Firebase AI: Billable Characters is nil when using backend as GoogleAI

[SeanChinJunKai]

Description

I am getting nil for billable characters when using backend as GoogleAI but it is non-nil for Vertex AI

Reproducing the issue

// Code using .googleAI() prints Total billable characters: nil
let ai = FirebaseAI.firebaseAI(backend: .googleAI())
let model = ai.generativeModel(modelName: "gemini-2.0-flash")
let result = try await model.countTokens(prompt)
print("Total billable characters: (billableCharacters)")

Firebase SDK Version

11.14.0

Xcode Version

16.3

Installation Method

Swift Package Manager

Firebase Product(s)

AI Logic

Targeted Platforms

iOS

Relevant Log Output

If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet

{
  "originHash" : "c63c63846d9c539229e96de38d6af51417e28c0ee9a0bc48bd0f0f19d923c329",
  "pins" : [
    {
      "identity" : "abseil-cpp-binary",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/abseil-cpp-binary.git",
      "state" : {
        "revision" : "bbe8b69694d7873315fd3a4ad41efe043e1c07c5",
        "version" : "1.2024072200.0"
      }
    },
    {
      "identity" : "app-check",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/app-check.git",
      "state" : {
        "revision" : "61b85103a1aeed8218f17c794687781505fbbef5",
        "version" : "11.2.0"
      }
    },
    {
      "identity" : "firebase-ios-sdk",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/firebase-ios-sdk",
      "state" : {
        "revision" : "45d327fcbe7793747295346c2209ad419bdead74",
        "version" : "11.14.0"
      }
    },
    {
      "identity" : "google-ads-on-device-conversion-ios-sdk",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/googleads/google-ads-on-device-conversion-ios-sdk",
      "state" : {
        "revision" : "70a7857886f065a40486a7607268781c49db04ae",
        "version" : "2.0.0"
      }
    },
    {
      "identity" : "googleappmeasurement",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/GoogleAppMeasurement.git",
      "state" : {
        "revision" : "406f72d0d5e9445fd1cf782db3e9e338cee2bed4",
        "version" : "11.14.0"
      }
    },
    {
      "identity" : "googledatatransport",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/GoogleDataTransport.git",
      "state" : {
        "revision" : "617af071af9aa1d6a091d59a202910ac482128f9",
        "version" : "10.1.0"
      }
    },
    {
      "identity" : "googleutilities",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/GoogleUtilities.git",
      "state" : {
        "revision" : "60da361632d0de02786f709bdc0c4df340f7613e",
        "version" : "8.1.0"
      }
    },
    {
      "identity" : "grpc-binary",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/grpc-binary.git",
      "state" : {
        "revision" : "cc0001a0cf963aa40501d9c2b181e7fc9fd8ec71",
        "version" : "1.69.0"
      }
    },
    {
      "identity" : "gtm-session-fetcher",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/gtm-session-fetcher.git",
      "state" : {
        "revision" : "c756a29784521063b6a1202907e2cc47f41b667c",
        "version" : "4.5.0"
      }
    },
    {
      "identity" : "interop-ios-for-google-sdks",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/interop-ios-for-google-sdks.git",
      "state" : {
        "revision" : "040d087ac2267d2ddd4cca36c757d1c6a05fdbfe",
        "version" : "101.0.0"
      }
    },
    {
      "identity" : "leveldb",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/leveldb.git",
      "state" : {
        "revision" : "a0bc79961d7be727d258d33d5a6b2f1023270ba1",
        "version" : "1.22.5"
      }
    },
    {
      "identity" : "nanopb",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/nanopb.git",
      "state" : {
        "revision" : "b7e1104502eca3a213b46303391ca4d3bc8ddec1",
        "version" : "2.30910.0"
      }
    },
    {
      "identity" : "promises",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/promises.git",
      "state" : {
        "revision" : "540318ecedd63d883069ae7f1ed811a2df00b6ac",
        "version" : "2.4.0"
      }
    },
    {
      "identity" : "swift-protobuf",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/apple/swift-protobuf.git",
      "state" : {
        "revision" : "102a647b573f60f73afdce5613a51d71349fe507",
        "version" : "1.30.0"
      }
    }
  ],
  "version" : 3
}

If using CocoaPods, the project's Podfile.lock

Expand Podfile.lock snippet

Replace this line with the contents of your Podfile.lock!

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[paulb777]

Based on #13721, this looks like expected behavior. @andrewheard, anything else to add?

[andrewheard]

@paulb777 @rachelsaunders This is expected behaviour but we should update the documentation. I think we should also consider deprecating the totalBillableCharacters field to clarify this (since the Gemini 1.5 series models are restricted to existing users on Vertex AI and Gemini 1.0 series models are retired).

@SeanChinJunKai Previously, Vertex AI billed by character counts and Google AI (Gemini Developer API) billed by token counts. For Gemini 2.0 series models, and newer however, both Vertex AI and Google AI bill by token counts instead of character counts.

I'll update this issue with a new code snippet to use until we get the ones updated on the doc site.

[SeanChinJunKai]

Hi @andrewheard thanks for sharing 😄. I suppose this applies to the android sdk too?

[andrewheard]

Hi @andrewheard thanks for sharing 😄. I suppose this applies to the android sdk too?

No problem @SeanChinJunKai and thank you for reporting the issue! This does apply to the Android SDK as well (note: unrelated to firebase/firebase-android-sdk#7008 though -- separate issue). This also applies to the Web / Flutter / Unity SDKs so I'll bring it up with the SDK teams.

These two new snippets are what I'd recommend now in Swift.

Text-only Input:

let response = try await model.countTokens("Write a story about a magic backpack.")

print("Total Tokens: \(response.totalTokens)")

Multimodal Input:

let response = try await model.countTokens(image, "What's in this picture?")

print("Total Tokens: \(response.totalTokens)")
// Print tokens by modality, for example "TEXT Tokens: 7" and "IMAGE Tokens: 258"
for promptTokensDetail in response.promptTokensDetails {
  print("\(promptTokensDetail.modality.rawValue) Tokens: \(promptTokensDetail.tokenCount)")
}