diff --git a/frontend/src/workspaces/drafts.test.ts b/frontend/src/workspaces/drafts.test.ts
index 3d00e05f..0648e0ab 100644
--- a/frontend/src/workspaces/drafts.test.ts
+++ b/frontend/src/workspaces/drafts.test.ts
@@ -10,6 +10,12 @@ test("workspace module exposes validation and in-memory coordination but no draf
   expect(workspaceModule).not.toHaveProperty("workspaceDeletionDrafts");
 });
 
+test("canonical sanitizer accepts schema-v4 workspaces without an authored dwh block", () => {
+  const { dwh: _catalogOwnedDwh, ...workspace } = canonicalWorkspaceFixture("psd-clinical");
+
+  expect(workspaceModule.sanitizeCanonicalWorkspace(workspace)).toEqual(workspace);
+});
+
 test("canonical sanitizer rejects unknown fields rather than persisting them", () => {
   expect(workspaceModule.sanitizeCanonicalWorkspace({
     ...canonicalWorkspaceFixture("psd-clinical"),
diff --git a/frontend/src/workspaces/drafts.ts b/frontend/src/workspaces/drafts.ts
index 999e50a3..99601e30 100644
--- a/frontend/src/workspaces/drafts.ts
+++ b/frontend/src/workspaces/drafts.ts
@@ -375,26 +375,48 @@ function copyDiagnostics(value: unknown): CanonicalDiagnostics | undefined {
 export function sanitizeCanonicalWorkspace(value: unknown): CanonicalWorkspace | undefined {
   const source = exactRecord(value, ["workspace", "dwh", "diagnostics", "evidence"]);
   const metadata = exactRecord(source?.workspace, ["schema_version", "id", "name", "description", "language"]);
-  const dwh = exactRecord(source?.dwh, ["engine", "database", "schema", "port", "timeout_ms", "supported_transports"]);
   const diagnostics = source?.diagnostics === undefined ? undefined : copyDiagnostics(source.diagnostics);
-  if (!metadata || !dwh) return undefined;
+  if (!metadata) return undefined;
   const id = workspaceId(metadata.id);
   const evidence = id && source?.evidence !== undefined ? copyEvidence(source.evidence, id) : undefined;
   const name = text(metadata.name);
   const language = oneOf(metadata.language, ["en", "it"] as const);
   const description = metadata.description === undefined ? undefined : text(metadata.description);
-  const database = identifier(dwh.database);
-  const schema = identifier(dwh.schema);
-  const dwhPort = dwh.port === undefined ? undefined : positiveInteger(dwh.port, 65_535);
-  const dwhTimeout = dwh.timeout_ms === undefined ? undefined : positiveInteger(dwh.timeout_ms);
-  const dwhTransports = uniqueChoices(dwh.supported_transports, ["postgres_direct", "rest_api", "ssh_tunnel"] as const);
   if (
-    metadata.schema_version !== 4 || !id || !name || !language || (metadata.description !== undefined && !description)
-    || dwh.engine !== "postgres" || !database || !schema || (dwh.port !== undefined && !dwhPort) || (dwh.timeout_ms !== undefined && !dwhTimeout) || !dwhTransports
+    metadata.schema_version !== 4 || !id || !name || !language
+    || (metadata.description !== undefined && !description)
   ) return undefined;
   if (source?.diagnostics !== undefined && !diagnostics) return undefined;
   if (source?.evidence !== undefined && !evidence) return undefined;
-  if (diagnostics?.dwh_rest && !dwhTransports.includes("rest_api")) return undefined;
+
+  let dwh: CanonicalWorkspace["dwh"];
+  if (source?.dwh !== undefined) {
+    const rawDwh = exactRecord(
+      source.dwh,
+      ["engine", "database", "schema", "port", "timeout_ms", "supported_transports"],
+    );
+    if (!rawDwh) return undefined;
+    const database = identifier(rawDwh.database);
+    const schema = identifier(rawDwh.schema);
+    const port = rawDwh.port === undefined ? undefined : positiveInteger(rawDwh.port, 65_535);
+    const timeout = rawDwh.timeout_ms === undefined ? undefined : positiveInteger(rawDwh.timeout_ms);
+    const transports = uniqueChoices(
+      rawDwh.supported_transports,
+      ["postgres_direct", "rest_api", "ssh_tunnel"] as const,
+    );
+    if (
+      rawDwh.engine !== "postgres" || !database || !schema || !transports
+      || (rawDwh.port !== undefined && !port)
+      || (rawDwh.timeout_ms !== undefined && !timeout)
+    ) return undefined;
+    dwh = {
+      engine: "postgres", database, schema,
+      ...(port ? { port } : {}),
+      ...(timeout ? { timeout_ms: timeout } : {}),
+      supported_transports: transports,
+    };
+  }
+  if (diagnostics?.dwh_rest && !dwh?.supported_transports.includes("rest_api")) return undefined;
   return {
     workspace: {
       schema_version: 4,
@@ -403,12 +425,7 @@ export function sanitizeCanonicalWorkspace(value: unknown): CanonicalWorkspace |
       ...(description ? { description } : {}),
       language,
     },
-    dwh: {
-      engine: "postgres", database, schema,
-      ...(dwhPort ? { port: dwhPort } : {}),
-      ...(dwhTimeout ? { timeout_ms: dwhTimeout } : {}),
-      supported_transports: dwhTransports,
-    },
+    ...(dwh ? { dwh } : {}),
     ...(diagnostics ? { diagnostics } : {}),
     ...(evidence ? { evidence } : {}),
   };