fix(heartbeat): fit selected prompt diagnostics within budget

loopx/control_plane/heartbeat/builder.py

@@ -604,6 +604,14 @@ def build_heartbeat_prompt(
         ):
             if not payload.get(key):
                 payload.pop(key, None)
+    elif brief:
+        # The brief task body already embeds its compact-detail command. Keep
+        # only the selected brief command as top-level regeneration metadata;
+        # repeating the other mode commands can exceed the registered output
+        # budget when the CLI/runtime paths are long.
+        payload.pop("expanded_prompt_command", None)
+        payload.pop("compact_prompt_command", None)
+        payload.pop("thin_prompt_command", None)
     return payload
 def build_heartbeat_prompt_error_payload(
     *,

loopx/control_plane/heartbeat/task_body.py

@@ -741,13 +741,26 @@ def render_heartbeat_generator_inputs_markdown(payload: dict[str, Any]) -> str:
         f"- agent_model: `{payload.get('agent_model')}`",
         f"- agent_role: `{payload.get('agent_role')}`",
     ]
+    lines.append(f"- agent_scopes: `{payload.get('agent_scopes')}`")
+    if payload.get("thin") is True:
+        lines.append(
+            f"- thin_prompt_command: `{payload.get('thin_prompt_command')}`"
+        )
+    elif payload.get("brief") is True:
+        lines.append(
+            f"- brief_prompt_command: `{payload.get('brief_prompt_command')}`"
+        )
+    else:
+        lines.extend(
+            [
+                f"- expanded_prompt_command: `{payload.get('expanded_prompt_command')}`",
+                f"- compact_prompt_command: `{payload.get('compact_prompt_command')}`",
+                f"- brief_prompt_command: `{payload.get('brief_prompt_command')}`",
+                f"- thin_prompt_command: `{payload.get('thin_prompt_command')}`",
+            ]
+        )
     lines.extend(
         [
-            f"- agent_scopes: `{payload.get('agent_scopes')}`",
-            f"- expanded_prompt_command: `{payload.get('expanded_prompt_command')}`",
-            f"- compact_prompt_command: `{payload.get('compact_prompt_command')}`",
-            f"- brief_prompt_command: `{payload.get('brief_prompt_command')}`",
-            f"- thin_prompt_command: `{payload.get('thin_prompt_command')}`",
             "- pr_review_pre_quota_command: "
             f"`{payload.get('pr_review_pre_quota_command')}`",
             f"- quota_guard_command: `{payload.get('quota_guard_command')}`",

tests/control_plane/test_heartbeat_prompt_support.py

@@ -230,6 +230,32 @@ def test_public_facade_still_builds_and_renders_prompts() -> None:
     assert render_heartbeat_prompt_markdown(payload)
 
 
+def test_thin_markdown_diagnostics_only_show_the_selected_prompt_command() -> None:
+    payload = build_heartbeat_prompt(goal_id="loopx-meta", thin=True)
+    rendered = render_heartbeat_prompt_markdown(payload)
+
+    assert payload["task_body"] in rendered
+    assert "- thin_prompt_command:" in rendered
+    assert "- expanded_prompt_command:" not in rendered
+    assert "- compact_prompt_command:" not in rendered
+    assert "- brief_prompt_command:" not in rendered
+
+
+def test_brief_diagnostics_keep_only_the_selected_prompt_command() -> None:
+    payload = build_heartbeat_prompt(goal_id="loopx-meta", brief=True)
+    rendered = render_heartbeat_prompt_markdown(payload)
+
+    assert payload["brief_prompt_command"]
+    assert "compact_prompt_command" not in payload
+    assert "expanded_prompt_command" not in payload
+    assert "thin_prompt_command" not in payload
+    assert "heartbeat-prompt --compact" in payload["task_body"]
+    assert "- brief_prompt_command:" in rendered
+    assert "- expanded_prompt_command:" not in rendered
+    assert "- compact_prompt_command:" not in rendered
+    assert "- thin_prompt_command:" not in rendered
+
+
 @pytest.mark.parametrize(
     ("mode", "base_budget"),
     [("full", 12000), ("compact", 6500), ("brief", 4300), ("thin", 3000)],