fix: Revert pnpm from 10.27.0 to 10.26.2 (#3022)

[KATO-Hiro]

close #3022

Summary by CodeRabbit

• Bug Fixes

  • Resolved out-of-memory crashes occurring in the development server caused by a package manager incompatibility that altered the global store structure.

• Documentation

  • Added comprehensive investigation notes documenting symptoms, root cause analysis, and remediation steps for the development environment stability issue.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

This PR resolves a memory leak in pnpm v10.27.0 that caused the development server to crash with out-of-memory errors. The fix downgrades pnpm to v10.26.2 and includes comprehensive documentation of the investigation and remediation process.

Changes

Cohort / File(s)	Summary
Documentation: pnpm 10.27.0 Regression Report docs/dev-notes/2026-01-02/pnpm-10.27-regression/report.md	New documentation detailing memory leak investigation, root cause (semi-breaking change in pnpm v10.27.0 altering global store structure), and remediation steps (downgrade to 10.26.2). Includes symptom verification, environment notes, and future action suggestions.
Package Manager Downgrade package.json	Updated pnpm version from 10.27.0 to 10.26.2 in both packageManager field and devDependencies to resolve the memory leak.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A leaky heap caused quite the fright,
Our dev server crashed mid-night!
Version down, ten-twenty-six,
Memory mends—no more fix!
Watch mode runs, and all feels right. 🎉

Pre-merge checks

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'fix: Revert pnpm from 10.27.0 to 10.26.2' directly and clearly summarizes the main change—reverting the pnpm version as the remediation for the dev server OOM issue.
Linked Issues check	✅ Passed	The code changes directly address the linked issue #3022 by reverting pnpm to 10.26.2, which resolves the heap OOM error preventing the dev server from starting.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to the issue: package.json version updates and a documentation report detailing the investigation and remediation. No out-of-scope modifications detected.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

docs/dev-notes/2026-01-02/pnpm-10.27-regression/report.md (1)

44-44: Consider using proper heading syntax.

Lines 44 and 58 use bold emphasis for what appear to be section headings. Consider converting them to proper Markdown headings for better document structure and to resolve the markdownlint warnings.

🔎 Suggested changes

For line 44:

-**pnpm v10.27.0 の semi-breaking change**
+### pnpm v10.27.0 の semi-breaking change

For line 58:

-**pnpm をダウングレード：v10.27.0 → v10.26.2**
+### pnpm をダウングレード：v10.27.0 → v10.26.2

Also applies to: 58-58

📜 Review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Cache: Disabled due to data retention organization setting

Knowledge base: Disabled due to data retention organization setting

📥 Commits

Reviewing files that changed from the base of the PR and between 1761c55 and fa39cc1.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (2)

• docs/dev-notes/2026-01-02/pnpm-10.27-regression/report.md
• package.json

🧰 Additional context used

🪛 markdownlint-cli2 (0.18.1)

docs/dev-notes/2026-01-02/pnpm-10.27-regression/report.md

44-44: Emphasis used instead of a heading

(MD036, no-emphasis-as-heading)

---

58-58: Emphasis used instead of a heading

(MD036, no-emphasis-as-heading)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: preview

🔇 Additional comments (3)

package.json (2)

91-91: Consistent version across package.json.

The packageManager field correctly matches the pnpm devDependency version (10.26.2), ensuring consistency throughout the package configuration.

---

48-48: Downgrade to pnpm 10.26.2 is justified and secure.

This change correctly addresses the heap out-of-memory issue by avoiding the semi-breaking changes introduced in pnpm 10.27.0. The 10.27.0 release modified the global virtual store structure (moving unscoped packages to an "@" directory and registering projects under {storeDir}/v10/projects/), which requires store migration. Version 10.26.2 is stable with no known security advisories and includes the latest security defaults. The change is approved.

docs/dev-notes/2026-01-02/pnpm-10.27-regression/report.md (1)

1-132: Excellent documentation of the investigation and resolution.

This document provides comprehensive documentation of the memory issue investigation, including:

• Clear problem symptoms and error messages
• Systematic hypothesis testing with results
• Root cause analysis with external references
• Step-by-step resolution instructions
• Acknowledgment of environment-specific factors and uncertainty

The thorough documentation will be valuable for future maintenance and similar issues.

[KATO-Hiro]

LGTM