LTX 2 / firstLastFrameToVideo

The frame-anchored generator of the LTX 2 family, running on Civitai's cloud: you provide a first frame, a last frame, or both, plus a prompt, and it fills in the video between them. It's the 19B-era sibling of the LTX 2.3 firstLastFrameToVideo node - same idea, older engine.

This is the node for shots with a defined beginning and end. Instead of crossing your fingers that the prompt lands the final composition, you show the model exactly where the scene starts and where it has to finish, and let it invent the middle. That's a genuinely useful creative control: a camera move from wide to close, a character crossing a room, a time-lapse from dawn to dusk. It's also the pattern the KB's LTX material associates with frame conditioning being one of LTX's strengths - an area where the family has been ahead of its reputation.

How it works

Standard orchestration plumbing: videoGen workflow with the LTX 2 engine, submit to the Civitai Orchestration API, long-poll, download as VIDEO. The guide frames are passed in as conditioning - the tooltip is explicit that at least one of first_frame or last_frame must be provided - and frame_guide_strength (0–1, default 0.7) controls how hard the output holds to them. High strength glues the video to your frames; lower strength lets the model improvise more between the bookends.

Inputs and outputs that matter

• prompt (required) - the action between the frames.
• first_frame - opening guide image (string input; URL/DataURL/Base64 per the pack convention).
• last_frame - ending guide image.
• frame_guide_strength - 0–1, default 0.7; the main creative dial.
• negative_prompt - what to avoid.
• duration - tooltip: 3 or 5 seconds.
• width / height - default 1280×720.
• fps - default 24; steps - default 20 (8–50); guidance_scale - default 4; generate_audio - default true.
• model - 19b-dev / 19b-distilled.
• loras - CIVITAI_LORAS socket.
• api_config - auth override.

Outputs: video, workflow_id, raw_json.

Installing it

ComfyUI Manager → Custom Nodes Manager → "Civitai Comfy Nodes" (publisher civitai) → Install → restart, or clone + pip install -r civitai-comfy-nodes/requirements.txt. Only requests; no models.

Common issues

• Auth & Buzz. Civitai account with Buzz; CIVITAI_API_TOKEN for headless.
• Both frames empty = provider error. At least one frame is required; if neither is wired, the job fails server-side rather than locally, which reads as a confusing generic failure. Wire one first, then debug everything else.
• Weak anchoring. Raise frame_guide_strength toward 1.0 if the middle ignores the frames; back it off if the output looks like a morph between two stills.
• Style mismatch between frames. Two frames from different styles or lighting confuse the 19B more than the 2.3 engine. Keep bookends visually consistent.
• LTX 2's middle is LTX 2's middle. The 19B can still freeze or smudge mid-scene; if the between is what matters to you, the 2.3 version of this node is the better engine.
• Early preview. Behavior may change without notice; pin the version.
• Cost. Full cloud job per run - check the per-run cost on the node.