Module session_table 

Persistent per-session script VMs, as one owned aggregate, with a crisp two-tier lifetime:

• The VM (globalThis, compiled plugin bytecode, timers) is the heavy, disposable tier. It is rebuilt on poison (timeout/OOM), on a browser-session swap (relaunch/reconnect under the same name), and dropped under the warm-VM cap when another session needs a slot.
• vars is the light, durable tier: a string store that lives for the logical session’s whole lifetime. It survives every VM rebuild above — cap eviction drops only the VM, not the session record. The single thing globalThis cannot give you.

A logical session ends (and its vars are released) only on: an idle-TTL reap, an explicit SessionTable::remove, or SessionTable::clear (server shutdown). That is the whole vars durability contract — no fuzzier than that.

Browser-agnostic by construction: a RunContext carries whatever browser handles a call has (or None) and the browser epoch is passed in, so every policy here is unit-testable without a browser.

Structs

BrowserSession

One logical session: the (disposable) persistent VM, the (durable) session-scoped vars, and the browser generation the live VM was built against. Access is serialized by the AsyncMutex SessionTable hands out — that slot lock IS the per-session execution guard, so the invariant is structural, not a comment.

SessionTable

The set of live sessions plus the retention policy. Cheap to share (Arc it); every method takes &self.