diff --git a/cockpit/langgraph/client-tools/python/src/__init__.py b/cockpit/langgraph/client-tools/python/src/__init__.py
deleted file mode 100644
index 548d2d447..000000000
--- a/cockpit/langgraph/client-tools/python/src/__init__.py
+++ /dev/null
@@ -1 +0,0 @@
-# SPDX-License-Identifier: MIT
diff --git a/scripts/generate-shared-deployment-config.ts b/scripts/generate-shared-deployment-config.ts
index bde5285f4..ff9f4472f 100644
--- a/scripts/generate-shared-deployment-config.ts
+++ b/scripts/generate-shared-deployment-config.ts
@@ -1,4 +1,4 @@
-import { cpSync, mkdirSync, readFileSync, rmSync, writeFileSync } from 'fs';
+import { cpSync, existsSync, mkdirSync, readFileSync, rmSync, writeFileSync } from 'fs';
 import { dirname, resolve } from 'path';
 import { capabilities } from '../apps/cockpit/scripts/capability-registry';
 
@@ -41,6 +41,19 @@ const stageDependency = (sourceRoot: string, alias: string): string => {
   const stagedDir = resolve(stagedDependenciesDir, alias);
   cpSync(sourceDir, stagedDir, { recursive: true });
 
+  // Every dep ships a `src/` package and they must all merge as PEP 420
+  // namespace portions on the deployment's sys.path. A single
+  // `src/__init__.py` turns that dep's `src` into a REGULAR package which
+  // wins exclusively, so every other dep's `from src.x import ...` raises
+  // ModuleNotFoundError at startup and the whole revision fails to deploy
+  // (this exact failure shipped in #642 and broke deploys from Aug 7).
+  const initPy = resolve(stagedDir, 'src/__init__.py');
+  if (existsSync(initPy)) {
+    throw new Error(
+      `${sourceRoot}/src/__init__.py breaks the shared deployment's namespace-package merge — delete it (deps' src dirs must be namespace packages)`,
+    );
+  }
+
   const relativePath = `./deps/${alias}`;
   stagedDependencyRoots.set(sourceRoot, relativePath);
   dependencies.add(relativePath);