Protects all models in the Primary/Backup chain regardless of context window:
- _context_budget(): 75% of model_cfg["context_k"] * 1000 (default 32k if unset)
- _estimate_tokens(): char count / 4 + 3k overhead for tool schemas
- _compact_messages(): truncates old tool results to 400 chars, keeps last 6
intact (~2 recent rounds), logs chars saved per compaction pass
- Compaction runs before every API call; log line now shows estimated token count
- Malformed tool call args logged with model/args detail instead of silent {}
- finish_reason check accepts "stop" and None alongside "tool_calls" (some
models return wrong reason even when tool_calls are present)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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