Two Claude Code sessions duplicate T-408 twice in one file

The article describes a workflow where a developer keeps all tasks in a single file outside the code repository, using lines formatted like "- [ ] **T-408** content". Two Claude Code sessions ran at once: one auto-continuing a long job via a custom script, and one assigning work. The assigning session, according to the article, did not re-read the file immediately before writing; it relied on the last number it had seen earlier. Meanwhile the other session had already consumed that number, so within about an hour two different problems landed under T-408.

The repair was asymmetric. Because the earlier writer's T-408 had already reached the main branch's code and handoff notes, the later writer was the one changed, to T-410 (T-409 having been taken in the meantime). That later number also appeared in code comments, tests, and a screen-capture script, so five files beyond the task file needed edits. The article's recommended request to Claude Code is to fetch the number from the file by command right before writing, not from memory, and to verify immediately after writing that the number does not appear twice. The article also notes a residual race: the other session can write between the read and the write, so the post-write check remains necessary. A stronger prevention, it says, is to let only one session add tasks, or to pre-assign number ranges (for example, telling one side to start at 500), as long as both sessions follow that rule.