diff --git a/tests/bluesky-pds/_p4.py b/tests/bluesky-pds/_p4.py
new file mode 100644
index 0000000..58063e1
--- /dev/null
+++ b/tests/bluesky-pds/_p4.py
@@ -0,0 +1,75 @@
+"""Shared bluesky-pds P4 data-integrity helpers.
+
+The marker is a DETERMINISTIC atproto account (recipe-aware data living in the PDS's sqlite store
+under /pds), NOT a loose file — so the restore assertion genuinely catches a restore that fails to
+bring the account back (e.g. if the running PDS holds its sqlite open and never reloads the restored
+files, the same data-loss class cc-ci caught in immich/mattermost). The handle is derived from the
+per-run domain so ops.py (seed/wipe) and the test_<op>.py overlays agree without passing state.
+"""
+
+from __future__ import annotations
+
+import os
+import re
+import shlex
+import sys
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "..", "runner"))
+from harness import http as harness_http, lifecycle  # noqa: E402
+
+PDS_HOST_LOCAL = "http://localhost:3000"
+_PW = "ccci-P4-marker-pw-2026"
+
+
+def _handle(domain: str) -> str:
+    return f"ccci-p4.{domain}"
+
+
+def _email(domain: str) -> str:
+    return f"ccci-p4@{domain}"
+
+
+def _goat_admin(domain: str, args: str) -> str:
+    """`goat pds admin <args>` inside the PDS `app` container (admin bypasses invite requirement)."""
+    cmd = (
+        f"goat pds admin {args} "
+        f'--admin-password "$(cat /run/secrets/pds_admin_password)" '
+        f"--pds-host {PDS_HOST_LOCAL} 2>&1"
+    )
+    return lifecycle.exec_in_app(domain, ["sh", "-c", cmd], timeout=120)
+
+
+def account_did(domain: str) -> str | None:
+    """The marker account's DID if it exists (public XRPC describeRepo by handle), else None."""
+    st, body = harness_http.http_get(
+        f"https://{domain}/xrpc/com.atproto.repo.describeRepo?repo={_handle(domain)}"
+    )
+    if st == 200 and isinstance(body, dict):
+        return body.get("did")
+    return None
+
+
+def account_exists(domain: str) -> bool:
+    return account_did(domain) is not None
+
+
+def create_account(domain: str) -> str:
+    """Idempotently create the deterministic marker account; return its DID."""
+    did = account_did(domain)
+    if did:
+        return did
+    out = _goat_admin(
+        domain,
+        f"account create --handle {shlex.quote(_handle(domain))} "
+        f"--email {shlex.quote(_email(domain))} --password {shlex.quote(_PW)}",
+    )
+    m = re.search(r"did:plc:[a-z0-9]+", out)
+    assert m, f"goat account create produced no DID. Output:\n{out[:400]!r}"
+    return m.group(0)
+
+
+def delete_account(domain: str) -> None:
+    """Delete the marker account (so a successful restore is observable). No-op if already gone."""
+    did = account_did(domain)
+    if did:
+        _goat_admin(domain, f"account delete {did}")
diff --git a/tests/bluesky-pds/ops.py b/tests/bluesky-pds/ops.py
new file mode 100644
index 0000000..e2bafd9
--- /dev/null
+++ b/tests/bluesky-pds/ops.py
@@ -0,0 +1,22 @@
+"""bluesky-pds — pre-op seed hooks (Phase 1e HC3). The P4 marker is a deterministic atproto account
+(recipe-aware data in the PDS sqlite under /pds, the backed-up volume) — see _p4.py. pre_restore
+deletes the account so a successful restore is observable (non-vacuous)."""
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(__file__))
+import _p4  # noqa: E402
+
+
+def pre_upgrade(domain, meta):
+    _p4.create_account(domain)
+
+
+def pre_backup(domain, meta):
+    _p4.create_account(domain)
+
+
+def pre_restore(domain, meta):
+    _p4.delete_account(domain)
+    assert not _p4.account_exists(domain), "marker account delete did not take (pre_restore)"
diff --git a/tests/bluesky-pds/test_backup.py b/tests/bluesky-pds/test_backup.py
new file mode 100644
index 0000000..660f710
--- /dev/null
+++ b/tests/bluesky-pds/test_backup.py
@@ -0,0 +1,13 @@
+"""bluesky-pds — BACKUP overlay (Phase 1e HC3): assertion-only + additive.
+ops.pre_backup created the deterministic marker account before the backup op; this overlay asserts it
+is present at backup time (so the backup archive captures it)."""
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(__file__))
+import _p4  # noqa: E402
+
+
+def test_backup_captures_state(live_app):
+    assert _p4.account_exists(live_app), "seeded marker account not present at backup time"
diff --git a/tests/bluesky-pds/test_restore.py b/tests/bluesky-pds/test_restore.py
new file mode 100644
index 0000000..7bfa04f
--- /dev/null
+++ b/tests/bluesky-pds/test_restore.py
@@ -0,0 +1,16 @@
+"""bluesky-pds — RESTORE overlay (Phase 1e HC3): data-integrity, assertion-only + additive.
+ops.pre_restore deleted the marker account (diverge); the orchestrator restored once. This overlay
+asserts the account is back — i.e. the PDS data volume (atproto sqlite) genuinely round-tripped
+through backup→restore (not just service-up)."""
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(__file__))
+import _p4  # noqa: E402
+
+
+def test_restore_returns_state(live_app):
+    assert _p4.account_exists(live_app), (
+        "restore did not bring back the seeded marker account (PDS data did not survive restore)"
+    )
diff --git a/tests/bluesky-pds/test_upgrade.py b/tests/bluesky-pds/test_upgrade.py
new file mode 100644
index 0000000..6624d1c
--- /dev/null
+++ b/tests/bluesky-pds/test_upgrade.py
@@ -0,0 +1,13 @@
+"""bluesky-pds — UPGRADE overlay (Phase 1e HC3): data-continuity, assertion-only + additive.
+ops.pre_upgrade created the deterministic marker account before the upgrade; this overlay asserts it
+survived the prev→PR-head chaos crossover."""
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(__file__))
+import _p4  # noqa: E402
+
+
+def test_upgrade_preserves_data(live_app):
+    assert _p4.account_exists(live_app), "marker account did not survive the upgrade"