diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..bb067cd
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,73 @@
+# Dependabot configuration for cwl-spawn.
+# https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+#
+# Why this file exists: the actions in .github/workflows are pinned to commit SHAs
+# (#6), which closes the mutable-tag hole but opens a staleness one — a SHA never
+# moves, including past a security fix, and unlike `@v5` nothing updates it.
+# Pinning is only safe when something bumps the pins. That something is this file.
+#
+# The exposure here is narrower than the suite's npm/PyPI publishers — nothing
+# here publishes a package — but release.yml holds `contents: write` to create the
+# GitHub Release, so a compromised action in that job can write to this repo.
+
+version: 2
+updates:
+  # GitHub Actions. Dependabot understands SHA pins: it rewrites both the SHA and
+  # the trailing `# vX.Y.Z` comment, so the pins stay readable and reviewable.
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "09:00"
+      timezone: "America/Los_Angeles"
+    # Don't propose a release the day it ships; let it sit a week first. A fresh
+    # action tag is exactly when a compromised or broken one is still unnoticed.
+    cooldown:
+      default-days: 7
+    open-pull-requests-limit: 5
+    labels:
+      - "dependencies"
+    commit-message:
+      prefix: "deps(actions)"
+      include: "scope"
+    # No `reviewers:` key on purpose — it's deprecated and inert. Every one of the
+    # umbrella repo's Dependabot PRs asks for a reviewer and none has ever had a
+    # review request. Use CODEOWNERS if you want one.
+    groups:
+      # One PR for all of them. The pattern is "*", not "actions/*", because
+      # softprops/action-gh-release (which creates the GitHub Release, with
+      # `contents: write`) is not under actions/ — with "actions/*" it would fall
+      # outside the group, which is how updates get quietly ignored.
+      github-actions:
+        patterns:
+          - "*"
+
+  # Python dependencies from pyproject.toml.
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "09:00"
+      timezone: "America/Los_Angeles"
+    cooldown:
+      default-days: 7
+    open-pull-requests-limit: 5
+    labels:
+      - "dependencies"
+    commit-message:
+      prefix: "deps"
+      include: "scope"
+    groups:
+      minor-and-patch:
+        update-types:
+          - "minor"
+          - "patch"
+    ignore:
+      # ruff 0.16 moved a large set of opinionated rules into the DEFAULT rule set,
+      # so a bump reddens `ruff check .` with no code change. The `<0.16` cap in
+      # pyproject.toml is deliberate; lift the ceiling and this ignore together,
+      # after choosing which new rules to adopt via an explicit select.
+      - dependency-name: "ruff"
+        versions: [">=0.16"]
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fc68cb7..47ac63d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,25 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Security
+- **Added Dependabot, so the SHA-pinned actions actually get bumped**
+  ([#6](https://github.com/spore-host/cwl-spawn/issues/6)). All 5 `uses:` refs were already pinned to commit SHAs — which
+  is exactly the situation that needs this: a SHA never moves, including past a
+  security fix, and unlike `@v5` nothing updates it. Pinning and Dependabot are one
+  control, not two; shipping only the pin trades a mutable-tag hole for a slow one.
+  - The new `.github/dependabot.yml` covers `github-actions` and `pip`, weekly with
+    a 7-day cooldown — a freshly published tag is exactly when a compromised or
+    broken one is still unnoticed. Group pattern is `*`, not `actions/*`, because
+    `softprops/action-gh-release` (which creates the GitHub Release under
+    `contents: write`) would otherwise fall outside the group and stop being
+    bumped. `ruff >=0.16` is ignored so a bump can't undo the deliberate cap.
+  - `tests/test_ci_hygiene.py` makes both halves regressions rather than
+    conventions: reverting a pin or dropping the Dependabot entry now fails
+    `pytest`, which CI already runs. `pyyaml` joins the `[dev]` extra for it and is
+    imported unguarded — a `try`/`except` import degrades to a skip, and a skipped
+    wiring test reports green while asserting nothing.
+  No behaviour change — CI wiring and tests only.
+
 ### Fixed
 - **CI was red on `main` and `ruff` is now capped `<0.16`.** ruff 0.16 moved a
   large set of opinionated rules (`BLE`, `PLW`, `TRY`, `C408`, `EXE`, `B017`,
diff --git a/pyproject.toml b/pyproject.toml
index 59f45e9..2a8e37a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,7 +27,11 @@ dependencies = [
 # airflow-spawn, miniwdl-spawn and snakemake-executor-plugin-spawn. Raising it is
 # a deliberate change: pick the rules to adopt via an explicit
 # `[tool.ruff.lint] select`, don't inherit them.
-dev = ["pytest>=7", "ruff>=0.5,<0.16", "mypy>=1.8"]
+# `pyyaml` is a test-only dependency: tests/test_ci_hygiene.py parses
+# .github/dependabot.yml. It is imported unguarded there on purpose — a
+# try/except import degrades to a skip, and a skipped wiring test reports green
+# while asserting nothing.
+dev = ["pytest>=7", "ruff>=0.5,<0.16", "mypy>=1.8", "pyyaml>=6"]
 
 [project.scripts]
 # cwltool has no plugin entry-point (unlike miniwdl's container_backend), so the
diff --git a/tests/test_ci_hygiene.py b/tests/test_ci_hygiene.py
new file mode 100644
index 0000000..7354731
--- /dev/null
+++ b/tests/test_ci_hygiene.py
@@ -0,0 +1,136 @@
+"""Tests that assert on repo wiring rather than on code.
+
+Wiring is what rots: a pin reverted to `@v5` or a deleted Dependabot entry is a
+one-line change whose absence is completely silent — nothing fails, the supply
+chain just quietly goes back to being mutable. These make that fail a test.
+
+`release.yml` holds `contents: write` to create the GitHub Release, so a
+compromised action in that job can write to this repo and alter published release
+artifacts. (#6)
+"""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+# PyYAML is a declared dev dependency (pyproject.toml `[dev]`), imported directly
+# rather than behind a try/except: a guarded import degrades to a skip, and a
+# skipped wiring test reports green while asserting nothing — the same silent
+# no-op these tests exist to catch.
+import yaml
+
+REPO = Path(__file__).resolve().parent.parent
+WORKFLOWS = REPO / ".github" / "workflows"
+
+# owner/action@<40-hex> followed by a `# vX.Y.Z` comment. The comment is required:
+# a bare SHA is unreadable, and the version is what makes a bump reviewable —
+# without it nobody can tell whether a pin is current or two years stale.
+PINNED = re.compile(r"^[^@\s]+@[0-9a-f]{40}\s+#\s*v?\d")
+
+
+def _uses_refs() -> list[tuple[str, int, str]]:
+    """Every registry action ref in the workflows, as (file, line_no, ref)."""
+    refs = []
+    for path in sorted(WORKFLOWS.glob("*.y*ml")):
+        for i, line in enumerate(path.read_text().splitlines(), start=1):
+            stripped = line.strip().removeprefix("- ")
+            if not stripped.startswith("uses:"):
+                continue
+            ref = stripped[len("uses:") :].strip()
+            if ref.startswith("./"):  # a local path, not a registry ref
+                continue
+            refs.append((path.name, i, ref))
+    return refs
+
+
+def _glob(pattern: str, value: str) -> bool:
+    """Dependabot's only wildcard is `*`, matching any run of characters."""
+    parts = pattern.split("*")
+    if len(parts) == 1:
+        return pattern == value
+    if not value.startswith(parts[0]):
+        return False
+    value = value[len(parts[0]) :]
+    for middle in parts[1:-1]:
+        idx = value.find(middle)
+        if idx < 0:
+            return False
+        value = value[idx + len(middle) :]
+    return value.endswith(parts[-1])
+
+
+def _dependabot() -> dict:
+    return yaml.safe_load((REPO / ".github" / "dependabot.yml").read_text())
+
+
+def test_actions_are_pinned_to_shas() -> None:
+    """Every `uses:` must name a full commit SHA, not a tag or branch.
+
+    A tag is mutable: `@v5` means "whatever v5 points at when the job runs".
+    `actions/checkout@v6` really did move (df4cb1c 2026-06-02 → d23441a 2026-07-16)
+    with no signal to consumers, so this is not hypothetical.
+    """
+    refs = _uses_refs()
+    # Anti-vacuous: a parser that silently stops matching would pass forever.
+    assert refs, f"no `uses:` lines found under {WORKFLOWS} — this test asserts nothing"
+
+    unpinned = [f"{name}:{line}: {ref}" for name, line, ref in refs if not PINNED.match(ref)]
+    assert not unpinned, (
+        "these actions are not pinned to a full commit SHA with a version comment:\n  "
+        + "\n  ".join(unpinned)
+        + "\nA tag or branch is mutable, so the code CI runs can change with no commit "
+        "here. Use:\n    uses: owner/action@<40-hex-sha> # vX.Y.Z"
+    )
+
+
+def test_dependabot_covers_every_action() -> None:
+    """The other half of pinning: something must bump the pins.
+
+    A SHA never moves, including past a security fix. Pinning without Dependabot
+    just trades a mutable-tag hole for a staleness one, so the two are one control.
+    The check that matters is coverage — an ecosystem entry whose group patterns
+    don't match an action leaves it outside the grouped PR, silently.
+    """
+    config = REPO / ".github" / "dependabot.yml"
+    assert config.exists(), (
+        "no .github/dependabot.yml: the actions here are pinned to SHAs, so without "
+        "Dependabot nothing ever bumps them"
+    )
+    cfg = _dependabot()
+    assert cfg.get("version") == 2, f"dependabot version must be 2, got {cfg.get('version')}"
+
+    patterns: list[str] = []
+    found_entry = False
+    for update in cfg.get("updates", []):
+        if update.get("package-ecosystem") != "github-actions":
+            continue
+        found_entry = True
+        dirs = update.get("directories") or [update.get("directory")]
+        assert dirs == ["/"], (
+            f"the github-actions entry watches {dirs}; workflows live in "
+            '.github/workflows, which Dependabot finds via directory "/"'
+        )
+        for group in (update.get("groups") or {}).values():
+            patterns.extend(group.get("patterns", []))
+    assert found_entry, (
+        "dependabot.yml has no `github-actions` entry, so the SHA-pinned actions "
+        "are never bumped"
+    )
+
+    for name, _, ref in _uses_refs():
+        action = ref.split("@", 1)[0]
+        assert any(_glob(p, action) for p in patterns), (
+            f"{action} (in {name}) is not matched by any Dependabot group pattern "
+            f"{patterns}, so it would fall outside the grouped PR and its bumps get "
+            "missed. Widen the pattern."
+        )
+
+
+def test_dependabot_covers_python_dependencies() -> None:
+    """pyproject.toml's dependencies need bumping too, not just the actions."""
+    ecosystems = {u.get("package-ecosystem") for u in _dependabot().get("updates", [])}
+    assert "pip" in ecosystems, (
+        "dependabot.yml has no `pip` entry, so pyproject.toml's dependencies are "
+        f"never updated (found: {sorted(e for e in ecosystems if e)})"
+    )