ci(migration): add runtime contract marker validation

Author: t81dev

.github/workflows/ci.yml

@@ -28,3 +28,35 @@ jobs:
 
       - name: fmt
         run: cargo fmt --all -- --check
+
+  runtime-contract:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout ternary-tools
+        uses: actions/checkout@v4
+        with:
+          path: ternary-tools
+
+      - name: Checkout t81-vm
+        uses: actions/checkout@v4
+        with:
+          repository: t81dev/t81-vm
+          path: t81-vm
+          ref: main
+
+      - name: Validate runtime contract marker
+        run: |
+          python3 - <<'PY'
+          import json
+          from pathlib import Path
+
+          repo = Path("ternary-tools/contracts/runtime-contract.json")
+          vm = Path("t81-vm/docs/contracts/vm-compatibility.json")
+          repo_contract = json.loads(repo.read_text(encoding="utf-8"))
+          vm_contract = json.loads(vm.read_text(encoding="utf-8"))
+
+          if repo_contract.get("contract_version") != vm_contract.get("contract_version"):
+              raise SystemExit("contract_version mismatch between ternary-tools and t81-vm")
+
+          print("runtime contract marker: ok")
+          PY

README.md

@@ -98,6 +98,7 @@ MIT — because even in the ternary age, some things must remain balanced.
 ## Migration integration
 
 - Phase 2 checklist: `docs/phase2-inspection-checklist.md`
+- Runtime contract marker: `contracts/runtime-contract.json`
 
 ---
 

contracts/runtime-contract.json

@@ -0,0 +1,7 @@
+{
+  "runtime_tag": "runtime-contract-v0.4",
+  "contract_version": "2026-02-08-v4",
+  "vm_main_pin": "fc9d55eba258aa2d17d7778e29e186f0bf62e2d8",
+  "contract_source": "https://github.com/t81dev/t81-vm/blob/main/docs/contracts/vm-compatibility.json",
+  "owner": "ternary-tools"
+}