The registrar

The registrar is the runtime. The registrar runs the agent loop, examines each action against the writ, and writes each result to the record.

You do not write the loop. The registrar is the loop.

The cycle

For each iteration, the registrar does these steps:

1. It sends the mandate, the history, and the permitted actions to the holder model.
2. It receives an answer. The answer contains text, an action request, or a statement that the work is complete.
3. It examines the action request against the grants, the bounds, and the invariants.
4. It permits the action, or it denies the action.
5. It does the permitted action and adds the result to the history.
6. It writes the action, each check, and each result to the record.

The registrar repeats the cycle until one of these things occurs:

• The satisfaction clauses pass.
• A bound stops the run.
• A remedy stops the run.
• The model stops.

The order of the checks

The registrar makes the checks in this order, and stops at the first failure:

1. Grants. Does a grant permit this type of action, with these arguments?
2. Bounds. Does the run have enough of each budget for this action?
3. Invariants. Does this action break a condition that must stay true?

A letter check happens on each action. A judgment check happens at the checkpoint of its clause. An assent check stops the run and waits for a person.

A denial is information

When the registrar denies an action, the registrar tells the model which clause failed and why. The model then plans inside its limits.

This behaviour is important. A model that gets “permission denied” tries the same action again. A model that gets “the invariant untouched protects tests/test_sync.py” changes its plan.

What the registrar does not do

• The registrar does not plan. The model selects each step.
• The registrar does not make the model better.
• The registrar does not check the mandate. The registrar checks the satisfaction clauses.
• The registrar does not compare your declared prices with the prices of the provider.

Sidecar mode

The registrar can also run as an MCP proxy. In this mode, the registrar governs an agent that you already have. The proxy applies the mcp grants at the tool boundary, and your agent code does not change.

Sidecar mode governs tool calls by name. The proxy cannot see the cost of the agent, the iterations of the agent, or the effects outside the tool calls, and the record does not claim to cover them.

Read more about writ proxy.