ADR 0003: Execute one turn and leave scheduling to the host

• Status: Accepted
• Date: 2026-08-03

Context

An experiment harness combines several different concerns: it creates experimental state, runs autonomous ticks, starts fresh processes, captures transcripts, evaluates results, performs rollback, and writes artifacts. A product host has recurring background behavior of its own, but its scheduling is tied to product delivery, user policy, and billing.

Putting those loops into SharedOS would make the runtime depend on either experiment concepts or product policy. It would also make one execution request ambiguous: a caller could not tell whether it starts a bounded action or an autonomous scheduler.

Decision

SharedOS owns one bounded, permission-controlled agent turn. The turn can emit events and request authorized provider operations, but it does not decide when the next turn begins.

An evaluation host owns:

• the number and order of ticks;
• run budgets, retries, resume behavior, and stopping conditions;
• snapshots, judges, gold labels, metrics, statistics, and artifacts.

A product host owns:

• recurring background and cron scheduling;
• delivery and retry policy;
• product billing and user-facing lifecycle.

The useful single-turn logic in experimental scripts may be extracted into SharedOS. The surrounding scheduler and evaluation loop stays in the host.

Consequences

Positive

• Every SharedOS call has a bounded lifecycle.
• An evaluation host can reproduce and compare explicit scheduler policies.
• A product host can evolve its background scheduling without changing the shared runtime.
• SharedOS workers remain passive command executors rather than hidden autonomous processes.

Costs

• Hosts must implement or choose a scheduler.
• Retry semantics spanning several turns are not automatically portable.
• A scheduler conformance layer, if later required, must be designed separately.

Rejected alternatives

Use experiment_v2.ts as the SharedOS startup engine. Rejected because it mixes benchmark control-plane behavior with production execution.

Put all heartbeat behavior in SharedOS. Rejected because timing, billing, delivery, and stopping are host policies rather than permission-kernel concerns.