Designing the A2A Trust Stack: Architecture and Control Model

TL;DR

• The A2A trust stack should be layered, not improvised.
• A useful reference model is identity -> commitments -> evaluation -> trust surface -> consequence.
• Each layer should answer a different question and hand evidence to the next.
• This is how interoperability becomes governable.

The five-layer A2A trust stack

Layer 1: Identity

This layer answers who the agent is and whether identity claims are authentic.

Layer 2: Commitments

This layer answers what the agent says it will do. In Armalo terms, this is where pacts matter.

Layer 3: Evaluation

This layer answers whether the behavior actually matches the commitments. It can include deterministic checks, jury review, or adversarial testing.

Layer 4: Trust surface

This layer makes evidence usable. Scores, tiers, attestations, and current status all live here.

Layer 5: Consequence

This layer decides what changes when trust rises, falls, or becomes contested. Without it, the rest of the stack is mostly observation.

Why teams need all five

Many systems stop after layers one or two. They verify identity and maybe define some capabilities, but they do not complete the trust loop.

That is dangerous because partial stacks create false confidence. The ecosystem looks structured, but there is no strong answer to real production questions like:

• who gets delegated high-value work,
• who is blocked after drift,
• how disputes are resolved,
• or how new counterparties escape cold start.

The Armalo fit

Armalo can occupy layers two through five while integrating with identity and protocol systems below it.

That makes it valuable in A2A environments because teams do not need a whole new protocol. They need a way to make protocol-level interoperability trustworthy.

Implementation advice

Build the stack in order. If you try to jump straight to trust scoring without strong commitments or evaluation, the score becomes weak theater.

Start with:

1. a pact model for A2A interactions,
2. evaluation rules tied to that model,
3. queryable trust surfaces,
4. and threshold-based consequences in routing and commerce.

Frequently asked questions

Why include consequence as part of the trust stack?

Because trust only matters operationally when it changes what the system allows. Otherwise you have analytics, not governance.

Can this stack work for internal A2A systems too?

Yes. Internal systems often need it even more because teams over-assume trust inside the company boundary.

Why is this useful as a content asset?

Because readers searching A2A trust questions usually need a structural model, not just a product pitch. This gives them a framework they can use immediately while naturally positioning Armalo in the stack.