edit.ts: oldString not found error does not include file content, causing AI to guess blindly

Description

File: packages/core/src/tool/edit.ts:141,146-151

const source = decodeUtf8(yield* unableToEdit(fs.readFile(readable.canonical)))
// ...
if (replacements === 0) {
  return yield* new ToolFailure({
    message: "Could not find oldString in the file. It must match exactly...",
  })
}

source (L141) already holds the full file content, but the error at L146-151 discards it. AI gets "oldString not found" with no file-state information → must guess the correct text → wastes turns → hits MAX_STEPS.

Fix: Include a snippet of source.text in the error message.

OpenCode version

v1.16.0 (commit 3cf1cef)

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• [BUG]: Prompt/instruction gaps — 5/7 prompts missing read-before-edit, edit errors encourage guessing #30792: Same author, same root problem — edit error messages encourage guessing rather than re-reading the file. Gap 2 in that issue explicitly covers the edit.ts error message fix requested here.
• Bug Model enters infinite loop due to hallucinated oldString in edit tool calls #21850: Reports the same symptom — AI loops on hallucinated oldString because the error message provides no file-state context.

If this is intentionally a narrower, focused follow-on to #30792, please clarify that relationship in the issue description.

Reproduction: edit.ts oldString error lacks file content

The edit tool error messages tell the AI to "match exactly" or "provide more context" but NEVER tell the AI to re-read the file for the current content. Combined with replaceAll: true, a short common string matched multiple times can corrupt the file without the AI ever calling Read.

This is the root cause of the infinite retry loop described in #21850.

Suggested fix: change error messages to include "Use the Read tool to re-read the file first, or check its current content."

已提交此问题的修复 PR #31892（tool error handling, read-before-edit enforcement）