> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getsly.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Streams

> Continuous per-second payment flows with buffers, runways, and programmable termination.

A **stream** is a continuous flow of money between two wallets, denominated in a rate per unit time. Unlike [transfers](/core-concepts/transfers), which are discrete events, streams accrue value every second.

Streams are ideal for:

* **Payroll / contractor pay** — the recipient withdraws earned balance on their own schedule
* **Subscriptions** — cancel any moment, get refunded for unused time
* **Service-tier SLAs** — pay-per-millisecond for AI inference, compute, bandwidth
* **Agent-to-agent retainers** — one agent pays another to keep availability

## Anatomy

```
┌─────────────────┐
│ Sender wallet   │
│  (wrapped       │
│   funds)        │
└────────┬────────┘
         │ flows at rate
         ▼
┌─────────────────┐        ┌─────────────────┐
│ Stream          │──────▶ │ Recipient       │
│  • flow_rate    │        │  balance        │
│  • buffer       │        │  (withdrawable) │
│  • runway       │        └─────────────────┘
└─────────────────┘
```

Key numbers on every stream:

* **`flow_rate`** — amount per second (e.g. `"0.00005"` USDC = $0.00005/s ≈ $4.32/day)
* **`wrapped_balance`** — sender's locked-up funds powering the stream
* **`buffer`** — reserved slack to prevent accidental underrun
* **`runway_seconds`** — time until the wrapped balance runs out at current flow rate
* **`recipient_balance`** — accrued, withdrawable by the recipient

## Create a stream

```bash theme={null}
curl -X POST https://sandbox.getsly.ai/v1/streams \
  -H "Authorization: Bearer pk_test_..." \
  -H "Content-Type: application/json" \
  -d '{
    "from_wallet_id": "wal_sender_...",
    "to_wallet_id": "wal_recipient_...",
    "flow_rate": "0.00005",
    "currency": "USDC",
    "initial_deposit": "1000.00",
    "buffer": "50.00"
  }'
```

This locks $1000 into the stream, starts flowing at $0.00005/s, and keeps a $50 buffer. The recipient accrues ~$4.32/day and can withdraw at any point.

## Recipient withdraws

```bash theme={null}
curl -X POST https://api.getsly.ai/v1/streams/str_.../withdraw \
  -H "Authorization: Bearer pk_live_..." \
  -d '{ "amount": "10.00" }'  # omit to withdraw all accrued
```

Withdrawal creates a `stream_withdraw` transfer into the recipient's wallet.

## Top up or adjust

```bash theme={null}
# Add more funds
curl -X POST /v1/streams/str_.../topup -d '{ "amount": "500.00" }'

# Change flow rate (reflective of new runway)
curl -X PATCH /v1/streams/str_... -d '{ "flow_rate": "0.0001" }'
```

## Pause and resume

```bash theme={null}
curl -X POST /v1/streams/str_.../pause
curl -X POST /v1/streams/str_.../resume
```

Paused streams don't accrue. Wrapped funds remain locked until cancellation.

## Cancel

```bash theme={null}
curl -X POST /v1/streams/str_.../cancel
```

* Accrued balance transfers to the recipient
* Unused wrapped funds return to the sender
* The stream record remains for audit

## Runway and alerts

When `runway_seconds` drops below a threshold, Sly fires a `stream_alert` webhook and pushes a `stream_alert` SSE event to any connected agents that manage the stream:

```json theme={null}
{
  "event": "stream_alert",
  "severity": "warning",
  "stream_id": "str_...",
  "runway_seconds": 3600,
  "message": "Stream will exhaust in 1 hour"
}
```

Severity levels: `warning` (\<24h), `critical` (\<1h), `exhausted` (runway=0).

## Agent permissions

When an agent creates or manages a stream, their wallet policy grants them granular permissions:

* `streams:create` — open new streams
* `streams:modify` — change flow rate, topup
* `streams:pause` — pause/resume
* `streams:terminate` — cancel

See [wallet policies](/agents/wallet-policies) for how to scope these.

## Why streams over periodic transfers

|                     | Stream                            | Batch of transfers                |
| ------------------- | --------------------------------- | --------------------------------- |
| Granularity         | Per-second                        | Per period (daily/weekly/monthly) |
| Refunds             | Automatic (cancel returns unused) | Manual (via refunds API)          |
| Gas / fees          | Paid once on wrap                 | Paid per transfer                 |
| Recipient cash flow | Continuous                        | Lumpy                             |
| Auditability        | Every second is on-ledger         | Per-transfer                      |

For anything ongoing, prefer a stream.