fix(acp): emit diff content block directly from edit metadata (avoid applyPatch)

[skavans]

Issue for this PR

Closes#37266

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

The toolCall.content block (type: "diff") is silently dropped from edit permission requests whenever the edited hunk sits entirely inside an indented block. ACP clients then have no diff to show next to the approval prompt. The actual edit still applies correctly via the fuzzy replacers in edit.ts — this is a preview-only regression.

Why it happens:edit.ts trims common indentation from the unified diff (trimDiff) for readability. Then permission.ts::diffContentForPatch tries to reconstruct the result by re-applying that indentation-stripped patch via applyPatch(fileContent, trimmedDiff). applyPatch returns false because the context lines no longer match the file (their indentation was removed). With fuzzFactor: 0 there is no tolerance, so the hunk can't be located, and no content block is emitted.

This was introduced by #34079, which added the applyPatch reconstruction. The earlier PR #31783 by @ReeSilva proposed a simpler approach — passing oldString/newString directly from the edit tool metadata — but was closed in favor of #34079's broader scope. This PR revives that approach and extends it to the multi-file path (apply_patch.ts).

The fix:edit.ts, write.ts, and apply_patch.ts already compute contentOld/contentNew before asking for permission. Pass them through metadata (oldString/newString), and in permission.ts read them directly instead of re-deriving via applyPatch. This avoids the trim/apply round-trip entirely and has no failure mode.

How did you verify your code works?

Standalone repro from the issue — previously applyPatch(trimmed) → FAILED; after this change the content block is always emitted:

import{applyPatch,createTwoFilesPatch}from"diff"// trimDiff, copied verbatim from packages/opencode/src/tool/edit.tsfunctiontrimDiff(diff){constlines=diff.split("\n")constcontentLines=lines.filter((l)=>(l.startsWith("+")||l.startsWith("-")||l.startsWith(" "))&&!l.startsWith("---")&&!l.startsWith("+++"),)if(contentLines.length===0)returndiffletmin=Infinityfor(constlineofcontentLines){constc=line.slice(1)if(c.trim().length>0){constm=c.match(/^(\s*)/);if(m)min=Math.min(min,m[1].length)}}if(min===Infinity||min===0)returndiffreturnlines.map((l)=>(l.startsWith("+")||l.startsWith("-")||l.startsWith(" "))&&!l.startsWith("---")&&!l.startsWith("+++")
? l[0]+l.slice(1).slice(min) : l,).join("\n")}constold=`function compute() { const v0 = 0 const v1 = 1 const v2 = 2 const v3 = 3 const v4 = 4 const v5 = 5 const v6 = 6 const v7 = 7 const v8 = 8 const v9 = 9 const v10 = 10 return sum}`constnext=old.replace(" const v5 = 5"," const v5 = 50")constraw=createTwoFilesPatch("f","f",old,next)consttrimmed=trimDiff(raw)console.log("applyPatch(raw): ",applyPatch(old,raw)===false ? "FAILED" : "OK")console.log("applyPatch(trimmed): ",applyPatch(old,trimmed)===false ? "FAILED <- no preview" : "OK")

Also tested end-to-end against an ACP client over opencode acp: edits inside indented blocks now render a diff next to the approval prompt, matching edits near the top level.

Screenshots / recordings

N/A — not a UI change in the TUI. The effect is visible only in external ACP clients.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

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