fromResponseParts drops metadata when converting tool-call/tool-result parts #5954
Description
What version of Effect is running?
3.19.13
What steps can reproduce the bug?
Prompt.fromResponseParts doesn't copy metadata to options when converting Response.ToolCallPart and Response.ToolResultPart to prompt parts. This breaks Google's Gemini API which requires thoughtSignature (stored in metadata.google.thoughtSignature) to be present in follow-up requests for multi-turn tool calls.
To reproduce this, set up a multi-tool flow with Google as the provider, you will get back the following error:
{
\"module\": \"GoogleClient\",
\"method\": \"streamRequest\",
\"request\": {
\"method\": \"POST\",
\"url\": \"https://generativelanguage.googleapis.com/v1beta/models/gemini-3-flash-preview:streamGenerateContent\",
\"urlParams\": [
[
\"alt\",
\"sse\"
]
],
\"hash\": {
\"_id\": \"Option\",
\"_tag\": \"None\"
},
\"headers\": {
\"content-type\": \"application/json\",
\"content-length\": \"22010\",
\"x-goog-api-key\": \"AIzaSyDUyvTLlvd6mo8UwiYRUa-ApXHSkidRwLY\",
\"accept\": \"application/json\",
\"b3\": \"7ce22b39ac3e31687aa623f0ed43f558-09babdb4c653ccec-1-eb23f7e393f687bd\",
\"traceparent\": \"00-7ce22b39ac3e31687aa623f0ed43f558-09babdb4c653ccec-01\"
}
},
\"response\": {
\"status\": 400,
\"headers\": {
\"alt-svc\": \"h3=\":443\"; ma=2592000,h3-29=\":443\"; ma=2592000\",
\"content-length\": \"435\",
\"content-type\": \"text/event-stream\",
\"date\": \"Tue, 06 Jan 2026 18:32:33 GMT\",
\"server\": \"scaffolding on HTTPServer2\",
\"server-timing\": \"gfet4t7; dur=153\",
\"vary\": \"Origin, X-Origin, Referer\",
\"x-content-type-options\": \"nosniff\",
\"x-frame-options\": \"SAMEORIGIN\",
\"x-xss-protection\": \"0\"
}
},
\"body\": \"\"{\\n \\\"error\\\": {\\n \\\"code\\\": 400,\\n \\\"message\\\": \\\"Function call is missing a thought_signature in functionCall parts. This is required for tools to work correctly, and missing thought_signature may lead to degraded model performance. Additional data, function call `default_api:vectorQuery` , position 2. Please refer to https://ai.google.dev/gemini-api/docs/thought-signatures for more details.\\\",\\n \\\"status\\\": \\\"INVALID_ARGUMENT\\\"\\n }\\n}\\n\"\",
\"reason\": \"StatusCode\",
\"description\": \"non 2xx status code\",
\"_tag\": \"HttpResponseError\",
\"~@effect/ai/AiError\": \"~@effect/ai/AiError\"
}```
### What is the expected behavior?
_No response_
### What do you see instead?
_No response_
### Additional information
_No response_