fix(tools): isolate fuzzy-equivalent edit no-ops

vincentkoc · vincentkoc · commit be67a514a2a6 · 2026-06-26T15:28:16.000-07:00
diff --git a/src/agents/sessions/tools/edit-diff.ts b/src/agents/sessions/tools/edit-diff.ts
@@ -455,6 +455,29 @@ export function validateNoOpEditTargets(
   }
 }
 
+export function splitNoOpEdits(
+  normalizedContent: string,
+  edits: Edit[],
+  path: string,
+): { noOpEdits: Edit[]; realEdits: Edit[] } {
+  const noOpEdits: Edit[] = [];
+  const realEdits: Edit[] = [];
+  for (const edit of edits) {
+    const fuzzyNoOp = normalizeForFuzzyMatch(edit.oldText) === normalizeForFuzzyMatch(edit.newText);
+    if (edit.oldText === edit.newText || fuzzyNoOp) {
+      applyEditsToNormalizedContent(
+        normalizedContent,
+        [{ oldText: edit.oldText, newText: "" }],
+        path,
+      );
+      noOpEdits.push(edit);
+    } else {
+      realEdits.push(edit);
+    }
+  }
+  return { noOpEdits, realEdits };
+}
+
 /**
  * Compute the diff for one or more edit operations without applying them.
  * Used for preview rendering in the TUI before the tool executes.
@@ -496,8 +519,7 @@ export async function computeEditsDiff(
     // Strip BOM before matching (LLM won't include invisible BOM in oldText)
     const { text: content } = stripBom(rawContent);
     const normalizedContent = normalizeToLF(content);
-    const noOpEdits = edits.filter((edit) => edit.oldText === edit.newText);
-    const realEdits = edits.filter((edit) => edit.oldText !== edit.newText);
+    const { noOpEdits, realEdits } = splitNoOpEdits(normalizedContent, edits, path);
     validateNoOpEditTargets(normalizedContent, noOpEdits, realEdits, path);
     if (realEdits.length === 0) {
       return { diff: "", firstChangedLine: undefined };
diff --git a/src/agents/sessions/tools/edit.test.ts b/src/agents/sessions/tools/edit.test.ts
@@ -423,6 +423,25 @@ describe("edit tool", () => {
     await expect(fs.readFile(filePath, "utf-8")).resolves.toBe("bazbar\n");
   });
 
+  it("preserves unrelated whitespace beside a fuzzy-equivalent no-op", async () => {
+    const filePath = await createTempFile("foo  \nkeep  \n");
+    const tool = createEditTool(tmpDir);
+
+    await tool.execute(
+      "call-1",
+      {
+        path: filePath,
+        edits: [
+          { oldText: "foo  ", newText: "foo" },
+          { oldText: "keep", newText: "changed" },
+        ],
+      },
+      undefined,
+    );
+
+    await expect(fs.readFile(filePath, "utf-8")).resolves.toBe("foo  \nchanged  \n");
+  });
+
   it("rejects duplicate no-op entries", async () => {
     const filePath = await createTempFile("foo\n");
     const tool = createEditTool(tmpDir);
diff --git a/src/agents/sessions/tools/edit.ts b/src/agents/sessions/tools/edit.ts
@@ -27,6 +27,7 @@ import {
   generateUnifiedPatch,
   normalizeToLF,
   restoreLineEndings,
+  splitNoOpEdits,
   stripBom,
   validateNoOpEditTargets,
 } from "./edit-diff.js";
@@ -42,10 +43,6 @@ type EditRenderState = {
   callComponent?: EditCallRenderComponent;
 };
 
-function filterNoOpEdits(edits: Edit[]): Edit[] {
-  return edits.filter((edit) => edit.oldText !== edit.newText);
-}
-
 const replaceEditSchema = Type.Object(
   {
     oldText: Type.String({
@@ -406,7 +403,7 @@ export function createEditToolDefinition(
           throw new Error("Operation aborted");
         }
 
-        const realEdits = filterNoOpEdits(originalEdits);
+        let realEdits: Edit[] = [];
 
         try {
           await ops.access(absolutePath);
@@ -430,7 +427,9 @@ export function createEditToolDefinition(
           const { bom, text: content } = stripBom(rawContent);
           const originalEnding = detectLineEnding(content);
           const normalizedContent = normalizeToLF(content);
-          const noOpEdits = originalEdits.filter((edit) => edit.oldText === edit.newText);
+          const editSets = splitNoOpEdits(normalizedContent, originalEdits, path);
+          const noOpEdits = editSets.noOpEdits;
+          realEdits = editSets.realEdits;
           validateNoOpEditTargets(normalizedContent, noOpEdits, realEdits, path);
           if (realEdits.length === 0) {
             return {
