Retry short-lived 5xx/capacity errors (500/502/503/504 + message
patterns) with bounded backoff capped at 15s; honor Retry-After/reset
hints and skip when wait is too long. Keep 400 non-retryable. Enable the
retry hook for 500 alongside existing 429/503.
Deduplicate sanitized Antigravity tool names before emitting the single
functionDeclarations group to avoid upstream "Tool names must be unique"
rejections.
Add Headroom size diagnostics and phantom-savings warning when reported
token delta does not shrink the outbound payload.
Co-authored-by: Cursor <cursoragent@cursor.com>
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