fix(skills): overwrite existing installations

Replace an existing skill directory instead of rejecting a duplicate installation.

Remove stale supporting files so the installed directory exactly matches the new upload.

server/modules/providers/shared/skills/skills.provider.ts

@@ -1,5 +1,5 @@
 import path from 'node:path';
-import { mkdir, stat, writeFile } from 'node:fs/promises';
+import { mkdir, rm, writeFile } from 'node:fs/promises';
 
 import type { IProviderSkills } from '@/shared/interfaces.js';
 import type {
@@ -44,19 +44,6 @@ type PendingSkillInstall = {
   skill: ProviderSkill;
 };
 
-const pathExists = async (targetPath: string): Promise<boolean> => {
-  try {
-    await stat(targetPath);
-    return true;
-  } catch (error) {
-    if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
-      return false;
-    }
-
-    throw error;
-  }
-};
-
 const resolveSkillSupportingFilePath = (
   skillDirectoryPath: string,
   relativePath: string,
@@ -196,13 +183,6 @@ export abstract class SkillsProvider implements IProviderSkills {
       }
 
       seenSkillPaths.add(normalizedSkillPath);
-      if (await pathExists(skillDirectoryPath)) {
-        throw new AppError(`Skill target "${resolvedDirectoryName}" already exists.`, {
-          code: 'PROVIDER_SKILL_ALREADY_EXISTS',
-          statusCode: 409,
-        });
-      }
-
       const supportingFiles = (entry.files ?? []).map((file) => ({
         targetPath: resolveSkillSupportingFilePath(skillDirectoryPath, file.relativePath, index),
         content: file.encoding === 'base64'
@@ -243,6 +223,8 @@ export abstract class SkillsProvider implements IProviderSkills {
     }
 
     for (const install of pendingInstalls) {
+      // Replace the complete skill directory so removed scripts or assets do not remain stale.
+      await rm(install.skillDirectoryPath, { recursive: true, force: true });
       await mkdir(install.skillDirectoryPath, { recursive: true });
       await writeFile(install.skillPath, `${install.content}\n`, 'utf8');
       for (const file of install.supportingFiles) {

server/modules/providers/tests/skills.test.ts

@@ -585,18 +585,20 @@ test('providerSkillsService adds global skills for claude, codex, gemini, and cu
       true,
     );
 
+    const replacedCodexSkills = await providerSkillsService.addProviderSkills('codex', {
+      entries: [
+        {
+          directoryName: 'uploaded-codex-folder',
+          content: '---\nname: replacement\ndescription: Replacement skill\n---\n\nReplacement body.\n',
+        },
+      ],
+    });
+    assert.equal(replacedCodexSkills[0]?.command, '$replacement');
+    assert.match(await fs.readFile(createdCodexSkill.sourcePath, 'utf8'), /Replacement body\./);
     await assert.rejects(
-      providerSkillsService.addProviderSkills('codex', {
+      fs.stat(path.join(path.dirname(createdCodexSkill.sourcePath), 'scripts', 'run.js')),
-        entries: [
+      { code: 'ENOENT' },
-          {
-            directoryName: 'uploaded-codex-folder',
-            content: '---\nname: replacement\n---\n\nReplacement body.\n',
-          },
-        ],
-      }),
-      /already exists/i,
     );
-    assert.match(await fs.readFile(createdCodexSkill.sourcePath, 'utf8'), /Codex body\./);
 
     const pendingBatchSkillPath = path.join(tempRoot, '.agents', 'skills', 'pending-batch', 'SKILL.md');
     await assert.rejects(
@@ -652,7 +654,7 @@ test('providerSkillsService adds global skills for claude, codex, gemini, and cu
     assert.equal(listedClaudeSkills.some((skill) => skill.name === 'claude-global'), true);
 
     const listedCodexSkills = await providerSkillsService.listProviderSkills('codex');
-    assert.equal(listedCodexSkills.some((skill) => skill.name === 'codex-global'), true);
+    assert.equal(listedCodexSkills.some((skill) => skill.name === 'replacement'), true);
 
     const listedGeminiSkills = await providerSkillsService.listProviderSkills('gemini');
     assert.equal(listedGeminiSkills.some((skill) => skill.name === 'gemini-global'), true);