VS Code extension: "NO MODELS AVAILABLE" when opening historical sessions with custom ANTHROPIC_BASE_URL

Description

When using Claude Code with a custom ANTHROPIC_BASE_URL (pointing to a third-party API) and modelOverrides, the VS Code extension fails to resolve the model when opening a historical session from the SESSIONS sidebar.

Steps to reproduce

1. Configure ~/.claude/settings.json with a custom API base URL and model overrides:

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://api.deepseek.com/anthropic",
    "ANTHROPIC_MODEL": "claude-sonnet-4-6"
  },
  "modelOverrides": {
    "claude-sonnet-4-6": "deepseek-v4-pro",
    "claude-haiku-4-5": "deepseek-v4-flash"
  }
}

1. Open VS Code, start a new Claude Code session — the model bar correctly shows the custom model (e.g. "DEEPSEEK"), chat works fine
2. Click on any historical session in the SESSIONS sidebar

Actual behavior

• Model bar changes to "NO MODELS AVAILABLE"
• Chat input box becomes disabled, making the session unusable

Expected behavior

• Historical sessions should inherit the current model/provider configuration from settings.json
• Model bar should show the configured model and chat input should remain functional

Workaround

Using the CLI directly works correctly — the issue only affects the extension SESSIONS sidebar UI:

claude --resume <session-id>
claude --continue

Environment

• OS: Windows 11
• Extension version: anthropic.claude-code 2.1.227
• Configuration: custom ANTHROPIC_BASE_URL + modelOverrides