diff --git a/Yattee/Services/Navigation/URLRouter.swift b/Yattee/Services/Navigation/URLRouter.swift
index 98c9e45f..f3836d7d 100644
--- a/Yattee/Services/Navigation/URLRouter.swift
+++ b/Yattee/Services/Navigation/URLRouter.swift
@@ -145,9 +145,11 @@ struct URLRouter: Sendable {
         let trimmed = raw.trimmingCharacters(in: .whitespaces)
         guard !trimmed.isEmpty else { return nil }
 
-        // Plain numeric value (e.g. "90", "90.5")
+        // Plain numeric value (e.g. "90", "90.5"). Reject non-finite values
+        // ("inf"/"infinity"/"nan") that `TimeInterval(_:)` accepts — a `?t=inf`
+        // link would otherwise seek the player to `Double.infinity`.
         if let value = TimeInterval(trimmed) {
-            return value >= 0 ? value : nil
+            return (value.isFinite && value >= 0) ? value : nil
         }
 
         // Compound form like "1h2m3s", "2m30s", "90s"
diff --git a/YatteeTests/NavigationTests.swift b/YatteeTests/NavigationTests.swift
index aa46c789..c0bcedb5 100644
--- a/YatteeTests/NavigationTests.swift
+++ b/YatteeTests/NavigationTests.swift
@@ -123,6 +123,20 @@ struct URLRouterTests {
         #expect(URLRouter.parseTimestampValue("90.5") == 90.5)
     }
 
+    @Test("Reject non-finite and negative plain timestamp values")
+    func rejectInvalidPlainTimestampValues() {
+        // Plain numeric values that are accepted by TimeInterval(_:) but are not
+        // valid seek targets must return nil rather than poisoning the player.
+        #expect(URLRouter.parseTimestampValue("inf") == nil)
+        #expect(URLRouter.parseTimestampValue("infinity") == nil)
+        #expect(URLRouter.parseTimestampValue("nan") == nil)
+        #expect(URLRouter.parseTimestampValue("-5") == nil)
+        // Valid plain seconds still parse.
+        #expect(URLRouter.parseTimestampValue("0") == 0)
+        #expect(URLRouter.parseTimestampValue("90") == 90)
+        #expect(URLRouter.parseTimestampValue("90.5") == 90.5)
+    }
+
     // MARK: - Share Extension Wrapper Tests
 
     @Test("Unwrap yattee://open wrapper to inner URL with timestamp")