context-optimization

A set of techniques for fitting more useful information into an AI agent’s available conversation space. It includes reusing cached context, hiding unnecessary tool output, dividing context, and retrieving only relevant information.

In plain words
What is it for?
Use it to reduce token use and latency, handle large context loads, design cache-friendly prompts, mask verbose observations, and build long-running agent systems.
Why use it?
Long conversations and tool results can consume the available space, increasing cost and delay or causing important details to be lost.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/viktorbezdek/skillstack/context-optimization
Any agent
npx skills add viktorbezdek/skillstack --skill context-optimization
Clone the repo
git clone --depth 1 https://github.com/viktorbezdek/skillstack

Made for: Claude Code, Codex.

Per session 117 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,706 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00117 $0.01706
Opus 5 $0.00059 $0.00853
Sonnet 5 $0.00023 $0.00341
Haiku 4.5 $0.00012 $0.00171

Measured 2d ago against content hash b4f41644d38e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

context-optimization scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

context-optimization/skills/context-optimization/SKILL.md · 166 lines

How it starts

The opening of the file, as written. The whole thing — 166 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Context Optimization Techniques

Context optimization extends effective capacity through strategic compression, masking, caching, and partitioning. The goal is making better use of available capacity — not magically increasing windows. Effective optimization can double or triple effective context without larger models.

When to Use / Not Use

Use when:

  • Context limits constrain task complexity
  • Optimizing for cost reduction (fewer tokens = lower costs)
  • Reducing latency for long conversations
  • Implementing long-running agent systems
  • Building production systems at scale

Do NOT use when:

  • Compressing or summarizing context -> use context-compression
  • Diagnosing context failures or degradation -> use context-degradation
  • Learning context basics -> use context-fundamentals
  • File-based context patterns or scratch pads -> use filesystem-context

Decision Tree

What optimization problem are you solving?
├── Tool outputs dominate token usage (>80%)
│   └── Observation Masking -> Replace verbose outputs with references
├── Context approaching limits (>70% utilization)
│   ├── Message history dominates -> Compaction + Summarization
│   ├── Retrieved docs dominate -> Summarization or Partitioning
│   └── Multiple components -> Combine strategies
├── Repeated requests with common prefixes
│   └── KV-Cache Optimization -> Stable prefix ordering
├── Single context too large for one agent
│   └── Context Partitioning -> Sub-agent isolation
├── Need to measure if optimization is working
│   └── See §Performance Targets
└── Not about extending capacity? -> See related skills

Four Primary Strategies

Strategy Mechanism Best For Expected Savings
Compaction Summarize context near limits, reinitialize with summary Message history dominating 50-70% token reduction
Observation Masking Replace verbose tool outputs with compact references Tool output dominance (80%+ of tokens) 60-80% reduction in masked obs
KV-Cache Optimization Reuse cached KV computations across shared prefixes Repeated requests with stable prefixes 70%+ cache hit rate
Context Partitioning Split work across sub-agents with isolated contexts Single context too large Isolation + clean focus

Read the full file on GitHub · 166 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 166 lines · 117 tokens per session scan A b4f41644d38e

Subscribe to this mod's changes

context-optimization is a skill published in the GitHub repository viktorbezdek/skillstack (11 stars, last pushed 2mo ago), licensed MIT. It adds 117 tokens to every session and 1,706 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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