Single-container tenant architecture: Go platform (:8080) + Canvas
Node.js (:3000) in one Fly machine, with Go's NoRoute handler reverse-
proxying non-API routes to the canvas. Browser only talks to :8080.
Changes:
platform/Dockerfile.tenant — multi-stage build (Go + Node + runtime).
Bakes workspace-configs-templates/ + org-templates/ into the image.
Build context: repo root.
platform/entrypoint-tenant.sh — starts both processes, kills both if
either exits. Fly health check on :8080 covers the Go binary; canvas
health is implicit (proxy returns 502 if canvas is down).
platform/internal/router/canvas_proxy.go — httputil.ReverseProxy that
forwards unmatched routes to CANVAS_PROXY_URL (http://localhost:3000).
Activated by NoRoute when CANVAS_PROXY_URL env is set.
platform/internal/router/router.go — wire NoRoute → canvasProxy when
CANVAS_PROXY_URL is present; no-op otherwise (local dev unchanged).
platform/internal/middleware/securityheaders.go — relaxed CSP to allow
Next.js inline scripts/styles/eval + WebSocket + data: URIs. The
strict `default-src 'self'` was blocking all canvas rendering.
canvas/src/lib/api.ts — changed `||` to `??` for NEXT_PUBLIC_PLATFORM_URL
so empty string means "same-origin" (combined image) instead of falling
back to localhost:8080.
canvas/src/components/tabs/TerminalTab.tsx — same `??` fix for WS URL.
Verified: tenant machine boots, canvas renders, 8 runtime templates +
4 org templates visible, API routes work through the same port.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Closes#282. CLAUDE.md documented the SecurityHeaders() middleware as
setting 6 headers (X-Content-Type-Options, X-Frame-Options, Referrer-
Policy, Content-Security-Policy, Permissions-Policy, HSTS) but the
implementation only set 4 — Referrer-Policy and Permissions-Policy
were silently missing.
Adds:
- Referrer-Policy: strict-origin-when-cross-origin — prevents
browsers from leaking full paths/queries in Referer on cross-
origin navigation. Particularly relevant for canvas embeds of
Langfuse trace URLs that may contain trace IDs.
- Permissions-Policy: camera=(), microphone=(), geolocation=() —
denies sensor access by default. Iframes the canvas embeds
(Langfuse trace viewer etc.) can no longer request these
without an explicit delegation.
Regression tests added to securityheaders_test.go — both headers
are now in the same table-driven assertion loop as the other 4,
so a future edit that drops them again fails CI loudly.
LOW severity — this is defense-in-depth, not a direct exploit path.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
