host,
+            ..CLAUDE_OAUTH_CONFIG
+        }
+    }
+
+    /// PKCE codes: verifier/challenge are non-empty base64url (no padding), the
+    /// challenge is the base64url SHA-256 of the verifier, and state == verifier.
+    #[test]
+    fn generate_pkce_produces_valid_s256_codes() {
+        let pkce = generate_pkce();
+        assert_eq!(pkce.state, pkce.verifier, "state must equal the verifier");
+        assert!(!pkce.verifier.is_empty() && !pkce.challenge.is_empty());
+        for s in [&pkce.verifier, &pkce.challenge] {
+            assert!(
+                s.chars()
+                    .all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_'),
+                "base64url (no pad) only: {s}"
+            );
+            assert!(!s.contains('='), "no padding: {s}");
+        }
+        // challenge == base64url(SHA-256(verifier)).
+        let expect = base64::engine::general_purpose::URL_SAFE_NO_PAD
+            .encode(Sha256::digest(pkce.verifier.as_bytes()));
+        assert_eq!(pkce.challenge, expect);
+        // Fresh entropy each call.
+        assert_ne!(pkce.verifier, generate_pkce().verifier);
+    }
+
+    /// The authorize URL carries the fixed params + the PKCE state and S256
+    /// challenge, and targets `claude.ai/oauth/authorize`.
+    #[test]
+    fn authorize_url_has_state_and_s256_challenge() {
+        let pkce = generate_pkce();
+        let redirect = redirect_uri(53692);
+        let url = build_authorize_url(&CLAUDE_OAUTH_CONFIG, &redirect, &pkce);
+        let parsed = url::Url::parse(&url).expect("valid URL");
+        assert_eq!(parsed.host_str(), Some("claude.ai"));
+        assert_eq!(parsed.path(), "/oauth/authorize");
+        let q: std::collections::HashMap<_, _> = parsed.query_pairs().into_owned().collect();
+        assert_eq!(q.get("response_type").map(String::as_str), Some("code"));
+        assert_eq!(
+            q.get("code_challenge_method").map(String::as_str),
+            Some("S256")
+        );
+        assert_eq!(
+            q.get("state").map(String::as_str),
+            Some(pkce.state.as_str())
+        );
+        assert_eq!(
+            q.get("code_challenge").map(String::as_str),
+            Some(pkce.challenge.as_str())
+        );
+        assert_eq!(
+            q.get("client_id").map(String::as_str),
+            Some(CLAUDE_OAUTH_CONFIG.client_id)
+        );
+        assert_eq!(
+            q.get("redirect_uri").map(String::as_str),
+            Some(redirect.as_str())
+        );
+        // The verifier itself must NEVER appear in the browser URL.
+        assert!(
+            !url.contains("code_verifier"),
+            "the verifier must not ride the authorize URL"
+        );
+    }
+
+    /// STRICT state validation: an exact match passes; a mismatch or an absent
+    /// state is REJECTED (CSRF guard — the flow must never proceed).
+    #[test]
+    fn state_validation_is_strict() {
+        let ok = CallbackParams {
+            code: "c".into(),
+            state: Some("expected".into()),
+        };
+        assert!(validate_state(&ok, "expected").is_ok());
+        let mismatch = CallbackParams {
+            code: "c".into(),
+            state: Some("attacker".into()),
+        };
+        assert!(
+            validate_state(&mismatch, "expected").is_err(),
+            "a state mismatch MUST be rejected"
+        );
+        let missing = CallbackParams {
+            code: "c".into(),
+            state: None,
+        };
+        assert!(
+            validate_state(&missing, "expected").is_err(),
+            "an absent state MUST be rejected"
+        );
+    }
+
+    /// A loopback `/callback` with the WRONG state is rejected end-to-end (the
+    /// listener returns an error, never a code) — the CSRF guard on the wire.
+    #[tokio::test]
+    async fn loopback_rejects_state_mismatch() {
+        // Ephemeral port: bind, learn the port, then drive a client at it.
+        let probe = tokio::net::TcpListener::bind(("127.0.0.1", 0))
+            .await
+            .unwrap();
+        let port = probe.local_addr().unwrap().port();
+        drop(probe);
+
+        let server = tokio::spawn(async move { await_loopback_code(port, "the-real-state").await });
+        // Give the listener a moment to bind.
+        tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+        // Attacker callback: valid code, WRONG state.
+        let _ = reqwest::get(format!(
+            "http://127.0.0.1:{port}/callback?code=stolen&state=wrong-state"
+        ))
+        .await;
+        let outcome = server.await.unwrap();
+        let err = outcome.expect_err("a state mismatch must be rejected, never yield a code");
+        assert!(err.to_string().contains("state mismatch"), "{err}");
+    }
+
+    /// A loopback `/callback` with the MATCHING state yields the code.
+    #[tokio::test]
+    async fn loopback_returns_code_on_valid_state() {
+        let probe = tokio::net::TcpListener::bind(("127.0.0.1", 0))
+            .await
+            .unwrap();
+        let port = probe.local_addr().unwrap().port();
+        drop(probe);
+
+        let server = tokio::spawn(async move { await_loopback_code(port, "good-state").await });
+        tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+        let _ = reqwest::get(format!(
+            "http://127.0.0.1:{port}/callback?code=auth-code-123&state=good-state"
+        ))
+        .await;
+        let code = server.await.unwrap().expect("valid state yields the code");
+        assert_eq!(code, "auth-code-123");
+    }
+
+    /// Manual-paste parsing: full redirect URL, `code#state`, and bare code.
+    #[test]
+    fn manual_paste_parses_all_three_forms() {
+        let from_url =
+            parse_manual_paste("http://localhost:53692/callback?code=abc123&state=st-9").unwrap();
+        assert_eq!(from_url.code, "abc123");
+        assert_eq!(from_url.state.as_deref(), Some("st-9"));
+
+        let from_hash = parse_manual_paste("abc123#st-9").unwrap();
+        assert_eq!(from_hash.code, "abc123");
+        assert_eq!(from_hash.state.as_deref(), Some("st-9"));
+
+        let bare = parse_manual_paste("  abc123  ").unwrap();
+        assert_eq!(bare.code, "abc123");
+        assert_eq!(bare.state, None);
+
+        assert!(parse_manual_paste("").is_err());
+        // A pasted redirect that carries an error param surfaces the error.
+        assert!(parse_manual_paste("http://localhost/callback?error=access_denied").is_err());
+    }
+
+    /// Code → token exchange: JSON body carries the grant + verifier, response
+    /// materializes a `KimiAuth` with the rotating refresh token.
+    #[tokio::test]
+    async fn exchange_code_posts_json_and_returns_auth() {
+        let server = MockServer::start().await;
+        let host: &'static str = Box::leak(server.uri().into_boxed_str());
+        Mock::given(method("POST"))
+            .and(path("/v1/oauth/token"))
+            .and(body_string_contains(
+                "\"grant_type\":\"authorization_code\"",
+            ))
+            .and(body_string_contains("\"code\":\"auth-code-xyz\""))
+            .and(body_string_contains("\"code_verifier\""))
+            .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
+                "access_token": "sk-ant-oat-new",
+                "refresh_token": "sk-ant-ort-new",
+                "expires_in": 3600,
+                "token_type": "bearer",
+            })))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let cfg = mock_cfg(host);
+        let pkce = generate_pkce();
+        let auth = exchange_code(&cfg, "auth-code-xyz", &pkce, &redirect_uri(53692))
+            .await
+            .unwrap();
+        assert_eq!(auth.key, "sk-ant-oat-new");
+        assert_eq!(auth.refresh_token.as_deref(), Some("sk-ant-ort-new"));
+        assert_eq!(auth.expires_in, Some(3600));
+    }
+
+    /// Refresh rotates the refresh token (JSON body, refresh grant).
+    #[tokio::test]
+    async fn refresh_rotates_refresh_token() {
+        let server = MockServer::start().await;
+        let host: &'static str = Box::leak(server.uri().into_boxed_str());
+        Mock::given(method("POST"))
+            .and(path("/v1/oauth/token"))
+            .and(body_string_contains("\"grant_type\":\"refresh_token\""))
+            .and(body_string_contains("\"refresh_token\":\"ort-old\""))
+            .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
+                "access_token": "oat-fresh",
+                "refresh_token": "ort-rotated",
+                "expires_in": 3600,
+            })))
+            .expect(1)
+            .mount(&server)
+            .await;
+        let auth = refresh_token(&mock_cfg(host), "ort-old").await.unwrap();
+        assert_eq!(auth.key, "oat-fresh");
+        assert_eq!(
+            auth.refresh_token.as_deref(),
+            Some("ort-rotated"),
+            "the rotated refresh token must be adopted"
+        );
+    }
+
+    /// A 401 on refresh maps to Unauthorized (drives the permanent-failure path).
+    #[tokio::test]
+    async fn refresh_401_maps_to_unauthorized() {
+        let server = MockServer::start().await;
+        let host: &'static str = Box::leak(server.uri().into_boxed_str());
+        Mock::given(method("POST"))
+            .and(path("/v1/oauth/token"))
+            .respond_with(
+                ResponseTemplate::new(401)
+                    .set_body_json(serde_json::json!({ "error_description": "refresh revoked" })),
+            )
+            .expect(1)
+            .mount(&server)
+            .await;
+        let err = refresh_token(&mock_cfg(host), "ort-dead")
+            .await
+            .unwrap_err();
+        match err {
+            RefreshError::Unauthorized {
+                status,
+                description,
+            } => {
+                assert_eq!(status, 401);
+                assert_eq!(description, "refresh revoked");
+            }
+            other => panic!("expected Unauthorized, got {other:?}"),
+        }
+    }
+}
diff --git a/crates/codegen/kigi-shell/src/auth/oauth_registry.rs b/crates/codegen/kigi-shell/src/auth/oauth_registry.rs
index aa7b8bc..0ca3af6 100644
--- a/crates/codegen/kigi-shell/src/auth/oauth_registry.rs
+++ b/crates/codegen/kigi-shell/src/auth/oauth_registry.rs
@@ -141,6 +141,52 @@ mod tests {
             .expect("xai-grok carries an OAuthConfig")
     }
 
+    fn claude_oauth() -> &'static kigi_models::OAuthConfig {
+        kigi_models::PlatformId::ClaudeProMax
+            .oauth()
+            .expect("claude-pro-max carries an OAuthConfig")
+    }
+
+    /// A `claude-pro-max/<model>` turn resolves to the process-global pooled
+    /// claude-pro-max manager (its OWN `oauth/claude-pro-max` scope), NEVER the
+    /// primary Kimi manager — the same leak-safe routing as xai-grok, and a
+    /// DISTINCT pool entry from the xai manager.
+    #[tokio::test]
+    async fn claude_pro_max_model_resolves_to_its_own_manager_not_kimi() {
+        let (_kd, kimi) = primary_with_token("kimi-tok");
+        let home = tempfile::tempdir().unwrap();
+        let resolved =
+            manager_for_model(home.path(), "claude-pro-max/claude-opus-4-8", Some(&kimi))
+                .expect("claude-pro-max model resolves to its pooled manager");
+        assert!(
+            !Arc::ptr_eq(&resolved, &kimi),
+            "claude-pro-max must NOT resolve to the Kimi manager"
+        );
+        assert!(
+            Arc::ptr_eq(&resolved, &global_manager_for(home.path(), claude_oauth())),
+            "claude-pro-max must resolve to its OWN process-global pooled manager"
+        );
+        // And it is a DIFFERENT manager than xai-grok's pooled one.
+        assert!(
+            !Arc::ptr_eq(&resolved, &global_manager_for(home.path(), xai_oauth())),
+            "claude-pro-max and xai-grok must not share a pooled manager"
+        );
+    }
+
+    /// Fail-fast (no Kimi fallback): a claude-pro-max key with a Kimi primary
+    /// never yields the Kimi session token — it draws from the claude pool (its
+    /// own token, or `None`), so the Kimi bearer can never reach api.anthropic.
+    #[tokio::test]
+    async fn session_key_for_claude_pro_max_is_never_the_kimi_primary() {
+        let (_kd, kimi) = primary_with_token("kimi-tok");
+        let home = tempfile::tempdir().unwrap();
+        assert_ne!(
+            session_key_for_model(home.path(), "claude-pro-max/claude-opus-4-8", Some(&kimi)),
+            Some("kimi-tok".to_string()),
+            "a claude-pro-max model must never receive the primary Kimi session token"
+        );
+    }
+
     /// A non-OAuth managed key (moonshot-cn/…) and an unprefixed bare id both
     /// route to the primary Kimi manager — the Kimi / first-party path is
     /// untouched and never consults the pool (no runtime needed).
diff --git a/crates/codegen/kigi-shell/src/auth/refresh/generic_refresher.rs b/crates/codegen/kigi-shell/src/auth/refresh/generic_refresher.rs
index eff9be0..cc41249 100644
--- a/crates/codegen/kigi-shell/src/auth/refresh/generic_refresher.rs
+++ b/crates/codegen/kigi-shell/src/auth/refresh/generic_refresher.rs
@@ -9,12 +9,12 @@
 
 use std::sync::Arc;
 
-use kigi_models::OAuthConfig;
+use kigi_models::{OAuthConfig, OAuthTokenBody};
 
 use crate::auth::error::RefreshTokenFailedReason;
 use crate::auth::kimi_oauth::RefreshError;
 use crate::auth::manager::RefreshReason;
-use crate::auth::oauth_device::{self};
+use crate::auth::{oauth_device, oauth_pkce};
 
 use super::{AuthSnapshot, RefreshOutcome, TokenRefresher};
 
@@ -104,7 +104,14 @@ impl TokenRefresher for GenericDeviceRefresher {
             "auth: sending refresh_token grant (generic oauth)"
         );
 
-        match oauth_device::refresh_token(self.cfg, &refresh_token).await {
+        // Refresh over the provider's token-body encoding: xai's endpoint is
+        // form-encoded (device wire); Claude's is JSON (PKCE wire). Both return
+        // the same `Result<KimiAuth, RefreshError>`.
+        let wire_result = match self.cfg.token_body {
+            OAuthTokenBody::Form => oauth_device::refresh_token(self.cfg, &refresh_token).await,
+            OAuthTokenBody::Json => oauth_pkce::refresh_token(self.cfg, &refresh_token).await,
+        };
+        match wire_result {
             Ok(new_auth) => {
                 kigi_log::unified_log::info(
                     "auth.refresh.token_rotated",
diff --git a/crates/codegen/kigi-shell/src/session/acp_session_impl/sampler_turn.rs b/crates/codegen/kigi-shell/src/session/acp_session_impl/sampler_turn.rs
index 60cc8ff..233d038 100644
--- a/crates/codegen/kigi-shell/src/session/acp_session_impl/sampler_turn.rs
+++ b/crates/codegen/kigi-shell/src/session/acp_session_impl/sampler_turn.rs
@@ -259,6 +259,21 @@ impl SessionActor {
             .and_then(|(platform, _)| platform.oauth())
             .is_some()
     }
+    /// Whether `model` routes to the Claude Pro/Max OAuth-Messages platform
+    /// (claude-pro-max) — the gate for the sampler's OAuth Messages adaptation
+    /// (identity headers + "You are Claude Code" system prefix). A generic-OAuth
+    /// platform speaking the Messages wire; every other model (incl. xai-grok,
+    /// which is ChatCompletions) returns `false`, keeping the API-key Anthropic
+    /// / MiniMax Messages requests byte-identical.
+    fn model_is_anthropic_oauth(&self, model: &str) -> bool {
+        let managed_key = self.managed_key_for_model(model);
+        kigi_models::parse_managed_model_key(managed_key.as_deref().unwrap_or(model)).is_some_and(
+            |(platform, _)| {
+                platform.oauth().is_some()
+                    && platform.wire_api() == kigi_models::PlatformWireApi::Messages
+            },
+        )
+    }
     /// LEAK guard for the stamped aux paths (auto-mode classifier, image
     /// describe). After [`crate::agent::config::stamp_session_local_sampler_fields`]
     /// has copied the SESSION model's `bearer_resolver` onto an aux
@@ -365,6 +380,9 @@ impl SessionActor {
         } else {
             None
         };
+        // Claude Pro/Max OAuth Messages adaptation for THIS turn's model
+        // (captured before `cfg.model` is moved into the struct below).
+        let anthropic_oauth = self.model_is_anthropic_oauth(&cfg.model);
         let auth_scheme = model_facts.auth_scheme;
         let mut extra_headers = cfg.extra_headers;
         crate::agent::config::inject_url_derived_headers(
@@ -405,6 +423,7 @@ impl SessionActor {
             top_p: cfg.top_p,
             api_backend: cfg.api_backend,
             auth_scheme,
+            anthropic_oauth,
             chat_compat: cfg.chat_compat,
             extra_headers,
             context_window: cfg.context_window.get(),
diff --git a/crates/codegen/kigi-shell/src/session/acp_session_tests/auth_error_no_retry_tests.rs b/crates/codegen/kigi-shell/src/session/acp_session_tests/auth_error_no_retry_tests.rs
index 0ce2311..da7a0a9 100644
--- a/crates/codegen/kigi-shell/src/session/acp_session_tests/auth_error_no_retry_tests.rs
+++ b/crates/codegen/kigi-shell/src/session/acp_session_tests/auth_error_no_retry_tests.rs
@@ -849,6 +849,7 @@ async fn set_session_model_invalidates_byok_memo_for_same_model_id() {
                 api_backend: crate::sampling::ApiBackend::ChatCompletions,
                 chat_compat: Default::default(),
                 auth_scheme: Default::default(),
+                anthropic_oauth: false,
                 extra_headers: Default::default(),
                 context_window: 256_000,
                 force_http1: false,
diff --git a/crates/codegen/kigi-shell/src/session/acp_session_tests/cancel_running_task_tests.rs b/crates/codegen/kigi-shell/src/session/acp_session_tests/cancel_running_task_tests.rs
index e9155e7..ad60b01 100644
--- a/crates/codegen/kigi-shell/src/session/acp_session_tests/cancel_running_task_tests.rs
+++ b/crates/codegen/kigi-shell/src/session/acp_session_tests/cancel_running_task_tests.rs
@@ -46,6 +46,7 @@ async fn persist_ack_waits_for_disk_flush_before_success() {
                 api_backend: Default::default(),
                 chat_compat: Default::default(),
                 auth_scheme: Default::default(),
+                anthropic_oauth: false,
                 extra_headers: Default::default(),
                 context_window: 100_000,
                 force_http1: false,
@@ -342,6 +343,7 @@ async fn first_turn_memory_injection_persists_to_chat_history() {
                 api_backend: Default::default(),
                 chat_compat: Default::default(),
                 auth_scheme: Default::default(),
+                anthropic_oauth: false,
                 context_window: 100_000,
                 force_http1: false,
                 max_retries: None,
@@ -472,6 +474,7 @@ async fn first_turn_memory_injection_disabled_does_not_persist_to_chat_history()
                 api_backend: Default::default(),
                 chat_compat: Default::default(),
                 auth_scheme: Default::default(),
+                anthropic_oauth: false,
                 context_window: 100_000,
                 force_http1: false,
                 max_retries: None,
@@ -1740,6 +1743,7 @@ async fn cancel_propagates_to_sampler_handle_so_no_further_emission() {
                 api_backend: kigi_sampler::ApiBackend::Responses,
                 chat_compat: Default::default(),
                 auth_scheme: Default::default(),
+                anthropic_oauth: false,
                 extra_headers: Default::default(),
                 context_window: 100_000,
                 force_http1: false,
diff --git a/crates/codegen/kigi-shell/src/session/helpers/session_compact.rs b/crates/codegen/kigi-shell/src/session/helpers/session_compact.rs
index 0cf7dbf..58d2727 100644
--- a/crates/codegen/kigi-shell/src/session/helpers/session_compact.rs
+++ b/crates/codegen/kigi-shell/src/session/helpers/session_compact.rs
@@ -1590,6 +1590,7 @@ mod reasoning_compaction_regression_tests {
             api_backend: ApiBackend::ChatCompletions,
             chat_compat: Default::default(),
             auth_scheme: Default::default(),
+            anthropic_oauth: false,
             extra_headers: Default::default(),
             context_window: 256_000,
             force_http1: false,
diff --git a/crates/codegen/kigi-shell/src/test_support/lsp_runtime.rs b/crates/codegen/kigi-shell/src/test_support/lsp_runtime.rs
index 0786b8b..3e10b0c 100644
--- a/crates/codegen/kigi-shell/src/test_support/lsp_runtime.rs
+++ b/crates/codegen/kigi-shell/src/test_support/lsp_runtime.rs
@@ -46,6 +46,7 @@ pub(crate) fn ctx_with_toggle(toggle: HashMap<String, bool>) -> SubagentSpawnCon
             api_backend: Default::default(),
             chat_compat: Default::default(),
             auth_scheme: Default::default(),
+            anthropic_oauth: false,
             extra_headers: Default::default(),
             context_window: 256_000,
             force_http1: false,
diff --git a/crates/codegen/kigi-shell/tests/common/mod.rs b/crates/codegen/kigi-shell/tests/common/mod.rs
index c2f7217..1cfe592 100644
--- a/crates/codegen/kigi-shell/tests/common/mod.rs
+++ b/crates/codegen/kigi-shell/tests/common/mod.rs
@@ -38,6 +38,7 @@ pub fn test_sampler_config(
         top_p: None,
         api_backend,
         auth_scheme: Default::default(),
+        anthropic_oauth: false,
         chat_compat: Default::default(),
         extra_headers: extra_headers
             .iter()
diff --git a/crates/codegen/kigi-tui/src/app/app_view.rs b/crates/codegen/kigi-tui/src/app/app_view.rs
index 6ae6233..dde44fd 100644
--- a/crates/codegen/kigi-tui/src/app/app_view.rs
+++ b/crates/codegen/kigi-tui/src/app/app_view.rs
@@ -6894,7 +6894,7 @@ pub(crate) mod tests {
     #[test]
     fn pending_menu_items_lists_interactive_methods_plus_quit() {
         let items = pending_menu_items(&fresh_user_auth_methods(), None);
-        assert_eq!(items.len(), 27, "26 login rows + Quit, got {items:?}");
+        assert_eq!(items.len(), 28, "27 login rows + Quit, got {items:?}");
         assert!(
             matches!(&items[0], PendingMenuItem::Login { label } if label == "Kimi Code (OAuth)"),
             "row 0 must be the OAuth login, got {:?}",
@@ -6905,22 +6905,27 @@ pub(crate) mod tests {
             "row 1 must be the xai-grok OAuth login (interactive, after kimi-code), got {:?}",
             items[1]
         );
+        assert!(
+            matches!(&items[2], PendingMenuItem::Login { label } if label == "Claude Pro/Max (subscription) (OAuth)"),
+            "row 2 must be the claude-pro-max OAuth login (after xai-grok), got {:?}",
+            items[2]
+        );
         assert_eq!(
-            items[2],
+            items[3],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::MoonshotCn),
                 label: "Moonshot Open Platform (API key \u{b7} moonshot.cn)".into(),
             }
         );
         assert_eq!(
-            items[3],
+            items[4],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::MoonshotAi),
                 label: "Moonshot Open Platform (API key \u{b7} moonshot.ai)".into(),
             }
         );
         assert_eq!(
-            items[4],
+            items[5],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::OpenAi),
                 label: "OpenAI (API key)".into(),
@@ -6928,153 +6933,153 @@ pub(crate) mod tests {
             "new registry rows must appear in the picker with zero TUI changes"
         );
         assert_eq!(
-            items[5],
+            items[6],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Anthropic),
                 label: "Anthropic (API key)".into(),
             }
         );
         assert_eq!(
-            items[6],
+            items[7],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::DeepSeek),
                 label: "DeepSeek (API key)".into(),
             }
         );
         assert_eq!(
-            items[7],
+            items[8],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Groq),
                 label: "Groq (API key)".into(),
             }
         );
         assert_eq!(
-            items[8],
+            items[9],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Mistral),
                 label: "Mistral (API key)".into(),
             }
         );
         assert_eq!(
-            items[9],
+            items[10],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Fireworks),
                 label: "Fireworks AI (API key)".into(),
             }
         );
         assert_eq!(
-            items[10],
+            items[11],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Google),
                 label: "Google Gemini (API key)".into(),
             }
         );
         assert_eq!(
-            items[11],
+            items[12],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::OpenRouter),
                 label: "OpenRouter (API key)".into(),
             }
         );
         assert_eq!(
-            items[12],
+            items[13],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Together),
                 label: "Together AI (API key)".into(),
             }
         );
         assert_eq!(
-            items[13],
+            items[14],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Cerebras),
                 label: "Cerebras (API key)".into(),
             }
         );
         assert_eq!(
-            items[14],
+            items[15],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Nvidia),
                 label: "NVIDIA NIM (API key)".into(),
             }
         );
         assert_eq!(
-            items[15],
+            items[16],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Vercel),
                 label: "Vercel AI Gateway (API key)".into(),
             }
         );
         assert_eq!(
-            items[16],
+            items[17],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Xai),
                 label: "xAI (Grok) (API key)".into(),
             }
         );
         assert_eq!(
-            items[17],
+            items[18],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::QwenTokenPlan),
                 label: "Qwen Token Plan (API key)".into(),
             }
         );
         assert_eq!(
-            items[18],
+            items[19],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::QwenTokenPlanCn),
                 label: "Qwen Token Plan China (API key)".into(),
             }
         );
         assert_eq!(
-            items[19],
+            items[20],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::KimiCoding),
                 label: "Kimi For Coding (API key)".into(),
             }
         );
         assert_eq!(
-            items[20],
+            items[21],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Zai),
                 label: "Z.AI (API key)".into(),
             }
         );
         assert_eq!(
-            items[21],
+            items[22],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::ZaiCodingCn),
                 label: "Z.AI Coding China (API key)".into(),
             }
         );
         assert_eq!(
-            items[22],
+            items[23],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Xiaomi),
                 label: "Xiaomi MiMo (API key)".into(),
             }
         );
         assert_eq!(
-            items[23],
+            items[24],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::XiaomiTokenPlanCn),
                 label: "Xiaomi Token Plan China (API key)".into(),
             }
         );
         assert_eq!(
-            items[24],
+            items[25],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::Minimax),
                 label: "MiniMax (API key)".into(),
             }
         );
         assert_eq!(
-            items[25],
+            items[26],
             PendingMenuItem::ApiKey {
                 target: PlatformLogin(kigi_shell::models::PlatformId::MinimaxCn),
                 label: "MiniMax China (API key)".into(),
             }
         );
-        assert_eq!(items[26], PendingMenuItem::Quit);
+        assert_eq!(items[27], PendingMenuItem::Quit);
         // The non-interactive methods must never appear as rows.
         let byok = kigi_shell::agent::auth_method::build_auth_methods(
             kigi_shell::agent::auth_method::AuthMethodsBuildInputs {
@@ -7085,8 +7090,8 @@ pub(crate) mod tests {
         );
         assert_eq!(
             pending_menu_items(&byok.methods, None).len(),
-            27,
-            "xai.api_key / cached_token must not add rows (26 login rows + Quit)"
+            28,
+            "xai.api_key / cached_token must not add rows (27 login rows + Quit)"
         );
     }
     /// Startup lands on the picker only when there is a real choice: the
@@ -7108,7 +7113,9 @@ pub(crate) mod tests {
         app.auth_state = AuthState::Pending { error: None };
         app.welcome_prompt_focused = false;
         // Interactive OAuth logins come first: row 0 (kimi-code), row 1
-        // (xai-grok); the first API-key row (moonshot-cn) is now row 2.
+        // (xai-grok), row 2 (claude-pro-max); the first API-key row
+        // (moonshot-cn) is now row 3, so four Downs land on it.
+        app.handle_input(&key_event(KeyCode::Down, KeyModifiers::NONE));
         app.handle_input(&key_event(KeyCode::Down, KeyModifiers::NONE));
         app.handle_input(&key_event(KeyCode::Down, KeyModifiers::NONE));
         app.handle_input(&key_event(KeyCode::Down, KeyModifiers::NONE));
@@ -7120,7 +7127,7 @@ pub(crate) mod tests {
                     kigi_shell::models::PlatformId::MoonshotCn
                 )))
             ),
-            "Enter on row 1 must open moonshot-cn key entry, got {outcome:?}"
+            "Enter on the moonshot-cn row must open its key entry, got {outcome:?}"
         );
         // 'l' is muscle-memory for the first (OAuth) row regardless of the
         // arrow selection.
diff --git a/crates/codegen/kigi-tui/src/views/welcome/mod.rs b/crates/codegen/kigi-tui/src/views/welcome/mod.rs
index a7aaeec..45c4233 100644
--- a/crates/codegen/kigi-tui/src/views/welcome/mod.rs
+++ b/crates/codegen/kigi-tui/src/views/welcome/mod.rs
@@ -2106,6 +2106,14 @@ mod tests {
         // lists ~20 platforms); this asserts content coverage, not fit.
         let text = render_done_text_h(&params, 72);
         assert!(text.contains("Kimi Code (OAuth)"), "{text}");
+        assert!(
+            text.contains("xAI Grok (subscription) (OAuth)"),
+            "the xai-grok interactive OAuth login row must render: {text}"
+        );
+        assert!(
+            text.contains("Claude Pro/Max (subscription) (OAuth)"),
+            "the claude-pro-max interactive OAuth login row must render: {text}"
+        );
         assert!(
             text.contains("Moonshot Open Platform (API key \u{b7} moonshot.cn)"),
             "{text}"