- Expanded `isAnthropicFastModeUnsupportedError` to treat 429 `rate_limit_error` responses mentioning fast mode as unsupported alongside 400 `invalid_request_error` speed-rejection cases.
- Added tests for unsupported-fast-mode detection covering 400, 429, and unrelated error payloads.
- Added `AgentSession.isFastModeActive()` with provider-scoped resolution and switched status-line rendering to use it for the fast-mode icon.