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ai-context-engineer

Skill8 starsChanged 6 months agoMITView on GitHub

Guides context engineering for LLM systems—assembling prompts, budgeting tokens, prioritizing sources, compressing history, caching, structured context blocks, and debugging context-related failures (lost instructions, overflow, distraction). Use when designing what enters the model context each turn, optimizing cost/latency via context strategy, building context pipelines for agents, implementing summarization or compaction, or fixing "model ignored X" issues—not for persistent memory store design (ai-memory-developer), full RAG index pipelines (ai-engineer), or AI org operations (ai-lead-ops). For a structured token/cost improvement roadmap with phased initiatives and KPIs, use ai-token-improvement-plan-engineer. For commercial/enterprise AI solution architecture (RAG, copilots, platform selection), use applied-ai-architect-commercial-enterprise. Token research and compression ablations: research-engineer-scientist-tokens.

1 other project uses a version of this.

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  1. Very specific:

    Use explicit XML/markdown sections: <policy>, <tools>, <context>, <history>, <user>.

    line 62

≈ “Common” is an estimate: at least 1 in 5 of the 350,495 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

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SKILL.md

AI Context Engineer

When to Use

  • Designing what enters the model context each turn
  • Optimizing cost/latency via context strategy and token budgeting
  • Building context pipelines for agents (prefix, retrieval, history, user input)
  • Implementing summarization, compaction, or rolling history
  • Debugging context-related failures (lost instructions, overflow, distraction, ignored constraints)
  • Choosing delimiters, XML blocks, or structured context formats

When NOT to Use

  • Persistent memory store design or long-term recall architecture → ai-memory-developer
  • Full RAG ingest/chunk/embed/index pipelines → ai-engineer
  • AI org operations, release governance, or SLOs → ai-lead-ops
  • Structured token/cost improvement roadmaps with phased KPIs → ai-token-improvement-plan-engineer
  • Commercial/enterprise AI solution architecture → applied-ai-architect-commercial-enterprise

Related skills

NeedSkill
Memory stores and long-term recallai-memory-developer
RAG ingest/chunk/embedai-engineer
System and tool promptsprompt-engineer
Red-team injection via contextai-redteam
Cost and production SLAsai-lead-ops
Token reduction program and roadmapai-token-improvement-plan-engineer
Commercial/enterprise AI architectureapplied-ai-architect-commercial-enterprise
Token efficiency research and ablationsresearch-engineer-scientist-tokens

Core Workflows

1. Context budget and layout

Allocate tokens (example 128k window):

BlockBudget %Priority
System policy + tools15–25%Fixed, never truncated
Retrieved docs / memory30–45%High, reranked
Conversation history25–40%Compress oldest first
User current message5–10%Never drop

Use explicit XML/markdown sections: <policy>, <tools>, <context>, <history>, <user>.

See references/context_layout.md for templates and delimiter rules.

2. History management

StrategyWhen
Full recent windowShort chats, high-stakes instructions in last N turns
Rolling summaryLong sessions; summarize every K turns
Anchor messagesPin system + key user constraints; summarize middle
Structured stateReplace chat with JSON task state for agents

Preserve: user goals, constraints, unresolved tool errors, pending confirmations.

See references/history_compression.md for summarization prompts and pitfalls.

3. Retrieval into context

  1. Query from user message + state summary
  2. Retrieve candidates (RAG chunks, memories, tool outputs)
  3. Deduplicate overlapping passages
  4. Order by relevance; add source labels
  5. Truncate with sentence boundaries; show "[truncated]" when cut

See references/retrieval_packing.md for packing algorithms and citation format.

4. Caching and prefetch

  • Cache stable prefix (system + tools) where provider supports prompt caching
  • Prefetch retrieval while user types (optional)
  • Invalidate cache on prompt version change

See references/caching_prefetch.md for provider notes and invalidation.

5. Debug context failures

SymptomLikely causeFix
Ignored instructionBuried in middle / summarized awayMove to system or last user turn
Hallucinated docWeak retrievalRaise threshold; require citation
Overflow errorNo budget enforcementPre-flight token count; compress
Tool confusionAmbiguous schemas in contextSeparate tool block; shorten descriptions

Log token counts per block in dev/staging.

See references/debugging_context.md for instrumentation checklist.

When to load references

  • Layout and budgets → references/context_layout.md
  • Summarization → references/history_compression.md
  • RAG/memory packing → references/retrieval_packing.md
  • Caching → references/caching_prefetch.md
  • Debugging → references/debugging_context.md

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