fix(gateway): sync compression split on failed turns

Sync gateway session pointers immediately after context compression rotates the agent session, even when the follow-up model call fails before a final response.

Co-authored-from: https://github.com/NousResearch/hermes-agent/pull/25747

gateway/run.py

@@ -14565,6 +14565,32 @@ class GatewayRunner(GatewayAuthorizationMixin, GatewayKanbanWatchersMixin, Gatew
                 _context_length = getattr(_agent.context_compressor, "context_length", 0) or 0
             _resolved_model = getattr(_agent, "model", None) if _agent else None
 
+            # Compression can rotate the agent to a new session before the
+            # follow-up model call succeeds. Sync that rotation before any
+            # early return so the next gateway turn reloads the compressed
+            # child transcript instead of the stale pre-compression parent.
+            agent = agent_holder[0]
+            _session_was_split = False
+            effective_session_id = getattr(agent, 'session_id', session_id) if agent else session_id
+            if agent and session_key and effective_session_id != session_id:
+                _session_was_split = True
+                logger.info(
+                    "Session split detected: %s → %s (compression)",
+                    session_id, effective_session_id,
+                )
+                entry = self.session_store._entries.get(session_key)
+                if entry:
+                    entry.session_id = effective_session_id
+                    self.session_store._save()
+                    self._sync_telegram_topic_binding(
+                        source, entry, reason="agent-result-compression",
+                    )
+
+            # When compression created a new session, the messages list was
+            # shortened. Using the original history offset would make gateway
+            # persistence slice away the compressed handoff/tail on failure.
+            _effective_history_offset = 0 if _session_was_split else len(agent_history)
+
             if not final_response:
                 error_msg = f"⚠️ {result['error']}" if result.get("error") else ""
                 return {
@@ -14579,7 +14605,8 @@ class GatewayRunner(GatewayAuthorizationMixin, GatewayKanbanWatchersMixin, Gatew
                     "error": result.get("error"),
                     "compression_exhausted": result.get("compression_exhausted", False),
                     "tools": tools_holder[0] or [],
-                    "history_offset": len(agent_history),
+                    "history_offset": _effective_history_offset,
+                    "session_id": effective_session_id,
                     "last_prompt_tokens": _last_prompt_toks,
                     "input_tokens": _input_toks,
                     "output_tokens": _output_toks,
@@ -14625,23 +14652,7 @@ class GatewayRunner(GatewayAuthorizationMixin, GatewayKanbanWatchersMixin, Gatew
                         unique_tags.insert(0, "[[audio_as_voice]]")
                     final_response = final_response + "\n" + "\n".join(unique_tags)
             
-            # Sync session_id: the agent may have created a new session during
+            if _session_was_split:
-            # mid-run context compression (_compress_context splits sessions).
-            # If so, update the session store entry so the NEXT message loads
-            # the compressed transcript, not the stale pre-compression one.
-            agent = agent_holder[0]
-            _session_was_split = False
-            if agent and session_key and hasattr(agent, 'session_id') and agent.session_id != session_id:
-                _session_was_split = True
-                logger.info(
-                    "Session split detected: %s → %s (compression)",
-                    session_id, agent.session_id,
-                )
-                entry = self.session_store._entries.get(session_key)
-                if entry:
-                    entry.session_id = agent.session_id
-                    self.session_store._save()
-
                 # If this is a Telegram DM and source.thread_id was lost during
                 # the session split (synthetic / recovered event), restore it
                 # from the binding so _thread_metadata_for_source produces the
@@ -14673,15 +14684,6 @@ class GatewayRunner(GatewayAuthorizationMixin, GatewayKanbanWatchersMixin, Gatew
                             exc_info=True,
                         )
 
-            effective_session_id = getattr(agent, 'session_id', session_id) if agent else session_id
-
-            # When compression created a new session, the messages list was
-            # shortened.  Using the original history offset would produce an
-            # empty new_messages slice, causing the gateway to write only a
-            # user/assistant pair — losing the compressed summary and tail.
-            # Reset to 0 so the gateway writes ALL compressed messages.
-            _effective_history_offset = 0 if _session_was_split else len(agent_history)
-
             # Auto-generate session title after first exchange (non-blocking)
             if final_response and self._session_db:
                 try:

tests/gateway/test_compression_failure_session_sync.py

@@ -0,0 +1,196 @@
+import asyncio
+import sys
+import threading
+import types
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, MagicMock
+
+import gateway.run as gateway_run
+from gateway.config import Platform
+from gateway.session import SessionSource
+
+
+SESSION_KEY = "agent:main:telegram:dm:12345"
+
+
+class _SaveTrackingSessionStore:
+    def __init__(self):
+        self.entry = SimpleNamespace(session_id="session-before-compression")
+        self._entries = {SESSION_KEY: self.entry}
+        self.save_calls = 0
+        self.topic_sync_calls = []
+
+    def _save(self):
+        self.save_calls += 1
+
+
+class _CompressionThenFailureAgent:
+    def __init__(self, **kwargs):
+        self.session_id = kwargs["session_id"]
+        self.model = kwargs["model"]
+        self.tools = []
+        self.context_compressor = SimpleNamespace(
+            last_prompt_tokens=4321,
+            context_length=200000,
+        )
+        self.session_prompt_tokens = 4321
+        self.session_completion_tokens = 0
+
+    def run_conversation(self, user_message, conversation_history=None, task_id=None):
+        self.session_id = "session-after-compression"
+        return {
+            "failed": True,
+            "error": (
+                "APIConnectionError: Codex auxiliary Responses stream exceeded "
+                "120.0s total timeout"
+            ),
+            "messages": [
+                {
+                    "role": "user",
+                    "content": (
+                        "[Context compressed: previous long transcript was "
+                        "summarized before retry]"
+                    ),
+                },
+                {"role": "user", "content": user_message},
+            ],
+            "api_calls": 1,
+        }
+
+    def interrupt(self, *_args, **_kwargs):
+        pass
+
+
+class _ImmediateStreamConsumer:
+    final_response_sent = False
+
+    def __init__(self, *_args, **_kwargs):
+        pass
+
+    async def run(self):
+        return None
+
+    def finish(self):
+        pass
+
+
+class _QuietAdapter:
+    SUPPORTS_MESSAGE_EDITING = True
+    _pending_messages = {}
+
+    def get_pending_message(self, _session_key):
+        return None
+
+
+def _install_fake_agent(monkeypatch):
+    fake_run_agent = types.ModuleType("run_agent")
+    fake_run_agent.AIAgent = _CompressionThenFailureAgent
+    monkeypatch.setitem(sys.modules, "run_agent", fake_run_agent)
+
+
+def _make_runner(session_store):
+    runner = object.__new__(gateway_run.GatewayRunner)
+    runner.adapters = {
+        Platform.TELEGRAM: _QuietAdapter(),
+    }
+    runner._ephemeral_system_prompt = ""
+    runner._prefill_messages = []
+    runner._reasoning_config = None
+    runner._provider_routing = {}
+    runner._fallback_model = None
+    runner._running_agents = {}
+    runner._pending_model_notes = {}
+    runner._pending_skills_reload_notes = {}
+    runner._session_db = None
+    runner._agent_cache = {}
+    runner._agent_cache_lock = threading.Lock()
+    runner._session_model_overrides = {}
+    runner._draining = False
+    runner.config = SimpleNamespace(streaming=None)
+    runner.hooks = SimpleNamespace(loaded_hooks=False, emit=AsyncMock())
+    runner.session_store = session_store
+    runner._get_proxy_url = lambda: None
+    runner._resolve_session_agent_runtime = lambda **_kwargs: (
+        "gpt-5.4",
+        {
+            "provider": "openai-codex",
+            "api_mode": "codex_responses",
+            "base_url": "https://chatgpt.com/backend-api/codex",
+            "api_key": "token",
+        },
+    )
+    runner._resolve_session_reasoning_config = lambda **_kwargs: None
+    runner._resolve_turn_agent_config = lambda message, model, runtime: {
+        "model": model,
+        "runtime": runtime,
+    }
+    runner._load_service_tier = lambda: None
+    runner._agent_config_signature = lambda *_args, **_kwargs: ("sig",)
+    runner._extract_cache_busting_config = lambda _config: ()
+    runner._thread_metadata_for_source = lambda *_args, **_kwargs: None
+    runner._is_telegram_topic_lane = lambda _source: False
+    runner._sync_telegram_topic_binding = lambda source, entry, *, reason: session_store.topic_sync_calls.append(
+        (source, entry.session_id, reason)
+    )
+    runner._release_running_agent_state = MagicMock()
+    return runner
+
+
+def _source():
+    return SessionSource(
+        platform=Platform.TELEGRAM,
+        chat_id="12345",
+        chat_type="dm",
+        user_id="user-1",
+    )
+
+
+def test_failed_turn_still_syncs_compression_session_split(monkeypatch):
+    """A post-compression API failure must not leave the session store on the
+    stale pre-compression transcript.
+    """
+    _install_fake_agent(monkeypatch)
+    monkeypatch.setenv("HERMES_TOOL_PROGRESS_MODE", "off")
+    monkeypatch.setenv("HERMES_AGENT_TIMEOUT", "0")
+    monkeypatch.setattr(gateway_run, "_load_gateway_config", lambda: {})
+    monkeypatch.setattr(
+        "gateway.stream_consumer.GatewayStreamConsumer",
+        _ImmediateStreamConsumer,
+    )
+
+    import hermes_cli.tools_config as tools_config
+
+    monkeypatch.setattr(
+        tools_config,
+        "_get_platform_tools",
+        lambda *_args, **_kwargs: {"core"},
+    )
+
+    session_store = _SaveTrackingSessionStore()
+    runner = _make_runner(session_store)
+
+    result = asyncio.run(
+        asyncio.wait_for(
+            runner._run_agent(
+                message="continue",
+                context_prompt="",
+                history=[
+                    {"role": "user", "content": "old question"},
+                    {"role": "assistant", "content": "old answer"},
+                ],
+                source=_source(),
+                session_id="session-before-compression",
+                session_key=SESSION_KEY,
+            ),
+            timeout=2,
+        ),
+    )
+
+    assert result["failed"] is True
+    assert result["session_id"] == "session-after-compression"
+    assert result["history_offset"] == 0
+    assert session_store.entry.session_id == "session-after-compression"
+    assert session_store.save_calls == 1
+    assert session_store.topic_sync_calls == [
+        (_source(), "session-after-compression", "agent-result-compression")
+    ]