diff --git a/src/costrict/provider/fetch.ts b/src/costrict/provider/fetch.ts
index 14dbefc92..c974749e5 100644
--- a/src/costrict/provider/fetch.ts
+++ b/src/costrict/provider/fetch.ts
@@ -89,6 +89,7 @@ export function createCoStrictFetch(): CoStrictFetch {
     // ========== 步骤 3: 构建 headers ==========
     const headers = new Headers(init?.headers)
     headers.set('Authorization', `Bearer ${creds.access_token}`)
+    headers.set('User-Agent', `csc/${VERSION}`)
     headers.set('HTTP-Referer', 'https://github.com/zgsm-ai/costrict-cli')
     headers.set('X-Title', 'CoStrict-CLI')
     headers.set('X-Costrict-Version', `costrict-cli-${VERSION}`)
diff --git a/src/costrict/provider/index.ts b/src/costrict/provider/index.ts
index 1dcede320..0db3ebe0a 100644
--- a/src/costrict/provider/index.ts
+++ b/src/costrict/provider/index.ts
@@ -16,6 +16,7 @@ import type { Tools } from '../../Tool.js'
 import type { Options } from '../../services/api/claude.js'
 import OpenAI from 'openai'
 import { getProxyFetchOptions } from '../../utils/proxy.js'
+import { getUserAgent } from '../../utils/http.js'
 import { anthropicMessagesToOpenAI, anthropicToolsToOpenAI, anthropicToolChoiceToOpenAI, adaptOpenAIStreamToAnthropic } from '@ant/model-provider'
 import { normalizeMessagesForAPI } from '../../utils/messages.js'
 import { toolToAPISchema } from '../../utils/api.js'
@@ -103,6 +104,7 @@ export async function* queryModelCoStrict(
         forAnthropicAPI: false,
       }) as any,
       fetch: costrictFetch as any,
+      defaultHeaders: { 'User-Agent': getUserAgent() },
     })
 
     logForDebugging(
diff --git a/src/services/api/grok/client.ts b/src/services/api/grok/client.ts
index 060d12636..232583574 100644
--- a/src/services/api/grok/client.ts
+++ b/src/services/api/grok/client.ts
@@ -1,5 +1,6 @@
 import OpenAI from 'openai'
 import { getProxyFetchOptions } from 'src/utils/proxy.js'
+import { getUserAgent } from 'src/utils/http.js'
 
 /**
  * Environment variables:
@@ -30,6 +31,7 @@ export function getGrokClient(options?: {
     dangerouslyAllowBrowser: true,
     fetchOptions: getProxyFetchOptions({ forAnthropicAPI: false }),
     ...(options?.fetchOverride && { fetch: options.fetchOverride }),
+    defaultHeaders: { 'User-Agent': getUserAgent() },
   })
 
   if (!options?.fetchOverride) {
diff --git a/src/services/api/openai/client.ts b/src/services/api/openai/client.ts
index f7c4b27e8..d34ca7a42 100644
--- a/src/services/api/openai/client.ts
+++ b/src/services/api/openai/client.ts
@@ -3,6 +3,7 @@ import { openaiAdapter } from 'src/services/providerUsage/adapters/openai.js'
 import { updateProviderBuckets } from 'src/services/providerUsage/store.js'
 import { getProxyFetchOptions } from 'src/utils/proxy.js'
 import { isEnvTruthy } from 'src/utils/envUtils.js'
+import { getUserAgent } from 'src/utils/http.js'
 
 /**
  * Environment variables:
@@ -60,6 +61,7 @@ export function getOpenAIClient(options?: {
     ...(process.env.OPENAI_PROJECT_ID && { project: process.env.OPENAI_PROJECT_ID }),
     fetchOptions: getProxyFetchOptions({ forAnthropicAPI: false }),
     fetch: wrappedFetch,
+    defaultHeaders: { 'User-Agent': getUserAgent() },
   })
 
   if (!options?.fetchOverride) {
diff --git a/src/utils/http.ts b/src/utils/http.ts
index 93b87e8e0..45d8cce87 100644
--- a/src/utils/http.ts
+++ b/src/utils/http.ts
@@ -31,7 +31,7 @@ export function getUserAgent(): string {
   // so the read picks up the same setWorkload() value as getAttributionHeader.
   const workload = getWorkload()
   const workloadSuffix = workload ? `, workload/${workload}` : ''
-  return `claude-cli/${MACRO.VERSION} (${process.env.USER_TYPE}, ${process.env.CLAUDE_CODE_ENTRYPOINT ?? 'cli'}${agentSdkVersion}${clientApp}${workloadSuffix})`
+  return `csc/${MACRO.VERSION}`
 }
 
 export function getMCPUserAgent(): string {
@@ -46,7 +46,7 @@ export function getMCPUserAgent(): string {
     parts.push(`client-app/${process.env.CLAUDE_AGENT_SDK_CLIENT_APP}`)
   }
   const suffix = parts.length > 0 ? ` (${parts.join(', ')})` : ''
-  return `claude-code/${MACRO.VERSION}${suffix}`
+  return `csc/${MACRO.VERSION}${suffix}`
 }
 
 // User-Agent for WebFetch requests to arbitrary sites. `Claude-User` is
diff --git a/src/utils/sideQuery.ts b/src/utils/sideQuery.ts
index ab1ba9715..9e99c63fa 100644
--- a/src/utils/sideQuery.ts
+++ b/src/utils/sideQuery.ts
@@ -32,6 +32,7 @@ import { resolveCoStrictModel } from '../costrict/provider/modelMapping.js'
 import { getCoStrictBaseURL } from '../costrict/provider/auth.js'
 import { loadCoStrictCredentials } from '../costrict/provider/credentials.js'
 import { getProxyFetchOptions } from './proxy.js'
+import { getUserAgent } from './http.js'
 import { getMainLoopModel } from './model/model.js'
 import OpenAI from 'openai'
 
@@ -145,6 +146,7 @@ export async function sideQuery(opts: SideQueryOptions): Promise<BetaMessage> {
       dangerouslyAllowBrowser: true,
       fetchOptions: getProxyFetchOptions({ forAnthropicAPI: false }) as Record<string, unknown>,
       fetch: createCoStrictFetch() as unknown as typeof fetch,
+      defaultHeaders: { 'User-Agent': getUserAgent() },
     })
     return sideQueryOpenAICompat(opts, client, resolveCoStrictModel(getMainLoopModel()), 'CoStrict')
   }