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/vinilana/dotcontext/bound-subprocess-outputnpx skills add vinilana/dotcontext --skill bound-subprocess-outputgit clone --depth 1 https://github.com/vinilana/dotcontextWrote 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/vinilana/dotcontext/bound-subprocess-output)<a href="https://agentmods.dev/skills/vinilana/dotcontext/bound-subprocess-output"><img src="https://agentmods.dev/badge/skills/vinilana/dotcontext/bound-subprocess-output.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 | $0.00054 | $0.00500 |
| Opus 5 | $0.00027 | $0.00250 |
| Sonnet 5 | $0.00011 | $0.00100 |
| Haiku 4.5 | $0.00005 | $0.00050 |
Grade A, and why
bound-subprocess-output 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 — 53 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Bound Subprocess Output
Keep memory proportional to configured diagnostics, never to total child output.
Workflow
- Identify what the caller actually needs: exit code, a tail, structured output, or a durable export.
- Define separate byte limits for stdout, stderr, structured result files, and combined output before editing code.
- Retain data online with a ring/tail buffer. Do not collect all chunks and trim at process exit.
- Track total, retained, and dropped bytes without logging content.
- Define explicit behavior for timeout, output ceiling, spawn error, non-zero exit, and malformed structured output.
- Preserve shell:false and argv-array execution.
- Add volume tests that exceed every limit.
Required invariants
- Never let an array of chunks scale with total output.
- Never call Buffer.concat over the full historical stream.
- Measure limits in UTF-8 bytes, not JavaScript string length.
- Bound stdout and stderr independently.
- Apply hard ceilings while the process is running.
- Kill and reap the child when a hard ceiling or timeout fires.
- Expose truncated, droppedBytes, and termination reason.
- Persist only bounded tails in traces and plan tracking.
Structured test output
Write large machine-readable results to a temporary file when a parser needs more than a tail. Check file size before reading, parse only required fields, and remove the file in finally. Keep console streams bounded even when using a result file.
Dotcontext routing
- Put pure bounding rules in src/harness/domain.
- Keep subprocess orchestration in the existing harness execution or adapter boundary.
- Apply the same collector to sensors and plan acceptance.
- Follow F-01.
Review gate
Reject the change if any answer is no:
- Is there a documented default and absolute maximum?
- Does memory stay bounded before process exit?
- Does every failure path reap the child?
- Are truncation counters visible?
- Does a 100 MiB-output regression test pass without retaining 100 MiB?
- Do npm run build and npm test -- --runInBand pass?
What ships with it
1 file 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.
- 4d ago First seen · 53 lines · 54 tokens per session scan A badbb87a2ae4
bound-subprocess-output is a skill published in the GitHub repository vinilana/dotcontext (561 stars, last pushed 1mo ago), licensed MIT. It adds 54 tokens to every session and 500 once invoked, about $0.0003 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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