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.
npx agentmods add skills/viktorbezdek/skillstack/context-optimizationnpx skills add viktorbezdek/skillstack --skill context-optimizationgit clone --depth 1 https://github.com/viktorbezdek/skillstackWhat 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.
| Model | Per session | Once 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 |
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.
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 |
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.
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.
- 2d ago First seen · 166 lines · 117 tokens per session scan A b4f41644d38e
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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