diff --git a/apps/webapp/app/services/dataStores/organizationDataStoresRegistry.server.ts b/apps/webapp/app/services/dataStores/organizationDataStoresRegistry.server.ts
index dff741cab0f..07a4f1d3592 100644
--- a/apps/webapp/app/services/dataStores/organizationDataStoresRegistry.server.ts
+++ b/apps/webapp/app/services/dataStores/organizationDataStoresRegistry.server.ts
@@ -7,7 +7,19 @@ import { getSecretStore } from "../secrets/secretStore.server";
 import { ClickhouseConnectionSchema } from "../clickhouse/clickhouseSecretSchemas.server";
 
 export class OrganizationDataStoresRegistry {
-  private _prisma: PrismaClient | PrismaReplicaClient;
+  /**
+   * Writer client — used by every method that mutates state
+   * (`addDataStore` / `updateDataStore` / `deleteDataStore` and their backing
+   * SecretStore writes). Must be the primary connection; replica-targeted
+   * writes are rejected by Postgres with code 25006 (read-only transaction).
+   */
+  private _writer: PrismaClient;
+  /**
+   * Read client used by the polling `loadFromDatabase()` (and its
+   * `SecretStore.getSecret` lookups). Can be a replica — these are
+   * cache-fillers, not on hot user-facing paths.
+   */
+  private _replica: PrismaClient | PrismaReplicaClient;
   /** Keyed by `${organizationId}:${kind}` */
   private _lookup: Map<string, ParsedDataStore> = new Map();
   private _loaded = false;
@@ -21,8 +33,9 @@ export class OrganizationDataStoresRegistry {
    */
   readonly isReady: Promise<void>;
 
-  constructor(prisma: PrismaClient | PrismaReplicaClient) {
-    this._prisma = prisma;
+  constructor(writer: PrismaClient, replica: PrismaClient | PrismaReplicaClient) {
+    this._writer = writer;
+    this._replica = replica;
     this.isReady = new Promise<void>((resolve) => {
       this._readyResolve = resolve;
     });
@@ -37,10 +50,10 @@ export class OrganizationDataStoresRegistry {
     // same `${orgId}:${kind}` appears in multiple rows. The registry must never
     // throw on overlap — failing the load would break every customer, not just the
     // misconfigured orgs — so we keep the first entry and log an error instead.
-    const rows = await this._prisma.organizationDataStore.findMany({
+    const rows = await this._replica.organizationDataStore.findMany({
       orderBy: { key: "asc" },
     });
-    const secretStore = getSecretStore("DATABASE", { prismaClient: this._prisma });
+    const secretStore = getSecretStore("DATABASE", { prismaClient: this._replica });
 
     const lookup = new Map<string, ParsedDataStore>();
     /** Tracks which row's `key` already owns each `${orgId}:${kind}` so we can log conflicts. */
@@ -125,10 +138,10 @@ export class OrganizationDataStoresRegistry {
   }) {
     const secretKey = this.#secretKey(key, kind);
 
-    const secretStore = getSecretStore("DATABASE", { prismaClient: this._prisma });
+    const secretStore = getSecretStore("DATABASE", { prismaClient: this._writer });
     await secretStore.setSecret(secretKey, config);
 
-    return this._prisma.organizationDataStore.create({
+    return this._writer.organizationDataStore.create({
       data: {
         key,
         organizationIds,
@@ -153,11 +166,11 @@ export class OrganizationDataStoresRegistry {
     const secretKey = this.#secretKey(key, kind);
 
     if (config) {
-      const secretStore = getSecretStore("DATABASE", { prismaClient: this._prisma });
+      const secretStore = getSecretStore("DATABASE", { prismaClient: this._writer });
       await secretStore.setSecret(secretKey, config);
     }
 
-    return this._prisma.organizationDataStore.update({
+    return this._writer.organizationDataStore.update({
       where: {
         key,
       },
@@ -170,12 +183,12 @@ export class OrganizationDataStoresRegistry {
 
   async deleteDataStore({ key, kind }: { key: string; kind: DataStoreKind }) {
     const secretKey = this.#secretKey(key, kind);
-    const secretStore = getSecretStore("DATABASE", { prismaClient: this._prisma });
+    const secretStore = getSecretStore("DATABASE", { prismaClient: this._writer });
     await secretStore.deleteSecret(secretKey).catch(() => {
       // Secret may not exist — proceed with deletion
     });
 
-    await this._prisma.organizationDataStore.delete({ where: { key } });
+    await this._writer.organizationDataStore.delete({ where: { key } });
   }
 
   /**
diff --git a/apps/webapp/app/services/dataStores/organizationDataStoresRegistryInstance.server.ts b/apps/webapp/app/services/dataStores/organizationDataStoresRegistryInstance.server.ts
index 24ec572c5d5..239683965ea 100644
--- a/apps/webapp/app/services/dataStores/organizationDataStoresRegistryInstance.server.ts
+++ b/apps/webapp/app/services/dataStores/organizationDataStoresRegistryInstance.server.ts
@@ -1,5 +1,5 @@
 import pRetry from "p-retry";
-import { $replica } from "~/db.server";
+import { $replica, prisma } from "~/db.server";
 import { env } from "~/env.server";
 import { logger } from "~/services/logger.server";
 import { signalsEmitter } from "~/services/signals.server";
@@ -7,7 +7,7 @@ import { singleton } from "~/utils/singleton";
 import { OrganizationDataStoresRegistry } from "./organizationDataStoresRegistry.server";
 
 export const organizationDataStoresRegistry = singleton("organizationDataStoresRegistry", () => {
-  const registry = new OrganizationDataStoresRegistry($replica);
+  const registry = new OrganizationDataStoresRegistry(prisma, $replica);
 
   // Runs as soon as this singleton is created (first import of this module). The
   // registry’s `isReady` promise resolves when this eventually succeeds.
diff --git a/apps/webapp/test/clickhouseFactory.test.ts b/apps/webapp/test/clickhouseFactory.test.ts
index 501462ab677..7f19ea1f218 100644
--- a/apps/webapp/test/clickhouseFactory.test.ts
+++ b/apps/webapp/test/clickhouseFactory.test.ts
@@ -16,7 +16,7 @@ describe("ClickHouse Factory", () => {
   postgresTest(
     "returns default client when org has no data store",
     async ({ prisma }) => {
-      const registry = new OrganizationDataStoresRegistry(prisma);
+      const registry = new OrganizationDataStoresRegistry(prisma, prisma);
       await registry.loadFromDatabase();
 
       const factory = new ClickhouseFactory(registry);
@@ -28,7 +28,7 @@ describe("ClickHouse Factory", () => {
   postgresTest(
     "returns org-specific client when a data store is configured",
     async ({ prisma }) => {
-      const registry = new OrganizationDataStoresRegistry(prisma);
+      const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
       await registry.addDataStore({
         key: "factory-store",
@@ -52,7 +52,7 @@ describe("ClickHouse Factory", () => {
   postgresTest(
     "two orgs sharing the same data store get the same cached client",
     async ({ prisma }) => {
-      const registry = new OrganizationDataStoresRegistry(prisma);
+      const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
       await registry.addDataStore({
         key: "shared-factory-store",
@@ -75,7 +75,7 @@ describe("ClickHouse Factory", () => {
   postgresTest(
     "two data stores with different URLs produce different clients",
     async ({ prisma }) => {
-      const registry = new OrganizationDataStoresRegistry(prisma);
+      const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
       await registry.addDataStore({
         key: "store-a",
@@ -104,7 +104,7 @@ describe("ClickHouse Factory", () => {
   postgresTest(
     "after reload with a deleted store, org falls back to default",
     async ({ prisma }) => {
-      const registry = new OrganizationDataStoresRegistry(prisma);
+      const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
       await registry.addDataStore({
         key: "removable-store",
diff --git a/apps/webapp/test/organizationDataStoresRegistry.test.ts b/apps/webapp/test/organizationDataStoresRegistry.test.ts
index f8ff9dde41f..9d94e0447fe 100644
--- a/apps/webapp/test/organizationDataStoresRegistry.test.ts
+++ b/apps/webapp/test/organizationDataStoresRegistry.test.ts
@@ -13,19 +13,19 @@ const TEST_URL_2 = "https://default:password@clickhouse2.example.com:8443";
 
 describe("OrganizationDataStoresRegistry", () => {
   postgresTest("isLoaded is false before loadFromDatabase", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
     expect(registry.isLoaded).toBe(false);
     expect(registry.get("any-org", "CLICKHOUSE")).toBeNull();
   });
 
   postgresTest("isLoaded is true after loadFromDatabase", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
     await registry.loadFromDatabase();
     expect(registry.isLoaded).toBe(true);
   });
 
   postgresTest("isReady resolves after loadFromDatabase", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
     let resolved = false;
     registry.isReady.then(() => {
       resolved = true;
@@ -36,13 +36,13 @@ describe("OrganizationDataStoresRegistry", () => {
   });
 
   postgresTest("get returns null when no data stores exist", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
     await registry.loadFromDatabase();
     expect(registry.get("org-1", "CLICKHOUSE")).toBeNull();
   });
 
   postgresTest("addDataStore creates a row and stores the secret", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
     await registry.addDataStore({
       key: "test-store",
@@ -63,7 +63,7 @@ describe("OrganizationDataStoresRegistry", () => {
   });
 
   postgresTest("loadFromDatabase resolves secrets and makes orgs available via get", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
     await registry.addDataStore({
       key: "hipaa-store",
@@ -81,7 +81,7 @@ describe("OrganizationDataStoresRegistry", () => {
   });
 
   postgresTest("get returns null for orgs not in any data store", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
     await registry.addDataStore({
       key: "partial-store",
@@ -97,7 +97,7 @@ describe("OrganizationDataStoresRegistry", () => {
   });
 
   postgresTest("multiple orgs can share the same data store", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
     await registry.addDataStore({
       key: "shared-store",
@@ -120,7 +120,7 @@ describe("OrganizationDataStoresRegistry", () => {
   postgresTest(
     "when an org appears in multiple data stores, first row by id asc wins",
     async ({ prisma }) => {
-      const registry = new OrganizationDataStoresRegistry(prisma);
+      const registry = new OrganizationDataStoresRegistry(prisma, prisma);
       const sharedOrg = "org-dup-overlap";
 
       await registry.addDataStore({
@@ -151,7 +151,7 @@ describe("OrganizationDataStoresRegistry", () => {
   );
 
   postgresTest("updateDataStore updates organizationIds and rotates the secret", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
     await registry.addDataStore({
       key: "update-store",
@@ -176,7 +176,7 @@ describe("OrganizationDataStoresRegistry", () => {
   });
 
   postgresTest("reload picks up changes made after initial load", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
     await registry.loadFromDatabase();
     expect(registry.get("org-reload", "CLICKHOUSE")).toBeNull();
 
@@ -194,7 +194,7 @@ describe("OrganizationDataStoresRegistry", () => {
   });
 
   postgresTest("deleteDataStore removes the row and its secret", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
     await registry.addDataStore({
       key: "delete-store",
@@ -210,7 +210,7 @@ describe("OrganizationDataStoresRegistry", () => {
   });
 
   postgresTest("after delete and reload, org no longer has a data store", async ({ prisma }) => {
-    const registry = new OrganizationDataStoresRegistry(prisma);
+    const registry = new OrganizationDataStoresRegistry(prisma, prisma);
 
     await registry.addDataStore({
       key: "ephemeral-store",