[containers-shared] Fix Docker spawn opening console windows on Windows

[petebacondarwin]

Fixes #12963.

When running wrangler deploy on Windows with [[containers]] configured, the Docker build step spawns numerous console windows that flash open during the build process.

This is caused by detached: true in child_process.spawn() calls — on Windows, detached: true gives each child process its own visible console window (Node.js docs).

The fix:

• Sets detached conditionally: true on Unix/macOS (needed for process group cleanup via process.kill(-pid)), false on Windows
• Adds windowsHide: true to further suppress console windows on Windows (no-op on other platforms)
• Guards the process.kill(-child.pid) abort logic with a platform check: uses child.kill() on Windows since negative-PID process group kill is a Unix-only concept

Both dockerBuild() in build.ts and runDockerCmd() in utils.ts are updated.

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because: This is a platform-specific behavior change (Windows detached and windowsHide options). Existing tests pass. The behavior difference is only observable on Windows with Docker Desktop, which cannot be tested in CI. The logic change is minimal and well-documented in Node.js docs.
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: This is a bug fix with no user-facing API changes.

---

[changeset-bot]

🦋 Changeset detected

Latest commit: 777809a

The changes in this PR will be included in the next version bump.

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[workers-devprod]

Codeowners approval required for this PR:

• @cloudflare/wrangler
• ✅ @cloudflare/cloudchamber

Show detailed file reviewers

• packages/containers-shared/src/build.ts: [@cloudflare/wrangler]
• packages/containers-shared/src/utils.ts: [@cloudflare/wrangler]

[github-actions]

✅ All changesets look good

[ask-bonk]

I've reviewed the full diff and both affected files. Let me now analyze the changes:

1. detached: process.platform !== "win32" - Correct. On Windows, detached: true creates new console windows. On Unix, it's needed for process group management.

2. windowsHide: true - Correct. Belt-and-suspenders approach, no-op on non-Windows.

3. Abort logic platform guard - On Windows, falls back to child.kill() since process.kill(-pid) (negative PID / process group kill) is a Unix-only concept. This is correct.

4. Changeset targets "wrangler": patch — the changed package is @cloudflare/containers-shared which is private and not published independently. Since containers-shared is bundled into wrangler, attributing the changeset to wrangler is correct.

5. Code duplication — The spawn options and abort logic are now identically duplicated between build.ts and utils.ts. This is a pre-existing concern and not introduced by this PR (the duplication existed before), so not actionable here.

6. Windows abort only kills the direct child — On Windows with detached: false, child.kill() only terminates the direct child process, not its descendants. Docker's child processes (buildkit, etc.) could potentially be left behind. However, this is a pragmatic trade-off: the previous behavior on Windows was worse (flashing console windows), and Docker Desktop on Windows generally handles its own subprocess cleanup. This is not a regression since detached: true + process.kill(-pid) on Windows would have been unreliable anyway (the Node.js docs state the behavior differs).

The logic is sound, the platform checks are correct, and the comments are accurate.

LGTM

github run

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.

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commit: 777809a