In-Memory Thread Lifecycle#

InMemoryThreadList manages a set of thread resources where each thread is keyed by a string thread ID. The key determines resource identity: when the selected thread ID changes, the previously mounted OwnedThread resource is unmounted and a new one is mounted for the incoming ID. This is a soft unmount — the thread's per-ID AbortSignal is not aborted on an ordinary selection change 12.

Thread Identity and State Isolation#

The InMemoryThreadListProps.thread factory receives a threadId string and returns a ResourceElement<ClientOutput<"thread">>. The JSDoc explicitly states that "thread-owned state does not survive a selection change" because the resource is keyed by threadId 3. This means:

• Composer/draft state lives inside the keyed OwnedThread resource. Switching to a different thread ID replaces the resource and resets composer state.
• Switching back to a prior thread ID creates a fresh resource instance — draft state from the first visit is gone unless the host persists it externally.
• Scope derivations (composer, threadListItem) are re-derived from the new main thread automatically 4.

Per-Thread Lifetime Signals (createThreadLifetimes)#

InMemoryThreadList maintains one AbortController per thread ID via the createThreadLifetimes factory. Two distinct lifecycle events abort a thread's signal:

The signal is injected into the thread subtree via useDestroySignalProvider, which provides the signal as React context. Its documentation describes it as signalling only permanent teardown of the owner — never a soft resource unmount that may recur 9.

In-Flight Sends and Tool Executions#

ToolInvocationTracker 10 manages the client-side tool execution pipeline for external-store thread runtimes. Its abort() and reset() lifecycle are not driven by thread selection changes or per-thread destroy signals. Instead, they are called on explicit run-boundary events inside ExternalStoreThreadRuntimeCore:

• abort({ discardPending: true }) — called before starting a new run (append) and before a reload (startRun), cancelling any in-flight execute() calls so stale results don't land in the new turn 1112.
• abort() (without discardPending) — called during message deletion while running 13, and on cancelRun 14.
• reset() — called when the adapter's message repository instance changes 15, when the tool-invocations feature is disabled 16, on importExternalState 17, and on unstable_notifySessionReset 18.

When an in-memory thread is switched (not deleted), the underlying ExternalStoreThreadRuntimeCore is replaced or disposed. Per the runtime disposal path, this ends the old runtime's generation signals — but the ToolInvocationTracker.abort() is not explicitly wired to thread disposal in the paths covered; in-flight executions from the old runtime may settle after unmount but their onAddToolResult callbacks are no-ops if the tool call ID no longer exists in the current snapshot 19.

Key Entry Points#