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/jl-cmd/claude-dev-env/condensing-instructionsnpx skills add jl-cmd/claude-dev-env --skill condensing-instructionsgit clone --depth 1 https://github.com/jl-cmd/claude-dev-envWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/jl-cmd/claude-dev-env/condensing-instructions)<a href="https://agentmods.dev/skills/jl-cmd/claude-dev-env/condensing-instructions"><img src="https://agentmods.dev/badge/skills/jl-cmd/claude-dev-env/condensing-instructions.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00083 | $0.00883 |
| Opus 5 | $0.00042 | $0.00441 |
| Sonnet 5 | $0.00017 | $0.00177 |
| Haiku 4.5 | $0.00008 | $0.00088 |
Grade A, and why
condensing-instructions 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 4d 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 — 73 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Condensing Instructions
Cut an instruction document to what a Claude 5 generation model needs, and move the rest to the surface that loads it on demand. Over 80% of Claude Code's system prompt came out for Claude Opus 5 and Claude Fable 5 with no measurable drop in performance, so treat a long instruction document as a place with room to cut.
Clear the conflicts first
Read the system prompt, the CLAUDE.md, and the skills as one body of text and find the lines that pull against each other — "leave documentation as appropriate" sitting beside "DO NOT add comments". A conflict makes the model deliberate at length before it acts. Resolve each pair into one statement, or delete both when neither changes what the model does.
Trade rules for judgment
Delete a rule written to block a worst case, such as file deletion. Claude 5 generation models read the surrounding context and decide well without it, and a rigid rule blocks the user who has a real reason to want the behavior it forbids.
State the outcome and the signal the model should read:
- Cut: "Default to writing no comments. Never write multi-paragraph docstrings or multi-line comment blocks — one short line max. Don't create planning, decision, or analysis documents unless the user asks for them."
- Keep: "Write code that reads like the surrounding code: match its comment density, naming, and idiom."
Design the interface in place of examples
Examples constrain exploration. Carry usage in the tool's own shape: expressive names, expressive parameters, and types that signal intent. A status parameter enumerated as pending, in_progress, completed shows correct use with no example attached.
Load detail at the point of use
Move detail out of always-on text and into a surface the model reaches for:
- A skill the model calls when the task calls for it. Code review and verification detail belongs here.
- A linked file the model opens on demand.
- A tool with deferred loading, where the model searches for the definition before it uses the tool.
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.
- 4d ago First seen · 73 lines · 83 tokens per session scan A 24c96e77b035
condensing-instructions is a skill published in the GitHub repository jl-cmd/claude-dev-env (5 stars, last pushed today), licensed MIT. It adds 83 tokens to every session and 883 once invoked, about $0.0004 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 2026-08-31.
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