fix(cli): stream UTF-8 reads in read tool again

[kilo-code-bot]

Summary

The previous `lines()` always called `Encoding.read`, which buffers the entire file into memory before line splitting -- even for plain UTF-8 files that never needed encoding translation. Bad for large logs and build artifacts that the caller is going to truncate at the line / 50 KB byte cap anyway.

Optimistically stream the file as UTF-8 using a fatal-mode `TextDecoder` (with `{ stream: true }` for partial multibyte sequences across chunk boundaries). Only fall back to the iconv full-file decode when the bytes turn out not to be valid UTF-8.

The streaming + retry logic lives in a new helper at `packages/opencode/src/kilocode/text-stream.ts` so the `lines` function in `tool/read.ts` stays close to upstream OpenCode's shape.

[kilo-code-bot]

Code Review Summary

Status: 1 Issue Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	1
SUGGESTION	0

Issue Details (click to expand)

WARNING

File	Line	Issue
packages/opencode/src/kilocode/text-stream.ts	—	UTF-8 BOM regression: openUtf8 passes U+FEFF through to the consumer unchanged. For UTF-8-BOM files, the BOM leaks into line 1 of the tool output as a junk character visible to the LLM. The openDecoded fallback path (via iconv-lite) still strips BOMs, creating an inconsistency between the two paths. The main branch always stripped BOMs via Encoding.read(). Fix: add first-line BOM normalization to readLines — e.g. const line_text = count === 1 && text.charCodeAt(0) === 0xfeff ? text.slice(1) : text — or restore the first-flag stripping inside openUtf8.

Fix these issues in Kilo Cloud

Previously Resolved

• WARNING (read.ts): Encoding detection only sampled the first 4KB — resolved by switching to optimistic UTF-8 streaming
• WARNING (text-stream.ts): raw stream not destroyed on consumer early-exit — resolved by out.on("close", () => raw.destroy()) in commit bc5dc59

Files Reviewed (3 files)

• .changeset/read-stream-utf8.md - 0 issues
• packages/opencode/src/kilocode/text-stream.ts - 1 issue (latest commit: doc trimming only, no logic change)
• packages/opencode/src/tool/read.ts - 0 issues

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_{Reviewed by claude-sonnet-4.6 · 395,357 tokens}