[cynthiajoan]

Description

DeveloperSerialization.parseCountTokensResponse (lib/src/developer/api.dart) dropped promptTokensDetails returned by the Gemini Developer API (googleAI backend), so per-modality token counts such as TEXT and AUDIO were always null, and it threw Unhandled format for CountTokensResponse when the server omitted totalTokens (protobuf JSON omits zero values, returning {} or only promptTokensDetails).

parseCountTokensResponse now defaults totalTokens to 0 on an empty object or when promptTokensDetails is present without totalTokens, parses promptTokensDetails with the existing parseUsageMetadata helper (matching the agentPlatform serializer), and rejects non-integer totalTokens or non-list promptTokensDetails with unhandledFormat. The LiveSession.receive() doc comment is also corrected: the stream stays open across turns until the session is closed.

Verification

• Change kind: bugfix
• Red (base d07113e3a + only the new tests): flutter test --no-pub test/developer_api_test.dart → exit 1, 25 passed, 3 failed; new tests failing: parses promptTokensDetails when present, defaults totalTokens to 0 on empty JSON object:

  00:00 +20 -1: DeveloperSerialization parseCountTokensResponse parses promptTokensDetails when present [E]
    Expected: not null
      Actual: <null>
    package:matcher                                     expect
    package:flutter_test/src/widget_tester.dart 473:18  expect
    test/developer_api_test.dart 636:9                  main.<fn>.<fn>.<fn>
  00:00 +20 -1: DeveloperSerialization parseCountTokensResponse defaults totalTokens to 0 on empty JSON object
  00:00 +20 -2: DeveloperSerialization parseCountTokensResponse defaults totalTokens to 0 on empty JSON object [E]
    Unhandled format for CountTokensResponse: {}
    This indicates a problem with the Firebase AI Logic SDK. Try updating to the latest version (https://pub.dev/packages/firebase_ai/versions), or file an issue at https://github.com/firebase/flutterfire/issues.
    package:firebase_ai/src/developer/api.dart 106:5  DeveloperSerialization.parseCountTokensResponse
    test/developer_api_test.dart 647:51               main.<fn>.<fn>.<fn>
  00:00 +20 -2: DeveloperSerialization parseCountTokensResponse defaults totalTokens to 0 when omitted with promptTokensDetails
  00:00 +20 -3: DeveloperSerialization parseCountTokensResponse defaults totalTokens to 0 when omitted with promptTokensDetails [E]
    Unhandled format for CountTokensResponse: {promptTokensDetails: [{modality: TEXT, tokenCount: 0}]}
    This indicates a problem with the Firebase AI Logic SDK. Try updating to the latest version (https://pub.dev/packages/firebase_ai/versions), or file an issue at https://github.com/firebase/flutterfire/issues.
    package:firebase_ai/src/developer/api.dart 106:5  DeveloperSerialization.parseCountTokensResponse
    test/developer_api_test.dart 663:53               main.<fn>.<fn>.<fn>
  00:00 +20 -3: DeveloperSerialization parseCountTokensResponse throws FirebaseAIException on error response
  00:00 +21 -3: DeveloperSerialization parseCountTokensResponse throws unhandledFormat on invalid JSON
  

• Green (head 5d2cc3751): flutter test --no-pub test/developer_api_test.dart → exit 0, 28 passed (4s).
• Fork CI: fork CI (all_plugins, e2e-ai, e2e-smoke, pr_title)

Related Issues

N/A (AI-COUNT-TOKENS-1)

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---

Prepared with the Firebase SDK dev-loop agent (Google-internal, built on Jetski) and reviewed by @cynthiajoan before opening. Evidence: red/green captured by verify-redgreen (verdict verified) at base d07113e3a / head 5d2cc3751.

[gemini-code-assist]

Code Review

This pull request updates parseCountTokensResponse in the developer API to parse promptTokensDetails and handle empty JSON objects, updates documentation for LiveSession.receive(), and adds corresponding unit tests. Feedback highlights a potential parsing failure if totalTokens is omitted while promptTokensDetails is present, and recommends avoiding the ! operator in tests to comply with the repository's null safety style guide.

[Lyokone]

Optional: iOS and Android return 0 for any JSON object, while this still rejects an object that has neither totalTokens nor promptTokensDetails. No current response hits that, but dropping the isEmpty branch and this check (totalTokens ?? 0 for any map) would match the other SDKs and be simpler. It would mean replacing the {'wrongKey': 123} case in throws unhandledFormat on invalid JSON.

[Lyokone]

The stream also ends when the server or the network closes the socket: onDone closes _messageController. Maybe "until the session is closed or the connection ends"? (resumeSession() doesn't reopen it after that either, but that's a separate, older bug.)

[Lyokone]

Nit: CountTokensResponse.promptTokensDetails isn't deprecated, so this // ignore: deprecated_member_use_from_same_package (left over from totalBillableCharacters, removed in #18708) and the three new ones below can go.