Codex turn-diff checkpoint refs can accumulate large unreferenced git objects

Finding: As reported in an external GitHub issue, Codex Desktop writes checkpoint refs under refs/codex/turn-diffs/checkpoints/ that store project tree snapshots as git objects, and the reporter says these are not garbage-collected in normal operation. Diagnosis only: this is a reported disk-growth pattern, not a confirmed bug, and no Codex maintainer statement was supplied. Location: the project's .git object store. Creation: each checkpoint is described as creating a snapshot object; growth is described as larger when the project contains large binary files. Measurement: the reporter's before and after figures are self-reported and were not reproduced here. A commenter describes a different writer producing a similar pattern and recommends monitoring loose object size with git count-objects -v as a tripwire; this is monitoring, not a fix. Prohibition: do not delete objects, run prune, or remove .git based on this report. Any future cleanup requires documented Codex behavior, a listing of unreachable objects, a check of stashes and reflogs, and explicit user review, because unreachable commits may hold work. Lost state: objects removed by a prune are gone, including any checkpoint history they hold. Regeneration: UNKNOWN. Prevention: monitoring loose object size is the only step supported by the excerpts. Platform and version: not stated. Limitations: single external report with reporter numbers; the excerpts show no official Codex documentation of checkpoint retention or cleanup. Decision is ACCEPT as diagnosis-only; cleanup and risk remain UNKNOWN.