diff --git a/apps/server/src/services/adapters/config-kv.test.ts b/apps/server/src/services/adapters/config-kv.test.ts
index f10f9394b..c2643532d 100644
--- a/apps/server/src/services/adapters/config-kv.test.ts
+++ b/apps/server/src/services/adapters/config-kv.test.ts
@@ -151,6 +151,174 @@ describe('configKVService', () => {
     })
   })
 
+  it('llm router config should preserve explicit LLM and TTS provider groups', async () => {
+    await service.set('LLM_ROUTER_CONFIG', {
+      llm: {
+        models: {
+          'step-3.5-flash': {
+            upstreams: [
+              {
+                id: 'plan',
+                baseURL: 'https://api.stepfun.com/step_plan/v1',
+                keys: [{ id: 'plan-key', ciphertext: 'plan-ciphertext' }],
+                headerTemplate: 'Bearer {KEY}',
+              },
+              {
+                id: 'paygo',
+                baseURL: 'https://api.stepfun.com/v1',
+                keys: [{ id: 'paygo-key', ciphertext: 'paygo-ciphertext' }],
+                headerTemplate: 'Bearer {KEY}',
+              },
+            ],
+            routing: {
+              groups: [
+                {
+                  id: 'plan',
+                  upstreamIds: ['plan'],
+                  retryOn: { httpCodes: [402, 429, 500, 502, 503, 504], onTimeout: true },
+                  continueOn: { httpCodes: [402], onTimeout: false },
+                },
+                {
+                  id: 'paygo',
+                  upstreamIds: ['paygo'],
+                  retryOn: { httpCodes: [429, 500, 502, 503, 504], onTimeout: true },
+                },
+              ],
+            },
+            fallbackTriggers: {
+              httpCodes: [401, 402, 403, 429, 500, 502, 503, 504],
+              onTimeout: true,
+            },
+          },
+        },
+      },
+      tts: {
+        models: {
+          'stepfun/stepaudio-2.5-tts': {
+            provider: 'stepfun',
+            upstreams: [
+              {
+                id: 'plan',
+                baseURL: 'https://api.stepfun.com',
+                keys: [{ id: 'plan-key', ciphertext: 'plan-ciphertext' }],
+                adapterParams: { endpointProfile: 'step-plan' },
+                maxConcurrency: 1,
+              },
+              {
+                id: 'paygo',
+                baseURL: 'https://api.stepfun.com',
+                keys: [{ id: 'paygo-key', ciphertext: 'paygo-ciphertext' }],
+                adapterParams: { endpointProfile: 'default' },
+              },
+            ],
+            routing: {
+              groups: [
+                {
+                  id: 'plan',
+                  upstreamIds: ['plan'],
+                  strategy: 'least-inflight',
+                  retryOn: { httpCodes: [402, 429, 500, 502, 503, 504], onTimeout: true },
+                  continueOn: { httpCodes: [402], onTimeout: false },
+                },
+                {
+                  id: 'paygo',
+                  upstreamIds: ['paygo'],
+                  strategy: 'ordered',
+                  retryOn: { httpCodes: [429, 500, 502, 503, 504], onTimeout: true },
+                },
+              ],
+            },
+            fallbackTriggers: {
+              httpCodes: [401, 402, 429, 500, 502, 503, 504],
+              onTimeout: true,
+            },
+          },
+        },
+      },
+      defaults: {
+        perAttemptTimeoutMs: 30000,
+        fullChainTimeoutMs: 60000,
+        fallbackHttpCodes: [401, 402, 403, 429, 500, 502, 503, 504],
+      },
+    })
+
+    const value = await service.getOrThrow('LLM_ROUTER_CONFIG')
+    const model = value.tts.models['stepfun/stepaudio-2.5-tts']
+
+    expect(value.llm.models['step-3.5-flash'].routing?.groups.map(group => group.id)).toEqual(['plan', 'paygo'])
+    expect(model.routing?.groups.map(group => group.id)).toEqual(['plan', 'paygo'])
+    expect(model.routing?.groups[0].continueOn).toEqual({
+      httpCodes: [402],
+      onTimeout: false,
+    })
+  })
+
+  it('rejects a TTS provider group that references an unknown upstream', async () => {
+    redis._store.set(configRedisKey('LLM_ROUTER_CONFIG'), JSON.stringify({
+      llm: { models: {} },
+      tts: {
+        models: {
+          tts: {
+            provider: 'stepfun',
+            upstreams: [{
+              id: 'plan',
+              baseURL: 'https://api.stepfun.com',
+              keys: [{ id: 'plan-key', ciphertext: 'ciphertext' }],
+            }],
+            routing: {
+              groups: [{
+                id: 'plan',
+                upstreamIds: ['missing'],
+                strategy: 'ordered',
+                retryOn: { httpCodes: [402], onTimeout: false },
+              }],
+            },
+          },
+        },
+      },
+    }))
+
+    await expect(service.getOptional('LLM_ROUTER_CONFIG'))
+      .rejects
+      .toMatchObject({
+        statusCode: 503,
+        errorCode: 'CONFIG_INVALID',
+      })
+  })
+
+  it('rejects least-inflight routing without an explicit concurrency cap', async () => {
+    redis._store.set(configRedisKey('LLM_ROUTER_CONFIG'), JSON.stringify({
+      llm: { models: {} },
+      tts: {
+        models: {
+          tts: {
+            provider: 'stepfun',
+            upstreams: [{
+              id: 'plan',
+              baseURL: 'https://api.stepfun.com',
+              keys: [{ id: 'plan-key', ciphertext: 'ciphertext' }],
+            }],
+            routing: {
+              groups: [{
+                id: 'plan',
+                upstreamIds: ['plan'],
+                strategy: 'least-inflight',
+                retryOn: { httpCodes: [402], onTimeout: false },
+              }],
+            },
+          },
+        },
+      },
+    }))
+
+    await expect(service.getOptional('LLM_ROUTER_CONFIG'))
+      .rejects
+      .toMatchObject({
+        statusCode: 503,
+        errorCode: 'CONFIG_INVALID',
+      })
+  })
+
   it('set should store string values as JSON strings', async () => {
     await service.set('STRIPE_FLUX_PRODUCT_ID', 'prod_abc123')
 
diff --git a/apps/server/src/services/adapters/config-kv.ts b/apps/server/src/services/adapters/config-kv.ts
index ca11562ff..c572c1a78 100644
--- a/apps/server/src/services/adapters/config-kv.ts
+++ b/apps/server/src/services/adapters/config-kv.ts
@@ -9,8 +9,9 @@ import { configRedisKey } from '../../utils/redis-keys'
 
 /**
  * LLM/TTS router config tree. Single composite entry under configKV holds the
- * entire routing surface: per-model upstream list, per-upstream key array
- * (envelope-encrypted ciphertexts), fallback triggers, default timeouts.
+ * entire routing surface: per-model upstream list, optional candidate groups,
+ * per-upstream key array (envelope-encrypted ciphertexts), transition policies,
+ * and default timeouts.
  *
  * Schema enforces:
  * - key entry id must not contain `|` — the envelope-crypto AAD uses `|` as
@@ -30,6 +31,18 @@ export const fallbackTriggersSchema = optional(
   { httpCodes: [401, 402, 403, 429, 500, 502, 503, 504], onTimeout: true },
 )
 
+/**
+ * Explicit allow-list for one routing transition.
+ *
+ * Unlike {@link fallbackTriggersSchema}, this contract has no permissive
+ * defaults: an omitted status or timeout never authorizes a transition across
+ * a configured routing boundary.
+ */
+export const routeFailureTriggersSchema = object({
+  httpCodes: optional(array(number()), []),
+  onTimeout: optional(boolean(), false),
+})
+
 export const keyEntrySchema = object({
   id: pipe(
     string(),
@@ -40,6 +53,11 @@ export const keyEntrySchema = object({
 })
 
 export const llmUpstreamSchema = object({
+  id: optional(pipe(
+    string(),
+    nonEmpty('llm.upstreams[].id must not be empty'),
+    regex(/^[^|]+$/, 'llm.upstreams[].id must not contain "|"'),
+  )),
   baseURL: pipe(string(), nonEmpty('llm.upstreams[].baseURL must not be empty')),
   overrideModel: optional(string()),
   keys: pipe(array(keyEntrySchema), check(v => v.length >= 1, 'llm.upstreams[].keys must contain at least 1 entry')),
@@ -47,15 +65,58 @@ export const llmUpstreamSchema = object({
   timeoutMs: optional(number()),
 })
 
-export const llmModelSchema = object({
-  upstreams: pipe(array(llmUpstreamSchema), check(v => v.length >= 1, 'llm.models[].upstreams must contain at least 1 entry')),
-  fallbackTriggers: fallbackTriggersSchema,
+export const llmRoutingGroupSchema = object({
+  id: pipe(string(), nonEmpty('llm.routing.groups[].id must not be empty')),
+  upstreamIds: pipe(
+    array(pipe(string(), nonEmpty('llm.routing.groups[].upstreamIds[] must not be empty'))),
+    check(v => v.length >= 1, 'llm.routing.groups[].upstreamIds must contain at least 1 entry'),
+    check(v => new Set(v).size === v.length, 'llm.routing.groups[].upstreamIds must be unique'),
+  ),
+  retryOn: routeFailureTriggersSchema,
+  continueOn: optional(routeFailureTriggersSchema),
 })
 
+export const llmRoutingSchema = object({
+  groups: pipe(
+    array(llmRoutingGroupSchema),
+    check(v => v.length >= 1, 'llm.routing.groups must contain at least 1 entry'),
+    check(v => new Set(v.map(group => group.id)).size === v.length, 'llm.routing.groups[].id must be unique'),
+  ),
+})
+
+export const llmModelSchema = pipe(
+  object({
+    upstreams: pipe(array(llmUpstreamSchema), check(v => v.length >= 1, 'llm.models[].upstreams must contain at least 1 entry')),
+    routing: optional(llmRoutingSchema),
+    fallbackTriggers: fallbackTriggersSchema,
+  }),
+  check((model) => {
+    if (model.routing == null)
+      return true
+    const upstreamIds = model.upstreams.map(upstream => upstream.id)
+    return upstreamIds.every(id => id != null)
+      && new Set(upstreamIds).size === upstreamIds.length
+  }, 'llm.models[].upstreams must have unique ids when routing is configured'),
+  check((model) => {
+    if (model.routing == null)
+      return true
+    const upstreamIds = new Set(model.upstreams.map(upstream => upstream.id))
+    const referencedIds = model.routing.groups.flatMap(group => group.upstreamIds)
+    return referencedIds.length === upstreamIds.size
+      && new Set(referencedIds).size === referencedIds.length
+      && referencedIds.every(id => upstreamIds.has(id))
+  }, 'llm.routing.groups must reference every upstream id exactly once'),
+)
+
 const ttsProviderSchema = picklist(['azure', 'dashscope-cosyvoice', 'stepfun', 'volcengine'])
 const asrProviderSchema = picklist(['aliyun-nls'])
 
 export const ttsUpstreamSchema = object({
+  id: optional(pipe(
+    string(),
+    nonEmpty('tts.upstreams[].id must not be empty'),
+    regex(/^[^|]+$/, 'tts.upstreams[].id must not contain "|"'),
+  )),
   baseURL: pipe(string(), nonEmpty('tts.upstreams[].baseURL must not be empty')),
   keys: pipe(array(keyEntrySchema), check(v => v.length >= 1, 'tts.upstreams[].keys must contain at least 1 entry')),
   adapterParams: optional(record(string(), any()), {}),
@@ -68,6 +129,26 @@ export const ttsUpstreamSchema = object({
   maxConcurrency: optional(pipe(number(), check(v => v >= 1, 'tts.upstreams[].maxConcurrency must be >= 1 when set'))),
 })
 
+export const ttsRoutingGroupSchema = object({
+  id: pipe(string(), nonEmpty('tts.routing.groups[].id must not be empty')),
+  upstreamIds: pipe(
+    array(pipe(string(), nonEmpty('tts.routing.groups[].upstreamIds[] must not be empty'))),
+    check(v => v.length >= 1, 'tts.routing.groups[].upstreamIds must contain at least 1 entry'),
+    check(v => new Set(v).size === v.length, 'tts.routing.groups[].upstreamIds must be unique'),
+  ),
+  strategy: optional(picklist(['ordered', 'least-inflight']), 'ordered'),
+  retryOn: routeFailureTriggersSchema,
+  continueOn: optional(routeFailureTriggersSchema),
+})
+
+export const ttsRoutingSchema = object({
+  groups: pipe(
+    array(ttsRoutingGroupSchema),
+    check(v => v.length >= 1, 'tts.routing.groups must contain at least 1 entry'),
+    check(v => new Set(v.map(group => group.id)).size === v.length, 'tts.routing.groups[].id must be unique'),
+  ),
+})
+
 export const streamingTtsUpstreamSchema = object({
   baseURL: pipe(string(), nonEmpty('UNSPEECH_UPSTREAM.streaming.baseURL must not be empty')),
   keys: pipe(array(keyEntrySchema), check(v => v.length >= 1, 'UNSPEECH_UPSTREAM.streaming.keys must contain at least 1 entry')),
@@ -88,11 +169,39 @@ export const unspeechUpstreamSchema = object({
   streaming: optional(streamingTtsUpstreamSchema),
 })
 
-export const ttsModelSchema = object({
-  provider: ttsProviderSchema,
-  upstreams: pipe(array(ttsUpstreamSchema), check(v => v.length >= 1, 'tts.models[].upstreams must contain at least 1 entry')),
-  fallbackTriggers: fallbackTriggersSchema,
-})
+export const ttsModelSchema = pipe(
+  object({
+    provider: ttsProviderSchema,
+    upstreams: pipe(array(ttsUpstreamSchema), check(v => v.length >= 1, 'tts.models[].upstreams must contain at least 1 entry')),
+    routing: optional(ttsRoutingSchema),
+    fallbackTriggers: fallbackTriggersSchema,
+  }),
+  check((model) => {
+    if (model.routing == null)
+      return true
+    const upstreamIds = model.upstreams.map(upstream => upstream.id)
+    return upstreamIds.every(id => id != null)
+      && new Set(upstreamIds).size === upstreamIds.length
+  }, 'tts.models[].upstreams must have unique ids when routing is configured'),
+  check((model) => {
+    if (model.routing == null)
+      return true
+    const upstreamIds = new Set(model.upstreams.map(upstream => upstream.id))
+    const referencedIds = model.routing.groups.flatMap(group => group.upstreamIds)
+    return referencedIds.length === upstreamIds.size
+      && new Set(referencedIds).size === referencedIds.length
+      && referencedIds.every(id => upstreamIds.has(id))
+  }, 'tts.routing.groups must reference every upstream id exactly once'),
+  check((model) => {
+    if (model.routing == null)
+      return true
+    const upstreamById = new Map(model.upstreams.map(upstream => [upstream.id, upstream]))
+    return model.routing.groups.every(group =>
+      group.strategy !== 'least-inflight'
+      || group.upstreamIds.every(id => upstreamById.get(id)?.maxConcurrency != null),
+    )
+  }, 'tts.routing least-inflight groups require maxConcurrency on every upstream'),
+)
 
 export const asrUpstreamSchema = object({
   keys: pipe(array(keyEntrySchema), check(v => v.length >= 1, 'asr.upstreams[].keys must contain at least 1 entry')),
diff --git a/apps/server/src/services/adapters/tts/index.test.ts b/apps/server/src/services/adapters/tts/index.test.ts
index 092dbd02d..0d0aa59b0 100644
--- a/apps/server/src/services/adapters/tts/index.test.ts
+++ b/apps/server/src/services/adapters/tts/index.test.ts
@@ -298,7 +298,7 @@ describe('azureAdapter.send', () => {
 })
 
 describe('stepfunAdapter', () => {
-  it('lists StepFun voices through unspeech provider=stepfun', async () => {
+  it('uses unspeech as the StepFun voice-catalog source', async () => {
     const adapter = getAdapter('stepfun')
     const fetchImpl = vi.fn(async () => new Response(JSON.stringify({
       voices: [{
@@ -323,6 +323,7 @@ describe('stepfunAdapter', () => {
         }),
       ]),
     )
+    expect(fetchImpl).toHaveBeenCalledTimes(1)
     const [calledUrl] = (fetchImpl as unknown as { mock: { calls: [string, RequestInit][] } }).mock.calls[0]
     expect(calledUrl).toBe('http://unspeech.local/api/voices?provider=stepfun')
   })
@@ -348,7 +349,7 @@ describe('stepfunAdapter', () => {
       },
       {
         keyPlaintext: Buffer.from('step-key', 'utf8'),
-        baseURL: 'https://api.stepfun.com/v1/audio/speech',
+        baseURL: 'https://api.stepfun.com',
         unspeechBaseURL: 'http://unspeech.local:5933',
         adapterParams: { model: 'stepaudio-2.5-tts' },
         fetchImpl,
@@ -379,6 +380,57 @@ describe('stepfunAdapter', () => {
     expect(result.body).toBeInstanceOf(ArrayBuffer)
   })
 
+  it('passes the Step Plan endpoint profile to unspeech', async () => {
+    const adapter = getAdapter('stepfun')
+    const fetchImpl = vi.fn(async () => new Response(new Uint8Array([1, 2, 3]), {
+      status: 200,
+      headers: { 'content-type': 'audio/mpeg' },
+    })) as unknown as typeof fetch
+
+    const result = await adapter.send(
+      {
+        text: '你好',
+        voice: 'cixingnansheng',
+        responseFormat: 'mp3',
+        speed: 1.1,
+        extraOptions: {
+          instruction: '温柔、克制',
+        },
+      },
+      {
+        keyPlaintext: Buffer.from('step-plan-key', 'utf8'),
+        baseURL: 'https://api.stepfun.com',
+        unspeechBaseURL: 'http://unspeech.local:5933',
+        adapterParams: {
+          endpointProfile: 'step-plan',
+          model: 'stepaudio-2.5-tts',
+        },
+        fetchImpl,
+      },
+    )
+
+    const [calledURL, init] = (fetchImpl as unknown as { mock: { calls: [string, RequestInit][] } }).mock.calls[0]
+    expect(calledURL).toBe('http://unspeech.local:5933/v1/audio/speech')
+    expect(init.method).toBe('POST')
+    expect(init.headers).toMatchObject({
+      'Authorization': 'Bearer step-plan-key',
+      'Content-Type': 'application/json',
+    })
+    expect(JSON.parse(init.body as string)).toEqual({
+      model: 'stepfun/stepaudio-2.5-tts',
+      input: '你好',
+      voice: 'cixingnansheng',
+      response_format: 'mp3',
+      speed: 1.1,
+      extra_body: {
+        endpoint_profile: 'step-plan',
+        instruction: '温柔、克制',
+      },
+    })
+    expect(result.contentType).toBe('audio/mpeg')
+    expect(result.body).toBeInstanceOf(ArrayBuffer)
+  })
+
   it('passes voice_label through to unspeech for provider-level validation', async () => {
     const adapter = getAdapter('stepfun')
     const fetchImpl = vi.fn(async () => new Response(new Uint8Array([1]), {
@@ -395,7 +447,7 @@ describe('stepfunAdapter', () => {
       },
       {
         keyPlaintext: Buffer.from('step-key', 'utf8'),
-        baseURL: 'https://api.stepfun.com/v1/audio/speech',
+        baseURL: 'https://api.stepfun.com',
         unspeechBaseURL: 'http://unspeech.local',
         adapterParams: { model: 'stepaudio-2.5-tts' },
         fetchImpl,
@@ -415,13 +467,35 @@ describe('stepfunAdapter', () => {
       { text: 'hi', voice: 'cixingnansheng' },
       {
         keyPlaintext: Buffer.from('bad-key', 'utf8'),
-        baseURL: 'https://api.stepfun.com/v1/audio/speech',
+        baseURL: 'https://api.stepfun.com',
         unspeechBaseURL: 'http://unspeech.local',
         adapterParams: { model: 'stepaudio-2.5-tts' },
         fetchImpl,
       },
     )).rejects.toMatchObject({ status: 401 })
   })
+
+  it('preserves an unspeech request abort for router timeout classification', async () => {
+    const adapter = getAdapter('stepfun')
+    const abortController = new AbortController()
+    const abortError = new Error('attempt-timeout')
+    abortController.abort(abortError)
+    const fetchImpl = vi.fn(async (_input: string | URL | Request, init?: RequestInit) => {
+      throw init?.signal?.reason ?? new Error('aborted')
+    }) as unknown as typeof fetch
+
+    await expect(adapter.send(
+      { text: 'hi', voice: 'cixingnansheng' },
+      {
+        keyPlaintext: Buffer.from('step-key', 'utf8'),
+        baseURL: 'https://api.stepfun.com',
+        unspeechBaseURL: 'http://unspeech.local',
+        adapterParams: { model: 'stepaudio-2.5-tts' },
+        fetchImpl,
+        abortSignal: abortController.signal,
+      },
+    )).rejects.toBe(abortError)
+  })
 })
 
 describe('volcengineAdapter.send', () => {
diff --git a/apps/server/src/services/adapters/tts/stepfun.ts b/apps/server/src/services/adapters/tts/stepfun.ts
index 064151332..44d676720 100644
--- a/apps/server/src/services/adapters/tts/stepfun.ts
+++ b/apps/server/src/services/adapters/tts/stepfun.ts
@@ -15,8 +15,8 @@ const STEPFUN_DEFAULT_VOICE = 'cixingnansheng'
  * StepFun TTS adapter.
  *
  * Use when:
- * - Routing hosted speech synthesis to StepFun through unspeech's
- *   OpenAI-compatible `stepfun/*` backend.
+ * - Routing speech synthesis to StepFun through unspeech's OpenAI-compatible
+ *   `stepfun/*` backend.
  *
  * Expects:
  * - `ctx.unspeechBaseURL` points at an unspeech deployment that includes the
@@ -24,6 +24,8 @@ const STEPFUN_DEFAULT_VOICE = 'cixingnansheng'
  * - `ctx.keyPlaintext` is the StepFun API key.
  * - `ctx.adapterParams.model` optionally selects `stepaudio-2.5-tts`,
  *   `step-tts-2`, or `step-tts-mini`.
+ * - `ctx.adapterParams.endpointProfile` optionally selects a provider-owned
+ *   endpoint profile such as `step-plan`; AIRI never owns the endpoint URL.
  *
  * Returns:
  * - {@link TtsResult} with the upstream audio body and content type.
@@ -41,6 +43,7 @@ export const stepfunAdapter: TtsAdapter = {
     const responseFormat = input.responseFormat ?? (typeof ctx.adapterParams.responseFormat === 'string' && ctx.adapterParams.responseFormat
       ? ctx.adapterParams.responseFormat
       : STEPFUN_DEFAULT_FORMAT)
+    const extraBody = buildExtraBody(input, ctx)
 
     return sendSpeechViaUnSpeech({
       ctx,
@@ -49,7 +52,7 @@ export const stepfunAdapter: TtsAdapter = {
       voice,
       speed: input.speed,
       responseFormat,
-      extraBody: buildExtraBody(input, ctx),
+      extraBody,
       fallbackContentType: audioMimeFromFormat(responseFormat),
       providerLabel: 'stepfun',
     })
@@ -68,6 +71,9 @@ function buildExtraBody(input: TtsInput, ctx: TtsAdapterContext): Record<string,
   const extraOptions = input.extraOptions ?? {}
   const body: Record<string, unknown> = {}
 
+  if (typeof ctx.adapterParams.endpointProfile === 'string' && ctx.adapterParams.endpointProfile)
+    body.endpoint_profile = ctx.adapterParams.endpointProfile
+
   if (typeof extraOptions.volume === 'number' && Number.isFinite(extraOptions.volume))
     body.volume = extraOptions.volume
   else if (typeof ctx.adapterParams.volume === 'number' && Number.isFinite(ctx.adapterParams.volume))
diff --git a/apps/server/src/services/adapters/tts/types.ts b/apps/server/src/services/adapters/tts/types.ts
index 176d567a2..1c52ef44c 100644
--- a/apps/server/src/services/adapters/tts/types.ts
+++ b/apps/server/src/services/adapters/tts/types.ts
@@ -42,16 +42,11 @@ export interface TtsAdapterContext {
   /**
    * Per-upstream baseURL from `LLM_ROUTER_CONFIG.tts.upstreams[i].baseURL`.
    *
-   * Historically the upstream provider URL (e.g.
-   * `https://eastasia.tts.speech.microsoft.com/cognitiveservices/v1`). After
-   * the Phase-B unspeech migration, adapters no longer call upstreams
-   * directly — every `send()` forwards through unspeech REST — so this field
-   * is informational only and adapters MAY ignore it. Kept on the context so
-   * existing operator configs continue to validate (the schema requires a
-   * non-empty string).
+   * Adapters forward through unspeech and may use this as provider metadata.
+   * Provider endpoint selection belongs to unspeech, not this URL.
    */
   baseURL: string
-  /** unspeech REST base URL (no trailing slash) — adapters POST to `<this>/v1/audio/speech`. */
+  /** unspeech REST base URL (no trailing slash). */
   unspeechBaseURL: string
   /** Free-form adapter-specific params from `tts.upstreams[i].adapterParams` (e.g. Volcengine `appid` / `cluster`). */
   adapterParams: Record<string, unknown>
@@ -90,12 +85,10 @@ export type TtsAdapterId = 'azure' | 'dashscope-cosyvoice' | 'stepfun' | 'volcen
  * `keyPlaintext` and `region` are mandatory for live providers (Azure) that
  * proxy through unspeech and call the upstream provider with a subscription
  * key; the router decrypts the envelope key and forwards `adapterParams.region`
- * verbatim. Providers with static, credential-less catalogs (DashScope
- * cosyvoice, Volcengine) ignore both fields.
+ * verbatim. Unspeech-backed static catalogs ignore both fields.
  *
- * `unspeechBaseURL` is `UNSPEECH_UPSTREAM.restBaseURL` resolved by the
- * router. Passing it through the context keeps adapters free of configKV
- * coupling — they receive a fully-resolved URL string.
+ * `unspeechBaseURL` is `UNSPEECH_UPSTREAM.restBaseURL` resolved by the router.
+ * Passing it through the context keeps adapters free of configKV coupling.
  */
 export interface TtsVoiceCatalogContext {
   /** Decrypted upstream credential (live providers only). */
@@ -139,10 +132,9 @@ export interface TtsAdapter {
   /**
    * Returns the voice catalog for the provider.
    *
-   * Live providers (Azure) call upstream via unspeech using the supplied
-   * region + plaintext key. Static providers (dashscope-cosyvoice, volcengine)
-   * return their compiled-in JSON and ignore the context fields. Adapters
-   * MUST throw on upstream failure — no empty-array fallback.
+   * Live providers (Azure) call upstream through unspeech using the supplied
+   * region + plaintext key. Static provider catalogs are also owned and served
+   * by unspeech. Adapters MUST throw on upstream failure — no empty fallback.
    */
   getVoiceCatalog: (ctx: TtsVoiceCatalogContext) => Promise<Voice[]>
 }
diff --git a/apps/server/src/services/adapters/tts/unspeech.ts b/apps/server/src/services/adapters/tts/unspeech.ts
index 7ad388582..9d8117262 100644
--- a/apps/server/src/services/adapters/tts/unspeech.ts
+++ b/apps/server/src/services/adapters/tts/unspeech.ts
@@ -66,6 +66,11 @@ export async function sendSpeechViaUnSpeech(options: SendSpeechOptions): Promise
     }
   }
   catch (error) {
+    // Keep abort identity intact so the router can apply `onTimeout`
+    // independently from HTTP 500 fallback policy.
+    if (ctx.abortSignal?.aborted)
+      throw error
+
     if (error instanceof UnSpeechAPIError) {
       const err = new Error(`${providerLabel} tts upstream ${error.status}: ${error.responseBody.slice(0, 256)}`) as Error & { status?: number }
       err.status = error.status
diff --git a/apps/server/src/services/domain/admin/router-config/index.ts b/apps/server/src/services/domain/admin/router-config/index.ts
index 4b34cb14d..0ddca8faf 100644
--- a/apps/server/src/services/domain/admin/router-config/index.ts
+++ b/apps/server/src/services/domain/admin/router-config/index.ts
@@ -391,7 +391,7 @@ export function buildStepfunSlice(input: StepfunSliceInput, envelope: EnvelopeCr
     model: {
       provider: 'stepfun',
       upstreams: [{
-        baseURL: 'https://api.stepfun.com/v1/audio/speech',
+        baseURL: 'https://api.stepfun.com',
         keys: [{ id: keyEntryId, ciphertext }],
         adapterParams: {
           model: input.upstreamModel ?? 'stepaudio-2.5-tts',
@@ -604,7 +604,7 @@ function buildStepfunSlicePreservingKey(input: StepfunSliceInput, envelope: Enve
     model: {
       provider: 'stepfun',
       upstreams: [{
-        baseURL: 'https://api.stepfun.com/v1/audio/speech',
+        baseURL: 'https://api.stepfun.com',
         keys: [key],
         adapterParams: {
           model: input.upstreamModel ?? 'stepaudio-2.5-tts',
@@ -715,6 +715,11 @@ export function buildSlice(
  * - The next config tree, ready to feed `configKV.set('LLM_ROUTER_CONFIG', ...)`.
  *   `defaults` is preserved verbatim when merging — the admin endpoint does
  *   not currently re-tune timeouts via this path.
+ *
+ * Throws:
+ * - When merge mode targets a grouped LLM/TTS model. The legacy slice contract
+ *   cannot identify one upstream or represent routing groups, so replacing that
+ *   model would silently erase its routing policy.
  */
 export function buildNextRouterConfig(
   mode: 'merge' | 'reset',
@@ -729,12 +734,25 @@ export function buildNextRouterConfig(
     = mode === 'merge' && existing?.asr?.models ? { ...existing.asr.models } : {}
 
   for (const slice of slices) {
-    if (slice.surface === 'llm')
+    if (slice.surface === 'llm') {
+      if (mode === 'merge' && llmModels[slice.modelName]?.routing != null) {
+        throw new Error(
+          `Legacy admin config cannot update grouped llm model ${slice.modelName}; use a group-aware router config update`,
+        )
+      }
       llmModels[slice.modelName] = slice.model
-    else if (slice.surface === 'tts')
+    }
+    else if (slice.surface === 'tts') {
+      if (mode === 'merge' && ttsModels[slice.modelName]?.routing != null) {
+        throw new Error(
+          `Legacy admin config cannot update grouped tts model ${slice.modelName}; use a group-aware router config update`,
+        )
+      }
       ttsModels[slice.modelName] = slice.model
-    else
+    }
+    else {
       asrModels[slice.modelName] = slice.model
+    }
   }
 
   // Defaults live alongside the models but aren't editable through this
diff --git a/apps/server/src/services/domain/admin/router-config/tests/admin-router-config.test.ts b/apps/server/src/services/domain/admin/router-config/tests/admin-router-config.test.ts
index 82e7cbde5..a873d0f99 100644
--- a/apps/server/src/services/domain/admin/router-config/tests/admin-router-config.test.ts
+++ b/apps/server/src/services/domain/admin/router-config/tests/admin-router-config.test.ts
@@ -271,7 +271,7 @@ describe('buildStepfunSlice', () => {
 
     expect(built.kind).toBe('stepfun')
     expect(built.model.provider).toBe('stepfun')
-    expect(built.model.upstreams[0].baseURL).toBe('https://api.stepfun.com/v1/audio/speech')
+    expect(built.model.upstreams[0].baseURL).toBe('https://api.stepfun.com')
     expect(built.model.upstreams[0].adapterParams).toEqual({
       model: 'stepaudio-2.5-tts',
       defaultVoice: 'cixingnansheng',
@@ -582,6 +582,70 @@ describe('createAdminRouterConfigService', () => {
     expect(Object.keys(written.tts.models)).toEqual(['microsoft/v1'])
   })
 
+  it('rejects legacy merge updates that would replace a grouped TTS model', async () => {
+    const modelName = 'stepfun/stepaudio-2.5-tts'
+    const existingConfig = {
+      llm: { models: {} },
+      tts: {
+        models: {
+          [modelName]: {
+            provider: 'stepfun' as const,
+            upstreams: [
+              {
+                id: 'plan',
+                baseURL: 'https://api.stepfun.com',
+                keys: [{ id: 'plan-key', ciphertext: 'plan-ciphertext' }],
+                adapterParams: { endpointProfile: 'step-plan', model: 'stepaudio-2.5-tts' },
+              },
+              {
+                id: 'paygo',
+                baseURL: 'https://api.stepfun.com',
+                keys: [{ id: 'paygo-key', ciphertext: 'paygo-ciphertext' }],
+                adapterParams: { endpointProfile: 'default', model: 'stepaudio-2.5-tts' },
+              },
+            ],
+            routing: {
+              groups: [
+                {
+                  id: 'plan',
+                  upstreamIds: ['plan'],
+                  strategy: 'ordered' as const,
+                  retryOn: { httpCodes: [402], onTimeout: false },
+                  continueOn: { httpCodes: [402], onTimeout: false },
+                },
+                {
+                  id: 'paygo',
+                  upstreamIds: ['paygo'],
+                  strategy: 'ordered' as const,
+                  retryOn: { httpCodes: [429, 500], onTimeout: true },
+                },
+              ],
+            },
+            fallbackTriggers: DEFAULT_FALLBACK_TRIGGERS,
+          },
+        },
+      },
+      defaults: { perAttemptTimeoutMs: 30000, fullChainTimeoutMs: 60000, fallbackHttpCodes: [500] },
+    }
+    kv.store.set('LLM_ROUTER_CONFIG', existingConfig)
+
+    const service = createAdminRouterConfigService({ configKV: kv.service, envelope, redis })
+
+    await expect(service.apply({
+      mode: 'merge',
+      dryRun: false,
+      slices: [{
+        kind: 'stepfun',
+        modelName,
+        upstreamModel: 'stepaudio-2.5-tts',
+        plaintextKey: 'rotated-key',
+      }],
+    })).rejects.toThrow(/cannot update grouped tts model/i)
+
+    expect(kv.store.get('LLM_ROUTER_CONFIG')).toBe(existingConfig)
+    expect(captured).toEqual([])
+  })
+
   it('current returns editable slices from configKV without exposing raw ciphertext', async () => {
     kv.store.set('LLM_ROUTER_CONFIG', {
       llm: {
diff --git a/apps/server/src/services/domain/llm-router/router.ts b/apps/server/src/services/domain/llm-router/router.ts
index 99150dd35..9e530f871 100644
--- a/apps/server/src/services/domain/llm-router/router.ts
+++ b/apps/server/src/services/domain/llm-router/router.ts
@@ -8,7 +8,7 @@ import type { EnvelopeCrypto } from '../../../utils/envelope-crypto'
 import type { ConfigKVService } from '../../adapters/config-kv'
 import type { TtsAdapterId, TtsInput } from '../../adapters/tts/types'
 import type { ConcurrencyLedger } from './concurrency-ledger'
-import type { LlmRouteContext, LlmRouteRequest, LlmUpstream, TtsUpstream } from './types'
+import type { LlmRouteContext, LlmRouteRequest, LlmRoutingGroup, LlmUpstream, RouteFailureTriggers, TtsRoutingGroup, TtsUpstream } from './types'
 
 import { Buffer as NodeBuffer } from 'node:buffer'
 
@@ -95,13 +95,34 @@ function deriveProviderTag(baseURL: string): string {
 /**
  * Identity of the pool (concurrency pool) one TTS upstream belongs to. One
  * upstream == one app_id, so the Volcengine `adapterParams.appid` is the pool
- * key when present; the baseURL is a stable fallback for providers without an
- * app_id concept. Two upstreams sharing an app_id would (correctly) share one
- * concurrency budget, though thetypical config gives each app_id its own upstream.
+ * key when present. Other providers use a model-scoped upstream id, then a
+ * model-scoped baseURL for configs without ids. This prevents model-local ids
+ * such as `plan` from sharing Redis counters across unrelated models. Two
+ * upstreams sharing an app_id correctly share one global concurrency budget.
  */
-function ttsPoolId(upstream: TtsUpstream): string {
+function ttsPoolId(upstream: TtsUpstream, modelName: string): string {
   const appid = upstream.adapterParams?.appid
-  return typeof appid === 'string' && appid.length > 0 ? appid : upstream.baseURL
+  if (typeof appid === 'string' && appid.length > 0)
+    return appid
+  return `model:${JSON.stringify([
+    modelName,
+    upstream.id == null ? 'baseURL' : 'id',
+    upstream.id ?? upstream.baseURL,
+  ])}`
+}
+
+function failuresMatch(
+  statuses: ReadonlyArray<number | 'timeout'>,
+  triggers: RouteFailureTriggers | undefined,
+): boolean {
+  if (statuses.length === 0 || triggers == null)
+    return false
+
+  return statuses.every((status) => {
+    if (status === 'timeout')
+      return triggers.onTimeout
+    return triggers.httpCodes.includes(status)
+  })
 }
 
 export interface CreateLlmRouterServiceOptions {
@@ -311,10 +332,10 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
           status_code: status,
         })
         if (!fallbackHttpCodes.includes(status)) {
-          // Status not in the fallback whitelist — surface as the last
-          // status and stop walking this upstream. We still let the outer
-          // loop try the next upstream (KTD-13: cross-upstream fallback
-          // happens in the same request, regardless of per-status policy).
+          // Status not in the key-level fallback whitelist — surface as the
+          // last status and stop walking this upstream. A configured provider
+          // group decides separately whether another account may be attempted;
+          // models without groups preserve the historical KTD-13 behavior.
           attemptIndex += 1
           break
         }
@@ -367,14 +388,14 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
       throw new Error(`Expected llm model slice for ${req.modelName}, got ${slice.kind}`)
     }
 
+    const llmModel = slice.model
     const defaults = slice.defaults ?? { perAttemptTimeoutMs: 30000, fullChainTimeoutMs: 60000, fallbackHttpCodes: [401, 402, 403, 429, 500, 502, 503, 504] }
-    const fallbackHttpCodes = slice.model.fallbackTriggers?.httpCodes ?? defaults.fallbackHttpCodes ?? [401, 402, 403, 429, 500, 502, 503, 504]
+    const fallbackHttpCodes = llmModel.fallbackTriggers?.httpCodes ?? defaults.fallbackHttpCodes ?? [401, 402, 403, 429, 500, 502, 503, 504]
 
     const allFailures: Array<{ provider: string, keyId: string, status: number | 'timeout', bodySnippet?: string, errorMessage?: string }> = []
     let triedUpstreams = 0
 
-    for (let i = 0; i < slice.model.upstreams.length; i += 1) {
-      const upstream = slice.model.upstreams[i]
+    async function attemptUpstream(upstream: LlmUpstream, index: number) {
       const provider = deriveProviderTag(upstream.baseURL)
       triedUpstreams += 1
       // Surface the current upstream so the caller can label success metrics
@@ -387,7 +408,7 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
 
       const result = await dispatchOneUpstream(
         upstream,
-        i,
+        index,
         req,
         perAttemptTimeoutMs,
         fallbackHttpCodes,
@@ -397,14 +418,70 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
       if (result.kind === 'ok') {
         if (ctx)
           ctx.upstreamModel = result.upstreamModel
-        return result.response
+        return { kind: 'ok' as const, response: result.response }
       }
 
-      // This upstream exhausted; record and continue.
       options.gatewayMetrics?.keyExhaustedCount.add(1, { provider })
+      return {
+        kind: 'exhausted' as const,
+        statuses: result.failures.map(failure => failure.status),
+      }
     }
 
-    // FULL exhaustion: every upstream's every key failed.
+    async function routeGroup(group: LlmRoutingGroup): Promise<
+      | { kind: 'ok', response: Response }
+      | { kind: 'exhausted', statuses: Array<number | 'timeout'>, transitionBlocked: boolean }
+    > {
+      const statuses: Array<number | 'timeout'> = []
+      for (let groupCandidateIndex = 0; groupCandidateIndex < group.upstreamIds.length; groupCandidateIndex += 1) {
+        const upstreamId = group.upstreamIds[groupCandidateIndex]
+        const index = llmModel.upstreams.findIndex(upstream => upstream.id === upstreamId)
+        if (index === -1) {
+          throw new Error(
+            `LLM routing group ${group.id} references unknown upstream ${upstreamId} for model ${req.modelName}`,
+          )
+        }
+
+        const result = await attemptUpstream(llmModel.upstreams[index], index)
+        if (result.kind === 'ok')
+          return result
+        statuses.push(...result.statuses)
+        const hasNextCandidate = groupCandidateIndex < group.upstreamIds.length - 1
+        if (hasNextCandidate && !failuresMatch(result.statuses, group.retryOn))
+          return { kind: 'exhausted', statuses, transitionBlocked: true }
+      }
+
+      return { kind: 'exhausted', statuses, transitionBlocked: false }
+    }
+
+    if (llmModel.routing != null) {
+      for (let groupIndex = 0; groupIndex < llmModel.routing.groups.length; groupIndex += 1) {
+        const group = llmModel.routing.groups[groupIndex]
+        const result = await routeGroup(group)
+        if (result.kind === 'ok')
+          return result.response
+
+        const hasNextGroup = groupIndex < llmModel.routing.groups.length - 1
+        if (
+          result.transitionBlocked
+          || !hasNextGroup
+          || !failuresMatch(result.statuses, group.continueOn)
+        ) {
+          break
+        }
+      }
+    }
+    else {
+      for (let index = 0; index < llmModel.upstreams.length; index += 1) {
+        const result = await attemptUpstream(llmModel.upstreams[index], index)
+        if (result.kind === 'ok')
+          return result.response
+      }
+    }
+
+    // Terminal exhaustion: every transition allowed by the active provider
+    // route has failed. A policy boundary may intentionally leave later
+    // upstreams untouched.
     const lastFailure = allFailures.at(-1)
     if (lastFailure == null) {
       // Should not happen: schema guarantees ≥1 upstream and ≥1 key. Treat
@@ -412,9 +489,9 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
       throw new Error(`Router exhausted with no recorded failures for model ${req.modelName}`)
     }
 
-    // Same-status exhaustion: every recorded failure shares the same
-    // status (or 'timeout'). Strong signal of an account-level / shared-
-    // backend cap that ordinary fallback cannot recover from.
+    // Same-status exhaustion: every recorded failure shares one status (or
+    // timeout). This is a strong signal of a shared upstream constraint that
+    // ordinary candidate fallback cannot recover from.
     const distinctStatuses = new Set(allFailures.map(f => f.status))
     if (distinctStatuses.size === 1) {
       const status = allFailures[0].status
@@ -553,8 +630,9 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
             status_code: rawStatus,
           })
           if (!fallbackHttpCodes.includes(rawStatus)) {
-            // Same policy as chat: non-fallback status stops this upstream
-            // but the outer loop still tries the next upstream.
+            // Same key-level policy as chat: stop rotating credentials in this
+            // candidate. The enclosing group separately decides whether another
+            // candidate may be tried.
             attemptIndex += 1
             break
           }
@@ -572,14 +650,14 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
   }
 
   /**
-   * Capacity-aware layer over {@link dispatchOneTtsUpstream}: spreads one TTS
-   * request across the model's pool (one app_id per upstream) by least-loaded
-   * ordering, gating each dispatch on an atomic concurrency-slot acquire.
+   * Capacity-aware layer over {@link dispatchOneTtsUpstream}: gates each capped
+   * dispatch on an atomic concurrency-slot acquire. It can preserve configured
+   * order or rank equivalent accounts by current in-flight usage.
    *
    * Returns:
-   * - the 2xx `Response` on success,
-   * - `null` when every dispatched upstream exhausted (caller maps the recorded
-   *   failures to an upstream error via the shared exhaustion path),
+   * - an `ok` result with the 2xx `Response`,
+   * - an `exhausted` result with every attempted status and whether a retry
+   *   policy blocked the remaining peers,
    * - throws 503 `TTS_POOL_SATURATED` when every pool was at capacity or in a
    *   429 cool-down so nothing was dispatched - fail-fast with context, never a
    *   silent stall (origin R3).
@@ -589,9 +667,14 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
     modelName: string,
     attemptUpstream: (upstream: TtsUpstream, index: number) => Promise<
       | { kind: 'ok', response: Response }
-      | { kind: 'exhausted', sawTooManyRequests: boolean }
+      | { kind: 'exhausted', sawTooManyRequests: boolean, statuses: Array<number | 'timeout'> }
     >,
-  ): Promise<Response | null> {
+    retryOn?: RouteFailureTriggers,
+    strategy: 'least-inflight' | 'ordered' = 'least-inflight',
+  ): Promise<
+    | { kind: 'ok', response: Response }
+    | { kind: 'exhausted', statuses: Array<number | 'timeout'>, transitionBlocked: boolean }
+  > {
     async function markSaturated(upstream: TtsUpstream, poolId: string): Promise<void> {
       await ledger.markSaturated(poolId, ttsPoolSaturationTtlSeconds)
       options.gatewayMetrics?.poolSaturationMarked.add(1, {
@@ -600,12 +683,11 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
       })
     }
 
-    // Best-effort pre-read: order pools least-loaded-first (spreads load) and
-    // drop pools already full or in a saturation cool-down. tryAcquire below is
-    // the authoritative gate against the cross-replica race — ordering only
-    // decides *preference*, not correctness.
-    const ranked = (await Promise.all(upstreams.map(async (upstream, index) => {
-      const poolId = ttsPoolId(upstream)
+    // Best-effort pre-read drops pools already full or in a saturation
+    // cool-down. tryAcquire below remains the authoritative gate against the
+    // cross-replica race.
+    const candidates = await Promise.all(upstreams.map(async (upstream, index) => {
+      const poolId = ttsPoolId(upstream, modelName)
       const maxConcurrency = typeof upstream.maxConcurrency === 'number' ? upstream.maxConcurrency : null
       const saturated = await ledger.isSaturated(poolId)
       if (saturated) {
@@ -614,30 +696,39 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
           index,
           poolId,
           maxConcurrency,
-          remaining: maxConcurrency == null ? Number.POSITIVE_INFINITY : 0,
+          inflight: Number.POSITIVE_INFINITY,
           eligible: false,
         }
       }
       if (maxConcurrency == null)
-        return { upstream, index, poolId, maxConcurrency, remaining: Number.POSITIVE_INFINITY, eligible: true }
+        return { upstream, index, poolId, maxConcurrency, inflight: 0, eligible: true }
 
       const inflight = await ledger.currentInflight(poolId)
-      const remaining = maxConcurrency - inflight
-      return { upstream, index, poolId, maxConcurrency, remaining, eligible: remaining > 0 }
-    })))
-      .filter(c => c.eligible)
-      .sort((a, b) => b.remaining - a.remaining)
+      return { upstream, index, poolId, maxConcurrency, inflight, eligible: inflight < maxConcurrency }
+    }))
+    const eligible = candidates.filter(c => c.eligible)
+    const ranked = strategy === 'least-inflight'
+      ? eligible.sort((a, b) => a.inflight - b.inflight)
+      : eligible
 
     let dispatchedAny = false
-    for (const { upstream, index, poolId, maxConcurrency } of ranked) {
+    let attemptedPools = 0
+    const statuses: Array<number | 'timeout'> = []
+    for (let rankedIndex = 0; rankedIndex < ranked.length; rankedIndex += 1) {
+      const { upstream, index, poolId, maxConcurrency } = ranked[rankedIndex]
+      const hasNextCandidate = rankedIndex < ranked.length - 1
       if (maxConcurrency == null) {
         // Unlimited pool — dispatch without occupying a slot.
         dispatchedAny = true
+        attemptedPools += 1
         const result = await attemptUpstream(upstream, index)
         if (result.kind === 'ok')
-          return result.response
+          return result
+        statuses.push(...result.statuses)
         if (result.sawTooManyRequests)
           await markSaturated(upstream, poolId)
+        if (hasNextCandidate && retryOn != null && !failuresMatch(result.statuses, retryOn))
+          return { kind: 'exhausted', statuses, transitionBlocked: true }
         continue
       }
 
@@ -652,12 +743,16 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
       }
 
       dispatchedAny = true
+      attemptedPools += 1
       try {
         const result = await attemptUpstream(upstream, index)
         if (result.kind === 'ok')
-          return result.response
+          return result
+        statuses.push(...result.statuses)
         if (result.sawTooManyRequests)
           await markSaturated(upstream, poolId)
+        if (hasNextCandidate && retryOn != null && !failuresMatch(result.statuses, retryOn))
+          return { kind: 'exhausted', statuses, transitionBlocked: true }
       }
       finally {
         await ledger.release(poolId)
@@ -672,7 +767,15 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
       )
     }
 
-    return null
+    // Advancing past a group requires evidence from every candidate. A pool
+    // skipped because it was full, circuit-broken, or lost the acquire race has
+    // not produced a failure status, so it must block the transition even when
+    // every dispatched pool returned an allowed status.
+    return {
+      kind: 'exhausted',
+      statuses,
+      transitionBlocked: attemptedPools !== upstreams.length,
+    }
   }
 
   async function routeTts(req: { modelName: string, input: TtsInput, abortSignal?: AbortSignal }, ctx?: LlmRouteContext): Promise<Response> {
@@ -694,9 +797,6 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
     const defaults = slice.defaults ?? { perAttemptTimeoutMs: 30000, fullChainTimeoutMs: 60000, fallbackHttpCodes: [401, 402, 403, 429, 500, 502, 503, 504] }
     const fallbackHttpCodes = ttsModel.fallbackTriggers?.httpCodes ?? defaults.fallbackHttpCodes ?? [401, 402, 403, 429, 500, 502, 503, 504]
 
-    // Adapters POST to unspeech `/v1/audio/speech`; resolve the base URL once
-    // per request rather than per upstream attempt so a single configKV miss
-    // surfaces as a clean 503 before any key rotation happens.
     const unspeechBaseURL = (await options.configKV.getOrThrow('UNSPEECH_UPSTREAM')).restBaseURL
 
     const allFailures: Array<{ provider: string, keyId: string, status: number | 'timeout', errorMessage?: string }> = []
@@ -712,7 +812,7 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
     // so the caller can circuit-break thatpool.
     async function attemptUpstream(upstream: TtsUpstream, index: number): Promise<
       | { kind: 'ok', response: Response }
-      | { kind: 'exhausted', sawTooManyRequests: boolean }
+      | { kind: 'exhausted', sawTooManyRequests: boolean, statuses: Array<number | 'timeout'> }
     > {
       const providerTag = deriveProviderTag(upstream.baseURL)
       triedUpstreams += 1
@@ -741,25 +841,93 @@ export function createLlmRouterService(options: CreateLlmRouterServiceOptions) {
       }
 
       options.gatewayMetrics?.keyExhaustedCount.add(1, { provider: providerTag })
-      return { kind: 'exhausted', sawTooManyRequests: result.failures.some(f => f.status === 429) }
+      return {
+        kind: 'exhausted',
+        sawTooManyRequests: result.failures.some(f => f.status === 429),
+        statuses: result.failures.map(failure => failure.status),
+      }
     }
 
-    // A model "uses the pool" when any upstream declares a concurrency cap. Models
-    // without one keep the original fixed-order fallback and make zero Redis
-    // calls — no behavior change for existing single-app configs.
-    const poolingEnabled = ttsModel.upstreams.some(u => typeof u.maxConcurrency === 'number')
+    async function routeGroup(group: TtsRoutingGroup): Promise<
+      | { kind: 'ok', response: Response }
+      | { kind: 'exhausted', statuses: Array<number | 'timeout'>, transitionBlocked: boolean }
+    > {
+      const indexedUpstreams = group.upstreamIds.map((upstreamId) => {
+        const index = ttsModel.upstreams.findIndex(upstream => upstream.id === upstreamId)
+        if (index === -1) {
+          throw new Error(
+            `TTS routing group ${group.id} references unknown upstream ${upstreamId} for model ${req.modelName}`,
+          )
+        }
+        return { upstream: ttsModel.upstreams[index], index }
+      })
 
-    if (!poolingEnabled) {
-      for (let i = 0; i < ttsModel.upstreams.length; i += 1) {
-        const result = await attemptUpstream(ttsModel.upstreams[i], i)
+      const capacityManaged = indexedUpstreams.some(({ upstream }) => upstream.maxConcurrency != null)
+      if (group.strategy === 'least-inflight' || capacityManaged) {
+        const indexByUpstream = new Map(indexedUpstreams.map(({ upstream, index }) => [upstream, index]))
+        return routeTtsAcrossPools(
+          indexedUpstreams.map(({ upstream }) => upstream),
+          req.modelName,
+          (upstream) => {
+            const index = indexByUpstream.get(upstream)
+            if (index == null)
+              throw new Error(`TTS routing lost upstream index for model ${req.modelName}`)
+            return attemptUpstream(upstream, index)
+          },
+          group.retryOn,
+          group.strategy,
+        )
+      }
+
+      const statuses: Array<number | 'timeout'> = []
+      for (let groupCandidateIndex = 0; groupCandidateIndex < indexedUpstreams.length; groupCandidateIndex += 1) {
+        const { upstream, index } = indexedUpstreams[groupCandidateIndex]
+        const result = await attemptUpstream(upstream, index)
+        if (result.kind === 'ok')
+          return result
+        statuses.push(...result.statuses)
+        const hasNextCandidate = groupCandidateIndex < indexedUpstreams.length - 1
+        if (hasNextCandidate && !failuresMatch(result.statuses, group.retryOn))
+          return { kind: 'exhausted', statuses, transitionBlocked: true }
+      }
+
+      return { kind: 'exhausted', statuses, transitionBlocked: false }
+    }
+
+    if (ttsModel.routing != null) {
+      for (let groupIndex = 0; groupIndex < ttsModel.routing.groups.length; groupIndex += 1) {
+        const group = ttsModel.routing.groups[groupIndex]
+        const result = await routeGroup(group)
         if (result.kind === 'ok')
           return result.response
+
+        const hasNextGroup = groupIndex < ttsModel.routing.groups.length - 1
+        if (
+          result.transitionBlocked
+          || !hasNextGroup
+          || !failuresMatch(result.statuses, group.continueOn)
+        ) {
+          break
+        }
       }
     }
     else {
-      const served = await routeTtsAcrossPools(ttsModel.upstreams, req.modelName, attemptUpstream)
-      if (served != null)
-        return served
+      // Models without an explicit provider route preserve the established
+      // behavior: fixed order unless any upstream declares a concurrency cap.
+      const poolingEnabled = ttsModel.upstreams.some(u => typeof u.maxConcurrency === 'number')
+
+      if (!poolingEnabled) {
+        for (let i = 0; i < ttsModel.upstreams.length; i += 1) {
+          const result = await attemptUpstream(ttsModel.upstreams[i], i)
+          if (result.kind === 'ok')
+            return result.response
+        }
+      }
+      else {
+        const result = await routeTtsAcrossPools(ttsModel.upstreams, req.modelName, attemptUpstream)
+        if (result.kind === 'ok')
+          return result.response
+      }
     }
 
     const lastFailure = allFailures.at(-1)
diff --git a/apps/server/src/services/domain/llm-router/tests/router.test.ts b/apps/server/src/services/domain/llm-router/tests/router.test.ts
index c9627ef4c..a6546d262 100644
--- a/apps/server/src/services/domain/llm-router/tests/router.test.ts
+++ b/apps/server/src/services/domain/llm-router/tests/router.test.ts
@@ -77,7 +77,7 @@ function makeLedger(overrides: Partial<ConcurrencyLedger> = {}): ConcurrencyLedg
 function makeConfigKV(config: RouterConfig | null): ConfigKVService {
   return {
     getOptional: vi.fn(async (key: string) => (key === 'LLM_ROUTER_CONFIG' ? config : null)),
-    // routeTts reads UNSPEECH_UPSTREAM once per request via getOrThrow.
+    // routeTts resolves UNSPEECH_UPSTREAM lazily when the chosen adapter needs it.
     // LLM-side tests never invoke routeTts so the value is irrelevant; TTS
     // tests need a populated restBaseURL.
     getOrThrow: vi.fn(async (key: string) => {
@@ -691,6 +691,121 @@ describe('createLlmRouterService', () => {
     expect((configKV.getOptional as ReturnType<typeof vi.fn>).mock.calls.length).toBe(2)
   })
 
+  describe('route LLM provider groups', () => {
+    function makeGroupedLlmRouter(fetchImpl: typeof fetch) {
+      const { config, crypto } = makeConfig({
+        upstreams: [
+          { baseURL: 'https://api.stepfun.com/step_plan/v1', keyIds: ['plan-a'] },
+          { baseURL: 'https://api.stepfun.com/step_plan/v1', keyIds: ['plan-b'] },
+          { baseURL: 'https://api.stepfun.com/v1', keyIds: ['paygo'] },
+        ],
+      })
+      const model = config.llm.models['openai/gpt-5-mini']
+      Object.assign(model.upstreams[0], { id: 'plan-a' })
+      Object.assign(model.upstreams[1], { id: 'plan-b' })
+      Object.assign(model.upstreams[2], { id: 'paygo' })
+      Object.assign(model, {
+        routing: {
+          groups: [
+            {
+              id: 'plan',
+              upstreamIds: ['plan-a', 'plan-b'],
+              retryOn: {
+                httpCodes: [402, 429, 500, 502, 503, 504],
+                onTimeout: true,
+              },
+              continueOn: {
+                httpCodes: [402],
+                onTimeout: false,
+              },
+            },
+            {
+              id: 'paygo',
+              upstreamIds: ['paygo'],
+              retryOn: {
+                httpCodes: [429, 500, 502, 503, 504],
+                onTimeout: true,
+              },
+            },
+          ],
+        },
+      })
+
+      return createLlmRouterService({
+        configKV: makeConfigKV(config),
+        envelopeCrypto: crypto,
+        gatewayMetrics: makeMetrics(),
+        fetchImpl,
+        redis: makeRedisStub(),
+        concurrencyLedger: makeLedger(),
+      })
+    }
+
+    it('uses the ordinary LLM API only after every Plan account returns 402', async () => {
+      const calledURLs: string[] = []
+      const fetchImpl = vi.fn(async (input: string | URL | Request) => {
+        const url = String(input)
+        calledURLs.push(url)
+        if (url.includes('/step_plan/'))
+          return failResponse(402, { error: { code: 'quota_exceeded' } })
+        return happyResponse({ id: 'completion' })
+      }) as unknown as typeof fetch
+
+      const router = makeGroupedLlmRouter(fetchImpl)
+      const response = await router.route({
+        modelName: 'openai/gpt-5-mini',
+        body: { messages: [] },
+      })
+
+      expect(response.status).toBe(200)
+      expect(calledURLs).toEqual([
+        'https://api.stepfun.com/step_plan/v1/chat/completions',
+        'https://api.stepfun.com/step_plan/v1/chat/completions',
+        'https://api.stepfun.com/v1/chat/completions',
+      ])
+    })
+
+    it('does not spend ordinary LLM API balance when the Plan group is rate-limited', async () => {
+      const calledURLs: string[] = []
+      const fetchImpl = vi.fn(async (input: string | URL | Request) => {
+        calledURLs.push(String(input))
+        return failResponse(429)
+      }) as unknown as typeof fetch
+
+      const router = makeGroupedLlmRouter(fetchImpl)
+
+      await expect(router.route({
+        modelName: 'openai/gpt-5-mini',
+        body: { messages: [] },
+      })).rejects.toBeInstanceOf(ApiError)
+
+      expect(calledURLs).toEqual([
+        'https://api.stepfun.com/step_plan/v1/chat/completions',
+        'https://api.stepfun.com/step_plan/v1/chat/completions',
+      ])
+      expect(calledURLs).not.toContain('https://api.stepfun.com/v1/chat/completions')
+    })
+
+    it('stops the LLM provider route immediately on Plan authentication failure', async () => {
+      const calledURLs: string[] = []
+      const fetchImpl = vi.fn(async (input: string | URL | Request) => {
+        calledURLs.push(String(input))
+        return failResponse(401)
+      }) as unknown as typeof fetch
+
+      const router = makeGroupedLlmRouter(fetchImpl)
+
+      await expect(router.route({
+        modelName: 'openai/gpt-5-mini',
+        body: { messages: [] },
+      })).rejects.toBeInstanceOf(ApiError)
+
+      expect(calledURLs).toEqual([
+        'https://api.stepfun.com/step_plan/v1/chat/completions',
+      ])
+    })
+  })
+
   // --- routeTts adapter error contract -------------------------------------
   //
   // ROOT CAUSE:
@@ -899,9 +1014,305 @@ describe('createLlmRouterService', () => {
     })
   })
 
+  describe('routeTts provider groups', () => {
+    function endpointProfileFrom(init?: RequestInit): string {
+      const body = JSON.parse(String(init?.body)) as {
+        extra_body?: { endpoint_profile?: string }
+      }
+      return body.extra_body?.endpoint_profile ?? 'default'
+    }
+
+    function makeGroupedStepfunConfig(): { config: RouterConfig, crypto: ReturnType<typeof createEnvelopeCrypto> } {
+      const crypto = createEnvelopeCrypto({ masterKey: freshMasterKey() })
+      const modelName = 'stepfun/stepaudio-2.5-tts'
+      const upstreams = [
+        {
+          id: 'plan-a',
+          baseURL: 'https://api.stepfun.com',
+          keyId: 'plan-key-a',
+          endpointProfile: 'step-plan',
+        },
+        {
+          id: 'plan-b',
+          baseURL: 'https://api.stepfun.com',
+          keyId: 'plan-key-b',
+          endpointProfile: 'step-plan',
+        },
+        {
+          id: 'paygo',
+          baseURL: 'https://api.stepfun.com',
+          keyId: 'paygo-key',
+          endpointProfile: 'default',
+        },
+      ].map(upstream => ({
+        id: upstream.id,
+        baseURL: upstream.baseURL,
+        keys: [{
+          id: upstream.keyId,
+          ciphertext: crypto.encryptKey(`sk-${upstream.keyId}`, {
+            modelName,
+            keyEntryId: upstream.keyId,
+          }),
+        }],
+        adapterParams: {
+          endpointProfile: upstream.endpointProfile,
+          model: 'stepaudio-2.5-tts',
+        },
+      }))
+
+      const config = {
+        llm: { models: {} },
+        tts: {
+          models: {
+            [modelName]: {
+              provider: 'stepfun',
+              upstreams,
+              routing: {
+                groups: [
+                  {
+                    id: 'plan',
+                    upstreamIds: ['plan-a', 'plan-b'],
+                    strategy: 'ordered',
+                    retryOn: {
+                      httpCodes: [402, 429, 500, 502, 503, 504],
+                      onTimeout: true,
+                    },
+                    continueOn: {
+                      httpCodes: [402],
+                      onTimeout: false,
+                    },
+                  },
+                  {
+                    id: 'paygo',
+                    upstreamIds: ['paygo'],
+                    strategy: 'ordered',
+                    retryOn: {
+                      httpCodes: [429, 500, 502, 503, 504],
+                      onTimeout: true,
+                    },
+                  },
+                ],
+              },
+              fallbackTriggers: {
+                httpCodes: [401, 402, 429, 500, 502, 503, 504],
+                onTimeout: true,
+              },
+            },
+          },
+        },
+        defaults: {
+          perAttemptTimeoutMs: 5000,
+          fullChainTimeoutMs: 10000,
+          fallbackHttpCodes: [401, 402, 429, 500, 502, 503, 504],
+        },
+      } as unknown as RouterConfig
+
+      return { config, crypto }
+    }
+
+    function makeGroupedStepfunRouter(
+      fetchImpl: typeof fetch,
+    ): ReturnType<typeof createLlmRouterService> {
+      const { config, crypto } = makeGroupedStepfunConfig()
+      return createLlmRouterService({
+        configKV: makeConfigKV(config),
+        envelopeCrypto: crypto,
+        gatewayMetrics: makeMetrics(),
+        fetchImpl,
+        redis: makeRedisStub(),
+        concurrencyLedger: makeLedger(),
+      })
+    }
+
+    it('uses pay-as-you-go only after every Plan account reports quota exhaustion', async () => {
+      const calledProfiles: string[] = []
+      const fetchImpl = vi.fn(async (input: string | URL | Request, init?: RequestInit) => {
+        expect(String(input)).toBe('http://unspeech.local:5933/v1/audio/speech')
+        const profile = endpointProfileFrom(init)
+        calledProfiles.push(profile)
+        if (profile === 'step-plan')
+          return failResponse(402, { error: { code: 'quota_exceeded' } })
+        return new Response(new Uint8Array([0x01]), {
+          status: 200,
+          headers: { 'content-type': 'audio/mpeg' },
+        })
+      }) as unknown as typeof fetch
+
+      const router = makeGroupedStepfunRouter(fetchImpl)
+      const response = await router.routeTts({
+        modelName: 'stepfun/stepaudio-2.5-tts',
+        input: { text: '你好' },
+      })
+
+      expect(response.status).toBe(200)
+      expect(calledProfiles).toEqual(['step-plan', 'step-plan', 'default'])
+    })
+
+    it('stays inside the Plan group when a Plan account succeeds', async () => {
+      const calledProfiles: string[] = []
+      const fetchImpl = vi.fn(async (input: string | URL | Request, init?: RequestInit) => {
+        expect(String(input)).toBe('http://unspeech.local:5933/v1/audio/speech')
+        calledProfiles.push(endpointProfileFrom(init))
+        return new Response(new Uint8Array([0x01]), {
+          status: 200,
+          headers: { 'content-type': 'audio/mpeg' },
+        })
+      }) as unknown as typeof fetch
+
+      const router = makeGroupedStepfunRouter(fetchImpl)
+      const response = await router.routeTts({
+        modelName: 'stepfun/stepaudio-2.5-tts',
+        input: { text: '你好' },
+      })
+
+      expect(response.status).toBe(200)
+      expect(calledProfiles).toEqual(['step-plan'])
+    })
+
+    it('requires UNSPEECH_UPSTREAM for an endpoint-profile request', async () => {
+      const { config, crypto } = makeGroupedStepfunConfig()
+      const configKV = makeConfigKV(config)
+      const getOrThrow = vi.fn(async () => {
+        throw new Error('UNSPEECH_UPSTREAM not configured')
+      })
+      Object.assign(configKV, { getOrThrow })
+      const fetchImpl = vi.fn(async () => new Response(new Uint8Array([0x01]), {
+        status: 200,
+        headers: { 'content-type': 'audio/mpeg' },
+      })) as unknown as typeof fetch
+      const router = createLlmRouterService({
+        configKV,
+        envelopeCrypto: crypto,
+        gatewayMetrics: makeMetrics(),
+        fetchImpl,
+        redis: makeRedisStub(),
+        concurrencyLedger: makeLedger(),
+      })
+
+      await expect(router.routeTts({
+        modelName: 'stepfun/stepaudio-2.5-tts',
+        input: { text: '你好' },
+      })).rejects.toThrow('UNSPEECH_UPSTREAM not configured')
+
+      expect(fetchImpl).not.toHaveBeenCalled()
+      expect(getOrThrow).toHaveBeenCalledWith('UNSPEECH_UPSTREAM')
+    })
+
+    it('requires UNSPEECH_UPSTREAM for the StepFun voice catalog', async () => {
+      const { config, crypto } = makeGroupedStepfunConfig()
+      const configKV = makeConfigKV(config)
+      const getOrThrow = vi.fn(async () => {
+        throw new Error('UNSPEECH_UPSTREAM not configured')
+      })
+      Object.assign(configKV, { getOrThrow })
+      const fetchImpl = vi.fn() as unknown as typeof fetch
+      const router = createLlmRouterService({
+        configKV,
+        envelopeCrypto: crypto,
+        gatewayMetrics: makeMetrics(),
+        fetchImpl,
+        redis: makeRedisStub(),
+        concurrencyLedger: makeLedger(),
+      })
+
+      await expect(
+        router.listTtsVoices('stepfun/stepaudio-2.5-tts'),
+      ).rejects.toThrow('UNSPEECH_UPSTREAM not configured')
+
+      expect(fetchImpl).not.toHaveBeenCalled()
+      expect(getOrThrow).toHaveBeenCalledWith('UNSPEECH_UPSTREAM')
+    })
+
+    it('keeps a Step Plan attempt timeout distinct from HTTP 500 at the paid boundary', async () => {
+      const { config, crypto } = makeGroupedStepfunConfig()
+      config.defaults!.perAttemptTimeoutMs = 10
+      const model = config.tts.models['stepfun/stepaudio-2.5-tts']
+      model.routing!.groups[0].continueOn = {
+        httpCodes: [500],
+        onTimeout: false,
+      }
+      const calledProfiles: string[] = []
+      const fetchImpl = vi.fn((input: string | URL | Request, init?: RequestInit) => {
+        expect(String(input)).toBe('http://unspeech.local:5933/v1/audio/speech')
+        const profile = endpointProfileFrom(init)
+        calledProfiles.push(profile)
+        if (profile !== 'step-plan') {
+          return Promise.resolve(new Response(new Uint8Array([0x01]), {
+            status: 200,
+            headers: { 'content-type': 'audio/mpeg' },
+          }))
+        }
+
+        return new Promise<Response>((_, reject) => {
+          const rejectAbort = () => reject(init?.signal?.reason ?? new Error('aborted'))
+          if (init?.signal?.aborted)
+            rejectAbort()
+          else
+            init?.signal?.addEventListener('abort', rejectAbort, { once: true })
+        })
+      }) as unknown as typeof fetch
+      const router = createLlmRouterService({
+        configKV: makeConfigKV(config),
+        envelopeCrypto: crypto,
+        gatewayMetrics: makeMetrics(),
+        fetchImpl,
+        redis: makeRedisStub(),
+        concurrencyLedger: makeLedger(),
+      })
+
+      await expect(router.routeTts({
+        modelName: 'stepfun/stepaudio-2.5-tts',
+        input: { text: '你好' },
+      })).rejects.toMatchObject({
+        statusCode: 504,
+        details: expect.objectContaining({ lastStatusCode: 'timeout' }),
+      })
+
+      expect(calledProfiles).toEqual(['step-plan', 'step-plan'])
+      expect(calledProfiles).not.toContain('default')
+    })
+
+    it('does not cross the paid boundary when the Plan group is rate-limited', async () => {
+      const calledProfiles: string[] = []
+      const fetchImpl = vi.fn(async (input: string | URL | Request, init?: RequestInit) => {
+        expect(String(input)).toBe('http://unspeech.local:5933/v1/audio/speech')
+        calledProfiles.push(endpointProfileFrom(init))
+        return failResponse(429)
+      }) as unknown as typeof fetch
+
+      const router = makeGroupedStepfunRouter(fetchImpl)
+
+      await expect(router.routeTts({
+        modelName: 'stepfun/stepaudio-2.5-tts',
+        input: { text: '你好' },
+      })).rejects.toBeInstanceOf(ApiError)
+
+      expect(calledProfiles).toEqual(['step-plan', 'step-plan'])
+      expect(calledProfiles).not.toContain('default')
+    })
+
+    it('stops the provider route immediately on a Plan authentication failure', async () => {
+      const calledProfiles: string[] = []
+      const fetchImpl = vi.fn(async (input: string | URL | Request, init?: RequestInit) => {
+        expect(String(input)).toBe('http://unspeech.local:5933/v1/audio/speech')
+        calledProfiles.push(endpointProfileFrom(init))
+        return failResponse(401)
+      }) as unknown as typeof fetch
+
+      const router = makeGroupedStepfunRouter(fetchImpl)
+
+      await expect(router.routeTts({
+        modelName: 'stepfun/stepaudio-2.5-tts',
+        input: { text: '你好' },
+      })).rejects.toBeInstanceOf(ApiError)
+
+      expect(calledProfiles).toEqual(['step-plan'])
+    })
+  })
+
   describe('routeTtspool capacity-aware routing', () => {
     // One app_id == one upstream (Volcengine `adapterParams.appid`), each capped
-    // at `maxConcurrency`. The router spreads load least-loaded-first across pools
+    // at `maxConcurrency`. The router spreads load least-inflight-first across pools
     // and circuit-breaks a pool on 429 (app_id concurrency exceeded upstream-side).
     function makePoolConfig(
       upstreams: Array<{ baseURL: string, appid: string, maxConcurrency?: number }>,
@@ -934,7 +1345,7 @@ describe('createLlmRouterService', () => {
       return { config, crypto }
     }
 
-    // Stateful in-memory ledger so least-loaded ordering and capacity gating are
+    // Stateful in-memory ledger so least-inflight ordering and capacity gating are
     // observable. `seed` pre-loads inflight counts to drive deterministic ranking.
     function makeStatefulLedger(seed: Record<string, number> = {}, saturatedSeed: string[] = []) {
       const inflight = new Map<string, number>(Object.entries(seed))
@@ -974,7 +1385,7 @@ describe('createLlmRouterService', () => {
       })
     }
 
-    it('routes to the least-loadedpool (covers AE1 — load spread, not first-fill)', async () => {
+    it('routes to the least-inflight pool (covers AE1 — load spread, not first-fill)', async () => {
       // @example two app_ids cap 10, seeded 8 vs 2 in-flight -> the new request
       // goes to the freer pool (app-2), not the config-first pool (app-1).
       const { config, crypto } = makePoolConfig([
@@ -992,6 +1403,208 @@ describe('createLlmRouterService', () => {
       expect(tryAcquire.mock.calls[0][0]).toBe('app-2')
     })
 
+    it('ranks least-inflight accounts by current usage when concurrency caps differ', async () => {
+      const { config, crypto } = makePoolConfig([
+        { baseURL: 'https://up-a.example', appid: 'app-1', maxConcurrency: 100 },
+        { baseURL: 'https://up-b.example', appid: 'app-2', maxConcurrency: 10 },
+      ])
+      const { ledger, tryAcquire } = makeStatefulLedger({ 'app-1': 50, 'app-2': 0 })
+      const fetchImpl = vi.fn(async () => happyResponse({ ok: 1 })) as unknown as typeof fetch
+
+      const router = makePoolRouter(config, crypto, ledger, fetchImpl)
+      const response = await router.routeTts({ modelName: 'tts-pool', input: { text: 'hi' } })
+
+      expect(response.status).toBe(200)
+      expect(tryAcquire).toHaveBeenCalledTimes(1)
+      expect(tryAcquire).toHaveBeenCalledWith('app-2', 10)
+    })
+
+    it('namespaces a non-appid pool by model and upstream id', async () => {
+      const crypto = createEnvelopeCrypto({ masterKey: freshMasterKey() })
+      const modelName = 'stepfun/stepaudio-2.5-tts'
+      const keyEntryId = 'plan-key'
+      const config = {
+        llm: { models: {} },
+        tts: {
+          models: {
+            [modelName]: {
+              provider: 'stepfun',
+              upstreams: [{
+                id: 'plan',
+                baseURL: 'https://api.stepfun.com',
+                keys: [{
+                  id: keyEntryId,
+                  ciphertext: crypto.encryptKey('sk-plan', { modelName, keyEntryId }),
+                }],
+                adapterParams: {
+                  endpointProfile: 'step-plan',
+                  model: 'stepaudio-2.5-tts',
+                },
+                maxConcurrency: 1,
+              }],
+              routing: {
+                groups: [{
+                  id: 'plan',
+                  upstreamIds: ['plan'],
+                  strategy: 'least-inflight',
+                  retryOn: { httpCodes: [402, 429, 500, 502, 503, 504], onTimeout: true },
+                }],
+              },
+              fallbackTriggers: { httpCodes: [402, 429, 500, 502, 503, 504], onTimeout: true },
+            },
+          },
+        },
+        defaults: {
+          perAttemptTimeoutMs: 5000,
+          fullChainTimeoutMs: 10000,
+          fallbackHttpCodes: [402, 429, 500, 502, 503, 504],
+        },
+      } as RouterConfig
+      const { ledger, tryAcquire } = makeStatefulLedger()
+      const fetchImpl = vi.fn(async () => new Response(new Uint8Array([0x01]), {
+        status: 200,
+        headers: { 'content-type': 'audio/mpeg' },
+      })) as unknown as typeof fetch
+
+      const router = makePoolRouter(config, crypto, ledger, fetchImpl)
+      const response = await router.routeTts({ modelName, input: { text: 'hi' } })
+
+      expect(response.status).toBe(200)
+      expect(tryAcquire).toHaveBeenCalledWith(
+        'model:["stepfun/stepaudio-2.5-tts","id","plan"]',
+        1,
+      )
+    })
+
+    it('enforces maxConcurrency for an ordered provider group', async () => {
+      const { config, crypto } = makePoolConfig([
+        { baseURL: 'https://up-a.example', appid: 'app-1', maxConcurrency: 10 },
+      ])
+      const model = config.tts.models['tts-pool']
+      Object.assign(model.upstreams[0], { id: 'primary' })
+      Object.assign(model, {
+        routing: {
+          groups: [{
+            id: 'primary',
+            upstreamIds: ['primary'],
+            strategy: 'ordered',
+            retryOn: { httpCodes: [429, 500, 502, 503, 504], onTimeout: true },
+          }],
+        },
+      })
+      const { ledger, tryAcquire, release } = makeStatefulLedger()
+      const fetchImpl = vi.fn(async () => happyResponse({ ok: 1 })) as unknown as typeof fetch
+
+      const router = makePoolRouter(config, crypto, ledger, fetchImpl)
+      const response = await router.routeTts({ modelName: 'tts-pool', input: { text: 'hi' } })
+
+      expect(response.status).toBe(200)
+      expect(tryAcquire).toHaveBeenCalledWith('app-1', 10)
+      expect(release).toHaveBeenCalledWith('app-1')
+    })
+
+    it('keeps least-inflight selection inside the active group before considering pay-as-you-go', async () => {
+      const { config, crypto } = makePoolConfig([
+        { baseURL: 'https://plan-a.example', appid: 'plan-a', maxConcurrency: 10 },
+        { baseURL: 'https://plan-b.example', appid: 'plan-b', maxConcurrency: 10 },
+        { baseURL: 'https://paygo.example', appid: 'paygo' },
+      ])
+      const model = config.tts.models['tts-pool']
+      Object.assign(model.upstreams[0], { id: 'plan-a' })
+      Object.assign(model.upstreams[1], { id: 'plan-b' })
+      Object.assign(model.upstreams[2], { id: 'paygo' })
+      Object.assign(model, {
+        routing: {
+          groups: [
+            {
+              id: 'plan',
+              upstreamIds: ['plan-a', 'plan-b'],
+              strategy: 'least-inflight',
+              retryOn: { httpCodes: [429, 500, 502, 503, 504], onTimeout: true },
+              continueOn: { httpCodes: [402], onTimeout: false },
+            },
+            {
+              id: 'paygo',
+              upstreamIds: ['paygo'],
+              strategy: 'ordered',
+              retryOn: { httpCodes: [429, 500, 502, 503, 504], onTimeout: true },
+            },
+          ],
+        },
+      })
+      const { ledger, tryAcquire } = makeStatefulLedger({ 'plan-a': 8, 'plan-b': 2 })
+      const selectedAppIds: string[] = []
+      const fetchImpl = vi.fn(async (_input: string | URL | Request, init?: RequestInit) => {
+        const body = JSON.parse(String(init?.body)) as { extra_body?: { app?: { appid?: string } } }
+        selectedAppIds.push(body.extra_body?.app?.appid ?? 'unknown')
+        return new Response(new Uint8Array([0x01]), {
+          status: 200,
+          headers: { 'content-type': 'audio/mpeg' },
+        })
+      }) as unknown as typeof fetch
+
+      const router = makePoolRouter(config, crypto, ledger, fetchImpl)
+      const response = await router.routeTts({ modelName: 'tts-pool', input: { text: 'hi' } })
+
+      expect(response.status).toBe(200)
+      expect(selectedAppIds).toEqual(['plan-b'])
+      expect(tryAcquire).toHaveBeenCalledTimes(1)
+      expect(tryAcquire).toHaveBeenCalledWith('plan-b', 10)
+    })
+
+    it('does not cross groups when a Plan account was skipped at its concurrency limit', async () => {
+      const { config, crypto } = makePoolConfig([
+        { baseURL: 'https://plan-a.example', appid: 'plan-a', maxConcurrency: 10 },
+        { baseURL: 'https://plan-b.example', appid: 'plan-b', maxConcurrency: 10 },
+        { baseURL: 'https://paygo.example', appid: 'paygo' },
+      ])
+      const model = config.tts.models['tts-pool']
+      Object.assign(model.upstreams[0], { id: 'plan-a' })
+      Object.assign(model.upstreams[1], { id: 'plan-b' })
+      Object.assign(model.upstreams[2], { id: 'paygo' })
+      Object.assign(model, {
+        routing: {
+          groups: [
+            {
+              id: 'plan',
+              upstreamIds: ['plan-a', 'plan-b'],
+              strategy: 'least-inflight',
+              retryOn: { httpCodes: [402, 429, 500, 502, 503, 504], onTimeout: true },
+              continueOn: { httpCodes: [402], onTimeout: false },
+            },
+            {
+              id: 'paygo',
+              upstreamIds: ['paygo'],
+              strategy: 'ordered',
+              retryOn: { httpCodes: [429, 500, 502, 503, 504], onTimeout: true },
+            },
+          ],
+        },
+      })
+      const { ledger } = makeStatefulLedger({ 'plan-a': 10, 'plan-b': 0 })
+      const selectedAppIds: string[] = []
+      const fetchImpl = vi.fn(async (_input: string | URL | Request, init?: RequestInit) => {
+        const body = JSON.parse(String(init?.body)) as { extra_body?: { app?: { appid?: string } } }
+        const appid = body.extra_body?.app?.appid ?? 'unknown'
+        selectedAppIds.push(appid)
+        if (appid === 'plan-b')
+          return failResponse(402, { error: { code: 'quota_exceeded' } })
+        return new Response(new Uint8Array([0x01]), {
+          status: 200,
+          headers: { 'content-type': 'audio/mpeg' },
+        })
+      }) as unknown as typeof fetch
+
+      const router = makePoolRouter(config, crypto, ledger, fetchImpl)
+
+      await expect(router.routeTts({
+        modelName: 'tts-pool',
+        input: { text: 'hi' },
+      })).rejects.toBeInstanceOf(ApiError)
+
+      expect(selectedAppIds).toEqual(['plan-b'])
+    })
+
     it('skips a fullpool and dispatches to one with capacity', async () => {
       // @example app-1 at cap (10/10) -> filtered out; app-2 (0/10) serves.
       const { config, crypto } = makePoolConfig([
diff --git a/apps/server/src/services/domain/llm-router/types.ts b/apps/server/src/services/domain/llm-router/types.ts
index 6c8e72fab..ebce6fd4d 100644
--- a/apps/server/src/services/domain/llm-router/types.ts
+++ b/apps/server/src/services/domain/llm-router/types.ts
@@ -14,8 +14,13 @@ import type {
   llmModelSchema,
   llmRouterConfigSchema,
   llmRouterDefaultsSchema,
+  llmRoutingGroupSchema,
+  llmRoutingSchema,
   llmUpstreamSchema,
+  routeFailureTriggersSchema,
   ttsModelSchema,
+  ttsRoutingGroupSchema,
+  ttsRoutingSchema,
   ttsUpstreamSchema,
 } from '../../adapters/config-kv'
 
@@ -31,25 +36,45 @@ export type RouterConfig = InferOutput<typeof llmRouterConfigSchema>
 export type RouterDefaults = InferOutput<typeof llmRouterDefaultsSchema>
 
 /**
- * LLM upstream — one provider endpoint with its ordered key list.
+ * LLM upstream — one candidate endpoint with its ordered key list.
  */
 export type LlmUpstream = InferOutput<typeof llmUpstreamSchema>
 
 /**
- * LLM model entry — ordered list of upstreams to try in fallback order.
+ * LLM model entry — upstream candidates plus an optional grouped route.
  */
 export type LlmModel = InferOutput<typeof llmModelSchema>
 
 /**
- * TTS upstream — one provider endpoint with adapter params + key list.
+ * LLM route composed from ordered candidate groups.
+ */
+export type LlmRouting = InferOutput<typeof llmRoutingSchema>
+
+/**
+ * One ordered group of interchangeable LLM candidates.
+ */
+export type LlmRoutingGroup = InferOutput<typeof llmRoutingGroupSchema>
+
+/**
+ * TTS upstream — one candidate endpoint with adapter params + key list.
  */
 export type TtsUpstream = InferOutput<typeof ttsUpstreamSchema>
 
 /**
- * TTS model entry — provider tag + ordered upstreams.
+ * TTS model entry — provider tag, upstream candidates, and optional grouped route.
  */
 export type TtsModel = InferOutput<typeof ttsModelSchema>
 
+/**
+ * TTS route composed from ordered candidate groups.
+ */
+export type TtsRouting = InferOutput<typeof ttsRoutingSchema>
+
+/**
+ * One group of interchangeable TTS candidates.
+ */
+export type TtsRoutingGroup = InferOutput<typeof ttsRoutingGroupSchema>
+
 /**
  * ASR model entry — provider tag + ordered upstreams for realtime transcription.
  */
@@ -66,6 +91,11 @@ export type AsrUpstream = InferOutput<typeof asrUpstreamSchema>
  */
 export type FallbackTriggers = InferOutput<typeof fallbackTriggersSchema>
 
+/**
+ * Failure allow-list that authorizes a routing transition.
+ */
+export type RouteFailureTriggers = InferOutput<typeof routeFailureTriggersSchema>
+
 /**
  * One entry in `upstream.keys`: stable id + at-rest envelope ciphertext.
  * The plaintext key is only produced lazily by the key-rotator at call time.
diff --git a/apps/server/src/utils/redis-keys.ts b/apps/server/src/utils/redis-keys.ts
index 435db6d86..5146ebb34 100644
--- a/apps/server/src/utils/redis-keys.ts
+++ b/apps/server/src/utils/redis-keys.ts
@@ -46,9 +46,10 @@ export function lockRedisKey(domain: string, ...identifiers: RedisKeyPart[]): st
 
 /**
  * In-flight request counter for one TTSpool (per app_id concurrency pool).
- * `poolId` is the upstream's `adapterParams.appid` (or baseURL fallback). The
- * counter is INCR'd on slot acquire and DECR'd on release; a short TTL bounds
- * leakage if a replica crashes between acquire and release.
+ * `poolId` is the upstream's global `adapterParams.appid` or a model-scoped
+ * upstream identity for providers without app ids. The counter is INCR'd on
+ * slot acquire and DECR'd on release; a short TTL bounds leakage if a replica
+ * crashes between acquire and release.
  */
 export function ttsPoolInflightRedisKey(poolId: string): string {
   return redisKeyFrom('tts', 'pool', 'inflight', poolId)