yawkat · yawkat · Jul 18, 2026 · Jul 18, 2026 · Jul 18, 2026 · Jul 18, 2026
diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
@@ -0,0 +1,54 @@
+name: Documentation
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+  workflow_dispatch: {}
+
+jobs:
+  images:
+    runs-on: ubuntu-latest
+    env:
+      GALLIUM_DRIVER: softpipe
+      LIBGL_ALWAYS_SOFTWARE: "1"
+      MESA_LOADER_DRIVER_OVERRIDE: softpipe
+    steps:
+      - name: Checkout
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
+        with:
+          submodules: true
+
+      - name: Setup Python
+        uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1 # v6.3.0
+        with:
+          python-version: "3.13"
+
+      - name: Setup uv
+        uses: astral-sh/setup-uv@11f9893b081a58869d3b5fccaea48c9e9e46f990 # v8.3.2
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y just libegl1 libgl1-mesa-dri libopengl0
+          uv sync --frozen
+
+      - name: Generate documentation images
+        run: just docs
+
+      - name: Check documentation images
+        run: |
+          # Make newly generated, untracked images visible to git diff as well.
+          git add --intent-to-add docs/images
+          git diff --exit-code -- docs/images
+
+      - name: Upload changed documentation images
+        if: failure()
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
+        with:
+          name: documentation-images
+          path: docs/images
+          retention-days: 1
diff --git a/README.md b/README.md
@@ -226,7 +226,7 @@ Pull the pusher back into its original position to release the baseplate. You ca
 <!-- These images are generated for regression detection purposes. -->
 <!-- openscad -o docs/images/jig-main.png --camera=0,0,0,40,0,10,200 -D part='"jig"' mag_insert_jig.scad -->
 <!-- openscad -o docs/images/jig-pusher.png --camera=0,0,0,40,0,10,200 -D part='"pusher"' mag_insert_jig.scad -->
-<!-- openscad -o docs/images/jig-main-below.png --camera=0,0,0,140,0,10,200 -D part='"jig"' mag_insert_jig.scad -->
+<!-- openscad -o docs/images/jig-main-below.png --camera=0,0,0,175,0,10,200 -D part='"jig"' mag_insert_jig.scad -->
 <!-- openscad -o docs/images/jig-pusher-below.png --camera=0,0,0,140,0,10,200 -D part='"pusher"' mag_insert_jig.scad -->
 
 ### Release slot
@@ -331,15 +331,15 @@ The depth of the tab can be configured with `clickgroove_depth`. Changing this v
 
 The `clickgroove_strength` property controls the thickness of the latch itself. This is measured from the very bottom of the latch which, if you look at the gridfinity specification, has a chamfer of 0.7mm, so the strength needs to be higher than this to get any reasonable latch height. Here's an example with `clickgroove_strength=2.5` (and `clickgroove_wall_strength=0`, or else there would not be enough space):
 
-<!-- openscad -o docs/images/click1-strength-2.5.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click=true -D click_style=1 -D clickgroove_strength=2.5 -D clickgroove_wall_strength=0 -->
-<img src="docs/images/click1-strength-2.5.png" alt="Click latch with clickgroove_strength=2.5" />
+<!-- openscad -o docs/images/click2-strength-2.5.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click=true -D click_style=1 -D clickgroove_strength=2.5 -D clickgroove_wall_strength=0 -->
+<img src="docs/images/click2-strength-2.5.png" alt="Click latch with clickgroove_strength=2.5" />
 
 #### Latch Wall Strength
 
 The `clickgroove_wall_strength` property controls the thickness of the wall behind the latch. This wall serves two purposes: It adds rigidity to the baseplate, and it prevents the click latch from bending too far. Note that the wall is measured per cell, so if you have two neighbouring cells, the actual wall thickness will be double this value. An example with `clickgroove_wall_strength=2` (and reduced `clickgroove_strength`):
 
-<!-- openscad -o docs/images/click1-wall-strength-2.png --camera=0,0,0,40,0,10,100 -D plate_size='[84, 42]' -D click=true -D click_style=1 -D clickgroove_strength=0.8 -D clickgroove_wall_strength=2 -->
-<img src="docs/images/click1-wall-strength-2.png" alt="Click latch with clickgroove_wall_strength=2" />
+<!-- openscad -o docs/images/click2-wall-strength-2.png --camera=0,0,0,40,0,10,100 -D plate_size='[84, 42]' -D click=true -D click_style=1 -D clickgroove_strength=0.8 -D clickgroove_wall_strength=2 -->
+<img src="docs/images/click2-wall-strength-2.png" alt="Click latch with clickgroove_wall_strength=2" />
 
 ### Arc Style Latch
 

diff --git a/docs/images/align-center.png b/docs/images/align-center.png
diff --git a/docs/images/align-east.png b/docs/images/align-east.png
diff --git a/docs/images/align-west.png b/docs/images/align-west.png
diff --git a/docs/images/bottom-chamfer.png b/docs/images/bottom-chamfer.png
diff --git a/docs/images/click1-distance-0.png b/docs/images/click1-distance-0.png
diff --git a/docs/images/click1-distance-5.png b/docs/images/click1-distance-5.png
diff --git a/docs/images/click1-height-0.5.png b/docs/images/click1-height-0.5.png
diff --git a/docs/images/click1-inner-length-20.png b/docs/images/click1-inner-length-20.png
diff --git a/docs/images/click1-outer-length-20.png b/docs/images/click1-outer-length-20.png
diff --git a/docs/images/click1-steepness-0.1.png b/docs/images/click1-steepness-0.1.png
diff --git a/docs/images/click1-steepness-5.png b/docs/images/click1-steepness-5.png
diff --git a/docs/images/click1-strength-2.5.png b/docs/images/click1-strength-2.5.png
diff --git a/docs/images/click1-wall-strength-0.png b/docs/images/click1-wall-strength-0.png
diff --git a/docs/images/click1-wall-strength-2.png b/docs/images/click1-wall-strength-2.png
diff --git a/docs/images/click1.png b/docs/images/click1.png
diff --git a/docs/images/click2-bin.png b/docs/images/click2-bin.png
diff --git a/docs/images/click2-bottom-chamfer-1.png b/docs/images/click2-bottom-chamfer-1.png
diff --git a/docs/images/click2-bottom-chamfer-2.png b/docs/images/click2-bottom-chamfer-2.png
diff --git a/docs/images/click2-bottom-chamfer-3.png b/docs/images/click2-bottom-chamfer-3.png
diff --git a/docs/images/click2-bottom-chamfer-4.png b/docs/images/click2-bottom-chamfer-4.png
diff --git a/docs/images/click2-depth.png b/docs/images/click2-depth.png
diff --git a/docs/images/click2-gap-length.png b/docs/images/click2-gap-length.png
diff --git a/docs/images/click2-strength-2.5.png b/docs/images/click2-strength-2.5.png
diff --git a/docs/images/click2-tab-length.png b/docs/images/click2-tab-length.png
diff --git a/docs/images/click2-wall-strength-2.png b/docs/images/click2-wall-strength-2.png
diff --git a/docs/images/click2.png b/docs/images/click2.png
diff --git a/docs/images/closeup.png b/docs/images/closeup.png
diff --git a/docs/images/corner-radius-1.png b/docs/images/corner-radius-1.png
diff --git a/docs/images/corner-radius.png b/docs/images/corner-radius.png
diff --git a/docs/images/custom-cell.png b/docs/images/custom-cell.png
diff --git a/docs/images/edge-adjustment-cut.png b/docs/images/edge-adjustment-cut.png
diff --git a/docs/images/edge-adjustment-default.png b/docs/images/edge-adjustment-default.png
diff --git a/docs/images/edge-adjustment-pad.png b/docs/images/edge-adjustment-pad.png
diff --git a/docs/images/edge-adjustment-shift.png b/docs/images/edge-adjustment-shift.png
diff --git a/docs/images/edge-puzzle-clickgroove.png b/docs/images/edge-puzzle-clickgroove.png
diff --git a/docs/images/edge-puzzle-full-height.png b/docs/images/edge-puzzle-full-height.png
diff --git a/docs/images/edge-puzzle-multi.png b/docs/images/edge-puzzle-multi.png
diff --git a/docs/images/edge-puzzle-unconnected.png b/docs/images/edge-puzzle-unconnected.png
diff --git a/docs/images/edge-puzzle.png b/docs/images/edge-puzzle.png
diff --git a/docs/images/filler-dynamic-expand-always.png b/docs/images/filler-dynamic-expand-always.png
diff --git a/docs/images/filler-dynamic-expand.png b/docs/images/filler-dynamic-expand.png
diff --git a/docs/images/filler-dynamic.png b/docs/images/filler-dynamic.png
diff --git a/docs/images/filler-half.png b/docs/images/filler-half.png
diff --git a/docs/images/filler-none.png b/docs/images/filler-none.png
diff --git a/docs/images/filler-third.png b/docs/images/filler-third.png
diff --git a/docs/images/hscrews.png b/docs/images/hscrews.png
diff --git a/docs/images/intersection-puzzle-loose.png b/docs/images/intersection-puzzle-loose.png
diff --git a/docs/images/intersection-puzzle-tight.png b/docs/images/intersection-puzzle-tight.png
diff --git a/docs/images/intersection-puzzle.png b/docs/images/intersection-puzzle.png
diff --git a/docs/images/irregular-base-shape.png b/docs/images/irregular-base-shape.png
diff --git a/docs/images/irregular-no-override.png b/docs/images/irregular-no-override.png
diff --git a/docs/images/irregular-override.png b/docs/images/irregular-override.png
diff --git a/docs/images/jig-main-below.png b/docs/images/jig-main-below.png
diff --git a/docs/images/jig-main.png b/docs/images/jig-main.png
diff --git a/docs/images/jig-pusher-below.png b/docs/images/jig-pusher-below.png
diff --git a/docs/images/jig-pusher.png b/docs/images/jig-pusher.png
diff --git a/docs/images/magnet-border-1.png b/docs/images/magnet-border-1.png
diff --git a/docs/images/magnets-glue-in-bottom.png b/docs/images/magnets-glue-in-bottom.png
diff --git a/docs/images/magnets-glue-in.png b/docs/images/magnets-glue-in.png
diff --git a/docs/images/magnets-none.png b/docs/images/magnets-none.png
diff --git a/docs/images/magnets-press-fit-below.png b/docs/images/magnets-press-fit-below.png
diff --git a/docs/images/magnets-press-fit.png b/docs/images/magnets-press-fit.png
diff --git a/docs/images/magnets-solid.png b/docs/images/magnets-solid.png
diff --git a/docs/images/numbering-squeeze.png b/docs/images/numbering-squeeze.png
diff --git a/docs/images/numbering.png b/docs/images/numbering.png
diff --git a/docs/images/override-empty.png b/docs/images/override-empty.png
diff --git a/docs/images/override-normal.png b/docs/images/override-normal.png
diff --git a/docs/images/override-solid.png b/docs/images/override-solid.png
diff --git a/docs/images/segment-x-ideal.png b/docs/images/segment-x-ideal.png
diff --git a/docs/images/segment-x-incremental-override.png b/docs/images/segment-x-incremental-override.png
diff --git a/docs/images/segment-x-incremental.png b/docs/images/segment-x-incremental.png
diff --git a/docs/images/segment-y-override.png b/docs/images/segment-y-override.png
diff --git a/docs/images/segment-y.png b/docs/images/segment-y.png
diff --git a/docs/images/separate-edge.png b/docs/images/separate-edge.png
diff --git a/docs/images/solid_base.png b/docs/images/solid_base.png
diff --git a/docs/images/stacked-print-duplicate.png b/docs/images/stacked-print-duplicate.png
diff --git a/docs/images/stacked-print-gap-exaggerated.png b/docs/images/stacked-print-gap-exaggerated.png
diff --git a/docs/images/stacked-print-gap-normal.png b/docs/images/stacked-print-gap-normal.png
diff --git a/docs/images/stacked-print.png b/docs/images/stacked-print.png
diff --git a/docs/images/thumb-screw-base-magnet.png b/docs/images/thumb-screw-base-magnet.png
diff --git a/docs/images/thumb-screw-base.png b/docs/images/thumb-screw-base.png
diff --git a/docs/images/thumb-screw-magnet.png b/docs/images/thumb-screw-magnet.png
diff --git a/docs/images/top-chamfer.png b/docs/images/top-chamfer.png
diff --git a/docs/images/top-slice.png b/docs/images/top-slice.png
diff --git a/docs/images/vscrews-counterbore.png b/docs/images/vscrews-counterbore.png
diff --git a/docs/images/vscrews-counterboth.png b/docs/images/vscrews-counterboth.png
diff --git a/docs/images/vscrews-countersink.png b/docs/images/vscrews-countersink.png
diff --git a/docs/images/vscrews-diameter.png b/docs/images/vscrews-diameter.png
diff --git a/docs/images/vscrews-else.png b/docs/images/vscrews-else.png
diff --git a/docs/images/vscrews-most.png b/docs/images/vscrews-most.png
diff --git a/docs/images/vscrews-plate-corners-mod.png b/docs/images/vscrews-plate-corners-mod.png
diff --git a/docs/images/vscrews-plate-corners.png b/docs/images/vscrews-plate-corners.png
diff --git a/docs/images/vscrews-plate-edges.png b/docs/images/vscrews-plate-edges.png
diff --git a/docs/images/vscrews-segment-corners.png b/docs/images/vscrews-segment-corners.png
diff --git a/docs/images/vscrews-segment-edges.png b/docs/images/vscrews-segment-edges.png
diff --git a/docs/images/vscrews.png b/docs/images/vscrews.png
diff --git a/docs/images/wall-bottom.png b/docs/images/wall-bottom.png
diff --git a/docs/images/wall-top.png b/docs/images/wall-top.png
diff --git a/docs/images/whole.png b/docs/images/whole.png
diff --git a/justfile b/justfile
@@ -1,6 +1,6 @@
 paths:
     mkdir -p paths
-    uv run extract_paths.py puzzle.svg paths/puzzle.scad
+    uv run scripts/extract_paths.py puzzle.svg paths/puzzle.scad
 
 test:
     openscad -o /dev/null --export-format=stl test.scad
@@ -14,53 +14,8 @@ banner name:
 
 banners: (banner "banner-generator-yawkat") (banner "banner-generator-perplexinglabs")
 
-docs:
-    #!/usr/bin/env -S uv run --script
-    import re
-    import shlex
-    import subprocess
-    import os
-    import asyncio
-
-    openscad_pattern = re.compile(r"^\s*<!--\s*openscad (.+)\s*-->\s*$")
-    concurrency = asyncio.Semaphore(8)
-
-    async def run(cmd, output):
-        max_attempts = 5
-        for attempt in range(1, max_attempts + 1):
-            async with concurrency:
-                print("Running: " + shlex.join(cmd))
-                proc = await asyncio.create_subprocess_exec(*cmd)
-                await proc.wait()
-                assert proc.returncode == 0
-            if os.path.getsize(output) != 7763:
-                return
-            # render failure, retry
-            print(f"Render failure for `{shlex.join(cmd)}` ({attempt}/{max_attempts}), retrying")
-        raise RuntimeError(f"Render failure after {max_attempts} attempts: {shlex.join(cmd)}")
-
-    async def main():
-        tasks = []
-        written = []
-        for line in open("README.md"):
-            match = openscad_pattern.match(line)
-            if match:
-                cmd = ["openscad", "--hardwarnings", "--projection=ortho", "--colorscheme=Starnight", "--render", "--imgsize=2500,1000", *shlex.split(match.group(1))]
-                # use gridflock.scad if no other file specified
-                for c in cmd:
-                    if ".scad" in c:
-                        break
-                else:
-                    cmd.append("gridflock.scad")
-                output = cmd[cmd.index("-o") + 1]
-                tasks.append(run(cmd, output))
-                written.append(output)
-        for f in os.listdir("docs/images"):
-            if os.path.join("docs/images", f) not in written:
-                os.unlink(os.path.join("docs/images", f))
-        await asyncio.gather(*tasks)
-
-    asyncio.run(main())
+docs: paths
+    uv run scripts/generate_docs.py
 
 overlay-png name:
     inkscape -w 1600 -h 1200 docs/{{name}}.svg -o build/{{name}}.png

diff --git a/mag_insert_jig.scad b/mag_insert_jig.scad
@@ -342,7 +342,7 @@ if (part == "jig") {
       jig_with_pusher();
     }
   } else {
-    jig_with_pusher();
+    color([1.0, 0.2, 0.2, jig_alpha]) jig_with_pusher();
   }
 } else if (part == "pusher") {
   pusher_combined();

diff --git a/pyproject.toml b/pyproject.toml
@@ -5,5 +5,7 @@ description = "Add your description here"
 readme = "README.md"
 requires-python = ">=3.13"
 dependencies = [
+    "pypng>=0.20220715.0",
     "svgelements>=1.9.6",
+    "zopfli>=0.4.3",
 ]
diff --git a/scripts/canonicalize_png.py b/scripts/canonicalize_png.py
@@ -0,0 +1,40 @@
+import os
+import sys
+from pathlib import Path
+
+import png
+from zopfli.zlib import compress
+
+
+class _ZopfliCompressor:
+    def __init__(self) -> None:
+        self.data = bytearray()
+
+    def compress(self, data: bytes) -> bytes:
+        self.data.extend(data)
+        return b""
+
+    def flush(self) -> bytes:
+        return compress(bytes(self.data), numiterations=1)
+
+
+def canonicalize(path: Path | str) -> None:
+    path = Path(path)
+    temporary_path = path.with_name(f".{path.name}.canonical.png")
+    original_compressobj = png.zlib.compressobj
+    try:
+        width, height, rows, _ = png.Reader(filename=path).asRGB8()
+        # PyPNG always uses PNG filter 0. Substitute its streaming zlib object
+        # with Zopfli so compression is deterministic across zlib versions.
+        png.zlib.compressobj = lambda *_args, **_kwargs: _ZopfliCompressor()
+        with temporary_path.open("wb") as output:
+            png.Writer(width, height, greyscale=False, alpha=False).write(output, rows)
+        os.replace(temporary_path, path)
+    finally:
+        png.zlib.compressobj = original_compressobj
+        temporary_path.unlink(missing_ok=True)
+
+
+if __name__ == "__main__":
+    for argument in sys.argv[1:]:
+        canonicalize(Path(argument))
diff --git a/extract_paths.py → scripts/extract_paths.py b/extract_paths.py → scripts/extract_paths.py
diff --git a/scripts/generate_docs.py b/scripts/generate_docs.py
@@ -0,0 +1,102 @@
+import asyncio
+import os
+import re
+import shlex
+from concurrent.futures import ProcessPoolExecutor
+from pathlib import Path
+
+from canonicalize_png import canonicalize
+from pinned_openscad import openscad_path
+
+
+OPENSCAD_PATTERN = re.compile(r"^\s*<!--\s*openscad (.+)\s*-->\s*$")
+CONCURRENCY = asyncio.Semaphore(8)
+CANONICALIZE_POOL = ProcessPoolExecutor(max_workers=8)
+OPENSCAD_ENVIRONMENT = os.environ | {
+    "GALLIUM_DRIVER": "softpipe",
+    "LIBGL_ALWAYS_SOFTWARE": "1",
+    "MESA_LOADER_DRIVER_OVERRIDE": "softpipe",
+}
+
+
+async def render(command: list[str], output: str) -> None:
+    output_path = Path(output)
+    temporary_output = output_path.with_name(f".{output_path.name}.rendering.png")
+    render_command = command.copy()
+    render_command[render_command.index("-o") + 1] = str(temporary_output)
+    max_attempts = 5
+    try:
+        for attempt in range(1, max_attempts + 1):
+            async with CONCURRENCY:
+                print("Running: " + shlex.join(command))
+                process = await asyncio.create_subprocess_exec(
+                    *render_command,
+                    env=OPENSCAD_ENVIRONMENT,
+                )
+                await process.wait()
+                if process.returncode != 0:
+                    raise RuntimeError(
+                        f"OpenSCAD exited with {process.returncode}: {shlex.join(command)}"
+                    )
+            if temporary_output.stat().st_size != 7763:
+                loop = asyncio.get_running_loop()
+                await loop.run_in_executor(
+                    CANONICALIZE_POOL, canonicalize, temporary_output
+                )
+                os.replace(temporary_output, output_path)
+                return
+            print(
+                f"Render failure for `{shlex.join(command)}` "
+                f"({attempt}/{max_attempts}), retrying"
+            )
+        raise RuntimeError(
+            f"Render failure after {max_attempts} attempts: {shlex.join(command)}"
+        )
+    finally:
+        temporary_output.unlink(missing_ok=True)
+
+
+async def render_group(commands: list[list[str]], output: str) -> None:
+    # Some README examples intentionally use the same output for legacy and
+    # renamed options. Run those sequentially so they cannot race over the
+    # shared temporary and final paths.
+    for command in commands:
+        await render(command, output)
+
+
+async def main() -> None:
+    openscad = str(openscad_path())
+    commands_by_output: dict[str, list[list[str]]] = {}
+    with Path("README.md").open() as readme:
+        for line in readme:
+            match = OPENSCAD_PATTERN.match(line)
+            if match:
+                command = [
+                    openscad,
+                    "--enable",
+                    "predictible-output",
+                    "--hardwarnings",
+                    "--projection=ortho",
+                    "--colorscheme=Starnight",
+                    "--render",
+                    "--imgsize=2500,1000",
+                    *shlex.split(match.group(1)),
+                ]
+                if not any(".scad" in argument for argument in command):
+                    command.append("gridflock.scad")
+                output = command[command.index("-o") + 1]
+                commands_by_output.setdefault(output, []).append(command)
+
+    for image in Path("docs/images").iterdir():
+        if str(image) not in commands_by_output:
+            image.unlink()
+    await asyncio.gather(
+        *(
+            render_group(commands, output)
+            for output, commands in commands_by_output.items()
+        )
+    )
+
+
+if __name__ == "__main__":
+    asyncio.run(main())
diff --git a/scripts/pinned_openscad.py b/scripts/pinned_openscad.py
@@ -0,0 +1,75 @@
+import hashlib
+import os
+import platform
+import shutil
+import stat
+import subprocess
+import sys
+import tempfile
+import urllib.request
+from pathlib import Path
+
+
+OPENSCAD_VERSION = "2026.07.16"
+OPENSCAD_URL = (
+    f"https://files.openscad.org/snapshots/"
+    f"OpenSCAD-{OPENSCAD_VERSION}-x86_64.AppImage"
+)
+OPENSCAD_SHA256 = "85000c7839cf96ca824511d9da38091683e3c6f71a390205ef4dd07e62ed97b4"
+BUILD_DIRECTORY = Path(__file__).resolve().parent.parent / "build"
+
+
+def _download(destination: Path) -> None:
+    digest = hashlib.sha256()
+    print(f"Downloading OpenSCAD {OPENSCAD_VERSION} AppImage", file=sys.stderr)
+    with urllib.request.urlopen(OPENSCAD_URL) as response, destination.open("wb") as output:
+        while chunk := response.read(1024 * 1024):
+            digest.update(chunk)
+            output.write(chunk)
+    actual_sha256 = digest.hexdigest()
+    if actual_sha256 != OPENSCAD_SHA256:
+        raise RuntimeError(
+            f"OpenSCAD AppImage checksum mismatch: expected {OPENSCAD_SHA256}, "
+            f"got {actual_sha256}"
+        )
+    destination.chmod(destination.stat().st_mode | stat.S_IXUSR)
+
+
+def openscad_path() -> Path:
+    if platform.system() != "Linux" or platform.machine() not in {"x86_64", "AMD64"}:
+        raise RuntimeError("The pinned OpenSCAD AppImage requires x86_64 Linux")
+
+    cache_parent = BUILD_DIRECTORY
+    cache_directory = cache_parent / f"openscad-{OPENSCAD_VERSION}-{OPENSCAD_SHA256[:12]}"
+    executable = cache_directory / "AppRun"
+    if executable.is_file():
+        return executable
+
+    cache_parent.mkdir(parents=True, exist_ok=True)
+    temporary_directory = Path(tempfile.mkdtemp(prefix="openscad-", dir=cache_parent))
+    try:
+        appimage = temporary_directory / "OpenSCAD.AppImage"
+        _download(appimage)
+        subprocess.run(
+            [appimage, "--appimage-extract"],
+            cwd=temporary_directory,
+            check=True,
+            stdout=subprocess.DEVNULL,
+        )
+        extracted = temporary_directory / "squashfs-root"
+        try:
+            extracted.rename(cache_directory)
+        except FileExistsError:
+            # Another concurrent invocation populated the same immutable cache.
+            pass
+    finally:
+        shutil.rmtree(temporary_directory, ignore_errors=True)
+
+    if not executable.is_file():
+        raise RuntimeError("OpenSCAD AppImage extraction did not produce AppRun")
+    return executable
+
+
+if __name__ == "__main__":
+    executable = openscad_path()
+    os.execv(executable, [str(executable), *sys.argv[1:]])