The Bugs That Aren't in the Text: What Deep Relational Introspection Catches
Part 2 of 4: How a data engineering harness eliminates the AI coding agent errors that survive review.
Introduction
"Why do I need that? Isn't Claude Code good enough?"
We get that question a lot. We are building an open-source data engineering harness, the tooling and guardrails that a coding agent uses to build data pipelines. Claude Code, Codex, and OpenCode already write plausible data pipeline code. So what is the harness for?
Part 1 was about the seams between systems, and how a transpiler generates them deterministically. Part 2 is about a harder problem.
Some bugs have no correctness condition in the query text at all. The condition lives in the relationship between a query, the data it reads, and how that data changes over time. An agent reads SQL/code as text, and at the text level these bugs are invisible until the production deployment fails.
