Refactor the inlined `re.sub(...)[:4000].strip()` cleanup at the
auto-TTS site in `_process_message_background` into an overridable
method `BasePlatformAdapter.prepare_tts_text(text: str) -> str`.
The default implementation is byte-identical to the previous inline
expression — strip `* _ \` # [ ] ( )` and truncate to 4000 chars — so
every existing adapter (Telegram, Discord, Slack, Matrix, IRC, etc.)
gets exactly the same behaviour as before. Zero behaviour change for
any consumer that doesn't override the method.
Why add the hook: voice-first platform adapters need stricter
cleanup than text-bubble platforms. The default strips a handful of
markdown sigils, which is fine when the output goes into a Discord
embed or a Telegram message bubble — but read aloud by a TTS engine,
URLs (`https://example.com/foo`), fenced code blocks, file paths
(`/Users/x/foo.py`), and `MEDIA:` tags turn into long sequences of
unintelligible characters. With this hook an adapter can drop those
spans before TTS while leaving the data-channel transcript intact
for visual rendering.
Without the hook, voice adapters have to either
- duplicate the auto-TTS flow inside their own `handle_response`
pipeline, which means re-implementing the entire `extract_media`,
`extract_images`, `extract_local_files`, attachment routing and
error-handling sequence in `_process_message_background`, or
- live with TTS speaking URLs character-by-character.
Both are worse than a 7-line method addition.
Example consumer:
https://github.com/kortexa-ai/hermes-livekit — LiveKit WebRTC voice
gateway plugin. Its `LiveKitAdapter.prepare_tts_text()` additionally
strips fenced code blocks, inline code, URLs, file paths, and
`MEDIA:` tags before TTS synthesis, while the full response still
reaches connected clients via the data channel. Drop-in installable
via `pip install git+https://github.com/kortexa-ai/hermes-livekit.git`.
Carved out of #3894 (LiveKit WebRTC gateway PR) so the generic hook
can land independently of the LiveKit platform itself.
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