diff --git a/plugins/wasm-go/extensions/ai-proxy/provider/bedrock_thinking_test.go b/plugins/wasm-go/extensions/ai-proxy/provider/bedrock_thinking_test.go
index a9504ed06..c72813bef 100644
--- a/plugins/wasm-go/extensions/ai-proxy/provider/bedrock_thinking_test.go
+++ b/plugins/wasm-go/extensions/ai-proxy/provider/bedrock_thinking_test.go
@@ -115,6 +115,28 @@ func TestBedrockStreamPreservesClaudeNativeIndexesAndStops(t *testing.T) {
 	assert.Equal(t, 2, *events[0].Payload.Index)
 }
 
+func TestBedrockStreamToolCallArgumentDeltaIncludesFunctionType(t *testing.T) {
+	provider := &bedrockProvider{}
+	ctx := newMockMultipartHttpContext()
+
+	chunk, err := provider.convertEventFromBedrockToOpenAI(ctx, ConverseStreamEvent{
+		ContentBlockIndex: 0,
+		Delta: &converseStreamEventContentBlockDelta{
+			ToolUse: &toolUseBlockDelta{Input: `{"path":"/tmp/example"}`},
+		},
+	})
+	require.NoError(t, err)
+
+	body := strings.TrimPrefix(strings.TrimSpace(string(chunk)), ssePrefix)
+	var event chatCompletionResponse
+	require.NoError(t, json.Unmarshal([]byte(body), &event))
+	require.Len(t, event.Choices, 1)
+	require.NotNil(t, event.Choices[0].Delta)
+	require.Len(t, event.Choices[0].Delta.ToolCalls, 1)
+	assert.Equal(t, "function", event.Choices[0].Delta.ToolCalls[0].Type)
+	assert.Equal(t, `{"path":"/tmp/example"}`, event.Choices[0].Delta.ToolCalls[0].Function.Arguments)
+}
+
 func TestBedrockResponsePreservesClaudeNativeRedactedThinking(t *testing.T) {
 	provider := &bedrockProvider{}
 	ctx := newMockMultipartHttpContext()
diff --git a/plugins/wasm-go/extensions/ai-proxy/provider/claude.go b/plugins/wasm-go/extensions/ai-proxy/provider/claude.go
index b79f56b83..7842feb2a 100644
--- a/plugins/wasm-go/extensions/ai-proxy/provider/claude.go
+++ b/plugins/wasm-go/extensions/ai-proxy/provider/claude.go
@@ -925,6 +925,7 @@ func (c *claudeProvider) streamResponseClaude2OpenAI(ctx wrapper.HttpContext, or
 					ToolCalls: []toolCall{
 						{
 							Index: index,
+							Type:  "function",
 							Function: functionCall{
 								Arguments: origResponse.Delta.PartialJson,
 							},
diff --git a/plugins/wasm-go/extensions/ai-proxy/provider/claude_test.go b/plugins/wasm-go/extensions/ai-proxy/provider/claude_test.go
index d1ec356e4..d02ee166c 100644
--- a/plugins/wasm-go/extensions/ai-proxy/provider/claude_test.go
+++ b/plugins/wasm-go/extensions/ai-proxy/provider/claude_test.go
@@ -443,6 +443,28 @@ func TestClaudeProvider_StreamPreservesNativeSignatureAndStopsForClaudeConversio
 	assert.Equal(t, "content_block_stop", events[0].Name)
 }
 
+func TestClaudeProvider_StreamToolCallArgumentDeltaIncludesFunctionType(t *testing.T) {
+	provider := &claudeProvider{}
+	ctx := newMockMultipartHttpContext()
+	index := 0
+
+	response := provider.streamResponseClaude2OpenAI(ctx, &claudeTextGenStreamResponse{
+		Type:  "content_block_delta",
+		Index: &index,
+		Delta: &claudeTextGenDelta{
+			Type:        "input_json_delta",
+			PartialJson: `{"path":"/tmp/example"}`,
+		},
+	})
+
+	require.NotNil(t, response)
+	require.Len(t, response.Choices, 1)
+	require.NotNil(t, response.Choices[0].Delta)
+	require.Len(t, response.Choices[0].Delta.ToolCalls, 1)
+	assert.Equal(t, "function", response.Choices[0].Delta.ToolCalls[0].Type)
+	assert.Equal(t, `{"path":"/tmp/example"}`, response.Choices[0].Delta.ToolCalls[0].Function.Arguments)
+}
+
 func TestClaudeProvider_BuildClaudeTextGenRequest_ClaudeCodeMode(t *testing.T) {
 	provider := &claudeProvider{
 		config: ProviderConfig{