How to use Codex to generate solvable murder mysteries

The Cold Case creators gave Codex a design specification for a replayable noir mystery. The hard requirement was fairness: each generated case had to expose enough evidence to identify one culprit, rather than leaving the player with an arbitrary hidden answer.

Codex implemented a generator that constructed the crime backward. It selected a killer, gave innocent suspects independently supported alibis, introduced the killer’s false account, and placed contradicting evidence. A solvability check rejected a generated case unless the culprit remained uniquely identifiable.

The same session built interrogation, a draggable evidence board, an updating timeline, and accusation outcomes. Every random choice used one seeded generator so a shared seed reproduced the same cast, clues, and dialogue. The creators iterated on bugs, interface changes, and noir presentation through that session.

The result was an offline single-file browser game. The authors report stress-testing generated cases across difficulty settings, but this account does not turn their finite checks into a proof about every possible seed. The useful pattern is pairing procedural variety with a verifier that can reject an unfair puzzle before the player receives it. Human direction still defined what counted as fair and what the story should feel like.

Prompt
Suggested prompt (written by Agents In Use, not the author's)

Source: Devpost · Aayan Zahoor and Munhim Qazi