refactor(better-auth): login/signup

[jog1t]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[railway-app]

🚅 Deployed to the rivet-pr-4592 environment in rivet-frontend

Service	Status	Web	Updated (UTC)
frontend-inspector	❌ Build Failed (View Logs)	Web	Apr 8, 2026 at 6:47 pm
frontend-cloud	❌ Build Failed (View Logs)	Web	Apr 8, 2026 at 6:46 pm
mcp-hub	✅ Success (View Logs)	Web	Apr 8, 2026 at 6:46 pm
kitchen-sink	❌ Build Failed (View Logs)	Web	Apr 8, 2026 at 6:46 pm
website	❌ Build Failed (View Logs)	Web	Apr 8, 2026 at 6:46 pm
ladle	❌ Build Failed (View Logs)	Web	Apr 8, 2026 at 6:46 pm

[jog1t]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• refactor(better-auth): login/signup #4592 👈 (View in Graphite)
• chore: migrate frontend auth from Clerk to Better Auth #4568
• main

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[claude]

PR Review: refactor(better-auth): login/signup

This is a solid refactor that replaces the compile-time APP_TYPE global with a runtime feature-flag system and simplifies the login/signup forms. The overall direction is good. A few issues to address before merging.

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Bugs

from param dropped in login.tsx and sign-up.tsx

In both files, from is extracted from the search params but never forwarded to redirectToOrganization. The original code passed from ? { from } : {}. Users who follow a deep link to the login page will always be redirected to their org root instead of the originally-intended URL after login.

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No-org fallback is silent

redirectToOrganization now returns false when the user has no orgs (instead of redirecting to /onboarding/choose-organization). The callers do not handle this case -- if the return value is false, nothing happens and the user stays on the login page with no feedback.

This leaves new users stuck on the login page after a successful authentication. The removed /onboarding/choose-organization redirect covered this case previously. Consider either restoring that redirect or adding an explicit fallback navigation here.

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crypto.randomUUID() as org slug

create-organization-frame.tsx now sends crypto.randomUUID() as the slug. The comment says the server generates the real slug, but this assumption should be verified. If the better-auth organization.create API stores whatever slug the client sends, org slugs will be unreadable UUIDs in URLs and the database.

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Design Concerns

attemptAsync for redirect handling is non-idiomatic

TanStack Router redirects are thrown errors, and the router catches them when they propagate naturally up the call stack. Using attemptAsync to catch the throw and then re-navigating manually adds an extra layer of indirection with no clear benefit. The original pattern of re-throwing redirect errors was awkward, but this approach adds a new dependency (es-toolkit) to solve the same problem less clearly. Consider using a try/catch that only catches non-redirect errors, or restructuring redirectToOrganization to return a navigation target instead of throwing.

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Feature flags default to all-on

The inverted default (raw === undefined ? null : new Set(...)) means a deployment that forgets to set VITE_FEATURE_FLAGS silently enables every feature, including auth, billing, and multitenancy. Worth documenting in an env var reference or .env.example so operators know to explicitly set the var for engine/inspector builds.

Also: if someone sets localStorage.FEATURE_FLAGS to an empty string in dev to clear an override, they get all flags disabled (empty Set) rather than falling back to the env var default. The empty-string case and the unset case are not treated symmetrically.

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Minor

• Route renames and existing deep links. Routes under _context/_cloud/ and _context/_engine/ are flattened to _context/. Since TanStack uses _ prefixes for pathless layouts, these segments likely were not visible in URLs -- but worth a quick confirm.

• orgs.organization.tsx setActive guard -- the optimization to skip setActive when the org is already active is a nice improvement.

• The PR description is empty. Even a one-line summary of the motivation (replace compile-time APP_TYPE with runtime feature flags) would help reviewers and the git log.