# Orchestrator Advanced Flows — Design

## Architecture

```
┌───────────── Step dispatch ─────────────────┐
│                                              │
│  Flow-runner resolves step:                  │
│    1. Check trigger_rule on deps             │
│    2. Substitute $vars in prompt             │
│    3. If approval gate → pause for user      │
│    4. INSERT task row → dispatcher picks up  │
│    5. On terminal: append to event log       │
│    6. Advance next ready step                │
│                                              │
└──────────────────────────────────────────────┘
```

## Type Changes

### `apps/coder/src/conductor/types.ts`

```typescript
export type TriggerRule = 'all_success' | 'one_success' | 'all_done';

export interface Step {
  id: string;
  kind: StepKind | 'approval';         // + new kind
  deps?: string[];
  trigger_rule?: TriggerRule;            // NEW: default 'all_success'
  agent?: string;
  run: (ctx: StepContext) => string | Promise<string>;
  when?: (ctx: StepContext) => boolean;
}
```

### `apps/coder/src/services/flow-runner.ts`

| Change | Detail |
|--------|--------|
| Trigger evaluation | Before dispatching a step, check deps statuses against `trigger_rule`. Skip if conditions not met |
| Variable substitution | Scan prompt for `$word.word` patterns, resolve from previous step outputs |
| Approval gate | When `step.kind === 'approval'`, insert a `tasks` row with `state='blocked'` and publish a `permission_requested` WS frame. Wait for `permission_resolved` to unblock |
| Event log | Append-only per-step events: `{ step_id, event: 'started'|'completed'|'failed'|'paused'|'resumed', at: timestamp }` in `flow_step_events` table |

## Schema

```sql
CREATE TABLE IF NOT EXISTS flow_step_events (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  run_id UUID NOT NULL REFERENCES flow_runs(id),
  step_id VARCHAR(64) NOT NULL,
  event VARCHAR(32) NOT NULL,  -- started, completed, failed, paused, resumed, skipped
  payload JSONB,
  created_at TIMESTAMPTZ NOT NULL DEFAULT clock_timestamp()
);
```

## Resolution Order

1. Collect all completed steps in the run
2. For each unstarted step whose deps are met:
   - Evaluate `trigger_rule` against dep statuses
   - If met → advance the step (with variable substitution)
   - If not met → skip (for `one_success`, mark it complete when any dep succeeds)
3. For approval gates: pause, publish frame, wait for user response

## Rollback

All changes are additive to the Step type. Existing flows without `trigger_rule` default to `all_success`, preserving current behavior. Approval gates are opt-in per step definition.
