Earlybird

Earlybird is a 16.8 MB on-device speech-to-text model that predicts each word before the speaker finishes saying it, along with a confidence score. On audiobook speech, a typical word is predicted correctly 90 ms before it ends. Released streaming models predict it correctly 90–400 ms after.

• Write-up: https://sahilmahendrakar.com/writings/earlybird
• Code: https://github.com/sahilmahendrakar/earlybird
• Demo: https://huggingface.co/spaces/sahilmahendrakar/earlybird
• Paper: arXiv:2611.14421

Why earlier words matter

Streaming speech recognizers output a word only after the speaker has finished it, typically 90–400 ms later. For a voice agent, that delay is time it could have spent starting a search, fetching a record, or planning a reply while the speaker is still talking.

How it works

Earlybird is fine-tuned from Moonshine Tiny. It learns from audio cut off at random points, including partway through a word, and is asked to write every word heard so far, with the half-heard word in full, plus a guess of the next two words. Its raw token probabilities give a confidence for every word, including the one still being spoken.

I cut Moonshine Tiny's vocabulary to the 19,007 tokens that English speech uses, which brings it to 29M parameters with almost no loss in accuracy, and quantized it to 4 bits.

Results

I compare Earlybird with three released models on the same audio: Moonshine Tiny, Whistle and Whisper base. Each recording was streamed into each model 80 ms at a time, as if it were live. A word's latency is the first moment it is on screen, spelled correctly and in the right location, measured from when the speaker finishes it. A negative number means the model outputted the word before the speaker finished saying it.

Each cell: median word latency · word error rate.

Share of words predicted correctly before they end.

On the 8 English test sets of the Hugging Face Open ASR Leaderboard, Earlybird makes fewer errors than Moonshine Tiny on all 8 and roughly ties Whistle. Whisper base is more accurate, at about 9 times the size.

Earlybird is the only model under 1 GB that predicts the median word correctly before it ends. Its accuracy is in line with the other models under 100 MB: close to Whistle and Whisper tiny, and ahead of Moonshine Tiny.

Confidence

Earlybird gives every word it shows a confidence, which measures the probability that the word is right. This is the model's raw output, with no extra calibration step, and it matches how often the model is right: when Earlybird is at least 90% confident in a word it hasn't heard the end of, it is right 91–96% of the time.

Usage

The weights use a custom 4-bit format, so they load through earlybird.py, which ships in this repo and in the GitHub repo:

pip install torch "transformers>=5" soundfile huggingface_hub
hf download sahilmahendrakar/Earlybird-29M earlybird.py --local-dir .

from earlybird import Earlybird

eb = Earlybird.from_pretrained("sahilmahendrakar/Earlybird-29M")
print(eb.transcribe("speech.wav"))

# Live: feed 16 kHz mono float32 audio in chunks of any size
stream = eb.stream()
for chunk in mic_chunks:
    for u in stream.feed(chunk):          # one update per 80 ms of audio
        print(u.text, u.words, u.guess)   # words/guess: [(word, confidence), ...]
print(stream.finish().text)

Or from the command line: python earlybird.py speech.wav (add --live to play it at real-time speed).

Audio is 16 kHz mono, fed in 80 ms steps. It runs about twice as fast as real time on one CPU thread.

Limits

• Accuracy. Whisper base, 2.5 times larger, makes fewer errors on every test set except audiobooks, where they tie. The gap is widest with background chatter: at 10 dB, Earlybird gets 32% of words wrong and Whisper base 8.9%.
• Rewrites. Showing words early means changing them more often: 1.3 changes per word on audiobooks, and 2–6 on spontaneous or noisy speech.
• Next-word guesses help less. At 50% confidence or more, about 1 word in 7 is guessed correctly before it ends. Most early words come from the transcript itself.
• English only.

Training data

About 1,000 hours of public English speech (LibriSpeech, People's Speech), plus about 25 hours of synthetic speech.

License and credit

MIT. Earlybird is fine-tuned from Moonshine Tiny (Moonshine, by Moonshine AI), released under the MIT license:

MIT License

Copyright (c) 2025 Useful Sensors, Inc. (dba Moonshine AI)

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Citation

@misc{mahendrakar2026earlybird,
  title         = {Earlybird: Predictive Streaming Speech Recognition in 29M Parameters},
  author        = {Mahendrakar, Sahil},
  year          = {2026},
  eprint        = {2611.14421},
  archivePrefix = {arXiv},
  primaryClass  = {cs.SD},
  url           = {https://arxiv.org/abs/2611.14421}
}