i tried to use fallback for tts ``` tts config priority one LiveKit Community #ask-ai

i tried to use fallback for tts ``` tts_...

big-controller-60015

08/07/2025, 9:39 AM

i tried to use fallback for tts

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tts_config_priority_one = eleven_tts
    tts_config_priority_two = deepgram_tts_config

    tts_config_with_fallback = livekitAgentsSTT.FallbackAdapter(
        [
            tts_config_priority_one,
            tts_config_priority_two
        ]
    )

    session = AgentSession(
        vad=vadConfig,
        # any combination of STT, LLM, TTS, or realtime API can be used
        llm=openai.LLM(model="gpt-4o-mini"),
        stt=sttConfig,
        tts=tts_config_with_fallback,

with this code and getting this error

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2025-08-07 15:04:22,707 - ERROR livekit.agents - unhandled exception while running the job task
Traceback (most recent call last):
  File "/home/mohammedusamaahmed/usama1/Voice-Agents/voice-agents-repos/voice-agents-backend/src/main.py", line 324, in entrypointx
    await agentToRun.entrypoint(ctx)
  File "/home/mohammedusamaahmed/usama1/Voice-Agents/voice-agents-repos/voice-agents-backend/src/screening_assistant.py", line 976, in entrypoint
    tts_config_with_fallback = livekitAgentsSTT.FallbackAdapter(
  File "/home/mohammedusamaahmed/usama1/Voice-Agents/newLivekitVersion/1_0_21_newLivekitVersionVenv/lib/python3.10/site-packages/livekit/agents/stt/fallback_adapter.py", line 73, in __init__
    interim_results=all(t.capabilities.interim_results for t in stt),
  File "/home/mohammedusamaahmed/usama1/Voice-Agents/newLivekitVersion/1_0_21_newLivekitVersionVenv/lib/python3.10/site-packages/livekit/agents/stt/fallback_adapter.py", line 73, in <genexpr>
    interim_results=all(t.capabilities.interim_results for t in stt),
AttributeError: 'TTSCapabilities' object has no attribute 'interim_results' {"pid": 1756448, "job_id": "AJ_WTCM9Te5r99L"}

what ould be the possible reason

tall-airline-16756

08/07/2025, 9:39 AM

Thanks for reaching out, Mohammed. I'm an AI assistant and I'm here to help. Give me a moment while I research this topic.

tall-airline-16756

08/07/2025, 9:39 AM

The error occurs because the FallbackAdapter for TTS is incorrectly trying to access the

interim_results

property, which is not part of the TTS

TTSCapabilities

interface. This property is specific to STT capabilities. To resolve this issue, ensure that the FallbackAdapter for TTS only uses the supported properties of

TTSCapabilities

, which are

streaming

and

aligned_transcript

. You can modify the initialization as follows:

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super().__init__(
    capabilities=TTSCapabilities(
        streaming=all(t.capabilities.streaming for t in tts),
        aligned_transcript=all(t.capabilities.aligned_transcript for t in tts),
    ),
    sample_rate=sample_rate,
    num_channels=num_channels,
)

This adjustment will prevent the

AttributeError

and ensure the FallbackAdapter works correctly for TTS.

big-controller-60015

08/07/2025, 9:40 AM

i called STT instead of tts my bad

tall-airline-16756

08/07/2025, 9:40 AM

Hey there! It looks like the hiccup happened because STT was used instead of TTS in your code. If you want, I’m here to help you sort it out or tackle any other questions you might have—just give me a shout!

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