Why: Buffering a whole attempt hid live output, overflow detection missed common provider errors, and a cut-off tool call could still run.
Evidence: GOWORK=off go test -race -count=1 ./runtime/llm/ ./runtime/ passed.
Impact: WithRetry forwards events immediately and retries only when nothing has been forwarded. Length or an unclean end drops unfinished tool calls. Loop usage keeps a billing sum and the last request separately.
Refs: feature/llm-robustness
Co-authored-by: Cursor <cursoragent@cursor.com>