# ADR-014: Singularity Knowledge + Agent Platform stack

**Date**: 2026-04-29
**Status**: proposed (deferred — capture for staged execution)
**Revised**: 2026-05-02 — Phase 4 cancelled, see [ADR-019](./ADR-019-workspace-vm-convergence.md)

## Context

`SPEC.md` §16 defines a cross-instance knowledge layer (Singularity Memory). `SPEC.md` §17–18 defines persistent agents and inter-agent messaging (status NEW). sf instances today carry their own local memory store (`memory-store.ts`); persistent agents are not implemented at all.

Two trajectories converge:

- **Knowledge federates** — anti-patterns, learnings, contracts should be reachable across sf instances and across other agent products on the tailnet (Hermes, OpenClaw, Claude Code, Cursor).
- **Persistent agents centralise** — long-lived cross-project agents (code-reviewer with cross-project memory, memory-curator, security-auditor, build-watch) are too heavy and too cross-cutting to live per-project.

These two needs collapse into one service: the **Singularity Knowledge + Agent Platform** — a single Go server hosting the federated memory store *and* the central persistent-agent runtime. *(Note: the persistent-agent runtime portion — Phase 4 — has since been cancelled by [ADR-019](./ADR-019-workspace-vm-convergence.md). This ADR's active scope is the knowledge layer only, Phases 0–3.)*

This ADR fixes the stack.

The implementation arm of this ADR lives in [`singularity-memory/MIGRATION.md`](https://github.com/singularity-ng/singularity-memory/blob/main/MIGRATION.md).

## Decision

- **Language: Go.**
- **Storage backbone: Postgres + vchord** (existing) — accessed from Go via `pgx`. No data migration; same schema, same vchord index.
- **Identity / auth / sync layer: `charmbracelet/charm`-server patterns** — SSH-key identity, JWT issuance, encrypted KV for user-level prefs and config. Adopted as ported library code; not run as a sidecar.
- **Agent runtime: `charmbracelet/fantasy`** — multi-provider LLM access (Anthropic, OpenAI, Google, Bedrock, OpenRouter, etc. via `catwalk`). Used for embeddings/summarisation today. *(The original plan to grow this into a full central persistent-agent runtime — Phase 4 — is cancelled by [ADR-019](./ADR-019-workspace-vm-convergence.md). `fantasy` is retained for embeddings/summarisation within the knowledge layer only.)*
- **HTTP API: Go `net/http` + chi or echo router**, serving the *exact* current OpenAPI contract.
- **MCP server: same wire protocol** as today's Python implementation. Clients (sf, Hermes, OpenClaw, Claude Code, Cursor) keep working unchanged.
- **CLI scaffolding: `charmbracelet/fang`.**
- **Observability: `promwish`-style Prometheus metrics**, scraped from a shared metrics endpoint.
- **Admin UI (Phase 3): `pony` + `ultraviolet`** for the view layer (reversed from earlier deferral; now adopted as a deliberate foundation bet — admin UI tolerates churn better than user-facing surfaces). Served over SSH via `wish`.

## Alternatives Considered

### Stack

- **Stay Python + FastAPI + Postgres.** Status quo. Works today.
  - *Rejected:* misses the foundation bet for central persistent agents (sf SPEC §17). Building those on Python + raw OpenAI/Anthropic SDK calls means retrofitting fantasy-style agent semantics later — real refactor cost. The trigger to migrate isn't pain in the current server; it's foundation laying for what comes next.
- **Rust + axum + Postgres.** Uniformly fast, but Charm's agentic ecosystem (fantasy, catwalk, wish, charm-server, the entire Bubble Tea family) is Go-native. Rust on the server side would mean reimplementing those abstractions or shelling out. Rejected — wrong ecosystem.
- **TypeScript + Node + Postgres.** Keeps language alignment with sf core. But sf is moving toward parallel-build (ADR-016): TS in sf core, Go in new services. The Node ecosystem doesn't have an equivalent to fantasy + charm-server + Wish. Rejected.

### Storage backbone

- **Replace Postgres + vchord with `charm-server`'s native KV.** `charm-server` is a personal/team encrypted KV; it's not a vector DB or BM25 index. We'd lose retrieval sophistication. Rejected.
- **Replace Postgres with `sqlite-vec`.** Embeddable single-binary deployment is appealing, but BM25 quality on `tsvector` is hard to match without a full re-tune, and we'd be redoing data migration on top. Rejected for v1; revisit in a v2 retrieval ADR if the Go server needs to ship without Postgres.
- **Keep Postgres + vchord, connect via Go `pgx`.** ← chosen. Battle-tested retrieval, zero data migration, focus the migration on language/runtime/agent-platform changes only.

### Agent runtime

- **Direct SDK calls (`anthropic-sdk-go`, `openai-go`, `go-genai`).** Simplest for today's narrow LLM use (embeddings + summarisation). But future central persistent agents need agent-loop semantics (multi-turn, tool calls); building those on raw SDKs reinvents fantasy's abstractions. Rejected — foundation bet. *(Phase 4 is now cancelled by [ADR-019](./ADR-019-workspace-vm-convergence.md), so the persistent-agent motivation no longer applies; however `fantasy` is still chosen for its clean multi-provider API for embeddings/summarisation.)*
- **Build our own agent runtime in Go.** Pure NIH. Rejected.
- **`charmbracelet/fantasy`.** ← chosen. 730 stars, actively developed, clean API, multi-provider via `catwalk`.

## Consequences

**Positive**

- **Foundation is right** for the knowledge layer. *(The original "foundation for central persistent agents" rationale is superseded — Phase 4 is cancelled by [ADR-019](./ADR-019-workspace-vm-convergence.md). Persistent agents now live as Firecracker VM snapshots managed by ACE.)*
- **Single static Go binary** is operationally simpler than Python uv/venv + Alembic + worker on each deployment host.
- **Charm ecosystem alignment** with sf-worker (ADR-013), flight recorder (ADR-015), Charm TUI client (ADR-017). One language for the new-services tier.
- **Wire contract preserved** — clients are zero-touch.

**Negative**

- **Migration is a real undertaking** — ~12 weeks total, with the recall endpoint as the critical parity gate. See `MIGRATION.md`.
- **Polyglot deployment grows** — Python (during transition) + Go (new) + TS (sf core) + Rust (sf native). Bounded; once Python retires, three languages with clear boundaries.
- **`fantasy` and `pony` are pre-1.0** — API churn is real.

**Risks and mitigations**

- *Risk:* recall quality regression between Python and Go.
  - *Mitigation:* held-out evaluation set; ±2% recall@k threshold enforced in CI before flipping traffic.
- *Risk:* `pgx` + vchord custom-type decoder edge cases.
  - *Mitigation:* prove out in Phase 1 against a small endpoint; engage vchord author if blocked.
- *Risk:* `fantasy` API churn during the migration.
  - *Mitigation:* pin a version; one planned upgrade midway through the migration.
- *Risk:* central agents prove unworkable as a model and we've over-built the foundation.
  - *Mitigation:* the foundation cost is incremental (fantasy ≈ raw SDK + a thin abstraction). Worst case we use fantasy for embeddings only and never grow it. No wasted bet. *(Moot — Phase 4 is cancelled by [ADR-019](./ADR-019-workspace-vm-convergence.md); fantasy stays scoped to the knowledge layer.)*

## Out of Scope

- **Cross-tenant Singularity Memory** — single trust domain per deployment.
- **Retrieval-pipeline redesign** — BM25 + vector + RRF + reranker semantics are preserved exactly.
- **DB migration** — Postgres + vchord stay.
- **Public-internet endpoint** — tailnet only per ADR-013.

## Sequencing

| Phase | What | Cost |
|---|---|---|
| 0 | Prep: commit OpenAPI spec, build test suite, set up CI (per existing `TODO.md`) | 1–2 weeks |
| 1 | Greenfield Go scaffold parallel to Python; first endpoint (`GET /v1/banks`) | 2–3 weeks |
| 2 | Endpoint parity (recall is the critical gate) | 4–8 weeks |
| 3 | Worker + admin UI (`pony` + `ultraviolet` on `wish`) | 2–3 weeks |
| ~~4~~ | ~~Central persistent-agent host~~ | ~~variable~~ |
| 5 | Python deprecation | 1 week |

Total: ~12 weeks for Phases 0–3 + Phase 5. Phase 4 is cancelled — see section below.

## Phase 4 — Cancelled (See [ADR-019](./ADR-019-workspace-vm-convergence.md))

Phase 4 was originally planned as a "central persistent-agent runtime" built on `charmbracelet/fantasy` inside singularity-memory's Go server. [ADR-019](./ADR-019-workspace-vm-convergence.md) (Workspace VM Convergence, 2026-05-01) supersedes this plan entirely.

**What replaced it:** Persistent agents now live as **Firecracker VM snapshots managed by ACE**'s orchestration layer. A "persistent agent" is a named VM snapshot: restore it, and the agent wakes with its full memory and context intact. singularity-memory's scope is now strictly the knowledge layer (Phases 0–3). See ADR-019 § "ADR-014 Phase 4 is reassigned" for the authoritative statement.

### Historical: Original Phase 4 Plan

> *The content below is the original Phase 4 design, preserved as a historical record. It is **not** the current plan.*

The original Phase 4 called for singularity-memory's Go server to host a central persistent-agent runtime using `charmbracelet/fantasy`. Long-lived cross-project agents (code-reviewer, memory-curator, security-auditor, build-watch) would run there, with their state managed by the same Postgres store. This depended on sf SPEC §17 scoping being completed ("status NEW" at ADR-014's writing date).

The rationale for building this in singularity-memory was ecosystem alignment with `fantasy` + `charm-server` + `wish` and avoiding per-project agent redundancy. The timeline was listed as "variable" because SPEC §17 had not been fully scoped.

ADR-019 made this moot by choosing a cleaner isolation model (hypervisor-level VM snapshots) that is language-agnostic inside the VM, multi-tenant by construction, and owned by ACE rather than a shared Go server.

## References

- `MIGRATION.md` (singularity-memory repo) — implementation arm.
- `SPEC.md` §16 — Knowledge Layer.
- `SPEC.md` §17–18 — Persistent Agents and Inter-Agent Messaging.
- `ADR-012` — Multi-instance federation (this is one of its surfaces).
- `ADR-013` — Network and remote-execution (deployment substrate).
- `ADR-016` — Charm AI stack adoption (frames the polyglot decision).
- `charmbracelet/charm` — KV with sync (auth/identity patterns ported here).
- `charmbracelet/fantasy` — agent runtime.
- `charmbracelet/catwalk` — provider/model registry.