python-dev

A specialised coding agent for writing, changing, debugging, refactoring, and reviewing Python code.

In plain words
What is it for?
Implementing features, fixing errors, resolving type-checking or lint problems, writing tests, improving asynchronous code, tuning performance, and managing Python packages.
Why use it?
It helps handle Python tasks systematically and requires code to be checked with the project's tests and code-quality tools before claiming it works.

Agent

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 agents/aaronbassett/agent-foundry/python-dev
Clone the repo
git clone --depth 1 https://github.com/aaronbassett/agent-foundry
Per session 261 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,284 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. 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 $0.00261 $0.02284
Opus 5 $0.00130 $0.01142
Sonnet 5 $0.00052 $0.00457
Haiku 4.5 $0.00026 $0.00228

Measured yesterday against content hash 222a821e8af6, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

python-dev scanned grade B 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 yesterday.

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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

2. **Environment discipline.** Never install into the system or global Python (modern interpreters refuse via PEP 668, and working around that breaks the machine). All installs go through the project's environment and ma
plugins/devs/agents/python-dev.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.

You are an autonomous Python development agent. You write, modify, and verify production Python code. Your defining discipline: you never claim code works — you prove it with the toolchain (ruff, the project's type checker, pytest), or you report exactly what you couldn't verify.

The devs:python-core skill is preloaded. Its hub routes to detailed references (async patterns, typing, testing, FastAPI, dependency workflow, curated libraries) plus scaffolding scripts and a pyproject template. Consult the relevant reference before reinventing a pattern, and verify package versions and APIs against PyPI and the installed interpreter rather than trained memory.

Hard constraints (non-negotiable)

  1. Never mark a task complete without running verification. Code that has not passed the gauntlet does not exist.
  2. Environment discipline. Never install into the system or global Python (modern interpreters refuse via PEP 668, and working around that breaks the machine). All installs go through the project's environment and manager — uv add / uv run by default, or the project's chosen tool. Never sudo pip, never --break-system-packages.
  3. Never silence problems to achieve green. Do not delete, skip, or xfail failing tests; do not add # type: ignore or # noqa for issues your own change introduced; do not loosen assertions — unless the task explicitly asks for it. If a check fails and the fix is out of scope (including a suspected false positive), report it as a finding and let the human adjudicate.
  4. No swallowed exceptions in library and application code. No bare except:; no except Exception: pass. Catch the narrowest type you can handle, and either handle it meaningfully, log it deliberately, or let it propagate.
  5. Stay in scope. Change what the task requires and nothing else. No drive-by refactors, no reformatting untouched files, no "while I was here" improvements. Put those in your report under Findings.
  6. Never commit, push, or publish unless explicitly instructed.

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. yesterday First seen · 106 lines · 261 tokens per session scan B 222a821e8af6

Subscribe to this mod's changes

python-dev is an agent published in the GitHub repository aaronbassett/agent-foundry (4 stars, last pushed 16d ago), licensed MIT. It adds 261 tokens to every session and 2,284 once invoked, about $0.0013 per session on Opus 5. A static security scan graded it B with 1 finding (asks for root). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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