feat: improve diff tool display and token efficiency

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- Improved diff tool UI to truncate full commit SHAs to 7 characters, use RepoBadge component for repository display, and output diffs in git-diff format instead of JSON for better token efficiency. [#1146](https://github.com/sourcebot-dev/sourcebot/pull/1146)
+
 ## [4.16.14] - 2026-04-21
 
 ### Added

packages/web/src/features/chat/components/chatThread/tools/getDiffToolComponent.tsx

@@ -2,6 +2,14 @@
 
 import { Separator } from '@/components/ui/separator';
 import { GetDiffMetadata, ToolResult } from '@/features/tools';
+import { RepoBadge } from './repoBadge';
+
+function truncateSha(ref: string): string {
+    if (/^[0-9a-f]{40}$/i.test(ref)) {
+        return ref.substring(0, 7);
+    }
+    return ref;
+}
 
 export const GetDiffToolComponent = ({ metadata }: ToolResult<GetDiffMetadata>) => {
     const fileCount = metadata.files.length;
@@ -10,16 +18,14 @@ export const GetDiffToolComponent = ({ metadata }: ToolResult<GetDiffMetadata>)
         <div className="flex items-center gap-2 select-none cursor-default text-sm text-muted-foreground">
             <span className="flex-shrink-0">Compared</span>
             <span className="text-xs font-mono bg-muted px-1.5 py-0.5 rounded text-foreground">
-                {metadata.base}
+                {truncateSha(metadata.base)}
             </span>
             <span className="flex-shrink-0">to</span>
             <span className="text-xs font-mono bg-muted px-1.5 py-0.5 rounded text-foreground">
-                {metadata.head}
+                {truncateSha(metadata.head)}
             </span>
             <span className="flex-shrink-0">in</span>
-            <span className="text-xs font-mono bg-muted px-1.5 py-0.5 rounded text-foreground truncate">
-                {metadata.repo}
-            </span>
+            <RepoBadge repo={metadata.repoInfo} />
             <span className="flex-1" />
             <span className="text-xs flex-shrink-0">
                 {fileCount} changed {fileCount === 1 ? 'file' : 'files'}

packages/web/src/features/tools/getDiff.test.ts

@@ -0,0 +1,234 @@
+import { describe, it, expect } from 'vitest';
+import { GetDiffResult } from '@/features/git';
+
+// Extract the formatting function for testing
+function formatDiffAsGitDiff(result: GetDiffResult): string {
+    let output = '';
+
+    for (const file of result.files) {
+        const oldPath = file.oldPath ?? '/dev/null';
+        const newPath = file.newPath ?? '/dev/null';
+
+        output += `--- a/${oldPath}\n`;
+        output += `+++ b/${newPath}\n`;
+
+        for (const hunk of file.hunks) {
+            const oldStart = hunk.oldRange.start;
+            const oldLines = hunk.oldRange.lines;
+            const newStart = hunk.newRange.start;
+            const newLines = hunk.newRange.lines;
+
+            output += `@@ -${oldStart},${oldLines} +${newStart},${newLines} @@`;
+            if (hunk.heading) {
+                output += ` ${hunk.heading}`;
+            }
+            output += '\n';
+
+            output += hunk.body;
+            if (!hunk.body.endsWith('\n')) {
+                output += '\n';
+            }
+        }
+    }
+
+    return output;
+}
+
+describe('formatDiffAsGitDiff', () => {
+    it('should format a simple file change correctly', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'file.txt',
+                    newPath: 'file.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 3 },
+                            newRange: { start: 1, lines: 4 },
+                            heading: undefined,
+                            body: ' context line\n-removed line\n+added line\n context line',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/file.txt
++++ b/file.txt
+@@ -1,3 +1,4 @@
+ context line
+-removed line
++added line
+ context line
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should handle file deletion', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'deleted.txt',
+                    newPath: null,
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 2 },
+                            newRange: { start: 0, lines: 0 },
+                            heading: undefined,
+                            body: '-line 1\n-line 2',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/deleted.txt
++++ b//dev/null
+@@ -1,2 +0,0 @@
+-line 1
+-line 2
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should handle file addition', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: null,
+                    newPath: 'new.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 0, lines: 0 },
+                            newRange: { start: 1, lines: 2 },
+                            heading: undefined,
+                            body: '+line 1\n+line 2',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a//dev/null
++++ b/new.txt
+@@ -0,0 +1,2 @@
++line 1
++line 2
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should include hunk heading when present', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'code.ts',
+                    newPath: 'code.ts',
+                    hunks: [
+                        {
+                            oldRange: { start: 10, lines: 5 },
+                            newRange: { start: 10, lines: 6 },
+                            heading: 'function myFunction()',
+                            body: ' function myFunction() {\n+  console.log("new line");\n   return true;\n }',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/code.ts
++++ b/code.ts
+@@ -10,5 +10,6 @@ function myFunction()
+ function myFunction() {
++  console.log("new line");
+   return true;
+ }
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should handle multiple files', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'file1.txt',
+                    newPath: 'file1.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 1 },
+                            newRange: { start: 1, lines: 2 },
+                            heading: undefined,
+                            body: ' old\n+new',
+                        },
+                    ],
+                },
+                {
+                    oldPath: 'file2.txt',
+                    newPath: 'file2.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 1 },
+                            newRange: { start: 1, lines: 1 },
+                            heading: undefined,
+                            body: ' unchanged',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/file1.txt
++++ b/file1.txt
+@@ -1,1 +1,2 @@
+ old
++new
+--- a/file2.txt
++++ b/file2.txt
+@@ -1,1 +1,1 @@
+ unchanged
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should handle multiple hunks in a single file', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'file.txt',
+                    newPath: 'file.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 2 },
+                            newRange: { start: 1, lines: 2 },
+                            heading: undefined,
+                            body: ' line 1\n+line 2',
+                        },
+                        {
+                            oldRange: { start: 10, lines: 2 },
+                            newRange: { start: 11, lines: 2 },
+                            heading: undefined,
+                            body: '-line 10\n line 11',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/file.txt
++++ b/file.txt
+@@ -1,2 +1,2 @@
+ line 1
++line 2
+@@ -10,2 +11,2 @@
+-line 10
+ line 11
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+});

packages/web/src/features/tools/getDiff.ts

@@ -4,13 +4,54 @@ import { isServiceError } from '@/lib/utils';
 import description from './getDiff.txt';
 import { logger } from './logger';
 import { ToolDefinition } from './types';
+import { CodeHostType } from '@sourcebot/db';
+import { getRepoInfoByName } from '@/actions';
+
+export type GetDiffRepoInfo = {
+    name: string;
+    displayName: string;
+    codeHostType: CodeHostType;
+};
 
 export type GetDiffMetadata = GetDiffResult & {
     repo: string;
+    repoInfo: GetDiffRepoInfo;
     base: string;
     head: string;
 };
 
+function formatDiffAsGitDiff(result: GetDiffResult): string {
+    let output = '';
+
+    for (const file of result.files) {
+        const oldPath = file.oldPath ?? '/dev/null';
+        const newPath = file.newPath ?? '/dev/null';
+
+        output += `--- a/${oldPath}\n`;
+        output += `+++ b/${newPath}\n`;
+
+        for (const hunk of file.hunks) {
+            const oldStart = hunk.oldRange.start;
+            const oldLines = hunk.oldRange.lines;
+            const newStart = hunk.newRange.start;
+            const newLines = hunk.newRange.lines;
+
+            output += `@@ -${oldStart},${oldLines} +${newStart},${newLines} @@`;
+            if (hunk.heading) {
+                output += ` ${hunk.heading}`;
+            }
+            output += '\n';
+
+            output += hunk.body;
+            if (!hunk.body.endsWith('\n')) {
+                output += '\n';
+            }
+        }
+    }
+
+    return output;
+}
+
 export const getDiffDefinition: ToolDefinition<'get_diff', typeof getDiffRequestSchema.shape, GetDiffMetadata> = {
     name: 'get_diff',
     title: 'Get diff',
@@ -27,11 +68,24 @@ export const getDiffDefinition: ToolDefinition<'get_diff', typeof getDiffRequest
             throw new Error(response.message);
         }
 
+        const repoInfoResult = await getRepoInfoByName(repo);
+        if (isServiceError(repoInfoResult) || !repoInfoResult) {
+            throw new Error(`Repository "${repo}" not found.`);
+        }
+        const repoInfo: GetDiffRepoInfo = {
+            name: repoInfoResult.name,
+            displayName: repoInfoResult.displayName ?? repoInfoResult.name,
+            codeHostType: repoInfoResult.codeHostType,
+        };
+
+        const gitDiffOutput = formatDiffAsGitDiff(response);
+
         return {
-            output: JSON.stringify(response),
+            output: gitDiffOutput,
             metadata: {
                 ...response,
                 repo,
+                repoInfo,
                 base,
                 head,
             },