rust(fix): send a User-Agent on the MCP feature flag request, release 0.7.2

rust/crates/sift_cli/CHANGELOG.md

@@ -7,6 +7,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### What's New
 
+- `sift-cli mcp` now sends a `User-Agent` when it fetches account feature flags.
+  Hosts that reject requests without one no longer disable flag-gated tools.
+
 ## [v0.7.1] - September 22, 2026
 
 ### What's New

rust/crates/sift_cli/src/cmd/mcp.rs

@@ -52,15 +52,21 @@ pub async fn run(ctx: Context, args: McpArgs, app_uri: String) -> Result<ExitCod
     if client_event_config.is_none() {
         tracing::info!("non-essential traffic is disabled");
     }
-    let feature_flags = sift_mcp::FeatureFlags::fetch(&ctx.rest_uri, &ctx.api_key)
-        .await
-        .unwrap_or_else(|error| {
-            tracing::warn!(
-                error = format!("{error:#}"),
-                "failed to fetch feature flags; flag-gated tools are disabled"
-            );
-            sift_mcp::FeatureFlags::default()
-        });
+    let client_name = if args.chat {
+        sift_mcp::ClientName::Chat
+    } else {
+        sift_mcp::ClientName::SiftMcp
+    };
+    let feature_flags =
+        sift_mcp::FeatureFlags::fetch(&ctx.rest_uri, &ctx.api_key, client_name, &cli_version)
+            .await
+            .unwrap_or_else(|error| {
+                tracing::warn!(
+                    error = format!("{error:#}"),
+                    "failed to fetch feature flags; flag-gated tools are disabled"
+                );
+                sift_mcp::FeatureFlags::default()
+            });
 
     let rest_config = sift_mcp::RestConfig::new(ctx.rest_uri.clone(), ctx.api_key.clone());
     let credentials = Credentials::Config {
@@ -79,11 +85,7 @@ pub async fn run(ctx: Context, args: McpArgs, app_uri: String) -> Result<ExitCod
         feature_flags,
         Some(rest_config),
         args.ignore_tool,
-        if args.chat {
-            sift_mcp::ClientName::Chat
-        } else {
-            sift_mcp::ClientName::SiftMcp
-        },
+        client_name,
     )
     .await
     {

rust/crates/sift_mcp/src/feature_flags.rs

@@ -1,8 +1,11 @@
 use std::{collections::HashMap, time::Duration};
 
 use anyhow::{Context, Result};
+use reqwest::header::USER_AGENT;
 use serde::Deserialize;
 
+use crate::ClientName;
+
 const FEATURE_FLAGS_PATH: &str = "/api/v1/feature-flags/variants";
 const REQUEST_TIMEOUT: Duration = Duration::from_secs(5);
 
@@ -41,12 +44,21 @@ impl FeatureFlags {
             .is_some_and(|variant| !variant.value.is_empty() && variant.value != "off")
     }
 
-    pub async fn fetch(rest_uri: &str, api_key: &str) -> Result<Self> {
+    pub async fn fetch(
+        rest_uri: &str,
+        api_key: &str,
+        client_name: ClientName,
+        cli_version: &str,
+    ) -> Result<Self> {
         let endpoint = format!("{}{FEATURE_FLAGS_PATH}", rest_uri.trim_end_matches('/'));
         reqwest::Client::new()
             .get(endpoint)
             .timeout(REQUEST_TIMEOUT)
             .bearer_auth(api_key)
+            .header(
+                USER_AGENT,
+                format!("{}/{cli_version}", client_name.as_str()),
+            )
             .send()
             .await
             .context("feature flag request failed")?
@@ -63,7 +75,7 @@ mod tests {
     use std::collections::HashMap;
 
     use super::{FeatureFlagVariant, FeatureFlags};
-    use crate::client_event::start_http_server;
+    use crate::{ClientName, client_event::start_http_server};
 
     fn response(status: &str, body: &str) -> Vec<u8> {
         format!(
@@ -121,9 +133,14 @@ mod tests {
         ))
         .await;
 
-        let flags = FeatureFlags::fetch(&format!("{rest_uri}/"), "test-key")
-            .await
-            .unwrap();
+        let flags = FeatureFlags::fetch(
+            &format!("{rest_uri}/"),
+            "test-key",
+            ClientName::SiftMcp,
+            "1.2.3",
+        )
+        .await
+        .unwrap();
         assert!(flags.enabled("test-reports"));
 
         let request = String::from_utf8(server.await.unwrap()).unwrap();
@@ -134,10 +151,19 @@ mod tests {
                 .lines()
                 .any(|line| line.eq_ignore_ascii_case("authorization: Bearer test-key"))
         );
+        assert!(
+            headers
+                .lines()
+                .any(|line| line.eq_ignore_ascii_case("user-agent: sift_mcp/1.2.3"))
+        );
 
         let (rest_uri, server) =
             start_http_server(response("500 Internal Server Error", "{}")).await;
-        assert!(FeatureFlags::fetch(&rest_uri, "test-key").await.is_err());
+        assert!(
+            FeatureFlags::fetch(&rest_uri, "test-key", ClientName::SiftMcp, "1.2.3")
+                .await
+                .is_err()
+        );
         server.await.unwrap();
     }
 }