feat: add GitHub Copilot CLI as supported ACP backend

[Reese-max]

Summary

Add first-class support for GitHub Copilot CLI via its native --acp mode, following the same pattern as the existing Gemini integration.

Changes

File	Change	Description
Dockerfile.copilot	NEW	Runtime image with Copilot CLI installed via npm + gh CLI for auth
README.md	MOD	Add Copilot to backend table, Helm install example, manual config.toml example

How it works

OpenAB (Rust)
       │ stdio JSON-RPC (ACP protocol)
       ▼
  copilot --acp (native ACP server mode)
       │ Copilot SDK internal
       ▼
  GitHub Copilot service

No third-party adapter needed — Copilot CLI ships built-in ACP support.

Configuration

Helm

helm install openab openab/openab \
  --set agents.kiro.enabled=false \
  --set agents.copilot.discord.botToken="$DISCORD_BOT_TOKEN" \
  --set-string 'agents.copilot.discord.allowedChannels[0]=YOUR_CHANNEL_ID' \
  --set agents.copilot.image=ghcr.io/openabdev/openab-copilot:latest \
  --set agents.copilot.command=copilot \
  --set 'agents.copilot.args={--acp}' \
  --set agents.copilot.workingDir=/home/node

Manual config.toml

[agent]
command = "copilot"
args = ["--acp"]
working_dir = "/home/node"

Auth

# Inside the container or on the host
gh auth login          # GitHub OAuth
# or
copilot auth           # Copilot-specific auth

Tested capabilities

Feature	Status
Basic chat	✅
Model switching (8 models)	✅
Mode switching (agent/plan/autopilot)	✅
Tool execution	✅
usage_update notifications	✅
configOptions (filtered model list)	✅

[Copilot]

Pull request overview

Adds first-class support for running GitHub Copilot CLI as an ACP backend (via native copilot --acp), alongside the existing CLI backends.

Changes:

• Add a new runtime Docker image (Dockerfile.copilot) that bundles Copilot CLI + gh for authentication.
• Update README.md to list Copilot as a supported backend and document Helm/manual configuration examples.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
README.md	Documents Copilot as a supported ACP backend and adds Helm/manual config examples.
Dockerfile.copilot	Introduces a dedicated container image that installs Copilot CLI and gh and runs openab.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

In the manual config.toml examples, the Gemini block now ends right after args = ["--acp"], so working_dir / env are no longer shown for Gemini even though the following working_dir line appears intended for the Gemini example. This makes the sample config misleading; please keep Gemini’s working_dir (and env if needed) within the Gemini example block, and start the Copilot example as a separate, complete snippet.

Suggested change

	# GitHub Copilot (native ACP — requires copilot CLI in PATH)
	[agent]
	command = "copilot"
	args = ["--acp"]
	working_dir = "/home/node"
	env = { GEMINI_API_KEY = "${GEMINI_API_KEY}" }
	working_dir = "/home/node"
	env = { GEMINI_API_KEY = "${GEMINI_API_KEY}" }
	# GitHub Copilot (native ACP — requires copilot CLI in PATH)
	[agent]
	command = "copilot"
	args = ["--acp"]
	working_dir = "/home/node"

[Copilot]

The Copilot config.toml example includes env = { GEMINI_API_KEY = "${GEMINI_API_KEY}" }, which appears to be copied from the Gemini section and is unrelated to Copilot auth. This will confuse users and may lead to incorrect setups; remove it or replace it with Copilot-relevant environment/auth guidance.

Suggested change

env = { GEMINI_API_KEY = "${GEMINI_API_KEY}" }

[Copilot]

The image installs @githubnext/github-copilot-cli without a version pin, making builds non-reproducible and potentially introducing breaking changes when the upstream package updates. Consider pinning to a known-good version (similar to the pinned dependencies in Dockerfile.claude / Dockerfile.codex) to improve release stability.

Suggested change

	RUN npm install -g @githubnext/github-copilot-cli --retry 3
	ARG GITHUB_COPILOT_CLI_VERSION=0.0.82
	RUN npm install -g @githubnext/github-copilot-cli@${GITHUB_COPILOT_CLI_VERSION} --retry 3

[Reese-max]

Note for maintainer: Dockerfile.copilot needs to be added to the CI build matrix in .github/workflows/build.yml:

- { suffix: "-copilot", dockerfile: "Dockerfile.copilot", artifact: "copilot" }

I couldn't push this change because OAuth tokens can't modify workflow files (requires workflow scope). Happy to submit a separate PR if you grant the scope, or you can add this one line when merging.

[Reese-max]

Closing — will resubmit after more thorough review and CI matrix fix.