feat: per-agent model routing — route different agents to different providers (#238)

* feat: add agentModels and agentRouting to SettingsSchema

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add agentRouting module for per-agent provider resolution

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: thread providerOverride through OpenAI shim for per-agent routing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: getAnthropicClient accepts providerOverride for agent routing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: thread providerOverride through Options and queryModel calls

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: thread providerOverride through query loop and ToolUseContext

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: resolve agent routing in runAgent and inject providerOverride

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* docs: add Agent Routing configuration guide to README

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* test: add unit tests for resolveAgentProvider + plaintext api_key note

- 15 tests covering priority chain (name > subagentType > default > null)
- normalize() case-insensitive and hyphen/underscore equivalence
- Edge cases: null settings, missing config sections, non-existent model
- README note about api_key stored in plaintext

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* security: address code review — SSRF, credential leak, key collision

- base_url schema now uses z.string().url() for SSRF mitigation
- Strip auth headers (Authorization, x-api-key, api-key) from
  defaultHeaders when providerOverride is active, preventing
  Anthropic credentials from leaking to third-party endpoints
- Warn on duplicate normalized routing keys to prevent silent shadowing
- providerOverride.apiKey is never logged (verified via grep)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: 冯俊辉 <fengjunhui@shiyanjia.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/api/agentRouting.test.ts

@@ -0,0 +1,125 @@
+import { describe, expect, test } from 'bun:test'
+import { resolveAgentProvider } from './agentRouting.js'
+import type { SettingsJson } from '../../utils/settings/types.js'
+
+const baseSettings = {
+  agentModels: {
+    'deepseek-chat': { base_url: 'https://api.deepseek.com/v1', api_key: 'sk-ds' },
+    'gpt-4o': { base_url: 'https://api.openai.com/v1', api_key: 'sk-oai' },
+  },
+  agentRouting: {
+    Explore: 'deepseek-chat',
+    'general-purpose': 'gpt-4o',
+    'frontend-dev': 'deepseek-chat',
+    default: 'gpt-4o',
+  },
+} as unknown as SettingsJson
+
+describe('resolveAgentProvider', () => {
+  // ── Priority chain ──────────────────────────────────────────
+
+  test('name takes priority over subagentType', () => {
+    const result = resolveAgentProvider('frontend-dev', 'Explore', baseSettings)
+    expect(result).toEqual({
+      model: 'deepseek-chat',
+      baseURL: 'https://api.deepseek.com/v1',
+      apiKey: 'sk-ds',
+    })
+  })
+
+  test('subagentType used when name has no match', () => {
+    const result = resolveAgentProvider('unknown-name', 'Explore', baseSettings)
+    expect(result).toEqual({
+      model: 'deepseek-chat',
+      baseURL: 'https://api.deepseek.com/v1',
+      apiKey: 'sk-ds',
+    })
+  })
+
+  test('falls back to "default" when neither name nor subagentType match', () => {
+    const result = resolveAgentProvider('nobody', 'unknown-type', baseSettings)
+    expect(result).toEqual({
+      model: 'gpt-4o',
+      baseURL: 'https://api.openai.com/v1',
+      apiKey: 'sk-oai',
+    })
+  })
+
+  test('returns null when no routing match and no default', () => {
+    const settings = {
+      agentModels: baseSettings.agentModels,
+      agentRouting: { Explore: 'deepseek-chat' },
+    } as unknown as SettingsJson
+    const result = resolveAgentProvider('nobody', 'unknown-type', settings)
+    expect(result).toBeNull()
+  })
+
+  test('returns null when name and subagentType are both undefined', () => {
+    const settings = {
+      agentModels: baseSettings.agentModels,
+      agentRouting: { Explore: 'deepseek-chat' },
+    } as unknown as SettingsJson
+    const result = resolveAgentProvider(undefined, undefined, settings)
+    expect(result).toBeNull()
+  })
+
+  // ── normalize() matching ────────────────────────────────────
+
+  test('matching is case-insensitive', () => {
+    const result = resolveAgentProvider(undefined, 'explore', baseSettings)
+    expect(result?.model).toBe('deepseek-chat')
+  })
+
+  test('matching is case-insensitive (UPPER)', () => {
+    const result = resolveAgentProvider(undefined, 'EXPLORE', baseSettings)
+    expect(result?.model).toBe('deepseek-chat')
+  })
+
+  test('hyphen and underscore are equivalent', () => {
+    const result = resolveAgentProvider(undefined, 'general_purpose', baseSettings)
+    expect(result?.model).toBe('gpt-4o')
+  })
+
+  test('underscore in config matches hyphen in input', () => {
+    const settings = {
+      agentModels: baseSettings.agentModels,
+      agentRouting: { general_purpose: 'deepseek-chat' },
+    } as unknown as SettingsJson
+    const result = resolveAgentProvider(undefined, 'general-purpose', settings)
+    expect(result?.model).toBe('deepseek-chat')
+  })
+
+  // ── Edge cases ──────────────────────────────────────────────
+
+  test('returns null when settings is null', () => {
+    expect(resolveAgentProvider('Explore', 'Explore', null)).toBeNull()
+  })
+
+  test('returns null when agentRouting is missing', () => {
+    const settings = { agentModels: baseSettings.agentModels } as unknown as SettingsJson
+    expect(resolveAgentProvider(undefined, 'Explore', settings)).toBeNull()
+  })
+
+  test('returns null when agentModels is missing', () => {
+    const settings = { agentRouting: baseSettings.agentRouting } as unknown as SettingsJson
+    expect(resolveAgentProvider(undefined, 'Explore', settings)).toBeNull()
+  })
+
+  test('returns null when routing references non-existent model', () => {
+    const settings = {
+      agentModels: {},
+      agentRouting: { Explore: 'non-existent-model' },
+    } as unknown as SettingsJson
+    expect(resolveAgentProvider(undefined, 'Explore', settings)).toBeNull()
+  })
+
+  test('subagentType only (no name)', () => {
+    const result = resolveAgentProvider(undefined, 'Explore', baseSettings)
+    expect(result?.model).toBe('deepseek-chat')
+  })
+
+  test('name only (no subagentType)', () => {
+    const result = resolveAgentProvider('frontend-dev', undefined, baseSettings)
+    expect(result?.model).toBe('deepseek-chat')
+  })
+})