Comment by bionhoward
1 day ago
> plan mode has always been a prompt — it has never changed the toolset because doing so would break the prompt cache, and so would be expensive
seems like plan mode could turn off some tools, even if it doesn't change the set offered to the model, the ones that they have which would mutate your codebase could just not work with an error message, and plan mode could change permissions in the security approval prompt for "auto"
anyway, isnt the right way to know if plan mode helps or not, to run an experiment? we're all guessing unless we have data
read only agent mode sounds straightforward and useful to me
It’s bizarre to me that Claude Code doesn’t have more guardrails on plan mode. I mostly use Copilot and the plan mode there has teeth. In plan the agent does not have permission to write to the filesystem outside of a temp directory and the plan document itself, and tool calling is heavily restricted.
There’s also a “ask” mode which is read only. Both are enforced by the permissions model, not just a system prompt instruction. I’ve seen the model “forget” and try to start coding - it bounces off a hard permissions failure and that “reminds” it that it’s in plan mode.