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/rosenfan/matrix/matrix-buildnpx skills add Rosenfan/Matrix --skill matrix-buildgit clone --depth 1 https://github.com/Rosenfan/MatrixWrote 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/rosenfan/matrix/matrix-build)<a href="https://agentmods.dev/skills/rosenfan/matrix/matrix-build"><img src="https://agentmods.dev/badge/skills/rosenfan/matrix/matrix-build.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 | $0.00024 | $0.00518 |
| Opus 5 | $0.00012 | $0.00259 |
| Sonnet 5 | $0.00005 | $0.00104 |
| Haiku 4.5 | $0.00002 | $0.00052 |
Grade C, and why
matrix-build scanned grade C with 1 finding 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 today.
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.
Harvests environment variableshighData exfiltration
Enumerating or grepping the environment for keys collects credentials unrelated to what the mod says it does.
- invoke `wizard` only to generate and statically verify human-run shell steps required by the Contract; never execute the wizard end-to-end or collect secrets. How it starts
The opening of the file, as written. The whole thing — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Matrix Build
Run node <matrix-skill-directory>/scripts/matrix-runtime.mjs inspect and implement only its approved Contract. Full and legacy-full read proposal/design/plan. lightweight reads the approved compact proposal and must not backfill Design artifacts.
Write build evidence and user-facing explanations in artifact_language; preserve any Runtime-required English heading tokens.
Prim
Use Matrix's own implementation and test discipline.
Arch
- invoke
tddwhen the change modifies observable behavior at a testable seam; - invoke
diagnosing-bugsonly when an actual failure exists and root cause is not established; - invoke
writing-for-agentswhen the approved Contract changes agent-facing instructions; - invoke
wizardonly to generate and statically verify human-run shell steps required by the Contract; never execute the wizard end-to-end or collect secrets.
Resolve an in-progress merge/rebase through Matrix-owned conflict handling. Do not invoke raw resolving-merge-conflicts, because it can stage, continue, and commit outside Matrix lifecycle ownership. Never invoke implement inside an active Change.
Announce each triggered capability and reason. No companion may commit, review, transition, archive, or broaden scope. A correctly installed capability gets at most one Matrix-owned fallback for that same capability; record the Skill, failure, fallback, and evidence. Installation-integrity failure stops the phase.
Scope Discipline
If implementation exposes a scope or design change, stop and run; a lightweight change is upgraded to full by this Return:
node <matrix-skill-directory>/scripts/matrix-runtime.mjs return design --reason design-gap
Then enter $matrix-design; do not amend the plan silently. The Runtime preserves old verification evidence in revision history and requires fresh evidence after the redesigned plan returns to Build.
Process
- Implement the approved plan in bounded vertical slices.
- Use only triggered Arch capabilities.
- Record common facts under
## Build evidence. Hotfix also requires## Reproduction evidenceand## Root cause; tweak also requires## Scope evidence. - Run the guard and transition, then enter
$matrix-verify.
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.
- today Changed · +3 lines scan A → C 55dad363ad35
- 4d ago First seen · 45 lines · 24 tokens per session scan A 5d7536188d9d
matrix-build is a skill published in the GitHub repository Rosenfan/Matrix (5 stars, last pushed 3d ago), licensed MIT. It adds 24 tokens to every session and 518 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it C with 1 finding (harvests environment variables). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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