Flux 2

Flux 2 on RunAPI

Choose route

• For a one-off artifact or result, use the registered flux-2 service in the runapi CLI. If the installed command catalog does not list it, stop and report the missing service instead of inventing a command.
• For an app, backend, worker, library, webhook pipeline, or production codebase, go directly to Integrate with SDK. Never shell out to the CLI as the production runtime.

Discover contract

Authenticate, then inspect the installed command catalog and the selected operation's current contract:

runapi auth status > auth.json
jq -e '.authenticated == true' auth.json
runapi flux-2 --help
runapi flux-2 <operation> --help
curl --fail --location https://runapi.ai/docs/api/flux-2/<operation>.md --output contract.md

If authentication is false, stop before submitting. Ask the user to provide a valid RUNAPI_API_KEY, or import a user-provided key from stdin with runapi auth import-token --token -; use interactive browser login only when the user explicitly requests it. Choose <operation> only from service help. Treat command help as authoritative for the installed operation, model, and top-level field roster. Treat its API Reference as authoritative for the complete request schema, nested fields, conditional rules, task behavior, and response variants. If the two surfaces disagree, stop and report the contract mismatch instead of guessing.

Build request

Create request.json as valid JSON using only fields accepted by the discovered operation contract. For the chosen model and values, evaluate every applicable conditional rule as a set: satisfy every required field, omit every forbidden field, and stop on unresolved contradictions.

Traverse nested objects and arrays before execution. Close every relationship stated by the discovered contract, including uniqueness constraints and cross-references between nested values.

For a discovered local media input, including file-typed fields and top-level media URL fields, put an agent-readable local file path directly in request.json. The CLI consumes file fields as declared and uploads local paths in top-level media URL fields. Use runapi files create only when the user needs a reusable URL, provides Base64, or the discovered contract explicitly requires a separate upload.

Validate the file before sending it:

jq empty request.json

Execute

Submit exactly once and persist the task response before waiting:

runapi flux-2 <operation> --async --input-file request.json > task.json
task_id="$(jq -er '.id' task.json)"

For a one-off result, immediately wait for that same task and save the complete JSON response. This blocking wait is the default:

runapi wait "$task_id" --service flux-2 --action <operation> > result.json

Only when the user explicitly asks for background execution, polling, or webhook integration may you stop after validating task.json. Report the task id and do not claim that the deliverable is complete.

Verify

A success status is not the deliverable. Read and validate the complete response according to the discovered result contract. Preserve the complete non-media result in the exact requested format, including JSON, text, SRT, or VTT.

For every requested media deliverable listed anywhere in the response, download all of them rather than returning only the first URL. Before downloading, derive its expected MIME type or family from response metadata when present, then the selected output format, then an unambiguous result field such as videos, images, or audios in the API Reference. The Catalog-declared fallback families for this skill are image/*. Stop only when no single expected type or family can be established from those sources.

For every downloaded file, require both a non-empty file and the expected MIME type or family:

curl --fail --location <deliverable-url> --output <downloaded-file>
for file in <downloaded-files>; do
  expected_mime=<expected-MIME-or-family-pattern-for-this-file>
  test -s "$file"
  [[ "$(file --brief --mime-type "$file")" == $expected_mime ]]
done

Do not report completion when any requested deliverable is missing, empty, or has an unexpected MIME type. Record Skill Conformance separately from Task Outcome so a service failure does not hide whether this recipe was followed.

Recover or stop

• Correct a request shape at most once, and only when the discovered contract or returned validation error identifies the correction.
• Retry a transient transport failure at most once, and only when evidence confirms that no task was created, no billing occurred, and retrying is safe.
• If waiting times out or loses transport after task.json exists, preserve the error and rerun runapi wait for that same task at most once. Never submit a replacement task.
• On a terminal RunAPI or service failure, preserve the task/error evidence and stop. Keep the selected model and capability, and do not submit another paid request without user authorization.
• If the contract is missing a fact required to build or verify the request, stop and report the contract gap. Do not turn a product defect into a permanent skill workaround.

Integrate with SDK

Use this route only for application or production-code integration. Open the current RunAPI SDK reference below, select the package for the target language and Flux 2, and confirm its install command, client methods, request types, response types, and error classes before coding. Build the request from the same discovered product contract and apply the same deliverable verification and stop rules. Do not invoke runapi as a subprocess from production code.

References

• Model overview, pricing, and rate limits: https://runapi.ai/models/flux-2.md
• Provider overview: https://runapi.ai/providers/black-forest-labs.md
• Full model catalog: https://runapi.ai/models.md
• SDK integration: https://github.com/runapi-ai/flux-2-sdk

Variants

• flux-2-flex-remix-image: https://runapi.ai/models/flux-2/flex-remix-image.md
• flux-2-flex-text-to-image: https://runapi.ai/models/flux-2/flex-text-to-image.md
• flux-2-max-remix-image: https://runapi.ai/models/flux-2/max-remix-image.md
• flux-2-max-text-to-image: https://runapi.ai/models/flux-2/max-text-to-image.md
• flux-2-pro-remix-image: https://runapi.ai/models/flux-2/pro-remix-image.md
• flux-2-pro-text-to-image: https://runapi.ai/models/flux-2/pro-text-to-image.md