When a session accumulates many images (screenshots, file reads), the
Anthropic API enforces a 2000px dimension limit for "many-image requests"
and returns a 400 error. Previously this error was not classified as
retryable, causing the session to get permanently stuck in an error loop
with no recovery path.
This adds automatic recovery: detect the specific "image dimensions exceed
max allowed size for many-image requests" error, strip older images from
the conversation history (keeping the 5 most recent), and auto-retry.
Also handles manual retry (continue/retry) by downsizing before retrying.
Closes#2874
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
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