fix(compression): preserve iterative summary continuity

tests/agent/test_context_compressor_summary_continuity.py

@@ -0,0 +1,67 @@
+"""Regression tests for iterative context-summary continuity."""
+
+from unittest.mock import MagicMock, patch
+
+from agent.context_compressor import ContextCompressor, SUMMARY_PREFIX
+
+
+def _compressor() -> ContextCompressor:
+    with patch("agent.context_compressor.get_model_context_length", return_value=100000):
+        return ContextCompressor(
+            model="test/model",
+            threshold_percent=0.85,
+            protect_first_n=1,
+            protect_last_n=1,
+            quiet_mode=True,
+        )
+
+
+def _response(content: str):
+    mock_response = MagicMock()
+    mock_response.choices = [MagicMock()]
+    mock_response.choices[0].message.content = content
+    return mock_response
+
+
+def _messages_with_handoff(summary_body: str):
+    return [
+        {"role": "system", "content": "system prompt"},
+        {"role": "user", "content": f"{SUMMARY_PREFIX}\n{summary_body}"},
+        {"role": "user", "content": "new user turn after resume"},
+        {"role": "assistant", "content": "new assistant work after resume"},
+        {"role": "user", "content": "more new work after resume"},
+        {"role": "assistant", "content": "latest tail response"},
+    ]
+
+
+def test_existing_previous_summary_is_not_serialized_again_as_new_turn():
+    """Same-process iterative compression should not feed the old handoff twice."""
+    compressor = _compressor()
+    old_summary = "OLD-SUMMARY-BODY unique continuity facts"
+    compressor._previous_summary = old_summary
+
+    with patch("agent.context_compressor.call_llm", return_value=_response("updated summary")) as mock_call:
+        compressor.compress(_messages_with_handoff(old_summary))
+
+    prompt = mock_call.call_args.kwargs["messages"][0]["content"]
+    assert "PREVIOUS SUMMARY:" in prompt
+    assert "NEW TURNS TO INCORPORATE:" in prompt
+    assert prompt.count(old_summary) == 1
+    assert f"[USER]: {SUMMARY_PREFIX}" not in prompt
+
+
+def test_resume_rehydrates_previous_summary_from_handoff_message():
+    """After restart/resume, the persisted handoff should regain summary identity."""
+    compressor = _compressor()
+    old_summary = "RESUMED-SUMMARY-BODY durable continuity facts"
+    assert compressor._previous_summary is None
+
+    with patch("agent.context_compressor.call_llm", return_value=_response("updated summary")) as mock_call:
+        compressor.compress(_messages_with_handoff(old_summary))
+
+    prompt = mock_call.call_args.kwargs["messages"][0]["content"]
+    assert "PREVIOUS SUMMARY:" in prompt
+    assert "NEW TURNS TO INCORPORATE:" in prompt
+    assert "TURNS TO SUMMARIZE:" not in prompt
+    assert prompt.count(old_summary) == 1
+    assert f"[USER]: {SUMMARY_PREFIX}" not in prompt