- Add httpx.TransportError to the transient-exception set so
incomplete chunked reads on streamed responses trigger a
fallback instead of cancelling the run (#1694 / c9f6dd86).
- Rewrite fallback to alternate primary/fallback with exponential
backoff instead of a single failover, so the agent survives
multi-minute gateway outages spanning both providers (#1695 /
c9a9a7cd).
- Default backoff schedule (0, 5, 15, 30, 45) reaches past the
gateway's ~30s recovery window; jittered ±25%.
- On exhaustion, surface a terminal AIMessage explaining the
outage instead of crashing — progress is checkpointed so the
user can retrigger to continue.
- Preserve fork conventions: Bedrock ClientError retryability
check, sync wrap_model_call (using time.sleep instead of
asyncio.sleep), and existing access-error surfacing for
Anthropic, OpenAI, and Bedrock (botocore) provider errors.
- Update triage ledger (c9f6dd86, c9a9a7cd → landed) and
re-render triage.md.
Refs: #139
When the primary model raises a transient provider error (5xx, 429,
connection/timeout) the request is retried once against a fallback
model from the other provider. Anthropic primaries fall back to
OpenAI and vice versa. Also bumps the SDK max_retries from the
default 2 to 6 so quick blips stay on the primary and keep prompt
caching warm.
Triggered by 529 OverloadedError traces that ended runs silently
with no Slack/Linear/PR reply.
