diff --git a/packages/openrouter-realm/model-cost.test.gts b/packages/openrouter-realm/model-cost.test.gts
index 666b0ce9ebe..de5fc96bf21 100644
--- a/packages/openrouter-realm/model-cost.test.gts
+++ b/packages/openrouter-realm/model-cost.test.gts
@@ -79,7 +79,7 @@ export function runTests() {
         assert.strictEqual(modelCostTierLabel('0.000003 USD', '0'), undefined);
       });
 
-      test('maps blended cost across the 1/5/20 tier bounds', function (assert) {
+      test('maps blended cost across the 1/5/15 tier bounds', function (assert) {
         // Encode a target blended $/M as a completion-only per-token price:
         // blended = (completion/4)*1e6 => completion = blended*4/1e6. Values are
         // kept off the exact bounds so floating-point wobble can't flip a tier.
@@ -89,17 +89,24 @@ export function runTests() {
         assert.strictEqual(byBlended(1.1), '$$', 'just above $1/M');
         assert.strictEqual(byBlended(4.9), '$$', 'just below $5/M');
         assert.strictEqual(byBlended(5.1), '$$$', 'just above $5/M');
-        assert.strictEqual(byBlended(19), '$$$', 'just below $20/M');
-        assert.strictEqual(byBlended(21), '$$$$', 'just above $20/M');
-        assert.strictEqual(byBlended(200), '$$$$', 'well above $20/M');
+        assert.strictEqual(byBlended(14), '$$$', 'just below $15/M');
+        assert.strictEqual(byBlended(16), '$$$$', 'just above $15/M');
+        assert.strictEqual(byBlended(200), '$$$$', 'well above $15/M');
       });
 
-      test('bounds are inclusive: exactly 1/5/20 land in the lower tier', function (assert) {
+      test('bounds are inclusive: exactly 1/5/15 land in the lower tier', function (assert) {
         // Completion-only prices whose blended $/M is float-exact at each bound:
-        // (completion/4)*1e6 with 0.000004 / 0.00002 / 0.00008 => 1 / 5 / 20.
+        // (completion/4)*1e6 with 0.000004 / 0.00002 / 0.00006 => 1 / 5 / 15.
         assert.strictEqual(modelCostTierLabel('0', '0.000004'), '$');
         assert.strictEqual(modelCostTierLabel('0', '0.00002'), '$$');
-        assert.strictEqual(modelCostTierLabel('0', '0.00008'), '$$$');
+        assert.strictEqual(modelCostTierLabel('0', '0.00006'), '$$$');
+      });
+
+      test('float noise cannot tip an exact-bound price into the tier above', function (assert) {
+        // gpt-4-turbo: in $10/M out $30/M => blended exactly 15, but the raw
+        // float math yields 15.000000000000002. The blend rounds that noise
+        // away, so the price lands on the inclusive bound and stays $$$.
+        assert.strictEqual(modelCostTierLabel('0.00001', '0.00003'), '$$$');
       });
 
       test('classifies representative frontier models (tier + label)', function (assert) {
@@ -118,6 +125,11 @@ export function runTests() {
           tier: 3,
           label: '$$$',
         });
+        // claude-fable-5: in $10/M out $50/M => blended 20 => $$$$
+        assert.deepEqual(modelCostTier('0.00001', '0.00005'), {
+          tier: 4,
+          label: '$$$$',
+        });
         // o1: in $15/M out $60/M => blended 26.25 => $$$$
         assert.deepEqual(modelCostTier('0.000015', '0.00006'), {
           tier: 4,
diff --git a/packages/openrouter-realm/model-cost.ts b/packages/openrouter-realm/model-cost.ts
index e0e10601b51..4b80d9f5388 100644
--- a/packages/openrouter-realm/model-cost.ts
+++ b/packages/openrouter-realm/model-cost.ts
@@ -14,8 +14,10 @@
 
 // Upper bounds (inclusive) for the blended $/M cost of each dollar tier. Fixed,
 // human-round thresholds — not quantiles — so a model's badge stays stable as
-// the catalog churns. Grounded in the live OpenRouter price distribution.
-export const COST_TIER_UPPER_BOUNDS = [1, 5, 20] as const; // $, $$, $$$ (>20 => $$$$)
+// the catalog churns. Grounded in the live OpenRouter price distribution; the
+// top bound sits below premium-priced frontier models (blended $20/M and up)
+// so they read as $$$$ rather than sharing $$$ with standard Opus-tier pricing.
+export const COST_TIER_UPPER_BOUNDS = [1, 5, 15] as const; // $, $$, $$$ (>15 => $$$$)
 
 const DOLLAR_LABELS = ['$', '$$', '$$$', '$$$$'] as const;
 
@@ -59,7 +61,12 @@ export function blendedCostPerMillion(
     (3 * (prompt === 'absent' ? 0 : prompt) +
       (completion === 'absent' ? 0 : completion)) /
     4;
-  return perToken * 1_000_000;
+  // Round to a micro-dollar per million tokens. The blend of per-token decimal
+  // strings picks up binary float noise (e.g. $10/$30 blends to
+  // 15.000000000000002), which would tip a price sitting exactly on an
+  // inclusive tier bound into the tier above. No real price distinction lives
+  // below $0.000001/M, so rounding here only removes representation error.
+  return Math.round(perToken * 1_000_000 * 1_000_000) / 1_000_000;
 }
 
 // Maps OpenRouter pricing to a cost tier, or `undefined` when pricing is