Merge 91789da296 into 9c05c158cb

litellm/litellm_core_utils/prompt_templates/factory.py

@@ -1,4 +1,5 @@
 import base64
+import binascii
 import copy
 import hashlib
 import json
@@ -65,6 +66,7 @@ BAD_MESSAGE_ERROR_STR: Final = "Invalid Message "
 # Separator used to embed Gemini thought signatures in tool call IDs
 # See: https://ai.google.dev/gemini-api/docs/thought-signatures
 THOUGHT_SIGNATURE_SEPARATOR: Final = "__thought__"
+THOUGHT_SIGNATURE_CHECKSUM_SEPARATOR: Final = "__checksum__"
 
 # used to interweave user messages, to ensure user/assistant alternating
 DEFAULT_USER_CONTINUE_MESSAGE: Final = {
@@ -1133,7 +1135,7 @@ def _gemini_tool_call_invoke_helper(
         args=arguments_dict,
     )
     if tool_call_id:
-        clean_id: Final = tool_call_id.split(THOUGHT_SIGNATURE_SEPARATOR, 1)[0]
+        clean_id, _ = _decode_tool_call_id_with_signature(tool_call_id)
         if clean_id:
             function_call["id"] = clean_id
     return function_call
@@ -1149,15 +1151,48 @@ def _encode_tool_call_id_with_signature(tool_call_id: str, thought_signature: st
 
     Returns:
         Tool call ID with embedded signature if present, otherwise original ID
-        Format: call_<uuid>__thought__<base64_signature>
+        Format: call_<uuid>__checksum__<sha256>__thought__<base64_signature>
 
     See: https://ai.google.dev/gemini-api/docs/thought-signatures
     """
     if thought_signature:
-        return f"{tool_call_id}{THOUGHT_SIGNATURE_SEPARATOR}{thought_signature}"
+        checksum: Final = hashlib.sha256(thought_signature.encode("utf-8")).hexdigest()
+        return (
+            f"{tool_call_id}{THOUGHT_SIGNATURE_CHECKSUM_SEPARATOR}{checksum}"
+            f"{THOUGHT_SIGNATURE_SEPARATOR}{thought_signature}"
+        )
     return tool_call_id
 
 
+def _is_valid_thought_signature(signature: str) -> bool:
+    """Check strict standard-alphabet base64 while allowing omitted padding."""
+    if not signature:
+        return False
+    try:
+        padding = "=" * (-len(signature) % 4)
+        base64.b64decode(signature + padding, validate=True)
+    except (binascii.Error, ValueError):
+        return False
+    return True
+
+
+def _decode_tool_call_id_with_signature(tool_call_id: str) -> tuple[str, str | None]:
+    payload, signature_separator, signature = tool_call_id.partition(THOUGHT_SIGNATURE_SEPARATOR)
+    if not signature_separator:
+        return tool_call_id, None
+
+    base_id, checksum_separator, checksum = payload.rpartition(THOUGHT_SIGNATURE_CHECKSUM_SEPARATOR)
+    if not checksum_separator:
+        return payload, None
+    if not _is_valid_thought_signature(signature):
+        return base_id, None
+
+    expected_checksum: Final = hashlib.sha256(signature.encode("utf-8")).hexdigest()
+    if checksum != expected_checksum:
+        return base_id, None
+    return base_id, signature
+
+
 def _get_thought_signature_from_tool(tool: dict) -> str | None:
     """Extract thought signature from tool call's provider_specific_fields.
 
@@ -1190,11 +1225,9 @@ def _get_thought_signature_from_tool(tool: dict) -> str | None:
                     return signature
     # Check if thought signature is embedded in tool call ID
     tool_call_id: Final = tool.get("id")
-    if tool_call_id and THOUGHT_SIGNATURE_SEPARATOR in tool_call_id:
-        parts: Final = tool_call_id.split(THOUGHT_SIGNATURE_SEPARATOR, 1)
-        if len(parts) == 2:
-            _, signature = parts
-            return signature
+    if tool_call_id and isinstance(tool_call_id, str):
+        _, signature = _decode_tool_call_id_with_signature(tool_call_id)
+        return signature
     return None
 
 
@@ -1453,7 +1486,7 @@ def convert_to_gemini_tool_call_result(
     if forward_function_call_id:
         raw_tool_call_id: Final = message.get("tool_call_id")
         if raw_tool_call_id and isinstance(raw_tool_call_id, str):
-            stripped_id: Final = raw_tool_call_id.split(THOUGHT_SIGNATURE_SEPARATOR, 1)[0]
+            stripped_id, _ = _decode_tool_call_id_with_signature(raw_tool_call_id)
             if stripped_id:
                 gemini_call_id = stripped_id
 

tests/test_litellm/llms/vertex_ai/gemini/test_thought_signature_in_tool_call_id.py

@@ -9,13 +9,19 @@ Note: Embedding signatures in tool call IDs is a beta feature that requires
 enable_preview_features=True to be enabled.
 """
 
+import base64
+
 import pytest
 
 import litellm
 from litellm.litellm_core_utils.prompt_templates.factory import (
+    THOUGHT_SIGNATURE_CHECKSUM_SEPARATOR,
     THOUGHT_SIGNATURE_SEPARATOR,
+    _decode_tool_call_id_with_signature,
     _encode_tool_call_id_with_signature,
+    _get_dummy_thought_signature,
     _get_thought_signature_from_tool,
+    _is_valid_thought_signature,
     convert_to_gemini_tool_call_invoke,
 )
 from litellm.llms.vertex_ai.gemini.vertex_and_google_ai_studio_gemini import (
@@ -32,6 +38,7 @@ def test_encode_decode_tool_call_id_with_signature():
     # Test encoding
     encoded_id = _encode_tool_call_id_with_signature(base_id, test_signature)
     assert THOUGHT_SIGNATURE_SEPARATOR in encoded_id
+    assert THOUGHT_SIGNATURE_CHECKSUM_SEPARATOR in encoded_id
     assert encoded_id.startswith(base_id)
 
     # Test decoding using factory function with realistic tool call structure
@@ -48,7 +55,7 @@ def test_encode_decode_tool_call_id_with_signature():
     assert extracted_signature == test_signature
 
     # Verify base ID is preserved
-    decoded_base_id = encoded_id.split(THOUGHT_SIGNATURE_SEPARATOR)[0]
+    decoded_base_id, _ = _decode_tool_call_id_with_signature(encoded_id)
     assert decoded_base_id == base_id
 
 
@@ -94,10 +101,7 @@ def test_tool_call_id_includes_signature_in_response(enable_preview_features):
     tool_call_id = tools[0]["id"]
 
     # Verify signature is always in provider_specific_fields
-    assert (
-        tools[0].get("provider_specific_fields", {}).get("thought_signature")
-        == test_signature
-    )
+    assert tools[0].get("provider_specific_fields", {}).get("thought_signature") == test_signature
 
     # When preview features enabled, signature should be embedded in ID
     assert THOUGHT_SIGNATURE_SEPARATOR in tool_call_id
@@ -234,9 +238,7 @@ def test_openai_client_e2e_flow(enable_preview_features):
         ],
     }
     # Step 4: LiteLLM converts back to Gemini format, extracting signature
-    gemini_parts_converted = convert_to_gemini_tool_call_invoke(
-        openai_assistant_message
-    )
+    gemini_parts_converted = convert_to_gemini_tool_call_invoke(openai_assistant_message)
 
     # Verify signature is preserved through the round trip
     assert len(gemini_parts_converted) == 1
@@ -247,7 +249,7 @@ def test_openai_client_e2e_flow(enable_preview_features):
 @pytest.mark.parametrize("enable_preview_features", [True, False])
 def test_parallel_tool_calls_with_signatures(enable_preview_features):
     """Test that parallel tool calls preserve signatures correctly"""
-    signature1 = "signature_for_first_call"
+    signature1 = base64.b64encode(b"signature_for_first_call").decode("ascii")
     # Only first call has signature (Gemini behavior for parallel calls)
 
     gemini_parts = [
@@ -271,10 +273,7 @@ def test_parallel_tool_calls_with_signatures(enable_preview_features):
     assert len(tools) == 2
 
     # First tool call should have signature in provider_specific_fields
-    assert (
-        tools[0].get("provider_specific_fields", {}).get("thought_signature")
-        == signature1
-    )
+    assert tools[0].get("provider_specific_fields", {}).get("thought_signature") == signature1
 
     # When preview features enabled, first tool call has signature in ID
     assert THOUGHT_SIGNATURE_SEPARATOR in tools[0]["id"]
@@ -285,3 +284,131 @@ def test_parallel_tool_calls_with_signatures(enable_preview_features):
     assert THOUGHT_SIGNATURE_SEPARATOR not in tools[1]["id"]
     sig2 = _get_thought_signature_from_tool({"id": tools[1]["id"], "type": "function"})
     assert sig2 is None
+
+
+REAL_SIGNATURE = (
+    "Co4CAdHtim/rWgXbz2Ghp4tShzLeMASrPw6JJyYIC3cbVyZnKzU3uv8/wVzyS2sKRPL2m8QQHHXbNQhEEz500G7n/4ZMmksdT"
+    "tfQcJMoT76S1DGwhnAiLwTgWCNXs3lEb4M19EVYoWFxhrH5Lr9YMIquoU9U4paydGwvZyIyigamIg4B6WnxrRsf0KZV12gJed"
+    "0DZuKczvOFtHz3zUnmZRlOiTzd5gBVyQM+5jv1VI8m4WUKd6cN/5a5ZvaA0ggiO6kdVhlpIVs7GczSEVJD8KH4u02X7VSnb7C"
+    "vykqDntZzV0y8rZFBEFGKrChmeHlWXP4D1IB3F9KQyhuLgWImMzg4BajKVxxMU737JGnNISy5"
+)
+
+
+@pytest.mark.parametrize(
+    "mangled_signature",
+    [
+        "AY89a1/_57b05e78dc",
+        "AY89a1/_ee781c9832",
+        "AY89a1_S3YvIpUCcBTFSgDfesRLDnA_775ff49bcd",
+    ],
+)
+def test_is_valid_thought_signature_rejects_client_normalized_values(mangled_signature):
+    assert _is_valid_thought_signature(REAL_SIGNATURE) is True
+    assert _is_valid_thought_signature(mangled_signature) is False
+
+
+def test_is_valid_thought_signature_tolerates_missing_padding():
+    encoded = base64.b64encode(b"hello").decode("ascii").rstrip("=")
+    assert "=" not in encoded
+    assert _is_valid_thought_signature(encoded) is True
+
+
+def test_get_thought_signature_rejects_decodable_tampering():
+    encoded_id = _encode_tool_call_id_with_signature("call_abc123", REAL_SIGNATURE)
+    checksum = encoded_id.split(THOUGHT_SIGNATURE_CHECKSUM_SEPARATOR, 1)[1].split(THOUGHT_SIGNATURE_SEPARATOR, 1)[0]
+    decodable_but_wrong = base64.b64encode(b"not-the-real-signature").decode("ascii")
+    tampered_id = (
+        f"call_abc123{THOUGHT_SIGNATURE_CHECKSUM_SEPARATOR}{checksum}{THOUGHT_SIGNATURE_SEPARATOR}{decodable_but_wrong}"
+    )
+
+    assert _is_valid_thought_signature(decodable_but_wrong) is True
+    assert _get_thought_signature_from_tool({"id": tampered_id, "type": "function"}) is None
+
+
+def test_get_thought_signature_rejects_unsigned_embedded_signature():
+    unsigned_id = f"call_abc123{THOUGHT_SIGNATURE_SEPARATOR}{REAL_SIGNATURE}"
+
+    assert _get_thought_signature_from_tool({"id": unsigned_id, "type": "function"}) is None
+
+
+def test_get_thought_signature_drops_client_mangled_id_suffix():
+    """When the segment after ``__thought__`` isn't valid base64, the extractor
+    must return ``None`` so the caller can either fall back to the dummy
+    skip-validator signature (Gemini 3+) or drop the signature entirely
+    (Gemini 2.x), instead of forwarding a corrupted value that Vertex would
+    reject. Regression test for issue #37849."""
+    mangled_id = _encode_tool_call_id_with_signature("call_2156408", "AY89a1/_57b05e78dc")
+    tool = {"id": mangled_id, "type": "function"}
+
+    assert _get_thought_signature_from_tool(tool) is None
+
+
+def test_get_thought_signature_still_prefers_provider_fields_even_when_id_mangled():
+    """A valid signature in ``provider_specific_fields`` must win over the
+    mangled tail so we don't downgrade a good signal."""
+    mangled_id = f"call_abc{THOUGHT_SIGNATURE_SEPARATOR}not_base64!!"
+    tool = {
+        "id": mangled_id,
+        "type": "function",
+        "function": {"name": "get_temperature", "arguments": '{"location": "Paris"}'},
+        "provider_specific_fields": {"thought_signature": REAL_SIGNATURE},
+    }
+
+    assert _get_thought_signature_from_tool(tool) == REAL_SIGNATURE
+
+
+def test_convert_to_gemini_uses_dummy_signature_when_client_mangles_id_on_gemini_3():
+    """On Gemini 3+ a mangled id must degrade to the documented skip-validator
+    dummy signature rather than forwarding the corrupted bytes."""
+    mangled_id = f"call_2156408{THOUGHT_SIGNATURE_SEPARATOR}AY89a1/_57b05e78dc"
+    assistant_message = {
+        "role": "assistant",
+        "content": None,
+        "tool_calls": [
+            {
+                "id": mangled_id,
+                "type": "function",
+                "function": {
+                    "name": "get_temperature",
+                    "arguments": '{"location": "Paris"}',
+                },
+            }
+        ],
+    }
+
+    parts = convert_to_gemini_tool_call_invoke(
+        assistant_message,
+        model="vertex_ai/gemini-3.1-pro-preview",
+    )
+
+    assert len(parts) == 1
+    assert parts[0].get("thoughtSignature") == _get_dummy_thought_signature()
+
+
+def test_convert_to_gemini_drops_signature_when_client_mangles_id_on_gemini_2():
+    """On older Gemini models the placeholder fallback doesn't apply, so a
+    mangled id must simply drop the signature (rather than forward a value
+    Vertex will 400 on)."""
+    mangled_id = f"call_2158562{THOUGHT_SIGNATURE_SEPARATOR}AY89a1/_ee781c9832"
+    assistant_message = {
+        "role": "assistant",
+        "content": None,
+        "tool_calls": [
+            {
+                "id": mangled_id,
+                "type": "function",
+                "function": {
+                    "name": "get_temperature",
+                    "arguments": '{"location": "Paris"}',
+                },
+            }
+        ],
+    }
+
+    parts = convert_to_gemini_tool_call_invoke(
+        assistant_message,
+        model="vertex_ai/gemini-2.5-pro",
+    )
+
+    assert len(parts) == 1
+    assert "thoughtSignature" not in parts[0]