X-in-the-Middle Development
Agent-written code is an X in the middle. We should strive to make confidence independent of understanding every internal step. To earn that confidence, define the input and expected result, apply the input to X, then compare the actual with the expected. The more completely we do that, and the more tightly we define1 what we expect from X, the more we can trust the X in the middle.
INPUT → [ X ] → ACTUAL ?= EXPECTED
X might also be a model, a service, a workflow, or a person. In every case, the decisive question comes before any test result: who authors EXPECTED, who may change it, and what evidence may close the box? Tests are instruments inside that governance. Confidence is limited to the box and its authorship.
The tighter the box, the less X matters.
1Define means independently authoring the expected outcomes and accepted evidence, then specifying the tests and coverage, runtime conditions, dependencies, permissions, limits, and scope that establish the box around X. The box does not authenticate itself.
The philosophy in practice
X-in-the-Middle is the philosophy. Expectation-Driven Development governs what evidence is sufficient to accept stateful software. Gold-State Parity™ is the deterministic write-path gate that enforces that decision.