Refactor AuthPlugin to align with better-auth best practices (basePath, handler forwarding)

[Copilot]

AuthManager hardcoded basePath: '/' and AuthPlugin compensated by manually rewriting request URLs (stripping the prefix, reconstructing a new Request with duplex: 'half'). This breaks better-auth's assumptions about path matching and is fragile.

Changes

• auth-manager.ts: Set basePath to this.config.basePath || '/api/v1/auth' instead of '/'. Added basePath to AuthManagerOptions.
• auth-plugin.ts: Removed 13 lines of URL rewriting. Route handler now forwards directly:

  const response = await this.authManager!.handleRequest(c.req.raw);

• auth-manager.test.ts: Added tests verifying basePath defaults correctly and accepts custom values.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Refactor AuthPlugin to align with better-auth best practices (basePath, handler forwarding)</issue_title>
<issue_description>## Problem
Current AuthPlugin implementation does not fully align with better-auth server integration best practices, causing hidden routing and parsing bugs:

• auth-manager.ts sets basePath: '/' instead of the expected /api/v1/auth
• auth-plugin.ts manually rewrites the request URL, stripping the API prefix. This forces manual path handling and may break better-auth assumptions about basePath

Recommended Fix

High priority—refactor the integration as follows:

1. In auth-manager.ts, set basePath to /api/v1/auth (instead of /).
2. In auth-plugin.ts, remove custom path rewriting. Forward the original request object directly:

   return this.authManager.handleRequest(c.req.raw);

3. Ensure that all route registration and forwarding strictly follow better-auth's official usage and expectations.

---</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Refactor AuthPlugin to align with better-auth best practices (basePath, handler forwarding) #899

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Project	Deployment	Actions	Updated (UTC)
objectstack-play	Ready	Preview, Comment	Mar 10, 2026 5:48am
spec	Ready	Preview, Comment	Mar 10, 2026 5:48am

[Copilot]

Pull request overview

This PR refactors the AuthPlugin and AuthManager to align with better-auth's proper integration model. Previously, AuthManager set basePath: '/' and AuthPlugin compensated by manually rewriting request URLs (stripping the API prefix), which was fragile and broke better-auth's path matching assumptions. The fix correctly configures better-auth's basePath to match the actual route prefix and removes the unnecessary URL rewriting.

Changes:

• AuthManager.createAuthInstance() now uses this.config.basePath || '/api/v1/auth' instead of the hardcoded '/', and basePath is added as a documented field in AuthManagerOptions.
• AuthPlugin.registerAuthRoutes() removes 13 lines of URL rewriting (stripping prefix, reconstructing Request, using duplex: 'half') and replaces them with a single direct this.authManager!.handleRequest(c.req.raw) call.
• Two new tests in auth-manager.test.ts verify that basePath defaults correctly and accepts custom values.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/plugins/plugin-auth/src/auth-manager.ts	Adds basePath field to AuthManagerOptions with @default '/api/v1/auth'; changes basePath in betterAuth config from hardcoded '/' to this.config.basePath || '/api/v1/auth'
packages/plugins/plugin-auth/src/auth-plugin.ts	Removes manual URL rewriting; forwards c.req.raw directly to handleRequest; updates route registration comment
packages/plugins/plugin-auth/src/auth-manager.test.ts	Adds basePath configuration test suite with two tests verifying default and custom basePath behavior