diff --git a/e2e/perstack-cli/reasoning-budget.test.ts b/e2e/perstack-cli/reasoning-budget.test.ts
index a281ea60..0a92dc91 100644
--- a/e2e/perstack-cli/reasoning-budget.test.ts
+++ b/e2e/perstack-cli/reasoning-budget.test.ts
@@ -109,8 +109,7 @@ describe("Reasoning Budget", () => {
         // Extended thinking should produce reasoning tokens or thinking text
         // Note: AI SDK currently doesn't report reasoningTokens for Anthropic,
         // but we can verify thinking content is generated
-        const hasThinking =
-          result.reasoningTokens > 0 || (result.thinking && result.thinking.length > 0)
+        const hasThinking = result.reasoningTokens > 0 || (result.thinking?.length ?? 0) > 0
         expect(hasThinking).toBe(true)
       },
       LLM_TIMEOUT,
@@ -166,10 +165,9 @@ describe("Reasoning Budget", () => {
         // Both should produce reasoning tokens or thinking text
         // Note: AI SDK currently doesn't report reasoningTokens for Anthropic
         const minimalHasThinking =
-          minimalResult.reasoningTokens > 0 ||
-          (minimalResult.thinking && minimalResult.thinking.length > 0)
+          minimalResult.reasoningTokens > 0 || (minimalResult.thinking?.length ?? 0) > 0
         const highHasThinking =
-          highResult.reasoningTokens > 0 || (highResult.thinking && highResult.thinking.length > 0)
+          highResult.reasoningTokens > 0 || (highResult.thinking?.length ?? 0) > 0
         expect(minimalHasThinking).toBe(true)
         expect(highHasThinking).toBe(true)
       },
@@ -202,8 +200,7 @@ describe("Reasoning Budget", () => {
         expect(result.success).toBe(true)
         // OpenAI reasoning models may not always surface reasoning token counts,
         // so verify either tokens or thinking text is present
-        const hasReasoning =
-          result.reasoningTokens > 0 || (result.thinking && result.thinking.length > 0)
+        const hasReasoning = result.reasoningTokens > 0 || (result.thinking?.length ?? 0) > 0
         expect(hasReasoning).toBe(true)
       },
       LLM_TIMEOUT,
@@ -221,7 +218,7 @@ describe("Reasoning Budget", () => {
 
         // At least one budget level should produce reasoning tokens or thinking text
         const highHasReasoning =
-          highResult.reasoningTokens > 0 || (highResult.thinking && highResult.thinking.length > 0)
+          highResult.reasoningTokens > 0 || (highResult.thinking?.length ?? 0) > 0
         expect(highHasReasoning).toBe(true)
       },
       LLM_TIMEOUT * 2, // Two API calls
@@ -252,8 +249,7 @@ describe("Reasoning Budget", () => {
 
         expect(result.success).toBe(true)
         // Flash thinking should produce reasoning tokens or thinking text
-        const hasThinking =
-          result.reasoningTokens > 0 || (result.thinking && result.thinking.length > 0)
+        const hasThinking = result.reasoningTokens > 0 || (result.thinking?.length ?? 0) > 0
         expect(hasThinking).toBe(true)
       },
       LLM_TIMEOUT,
@@ -271,10 +267,9 @@ describe("Reasoning Budget", () => {
 
         // Both should produce reasoning tokens or thinking text
         const minimalHasThinking =
-          minimalResult.reasoningTokens > 0 ||
-          (minimalResult.thinking && minimalResult.thinking.length > 0)
+          minimalResult.reasoningTokens > 0 || (minimalResult.thinking?.length ?? 0) > 0
         const highHasThinking =
-          highResult.reasoningTokens > 0 || (highResult.thinking && highResult.thinking.length > 0)
+          highResult.reasoningTokens > 0 || (highResult.thinking?.length ?? 0) > 0
         expect(minimalHasThinking).toBe(true)
         expect(highHasThinking).toBe(true)
       },