fix(compressor): widen empty-content abort to sibling no-response shapes + snapshot state field

Follow-up to PR #94531 salvage:
- classify the auxiliary boundary's terminal 'None response' /
  'invalid response' errors (#7264) into the same empty-content abort
  carve-out so those shapes also preserve the session (#94459's wider
  classification, sibling shapes from #94448)
- register _last_summary_empty_content_failure in
  _COMPRESSOR_ATTEMPT_STATE_FIELDS so pre-commit hard-cancel rollback
  restores the flag (conversation_compression snapshot allow-list)
- tests: cooldown re-entry keeps aborting; both sibling shapes abort
- attribution: map zhangyswx@163.com -> YusenZhang0601

agent/context_compressor.py

@@ -5150,8 +5150,14 @@ This compaction should PRIORITISE preserving all information related to the focu
             _is_streaming_closed = _is_connection_error(e)
             # Provider returned HTTP 200 with empty or whitespace body (e.g.
             # degraded proxy channel / upstream provider fault; #94448).
-            _is_empty_content = (
-                isinstance(e, RuntimeError) and "empty content" in _err_str
+            _is_empty_content = isinstance(e, RuntimeError) and (
+                "empty content" in _err_str
+                # Sibling terminal "no usable response" shapes from the
+                # auxiliary boundary's _validate_llm_response (#7264): a None
+                # response or a malformed/missing choices[0].message — same
+                # degraded-provider class (#94448).
+                or "llm returned none response" in _err_str
+                or "llm returned invalid response" in _err_str
             )
             # Authentication, permission, and exhausted-quota failures are NOT
             # transient or fixable by retrying the same request. Flag them so

agent/conversation_compression.py

@@ -289,6 +289,7 @@ _COMPRESSOR_ATTEMPT_STATE_FIELDS = (
     "_last_compress_aborted",
     "_last_summary_auth_failure",
     "_last_summary_network_failure",
+    "_last_summary_empty_content_failure",
     "_last_aux_model_failure_error",
     "_last_aux_model_failure_model",
     "_summary_model_fallen_back",

contributors/emails/zhangyswx@163.com

@@ -0,0 +1,2 @@
+YusenZhang0601
+# PR #94531 salvage (#94448)

tests/agent/test_context_compressor.py

@@ -966,6 +966,61 @@ class TestAuthFailureAborts:
         assert c._last_summary_fallback_used is False
         assert c._last_summary_dropped_count == 0
 
+        # Cooldown re-entry must keep aborting, same as network/auth —
+        # _generate_summary() returns None from the cooldown early-return
+        # without re-asserting the flag, so compress() must still see it.
+        second = c.compress(msgs, current_tokens=999999)
+        assert second == msgs
+        assert c._last_compress_aborted is True
+        assert c._last_summary_fallback_used is False
+
+    def test_auxiliary_none_response_aborts_compression(self):
+        """Sibling shape (#94459, from #7264): the auxiliary boundary's own
+        terminal "None response" error is the same degraded-provider class
+        and must ABORT, not fall through to the destructive fallback."""
+        with patch("agent.context_compressor.get_model_context_length", return_value=100000):
+            c = ContextCompressor(
+                model="test",
+                quiet_mode=True,
+                protect_first_n=2,
+                protect_last_n=2,
+                abort_on_summary_failure=False,
+            )
+        msgs = self._msgs(12)
+        with patch(
+            "agent.context_compressor.call_llm",
+            side_effect=RuntimeError("Auxiliary compression: LLM returned None response"),
+        ):
+            result = c.compress(msgs, current_tokens=999999, force=True)
+        assert result == msgs
+        assert c._last_compress_aborted is True
+        assert c._last_summary_empty_content_failure is True
+
+    def test_auxiliary_invalid_response_aborts_compression(self):
+        """Sibling shape (#94459, from #7264): malformed/missing
+        choices[0].message terminal error must ABORT the same way."""
+        with patch("agent.context_compressor.get_model_context_length", return_value=100000):
+            c = ContextCompressor(
+                model="test",
+                quiet_mode=True,
+                protect_first_n=2,
+                protect_last_n=2,
+                abort_on_summary_failure=False,
+            )
+        msgs = self._msgs(12)
+        with patch(
+            "agent.context_compressor.call_llm",
+            side_effect=RuntimeError(
+                "Auxiliary compression: LLM returned invalid response "
+                "(type=str): 'oops'. Expected object with .choices[0].message "
+                "— check provider adapter or custom endpoint compatibility."
+            ),
+        ):
+            result = c.compress(msgs, current_tokens=999999, force=True)
+        assert result == msgs
+        assert c._last_compress_aborted is True
+        assert c._last_summary_empty_content_failure is True
+
 
 class TestSummaryFallbackToMainModel:
     """When ``summary_model`` differs from the main model and the summary LLM