diff --git a/backend/src/workspace-maintenance.ts b/backend/src/workspace-maintenance.ts
index dbb06eb5..248a96f9 100644
--- a/backend/src/workspace-maintenance.ts
+++ b/backend/src/workspace-maintenance.ts
@@ -20,11 +20,15 @@ export interface WorkspaceMaintenanceIo {
 
 type Command = "inspect" | "preprocess-dwh" | "schema-suggest-fks" | "schema-check" | "index-schema" | "preprocess-evidence" | "preprocess-run";
 
-function failureResult(operation: string, workspaceId = ""): WorkspaceOperationResult {
+function failureResult(
+  operation: string,
+  workspaceId = "",
+  code: WorkspaceOperationResult["code"] = "workspace_not_activatable",
+): WorkspaceOperationResult {
   return {
     schemaVersion: 1,
     status: "failed",
-    code: "workspace_not_activatable",
+    code,
     workspaceId,
     workspaceRevision: "",
     descriptorBlob: "",
@@ -33,6 +37,11 @@ function failureResult(operation: string, workspaceId = ""): WorkspaceOperationR
   };
 }
 
+const STATE_ERROR_CODES: Record<string, WorkspaceOperationResult["code"]> = {
+  preprocessing_resume_mismatch: "preprocessing_resume_mismatch",
+  preprocessing_conflict: "preprocessing_conflict",
+};
+
 function boundedJson(result: WorkspaceOperationResult): string {
   const encoded = JSON.stringify(result);
   if (Buffer.byteLength(encoded, "utf8") > 1024 * 1024) {
@@ -131,9 +140,15 @@ export async function runWorkspaceMaintenanceCli(
     io.writeStdout(boundedJson(result));
     return exitCodeFor(result);
   } catch (error) {
+    const failureCode = error instanceof Error
+      && "code" in error
+      && typeof (error as { code?: unknown }).code === "string"
+      && (error as { code: string }).code in STATE_ERROR_CODES
+      ? STATE_ERROR_CODES[(error as { code: string }).code]
+      : "workspace_not_activatable";
     const result = failureResult(command, (() => {
       try { return JSON.parse(io.stdin).workspaceId ?? ""; } catch { return ""; }
-    })());
+    })(), failureCode);
     if (process.env.P2_CHILD_DEBUG === "1") {
       const detail = String((error as Error).message ?? "").replace(/[\r\n]+/g, " ").slice(0, 2048);
       result.warnings = detail.length > 0 ? [detail] : undefined;