Flux 3 Generate Agent Skill

FLUX 3 Generate

Execute a ready plan through the asynchronous API, preserve expiring artifacts, and

verify the MP4. Read the FLUX 3 API reference 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

• Submit once. Persist the returned task id and polling_url with the

secret-free request.

• 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.
• 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.

• 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