diff --git a/cli/windmill-utils-internal/package-lock.json b/cli/windmill-utils-internal/package-lock.json
index 57d295218f..e9ce5e3c9a 100644
--- a/cli/windmill-utils-internal/package-lock.json
+++ b/cli/windmill-utils-internal/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "windmill-utils-internal",
-  "version": "1.3.5",
+  "version": "1.3.6",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "windmill-utils-internal",
-      "version": "1.3.5",
+      "version": "1.3.6",
       "license": "Apache 2.0",
       "devDependencies": {
         "@types/node": "^24.2.0",
diff --git a/cli/windmill-utils-internal/package.json b/cli/windmill-utils-internal/package.json
index d5c428b35f..07cf8b90b0 100644
--- a/cli/windmill-utils-internal/package.json
+++ b/cli/windmill-utils-internal/package.json
@@ -1,6 +1,6 @@
 {
   "name": "windmill-utils-internal",
-  "version": "1.3.5",
+  "version": "1.3.7",
   "description": "Internal utility functions for Windmill",
   "main": "dist/cjs/index.js",
   "module": "dist/esm/index.js",
diff --git a/cli/windmill-utils-internal/src/config/index.ts b/cli/windmill-utils-internal/src/config/index.ts
index f3ae42b3c8..e23ba6ca86 100644
--- a/cli/windmill-utils-internal/src/config/index.ts
+++ b/cli/windmill-utils-internal/src/config/index.ts
@@ -1 +1 @@
-export * from "./config.ts";
\ No newline at end of file
+export * from "./config";
\ No newline at end of file
diff --git a/cli/windmill-utils-internal/src/index.ts b/cli/windmill-utils-internal/src/index.ts
index 635893e2d1..da314a7c5a 100644
--- a/cli/windmill-utils-internal/src/index.ts
+++ b/cli/windmill-utils-internal/src/index.ts
@@ -8,8 +8,8 @@
  * - Cross-platform path constants
  */
 
-export * from "./inline-scripts.ts";
-export * from "./path-utils.ts";
-export * from "./parse.ts";
-export * from "./config.ts";
-export { SEP, DELIMITER } from "./constants.ts";
\ No newline at end of file
+export * from "./inline-scripts";
+export * from "./path-utils";
+export * from "./parse";
+export * from "./config";
+export { SEP, DELIMITER } from "./constants";
\ No newline at end of file
diff --git a/cli/windmill-utils-internal/src/inline-scripts/extractor.ts b/cli/windmill-utils-internal/src/inline-scripts/extractor.ts
index a3572ce7eb..0ad1bb8302 100644
--- a/cli/windmill-utils-internal/src/inline-scripts/extractor.ts
+++ b/cli/windmill-utils-internal/src/inline-scripts/extractor.ts
@@ -1,5 +1,5 @@
-import { newPathAssigner, PathAssigner } from "../path-utils/path-assigner.ts";
-import { FlowModule, RawScript, ScriptLang } from "../gen/types.gen.ts";
+import { newPathAssigner, PathAssigner } from "../path-utils/path-assigner";
+import { FlowModule, RawScript, ScriptLang } from "../gen/types.gen";
 
 /**
  * Represents an inline script extracted from a flow module
diff --git a/cli/windmill-utils-internal/src/inline-scripts/index.ts b/cli/windmill-utils-internal/src/inline-scripts/index.ts
index bb3c917dbb..eace8d3e4f 100644
--- a/cli/windmill-utils-internal/src/inline-scripts/index.ts
+++ b/cli/windmill-utils-internal/src/inline-scripts/index.ts
@@ -1,2 +1,2 @@
-export * from "./replacer.ts";
-export * from "./extractor.ts";
\ No newline at end of file
+export * from "./replacer";
+export * from "./extractor";
\ No newline at end of file
diff --git a/cli/windmill-utils-internal/src/inline-scripts/replacer.ts b/cli/windmill-utils-internal/src/inline-scripts/replacer.ts
index 11b2cfaa1b..c5651752f1 100644
--- a/cli/windmill-utils-internal/src/inline-scripts/replacer.ts
+++ b/cli/windmill-utils-internal/src/inline-scripts/replacer.ts
@@ -1,4 +1,4 @@
-import { AiAgent, FlowModule, FlowValue, RawScript } from "../gen/types.gen.ts";
+import { AiAgent, FlowModule, FlowValue, RawScript } from "../gen/types.gen";
 
 export type LocalScriptInfo = {
   content: string;
diff --git a/cli/windmill-utils-internal/src/parse/index.ts b/cli/windmill-utils-internal/src/parse/index.ts
index 41d09ed00d..fc26ce611a 100644
--- a/cli/windmill-utils-internal/src/parse/index.ts
+++ b/cli/windmill-utils-internal/src/parse/index.ts
@@ -1 +1 @@
-export * from "./parse-schema.ts";
\ No newline at end of file
+export * from "./parse-schema";
\ No newline at end of file
diff --git a/cli/windmill-utils-internal/src/path-utils/index.ts b/cli/windmill-utils-internal/src/path-utils/index.ts
index 6f5c8d68be..ef23185664 100644
--- a/cli/windmill-utils-internal/src/path-utils/index.ts
+++ b/cli/windmill-utils-internal/src/path-utils/index.ts
@@ -1 +1 @@
-export * from "./path-assigner.ts";
\ No newline at end of file
+export * from "./path-assigner";
\ No newline at end of file
diff --git a/cli/windmill-utils-internal/src/path-utils/path-assigner.ts b/cli/windmill-utils-internal/src/path-utils/path-assigner.ts
index 3fedbd8d37..a2fc5b8cab 100644
--- a/cli/windmill-utils-internal/src/path-utils/path-assigner.ts
+++ b/cli/windmill-utils-internal/src/path-utils/path-assigner.ts
@@ -1,4 +1,4 @@
-import { RawScript } from "../gen/types.gen.ts";
+import { RawScript } from "../gen/types.gen";
 
 const INLINE_SCRIPT_PREFIX = "inline_script";
 
@@ -111,6 +111,28 @@ export function getLanguageFromExtension(
   return undefined;
 }
 
+/**
+ * Sanitizes a summary string for use as a filesystem-safe name.
+ * Removes or replaces characters that are invalid on common filesystems.
+ */
+const WINDOWS_RESERVED = /^(con|prn|aux|nul|com[0-9]|lpt[0-9])$/;
+
+export function sanitizeForFilesystem(summary: string): string {
+  const name = summary
+    .toLowerCase()
+    .replaceAll(" ", "_")
+    // Remove characters invalid on Windows/Unix/Mac: / \ : * ? " < > |
+    // Also remove control characters (0x00-0x1F) and DEL (0x7F)
+    // deno-lint-ignore no-control-regex
+    .replace(/[/\\:*?"<>|\x00-\x1f\x7f]/g, "")
+    // Collapse consecutive underscores
+    .replace(/_+/g, "_")
+    // Trim leading/trailing dots and underscores (hidden files, Windows edge cases)
+    .replace(/^[._]+|[._]+$/g, "");
+  // Prefix Windows reserved device names (CON, PRN, AUX, NUL, COM0-9, LPT0-9)
+  return WINDOWS_RESERVED.test(name) ? `_${name}` : name;
+}
+
 export interface PathAssigner {
   assignPath(summary: string | undefined, language: SupportedLanguage): [string, string];
 }
@@ -144,7 +166,7 @@ export function newPathAssigner(defaultTs: "bun" | "deno" | PathAssignerOptions,
   ): [string, string] {
     let name;
 
-    name = summary?.toLowerCase()?.replaceAll(" ", "_") ?? "";
+    name = summary ? sanitizeForFilesystem(summary) : "";
 
     let original_name = name;
 
@@ -185,7 +207,7 @@ export function newRawAppPathAssigner(defaultTs: "bun" | "deno"): PathAssigner {
   ): [string, string] {
     let name;
 
-    name = summary?.toLowerCase()?.replaceAll(" ", "_") ?? "";
+    name = summary ? sanitizeForFilesystem(summary) : "";
 
     let original_name = name;