diff --git a/src/app/api/chat/route.ts b/src/app/api/chat/route.ts
index 18923c4..f4c092d 100644
--- a/src/app/api/chat/route.ts
+++ b/src/app/api/chat/route.ts
@@ -47,7 +47,7 @@ const zen = (sessionId: string) =>
     },
   });
 
-const MODEL_ID = 'glm-5.3-flash';
+const MODEL_ID = 'gpt-6-luna';
 
 const model = (sessionId: string) => zen(sessionId).chatModel(MODEL_ID);
 
diff --git a/src/lib/abuse/__tests__/cost.test.ts b/src/lib/abuse/__tests__/cost.test.ts
index e54a492..0fa9a80 100644
--- a/src/lib/abuse/__tests__/cost.test.ts
+++ b/src/lib/abuse/__tests__/cost.test.ts
@@ -11,8 +11,8 @@ describe('estimateTokens', () => {
 
 describe('calculateCost', () => {
   it('scales tokens to USD', () => {
-    expect(calculateCost(1_000_000)).toBeCloseTo(0.28);
-    expect(calculateCost(500_000)).toBeCloseTo(0.14);
+    expect(calculateCost(1_000_000)).toBeCloseTo(0.5);
+    expect(calculateCost(500_000)).toBeCloseTo(0.25);
   });
 });
 
@@ -31,7 +31,7 @@ describe('checkCostLimit', () => {
     vi.useFakeTimers();
     vi.setSystemTime(new Date('2026-01-01T00:00:00Z'));
     for (let i = 0; i < 6; i++) {
-      checkCostLimit('u1', 300_000); // ~$0.084 each
+      checkCostLimit('u1', 300_000); // ~$0.15 each
     }
     const result = checkCostLimit('u1', 300_000);
     expect(result.allowed).toBe(false);
@@ -52,9 +52,9 @@ describe('recordActualUsage', () => {
   it('corrects the last estimate with actual usage', () => {
     checkCostLimit('u1', 40_000);
     recordActualUsage('u1', 10_000);
-    // Exhausting the budget now: ~$0.0589 spent (actual) + next estimate must
-    // still fit — verifies the estimate was replaced, not appended.
-    const result = checkCostLimit('u1', 1_000_000);
+    // ~$0.005 spent (actual) + next estimate must still fit — verifies the
+    // estimate was replaced, not appended.
+    const result = checkCostLimit('u1', 900_000);
     expect(result.allowed).toBe(true);
   });
 
diff --git a/src/lib/abuse/cost.ts b/src/lib/abuse/cost.ts
index e4112b7..c47d24e 100644
--- a/src/lib/abuse/cost.ts
+++ b/src/lib/abuse/cost.ts
@@ -8,7 +8,7 @@
 
 export const MAX_TOKENS_PER_REQUEST = 4000;
 const MAX_COST_PER_HOUR_USD = 0.5; // ~$0.50/hour budget
-const TOKEN_COST_PER_1M = 0.28; // glm-5.3-flash on OpenCode Go (conservative upper bound)
+const TOKEN_COST_PER_1M = 0.5; // gpt-6-luna on OpenCode Zen (output upper bound)
 const USAGE_WINDOW_MS = 60 * 60 * 1000; // 1 hour
 const CLEANUP_INTERVAL_MS = 300_000; // 5 min