diff --git a/relay/channel/claude/relay-claude.go b/relay/channel/claude/relay-claude.go
index bdb376ed..ad9d2234 100644
--- a/relay/channel/claude/relay-claude.go
+++ b/relay/channel/claude/relay-claude.go
@@ -544,6 +544,30 @@ type ClaudeResponseInfo struct {
 	Done         bool
 }
 
+// enrichMessageDeltaUsage 补全 message_delta 事件中缺失的 input_tokens 和 cache 相关字段
+// 当上游（如 AWS Bedrock）的 message_delta 不包含这些字段时，从 claudeInfo 中积累的数据补全
+func enrichMessageDeltaUsage(claudeResponse *dto.ClaudeResponse, claudeInfo *ClaudeResponseInfo) {
+	if claudeResponse.Usage == nil {
+		claudeResponse.Usage = &dto.ClaudeUsage{}
+	}
+	if claudeResponse.Usage.InputTokens == 0 && claudeInfo.Usage.PromptTokens > 0 {
+		claudeResponse.Usage.InputTokens = claudeInfo.Usage.PromptTokens
+	}
+	if claudeResponse.Usage.CacheReadInputTokens == 0 && claudeInfo.Usage.PromptTokensDetails.CachedTokens > 0 {
+		claudeResponse.Usage.CacheReadInputTokens = claudeInfo.Usage.PromptTokensDetails.CachedTokens
+	}
+	if claudeResponse.Usage.CacheCreationInputTokens == 0 && claudeInfo.Usage.PromptTokensDetails.CachedCreationTokens > 0 {
+		claudeResponse.Usage.CacheCreationInputTokens = claudeInfo.Usage.PromptTokensDetails.CachedCreationTokens
+	}
+	if claudeResponse.Usage.CacheCreation == nil &&
+		(claudeInfo.Usage.ClaudeCacheCreation5mTokens > 0 || claudeInfo.Usage.ClaudeCacheCreation1hTokens > 0) {
+		claudeResponse.Usage.CacheCreation = &dto.ClaudeCacheCreationUsage{
+			Ephemeral5mInputTokens: claudeInfo.Usage.ClaudeCacheCreation5mTokens,
+			Ephemeral1hInputTokens: claudeInfo.Usage.ClaudeCacheCreation1hTokens,
+		}
+	}
+}
+
 func FormatClaudeResponseInfo(claudeResponse *dto.ClaudeResponse, oaiResponse *dto.ChatCompletionsStreamResponse, claudeInfo *ClaudeResponseInfo) bool {
 	if claudeInfo == nil {
 		return false
@@ -638,6 +662,13 @@ func HandleStreamResponseData(c *gin.Context, info *relaycommon.RelayInfo, claud
 			if claudeResponse.Message != nil {
 				info.UpstreamModelName = claudeResponse.Message.Model
 			}
+		} else if claudeResponse.Type == "message_delta" {
+			// 确保 message_delta 的 usage 包含完整的 input_tokens 和 cache 相关字段
+			// 解决 AWS Bedrock 等上游返回的 message_delta 缺少这些字段的问题
+			enrichMessageDeltaUsage(&claudeResponse, claudeInfo)
+			if newData, err := json.Marshal(claudeResponse); err == nil {
+				data = string(newData)
+			}
 		}
 		helper.ClaudeChunkData(c, claudeResponse, data)
 	} else if info.RelayFormat == types.RelayFormatOpenAI {
diff --git a/relay/channel/claude/relay-claude_test.go b/relay/channel/claude/relay-claude_test.go
new file mode 100644
index 00000000..82c91018
--- /dev/null
+++ b/relay/channel/claude/relay-claude_test.go
@@ -0,0 +1,305 @@
+package claude
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/QuantumNous/new-api/dto"
+)
+
+func TestFormatClaudeResponseInfo_MessageStart(t *testing.T) {
+	claudeInfo := &ClaudeResponseInfo{
+		Usage: &dto.Usage{},
+	}
+	claudeResponse := &dto.ClaudeResponse{
+		Type: "message_start",
+		Message: &dto.ClaudeMediaMessage{
+			Id:    "msg_123",
+			Model: "claude-3-5-sonnet",
+			Usage: &dto.ClaudeUsage{
+				InputTokens:              100,
+				OutputTokens:             1,
+				CacheCreationInputTokens: 50,
+				CacheReadInputTokens:     30,
+			},
+		},
+	}
+
+	ok := FormatClaudeResponseInfo(claudeResponse, nil, claudeInfo)
+	if !ok {
+		t.Fatal("expected true")
+	}
+	if claudeInfo.Usage.PromptTokens != 100 {
+		t.Errorf("PromptTokens = %d, want 100", claudeInfo.Usage.PromptTokens)
+	}
+	if claudeInfo.Usage.PromptTokensDetails.CachedTokens != 30 {
+		t.Errorf("CachedTokens = %d, want 30", claudeInfo.Usage.PromptTokensDetails.CachedTokens)
+	}
+	if claudeInfo.Usage.PromptTokensDetails.CachedCreationTokens != 50 {
+		t.Errorf("CachedCreationTokens = %d, want 50", claudeInfo.Usage.PromptTokensDetails.CachedCreationTokens)
+	}
+	if claudeInfo.ResponseId != "msg_123" {
+		t.Errorf("ResponseId = %s, want msg_123", claudeInfo.ResponseId)
+	}
+	if claudeInfo.Model != "claude-3-5-sonnet" {
+		t.Errorf("Model = %s, want claude-3-5-sonnet", claudeInfo.Model)
+	}
+}
+
+func TestFormatClaudeResponseInfo_MessageDelta_FullUsage(t *testing.T) {
+	// message_start 先积累 usage
+	claudeInfo := &ClaudeResponseInfo{
+		Usage: &dto.Usage{
+			PromptTokens: 100,
+			PromptTokensDetails: dto.InputTokenDetails{
+				CachedTokens:         30,
+				CachedCreationTokens: 50,
+			},
+			CompletionTokens: 1,
+		},
+	}
+
+	// message_delta 带完整 usage（原生 Anthropic 场景）
+	claudeResponse := &dto.ClaudeResponse{
+		Type: "message_delta",
+		Usage: &dto.ClaudeUsage{
+			InputTokens:              100,
+			OutputTokens:             200,
+			CacheCreationInputTokens: 50,
+			CacheReadInputTokens:     30,
+		},
+	}
+
+	ok := FormatClaudeResponseInfo(claudeResponse, nil, claudeInfo)
+	if !ok {
+		t.Fatal("expected true")
+	}
+	if claudeInfo.Usage.PromptTokens != 100 {
+		t.Errorf("PromptTokens = %d, want 100", claudeInfo.Usage.PromptTokens)
+	}
+	if claudeInfo.Usage.CompletionTokens != 200 {
+		t.Errorf("CompletionTokens = %d, want 200", claudeInfo.Usage.CompletionTokens)
+	}
+	if claudeInfo.Usage.TotalTokens != 300 {
+		t.Errorf("TotalTokens = %d, want 300", claudeInfo.Usage.TotalTokens)
+	}
+	if !claudeInfo.Done {
+		t.Error("expected Done = true")
+	}
+}
+
+func TestFormatClaudeResponseInfo_MessageDelta_OnlyOutputTokens(t *testing.T) {
+	// 模拟 Bedrock: message_start 已积累 usage
+	claudeInfo := &ClaudeResponseInfo{
+		Usage: &dto.Usage{
+			PromptTokens: 100,
+			PromptTokensDetails: dto.InputTokenDetails{
+				CachedTokens:         30,
+				CachedCreationTokens: 50,
+			},
+			CompletionTokens:            1,
+			ClaudeCacheCreation5mTokens: 10,
+			ClaudeCacheCreation1hTokens: 20,
+		},
+	}
+
+	// Bedrock 的 message_delta 只有 output_tokens，缺少 input_tokens 和 cache 字段
+	claudeResponse := &dto.ClaudeResponse{
+		Type: "message_delta",
+		Usage: &dto.ClaudeUsage{
+			OutputTokens: 200,
+			// InputTokens, CacheCreationInputTokens, CacheReadInputTokens 都是 0
+		},
+	}
+
+	ok := FormatClaudeResponseInfo(claudeResponse, nil, claudeInfo)
+	if !ok {
+		t.Fatal("expected true")
+	}
+	// PromptTokens 应保持 message_start 的值（因为 message_delta 的 InputTokens=0，不更新）
+	if claudeInfo.Usage.PromptTokens != 100 {
+		t.Errorf("PromptTokens = %d, want 100", claudeInfo.Usage.PromptTokens)
+	}
+	if claudeInfo.Usage.CompletionTokens != 200 {
+		t.Errorf("CompletionTokens = %d, want 200", claudeInfo.Usage.CompletionTokens)
+	}
+	if claudeInfo.Usage.TotalTokens != 300 {
+		t.Errorf("TotalTokens = %d, want 300", claudeInfo.Usage.TotalTokens)
+	}
+	// cache 字段应保持 message_start 的值
+	if claudeInfo.Usage.PromptTokensDetails.CachedTokens != 30 {
+		t.Errorf("CachedTokens = %d, want 30", claudeInfo.Usage.PromptTokensDetails.CachedTokens)
+	}
+	if claudeInfo.Usage.PromptTokensDetails.CachedCreationTokens != 50 {
+		t.Errorf("CachedCreationTokens = %d, want 50", claudeInfo.Usage.PromptTokensDetails.CachedCreationTokens)
+	}
+	if claudeInfo.Usage.ClaudeCacheCreation5mTokens != 10 {
+		t.Errorf("ClaudeCacheCreation5mTokens = %d, want 10", claudeInfo.Usage.ClaudeCacheCreation5mTokens)
+	}
+	if claudeInfo.Usage.ClaudeCacheCreation1hTokens != 20 {
+		t.Errorf("ClaudeCacheCreation1hTokens = %d, want 20", claudeInfo.Usage.ClaudeCacheCreation1hTokens)
+	}
+	if !claudeInfo.Done {
+		t.Error("expected Done = true")
+	}
+}
+
+func TestFormatClaudeResponseInfo_NilClaudeInfo(t *testing.T) {
+	claudeResponse := &dto.ClaudeResponse{Type: "message_start"}
+	ok := FormatClaudeResponseInfo(claudeResponse, nil, nil)
+	if ok {
+		t.Error("expected false for nil claudeInfo")
+	}
+}
+
+func TestFormatClaudeResponseInfo_ContentBlockDelta(t *testing.T) {
+	text := "hello"
+	claudeInfo := &ClaudeResponseInfo{
+		Usage:        &dto.Usage{},
+		ResponseText: strings.Builder{},
+	}
+	claudeResponse := &dto.ClaudeResponse{
+		Type: "content_block_delta",
+		Delta: &dto.ClaudeMediaMessage{
+			Text: &text,
+		},
+	}
+
+	ok := FormatClaudeResponseInfo(claudeResponse, nil, claudeInfo)
+	if !ok {
+		t.Fatal("expected true")
+	}
+	if claudeInfo.ResponseText.String() != "hello" {
+		t.Errorf("ResponseText = %q, want %q", claudeInfo.ResponseText.String(), "hello")
+	}
+}
+
+// TestEnrichMessageDeltaUsage 测试 message_delta 事件的 usage 补全逻辑
+// 这是修复 issue #2881 的核心逻辑：当上游（如 Bedrock）的 message_delta 缺少
+// input_tokens 和 cache 相关字段时，用 claudeInfo 中积累的数据补全
+func TestEnrichMessageDeltaUsage(t *testing.T) {
+	tests := []struct {
+		name          string
+		claudeInfo    *ClaudeResponseInfo
+		deltaUsage    *dto.ClaudeUsage
+		wantInput     int
+		wantCacheRead int
+		wantCacheCreate int
+		wantOutput    int
+		want5m        int
+		want1h        int
+	}{
+		{
+			name: "Bedrock: delta 只有 output_tokens，从 claudeInfo 补全其他字段",
+			claudeInfo: &ClaudeResponseInfo{
+				Usage: &dto.Usage{
+					PromptTokens: 100,
+					PromptTokensDetails: dto.InputTokenDetails{
+						CachedTokens:         30,
+						CachedCreationTokens: 50,
+					},
+					ClaudeCacheCreation5mTokens: 10,
+					ClaudeCacheCreation1hTokens: 20,
+				},
+			},
+			deltaUsage:      &dto.ClaudeUsage{OutputTokens: 200},
+			wantInput:       100,
+			wantCacheRead:   30,
+			wantCacheCreate: 50,
+			wantOutput:      200,
+			want5m:          10,
+			want1h:          20,
+		},
+		{
+			name: "原生 Anthropic: delta 已包含所有字段，不覆盖",
+			claudeInfo: &ClaudeResponseInfo{
+				Usage: &dto.Usage{
+					PromptTokens: 100,
+					PromptTokensDetails: dto.InputTokenDetails{
+						CachedTokens:         30,
+						CachedCreationTokens: 50,
+					},
+				},
+			},
+			deltaUsage: &dto.ClaudeUsage{
+				InputTokens:              100,
+				OutputTokens:             200,
+				CacheReadInputTokens:     30,
+				CacheCreationInputTokens: 50,
+			},
+			wantInput:       100,
+			wantCacheRead:   30,
+			wantCacheCreate: 50,
+			wantOutput:      200,
+		},
+		{
+			name: "delta usage 为 nil，创建并补全",
+			claudeInfo: &ClaudeResponseInfo{
+				Usage: &dto.Usage{
+					PromptTokens: 80,
+					PromptTokensDetails: dto.InputTokenDetails{
+						CachedTokens:         20,
+						CachedCreationTokens: 40,
+					},
+				},
+			},
+			deltaUsage:      nil,
+			wantInput:       80,
+			wantCacheRead:   20,
+			wantCacheCreate: 40,
+			wantOutput:      0,
+		},
+		{
+			name: "没有 cache 数据，不补全",
+			claudeInfo: &ClaudeResponseInfo{
+				Usage: &dto.Usage{
+					PromptTokens: 100,
+				},
+			},
+			deltaUsage:      &dto.ClaudeUsage{OutputTokens: 50},
+			wantInput:       100,
+			wantCacheRead:   0,
+			wantCacheCreate: 0,
+			wantOutput:      50,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			claudeResponse := &dto.ClaudeResponse{
+				Type:  "message_delta",
+				Usage: tt.deltaUsage,
+			}
+
+			// 模拟 HandleStreamResponseData 中 Claude 格式的补全逻辑
+			enrichMessageDeltaUsage(claudeResponse, tt.claudeInfo)
+
+			if claudeResponse.Usage == nil {
+				t.Fatal("Usage should not be nil after enrichment")
+			}
+			if claudeResponse.Usage.InputTokens != tt.wantInput {
+				t.Errorf("InputTokens = %d, want %d", claudeResponse.Usage.InputTokens, tt.wantInput)
+			}
+			if claudeResponse.Usage.CacheReadInputTokens != tt.wantCacheRead {
+				t.Errorf("CacheReadInputTokens = %d, want %d", claudeResponse.Usage.CacheReadInputTokens, tt.wantCacheRead)
+			}
+			if claudeResponse.Usage.CacheCreationInputTokens != tt.wantCacheCreate {
+				t.Errorf("CacheCreationInputTokens = %d, want %d", claudeResponse.Usage.CacheCreationInputTokens, tt.wantCacheCreate)
+			}
+			if claudeResponse.Usage.OutputTokens != tt.wantOutput {
+				t.Errorf("OutputTokens = %d, want %d", claudeResponse.Usage.OutputTokens, tt.wantOutput)
+			}
+			if tt.want5m > 0 || tt.want1h > 0 {
+				if claudeResponse.Usage.CacheCreation == nil {
+					t.Fatal("CacheCreation should not be nil")
+				}
+				if claudeResponse.Usage.CacheCreation.Ephemeral5mInputTokens != tt.want5m {
+					t.Errorf("Ephemeral5mInputTokens = %d, want %d", claudeResponse.Usage.CacheCreation.Ephemeral5mInputTokens, tt.want5m)
+				}
+				if claudeResponse.Usage.CacheCreation.Ephemeral1hInputTokens != tt.want1h {
+					t.Errorf("Ephemeral1hInputTokens = %d, want %d", claudeResponse.Usage.CacheCreation.Ephemeral1hInputTokens, tt.want1h)
+				}
+			}
+		})
+	}
+}