fix(web): align outputFileTracingRoot with turbopack.root for monorepo

[kilo-code-bot]

Summary

• Fix the Turbopack build failure caused by outputFileTracingRoot and turbopack.root diverging during vercel build --prod.
• The root cause: vercel build sets NEXT_PRIVATE_OUTPUT_TRACE_ROOT to the project directory (apps/web), which becomes the default outputFileTracingRoot. When only turbopack.root was set to the monorepo root (../..), Next.js detected a mismatch and overrode turbopack.root with the wrong outputFileTracingRoot value, causing next/package.json resolution to fail.
• The fix explicitly sets both outputFileTracingRoot and turbopack.root to the same monorepo root (resolve(import.meta.dirname, '../..')), ensuring they stay in sync regardless of the Vercel CLI's default.

Verification

• CI build check: pass (pnpm run build / next build)
• CI typecheck check: pass
• CI lint check: pass
• Reviewed Next.js config resolution source (packages/next/src/server/config.ts) to confirm that explicit outputFileTracingRoot overrides the NEXT_PRIVATE_OUTPUT_TRACE_ROOT env var default, and that matching values bypass the "both set but differ" warning.

Visual Changes

N/A

Reviewer Notes

• The vercel build CLI does NOT set link.repoRoot when using prebuilt deploys via vercel link + vercel build --prod in CI, so NEXT_PRIVATE_OUTPUT_TRACE_ROOT defaults to the CWD (apps/web), not the monorepo root.
• Next.js 16.1.6 behavior: when both outputFileTracingRoot and turbopack.root are set but differ, Next.js warns and uses outputFileTracingRoot, overriding turbopack.root. This is why only setting turbopack.root was insufficient.
• The Vercel adapter path (NEXT_ADAPTER_PATH) is NOT enabled for Next.js 16.1.6 (minimum is v16.2.0-canary.28), so no adapter-level config override is in play.

Built for John Fawcett by Kilo for Slack

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (1 files)

• apps/web/next.config.mjs

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_{Reviewed by gpt-5.4-20260305 · 91,654 tokens}