Extend Music · V5

Suno's extend endpoint takes a track that already exists and carries it further from a point you choose. This node is that endpoint at the V5 tier, which KIE's docs list as discontinued - so its real use is continuity: extending a song your workflow already made on V5 without switching model generations mid-song.

Why that matters: a different Suno tier is not a louder or quieter version of the same singer, it's a different model with different vocal character. Extend a V5 track with a V5.5 or V6 node and the seam is audible. If you're maintaining an older workflow, keep the tier matched and this node keeps working.

How it works

Like every model node here, this class was generated from KIE's published API documentation at startup - one node per documented model version, so V5 is baked in and there's no dropdown. The node builds the documented request body, submits it to KIE's task endpoint (envelope model ai-music-api/extend, inner model V5), then polls KIE's record-info endpoint every couple of seconds with exponential backoff until the task completes. It downloads the resulting mp3 and returns a native ComfyUI AUDIO; a failed task raises with the task id and the provider's error.

The inputs that matter

• audio_id - the track to extend, and this is the field people get wrong. It is a Suno track identifier, not a URL and not a local file. You get it from a previous generation's raw_json or task_id outputs. If your source is a file you own, this is the wrong node - use Upload And Extend Audio, which takes an upload_url.
• prompt - used as lyrics only when lyrics is empty, and it must not be set when instrumental is true.
• continue_at - seconds, default 60. Per the docs it has to be greater than 0 and less than the total duration of the source. This is the knob that decides whether you get a continuation or a remix.

Optional steering: style (keep it aligned with the original for the best join), title, negative_tags, vocal_gender, style_weight, weirdness_constraint, audio_weight, persona_id / persona_model, lyrics, variety (0–4), instrumental (false by default on this node), timeout_seconds (1200), and callback_url, which you should leave empty.

Outputs: audio, url, all_urls_json, task_id, raw_json, credits_consumed, credits_left. Extension returns a new track rather than editing the source, so keep task_id around if you plan to extend again - the chain you build is generate → extend → extend, each step consuming the previous result.

Installing

ComfyUI Manager, search "KIE Nodes Next". The README still describes registry publication as being prepared, so the manual install is the one that reliably works today:

cd ComfyUI/custom_nodes
git clone https://github.com/felipederosilva/ComfyUI-KIE-Nodes-Next
pip install -r ComfyUI-KIE-Nodes-Next/requirements.txt

Restart, then paste your key once at Settings → KIE.ai Nodes Next → Connection. It's checked against KIE before it replaces a stored key, and only a masked fingerprint is ever shown; KIE_API_KEY wins over the saved key on servers. Dependencies are requests, Pillow, numpy and PyYAML - no torch, no model downloads, zero VRAM, which is the entire appeal of an API-node pack.

Where people get burned

• Passing a URL as audio_id. The node will happily submit and KIE will fail the task. Upload And Extend is the node for files.
• continue_at past the end of the track. The docs require it to be inside the source duration; a value of 60 on a 40-second track is a guaranteed failure.
• No key configured throws an error naming the settings path - check it before anything else.
• A timeout is not a cancellation. The node stops polling at timeout_seconds; the remote task may still complete, and you'll have paid for it. Check credits_consumed before rerunning.
• Mixed installs are refused on startup. If the pack reports a version and generated-node build mismatch, delete the whole folder and reinstall from the repo.
• Discontinued tier. V5 is what the docs say it is. Use the V6 sibling for new work; use this one to keep an old song's voice intact.

One habit worth having: extend in short hops. Two extensions of fifteen seconds generally hold together better than one of thirty, and the join is where things go wrong, not the length.