diff --git a/.github/workflows/integration-tests-nextjs.yml b/.github/workflows/integration-tests-nextjs.yml
new file mode 100644
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+++ b/.github/workflows/integration-tests-nextjs.yml
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+name: Next.js Integration Tests (downstream)
+
+# Runs the @harperfast/nextjs adapter's Playwright integration suite against THIS
+# PR's harper build, so a harper change that breaks the Next.js framework-hosting
+# integration (HTTP server, REST, ISR/`use cache` backed by Harper tables) is
+# caught here rather than in the downstream adapter repo.
+#
+# It calls the reusable workflow in HarperFast/nextjs, passing this PR's head SHA
+# as `harper_ref`; the reusable workflow checks out + builds harper at that ref and
+# resolves it as the `harper` the test harness and fixtures run against.
+#
+# Scoped to PRs that touch the HTTP / cache / resource / server code paths the
+# adapter exercises (tune the paths filter as coverage evolves).
+#
+# ── BEFORE MERGE ───────────────────────────────────────────────────────────────
+#   1. Depends on HarperFast/nextjs#49 — the `workflow_call` + `harper_ref` input
+#      must be on nextjs `main` first, or this caller has nothing to call.
+#   2. Replace the mutable `@main` ref below with the 40-char merge-commit SHA of
+#      nextjs#49 (cross-repo reusable `uses:` should pin to a SHA, matching the
+#      convention in validate-caller-workflows.yml).
+
+on:
+  pull_request:
+    paths:
+      - 'cache/**'
+      - 'resources/**'
+      - 'server/**'
+      - 'dataLayer/**'
+      - 'components/**'
+      - 'config/**'
+      - 'package.json'
+      - 'package-lock.json'
+
+jobs:
+  nextjs-integration:
+    name: Next.js adapter integration (against this PR's harper)
+    uses: HarperFast/nextjs/.github/workflows/integration-tests.yml@main # TODO: pin to nextjs#49 merge SHA before merging
+    with:
+      harper_ref: ${{ github.event.pull_request.head.sha }}