agent_version: latest causes 400 Bad Request with gemini-3-pro-preview model

Summary

Workflows compiled with gh-aw v0.57.2+ use agent_version: "latest" (via install_copilot_cli.sh latest). This causes a 400 Bad Request from the Copilot API when the workflow model is gemini-3-pro-preview. Other models (Claude Opus 4.6, GPT-5.2 Codex) work fine with latest.

Symptoms

The agent exits immediately (~11 seconds) with:

Execution failed: CAPIError: 400 400 Bad Request
 (Request ID: A000:2F4631:E470BB:FA2910:69B4285C)

Total usage est:        0 Premium requests
API time spent:         0s
Total session time:     11s
Total code changes:     +0 -0

No tool calls are made. Zero safe-outputs produced.

Repro

1. Compile any workflow with COPILOT_MODEL: gemini-3-pro-preview using gh-aw v0.57.2 or v0.58.0
2. The compiled lock file will contain:

   GH_AW_INFO_AGENT_VERSION: "latest"
   run: /opt/gh-aw/actions/install_copilot_cli.sh latest

3. Dispatch the workflow → immediate 400 failure

Workaround

Pinning agent_version to 0.0.420 fixes the issue:

GH_AW_INFO_AGENT_VERSION: "0.0.420"
run: /opt/gh-aw/actions/install_copilot_cli.sh 0.0.420

This was confirmed by running the same workflow from a branch with v0.53.x lock files (which pin to 0.0.420) — Gemini succeeds.

Evidence

Environment

• gh-aw extension: v0.58.0
• Firewall: v0.23.0