ex_athena: Instructions file for Claude Code

CLAUDE.md

ex_athena CLAUDE.md is an instructions file for Claude Code from udin-io/ex_athena. It costs 1,128 tokens per session, scanned A, original, Apache-2.0.

Repository-specific instructions for the ex_athena project, including its documentation structure, source-of-truth files, design records, and test guidance.

In plain words
What is it for?
Use it when changing ex_athena so project notes, design decisions, documentation, and test-related requirements are handled as specified.
Why use it?
It gives an agent the rules and known constraints for working safely in that particular codebase.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions subagents.

This is udin-io/ex_athena's own configuration. It tells Claude Code how to work on ex_athena itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything ex_athena configures →

Reuse

Borrowing it

Nothing to install: this file belongs to udin-io/ex_athena. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/udin-io/ex_athena/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/udin-io/ex_athena

Made for: Claude Code.

Wrote 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.

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README.md
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Your own site
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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.

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Per session 1,128 This file is loaded in full into every session.
When invoked 1,128 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.01128 $0.01128
Opus 5 $0.00564 $0.00564
Sonnet 5 $0.00226 $0.00226
Haiku 4.5 $0.00113 $0.00113

Measured today against content hash 025139f0f187, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-19, from the pricing page.

Security

Grade A, and why

ex_athena CLAUDE.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 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.

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.

CLAUDE.md · 98 lines

How it starts

The opening of the file, as written. The whole thing — 98 lines — stays where its author put it; the contents beside it link to each section on GitHub.

ex_athena — project notes

Rules that are true of THIS repo. The global rules still apply; nothing here repeats them.

Project source of truth

docs/PROJECT.md and its pages (roadmap.md, architecture.md, risks.md, decisions.md) do not exist yet and must be created. Until they do, every session that touches this repo should treat creating them as the first outstanding task, and README.md must link to the hub near the top once it exists.

There is an adr/ directory with 20+ entries. It must be migrated into docs/decisions.md — one dated entry per decision that still shapes the system, dropping the ones that were really bug fixes — and then deleted, in the same PR as the migration. Do not add new ADRs. Two entries matter most to anyone touching the loop's mistake counter: adr/0007 (propagate resets through the parallel fold) and adr/0020 (reset at the turn boundary, not per call).

Once the pages exist: every PR that changes behaviour, structure, a risk or a decision updates them in the SAME PR, and a merge is not finished until they describe main as it now is.

Running the tests

There is no database. Skip every DB and partition-setup step in the global rules. The suite still needs MIX_TEST_PARTITION set, because config/test.exs derives :web_dir from it to isolate the session store between concurrent runs:

MIX_TEST_PARTITION=_issue_<num> mix test

Omitting it makes two concurrent runs share one web session directory, which fails in ways that look like flakes but are not.

Known failures that are not yours

Measured 2026-09-13 on main (5db70d8). Do not chase these:

  • 3 symlink-canonicalisation tests in ExAthena.ToolContextTest.
  • 1 ExAthena.Tools.BashTest confinement test, "writes inside a root succeed". NOT a missing bwrap — the binary is on PATH here (/usr/bin/bwrap, 0.8.0) and the test still fails. It cannot create a user namespace inside the dev container: bwrap --dev-bind / / true exits 1 with "No permissions to create new namespace". ExAthena.Sandbox.available?/1 only checks that the helper exists, so the confined path runs, every command under it fails, and the write never lands. Run that one-liner before believing any other explanation.
  • ExAthena.Tools.AskUserTest flakes intermittently.
  • The LSP / ImplicitDiagnostics family flakes in CI; re-run the job once before treating a failure there as real.

Read the full file on GitHub · 98 lines

Changes

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.

  1. today Changed · +1 lines · +2 tokens per session 025139f0f187
  2. 4d ago Changed · +7 lines · +126 tokens per session a6f27d4f1fbc
  3. 5d ago First seen · 90 lines · 1,000 tokens per session scan A e82078c8c32d

Subscribe to this mod's changes

ex_athena CLAUDE.md is an instructions file published in the GitHub repository udin-io/ex_athena (3 stars, last pushed yesterday), licensed Apache-2.0. It adds 1,128 tokens to every session, about $0.0056 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 2026-09-13.

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