diff --git a/.github/actions/skip-if-already-ran/action.yml b/.github/actions/skip-if-already-ran/action.yml
new file mode 100644
index 0000000..dd87c8c
--- /dev/null
+++ b/.github/actions/skip-if-already-ran/action.yml
@@ -0,0 +1,90 @@
+# Copyright (c) Cratis. All rights reserved.
+# Licensed under the MIT license. See LICENSE file in the project root for full license information.
+# Caller contract: the job needs permissions: actions: read and runs on the repo's
+# own cheapest runner (cratis-arc / RUNNER_GATE for private repositories).
+# Only successful runs count; failed or cancelled runs run again next night.
+# Floating toolchains and other inputs outside the commit are not part of the key.
+# Do not use in a reusable workflow that has a scheduled caller: it sees the caller's runs.
+name: Skip if already ran
+description: Reports whether this workflow already succeeded for the same commit and an allowed event.
+
+inputs:
+  events:
+    description: Comma-separated events eligible for skipping and counted as prior successes.
+    required: false
+    default: schedule
+  sha:
+    description: Commit to check; override for workflows that push their own bot commit.
+    required: false
+    default: ${{ github.sha }}
+  token:
+    description: Token with actions read permission in the current repository.
+    required: false
+    default: ${{ github.token }}
+
+outputs:
+  skip:
+    description: "'true' when a prior success exists; otherwise 'false', including on API errors."
+    value: ${{ steps.check.outputs.skip }}
+  previous-run-url:
+    description: Link to the prior successful run, or empty when not skipping.
+    value: ${{ steps.check.outputs.previous-run-url }}
+
+runs:
+  using: composite
+  steps:
+    - name: Check for a prior successful run
+      id: check
+      shell: bash
+      env:
+        EVENT_NAME: ${{ github.event_name }}
+        EVENTS: ${{ inputs.events }}
+        SHA: ${{ inputs.sha }}
+        GH_TOKEN: ${{ inputs.token }}
+        REPO: ${{ github.repository }}
+        RUN_ID: ${{ github.run_id }}
+        RUN_ATTEMPT: ${{ github.run_attempt }}
+      run: |
+        set -euo pipefail
+        run_needed() {
+          printf 'skip=false\nprevious-run-url=\n' >> "$GITHUB_OUTPUT"
+        }
+        fail_open() {
+          echo "::warning::skip-if-already-ran: $1; running normally"
+          run_needed
+          exit 0
+        }
+        if [[ "$EVENT_NAME" == workflow_dispatch || "$RUN_ATTEMPT" -gt 1 ]]; then
+          run_needed
+          exit 0
+        fi
+        EVENTS="${EVENTS//[[:space:]]/}"
+        case ",$EVENTS," in
+          *",$EVENT_NAME,"*) ;;
+          *) run_needed; exit 0 ;;
+        esac
+        command -v gh >/dev/null || fail_open "gh is not installed"
+        if ! workflow_id=$(gh api "repos/$REPO/actions/runs/$RUN_ID" --jq .workflow_id); then
+          fail_open "Could not resolve the workflow id"
+        fi
+        [[ "$workflow_id" =~ ^[0-9]+$ ]] || fail_open "Invalid workflow id"
+        # The single quotes are deliberate: $ENV and $event are jq variables, not shell ones.
+        # shellcheck disable=SC2016
+        if ! previous_url=$(gh api \
+          "repos/$REPO/actions/workflows/$workflow_id/runs?head_sha=$SHA&status=success&per_page=100" \
+          --jq '.workflow_runs | map(select(.id != ($ENV.RUN_ID | tonumber) and
+            (.event as $event | ($ENV.EVENTS | split(",") | index($event)) != null))) |
+            .[0].html_url // empty'); then
+          fail_open "Could not query prior successful runs"
+        fi
+        if [[ -z "$previous_url" ]]; then
+          run_needed
+          exit 0
+        fi
+        [[ "$previous_url" =~ ^https://[^[:space:]]+$ ]] || fail_open "Invalid previous run URL"
+        if ! printf 'Skipped: this workflow already succeeded on this commit: [previous run](%s).\n' \
+          "$previous_url" >> "$GITHUB_STEP_SUMMARY"; then
+          fail_open "Could not write the step summary"
+        fi
+        printf 'skip=true\nprevious-run-url=%s\n' "$previous_url" >> "$GITHUB_OUTPUT"
+        echo "::notice title=skip-if-already-ran::Already succeeded on this commit: $previous_url"
diff --git a/.github/scripts/tests/skip-if-already-ran.test.py b/.github/scripts/tests/skip-if-already-ran.test.py
new file mode 100644
index 0000000..0c237c6
--- /dev/null
+++ b/.github/scripts/tests/skip-if-already-ran.test.py
@@ -0,0 +1,167 @@
+# Copyright (c) Cratis. All rights reserved.
+# Licensed under the MIT license. See LICENSE file in the project root for full license information.
+"""Run the production composite script offline, with a fake gh and real jq."""
+from pathlib import Path
+import json
+import re
+import shutil
+import subprocess
+import sys
+import tempfile
+import unittest
+
+import yaml
+
+ROOT = Path(__file__).resolve().parents[3]
+ACTION = ROOT / ".github/actions/skip-if-already-ran/action.yml"
+BASH = shutil.which("bash")
+JQ = shutil.which("jq")
+SHA = "a" * 40
+URL = "https://github.com/Cratis/Workflows/actions/runs/41"
+FAKE_GH = '''
+import json, os, subprocess, sys
+from pathlib import Path
+with open(os.environ["CALLS"], "a") as log:
+    log.write(json.dumps(sys.argv[1:]) + "\\n")
+is_lookup = "/actions/runs/" in sys.argv[2]
+if os.environ["FAIL_AT"] == ("lookup" if is_lookup else "runs"):
+    sys.exit(1)
+data = {"workflow_id": 7} if is_lookup else json.loads(Path(os.environ["RUNS"]).read_text())
+result = subprocess.run([os.environ["JQ"], "-r", sys.argv[4]], input=json.dumps(data), text=True)
+sys.exit(result.returncode)
+'''
+
+
+def load():
+    return yaml.safe_load(ACTION.read_text())
+
+
+def check_step():
+    return next(s for s in load()["runs"]["steps"] if s.get("id") == "check")
+
+
+def prior_run():
+    return dict(id=41, event="schedule", head_sha=SHA, conclusion="success", html_url=URL)
+
+
+def execute(runs=None, *, missing_gh=False, response=None, **overrides):
+    with tempfile.TemporaryDirectory() as temp:
+        directory = Path(temp)
+        for name in ("output", "summary", "calls"):
+            (directory / name).write_text("")
+        (directory / "runs").write_text(json.dumps(
+            response if response is not None else {"workflow_runs": runs or []}))
+        if not missing_gh:
+            fake = directory / "gh"
+            fake.write_text(f"#!{sys.executable}\n" + FAKE_GH)
+            fake.chmod(0o755)
+        env = dict(PATH=temp, GITHUB_OUTPUT=str(directory / "output"),
+                   GITHUB_STEP_SUMMARY=str(directory / "summary"), GH_TOKEN="test-token",
+                   EVENT_NAME="schedule", EVENTS="schedule", SHA=SHA, GITHUB_SHA=SHA,
+                   REPO="Cratis/Workflows", RUN_ID="42", RUN_ATTEMPT="1",
+                   FAIL_AT="", JQ=JQ, RUNS=str(directory / "runs"), CALLS=str(directory / "calls"))
+        env.update(overrides)
+        env["GITHUB_RUN_ATTEMPT"] = env["RUN_ATTEMPT"]
+        result = subprocess.run([BASH, "-c", check_step()["run"]], env=env,
+                                cwd=ROOT, capture_output=True, text=True)
+        outputs = dict(line.split("=", 1) for line in (directory / "output").read_text().splitlines())
+        calls = [json.loads(line) for line in (directory / "calls").read_text().splitlines()]
+        return result, outputs, calls, (directory / "summary").read_text()
+
+
+class ActionShapeTests(unittest.TestCase):
+    def test_composite_contract(self):
+        action = load()
+        self.assertEqual(action["runs"]["using"], "composite")
+        self.assertEqual(set(action["outputs"]), {"skip", "previous-run-url"})
+        for name in action["outputs"]:
+            self.assertEqual(action["outputs"][name]["value"], "${{ steps.check.outputs." + name + " }}")
+        self.assertEqual({key: value["default"] for key, value in action["inputs"].items()},
+                         dict(events="schedule", sha="${{ github.sha }}", token="${{ github.token }}"))
+        self.assertEqual(check_step()["shell"], "bash")
+        self.assertTrue(check_step()["run"].startswith("set -euo pipefail\n"))
+        self.assertNotIn("${{", check_step()["run"])
+        expected = dict(EVENT_NAME="github.event_name", EVENTS="inputs.events", SHA="inputs.sha",
+                        GH_TOKEN="inputs.token", REPO="github.repository", RUN_ID="github.run_id",
+                        RUN_ATTEMPT="github.run_attempt")
+        self.assertEqual(check_step()["env"], {k: "${{ " + v + " }}" for k, v in expected.items()})
+        for step in action["runs"]["steps"]:
+            if "uses" in step:
+                self.assertRegex(step["uses"], re.compile(r"^[^@\s]+@[0-9a-f]{40}$"))
+
+    def test_bash_syntax_and_shellcheck(self):
+        script = check_step()["run"]
+        subprocess.run([BASH, "-n"], input=script, text=True, check=True)
+        if shutil.which("shellcheck"):
+            subprocess.run(["shellcheck", "--shell=bash", "-"], input=script, text=True, check=True)
+
+
+class ActionBehaviorTests(unittest.TestCase):
+    def assert_result(self, execution, skip):
+        result, outputs, calls, summary = execution
+        self.assertEqual(result.returncode, 0, result.stdout + result.stderr)
+        self.assertEqual(outputs, {"skip": str(skip).lower(), "previous-run-url": URL if skip else ""})
+        return result.stdout, calls, summary
+
+    def test_manual_dispatch_always_runs_even_when_listed(self):
+        _, calls, _ = self.assert_result(execute(EVENT_NAME="workflow_dispatch", EVENTS="workflow_dispatch"), False)
+        self.assertEqual(calls, [])
+
+    def test_unlisted_event_does_not_query(self):
+        _, calls, _ = self.assert_result(execute(EVENT_NAME="pull_request"), False)
+        self.assertEqual(calls, [])
+
+    def test_event_matching_is_not_a_substring(self):
+        _, calls, _ = self.assert_result(execute(EVENTS="schedule_other"), False)
+        self.assertEqual(calls, [])
+
+    def test_manual_rerun_does_not_query(self):
+        _, calls, _ = self.assert_result(execute(RUN_ATTEMPT="2"), False)
+        self.assertEqual(calls, [])
+
+    def test_prior_success_skips_with_notice_and_summary_link(self):
+        stdout, calls, summary = self.assert_result(execute(runs=[prior_run()]), True)
+        self.assertIn("::notice title=skip-if-already-ran::", stdout)
+        self.assertIn(URL, stdout)
+        self.assertIn(URL, summary)
+        self.assertEqual(calls[0], ["api", "repos/Cratis/Workflows/actions/runs/42", "--jq", ".workflow_id"])
+        self.assertEqual(calls[1][1],
+                         f"repos/Cratis/Workflows/actions/workflows/7/runs?head_sha={SHA}&status=success&per_page=100")
+
+    def test_current_run_is_not_a_prior_success(self):
+        run = prior_run()
+        run["id"] = 42
+        self.assert_result(execute(runs=[run]), False)
+
+    def test_events_control_which_prior_runs_count(self):
+        run = prior_run()
+        run["event"] = "push"
+        self.assert_result(execute(runs=[run]), False)
+        self.assert_result(execute(runs=[run], EVENTS="schedule,push"), True)
+        self.assert_result(execute(runs=[run], EVENTS="schedule, push"), True)
+
+    def test_no_success_runs_again(self):
+        self.assert_result(execute(), False)
+
+    def test_sha_override_is_used_in_query(self):
+        _, calls, _ = self.assert_result(execute(SHA="b" * 40), False)
+        self.assertIn("head_sha=" + "b" * 40, calls[1][1])
+
+    def test_api_errors_fail_open_at_either_request(self):
+        for fail_at in ("lookup", "runs"):
+            with self.subTest(fail_at=fail_at):
+                stdout, _, _ = self.assert_result(execute(FAIL_AT=fail_at), False)
+                self.assertIn("::warning::", stdout)
+
+    def test_missing_gh_fails_open(self):
+        stdout, calls, _ = self.assert_result(execute(missing_gh=True), False)
+        self.assertIn("::warning::", stdout)
+        self.assertEqual(calls, [])
+
+    def test_malformed_api_response_fails_open(self):
+        stdout, _, _ = self.assert_result(execute(response={"message": "not run data"}), False)
+        self.assertIn("::warning::", stdout)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/.github/workflows/verify-skip-if-already-ran.yml b/.github/workflows/verify-skip-if-already-ran.yml
new file mode 100644
index 0000000..aff1d28
--- /dev/null
+++ b/.github/workflows/verify-skip-if-already-ran.yml
@@ -0,0 +1,56 @@
+# Copyright (c) Cratis. All rights reserved.
+# Licensed under the MIT license. See LICENSE file in the project root for full license information.
+name: Verify Skip If Already Ran
+
+on:
+  pull_request:
+    paths:
+      - .github/actions/skip-if-already-ran/**
+      - .github/scripts/tests/skip-if-already-ran.test.py
+      - .github/workflows/verify-skip-if-already-ran.yml
+  push:
+    branches: [main]
+    paths:
+      - .github/actions/skip-if-already-ran/**
+      - .github/scripts/tests/skip-if-already-ran.test.py
+      - .github/workflows/verify-skip-if-already-ran.yml
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  verify:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: read
+      actions: read
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Check the action offline
+        run: python3 -B .github/scripts/tests/skip-if-already-ran.test.py
+      - name: Default events never skip pull requests or pushes
+        id: defaults
+        uses: ./.github/actions/skip-if-already-ran
+      - name: Exercise the real API for the current event
+        id: live
+        uses: ./.github/actions/skip-if-already-ran
+        with:
+          events: ${{ github.event_name }}
+      - name: Assert live outputs
+        env:
+          DEFAULT_SKIP: ${{ steps.defaults.outputs.skip }}
+          LIVE_SKIP: ${{ steps.live.outputs.skip }}
+          LIVE_OUTCOME: ${{ steps.live.outcome }}
+        run: |
+          set -euo pipefail
+          [[ "$DEFAULT_SKIP" == false ]]
+          [[ "$LIVE_SKIP" == true || "$LIVE_SKIP" == false ]]
+          [[ "$LIVE_OUTCOME" == success ]]
+          echo "Checked 3 live action assertions"
diff --git a/README.md b/README.md
index 896032a..fccab22 100644
--- a/README.md
+++ b/README.md
@@ -725,6 +725,35 @@ The key is `<key-prefix>-<runner.os>-<hashFiles(<working-directory>/yarn.lock, <
 
 ---
 
+## Skip scheduled runs that already ran on this commit
+
+`Cratis/Workflows/.github/actions/skip-if-already-ran@main` reports `skip=true` when the same workflow already succeeded on the same commit for an event in `events` (default: `schedule`). Failed or cancelled runs do not count. Manual dispatches and manual re-runs always run; API errors warn and run normally. `previous-run-url` links to the prior success. See [#205](https://github.com/Cratis/Workflows/issues/205).
+
+Place the step in an existing cheap gate job and expose its output, or add a small `already-ran` job:
+
+```yaml
+already-ran:
+  runs-on: ubuntu-latest # Private repos: use cratis-arc / your RUNNER_GATE instead.
+  timeout-minutes: 5
+  permissions:
+    actions: read
+  outputs:
+    skip: ${{ steps.check.outputs.skip }}
+  steps:
+    - id: check
+      uses: Cratis/Workflows/.github/actions/skip-if-already-ran@main
+build:
+  needs: [already-ran]
+  if: needs.already-ran.outputs.skip != 'true'
+  # ...existing job configuration...
+```
+
+**Every other job must directly list the gate in `needs`**, and add `needs.<gate>.outputs.skip != 'true' && (…existing condition…)` to its `if` (or just the skip condition if it has none). This includes `always()`, `!cancelled()` and `failure()` aggregators and notification jobs; otherwise a deliberate skip can report red. Do not use the action in a reusable workflow with a scheduled caller: it would look up the caller's runs.
+
+For workflows that push their own bot commit, pass `sha:` with the last relevant source commit rather than the bot-updated HEAD. The key excludes floating toolchains, runner images, repository variables and other external inputs: use this only to validate the repository's own commit, not live health, latest dependencies or live-data reports. External changes without a commit need a manual dispatch.
+
+---
+
 ## Verifying release intent and release notes
 
 **`verify-pull-request-policy.yml`** combines release notes, warn-only release-note drift,