Neither half of the validation was covered. Dropping `&& -c $cached` from the wrapper left the whole file green: all three poison values fail on the pathname prefix, so none of them ever reached the character-device test. A path that matches the hiddev glob but is not a device now covers it, and it is the real case rather than a synthetic one -- the display replugs, the interface renumbers, and the cached node is gone. It is added only when the host has no such node, so a machine with the display attached cannot fail there spuriously.
The no-XDG_RUNTIME_DIR assertion had the same problem for the opposite reason: its decoy held a path the validation rejects on its own, so restoring the `${XDG_RUNTIME_DIR:-/tmp}` fallback left it passing. It asserts on the open now instead of on the contents -- a FIFO with no writer blocks whoever opens it, so a wrapper that consults the path hangs and one that ignores it exits. mkfifo is atomic and fails outright if the path is taken, so it still neither overwrites a file nor follows a symlink at the fixed path.
Clearing created_tmp_cache as soon as the decoy is removed keeps this run's EXIT trap from deleting a concurrent run's decoy at the same fixed path, which would have let that run pass against the old code.
🤖 Generated by Opus 5 in Claude Code.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Codex XHigh <noreply@openai.com>
The /tmp-fallback case did check-then-create on a fixed /tmp name, a
TOCTOU/symlink race, and the EXIT trap only cleaned $TMPDIR. Create the decoy
atomically with noclobber (O_EXCL) so it refuses to overwrite an existing file
or follow a symlink at that path, and remove it on exit only when this test
created it. The fixed path is required (it is exactly the path the old code
would form), so a random mktemp name cannot replace it. Addresses the Copilot
review on #8198; the wrapper fix is unchanged.
The cached device path was trusted for merely existing, not for being a hiddev node, and fell back to a predictable /tmp path when XDG_RUNTIME_DIR was unset. Validate the cache shape (hiddev char device) and cache only under the user-private runtime dir; asdcontrol already gates non-Apple devices downstream, so this is defense-in-depth in the layer Omarchy owns.
