Borrowing it
Nothing to install: this file belongs to davekilleen/Dex. 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/davekilleen/Dex/main/AGENTS.mdgit clone --depth 1 https://github.com/davekilleen/DexWrote 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/davekilleen/dex/agents-md)<a href="https://agentmods.dev/instructions/davekilleen/dex/agents-md"><img src="https://agentmods.dev/badge/instructions/davekilleen/dex/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/davekilleen/dex/agents-md"><img src="https://agentmods.dev/badge/instructions/davekilleen/dex/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 | $0.01578 | $0.01578 |
| Opus 5.5 | $0.00631 | $0.00631 |
| Sonnet 5.5 | $0.00316 | $0.00316 |
| Haiku 4.5 | $0.00158 | $0.00158 |
Grade A, and why
Dex AGENTS.md 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 1mo 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 — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Working on dex-core (agent instructions)
Instructions for AI agents (and humans) developing this repository. Not the
product persona — the root CLAUDE.md is seed prose shipped into user vaults
("You are Dex…"); it is a product surface, not contributor guidance. Edit it like
UI copy, not like docs.
Communicating with the founder
The founder is non-technical. Lead with the outcome and explain what is happening in plain language; briefly explain an unavoidable technical term the first time it appears.
- Use an ADHD-friendly structure: keep steps short and numbered, make the one required action unmistakable, and prefer copy-paste prompts or commands.
- When the founder must act, begin with a What I need from you block stating the exact action, where to do it, why the founder is needed, and what will happen next.
- When blocked, state the exact blocker, what is and is not affected, the lowest-lift recovery action, and how to prevent the issue recurring.
- Never ask the founder to diagnose Git, mounts, permissions, credentials, or similar mechanics, and never ask for secrets to be pasted into chat.
- Never claim something is fixed, committed, pushed, merged, published, or live without verifying the result the user will actually experience.
GitHub access in managed Codex runners
The normal Devbox terminal and a managed Codex runner are separate execution contexts. A successful GitHub check in one does not prove that the other has working DNS or credentials. Before any GitHub fetch, push, or remote inspection from a managed runner, run these read-only checks in that same runner:
getent hosts github.com
gh auth status --hostname github.com
gh api user --hostname github.com --jq '"GITHUB_OK: @" + .login'
git ls-remote origin HEAD
If a check fails, classify the failure precisely:
- Managed-runner DNS:
getent hosts github.comcannot resolve the name. - Managed-runner HTTPS credentials: DNS works but
gh apior HTTPS Git authentication fails. - SSH key or route: the repository uses SSH and the SSH remote fails.
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.
- 1mo ago First seen · 122 lines · 1,578 tokens per session scan A 12b843d246ee
Dex AGENTS.md is an instructions file published in the GitHub repository davekilleen/Dex (508 stars, last pushed 3d ago), licensed MIT. It adds 1,578 tokens to every session, about $0.0063 per session on Opus 5.5. 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 2026-09-03.
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