Expo iOS Development MCP Server

Instructions

Implementation Reference

• src/simulator/logs.ts:19-76 (handler)

  Core implementation of startLogStream(): starts a log streaming process using 'xcrun simctl spawn booted log stream', handles output via logger, manages process state

  export async function startLogStream(): Promise<LogStreamInfo> {
    logger.info("simulator", "Starting simulator log stream");
  
    if (logStreamProcess) {
      throw createError("SIMCTL_FAILED", "Log stream is already running");
    }
  
    // Check if simulator is booted
    if (!stateManager.isSimulatorReady()) {
      const bootedDevice = await getBootedDevice();
      if (!bootedDevice) {
        throw createError("SIM_NOT_BOOTED", "No simulator is currently booted", {
          details: "Boot a simulator first using simulator.boot",
        });
      }
      stateManager.updateSimulator({
        state: "booted",
        udid: bootedDevice.udid,
        deviceName: bootedDevice.name,
      });
    }
  
    // Start log stream
    logStreamProcess = execa("xcrun", ["simctl", "spawn", "booted", "log", "stream", "--style", "compact"], {
      reject: false,
    });
  
    isStreaming = true;
    const startedAt = new Date().toISOString();
  
    // Process stdout line by line
    logStreamProcess.stdout?.on("data", (chunk: Buffer) => {
      const lines = chunk.toString().split("\n").filter(Boolean);
      for (const line of lines) {
        logger.debug("simulator", line);
      }
    });
  
    logStreamProcess.stderr?.on("data", (chunk: Buffer) => {
      const lines = chunk.toString().split("\n").filter(Boolean);
      for (const line of lines) {
        logger.warn("simulator", `[stderr] ${line}`);
      }
    });
  
    logStreamProcess.on("exit", (code: number | null) => {
      logger.info("simulator", `Log stream ended with code ${code}`);
      isStreaming = false;
      logStreamProcess = null;
    });
  
    logger.info("simulator", "Simulator log stream started");
  
    return {
      isStreaming: true,
      startedAt,
    };
  }

• src/mcp/server.ts:230-249 (registration)

  MCP server.tool registration for 'simulator.log_stream.start', which invokes startLogStream() and formats the MCP response

  server.tool(
    "simulator.log_stream.start",
    "Start streaming simulator system logs",
    {},
    async () => {
      try {
        const result = await startLogStream();
        return {
          content: [
            {
              type: "text",
              text: JSON.stringify({ success: true, ...result }, null, 2),
            },
          ],
        };
      } catch (error) {
        return handleToolError(error);
      }
    }
  );