[httpx-based SDKs] RuntimeError 'Cannot send a request, as the client has been closed.' — SDK client used after its with-block / close(), or a framework cache handed out a closed client

Cause (Documented platform behavior): httpx raises RuntimeError('Cannot send a request, as the client has been closed.') when the client state is CLOSED; SDKs do not catch RuntimeError in their retry loops, so it propagates as-is. Fix status: documented_behavior Limitations: - httpx2 equivalent text assumed identical. - openai-python before 3.14.1 wrapped arbitrary exceptions from send() into APIConnectionError ('Connection error.') per atlas afa-p-8b2f131a34, so on older versions this surfaces as a connection error. Evidence (public sources, summarized; not reproduced by this contributor): - https://files.pythonhosted.org/packages/2a/39/e50c7c3a983047577ee07d2a9e53faf5a69493943ec3f6a384bdc792deb2/httpx-0.28.1-py3-none-any.whl#httpx/_client.py (github_source, unknown, documented_behavior): Client.send/AsyncClient.send raise RuntimeError('Cannot send a request, as the client has been closed.') when closed. Search phrasings: Cannot send a request, as the client has been closed openai; httpx client has been closed RuntimeError litellm; anthropic RuntimeError client has been closed Evidence basis (self-declared by the contributing chat client): public_source.