diff --git a/CHANGELOG.md b/CHANGELOG.md
index e491e12..d8fb252 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,24 @@ The format is inspired by Keep a Changelog and SemVer.
 
 ## [Unreleased]
 
+### Fixed
+- **Loading a Koolook workflow whose name collides with an existing
+  native ComfyUI workflow file no longer breaks ComfyUI's native save.**
+  Before: loading `MyFlow` from the Kforge Labs sidebar named the
+  resulting temporary tab `workflows/MyFlow.json`. If the user already
+  had a native ComfyUI workflow saved at `user/default/workflows/
+  MyFlow.json`, hitting ComfyUI's native save threw a confusing
+  `Error storing user data file 'workflows/MyFlow.json': 409 Conflict`
+  — because ComfyUI's frontend saves temporary tabs with
+  `overwrite=false` (see
+  `Comfy-Org/ComfyUI_frontend/src/stores/userFileStore.ts`), so any
+  name collision with an existing file 409s. Now: `loadWorkflowOntoCanvas`
+  HEADs `/userdata/workflows/<name>.json` before loading and, on a hit,
+  appends ` (Koolook)` to the tab name. The tab still loads, save-back
+  writes a clean new artifact, and the load toast surfaces the renaming
+  so the user knows why. Bare `<name>` is preserved when there's no
+  collision.
+
 ### Changed
 - **Save selection toast distinguishes "no selection" from "selection
   points at deleted nodes."** Previously both produced the generic
diff --git a/web/sidebar/canvas_io.js b/web/sidebar/canvas_io.js
index f370da9..cc809a3 100644
--- a/web/sidebar/canvas_io.js
+++ b/web/sidebar/canvas_io.js
@@ -104,6 +104,35 @@ export function canvasIsNonEmpty() {
     }
 }
 
+// Returns `true` when a workflow file already exists at
+// `/userdata/workflows/<wfName>.json` on the ComfyUI server.
+//
+// Why we care: workflows we load via `loadGraphData(..., wfName, {})` become
+// **temporary** workflow tabs in ComfyUI's frontend. Per
+// `Comfy-Org/ComfyUI_frontend/src/stores/userFileStore.ts`, save calls pass
+// `overwrite: this.isPersisted` — `false` for temporary workflows. If the
+// user clicks ComfyUI's native save on a Koolook-loaded tab whose name
+// matches an existing native workflow file, the server returns 409 because
+// the POST didn't authorize an overwrite. This pre-load check lets us
+// suffix the tab name when a collision exists, so save-back writes a
+// clean new artifact instead of 409-ing.
+//
+// HEAD avoids transferring the file body. If the deployment doesn't
+// support HEAD (rare), the catch falls through and we behave as before
+// — the user's worst case is the same 409 they already know how to
+// work around with Save As.
+async function existingNativeWorkflowFileExists(wfName) {
+    try {
+        const resp = await fetch(
+            `/userdata/workflows/${encodeURIComponent(wfName)}.json`,
+            { method: "HEAD" }
+        );
+        return resp.ok;
+    } catch (e) {
+        return false;
+    }
+}
+
 export async function loadWorkflowOntoCanvas(dirPath, wfName) {
     const graph = getWorkflowGraph(dirPath, wfName);
     if (!graph) {
@@ -120,26 +149,38 @@ export async function loadWorkflowOntoCanvas(dirPath, wfName) {
         } catch (e) {
             previousGraph = null;
         }
+        // Resolve a collision-free tab name. If a native ComfyUI workflow file
+        // already exists at `workflows/<wfName>.json`, append `(Koolook)` so
+        // ComfyUI's native save flow doesn't 409 (its POST passes
+        // `overwrite=false` for temporary tabs by design — see comment on
+        // `existingNativeWorkflowFileExists`). When there's no collision, the
+        // bare name is used so the tab stays clean.
+        const collides = await existingNativeWorkflowFileExists(wfName);
+        const tabName = collides ? `${wfName} (Koolook)` : wfName;
         try {
-            // Passing `wfName` as the 4th arg makes loadGraphData create a
+            // Passing `tabName` as the 4th arg makes loadGraphData create a
             // temporary workflow tab titled with that name (instead of
             // "Unsaved Workflow (N)"). Frontend reference: ComfyUI_frontend
             // src/scripts/app.ts (loadGraphData) →
             // workflowService.afterLoadNewGraph → createNewTemporary, which
-            // builds path `workflows/<wfName>.json` and binds it to the tab.
-            await app.loadGraphData(graph, true, true, wfName, {});
+            // builds path `workflows/<tabName>.json` and binds it to the tab.
+            await app.loadGraphData(graph, true, true, tabName, {});
 
             // Defensive fallback for frontends that didn't honor the 4th arg.
             try {
                 const wf = app.extensionManager?.workflow?.activeWorkflow;
-                if (wf && wf.isTemporary && typeof wf.rename === "function" && wf.filename !== wfName) {
-                    await wf.rename(`workflows/${wfName}.json`);
+                if (wf && wf.isTemporary && typeof wf.rename === "function" && wf.filename !== tabName) {
+                    await wf.rename(`workflows/${tabName}.json`);
                 }
             } catch (e) {
                 console.warn("[Koolook] workflow rename fallback failed:", e);
             }
 
-            toast(`Loaded "${wfName}".`);
+            if (collides) {
+                toast(`Loaded "${wfName}" as "${tabName}" — a native workflow file with the original name already exists.`);
+            } else {
+                toast(`Loaded "${wfName}".`);
+            }
         } catch (e) {
             console.error("[Koolook] loadGraphData failed:", e);
             if (previousGraph) {