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+---
+title: "Agent Authentication Contract"
+description: "ASG Agent Cloud v5.2.x API Key authentication specification"
+---
+
+# Agent Authentication Contract
+
+This document defines the authentication contract for programmatic (agent/bot) access to ASG Agent Cloud.
+
+## Authentication Hierarchy
+
+ASG Gateway supports two authentication methods, evaluated in order:
+
+1. **SIWS Session Cookie** (`asg_session`) — For console UI users
+2. **Bearer Token API Key** — For agents and programmatic access
+
+```
+Authorization: Bearer asc_sk_...
+```
+
+## API Key Format
+
+| Prefix | Environment | Example |
+|--------|-------------|---------|
+| `asc_sk_live_` | Production | `asc_sk_live_abc123...` |
+| `asc_sk_test_` | Staging/Dev | `asc_sk_test_xyz789...` |
+
+Keys are 64-character random strings prefixed with environment indicator.
+
+## Security Model
+
+### Key Storage
+
+- **Plain-text key**: Shown ONCE at creation time — user must save it
+- **Server stores**: BCrypt hash only (cost=10)
+- **No recovery**: Lost keys cannot be retrieved; user must rotate
+
+### Scopes
+
+| Scope | Description |
+|-------|-------------|
+| `read` | Query balance, history, usage stats (default) |
+| `fund` | Initiate deposits, manage billing (requires opt-in) |
+
+### Rate Limits
+
+| Tier | RPM Limit | Default |
+|------|-----------|---------|
+| Free | 60 | ✓ |
+| Plus | 300 | |
+| Pro | 1000 | |
+
+Limits are per-key, not per-wallet. 429 responses include `Retry-After` header.
+
+## Endpoints (Billing Plane)
+
+### Create Key
+
+```http
+POST /keys
+Content-Type: application/json
+Cookie: asg_session=...
+
+{
+  "name": "My Agent Bot",
+  "scopes": ["read"],
+  "rate_limit_rpm": 60
+}
+```
+
+**Response (201):**
+
+```json
+{
+  "key_id": "key_abc123",
+  "api_key": "asc_sk_live_...",  // ⚠️ SHOW ONCE
+  "name": "My Agent Bot",
+  "scopes": ["read"],
+  "rate_limit_rpm": 60,
+  "created_at": "2026-02-03T12:00:00Z"
+}
+```
+
+### List Keys
+
+```http
+GET /keys
+Cookie: asg_session=...
+```
+
+**Response:**
+
+```json
+{
+  "keys": [
+    {
+      "key_id": "key_abc123",
+      "name": "My Agent Bot",
+      "prefix": "asc_sk_live_abc...",  // First 16 chars only
+      "scopes": ["read"],
+      "rate_limit_rpm": 60,
+      "last_used_at": "2026-02-03T11:30:00Z",
+      "created_at": "2026-02-03T10:00:00Z"
+    }
+  ]
+}
+```
+
+### Revoke Key
+
+```http
+DELETE /keys/:key_id
+Cookie: asg_session=...
+```
+
+### Rotate Key
+
+```http
+POST /keys/:key_id/rotate
+Cookie: asg_session=...
+```
+
+**Response:** New key object (same as Create)
+
+### Validate Key (Internal)
+
+```http
+POST /keys/validate
+Content-Type: application/json
+
+{ "api_key": "asc_sk_live_..." }
+```
+
+**Response:**
+
+```json
+{
+  "valid": true,
+  "key_id": "key_abc123",
+  "owner_wallet": "ABC...xyz",
+  "scopes": ["read"],
+  "rate_limit_rpm": 60
+}
+```
+
+## Gateway Auth Middleware
+
+The gateway validates keys via billing-plane `/keys/validate` with 5-minute caching.
+
+```typescript
+// Request gets decorated with:
+interface AuthenticatedRequest extends Request {
+  apiKeyId?: string;       // e.g., "key_abc123"
+  ownerWallet?: string;    // Wallet that created the key
+  scopes?: string[];       // ["read"] or ["read", "fund"]
+  rateLimitRpm?: number;   // Per-key rate limit
+}
+```
+
+## Error Responses
+
+| Status | Code | Description |
+|--------|------|-------------|
+| 401 | `UNAUTHORIZED` | Missing or invalid API key |
+| 403 | `FORBIDDEN` | Missing required scope |
+| 429 | `RATE_LIMITED` | Rate limit exceeded |
+
+## Usage Example (Agent)
+
+```typescript
+const response = await fetch('https://agent.asgcompute.com/v1/account/balance', {
+  headers: {
+    'Authorization': 'Bearer asc_sk_live_your_key_here',
+    'Content-Type': 'application/json'
+  }
+});
+
+if (response.status === 401) {
+  // Re-authenticate or refresh key
+}
+
+const balance = await response.json();
+```
+
+## Related Documents
+
+- [Quickstart for Agents](/docs/guide/agent-quickstart)
+- [Rate Limiting](/docs/security/rate-limits)
+- [Error Codes](/docs/api/errors)