metacircular/PLATFORM_EVOLUTION.md

Platform Evolution

This document captures the planned evolution of the Metacircular platform from its current manually-wired state to fully declarative deployment. It is a living design document — not a spec, not a commitment, but a record of where we are, where we want to be, and what's between.

Last updated: 2026-03-27

---

Current State

The platform works. Services run on rift, fronted by mc-proxy, with MCIAS handling auth and Metacrypt managing secrets. MCP can deploy, stop, start, restart, and monitor containers. This is not nothing — the core infrastructure is real and operational.

But the wiring between services is manual:

• Port assignment: operators pick host ports by hand and record them in service definitions (ports = ["127.0.0.1:28443:8443"]). A mental register of "what port is free" is required.
• mc-proxy routing: routes are defined in a static TOML config file. Adding a service means editing mc-proxy-rift.toml, restarting mc-proxy, and hoping you didn't typo a port number.
• TLS certificates: provisioned manually. Certs are generated, placed in /srv/mc-proxy/certs/, and referenced by path in the mc-proxy config.
• DNS: records are manually configured in MCNS zone files.
• Container config boilerplate: operators specify network, user, restart, full image URLs, and port mappings per component, even though these are almost always the same values.
• mcdsl build wiring: the shared library requires replace directives or sibling directory tricks in Docker builds. It should be a normally-versioned Go module fetched by the toolchain.

Each new service requires touching 4-5 files across 3-4 repos. The process works but doesn't scale and is error-prone.

Target State

The operator writes a service definition that declares what they want, not how to wire it:

name = "metacrypt"
node = "rift"
version = "v1.0.0"

[build.images]
metacrypt = "Dockerfile.api"
metacrypt-web = "Dockerfile.web"

[[components]]
name = "api"

[[components.routes]]
name = "rest"
port = 8443
mode = "l4"

[[components.routes]]
name = "grpc"
port = 9443
mode = "l4"

[[components]]
name = "web"

[[components.routes]]
port = 443
mode = "l7"

Everything else is derived from conventions:

• Image name: <service> for the first/api component, <service>-<component> for others. Resolved against the registry URL from global MCP config (~/.config/mcp/mcp.toml).
• Version: the service-level version field applies to all components. Can be overridden per-component when needed.
• Volumes: /srv/<service>:/srv/<service> is the agent default. Only declare additional mounts.
• Network, user, restart: agent defaults (mcpnet, 0:0, unless-stopped). Override only when needed.
• Source path: defaults to <service> relative to the workspace root. Override with path if different.

mcp deploy metacrypt does the rest:

1. Agent assigns a free host port per route (random, check availability, retry on collision).
2. Agent requests TLS certs from Metacrypt CA for metacrypt.svc.mcp.metacircular.net.
3. Agent registers routes with mc-proxy via gRPC (mc-proxy persists them in SQLite).
4. Agent creates/updates DNS records in MCNS for metacrypt.svc.mcp.metacircular.net.
5. Agent starts containers with $PORT_REST, $PORT_GRPC, $PORT_WEB environment variables set to the assigned host ports.
6. Agent records the full state (port assignments, cert paths, route IDs) in its registry.

On teardown (mcp stop), the agent reverses the process: stops containers, removes mc-proxy routes, cleans up DNS records.

Port Environment Variables

Applications receive their assigned ports via environment variables:

Components with...	Env var	Example
Single route	$PORT	$PORT=8913
Multiple routes	$PORT_<NAME>	$PORT_REST=8913, $PORT_GRPC=9217

Route names come from the name field in [[components.routes]]. Applications read these in their config layer alongside existing env overrides (e.g., $MCR_SERVER_LISTEN_ADDR).

Hostname Convention

Every service gets <service>.svc.mcp.metacircular.net automatically. Public-facing services can additionally declare external hostnames:

[[components.routes]]
name = "web"
port = 443
mode = "l7"
hostname = "docs.metacircular.net"  # optional, public DNS

If hostname is omitted, the route uses the default <service>.svc.mcp.metacircular.net.

Multi-Node Considerations

This design targets single-node (rift) but should not prevent multi-node operation. Key design decisions that keep the door open:

• Port assignment is per-agent. Each node's agent manages its own port space. No cross-node coordination needed.
• Route registration uses the node's address, not 127.0.0.1. When mc-proxy and the service are on the same host, the backend is loopback. When they're on different hosts, the backend is the node's network address. The agent registers the appropriate address for its node. The mc-proxy route API already accepts arbitrary backend addresses.
• DNS can have multiple A records. MCNS can return multiple records for the same hostname (one per node) for simple load distribution.
• The CLI routes to the correct agent via the node field. Adding a second node is mcp node add orion <address> and then services can target node = "orion".

Nothing in the single-node implementation should hardcode assumptions about one node, one mc-proxy, or loopback-only backends.

---

Gap Analysis

What exists today and works

Capability	Status
MCP CLI + agent deploy/stop/start/restart	Working
MCP sync (push service definitions to agent)	Working
MCP status/monitoring/drift detection	Working
mc-proxy L4/L7 routing	Working
mc-proxy gRPC admin API	Working
MCIAS auth for all services	Working
Metacrypt CA (PKI engine)	Working
MCNS DNS serving	Working
MCR container registry	Working
Service definitions in ~/.config/mcp/services/	Working
Image build pipeline (being folded into MCP)	Working

What needs to change

1. mcdsl: Proper Module Versioning — DONE

mcdsl is already properly versioned and released:

• Tagged releases: v0.1.0, v1.0.0, v1.0.1
• All consuming services import by URL with pinned versions (mcr, mcat, mcns, mc-proxy → v1.0.0; metacrypt → v1.0.1)
• No replace directives anywhere
• Docker builds use standard go mod download
• uses_mcdsl eliminated from service definitions and docs

2. MCP Agent: Port Assignment

Gap: agent doesn't manage host ports. Service definitions specify them manually.

Work:

• Agent picks free host ports at deploy time (random + availability check).
• Agent records assignments in its registry.
• Agent passes $PORT / $PORT_<NAME> to containers.
• Agent releases ports on container stop/removal.
• New service definition format drops ports field, adds [[components.routes]].

Depends on: nothing (can be developed standalone).

3. MCP Agent: mc-proxy Route Registration

Gap: mc-proxy routes are static TOML. The gRPC admin API exists but MCP doesn't use it.

Work:

• Agent calls mc-proxy gRPC API to register/remove routes on deploy/stop.
• Route registration includes: hostname, backend address (node address
  • assigned port), mode (l4/l7), TLS cert paths.

Depends on: port assignment (#2), mc-proxy route persistence (#5).

4. MCP Agent: TLS Cert Provisioning

Gap: certs are manually provisioned and placed on disk. There is no automated issuance flow.

Work:

• Agent requests certs from Metacrypt CA via its API.
• Certs are stored in a standard location (/srv/mc-proxy/certs/<service>.pem).
• Cert renewal is handled automatically before expiry.

Depends on: Metacrypt cert issuance policy (#7).

5. mc-proxy: Route Persistence

Gap: mc-proxy loads routes from TOML on startup. Routes added via gRPC are lost on restart.

Work:

• mc-proxy persists gRPC-managed routes in its SQLite database.
• On startup, mc-proxy loads routes from the database.
• TOML route config is vestigial — kept only for mc-proxy's own bootstrap before MCP is operational. The gRPC API and mcproxyctl are the primary route management interfaces going forward.

Depends on: nothing (mc-proxy already has SQLite and gRPC API).

6. MCP Agent: DNS Registration

Gap: DNS records are manually configured in MCNS zone files.

Work:

• Agent creates/updates A records in MCNS for <service>.svc.mcp.metacircular.net.
• Agent removes records on service teardown.

Depends on: MCNS record management API (#8).

7. Metacrypt: Automated Cert Issuance Policy

Gap: no policy exists for automated cert issuance. The MCP agent doesn't have a Metacrypt identity or permissions.

Work:

• MCP agent gets an MCIAS service account.
• Metacrypt policy allows this account to issue certs scoped to *.svc.mcp.metacircular.net (and explicitly listed public hostnames).
• No wildcard certs — one cert per hostname per service.

Depends on: MCIAS service account provisioning (exists today, just needs the account created).

8. MCNS: Record Management API

Gap: MCNS is a CoreDNS precursor serving static zone files. There is no API for dynamic record management.

Work:

• MCNS needs an API (REST + gRPC per platform convention) for creating/updating/deleting DNS records.
• Records are stored in SQLite (replacing or supplementing zone files).
• MCIAS auth, scoped to allow MCP agent to manage *.svc.mcp.metacircular.net records.

Depends on: this is the largest gap. MCNS is currently a CoreDNS wrapper, not a full service. This may be the right time to build the real MCNS.

9. Application $PORT Convention

Gap: applications read listen addresses from their config files. They don't check $PORT env vars.

Work:

• Each service's config layer checks $PORT / $PORT_<NAME> and overrides the configured listen address if set.
• This fits naturally into the existing $SERVICENAME_* env override convention — it's just one more env var.
• Small change per service, but touches every service.

Depends on: nothing (can be done incrementally).

---

Suggested Sequencing

The dependencies form a rough order:

Phase A — Independent groundwork (parallel):
  #1  mcdsl proper module versioning ✓ DONE
  #2  MCP agent port assignment
  #5  mc-proxy route persistence
  #9  $PORT convention in applications

Phase B — MCP route registration:
  #3  Agent registers routes with mc-proxy
      (depends on #2 + #5)

Phase C — Automated TLS:
  #7  Metacrypt cert issuance policy
  #4  Agent provisions certs
      (depends on #7)

Phase D — DNS:
  #8  MCNS record management API
  #6  Agent registers DNS
      (depends on #8)

Phase A is partially complete. mcdsl is done. The remaining Phase A work (#2, #5, #9) can proceed in parallel.

After Phase A, services can be deployed with agent-assigned ports (manually registered in mc-proxy).

After Phase B, the manual steps are: cert provisioning and DNS. This is the biggest quality-of-life improvement — no more manual port picking or mc-proxy TOML editing.

After Phase C, only DNS remains manual.

After Phase D, mcp deploy is fully declarative.

Each phase is independently useful and deployable.

Immediate Next Steps

1. mc-proxy route persistence (#5) — mc-proxy already has SQLite and a gRPC API. Persist routes in the database, load on startup. This unblocks Phase B with no external dependencies.
2. MCP agent port assignment (#2) — new service definition parser, port allocation, $PORT_* injection. Can develop in parallel with #5.
3. $PORT convention (#9) — small per-service config change. Can start incrementally now, but only useful once #2 is deployed.
4. mcdoc implementation — fully designed, no platform evolution dependency. Deployable with a manually assigned port today.

---

Open Questions

• Cert rotation: when a Metacrypt-issued cert expires, does the agent renew it automatically? What's the renewal window? Does mc-proxy need to reload certs without restart?
• Public hostnames: services like mcdoc want docs.metacircular.net in addition to the .svc.mcp.metacircular.net name. Public DNS is managed outside MCNS (Cloudflare? registrar?). How does the agent handle the split between internal and external DNS?
• mc-proxy bootstrap: mc-proxy itself is a service that needs to be running before other services can be routed. Its own routes (if any) may need to be self-configured or seeded from a minimal static config at first start. Once operational, all route management goes through the gRPC API.
• Rollback: if cert provisioning fails mid-deploy, does the agent roll back the port assignment and mc-proxy route? What's the failure mode — partial deploy, full rollback, or best-effort?
• Service discovery between components: currently, components find each other via config (e.g., mcr-web knows mcr-api's gRPC address). With agent-assigned ports, components within a service need to discover each other's ports. The agent could set additional env vars ($PEER_API_GRPC=127.0.0.1:9217) or services could query the agent.