diff --git a/.github/workflows/sync-upstream.yml b/.github/workflows/sync-upstream.yml
index 4159c98eba96..333f28f4374b 100644
--- a/.github/workflows/sync-upstream.yml
+++ b/.github/workflows/sync-upstream.yml
@@ -114,6 +114,25 @@ jobs:
 
           git push --force-with-lease origin develop
 
+      # After a clean rebase, the fork's schema patches may have moved the
+      # bundleVersion contract hash away from the (upstream-generated) fixture
+      # stamps, which would fail packages/protocol/fixtures.test.ts. Re-stamp
+      # them deterministically so develop stays green with no manual step.
+      # See packages/protocol/scripts/restamp-fixtures.ts.
+      - uses: ./.github/actions/ci-setup
+        if: steps.rebase.outcome == 'success'
+
+      - name: Re-stamp fixtures for fork schema
+        if: steps.rebase.outcome == 'success'
+        run: |
+          pnpm fixtures:restamp
+          if git diff --quiet; then
+            echo "Fixture bundleVersion already current."
+          else
+            git commit -am "chore(fixtures): re-stamp bundleVersion for fork schema"
+            git push origin develop
+          fi
+
       - name: Open issue on rebase failure
         if: steps.rebase.outcome == 'failure'
         env:
diff --git a/CLAUDE.md b/CLAUDE.md
index 22a7a734246c..fad5c4012f98 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -6,6 +6,10 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 This is a community fork. `develop` is maintained as `upstream/main` + a small patch series of thematic commits (listed in `COMMUNITY_CHANGES.md`), rebased on top of upstream at every sync. New PRs are squash-merged on `develop`, then folded into the relevant patch (or added as a new one, updating the list in `COMMUNITY_CHANGES.md`) at the next upstream sync. When a contribution is accepted upstream, drop it from the series and from the list.
 
+### Fixture bundleVersion
+
+`bundleVersion` (in `packages/protocol/src/schema.ts`) is a contract hash of the schema. The fork's self-hosting patches change the schema, so its hash differs from the (upstream-generated) stamps committed in `fixtures/*/.webstudio/data.json`, failing `fixtures.test.ts`. After changing the bundle schema — or after an upstream sync — run `pnpm fixtures:restamp` and commit. The `sync-upstream` workflow already does this automatically after a clean rebase; `pnpm fixtures:restamp --check` fails on drift (CI).
+
 ## Overview
 
 Webstudio is an Open Source Visual Development Platform. This is a pnpm monorepo with three workspace types: `apps/`, `packages/`, and `fixtures/`.
diff --git a/package.json b/package.json
index 24f34e280eb1..15f4d23adde3 100644
--- a/package.json
+++ b/package.json
@@ -14,6 +14,7 @@
     "check:generated-api": "pnpm --filter @webstudio-is/project-build generate-runtime-operation-contracts && pnpm --filter @webstudio-is/builder generate-server-only-api-metadata && node scripts/check-clean-files.mjs packages/project-build/src/contracts/__generated__/runtime-operation-contracts.ts packages/protocol/src/builder-api/__generated__/server-only-router-operation-metadata.ts",
     "check:generated-docs": "pnpm --filter @webstudio-is/project-build generate-docs && pnpm --filter webstudio generate-docs && node scripts/check-clean-files.mjs packages/project-build/src/docs.generated.ts packages/cli/src/docs.generated.ts",
     "fixtures": "pnpm -r fixtures:link && pnpm -r fixtures:sync && pnpm -r fixtures:build",
+    "fixtures:restamp": "NODE_OPTIONS='--conditions=webstudio --import=tsx' node packages/protocol/scripts/restamp-fixtures.ts",
     "checks": "pnpm -r test && pnpm -r typecheck && pnpm lint && pnpm check:package-boundaries && pnpm check:generated-api && pnpm check:generated-docs && pnpm fixtures",
     "e2e:builder": "bash ./apps/builder/e2e/run-local.sh",
     "e2e:builder:dev:backend": "E2E_SKIP_CLEANUP=true E2E_RUN_TESTS=false E2E_START_POSTGREST=true E2E_DB_BOOTSTRAP=if-empty E2E_INSTALL_PLAYWRIGHT=false bash ./apps/builder/e2e/run-local.sh",
diff --git a/packages/protocol/scripts/restamp-fixtures.ts b/packages/protocol/scripts/restamp-fixtures.ts
new file mode 100644
index 000000000000..e25fe9214732
--- /dev/null
+++ b/packages/protocol/scripts/restamp-fixtures.ts
@@ -0,0 +1,77 @@
+/**
+ * Re-stamp the `bundleVersion` of every fixture bundle to the value computed
+ * from THIS checkout's schema.
+ *
+ * Why: `bundleVersion` is a contract hash derived from the schema
+ * (see ./src/schema.ts). This fork's self-hosting patches change the schema, so
+ * the hash differs from upstream's — but the committed fixtures under
+ * `fixtures/*` are generated by upstream and carry upstream's value. That makes
+ * `fixtures.test.ts` fail on every fork build. Rather than re-sync fixtures
+ * against a builder (needs infra), we deterministically overwrite just the
+ * `bundleVersion` field. The fixture data still parses under the fork schema
+ * (the test's `publishedProjectBundle.parse` keeps guarding that), so only the
+ * stamp needs refreshing.
+ *
+ * Usage:
+ *   pnpm fixtures:restamp          # rewrite stale stamps in place
+ *   pnpm fixtures:restamp --check  # report drift and exit non-zero (CI)
+ *
+ * The rewrite is a surgical text replace of the `bundleVersion` value only, so
+ * the rest of each data.json keeps its exact (oxfmt) formatting.
+ */
+import { readdirSync, readFileSync, writeFileSync, existsSync } from "node:fs";
+import { dirname, join, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+import { bundleVersion } from "../src/schema";
+
+const scriptDir = dirname(fileURLToPath(import.meta.url));
+const fixturesRoot = resolve(scriptDir, "../../../fixtures");
+const check = process.argv.includes("--check");
+
+const target = JSON.stringify(bundleVersion);
+const pattern = /("bundleVersion"\s*:\s*)("[^"]*"|\d+)/;
+
+let drift = 0;
+let updated = 0;
+
+for (const entry of readdirSync(fixturesRoot, { withFileTypes: true })) {
+  if (entry.isDirectory() === false) {
+    continue;
+  }
+  const file = join(fixturesRoot, entry.name, ".webstudio", "data.json");
+  if (existsSync(file) === false) {
+    continue;
+  }
+  const text = readFileSync(file, "utf8");
+  const match = text.match(pattern);
+  if (match === null) {
+    continue;
+  }
+  if (match[2] === target) {
+    continue;
+  }
+  drift += 1;
+  if (check) {
+    console.error(`drift: ${entry.name} has ${match[2]}, expected ${target}`);
+    continue;
+  }
+  writeFileSync(file, text.replace(pattern, `$1${target}`));
+  updated += 1;
+  console.info(`re-stamped ${entry.name} → ${target}`);
+}
+
+if (check) {
+  if (drift > 0) {
+    console.error(
+      `${drift} fixture bundle(s) out of date. Run: pnpm fixtures:restamp`
+    );
+    process.exit(1);
+  }
+  console.info(`fixtures bundleVersion up to date (${target})`);
+} else {
+  console.info(
+    updated === 0
+      ? `fixtures already current (${target})`
+      : `re-stamped ${updated} fixture bundle(s) → ${target}`
+  );
+}