tests/test_agent_loop_metadata.py

@@ -45,7 +45,7 @@ async def test_process_direct_passes_metadata():
 
 @pytest.mark.asyncio
 async def test_suppress_mode_adds_hidden_prefix():
-    """Test that suppress_output metadata adds [HIDDEN] prefix."""
+    """Test that suppress_output metadata adds [HIDDEN:signature] prefix."""
     bus = MessageBus()
     provider = MagicMock(spec=LLMProvider)
     provider.chat = AsyncMock(return_value=LLMResponse(
@@ -66,14 +66,20 @@ async def test_suppress_mode_adds_hidden_prefix():
         metadata={"suppress_output": True}
     )
 
-    # Response content should have [HIDDEN] prefix
+    # Response content should have [HIDDEN:signature] prefix with 8-char hex signature
-    assert response.startswith("[HIDDEN]")
+    assert response.startswith("[HIDDEN:")
+    assert "]" in response
+    # Extract signature part between [HIDDEN: and ]
+    prefix_end = response.index("]")
+    signature = response[8:prefix_end]  # Skip "[HIDDEN:" to get signature
+    assert len(signature) == 8  # 8-character hex signature
+    assert all(c in "0123456789abcdef" for c in signature)  # Valid hex
     assert "This is the agent response" in response
 
 
 @pytest.mark.asyncio
 async def test_normal_mode_no_hidden_prefix():
-    """Test that normal messages don't get [HIDDEN] prefix."""
+    """Test that normal messages don't get [HIDDEN:signature] prefix."""
     bus = MessageBus()
     provider = MagicMock(spec=LLMProvider)
     provider.chat = AsyncMock(return_value=LLMResponse(
@@ -91,6 +97,6 @@ async def test_normal_mode_no_hidden_prefix():
     # Call without suppress_output
     response = await loop.process_direct(content="test message")
 
-    # Response should NOT have [HIDDEN] prefix
+    # Response should NOT have [HIDDEN:signature] prefix
-    assert not response.startswith("[HIDDEN]")
+    assert not response.startswith("[HIDDEN:")
     assert response == "Normal response"

tests/test_idle_heartbeat_integration.py

@@ -15,7 +15,7 @@ from unittest.mock import AsyncMock, MagicMock
 async def test_idle_heartbeat_end_to_end(tmp_path):
     """
     Integration test: heartbeat triggers when idle, runs in main session,
-    output is suppressed, session contains [HIDDEN] content.
+    output is suppressed, session contains [HIDDEN:signature] content.
     """
     workspace = tmp_path / "test-integration"
     workspace.mkdir()
@@ -91,14 +91,20 @@ async def test_idle_heartbeat_end_to_end(tmp_path):
     # 1. Session has new messages
     assert len(session.messages) > 1
 
-    # 2. Find the heartbeat response (assistant message)
+    # 2. Find the heartbeat response (assistant message with signed visibility marker)
     heartbeat_messages = [
         m for m in session.messages
-        if m.get("role") == "assistant" and "[HIDDEN]" in m.get("content", "")
+        if m.get("role") == "assistant" and "[HIDDEN:" in m.get("content", "")
     ]
-    assert len(heartbeat_messages) == 1, "Expected exactly 1 [HIDDEN] heartbeat message"
+    assert len(heartbeat_messages) == 1, "Expected exactly 1 [HIDDEN:signature] heartbeat message"
 
-    # 3. Verify content is prefixed with [HIDDEN]
+    # 3. Verify content is prefixed with [HIDDEN:signature]
     heartbeat_msg = heartbeat_messages[0]
-    assert heartbeat_msg["content"].startswith("[HIDDEN]")
+    assert heartbeat_msg["content"].startswith("[HIDDEN:")
+    # Verify signature format (8-char hex)
+    content = heartbeat_msg["content"]
+    prefix_end = content.index("]")
+    signature = content[8:prefix_end]  # Skip "[HIDDEN:" to get signature
+    assert len(signature) == 8, f"Expected 8-char signature, got {len(signature)}"
+    assert all(c in "0123456789abcdef" for c in signature), "Signature should be hex"
     assert "Heartbeat executed successfully" in heartbeat_msg["content"]