# Flux 3 Generate

> Use when submitting or polling a FLUX 3 video API job. Also covers drafts, downloads, and technical validation.

- Skill: `black-forest-labs/flux-3-generate` (Agent Skill, multi-file: 3 files)
- Install (CLI): `npx skillmds@latest add black-forest-labs/flux-3-generate`
- Raw SKILL.md: https://api.skillmd.com/api/skills/black-forest-labs/flux-3-generate/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: black-forest-labs (https://skillmd.com/u/black-forest-labs)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/black-forest-labs/flux-3-generate

---


# FLUX 3 Generate

Execute a ready plan through the asynchronous API, preserve expiring artifacts, and
verify the MP4. Read the [FLUX 3 API reference](https://docs.bfl.ai) before building a
request; it is authoritative wherever this skill disagrees. Authenticate with the
`x-key` header from `BFL_API_KEY`; check the variable exists without printing it, and
never put keys in prompts, logs, or saved request bodies.

## Request shape

Every request names its `mode` (required, exact strings) and carries the matching media
field:

| `mode` | Media field | What the model does |
| --- | --- | --- |
| `t2v` | none | Generates the clip from your text alone |
| `i2v` | `keyframes` (required) | Puts your images on screen, pixel for pixel, as pinned frames |
| `v2v` | `start_video` (required) | Continues from the final frames of your clip |
| `draft_enhance` | `draft_cache` (required) | Replays a cached draft at full quality; accepts no other fields, not even `prompt` |

- The schema is strict: any field it does not know returns a `422` naming it
  (`Extra inputs are not permitted`). A missing required field 422s the same way.
- Settings on the generating modes: `aspect_ratio` (`auto`, `21:9`, `2:1`, `16:9`,
  `4:3`, `1:1`, `3:4`, `9:16`), `duration` (integer 5-20 or `"auto"`), `resolution`
  (`hd` or `fhd`), `generate_audio` (bool), `draft` (bool), `version`.
- Constraints couple (a video input at higher resolution may cap duration): read the
  reference rather than assuming fields are independent.
- Three or more bare keyframes, and all `[seconds, image]` timestamped keyframes, need
  an integer `duration`. Media travels as a public URL or inline base64; keyframe
  images are at least 256x256.

## Run a job

1. **Submit once.** Persist the returned task `id` and `polling_url` with the
   secret-free request.
2. **Poll every 6 seconds** to a terminal state with the `x-key` header, following
   redirects. Planning time on a complex brief is normal, not a stall. The API status
   strings are exact. KEEP POLLING on `Pending`, `Reasoning`, `Generating`. STOP on
   `Ready` (success) and on `Error`, `Request Moderated`, `Content Moderated`, or
   `Task not found` (failures). None of these terminal statuses ever later becomes
   `Ready`.
   - `429` on submit means your org's concurrency ceiling is full and **no task was
     created**. There is nothing to poll. Wait for a slot, then resubmit the same body.
   - `429` on poll means the task exists and is unaffected. Back off and keep polling
     the same `polling_url`. Never resubmit, or you pay for a second render.
   - `503`: bounded backoff.
3. **Download immediately.** Observed signed sample and draft cache URLs expire roughly
   one hour after the result is ready. The `se=` query parameter on the URL itself is
   the authoritative expiry. Read it rather than assuming a fixed window. Video
   outputs arrive in `result.samples`, which is a list. Draft bundles arrive in
   `result.draft_caches`, which is also a list. The singular `result.draft_cache` is
   the first element of that list, not the complete set. Iterate every element of both
   lists and download all of them before doing anything else, recording the local path
   and task ID per element. A client reading only the singular `result.draft_cache` key
   silently drops paid artifacts that cannot be recovered once the signed URLs expire.
   Save the downloaded files, plus task ID and status.
4. **Validate**: container decodes, duration/resolution/aspect match intent, audio
   present exactly when requested. Technical validity is not creative approval; hand
   review to the specialist that owns it.

## Drafts

Add `draft: true` while a concept is unproven: a fast low-step preview plus a
`draft_cache` costs far less than a full render. Judge a draft on event legibility,
composition, and continuity; softness is the low-step trade and resolves at full
quality. Enhance only the chosen cache (it replays the same generation, so preserve
draft-to-cache identity when several are in play).

Between reruns change one consequential dimension. After two structurally similar
misses, return to the creative skill instead of accumulating adjectives.

## References

- [references/api-quick-reference.md](references/api-quick-reference.md)