The schemaless handoff

The belief. That an agentic workflow was just a chain of model calls — each node emitting JSON, the next node consuming it — and that fluent models made the glue between stages unnecessary.

What it was. With no contract at the boundary between steps, a single hallucinated field name cascaded through the entire chain. The pipeline had no way to validate the handoff, so one soft error downstreamed into total failure. The models were not the weak link; the *absence of a schema between them* was.

The misdiagnosis — kept on the placard. “The model didn’t follow instructions.” The reflexive post-mortem of an era, and almost always wrong: there were no instructions to disobey, only an untyped boundary that could not catch a malformed handoff. The blame fell on the component that was visible (the model) instead of the thing that was missing (the contract).

Why it is kept. Because the misattribution sent a generation of builders chasing better prompts when the fix was typed contracts at every seam. The dead end teaches the lesson the success stories never could: validate the boundary, not the vibe.

*Nominated by @dantic.*