dsh-python-env

dsh-python-env

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Workspace-scoped Python virtual environment management for a DeepSeek Harness project — discover, create, install into, and remove virtual environments without sandbox, network, or subprocess pitfalls.

A DeepSeek Harness plugin that gives one project (workspace) agent-facing Python virtual environment management:

• Five model tools — pyenv_discover, pyenv_create, pyenv_install, pyenv_uninstall, pyenv_remove — plus the python-env skill and a system-prompt guidance section.
• Runs the standard library python -m venv / pip through the platform subprocess channel (host process) instead of the sandboxed shell, so venv creation, ensurepip bootstrapping, and package-index network access work where shell-side pip fails.
• Mirror and proxy fallback — on a network-classified failure, installs retry across PyPI mirrors (TUNA, Aliyun, USTC) and probe common local proxy ports; index / proxy arguments pin either.
• Workspace confinement — every path resolves inside the session workspace (case-insensitive on Windows); caches and temp state live under <workspace>/.dsh-pyenv/; commands are argv arrays (no shell); the global Python environment, host pip cache, and system temp are never touched.
• Cross-platform — Windows / macOS / Linux layouts and interpreter chains (Scripts vs bin, py -3 vs python3).
• No third-party dependency — no uv, no virtualenv, no other plugin. A pip-less environment is repaired offline via ensurepip.
• Session policy parity — the mutating tools consult the session's sandbox policy and refuse to run in read-only sessions; discovery stays available everywhere.

Requirements

• Node.js >= 20
• A DSH profile composed from @deepseek-ai/dsh-base (it provides the subprocess, jobs, tools, and skills services the plugin uses)
• Python >= 3.8 (on PATH, or passed explicitly) — only for the environments the plugin manages

Install

From npm:

dsh plugin --profile web add dsh-python-env

From a local checkout (development):

dsh plugin --profile web add link:<absolute-path-to-this-repo>

Then restart the DSH backend — the host composition loads at process start. The tools appear in new sessions: pyenv_discover, pyenv_create, pyenv_install, pyenv_uninstall, pyenv_remove, plus the python-env skill.

Usage

Agent side:

Tool	What it does
pyenv_discover	Find environments up to two levels deep by the pyvenv.cfg marker or conventional names (.venv, venv, env, .env, virtualenv); report path, interpreter, version, pip availability.
pyenv_create	Create an environment with python -m venv — name / root_dir / base python arguments, idempotent on existing environments.
pyenv_install	Install packages and/or a requirements file into an environment (explicit venv / discovered / auto-created .venv); repairs missing pip via ensurepip; mirror/proxy fallback; upgrade flag; editable installs of local projects; run_in_background for long installs.
pyenv_uninstall	Remove packages from an environment (pip uninstall -y); offline; never auto-creates an environment.
pyenv_remove	Delete a real workspace environment only (refuses non-environments and workspace escapes).

pyenv_create                                  # -> .venv, interpreter path reported
pyenv_install { packages: ["pytest>=8"] }     # installs into .venv
pyenv_install { requirements: "requirements.txt" }
pyenv_uninstall { packages: ["pytest"] }      # removes packages again
pyenv_discover                                # inspect every environment
# run code with the reported interpreter:
#   Windows: <venv>\Scripts\python.exe    macOS/Linux: <venv>/bin/python

Behavior notes:

• The mutating tools (create / install / uninstall / remove) respect the session sandbox mode and refuse to run in read-only sessions; discovery still works.
• Common flows are all covered: pin versions ("pkg==1.2.3"), upgrade (upgrade: true), install from requirements.txt (requirements), and editable installs of local projects (packages: ["-e", "."] — the editable path must stay inside the workspace; remote/VCS editable URLs are rejected).
• Without a venv argument, pyenv_install uses the single discovered environment (preferring .venv), auto-creates .venv when none exists, and asks for an explicit venv when several exist.
• Background installs register with the jobs registry — poll with job_output, stop with job_kill.
• Two-minute budget. Every pyenv tool must finish within 2 minutes (discovery within 1). A tool that exceeds its budget terminates the running process tree and returns a detailed stop-reason — what was still running, the attempts tried, the last output, likely causes, and next steps — instead of hanging or reporting a bare timeout. Background installs share the same 2-minute cap; a per-call timeoutMs override on install/uninstall is honored but capped at 120000 ms.

How it works

• Subprocess channel — the DSH shell sandbox blocks CPython's owner-only temp directories (Windows [Errno 13] during ensurepip/wheel unpacking) and package-index network access. Plugin code runs in the host process, so every python/pip/venv invocation goes through ctx.subprocess (the same channel the graphlint plugin uses) with argv arrays, byte-capped collected output, and tree-scoped termination. The unrestricted token is compensated by the confinement model below — not by weakening the sandbox.
• Confinement — every model-influenced path passes guardWorkspacePath (absolute resolution + containment, ..-safe); venv names are single-segment regex-validated and re-guarded after join; children get PIP_CACHE_DIR / TMP / TEMP / TMPDIR re-pointed into <workspace>/.dsh-pyenv/.
• Install attempt chain — default index first; a network-classified failure (connection reset/timeout/DNS — never "No matching distribution found" or TLS errors) falls back across TUNA → Aliyun → USTC mirrors and, once, probes common local proxy ports (7890, 7891, 10809, 10808, 8888) to retry the same index through a live one.
• ensurepip repair — <venv-python> -m ensurepip --upgrade bootstraps pip offline from bundled wheels; when ensurepip itself is absent the error carries the Debian/Ubuntu python3-venv hint.
• Concurrency — mutating tools declare isConcurrencySafe: false, so the scheduler serializes them; discovery stays read-only.
• Skill & guidance — the python-env skill teaches tool-first usage and the "never escalate for pip" rule; one system-prompt section (dsh-python-env:guidance, order 120) reminds every session that the pyenv tools are the sanctioned path.

Project layout

Path	Purpose
cordis.patch.yml	Profile patch layer inserting the dsh-python-env row
lib/index.js	Host plugin: registers the five tools, the skill, and the guidance section
lib/tools/	The five model tools (discover / create / install / uninstall / remove)
lib/guard.js, lib/venv.js, lib/layout.js, lib/paths.js, lib/python.js	Workspace confinement, venv resolution, discovery, platform layouts, interpreter chains
lib/runner.js, lib/pip.js, lib/envdir.js	Subprocess seam, install chain, workspace caches
test/	Runtime-free behavior tests (see Development)
docs/	Design and analysis documents

Development

No build step: the plugin is plain ESM and the tests run with Node directly (the mock ctx stands in for the DSH services; the real defineTool validates every schema):

npm test
# or: node --test --test-isolation=none "test/*.test.js"

See CONTRIBUTING.md for the development loop, including offline dependency resolution.

Compatibility

When DSH also has the dsh-multi-folder plugin installed, the Agent can use the tools provided by dsh-python-env to manage the secondary working directories specified by the user in dsh-multi-folder, even when those working directories are outside the main working directory. Environment management permissions for the secondary working directories are the same as for the main working directory; when the Agent runs in Read Only mode, the tools refuse any operation. This compatibility is automatic and optional — it takes effect automatically whenever both dsh-multi-folder and dsh-python-env are installed in the DSH environment. If dsh-multi-folder is not installed, dsh-python-env's functionality is unaffected. This compatibility introduces no additional performance burden or context overhead.

Security

Installing packages means executing third-party code: pyenv_install (including the auto-created .venv path) downloads and runs code from the configured index with the host user's privileges, and editable installs import in-workspace projects as-is. The plugin mitigates this with HTTPS-only indexes, workspace-only blast radius (a compromised environment is disposable via pyenv_remove), full routing transparency, session policy parity (read-only sessions cannot trigger any of it), and per-profile opt-in. See SECURITY.md for the complete threat model and mitigation list.

Documentation

• docs/design.md — architecture, confinement model, install chain, known limitations
• SECURITY.md — threat model and compensating controls

Contributing

See CONTRIBUTING.md. Issues and pull requests are welcome.

License

MIT