Known Issues

Context

bun install --frozen-lockfile regressed in CI from sub-minute to multi-minute and also became noticeably slower locally for no-op installs.

Referenced CI runs:

• Faster baseline: https://github.com/trainstackhq/app/actions/runs/22264877071/job/64409029256
• Slower regression window: https://github.com/trainstackhq/app/actions/runs/22275116582/job/64435880121

What Was Measured

• CI run 22264877071 -> commit e8f7726 (2026-02-21)
• CI run 22275116582 -> commit 69bb740 (2026-02-22)
• Local no-op install timings (same machine, same Bun major/minor):
  • e8f7726: ~4s
  • 69bb740: ~15s
• Bisect across that range showed the jump starts at commit 66dfa69 (PostHog wizard commit).
• CI logs for install phase:
  • Faster run: ~16s
  • Slower run: ~137s
  • Dependency resolution/download were fast in both; most time was spent after extraction (linking/layout work).

Key Findings

• This does not appear to be caused by Bun 1.3.9 specifically (similar pattern reproduced on 1.3.4).
• Root prepare script is not the dominant factor (--ignore-scripts stayed around ~21s locally).
• Linker mode is the biggest lever in this repository:
  • Default install in current repo state: ~21-22s no-op
  • --linker=hoisted: ~0.4s no-op after first run
• expo-doctor duplicate-native-module warnings are still noisy under Bun layout and were not fully resolved by linker switching alone.

Decision

Use hoisted linking by default for now:

• Add root bunfig.toml:
  • [install]
  • linker = "hoisted"
• Pin CI install command to:
  • bun install --frozen-lockfile --linker=hoisted

This is a pragmatic mitigation to restore install speed while we continue tracking Bun/Expo ecosystem behavior.

Upstream References

• Bun install configuration (install.linker): https://bun.com/docs/pm/cli/install#configuration
• Bun issue (slow no-op install regression): https://github.com/oven-sh/bun/issues/23969
• Bun issue (monorepo/workspace install hang): https://github.com/oven-sh/bun/issues/22846