diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
index 598e8ab..d07b3aa 100644
--- a/.github/PULL_REQUEST_TEMPLATE.md
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -27,7 +27,7 @@ Merge bottom up with merge commits; retarget the next PR to main before merging
 
 ## Verification
 
-- [ ] `python scripts/check_docs.py` (and `python -m unittest discover -s scripts -p "test_*.py"` if scripts changed)
+- [ ] `python scripts/check_docs.py` (and `python -m pytest scripts` if scripts changed)
 - [ ] `cd game && npm run typecheck && npm run build` (game changes)
 - [ ] Played on the Vercel preview (link): keyboard and gamepad
 - [ ] Art: Design review on the board says Approved before export
diff --git a/.github/workflows/art-pipeline.yml b/.github/workflows/art-pipeline.yml
index 661bd3f..8e240ce 100644
--- a/.github/workflows/art-pipeline.yml
+++ b/.github/workflows/art-pipeline.yml
@@ -6,9 +6,20 @@ on:
       - requirements-art.txt
       - .github/workflows/art-pipeline.yml
       - art/**
+  # main is checked again after every merge: a stack merged bottom-up can still break it
+  push:
+    branches: [main]
+    paths:
+      - scripts/**
+      - requirements-art.txt
+      - .github/workflows/art-pipeline.yml
+      - art/**
   workflow_dispatch:
 permissions:
   contents: read
+concurrency:
+  group: art-pipeline-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 jobs:
   art-pipeline:
     runs-on: ubuntu-latest
@@ -20,7 +31,8 @@ jobs:
           cache: pip
           cache-dependency-path: requirements-art.txt
       - run: python -m pip install -r requirements-art.txt
-      - run: python -m unittest discover -s scripts -p 'test_*.py' -v
+      # pytest runs both styles: unittest classes and plain test functions (unittest discover skipped the latter)
+      - run: python -m pytest scripts -v -p no:cacheprovider
       - run: python scripts/creek_layers.py
       - run: python scripts/split_layers.py --check
       - run: python scripts/collision_check.py
diff --git a/AGENTS.md b/AGENTS.md
index 018a5d6..d39ab33 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -45,7 +45,7 @@ Alexander, 24 Oct: everything is done the way the HUD and the pocket computer we
 - Work only from an issue you were given. Branch from `main` as `<type>/<issue>-<slug>` (`feature/`, `fix/`, `docs/`, `art/`, `chore/`, `ci/`). One issue, one branch, one PR. Commit as `arudaev <hlexhelftd@gmail.com>`, conventional subjects (plus `art:` for assets), no attribution trailers.
 - Open a **draft** PR with `Closes #<issue>` (never an epic) and fill in the template. A change bigger than ~400 lines of code is a **stack** of PRs: titles `[n/N] type: subject`, each based on the branch below, the stack listed in every body ([CONTRIBUTING.md](CONTRIBUTING.md#stacked-prs)).
 - Don't `/take` issues, set board fields or change Design review – the team does that.
-- Before committing: `git diff --cached --check`, `python scripts/check_docs.py`, and `python -m unittest discover -s scripts -p "test_*.py"` if scripts changed.
+- Before committing: `git diff --cached --check`, `python scripts/check_docs.py`, and `python -m pytest scripts` if scripts changed (pip install -r requirements-art.txt).
 - Agents don't merge, don't push to `main`, don't force-push, don't enable auto-merge, and never touch `.env` or keys.
 - This repo is a submodule of `dotPrivate`: commit here first; the parent gitlink is updated separately. Don't touch other gitlinks.
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 7de74b7..9d45787 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -131,7 +131,7 @@ Every committed image is produced by a script from a config with real references
 ```bash
 git diff --cached --check
 python scripts/check_docs.py
-python -m unittest discover -s scripts -p "test_*.py"     # if scripts changed
+python -m pytest scripts                                 # if scripts changed
 cd game && npm run typecheck && npm test && npm run build  # game code
 python scripts/compare.py lineup hero-move:walk-03 …       # on-screen changes: the comparison for the PR
 ```
diff --git a/requirements-art.txt b/requirements-art.txt
index 4530f64..bd42f49 100644
--- a/requirements-art.txt
+++ b/requirements-art.txt
@@ -2,3 +2,6 @@
 # belong to the installed imagegen CLI environment; no API key is needed here.
 Pillow>=11.0,<13
 numpy>=2.0,<3
+scipy>=1.13,<2
+# tests (CI runs python -m pytest scripts)
+pytest>=8,<9