diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6d5db35..aea9675 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,9 +9,11 @@ permissions:
   contents: read
 jobs:
   flutter:
-    runs-on: ubuntu-latest
+    runs-on: sylphx-linux-standard
     steps:
       - uses: actions/checkout@v4
+      - name: Verify static owned runner profiles
+        run: bash scripts/check-owned-runner-profiles.sh
       - uses: subosito/flutter-action@v2
         with:
           channel: stable
diff --git a/scripts/check-owned-runner-profiles.sh b/scripts/check-owned-runner-profiles.sh
new file mode 100755
index 0000000..9c0b9e6
--- /dev/null
+++ b/scripts/check-owned-runner-profiles.sh
@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+# Enforce the fleet-owned runner contract for this repository's direct jobs.
+# Reusable workflows are governed by the repository that owns their source.
+set -euo pipefail
+
+ROOT="${1:-$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)}"
+
+python3 - "$ROOT" <<'PY'
+from pathlib import Path
+import re
+import sys
+
+root = Path(sys.argv[1])
+workflow_dir = root / ".github" / "workflows"
+selection = re.compile(r"^\s*runs-on\s*:\s*(?P<value>.*?)(?:\s+#.*)?$")
+linux = re.compile(r"^sylphx-linux-(?:standard|large|xlarge|2xlarge)$")
+macos = re.compile(r"^\[\s*self-hosted\s*,\s*sylphx\s*,\s*macos\s*,\s*(?:nano|small|standard|large|xlarge|2xlarge)\s*\]$")
+hosted = re.compile(r"\b(?:ubuntu|macos|windows)-(?:latest|\d+(?:\.\d+)?)\b", re.I)
+
+violations = []
+checked = 0
+for workflow in sorted((*workflow_dir.glob("*.yml"), *workflow_dir.glob("*.yaml"))):
+    for line_no, line in enumerate(workflow.read_text().splitlines(), start=1):
+        match = selection.match(line)
+        if not match:
+            continue
+        checked += 1
+        value = match.group("value").strip().strip("\"'")
+        if "${{" in value:
+            violations.append((workflow, line_no, "dynamic runner selection", value))
+        elif hosted.search(value):
+            violations.append((workflow, line_no, "GitHub-hosted runner", value))
+        elif not (linux.fullmatch(value) or macos.fullmatch(value)):
+            violations.append((workflow, line_no, "not a published static Sylphx profile", value))
+
+if checked == 0:
+    raise SystemExit("no direct workflow runner selections found")
+if violations:
+    for workflow, line_no, reason, value in violations:
+        print(f"{workflow.relative_to(root)}:{line_no}: {reason}: {value}", file=sys.stderr)
+    raise SystemExit("owned-runner profile contract failed")
+
+print(f"OK: {checked} direct workflow job(s) use static Sylphx-owned runner profiles")
+PY