[BUG] AI binding fails to handle binary responses from image generation models #783
Description
Is there an existing issue for this?
- I have searched the existing issues
What version of workers-rs are you using?
0.6.0
What version of wrangler are you using?
4.25.0
Describe the bug
The worker::Ai binding cannot properly handle binary responses from AI image
generation models like Stable Diffusion. When calling ai.run() with an image
generation model, the binary image data gets lost and converted to an empty object
{}.
Current Behavior
When using the AI binding to generate images, the response is always an empty
object instead of the actual image bytes:
let ai = env.ai("AI")?;
let request = ImageGenRequest {
prompt: "a beautiful sunset".to_string(),
};
// This returns an empty object {} instead of image bytes
let response: serde_json::Value =
ai.run("@cf/stabilityai/stable-diffusion-xl-base-1.0", &request).await?;
// response is Object({}) - the actual image data is lostExpected Behavior
The AI binding should return the raw image bytes. The JavaScript version works
correctly:
const imageResponse = await
env.AI.run("@cf/stabilityai/stable-diffusion-xl-base-1.0", { prompt });
// imageResponse contains the actual PNG image data
return new Response(imageResponse, {
headers: { "content-type": "image/png" }
});Steps To Reproduce
Reproduction
Minimal example that demonstrates the issue:
use worker::*;
use serde::{Deserialize, Serialize};
#[derive(Serialize)]
struct ImageGenRequest {
prompt: String,
}
#[event(fetch)]
async fn fetch(_req: Request, env: Env, _ctx: Context) -> Result<Response> {
let ai = env.ai("AI")?;
let request = ImageGenRequest {
prompt: "test image".to_string(),
};
// This fails - returns empty object instead of image bytes
let response: serde_json::Value =
ai.run("@cf/stabilityai/stable-diffusion-xl-base-1.0", &request).await?;
console_log!("Response: {:?}", response); // Logs: Response: Object({})
Response::error("Image data lost", 500)
}Impact
This makes it impossible to use Rust workers for AI image generation, speech
synthesis, or any other AI models that return binary data. This is a significant
limitation for developers wanting to use Rust for AI-powered applications on
Cloudflare Workers.
Console Output
Polished prompt: <prompt text>
Response from AI: Object({})
Error generating image: Error: invalid type: JsValue(Object({})), expected a
sequence
The error shows the worker is trying to deserialize to Vec<u8> but receives an
empty object instead.