Headless sessions leave smoke-test files in /tmp #23

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1. JacobStephens2

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   needs-triageMaintainer needs to evaluate this issueMaintainer needs to evaluate this issue

   on Sep 25, 2026
2. JacobStephens2 commented on Sep 25, 2026

   

   JacobStephens2

   on Sep 25, 2026

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   This was generated by AI during triage.

   Agent Brief

   Category: enhancement
   Summary: Give every Run's agent sessions their own temp directory, removed when the Run ends, and tell the sessions to put scratch files there instead of /tmp

   Current behavior:
   Agent sessions start from session::run with thirdshift's own environment, so TMPDIR is whatever the user has (usually unset, which means /tmp). No prompt or Factory skill says where scratch files belong. Sessions write smoke-test fixtures, server logs and PR body drafts straight to /tmp (for example, /tmp/vac5docs/, /tmp/vac5.log and /tmp/pr5-body.md from the vacation#5 Run). Cleanup removes only the worktree, the local Issue branch and the temporary plugin directory, so those files stay behind. The README's "What sessions leave behind" section calls this "by design".

   Desired behavior:

   • Each Run creates one temp directory for its agent sessions, under thirdshift's own temp location (honoring the TMPDIR thirdshift was started with), with a recognizable prefix such as thirdshift-tmp-.
   • Every agent session in the Run (implement, continuation, conflict Repair, CI-fix Repair) runs with TMPDIR set to that directory.
   • The directory is outside the worktree. The Failed run path commits everything in the worktree, so scratch files must never land there.
   • The directory and everything in it are removed when the Run ends, on every path the plugin directory is removed on: success, Failed run, and interrupt.
   • Each session is told, through the prompts or the Factory skills (whichever fits better), to put temporary and scratch files (fixtures, logs, drafts, downloaded one-off tools) under $TMPDIR and never write to /tmp directly. The skills are namespaced plugin copies (ADR-0001), so an instruction in them must hold up for headless sessions.
   • The README's "What sessions leave behind" section describes the new behavior: scratch files go to a per-Run temp directory that cleanup removes. This is best-effort, because auto mode can't stop an agent from writing elsewhere. Anything written outside it, such as toolchains installed under ~, still stays.

   Key interfaces:

   • session::run(kind, worktree, plugin_dir, prompt, log): needs the Run's temp directory (a new parameter, or a small struct bundling the Run's session environment) and sets TMPDIR on the claude command.
   • A per-Run temp directory owner shaped like Plugin (a tempfile::TempDir that is removed on drop), created alongside the plugin where sessions are set up.
   • The prompt builders in the prompt module (fresh, continuation, conflict_repair, ci_fix_repair), or the Factory implement skill, carry the scratch-file instruction.

   Acceptance criteria:

   • An integration test (using the fake claude in tests/fakes/) in which the fake session writes a file into $TMPDIR shows that $TMPDIR is not the thirdshift process's own TMPDIR and not inside the worktree, and that the file and its directory are gone after a successful Run (assert_cleaned_up still passes).
   • The same holds for a Failed run, and the scratch file is not in the commit pushed by the Failed run path.
   • Repair sessions get the same TMPDIR as the implement session in the same Run.
   • Every prompt an agent session is started with (or the skill it invokes) tells the session to use $TMPDIR for scratch files and not /tmp; a test asserts this for the prompts, if the instruction lives there.
   • The README's "What sessions leave behind" section is updated as described above.
   • cargo test and cargo clippy pass.

   Out of scope:

   • Stopping sessions from installing toolchains or writing under ~ (for example, ~/.local/jdk/). That stays documented as by design.
   • Sandboxing or blocking writes to /tmp (for example, with namespaces or permission rules).
   • Cleaning up files earlier Runs left in /tmp.
   • A git-ignored scratch directory inside the worktree (rejected: the Failed run path would commit it).
3. JacobStephens2

   added

   enhancementNew feature or requestNew feature or request

   ready-for-agentFully specified, ready for an AFK agentFully specified, ready for an AFK agent

   and removed

   needs-triageMaintainer needs to evaluate this issueMaintainer needs to evaluate this issue

   on Sep 25, 2026
4. JacobStephens2

   closed this as completedon Sep 25, 2026