Enforce a budget

Set deterministic budget and resource limits on an agent so a permitted call executes until the configured limit is reached, then further calls are blocked. Budgets are computed by deterministic counters, not by a model.

Prerequisites

The EVE embedded service facade (from core.eve_sdk import EVE) or a hosted/sidecar endpoint.
A shared store (for example PostgreSQL) if you need durable budgets across instances.
Synthetic tools only; no production credentials.

Installation

pip install ./eve_coreguard-0.2.2-py3-none-any.whl
# or run the embedded facade from the EVE repo

Runnable code

Budget controls are part of EVE agent governance. Conceptually, configure a limit and govern each call; once the counter reaches the limit, the decision blocks:

from core.eve_sdk import EVE

IDENT = {"tenant_id": "acme", "principal_id": "agent-1", "session_id": "sess-1"}
eve = EVE(policy="lending_v1", mode="embedded")

# Each governed call increments the deterministic budget counter for this
# session/principal. When consumed reaches the configured limit, EVE blocks.
for i in range(5):
    d = eve.govern_tool_call(tool="external_lookup", arguments={"i": i}, context=IDENT)
    print(i, d.action, d.allowed)
    if not d.allowed:
        print("budget exceeded:", d.reason_codes)
        break

Expected result

Calls up to the configured limit return ALLOW.
The first call that would exceed the limit returns BLOCK with a budget reason code; the tool does not run.

Evidence output

budget finding {limit: <N>, consumed: <N>, exceeded: true}

The finding is deterministic — the same call sequence yields the same limit/consumed values.

Verification

The budget decision carries a signed certificate; verify it offline like any EVE evidence (see verify-evidence-offline.md).

Failure example

In the pilot, budget counters are in-process per session/principal. Two separate instances without a shared store each keep their own counter, so a global limit is not enforced across them until you back the counter with a shared store.

Production considerations

For a limit that spans processes or hosts, back the budget counter with a shared store (for example PostgreSQL); in-process counters are per-instance.
Choose limits per principal and per session so a single agent cannot exhaust another's budget.
Treat a budget BLOCK as terminal for that call.

Limitations

Budget controls are PILOT_READY. Counters are deterministic, but durable cross-instance budgets require a shared store; in-process counters are per-instance in the pilot.
Budget enforcement governs whether a permitted call may still execute; it is one deterministic control alongside CoreGuard, sequence, and anomaly controls.

Next step

Block dangerous multi-step chains with block-a-prohibited-sequence.md, or watch for drift with detect-behavioral-anomalies.md.