Context Compression & MoA

源码版本v2026.7.20

Responsibility

Two things: (1) when history messages approach the provider's context limit, summarize/trim old messages to free up budget (context_compressor); (2) optionally use a Mixture-of-Agents path to aggregate outputs from multiple models (moa_loop). Both run inside the main loop — one keeps long conversations from overflowing the context window, the other aggregates multiple models for better answers.

Key Files

• context_compressor module — compression main entry (~3700 lines)
• budget estimate:190-242 — _estimate_msg_budget_tokens / _serialized_length_for_budget
• message sanitization:136-155 — _fresh_compaction_message_copy / _strip_persistence_markers
• tool call & path mention extraction:337-360 — _extract_tool_call_name_and_args / _collect_path_mentions
• content trimming:472-515 — _append_text_to_content / _strip_image_parts_from_parts
• moa_loop — Mixture-of-Agents aggregation
• IterationBudget — compression refund and budget coupling

Data Flow

1. Each turn the main loop evaluates whether compression is needed (see _should_run_preflight_estimate:213).
2. When the threshold is hit, context_compressor is called:
   • estimate each message's budget cost (agent/context_compressor.py:419)
   • make sanitized copies of old messages (agent/context_compressor.py:136), stripping persistence markers (agent/context_compressor.py:155)
   • preserve tool-call names/arguments and path mentions so summarization doesn't drop key operations (agent/context_compressor.py:337)
   • trim image parts and overlong content (agent/context_compressor.py:472)
3. The "new space" freed by compression is partially refunded via iteration_budget.refund() (agent/iteration_budget.py), letting the main loop run a few more turns.
4. If MoA is enabled, moa_loop calls multiple providers in parallel this turn and aggregates them as an enhancement or arbitration of the main answer.

Summary

The compressor is what keeps long conversations going; the core tradeoff is "what to drop, what to keep" — it prioritizes tool calls and path mentions, because losing them makes subsequent turns "amnesic". MoA is an orthogonal enhancement that can be toggled. Neither changes the main-loop structure; they only cut in at the right moment.