[Bug] MemOS 2.0.19 untagged cluster `_|_` enters L3 abstraction pipeline and causes 100% `llm_failed` due to missing `title`

[Memtensor-AI]

产品线：MemOS 正式版开源项目
仓库：https://github.com/MemTensor/MemOS
记录 ID：WeFBbZFjXX

MemOS 2.0.19 中 _|_ 无标签簇（untagged cluster）进入 L3 世界模型抽象流水线，因 abstractDraft 未做前置过滤，title 字段缺失，导致 world_model_generate 100% llm_failed。错误签名：kind=l3.failed / stage=abstract / error.code=llm_failed / error.message="l3.abstraction: 'title' must be a non-empty string" / clusterKey=|。本机累计 1686 次失败 / 26.2 小时持续无冷却重试（785 次来自 | 簇，历史 0 次成功）。
OpenClaw 知识库结果：NO_REPLY
判断依据：完整故障报告已提供：环境、错误签名、数据规模、失败率统计（785/785，100%）、根因分析（无标签簇无 title 但未前置拦截）、永久重试机制导致放大效应、本地临时规避方案及副作用均已说明。知识库无此 bug 的官方修复方案，需官方在算法层修复。
trace_id=ca1c022a8286b7d99eaf80aa31b09307
xiaoyi:9c5f3c1925f26ce47a38c05f
issue:5eed599b754d3c49961f3f6c

分析及待补充信息

反馈描述指向 MemOS 正式版开源项目，候选仓库唯一且注册表已明确归属为 GitHub 上的 MemOS。问题具备明确版本、错误签名、触发条件、影响范围、失败统计与根因分析，属于可复现且症状清晰的产品缺陷。根据规则，已有产品归属且症状明确的 bug 应先创建 GitHub issue 跟踪。

[Memtensor-AI]

🤖 AutoDev has picked up this issue and started working on it.

Task ID: 358488c1954c9ee6
Working branch: feature/autodev-2374-20260916030702169
Target branch: latest dev* branch
Workflow: opsp (analysis → coding → testing → PR)

I will post the PR link here once done. If I need more information, I will ask in the comments.

[Memtensor-AI]

✅ AutoDev task 358488c1954c9ee6 completed.

Summary: Fixed issue #2374: MemOS 2.0.19 L3 pipeline no longer feeds the _|_ untagged cluster into abstractDraft. When domainKeyOf returns the catch-all "_|_" key (all TAG_REGEX / TOOL_REGEX matchers missed), the cluster has no shared organising principle and the LLM consistently returns empty title, tripping abstract.ts::validate and yielding 100% llm_failed. Field data reported 785/785 _|_-cluster abstractions failing, roughly 47% of the 1686 total L3 failures over 26.2h.

The fix adds a per-cluster guard in runL3 (positioned after no_centroid, before cooldown/LLM) that: (1) records an AbstractionResult with the new skippedReason: "untagged_cluster" value, (2) emits an info-level "untagged.skipped" log on the abstract channel, and (3) continues without invoking abstractDraft, spending an LLM round-trip, marking cooldown, or emitting l3.failed. domainKeyOf / clusterPolicies / abstractDraft are unchanged so cluster-count metrics and tagged-cluster behaviour stay intact.

Test evidence — RED phase: the two new integration tests (skips the '_|_' untagged cluster before calling the LLM and still processes tagged clusters when mixed with an untagged bucket) initially failed on baseline (expected null to be 'untagged_cluster'). GREEN phase after the fix: 6/6 L3 integration tests, 35/35 L3 unit+integration tests, and the full plugin suite 1559 passed / 2 pre-existing skips / 0 failed. tsc --noEmit clean.

Three files changed under apps/memos-local-plugin/core/memory/l3/ (l3.ts +27, types.ts +1) and tests/unit/memory/l3/l3.integration.test.ts (+175). .ai-tasks/ and openspec/changes/ are gitignored via .git/info/exclude and stay out of the PR. opsp artifacts also archived and pushed to memos-autodev-specs main.

Base branch: main
Branch: feature/autodev-2374-20260916030702169
Commit: 612964e
PR: #2375
Assigned to: @hijzy
Reviewers: @MatthewZhuang, @CarltonXiang, @syzsunshine219, @World-controller