fix: skip memory prefetch on trivial user prompts (greetings)

Salvage of PR #25350 (commits 88ffede2d + 2b848a0b2 + 3136dc63a, squashed
and ported): the run_agent.py prefetch site the PR gated has since moved
into agent/turn_context.py's build_turn_context(), so the trivial-query
gate lands there instead.

- Gate the per-turn memory_manager.prefetch_all() on a trivial-prompt
  check so greetings/acknowledgements ('hi!', 'thanks', 'ok') no longer
  block the turn on provider network round-trips or inject stale context.
- Extend honcho's _TRIVIAL_PROMPT_RE with greetings and a trailing
  punctuation class so 'hey!' / 'hello.' classify as trivial.
- Add honcho classifier tests for greeting forms.

agent/turn_context.py

@@ -25,6 +25,7 @@ move-and-name refactor with no semantic change.
 from __future__ import annotations
 
 import logging
+import re
 import threading
 import time
 import uuid
@@ -49,6 +50,37 @@ from agent.model_metadata import (
 logger = logging.getLogger(__name__)
 
 
+# Trivial user-input pattern — used to gate the per-turn memory-provider
+# prefetch on short, semantically-empty queries. Covers greetings,
+# acknowledgements, and trailing-punctuation variants (e.g. "hi!", "hey.",
+# "thanks :)").
+_RE_TRIVIAL_USER_QUERY = re.compile(
+    r'^(yes|no|ok|okay|sure|thanks|thank you|y|n|yep|nope|yeah|nah|'
+    r'hi|hey|hello|yo|sup|'
+    r'continue|go ahead|do it|proceed|got it|cool|nice|great|done|next|lgtm|k)'
+    r'[\s!?.:;,"' + "'" + r'~\u2018\u2019\u201c\u201d\u2014\u2013\u2026()\[\]{}<>*&^%$#@!+=`\u00a0]*$',
+    re.IGNORECASE,
+)
+
+
+def _is_trivial_user_query(query: str) -> bool:
+    """Return True if the query is a greeting or too trivial to warrant prefetch.
+
+    Strips leading/trailing whitespace first, then checks against
+    _RE_TRIVIAL_USER_QUERY which permits common trailing punctuation
+    (exclamation, question mark, emoji, etc.) so variants like "hi!",
+    "hey.", and "thanks :)" register as trivial.
+    """
+    if not query:
+        return True
+    stripped = query.strip()
+    if not stripped:
+        return True
+    if stripped.startswith("/"):
+        return True
+    return bool(_RE_TRIVIAL_USER_QUERY.match(stripped))
+
+
 def compose_user_api_content(
     content: Any,
     ext_prefetch_cache: str,
@@ -1152,11 +1184,15 @@ def build_turn_context(
             pass
 
     # External memory provider: prefetch once before the tool loop.
+    #
+    # Skip prefetch on trivial prompts (greetings, acknowledgements) to
+    # prevent memory-context injection on turns that carry no semantic signal.
     ext_prefetch_cache = ""
     if agent._memory_manager:
         try:
             _query = original_user_message if isinstance(original_user_message, str) else ""
-            ext_prefetch_cache = agent._memory_manager.prefetch_all(_query) or ""
+            if not _is_trivial_user_query(_query):
+                ext_prefetch_cache = agent._memory_manager.prefetch_all(_query) or ""
         except Exception:
             pass
 

plugins/memory/honcho/__init__.py

@@ -1196,12 +1196,14 @@ class HonchoMemoryProvider(MemoryProvider):
                 return r
         return ""
 
-    # Prompts that carry no semantic signal — trivial acknowledgements, slash
-    # commands, empty input. Skipping injection here saves tokens and prevents
+    # Prompts that carry no semantic signal — trivial acknowledgements, greetings,
+    # slash commands, empty input. Skipping injection here saves tokens and prevents
     # stale user-model context from derailing one-word replies.
     _TRIVIAL_PROMPT_RE = re.compile(
         r'^(yes|no|ok|okay|sure|thanks|thank you|y|n|yep|nope|yeah|nah|'
-        r'continue|go ahead|do it|proceed|got it|cool|nice|great|done|next|lgtm|k)$',
+        r'hi|hey|hello|yo|sup|'
+        r'continue|go ahead|do it|proceed|got it|cool|nice|great|done|next|lgtm|k)'
+        r'[\s!?.:;,~]*$',
         re.IGNORECASE,
     )
 

tests/honcho_plugin/test_session.py

@@ -791,6 +791,10 @@ class TestTrivialPromptHeuristic:
         for t in ("ok", "OK", " ok ", "y", "yes", "sure", "thanks", "lgtm", "/help", "", "   "):
             assert HonchoMemoryProvider._is_trivial_prompt(t), f"expected trivial: {t!r}"
 
+    def test_classifier_catches_greetings(self):
+        """Greeting words must register as trivial so context injection is skipped."""
+        for t in ("hi", "HI", "hey", "hello", "yo", "sup", " hi ", "hey!", "hello."):
+            assert HonchoMemoryProvider._is_trivial_prompt(t), f"expected trivial: {t!r}"
 
     def test_prefetch_skips_on_trivial_prompt(self):
         provider = self._make_provider()