A local proxy that pools multiple ChatGPT/Codex and GitHub Copilot subscriptions behind one OpenAI-compatible endpoint.

                       ┌────────────────────────────────────┐
                       │            underclass              │
                       │                                    │
 opencode ────────────►│  /v1/responses                     │
 (any OpenAI-compatible│  /v1/chat/completions              │────► chatgpt.com
  client)              │  /v1/models                        │      (N Codex subs,
                       │                                    │       OAuth device flow)
 web UI ◄─────────────►│  sticky sessions · health pool     │
 (accounts, catalog,   │  fail-fast saturation · tracing    │────► api.githubcopilot.com
  live request feed)   │                                    │      (M Copilot subs,
                       └────────────────────────────────────┘       GitHub device flow)

One subscription runs out of quota? It leaves rotation until its window resets — and comes back on its own. Sessions stay pinned to one subscription so upstream prompt caches stay warm. When everything is exhausted, the proxy fails fast with the earliest reset time instead of hanging.

Subscription-based model access has a per-account quota. One account is a ceiling; twenty accounts are a pool. underclass turns a pile of personal subscriptions into a single durable endpoint that behaves like one well-provisioned provider:

• No client changes — the surface is plain /v1/*; point opencode (or anything OpenAI-compatible) at it.
• No quota whiplash — exhausted accounts cool down and recover automatically; clients never see account churn.
• No cache waste — sessions are sticky, so the upstream prompt cache keeps working across turns.

UNDERCLASS_PROXY_KEY="$(openssl rand -hex 32)" \
UNDERCLASS_UI_TOKEN="$(openssl rand -hex 32)" \
cargo run -- serve

underclass listening on http://127.0.0.1:8080
web ui: http://127.0.0.1:8080/

Keep the generated values in a password manager or runtime secret file; underclass never writes them to diagnostics. Open the web UI and paste the value supplied as UNDERCLASS_UI_TOKEN.

1. Open the web UI and paste the configured admin token.
2. Click Add account → pick ChatGPT / Codex or GitHub Copilot → enter the device code at the shown URL. The account is labeled automatically with the account's email or username.
3. Repeat for every subscription you want in the pool.
4. Point opencode at the pool:

cargo run -- connect
opencode --provider underclass --model underclass/gpt-5.5

underclass connect writes the provider block and credentials into your global opencode config (~/.config/opencode/opencode.json{,c} + auth.json), idempotently and with backups. Re-run it any time; --remove undoes it.

• Sticky sessions. Requests carrying prompt_cache_key / promptCacheKey (opencode sends the session ID when configured with setCacheKey: true) always land on the same subscription. Bindings live for 24h, survive restarts, and rebind preferentially within the same backend when an account cools.
• Health pool. A quota response moves an account to cooling until the upstream deadline or a per-backend default. Codex uses the later valid deadline from its usage-limit error and retry-after, and its account usage poll can extend cooldown to a later exhausted-window reset or readmit an account when upstream reports it allowed. 401s trigger one token refresh + retry, then the account needs re-login. Cooling accounts stay configured and return to rotation automatically.
• Codex usage and banked resets. The admin page shows per-account usage windows and available reset credits. When a live request finds every enabled ChatGPT/Codex account unavailable, underclass can redeem one banked reset, choosing the account that would otherwise wait longest for natural quota recovery. This is enabled by default; set auto_codex_resets = false in ~/.config/underclass/config.toml or UNDERCLASS_AUTO_CODEX_RESETS=false to disable automatic redemption.
• Token accounting. Each upstream attempt is recorded in SQLite with its model, account, prompt cache key, and reported input/output tokens. Missing counts remain marked unknown. The admin page shows current-month totals and filters; historical rows remain queryable after account removal.
• Fail fast. If every account eligible for the requested model is cooling, the proxy answers 429 + Retry-After = earliest reset. No queuing.
• Flat pool. Codex and Copilot accounts compete by least-in-flight, filtered by per-backend model catalogs. Unknown model IDs pass through to Codex so new models work without proxy changes.
• Pre-first-byte failover only. Once a stream starts, upstream errors pass through — no silent re-send of half-finished turns.

Design decisions and their trade-offs live in docs/adr/ — start with ADR 0010 for the routing model.

Optional ~/.config/underclass/config.toml:

Environment overrides: UNDERCLASS_BIND, UNDERCLASS_PROXY_KEY, UNDERCLASS_UI_TOKEN, UNDERCLASS_MONITOR_SOCKET (local socket path). For testing against a mock upstream: UNDERCLASS_CODEX_UPSTREAM, UNDERCLASS_COPILOT_UPSTREAM (default to the real endpoints).

State (credentials, sticky bindings, model catalog, minted keys) lives in ~/.local/share/underclass/pool.db. Delete it to start fresh.

underclass serve [--bind ADDR]
underclass top [--url HTTP_OR_HTTPS_ORIGIN]
underclass connect [--base-url URL] [--api-key KEY] [--model MODEL]
                   [--project] [--no-default-model] [--dry-run] [--remove]

connect targets the global opencode config by default; --project writes ./.opencode/opencode.json instead. --dry-run prints the merged documents without writing.

Run underclass top (or utop from the Nix package) in a second terminal while underclass serve is running for a continuously updating, read-only pool monitor. It shows live in-flight requests, a 60-minute attempt chart, current UTC month token accounting, account status and sticky sessions, Codex quota windows and banked resets, and recent outcomes. Account states and quota levels are color coded and also labeled in text. Press q to quit; use arrow keys, j/k, or Page Up/Down to scroll accounts. The dashboard reconnects if the server becomes unavailable. Locally it uses a Unix socket without a token; the NixOS service exposes /run/underclass/monitor.sock to local users. The socket serves only the monitor snapshot, which includes account labels and usage. If no socket is available, top can use the local admin token from UNDERCLASS_UI_TOKEN, config, or the existing database. For another server, pass --url and set UNDERCLASS_UI_TOKEN in the environment. The browser UI still requires its admin token. Copilot quota availability is shown as unknown because underclass has no Copilot quota snapshot. Counts are upstream attempts; token totals omit unknown usage.

Every response carries x-request-id; logs are JSON (RUST_LOG filters, --log-format json|pretty) and each request logs the account (label) that served it.

Accounting queries accept from_ms (inclusive), to_ms (exclusive), and exact model, account_id, or cache_key filters. Use missing_key=true to select requests without a key. Grouped summaries and request details accept limit (1–1000, default 100) and offset; summary responses also include unpaginated totals. With no time bounds, queries default to the current UTC month; provide from_ms=0 to query all history. Each summary includes measured and unknown request counts. Token totals sum reported values only; they are lower bounds when unknown requests exist. See ADR 0014.

When preflight fronts underclass, it generates a UUIDv4 and forwards it as x-request-id. Underclass preserves that ID in its response, routing/retry logs, and request history. Search the same request_id in both services to trace inspection through pool routing.

Underclass accepts one hyphenated RFC4122 UUIDv4 and normalizes it to lowercase. Missing, duplicate, invalid, nil, and other-version IDs are replaced before authentication or logging. Every handled response receives the resulting ID, including 401s, 429s, model discovery, and unmatched routes. Provider responses cannot replace it. Correlation IDs convey no authorization or proof that preflight inspected a request. See ADR 0012.

The catalog is data, not code: seeded with the Codex families (gpt-5.4, gpt-5.4-mini, gpt-5.3-codex-spark, gpt-5.5, gpt-5.6-sol, gpt-5.6-terra, gpt-5.6-luna, gpt-6-astra) and Copilot's live /models list. Edit it in the UI or via the admin API; routing eligibility and the opencode model block follow it. See ADR 0007.

The repository is a Nix flake: it exposes the CLI as a package/app and the devenv development shell as devShells.default.

Run the proxy without installing:

nix run github:ghuntley/underclass -- serve

Install it into your profile:

nix profile install github:ghuntley/underclass
utop

The installed package puts both underclass and utop on your PATH. utop runs underclass top and accepts the same --url option. You can also run it without installing with nix run github:ghuntley/underclass#utop. Enabling the NixOS service with its default package also adds both commands to the host PATH. utop connects to the service's local monitor socket without a token.

Use the devenv shell (Rust toolchain, cargo) for development:

nix develop --no-pure-eval
cargo test

--no-pure-eval is required for the devenv shell (devenv inspects the working directory; this matches devenv's own flake template). The package and app outputs are pure — nix run and nix profile install need no flags.

Long-term devenv users can keep using devenv shell / devenv test directly — nix develop and devenv shell activate the same devenv.nix.

Add underclass to your flake inputs and import its module:

{
  inputs.underclass.url = "github:ghuntley/underclass";

  outputs =
    { nixpkgs, underclass, ... }:
    {
      nixosConfigurations.my-host = nixpkgs.lib.nixosSystem {
        system = "x86_64-linux";
        modules = [
          underclass.nixosModules.default
          {
            services.underclass = {
              enable = true;
              bindAddress = "127.0.0.1:8080";
              environmentFile = "/run/secrets/underclass.env";
              settings = {
                codex_cooldown_secs = 1800;
                copilot_cooldown_secs = 1800;
              };
            };
          }
        ];
      };
    };
}

The runtime environment file can provide credentials without placing them in the Nix store:

UNDERCLASS_PROXY_KEY=sk-underclass-...
UNDERCLASS_UI_TOKEN=...

The service uses a dynamic user, persists its database in /var/lib/underclass, binds to localhost by default, and leaves the firewall closed. Set services.underclass.openFirewall = true only when intentionally binding beyond localhost.

The flake also exports overlays.default. Validate the module and its QEMU machine test with:

nix build .#checks.x86_64-linux.underclass-module
nix build .#checks.x86_64-linux.underclass-vm

Notes:

• The package builds from the committed Cargo.lock; dependency versions are pinned there.
• nix build skips cargo test because the property tests compile the Hegel engine as a build step, which needs network access that the Nix sandbox denies. CI runs the full suite via devenv (see .github/workflows/ci.yml).

• Access/refresh tokens, authorization headers, and prompt bodies are never logged.
• Account labels (email/username) appear in logs and the UI by design; raw UUID account IDs are truncated.
• auth.json written by connect uses 0600. Never commit pool.db or *.bak.
• The proxy binds to localhost by default; put it behind a tunnel only if you understand the exposure.
• OAuth tokens rotate: every Codex refresh persists the new refresh token immediately.

cargo build
cargo test        # 43 unit tests + 8 Hegel property tests + e2e suite

Testing is two-tier: plain unit tests for exact behavior (headers, merges, redaction), and Hegel property tests over the pure pool core — stickiness stability, health-state invariants, saturation minimums, TTL/cap bounds. The core (src/pool.rs, src/health.rs) is synchronous with an injected clock; async lives only at the edges. New backends implement the provider::Backend trait and register — nothing else changes.

Agent conventions and the ADR policy are in AGENTS.md. Architecture decision records: docs/adr/.

MIT

src/
  main.rs      bootstrap, router, background tasks
  config.rs    TOML + env config
  models.rs    domain types (Account, status, catalog, log entries)
  store.rs     SQLite persistence (accounts, bindings, catalog, config)
  pool.rs      pure pool core: stickiness, eligibility, selection
  health.rs    quota classification, retry-after parsing
  provider.rs  Backend trait
  codex.rs     ChatGPT/Codex backend (device flow, refresh, headers)
  copilot.rs   GitHub Copilot backend (device flow, catalog, headers)
  tokens.rs    single-flight token refresh
  proxy.rs     /v1/* handlers, failover, streaming
  logging.rs   structured logs, correlation IDs, redaction
  ui.rs        admin API
  ui.html      embedded single-page web UI
  cli.rs       `connect` verb, JSONC-safe opencode config merge
tests/
  properties.rs  Hegel property tests over the pure core
  e2e.rs         full-pool story against a mock upstream