Formal models and scripts: merge-on-commit-refresh-tla

Tools: TLA+/TLC

These are the working models and scripts this part of the hunt used. Some encode the code as it is (a counterexample is the expected result), others a fixed or correct variant; read the header comment of each file. Paths inside them were replaced by placeholders such as $LUCENE (a Lucene checkout) and $WORK.

Findings

• IndexWriter keeps a full-flush merge that registerMerge rejected: commit() does not throw the IllegalStateException that MergePolicy#findFullFlushMerges documents, the rejected merge's readers stay open after IndexWriter.close(), and commit/getReader wait the full maxFullFlushMergeWaitMillis for a merge that never runs (finding LFV-502; repro · finding page)

Files

• fullflush-merge-rejected-by-registermerge-still-awaited/model/PITMerge.tla (used for LFV-502)

How to run

• TLA+ with TLC: java -cp tla2tools.jar tlc2.TLC -config <Model>.cfg <Model>.tla (a counterexample trace is the finding when the model encodes the current code).

Snapshot of 2026-11-03. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.