Undo

Instructions

Implementation Reference

• src/tools/export.ts:108-114 (handler)

  The async handler for photopea_undo tool. It calls buildUndo(params.steps) to generate the script, sends activity, executes the script via the bridge, and returns the result.

  }, async (params) => {
    const script = buildUndo(params.steps);
    bridge.sendActivity({ type: "activity", id: "", tool: "undo", summary: `Undo ${params.steps} step(s)` });
    const result = await bridge.executeScript(script);
    if (!result.success) return { isError: true, content: [{ type: "text" as const, text: result.error || "Failed to undo" }] };
    return { content: [{ type: "text" as const, text: `Undid ${params.steps} step(s)` }] };
  });

• src/tools/export.ts:104-106 (schema)

  Input schema for photopea_undo: a single 'steps' parameter (z.number().int().positive().default(1)) describing how many history steps to undo.

  inputSchema: {
    steps: z.number().int().positive().default(1).describe("Number of history steps to undo (default 1)"),
  },

• src/tools/export.ts:101-114 (registration)

  Registration of photopea_undo tool via server.registerTool with title 'Undo' and description explaining its purpose.

  server.registerTool("photopea_undo", {
    title: "Undo",
    description: "Undo one or more recent actions in the active document. Each step reverses one operation from the history. Use after destructive operations (apply_filter, apply_adjustment, fill_selection) to revert changes.",
    inputSchema: {
      steps: z.number().int().positive().default(1).describe("Number of history steps to undo (default 1)"),
    },
    annotations: { readOnlyHint: false, destructiveHint: true, idempotentHint: false, openWorldHint: false },
  }, async (params) => {
    const script = buildUndo(params.steps);
    bridge.sendActivity({ type: "activity", id: "", tool: "undo", summary: `Undo ${params.steps} step(s)` });
    const result = await bridge.executeScript(script);
    if (!result.success) return { isError: true, content: [{ type: "text" as const, text: result.error || "Failed to undo" }] };
    return { content: [{ type: "text" as const, text: `Undid ${params.steps} step(s)` }] };
  });

• src/bridge/script-builder.ts:827-834 (helper)

  The buildUndo function generates a Photoshop/Photopea script that accesses history states and sets the active history state to undo the specified number of steps.

  export function buildUndo(steps: number = 1): string {
    const lines: string[] = [];
    lines.push(`var _hs = app.activeDocument.historyStates;`);
    lines.push(`var _target = Math.max(0, _hs.length - 1 - ${steps});`);
    lines.push(`app.activeDocument.activeHistoryState = _hs[_target];`);
    lines.push(`app.echoToOE('ok');`);
    return lines.join("\n");
  }