core/agent: refresh synthetic_tool todo nags to live stack

src/plyngent/agent/chat.py

@@ -23,6 +23,7 @@ from .todo_nag import (
     DEFAULT_TODO_NAG_STRATEGY,
     inject_todo_nag_for_stack_with_events,
     parse_todo_nag_strategy,
+    refresh_synthetic_todo_nags,
 )
 from .usage import TokenUsage
 
@@ -304,6 +305,9 @@ class ChatAgent:
         user_index = self._user_index(user_msg)
         if self.todo_stack is not None:
             self.todo_stack.begin_turn()
+            # Keep forged synthetic_tool nags aligned with the live stack so a
+            # previously dirty stack does not re-surface after it was cleaned.
+            _ = refresh_synthetic_todo_nags(self.messages, self.todo_stack)
 
         completed = False
         turn_usage = TokenUsage()

src/plyngent/agent/loop.py

@@ -37,7 +37,11 @@ from .events import (
     ToolResultEvent,
     UsageEvent,
 )
-from .todo_nag import DEFAULT_TODO_NAG_STRATEGY, inject_todo_nag_for_stack_with_events
+from .todo_nag import (
+    DEFAULT_TODO_NAG_STRATEGY,
+    inject_todo_nag_for_stack_with_events,
+    refresh_synthetic_todo_nags,
+)
 from .usage import resolve_round_usage, token_usage_from_api
 
 if TYPE_CHECKING:
@@ -349,12 +353,16 @@ async def run_chat_loop(  # noqa: C901 — multi-phase tool loop
     while True:
         while rounds_used < allowance:
             rounds_used += 1
+            # Request copy: shrink old tool dumps, then rewrite forged todo nags
+            # so cleaned stacks do not re-appear with stale OPEN WORK text.
             request_messages = compact_messages_for_request(
                 messages,
                 max_tokens=max_context_tokens,
                 prompt_tokens_hint=prompt_tokens_hint,
                 sent_estimate_tokens=sent_estimate_tokens,
             )
+            if todo_stack is not None:
+                _ = refresh_synthetic_todo_nags(request_messages, todo_stack)
             sent_est = estimate_messages_tokens(request_messages)
             param = ChatCompletionsParam(
                 messages=request_messages,

src/plyngent/agent/todo_nag.py

@@ -29,6 +29,8 @@ type TodoNagKind = Literal["turn_start", "end_of_turn"]
 TODO_NAG_STRATEGIES: frozenset[str] = frozenset({"developer", "user", "synthetic_tool", "none"})
 DEFAULT_TODO_NAG_STRATEGY: TodoNagStrategy = "developer"
 _SYNTHETIC_TOOL_NAME = "todo_list"
+# Forged call ids from :func:`_append_synthetic_todo_list` (not model-authored).
+_SYNTHETIC_CALL_ID_PREFIX = "todo-nag-"
 
 
 def parse_todo_nag_strategy(raw: str | None) -> TodoNagStrategy:
@@ -63,7 +65,7 @@ def synthetic_todo_list_result(stack: TodoStack) -> str:
 
 def _append_synthetic_todo_list(messages: list[AnyChatMessage], body: str) -> str:
     """Append forged todo_list call + result. Returns the synthetic tool_call id."""
-    call_id = f"todo-nag-{uuid.uuid4().hex[:12]}"
+    call_id = f"{_SYNTHETIC_CALL_ID_PREFIX}{uuid.uuid4().hex[:12]}"
     messages.append(
         AssistantChatMessage(
             content=UNSET,
@@ -82,6 +84,55 @@ def _append_synthetic_todo_list(messages: list[AnyChatMessage], body: str) -> st
     return call_id
 
 
+def is_synthetic_todo_nag_call_id(call_id: str) -> bool:
+    """True for forged ``todo_list`` nag tool_call ids (not model-authored)."""
+    return call_id.startswith(_SYNTHETIC_CALL_ID_PREFIX)
+
+
+def refresh_synthetic_todo_nags(
+    messages: list[AnyChatMessage],
+    stack: TodoStack,
+) -> int:
+    """Rewrite forged ``todo_list`` nag results to the live stack render.
+
+    Synthetic nags are append-only snapshots. After the stack is cleaned (or
+    otherwise mutated), older nag results still sit in history and re-surface
+    on later model requests with stale OPEN WORK. Call this on a **request
+    copy** (not necessarily durable history) before each completion so the
+    model always sees the current stack for forged nags.
+
+    Real model-authored ``todo_list`` results are left unchanged.
+    Returns the number of tool messages updated.
+    """
+    body = stack.render()
+    synth_ids: set[str] = set()
+    for msg in messages:
+        if not isinstance(msg, AssistantChatMessage):
+            continue
+        tool_calls = msg.tool_calls
+        if tool_calls is UNSET or not tool_calls:
+            continue
+        for call in tool_calls:
+            if (
+                isinstance(call, AssistantFunctionToolCall)
+                and is_synthetic_todo_nag_call_id(call.id)
+                and call.function.name == _SYNTHETIC_TOOL_NAME
+            ):
+                synth_ids.add(call.id)
+
+    updated = 0
+    for index, msg in enumerate(messages):
+        if not isinstance(msg, ToolChatMessage):
+            continue
+        if msg.tool_call_id not in synth_ids and not is_synthetic_todo_nag_call_id(msg.tool_call_id):
+            continue
+        if msg.content == body:
+            continue
+        messages[index] = ToolChatMessage(tool_call_id=msg.tool_call_id, content=body)
+        updated += 1
+    return updated
+
+
 def inject_todo_nag(
     messages: list[AnyChatMessage],
     body: str,