diff --git a/src/cli/commands/plugin-skills.ts b/src/cli/commands/plugin-skills.ts
index 5c3d986..1acd50f 100644
--- a/src/cli/commands/plugin-skills.ts
+++ b/src/cli/commands/plugin-skills.ts
@@ -113,7 +113,7 @@ async function recordSourceProvenance(opts: {
   });
 }
 
-function resolveFetchedSourcePath(source: string, cachePath: string): string {
+export function resolveFetchedSourcePath(source: string, cachePath: string): string {
   if (!isGitHubUrl(source)) return cachePath;
   const parsed = parseGitHubUrl(source);
   return parsed?.subpath ? join(cachePath, parsed.subpath) : cachePath;
@@ -458,13 +458,24 @@ type InstallSkillResult =
  *
  * In both cases, set the plugin to allowlist mode with only the requested skill.
  */
-async function installSkillFromSource(opts: {
+type InstallSkillFromSourceDeps = {
+  fetchPlugin?: typeof fetchPlugin;
+  parseMarketplaceManifest?: typeof parseMarketplaceManifest;
+  installSkillViaMarketplace?: typeof installSkillViaMarketplace;
+  installSkillDirect?: typeof installSkillDirect;
+};
+
+export async function installSkillFromSource(opts: {
   skill: string;
   from: string;
   isUser: boolean;
   workspacePath: string;
-}): Promise<InstallSkillResult> {
+}, deps: InstallSkillFromSourceDeps = {}): Promise<InstallSkillResult> {
   const { skill, from, isUser, workspacePath } = opts;
+  const fetchPluginFn = deps.fetchPlugin ?? fetchPlugin;
+  const parseMarketplaceManifestFn = deps.parseMarketplaceManifest ?? parseMarketplaceManifest;
+  const installSkillViaMarketplaceFn = deps.installSkillViaMarketplace ?? installSkillViaMarketplace;
+  const installSkillDirectFn = deps.installSkillDirect ?? installSkillDirect;
 
   if (!isJsonMode()) {
     console.log(`Installing skill '${skill}' from ${from}...`);
@@ -472,7 +483,7 @@ async function installSkillFromSource(opts: {
 
   // Fetch the source to a local cache so we can inspect it
   const parsed = isGitHubUrl(from) ? parseGitHubUrl(from) : null;
-  const fetchResult = await fetchPlugin(from, {
+  const fetchResult = await fetchPluginFn(from, {
     ...(parsed?.branch && { branch: parsed.branch }),
   });
   if (!fetchResult.success) {
@@ -482,14 +493,14 @@ async function installSkillFromSource(opts: {
   const sourcePath = resolveFetchedSourcePath(from, fetchResult.cachePath);
 
   // Check if the source is a marketplace
-  const manifestResult = await parseMarketplaceManifest(sourcePath);
+  const manifestResult = await parseMarketplaceManifestFn(sourcePath);
 
   if (manifestResult.success) {
-    return installSkillViaMarketplace({ skill, from, isUser, workspacePath });
+    return installSkillViaMarketplaceFn({ skill, from, isUser, workspacePath });
   }
 
   // Not a marketplace — install as a direct plugin
-  return installSkillDirect({ skill, from, isUser, workspacePath, cachePath: sourcePath });
+  return installSkillDirectFn({ skill, from, isUser, workspacePath, sourcePath });
 }
 
 /**
@@ -593,10 +604,9 @@ async function installSkillDirect(opts: {
   from: string;
   isUser: boolean;
   workspacePath: string;
-  cachePath: string;
+  sourcePath: string;
 }): Promise<InstallSkillResult> {
-  const { skill, from, isUser, workspacePath, cachePath } = opts;
-  const sourcePath = resolveFetchedSourcePath(from, cachePath);
+  const { skill, from, isUser, workspacePath, sourcePath } = opts;
 
   // Verify the skill exists in the cached plugin before installing
   const availableSkills = await discoverSkillNames(sourcePath);
diff --git a/tests/unit/cli/skills-add-standalone-install.test.ts b/tests/unit/cli/skills-add-standalone-install.test.ts
new file mode 100644
index 0000000..94688fb
--- /dev/null
+++ b/tests/unit/cli/skills-add-standalone-install.test.ts
@@ -0,0 +1,54 @@
+import { describe, expect, it, mock } from 'bun:test';
+import { installSkillFromSource } from '../../../src/cli/commands/plugin-skills.js';
+
+describe('installSkillFromSource', () => {
+  it('passes the resolved GitHub skill subpath to direct install without resolving it twice', async () => {
+    const source = 'https://github.com/NousResearch/hermes-agent/tree/main/skills/research/llm-wiki';
+    const installSkillDirectMock = mock(async (_opts: {
+      skill: string;
+      from: string;
+      isUser: boolean;
+      workspacePath: string;
+      sourcePath: string;
+    }) => ({
+      success: true as const,
+      pluginName: 'llm-wiki',
+      syncResult: { copied: 1, failed: 0 },
+    }));
+
+    const result = await installSkillFromSource(
+      {
+        skill: 'llm-wiki',
+        from: source,
+        isUser: false,
+        workspacePath: '/tmp/workspace',
+      },
+      {
+        fetchPlugin: async () => ({
+          success: true as const,
+          action: 'fetched' as const,
+          cachePath: '/tmp/fetched-hermes-agent',
+        }),
+        parseMarketplaceManifest: async () => ({
+          success: false as const,
+          error: 'not a marketplace',
+        }),
+        installSkillViaMarketplace: async () => ({
+          success: false as const,
+          error: 'unexpected marketplace path',
+        }),
+        installSkillDirect: installSkillDirectMock,
+      },
+    );
+
+    expect(result.success).toBe(true);
+    expect(installSkillDirectMock).toHaveBeenCalledTimes(1);
+    expect(installSkillDirectMock).toHaveBeenCalledWith({
+      skill: 'llm-wiki',
+      from: source,
+      isUser: false,
+      workspacePath: '/tmp/workspace',
+      sourcePath: '/tmp/fetched-hermes-agent/skills/research/llm-wiki',
+    });
+  });
+});
diff --git a/tests/unit/cli/skills-add-url-detection.test.ts b/tests/unit/cli/skills-add-url-detection.test.ts
index 97ad84a..02065a3 100644
--- a/tests/unit/cli/skills-add-url-detection.test.ts
+++ b/tests/unit/cli/skills-add-url-detection.test.ts
@@ -2,7 +2,11 @@ import { describe, it, expect } from 'bun:test';
 import { mkdtemp, writeFile, rm } from 'node:fs/promises';
 import { join } from 'node:path';
 import { tmpdir } from 'node:os';
-import { resolveSkillFromUrl, resolveSkillNameFromRepo } from '../../../src/cli/commands/plugin-skills.js';
+import {
+  resolveFetchedSourcePath,
+  resolveSkillFromUrl,
+  resolveSkillNameFromRepo,
+} from '../../../src/cli/commands/plugin-skills.js';
 import type { FetchResult } from '../../../src/core/plugin.js';
 
 describe('resolveSkillFromUrl', () => {
@@ -99,3 +103,18 @@ describe('resolveSkillNameFromRepo', () => {
     expect(result).toBe('fallback-name');
   });
 });
+
+describe('resolveFetchedSourcePath', () => {
+  it('appends the GitHub subpath to the fetched repo root once', () => {
+    expect(
+      resolveFetchedSourcePath(
+        'https://github.com/NousResearch/hermes-agent/tree/main/skills/research/llm-wiki',
+        '/tmp/hermes-agent-cache',
+      ),
+    ).toBe('/tmp/hermes-agent-cache/skills/research/llm-wiki');
+  });
+
+  it('leaves non-GitHub sources unchanged', () => {
+    expect(resolveFetchedSourcePath('/tmp/local-skill', '/tmp/local-skill')).toBe('/tmp/local-skill');
+  });
+});