Providers key prompt caches per model, so a mid-session /model switch makes
the next reply re-read the entire conversation at full input price. deepagents
gates user-initiated switches behind a confirmation once the active thread
exceeds a configurable token threshold; this ports the same protection into
Hermes' unified selection-guard registry so it renders on every surface at
once (CLI/TUI picker, gateway /model, Telegram/Discord pickers, dashboard).
- hermes_cli/model_selection_guards.py: new context_cache guard +
SelectionContext carrier + selection_context_for_agent() helper;
registry threads live-session facts to guards (6-arg signature with a
TypeError fallback for externally patched 5-arg guards).
- config: model.switch_context_confirm_tokens (default 100000, 0 disables).
- cli.py / gateway/slash_commands.py / tui_gateway/server.py: thread the
live agent's measured context into the guard call.
- docs: configuring-models.md mid-session switch section.
- tests: tests/hermes_cli/test_context_cache_switch_guard.py (13 cases).
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