kalshi-api Checked

def _headers(method: str, path: str) -> dict:

"""path must include /trade-api/v2 prefix and exclude query string."""

ts = str(int(time.time() * 1000)) # milliseconds

msg = f"{ts}{method}{path}".encode()

sig = PRIV.sign(

msg,

padding.PSS(mgf=padding.MGF1(hashes.SHA256()),

salt_length=padding.PSS.DIGEST_LENGTH),

hashes.SHA256(),

)

return {

"KALSHI-ACCESS-KEY": KEY_ID,

"KALSHI-ACCESS-TIMESTAMP": ts,

"KALSHI-ACCESS-SIGNATURE": base64.b64encode(sig).decode(),

}

def get(path: str, params=None):

Sign the path only — query goes into params, not the signature

r = httpx.get(BASE + path, params=params,

headers=_headers("GET", "/trade-api/v2" + path))

r.raise_for_status()

return r.json()

def post(path: str, body: dict):

r = httpx.post(BASE + path, json=body,

headers=_headers("POST", "/trade-api/v2" + path))

r.raise_for_status()

return r.json()

Example: open markets in a series

markets = get("/markets", params={"series_ticker": "KXHIGHNY", "status": "open"})

**Signature spec:** RSA-PSS, MGF1 over SHA-256, salt length = `PSS.DIGEST_LENGTH`. String to sign: `{timestamp_ms}{METHOD}{path}` where path includes `/trade-api/v2` and excludes the query string.

Headers: `KALSHI-ACCESS-KEY` (UUID), `KALSHI-ACCESS-TIMESTAMP` (ms), `KALSHI-ACCESS-SIGNATURE` (base64).

### 4. Candlestick history

Returns OHLC for yes_bid / yes_ask + volume + open_interest

Values are dollar strings: {"close": "0.42"}

candles = get(

f"/series/KXHIGHNY/markets/{ticker}/candlesticks",

params={"start_ts": start_epoch, "end_ts": end_epoch, "period_interval": 60},

)

`period_interval` is in **minutes**: `1`, `60`, or `1440`.

---

## YES/NO Order-Book Convention

On Kalshi, **`yes` and `no` are both resting BID ladders** — there is no separate ask book. To take the other side you lift the opposing bid:

no_ask = 1 − best_yes_bid # cost to buy NO right now (lift YES bids)

yes_ask = 1 − best_no_bid # cost to buy YES right now (lift NO bids)

P(YES) mid = (best_yes_bid + (1 − best_no_bid)) / 2

Getting this backwards silently inverts every signal. Use the helpers in `scripts/kalshi_orderbook.py`.

**Orderbook response** comes in two variants depending on API tier — normalize before using:

{"orderbook": {"yes": [[price, size], ...], "no": [[price, size], ...]}}

If a price value is `> 1.0`, it is integer cents — divide by 100.

---

## Order Schema

`POST /trade-api/v2/portfolio/orders` uses **fixed-point dollar STRINGS**, not integers. The old schema (integer cents, `count`, `yes_price`) returns `400 invalid_parameters`.

{

"ticker": "KXHIGHNY-26JUN02-B75.5",

"action": "buy",

"side": "yes",

"count_fp": "1.00",

"yes_price_dollars": "0.01",

"client_order_id": "my-strategy-001",

"time_in_force": "good_till_canceled"

}

Critical field rules — each violation returns `400`:

| Field | Rule | Common mistake that 400s |
|---|---|---|
| `count_fp` | fixed-point **string** `"1.00"` | integer `count: 1` |
| `{side}_price_dollars` | dollar **string** `"0.01"` | integer cents `yes_price: 1` |
| `time_in_force` | **required**: `good_till_canceled` \| `immediate_or_cancel` \| `fill_or_kill` | omitted |
| `client_order_id` | `[A-Za-z0-9-]` only | `.` or `:` in the string — bracket tickers contain `.`, so never copy the ticker directly |
| `type` | **do not send** | `"type": "limit"` |

For the full order lifecycle (amend, decrease, cancel, batch) and `strike_type` gotchas, see `references/auth-and-orders.md`.

---

## Endpoint Summary

| Category | Endpoint | Notes |
|---|---|---|
| Balance | `GET /portfolio/balance` | — |
| Positions | `GET /portfolio/positions` | — |
| Orders | `GET /portfolio/orders` | `?status=resting\|canceled\|executed` |
| Place order | `POST /portfolio/orders` | dollar-string schema above |
| Cancel | `DELETE /portfolio/orders/{id}` | returns `{"order": {...status: "canceled"}}` |
| Amend | `POST /portfolio/orders/{id}/amend` | `ticker` required in body |
| Decrease | `POST /portfolio/orders/{id}/decrease` | `{"reduce_by_fp": "1.00"}` |
| Batch | `POST /portfolio/orders/batched` | `{"orders": [...]}` |
| Fills | `GET /portfolio/fills` | `?limit=N` |
| Settlements | `GET /portfolio/settlements` | `?limit=N` |
| Markets | `GET /markets` | `?series_ticker=&status=open&limit=500` |
| Orderbook | `GET /markets/{ticker}/orderbook` | `?depth=N` |
| Candlesticks | `GET /series/{series}/markets/{ticker}/candlesticks` | `?start_ts=&end_ts=&period_interval=60` |
| Trades | `GET /markets/trades` | recent trade prints |

Full endpoint surface, market metadata fields, and rate limits: `references/endpoints-and-marketdata.md`.
WebSocket discovery pipeline: `references/websocket.md`.

---

## Files

### References
- `references/auth-and-orders.md` — RSA-PSS spec, dollar-string order schema, `time_in_force`, `client_order_id` sanitization, amend/decrease/cancel lifecycle, `strike_type` gotcha, fees
- `references/endpoints-and-marketdata.md` — Full endpoint table, orderbook variants, market metadata fields (`result`, `open_time`, `close_time`, `series_ticker`), candlesticks, rate limits
- `references/websocket.md` — WS host, discovery pipeline, channels, signing the WS upgrade

### Scripts
- `scripts/kalshi_orderbook.py` — YES/NO bid-ladder helpers (`no_ask`, `yes_ask`, `p_yes_mid`, `overround`, `kalshi_fee`). Pure stdlib, no keys, runs offline.