tune: optimist=1, max elevation=2, STUN enabled by default

- INFLIGHT_OPTIMIST 2→1: reduce initial pipeline depth
- MAX_ELEVATED_PER_DEPLOYMENT 30→2: tighten elevation cap
- block_stun default true→false: allow STUN/TURN by default

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: vahidlazio

src/bin/ui.rs

@@ -431,7 +431,7 @@ fn load_form() -> (FormState, Option<String>) {
             youtube_via_relay: false,
             passthrough_hosts: Vec::new(),
             block_quic: true,
-            block_stun: true,
+            block_stun: false,
             disable_padding: false,
             force_http1: false,
             tunnel_doh: true,
@@ -695,8 +695,8 @@ struct ConfigWire<'a> {
     /// emit only when the user has explicitly disabled the block.
     #[serde(skip_serializing_if = "is_true")]
     block_doh: bool,
-    /// Default true. Emit only when the user disables STUN/TURN blocking.
-    #[serde(skip_serializing_if = "is_true")]
+    /// Default false. Emit only when the user enables STUN/TURN blocking.
+    #[serde(skip_serializing_if = "is_false")]
     block_stun: bool,
     #[serde(skip_serializing_if = "Vec::is_empty")]
     fronting_groups: &'a Vec<FrontingGroup>,

src/config.rs

@@ -504,7 +504,7 @@ fn default_tunnel_doh() -> bool { true }
 /// Default for `block_quic`: `true`. QUIC over the TCP-based tunnel
 /// causes TCP-over-TCP meltdown (<1 Mbps). Browsers fall back to
 /// HTTPS/TCP within seconds of the silent UDP drop. Issue #793.
-fn default_block_stun() -> bool { true }
+fn default_block_stun() -> bool { false }
 fn default_block_quic() -> bool { true }
 
 /// Default for `block_doh`: `true` (browser DoH is rejected so the

src/tunnel_client.rs

@@ -69,7 +69,7 @@ const INFLIGHT_IDLE: usize = 1;
 
 /// Optimistic starting depth — every session gets 2 in-flight polls
 /// without needing an elevation permit. Drops to IDLE on first empty.
-const INFLIGHT_OPTIMIST: usize = 2;
+const INFLIGHT_OPTIMIST: usize = 1;
 
 /// Maximum pipeline depth when data is actively flowing. Ramps up on
 /// data-bearing replies, drops back to IDLE after consecutive empties.
@@ -79,7 +79,7 @@ const INFLIGHT_ACTIVE: usize = 4;
 const INFLIGHT_COOLDOWN: u32 = 3;
 
 /// Max sessions that can run at elevated pipeline depth per deployment.
-const MAX_ELEVATED_PER_DEPLOYMENT: u64 = 30;
+const MAX_ELEVATED_PER_DEPLOYMENT: u64 = 2;
 
 /// Adaptive coalesce defaults: after each new op arrives, wait another
 /// step for more ops. Resets on every arrival, up to max from the first