AI coding agents are fast at implementation, but a short product requirement can still hide behavior-changing decisions. "Users can export their monthly transactions" leaves timezone, transaction-state, and boundary rules unspecified. If an agent silently chooses one interpretation, the code may be valid and still be wrong.

Ambiguity Compiler is a pre-implementation contract compiler for product-minded developers. It accepts a requirement and a deliberately small, user-approved context bundle. GPT-5.6 returns two or three behaviorally different contracts with acceptance criteria and discriminating scenarios. The developer compares the outcomes, explicitly locks the intended contract, and records a Vitest verification result alongside a decision receipt that preserves selected and rejected alternatives.

The project combines a responsive web dashboard, a local MCP server, and a Codex skill. Codex prepares context, materializes selected contract tests in the local repository, runs the test workflow, and applies the implementation only after the human has chosen a contract. GPT-5.6 is used for strict structured-output analysis; deterministic Zod validation checks the schema, evidence anchors, scenario separation, and state transitions.

For the judge walkthrough, the monthly-transaction-export fixture exposes a timezone-boundary bug, verifies the chosen user-local calendar-month behavior with Vitest, and creates a receipt that links the requirement, contract, test, result, and patch hash.

Built With

  • bun
  • codex
  • gpt-5.6
  • model-context-protocol
  • openrouter
  • react
  • tanstack-start
  • typescript
  • vitest
  • zod
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