Add a persistent Parakeet helper for low-latency host integrations

[seyeong-han]

Summary

• Factor the Parakeet transcription core out of parakeet_runner into a shared ParakeetTranscriber class
• Add a new parakeet_helper binary plus a stdin/stdout helper protocol for long-lived host integrations
• Build the helper in the existing Parakeet CMake presets and document the helper workflow in the README

Why a helper?

The Voxtral Realtime macOS app (executorch-examples/voxtral_realtime/macos) didn't need any changes to the executorch repo because voxtral_realtime_runner was already designed as a streaming, long-running process — the app just launches it and feeds audio.

parakeet_runner is different: it's a one-shot batch CLI tool that loads the model, transcribes one WAV file, prints the result, and exits. There's no way to send it a second request without restarting the process and paying the ~1.4 s model-load cost again.

The ExecuWhisper macOS app (meta-pytorch/executorch-examples#232) runs repeated record-then-transcribe requests via system dictation, so a fresh process per recording is too slow. parakeet_helper fills that gap — it's the Parakeet equivalent of what the Voxtral Realtime runner already does natively: stay alive, keep the model warm, and accept multiple requests over stdin/stdout.

Test plan

• cmake --preset llm-metal-stats -DEXECUTORCH_BUILD_MLX=OFF
• cmake --build --preset llm-metal-stats-install
• cd examples/models/parakeet && cmake --build --preset parakeet-metal -- both parakeet_runner and parakeet_helper link successfully

Made-with: Cursor

[pytorch-bot]

🔗 Helpful Links

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❌ 2 New Failures, 1 Cancelled Job, 1 Unrelated Failure

As of commit b54a81c with merge base 411ede2 ():

NEW FAILURES - The following jobs have failed:

• MLX / test-mlx / test-mlx (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 1
• MLX / test-mlx-qwen35-moe / test-mlx-qwen35-moe (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 2

CANCELLED JOB - The following job was cancelled. Please retry:

• pull / unittest / windows / windows-job (gh)

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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