fix(anthropic): whitelist count tokens endpoint (#124)

Author: Kludex

gateway/src/providers/anthropic.ts

@@ -4,8 +4,10 @@ import { DefaultProviderProxy } from './default'
 
 export class AnthropicProvider extends DefaultProviderProxy {
   protected isWhitelistedEndpoint(): boolean {
+    // If there is a query string, drop the query string from the path.
+    const path = this.restOfPath.split('?')[0]
     // This endpoint is used by Claude Code.
-    return this.restOfPath === 'v1/messages/count_tokens'
+    return path === 'v1/messages/count_tokens'
   }
 
   protected modelAPI(): ModelAPI {

gateway/test/providers/anthropic.spec.ts

@@ -64,4 +64,19 @@ describe('anthropic', () => {
     expect(otelBatch, 'otelBatch length not 1').toHaveLength(1)
     expect(deserializeRequest(otelBatch[0]!)).toMatchSnapshot('span')
   })
+
+  test('should whitelist /v1/messages/count_tokens endpoint', async ({ gateway }) => {
+    const { fetch, otelBatch } = gateway
+
+    const client = new Anthropic({ authToken: 'healthy', baseURL: 'https://example.com/anthropic', fetch })
+
+    const result = await client.beta.messages.countTokens({
+      model: 'claude-sonnet-4-20250514',
+      messages: [{ role: 'user', content: 'What is the capital of France?' }],
+    })
+
+    expect(result).toMatchSnapshot('count_tokens')
+    expect(otelBatch, 'otelBatch should be empty for whitelisted endpoint').toHaveLength(1)
+    expect(deserializeRequest(otelBatch[0]!)).toMatchSnapshot('span')
+  })
 })

gateway/test/providers/anthropic.spec.ts.snap

@@ -591,3 +591,54 @@ exports[`anthropic > should call anthropic via gateway with stream > span 1`] =
   },
 ]
 `;
+
+exports[`anthropic > should whitelist /v1/messages/count_tokens endpoint > count_tokens 1`] = `
+{
+  "input_tokens": 14,
+}
+`;
+
+exports[`anthropic > should whitelist /v1/messages/count_tokens endpoint > span 1`] = `
+[
+  {
+    "attributes": {
+      "http.request.body.text": "{"model":"claude-sonnet-4-20250514","messages":[{"role":"user","content":"What is the capital of France?"}]}",
+      "http.request.header.accept": "application/json",
+      "http.request.header.anthropic-beta": "token-counting-2024-11-01",
+      "http.request.header.anthropic-version": "2023-06-01",
+      "http.request.header.authorization": "Bearer healthy",
+      "http.request.header.content-type": "application/json",
+      "http.request.header.user-agent": "Anthropic/JS 0.62.0",
+      "http.request.header.x-stainless-arch": "unknown",
+      "http.request.header.x-stainless-lang": "js",
+      "http.request.header.x-stainless-os": "Unknown",
+      "http.request.header.x-stainless-package-version": "0.62.0",
+      "http.request.header.x-stainless-retry-count": "0",
+      "http.request.header.x-stainless-runtime": "unknown",
+      "http.request.header.x-stainless-runtime-version": "unknown",
+      "http.request.method": "POST",
+      "http.response.header.content-length": "19",
+      "http.response.header.content-type": "application/json",
+      "http.response.header.server": "uvicorn",
+      "http.response.status_code": 200,
+      "logfire.json_schema": "{"type":"object","properties":{"http.request.method":{"type":"string"},"url.full":{"type":"string"},"http.request.header.accept":{"type":"string"},"http.request.header.anthropic-beta":{"type":"string"},"http.request.header.anthropic-version":{"type":"string"},"http.request.header.authorization":{"type":"string"},"http.request.header.content-type":{"type":"string"},"http.request.header.user-agent":{"type":"string"},"http.request.header.x-stainless-arch":{"type":"string"},"http.request.header.x-stainless-lang":{"type":"string"},"http.request.header.x-stainless-os":{"type":"string"},"http.request.header.x-stainless-package-version":{"type":"string"},"http.request.header.x-stainless-retry-count":{"type":"string"},"http.request.header.x-stainless-runtime":{"type":"string"},"http.request.header.x-stainless-runtime-version":{"type":"string"},"http.response.status_code":{"type":"number"},"http.response.header.content-length":{"type":"string"},"http.response.header.content-type":{"type":"string"},"http.response.header.server":{"type":"string"},"http.request.body.text":{"type":"string"}}}",
+      "logfire.level_num": 9,
+      "logfire.msg": "POST v1/messages/count_tokens?beta=true",
+      "url.full": "https://example.com/anthropic/v1/messages/count_tokens?beta=true",
+    },
+    "events": [],
+    "kind": 1,
+    "links": [],
+    "name": "POST v1/messages/count_tokens?beta=true",
+    "parentSpanId": undefined,
+    "resource": {
+      "service.name": "PAIG",
+      "service.version": "test",
+    },
+    "scope": "pydantic-ai-gateway",
+    "status": {
+      "code": 1,
+    },
+  },
+]
+`;

proxy-vcr/proxy_vcr/cassettes/anthropic-6f790aa5ed012c0702a8220c3507790e5636ee2f1c52e66e110d1dac712b2d63.yaml

@@ -0,0 +1,55 @@
+interactions:
+- request:
+    body: '{"model":"claude-sonnet-4-20250514","messages":[{"role":"user","content":"What
+      is the capital of France?"}]}'
+    headers:
+      accept:
+      - '*/*'
+      accept-encoding:
+      - gzip, deflate
+      anthropic-version:
+      - '2023-06-01'
+      connection:
+      - keep-alive
+      content-length:
+      - '108'
+      content-type:
+      - application/json
+      host:
+      - api.anthropic.com
+      user-agent:
+      - python-httpx/0.28.1
+    method: POST
+    uri: https://api.anthropic.com/v1/messages/count_tokens
+  response:
+    body:
+      string: '{"input_tokens":14}'
+    headers:
+      CF-RAY:
+      - 99a3fb68dde3fb9b-AMS
+      Connection:
+      - keep-alive
+      Content-Length:
+      - '19'
+      Content-Type:
+      - application/json
+      Date:
+      - Thu, 06 Nov 2025 10:42:04 GMT
+      Server:
+      - cloudflare
+      X-Robots-Tag:
+      - none
+      anthropic-organization-id:
+      - 44ae676c-958f-4d68-9108-eae9de7b366b
+      cf-cache-status:
+      - DYNAMIC
+      request-id:
+      - req_011CUrVifYHKXaAjjTXPgXS5
+      strict-transport-security:
+      - max-age=31536000; includeSubDomains; preload
+      x-envoy-upstream-service-time:
+      - '69'
+    status:
+      code: 200
+      message: OK
+version: 1