From c7efe8f002f8845bbdb4645c6a94e4b16e5f3d4e Mon Sep 17 00:00:00 2001
From: minpeter <minpeter@friendli.ai>
Date: Tue, 24 Feb 2026 14:07:21 +0900
Subject: [PATCH] fix(hashline-edit): preserve intentional whitespace removal
 in autocorrect
MIME-Version: 1.0
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restoreIndentForPairedReplacement() and restoreLeadingIndent() unconditionally
restored original indentation when replacement had none, preventing intentional
indentation changes (e.g. removing a tab from '\t1절' to '1절'). Skip indent
restoration when trimmed content is identical, indicating a whitespace-only edit.
---
 .../autocorrect-replacement-lines.ts          |  1 +
 .../hashline-edit/edit-operations.test.ts     | 22 +++++++++++++++++++
 .../hashline-edit/edit-text-normalization.ts  |  1 +
 3 files changed, 24 insertions(+)

diff --git a/src/tools/hashline-edit/autocorrect-replacement-lines.ts b/src/tools/hashline-edit/autocorrect-replacement-lines.ts
index 6b9d9a77..719f9d6c 100644
--- a/src/tools/hashline-edit/autocorrect-replacement-lines.ts
+++ b/src/tools/hashline-edit/autocorrect-replacement-lines.ts
@@ -159,6 +159,7 @@ export function restoreIndentForPairedReplacement(
     if (leadingWhitespace(line).length > 0) return line
     const indent = leadingWhitespace(originalLines[idx])
     if (indent.length === 0) return line
+    if (originalLines[idx].trim() === line.trim()) return line
     return `${indent}${line}`
   })
 }
diff --git a/src/tools/hashline-edit/edit-operations.test.ts b/src/tools/hashline-edit/edit-operations.test.ts
index 53910660..d66c2d94 100644
--- a/src/tools/hashline-edit/edit-operations.test.ts
+++ b/src/tools/hashline-edit/edit-operations.test.ts
@@ -177,6 +177,28 @@ describe("hashline edit operations", () => {
     expect(result).toEqual(["if (x) {", "  return 2", "}"])
   })
 
+  it("preserves intentional indentation removal (tab to no-tab)", () => {
+    //#given
+    const lines = ["# Title", "\t1절", "content"]
+
+    //#when
+    const result = applySetLine(lines, anchorFor(lines, 2), "1절")
+
+    //#then
+    expect(result).toEqual(["# Title", "1절", "content"])
+  })
+
+  it("preserves intentional indentation removal (spaces to no-spaces)", () => {
+    //#given
+    const lines = ["function foo() {", "    indented", "}"]
+
+    //#when
+    const result = applySetLine(lines, anchorFor(lines, 2), "indented")
+
+    //#then
+    expect(result).toEqual(["function foo() {", "indented", "}"])
+  })
+
   it("strips boundary echo around replace_lines content", () => {
     //#given
     const lines = ["before", "old 1", "old 2", "after"]
diff --git a/src/tools/hashline-edit/edit-text-normalization.ts b/src/tools/hashline-edit/edit-text-normalization.ts
index 8e38c50c..9bae8cc4 100644
--- a/src/tools/hashline-edit/edit-text-normalization.ts
+++ b/src/tools/hashline-edit/edit-text-normalization.ts
@@ -53,6 +53,7 @@ export function restoreLeadingIndent(templateLine: string, line: string): string
   const templateIndent = leadingWhitespace(templateLine)
   if (templateIndent.length === 0) return line
   if (leadingWhitespace(line).length > 0) return line
+  if (templateLine.trim() === line.trim()) return line
   return `${templateIndent}${line}`
 }