fix: emit claude message_delta for usage-only final stream chunk

relay/channel/claude/message_delta_usage_patch_test.go

@@ -85,7 +85,7 @@ func TestBuildMessageDeltaPatchUsage(t *testing.T) {
 		require.EqualValues(t, 50, usage.CacheCreationInputTokens)
 		require.EqualValues(t, 53, usage.OutputTokens)
 		require.NotNil(t, usage.CacheCreation)
-		require.EqualValues(t, 10, usage.CacheCreation.Ephemeral5mInputTokens)
+		require.EqualValues(t, 30, usage.CacheCreation.Ephemeral5mInputTokens)
 		require.EqualValues(t, 20, usage.CacheCreation.Ephemeral1hInputTokens)
 	})
 
@@ -108,4 +108,22 @@ func TestBuildMessageDeltaPatchUsage(t *testing.T) {
 		require.EqualValues(t, 7, usage.CacheReadInputTokens)
 		require.EqualValues(t, 6, usage.CacheCreationInputTokens)
 	})
+
+	t.Run("default aggregate cache creation to 5m when split missing", func(t *testing.T) {
+		claudeResponse := &dto.ClaudeResponse{Usage: &dto.ClaudeUsage{
+			OutputTokens:             53,
+			CacheCreationInputTokens: 50,
+		}}
+		claudeInfo := &ClaudeResponseInfo{Usage: &dto.Usage{
+			PromptTokensDetails: dto.InputTokenDetails{
+				CachedCreationTokens: 50,
+			},
+		}}
+
+		usage := buildMessageDeltaPatchUsage(claudeResponse, claudeInfo)
+		require.NotNil(t, usage)
+		require.NotNil(t, usage.CacheCreation)
+		require.EqualValues(t, 50, usage.CacheCreation.Ephemeral5mInputTokens)
+		require.EqualValues(t, 0, usage.CacheCreation.Ephemeral1hInputTokens)
+	})
 }

relay/channel/claude/relay-claude.go

@@ -648,6 +648,11 @@ func buildOpenAIStyleUsageFromClaudeUsage(usage *dto.Usage) dto.Usage {
 		return dto.Usage{}
 	}
 	clone := *usage
+	clone.ClaudeCacheCreation5mTokens, clone.ClaudeCacheCreation1hTokens = service.NormalizeCacheCreationSplit(
+		usage.PromptTokensDetails.CachedCreationTokens,
+		usage.ClaudeCacheCreation5mTokens,
+		usage.ClaudeCacheCreation1hTokens,
+	)
 	cacheCreationTokens := cacheCreationTokensForOpenAIUsage(usage)
 	totalInputTokens := usage.PromptTokens + usage.PromptTokensDetails.CachedTokens + cacheCreationTokens
 	clone.PromptTokens = totalInputTokens
@@ -677,11 +682,26 @@ func buildMessageDeltaPatchUsage(claudeResponse *dto.ClaudeResponse, claudeInfo
 	if usage.CacheCreationInputTokens == 0 && claudeInfo.Usage.PromptTokensDetails.CachedCreationTokens > 0 {
 		usage.CacheCreationInputTokens = claudeInfo.Usage.PromptTokensDetails.CachedCreationTokens
 	}
-	if usage.CacheCreation == nil && (claudeInfo.Usage.ClaudeCacheCreation5mTokens > 0 || claudeInfo.Usage.ClaudeCacheCreation1hTokens > 0) {
-		usage.CacheCreation = &dto.ClaudeCacheCreationUsage{
-			Ephemeral5mInputTokens: claudeInfo.Usage.ClaudeCacheCreation5mTokens,
-			Ephemeral1hInputTokens: claudeInfo.Usage.ClaudeCacheCreation1hTokens,
-		}
+	cacheCreation5m := 0
+	cacheCreation1h := 0
+	if usage.CacheCreation != nil {
+		cacheCreation5m = usage.CacheCreation.Ephemeral5mInputTokens
+		cacheCreation1h = usage.CacheCreation.Ephemeral1hInputTokens
+	} else {
+		cacheCreation5m = claudeInfo.Usage.ClaudeCacheCreation5mTokens
+		cacheCreation1h = claudeInfo.Usage.ClaudeCacheCreation1hTokens
+	}
+	cacheCreation5m, cacheCreation1h = service.NormalizeCacheCreationSplit(
+		usage.CacheCreationInputTokens,
+		cacheCreation5m,
+		cacheCreation1h,
+	)
+	if usage.CacheCreation == nil && (cacheCreation5m > 0 || cacheCreation1h > 0) {
+		usage.CacheCreation = &dto.ClaudeCacheCreationUsage{}
+	}
+	if usage.CacheCreation != nil {
+		usage.CacheCreation.Ephemeral5mInputTokens = cacheCreation5m
+		usage.CacheCreation.Ephemeral1hInputTokens = cacheCreation1h
 	}
 	return usage
 }

relay/channel/claude/relay_claude_test.go

@@ -258,6 +258,23 @@ func TestBuildOpenAIStyleUsageFromClaudeUsagePreservesCacheCreationRemainder(t *
 	}
 }
 
+func TestBuildOpenAIStyleUsageFromClaudeUsageDefaultsAggregateCacheCreationTo5m(t *testing.T) {
+	usage := &dto.Usage{
+		PromptTokens:     100,
+		CompletionTokens: 20,
+		PromptTokensDetails: dto.InputTokenDetails{
+			CachedTokens:         30,
+			CachedCreationTokens: 50,
+		},
+		UsageSemantic: "anthropic",
+	}
+
+	openAIUsage := buildOpenAIStyleUsageFromClaudeUsage(usage)
+
+	require.Equal(t, 50, openAIUsage.ClaudeCacheCreation5mTokens)
+	require.Equal(t, 0, openAIUsage.ClaudeCacheCreation1hTokens)
+}
+
 func TestRequestOpenAI2ClaudeMessage_IgnoresUnsupportedFileContent(t *testing.T) {
 	request := dto.GeneralOpenAIRequest{
 		Model: "claude-3-5-sonnet",