Each branch has its own views (its definitions as files), as each git worktree has its own checkout, and nothing reads another's: the codebase's own branch's are in .tcm/src, a session's in its directory (written as something needs them, a stack trace say), and a branch only read (`--branch`) is rendered, nothing written. What a session changed, code and a comment alone, is what `search`, `view` and `at` with `--branch` see from outside it; stack traces of the same code point at each branch's own views; and main's views, as an editor reads them, are untouched.