Canvas's browser bundle issues fetches to both CP endpoints
(/cp/auth/me, /cp/orgs, ...) AND tenant-platform endpoints
(/canvas/viewport, /approvals/pending, /org/templates). They
share ONE build-time base URL. Baking api.moleculesai.app
broke tenant calls with 404; baking the tenant subdomain broke
auth. Tried both today and saw exactly one failure mode per
attempt.
Real fix: same-origin fetches + tenant-side split. Adds:
internal/router/cp_proxy.go # /cp/* → CP_UPSTREAM_URL
mounted before NoRoute(canvasProxy). Now a tenant serves:
/cp/* → reverse-proxy to api.moleculesai.app
/canvas/viewport,
/approvals/pending,
/workspaces/:id/*,
/ws, /registry, → tenant platform (existing handlers)
/metrics
everything else → canvas UI (existing reverse-proxy)
Canvas middleware reverts to `connect-src 'self' wss:` for the
same-origin path (keeping explicit PLATFORM_URL whitelist as a
self-hosted escape hatch when the build-arg is non-empty).
CI build-arg flips to NEXT_PUBLIC_PLATFORM_URL="" so the bundle
issues relative fetches.
Security of cp_proxy:
- Cookie + Authorization PRESERVED across the hop (opposite of
canvas proxy) — they carry the WorkOS session, which is the
whole point.
- Host rewritten to upstream so CORS + cookie-domain on the CP
side see their own hostname.
- Upstream URL validated at construction: must parse, must be
http(s), must have a host — misconfig fails closed.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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