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POST
Start Auto Session

Authorizations

x-simli-api-key
string
header
required

Body

application/json
faceId
string
default:tmp9i8bbq7c
ttsProvider
enum<string>
default:Cartesia
Available options:
ElevenLabs,
Cartesia,
Inworld,
User
ttsAPIKey
string | null
ttsModel
string
default:sonic-turbo-2025-03-07
voiceId
string
default:a167e0f3-df7e-4d52-a9c3-f949145efdab
systemPrompt
string | null
default:You are Chatbot, a friendly, helpful robot. Your goal is to demonstrate your capabilities in a succinct way. Your output will be converted to audio so don't include special characters in your answers. Respond to what the user said in a creative and helpful way, but keep your responses brief.
firstMessage
string | null
introAnimation
enum<string> | null

An animation the avatar plays as it opens the session, when the user joins (with firstMessage, if there is one). Trinity-2 faces only; the others ignore it. Leave it out for no animation.

Available options:
g003_wave_goodbye_solo,
speaking_hands_explaining,
wave
maxSessionLength
integer
default:3600
maxIdleTime
integer
default:300
language
string
default:en
customLLMConfig
CustomLLMConfig · object | null
llmConfig
LLMConfig · object
createTranscript
boolean
default:false
model
enum<string>
default:fasttalk
Available options:
fasttalk
disableSuperRes
boolean
default:false

Turns off the face restoration pass on legacy faces.

streaming_width
integer
default:768

Width of the streamed video in pixels, Trinity-2 faces only (the others keep their own frame size). At least 512, and with streaming_height one of 1:1, 16:9 or 9:16, otherwise a 422. A canvas larger than the avatar's frame is padded with its background; a smaller one crops a window out of it.

Required range: x >= 512
streaming_height
integer
default:768

Height of the streamed video in pixels. See streaming_width.

Required range: x >= 512
avatar_position_x
number
default:0.5

Where the avatar sits across the canvas, from 0 (left) to 1 (right). Trinity-2 only.

Required range: 0 <= x <= 1
avatar_position_y
number
default:1

Where the avatar sits down the canvas, from 0 (top) to 1 (bottom). Trinity-2 only.

Required range: 0 <= x <= 1
camera
CameraSetting · object | null

The camera the session starts with, on top of the avatar's own framing. Trinity-2 only. Leave it out to keep the avatar's framing. A streaming session can move it afterwards with CAM_ messages.

background_id
string<uuid> | null

One of your uploaded backgrounds, by the id POST /assets/backgrounds returned, to show behind the avatar, cropped to fill the canvas. Trinity-2 only. Leave it out for the avatar's own. An id that is not one of your account's is dropped with a warning, and the session uses the avatar's own. An image is not accepted: upload it first. Your app can change it in the session by sending the room an app message {"type": "simli-background", "id": ""}.

foreground_id
string<uuid> | null

One of your uploaded foregrounds, by the id POST /assets/foregrounds returned, laid over the avatar through its transparency and cropped to fill the canvas. Trinity-2 only; otherwise as background_id. Your app can change it with {"type": "simli-foreground", "id": ""}.

Response

Successful Response

roomUrl
string
required
sessionId
string
required
warnings
string[]

Deprecations, starting camera fields outside their supported range, and background_id / foreground_id dropped as not your account's (the avatar's own is used). The session starts regardless.