diff --git a/src/adclaw/campaigns/diagnostics.py b/src/adclaw/campaigns/diagnostics.py
index 903345a..d44385c 100644
--- a/src/adclaw/campaigns/diagnostics.py
+++ b/src/adclaw/campaigns/diagnostics.py
@@ -366,8 +366,16 @@ async def run_smoke_test(meta, ad_account_id: str, actor: str) -> dict[str, Any]
     except Exception as exc:
         steps.append({"step": "create", "status": FAILED, "detail": str(exc)})
     finally:
-        target = (synced.meta_campaign_id if synced else None) or created.get(
-            "campaign_id",
+        # `campaign` last, and it is the one that matters: sync_campaign
+        # assigns meta_campaign_id on the spec it was handed *before* it
+        # creates the ad set, so a mid-chain failure leaves the campaign
+        # live in the account while `synced` is still None and `created` is
+        # still empty. Without this fallback that campaign is abandoned —
+        # which is exactly what happened on the first real run.
+        target = (
+            (synced.meta_campaign_id if synced else None)
+            or created.get("campaign_id")
+            or campaign.meta_campaign_id
         )
         if target:
             try:
diff --git a/tests/test_campaign_diagnostics.py b/tests/test_campaign_diagnostics.py
index 181e0b5..8b79760 100644
--- a/tests/test_campaign_diagnostics.py
+++ b/tests/test_campaign_diagnostics.py
@@ -418,3 +418,49 @@ async def test_no_token_blocks_the_connection_test(monkeypatch):
 
     assert report["can_smoke_test"] is False
     assert report["smoke_test_blocking"] == ["Meta access token"]
+
+
+# --- a half-built chain must not be abandoned ---
+
+
+async def test_a_failure_after_the_campaign_exists_still_deletes_it(page):
+    """The real failure mode, reproduced.
+
+    sync_campaign assigns meta_campaign_id on the spec before it creates
+    the ad set. When the ad set is rejected, `synced` is never bound and
+    `created` is never populated — so a cleanup keyed only on those two
+    leaves a live campaign sitting in the ad account. On the first real run
+    that is exactly what happened, and the reconciler then adopted the
+    orphan into the database.
+    """
+
+    class AdSetRejects(SmokeMeta):
+        async def create_ad_set(self, ad_account_id, **kwargs):
+            raise MetaError(
+                "Invalid parameter",
+                code=100,
+                subcode=2490487,
+                user_message="Bid amount or bid constraints required.",
+            )
+
+    meta = AdSetRejects()
+
+    result = await run_smoke_test(meta, "act_1", actor="farman")
+
+    assert result["passed"] is False
+    # The campaign was created, so it must have been deleted again.
+    assert meta.deleted == ["camp_1"]
+    cleanup = next(s for s in result["steps"] if s["step"] == "clean up")
+    assert cleanup["status"] == OK
+    assert "camp_1" in cleanup["detail"]
+
+
+async def test_nothing_is_deleted_when_the_campaign_was_never_created(page):
+    """No campaign id means no cleanup call — not a delete of None."""
+    meta = SmokeMeta()
+    meta.fail_on = "campaign"
+
+    result = await run_smoke_test(meta, "act_1", actor="farman")
+
+    assert meta.deleted == []
+    assert not [s for s in result["steps"] if s["step"] == "clean up"]