diff --git a/src/main/services/parsing/GitIdentityResolver.ts b/src/main/services/parsing/GitIdentityResolver.ts
index 19ba482b..8880bfb1 100644
--- a/src/main/services/parsing/GitIdentityResolver.ts
+++ b/src/main/services/parsing/GitIdentityResolver.ts
@@ -33,6 +33,36 @@ import * as path from 'path';
 const logger = createLogger('Service:GitIdentityResolver');
 
 class GitIdentityResolver {
+  /**
+   * Helper to find the nearest .git file or directory by searching upwards.
+   */
+  private async findGitPath(projectPath: string): Promise<{ repoRoot: string; gitPath: string; stats: fs.Stats } | null> {
+    try {
+      let currentPath = path.resolve(projectPath);
+
+      while (currentPath) {
+        const gitPath = path.join(currentPath, '.git');
+        try {
+          const stats = await fs.promises.stat(gitPath);
+          if (stats.isFile() || stats.isDirectory()) {
+            return { repoRoot: currentPath, gitPath, stats };
+          }
+        } catch {
+          // Ignore and continue upward
+        }
+        
+        const parentDir = path.dirname(currentPath);
+        if (parentDir === currentPath) {
+          break;
+        }
+        currentPath = parentDir;
+      }
+    } catch {
+      // Ignore resolving errors
+    }
+    return null;
+  }
+
   /**
    * Resolve repository identity from a project path.
    *
@@ -49,19 +79,10 @@ class GitIdentityResolver {
    */
   async resolveIdentity(projectPath: string): Promise<RepositoryIdentity | null> {
     try {
-      const gitPath = path.join(projectPath, '.git');
-
-      // First, try filesystem-based resolution
-      let gitPathExists = false;
-      try {
-        await fs.promises.access(gitPath);
-        gitPathExists = true;
-      } catch {
-        // Path doesn't exist
-      }
+      const gitInfo = await this.findGitPath(projectPath);
 
-      if (gitPathExists) {
-        const stats = await fs.promises.stat(gitPath);
+      if (gitInfo) {
+        const { repoRoot: currentPath, gitPath, stats } = gitInfo;
 
         let mainGitDir: string;
 
@@ -79,7 +100,7 @@ class GitIdentityResolver {
 
           // Handle relative paths in gitdir (resolve relative to the .git file location)
           if (!path.isAbsolute(worktreeGitDir)) {
-            worktreeGitDir = path.resolve(projectPath, worktreeGitDir);
+            worktreeGitDir = path.resolve(currentPath, worktreeGitDir);
           }
 
           mainGitDir = this.extractMainGitDir(worktreeGitDir);
@@ -264,12 +285,9 @@ class GitIdentityResolver {
 
     // Fallback: check filesystem if available
     try {
-      const gitPath = path.join(projectPath, '.git');
-      try {
-        const stats = await fs.promises.stat(gitPath);
-        return stats.isFile();
-      } catch {
-        // Path doesn't exist
+      const gitInfo = await this.findGitPath(projectPath);
+      if (gitInfo) {
+        return gitInfo.stats.isFile();
       }
     } catch {
       // Ignore errors - filesystem might not be available
@@ -426,15 +444,10 @@ class GitIdentityResolver {
    */
   async getBranch(projectPath: string): Promise<string | null> {
     try {
-      const gitPath = path.join(projectPath, '.git');
+      const gitInfo = await this.findGitPath(projectPath);
+      if (!gitInfo) return null;
 
-      try {
-        await fs.promises.access(gitPath);
-      } catch {
-        return null;
-      }
-
-      const stats = await fs.promises.stat(gitPath);
+      const { repoRoot, gitPath, stats } = gitInfo;
       let headPath: string;
 
       if (stats.isFile()) {
@@ -446,7 +459,12 @@ class GitIdentityResolver {
           return null;
         }
 
-        headPath = path.join(gitDirMatch[1], 'HEAD');
+        let worktreeGitDir = gitDirMatch[1].trim();
+        if (!path.isAbsolute(worktreeGitDir)) {
+          worktreeGitDir = path.resolve(repoRoot, worktreeGitDir);
+        }
+
+        headPath = path.join(worktreeGitDir, 'HEAD');
       } else {
         // Main repo
         headPath = path.join(gitPath, 'HEAD');
@@ -535,12 +553,9 @@ class GitIdentityResolver {
     // Check if it's a standard git repo (only if filesystem exists)
     // For deleted repos, we'll return 'git' as fallback since we can't verify
     try {
-      const gitPath = path.join(projectPath, '.git');
-      try {
-        await fs.promises.access(gitPath);
+      const gitInfo = await this.findGitPath(projectPath);
+      if (gitInfo) {
         return 'git';
-      } catch {
-        // Path doesn't exist
       }
     } catch {
       // Ignore errors - filesystem might not be available
@@ -666,21 +681,24 @@ class GitIdentityResolver {
    */
   private async getGitWorktreeName(projectPath: string): Promise<string | null> {
     try {
-      const gitPath = path.join(projectPath, '.git');
-      let stats: fs.Stats;
-      try {
-        stats = await fs.promises.stat(gitPath);
-      } catch {
-        return null;
-      }
-      if (!stats.isFile()) return null;
+      const gitInfo = await this.findGitPath(projectPath);
+      
+      if (!gitInfo) return null;
+      if (!gitInfo.stats.isFile()) return null;
+
+      const { repoRoot, gitPath } = gitInfo;
 
       const content = await fs.promises.readFile(gitPath, 'utf-8');
       const match = /gitdir:\s*(\S[^\r\n]*)/.exec(content);
       if (!match) return null;
 
+      let worktreeGitDir = match[1].trim();
+      if (!path.isAbsolute(worktreeGitDir)) {
+        worktreeGitDir = path.resolve(repoRoot, worktreeGitDir);
+      }
+
       // gitdir: /main/.git/worktrees/my-worktree-name
-      const gitdirParts = match[1].trim().split(path.sep);
+      const gitdirParts = worktreeGitDir.split(path.sep);
       const worktreesIdx = gitdirParts.lastIndexOf(WORKTREES_DIR);
       if (worktreesIdx >= 0 && gitdirParts[worktreesIdx + 1]) {
         return gitdirParts[worktreesIdx + 1];
diff --git a/test/main/services/discovery/WorktreeGrouper.test.ts b/test/main/services/discovery/WorktreeGrouper.test.ts
new file mode 100644
index 00000000..53b5b72c
--- /dev/null
+++ b/test/main/services/discovery/WorktreeGrouper.test.ts
@@ -0,0 +1,89 @@
+import { describe, expect, it, vi, beforeEach, afterEach } from 'vitest';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+import { WorktreeGrouper } from '@main/services/discovery/WorktreeGrouper';
+import { LocalFileSystemProvider } from '@main/services/infrastructure/LocalFileSystemProvider';
+import { Project } from '@main/types';
+import { gitIdentityResolver } from '@main/services/parsing/GitIdentityResolver';
+
+describe('WorktreeGrouper', () => {
+  let tmpDir: string;
+  let mainRepoDir: string;
+  let worktreeDir: string;
+  let projectsDir: string;
+  let grouper: WorktreeGrouper;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'worktree-grouper-test-'));
+    mainRepoDir = path.join(tmpDir, 'main-repo');
+    worktreeDir = path.join(tmpDir, 'my-worktree');
+    projectsDir = path.join(tmpDir, 'projects');
+
+    fs.mkdirSync(mainRepoDir);
+    fs.mkdirSync(path.join(mainRepoDir, '.git'));
+    fs.mkdirSync(path.join(mainRepoDir, '.git', 'worktrees'));
+    fs.mkdirSync(path.join(mainRepoDir, '.git', 'worktrees', 'my-worktree'));
+
+    fs.writeFileSync(
+      path.join(mainRepoDir, '.git', 'config'),
+      '[remote "origin"]\n\turl = git@github.com:matt1398/claude-devtools.git\n'
+    );
+
+    fs.mkdirSync(worktreeDir);
+    fs.writeFileSync(
+      path.join(worktreeDir, '.git'),
+      `gitdir: ${path.join(mainRepoDir, '.git', 'worktrees', 'my-worktree')}\n`
+    );
+
+    fs.mkdirSync(projectsDir);
+
+    grouper = new WorktreeGrouper(projectsDir, new LocalFileSystemProvider());
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it('groups main repo and worktree together', async () => {
+    // Mock the SubprojectRegistry so it returns no session filter, which allows all sessions
+    vi.mock('@main/services/discovery/SubprojectRegistry', () => ({
+      subprojectRegistry: {
+        getSessionFilter: () => null,
+      },
+    }));
+
+    // Mock SessionContentFilter to always return true (not noise)
+    vi.mock('@main/services/discovery/SessionContentFilter', () => ({
+      SessionContentFilter: {
+        hasNonNoiseMessages: vi.fn().mockResolvedValue(true),
+      },
+    }));
+
+    const projects: Project[] = [
+      {
+        id: 'main-repo-id',
+        path: mainRepoDir,
+        name: 'main-repo',
+        sessions: ['session1'],
+        createdAt: 1000,
+        mostRecentSession: 2000,
+      },
+      {
+        id: 'worktree-id',
+        path: worktreeDir,
+        name: 'my-worktree',
+        sessions: ['session2'],
+        createdAt: 1500,
+        mostRecentSession: 2500,
+      },
+    ];
+
+    const groups = await grouper.groupByRepository(projects);
+
+    expect(groups).toHaveLength(1);
+    expect(groups[0].worktrees).toHaveLength(2);
+    expect(groups[0].worktrees.find(w => w.isMainWorktree)?.path).toBe(mainRepoDir);
+    expect(groups[0].worktrees.find(w => !w.isMainWorktree)?.path).toBe(worktreeDir);
+  });
+});
diff --git a/test/main/services/parsing/GitIdentityResolver.test.ts b/test/main/services/parsing/GitIdentityResolver.test.ts
new file mode 100644
index 00000000..24369b67
--- /dev/null
+++ b/test/main/services/parsing/GitIdentityResolver.test.ts
@@ -0,0 +1,51 @@
+import { describe, expect, it, vi, beforeEach, afterEach } from 'vitest';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+import { gitIdentityResolver } from '@main/services/parsing/GitIdentityResolver';
+
+describe('GitIdentityResolver', () => {
+  let tmpDir: string;
+  let mainRepoDir: string;
+  let worktreeDir: string;
+
+  beforeEach(async () => {
+    tmpDir = await fs.promises.realpath(fs.mkdtempSync(path.join(os.tmpdir(), 'git-identity-test-')));
+    mainRepoDir = path.join(tmpDir, 'main-repo');
+    worktreeDir = path.join(tmpDir, 'my-worktree');
+
+    fs.mkdirSync(mainRepoDir);
+    fs.mkdirSync(path.join(mainRepoDir, '.git'));
+    fs.mkdirSync(path.join(mainRepoDir, '.git', 'worktrees'));
+    fs.mkdirSync(path.join(mainRepoDir, '.git', 'worktrees', 'my-worktree'));
+
+    fs.writeFileSync(
+      path.join(mainRepoDir, '.git', 'config'),
+      '[remote "origin"]\n\turl = git@github.com:matt1398/claude-devtools.git\n'
+    );
+
+    fs.mkdirSync(worktreeDir);
+    fs.writeFileSync(
+      path.join(worktreeDir, '.git'),
+      `gitdir: ${path.join(mainRepoDir, '.git', 'worktrees', 'my-worktree')}\n`
+    );
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it('resolves identity for main repo', async () => {
+    const identity = await gitIdentityResolver.resolveIdentity(mainRepoDir);
+    expect(identity).toBeDefined();
+    expect(identity?.mainGitDir).toBe(await fs.promises.realpath(path.join(mainRepoDir, '.git')));
+    expect(identity?.name).toBe('main-repo');
+  });
+
+  it('resolves identity for worktree', async () => {
+    const identity = await gitIdentityResolver.resolveIdentity(worktreeDir);
+    expect(identity).toBeDefined();
+    expect(identity?.mainGitDir).toBe(await fs.promises.realpath(path.join(mainRepoDir, '.git')));
+    expect(identity?.name).toBe('main-repo');
+  });
+});
diff --git a/test/main/services/parsing/GitIdentityResolver.upwards.test.ts b/test/main/services/parsing/GitIdentityResolver.upwards.test.ts
new file mode 100644
index 00000000..ec289601
--- /dev/null
+++ b/test/main/services/parsing/GitIdentityResolver.upwards.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, it, beforeEach, afterEach } from 'vitest';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+import { gitIdentityResolver } from '@main/services/parsing/GitIdentityResolver';
+
+describe('GitIdentityResolver - Upwards Search', () => {
+  let tmpDir: string;
+  let mainRepoDir: string;
+  let worktreeDir: string;
+
+  beforeEach(async () => {
+    tmpDir = await fs.promises.realpath(fs.mkdtempSync(path.join(os.tmpdir(), 'git-upwards-test-')));
+    mainRepoDir = path.join(tmpDir, 'main-repo');
+    worktreeDir = path.join(tmpDir, 'my-worktree');
+
+    fs.mkdirSync(mainRepoDir);
+    fs.mkdirSync(path.join(mainRepoDir, '.git'));
+    fs.mkdirSync(path.join(mainRepoDir, '.git', 'worktrees'));
+    fs.mkdirSync(path.join(mainRepoDir, '.git', 'worktrees', 'my-worktree'));
+
+    fs.writeFileSync(
+      path.join(mainRepoDir, '.git', 'config'),
+      '[remote "origin"]\n\turl = git@github.com:matt1398/claude-devtools.git\n'
+    );
+
+    fs.mkdirSync(worktreeDir);
+    fs.writeFileSync(
+      path.join(worktreeDir, '.git'),
+      `gitdir: ../main-repo/.git/worktrees/my-worktree\n`
+    );
+
+    // Create subdirectories
+    fs.mkdirSync(path.join(mainRepoDir, 'src'));
+    fs.mkdirSync(path.join(worktreeDir, 'src'));
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it('resolves identity when path is a subdirectory of main repo', async () => {
+    const identity = await gitIdentityResolver.resolveIdentity(path.join(mainRepoDir, 'src'));
+    expect(identity).toBeDefined();
+    expect(identity?.mainGitDir).toBe(await fs.promises.realpath(path.join(mainRepoDir, '.git')));
+    expect(identity?.remoteUrl).toBe('git@github.com:matt1398/claude-devtools.git');
+    expect(await gitIdentityResolver.isWorktree(path.join(mainRepoDir, 'src'))).toBe(false);
+  });
+
+  it('resolves identity when path is a subdirectory of a worktree (with relative gitdir)', async () => {
+    const identity = await gitIdentityResolver.resolveIdentity(path.join(worktreeDir, 'src'));
+    expect(identity).toBeDefined();
+    expect(identity?.mainGitDir).toBe(await fs.promises.realpath(path.join(mainRepoDir, '.git')));
+    expect(identity?.remoteUrl).toBe('git@github.com:matt1398/claude-devtools.git');
+    expect(await gitIdentityResolver.isWorktree(path.join(worktreeDir, 'src'))).toBe(true);
+  });
+});