Borrowing it
Nothing to install: this file belongs to openhonest/umbra. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/openhonest/umbra/main/AGENTS.mdgit clone --depth 1 https://github.com/openhonest/umbraWrote 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/instructions/openhonest/umbra/agents-md)<a href="https://agentmods.dev/instructions/openhonest/umbra/agents-md"><img src="https://agentmods.dev/badge/instructions/openhonest/umbra/agents-md/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/instructions/openhonest/umbra/agents-md"><img src="https://agentmods.dev/badge/instructions/openhonest/umbra/agents-md.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.02438 | $0.02438 |
| Opus 5.5 | $0.00975 | $0.00975 |
| Sonnet 5.5 | $0.00488 | $0.00488 |
| Haiku 4.5 | $0.00244 | $0.00244 |
Grade C, and why
umbra AGENTS.md 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 2mo 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.
Recursive force deletehighDestructive command
rm -rf with a variable or a broad path is one typo away from removing the wrong tree.
rm -rf directory # NOT: rm -r directory How it starts
The opening of the file, as written. The whole thing — 171 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Umbra: agent instructions
Umbra is an apophatic code auditor: it reports what a test suite is structurally unable to see, and proves each gap with a real failing test it writes. Built for the OpenAI Build Week Challenge (submit by 2026-07-21).
Read these first, in order:
docs/SPEC.mdis the authoritative build target. Build to it. If something here and SPEC.md ever seem to disagree, SPEC.md wins on what to build, this file wins on how to work.SUBMISSION.mdis the problem/solution/approach narrative. Keep the code honest to what it claims.docs/DEMO.mdis the 60-second demo the whole thing serves. The failing-case reveal is the point; protect it.docs/HONEST-CODE-PRINCIPLES.mdis the canonical standard for how Umbra itself must be written. Not a suggestion.docs/HONEST-TEST.mdis the coverage theory Umbra operationalizes. Read it before you design the silence model; the Silence Score measures the sampling-versus-total gap it defines, and its honesty properties (purity, mutation, idempotency) are silence categories Umbra should detect.
The one rule that defines this project: thoughtful use of GPT-5.6
Umbra is judged partly on thoughtful model use. That means using GPT-5.6 only where it belongs, and never anywhere else.
- Structure is deterministic. No model calls. Reachability, branch analysis, what the suite exercises, what the type hints encode. This is
astandcoverage.py, not a prompt. A model here is a bug. - GPT-5.6 runs only on an already-located gap. It receives one isolated silence site plus the function source and type contract, and returns structured JSON. It never sees the whole codebase and never chooses what to test.
- Never trust, always run. Every case the model proposes is executed. Only cases that genuinely FAIL or ERROR survive into the report. A silence Umbra cannot demonstrate, Umbra does not claim. This execution gate is not optional; it is the honesty of the tool.
If you are about to add a model call, first ask whether structure can answer it. If it can, do that instead.
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.
- 2mo ago First seen · 171 lines · 2,438 tokens per session scan C f8e8fe452759
umbra AGENTS.md is an instructions file published in the GitHub repository openhonest/umbra (3 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 2,438 tokens to every session, about $0.0098 per session on Opus 5.5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
deno copilot-instructions.md
Copilot instructions for denoland/deno, covering deno development guide for github copilot, network access, high level overview, key directories and key files to understand first.