Get cost of streamText using the ai gateway sdk

AI SDK
1

I’m trying to calculate the cost of doing a streamText.

Based on the docs here, I was under the impression I could use gateway.getGenerationInfo({ id: generationId }) in the onFinish hook. But here I just get:

"data": {
        "error": "Usage event not found",
        "id": "gen_01KT4BW3JSXKZG1CHRJRYQASH8",
        "message": "No usage event found with ID gen_01KT4BW3JSXKZG1CHRJRYQASH8."
      }

I can see that result.providerMetadata.gateway contains cost information when I log it:

{
  cost: '0.00849',
  marketCost: '0.00849',
  surchargeCost: '0',
  gatewayCost: '0.00849',
  inferenceCost: '0.00849',
  inputInferenceCost: '0.00744',
  outputInferenceCost: '0.00105',
  generationId: 'gen_01KT4C7A322AA7XN4JV02506VR'
}

However this is untyped in the typescript SDK, with the type JSONObject ?

So what’s the verdict here - do I parse/validate the result.providerMetadata.gateway, or should gateway.getGenerationInfo actually work?