What is 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.

Use it when developing, testing, or documenting Expedition-Python, especially when updating its Windows DLL bindings or channel and system enums.

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.

How TTCMarine/Expedition-Python configures Codex and OpenCode

Reuse

Borrowing it

Nothing to install: this file belongs to TTCMarine/Expedition-Python. 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/TTCMarine/Expedition-Python/main/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/TTCMarine/Expedition-Python

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/ttcmarine/expedition-python/agents-md/github.svg)](https://agentmods.dev/instructions/ttcmarine/expedition-python/agents-md)

Your own site

<a href="https://agentmods.dev/instructions/ttcmarine/expedition-python/agents-md"><img src="https://agentmods.dev/badge/instructions/ttcmarine/expedition-python/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/ttcmarine/expedition-python/agents-md"><img src="https://agentmods.dev/badge/instructions/ttcmarine/expedition-python/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

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. 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.

Model	Per session	Once invoked
Fable 5.1	$0.01402	$0.01402
Opus 5.5	$0.00561	$0.00561
Sonnet 5.5	$0.00280	$0.00280
Haiku 4.5	$0.00140	$0.00140

Measured 2mo ago against content hash 547d22bac697, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, 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 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.

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`	`ExLwy` → `Lwy`
`ExSysChannels`	`ExSys` (or `Ex` for `ExNumSysChannels`)	`ExSysMouseTime` → `MouseTime`
`ExSysBooleanChannels`	`ExSysBool`	`ExSysBoolAutoPan` → `AutoPan`
`ExSysIntChannels`	`ExSysInt`	`ExSysIntTheme` → `Theme`

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.

2mo 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 (11 stars, last pushed 3mo ago), licensed MIT. It adds 1,402 tokens to every session, about $0.0056 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 2026-08-31.

Languages Python

Expedition-Python AGENTS.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
Expedition-Python AGENTS.mdTTCMarine/Expedition-Python	Instructions file	11	3mo ago	MIT	A	1,402	Codex, OpenCode
vscode buildNext.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	9,719	GitHub Copilot
next.js AGENTS.mdvercel/next.js	Instructions file	143k	yesterday	MIT	A	7,461	Codex, OpenCode
langchain AGENTS.mdlangchain-ai/langchain	Instructions file	149k	yesterday	MIT	A	4,680	Codex, OpenCode
vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	5,516	GitHub Copilot
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	3,093	GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness	Instructions file	274k	2d ago	MIT	A	4,313	Codex, OpenCode

Expedition-Python: Instructions file for Codex