Why can't I make mastra with a function call?

WARN [2025-10-27 10:41:56.000 -0400] (Mastra CLI): Mastra telemetry config could not be extracted. Please make sure your entry file looks like this:
export const mastra = new Mastra({
  telemetry: <value>
})

import { D1Store } from '@mastra/cloudflare-d1';
import { Agent } from '@mastra/core/agent';
import { SamplingStrategyType } from '@mastra/core/ai-tracing';
import type { AITracingExporter } from '@mastra/core/ai-tracing';
import { Mastra } from '@mastra/core/mastra';
import { LangfuseExporter } from '@mastra/langfuse';
import { LibSQLStore } from '@mastra/libsql';

import { basicWorkflow } from './workflows/basic';

function buildExporters(env?: Env): AITracingExporter[] {
  const exporters: AITracingExporter[] = [];
  if (env?.LANGFUSE_PUBLIC_KEY && env?.LANGFUSE_SECRET_KEY) {
    exporters.push(
      new LangfuseExporter({
        ...
      }),
    );
  }
  return exporters;
}

function buildStorage(env?: Env) {
  if (env?.DB) {
    return new D1Store({ binding: env.DB });
  }
  return new LibSQLStore({ url: ':memory:' });
}

const defaultAgent = new Agent({
  name: 'default-agent',
  instructions: 'You are a helpful assistant.',
  model: 'openai/gpt-4o-mini',
});

export function createMastra(env?: Env) {
  const exporters = buildExporters(env);
  const storage = buildStorage(env);

  return new Mastra({
    agents: { defaultAgent },
    workflows: { basicWorkflow },
    storage,
    telemetry: {
      enabled: false,
    },
    observability: {
      default: { enabled: Boolean(exporters.length) },
      configs: {
        main: {
          exporters,
        },
      },
      configSelector: () => 'main',
    },
  });
}

export const mastra = createMastra();