tau runtime

A self-contained CPython with τ installed into it, for the tau code extension (ffwf.tau-code).

This extension does nothing on its own. It ships files and tells tau code where they are. Install it if you want tau code to work without installing Python and τ yourself; skip it if you already have a tau on PATH.

What is in it

runtime/
  manifest.json                    what this payload is, read by the extension
  bin/tau                          a shim, for your terminal
  python/
    bin/python3.11                 the interpreter
    lib/python3.11/                the standard library
      site-packages/               tau, pydantic, httpx, and pip

One interpreter, one copy of τ's RPC closure — 13 packages — and pip. No Textual: τ's TUI is not what an editor extension runs, and leaving it out is 12 packages and ~18 MB.

It does not touch your Python

The interpreter is spawned with -I, so PYTHONPATH, PYTHONHOME, your user site directory and the working directory are all off sys.path. Two of those are load-bearing, and each has a measured failure behind it.

Your user site directory. This is the one that bites without a project in sight, because ~/.local/lib/python3.11/site-packages is on every interpreter's path by default — including this one:

$ .../python/bin/python3.11 -c 'import typing_extensions as t; print(t.__file__)'
/home/you/.local/lib/python3.11/site-packages/typing_extensions.py   # yours

$ .../python/bin/python3.11 -I -c 'import typing_extensions as t; print(t.__file__)'
.../runtime/python/lib/python3.11/site-packages/typing_extensions.py # ours

An old typing_extensions there surfaces as ImportError: cannot import name 'sentinel' raised inside a model streaming call, nowhere near its cause.

The working directory. An agent's cwd is your project, and the shim runs -m, which puts cwd on sys.path[0]. A file called pydantic.py in your project would be imported instead of the real one:

$ cd a-project-with-a-pydantic.py
$ .../python/bin/python3.11 -m tau_coding_agent.cli --version
SHADOWED: the workspace pydantic.py was imported

$ .../bin/tau --version          # the shim, which passes -I
tau 0.10.3

This isolates τ's own imports, not its tools. The process's working directory is untouched, so @file completion, reads, writes and every shell command still resolve against your project exactly as a system τ does. -I governs sys.path; cwd is a separate thing, and only the first is closed.

The one place those two legitimately meet is a τ extension, which is project Python that τ imports. τ 0.10.3 puts the extension's own directory on sys.path for the length of its import, so a single-file extension's import helper resolves the same under this runtime as under any other. Against τ 0.10.2 or older that import fails — but it failed from a pip-installed tau too, for a different reason, so this runtime is not the thing that broke it.

Nothing here reads or writes anything of yours except the session store and config that τ itself uses — the same ~/.tau the TUI uses, so the two interoperate.

Using it yourself

The payload is a relocatable directory, not an editor-only thing. tau: Copy Runtime Interpreter Path puts the interpreter on your clipboard, and tau: Show Runtime Info prints everything below.

"$RUNTIME/bin/tau" --help                     # the shim; -I is already in it
"$RUNTIME/python/bin/python3.11" -m pip list  # its own pip, its own site-packages

pip install into it works and is how a τ extension's dependency gets there. It installs into this tree and reaches nothing else on your machine.

When both this and a system τ are installed

tau code decides, and says so — the panel carries a banner when the two are different versions, rather than picking quietly. tau-code.runtime chooses:


`auto` (default)	this runtime when installed, otherwise `tau` on `PATH`
`bundled`	only this runtime; an error when it is absent
`system`	only `PATH` or `tau-code.binary`; ignore this extension

A tau-code.binary you set explicitly beats all three. Naming a path is an instruction, and a path that does not work is an error rather than a reason to run something else.

Platform builds

One .vsix per platform, and the editor installs the one matching the machine that will run the agent. Over SSH, in WSL or in a devcontainer that is the remote machine, not your laptop — which is why this declares extensionKind: ["workspace"], the same as tau code.

Built from this repository: npm run package:runtime. Targets are linux-x64, linux-arm64, linux-armhf, alpine-x64, alpine-arm64, darwin-x64, darwin-arm64, win32-x64, win32-arm64.

Licence

MIT, for this extension. The payload redistributes CPython (PSF-2.0), pip (MIT), τ (MIT) and τ's dependencies, each under its own licence; every wheel's dist-info travels with it in site-packages.