vitest worker SIGBUS on /dev/shm-constrained hosts with task cache enabled

[TheHolyWaffle]

Describe the bug

On any host with a small /dev/shm (e.g. the default 64 MiB on GitLab Kubernetes runners, or Docker's default 64 MiB), vp run ... test reproducibly SIGBUSes a vitest forked worker as soon as the task's file-access tracking has written enough path records to fill /dev/shm:

Bus error (core dumped)
⎯⎯⎯⎯⎯⎯ Unhandled Errors ⎯⎯⎯⎯⎯⎯
Error: [vitest-pool]: Worker forks emitted error.
Caused by: Error: Worker exited unexpectedly

I probed the child worker env mid-run and /dev/shm usage climbs fast:

SHM usage: Filesystem      Size  Used Avail Use% Mounted on
shm              64M   60M  4.6M  93% /dev/shm

This matches vite-task's 4 GiB shared-memory IPC mapping (fspy::ipc::SHM_CAPACITY = 4 * 1024 * 1024 * 1024, https://github.com/voidzero-dev/vite-task/blob/main/crates/fspy/src/ipc.rs): once a child touches pages that can't be backed by /dev/shm, the mapping faults with SIGBUS.

Setting cache: false on the task resolves UserCacheConfig::Disabled in vite_task_graph::config, which skips the fspy IPC channel entirely, and the same workload completes cleanly.

I don't intend to submit a PR but I'm happy to test patches.

Reproduction

https://github.com/TheHolyWaffle/vite-plus-sigbus-repro

Steps to reproduce

git clone https://github.com/TheHolyWaffle/vite-plus-sigbus-repro
cd vite-plus-sigbus-repro
npm ci

# Fails — "Bus error (core dumped)" + "Worker exited unexpectedly" after ~10s
docker run --rm --shm-size=64m -v "$PWD":/work -w /work node:24.15.0 \
  bash -c 'npm ci --prefer-offline && npx vp run --filter "*" test --no-cache'

Then change the test task in vite.config.ts from { command: 'vp test --run' } to { command: 'vp test --run', cache: false } and re-run — passes cleanly (~49 s).

The repo also has a .github/workflows/repro.yml that runs both cases on ubuntu-latest under docker.

System Info

$ npx vp --version
VITE+ - The Unified Toolchain for the Web

vp v0.0.0

Local vite-plus:
  vite-plus  v0.1.19

Tools:
  vite             v8.0.8
  rolldown         v1.0.0-rc.16
  vitest           v4.1.4
  oxfmt            v0.45.0
  oxlint           v1.60.0
  oxlint-tsgolint  v0.21.1
  tsdown           v0.21.9

$ npx vp env current
error: Command 'env' not found
# `vp env current` isn't recognized as a subcommand on 0.1.19 — not sure what
# the template expects here; listing node + uname below instead.

$ node --version
v24.15.0

$ uname -a
Linux 6.6.119-0-virt #1-Alpine SMP PREEMPT_DYNAMIC 2025-12-10 08:04:08 aarch64 GNU/Linux

# Host: node:24.15.0 container, glibc (Debian base), aarch64 on Rancher Desktop.
# Also reproduced on x86_64 GitLab K8s runners with node:24.15.0.

Versions tested: vite-plus 0.1.16 and 0.1.19 — both affected.
Pre-fspy versions (0.1.14) are not affected on the same workload.Failing run (cache enabled, default):

=== RUN ===
 RUN  /work

⎯⎯⎯⎯⎯⎯ Unhandled Errors ⎯⎯⎯⎯⎯⎯

Vitest caught 1 unhandled error during the test run.

⎯⎯⎯⎯⎯⎯ Unhandled Error ⎯⎯⎯⎯⎯⎯⎯
Error: [vitest-pool]: Worker forks emitted error.
 ❯ EventEmitter.<anonymous> node_modules/@voidzero-dev/vite-plus-test/dist/chunks/cli-api.lDy4N9kC.js:3444:27
 ❯ EventEmitter.emit node:events:509:28
 ❯ ChildProcess.emitUnexpectedExit node_modules/@voidzero-dev/vite-plus-test/dist/chunks/cli-api.lDy4N9kC.js:3011:24
 ❯ ChildProcess.emit node:events:509:28
 ❯ Process.ChildProcess._handle.onexit node:internal/child_process:295:12

Caused by: Error: Worker exited unexpectedly
 ❯ ChildProcess.emitUnexpectedExit node_modules/@voidzero-dev/vite-plus-test/dist/chunks/cli-api.lDy4N9kC.js:3010:35
 ❯ ChildProcess.emit node:events:509:28
 ❯ Process.ChildProcess._handle.onexit node:internal/child_process:295:12

 Test Files  (1)
      Tests  (1)
     Errors  1 error
   Duration  10.13s

Bus error (core dumped)

---

Passing run with `cache: false`:

=== RUN (cache: false) ===
$ vp test --run --no-cache ⊘ cache disabled
 RUN  /work

 ✓ packages/heavy-io-test/src/heavy.spec.ts (1 test) 48896ms
 Test Files  1 passed (1)
      Tests  1 passed (1)
   Duration  49.02s

---

Possible fixes:

1. Probe /dev/shm size at startup and either reduce SHM_CAPACITY to fit, or fall back to a file/pipe-backed IPC.
2. When the first write to the shared mapping fails, degrade gracefully with a warning instead of producing SIGBUS in the test worker.
3. CLI `--no-cache` disables cache hit/store but still resolves the task to UserCacheConfig::Enabled, so fspy tracking still runs. Either make --no-cache imply no tracking (what users typically expect) or document the distinction so `cache: false` is the obvious knob for CI.

Used Package Manager

npm

Logs

Validations

• Read the Contributing Guidelines.
• Check that there isn't already an issue for the same bug.
• Confirm this is a Vite+ issue and not an upstream issue (Vite, Vitest, tsdown, Rolldown, or Oxc).
• The provided reproduction is a minimal reproducible example.