From 17db55a0bcb6c836a3677347ecb7bfc47c2d255f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois-Xavier=20Talbot?=
 <108630700+fetchfern@users.noreply.github.com>
Date: Wed, 7 Jan 2026 21:11:18 -0500
Subject: [PATCH] Include OS in theseus User-Agent (#5046)

---
 packages/app-lib/src/lib.rs           | 15 ++++++++++-----
 packages/app-lib/src/state/friends.rs |  3 +--
 packages/app-lib/src/util/fetch.rs    |  5 +++--
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/packages/app-lib/src/lib.rs b/packages/app-lib/src/lib.rs
index 45da6fbc..6f62495e 100644
--- a/packages/app-lib/src/lib.rs
+++ b/packages/app-lib/src/lib.rs
@@ -26,8 +26,13 @@ pub use event::{
 pub use logger::start_logger;
 pub use state::State;
 
-pub const LAUNCHER_USER_AGENT: &str = concat!(
-    "modrinth/theseus/",
-    env!("CARGO_PKG_VERSION"),
-    " (support@modrinth.com)"
-);
+pub fn launcher_user_agent() -> String {
+    const LAUNCHER_BASE_USER_AGENT: &str =
+        concat!("modrinth/theseus/", env!("CARGO_PKG_VERSION"),);
+
+    format!(
+        "{} ({}; support@modrinth.com)",
+        LAUNCHER_BASE_USER_AGENT,
+        std::env::consts::OS
+    )
+}
diff --git a/packages/app-lib/src/state/friends.rs b/packages/app-lib/src/state/friends.rs
index ad28ffeb..41487df8 100644
--- a/packages/app-lib/src/state/friends.rs
+++ b/packages/app-lib/src/state/friends.rs
@@ -1,5 +1,4 @@
 use crate::ErrorKind;
-use crate::LAUNCHER_USER_AGENT;
 use crate::data::ModrinthCredentials;
 use crate::event::FriendPayload;
 use crate::event::emit::emit_friend;
@@ -85,7 +84,7 @@ impl FriendsSocket {
 
             request.headers_mut().insert(
                 "User-Agent",
-                HeaderValue::from_str(LAUNCHER_USER_AGENT).unwrap(),
+                HeaderValue::from_str(&crate::launcher_user_agent()).unwrap(),
             );
 
             let res = connect_async(request).await;
diff --git a/packages/app-lib/src/util/fetch.rs b/packages/app-lib/src/util/fetch.rs
index fafba221..3ed23896 100644
--- a/packages/app-lib/src/util/fetch.rs
+++ b/packages/app-lib/src/util/fetch.rs
@@ -1,7 +1,6 @@
 //! Functions for fetching information from the Internet
 use super::io::{self, IOError};
 use crate::ErrorKind;
-use crate::LAUNCHER_USER_AGENT;
 use crate::event::LoadingBarId;
 use crate::event::emit::emit_loading;
 use bytes::Bytes;
@@ -21,8 +20,10 @@ pub struct FetchSemaphore(pub Semaphore);
 
 pub static REQWEST_CLIENT: LazyLock<reqwest::Client> = LazyLock::new(|| {
     let mut headers = reqwest::header::HeaderMap::new();
+
     let header =
-        reqwest::header::HeaderValue::from_str(LAUNCHER_USER_AGENT).unwrap();
+        reqwest::header::HeaderValue::from_str(&crate::launcher_user_agent())
+            .unwrap();
     headers.insert(reqwest::header::USER_AGENT, header);
     reqwest::Client::builder()
         .tcp_keepalive(Some(time::Duration::from_secs(10)))