feat(core): add embedded v2 session runtime and tool foundation (#30632)

packages/core/src/effect/keyed-mutex.ts

@@ -0,0 +1,43 @@
+export * as KeyedMutex from "./keyed-mutex"
+
+import { Effect, Semaphore } from "effect"
+
+export interface KeyedMutex<in Key> {
+  readonly size: Effect.Effect<number>
+  readonly withLock: (key: Key) => <A, E, R>(effect: Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>
+}
+
+/**
+ * Creates an in-memory mutex with one lock per key. Entries are removed when no
+ * holder or waiter remains.
+ *
+ *   same key      -> queue
+ *   different key -> run independently
+ *
+ * `users` counts holders and waiters so an entry is not removed while a waiter
+ * will reuse it.
+ */
+export const makeUnsafe = <Key>(): KeyedMutex<Key> => {
+  const locks = new Map<Key, { readonly semaphore: Semaphore.Semaphore; users: number }>()
+
+  const withLock = (key: Key) => <A, E, R>(effect: Effect.Effect<A, E, R>) =>
+    Effect.suspend(() => {
+      const current = locks.get(key)
+      const entry = current ?? { semaphore: Semaphore.makeUnsafe(1), users: 0 }
+      if (!current) locks.set(key, entry)
+      entry.users++
+      return entry.semaphore.withPermit(effect).pipe(
+        Effect.ensuring(
+          Effect.sync(() => {
+            entry.users--
+            if (entry.users === 0) locks.delete(key)
+          }),
+        ),
+      )
+    })
+
+  return { size: Effect.sync(() => locks.size), withLock }
+}
+
+/** Creates an in-memory keyed mutex inside an Effect workflow. */
+export const make = <Key>(): Effect.Effect<KeyedMutex<Key>> => Effect.sync(makeUnsafe<Key>)