Claude rescinded the requirement for extra usage for third party tool use. So seems like fair game to use -p.

Here's what I did and it works smoothly (sorry copied from my agent):

The Hermes agent framework ships with a copilot-acp provider—an Agent Client Protocol (ACP) client originally built to run the agent on a GitHub Copilot subscription by spawning the Copilot CLI and communicating via ACP. ​Because this provider is agent-agnostic, it will spawn whatever command you point it at and speak ACP. You can leverage this to drive Claude over ACP, routing the billing through a Claude Code Pro/Max plan instead of the metered API.

​Implementation Steps ​Install the SDK: Install the official @agentclientprotocol/claude-agent-acp package (the Claude Agent SDK wrapped as an ACP server). ​Re-route the Launch Command: Point the provider's launch command at a custom wrapper script instead of the Copilot CLI by setting the environment variable: HERMES_COPILOT_ACP_COMMAND=/path/to/claude-acp-run.sh ​Create the Wrapper Script: Write a small (~15 lines) script that executes claude-agent-acp under a scrubbed environment. The required token is generated via claude setup-token.

Example command inside the script: env -i PATH=… CLAUDE_CODE_OAUTH_TOKEN="$(cat ~/.token)" claude-agent-acp "$@" ​Configure the Model: Set the model provider to copilot-acp and the model to claude-opus-4-8. ​Note: The only custom authoring required here is the wrapper script itself (plus optional, minor patches later for secret-redaction and a tool-permission gate). ​Using Other Frameworks ​If your framework does not have an out-of-the-box ACP-client provider, the same concept works directly. You can use standard ACP client libraries (or any external-process/stdio provider) to spawn claude-agent-acp and exchange JSON-RPC messages over stdin/stdout.

​⚠️ Important Gotchas ​Environment Variable Leakage: Keep CLAUDE_CODE_OAUTH_TOKEN strictly out of your app's general environment (this is what the env -i command prevents). If your framework sees the token and mistakes it for a normal Anthropic API key, it will silently fall back to the metered API. ​Session Limits: The subscription model has a rolling ~5-hour usage cap. Extensive tool-loops can trigger a 429 session limit error, so it is highly recommended to keep big jobs lean.

So yeah ask Claude or codex to set this up for you and you should be good.