diff --git a/rust/src/core/cost_pricing.rs b/rust/src/core/cost_pricing.rs
index f78a58cb59..3c69b9633d 100755
--- a/rust/src/core/cost_pricing.rs
+++ b/rust/src/core/cost_pricing.rs
@@ -231,6 +231,16 @@ static CLAUDE_PRICING: LazyLock<HashMap<&'static str, ClaudePricing>> = LazyLock
             "claude-fable-5",
             ClaudePricing::new(1e-5, 5e-5, 1.25e-5, 1e-6),
         ),
+        // Mythos is served to verified organizations only and is absent from the models.dev
+        // anthropic catalog. Rates: https://platform.claude.com/docs/en/about-claude/pricing
+        (
+            "claude-mythos-5",
+            ClaudePricing::new(1e-5, 5e-5, 1.25e-5, 1e-6),
+        ),
+        (
+            "claude-mythos-5-1",
+            ClaudePricing::new(1e-5, 5e-5, 1.25e-5, 2.5e-7),
+        ),
         ("claude-haiku-4-5", CLAUDE_HAIKU_4_5),
         ("claude-haiku-4-5-20251001", CLAUDE_HAIKU_4_5),
         ("claude-opus-4-6", CLAUDE_OPUS_4_5),
diff --git a/rust/src/core/cost_pricing_tests.rs b/rust/src/core/cost_pricing_tests.rs
index dc8fc2edc8..18aed574b0 100644
--- a/rust/src/core/cost_pricing_tests.rs
+++ b/rust/src/core/cost_pricing_tests.rs
@@ -75,7 +75,12 @@ fn prices_codex_models() {
 
 #[test]
 fn prices_claude_models() {
-    for (model, expected) in [("claude-opus-4-8", 0.0175), ("claude-fable-5", 0.035)] {
+    for (model, expected) in [
+        ("claude-opus-4-8", 0.0175),
+        ("claude-fable-5", 0.035),
+        ("claude-mythos-5", 0.035),
+        ("claude-mythos-5-1", 0.035),
+    ] {
         let cost = CostUsagePricing::claude_cost_usd(model, 1_000, 0, 0, 500).unwrap();
         assert!((cost - expected).abs() < 1e-10, "{model}");
     }
@@ -790,6 +795,8 @@ gpt-6-astra 1e-5 5e-5 1e-6 Some(1.25e-5) None Some((2e-5, 7.5e-5, 2e-6, Some(2.5
 claude-fable-5 1e-5 5e-5 1.25e-5 1e-6 None None None None None
 claude-haiku-4-5 1e-6 5e-6 1.25e-6 1e-7 None None None None None
 claude-haiku-4-5-20251001 1e-6 5e-6 1.25e-6 1e-7 None None None None None
+claude-mythos-5 1e-5 5e-5 1.25e-5 1e-6 None None None None None
+claude-mythos-5-1 1e-5 5e-5 1.25e-5 2.5e-7 None None None None None
 claude-opus-4-1 1.5e-5 7.5e-5 1.875e-5 1.5e-6 None None None None None
 claude-opus-4-20250514 1.5e-5 7.5e-5 1.875e-5 1.5e-6 None None None None None
 claude-opus-4-5 5e-6 2.5e-5 6.25e-6 5e-7 None None None None None
diff --git a/rust/src/cost_scanner/tests/claude_rates.rs b/rust/src/cost_scanner/tests/claude_rates.rs
index 01c2354a1c..4a749ba262 100644
--- a/rust/src/cost_scanner/tests/claude_rates.rs
+++ b/rust/src/cost_scanner/tests/claude_rates.rs
@@ -216,6 +216,21 @@ fn claude_fable_5_prices_five_minute_and_one_hour_cache_writes() {
     }
 }
 
+#[test]
+fn claude_mythos_models_price_from_the_builtin_table() {
+    // (model, cache read price per million): Mythos 5.1 bills cache reads at $0.25/M,
+    // Mythos 5 at $1/M. Both bill $10 in, $12.50 cache write, $50 out per million.
+    for (model, cache_read_per_million) in [("claude-mythos-5", 1.00), ("claude-mythos-5-1", 0.25)]
+    {
+        let cost = ClaudePricing::cost_usd_with_cache_ttl(model, 100, 10, 0, 20, 5);
+        let expected = (100.0 / 1_000_000.0) * 10.00
+            + (10.0 / 1_000_000.0) * 12.50
+            + (20.0 / 1_000_000.0) * cache_read_per_million
+            + (5.0 / 1_000_000.0) * 50.00;
+        assert!((cost - expected).abs() < 1e-12, "{model}");
+    }
+}
+
 #[test]
 fn claude_scan_pricing_follows_the_canonical_table() {
     // Undated Sonnet 4.6 bills its full context at the standard $3/M: 240k = 0.72.