Android: read a whole session message aloud beside the copy button

[PrismaMind]

The Android session should be able to read one message aloud with the system text-to-speech engine. Please add the control immediately beside the existing copy button.

The shared mobile UI lives in apps/mobile. The copy control is CopyTextButton (apps/mobile/src/components/CopyTextButton.tsx). apps/mobile/src/features/threads/ThreadFeed.tsx places it in two spots:

• A user message has it in the trailing action row under the bubble, next to the timestamp.
• A finished assistant message has it first in the meta row under the text. That row appears only when showAssistantMeta is true, so a message that is still streaming has no copy button yet.

Read the same string the copy button uses: presentation.text for a user message and renderedText for an assistant message. This request is Android-only and uses android.speech.tts.TextToSpeech. iOS, cloud voices, and auto-reading a stream are out of scope.

speak() accepts at most TextToSpeech.getMaxSpeechInputLength() characters. The platform method returns 4000. A longer call does not read the rest. Split the message into chunks at or under that limit, on a paragraph or sentence boundary when one is nearby. Speak the first chunk with QUEUE_FLUSH and the rest with QUEUE_ADD, so one press reads the whole message in order.

The same button pauses and resumes. Android TTS has no pause call, only stop().

• Idle starts at the beginning.
• While speaking, a second press calls stop() and keeps the character offset.
• The next press continues from that offset, not from the start.
• If another app takes audio focus (AUDIOFOCUS_LOSS or AUDIOFOCUS_LOSS_TRANSIENT), treat that as the same pause and keep the offset.
• Remember the offset per message id. Starting another message stops the current one and leaves the previous offset in place.

UtteranceProgressListener.onRangeStart (API 26+) reports the range inside the current chunk. The saved position is the chunk start plus that range start. Some engines never fire onRangeStart. In that case remember the start of the chunk that was playing, so resume still does not jump back to the first character.

The icon should show speaking and paused. The accessibility label should say whether the next press reads, pauses, or continues.

Related, and closed: #3964 asked for a desktop read-aloud action. This request is the Android session control, including the character limit and resume after a pause or an interruption.

[juliusmarminge]

Note

Grok responding on behalf of Julius.

Thanks for the detailed spec! This is already covered by #12622, which asks for a Read Aloud action beside Copy on mobile agent responses, using native Android/iOS TTS with play/pause. Closing this as a duplicate so the discussion stays in one place. Please add your Android details there (chunking at getMaxSpeechInputLength(), resuming from the saved offset after stop() or audio-focus loss, per-message offsets); they're a useful addition to that thread.