025. A Claude process holds its task folder open

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Date: 2026-10-30
Agents: Claude Code
Measured on: real machine

Measured

2026-10-30, Claude Code 2.1.310 and 2.1.314, on Linux (Debian 13, x64). Two live interactive sessions in tmux. readlink read each entry of /proc/<pid>/fd. Measured on: real machine.

What was measured

A Claude process holds no transcript file open.
It holds one folder open: /tmp/claude-<uid>/<project key>/<session id>/tasks. The session ID in that path is the sessionId of ~/.claude/sessions/<pid>.json (fact 023).
Its other descriptors are its tty (8 descriptors), sockets, and anon_inode entries (eventpoll, eventfd, pidfd).

Mechanism

A reader that can read the open files of a process, but not the home folder of its user, can still get the session ID from the task folder.

Incident

None.

Screens

None.

Not measured

Whether the folder changes after /clear.
Sessions with no background task. Both sessions had run tasks.
The path on macOS and Windows, where the temporary folder is different.

2026-10-30, 2.1.314: before the first task, and after /clear

Measured on: real machine. Scenario scenarios/claude/dialog-states.sh (three runs) in a throwaway HOME, on the same Linux machine.

Before the first Bash tool call, the process held no folder below /tmp/claude-<uid>/ open, and the tasks folder did not exist. The first Bash call made the folder and opened it. That call was a foreground ls, not a background task (fact 034).
After /clear, the process still held the tasks folder of the first session ID. A background task after /clear wrote its output there. So the session ID in the path is the first session ID of the process, not always the sessionId of the pid file. The Mechanism above is correct only for a process that has had one session (fact 034).