# Policy Engine REST API

> **Audience:** Backend integrators, platform operators, and CI engineers invoking Policy Engine services programmatically.  
> **Base URL:** `/api/policy/*` (internal gateway route) – requires OAuth 2.0 bearer token issued by Authority with scopes listed below.

This document is the canonical reference for the Policy Engine REST surface described in Epic 2 (Policy Engine v2). Use it alongside the [DSL](../policy/dsl.md), [Lifecycle](../policy/lifecycle.md), and [Runs](../policy/runs.md) guides for end-to-end implementations.

---

## 1 · Authentication & Headers

- **Auth:** Bearer tokens (`Authorization: Bearer <token>`) with the following scopes as applicable:
- `policy:read`, `policy:author`, `policy:review`, `policy:approve`, `policy:operate`, `policy:run`, `policy:activate`, `policy:archive`, `policy:simulate`, `policy:runs`
  - `findings:read` (for effective findings APIs)
  - `effective:write` (service identity only; not exposed to clients)
- **Service identity:** Authority marks the Policy Engine client with `properties.serviceIdentity: policy-engine`. Tokens missing this marker cannot obtain `effective:write`.
- **Tenant:** Supply tenant context via `X-Stella-Tenant`. Tokens without multi-tenant claims default to `default`.
- **Idempotency:** For mutating endpoints, include `Idempotency-Key` (UUID). Retries with same key return original result.
- **Content type:** All request/response bodies are `application/json; charset=utf-8` unless otherwise noted.

---

## 2 · Error Model

All errors use HTTP semantics plus a structured payload:

```json
{
  "code": "ERR_POL_001",
  "message": "Policy syntax error",
  "details": [
    {"path": "rules[0].when", "error": "Unknown function foo()"}
  ],
  "traceId": "01HDV1C4E9Z4T5G6H7J8",
  "timestamp": "2025-10-26T14:07:03Z"
}
```

| Code | Meaning | Notes |
|------|---------|-------|
| `ERR_POL_001` | Policy syntax/compile error | Returned by `compile`, `submit`, `simulate`, `run` when DSL invalid. |
| `ERR_POL_002` | Policy not approved | Attempted to run or activate unapproved version. |
| `ERR_POL_003` | Missing inputs | Downstream service unavailable (Concelier/Excititor/SBOM). |
| `ERR_POL_004` | Determinism violation | Illegal API usage (wall-clock, RNG). Triggers incident mode. |
| `ERR_POL_005` | Unauthorized materialisation | Identity lacks `effective:write`. |
| `ERR_POL_006` | Run canceled or timed out | Includes cancellation metadata. |

---

## 3 · Policy Management

### 3.1 Create Draft

```
POST /api/policy/policies
Scopes: policy:author
```

**Request**

```json
{
  "policyId": "P-7",
  "name": "Default Org Policy",
  "description": "Baseline severity + VEX precedence",
  "dsl": {
    "syntax": "stella-dsl@1",
    "source": "policy \"Default Org Policy\" syntax \"stella-dsl@1\" { ... }"
  },
  "tags": ["baseline","vex"]
}
```

**Response 201**

```json
{
  "policyId": "P-7",
  "version": 1,
  "status": "draft",
  "digest": "sha256:7e1d…",
  "createdBy": "user:ali",
  "createdAt": "2025-10-26T13:40:00Z"
}
```

### 3.2 List Policies

```
GET /api/policy/policies?status=approved&tenant=default&page=1&pageSize=25
Scopes: policy:read
```

Returns paginated list with `X-Total-Count` header.

### 3.3 Fetch Version

```
GET /api/policy/policies/{policyId}/versions/{version}
Scopes: policy:read
```

Returns full DSL, metadata, provenance, simulation artefact references.

### 3.4 Update Draft Version

```
PUT /api/policy/policies/{policyId}/versions/{version}
Scopes: policy:author
```

Body identical to create. Only permitted while `status=draft`.

---

## 4 · Lifecycle Transitions

### 4.1 Submit for Review

```
POST /api/policy/policies/{policyId}/versions/{version}:submit
Scopes: policy:author
```

**Request**

```json
{
  "reviewers": ["user:kay","group:sec-reviewers"],
  "notes": "Simulated on golden SBOM set (diff attached)",
  "simulationArtifacts": [
    "blob://policy/P-7/v3/simulations/2025-10-26.json"
  ]
}
```

**Response 202** – submission recorded. `Location` header points to review resource.

### 4.2 Review Feedback

```
POST /api/policy/policies/{policyId}/versions/{version}/reviews
Scopes: policy:review
```

**Request**

```json
{
  "decision": "approve",     // approve | request_changes | comment
  "note": "Looks good, ensure incident playbook covers reachability data.",
  "blocking": false
}
```

### 4.3 Approve

```
POST /api/policy/policies/{policyId}/versions/{version}:approve
Scopes: policy:approve
```

Body requires approval note and confirmation of compliance gates:

```json
{
  "note": "All simulations and determinism checks passed.",
  "acknowledgeDeterminism": true,
  "acknowledgeSimulation": true
}
```

### 4.4 Activate

```
POST /api/policy/policies/{policyId}/versions/{version}:activate
Scopes: policy:activate, policy:run
```

Marks version as active for tenant; triggers optional immediate full run (`"runNow": true`).

### 4.5 Archive

```
POST /api/policy/policies/{policyId}/versions/{version}:archive
Scopes: policy:archive
```

Request includes `reason` and optional `incidentId`.

---

## 5 · Compilation & Validation

### 5.1 Compile

```
POST /api/policy/policies/{policyId}/versions/{version}:compile
Scopes: policy:author
```

**Response 200**

```json
{
  "digest": "sha256:7e1d…",
  "warnings": [],
  "rules": {
    "count": 24,
    "actions": {
      "block": 5,
      "warn": 4,
      "ignore": 3,
      "requireVex": 2
    }
  }
}
```

### 5.2 Lint / Simulate Quick Check

```
POST /api/policy/policies/{policyId}/lint
Scopes: policy:author
```

Slim wrapper used by CLI; returns 204 on success or `ERR_POL_001` payload.

---

## 6 · Run & Simulation APIs

> Schema reference: canonical policy run request/status/diff payloads ship with the Scheduler Models guide (`src/Scheduler/__Libraries/StellaOps.Scheduler.Models/docs/SCHED-MODELS-20-001-POLICY-RUNS.md`) and JSON fixtures under `samples/api/scheduler/policy-*.json`.

### 6.1 Trigger Run

```
POST /api/policy/policies/{policyId}/runs
Scopes: policy:run
```

**Request**

```json
{
  "mode": "incremental",           // full | incremental
  "runId": "run:P-7:2025-10-26:auto",   // optional idempotency key
  "sbomSet": ["sbom:S-42","sbom:S-318"],
  "env": {"exposure": "internet"},
  "priority": "normal"             // normal | high | emergency
}
```

**Response 202**

```json
{
  "runId": "run:P-7:2025-10-26:auto",
  "status": "queued",
  "queuedAt": "2025-10-26T14:05:00Z"
}
```

### 6.2 Get Run Status

```
GET /api/policy/policies/{policyId}/runs/{runId}
Scopes: policy:runs
```

Includes status, stats, determinism hash, failure diagnostics.

### 6.3 List Runs

```
GET /api/policy/policies/{policyId}/runs?mode=incremental&status=failed&page=1&pageSize=20
Scopes: policy:runs
```

Supports filtering by `mode`, `status`, `from`/`to` timestamps, `tenant`.

### 6.4 Simulate

```
POST /api/policy/policies/{policyId}/simulate
Scopes: policy:simulate
```

**Request**

```json
{
  "baseVersion": 3,
  "candidateVersion": 4,
  "sbomSet": ["sbom:S-42","sbom:S-318"],
  "env": {"sealed": false},
  "explain": true
}
```

**Response 200**

```json
{
  "diff": {
    "added": 12,
    "removed": 8,
    "unchanged": 657,
    "bySeverity": {
      "Critical": {"up": 1, "down": 0},
      "High": {"up": 3, "down": 4}
    }
  },
  "explainUri": "blob://policy/P-7/simulations/2025-10-26-4-vs-3.json"
}
```

### 6.5 Replay Run

```
POST /api/policy/policies/{policyId}/runs/{runId}:replay
Scopes: policy:runs, policy:simulate
```

Produces sealed bundle for determinism verification; returns location of bundle.

---

## 7 · Effective Findings APIs

### 7.1 List Findings

```
GET /api/policy/findings/{policyId}?sbomId=S-42&status=affected&severity=High,Critical&page=1&pageSize=100
Scopes: findings:read
```

Response includes cursor-based pagination:

```json
{
  "items": [
    {
      "findingId": "P-7:S-42:pkg:npm/lodash@4.17.21:CVE-2021-23337",
      "status": "affected",
      "severity": {"normalized": "High", "score": 7.5},
      "sbomId": "sbom:S-42",
      "advisoryIds": ["CVE-2021-23337"],
      "vex": {"winningStatementId": "VendorX-123"},
      "policyVersion": 4,
      "updatedAt": "2025-10-26T14:06:01Z"
    }
  ],
  "nextCursor": "eyJwYWdlIjoxfQ=="
}
```

### 7.2 Fetch Explain Trace

```
GET /api/policy/findings/{policyId}/{findingId}/explain?mode=verbose
Scopes: findings:read
```

Returns rule hit sequence:

```json
{
  "findingId": "P-7:S-42:pkg:npm/lodash@4.17.21:CVE-2021-23337",
  "policyVersion": 4,
  "steps": [
    {"rule": "vex_precedence", "status": "not_affected", "inputs": {"statementId": "VendorX-123"}},
    {"rule": "severity_baseline", "severity": {"normalized": "Low", "score": 3.4}}
  ],
  "sealedHints": [{"message": "Using cached EPSS percentile from bundle 2025-10-20"}]
}
```

---

## 8 · Events & Webhooks

- `policy.run.completed` – emitted with `runId`, `policyId`, `mode`, `stats`, `determinismHash`.
- `policy.run.failed` – includes error code, retry count, guidance.
- `policy.lifecycle.*` – mirrored from lifecycle APIs (see [Lifecycle guide](../policy/lifecycle.md)).
- Webhook registration occurs via `/api/policy/webhooks` (future work, reserved). For now, integrate with Notifier streams documented in `/docs/notifications/*`.

---

## 9 · Compliance Checklist

- [ ] **Scopes enforced:** Endpoint access requires correct Authority scope mapping (see `/src/Authority/StellaOps.Authority/TASKS.md`).
- [ ] **Schemas current:** JSON examples align with Scheduler Models (`SCHED-MODELS-20-001`) and Policy Engine DTOs; update when contracts change.
- [ ] **Error codes mapped:** `ERR_POL_*` table reflects implementation and CI tests cover edge cases.
- [ ] **Pagination documented:** List endpoints specify page/size and cursor semantics; responses include `X-Total-Count` or `nextCursor`.
- [ ] **Idempotency described:** Mutating endpoints mandate `Idempotency-Key`.
- [ ] **Offline parity noted:** Simulate/run endpoints explain `--sealed` behaviour and bundle generation.
- [ ] **Cross-links added:** References to lifecycle, runs, DSL, and observability docs verified.

---

*Last updated: 2025-10-26 (Sprint 20).*