Allow tts_text_transforms to be set per-Agent, not just on AgentSession

[kaushal-aubie]

Feature Type

Would make my life easier

Feature Description

Description

tts_text_transforms (and the built-in text_transforms.replace() helper) is currently only configurable on AgentSession. In multi-agent workflows/handoffs, different Agent instances often need different TTS text handling — e.g. a billing agent that needs replace() overrides for account/product terminology, while a support agent needs a different set (or none at all). Today the only workaround is manually re-running transforms per agent via a custom tts_node/transcription_node override, which duplicates logic that already exists at the session level.

This is inconsistent with the rest of the framework: Agent already supports per-agent overrides for stt, llm, tts, and vad (used heavily in handoff patterns), so tts_text_transforms feels like a gap.

Solution

Support tts_text_transforms as a constructor option on Agent (Python) / voice.Agent (Node.js), mirroring the existing per-agent stt/llm/tts override pattern. Suggested behavior:

• If an Agent sets tts_text_transforms, use it in place of the session-level transforms for that agent's turns.
• If unset, fall back to AgentSession's tts_text_transforms (current behavior), preserving backward compatibility.
• Optionally support merging/extending session-level transforms rather than only full override, similar to how instructions can be composed.

Workarounds / Alternatives

Overriding tts_node/transcription_node per agent to reapply text_transforms.replace() manually — works, but duplicates built-in logic and loses the "applied in order" composition the session-level API already provides.

Additional Context

Docs reference: https://docs.livekit.io/agents/multimodality/text/#built-in-replace-transform

[AbarnaaSree]

I’d like to work on this issue. I’ll implement per-Agent tts_text_transforms with the session-level fallback behavior, update the relevant Python and Node APIs, and add regression tests covering agent overrides and inherited session transforms.