maintenance(shell): guard against unwritable inherited TMPDIR in headless contexts

[abarrows]

Problem

The 24/7 headless Mac mini agent (and any launchd-launched shell) inherits the generic macOS fallback temp dir:

TMPDIR=/var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/T   # owned root:wheel, mode 0700

instead of the per-user temp — because a launchd-less/headless context never sets up the DARWIN_USER_TEMP_DIR bootstrap. That directory is not writable by the user, so any tool that writes to $TMPDIR fails with EACCES:

• vitest run — its coverage provider mkdirs a working dir under $TMPDIR
• npm, esbuild, and other temp-writing tooling, intermittently

It is not a sandbox/permissions issue — the bad TMPDIR is inherited from the launch environment.

Fix

Add a guard to shell/.zprofile that repoints TMPDIR/TMP/TEMP at ~/.claude/tmp only when the inherited value is unset or not writable. Healthy interactive machines (which get a proper writable per-user temp) are left untouched.

if [ -z "$TMPDIR" ] || [ ! -w "${TMPDIR%/}" ]; then
  export TMPDIR="$HOME/.claude/tmp"
  export TMP="$TMPDIR"
  export TEMP="$TMPDIR"
  mkdir -p "$TMPDIR"
fi

Testing

• bash -n and zsh -n pass.
• Guard verified across states: unset → override; root-owned zz fallback → override; writable dir / real per-user temp → keep system temp.

Relates to the Mac mini agent hardening (WR-18897). Claude Code itself is already covered live via env.TMPDIR in ~/.claude/settings.json; this extends the fix to the whole shell-launched agent context.

🤖 Generated with Claude Code

Summary by Sourcery

Enhancements:

• Add a zprofile guard that rewrites TMPDIR/TMP/TEMP to a per-user temp directory when the inherited TMPDIR is unset or not writable to prevent EACCES failures in headless environments.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adds a guarded TMPDIR/TMP/TEMP override in the shell profile to ensure a writable temp directory in headless or launchd-launched contexts while leaving normal interactive shells untouched.

Flow diagram for guarded TMPDIR override in .zprofile

flowchart TD
  A[Shell startup
.zprofile] --> B[Check TMPDIR is set]
  B -->|unset| D[Override TMPDIR TMP TEMP to ~/.claude/tmp]
  B -->|set| C[Check TMPDIR is writable]
  C -->|not writable| D
  C -->|writable| E[Keep inherited TMPDIR]
  D --> F[mkdir -p ~/.claude/tmp]
  F --> G[Continue shell init]
  E --> G

Loading

File-Level Changes

Change	Details	Files
Guard TMPDIR/TMP/TEMP to point to a user-writable temp directory when the inherited TMPDIR is unset or not writable.	Insert a comment block documenting the macOS headless TMPDIR issue and the rationale for the guard. Add a conditional that detects unset or non-writable TMPDIR (trimming any trailing slash) before overriding. Export TMPDIR, TMP, and TEMP to a user-specific temp path under the home directory and ensure it exists via mkdir -p. Place the guard early in the profile so later commands run with a valid temp directory while preserving system temp on healthy interactive shells.	shell/.zprofile

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