The hidden side effectThe addressed session changes immediately, then the same selection is persisted under agent-default-model.

Four states. Four lifetimes.

01 / bundleComposition default

Engineering fallback.

02 / deploymentSettings default

Initial route for future Agents.

03 / live sessionCurrent selection

Used by the next assembly.

04 / durableRequest header

What was actually consumed.

The same click crosses two ownership boundaries.

Expected local effectSession A changesselectionFor(agent).current
+
Current rc.7 effectFuture Agents changesaveDefaultModelSelection

Do not infer spend from the visible picker.

Actual route evidence

Inspect the next durable request/header for provider, model, and reasoning effort. For a new subagent, verify its first request independently.

Operate rc.7 safely.

  1. 01Record

    Capture the deployment default.

  2. 02Switch

    Select the specialist route.

  3. 03Verify

    Read the next request header.

  4. 04Restore

    Return the intended future default.

Acceptance gates.

Primary evidence.

Keep the full routing runbook.

The canonical guide includes safe operations, persistence semantics, source boundaries, and seven verification gates.

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