default_language_version: Pin the Interpreter

default_language_version sets the interpreter version pre-commit uses when it builds each language environment.

Hook environments are built with a specific interpreter. Pinning it makes local and CI runs identical and avoids "executable not found" when a runner lacks the default.

What it does

default_language_version is a top-level map from language to version, e.g. python: python3.11. pre-commit uses that interpreter to create the virtualenv or environment for hooks of that language. A per-hook language_version overrides it.

Common usage

.pre-commit-config.yaml

default_language_version:
  python: python3.11
  node: 20.11.1
repos:
  - repo: https://github.com/psf/black
    rev: 24.4.2
    hooks:
      - id: black
        language_version: python3.12   # override for one hook

Keys

Key	What it does
default_language_version	Top-level map of language to interpreter version
python: python3.11	Interpreter pre-commit invokes for python hooks
node: <version>	Node version for node-language hooks
language_version	Per-hook override of the version
default	Special value meaning "use the system default"

In CI

Make sure the pinned interpreter actually exists on the runner, or install it first. The default_language_version must name an executable on PATH (python3.11), not a bare version number for python. Pinning it keeps CI deterministic across runner image upgrades.

Common errors in CI

"[ERROR] Executable python3.11 not found" means the pinned interpreter is absent from the runner; install it (e.g. via setup-python) or change the pin. "[ERROR] ... is not a valid python version" appears when the value is malformed. For node, a missing version makes pre-commit download one, which can fail behind a proxy.