Expedition-Python AGENTS.md

A contributor guide for a Python package that connects sailing-navigation software to Windows through its Expedition DLL, a library used by other programs. It explains the project layout, local reference headers, naming rules, and the uv development workflow.

In plain words
What is it for?
Use it when developing, testing, or documenting Expedition-Python, especially when updating its Windows DLL bindings or channel and system enums.
Why use it?
It gives coding agents and contributors the project-specific rules needed to change the DLL wrapper, enums, tests, and documentation safely. It also clarifies Windows-only limits and which proprietary files must stay local.

Instructions file for CodexOpenCode

Install

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.

agentmods
npx agentmods add instructions/ttcmarine/expedition-python/agents-md
Clone the repo
git clone --depth 1 https://github.com/TTCMarine/Expedition-Python

Made for: Codex, OpenCode.

Per session 1,402 This file is loaded in full into every session.
When invoked 1,402 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
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 $0.01402 $0.01402
Opus 5 $0.00701 $0.00701
Sonnet 5 $0.00280 $0.00280
Haiku 4.5 $0.00140 $0.00140

Measured 2d ago against content hash 547d22bac697, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Expedition-Python 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 2d 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.

AGENTS.md · 106 lines

How it starts

The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent and contributor guide

This file helps AI assistants (Cursor, etc.) and contributors work effectively on Expedition-Python.

What this project is

A Python ctypes wrapper around Expedition’s ExpDLL.dll for sailing navigation integration on Windows.

Area Location
DLL wrapper Expedition/dll_wrapper.py
Channel / system enums Expedition/enums.py
Package version Expedition/version.py (dynamic in pyproject.toml)
Tests tests/test_expedition.py
User docs (Sphinx) docs/, built via readthedocs.yaml

Runtime: Windows only for real DLL use. CI runs on Windows only; integration tests skip when ExpDLL.dll is unavailable.

Reference headers (local dev, not in git)

Expedition’s C headers are proprietary. Sync them locally for binding work and enum maintenance:

uv run python scripts/sync_expedition_headers.py
uv run python scripts/check_enums_against_headers.py
  • Headers live under reference/expedition/ (gitignored). See reference/README.md.
  • Do not commit headers or bundle them in the wheel.
  • CoreMem.h is not shipped with Expedition; channel layout comes from user_channels.h / sys_channels.h.
  • After an Expedition upgrade: sync headers → generate_enums_from_headers.py --write → check-enums → review ExpDLL.h exports → verify ValType in Expedition/exval.py against e_ValType if sys_val.h / time_dev.h changed → update dll_wrapper.py if needed → run tests.

Enum naming (2.0+)

Python enum members use mechanical names from the C headers (no override tables):

C enum Strip prefix Example
ExChannels Ex ExLwyLwy
ExSysChannels ExSys (or Ex for ExNumSysChannels) ExSysMouseTimeMouseTime
ExSysBooleanChannels ExSysBool ExSysBoolAutoPanAutoPan
ExSysIntChannels ExSysInt ExSysIntThemeTheme

Read the full file on GitHub · 106 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. 2d ago First seen · 106 lines · 1,402 tokens per session scan A 547d22bac697

Subscribe to this mod's changes

Expedition-Python AGENTS.md is an instructions file published in the GitHub repository TTCMarine/Expedition-Python (10 stars, last pushed 1mo ago), licensed MIT. It adds 1,402 tokens to every session, about $0.0070 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 2026-08-31.

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