diff --git a/internal/runtime/executor/helps/usage_helpers.go b/internal/runtime/executor/helps/usage_helpers.go
index 312a1d35c..e6be94aaa 100644
--- a/internal/runtime/executor/helps/usage_helpers.go
+++ b/internal/runtime/executor/helps/usage_helpers.go
@@ -248,7 +248,7 @@ func resolveUsageAuthType(auth *cliproxyauth.Auth) string {
 
 func ParseCodexUsage(data []byte) (usage.Detail, bool) {
 	usageNode := gjson.ParseBytes(data).Get("response.usage")
-	if !usageNode.Exists() {
+	if !hasOpenAIStyleUsageTokenFields(usageNode) {
 		return usage.Detail{}, false
 	}
 	return parseOpenAIStyleUsageNode(usageNode), true
@@ -256,7 +256,7 @@ func ParseCodexUsage(data []byte) (usage.Detail, bool) {
 
 func ParseCodexImageToolUsage(data []byte) (usage.Detail, bool) {
 	usageNode := gjson.ParseBytes(data).Get("response.tool_usage.image_gen")
-	if !usageNode.Exists() || !usageNode.IsObject() {
+	if !hasOpenAIStyleUsageTokenFields(usageNode) {
 		return usage.Detail{}, false
 	}
 	return parseOpenAIStyleUsageNode(usageNode), true
@@ -264,12 +264,27 @@ func ParseCodexImageToolUsage(data []byte) (usage.Detail, bool) {
 
 func ParseOpenAIUsage(data []byte) usage.Detail {
 	usageNode := gjson.ParseBytes(data).Get("usage")
-	if !usageNode.Exists() {
+	if !hasOpenAIStyleUsageTokenFields(usageNode) {
 		return usage.Detail{}
 	}
 	return parseOpenAIStyleUsageNode(usageNode)
 }
 
+func hasOpenAIStyleUsageTokenFields(usageNode gjson.Result) bool {
+	if !usageNode.Exists() || !usageNode.IsObject() {
+		return false
+	}
+	return usageNode.Get("prompt_tokens").Exists() ||
+		usageNode.Get("input_tokens").Exists() ||
+		usageNode.Get("completion_tokens").Exists() ||
+		usageNode.Get("output_tokens").Exists() ||
+		usageNode.Get("total_tokens").Exists() ||
+		usageNode.Get("prompt_tokens_details.cached_tokens").Exists() ||
+		usageNode.Get("input_tokens_details.cached_tokens").Exists() ||
+		usageNode.Get("completion_tokens_details.reasoning_tokens").Exists() ||
+		usageNode.Get("output_tokens_details.reasoning_tokens").Exists()
+}
+
 func parseOpenAIStyleUsageNode(usageNode gjson.Result) usage.Detail {
 	inputNode := usageNode.Get("prompt_tokens")
 	if !inputNode.Exists() {
@@ -307,21 +322,10 @@ func ParseOpenAIStreamUsage(line []byte) (usage.Detail, bool) {
 		return usage.Detail{}, false
 	}
 	usageNode := gjson.GetBytes(payload, "usage")
-	if !usageNode.Exists() {
+	if !hasOpenAIStyleUsageTokenFields(usageNode) {
 		return usage.Detail{}, false
 	}
-	detail := usage.Detail{
-		InputTokens:  usageNode.Get("prompt_tokens").Int(),
-		OutputTokens: usageNode.Get("completion_tokens").Int(),
-		TotalTokens:  usageNode.Get("total_tokens").Int(),
-	}
-	if cached := usageNode.Get("prompt_tokens_details.cached_tokens"); cached.Exists() {
-		detail.CachedTokens = cached.Int()
-	}
-	if reasoning := usageNode.Get("completion_tokens_details.reasoning_tokens"); reasoning.Exists() {
-		detail.ReasoningTokens = reasoning.Int()
-	}
-	return detail, true
+	return parseOpenAIStyleUsageNode(usageNode), true
 }
 
 func ParseClaudeUsage(data []byte) usage.Detail {
diff --git a/internal/runtime/executor/helps/usage_helpers_test.go b/internal/runtime/executor/helps/usage_helpers_test.go
index ef2c7de58..644ff0961 100644
--- a/internal/runtime/executor/helps/usage_helpers_test.go
+++ b/internal/runtime/executor/helps/usage_helpers_test.go
@@ -48,6 +48,44 @@ func TestParseOpenAIUsageResponses(t *testing.T) {
 	}
 }
 
+func TestParseOpenAIUsageIgnoresNullUsage(t *testing.T) {
+	data := []byte(`{"usage":null}`)
+	detail := ParseOpenAIUsage(data)
+	if detail != (usage.Detail{}) {
+		t.Fatalf("detail = %+v, want zero detail", detail)
+	}
+}
+
+func TestParseOpenAIStreamUsageIgnoresNullUsage(t *testing.T) {
+	line := []byte(`data: {"id":"chunk_1","object":"chat.completion.chunk","choices":[{"index":0,"delta":{"content":"hi"},"finish_reason":null}],"usage":null}`)
+	if detail, ok := ParseOpenAIStreamUsage(line); ok {
+		t.Fatalf("ParseOpenAIStreamUsage() = (%+v, true), want false for null usage", detail)
+	}
+}
+
+func TestParseOpenAIStreamUsageResponsesFields(t *testing.T) {
+	line := []byte(`data: {"id":"chunk_1","object":"chat.completion.chunk","choices":[],"usage":{"input_tokens":8,"output_tokens":5,"total_tokens":13,"input_tokens_details":{"cached_tokens":3},"output_tokens_details":{"reasoning_tokens":2}}}`)
+	detail, ok := ParseOpenAIStreamUsage(line)
+	if !ok {
+		t.Fatal("ParseOpenAIStreamUsage() ok = false, want true")
+	}
+	if detail.InputTokens != 8 {
+		t.Fatalf("input tokens = %d, want %d", detail.InputTokens, 8)
+	}
+	if detail.OutputTokens != 5 {
+		t.Fatalf("output tokens = %d, want %d", detail.OutputTokens, 5)
+	}
+	if detail.TotalTokens != 13 {
+		t.Fatalf("total tokens = %d, want %d", detail.TotalTokens, 13)
+	}
+	if detail.CachedTokens != 3 {
+		t.Fatalf("cached tokens = %d, want %d", detail.CachedTokens, 3)
+	}
+	if detail.ReasoningTokens != 2 {
+		t.Fatalf("reasoning tokens = %d, want %d", detail.ReasoningTokens, 2)
+	}
+}
+
 func TestParseGeminiCLIUsage_TopLevelUsageMetadata(t *testing.T) {
 	data := []byte(`{"usageMetadata":{"promptTokenCount":11,"candidatesTokenCount":7,"thoughtsTokenCount":3,"totalTokenCount":21,"cachedContentTokenCount":5}}`)
 	detail := ParseGeminiCLIUsage(data)