I can only talk about GLM 5.1 which is roughly at sonnet 4 levels imo.
It's good, does most tasks well that I throw at it, but will fail at anything congitive/complex. It gets stuck often. It costs ~6$ a month though
This was my experience using GLM 5.1 in Claude Code but it works far better in OpenCode, I’d really like to understand why. I think it’s a bit stronger than Sonnet 4.6.
I use the oh-my-openagent planning system and haven’t used vanilla OpenCode enough to know how much that is contributing.
The answer is easy, CC is bug for bug optimized for Anthropic models. They don't even test it with other models, let alone provide support for all small compatibility quirks of different provider implementations.
On the other hand, Opencode, Pi agent and other open source tool offer much better support for all models, including open source.