oh-my-opencode/src/plugin/system-transform.ts

import type { DefaultModeConfig } from "../config/schema/default-mode"

const ULTRAWORK_MODE_TAG = "<ultrawork-mode>"

export function createSystemTransformHandler(
  defaultMode?: DefaultModeConfig,
  getUltraworkMessage?: (agentName?: string, modelID?: string) => string,
): (
  input: { sessionID?: string; model: { id: string; providerID: string; [key: string]: unknown } },
  output: { system: string[] },
) => Promise<void> {
  return async (input, output): Promise<void> => {
    if (!defaultMode?.ultrawork || !getUltraworkMessage) return

    // When ralph_loop is also enabled, skip system prompt injection: the loop's
    // own continuation mechanism handles ultrawork re-injection on each iteration.
    // Injecting both would be redundant — the continuation prompt prepends
    // "ultrawork" and re-triggers keyword detection, defeating invisibility.
    // The `ultrawork` flag still controls loop behavior (500 iters + Oracle gate).
    if (defaultMode?.ralph_loop) return

    // Avoid re-injecting if the ultrawork prompt is already in the system prompt
    // (e.g. after compaction the system prompt is rebuilt and this hook fires again)
    if (output.system.some((part) => part.includes(ULTRAWORK_MODE_TAG))) return

    const modelID = input.model?.id
    const ultraworkMessage = getUltraworkMessage("sisyphus", modelID)
    if (!ultraworkMessage) return

    output.system.push(ultraworkMessage)
  }
}