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fix: preserve thought_signature in functionCall roundtrip to fix multi-turn tool use #27

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fix: preserve thought_signature in functionCall roundtrip to fix multi-turn tool use #27

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44735ec
fix: preserve thought_signature in tool call serialization roundtrip
May 5, 2026
f5c32f0
fix: preserve empty-string thought_signature and remove dead code fro…
May 5, 2026
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37 changes: 28 additions & 9 deletions amplifier_module_provider_gemini/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -966,6 +966,14 @@ def _convert_to_chat_response(self, response) -> GeminiChatResponse:
fc = part.function_call
tool_call_id = self._generate_tool_call_id()

# Preserve thought_signature if Gemini returned one. The API
# requires it to be re-submitted verbatim in subsequent turns
# (inside the functionCall part of the model-role content);
# omitting it causes INVALID_ARGUMENT on the second tool-using
# turn. Both ToolCallBlock and ToolCall carry
# extra="allow" so the field survives model_dump() round-trips.
thought_signature = getattr(fc, "thought_signature", None)

# Create ToolCallBlock
content_blocks.append(
ToolCallBlock(
Expand All @@ -978,8 +986,16 @@ def _convert_to_chat_response(self, response) -> GeminiChatResponse:
# Create ToolCall for tool_calls list
from amplifier_core.message_models import ToolCall as TCModel

tc_extra: dict[str, Any] = {}
if thought_signature is not None:
tc_extra["thought_signature"] = thought_signature
tool_calls.append(
TCModel(id=tool_call_id, name=fc.name, arguments=dict(fc.args))
TCModel(
id=tool_call_id,
name=fc.name,
arguments=dict(fc.args),
**tc_extra,
)
)
event_blocks.append(
ToolCallContent(
Expand Down Expand Up @@ -1123,14 +1139,17 @@ def _convert_messages(
# Extract name - handle both old format (tool) and new format (name)
tool_name = tc.get("name") or tc.get("tool", "")

parts.append(
{
"function_call": {
"name": tool_name,
"args": tc.get("arguments", {}),
}
}
)
fc_part: dict[str, Any] = {
"name": tool_name,
"args": tc.get("arguments", {}),
}
# Re-attach thought_signature when present so Gemini does
# not reject the request with INVALID_ARGUMENT on the
# second (and subsequent) tool-using turns.
thought_sig = tc.get("thought_signature")
if thought_sig is not None:
fc_part["thought_signature"] = thought_sig
parts.append({"function_call": fc_part})

gemini_contents.append({"role": gemini_role, "parts": parts})

Expand Down
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