Expressivity for Flux TTS voices, and two new OpenAI models
By Steven Van ·
expressivity for Flux TTS agent.speak.provider.expressivity shifts a Flux TTS voice's delivery register along a calm to animated axis.
Deepgram announced Expressivity for Flux TTS voices, and two new OpenAI models on August 19, 2026.
What changed
expressivity for Flux TTS agent.speak.provider.expressivity shifts a Flux TTS voice's delivery register along a calm to animated axis. It accepts the whole numbers -2 to 2 and defaults to 0, the voice's tuned delivery. Negative values produce calmer, steadier delivery; positive values produce more animated delivery with a wider pitch range. Every Flux voice supports it, and the value applies for the whole session. { "agent": { "speak": { "provider": { "type": "deepgram", "version": "v2", "model": "flux-haley-en", "expressivity": -1 } } } } expressivity is a beta parameter: its behavior may be tuned in future model versions, and non-default values raise the chance of hallucinations and pronunciation errors, so audition the value you plan to ship. 0 remains the only value validated for production. For value-by-value guidance, see Expressivity and Configure the Voice Agent. Two new OpenAI LLM models Deepgram's managed OpenAI provider adds two models: Model Pricing Tier gpt-5.6-luna Standard gpt-5.6-terra Advanced { "agent": { "think": { "provider": { "type": "open_ai", "model": "gpt-5.6-luna" } } } } For the full catalog, see LLM Models.