rb_errata
★ 1

Core Rules v1.5In force since 16 Oct 2026

Rules change.
Search engines don't notice.

Ask a Riftbound rules question with a date. rb_errata answers from the rules that were in force that day, and cites the exact rule and version, like core@1.4:419.4.a. It runs on your own computer, offline.

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ErratumCore Rules v1.2 to v1.3

“If my spell gets countered, does it still count for Legion?”

  1. −

    No.Legion needed you to have played another card, and a countered card was not played.

    core@1.2:406.4.b12 Dec 2025 to 30 Mar 2026
  2. +

    Yes.Play triggers still don't fire, but Legion checks whether another card was Finalized. A countered spell was.

    core@1.3:812.1.csince 30 Mar 2026, unchanged through v1.5
Same question, two right answers. Which one you get depends on the date you ask about.
  1. v1.124 Oct 2025
  2. v1.212 Dec 2025
  3. v1.330 Mar 2026
  4. v1.424 Jul 2026
  5. v1.516 Oct 2026
  6. today: 4 Nov 2026
Outdated rule shown first
28%failure ratenaive search
0%failure ratedate filter
On 54 version-change questions, naive search ranked an outdated rule above the current one 15 times. With the date filter: 0 times.
Right rule found, version changes
39%hit ratenaive search
80%hit ratecurrent search
Right rule, right version, in the top 5 results: 21 of 54 questions before, 45 of 56 now (date filter plus the Qwen3 embedder). 95% interval for 80%: 68 to 89%.
Right rule found, expert rulings
44%hit ratenaive search
63%hit ratecurrent search
160 rulings by an experienced rules author: 70 found before, 100 now. 95% interval for 63%: 55 to 70%.
Dates

Answers as of a date

Every rules version carries the dates it was in force. Rules that weren't in force on your date are removed before ranking, so an outdated rule can't come out on top.

Tools

Works inside Claude Desktop

An MCP server gives AI apps tools to search the rules, see what changed, read one rule and list versions. Every result says which version it came from.

Local

Local, offline, measured

Postgres and Ollama on your machine, no API key. Every claim about quality is measured on labelled questions, with the predictions that were wrong published next to the right ones.

How it works

  1. You ask with a date. “Does a countered spell count as played?” as of 4 Feb 2026.
  2. Only rules in force that day are searched. That date falls in v1.2, so the wording Riot changed in v1.3 is out.
  3. The answer cites the version. Every claim points at a rule like core@1.2:412.1.b.
// search_rules, called by Claude Desktop
{
  "question": "Does a countered spell count as played?",
  "as_of": "2026-02-04"
}
// result (rule text omitted here)
[{
  "ref": "core@1.2:412.1",
  "rules": ["core@1.2:412.1", "core@1.2:412.1.a", "core@1.2:412.1.b"],
  "valid_from": "2025-12-12",
  "valid_to": "2026-03-30",
  "newer_version_exists": true
}]