fix(compression): preserve iterative summary continuity

agent/context_compressor.py

@@ -993,15 +993,39 @@ The user has requested that this compaction PRIORITISE preserving all informatio
             return None
 
     @staticmethod
-    def _with_summary_prefix(summary: str) -> str:
-        """Normalize summary text to the current compaction handoff format."""
+    def _strip_summary_prefix(summary: str) -> str:
+        """Return summary body without the current or legacy handoff prefix."""
         text = (summary or "").strip()
-        for prefix in (LEGACY_SUMMARY_PREFIX, SUMMARY_PREFIX):
+        for prefix in (SUMMARY_PREFIX, LEGACY_SUMMARY_PREFIX):
             if text.startswith(prefix):
-                text = text[len(prefix):].lstrip()
-                break
+                return text[len(prefix):].lstrip()
+        return text
+
+    @classmethod
+    def _with_summary_prefix(cls, summary: str) -> str:
+        """Normalize summary text to the current compaction handoff format."""
+        text = cls._strip_summary_prefix(summary)
         return f"{SUMMARY_PREFIX}\n{text}" if text else SUMMARY_PREFIX
 
+    @staticmethod
+    def _is_context_summary_content(content: Any) -> bool:
+        text = _content_text_for_contains(content).lstrip()
+        return text.startswith(SUMMARY_PREFIX) or text.startswith(LEGACY_SUMMARY_PREFIX)
+
+    @classmethod
+    def _find_latest_context_summary(
+        cls,
+        messages: List[Dict[str, Any]],
+        start: int,
+        end: int,
+    ) -> tuple[Optional[int], str]:
+        """Find the newest handoff summary inside a compression window."""
+        for idx in range(end - 1, start - 1, -1):
+            content = messages[idx].get("content")
+            if cls._is_context_summary_content(content):
+                return idx, cls._strip_summary_prefix(_content_text_for_contains(content))
+        return None, ""
+
     # ------------------------------------------------------------------
     # Tool-call / tool-result pair integrity helpers
     # ------------------------------------------------------------------
@@ -1308,6 +1332,15 @@ The user has requested that this compaction PRIORITISE preserving all informatio
             return messages
 
         turns_to_summarize = messages[compress_start:compress_end]
+        summary_idx, summary_body = self._find_latest_context_summary(
+            messages,
+            compress_start,
+            compress_end,
+        )
+        if summary_idx is not None:
+            if summary_body and not self._previous_summary:
+                self._previous_summary = summary_body
+            turns_to_summarize = messages[summary_idx + 1:compress_end]
 
         if not self.quiet_mode:
             logger.info(

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