Image generation

Image generation in Meerkat is exposed as the session-scoped generate_image builtin tool. The model asks for an image during a normal turn, Meerkat routes the request to a configured image provider, stores generated bytes in the realm blob store, and returns durable image references back into the session. This is not a standalone image/generate RPC. Use it by running a session with builtins enabled and telling the agent to call generate_image when an image artifact is required.

Requirements

A runtime-backed session surface with builtins enabled. The CLI default --tools safe enables builtins; --tools none hides generate_image.
At least one configured image provider. OpenAI uses RKAT_OPENAI_API_KEY or OPENAI_API_KEY; Azure OpenAI uses AZURE_OPENAI_API_KEY, AZURE_OPENAI_ENDPOINT, and AZURE_OPENAI_IMAGE_GENERATION_DEPLOYMENT; Gemini uses RKAT_GEMINI_API_KEY, GEMINI_API_KEY, or GOOGLE_API_KEY.
A blob store. CLI, REST, RPC, MCP, and persistent SDK-backed sessions wire this automatically through the runtime-backed surface.
count must be 1. Multiple image output is rejected today with unsupported_count; run multiple operations if you need several variants.

generate_image is separate from view_image. view_image reads an existing file into the model as image input. generate_image creates a new assistant-owned image and stores it as a blob. When the model needs to save a generated blob to disk during the same run, it can call blob_save_file.

CLI quickstart

The safest way to force a first turn to use image generation is to allow only the image tool for that turn:

rkat run \
  --model gpt-5.5 \
  --allow-tool generate_image \
  "Use generate_image to create a square PNG of a cozy tabby cat by a sunlit window. Return the blob id and a one-sentence caption."

When the tool succeeds, the tool result includes images[].blob_ref.blob_id. Save the generated image with:

rkat blob get <blob_id> --output cat.png

You can also ask the agent to save the image itself:

rkat run "Create a PNG infographic about today's top news and save it to top-news-infographic.png" --yolo -m gpt-5.5

Inspect the stored payload instead of writing raw bytes:

rkat blob get <blob_id> --json

Request Shape

The tool accepts one top-level field, request. For normal use, pass the simple request shape:

{
  "request": {
    "intent": "generate",
    "prompt": "a cozy tabby cat by a sunlit window",
    "size": "1024x1024",
    "quality": "auto",
    "format": "png",
    "count": 1
  }
}

This is the Meerkat generate_image tool input, not a raw OpenAI Responses API request. Meerkat lowers universal fields such as size, quality, and format into the selected provider’s native request. For OpenAI, format becomes the provider-side output_format option. For edits, set intent to edit, provide an instruction, and include at least one source_images entry:

{
  "request": {
    "intent": "edit",
    "instruction": "replace the background with a plain white studio backdrop and keep the subject unchanged",
    "source_images": [
      {
        "kind": "assistant_image",
        "image_id": "01985f61-8f7b-7000-8000-000000000001"
      }
    ],
    "format": "png"
  }
}

Reference an existing blob when the source image did not come from a previous generate_image result:

{
  "kind": "blob",
  "blob_ref": {
    "blob_id": "sha256:...",
    "media_type": "image/png"
  }
}

Fields

Field	Values	Notes
`intent`	`generate`, `edit`	Defaults to `generate` when `prompt` is present.
`prompt`	string	Required for `generate`. Object form `{ "content": "..." }` is also accepted.
`instruction`	string	Required for `edit`. Object form `{ "content": "..." }` is also accepted.
`source_images`	array	Required for `edit`; use `assistant_image`, `blob`, `transcript_block`, or `provider_native` references.
`reference_images`	array	Optional image references for generation. Provider support varies.
`size`	`auto`, `1024x1024`, `1024x1536`, `1536x1024`, `WIDTHxHEIGHT`	Custom sizes are parsed and then accepted or rejected by the selected provider.
`quality`	`auto`, `low`, `medium`, `high`	Provider support varies.
`format`	`auto`, `png`, `jpeg`, `jpg`, `webp`	`jpg` is accepted as `jpeg`.
`count` / `n`	`1`	Only `1` is supported today.
`target`	`auto` or provider/model target	Use the shorthand `provider` and `model` fields unless you need the canonical tagged target shape.
`provider`	`openai`, `gemini`, `google`	Forces a provider default image model. `google` is a Gemini alias.
`model`	provider-owned model id	Requires `provider` unless Meerkat can infer the owning provider from the model id.
`provider_params`	object	Provider-specific options. Unknown fields are rejected by provider profiles that define a closed parameter shape.

Target Selection

By default, target is auto.

If a configured image_generation_provider exists (mob definition top-level key or per-profile field in mob.toml), auto resolves against that provider’s default image target — even when the session’s text provider (for example Anthropic) has no image profile.
Otherwise, if the current session model belongs to a provider with an image profile, auto uses that provider’s default image target.
If neither applies, set provider explicitly per request.
To force a model, pass both provider and model.

OpenAI default:

{
  "request": {
    "intent": "generate",
    "prompt": "a clean product render of a matte black desk lamp",
    "provider": "openai",
    "size": "1024x1024",
    "quality": "auto",
    "format": "webp"
  }
}

Gemini default:

{
  "request": {
    "intent": "generate",
    "prompt": "a widescreen storyboard frame of a rover crossing red dunes",
    "provider": "gemini",
    "size": "1536x1024",
    "provider_params": {
      "aspect_ratio": "16:9",
      "image_size": "2K"
    }
  }
}

Provider Options

OpenAI

provider: "openai" uses the OpenAI image default, currently gpt-image-2. Meerkat fields and OpenAI lowering:

Field	Values	Notes
`size`	`auto`, `1024x1024`, `1024x1536`, `1536x1024`, `WIDTHxHEIGHT`	Universal Meerkat field. Lowered to OpenAI `size`.
`quality`	`auto`, `low`, `medium`, `high`	Universal Meerkat field. Lowered to OpenAI `quality`.
`format`	`auto`, `png`, `jpeg`, `jpg`, `webp`	Universal Meerkat field. Lowered to OpenAI `output_format`; `jpg` normalizes to `jpeg`.
`provider_params.background`	`auto`, `opaque`	Advanced OpenAI override. `gpt-image-2` does not support transparent backgrounds. Use an opaque background and post-process if you need transparency.
`provider_params.output_compression`	`0` to `100`	Advanced OpenAI override. Applies only when the universal `format` is `jpeg` or `webp`.
`provider_params.moderation`	`auto`, `low`	Advanced GPT Image moderation strictness override. Omit it for OpenAI’s default filtering.
`provider_params.action`	`auto`, `generate`, `edit`	Advanced hosted Responses image-tool override. Normal Meerkat calls should use top-level `intent` and omit `action`; Images API routes reject it.
`provider_params.reasoning_effort`	Backing model’s advertised effort ladder	Hosted Responses route only. The current `gpt-image-2` default is backed by GPT-5.4 and stops at `xhigh`; GPT-5.6 text-model routes also accept `max`.
`provider_params.web_search`	`true`, `false`, `null`, or object	Hosted `gpt-image-2` route only. `true`/`{}` enables OpenAI `web_search`; object values may include OpenAI web-search options such as `search_context_size`, `filters`, `user_location`, `external_web_access`, and `return_token_budget`.

Model behavior:

gpt-image-2 uses the hosted Responses image tool internally, but callers still pass Meerkat’s generate_image request shape.
On the azure_openai backend, hosted image generation requires backend option image_generation_deployment (for example gpt-image-2). The session model remains the Azure text deployment name, and Meerkat selects the image deployment with Azure’s Responses image-generation header.
gpt-image-2 accepts flexible WIDTHxHEIGHT sizes when they satisfy OpenAI’s constraints: both edges are multiples of 16 px, max edge is 3840 px, aspect ratio is at most 3:1, and total pixels are between 655,360 and 8,294,400. Common values include 1024x1024, 1536x1024, 1024x1536, 2048x2048, 2048x1152, 3840x2160, and 2160x3840.
Do not copy raw Responses API JSON into provider_params. Use Meerkat’s universal size, quality, format, and intent fields, and reserve provider_params for the advanced OpenAI overrides above.
For fresh/current image-only requests, prefer passing provider_params.web_search to generate_image over doing a separate search turn first.
Do not pass background: "transparent" for gpt-image-2; OpenAI rejects it. Do not pass input_fidelity; Meerkat’s OpenAI adapter uses a closed provider-params shape and rejects unknown fields.
Other OpenAI-owned gpt-image* or dall-e* models use the Images API path.
The Images API path currently rejects edit requests, reference images, action, reasoning_effort, and web_search.

Gemini

provider: "gemini" and provider: "google" use the Gemini image default, currently gemini-3.1-flash-image-preview. Supported Gemini image models:

gemini-3.1-flash-image-preview
gemini-3-pro-image-preview
gemini-2.5-flash-image

Gemini provider_params:

Field	Values	Notes
`aspect_ratio`	`1:1`, `16:9`, `9:16`, `square1x1`, `landscape16x9`, `portrait9x16`	Overrides the universal `size` to aspect-ratio mapping.
`image_size`	`1K`, `2K`, `4K`, `one_k`, `two_k`, `four_k`	Ignored for `gemini-2.5-flash-image`, which does not use an explicit image-size field.

Gemini image generation runs through a scoped image-model turn internally. The user and model still use one generate_image operation; they do not need to call switch_turn.

Result Shape

generate_image returns structured JSON:

{
  "operation_id": "01985f61-8f7b-7000-8000-000000000002",
  "terminal": { "terminal": "generated" },
  "images": [
    {
      "image_id": "01985f61-8f7b-7000-8000-000000000003",
      "blob_ref": {
        "blob_id": "sha256:...",
        "media_type": "image/png"
      },
      "media_type": "image/png",
      "width": 1024,
      "height": 1024
    }
  ],
  "provider_text": { "disposition": "not_emitted" },
  "revised_prompt": { "disposition": "not_requested" },
  "native_metadata": {
    "provider": "open_ai",
    "target_model": "gpt-5.4",
    "response_id": "resp_..."
  },
  "warnings": []
}

Important fields:

Field	Meaning
`operation_id`	Runtime identity for this image operation.
`terminal`	Final state: `generated`, `empty_result`, `denied`, `refused_by_provider`, `safety_filtered`, `failed`, `cancelled`, `timeout`, or `scoped_restore_failed`.
`images`	Durable assistant image references. Use `blob_ref.blob_id` with `blob_save_file` inside a run or `rkat blob get` outside the run.
`provider_text`	Captured provider-side text when the image backend emits text alongside images.
`revised_prompt`	Provider-revised prompt when the backend returns one.
`native_metadata`	Provider-specific metadata such as response ids and target model.
`warnings`	Non-terminal warnings such as fewer returned images, provider execution failure, or blob commit failure.

Troubleshooting

Symptom	Cause	Fix
`denied` with `unsupported_target`	No configured image provider owns the requested target, or `auto` resolved to a non-image provider.	Set `provider: "openai"` or `provider: "gemini"` and verify credentials with `rkat doctor`.
`denied` with `unsupported_count`	`count` or `n` was greater than `1`.	Run one image operation per variant.
`denied` with `projection_unsupported`	The selected backend cannot represent the request or provider params.	Remove unsupported params, avoid edits/reference images on the OpenAI Images API path, or use the provider default target.
`denied` with `realtime_transport_conflict`	The operation would require an internal scoped image-model turn while a realtime binding is active.	Run image generation from a non-realtime session or choose an image target that does not require a scoped override.
`safety_filtered` or `refused_by_provider`	The provider rejected the prompt or output.	Revise the prompt and retry.
`failed` with `provider_execution_failed`	Provider call failed after planning.	Check provider credentials, model access, rate limits, and network connectivity.
`failed` with `blob_commit_failed`	Image bytes were returned but could not be stored.	Check the realm’s blob-store backend and disk permissions.

Tools for how builtins are enabled and scoped.
Built-in tools reference for the concise parameter reference.
Providers for provider credentials and model catalog behavior.
Built-in tools reference for the model-facing tool contract.

Getting started

Concepts

Guides: Models And Hosting

Guides: Runtime Behavior

Guides: Orchestration

Examples: Foundations

Examples: Capabilities

Examples: Orchestration And Deployment

Image generation

Requirements

CLI quickstart

Request Shape

Fields

Target Selection

Provider Options

OpenAI

Gemini

Result Shape

Troubleshooting

​Requirements

​CLI quickstart

​Request Shape

​Fields

​Target Selection

​Provider Options

​OpenAI

​Gemini

​Result Shape

​Troubleshooting

​Related Docs

Requirements

CLI quickstart

Request Shape

Fields

Target Selection

Provider Options

OpenAI

Gemini

Result Shape

Troubleshooting

Related Docs