diff --git a/.changeset/events-unknown-project-404.md b/.changeset/events-unknown-project-404.md
new file mode 100644
index 0000000000..15899aab4e
--- /dev/null
+++ b/.changeset/events-unknown-project-404.md
@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Dashboard event streams for an unknown project now return 404 instead of logging a 500 server error.
+category: fix
+dev: `/api/events` maps project-not-found store-resolution failures to 404 with a clean message; stale client tabs and e2e fixture pages no longer fill operator logs with startup-factory construction errors.
diff --git a/packages/dashboard/src/server.ts b/packages/dashboard/src/server.ts
index 122d5c0b96..b911b65d4f 100644
--- a/packages/dashboard/src/server.ts
+++ b/packages/dashboard/src/server.ts
@@ -1285,7 +1285,20 @@ export function createServer(store: TaskStore, options?: ServerOptions): ReturnT
         automationStore,
       )(req, res);
     } catch (err: unknown) {
-      sendErrorResponse(res, 500, err instanceof Error ? err.message : "Failed to open project event stream");
+      /*
+      FNXC:ProjectScoping 2026-08-16-05:28:
+      An SSE subscription for a nonexistent project (e.g. a stale client tab or an
+      e2e fixture page using projectId "fixture") is a client addressing error, not a
+      server fault. Surfacing the startup-factory construction chain as a 500 filled
+      operator logs with alarming "failed to construct TaskStore" errors on every
+      poll; map project-not-found to 404 with a clean message instead.
+      */
+      const message = err instanceof Error ? err.message : "Failed to open project event stream";
+      if (/Project (?:"[^"]*" )?not found/.test(message)) {
+        sendErrorResponse(res, 404, `Project "${projectId}" not found`);
+        return;
+      }
+      sendErrorResponse(res, 500, message);
     }
   });