> ## Documentation Index
> Fetch the complete documentation index at: https://docs.manthan.systems/llms.txt
> Use this file to discover all available pages before exploring further.

# Replay

> Two separate things share this name today — what each actually does.

<Warning>
  **\[PARTIAL], and more precisely split than the name suggests.** There are two unconnected
  things called "replay" in the current codebase. Conflating them would overclaim what
  either one does.
</Warning>

## 1. `POST /replay` (what the SDKs and HTTP API expose)

This is what `client.replay.replay(transaction_id)` actually calls. Its real
implementation, `ExecutionTrustApplication.replay()`
(`packages/runtime/src/ExecutionTrustApplication.ts:142-171`):

```typescript theme={null}
async replay(businessTransactionId: string): Promise<{
  businessTransactionId: string;
  trustRecordHash: string;
  verified: boolean;
}> {
  const trustRecord = await this.trustRecords.findByTransactionId(businessTransactionId);
  if (!trustRecord) throw new Error("Execution Trust Record not found.");
  const verified = await this.crypto.verify(trustRecord);
  return { businessTransactionId, trustRecordHash: trustRecord.trustRecordHash, verified };
}
```

**This re-verifies the Trust Record's cryptographic signature — it does not reconstruct or
re-execute anything.** \[AVAILABLE], but narrower than "replay" implies: it's a signature
recheck with a `replay`-shaped response, not deterministic execution reconstruction.

## 2. `packages/replay` (the deterministic reconstruction engine)

A separate, real package: `ReplayEngine`, `ReplayPipeline`, `ReplayExecutor`,
`ReplayBuilder` — builds an execution plan from recorded execution IDs and replays it,
proven deterministic regardless of input order (`ReplayDeterminism.test.ts` — "should
produce identical output regardless of input order"; `ReplayEngine.test.ts`; 9 tests
total).

<Warning>
  **Confirmed disconnected: nothing in `packages/api` or `packages/runtime` imports
  `@parmana/replay`.** This engine is not reachable through `POST /replay` or any other
  route today. It's real, tested, standalone library code — not yet wired into the
  runtime or the HTTP surface.
</Warning>

## What "semantic verification" would add — not built yet

CLAIMS.md explicitly withholds this claim: *"Replay semantically verifies every trust
artifact"* is listed under Future Claims, not Supported Claims. Neither of the two
mechanisms above re-evaluates the original policy against the recorded signals and
confirms the same Decision would result — that's what "semantic" replay verification
would mean, and it doesn't exist yet. See [Roadmap](/roadmap).