What causes "failed to write model field: %w" in sipeed/picoclaw?

Increase memory headroom or cap audio input size.

failed to write model field: %w

Error message

failed to write model field: %w

What it means

Thrown when writer.WriteField("model", t.modelID) fails in WhisperTranscriber's multipart builder. WriteField appends a short constant-size field to an in-memory bytes.Buffer; failure means buffer allocation failure under memory exhaustion. Not input-dependent and not network-related.

Source

Thrown at pkg/audio/asr/whisper_transcriber.go:117

	})

	var requestBody bytes.Buffer
	writer := multipart.NewWriter(&requestBody)

	part, err := writer.CreateFormFile("file", filename)
	if err != nil {
		logger.ErrorCF("voice", "Failed to create whisper form file", map[string]any{"error": err})
		return nil, fmt.Errorf("failed to create form file: %w", err)
	}

	if _, copyErr := io.Copy(part, bytes.NewReader(data)); copyErr != nil {
		logger.ErrorCF("voice", "Failed to copy whisper file content", map[string]any{"error": copyErr})
		return nil, fmt.Errorf("failed to copy file content: %w", copyErr)
	}

	if err = writer.WriteField("model", t.modelID); err != nil {
		logger.ErrorCF("voice", "Failed to write whisper model field", map[string]any{"error": err})
		return nil, fmt.Errorf("failed to write model field: %w", err)
	}

	if err = writer.WriteField("response_format", "json"); err != nil {
		logger.ErrorCF("voice", "Failed to write whisper response_format field", map[string]any{"error": err})
		return nil, fmt.Errorf("failed to write response_format field: %w", err)
	}

	if err = writer.Close(); err != nil {
		logger.ErrorCF("voice", "Failed to close whisper multipart writer", map[string]any{"error": err})
		return nil, fmt.Errorf("failed to close multipart writer: %w", err)
	}

	return t.doRequest(ctx, &requestBody, writer.FormDataContentType(), int64(len(data)))
}

func (t *WhisperTranscriber) Transcribe(ctx context.Context, audioFilePath string) (*TranscriptionResponse, error) {
	logger.InfoCF("voice", "Starting whisper transcription", map[string]any{
		"audio_file": audioFilePath,

View on GitHub (pinned to 49183d7e8d)

Solutions

Increase memory headroom or cap audio input size.
Profile memory: the multipart body duplicates the audio in RAM.

Defensive patterns

Strategy: try-catch

Validate before calling

if len(data) > maxInMemoryAudio { return errors.New("audio too large; multipart build may exhaust memory") }

Try / catch

if _, err := whisper.TranscribeWithData(ctx, data, name); err != nil {
    // WriteField into bytes.Buffer: only OOM-class failures; shrink input or raise limits, do not blind-retry.
    return err
}

Prevention

Cap input size at intake; alert on memory pressure near transcription calls.
Keep a 2x-headroom rule between the memory limit and the largest accepted recording.

When it happens

Trigger: Severe memory pressure while a large audio payload is being buffered; otherwise unreachable.

Common situations: Memory-capped containers transcribing large files; same class as 306/314.

Related errors

AI-assisted analysis of sipeed/picoclaw@49183d7e8d (2026-08-15). Data as JSON: /api/errors/ecd4cc5f4c67cc80. Report an issue: GitHub.