fal.ai Image

Use this skill when the user wants to generate or edit images through fal.ai, compare multiple marketplace image models, or build repeatable experiment workflows with prompts, references, outputs, and costs tracked in a consistent way.

Philosophy: Standardize The Harness, Not The Image Model

fal gives one platform surface for many image models, but the useful controls still differ by model family. The right abstraction is:

• standardize auth, queueing, file handling, output capture, and cost tracking
• keep model-specific knobs explicit
• compare models on the same task, not by pretending they all expose the same schema

Before generating, ask:

• Is this a fresh generation or an edit run?
• What must stay constant across models: prompt intent, reference images, size target, transparency, or output count?
• Which model-specific controls materially affect fairness and need to be frozen?
• Do we need pre-run cost estimates, per-run request IDs, or both?

Core principles:

1. Queue-first for tracked experiments: image calls can be synchronous, but queue mode gives request IDs, polling, and consistent logging.
2. Reference discipline matters: editing runs should pass only the images the model actually needs; too many references dilute control.
3. Prompt parity beats fake parity: keep the task stable, then document the real model-specific compromises.
4. Tracking is part of the run: a generation is not complete until prompt, request metadata, outputs, and cost signals are recorded.

What This Skill Provides

• A portable, repo-scoped fal image workflow with no repo-wide Python packaging requirement.
• A generic queue-based image runner for both text-to-image and edit endpoints.
• Model presets for:
  • grok-imagine-image-t2i
  • grok-imagine-image-edit
  • nano-banana-2-t2i
  • nano-banana-2-edit
  • nano-banana-pro-t2i
  • nano-banana-pro-edit
  • gpt-image-1.5-t2i
  • gpt-image-1.5-edit
• Platform tooling for:
  • model lookup
  • pricing
  • estimate-cost
  • usage
  • request audit
• A batch runner that executes the same image task across multiple fal models and appends a central ledger row per run.

Working With fal Images In This Repo

Core Execution Pattern

For tracked image jobs, this skill uses fal's queue API:

• submit: POST https://queue.fal.run/{endpoint_id}
• status: GET https://queue.fal.run/{endpoint_id}/requests/{request_id}/status
• result: GET https://queue.fal.run/{endpoint_id}/requests/{request_id}

Authentication uses:

• Authorization: Key $FAL_KEY

Important platform headers for repeatable comparison runs:

• X-Fal-Store-IO: 1
• x-app-fal-disable-fallback: true

The runner also captures response headers such as:

• x-fal-request-id
• x-fal-billable-units

Why This Skill Uses Queue HTTP

The official fal-client SDK is valid and supported, but this repo's main requirement is portability inside a Codex skill. The raw queue endpoints are documented and stable enough for a deterministic wrapper, so the scripts in this skill stay on Python stdlib and can still be invoked with uv run.

Prompting Guidance For Image Comparison

Prompt like art direction, not like marketing copy:

• subject identity
• composition
• camera/framing
• background
• rendering style
• edit constraints
• exclusions

For edit comparisons:

• explicitly say what must stay unchanged
• keep the edit localized in language even if the model edits holistically
• keep reference count low
• be specific about transparency or background removal if needed

Background handling matters more than the prompt wording suggests:

• gpt-image-1.5 is the safest option here when you genuinely need transparent output.
• nano-banana-2 and nano-banana-pro should be treated as chroma-key models for this workflow, not transparent-background models.
• In this repo's experiments, Grok behaved more like the Banana models than GPT for background handling, so prefer chroma there too unless a later run proves otherwise.
• For chroma-key runs, ask for an exact flat green background: #00FF00, with no gradients, no cast shadows on the background, no texture, and no green spill on the subject.
• Do not use magenta by default for this pirate workflow. #FF00FF sits too close to the warm red/purple bandana family and is more likely to contaminate edge colors.

For text-to-image comparisons:

• hold composition intent stable
• ask for one clear deliverable
• keep size/background expectations explicit

Do not overload first comparison runs with long prompt stacks. The first job is to test prompt adherence, identity preservation, and edit usefulness.

Scripts

• scripts/fal_queue_image_run.py
  • one text-to-image or image-edit queue run
  • writes request/result JSON
  • downloads image outputs
  • writes normalized run manifest
• scripts/fal_platform_models.py
  • query fal platform APIs for model metadata and cost surfaces
• scripts/fal_image_experiment_matrix.py
  • run the same task across multiple image presets
  • append central ledger rows

Repo Workflow

Machine-readable tracking:

• experiments/fal-image/ledger.jsonl
• experiments/fal-image/ledger.csv
• experiments/fal-image/<timestamp>-<slug>/batch.json

Human-readable tracking:

• prompts/<timestamp>-...-prompts.md
• learnings/<timestamp>-...-learnings.md

Generated images should still live under the appropriate public/assets/.../concepts/... path for the asset family being tested.

Anti-Patterns To Avoid

❌ Anti-pattern: flattening all image models into one fake prompt schema Why bad: you hide the controls that actually affect quality and cost. Better: use shared runner behavior plus explicit per-model presets and overrides.

❌ Anti-pattern: treating edit and generate as the same task Why bad: edit runs depend on reference discipline and preservation constraints that text-to-image runs do not. Better: keep separate presets and separate experiment configs for generation and editing.

❌ Anti-pattern: recording only prompts and final PNGs Why bad: you cannot audit request IDs, retries, or cost later. Better: always save raw JSON, normalized manifests, and ledger rows.

❌ Anti-pattern: comparing models with hidden fallback routing Why bad: you may think you tested one endpoint but actually hit another route. Better: set x-app-fal-disable-fallback: true on strict comparison runs.

❌ Anti-pattern: stuffing many reference images into every edit Why bad: it weakens edit control and makes failure analysis harder. Better: pass only the minimum reference images the edit actually needs.

❌ Anti-pattern: asking Banana-family models for transparency and trusting the result Why bad: you may get a faux-transparent dark backdrop instead of a clean extraction surface. Better: use an explicit chroma-key background and key it out later.

References

• Platform notes: references/fal-platform-notes.md
• Queue and inference notes: references/fal-queue-and-inference.md
• Image model notes: references/fal-image-models.md
• Model presets: assets/model-presets.json

Remember

A good fal image workflow is not just "can it render." It is:

• reproducible
• comparable
• cost-visible
• honest about model differences