feat(ecc2): infer tracked write modifications

scripts/hooks/session-activity-tracker.js

@@ -10,6 +10,7 @@
 
 const crypto = require('crypto');
 const path = require('path');
+const { spawnSync } = require('child_process');
 const {
   appendFile,
   getClaudeDir,
@@ -161,6 +162,33 @@ function buildPatchPreviewFromContent(content, prefix) {
   return lines.map(line => `${prefix} ${line}`).join('\n');
 }
 
+function buildDiffPreviewFromPatchPreview(patchPreview) {
+  if (typeof patchPreview !== 'string' || !patchPreview.trim()) {
+    return undefined;
+  }
+
+  const lines = patchPreview
+    .split(/\r?\n/)
+    .map(line => line.trim())
+    .filter(Boolean);
+  const removed = lines.find(line => line.startsWith('- ') || line.startsWith('-'));
+  const added = lines.find(line => line.startsWith('+ ') || line.startsWith('+'));
+
+  if (!removed && !added) {
+    return undefined;
+  }
+
+  const before = removed ? removed.replace(/^- ?/, '') : '';
+  const after = added ? added.replace(/^\+ ?/, '') : '';
+  if (before && after) {
+    return `${before} -> ${after}`;
+  }
+  if (before) {
+    return `${before} ->`;
+  }
+  return `-> ${after}`;
+}
+
 function inferDefaultFileAction(toolName) {
   const normalized = String(toolName || '').trim().toLowerCase();
   if (normalized.includes('read')) {
@@ -269,6 +297,104 @@ function fileEventPatchPreview(value, action) {
   return undefined;
 }
 
+function runGit(args, cwd) {
+  const result = spawnSync('git', args, {
+    cwd,
+    encoding: 'utf8',
+    timeout: 2500,
+  });
+
+  if (result.error || result.status !== 0) {
+    return null;
+  }
+
+  return String(result.stdout || '').trim();
+}
+
+function gitRepoRoot(cwd) {
+  return runGit(['rev-parse', '--show-toplevel'], cwd);
+}
+
+function repoRelativePath(repoRoot, filePath) {
+  const absolute = path.isAbsolute(filePath)
+    ? path.resolve(filePath)
+    : path.resolve(process.cwd(), filePath);
+  const relative = path.relative(repoRoot, absolute);
+  if (!relative || relative.startsWith('..') || path.isAbsolute(relative)) {
+    return null;
+  }
+  return relative.split(path.sep).join('/');
+}
+
+function patchPreviewFromGitDiff(repoRoot, repoRelative) {
+  const patch = runGit(
+    ['diff', '--no-ext-diff', '--no-color', '--unified=1', '--', repoRelative],
+    repoRoot
+  );
+  if (!patch) {
+    return undefined;
+  }
+
+  const relevant = patch
+    .split(/\r?\n/)
+    .filter(line =>
+      line.startsWith('@@')
+        || (line.startsWith('+') && !line.startsWith('+++'))
+        || (line.startsWith('-') && !line.startsWith('---'))
+    )
+    .slice(0, 6);
+
+  if (relevant.length === 0) {
+    return undefined;
+  }
+
+  return relevant.join('\n');
+}
+
+function trackedInGit(repoRoot, repoRelative) {
+  return runGit(['ls-files', '--error-unmatch', '--', repoRelative], repoRoot) !== null;
+}
+
+function enrichFileEventFromWorkingTree(toolName, event) {
+  if (!event || typeof event !== 'object' || !event.path) {
+    return event;
+  }
+
+  const repoRoot = gitRepoRoot(process.cwd());
+  if (!repoRoot) {
+    return event;
+  }
+
+  const repoRelative = repoRelativePath(repoRoot, event.path);
+  if (!repoRelative) {
+    return event;
+  }
+
+  const tool = String(toolName || '').trim().toLowerCase();
+  const tracked = trackedInGit(repoRoot, repoRelative);
+  const patchPreview = patchPreviewFromGitDiff(repoRoot, repoRelative) || event.patch_preview;
+  const diffPreview = buildDiffPreviewFromPatchPreview(patchPreview) || event.diff_preview;
+
+  if (tool.includes('write')) {
+    return {
+      ...event,
+      action: tracked ? 'modify' : event.action,
+      diff_preview: diffPreview,
+      patch_preview: patchPreview,
+    };
+  }
+
+  if (tracked && patchPreview) {
+    return {
+      ...event,
+      diff_preview: diffPreview,
+      patch_preview: patchPreview,
+    };
+  }
+
+  return event;
+}
+
 function collectFileEvents(toolName, value, events, key = null, parentValue = null) {
   if (!value) {
     return;
@@ -375,7 +501,9 @@ function buildActivityRow(input, env = process.env) {
   }
 
   const toolInput = input?.tool_input || {};
-  const fileEvents = extractFileEvents(toolName, toolInput);
+  const fileEvents = extractFileEvents(toolName, toolInput).map(event =>
+    enrichFileEventFromWorkingTree(toolName, event)
+  );
   const filePaths = fileEvents.length > 0
     ? [...new Set(fileEvents.map(event => event.path))]
     : extractFilePaths(toolInput);

tests/hooks/session-activity-tracker.test.js

@@ -40,13 +40,14 @@ function withTempHome(homeDir) {
   };
 }
 
-function runScript(input, envOverrides = {}) {
+function runScript(input, envOverrides = {}, options = {}) {
   const inputStr = typeof input === 'string' ? input : JSON.stringify(input);
   const result = spawnSync('node', [script], {
     encoding: 'utf8',
     input: inputStr,
     timeout: 10000,
     env: { ...process.env, ...envOverrides },
+    cwd: options.cwd,
   });
   return { code: result.status || 0, stdout: result.stdout || '', stderr: result.stderr || '' };
 }
@@ -210,6 +211,55 @@ function runTests() {
     fs.rmSync(tmpHome, { recursive: true, force: true });
   }) ? passed++ : failed++);
 
+  (test('reclassifies tracked Write activity as modify using git diff context', () => {
+    const tmpHome = makeTempDir();
+    const repoDir = fs.mkdtempSync(path.join(os.tmpdir(), 'session-activity-tracker-repo-'));
+
+    spawnSync('git', ['init'], { cwd: repoDir, encoding: 'utf8' });
+    spawnSync('git', ['config', 'user.email', 'ecc@example.com'], { cwd: repoDir, encoding: 'utf8' });
+    spawnSync('git', ['config', 'user.name', 'ECC Tests'], { cwd: repoDir, encoding: 'utf8' });
+
+    const srcDir = path.join(repoDir, 'src');
+    fs.mkdirSync(srcDir, { recursive: true });
+    const trackedFile = path.join(srcDir, 'app.ts');
+    fs.writeFileSync(trackedFile, 'const count = 1;\n', 'utf8');
+    spawnSync('git', ['add', 'src/app.ts'], { cwd: repoDir, encoding: 'utf8' });
+    spawnSync('git', ['commit', '-m', 'init'], { cwd: repoDir, encoding: 'utf8' });
+
+    fs.writeFileSync(trackedFile, 'const count = 2;\n', 'utf8');
+
+    const input = {
+      tool_name: 'Write',
+      tool_input: {
+        file_path: 'src/app.ts',
+        content: 'const count = 2;\n',
+      },
+      tool_output: { output: 'updated src/app.ts' },
+    };
+    const result = runScript(input, {
+      ...withTempHome(tmpHome),
+      CLAUDE_HOOK_EVENT_NAME: 'PostToolUse',
+      ECC_SESSION_ID: 'ecc-session-write-modify',
+    }, {
+      cwd: repoDir,
+    });
+    assert.strictEqual(result.code, 0);
+
+    const metricsFile = path.join(tmpHome, '.claude', 'metrics', 'tool-usage.jsonl');
+    const row = JSON.parse(fs.readFileSync(metricsFile, 'utf8').trim());
+    assert.deepStrictEqual(row.file_events, [
+      {
+        path: 'src/app.ts',
+        action: 'modify',
+        diff_preview: 'const count = 1; -> const count = 2;',
+        patch_preview: '@@ -1 +1 @@\n-const count = 1;\n+const count = 2;',
+      },
+    ]);
+
+    fs.rmSync(tmpHome, { recursive: true, force: true });
+    fs.rmSync(repoDir, { recursive: true, force: true });
+  }) ? passed++ : failed++);
+
   (test('prefers ECC_SESSION_ID over CLAUDE_SESSION_ID and redacts bash summaries', () => {
     const tmpHome = makeTempDir();
     const input = {