Function materializeForkedPartialSnapshot

src/node/services/workspaceService.ts:805–843

(params: {
  historyService: HistoryService;
  partialSnapshot: MuxMessage | null;
  sourceWorkspaceId: string;
  targetWorkspaceId: string;
})

}

async function materializeForkedPartialSnapshot(params: {
  historyService: HistoryService;
  partialSnapshot: MuxMessage | null;
  sourceWorkspaceId: string;
  targetWorkspaceId: string;
}): Promise<void> {
  if (!params.partialSnapshot) {
    return;
  }

  // Forking must be read-only with respect to the source workspace. During tool calls
  // such as task_await, deleting or committing the source partial can make the live
  // parent turn look interrupted. Instead, copy the partial into the fork and finalize
  // only that snapshot so the child has no inherited live-stream state. The snapshot
  // is captured before fork checkout/copy I/O so a parent stream that finishes mid-fork
  // cannot make the child miss the latest visible assistant state.
  const writeResult = await params.historyService.writePartial(
    params.targetWorkspaceId,
    params.partialSnapshot
  );
  if (!writeResult.success) {
    log.warn("Failed to snapshot source partial into fork", {
      sourceWorkspaceId: params.sourceWorkspaceId,
      targetWorkspaceId: params.targetWorkspaceId,
      error: writeResult.error,
    });
    return;
  }

  const commitResult = await params.historyService.commitPartial(params.targetWorkspaceId);
  if (!commitResult.success) {
    log.warn("Failed to finalize forked partial snapshot", {
      sourceWorkspaceId: params.sourceWorkspaceId,
      targetWorkspaceId: params.targetWorkspaceId,
      error: commitResult.error,
    });
    await params.historyService.deletePartial(params.targetWorkspaceId);
  }
}

function getOldestSequencedMessage(
  messages: readonly MuxMessage[]