fix(model-fetch): support /models for Anthropic-compat subpath providers

Providers like DeepSeek, Kimi, Zhipu GLM and MiniMax expose the
Anthropic-compatible API on a subpath (e.g. /anthropic) while the
OpenAI-style /models endpoint lives at the API root. The previous
heuristic blindly appended /v1/models to the Base URL, so every such
provider returned 404 and the UI mislabeled it as "provider does not
support fetching models".

Backend now generates a candidate list and tries them in order:
preset override -> baseURL /v1/models -> stripped-subpath /v1/models ->
stripped-subpath /models. Non-404/405 responses (auth, network) stop
immediately so we never retry against hostile status codes. Known
compat suffixes are kept in a length-descending constant so the
longest match wins; response bodies are truncated to 512 chars to
avoid HTML 404 pages bloating the error string.

Preset type gains an optional modelsUrl (DeepSeek points at
https://api.deepseek.com/models). Frontend threads the override
through fetchModelsForConfig when the current Base URL still matches
the preset default. A new fetchModelsEndpointNotFound i18n key
replaces the misleading "not supported" toast for exhausted-candidate
and 404/405 cases (zh/en/ja).

src/components/providers/forms/ClaudeFormFields.tsx

@@ -50,7 +50,10 @@ import type {
   ClaudeApiFormat,
   ClaudeApiKeyField,
 } from "@/types";
-import type { TemplateValueConfig } from "@/config/claudeProviderPresets";
+import {
+  providerPresets,
+  type TemplateValueConfig,
+} from "@/config/claudeProviderPresets";
 
 interface EndpointCandidate {
   url: string;
@@ -212,8 +215,16 @@ export function ClaudeFormFields({
       });
       return;
     }
+    // 当 baseURL 仍是某预设的默认值时，优先使用预设上的 modelsUrl 覆写
+    // 避免多走一次失败的候选请求（如 DeepSeek 把 /models 挂在根，而不是 /anthropic 子路径下）
+    const matchedPreset = providerPresets.find((p) => {
+      const env = (p.settingsConfig as { env?: Record<string, string> })?.env;
+      return env?.ANTHROPIC_BASE_URL === baseUrl;
+    });
+    const modelsUrl = matchedPreset?.modelsUrl;
+
     setIsFetchingModels(true);
-    fetchModelsForConfig(baseUrl, apiKey, isFullUrl)
+    fetchModelsForConfig(baseUrl, apiKey, isFullUrl, modelsUrl)
       .then((models) => {
         setFetchedModels(models);
         if (models.length === 0) {

src/config/claudeProviderPresets.ts

@@ -66,6 +66,10 @@ export interface ProviderPreset {
 
   // 是否在 UI 中隐藏该预设（预设仍存在，仅不在列表中显示）
   hidden?: boolean;
+
+  // 获取模型列表使用的完整 URL（覆写自动候选逻辑）
+  // 缺省时后端基于 baseURL 自动尝试 /v1/models、/models 以及剥离已知兼容子路径后的变体。
+  modelsUrl?: string;
 }
 
 export const providerPresets: ProviderPreset[] = [
@@ -136,6 +140,8 @@ export const providerPresets: ProviderPreset[] = [
       },
     },
     category: "cn_official",
+    // Anthropic 兼容层挂在 /anthropic 子路径；/models 是根上独立端点
+    modelsUrl: "https://api.deepseek.com/models",
     icon: "deepseek",
     iconColor: "#1E88E5",
   },

src/i18n/locales/en.json

@@ -874,6 +874,7 @@
     "fetchModelsNeedConfig": "Please fill in API endpoint and API Key first",
     "fetchModelsAuthFailed": "API Key is invalid or lacks permission",
     "fetchModelsNotSupported": "This provider does not support fetching model list",
+    "fetchModelsEndpointNotFound": "No reachable models endpoint found. Please check the Base URL or confirm whether the provider exposes this API.",
     "fetchModelsTimeout": "Request timed out, please check network connection"
   },
   "copilot": {

src/i18n/locales/ja.json

@@ -874,6 +874,7 @@
     "fetchModelsNeedConfig": "先に API エンドポイントと API Key を入力してください",
     "fetchModelsAuthFailed": "API Key が無効か、権限がありません",
     "fetchModelsNotSupported": "このプロバイダーはモデル一覧の取得に対応していません",
+    "fetchModelsEndpointNotFound": "利用可能なモデル一覧エンドポイントが見つかりません。Base URL を確認するか、プロバイダーが該当 API を公開しているかご確認ください",
     "fetchModelsTimeout": "リクエストがタイムアウトしました。ネットワーク接続を確認してください"
   },
   "copilot": {

src/i18n/locales/zh.json

@@ -874,6 +874,7 @@
     "fetchModelsNeedConfig": "请先填写 API 端点和 API Key",
     "fetchModelsAuthFailed": "API Key 无效或无权限",
     "fetchModelsNotSupported": "该供应商不支持获取模型列表",
+    "fetchModelsEndpointNotFound": "未找到可用的模型列表端点，请检查 Base URL 或确认供应商是否开放该接口",
     "fetchModelsTimeout": "请求超时，请检查网络连接"
   },
   "copilot": {

src/lib/api/model-fetch.ts

@@ -10,15 +10,21 @@ export interface FetchedModel {
 /**
  * 从供应商获取可用模型列表
  *
- * 使用 OpenAI 兼容的 GET /v1/models 端点。
- * 主要面向第三方聚合站（硅基流动、OpenRouter 等）。
+ * 使用 OpenAI 兼容的 GET /v1/models 端点。优先用 `modelsUrl` 精确覆写；
+ * 否则后端会对 baseURL 生成候选列表并按序尝试（含"剥离 /anthropic 等兼容子路径"兜底）。
  */
 export async function fetchModelsForConfig(
   baseUrl: string,
   apiKey: string,
   isFullUrl?: boolean,
+  modelsUrl?: string,
 ): Promise<FetchedModel[]> {
-  return invoke("fetch_models_for_config", { baseUrl, apiKey, isFullUrl });
+  return invoke("fetch_models_for_config", {
+    baseUrl,
+    apiKey,
+    isFullUrl,
+    modelsUrl,
+  });
 }
 
 /**
@@ -50,8 +56,13 @@ export function showFetchModelsError(
     toast.error(t("providerForm.fetchModelsAuthFailed"));
     return;
   }
+  // 所有候选端点均返回 404/405：供应商可能未开放 /models 接口，或 Base URL 有误
+  if (msg.includes("All candidates failed")) {
+    toast.error(t("providerForm.fetchModelsEndpointNotFound"));
+    return;
+  }
   if (msg.includes("HTTP 404") || msg.includes("HTTP 405")) {
-    toast.error(t("providerForm.fetchModelsNotSupported"));
+    toast.error(t("providerForm.fetchModelsEndpointNotFound"));
     return;
   }
   if (msg.includes("timeout") || msg.includes("timed out")) {