# AO technical stack

This is the source of truth for library and runtime choices in the AO rewrite.
Keep this document about durable technology decisions; use `status.md` for
implementation progress and `architecture.md` for component behavior and
invariants.

## Principles

- Prefer the Go standard library until a small dependency clearly earns its
  place.
- Keep the backend daemon boring: explicit process control, explicit SQL,
  narrow adapters, and observable failure modes.
- Shell out where AO needs the user's real developer-machine behavior, especially
  for Git and terminal multiplexers.
- Keep high-volume terminal output out of SQLite; store structured state in the
  database and stream/log payload-heavy data separately.

## Accepted stack

| Area | Decision | Status | Rationale |
|------|----------|--------|-----------|
| Backend language | Go 1.25.7 | Implemented | Matches `backend/go.mod`; small daemon, strong stdlib, easy local distribution. |
| Backend core | Go stdlib | Implemented | Domain, lifecycle, session, and adapter contracts should stay dependency-light. |
| Frontend shell | Electron + TypeScript | Implemented | Local desktop control plane paired with the daemon. |
| Runtime adapter | `zellij` CLI via `os/exec` | Implemented | Terminal multiplexing fits long-running sessions, attach/debug workflows, and adapter isolation. |
| Terminal PTY | `github.com/creack/pty` | Implemented | PTY-backed terminal sessions with resize/input/output control. |
| Git/worktrees | `git` CLI via `os/exec` | Implemented | Uses real repo behavior, credentials, hooks, LFS, submodules, and user config. |
| HTTP API | `net/http` + `github.com/go-chi/chi/v5` | Implemented | Lightweight, idiomatic router without committing AO to a large web framework. |
| WebSocket | `github.com/coder/websocket` | Implemented | Small WebSocket library for terminal streaming. |
| Storage | SQLite in WAL mode via `database/sql` | Implemented | Local daemon, single writer, many dashboard/API reads, no external DB setup. |
| SQLite driver | `modernc.org/sqlite` | Implemented | Current pure-Go driver in `backend/internal/storage/sqlite`; keep it swappable behind `database/sql`. |
| SQL generation | `github.com/sqlc-dev/sqlc` | Implemented | Hand-written SQL with generated typed methods from `backend/sqlc.yaml`. |
| Migrations | `github.com/pressly/goose/v3` | Implemented | Simple SQL migrations for the embedded/local database. |
| CLI | `github.com/spf13/cobra` | Implemented | Standard command structure for daemon startup, diagnostics, and admin commands. |
| Config | stdlib environment loading + SQLite-backed state/config | Implemented / evolving | `internal/config` handles daemon env/defaults; durable product config belongs in SQLite, so no config framework is selected for V1. |
| Logging | `log/slog` | Implemented | Stdlib structured logging before adding another logging dependency. |
| OpenAPI generation | `github.com/swaggest/openapi-go`, `github.com/swaggest/jsonschema-go`, `gopkg.in/yaml.v3` | Implemented | Generated OpenAPI keeps route contracts close to Go DTOs. |
| Testing | stdlib `testing` | Implemented | Keep pure domain logic and adapter contracts easy to test. |
| Test assertions | `github.com/stretchr/testify/require` | Planned if needed | Concise assertions for higher-level adapter and integration tests; do not add unless tests benefit. |
| Packaging | `github.com/goreleaser/goreleaser` | Planned | Cross-platform release automation, checksums, and future Homebrew support. |

## Pending decisions

### SQLite driver validation

Current main uses `modernc.org/sqlite`. Before release packaging is locked,
validate `github.com/ncruces/go-sqlite3/driver` against AO's WAL, migration,
and `change_log`/CDC workload. It is the preferred no-CGO candidate if it passes
compatibility and performance checks.

Keep the driver behind `database/sql` so the persistence layer can switch
drivers without changing store interfaces.

Required SQLite setup:

```sql
PRAGMA journal_mode = WAL;
PRAGMA busy_timeout = 5000;
PRAGMA foreign_keys = ON;
PRAGMA synchronous = NORMAL;
```

### Config model

Current daemon config is stdlib env/default loading. Project and product config
should be persisted in SQLite when it needs durability or user editing. Do not
add `github.com/spf13/viper` or `github.com/knadh/koanf` unless a real file-based
config surface appears.

## Explicitly avoided for V1

| Avoid | Reason |
|-------|--------|
| GORM | AO needs explicit transactional SQL and CDC-triggered writes. |
| Gin/Fiber | `net/http` + `chi` is enough for a local daemon API. |
| `go-git` as the primary Git engine | AO should match installed Git behavior, credentials, hooks, LFS, submodules, and user config. |
| `github.com/spf13/viper` / `github.com/knadh/koanf` by default | Env/default loading plus SQLite-backed config is enough for V1. |
| Temporal / NATS / Kafka / Redis | V1 is a local daemon with SQLite and CDC, not a distributed control plane. |
| Full plugin framework | Keep adapter interfaces narrow until product needs justify a plugin runtime. |
| Multi-sink CDC fan-out | Start with one durable local delivery path; add fan-out later if needed. |

## Current stack mapping

```txt
Go daemon
  net/http + github.com/go-chi/chi/v5
  github.com/coder/websocket
  github.com/creack/pty
  zellij runtime adapter via os/exec
  git worktree adapter via git CLI
  SQLite via database/sql + modernc.org/sqlite
  github.com/sqlc-dev/sqlc generated queries
  github.com/pressly/goose/v3 migrations
  log/slog
  github.com/spf13/cobra CLI
  SQLite change_log + CDC poller
```

This stack supports the current architecture: durable session/PR/project facts,
derived display status, SQLite `change_log` CDC, terminal sessions, and real Git
worktrees.