refactor(agents): use diff native APIs

src/agents/modes/interactive/components/diff.ts

@@ -3,7 +3,7 @@
  *
  * Produces colored line and intra-line highlights for the Pi TUI review surfaces.
  */
-import * as Diff from "diff";
+import { diffWords } from "diff";
 import { theme } from "../theme/theme.js";
 
 /**
@@ -37,59 +37,37 @@ function renderIntraLineDiff(
   oldContent: string,
   newContent: string,
 ): { removedLine: string; addedLine: string } {
-  const wordDiff = Diff.diffWords(oldContent, newContent);
-
   let removedLine = "";
   let addedLine = "";
-  let isFirstRemoved = true;
-  let isFirstAdded = true;
+  const seen = { added: false, removed: false };
 
-  for (const part of wordDiff) {
-    if (part.removed) {
-      let value = part.value;
-      // Strip leading whitespace from the first removed part
-      if (isFirstRemoved) {
-        const leadingWs = value.match(/^(\s*)/)?.[1] || "";
-        value = value.slice(leadingWs.length);
-        removedLine += leadingWs;
-        isFirstRemoved = false;
-      }
-      if (value) {
-        removedLine += theme.inverse(value);
-      }
-    } else if (part.added) {
-      let value = part.value;
-      // Strip leading whitespace from the first added part
-      if (isFirstAdded) {
-        const leadingWs = value.match(/^(\s*)/)?.[1] || "";
-        value = value.slice(leadingWs.length);
-        addedLine += leadingWs;
-        isFirstAdded = false;
-      }
-      if (value) {
-        addedLine += theme.inverse(value);
-      }
-    } else {
-      removedLine += part.value;
-      addedLine += part.value;
+  for (const part of diffWords(oldContent, newContent)) {
+    const kind = part.added ? "added" : part.removed ? "removed" : undefined;
+    let value = part.value;
+    if (kind) {
+      const changed = seen[kind] ? value : value.trimStart();
+      const leadingWhitespace = value.slice(0, value.length - changed.length);
+      value = leadingWhitespace + (changed ? theme.inverse(changed) : "");
+      seen[kind] = true;
+    }
+    if (!part.added) {
+      removedLine += value;
+    }
+    if (!part.removed) {
+      addedLine += value;
     }
   }
 
   return { removedLine, addedLine };
 }
 
-interface RenderDiffOptions {
-  /** File path (unused, kept for API compatibility) */
-  filePath?: string;
-}
-
 /**
  * Render a diff string with colored lines and intra-line change highlighting.
  * - Context lines: dim/gray
  * - Removed lines: red, with inverse on changed tokens
  * - Added lines: green, with inverse on changed tokens
  */
-export function renderDiff(diffText: string, _options: RenderDiffOptions = {}): string {
+export function renderDiff(diffText: string): string {
   const lines = diffText.split("\n");
   const result: string[] = [];
 

src/agents/sessions/tools/edit-diff.ts

@@ -5,7 +5,7 @@
 
 import { constants } from "node:fs";
 import { access, readFile } from "node:fs/promises";
-import * as Diff from "diff";
+import { createPatch, FILE_HEADERS_ONLY, structuredPatch } from "diff";
 import { levenshteinDistance } from "../../../shared/levenshtein-distance.js";
 import { resolveToCwd } from "./path-utils.js";
 
@@ -540,9 +540,9 @@ export function generateUnifiedPatch(
   newContent: string,
   contextLines = 4,
 ): string {
-  return Diff.createTwoFilesPatch(path, path, oldContent, newContent, undefined, undefined, {
+  return createPatch(path, oldContent, newContent, undefined, undefined, {
     context: contextLines,
-    headerOptions: Diff.FILE_HEADERS_ONLY,
+    headerOptions: FILE_HEADERS_ONLY,
   });
 }
 
@@ -555,7 +555,7 @@ export function generateDiffString(
   newContent: string,
   contextLines = 4,
 ): { diff: string; firstChangedLine: number | undefined } {
-  const hunks = Diff.structuredPatch("", "", oldContent, newContent, undefined, undefined, {
+  const hunks = structuredPatch("", "", oldContent, newContent, undefined, undefined, {
     context: contextLines,
   }).hunks;
   const oldLineCount = oldContent.split("\n").length;

src/agents/sessions/tools/edit.ts

@@ -291,13 +291,11 @@ function formatEditCall(
 }
 
 function formatEditResult(
-  args: RenderableEditArgs | undefined,
   preview: EditPreview | undefined,
   result: EditToolResultLike,
   theme: typeof import("../../modes/interactive/theme/theme.js").theme,
   isError: boolean,
 ): string | undefined {
-  const rawPath = str(args?.file_path ?? args?.path);
   const previewDiff = preview && !("error" in preview) ? preview.diff : undefined;
   const previewError = preview && "error" in preview ? preview.error : undefined;
   if (isError) {
@@ -313,7 +311,7 @@ function formatEditResult(
 
   const resultDiff = result.details?.diff;
   if (resultDiff && resultDiff !== previewDiff) {
-    return renderDiff(resultDiff, { filePath: rawPath ?? undefined });
+    return renderDiff(resultDiff);
   }
 
   return undefined;
@@ -579,13 +577,7 @@ export function createEditToolDefinition(
         }
       }
 
-      const output = formatEditResult(
-        context.args,
-        callComponent?.preview,
-        typedResult,
-        theme,
-        context.isError,
-      );
+      const output = formatEditResult(callComponent?.preview, typedResult, theme, context.isError);
       const component = (context.lastComponent as Container | undefined) ?? new Container();
       component.clear();
       if (!output) {