bastion: Instructions file for Codex

AGENTS.md

bastion AGENTS.md is an instructions file for Codex, OpenCode from JoakimCarlsson/bastion. It costs 2,030 tokens per session, scanned A, original, MIT.

A project instruction file for Bastion, a cooperative tower-defense game with a Go API, PostgreSQL database, and Bun/React web app. It sets the rules coding agents must follow when contributing to that repository.

In plain words
What is it for?
Use it before planning, coding, or reviewing Bastion changes, particularly API work, to follow its architecture rules and run live endpoint smoke tests.
Why use it?
It makes verification mandatory for observable behavior, especially HTTP endpoints, where unit tests alone may miss problems. It also records the project-specific commands and handoff details agents need.

Instructions file for CodexOpenCode

Written for Codex and OpenCode: the file is AGENTS.md. Also seen: reads .claude/ paths; mentions subagents; mentions Claude Code.

This is JoakimCarlsson/bastion's own configuration. It tells Codex and OpenCode how to work on bastion 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 bastion configures →

Reuse

Borrowing it

Nothing to install: this file belongs to JoakimCarlsson/bastion. 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/JoakimCarlsson/bastion/main/AGENTS.md
Clone the repo
git clone --depth 1 https://github.com/JoakimCarlsson/bastion

Made for: Codex, OpenCode.

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.

agentmods badge for bastion AGENTS.md

README.md
[![agentmods](https://agentmods.dev/badge/instructions/joakimcarlsson/bastion/agents-md.svg)](https://agentmods.dev/instructions/joakimcarlsson/bastion/agents-md)
Your own site
<a href="https://agentmods.dev/instructions/joakimcarlsson/bastion/agents-md"><img src="https://agentmods.dev/badge/instructions/joakimcarlsson/bastion/agents-md.svg" alt="Measured on agentmods" height="20"></a>
Per session 2,030 This file is loaded in full into every session.
When invoked 2,030 The same file — it is already loaded in full.
Security scan A 1 finding. 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 $0.02030 $0.02030
Opus 5 $0.01015 $0.01015
Sonnet 5 $0.00406 $0.00406
Haiku 4.5 $0.00203 $0.00203

Measured 6d ago against content hash 8894a5056053, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

bastion AGENTS.md scanned grade A 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 6d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

2. **New or changed API endpoints:** start the API (`go run ./cmd/api`, `docker compose up`, or equivalent), then **`curl` every new/changed route** — assert status code and response body match acceptance criteria.
AGENTS.md · 179 lines

How it starts

The opening of the file, as written. The whole thing — 179 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AGENTS.md — Bastion contributor and agent contract

Read this document first before planning, implementing, or reviewing Bastion work. It is the canonical source for architecture rules and mandatory verification.

Project summary

Bastion is a co-op tower defense game: a Go API (minmux router, PostgreSQL) and a Bun + React SPA under web/. The API serves JSON endpoints and, when built, static assets from web/dist.

Hard rules — verification (non-negotiable)

  1. Everything observable must be verified end-to-end. Unit tests alone are not enough for HTTP APIs or running services.
  2. New or changed API endpoints: start the API (go run ./cmd/api, docker compose up, or equivalent), then curl every new/changed route — assert status code and response body match acceptance criteria.
  3. Delivery agents follow .cursor/rules/subagents.mdc and .cursor/verify-commands.md for project-specific commands.
  4. Coder must list every new/changed route in HANDOFF:IMPLEMENTATIONsmoke_endpoints with concrete expect values.
  5. Smoke-tester must not mark pass without live endpoint evidence when the issue touches HTTP.

Smoke example

Start the API (database optional for /health; required for /ready):

go run ./cmd/api
# or: docker compose up --build

Verify health and readiness:

curl -s http://localhost:8080/health
curl -s http://localhost:8080/ready

Expected: /health returns {"status":"ok","version":"..."} (HTTP 200). /ready returns {"status":"ready"} (HTTP 200) when the database is reachable, or HTTP 503 with {"status":"not_ready"} otherwise.

Hard rules — architecture (Go)

Package by subsystem (bounded context), not by technical layer. Top-level directories under internal/ are domain slices. Prefer flat packages with many .go files; add sub-folders only when a sub-feature has its own vocabulary and roughly 10+ files.

Do not introduce:

internal/
  controllers/
  services/
  repositories/
  models/

Read the full file on GitHub · 179 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. 6d ago First seen · 179 lines · 2,030 tokens per session scan A 8894a5056053

Subscribe to this mod's changes

bastion AGENTS.md is an instructions file published in the GitHub repository JoakimCarlsson/bastion (2 stars, last pushed 3mo ago), licensed MIT. It adds 2,030 tokens to every session, about $0.0102 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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