[loop-cycle] fix: consume cycle_result.json after reading (#897) (#898)

scripts/cycle_retro.py

@@ -277,6 +277,8 @@ def main() -> None:
             args.tests_passed = int(cr["tests_passed"])
         if not args.notes and cr.get("notes"):
             args.notes = cr["notes"]
+        # Consume-once: delete after reading so stale results don't poison future cycles
+        CYCLE_RESULT_FILE.unlink(missing_ok=True)
 
     # Auto-detect issue from branch when not explicitly provided
     if args.issue is None:

tests/loop/test_cycle_retro.py

@@ -58,6 +58,55 @@ class TestDetectIssueFromBranch:
             assert mod.detect_issue_from_branch() is None
 
 
+class TestConsumeOnce:
+    """cycle_result.json must be deleted after reading."""
+
+    def test_cycle_result_deleted_after_read(self, mod, tmp_path):
+        """After _load_cycle_result() data is consumed in main(), the file is deleted."""
+        result_file = tmp_path / "cycle_result.json"
+        result_file.write_text('{"issue": 42, "type": "bug"}')
+
+        with (
+            patch.object(mod, "CYCLE_RESULT_FILE", result_file),
+            patch.object(mod, "RETRO_FILE", tmp_path / "retro" / "cycles.jsonl"),
+            patch.object(mod, "SUMMARY_FILE", tmp_path / "retro" / "summary.json"),
+            patch.object(mod, "EPOCH_COUNTER_FILE", tmp_path / "retro" / ".epoch_counter"),
+            patch(
+                "sys.argv",
+                ["cycle_retro", "--cycle", "1", "--success", "--main-green", "--duration", "60"],
+            ),
+        ):
+            mod.main()
+
+        assert not result_file.exists(), "cycle_result.json should be deleted after consumption"
+
+    def test_cycle_result_not_deleted_when_empty(self, mod, tmp_path):
+        """If cycle_result.json doesn't exist, no error occurs."""
+        result_file = tmp_path / "nonexistent_result.json"
+
+        with (
+            patch.object(mod, "CYCLE_RESULT_FILE", result_file),
+            patch.object(mod, "RETRO_FILE", tmp_path / "retro" / "cycles.jsonl"),
+            patch.object(mod, "SUMMARY_FILE", tmp_path / "retro" / "summary.json"),
+            patch.object(mod, "EPOCH_COUNTER_FILE", tmp_path / "retro" / ".epoch_counter"),
+            patch(
+                "sys.argv",
+                [
+                    "cycle_retro",
+                    "--cycle",
+                    "1",
+                    "--success",
+                    "--main-green",
+                    "--duration",
+                    "60",
+                    "--issue",
+                    "10",
+                ],
+            ),
+        ):
+            mod.main()  # Should not raise
+
+
 class TestBackfillExtractIssueNumber:
     """Tests for backfill_retro.extract_issue_number PR-number filtering."""