diff --git a/.changeset/fix-create-projection-seed-inference.md b/.changeset/fix-create-projection-seed-inference.md
new file mode 100644
index 000000000..2b97fdca4
--- /dev/null
+++ b/.changeset/fix-create-projection-seed-inference.md
@@ -0,0 +1,6 @@
+---
+"@solidjs/signals": patch
+"solid-js": patch
+---
+
+Fix `createProjection` seed typing so readonly store seeds do not override inference from the projection function return type.
diff --git a/packages/solid-signals/src/store/projection.ts b/packages/solid-signals/src/store/projection.ts
index 3efd2c3a2..3a6d67edb 100644
--- a/packages/solid-signals/src/store/projection.ts
+++ b/packages/solid-signals/src/store/projection.ts
@@ -17,6 +17,7 @@ import {
   STORE_WRAP,
   storeSetter,
   storeTraps,
+  type NoFn,
   type ProjectionOptions,
   type Store
 } from "./store.js";
@@ -107,7 +108,7 @@ export function createProjectionInternal<T extends object = {}>(
  */
 export function createProjection<T extends object = {}>(
   fn: (draft: T) => void | T | Promise<void | T> | AsyncIterable<void | T>,
-  seed: Partial<T>,
+  seed: NoFn<T> | Store<NoFn<T>>,
   options?: ProjectionOptions
 ): Refreshable<Store<T>> {
   return createProjectionInternal(fn, seed, options).store;
diff --git a/packages/solid/src/client/hydration.ts b/packages/solid/src/client/hydration.ts
index 9acb5ac27..1c33ca4cb 100644
--- a/packages/solid/src/client/hydration.ts
+++ b/packages/solid/src/client/hydration.ts
@@ -1017,7 +1017,7 @@ export const createOptimistic: {
  */
 export const createProjection: <T extends object = {}>(
   fn: (draft: T) => void | T | Promise<void | T> | AsyncIterable<void | T>,
-  initialValue: T,
+  initialValue: NoFn<T> | Store<NoFn<T>>,
   options?: ProjectionOptions
 ) => Refreshable<Store<T>> = ((...args: any[]) =>
   (_createProjection || coreProjection)(...args)) as any;