Module replay 

Replay — score a loop configuration against the immutable past.

The engine is a pure function of (file, policy, now): run never reads the clock, and the golden suite byte-pins queues because of it. So a candidate configuration has a measurable quality on the recorded past: which findings it would have produced at each historical pass, how many of those the humans went on to approve or reject, how many of the approved ones later regressed, and how much queue it would have made. Dream-RSI (arXiv 2609.14858) does this for exploration policies over discovery trees and always includes the incumbent in the candidate set; the same rule holds here — the report is a comparison, never a bare number. docs/loop-proposal.md §17 named this rung 1 of the ladder.

Three disciplines, all structural:

• Prefix only. Every step reads through PrefixView, which hides any grain created after the step’s now — the paper’s prefix rule, no leakage from the future.
• Zero writes. The view refuses every mutating method of OmsSubstrate, and the engine holds &S, not &mut S.
• Scope honesty. An LLM is not a pure function of the evidence and an external command is out of process, so neither is replayed; they appear in the report as not_replayed with the reason. Telemetry rollups are not time-indexed, so the telemetry-fed analyzers are not replayed either.

No auto-adoption: replay informs, and adopting the configuration remains the policy file or POST /api/loop/config, by a human.

Structs

NotReplayed

Something the replay did not rehearse, and why.

PrefixView

A read-only, prefix-bounded view of a substrate. Every grain created after until_ms is invisible, and every write is refused — the two properties a rehearsal needs to be exact and harmless, both enforced by the type rather than promised.

ReplayArm

One arm of the comparison: the incumbent or the candidate.

ReplayCandidate

A candidate loop configuration to score against the past.

ReplayFinding

One would-be finding at one step.

ReplayOptions

What to replay over.

ReplayReport

The report: a comparison, never a bare number.

ReplayRequest

The request every surface accepts (areev loop replay --config FILE reads the file into it and adds the flags; POST /api/loop/replay and the bindings take it whole): the candidate plus the window.

ReplayTally

Counts for one analyzer, or the total.

Enums

ReplayStep

How now steps through the window.