Add a specific "resource not found" error with optional URI data

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## 0.4.3 (2025-09-25)
+
+### Protocol
+
+- Defined `Resource not found` error type as code `-32002` (same as MCP)
+
+### Rust
+
+- impl `Agent` and `Client` for `Rc<T>` and `Arc<T>` where `T` implements either trait.
+
 ## 0.4.2 (2025-09-22)
 
 ### Rust

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "agent-client-protocol"
 authors = ["Zed <hi@zed.dev>"]
-version = "0.4.2"
+version = "0.4.3"
 edition = "2024"
 license = "Apache-2.0"
 description = "A protocol for standardizing communication between code editors and AI coding agents"

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@zed-industries/agent-client-protocol",
-  "version": "0.4.2",
+  "version": "0.4.3",
   "publishConfig": {
     "access": "public"
   },

rust/error.rs

@@ -94,6 +94,17 @@ impl Error {
         Error::new(ErrorCode::AUTH_REQUIRED)
     }
 
+    /// A given resource, such as a file, was not found.
+    #[must_use]
+    pub fn resource_not_found(uri: Option<String>) -> Self {
+        let err = Error::new(ErrorCode::RESOURCE_NOT_FOUND);
+        if let Some(uri) = uri {
+            err.with_data(serde_json::json!({ "uri": uri }))
+        } else {
+            err
+        }
+    }
+
     /// Converts a standard error into an internal JSON-RPC error.
     ///
     /// The error's string representation is included as additional data.
@@ -153,6 +164,13 @@ impl ErrorCode {
         code: -32000,
         message: "Authentication required",
     };
+
+    /// A given resource, such as a file, was not found.
+    /// This is an ACP-specific error code in the reserved range.
+    pub const RESOURCE_NOT_FOUND: ErrorCode = ErrorCode {
+        code: -32002,
+        message: "Resource not found",
+    };
 }
 
 impl From<ErrorCode> for (i32, String) {

typescript/acp.ts

@@ -963,6 +963,13 @@ export class RequestError extends Error {
     return new RequestError(-32000, "Authentication required", data);
   }
 
+  /**
+   * Resource, such as a file, was not found
+   */
+  static resourceNotFound(uri?: string): RequestError {
+    return new RequestError(-32002, "Resource not found", uri && { uri });
+  }
+
   toResult<T>(): Result<T> {
     return {
       error: {