Policy: availability-gated tools (check_fn probes — Docker, HASS_TOKEN,
OAuth…) are frozen for the life of a session. tools[] only changes on
/new, /reload-mcp, or compaction. Two doors remained after #100638:
* Gateway agent-cache eviction (LRU/idle sweep/cross-process invalidation)
rebuilds a fresh AIAgent for the SAME session and agent_init re-derives
agent.tools from live probes with no predecessor to preserve. Persist
the session's resolved tool-name order in a new `sessions.tool_names`
JSON column (declarative reconciliation, SCHEMA_VERSION 28), written
alongside the system prompt and re-pinned on every published refresh
(so /reload-mcp and compaction naturally reset it; /new mints a new
row). On restore-for-existing-session the fresh definitions are folded
onto the saved order via the SAME `_merge_preserving_prefix` helper —
a probe-flipped tool is carried forward from the registry schema, a
deregistered one dropped, new tools appended at the tail.
* /reload-mcp (CLI, gateway, TUI RPC) now also calls
`reprobe_tool_availability()` — drops the check_fn verdict cache and the
get_tool_definitions memo — so a user can consciously pick up a
credential/daemon that appeared mid-session. Docs updated.