diff --git a/src/core/plugin.ts b/src/core/plugin.ts
index e6e0c80..3ca6eb8 100644
--- a/src/core/plugin.ts
+++ b/src/core/plugin.ts
@@ -157,7 +157,8 @@ export async function fetchPlugin(
   }
 
   const { owner, repo } = parsed;
-  const cachePath = getPluginCachePath(owner, repo, branch);
+  const effectiveBranch = branch ?? parsed.branch;
+  const cachePath = getPluginCachePath(owner, repo, effectiveBranch);
 
   // Return cached result if this repo was already fetched this session
   const cached = fetchCache.get(cachePath);
@@ -170,7 +171,7 @@ export async function fetchPlugin(
     owner,
     repo,
     offline,
-    branch,
+    effectiveBranch,
     deps,
   );
   fetchCache.set(cachePath, promise);
diff --git a/tests/unit/core/plugin.test.ts b/tests/unit/core/plugin.test.ts
index 3e16c3a..44ef287 100644
--- a/tests/unit/core/plugin.test.ts
+++ b/tests/unit/core/plugin.test.ts
@@ -56,6 +56,42 @@ describe('fetchPlugin', () => {
     expect(result.cachePath).toContain('owner-repo');
   });
 
+  it('uses the branch encoded in a deep GitHub URL', async () => {
+    existsSyncMock.mockReturnValueOnce(false);
+
+    const result = await fetchPlugin(
+      'https://github.com/owner/repo/blob/main/skills/example',
+      {},
+      deps,
+    );
+
+    expect(result.success).toBe(true);
+    expect(result.cachePath).toContain('owner-repo@main');
+    expect(cloneToMock).toHaveBeenCalledWith(
+      'https://github.com/owner/repo.git',
+      expect.stringContaining('owner-repo@main'),
+      'main',
+    );
+  });
+
+  it('prefers an explicit branch override to the URL branch', async () => {
+    existsSyncMock.mockReturnValueOnce(false);
+
+    const result = await fetchPlugin(
+      'https://github.com/owner/repo/blob/main/skills/example',
+      { branch: 'release' },
+      deps,
+    );
+
+    expect(result.success).toBe(true);
+    expect(result.cachePath).toContain('owner-repo@release');
+    expect(cloneToMock).toHaveBeenCalledWith(
+      'https://github.com/owner/repo.git',
+      expect.stringContaining('owner-repo@release'),
+      'release',
+    );
+  });
+
   it('should handle authentication errors', async () => {
     existsSyncMock.mockReturnValueOnce(false);
     cloneToMock.mockRejectedValueOnce(