This is a very simple model that takes a string as input and returns a string with “hello” prepended to the input.

It runs fully on Rust (no Python or Go used anywhere), which is pretty cool I’d say. Here’s the source:

use cog_rust::Cog;
use anyhow::Result;
use schemars::JsonSchema;
use async_trait::async_trait;

#[derive(serde::Deserialize, JsonSchema)]
struct ModelRequest {
    /// Text to prefix with 'hello '
    text: String,
}

struct ExampleModel {
    prefix: String,
}

#[async_trait]
impl Cog for ExampleModel {
    type Request = ModelRequest;
    type Response = String;

    async fn setup() -> Result<Self> {
        Ok(Self {
            prefix: "hello".to_string(),
        })
    }

    fn predict(&self, input: Self::Request) -> Result<Self::Response> {
        Ok(format!("{} {}", self.prefix, input.text))
    }
}

cog_rust::start!(ExampleModel);