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Nexus App Integration into the ABI Monorepo

  • Document Type: ADR
  • Status: Accepted
  • Date: 2026-02-11

Context​

The Nexus frontend (Next.js) and its API (FastAPI) were maintained in a separate repository. This created friction: coordinating releases between the ABI Python monorepo and the Nexus repo required manual version pinning, delayed integration testing, and made it hard to ship full-stack features atomically.

Decision​

Integrate the Nexus app (both the Next.js web frontend and its FastAPI API layer) directly into the ABI monorepo at libs/naas-abi/naas_abi/apps/nexus/.

The Nexus API is wired into the ABI engine as a module: it receives the engine's configured services (TripleStore, VectorStore, BusService, etc.) at startup, rather than bootstrapping its own service instances. The Next.js frontend lives at apps/web/ and is managed with pnpm.

The Nexus FastAPI app is mounted on the same process as the ABI core API, sharing the app instance and middleware (including CORS - see 20260305_cors-single-source-of-truth).

Consequences​

Positive​

  • Full-stack features can be shipped in a single PR with atomic version bumps.
  • Integration tests cover the full ABI+Nexus surface in CI.
  • Eliminates cross-repo version drift.

Tradeoffs​

  • The monorepo grows in scope; developers need both Python (uv) and Node (pnpm) toolchains.
  • The Nexus web app's node_modules adds significant disk usage and pnpm install is required in setup.
  • Shared process means a crash or misconfiguration in Nexus can affect the core API and vice versa.