diff --git a/apps/webapp/app/env.server.ts b/apps/webapp/app/env.server.ts
index f5e0f0a671..9ecfb54b21 100644
--- a/apps/webapp/app/env.server.ts
+++ b/apps/webapp/app/env.server.ts
@@ -1713,9 +1713,13 @@ const EnvironmentSchema = z
 
     // --- Run-ops DB split — second replication source (the NEW dedicated run-ops DB). ---
     // Cloud-only; only consulted when isSplitEnabled() is true. Self-host never sets these.
-    // The NEW source's connection URL is RUN_OPS_DATABASE_URL; these add the NEW source's replication
-    // slot/publication and an explicit per-source enable so it can be brought up independently of the
-    // legacy source during the transition.
+    // Connection URL for the run-ops DB used by the runs-replication source. Required when the split is
+    // enabled (unset → boot fails via SplitReplicationMisconfiguredError, no silent fallback). Kept
+    // separate from the app's RUN_OPS_DATABASE_URL: replication can't run over a pooler, so this is direct.
+    RUN_REPLICATION_RUN_OPS_DATABASE_URL: z
+      .string()
+      .refine(isValidDatabaseUrl, "RUN_REPLICATION_RUN_OPS_DATABASE_URL is invalid")
+      .optional(),
     RUN_REPLICATION_NEW_SLOT_NAME: z.string().default("task_runs_to_clickhouse_v2"),
     RUN_REPLICATION_NEW_PUBLICATION_NAME: z
       .string()
diff --git a/apps/webapp/app/services/runsReplicationInstance.server.ts b/apps/webapp/app/services/runsReplicationInstance.server.ts
index ad048422ac..8d7eefc2c7 100644
--- a/apps/webapp/app/services/runsReplicationInstance.server.ts
+++ b/apps/webapp/app/services/runsReplicationInstance.server.ts
@@ -71,7 +71,7 @@ export class SplitReplicationMisconfiguredError extends Error {
       'RUN_OPS_SPLIT_ENABLED is on but the runs-replication sources[] has no "new" source: ' +
         "run-ops runs on the new DB would not replicate to ClickHouse, under-counting every " +
         "ClickHouse-fronted aggregate. Enable the new replication source " +
-        "(RUN_REPLICATION_NEW_ENABLED / RUN_OPS_DATABASE_URL) or turn the split off."
+        "(RUN_REPLICATION_NEW_ENABLED / RUN_REPLICATION_RUN_OPS_DATABASE_URL) or turn the split off."
     );
     this.name = "SplitReplicationMisconfiguredError";
   }
@@ -172,7 +172,7 @@ function initializeRunsReplicationInstance() {
         const sources = buildReplicationSources({
           splitEnabled,
           legacyUrl: DATABASE_URL,
-          newUrl: env.RUN_OPS_DATABASE_URL,
+          newUrl: env.RUN_REPLICATION_RUN_OPS_DATABASE_URL,
           newSourceOverride: env.RUN_REPLICATION_NEW_ENABLED === "disabled" ? false : undefined,
           legacySlotName: env.RUN_REPLICATION_SLOT_NAME,
           legacyPublicationName: env.RUN_REPLICATION_PUBLICATION_NAME,