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System Design

Context Engineering

The discipline replacing prompt engineering: designing dynamic context systems that give agents the right information at the right time. Covers lazy loading, memory-augmented architectures, and production patterns.

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Core30 min readFirst readYour First Agentic System

After this section you can

  • Explain why context engineering replaced prompt engineering for agentic systems, and name the four context layers — system instructions, policy & guardrails, knowledge, and user state — with what belongs in each
  • Plan a context budget for a 128K window: allocate fixed slices for system, tools, RAG, history, and scratchpad, enforce the keep-input-under-25% rule, and reserve the remainder for generation
  • Apply the five production patterns — lazy loading, memory-augmented context, compression, tool-based retrieval, and context routing — to a concrete agent design and defend each trade-off
  • Diagnose the four context failure modes (overflow, irrelevant retrieval, memory decay, tool-definition bloat) from their symptoms and pair each with the right fix
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Context Engineering

The discipline that replaced prompt engineering for agentic AI systems. Context engineering is the art of dynamically assembling the right information, tools, and state at runtime so an LLM can reliably complete complex tasks.

Prompt Engineering vs Context Engineering
PROMPT ENGINEERING 2022-2024
STATIC Fixed instructions written at design time
ONE-TIME Single prompt → single response
TEXT-ONLY Just text in, text out
MANUAL Human crafts the perfect prompt
FRAGILE Breaks when model or use case changes
Analogy: Writing a single email with all instructions upfront
CONTEXT ENGINEERING 2025+
DYNAMIC Context assembled at runtime from multiple sources
MULTI-TURN Ongoing loops with tools, memory, and state
MULTI-SOURCE RAG (retrieval-augmented generation — relevant docs fetched into the prompt at runtime) + tools + memory + user state + policies
SYSTEMIC Engineered pipelines that build context automatically
RESILIENT Adapts to model upgrades and new use cases
Analogy: Building a briefing system that assembles the right docs for every meeting
GARTNER 2025: "Context engineering is in, prompt engineering is out. 80% of AI tools by 2028 will use context engineering over static prompting."

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