fix: assign single-task kanban decompositions

tests/hermes_cli/test_kanban_decompose.py

@@ -114,7 +114,7 @@ def test_decompose_with_fanout_creates_children(kanban_home):
     assert c1.assignee == "engineer"
 
 
-def test_decompose_fanout_false_falls_back_to_specify(kanban_home):
+def test_decompose_fanout_false_assigns_default_when_unassigned(kanban_home):
     with kb.connect() as conn:
         tid = kb.create_task(conn, title="just one thing", triage=True)
 
@@ -125,11 +125,14 @@ def test_decompose_fanout_false_falls_back_to_specify(kanban_home):
         "body": "**Goal**\nDo the thing.",
     })
 
-    patches = _patch_list_profiles(["orchestrator"])
+    patches = _patch_list_profiles(["orchestrator", "fallback"])
     for p in patches:
         p.start()
     try:
-        with _patch_aux_client(llm_payload), _patch_extra_body():
+        with _patch_aux_client(llm_payload), _patch_extra_body(), patch(
+            "hermes_cli.kanban_decompose._load_config",
+            return_value={"kanban": {"default_assignee": "fallback"}},
+        ):
             outcome = decomp.decompose_task(tid, author="me")
     finally:
         for p in patches:
@@ -140,9 +143,113 @@ def test_decompose_fanout_false_falls_back_to_specify(kanban_home):
     assert outcome.new_title == "Tightened title"
     with kb.connect() as conn:
         task = kb.get_task(conn, tid)
+    assert task is not None
     # specify path with no parents -> recompute_ready flips to 'ready'
     assert task.status == "ready"
     assert task.title == "Tightened title"
+    assert task.assignee == "fallback"
+
+
+def test_decompose_fanout_false_preserves_existing_assignee(kanban_home):
+    with kb.connect() as conn:
+        tid = kb.create_task(
+            conn,
+            title="already routed",
+            assignee="engineer",
+            triage=True,
+        )
+
+    llm_payload = jsonlib.dumps({
+        "fanout": False,
+        "rationale": "single unit",
+        "title": "Tightened title",
+        "body": "Keep existing lane.",
+        "assignee": "fallback",
+    })
+
+    patches = _patch_list_profiles(["orchestrator", "engineer", "fallback"])
+    for p in patches:
+        p.start()
+    try:
+        with _patch_aux_client(llm_payload), _patch_extra_body(), patch(
+            "hermes_cli.kanban_decompose._load_config",
+            return_value={"kanban": {"default_assignee": "fallback"}},
+        ):
+            outcome = decomp.decompose_task(tid, author="me")
+    finally:
+        for p in patches:
+            p.stop()
+
+    assert outcome.ok, outcome.reason
+    with kb.connect() as conn:
+        task = kb.get_task(conn, tid)
+    assert task is not None
+    assert task.assignee == "engineer"
+    assert task.title == "Tightened title"
+
+
+def test_decompose_fanout_false_uses_valid_llm_assignee(kanban_home):
+    with kb.connect() as conn:
+        tid = kb.create_task(conn, title="route me", triage=True)
+
+    llm_payload = jsonlib.dumps({
+        "fanout": False,
+        "rationale": "single unit",
+        "title": "Tightened title",
+        "body": "Route to specialist.",
+        "assignee": "engineer",
+    })
+
+    patches = _patch_list_profiles(["orchestrator", "engineer", "fallback"])
+    for p in patches:
+        p.start()
+    try:
+        with _patch_aux_client(llm_payload), _patch_extra_body(), patch(
+            "hermes_cli.kanban_decompose._load_config",
+            return_value={"kanban": {"default_assignee": "fallback"}},
+        ):
+            outcome = decomp.decompose_task(tid, author="me")
+    finally:
+        for p in patches:
+            p.stop()
+
+    assert outcome.ok, outcome.reason
+    with kb.connect() as conn:
+        task = kb.get_task(conn, tid)
+    assert task is not None
+    assert task.assignee == "engineer"
+
+
+def test_decompose_fanout_false_invalid_llm_assignee_uses_default(kanban_home):
+    with kb.connect() as conn:
+        tid = kb.create_task(conn, title="route me safely", triage=True)
+
+    llm_payload = jsonlib.dumps({
+        "fanout": False,
+        "rationale": "single unit",
+        "title": "Tightened title",
+        "body": "Route to fallback.",
+        "assignee": "made_up",
+    })
+
+    patches = _patch_list_profiles(["orchestrator", "fallback"])
+    for p in patches:
+        p.start()
+    try:
+        with _patch_aux_client(llm_payload), _patch_extra_body(), patch(
+            "hermes_cli.kanban_decompose._load_config",
+            return_value={"kanban": {"default_assignee": "fallback"}},
+        ):
+            outcome = decomp.decompose_task(tid, author="me")
+    finally:
+        for p in patches:
+            p.stop()
+
+    assert outcome.ok, outcome.reason
+    with kb.connect() as conn:
+        task = kb.get_task(conn, tid)
+    assert task is not None
+    assert task.assignee == "fallback"
 
 
 def test_decompose_unknown_assignee_falls_back_to_default(kanban_home):