chore: import upstream snapshot with attribution

apps/sim/blocks/custom/server-overlay.ts

@@ -0,0 +1,57 @@
+import { AsyncLocalStorage } from 'node:async_hooks'
+import type { WorkflowInputField } from '@/lib/workflows/input-format'
+import { buildCustomBlockConfig, type CustomBlockRow } from '@/blocks/custom/build-config'
+import { registerBlockOverlayResolver } from '@/blocks/custom/overlay'
+import type { BlockConfig, BlockIcon } from '@/blocks/types'
+
+/** A row for the overlay, optionally carrying live-derived Start input fields. */
+type CustomBlockOverlayRow = CustomBlockRow & {
+  inputFields?: WorkflowInputField[]
+  /** When `false`, the block resolves but is hidden from the palette (disabled). */
+  enabled?: boolean
+}
+
+/**
+ * Server-side custom-block overlay. Resolves `custom_block_*` types during
+ * serialization + execution from a per-request, per-org map held in
+ * AsyncLocalStorage — keeping the `@/blocks/registry` accessors synchronous while
+ * isolating concurrent requests across different organizations.
+ */
+
+/** Icon is never rendered server-side (the serializer ignores it). */
+const PLACEHOLDER_ICON: BlockIcon = () => null as never
+
+const store = new AsyncLocalStorage<Map<string, BlockConfig>>()
+
+registerBlockOverlayResolver({
+  get: (type) => store.getStore()?.get(type),
+  all: () => [...(store.getStore()?.values() ?? [])],
+})
+
+/**
+ * Run `fn` with the given org's custom blocks resolvable via `getBlock`/
+ * `getAllBlocks`. Wrap every execution serializer entry point (execute route,
+ * trigger.dev task, scheduled/webhook runs) at the org-context boundary so a
+ * workflow containing a custom block can serialize and execute.
+ *
+ * Execution passes bare rows: `inputMapping` is schema-agnostic, so no per-field
+ * editors are needed. Agent-facing callers (`get_blocks_metadata`, `edit_workflow`)
+ * pass rows carrying `inputFields` so `getBlock` exposes the real input sub-blocks —
+ * matching what the VFS block files show — instead of an empty schema.
+ */
+export function withCustomBlockOverlay<T>(
+  rows: CustomBlockOverlayRow[],
+  fn: () => Promise<T>
+): Promise<T> {
+  const map = new Map<string, BlockConfig>()
+  for (const row of rows) {
+    map.set(
+      row.type,
+      buildCustomBlockConfig(row, row.inputFields ?? [], {
+        icon: PLACEHOLDER_ICON,
+        hideFromToolbar: row.enabled === false,
+      })
+    )
+  }
+  return store.run(map, fn)
+}