How they actually differ
GitHub Copilot and OpenCode are both AI coding tools but they ship in opposite shapes and reflect opposite trade-offs around lock-in, model choice, and where the agent lives.
GitHub Copilot is the polished, paid product from GitHub (Microsoft). It lives inside your IDE (VS Code, JetBrains, Neovim, Visual Studio) and ranges from autocomplete to chat to agent mode. The model is whatever GitHub chose (a rotation of GPT-class and Claude-class models on the back end) and you don't control which one. Strong autocomplete latency, deep IDE integration, enterprise SSO, GitHub-native context (your repos, issues, PRs). The trade-off is cost and lock-in: you pay a per-seat subscription and the product is opinionated about how you use it.
OpenCode is open-source software from Anomaly. Terminal-first, BYO API keys, choose your own model (Claude Opus 4.7, GPT-5, Devstral 2, Qwen3-Coder, anything you want). No IDE plugin by design. You run it from the command line, it operates on the repo in front of you, you pay only the underlying provider tokens. The trade-off is the inverse: you own the operational concerns and you give up the polished IDE UX.
Where the trade-off bites: Copilot wins for teams that want minimum friction, are already on GitHub, and value autocomplete-in-flow over autonomous agent work. OpenCode wins for teams that care about model choice (running fine-tuned models, swapping providers for cost reasons), want the agent available outside the editor, or want to avoid the per-seat Microsoft tax.
Where Respan fits. OpenCode runs cleanly through the Respan gateway with the proxy coding agents cookbook: one API key across 1,000+ models, per-developer cost tracking, fallback routing. Copilot is a closed product so the routing story does not apply, but you can still trace Copilot usage at the IDE layer if you self-instrument.
For the framing on which autonomous-coding-agent patterns actually ship, see agent workflow patterns.