Simmer has a built-in risk monitor. Every buy gets auto-enrolled with a stop-loss and take-profit. We detect breaches server-side on every price tick — you do not need to poll, subscribe to a WebSocket, or run your own monitoring loop.
If you are running a background loop that polls /api/sdk/positions every N seconds to decide when to sell, you are duplicating work the server already does in real time. Use set_monitor() (or rely on the defaults) and delete the loop.
How it works
You register a threshold
↓ set_monitor(market_id, side, stop_loss_pct=..., take_profit_pct=...)
↓ stored server-side
Price ticks on Polymarket (real-time WebSocket, server-side)
↓ we compute your live P&L against every registered threshold
↓ if breached → trigger exit:
┌─ Managed wallet: we cancel open orders + sell immediately, server-side
│
└─ External wallet: we write a risk alert; your SDK picks it up on the next
get_briefing() or SimmerClient() init and signs the sell locally using
your private key (we never hold your external wallet's key)
Auto-enrollment (the default)
Every successful buy via the SDK auto-enrolls a monitor for that position. Defaults:
| Setting | Default | Meaning |
|---|
stop_loss_pct | 0.20 | Close when position is down 20% |
take_profit_pct | null | No auto take-profit (prediction markets resolve naturally) |
auto_risk_monitor_enabled | true | Enabled for all users unless turned off |
client.update_settings(
default_stop_loss_pct=0.15, # 15% stop-loss
default_take_profit_pct=0.50, # 50% take-profit
)
client.update_settings(auto_risk_monitor_enabled=False)
Per-position thresholds
If you want different thresholds on a specific position, call set_monitor() after the trade (or anytime):
client.set_monitor(
market_id="87654321-...",
side="yes",
stop_loss_pct=0.10, # 10% stop-loss
take_profit_pct=0.95, # 95% take-profit
)
client.delete_monitor(market_id="...", side="yes")
monitors = client.list_monitors()
External wallets: what you need to do
External wallets (where you keep your own private key and we don’t) require one extra step: the SDK needs to be able to sign the sell order. Two requirements:
-
Pass your private key when constructing the client:
client = SimmerClient(
api_key="sk_live_...",
private_key="0x...", # EVM private key for Polymarket
)
-
Call
get_briefing() regularly (every heartbeat — a few times per hour is enough). Briefing responses include any triggered risk alerts, and the SDK auto-executes them before returning. You can also construct a new SimmerClient which processes pending alerts on init.
No WebSocket setup is required on your side. Detection happens server-side; your SDK only polls for ready-to-execute alerts.
If your bot never calls get_briefing() and never re-instantiates the client, alerts will sit in Redis (1 hour TTL) and eventually expire without being executed. Keep your heartbeat cadence under an hour.
Managed wallets
If you use a Simmer-managed wallet, the server holds the signing key, so we execute the exit ourselves the moment the threshold is hit. No SDK polling required — the sell is already done by the time you next call the API.
Choosing thresholds
- Stop-loss on prediction markets is different from stocks. Prices here are probabilities between 0 and 1. A position that moves from 0.50 → 0.40 is already a 20% loss. Set tighter stops than you would on equities.
- Take-profit is often unnecessary. Most prediction markets resolve within days or weeks. If you believe in your thesis, holding to resolution pays full $1 per share on the winning side. Default TP is off for this reason.
- “Forced liquidation before settlement” is not needed. Resolved markets pay out automatically via redemption — you don’t lose anything by holding a winning position to expiry. Exit early only if you have a view change, not to beat the clock.
When stops cannot help: gap-resolution markets
A stop-loss can only exit at a price the market actually trades through. Some markets do not decay toward their losing outcome. They gap. Weather temperature buckets are the clearest case: the NO side can sit near your entry all day, then jump straight to about 0 at resolution once the day’s reading is in. There is no intermediate price for a percentage stop to trigger on, and once the price is near zero there are no bids to sell into.
So a 20% stop on a weather NO position will not cap your loss at 20% if the market gaps. The monitor fires correctly the moment it sees a sub-threshold price, but by then the only available price is near 0 and the exit cannot fill. The same applies to any short-duration or thinly-traded market that resolves by a discontinuous jump rather than a gradual move.
How to manage it:
- Size for the full loss. Assume the stop may not fill. Risk only what you can lose at $0.
- Exit manually before resolution if your thesis weakens, rather than relying on the automated stop near the resolution window.
- Stops work as intended on markets that move gradually with live two-sided liquidity. They are not a substitute for sizing on gap-resolution markets.
Common mistakes
| Mistake | Fix |
|---|
Polling /api/sdk/positions in a loop to decide when to sell | Use set_monitor() instead. The server already watches every tick. |
| Building a custom risk monitor without registering thresholds | Thresholds must be in position_risk_settings for us to watch. External monitors can’t trigger our execution path. |
Instantiating SimmerClient without private_key for external wallets | The SDK can’t sign sells without it. Alerts will accumulate but never execute. |
Never calling get_briefing() | Alerts expire after 1 hour if not consumed. Call briefing at least every 30 minutes. |
Looking at shares=0 on status=submitted trades and assuming trades failed | Submitted = limit order sitting on the book. shares populates only after a fill. Check status=filled records for real positions. |
| Relying on a percentage stop to cap losses on weather or short-duration markets | These resolve by gapping to 0, not by decaying through your stop. Size for the full loss or exit manually before resolution. See gap-resolution markets. |
API reference
| Method | Endpoint | Purpose |
|---|
client.set_monitor() | POST /api/sdk/positions/{market_id}/monitor | Register or update thresholds for one position |
client.list_monitors() | GET /api/sdk/positions/monitors | List all active monitors |
client.delete_monitor() | DELETE /api/sdk/positions/{market_id}/monitor | Remove a monitor |
client.update_settings() | PATCH /api/sdk/user/settings | Change defaults (stop-loss, take-profit, enabled) |
client.get_briefing() | GET /api/sdk/briefing | Heartbeat; auto-processes pending risk alerts |
