Essence 2

Official guide to essence-2 — bitHuman's standard photoreal avatar model: a distilled renderer that runs everywhere (GPU, Apple Neural Engine, CPU, WebGPU/WASM), train-on-create from a photo, and pricing.

Note — Generally available. essence-2 (“Essence 2”) is the standard second-generation Essence model and the default for photorealistic humans — as a developer you simply select essence-2, and bitHuman serves the right tier for your hardware and quality needs. Coming from an earlier model name? See Naming & migration.

What it is

Essence 2 is the standard photoreal model of the second-generation Essence family: a distilled engine that keeps the Essence look — your identity’s footage at its native resolution (a full-HD 1080p identity video by default), lip-synced live at ~25 frames per second — at a fraction of the compute of Essence 2 Max, the highest-fidelity renderer it is distilled from. At creation the platform distills your identity into a compact bundle; that one artifact then runs everywhere: cloud GPU, the Apple Neural Engine (ANE), CPU, and in-browser WebGPU/WASM (in rollout) — including a fully on-device Apple Silicon build where audio and video never leave the hardware.

It is half the cloud price of Essence 2 Max and the only Essence 2 model with CPU, Neural Engine, and browser runtimes — the right default for photorealistic humans, kiosks, high-concurrency deployments, and privacy-sensitive environments.

When to choose it

• It’s the default. For photorealistic humans, start here — pick Essence 2 Max only when maximum fidelity is the whole point.
• Cost-effective at scale. 4 credits/min cloud (2 self-hosted) with CPU and Neural Engine runtimes that don’t need a server GPU per session.
• On-device or privacy-first. The Apple Silicon build runs entirely on-device on the Neural Engine — inference is local, and the ANE renders far faster than real time (hundreds of frames per second on M4-class hardware), leaving the CPU and GPU free for your app.
• Always-on deployments. Kiosks, lobby displays, and 24/7 assistants where per-minute GPU pricing would dominate.

If maximum image fidelity is the whole point, choose Essence 2 Max — the highest-fidelity renderer, served on dedicated cloud GPUs. If you want fully generated motion from a single photo, choose Expression 2. For the family-level decision, start at Essence 2 & Expression 2.

How creation works

Create the agent with POST /v1/agent/generate and model: "essence-2". Creation is asynchronous and costs 500 credits (one-time, per agent).

Tip — one creation, both Essence 2 models. essence-2 is the combined creation: the one 500-credit charge trains the standard Essence 2 and makes Essence 2 Max available from the same internally generated identity video — pick the model at launch. Like every Essence 2 creation, the input must be a photorealistic human subject (else 422 MODEL_SUBJECT_MISMATCH, nothing billed); model: "auto" routes automatically instead. You can also add essence-2 to an existing agent that has a stored identity video.

import requests

import os

resp = requests.post(
    "https://api.bithuman.ai/v1/agent/generate",
    headers={
        "Content-Type": "application/json",
        "api-secret": os.environ["BITHUMAN_API_SECRET"],
    },
    json={
        "prompt": "You are a helpful retail assistant.",
        "image": "https://example.com/portrait.jpg",
        "model": "essence-2",
    },
)
print(resp.json())
# {"success": true, "message": "Agent generation started",
#  "agent_id": "A66GYD8664", "status": "processing"}

Inputs. Creation is image-only: supply a portrait image of the identity (or let the prompt generate one), and the platform generates the identity video for you as a creation step before training — a 10-second clip authored to loop seamlessly, so idle playback never shows a seam (you’ll see current_step: "video" at ~45% progress). Video input is not part of the creation contract and is being removed platform-wide: do not send video — as the rollout completes, a request carrying it is rejected with 400 VIDEO_INPUT_NOT_SUPPORTED before anything is billed. A voice is prepared as part of creation (supply audio to clone one, or one is generated).

What happens. Poll GET /v1/agent/status/{agent_id}: the run moves through the standard steps (payment → persona → voice_image), generates the identity video (video), then enters the distillation step (reported as current_step: "lip_sync", ~70% progress) where the trainer builds the compact identity bundle on a cloud GPU. When status reaches ready, the agent is servable on every tier.

How long. Creation typically takes about 45 minutes end to end. Some identities take longer — the platform allows a run up to several hours before flagging it as stuck, so keep polling status rather than applying your own short timeout.

Serving tiers

A ready agent serves through every delivery surface — the embed widget, the viewer/share URL, the REST API, and the LiveKit plugin. By default (?model=essence-2, or no override at all) the platform routes each session down the serving chain — GPU → Apple Neural Engine → CPU — overflowing to the next tier on capacity, so sessions land on the most cost-efficient runtime that’s available.

For benchmarking or placement testing you can force one runtime tier with the ?model= override on the session URL (a forced tier never overflows and fails loudly if unavailable):

?model= slug	Runtime	Notes
essence-2	The full chain (default)	GPU → Neural Engine → CPU with automatic overflow — the public name.
essence-2-gpu	Cloud GPU	Force the GPU tier.
essence-2-ane	Apple Neural Engine	Force the ANE tier.
essence-2-cpu	Cloud CPU	Force the CPU tier — no GPU in the path.

https://bithuman.ai/embed/A66GYD8664?model=essence-2-cpu

Tier slugs are an advanced, operational surface. Saved links carrying pre-rename or retired slugs keep working — see Naming & migration. For production, omit ?model= and let the platform choose. See tier pinning on the embed widget.

On-device. The same distilled identity also runs fully on-device on Apple Silicon via the Swift SDK rail (preview maturity): the Neural Engine executes the model locally, so audio, video, and prompts never leave the device — the only network traffic is the once-per-minute billing heartbeat. (Essence 2 Max has no on-device runtime; the standard Essence 2 is the on-device Essence 2 model.)

In the browser. A browser-local tier is rolling out: appending ?render=local to a session URL downloads the identity’s compact web bundle and renders Essence 2 in the browser — WebGPU on Apple Silicon and desktop-class GPUs (real-time with headroom), WASM fallback elsewhere — with no server render in the path. It activates per identity as web bundles publish; sessions without a published bundle fall back to cloud serving. See browser rendering and the device/runtime matrix for current status.

Idle and speaking behavior

Essence 2 animates the identity’s footage — the internally generated identity video: the base video plays continuously and the engine renders lip-sync and expression over it. As of 2026-07-02, the base video loops forward-only on every tier — when the clip reaches its last frame it wraps back to the first, and it never plays in reverse. This applies both while idle and while speaking, so motion always reads as natural forward movement.

Pricing

Surface	Rate
Cloud serving (all runtimes)	4 credits/min
Self-hosted serving	2 credits/min
Agent creation	500 credits (one-time)
Talking-video renders	4 credits per minute of output (rounded up)

Per-minute serving is metered on active avatar minutes only — idle, paused, or disconnected time isn’t billed. Full schedule: Pricing & credits.

Limits and expectations

• Renders at ~25 fps across GPU, CPU, and Apple Neural Engine runtimes.
• Creation takes about 45 minutes (see above) — poll status rather than assuming the few-minute wall-clock of essence-1.
• Identity is fixed at creation. The bundle bakes the generated identity video’s look and framing; to change the face, create a new agent.
• First session on a fresh agent can take longer to connect while the identity bundle is provisioned onto the serving tier; subsequent sessions reuse it. See troubleshooting.
• Before distillation completes, launch surfaces that request this model reject it with 409 MODEL_NOT_GENERATED. Once the agent is ready, this model’s family appears in its supported_models (on status / get / list and the embed-token response). During the rename rollout, server responses may still report the family under an earlier name — see Naming & migration.

Next steps

• Essence 2 & Expression 2 — the family overview and model chooser.
• Second-generation gallery — talk to a live launch agent.
• Essence 2 Max — the premium, highest-fidelity model.
• Agents API — full create → poll → serve lifecycle.
• Embed widget — ship a live session in minutes.
• Session behavior & troubleshooting — latency, idle, common errors.
• Talking video generation — render offline mp4s with model: "essence-2".
• Download your model — the trained .lebundle.imx (licensed weights), via API or bithuman pull <code>.