diff --git a/novelforge/agents/chapter/pipeline.py b/novelforge/agents/chapter/pipeline.py
index 262fd00..3891a7b 100644
--- a/novelforge/agents/chapter/pipeline.py
+++ b/novelforge/agents/chapter/pipeline.py
@@ -186,7 +186,11 @@ def run_chapter_rhythm_classifier(
                 "chapter_num": chapter_num,
                 "failure_summary": failure_summary,
             })
-        return {PASS_FAILURE_KEY: failure_summary}
+        return {
+            PASS_FAILURE_KEY: failure_summary,
+            "recommended_shape_for_this_chapter": "",
+            "recommendation_reason": "",
+        }
 
 
 # ---------------------------------------------------------------------------
diff --git a/tests/conftest.py b/tests/conftest.py
index c345ff6..3c76a77 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -227,6 +227,14 @@ def _canned_llm_response(messages, *, action="", json_mode=False):
             ]
         })
 
+    # Chapter rhythm classifier (returns JSON with a named rhythm shape)
+    if "classifying" in act or ("rhythm" in act and "chapter" in act):
+        return json.dumps({
+            "detected_patterns": [],
+            "recommended_shape_for_this_chapter": "lyrical-interlude",
+            "recommendation_reason": "Default rhythm for test purposes.",
+        })
+
     if "revision" in act:
         return "The revised chapter content with improvements."
 
diff --git a/tests/test_chapter_agent_failures.py b/tests/test_chapter_agent_failures.py
index 24011ce..f8f38fb 100644
--- a/tests/test_chapter_agent_failures.py
+++ b/tests/test_chapter_agent_failures.py
@@ -180,10 +180,19 @@ def test_rhythm_classifier_returns_dict_with_pass_failure_key(self, monkeypatch)
         assert "boom" in result[PASS_FAILURE_KEY]
 
     def test_rhythm_classifier_fallback_is_otherwise_empty(self, monkeypatch):
-        """The fallback dict must not carry false business data (only PASS_FAILURE_KEY)."""
+        """The fallback dict must carry PASS_FAILURE_KEY and safe-default business keys."""
         _patch_chapter_call_llm(monkeypatch, _raise_runtime("x"))
         result = run_chapter_rhythm_classifier(**_CHAPTER_KWARGS_STR, title="Novel")
-        assert set(result.keys()) == {PASS_FAILURE_KEY}
+        assert PASS_FAILURE_KEY in result
+        # Minimal safe defaults must be present so callers can .get() without KeyError
+        assert "recommended_shape_for_this_chapter" in result
+        assert "recommendation_reason" in result
+        # No spurious keys beyond the three above
+        assert set(result.keys()) == {
+            PASS_FAILURE_KEY,
+            "recommended_shape_for_this_chapter",
+            "recommendation_reason",
+        }
 
 
 # ---------------------------------------------------------------------------
diff --git a/tests/test_illustration_job.py b/tests/test_illustration_job.py
index 9fe7bba..b6b1114 100644
--- a/tests/test_illustration_job.py
+++ b/tests/test_illustration_job.py
@@ -160,14 +160,17 @@ def test_warning_logged_when_novel_progress_entry_missing(
         # Patch progress_manager.update so that the first call (linking
         # illustration_token onto the novel entry) raises KeyError, simulating
         # a deleted entry.
-        original_update = pm.update
+        # NOTE: patch the *class* method, not the instance, to avoid leaving a
+        # stale instance attribute on the singleton after monkeypatch teardown
+        # (which would bypass class-level spies installed by other tests).
+        original_class_update = type(pm).update
 
-        def _raise_on_novel_token(tok, data):
+        def _raise_on_novel_token(self, tok, data):
             if "illustration_token" in data:
                 raise KeyError(tok)
-            return original_update(tok, data)
+            return original_class_update(self, tok, data)
 
-        monkeypatch.setattr(pm, "update", _raise_on_novel_token)
+        monkeypatch.setattr(type(pm), "update", _raise_on_novel_token)
 
         token = "deleted-novel-link"
         _done_novel(token)