diag: log per-transcription text length and preview at DEBUG

Author: rpurdel

src/OutgoingConnection.ts

@@ -183,11 +183,13 @@ export class OutgoingConnection {
 	private setupBackendHandlers(backend: TranscriptionBackend): void {
 		backend.onInterimTranscription = (message) => {
 			getInstruments().transcriptionsReceivedTotal.add(1, { provider: this.options.provider || 'unknown', is_interim: 'true' });
+			this.logTranscriptionSummary(message, true);
 			this.onInterimTranscription?.(message);
 		};
 
 		backend.onCompleteTranscription = (message) => {
 			getInstruments().transcriptionsReceivedTotal.add(1, { provider: this.options.provider || 'unknown', is_interim: 'false' });
+			this.logTranscriptionSummary(message, false);
 			this.clearIdleCommitTimeout();
 			this.onCompleteTranscription?.(message);
 		};
@@ -206,6 +208,18 @@ export class OutgoingConnection {
 		};
 	}
 
+	private logTranscriptionSummary(message: TranscriptionMessage, isInterim: boolean): void {
+		// DEBUG-only: summarises each transcription arriving from the backend so we
+		// can tell apart empty end-of-utterance finals from real speech without
+		// logging full PII.  Controlled by LOG_LEVEL=debug.
+		const segments = message.transcript ?? [];
+		const text = segments.map((s) => s.text ?? '').join(' ').trim();
+		const preview = text.length > 40 ? text.slice(0, 40) + '…' : text;
+		logger.debug(
+			`Backend ${isInterim ? 'interim' : 'final'} tag=${this.localTag} lang=${message.language ?? 'n/a'} segments=${segments.length} textLen=${text.length} preview=${JSON.stringify(preview)}`,
+		);
+	}
+
 	private async reinitializeDecoder(): Promise<void> {
 		if (!this.backend) {
 			throw new Error('Cannot initialize decoder without a backend');