Roadmap for Gemini 3 support + fix for “mandatory thought signature” tool-calling errors (gemini-3-pro-preview)

[fabio-lpd]

Hi Strands team 👋

First: awesome work on the SDK — we’re using Strands in production-style agent workflows and want to standardize on Gemini 3 for some workloads.

What I’m trying to do

Use the Gemini provider with:

• model_id="gemini-3-pro-preview"
• Tool calling enabled (regular Strands tools / function calling)

Current behavior

After the model performs a tool call, the next request fails with:

• google.genai.errors.ClientError: 400 Bad Request
• status: INVALID_ARGUMENT

This appears tied to Gemini 3’s requirement to pass back the “thought signature” (sometimes described as a mandatory signature) exactly as received when continuing the conversation after a tool call.

Related bug report:

• [BUG] INVALID_ARGUMENT using gemini-3-pro-preview [BUG] INVALID_ARGUMENT using gemini-3-pro-preview #1199

Expected behavior

Tool calling should work on Gemini 3 models the same way it works on Gemini 2.x / 2.5.x models (or at least fail with a clearer, actionable error + workaround).

Questions (roadmap + implementation)

1. Is Gemini 3 officially supported / planned?

   • If yes: what’s the target version/milestone?

2. Will Strands handle “thought signature” propagation automatically for Gemini 3 tool-calling flows?

   • e.g., persist and return the signature fields from model responses in the next request payloads.

3. If there’s a recommended workaround today (flags, provider settings, disabling a feature, etc.), could you share a minimal example?

4. Would you accept a PR if someone implements the signature propagation?

   • If yes: any pointers to the best place in the provider code where this should live?

Minimal repro (pseudo)

from strands import Agent
from strands.models.gemini import GeminiModel

model = GeminiModel(model_id="gemini-3-pro-preview")
agent = Agent(model=model, tools=[...])

agent("Do something that triggers a tool call")
# Next continuation after tool result → INVALID_ARGUMENT
Happy to provide:

a full runnable repro repo

debug logs / request traces (with secrets removed)

Thanks in advance — Gemini 3 support would be a huge unlock for teams standardizing on Google’s latest models.