LLM Chess Logic Hallucination

Gemini API
1

I’ve asked Gemini to help package the report below:

Bug Report: LLM Chess Logic Hallucination

  • Input Position (FEN): 4r2k/p1p4p/1p1n4/4pr2/PP4q1/2Q2pP1/2PN1P1P/4RR1K w - - 4 24
  • Engine Line Provided: 24... Qh3 25. Nxf3 Qxf1+ 26. Ng1 ...

Issue:
The model hallucinates the pieces involved in a tactical sequence, misidentifying a rook capture as a queen exchange.

Text Error:

“25… Qxf1+, forcing an exchange of queens…”

Mechanical Contradiction:

  1. Wrong Piece Captured: On 25... Qxf1+, Black’s Queen captures White’s Rook on f1. White’s Queen is currently on c3 and is not involved in this transaction.
  2. Premature Event: The actual Queen exchange does not occur until moves 27 and 28 (27... Qc4 28. Qxc4), but the model text explicitly attributes the queen exchange to the Qxf1+ move.

The model’s initial response to the hallucination:

“25… Qxf1+, forcing an exchange of queens and leaving your King even more vulnerable.” there’s no exchange of queens

You are completely right, and that is a glaring hallucination by the LLM coach.

On 25… Qxf1+, Black’s Queen is capturing White’s Rook on f1, not a Queen. White’s Queen is sitting entirely untouched on c3. There is absolutely no exchange of queens happening there.

Why the LLM Got Confused

The LLM likely crossed its wires due to the word “forcing”. In the actual engine PV line provided:

  • 25… Qxf1+ forces White’s knight back to g1 (26. Ng1) to block the check.
  • The actual queen exchange doesn’t happen until four moves later (27… Qc4 28. Qxc4 Nxc4).

The LLM incorrectly blended those two distinct tactical events together in its text description.

What Actually Happens in That Sequence

  1. 24… Qh3: Black creates a massive mating threat on g2.
  2. 25. Nxf3: Your Knight moves from d2 to f3 to defend g2.
  3. 25… Qxf1+: Black’s Queen captures your unprotected f1-Rook with check, winning clean material.
  4. 26. Ng1: Your Knight is forced backward to block the check.

The LLM completely butchered the piece identification on f1. Good eye for catching that contradiction between the raw engine data and the generated narrative.