在 Kalshi 與 Polymarket 之間篩查價差的交易台，需要同一事件的兩邊報價，以及這兩份合約是否按相同條件賠付。Narwhal 會在一次回應中回傳報價、各交易場所的規則文字、結算來源和成交量，以及任何規則標記。
在同一事件上讀取兩個交易場所
篩查從兩個交易場所都定了價的同一事件開始。下面的請求讀取 2026 年 12 月的聯準會決議，並按每個結果回傳各交易場所的報價。回應只保留升息 25 bps 這一結果，並省略了交易場所的規則文字，篩查會在下一步讀取它。
curl -s -H "Authorization: Bearer $NARWHAL_API_KEY" \
"https://api.narwhalapi.com/v1/predictions/scalar/usa-fed-2026-12"{
"event_id": "usa-fed-2026-12",
"question": "Federal Reserve rate decision, 9 December 2026",
"status": "trading",
"closes_at": "2026-12-09T18:59:00Z",
"resolves_at": "2026-12-09T19:00:00Z",
"as_of": "2026-11-03T03:09:00Z",
"stale": false,
"venues": [
{
"venue": "kalshi",
"url": "https://kalshi.com/markets/kxfeddecision/kxfeddecision-26dec",
"rules_url": "https://assets.kalshi.com/contract_terms/FEDDECISION.pdf",
"settlement_source": "Federal Reserve",
"weight": "0.0624",
"volume_24h_usd": "32792.43",
"open_interest_usd": "426866.37"
},
{
"venue": "polymarket",
"url": "https://polymarket.com/event/fed-decision-in-december-20260729232808632",
"settlement_source": "Federal Reserve",
"weight": "0.9376",
"volume_24h_usd": "665452.98"
}
],
"outcomes": [
{
"key": "hike_25",
"label": "Hike of 25 bps",
"lower": "12.5",
"upper": "37.5",
"probability": "0.7185",
"quotes": [
{
"venue": "kalshi",
"probability": "0.7073",
"market_ids": [
"KXFEDDECISION-26DEC-H25"
]
},
{
"venue": "polymarket",
"probability": "0.7192",
"market_ids": [
"111662129652828266889360374468657435151479595863413519836161861837506140152890"
]
}
]
}
]
}該事件只有一個 as_of、一個 closes_at 和一個 resolves_at，所以兩邊報價取自同一時刻。對於升息這一結果，Kalshi 報價 0.7073，Polymarket 報價 0.7192，價差為 0.0119。每個交易場所項目都帶有 settlement_source 和 volume_24h_usd，Kalshi 還帶有 open_interest_usd。weight 表示各交易場所在整體 probability 中所佔的比重。
規則不同時，把價差當作兩份合約來解讀
價差只說明兩個數字不同，並不說明兩份合約的賠付條件相同。衰退問題就是回應自己做了標記的例子：該交易場所項目會帶有 excluded_reason 和一則說明差異所在的 match 備註。
curl -s -H "Authorization: Bearer $NARWHAL_API_KEY" \
"https://api.narwhalapi.com/v1/predictions/binary/usa-recession-2026"{
"event_id": "usa-recession-2026",
"question": "US recession by end of 2026?",
"as_of": "2026-11-03T03:09:00Z",
"stale": false,
"probability": "0.0550",
"quotes": [
{
"venue": "kalshi",
"probability": "0.0250",
"market_ids": [
"KXRECSSNBER-26"
]
},
{
"venue": "polymarket",
"probability": "0.0550",
"market_ids": [
"100379208559626151022751801118534484742123694725746262280150222742563282755057"
]
}
],
"venues": [
{
"venue": "kalshi",
"url": "https://kalshi.com/markets/kxrecssnber/kxrecssnber-26",
"rules_url": "https://assets.kalshi.com/contract_terms/NBERRECSS.pdf",
"settlement_source": "Bureau of Economic Analysis",
"excluded_reason": "rules",
"match": {
"differences": [
"rules"
],
"note": "Kalshi resolves on two negative GDP quarters only; Polymarket also counts an NBER recession call"
},
"volume_24h_usd": "125.68",
"open_interest_usd": "17994.22"
},
{
"venue": "polymarket",
"url": "https://polymarket.com/event/us-recession-by-end-of-2026",
"settlement_source": "Bureau of Economic Analysis; NBER",
"weight": "1.0000",
"volume_24h_usd": "4195.50"
}
]
}Kalshi 報價 0.0250，Polymarket 報價 0.0550，價差為 0.0300。整體 probability 為 0.0550，這只是 Polymarket 的報價，因為 Kalshi 因 rules 被排除。備註說明，Kalshi 只在 GDP 連續兩個季度為負時才結算，而 Polymarket 還會把研究機構作出的衰退判定計入。兩邊的結算來源也不同。篩查應當把這個價差從候選清單中剔除，或標記為不同的合約。
篩查每個結果並寫入一列日誌
下面的腳本讀取一份事件清單，對兩個交易場所都有報價的每個結果，計算 Polymarket 減去 Kalshi 的價差，並為每個結果列印一列，附上交易台用來篩選的標記。
import csv, json, os, sys, urllib.request
from decimal import Decimal
def get(path):
req = urllib.request.Request("https://api.narwhalapi.com" + path,
headers={"Authorization": "Bearer " + os.environ["NARWHAL_API_KEY"]})
with urllib.request.urlopen(req, timeout=30) as r:
return json.load(r)
def scan(shape, event_id):
e = get(f"/v1/predictions/{shape}/{event_id}")
venues = {v["venue"]: v for v in e["venues"]}
flags = [v["venue"] + ":" + ",".join(v.get("match", {}).get("differences", [])) for v in e["venues"] if v.get("excluded_reason")]
sources = {v["settlement_source"] for v in e["venues"]}
rows = e["outcomes"] if shape == "scalar" else [{"key": "yes", "quotes": e["quotes"]}]
for row in rows:
q = {x["venue"]: Decimal(x["probability"]) for x in row["quotes"]}
if len(q) < 2:
continue
yield [e["as_of"], e["stale"], event_id, row["key"], q["kalshi"], q["polymarket"],
q["polymarket"] - q["kalshi"], len(sources), ";".join(flags) or "none",
venues["kalshi"]["volume_24h_usd"], venues["polymarket"]["volume_24h_usd"]]
out = csv.writer(sys.stdout)
out.writerow(["as_of", "stale", "event", "outcome", "kalshi", "polymarket", "gap", "sources", "flags", "k_vol_24h", "p_vol_24h"])
for shape, event_id in [("scalar", "usa-fed-2026-12"), ("binary", "usa-recession-2026")]:
out.writerows(scan(shape, event_id))
as_of,stale,event,outcome,kalshi,polymarket,gap,sources,flags,k_vol_24h,p_vol_24h
2026-11-03T03:09:00Z,False,usa-fed-2026-12,cut_50_plus,0.0049,0.0035,-0.0014,1,none,32792.43,665452.98
2026-11-03T03:09:00Z,False,usa-fed-2026-12,cut_25,0.0146,0.0055,-0.0091,1,none,32792.43,665452.98
2026-11-03T03:09:00Z,False,usa-fed-2026-12,hold,0.2586,0.2530,-0.0056,1,none,32792.43,665452.98
2026-11-03T03:09:00Z,False,usa-fed-2026-12,hike_25,0.7073,0.7192,0.0119,1,none,32792.43,665452.98
2026-11-03T03:09:00Z,False,usa-fed-2026-12,hike_50_plus,0.0146,0.0188,0.0042,1,none,32792.43,665452.98
2026-11-03T03:09:00Z,False,usa-recession-2026,yes,0.0250,0.0550,0.0300,2,kalshi:rules,125.68,4195.50五個 Fed 列共用同一個結算來源且沒有標記，因此在結算上可以比較。每個交易場所的五個報價加起來為 1.0000，所以價差之和為零。衰退列有兩個結算來源，並帶有 kalshi:rules 標記。規則措辭仍然需要人工或 diff 來核對：Kalshi 的文字稱，會議取消時「維持不變」這一結果按 Yes 結算；而 Polymarket 的文字則把變動到不在清單上的水準向上進位到最接近的 25 bps，並且在下一次例會結束前仍無聲明時，按「維持不變」區間結算。
每次掃描要記錄什麼
掃描只有在日後可以重播時才有用。請把輸入與價差一併記錄下來。
| 欄位 | 記錄原因 |
|---|---|
as_of 和 stale | 兩邊報價的時間，以及事件資料是否為最新 |
event_id 和結果的 key | 所比較的確切合約對 |
| 兩邊報價和價差 | 數值，以字串或小數形式保存 |
每個報價的 market_ids | 每個數字背後的交易場所合約 |
excluded_reason 和 match | 價差為何屬於不同的合約 |
各交易場所的 settlement_source | 結果是否由同一機構決定 |
volume_24h_usd, open_interest_usd | 報價背後有多少交易量支撐 |
每份 rules_text 的雜湊值 | 兩次掃描之間的規則修改會被發現 |
Fed 的例子說明了為什麼要記錄規模。在這次掃描中，Kalshi 的 24 小時成交量是 32,792.43 美元，Polymarket 的是 665,452.98，同樣的價差背後的深度相差懸殊。衰退列中 Kalshi 的成交量為 125.68。
出現價差是否意味著可以按這些價格成交？
API 並未這樣表示，本頁也不對收益作任何主張。報價是機率，不是委託單。回應裡沒有費率表，沒有委託簿深度，也沒有交易台可以成交的價格。篩查只是把需要細讀的事件清單縮小。
各交易場所的權重能告訴交易台什麼？
weight 是各交易場所在整體 probability 中所佔的份額，各權重之和為 1。在這次掃描中，Kalshi 為 0.0624，Polymarket 為 0.9376。把它們套用到維持不變的報價上得到 0.25335，而整體值為 0.2533。某個交易場所的權重很大，意味著整體值主要跟隨該場所，所以比較報價的篩查應當使用各交易場所自己的報價，而不是整體值。
如果交易場所對結果的劃分不同怎麼辦？
交易場所項目會在 match.differences 中報告 outcome_set，並在 match 備註中說明合併方式。此時 quotes 中的報價已經對齊到同一列。在按標籤比較兩份結果清單之前，請先閱讀 match。針對單一問題的步驟，見指南比較 Polymarket 與 Kalshi。
各交易場所的收盤時間和結算時間是否不同？
事件只給出一個 closes_at 和一個 resolves_at。各交易場所關於時間的措辭寫在 rules_text 中，所以關心這一點的篩查要比較兩份文字。該事件的 Polymarket 文字把 FOMC 聲明列為結算來源，並規定若未發布聲明則回退到「維持不變」區間。
發布於 。