context-engineering（情境工程）

Context Engineering

Context engineering curates the smallest high-signal token set for LLM tasks. The goal: maximize reasoning quality while minimizing token usage.

When to Activate

• Designing/debugging agent systems
• Context limits constrain performance
• Optimizing cost/latency
• Building multi-agent coordination
• Implementing memory systems
• Evaluating agent performance
• Developing LLM-powered pipelines

Core Principles

1. Context quality > quantity - High-signal tokens beat exhaustive content
2. Attention is finite - U-shaped curve favors beginning/end positions
3. Progressive disclosure - Load information just-in-time
4. Isolation prevents degradation - Partition work across sub-agents
5. Measure before optimizing - Know your baseline

Key Metrics

• Token utilization: Warning at 70%, trigger optimization at 80%
• Token variance: Explains 80% of agent performance variance
• Multi-agent cost: ~15x single agent baseline
• Compaction target: 50-70% reduction, <5% quality loss
• Cache hit target: 70%+ for stable workloads

Four-Bucket Strategy

1. Write: Save context externally (scratchpads, files)
2. Select: Pull only relevant context (retrieval, filtering)
3. Compress: Reduce tokens while preserving info (summarization)
4. Isolate: Split across sub-agents (partitioning)

Anti-Patterns

• Exhaustive context over curated context
• Critical info in middle positions
• No compaction triggers before limits
• Single agent for parallelizable tasks
• Tools without clear descriptions

Guidelines

1. Place critical info at beginning/end of context
2. Implement compaction at 70-80% utilization
3. Use sub-agents for context isolation, not role-play
4. Design tools with clear descriptions (what, when, inputs, returns)
5. Optimize for tokens-per-task, not tokens-per-request
6. Validate with probe-based evaluation
7. Monitor token usage in production
8. Start minimal, add complexity only when proven necessary

Skill Coordination

When multiple skills are active:

• Load only relevant skill content
• Use skill metadata for discovery
• Avoid loading full skill definitions unless needed
• Reference skills by pattern detection, not direct names

References

For detailed guidance, see:

• references/fundamentals.md - Context anatomy, attention mechanics
• references/degradation.md - Debugging failures, lost-in-middle, poisoning
• references/optimization.md - Compaction, masking, caching, partitioning
• references/compression.md - Long sessions, summarization strategies
• references/memory.md - Cross-session persistence, knowledge graphs
• references/multi-agent.md - Coordination patterns, context isolation
• references/evaluation.md - Testing agents, LLM-as-Judge, metrics
• references/tool-design.md - Tool consolidation, description engineering