fix(start-plugin-core): sort server fn manifest entries for deterministic build output

.changeset/silver-lions-sort.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/start-plugin-core': patch
+---
+
+Sort server function manifest entries by ID before emitting the resolver module. The `serverFnsById` map is populated in source-file scan order, which varies across machines and incremental builds, producing non-deterministic key ordering in the emitted `__tanstack-start-server-fn-resolver-*.mjs` artifact. Stable alphabetic sorting ensures reproducible builds, consistent content hashes, and clean `git diff` on committed artifacts.

packages/start-plugin-core/src/start-compiler/server-fn-resolver-module.ts

@@ -16,12 +16,19 @@ interface GenerateServerFnResolverModuleOptions {
 function getResolverManifestEntries(
   serverFnsById: Record<string, ServerFn>,
 ): Array<ResolverManifestEntry> {
-  return Object.entries(serverFnsById).map(([id, fn]) => ({
-    id,
-    functionName: fn.functionName,
-    extractedFilename: fn.extractedFilename,
-    isClientReferenced: fn.isClientReferenced ?? true,
-  }))
+  return (
+    Object.entries(serverFnsById)
+      // Sort entries by ID so that the generated manifest has a stable, deterministic order.
+      // Non-deterministic ordering causes the compiled hash of the same source file to change
+      // between builds, breaking content-addressed caching and reproducible deployments.
+      .sort(([a], [b]) => (a < b ? -1 : a > b ? 1 : 0))
+      .map(([id, fn]) => ({
+        id,
+        functionName: fn.functionName,
+        extractedFilename: fn.extractedFilename,
+        isClientReferenced: fn.isClientReferenced ?? true,
+      }))
+  )
 }
 
 function getClientReferencedCheck(