diff --git a/.forgejo/workflows/ci.yml b/.forgejo/workflows/ci.yml
index 0d63e35d5..7780893d7 100644
--- a/.forgejo/workflows/ci.yml
+++ b/.forgejo/workflows/ci.yml
@@ -99,19 +99,6 @@ jobs:
           fi
           echo "$files" | xargs nix develop -c shellcheck -S warning
 
-  ruff-vm-tests:
-    name: ruff (vm-tests)
-    if: vars.PUBLIC_FORGE != 'true'
-    runs-on: ${{ vars.PUBLIC_FORGE == 'true' && 'nixos' || 'hive-ci' }}
-    steps:
-      - uses: actions/checkout@v3
-      - name: lint
-        # ruff from this flake's nixpkgs pin, as the jq job does. The config in
-        # nix/vm-tests/ruff.toml names the globals the test driver provides.
-        run: |
-          nix shell --inputs-from . nixpkgs#ruff --command sh -c \
-            'ruff check nix/vm-tests && ruff format --check nix/vm-tests'
-
   prose-lint:
     name: prose lint (vale)
     if: vars.PUBLIC_FORGE != 'true'
diff --git a/docs/4-implementation/scheduler/ci.md b/docs/4-implementation/scheduler/ci.md
index 43299d379..dcc943203 100644
--- a/docs/4-implementation/scheduler/ci.md
+++ b/docs/4-implementation/scheduler/ci.md
@@ -129,9 +129,10 @@ Nix interpolation. Commands the script runs in the VM find their binaries on the
 node's `environment.systemPackages`. Build-time values (socket path, forge
 domain, store paths) arrive as `FULL_SETUP_*` environment variables, set in
 `nix/vm-tests/full-setup.nix` through `overrideTestDerivation`. To add a value,
-set one there and read it with `os.environ` in the script. The `ruff (vm-tests)`
-job checks and format-checks `nix/vm-tests/*.py`; `nix/vm-tests/ruff.toml` names
-the globals the test driver provides.
+set one there and read it with `os.environ` in the script. `nix fmt` formats and lints the Python (treefmt's
+`ruff-format` and `ruff-check`, which fixes what it can), and the `formatting`
+flake check fails on a file `nix fmt` would change. `nix/vm-tests/ruff.toml`
+names the globals the test driver provides.
 
 ## Configuration reference
 
diff --git a/docs/5-project/process/conventions.md b/docs/5-project/process/conventions.md
index e961a4ba7..50678737f 100644
--- a/docs/5-project/process/conventions.md
+++ b/docs/5-project/process/conventions.md
@@ -458,7 +458,7 @@ nix fmt                       # treefmt — authoritative, NOT bare cargo fmt
 
 `nix fmt` (treefmt) is the formatter CI gates on; bare `cargo fmt`
 misses the non-rust files treefmt also covers, so always run `nix
-fmt` before pushing.
+fmt` before pushing. It also formats and lints Python with ruff.
 
 **Clippy discipline — never add `#[allow(clippy::…)]`.** All lints are
 CI-fatal at `-D warnings` (pedantic included); every warning that fires
diff --git a/nix/devshell.nix b/nix/devshell.nix
index 215b27366..019bd02b2 100644
--- a/nix/devshell.nix
+++ b/nix/devshell.nix
@@ -20,6 +20,7 @@
         cargo
         cargo-llvm-cov
         clippy
+        ruff
         rust-analyzer
         rustc
         rustfmt
diff --git a/nix/treefmt.nix b/nix/treefmt.nix
index 1924f0c13..9e3d90c03 100644
--- a/nix/treefmt.nix
+++ b/nix/treefmt.nix
@@ -6,6 +6,8 @@
     keep-sorted.enable = true;
     nixfmt.enable = true;
     prettier.enable = true;
+    ruff-check.enable = true;
+    ruff-format.enable = true;
     rustfmt.enable = true;
     taplo.enable = true;
   };