fix(hashline-edit): align autocorrect, BOM/CRLF, and tool description with oh-my-pi

- Rewrite restoreOldWrappedLines to use oh-my-pi's span-scanning algorithm
- Add stripTrailingContinuationTokens and stripMergeOperatorChars helpers
- Fix detectLineEnding to use first-occurrence logic instead of any-match
- Fix applyAppend/applyPrepend to replace empty-line placeholder in empty files
- Enhance tool description with 7 critical rules, tag guidance, and anti-patterns

src/tools/hashline-edit/autocorrect-replacement-lines.ts

@@ -2,18 +2,63 @@ function normalizeTokens(text: string): string {
   return text.replace(/\s+/g, "")
 }
 
+function stripAllWhitespace(text: string): string {
+  return normalizeTokens(text)
+}
+
+export function stripTrailingContinuationTokens(text: string): string {
+  return text.replace(/(?:&&|\|\||\?\?|\?|:|=|,|\+|-|\*|\/|\.|\()\s*$/u, "")
+}
+
+export function stripMergeOperatorChars(text: string): string {
+  return text.replace(/[|&?]/g, "")
+}
+
 function leadingWhitespace(text: string): string {
   const match = text.match(/^\s*/)
   return match ? match[0] : ""
 }
 
 export function restoreOldWrappedLines(originalLines: string[], replacementLines: string[]): string[] {
-  if (replacementLines.length <= 1) return replacementLines
-  if (originalLines.length !== replacementLines.length) return replacementLines
-  const original = normalizeTokens(originalLines.join("\n"))
-  const replacement = normalizeTokens(replacementLines.join("\n"))
-  if (original !== replacement) return replacementLines
-  return originalLines
+  if (originalLines.length === 0 || replacementLines.length < 2) return replacementLines
+
+  const canonicalToOriginal = new Map<string, { line: string; count: number }>()
+  for (const line of originalLines) {
+    const canonical = stripAllWhitespace(line)
+    const existing = canonicalToOriginal.get(canonical)
+    if (existing) {
+      existing.count += 1
+    } else {
+      canonicalToOriginal.set(canonical, { line, count: 1 })
+    }
+  }
+
+  const candidates: { start: number; len: number; replacement: string; canonical: string }[] = []
+  for (let start = 0; start < replacementLines.length; start += 1) {
+    for (let len = 2; len <= 10 && start + len <= replacementLines.length; len += 1) {
+      const canonicalSpan = stripAllWhitespace(replacementLines.slice(start, start + len).join(""))
+      const original = canonicalToOriginal.get(canonicalSpan)
+      if (original && original.count === 1 && canonicalSpan.length >= 6) {
+        candidates.push({ start, len, replacement: original.line, canonical: canonicalSpan })
+      }
+    }
+  }
+  if (candidates.length === 0) return replacementLines
+
+  const canonicalCounts = new Map<string, number>()
+  for (const candidate of candidates) {
+    canonicalCounts.set(candidate.canonical, (canonicalCounts.get(candidate.canonical) ?? 0) + 1)
+  }
+
+  const uniqueCandidates = candidates.filter((candidate) => (canonicalCounts.get(candidate.canonical) ?? 0) === 1)
+  if (uniqueCandidates.length === 0) return replacementLines
+
+  uniqueCandidates.sort((a, b) => b.start - a.start)
+  const correctedLines = [...replacementLines]
+  for (const candidate of uniqueCandidates) {
+    correctedLines.splice(candidate.start, candidate.len, candidate.replacement)
+  }
+  return correctedLines
 }
 
 export function maybeExpandSingleLineMerge(

src/tools/hashline-edit/edit-operation-primitives.ts

@@ -134,6 +134,9 @@ export function applyAppend(lines: string[], text: string | string[]): string[]
   if (normalized.length === 0) {
     throw new Error("append requires non-empty text")
   }
+  if (lines.length === 1 && lines[0] === "") {
+    return [...normalized]
+  }
   return [...lines, ...normalized]
 }
 
@@ -142,6 +145,9 @@ export function applyPrepend(lines: string[], text: string | string[]): string[]
   if (normalized.length === 0) {
     throw new Error("prepend requires non-empty text")
   }
+  if (lines.length === 1 && lines[0] === "") {
+    return [...normalized]
+  }
   return [...normalized, ...lines]
 }
 

src/tools/hashline-edit/edit-operations.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it } from "bun:test"
 import { applyHashlineEdits, applyInsertAfter, applyReplace, applyReplaceLines, applySetLine } from "./edit-operations"
+import { applyAppend, applyPrepend } from "./edit-operation-primitives"
 import { computeLineHash } from "./hash-computation"
 import type { HashlineEdit } from "./types"
 
@@ -249,6 +250,72 @@ describe("hashline edit operations", () => {
     expect(result).toEqual(["if (x) {", "  return 3", "  return 4", "}"])
   })
 
+  it("collapses wrapped replacement span back to unique original single line", () => {
+    //#given
+    const lines = [
+      "const request = buildRequest({ method: \"GET\", retries: 3 })",
+      "const done = true",
+    ]
+
+    //#when
+    const result = applyReplaceLines(
+      lines,
+      anchorFor(lines, 1),
+      anchorFor(lines, 1),
+      ["const request = buildRequest({", "method: \"GET\", retries: 3 })"]
+    )
+
+    //#then
+    expect(result).toEqual([
+      "const request = buildRequest({ method: \"GET\", retries: 3 })",
+      "const done = true",
+    ])
+  })
+
+  it("keeps wrapped replacement when canonical match is not unique in original lines", () => {
+    //#given
+    const lines = ["const query = a + b", "const query = a+b", "const done = true"]
+
+    //#when
+    const result = applyReplaceLines(lines, anchorFor(lines, 1), anchorFor(lines, 2), ["const query = a +", "b"])
+
+    //#then
+    expect(result).toEqual(["const query = a +", "b", "const done = true"])
+  })
+
+  it("keeps wrapped replacement when same canonical candidate appears multiple times", () => {
+    //#given
+    const lines = ["const expression = alpha + beta + gamma", "const done = true"]
+
+    //#when
+    const result = applyReplaceLines(lines, anchorFor(lines, 1), anchorFor(lines, 1), [
+      "const expression = alpha +",
+      "beta + gamma",
+      "const expression = alpha +",
+      "beta + gamma",
+    ])
+
+    //#then
+    expect(result).toEqual([
+      "const expression = alpha +",
+      "beta + gamma",
+      "const expression = alpha +",
+      "beta + gamma",
+      "const done = true",
+    ])
+  })
+
+  it("keeps wrapped replacement when canonical match is shorter than threshold", () => {
+    //#given
+    const lines = ["a + b", "const done = true"]
+
+    //#when
+    const result = applyReplaceLines(lines, anchorFor(lines, 1), anchorFor(lines, 1), ["a +", "b"])
+
+    //#then
+    expect(result).toEqual(["a +", "b", "const done = true"])
+  })
+
   it("applies append and prepend operations", () => {
     //#given
     const content = "line 1\nline 2"
@@ -263,6 +330,28 @@ describe("hashline edit operations", () => {
     expect(result).toEqual("line 0\nline 1\nline 2\nline 3")
   })
 
+  it("appends to empty file without extra blank line", () => {
+    //#given
+    const lines = [""]
+
+    //#when
+    const result = applyAppend(lines, ["line1"])
+
+    //#then
+    expect(result).toEqual(["line1"])
+  })
+
+  it("prepends to empty file without extra blank line", () => {
+    //#given
+    const lines = [""]
+
+    //#when
+    const result = applyPrepend(lines, ["line1"])
+
+    //#then
+    expect(result).toEqual(["line1"])
+  })
+
   it("autocorrects single-line merged replacement into original line count", () => {
     //#given
     const lines = ["const a = 1;", "const b = 2;"]

src/tools/hashline-edit/file-text-canonicalization.ts

@@ -5,7 +5,11 @@ export interface FileTextEnvelope {
 }
 
 function detectLineEnding(content: string): "\n" | "\r\n" {
-  return content.includes("\r\n") ? "\r\n" : "\n"
+  const crlfIndex = content.indexOf("\r\n")
+  const lfIndex = content.indexOf("\n")
+  if (lfIndex === -1) return "\n"
+  if (crlfIndex === -1) return "\n"
+  return crlfIndex < lfIndex ? "\r\n" : "\n"
 }
 
 function stripBom(content: string): { content: string; hadBom: boolean } {

src/tools/hashline-edit/tool-description.ts

@@ -1,29 +1,23 @@
 export const HASHLINE_EDIT_DESCRIPTION = `Edit files using LINE#ID format for precise, safe modifications.
 
 WORKFLOW:
-1. Read the file and copy exact LINE#ID anchors.
-2. Submit one edit call with all related operations for that file.
-3. If more edits are needed after success, use the latest anchors from read/edit output.
-4. Use anchors as "LINE#ID" only (never include trailing ":content").
+1. Read target file/range and copy exact LINE#ID tags.
+2. Pick the smallest operation per logical mutation site.
+3. Submit one edit call per file with all related operations.
+4. If same file needs another call, re-read first.
+5. Use anchors as "LINE#ID" only (never include trailing ":content").
 
 VALIDATION:
  Payload shape: { "filePath": string, "edits": [...], "delete"?: boolean, "rename"?: string }
  Each edit must be one of: set_line, replace_lines, insert_after, insert_before, insert_between, replace, append, prepend
  text/new_text must contain plain replacement text only (no LINE#ID prefixes, no diff + markers)
+ CRITICAL: all operations validate against the same pre-edit file snapshot and apply bottom-up.
 
-LINE#ID FORMAT (CRITICAL - READ CAREFULLY):
-Each line reference must be in "LINE#ID" format where:
+LINE#ID FORMAT (CRITICAL):
+ Each line reference must be in "LINE#ID" format where:
  LINE: 1-based line number
  ID: Two CID letters from the set ZPMQVRWSNKTXJBYH
 
-OPERATION TYPES:
-1. set_line
-2. replace_lines
-3. insert_after
-4. insert_before
-5. insert_between
-6. replace
-
 FILE MODES:
  delete=true deletes file and requires edits=[] with no rename
  rename moves final content to a new path and removes old path
@@ -36,17 +30,34 @@ CONTENT FORMAT:
 FILE CREATION:
  append: adds content at EOF. If file does not exist, creates it.
  prepend: adds content at BOF. If file does not exist, creates it.
- CRITICAL: append/prepend are the ONLY operations that work without an existing file.
+ CRITICAL: append/prepend are the only operations that work without an existing file.
 
 OPERATION CHOICE:
- One line wrong \u2192 set_line
- Block rewrite \u2192 replace_lines
- New content between known anchors \u2192 insert_between (safest \u2014 dual-anchor pinning)
- New content at boundary \u2192 insert_after or insert_before
- New file or EOF/BOF addition \u2192 append or prepend
- No LINE#ID available \u2192 replace (last resort)
+ One line wrong -> set_line
+ Adjacent block rewrite or swap/move -> replace_lines (prefer one range op over many single-line ops)
+ Both boundaries known -> insert_between (ALWAYS prefer over insert_after/insert_before)
+ One boundary known -> insert_after or insert_before
+ New file or EOF/BOF addition -> append or prepend
+ No LINE#ID available -> replace (last resort)
 
-AUTOCORRECT (built-in \u2014 you do NOT need to handle these):
+RULES (CRITICAL):
+ 1. Minimize scope: one logical mutation site per operation.
+ 2. Preserve formatting: keep indentation, punctuation, line breaks, trailing commas, brace style.
+ 3. Prefer insertion over neighbor rewrites: anchor to structural boundaries (}, ], },), not interior property lines.
+ 4. No no-ops: replacement content must differ from current content.
+ 5. Touch only requested code: avoid incidental edits.
+ 6. Use exact current tokens: NEVER rewrite approximately.
+ 7. For swaps/moves: prefer one range operation over multiple single-line operations.
+
+TAG CHOICE (ALWAYS):
+ - Copy tags exactly from read output or >>> mismatch output.
+ - NEVER guess tags.
+ - Prefer insert_between over insert_after/insert_before when both boundaries are known.
+ - Anchor to structural lines (function/class/brace), NEVER blank lines.
+ - Anti-pattern warning: blank/whitespace anchors are fragile.
+ - Re-read after each successful edit call before issuing another on the same file.
+
+AUTOCORRECT (built-in - you do NOT need to handle these):
  Merged lines are auto-expanded back to original line count.
  Indentation is auto-restored from original lines.
  BOM and CRLF line endings are preserved automatically.

src/tools/hashline-edit/tools.test.ts

@@ -2,6 +2,7 @@ import { describe, it, expect, beforeEach, afterEach, mock } from "bun:test"
 import type { ToolContext } from "@opencode-ai/plugin/tool"
 import { createHashlineEditTool } from "./tools"
 import { computeLineHash } from "./hash-computation"
+import { canonicalizeFileText } from "./file-text-canonicalization"
 import * as fs from "node:fs"
 import * as os from "node:os"
 import * as path from "node:path"
@@ -262,4 +263,26 @@ describe("createHashlineEditTool", () => {
     expect(bytes[2]).toBe(0xbf)
     expect(bytes.toString("utf-8")).toBe("\uFEFFline1\r\nline2-updated\r\n")
   })
+
+  it("detects LF as line ending when LF appears before CRLF", () => {
+    //#given
+    const content = "line1\nline2\r\nline3"
+
+    //#when
+    const envelope = canonicalizeFileText(content)
+
+    //#then
+    expect(envelope.lineEnding).toBe("\n")
+  })
+
+  it("detects CRLF as line ending when CRLF appears before LF", () => {
+    //#given
+    const content = "line1\r\nline2\nline3"
+
+    //#when
+    const envelope = canonicalizeFileText(content)
+
+    //#then
+    expect(envelope.lineEnding).toBe("\r\n")
+  })
 })