diff --git a/litellm/litellm_core_utils/streaming_chunk_builder_utils.py b/litellm/litellm_core_utils/streaming_chunk_builder_utils.py
index 53252df0a28..76c7246b87e 100644
--- a/litellm/litellm_core_utils/streaming_chunk_builder_utils.py
+++ b/litellm/litellm_core_utils/streaming_chunk_builder_utils.py
@@ -1,6 +1,6 @@
 import base64
 import time
-from typing import TYPE_CHECKING, Any, Dict, List, Literal, Optional, Union, cast
+from typing import TYPE_CHECKING, Any, Dict, List, Optional, Union, cast
 
 from litellm.types.llms.openai import (
     ChatCompletionAssistantContentValue,
@@ -326,10 +326,22 @@ class ChunkProcessor:
         thinking_blocks: List[
             Union["ChatCompletionThinkingBlock", "ChatCompletionRedactedThinkingBlock"]
         ] = []
-        combined_thinking_text: Optional[str] = None
-        data: Optional[str] = None
-        signature: Optional[str] = None
-        type: Literal["thinking", "redacted_thinking"] = "thinking"
+        current_thinking_text_parts: List[str] = []
+        current_signature: Optional[str] = None
+
+        def _flush_thinking_block() -> None:
+            nonlocal current_thinking_text_parts, current_signature
+            if len(current_thinking_text_parts) > 0 and current_signature:
+                thinking_blocks.append(
+                    ChatCompletionThinkingBlock(
+                        type="thinking",
+                        thinking="".join(current_thinking_text_parts),
+                        signature=current_signature,
+                    )
+                )
+            current_thinking_text_parts = []
+            current_signature = None
+
         for chunk in chunks:
             choices = chunk["choices"]
             for choice in choices:
@@ -339,33 +351,25 @@ class ChunkProcessor:
                     for thinking_block in thinking:
                         thinking_type = thinking_block.get("type", None)
                         if thinking_type and thinking_type == "redacted_thinking":
-                            type = "redacted_thinking"
-                            data = thinking_block.get("data", None)
+                            _flush_thinking_block()
+                            redacted_data = thinking_block.get("data", None)
+                            if redacted_data:
+                                thinking_blocks.append(
+                                    ChatCompletionRedactedThinkingBlock(
+                                        type="redacted_thinking",
+                                        data=redacted_data,
+                                    )
+                                )
                         else:
-                            type = "thinking"
                             thinking_text = thinking_block.get("thinking", None)
                             if thinking_text:
-                                if combined_thinking_text is None:
-                                    combined_thinking_text = ""
-
-                                combined_thinking_text += thinking_text
+                                current_thinking_text_parts.append(thinking_text)
                             signature = thinking_block.get("signature", None)
+                            if signature:
+                                current_signature = signature
+                                _flush_thinking_block()
 
-        if combined_thinking_text and type == "thinking" and signature:
-            thinking_blocks.append(
-                ChatCompletionThinkingBlock(
-                    type=type,
-                    thinking=combined_thinking_text,
-                    signature=signature,
-                )
-            )
-        elif data and type == "redacted_thinking":
-            thinking_blocks.append(
-                ChatCompletionRedactedThinkingBlock(
-                    type=type,
-                    data=data,
-                )
-            )
+        _flush_thinking_block()
 
         if len(thinking_blocks) > 0:
             return thinking_blocks
diff --git a/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_utils.py b/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_utils.py
index eef206ca667..34c9efd8382 100644
--- a/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_utils.py
+++ b/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_utils.py
@@ -158,6 +158,78 @@ def test_get_combined_tool_content():
     ]
 
 
+def test_get_combined_thinking_content_preserves_interleaved_blocks():
+    base_chunk = {
+        "id": "chatcmpl-123",
+        "object": "chat.completion.chunk",
+        "created": 1234567890,
+        "model": "claude-sonnet-4-20250514",
+    }
+
+    def make_chunk(**delta_kwargs):
+        return ModelResponseStream(
+            **{
+                **base_chunk,
+                "choices": [
+                    {
+                        "index": 0,
+                        "delta": delta_kwargs,
+                        "finish_reason": None,
+                    }
+                ],
+            }
+        )
+
+    chunks = [
+        make_chunk(role="assistant", content=None),
+        make_chunk(
+            thinking_blocks=[
+                {"type": "thinking", "thinking": "Step 1 analysis...", "signature": None}
+            ]
+        ),
+        make_chunk(
+            thinking_blocks=[
+                {"type": "thinking", "thinking": None, "signature": "sig_block1"}
+            ]
+        ),
+        make_chunk(
+            thinking_blocks=[
+                {
+                    "type": "redacted_thinking",
+                    "data": "EuoBCoYBGAIi...encrypted...",
+                }
+            ]
+        ),
+        make_chunk(
+            thinking_blocks=[
+                {"type": "thinking", "thinking": "Step 2 analysis...", "signature": None}
+            ]
+        ),
+        make_chunk(
+            thinking_blocks=[
+                {"type": "thinking", "thinking": None, "signature": "sig_block2"}
+            ]
+        ),
+    ]
+
+    thinking_chunks = [
+        chunk for chunk in chunks if chunk["choices"][0]["delta"].get("thinking_blocks")
+    ]
+    processor = ChunkProcessor(chunks=chunks)
+    result = processor.get_combined_thinking_content(thinking_chunks)
+
+    assert result is not None
+    assert len(result) == 3
+    assert result[0]["type"] == "thinking"
+    assert result[0]["thinking"] == "Step 1 analysis..."
+    assert result[0]["signature"] == "sig_block1"
+    assert result[1]["type"] == "redacted_thinking"
+    assert result[1]["data"] == "EuoBCoYBGAIi...encrypted..."
+    assert result[2]["type"] == "thinking"
+    assert result[2]["thinking"] == "Step 2 analysis..."
+    assert result[2]["signature"] == "sig_block2"
+
+
 def test_cache_read_input_tokens_retained():
     chunk1 = ModelResponseStream(
         id="chatcmpl-95aabb85-c39f-443d-ae96-0370c404d70c",
@@ -441,4 +513,4 @@ def test_stream_chunk_builder_anthropic_web_search():
     assert usage.prompt_tokens == 50
     assert usage.completion_tokens == 27
     assert usage.total_tokens == 77    
-    assert usage.server_tool_use['web_search_requests'] == 2
\ No newline at end of file
+    assert usage.server_tool_use['web_search_requests'] == 2