Rule-change watch

What you’ll get

Every recorded version of one market’s contract terms with what changed between them, the rulebooks in force above it with their settlement sources, and a live feed of rule changes across every market. Then a checklist for the case that matters most: the terms a position or a proof rests on changed underneath it. On 2026-09-17 a Polymarket election market’s resolution metadata changed at 12:01 UTC, and a Kalshi tennis market’s strike and close time changed at 12:03.

Prerequisites

An API key in ROUTEUR_API_KEY
Python 3 with requests

Read a market's rules and their history

GET /v1/markets/{venue}/{id}/rules works for any market ever recorded, listed or not.

curl "https://api.routeur.app/v1/markets/polymarket/sweden-parliamentary-election-v-over-under-7-percent-20260812172023903/rules" \
  -H "X-API-Key: $ROUTEUR_API_KEY"

Trimmed, observed 2026-09-17 12:47 UTC (the rule text itself is in rules, left out here):

{
  "data": {
    "venue": "polymarket", "id": "sweden-parliamentary-election-v-over-under-7-percent-20260812172023903",
    "title": "Sweden Parliamentary Election: V Over/Under 7%?",
    "rules_hash": "3a3cd2fab54c0bf52fe24ebf9096efebb94ef000fcb93ff7d73a5e190ac2da5e",
    "rulebooks": [
      { "venue": "polymarket", "kind": "market", "id": "sweden-parliamentary-election-v-over-under-7-percent-20260812172023903",
        "content_hash": "369353b2d57ac1d826bf510ec22828a8e7cd8aaa3cf96b5fabdda04dd6ea7a00",
        "first_seen_at": "2026-09-17T12:01:36.414238Z", "last_seen_at": "2026-09-17T12:31:32.131815Z",
        "fields": { "negRisk": false, "negRiskOther": false, "resolutionSource": "", "umaResolutionStatuses": "[\"proposed\", \"proposed\"]" },
        "settlement_sources": [],
        "changed_fields": ["umaResolutionStatuses"],
        "diff": "--- market@4238e5c38e80\n+++ market@369353b2d57a\n@@ -2,5 +2,5 @@\n   \"negRisk\": false,\n   \"negRiskOther\": false,\n   \"resolutionSource\": \"\",\n-  \"umaResolutionStatuses\": \"[]\"\n+  \"umaResolutionStatuses\": \"[\\\"proposed\\\", \\\"proposed\\\"]\"\n }\n" }
    ],
    "versions": [
      { "rules_hash": "d441a7ef9a056aeff1dcf9e574e77af0de907aede7749195c312355cd856ec4b",
        "first_seen_at": "2026-09-14T17:30:29.428735Z", "last_seen_at": "2026-09-17T11:31:32.813899Z",
        "changed_fields": [], "rulebooks_changed": [] },
      { "rules_hash": "3a3cd2fab54c0bf52fe24ebf9096efebb94ef000fcb93ff7d73a5e190ac2da5e",
        "first_seen_at": "2026-09-17T12:01:36.414238Z", "last_seen_at": "2026-09-17T12:31:32.131815Z",
        "changed_fields": [],
        "summary": "The venue changed a term the recorded fields do not show, such as an expiration or settlement timestamp.",
        "rulebooks_changed": [ { "kind": "market", "id": "sweden-parliamentary-election-v-over-under-7-percent-20260812172023903",
                                 "content_hash": "369353b2d57ac1d826bf510ec22828a8e7cd8aaa3cf96b5fabdda04dd6ea7a00",
                                 "from_hash": "4238e5c38e800fd21f2df8066cb1a685926d8135bb7724b2ff5c34c7aaf14111" } ] }
    ],
    "changes": [
      { "scope": "contract", "from_hash": "d441a7ef9a05…", "to_hash": "3a3cd2fab54c…", "changed_at": "2026-09-17T12:01:36.414238Z",
        "changed_fields": [], "summary": "The venue changed a term the recorded fields do not show, such as an expiration or settlement timestamp." }
    ]
  }
}

The market’s own text did not change; its rulebook did. umaResolutionStatuses went from [] to ["proposed", "proposed"]: a resolution has been proposed on UMA, and the market is about to settle.

Print the versions, diffs and settlement sources

This script lists every contract version with its diff, the rulebooks in force with where each says the market settles, the ledger, and then reads each rulebook’s own history to say whether a settlement source changed.

Python

import os
import sys
import requests

API = "https://api.routeur.app"
session = requests.Session()
session.headers["X-API-Key"] = os.environ["ROUTEUR_API_KEY"]
venue, market_id = os.environ.get("VENUE", "kalshi"), os.environ["MARKET_ID"]


def sources(rulebook):
    return sorted(s["name"] for s in rulebook.get("settlement_sources", []))


# 1. Every version of the contract, with what changed.
res = session.get(f"{API}/v1/markets/{venue}/{market_id}/rules", timeout=30)
if res.status_code == 404:
    sys.exit("No contract terms recorded for this market.")
res.raise_for_status()
rules = res.json()["data"]

print(f"{rules['title']} · current version {rules['rules_hash'][:12]} · {len(rules['versions'])} version(s), {len(rules['changes'])} recorded change(s)")
for i, v in enumerate(rules["versions"], 1):
    print(f"\nversion {i} · {v['rules_hash'][:12]} · seen {v['first_seen_at']} → {v['last_seen_at']}")
    if v.get("changed_fields"):
        print(f"  changed: {', '.join(v['changed_fields'])}")
    if v.get("summary"):
        print(f"  {v['summary']}")
    if v.get("diff"):
        print("  " + v["diff"].replace("\n", "\n  "))
    for rb in v.get("rulebooks_changed", []):
        print(f"  rulebook {rb['kind']} {rb['id']} moved to {rb['content_hash'][:12]} (was {rb.get('from_hash', '?')[:12]})")

# 2. The rulebooks in force now, and where each one says the market settles.
print("\nrulebooks in force:")
for rb in rules["rulebooks"]:
    print(f"  {rb['kind']} {rb['id']} · {rb['content_hash'][:12]} · settles by {', '.join(sources(rb)) or 'no named source'}")
    if rb.get("changed_fields"):
        print(f"    changed from the previous version: {', '.join(rb['changed_fields'])}")
        if rb.get("diff"):
            print("    " + rb["diff"].replace("\n", "\n    "))
    doc = rb.get("document")
    if doc:
        print(f"    terms document {doc['url']} ({doc.get('content_hash', '?')[:12]}), fetched {doc.get('fetched_at')}")

# 3. The ledger: every change, whatever its scope.
if rules["changes"]:
    print("\nledger:")
    for c in rules["changes"]:
        print(f"  {c['changed_at']} · {c['scope']}{' ' + c['rulebook_id'] if c.get('rulebook_id') else ''} · {c['summary']}")

# 4. Did the settlement source change between rulebook versions? Read the rulebook's own history.
for rb in rules["rulebooks"]:
    detail = session.get(f"{API}/v1/rulebooks/{rb['venue']}/{rb['kind']}/{rb['id']}", timeout=30)
    if detail.status_code == 404:
        continue
    versions = detail.json()["data"]["versions"]
    for prev, cur in zip(versions, versions[1:]):
        if sources(prev) != sources(cur):
            print(f"\nSETTLEMENT SOURCE CHANGED on {rb['kind']} {rb['id']} at {cur['first_seen_at']}: "
                  f"{sources(prev) or 'none'} → {sources(cur) or 'none'}")
        elif cur.get("changed_fields"):
            print(f"\n{rb['kind']} {rb['id']} changed {cur['changed_fields']} at {cur['first_seen_at']} (sources unchanged)")

Output for the Polymarket market above, observed 2026-09-17 12:48 UTC:

Sweden Parliamentary Election: V Over/Under 7%? · current version 3a3cd2fab54c · 2 version(s), 1 recorded change(s)

version 1 · d441a7ef9a05 · seen 2026-09-14T17:30:29.428735Z → 2026-09-17T11:31:32.813899Z

version 2 · 3a3cd2fab54c · seen 2026-09-17T12:01:36.414238Z → 2026-09-17T12:31:32.131815Z
  The venue changed a term the recorded fields do not show, such as an expiration or settlement timestamp.
  rulebook market sweden-parliamentary-election-v-over-under-7-percent-20260812172023903 moved to 369353b2d57a (was 4238e5c38e80)

rulebooks in force:
  market sweden-parliamentary-election-v-over-under-7-percent-20260812172023903 · 369353b2d57a · settles by no named source
    changed from the previous version: umaResolutionStatuses
    --- market@4238e5c38e80
    +++ market@369353b2d57a
    @@ -2,5 +2,5 @@
       "negRisk": false,
       "negRiskOther": false,
       "resolutionSource": "",
    -  "umaResolutionStatuses": "[]"
    +  "umaResolutionStatuses": "[\"proposed\", \"proposed\"]"
     }

ledger:
  2026-09-17T12:01:36.414238Z · contract · The venue changed a term the recorded fields do not show, such as an expiration or settlement timestamp.

market sweden-parliamentary-election-v-over-under-7-percent-20260812172023903 changed ['umaResolutionStatuses'] at 2026-09-17T12:01:36.414238Z (sources unchanged)

And for a Kalshi market whose own contract changed, the same script:

$ VENUE=kalshi MARKET_ID=KXITFMATCH-26SEP17LAZMIK-LAZ python3 rules.py
George Lazarov wins · current version 57e5efec374c · 2 version(s), 1 recorded change(s)

version 1 · 121d560b329e · seen 2026-09-16T18:17:36.704272Z → 2026-09-17T11:48:20.072932Z

version 2 · 57e5efec374c · seen 2026-09-17T12:03:22.640221Z → 2026-09-17T12:03:22.640221Z
  changed: strike, closes_at
  Structured strike changed; close time moved from 2026-10-01T10:00:00Z to 2026-09-17T12:00:40Z.

rulebooks in force:
  event KXITFMATCH-26SEP17LAZMIK · 7b5a933a00d6 · settles by ESPN, Flashscore, Fox Sports, ITF

ledger:
  2026-09-17T12:03:22.640221Z · contract · Structured strike changed; close time moved from 2026-10-01T10:00:00Z to 2026-09-17T12:00:40Z.

Follow rule changes as they happen

The rules topic of /v1/stream sends one rule_change event per change, for every market or only the ones you name in markets.

curl -N "https://api.routeur.app/v1/stream?topics=rules" -H "X-API-Key: $ROUTEUR_API_KEY"

An event observed 2026-09-17 12:03 UTC (replayed with a cursor from earlier in the hour):

event: rule_change
data: {"venue":"kalshi","market_id":"KXITFMATCH-26SEP17LAZMIK-LAZ","title":"George Lazarov wins","scope":"contract","from_hash":"121d560b329e513f30cbb4590a911734da12d10835b46e99092e9d8bd88e13b2","to_hash":"57e5efec374c0d67a34952b7fdf6e5b321be23422c3f10f7a0209cfdc04d5534","changed_fields":["strike","closes_at"],"summary":"Structured strike changed; close time moved from 2026-10-01T10:00:00Z to 2026-09-17T12:00:40Z.","rules_path":"/v1/markets/kalshi/KXITFMATCH-26SEP17LAZMIK-LAZ/rules","changed_at":"2026-09-17T12:03:22.640221Z","recorded_at":"2026-09-17T12:03:22.640221Z"}

Set TOPICS = "rules" in the Stream consumer and replace its handler with one that keys on what changed:

Python

WATCHED = {("kalshi", "KXMLBTOTAL-26SEP171235MILPIT-9"), ("polymarket", "mlb-mil-pit-2026-09-17-total-8pt5")}


def handle(name, payload):
    if name != "rule_change":
        return
    key = (payload["venue"], payload["market_id"])
    fields = payload["changed_fields"]
    if payload["scope"] != "contract":
        level = "SETTLEMENT"      # a rulebook or terms document above the contract changed
    elif "rules" in fields or "strike" in fields:
        level = "TERMS"           # the payoff condition itself
    elif fields:
        level = "TIMING"          # closes_at, game_starts_at, title, labels
    else:
        level = "OTHER"           # a term the recorded fields do not show
    mark = " <-- WATCHED" if key in WATCHED else ""
    print(f"{level:<10} {payload['venue']} {payload['market_id']} · {payload['summary']} · read {payload['rules_path']}{mark}")

Between 12:01 and 12:36 UTC on 2026-09-17, 699 rule_change events arrived, 695 of them on Polymarket. 574 had changed_fields: [] (a term the recorded fields do not show, mostly resolution timestamps moving as games ended), 46 changed only game_starts_at, and 79 changed strike or closes_at. The last group is the one a position cares about; the handler above marks it TERMS or TIMING.

When the settlement source changes

A settlement source is where the venue says it will read the result. It lives in the rulebooks above the contract: a Kalshi event’s settlement_sources, a Polymarket market’s resolutionSource and umaResolutionStatuses, and the venue’s contract terms document. A change there does not change the market’s rules_hash, so it is easy to miss. When the stream sends a rule_change with scope other than contract, or the rulebook’s changed_fields names a source, do this:

Read the diff. GET /v1/rulebooks/{venue}/{kind}/{id} has every version with changed_fields, diff, and for Kalshi the terms document with its own diff. Decide whether the new source can disagree with the old one.
Re-check every proof the market is in. A proof holds for a contract version, and a relation’s evidence names what both contracts settle on. GET /v1/relations/{a}/{b} returns reproduced: false, or 404 relation_not_found, when the graph can no longer relate the current versions; a relation that survives is safe only if its evidence still describes the settlement you read in step 1.
Treat leads on the pair as void until the next graph run confirms them. Runs finish hourly (GET /v1/status), and a lead’s depth.limited_by becomes informational when the venues could settle differently.
If you hold a position, compare the sources, not the hashes. The script’s last section prints SETTLEMENT SOURCE CHANGED with the names before and after. A change from a named agency to none, or to a different one, is the case to act on.

A Polymarket umaResolutionStatuses going from [] to ["proposed", ...], as above, is not a source change: it means resolution has started on the same source. Expect the market to close and the price to go to 0 or 100¢.

Read the result

Field	Meaning
`rules_hash`	The current contract version. Every proof and lead names the version it holds for.
`versions[]`	Every contract version, oldest first, with `first_seen_at`, `last_seen_at`, `changed_fields` (rules, title, labels, event, strike, open, close, game start, outcome tokens), a `summary`, a unified `diff` of the rule text, and the rulebooks that changed with it.
`rulebooks[]`	The rulebook versions in force for the current contract: a Kalshi `event` (settlement sources, exclusivity, strike period) or `series` (contract terms document, prohibitions), or a Polymarket `market` (resolution metadata). `fields` is the venue’s data verbatim; `settlement_sources` is what was read from it.
`rulebooks[].document`	The venue’s contract terms document, with its text, hash, fetch time and a `diff` from the previous version.
`changes[]`	The ledger: every change to the market’s terms, whatever its `scope`: `contract`, `series`, `event`, `market` or `document`.
`rule_change.scope` (stream)	Which layer changed. `contract` is the market’s own terms; anything else changed above it under an unchanged contract. `rules_path` is where to read it.

Pitfalls

changed_fields: [] with a new hash is normal. It means the venue changed something the recorded fields do not show, such as an expiration or settlement timestamp. The summary says so. Do not treat every new version as a rules rewrite; do read the ledger when one lands on a market you hold.
Kalshi series rulebooks were not recorded on 2026-09-17. GET /v1/rulebooks/kalshi/series/KXBTCD (and KXMLBTOTAL, KXSB, KXITFMATCH) returned 404 rulebook_not_found; only event rulebooks were present. The script skips a missing rulebook; the series’ contract terms document is then not available through this endpoint.
A close time moving earlier is a settlement. The Kalshi tennis market’s closes_at moved from 2026-10-01 to 2026-09-17 12:00:40 because the match ended. Treat it as the market resolving, not as a rule change to argue with.
Hashes are 64 hex characters. The script prints 12 for readability; compare full values in code.
The stream replays one hour. A watcher that was down longer must reread /rules for the markets it cares about after the reset event.

Proof trail: the proof names the contract versions it holds for.
Stream consumer: a resumable consumer for the rules topic.
Venues: how each venue publishes its terms.
GET /v1/rulebooks/{venue}/{kind}/{id}: every version of a rulebook and the markets under it.

​What you’ll get

​Prerequisites

​Read the result

​Pitfalls

​Related

What you’ll get

Prerequisites

Read the result

Pitfalls

Related