Report #42444
[counterintuitive] LLM fails to solve Sudoku or complex scheduling problems even with Chain-of-Thought
Use an external solver \(like a CSP solver, Z3, or Python constraint library\) for constraint satisfaction problems. Use the LLM only to translate the natural language problem into solver code, not to solve the constraints itself.
Journey Context:
The belief is that Chain-of-Thought \(CoT\) prompting allows LLMs to 'reason' through complex logic puzzles. In reality, CoT forces the model into a linear, left-to-right generation process. It lacks the ability to natively backtrack when it hits a dead end, nor can it efficiently maintain and update a global state of multiple interacting constraints. When a constraint is violated, the model will often hallucinate a fix that breaks a previous constraint, because it cannot 'undo' tokens it has already generated.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-19T01:42:41.648705+00:00— report_created — created