diff --git a/backend/kernelCI_app/management/commands/backfill_lab_ids.py b/backend/kernelCI_app/management/commands/backfill_lab_ids.py
new file mode 100644
index 000000000..bc1c0c7ea
--- /dev/null
+++ b/backend/kernelCI_app/management/commands/backfill_lab_ids.py
@@ -0,0 +1,161 @@
+import time
+from collections.abc import Iterator
+
+from django.core.management.base import BaseCommand, CommandError
+from django.db import connections, transaction
+from django.db.backends.utils import CursorWrapper
+
+from kernelCI_app.constants.ingester import AUTOMATIC_LAB_FIELD, AUTOMATIC_LABS
+from kernelCI_app.helpers.logger import out
+
+
+def _real_lab_filter(misc_key: str) -> str:
+    """Keep non-automatic labs only (`_real_lab`). Named param: pattern."""
+    return f"""
+        misc->>'{misc_key}' IS NOT NULL
+        AND misc->>'{misc_key}' !~ %(pattern)s
+        AND misc->>'{AUTOMATIC_LAB_FIELD}' IS NULL
+    """
+
+
+def _collect_lab_names(cur: CursorWrapper) -> list[str]:
+    cur.execute(
+        f"""
+        SELECT DISTINCT lab FROM (
+            SELECT misc->>'lab' AS lab FROM builds
+            WHERE lab_id IS NULL
+              AND {_real_lab_filter("lab")}
+            UNION
+            SELECT misc->>'runtime' AS lab FROM tests
+            WHERE lab_id IS NULL
+              AND {_real_lab_filter("runtime")}
+        ) sub
+        """,
+        {"pattern": AUTOMATIC_LABS.pattern},
+    )
+    return [row[0] for row in cur.fetchall()]
+
+
+def _ensure_labs(cur: CursorWrapper, lab_names: list[str]) -> None:
+    cur.executemany(
+        "INSERT INTO labs (name) VALUES (%s) ON CONFLICT (name) DO NOTHING",
+        [(name,) for name in lab_names],
+    )
+    transaction.commit()
+
+
+def _stage_pending_ids(cur: CursorWrapper, table: str, misc_key: str) -> str:
+    temp = f"_backfill_{table}_ids"
+    cur.execute(f"DROP TABLE IF EXISTS {temp}")
+    cur.execute(
+        f"""
+        CREATE TEMP TABLE {temp} AS
+        SELECT id FROM {table}
+        WHERE lab_id IS NULL
+          AND {_real_lab_filter(misc_key)}
+        """,
+        {"pattern": AUTOMATIC_LABS.pattern},
+    )
+    return temp
+
+
+def _count_pending(cur: CursorWrapper, temp: str) -> int:
+    cur.execute(f"SELECT COUNT(*) FROM {temp}")
+    return cur.fetchone()[0]
+
+
+def _backfill_table(
+    cur: CursorWrapper,
+    table: str,
+    misc_key: str,
+    temp: str,
+    batch_size: int,
+) -> Iterator[int]:
+    """Yield cumulative updated row count after each batch."""
+    total = 0
+    while True:
+        cur.execute(
+            f"""
+            WITH batch AS (
+                DELETE FROM {temp}
+                WHERE id IN (SELECT id FROM {temp} LIMIT %s)
+                RETURNING id
+            ),
+            updated_rows AS (
+                UPDATE {table} AS target
+                SET lab_id = lab.id
+                FROM batch AS batch_row, labs AS lab
+                WHERE target.id = batch_row.id
+                  AND target.misc->>%s = lab.name
+                RETURNING target.id
+            )
+            SELECT
+                (SELECT COUNT(*) FROM batch),
+                (SELECT COUNT(*) FROM updated_rows)
+            """,
+            [batch_size, misc_key],
+        )
+        batch_count, updated = cur.fetchone()
+        if batch_count == 0:
+            return
+        total += updated
+        transaction.commit()
+        yield total
+
+
+class Command(BaseCommand):
+    help = (
+        "Backfill lab_id FK on builds and tests from JSONB misc fields "
+        "(builds: misc->>'lab', tests: misc->>'runtime'). "
+        "Skips automatic labs (shell/k8s* or misc.automatic_lab); leaves lab_id NULL."
+    )
+
+    def add_arguments(self, parser) -> None:
+        parser.add_argument(
+            "--batch-size",
+            type=int,
+            default=50_000,
+            help="Rows per UPDATE batch (default: 50000)",
+        )
+        parser.add_argument(
+            "--dry-run",
+            action="store_true",
+            help=(
+                "Stage pending ids into a temp table and print counts, "
+                "but do not insert labs or update lab_id"
+            ),
+        )
+
+    def handle(self, *args, **options) -> None:
+        batch_size: int = options["batch_size"]
+        dry_run: bool = options["dry_run"]
+
+        if batch_size < 1:
+            raise CommandError("--batch-size must be >= 1")
+
+        with connections["default"].cursor() as cur:
+            if not dry_run:
+                out("Collecting distinct lab names from JSONB...")
+                lab_names = _collect_lab_names(cur)
+                out(f"  Found {len(lab_names)} distinct lab names")
+                if lab_names:
+                    out("Inserting missing lab names into labs table...")
+                    _ensure_labs(cur, lab_names)
+
+            for table, misc_key in (("builds", "lab"), ("tests", "runtime")):
+                out(f"Staging {table} ids...")
+                temp = _stage_pending_ids(cur, table, misc_key)
+                pending_count = _count_pending(cur, temp)
+                out(f"{table.capitalize()} to backfill: {pending_count}")
+
+                if not pending_count or dry_run:
+                    continue
+
+                started_at = time.time()
+                for total in _backfill_table(cur, table, misc_key, temp, batch_size):
+                    out(
+                        f"  {table}: {total}/{pending_count} "
+                        f"({time.time() - started_at:.1f}s)"
+                    )
+
+        out("Dry run complete, no lab_id changes made." if dry_run else "Done.")