fix: treat empty-string ANTHROPIC_API_KEY / ANTHROPIC_AUTH_TOKEN as absent

[okxint]

Summary

os.environ.get() returns "" for an env var that is present but empty — not None. When either ANTHROPIC_API_KEY or ANTHROPIC_AUTH_TOKEN was set to an empty string (common in CI, containers, and in the Claude Code shell which exports both as empty), the SDK stored "" as the credential.

For ANTHROPIC_AUTH_TOKEN, _bearer_auth then built {"Authorization": "Bearer "} — a header with a trailing space and no token. h11 validates header values at write time and rejects b'Bearer ':

h11._util.LocalProtocolError: Illegal header value b'Bearer '

surfaced as anthropic.APIConnectionError on every request.

Fix

Apply or None to both env reads in Anthropic.__init__ and AsyncAnthropic.__init__:

# before
api_key = os.environ.get("ANTHROPIC_API_KEY")
auth_token = os.environ.get("ANTHROPIC_AUTH_TOKEN")

# after
api_key = os.environ.get("ANTHROPIC_API_KEY") or None
auth_token = os.environ.get("ANTHROPIC_AUTH_TOKEN") or None

This coerces empty strings to None so the SDK treats a present-but-empty var the same as unset.

Tests

Added test_empty_string_env_credentials_treated_as_absent to both TestAnthropic and TestAsyncAnthropic, verifying that api_key, auth_token, and auth_headers are all None / {} when the env vars are set to "".

Closes #1640