diff --git a/clients/go/ahptypes/state.generated.go b/clients/go/ahptypes/state.generated.go
index c7b72ec1..d0ccedd8 100644
--- a/clients/go/ahptypes/state.generated.go
+++ b/clients/go/ahptypes/state.generated.go
@@ -2267,6 +2267,10 @@ type ErrorInfo struct {
 	Message string `json:"message"`
 	// Stack trace
 	Stack *string `json:"stack,omitempty"`
+	// Additional provider-specific metadata for this error.
+	// Clients MAY look for well-known optional keys here to provide enhanced UI
+	// (e.g. a structured chat fetch error for richer, localized messaging).
+	Meta map[string]json.RawMessage `json:"_meta,omitempty"`
 }
 
 // A point-in-time snapshot of a subscribed resource's state, returned by
diff --git a/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt b/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt
index ebc4e7bc..416f6942 100644
--- a/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt
+++ b/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt
@@ -3193,7 +3193,14 @@ data class ErrorInfo(
     /**
      * Stack trace
      */
-    val stack: String? = null
+    val stack: String? = null,
+    /**
+     * Additional provider-specific metadata for this error.
+     * Clients MAY look for well-known optional keys here to provide enhanced UI
+     * (e.g. a structured chat fetch error for richer, localized messaging).
+     */
+    @SerialName("_meta")
+    val meta: Map<String, JsonElement>? = null
 )
 
 @Serializable
diff --git a/clients/rust/crates/ahp-types/src/state.rs b/clients/rust/crates/ahp-types/src/state.rs
index 5395b684..4e669ae5 100644
--- a/clients/rust/crates/ahp-types/src/state.rs
+++ b/clients/rust/crates/ahp-types/src/state.rs
@@ -2804,6 +2804,11 @@ pub struct ErrorInfo {
     /// Stack trace
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub stack: Option<String>,
+    /// Additional provider-specific metadata for this error.
+    /// Clients MAY look for well-known optional keys here to provide enhanced UI
+    /// (e.g. a structured chat fetch error for richer, localized messaging).
+    #[serde(rename = "_meta", default, skip_serializing_if = "Option::is_none")]
+    pub meta: Option<JsonObject>,
 }
 
 /// A point-in-time snapshot of a subscribed resource's state, returned by
diff --git a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift
index f2841874..17dcbdd6 100644
--- a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift
+++ b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift
@@ -3486,15 +3486,28 @@ public struct ErrorInfo: Codable, Sendable {
     public var message: String
     /// Stack trace
     public var stack: String?
+    /// Additional provider-specific metadata for this error.
+    /// Clients MAY look for well-known optional keys here to provide enhanced UI
+    /// (e.g. a structured chat fetch error for richer, localized messaging).
+    public var meta: [String: AnyCodable]?
+
+    enum CodingKeys: String, CodingKey {
+        case errorType
+        case message
+        case stack
+        case meta = "_meta"
+    }
 
     public init(
         errorType: String,
         message: String,
-        stack: String? = nil
+        stack: String? = nil,
+        meta: [String: AnyCodable]? = nil
     ) {
         self.errorType = errorType
         self.message = message
         self.stack = stack
+        self.meta = meta
     }
 }
 
diff --git a/schema/actions.schema.json b/schema/actions.schema.json
index b306559a..09b93f24 100644
--- a/schema/actions.schema.json
+++ b/schema/actions.schema.json
@@ -2025,6 +2025,11 @@
         "stack": {
           "type": "string",
           "description": "Stack trace"
+        },
+        "_meta": {
+          "type": "object",
+          "additionalProperties": {},
+          "description": "Additional provider-specific metadata for this error.\nClients MAY look for well-known optional keys here to provide enhanced UI\n(e.g. a structured chat fetch error for richer, localized messaging)."
         }
       },
       "required": [
diff --git a/schema/commands.schema.json b/schema/commands.schema.json
index 6d7a4bdd..691c6cfd 100644
--- a/schema/commands.schema.json
+++ b/schema/commands.schema.json
@@ -1554,6 +1554,11 @@
         "stack": {
           "type": "string",
           "description": "Stack trace"
+        },
+        "_meta": {
+          "type": "object",
+          "additionalProperties": {},
+          "description": "Additional provider-specific metadata for this error.\nClients MAY look for well-known optional keys here to provide enhanced UI\n(e.g. a structured chat fetch error for richer, localized messaging)."
         }
       },
       "required": [
diff --git a/schema/errors.schema.json b/schema/errors.schema.json
index e3e5ab92..b9a750bc 100644
--- a/schema/errors.schema.json
+++ b/schema/errors.schema.json
@@ -471,6 +471,11 @@
         "stack": {
           "type": "string",
           "description": "Stack trace"
+        },
+        "_meta": {
+          "type": "object",
+          "additionalProperties": {},
+          "description": "Additional provider-specific metadata for this error.\nClients MAY look for well-known optional keys here to provide enhanced UI\n(e.g. a structured chat fetch error for richer, localized messaging)."
         }
       },
       "required": [
diff --git a/schema/notifications.schema.json b/schema/notifications.schema.json
index f6c2cc4a..288e2359 100644
--- a/schema/notifications.schema.json
+++ b/schema/notifications.schema.json
@@ -600,6 +600,11 @@
         "stack": {
           "type": "string",
           "description": "Stack trace"
+        },
+        "_meta": {
+          "type": "object",
+          "additionalProperties": {},
+          "description": "Additional provider-specific metadata for this error.\nClients MAY look for well-known optional keys here to provide enhanced UI\n(e.g. a structured chat fetch error for richer, localized messaging)."
         }
       },
       "required": [
diff --git a/schema/state.schema.json b/schema/state.schema.json
index c18dd94a..72adb902 100644
--- a/schema/state.schema.json
+++ b/schema/state.schema.json
@@ -382,6 +382,11 @@
         "stack": {
           "type": "string",
           "description": "Stack trace"
+        },
+        "_meta": {
+          "type": "object",
+          "additionalProperties": {},
+          "description": "Additional provider-specific metadata for this error.\nClients MAY look for well-known optional keys here to provide enhanced UI\n(e.g. a structured chat fetch error for richer, localized messaging)."
         }
       },
       "required": [
diff --git a/types/common/state.ts b/types/common/state.ts
index fd22f7f9..4c01ffd4 100644
--- a/types/common/state.ts
+++ b/types/common/state.ts
@@ -313,6 +313,12 @@ export interface ErrorInfo {
   message: string;
   /** Stack trace */
   stack?: string;
+  /**
+   * Additional provider-specific metadata for this error.
+   * Clients MAY look for well-known optional keys here to provide enhanced UI
+   * (e.g. a structured chat fetch error for richer, localized messaging).
+   */
+  _meta?: Record<string, unknown>;
 }
 
 /**