fix: preserve custom provider thinking settings

Custom providers can point at user-defined model IDs that the CLI cannot
classify by built-in model tables. Declare the existing tier capability
overrides for custom provider roles so explicit thinking and effort settings
survive request construction.

Constraint: Issue #285 reports local proxy logs dropping user-defined model thinking and effort as passthrough with no config.
Rejected: Disable model capability checks globally | would relax behavior for built-in presets and non-custom providers.
Confidence: high
Scope-risk: narrow
Directive: Keep this scoped to custom providers unless each preset has explicit capability semantics.
Tested: bun test src/server/__tests__/providers.test.ts src/server/__tests__/provider-presets.test.ts src/utils/__tests__/thinking.test.ts
Tested: bun run check:server
Tested: bun run quality:pr
Tested: bun run quality:gate --mode baseline --allow-live --provider-model custom:main:custom-main
Tested: agent-browser custom provider UI smoke with request log showing thinking adaptive and effort max
Related: https://github.com/NanmiCoder/cc-haha/issues/285

src/server/__tests__/providers.test.ts

@@ -137,6 +137,33 @@ describe('ProviderService', () => {
       await expect(fs.readFile(path.join(tmpDir, 'cc-haha', 'settings.json'), 'utf-8')).rejects.toThrow()
     })
 
+    test('custom providers declare thinking and effort capability passthrough for user-defined models', async () => {
+      const svc = new ProviderService()
+      const provider = await svc.addProvider(sampleInput({
+        models: {
+          main: 'deepseek-ai/DeepSeek-V4-Pro',
+          haiku: 'deepseek-ai/DeepSeek-V4-Pro',
+          sonnet: 'deepseek-ai/DeepSeek-V4-Pro',
+          opus: 'deepseek-ai/DeepSeek-V4-Pro',
+        },
+      }))
+
+      await svc.activateProvider(provider.id)
+
+      const settings = await readSettings()
+      const env = settings.env as Record<string, string>
+      expect(env.ANTHROPIC_DEFAULT_SONNET_MODEL).toBe('deepseek-ai/DeepSeek-V4-Pro')
+      expect(env.ANTHROPIC_DEFAULT_SONNET_MODEL_SUPPORTED_CAPABILITIES).toBe(
+        'thinking,effort,adaptive_thinking,max_effort',
+      )
+      expect(env.ANTHROPIC_DEFAULT_HAIKU_MODEL_SUPPORTED_CAPABILITIES).toBe(
+        'thinking,effort,adaptive_thinking,max_effort',
+      )
+      expect(env.ANTHROPIC_DEFAULT_OPUS_MODEL_SUPPORTED_CAPABILITIES).toBe(
+        'thinking,effort,adaptive_thinking,max_effort',
+      )
+    })
+
     test('adding additional providers should keep activeId unchanged', async () => {
       const svc = new ProviderService()
       await svc.addProvider(sampleInput({ name: 'First' }))

src/server/services/providerService.ts

@@ -44,6 +44,8 @@ const MANAGED_ENV_KEYS = [
   MODEL_CONTEXT_WINDOWS_ENV_KEY,
 ] as const
 
+const CUSTOM_PROVIDER_MODEL_CAPABILITIES = 'thinking,effort,adaptive_thinking,max_effort'
+
 const DEFAULT_INDEX: ProvidersIndex = { activeId: null, providers: [] }
 const AUTH_ENV_KEYS = new Set(['ANTHROPIC_API_KEY', 'ANTHROPIC_AUTH_TOKEN'])
 
@@ -317,9 +319,18 @@ export class ProviderService {
     }
 
     const presetDefaultEnv = getPresetDefaultEnv(provider.presetId)
+    const customProviderCapabilityEnv =
+      provider.presetId === 'custom'
+        ? {
+            ANTHROPIC_DEFAULT_HAIKU_MODEL_SUPPORTED_CAPABILITIES: CUSTOM_PROVIDER_MODEL_CAPABILITIES,
+            ANTHROPIC_DEFAULT_SONNET_MODEL_SUPPORTED_CAPABILITIES: CUSTOM_PROVIDER_MODEL_CAPABILITIES,
+            ANTHROPIC_DEFAULT_OPUS_MODEL_SUPPORTED_CAPABILITIES: CUSTOM_PROVIDER_MODEL_CAPABILITIES,
+          }
+        : {}
 
     return {
       ...omitAuthEnv(presetDefaultEnv),
+      ...customProviderCapabilityEnv,
       ...(provider.autoCompactWindow !== undefined && {
         CLAUDE_CODE_AUTO_COMPACT_WINDOW: String(provider.autoCompactWindow),
       }),