> ## Documentation Index
> Fetch the complete documentation index at: https://docs.epode.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Rust SDK: Agent Feedback Tower Layer for Axum Apps
> Add Agent Feedback to any Axum application with a Tower layer. Finite JSON and HTML bodies are instrumented; bounded streams are left untouched.
The `agent-feedback` crate provides a cloneable Tower `Layer` and `Service` for Axum. Finite JSON object and HTML responses are instrumented in-place; responses without an exact bounded `Content-Length` — including streams — are left completely untouched. Telemetry is dispatched through a bounded Tokio `mpsc` channel and never blocks the product response.
## Requirements
* Rust 1.88 or later
* Axum 0.8
* Tower 0.5
* A Tokio async runtime
## Installation
```toml theme={null}
# Cargo.toml
[dependencies]
agent-feedback = "0.1"
```
Open the Agent Feedback dashboard, create a product, and copy the API key. Store it as `AGENT_FEEDBACK_KEY` in your environment.
***
## Creating the layer
Call `AgentFeedbackLayer::new` with an `Options` value built using the builder API. Clone the layer freely — all clones share the same telemetry queue.
```rust theme={null}
use agent_feedback::{AgentFeedbackLayer, Options};
use axum::{Router, routing::get};
#[tokio::main]
async fn main() -> Result<(), Box> {
let feedback = AgentFeedbackLayer::new(
Options::new(std::env::var("AGENT_FEEDBACK_KEY")?)
.include(["/search", "/docs/**"])
.customer_ref(|request| {
request
.headers()
.get("x-account-id")?
.to_str()
.ok()
.map(str::to_owned)
}),
)?;
let app = Router::new()
.route("/search", get(search))
.layer(feedback.clone());
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await?;
axum::serve(listener, app)
.with_graceful_shutdown(async {
tokio::signal::ctrl_c().await.ok();
feedback.shutdown().await;
})
.await?;
Ok(())
}
```
***
## Options builder methods
Construct an `Options` value using `Options::new(api_key)` and chain the builder methods below. Only the API key is required.
Constructs a new `Options` value with the given API key. The key must match the pattern `af_live__`. `AgentFeedbackLayer::new` returns an error if the key format is invalid.
Override the Agent Feedback API endpoint. Trailing slashes are trimmed. Defaults to `https://agent-feedback-api-production.up.railway.app`.
Glob-style path patterns that opt routes in. When empty, all routes are instrumented (subject to default and custom excludes). Supports `*` (single segment) and `**` (any path). Example: `.include(["/search", "/docs/**"])`.
Glob-style patterns to skip. The default exclusion list (`/health`, `/healthz`, `/metrics`, `/favicon.ico`, `/robots.txt`, `/_agent-feedback/*`, `/api/v2/outcomes`) is always applied. Patterns you provide here extend that list.
Closure that extracts an opaque customer identifier from the request. Used to group interactions by account in the dashboard.
Closure that extracts a session identifier from the request. Links a sequence of interactions for session-level analytics.
Closure that returns a hint about the agent runtime. Used for runtime-level breakdown in the dashboard.
***
## `FeedbackMode`
Set `feedback_mode` directly on the `Options` struct (it is a public field). The enum has three variants:
| Variant | Behaviour |
| ------------------------------ | ----------------------------------------------------------------------------- |
| `FeedbackMode::Auto` (default) | Instructs the agent to submit a review autonomously, without asking the user. |
| `FeedbackMode::Ask` | Instructs the agent to submit only when the outcome is unambiguous. |
| `FeedbackMode::Off` | Disables instrumentation entirely. |
```rust theme={null}
use agent_feedback::{FeedbackMode, Options};
let options = Options::new(api_key);
// options.feedback_mode is FeedbackMode::Auto by default
```
***
## Stream detection
The layer reads the response body size hint from the `http_body::Body` trait before buffering. Responses without an exact bounded size — including streams — bypass instrumentation entirely and are forwarded untouched to the client. The body size cap is 1 MiB; responses larger than this limit are also forwarded without modification.
***
## Graceful shutdown
Call `feedback.shutdown().await` at application shutdown. The method sends a shutdown signal to the Tokio telemetry worker and waits up to 2 seconds for in-flight events to flush.
```rust theme={null}
axum::serve(listener, app)
.with_graceful_shutdown(async {
tokio::signal::ctrl_c().await.ok();
feedback.shutdown().await;
})
.await?;
```
***
## Agent helper functions
The crate exports `feedback_from_response` and `submit_product_outcome` for building feedback-aware agent runtimes.
### `feedback_from_response`
Extracts the `Envelope` from a response's `HeaderMap` and body bytes. Checks the JSON body for `_agentFeedback`, then the HTML body for `