From 1ac082d075530507f447c25e532ec9cfa686c032 Mon Sep 17 00:00:00 2001
From: npub1t2tgm7d8f995uqvmnm8h88sg3wnpp9a5xysjf6dg3tjmgt3ltulqdp8ehr
 <5a968df9a7494b4e019b9ecf739e088ba61097b4312124e9a88ae5b42e3f5f3e@sprout-oss.stage.blox.sqprod.co>
Date: Sat, 27 Jun 2026 21:39:57 -0400
Subject: [PATCH] Preserve local relay host for desktop HTTP calls

Co-authored-by: npub1t2tgm7d8f995uqvmnm8h88sg3wnpp9a5xysjf6dg3tjmgt3ltulqdp8ehr <5a968df9a7494b4e019b9ecf739e088ba61097b4312124e9a88ae5b42e3f5f3e@sprout-oss.stage.blox.sqprod.co>
Signed-off-by: npub1t2tgm7d8f995uqvmnm8h88sg3wnpp9a5xysjf6dg3tjmgt3ltulqdp8ehr <5a968df9a7494b4e019b9ecf739e088ba61097b4312124e9a88ae5b42e3f5f3e@sprout-oss.stage.blox.sqprod.co>
---
 desktop/src-tauri/src/relay.rs | 40 +++++++++++-----------------------
 1 file changed, 13 insertions(+), 27 deletions(-)

diff --git a/desktop/src-tauri/src/relay.rs b/desktop/src-tauri/src/relay.rs
index 425ea835d..a0fb1c4bd 100644
--- a/desktop/src-tauri/src/relay.rs
+++ b/desktop/src-tauri/src/relay.rs
@@ -75,30 +75,16 @@ pub fn relay_http_base_url(relay_url: &str) -> String {
     let trimmed = relay_url.trim().trim_end_matches('/');
 
     if let Some(suffix) = trimmed.strip_prefix("wss://") {
-        return format!("https://{}", normalize_loopback_host(suffix));
+        return format!("https://{}", suffix);
     }
 
     if let Some(suffix) = trimmed.strip_prefix("ws://") {
-        return format!("http://{}", normalize_loopback_host(suffix));
+        return format!("http://{}", suffix);
     }
 
     trimmed.to_string()
 }
 
-/// Rewrite an exact `localhost` host to `127.0.0.1`, preserving port and path.
-///
-/// macOS resolves `localhost` to both `::1` and `127.0.0.1`; reqwest's
-/// happy-eyeballs may try `::1` first, which fails when the relay binds IPv4
-/// only (`0.0.0.0`). Forcing the IPv4 literal makes every HTTP write connect on
-/// the first attempt. Exact-match only — `localhost.evil.com` is untouched.
-fn normalize_loopback_host(authority: &str) -> String {
-    let host_len = authority.find([':', '/']).unwrap_or(authority.len());
-    if &authority[..host_len] == "localhost" {
-        return format!("127.0.0.1{}", &authority[host_len..]);
-    }
-    authority.to_string()
-}
-
 pub fn relay_api_base_url() -> String {
     if let Some(base) = configured_env_var("BUZZ_RELAY_HTTP") {
         return base.trim_end_matches('/').to_string();
@@ -669,21 +655,24 @@ mod tests {
         );
     }
 
-    // ── relay_http_base_url loopback normalization ───────────────────────────
+    // ── relay_http_base_url scheme conversion ────────────────────────────────
 
     #[test]
-    fn loopback_ws_localhost_rewritten_to_ipv4() {
+    fn loopback_ws_localhost_preserves_authority() {
+        // Tenant host-binding keys off the HTTP Host/authority. The desktop must
+        // not rewrite localhost to 127.0.0.1, or local dev HTTP calls target a
+        // different unmapped community than the WebSocket URL.
         assert_eq!(
             relay_http_base_url("ws://localhost:3000"),
-            "http://127.0.0.1:3000"
+            "http://localhost:3000"
         );
     }
 
     #[test]
-    fn loopback_trailing_slash_rewritten_to_ipv4() {
+    fn loopback_trailing_slash_removed_authority_preserved() {
         assert_eq!(
             relay_http_base_url("ws://localhost:3000/"),
-            "http://127.0.0.1:3000"
+            "http://localhost:3000"
         );
     }
 
@@ -704,9 +693,7 @@ mod tests {
     }
 
     #[test]
-    fn localhost_substring_host_not_rewritten() {
-        // Exact-match only: a host that merely starts with "localhost" must NOT
-        // be rewritten, or a malicious host could hijack the loopback path.
+    fn localhost_substring_host_unchanged() {
         assert_eq!(
             relay_http_base_url("ws://localhost.evil.com:3000"),
             "http://localhost.evil.com:3000"
@@ -714,11 +701,10 @@ mod tests {
     }
 
     #[test]
-    fn loopback_wss_localhost_rewritten_to_ipv4() {
-        // The wss:// dev arm normalizes identically to ws://.
+    fn loopback_wss_localhost_preserves_authority() {
         assert_eq!(
             relay_http_base_url("wss://localhost:3000"),
-            "https://127.0.0.1:3000"
+            "https://localhost:3000"
         );
     }