feat(save): LazyStore dual-mode WASM backend

marimo/_save/cache.py

@@ -41,6 +41,7 @@
     from marimo._runtime.state import State
     from marimo._save.hash import HashKey
     from marimo._save.loaders import Loader
+    from marimo._save.loaders.lazy import LazyLoader
     from marimo._save.stores import Store
 
 # NB. Increment on cache breaking changes.
@@ -76,6 +77,10 @@ class CacheState:
 
     store: Store
     hash_memo: dict[str, bytes] = field(default_factory=dict)
+    # Lazy-store session state; see `loaders/lazy.py:_cache_state`.
+    active_lazy_loaders: dict[str, LazyLoader] = field(default_factory=dict)
+    poisoned_keys: set[str] = field(default_factory=set)
+    wasm_dict_store: Store | None = None
 
     def is_memoizable(self, value: Any) -> bool:
         """Whether *value* is eligible for content-hash memoization.

marimo/_save/loaders/__init__.py

@@ -1,10 +1,11 @@
 # Copyright 2026 Marimo. All rights reserved.
 from __future__ import annotations
 
+from dataclasses import dataclass
 from typing import Literal
 
 from marimo._save.loaders.json import JsonLoader
-from marimo._save.loaders.lazy import LazyLoader
+from marimo._save.loaders.lazy import LazyLoader, WasmLazyLoader
 from marimo._save.loaders.loader import (
     BasePersistenceLoader,
     Loader,
@@ -13,18 +14,42 @@
 )
 from marimo._save.loaders.memory import MemoryLoader
 from marimo._save.loaders.pickle import PickleLoader
+from marimo._utils.platform import is_pyodide
 
 LoaderKey = Literal["memory", "pickle", "json", "lazy"]
 
-PERSISTENT_LOADERS: dict[LoaderKey, LoaderType] = {
+
+@dataclass(frozen=True)
+class DualLoader:
+    """A loader registered as a native/WASM pair under one name.
+
+    `resolve()` performs the *single* environment check and returns the
+    concrete loader class, so nothing downstream re-checks the platform.
+    Any loader can opt into dual behavior by registering one of these.
+    """
+
+    native: LoaderType
+    wasm: LoaderType
+
+    def resolve(self) -> LoaderType:
+        return self.wasm if is_pyodide() else self.native
+
+
+def resolve_loader(entry: LoaderType | DualLoader) -> LoaderType:
+    """Resolve a registry entry to a concrete loader class."""
+    return entry.resolve() if isinstance(entry, DualLoader) else entry
+
+
+PERSISTENT_LOADERS: dict[LoaderKey, LoaderType | DualLoader] = {
     "pickle": PickleLoader,
     "json": JsonLoader,
-    "lazy": LazyLoader,
+    "lazy": DualLoader(native=LazyLoader, wasm=WasmLazyLoader),
 }
 
 __all__ = [
     "PERSISTENT_LOADERS",
     "BasePersistenceLoader",
+    "DualLoader",
     "JsonLoader",
     "LazyLoader",
     "Loader",
@@ -33,4 +58,6 @@
     "LoaderType",
     "MemoryLoader",
     "PickleLoader",
+    "WasmLazyLoader",
+    "resolve_loader",
 ]