diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
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+name: Nightly (slow tests)
+
+# Run nightly at 03:00 UTC + on manual dispatch.
+# Owns the slow-test lanes that don't fit the PR feedback loop:
+#   - sitl: pytest -m sitl (gated by ARDUPILOT_SITL_HOST in tests)
+#   - e2e:  pytest -m e2e + e2e_slow against real datasets (when present)
+#
+# The on-demand SITL workflow lives in .github/workflows/sitl.yml and is unchanged.
+on:
+  schedule:
+    - cron: "0 3 * * *"
+  workflow_dispatch:
+
+jobs:
+  sitl:
+    name: SITL marker collection (scaffold — real SITL via sitl.yml)
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+          cache: pip
+      - run: sudo apt-get update -qq && sudo apt-get install -y --no-install-recommends libgl1 libglib2.0-0
+      - run: pip install --no-cache-dir -e ".[dev]"
+      - name: Collect SITL tests (skipped without ARDUPILOT_SITL_HOST)
+        # In nightly, ARDUPILOT_SITL_HOST is intentionally absent; tests self-skip.
+        # The on-demand .github/workflows/sitl.yml runs the actual SITL containers.
+        # This job exists so the -m sitl marker is exercised on a recurring basis
+        # and a collection regression is caught.
+        run: python -m pytest tests/ -m sitl --collect-only -q
+
+  e2e:
+    name: E2E real-flight dataset replay
+    runs-on: ubuntu-latest
+    timeout-minutes: 120
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+          cache: pip
+      - run: sudo apt-get update -qq && sudo apt-get install -y --no-install-recommends libgl1 libglib2.0-0
+      - run: pip install --no-cache-dir -e ".[dev]"
+      - name: Run e2e tests (skip when datasets are absent)
+        # tests/e2e/conftest.py fixtures self-skip tests when their dataset path is missing.
+        # If no dataset is present in the runner image, the job runs the collection but
+        # most assertions short-circuit on the skip fixture.
+        run: python -m pytest tests/ -m "e2e or e2e_slow" -v --tb=short || true
+        # `|| true` to allow soft-failure during Phase 2 bootstrap; flip to hard-fail in
+        # Phase 6 when FIXTURE-01 lands a CI-provisioned Azaion dataset.