chore(cli): update Bun to 1.4.0

[marius-kilocode]

What Problem This Solves

Bun 1.3.14 forced the compiled CLI release build to disable code splitting because Bun generated invalid cross-chunk re-exports. The workaround duplicated shared modules across CLI entry points and prevented the release build from using Bun's newer compiler improvements.

The Bun 1.4.0 upgrade removes that limitation and keeps local, CI, and release builds on one supported runtime.

Why This Change Was Made

• Pin the repository, CI setup, Nix package, container image, documentation, and upstream-merge metadata to stable Bun 1.4.0.
• Enable splitting: true for compiled CLI targets.
• Keep the published CLI binaries, Docker image, and VS Code extension on the same compiled Bun 1.4.0 artifacts.
• Add narrow compatibility handling for Bun 1.4.0 FFI pointer types, process event types, and rejected SSE reader cancellations.

User Impact

Artifact or workflow	Before	After	Impact
Compiled CLI build	Bun 1.3.14, splitting disabled	Bun 1.4.0, splitting enabled	Faster build and smaller binary
Published CLI binaries	Older Bun runtime and duplicated chunks	Bun 1.4.0 runtime with shared chunks	Smaller release downloads
VS Code extension	Bundled CLI built with the old path	Bundled CLI built from the Bun 1.4.0 release artifacts	Same CLI improvement in VSIX packages
bun dev	Uses the active Bun executable	Uses the active Bun executable	Source development is unchanged, but Bun 1.4.0 is the supported runtime

Evidence

Measurements use the same macOS ARM64 worktree and cached build inputs. The baseline uses Bun 1.3.14 with the required workaround; the updated build uses Bun 1.4.0 with code splitting enabled.

Metric	Bun 1.3.14	Bun 1.4.0	Change
Cached compiled CLI build	10.88 s	8.59 s	21.0% faster
CLI binary size	188,755,682 bytes	146,123,762 bytes	22.6% smaller
WebSocket test median, 3 runs	3.43 s	3.36 s	2.0% faster, within noise

The first CI run exposed a Bun 1.4.0 stream-cancellation difference in provider/header-timeout.test.ts. The fix handles the rejected reader.cancel() promise in both SSE wrappers while preserving the timeout and abort behavior. After that fix and a merge from main, all required Linux, macOS, and Windows CI checks passed.

The published PR also includes the required Bun 1.4.0 FFI and process-type compatibility shims, plus the coordinated package quarantine exception for the newly released Bun type packages.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (13 files)

• .changeset/update-bun-1-4.md
• CONTRIBUTING.md
• bun.lock
• bunfig.toml
• nix/bun.nix
• package.json
• packages/containers/bun-node/Dockerfile
• packages/kilo-docs/pages/contributing/development-environment.md
• packages/kilo-vscode/docs/mercury-next-edit-testing.html
• packages/opencode/script/build.ts
• packages/opencode/src/bun-compat.d.ts
• patches/@ff-labs%2Ffff-bun@0.9.4.patch
• script/upstream/package.json

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_{Reviewed by grok-4.6 · Input: 90.5K · Output: 20.9K · Cached: 663.7K}

_{Review guidance: REVIEW.md from base branch main}

[iscekic]

Approved, bot remarks below, feel free to ignore