# Architecture

## Purpose

Singularity Forge (SF) is an autonomous agent orchestration system. It runs long-horizon coding work as a state machine: milestones → slices → tasks. Each dispatch unit runs a fresh AI context, writes its output to disk, then terminates. A deterministic controller (not an LLM) reads disk state and decides what to dispatch next. The user is the end-gate — autonomous mode delivers work to human review, it does not merge to production unattended.

## Codemap

| Path | Purpose |
|------|---------|
| `src/loader.ts` | Entry point — initializes resources, registers extension |
| `src/headless.ts` | Non-interactive (headless) mode driver — exit codes 0/1/10/11/12 |
| `src/headless-events.ts` | Transcript event parsing and notification routing |
| `src/extension-registry.ts` | Registers SF as a Pi coding-agent extension |
| `src/resources/extensions/sf/` | All SF extension source (TypeScript) |
| `src/resources/extensions/sf/auto/` | Autonomous workflow orchestrator (state machine, dispatch, planning) |
| `src/resources/extensions/sf/bootstrap/` | Context injection, system prompt assembly |
| `src/resources/extensions/sf/prompts/` | Prompt templates (`.md`, loaded by `prompt-loader.ts`) |
| `src/resources/extensions/sf/tests/` | Unit and integration tests |
| `dist/resources/extensions/sf/` | Compiled JS (rebuilt by `npm run copy-resources`) |
| `~/.sf/agent/extensions/sf/` | Installed copy (synced from dist on startup) |
| `docs/` | Durable product, design, plan, reliability, and security context |
| `harness/` | Specs (behavior contracts), evals (model-output tests), graders |

## State layout (`.sf/`)

`.sf/` can be a **symlink** (external state, `~/.sf/projects/<hash>/`) or a **local directory** (tracking-enabled per ADR-001).

**Tracked in git** (travel with the branch, per ADR-001):
```
.sf/milestones/     — roadmaps, plans, summaries, task plans
.sf/PROJECT.md      — project overview
.sf/DECISIONS.md    — architectural decisions register
.sf/REQUIREMENTS.md — requirements register
.sf/QUEUE.md        — work queue / backlog
.sf/KNOWLEDGE.md    — project-specific rules for agents
```

**Gitignored** (runtime/ephemeral — managed by `ensureGitInfoExclude()` in `.git/info/exclude`):
```
.sf/activity/       — JSONL session dumps
.sf/audit/          — audit trail entries
.sf/exec/           — in-flight execution state
.sf/forensics/      — crash forensics
.sf/journal/        — SF journal entries
.sf/model-benchmarks/ — model benchmark results
.sf/parallel/       — parallel dispatch coordination
.sf/reports/        — generated reports
.sf/runtime/        — dispatch records, timeout tracking
.sf/worktrees/      — git worktree working directories
.sf/auto.lock       — crash detection sentinel
.sf/metrics.json    — token/cost accumulator
.sf/sf.db*          — SQLite cache (rebuilt from markdown by importers)
.sf/STATE.md        — derived state cache
.sf/notifications.jsonl, .sf/routing-history.json, .sf/self-feedback.jsonl, .sf/repo-meta.json
```

The symlink case uses a blanket `.sf` gitignore pattern (git cannot traverse symlinks). The directory case uses granular patterns so planning artifacts remain trackable.

## Key flows

**Autonomous dispatch loop** (`src/resources/extensions/sf/auto/`):
1. `deriveState()` reads disk and produces a typed state snapshot
2. Controller selects the next dispatch unit (research, plan, implement, verify, etc.)
3. A fresh agent context is started with the task plan injected via `system-context.ts`
4. Agent writes artifacts to disk, commits, exits
5. Loop repeats until milestone completes or a gate fails

**System context assembly** (`bootstrap/system-context.ts`):
`PREFERENCES.md` → `KNOWLEDGE.md` → `ARCHITECTURE.md` → `CODEBASE.md` → code intelligence → memories → worktree/VCS blocks

**Write gate** (`bootstrap/write-gate.ts`):
All file writes in autonomous mode pass through a gate. Protected files (CLAUDE.md, CODEBASE.md, certain spec files) require explicit override.

## Invariants

- The state machine (controller) is pure TypeScript — no LLM decisions in the dispatch loop itself.
- Each dispatch unit runs in a fresh context — no cross-turn state accumulation.
- Planning artifacts are tracked in git; runtime artifacts are never committed.
- `SF_RUNTIME_PATTERNS` in `gitignore.ts` is the canonical source of truth for runtime paths. `git-service.ts` (`RUNTIME_EXCLUSION_PATHS`) and `worktree-manager.ts` (`SKIP_*` arrays) must stay synchronized with it.
- The user is the end-gate. SF delivers for review, not to production.