fix: /balance cannot be used for providers.deepseek (#7055)

Produced by CodeWhale running in a Boat VM. Untested.

crates/tui/src/tui/ui/provider_routes.rs

@@ -208,11 +208,20 @@ async fn fetch_deepseek_user_balance(
     api_key: &str,
     base_url: &str,
 ) -> Option<crate::pricing::BalanceInfo> {
-    let url = format!("{}/user/balance", base_url.trim_end_matches('/'));
+    let url = deepseek_balance_url(base_url);
     let body: crate::pricing::BalanceResponse = balance_get_json(api_key, &url).await?;
     body.balance_infos.into_iter().next()
 }
 
+pub(crate) fn deepseek_balance_url(base_url: &str) -> String {
+    let origin = base_url.trim_end_matches('/');
+    let origin = origin
+        .strip_suffix("/beta")
+        .or_else(|| origin.strip_suffix("/v1"))
+        .unwrap_or(origin);
+    format!("{origin}/user/balance")
+}
+
 #[derive(serde::Deserialize)]
 struct OpenRouterCreditsResponse {
     data: OpenRouterCreditsData,

crates/tui/src/tui/ui/tests.rs

@@ -28993,6 +28993,26 @@ fn openrouter_credits_map_remaining_usd() {
     assert_eq!(info.chip_label().as_deref(), Some("$37.66"));
 }
 
+#[test]
+fn deepseek_balance_url_strips_beta_and_v1_prefixes() {
+    assert_eq!(
+        deepseek_balance_url("https://api.deepseek.com/beta"),
+        "https://api.deepseek.com/user/balance"
+    );
+    assert_eq!(
+        deepseek_balance_url("https://api.deepseek.com"),
+        "https://api.deepseek.com/user/balance"
+    );
+    assert_eq!(
+        deepseek_balance_url("https://api.deepseek.com/v1"),
+        "https://api.deepseek.com/user/balance"
+    );
+    assert_eq!(
+        deepseek_balance_url("https://api.deepseek.com/beta/"),
+        "https://api.deepseek.com/user/balance"
+    );
+}
+
 /// Regression for issue #244: visible session spend must not decrease.
 /// Sub-agent token usage events arrive out of order and may be reconciled
 /// later (cache adjustments, provisional → final swap). The displayed total