Heimdall/docs/implementation-plan.md

Heimdall Implementation Plan

What this file is

This file is the forward plan and active hypothesis ledger for Heimdall.

It is not the canonical shared architecture note. That lives in docs/architecture.md.

If the code or the architecture note disagrees with this plan, trust the code and the architecture note first, then fix this file.

Current machine

There is now a first landed Heimdall skeleton.

What exists right now is:

• the shared architecture note
• the concrete service contract in docs/service-contract.md
• app-binding notes for Repixelizer and StreamPixels
• a standalone TypeScript/Fastify service skeleton under src/
• Ed25519 JWT signing plus JWKS/discovery exposure
• OAuth start/callback contract surfaces with signed state
• app-profile-driven claim issuance for Repixelizer and StreamPixels
• in-memory/Postgres auth-control-plane storage
• persisted accounts, linked identities, sessions, grants, entitlement snapshots, and audit records
• a real Discord provider callback slice for Repixelizer access
• a direct backend callback handoff for same-host app integrations
• a one-time browser completion handoff so auth callback pages can post back to the opener instead of leaking final app auth in URL fragments, now retained as fallback rather than the preferred same-host path
• file-backed signing-key loading/bootstrap for stable service identity
• AES-256-GCM token sealing for managed provider credentials at rest
• a local verifier helper that app backends can use against Heimdall JWKS
• Repixelizer has consumed the direct backend callback flow in its hosted web layer and verifies Heimdall Ed25519 access tokens locally
• Heimdall is deployed on Yggdrasil at https://heimdall.gamecult.org with nginx/TLS, Postgres storage, stable file-backed signing, configured token custody, and public health/discovery/JWKS checks passing
• Repixelizer is deployed on Yggdrasil at https://repixelizer.gamecult.org with Heimdall mode enabled, Discord as the only public provider, required access, and queue protection
• explicit state/doctrine scaffolding so the plan does not immediately turn into soup

Primary objective

Build Heimdall as a shared auth authority service that can:

• own provider OAuth and identity linking
• issue signed sessions and app-facing claims
• refresh Discord and Patreon entitlements
• evaluate per-app capability rules
• expose a clean contract to app backends without owning their domain data

Current priorities

1. Lock the service boundary

Goals:

• keep Heimdall scoped to auth/control-plane machinery
• keep app-domain data in app-owned stores
• keep app profiles thin and explicit

2. Keep the contract tight while it goes live

Goals:

• define signed claim/session shapes
• define OAuth start/callback/link surfaces
• define grant and entitlement persistence boundaries
• define how app backends verify claims locally This now exists in reference form and Repixelizer has a Python consumer in its hosted web layer.

3. Launch Repixelizer with Discord first

Goals:

• deploy Heimdall on Yggdrasil with stable signing, encrypted token custody, and persistent Postgres storage
• configure the Discord OAuth app redirect URI to https://heimdall.gamecult.org/v1/oauth/discord/callback
• configure Heimdall's Discord client credentials, Repixelizer guild id, and the Repixelizer Discord access role ids in GC_ACCESS_APP_REPIXELIZER_DISCORD_ALLOWED_ROLE_IDS
• configure Repixelizer for GC_ACCESS_MODE=heimdall and GC_ACCESS_ALLOWED_PROVIDERS=discord
• run the live browser OAuth flow and confirm Repixelizer receives the backend callback, verifies the claim locally, adopts a local session, gates hosted access, and stamps queued jobs with account_id / session_id

Deployment/configuration status:

• the deployment and service wiring are done
• public health/discovery/JWKS/config checks pass
• public Repixelizer auth-start returns a Discord authorization URL using the Heimdall callback and Repixelizer backend handoff
• the Discord authorization URL requests only identify guilds.members.read
• the remaining launch check is the real interactive Discord browser flow

Current Discord policy:

• Heimdall grants Repixelizer entitlement.app_access only when the Discord member has one of the configured allowed role ids
• launch policy is intentionally role-gated: the GameCult Discord can remain public, but Repixelizer access is limited to members with either KLTST or the Patreon-synced Inner Sanctum role

4. Migrate StreamPixels without flattening its good local seams

Goals:

• move provider/linking authority toward Heimdall
• keep viewer profiles, creator memberships, connector creds, and audience data in StreamPixels
• keep creator/operator route authorization local to StreamPixels after claim verification

5. Capture the Yggdrasil deployment shape early

Goals:

• treat Heimdall as a localhost service behind nginx on Yggdrasil
• support same-host callers first
• avoid per-request network chatter for routine app authorization

Proposed phases

Phase 1: Contract and schema scaffold

Landed in the first pass:

• signed claim/session payload shape
• Ed25519 JWKS verification surface
• OAuth state and callback contract surfaces
• app profile / capability rule inputs and outputs

Still to do in this phase:

• key rotation policy instead of just stable key loading
• token custody retrieval/refresh surfaces beyond initial storage

Phase 2: Heimdall service skeleton

Landed in the first pass:

• provider OAuth start route scaffolding
• callback route scaffolding with signed-state validation
• session/claim issuance contract
• capability evaluation for shared app capabilities

Next in this phase:

• provider refresh/revocation flows
• connection lifecycle and token-rotation work

Phase 3: Repixelizer binding

Landed in Repixelizer:

• Heimdall hosted auth mode
• direct backend callback receipt
• local Ed25519 JWT verification against Heimdall JWKS
• httpOnly local session adoption
• hosted landing-page provider buttons
• hosted route and queue/job ownership checks

Still to do for this phase:

• deploy and configure both services
• verify the real Discord OAuth path end to end

Phase 4: StreamPixels authority migration

• replace provider/linking authority paths with Heimdall calls where they truly belong
• keep viewer/session expansion, creator memberships, and operator route enforcement local where they are app-domain concerns

Phase 5: Ops and deploy

• define nginx/systemd/env/runbook surfaces for Heimdall on Yggdrasil
• keep callers and state stores localhost-first where practical

Guardrails

• do not let auth reuse become data mixing
• do not turn Heimdall into a mandatory round-trip for every guarded app route
• do not fantasize about one shared cross-runtime embedded library; the apps can share contracts without sharing a runtime
• do not duplicate the shared architecture note into app profiles
• do not rip out app-local ownership and authorization logic that still belongs in the app
• keep one clear hypothesis per pass
• commit completed work before the planning notes start breeding