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fix(agent): move archived summary into system prompt for KV cache stability

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- Append [Archived Context Summary] to system prompt instead of injecting
  it into the user message runtime context, improving KV cache reuse across
  turns and avoiding consecutive same-role messages.
- _last_summary persists in metadata (no pop) for restart survival;
  summary is re-injected every turn via the stable system prompt.
- Remove dynamic "Inactive for X minutes" from _format_summary — use
  static last_active timestamp instead to preserve KV cache stability.
- Pass session_summary through build_messages() so both normal and
  ask_user paths receive the archived summary in the system prompt.
- estimate_session_prompt_tokens now reads _last_summary from metadata
  to include the summary in token budget estimation.
- Remove obsolete session_summary parameter from
  maybe_consolidate_by_tokens and estimate_session_prompt_tokens
  call sites in loop.py (summary flows through build_messages instead).
- Ensure /new (session.clear()) clears _last_summary from metadata.
This commit is contained in:
chengyongru 2026-05-07 16:17:27 +08:00 committed by Xubin Ren
parent 73a8d8a875
commit a6e993df25
8 changed files with 119 additions and 41 deletions
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12
nanobot/agent/autocompact.py
View File

@ -7,6 +7,7 @@ from datetime import datetime
from typing import TYPE_CHECKING, Any, Callable, Coroutine
from loguru import logger
from nanobot.session.manager import Session, SessionManager
if TYPE_CHECKING:
@ -34,8 +35,7 @@ class AutoCompact:
@staticmethod
def _format_summary(text: str, last_active: datetime) -> str:
idle_min = int((datetime.now() - last_active).total_seconds() / 60)
return f"Inactive for {idle_min} minutes.\nPrevious conversation summary: {text}"
return f"Previous conversation summary (last active {last_active.isoformat()}):\n{text}"
def _split_unconsolidated(
self, session: Session,
@ -111,13 +111,11 @@ class AutoCompact:
logger.info("Auto-compact: reloading session {} (archiving={})", key, key in self._archiving)
session = self.sessions.get_or_create(key)
# Hot path: summary from in-memory dict (process hasn't restarted).
# Also clean metadata copy so stale _last_summary never leaks to disk.
entry = self._summaries.pop(key, None)
if entry:
session.metadata.pop("_last_summary", None)
return session, self._format_summary(entry[0], entry[1])
if "_last_summary" in session.metadata:
meta = session.metadata.pop("_last_summary")
self.sessions.save(session)
# Cold path: summary persisted in session metadata (process restarted).
meta = session.metadata.get("_last_summary")
if isinstance(meta, dict):
return session, self._format_summary(meta["text"], datetime.fromisoformat(meta["last_active"]))
return session, None

21
nanobot/agent/context.py
View File

@ -10,7 +10,12 @@ from typing import Any
from nanobot.agent.memory import MemoryStore
from nanobot.agent.skills import SkillsLoader
from nanobot.utils.helpers import build_assistant_message, current_time_str, detect_image_mime, truncate_text
from nanobot.utils.helpers import (
build_assistant_message,
current_time_str,
detect_image_mime,
truncate_text,
)
from nanobot.utils.prompt_templates import render_template
@ -33,6 +38,7 @@ class ContextBuilder:
self,
skill_names: list[str] | None = None,
channel: str | None = None,
session_summary: str | None = None,
) -> str:
"""Build the system prompt from identity, bootstrap files, memory, and skills."""
parts = [self._get_identity(channel=channel)]
@ -64,6 +70,9 @@ class ContextBuilder:
history_text = truncate_text(history_text, self._MAX_HISTORY_CHARS)
parts.append("# Recent History\n\n" + history_text)
if session_summary:
parts.append(f"[Archived Context Summary]\n\n{session_summary}")
return "\n\n---\n\n".join(parts)
def _get_identity(self, channel: str | None = None) -> str:
@ -83,7 +92,7 @@ class ContextBuilder:
@staticmethod
def _build_runtime_context(
channel: str | None, chat_id: str | None, timezone: str | None = None,
session_summary: str | None = None, sender_id: str | None = None,
sender_id: str | None = None,
) -> str:
"""Build untrusted runtime metadata block for injection before the user message."""
lines = [f"Current Time: {current_time_str(timezone)}"]
@ -91,8 +100,6 @@ class ContextBuilder:
lines += [f"Channel: {channel}", f"Chat ID: {chat_id}"]
if sender_id:
lines += [f"Sender ID: {sender_id}"]
if session_summary:
lines += ["", "[Resumed Session]", session_summary]
return ContextBuilder._RUNTIME_CONTEXT_TAG + "\n" + "\n".join(lines) + "\n" + ContextBuilder._RUNTIME_CONTEXT_END
@staticmethod
@ -139,11 +146,11 @@ class ContextBuilder:
channel: str | None = None,
chat_id: str | None = None,
current_role: str = "user",
session_summary: str | None = None,
sender_id: str | None = None,
session_summary: str | None = None,
) -> list[dict[str, Any]]:
"""Build the complete message list for an LLM call."""
runtime_ctx = self._build_runtime_context(channel, chat_id, self.timezone, session_summary=session_summary, sender_id=sender_id)
runtime_ctx = self._build_runtime_context(channel, chat_id, self.timezone, sender_id=sender_id)
user_content = self._build_user_content(current_message, media)
# Merge runtime context and user content into a single user message
@ -153,7 +160,7 @@ class ContextBuilder:
else:
merged = [{"type": "text", "text": runtime_ctx}] + user_content
messages = [
{"role": "system", "content": self.build_system_prompt(skill_names, channel=channel)},
{"role": "system", "content": self.build_system_prompt(skill_names, channel=channel, session_summary=session_summary)},
*history,
]
if messages[-1].get("role") == current_role:

14
nanobot/agent/loop.py
View File

@ -706,12 +706,16 @@ class AgentLoop:
session: Session,
history: list[dict[str, Any]],
pending_ask_id: str | None,
pending_summary: Any,
pending_summary: str | None,
) -> list[dict[str, Any]]:
"""Build the initial message list for the LLM turn."""
if pending_ask_id:
system_prompt = self.context.build_system_prompt(
channel=msg.channel,
session_summary=pending_summary,
)
return ask_user_tool_result_messages(
self.context.build_system_prompt(channel=msg.channel),
system_prompt,
history,
pending_ask_id,
image_generation_prompt(msg.content, msg.metadata),
@ -719,11 +723,11 @@ class AgentLoop:
return self.context.build_messages(
history=history,
current_message=image_generation_prompt(msg.content, msg.metadata),
session_summary=pending_summary,
media=msg.media if msg.media else None,
channel=msg.channel,
chat_id=self._runtime_chat_id(msg),
sender_id=msg.sender_id,
session_summary=pending_summary,
)
async def _dispatch_command_inline(
@ -1179,7 +1183,6 @@ class AgentLoop:
await self.consolidator.maybe_consolidate_by_tokens(
session,
session_summary=pending,
replay_max_messages=self._max_messages,
)
is_subagent = msg.sender_id == "subagent"
@ -1203,9 +1206,9 @@ class AgentLoop:
current_message="" if is_subagent else msg.content,
channel=channel,
chat_id=chat_id,
session_summary=pending,
current_role=current_role,
sender_id=msg.sender_id,
session_summary=pending,
)
final_content, _, all_msgs, stop_reason, _ = await self._run_agent_loop(
messages, session=session, channel=channel, chat_id=chat_id,
@ -1413,7 +1416,6 @@ class AgentLoop:
async def _state_build(self, ctx: TurnContext) -> str:
await self.consolidator.maybe_consolidate_by_tokens(
ctx.session,
session_summary=ctx.pending_summary,
replay_max_messages=self._max_messages,
)
self._set_tool_context(

10
nanobot/agent/memory.py
View File

@ -590,19 +590,20 @@ class Consolidator:
def estimate_session_prompt_tokens(
self,
session: Session,
*,
session_summary: str | None = None,
) -> tuple[int, str]:
"""Estimate prompt size from the full unconsolidated session tail."""
history = self._full_unconsolidated_history(session, include_timestamps=True)
channel, chat_id = (session.key.split(":", 1) if ":" in session.key else (None, None))
# Include archived summary in estimation so the budget accounts for it.
meta = session.metadata.get("_last_summary")
summary = meta.get("text") if isinstance(meta, dict) else (meta if isinstance(meta, str) else None)
probe_messages = self._build_messages(
history=history,
current_message="[token-probe]",
channel=channel,
chat_id=chat_id,
session_summary=session_summary,
sender_id=None,
session_summary=summary,
)
return estimate_prompt_tokens_chain(
self.provider,
@ -669,7 +670,6 @@ class Consolidator:
self,
session: Session,
*,
session_summary: str | None = None,
replay_max_messages: int | None = None,
) -> None:
"""Loop: archive old messages until prompt fits within safe budget.
@ -691,7 +691,6 @@ class Consolidator:
try:
estimated, source = self.estimate_session_prompt_tokens(
session,
session_summary=session_summary,
)
except Exception:
logger.exception("Token estimation failed for {}", session.key)
@ -757,7 +756,6 @@ class Consolidator:
try:
estimated, source = self.estimate_session_prompt_tokens(
session,
session_summary=session_summary,
)
except Exception:
logger.exception("Token estimation failed for {}", session.key)

1
nanobot/session/manager.py
View File

@ -181,6 +181,7 @@ class Session:
self.messages = []
self.last_consolidated = 0
self.updated_at = datetime.now()
self.metadata.pop("_last_summary", None)
def retain_recent_legal_suffix(self, max_messages: int) -> None:
"""Keep a legal recent suffix constrained by a hard message cap."""

97
tests/agent/test_auto_compact.py
View File

@ -1020,14 +1020,14 @@ class TestSummaryPersistence:
assert summary is not None
assert "User said hello." in summary
assert "Inactive for" in summary
# Metadata should be cleaned up after consumption
assert "_last_summary" not in reloaded.metadata
assert "Previous conversation summary" in summary
# _last_summary persists in metadata for restart survival.
assert "_last_summary" in reloaded.metadata
await loop.close_mcp()
@pytest.mark.asyncio
async def test_metadata_cleanup_no_leak(self, tmp_path):
"""_last_summary should be removed from metadata after being consumed."""
async def test_metadata_persists_for_restart(self, tmp_path):
"""_last_summary stays in metadata so it survives process restarts."""
loop = _make_loop(tmp_path, session_ttl_minutes=15)
session = loop.sessions.get_or_create("cli:test")
_add_turns(session, 6, prefix="hello")
@ -1046,14 +1046,14 @@ class TestSummaryPersistence:
loop.sessions.invalidate("cli:test")
reloaded = loop.sessions.get_or_create("cli:test")
# First call: consumes from metadata
# Every call returns the summary from metadata (no _consumed_keys gate)
_, summary = loop.auto_compact.prepare_session(reloaded, "cli:test")
assert summary is not None
# Second call: no summary (already consumed)
_, summary2 = loop.auto_compact.prepare_session(reloaded, "cli:test")
assert summary2 is None
assert "_last_summary" not in reloaded.metadata
assert summary2 is not None
assert "Summary." in summary2
# _last_summary persists in metadata for restart survival.
assert "_last_summary" in reloaded.metadata
await loop.close_mcp()
@pytest.mark.asyncio
@ -1081,6 +1081,79 @@ class TestSummaryPersistence:
# In-memory path is taken (no restart)
_, summary = loop.auto_compact.prepare_session(reloaded, "cli:test")
assert summary is not None
# Metadata should also be cleaned up
assert "_last_summary" not in reloaded.metadata
# _last_summary persists in metadata for restart survival.
assert "_last_summary" in reloaded.metadata
await loop.close_mcp()
@pytest.mark.asyncio
async def test_new_summary_overrides_old(self, tmp_path):
"""A fresh archive writes a new summary that replaces the old one."""
loop = _make_loop(tmp_path, session_ttl_minutes=15)
session = loop.sessions.get_or_create("cli:test")
_add_turns(session, 6, prefix="hello")
session.updated_at = datetime.now() - timedelta(minutes=20)
loop.sessions.save(session)
async def _fake_archive(messages):
return "First summary."
loop.consolidator.archive = _fake_archive
await loop.auto_compact._archive("cli:test")
# Consume the first summary via hot path
_, summary1 = loop.auto_compact.prepare_session(
loop.sessions.get_or_create("cli:test"), "cli:test"
)
assert summary1 is not None
assert "First summary." in summary1
assert "cli:test" not in loop.auto_compact._summaries # popped by hot path
# Add new messages and archive again (simulating a later turn)
_add_turns(session, 4, prefix="world")
session.updated_at = datetime.now() - timedelta(minutes=20)
loop.sessions.save(session)
async def _fake_archive2(messages):
return "Second summary."
loop.consolidator.archive = _fake_archive2
await loop.auto_compact._archive("cli:test")
# The second archive writes a new summary
assert "cli:test" in loop.auto_compact._summaries
# prepare_session must return the new summary
reloaded = loop.sessions.get_or_create("cli:test")
_, summary2 = loop.auto_compact.prepare_session(reloaded, "cli:test")
assert summary2 is not None
assert "Second summary." in summary2
await loop.close_mcp()
@pytest.mark.asyncio
async def test_new_command_clears_last_summary(self, tmp_path):
"""/new should clear _last_summary so the new session starts fresh."""
loop = _make_loop(tmp_path, session_ttl_minutes=15)
session = loop.sessions.get_or_create("cli:test")
_add_turns(session, 6, prefix="hello")
session.updated_at = datetime.now() - timedelta(minutes=20)
loop.sessions.save(session)
async def _fake_archive(messages):
return "Old summary."
loop.consolidator.archive = _fake_archive
await loop.auto_compact._archive("cli:test")
# Verify summary exists before /new
reloaded = loop.sessions.get_or_create("cli:test")
assert "_last_summary" in reloaded.metadata
# Simulate /new command
session.clear()
loop.sessions.save(session)
loop.sessions.invalidate(session.key)
# After /new, metadata should no longer contain _last_summary
fresh = loop.sessions.get_or_create("cli:test")
assert "_last_summary" not in fresh.metadata
await loop.close_mcp()

4
tests/agent/test_loop_consolidation_tokens.py
View File

@ -190,7 +190,8 @@ async def test_consolidation_persists_summary_for_next_prepare_session(tmp_path,
reloaded, pending = loop.auto_compact.prepare_session(reloaded, "cli:test")
assert pending is not None
assert "User discussed project status." in pending
assert "_last_summary" not in reloaded.metadata
# _last_summary persists for restart survival.
assert "_last_summary" in reloaded.metadata
@pytest.mark.asyncio
@ -207,7 +208,6 @@ async def test_preflight_consolidation_receives_pending_summary(tmp_path) -> Non
loop.consolidator.maybe_consolidate_by_tokens.assert_any_await(
session,
session_summary="Previous conversation summary: earlier context",
replay_max_messages=loop._max_messages,
)

1
tests/agent/test_unified_session.py
View File

@ -399,7 +399,6 @@ class TestConsolidationUnaffectedByUnifiedSession:
# estimate was called (consolidation was attempted)
consolidator.estimate_session_prompt_tokens.assert_called_once_with(
session,
session_summary=None,
)
# but archive was not called (no valid boundary)
consolidator.archive.assert_not_called()