feat(openclaw-plugin): add topic-judge pre-filter to skip auto-recall on topic continuation

[duoyidavid-eng]

Problem

The before_agent_start auto-recall hook fires on every user message, triggering embedding + vector search + LLM filter calls even when the user is simply continuing the current conversation (follow-up questions, "ok", typos, error feedback). This wastes API calls and adds latency on every turn.

Solution

Add a topic-judge pre-filter using the existing Summarizer.judgeNewTopic() method (already implemented in all providers), extracted as a standalone topicJudgePreFilter() function for clean separation from the main recall logic.

Flow:

before_agent_start fires
  → Extract last N rounds from event.messages (default: 4 rounds)
  → Strip injected metadata, merge consecutive same-role
  → If < 2 context lines → skip recall (conservative)
  → Call summarizer.judgeNewTopic(context, query)
  → SAME → skip recall entirely (saves API calls)
  → NEW  → proceed with search
  → ERROR → fallback to search (safe default)

Config

New option recall.topicJudgeRounds (default: 4). Set to 0 to disable:

{
  "plugins": {
    "entries": {
      "memos-local-openclaw-plugin": {
        "config": {
          "recall": {
            "topicJudgeRounds": 4
          }
        }
      }
    }
  }
}

Value	Behavior
0	Disabled — recall runs on every turn
4 (default)	Uses last 4 rounds as context for LLM topic judgment
N > 0	Uses last N rounds

Design decisions

• Standalone function topicJudgePreFilter() returning "skip" | "proceed" — no inline logic in the hook
• Configurable rounds — users can tune context window or disable entirely
• Graceful fallback — LLM error → proceed with recall (never silently drops memories)
• Cost — 1 small LLM call per turn (max_tokens=10, ~100 input tokens) vs saving the full embedding + search + filter pipeline (~2-3s)

Files changed

• apps/memos-local-openclaw/index.ts — add topicJudgePreFilter(), call it before search
• apps/memos-local-openclaw/src/types.ts — add recall.topicJudgeRounds type
• apps/memos-local-openclaw/src/config.ts — resolve topicJudgeRounds with default 4