diff --git a/apps/journal/app/lib/sentry.client.ts b/apps/journal/app/lib/sentry.client.ts
index f4ea454..f68cba3 100644
--- a/apps/journal/app/lib/sentry.client.ts
+++ b/apps/journal/app/lib/sentry.client.ts
@@ -5,12 +5,23 @@ import { browserSentryConfig } from "@trails-cool/sentry-config";
 
 let initialized = false;
 
+// Build-time DSN injection: `VITE_SENTRY_DSN` (if set during `pnpm build`)
+// overrides the flagship default so self-hosters can ship their own
+// Sentry project. Set it to `""` (empty string) to disable Sentry on
+// the client entirely.
+const FLAGSHIP_JOURNAL_DSN =
+  "https://a32ffcc575d34be072e91b20f247eeee@o4509530546634752.ingest.de.sentry.io/4509530555547728";
+const CLIENT_DSN =
+  (import.meta.env as Record<string, string | undefined>).VITE_SENTRY_DSN ??
+  FLAGSHIP_JOURNAL_DSN;
+
 export function initSentryClient() {
   if (initialized) return;
   initialized = true;
+  if (!CLIENT_DSN) return;
 
   Sentry.init({
-    dsn: "https://a32ffcc575d34be072e91b20f247eeee@o4509530546634752.ingest.de.sentry.io/4509530555547728",
+    dsn: CLIENT_DSN,
     integrations: [
       Sentry.reactRouterV7BrowserTracingIntegration({
         useEffect,
diff --git a/apps/journal/server.ts b/apps/journal/server.ts
index 5e4f980..abb58ff 100644
--- a/apps/journal/server.ts
+++ b/apps/journal/server.ts
@@ -10,11 +10,20 @@ import { createBoss, startWorker } from "@trails-cool/jobs";
 import { getDatabaseUrl } from "@trails-cool/db";
 import postgres from "postgres";
 
-Sentry.init({
-  dsn: "https://a32ffcc575d34be072e91b20f247eeee@o4509530546634752.ingest.de.sentry.io/4509530555547728",
-  ...nodeSentryConfig("journal server"),
-  beforeSend: drop404s,
-});
+// Sentry DSN is read from env so self-hosted instances don't ship their
+// errors to the trails.cool flagship Sentry by default. The flagship
+// keeps its DSN as the fallback; setting SENTRY_DSN="" (or any other
+// truthy value) overrides. SENTRY_DISABLED=true skips init entirely.
+const FLAGSHIP_JOURNAL_SENTRY_DSN =
+  "https://a32ffcc575d34be072e91b20f247eeee@o4509530546634752.ingest.de.sentry.io/4509530555547728";
+const sentryDsn = process.env.SENTRY_DSN ?? FLAGSHIP_JOURNAL_SENTRY_DSN;
+if (process.env.SENTRY_DISABLED !== "true" && sentryDsn !== "") {
+  Sentry.init({
+    dsn: sentryDsn,
+    ...nodeSentryConfig("journal server"),
+    beforeSend: drop404s,
+  });
+}
 
 const port = Number(process.env.PORT ?? 3000);
 const CLIENT_DIR = resolve(import.meta.dirname, "build", "client");
diff --git a/apps/planner/server.ts b/apps/planner/server.ts
index f1b072c..c480bce 100644
--- a/apps/planner/server.ts
+++ b/apps/planner/server.ts
@@ -11,11 +11,17 @@ import { createBoss, startWorker } from "@trails-cool/jobs";
 import { expireSessionsJob } from "./app/jobs/expire-sessions.ts";
 import postgres from "postgres";
 
-Sentry.init({
-  dsn: "https://5215134cd78d5e6c199e29300b8425af@o4509530546634752.ingest.de.sentry.io/4511102546608208",
-  ...nodeSentryConfig("planner server"),
-  beforeSend: drop404s,
-});
+// See apps/journal/server.ts for the SENTRY_DSN / SENTRY_DISABLED contract.
+const FLAGSHIP_PLANNER_SENTRY_DSN =
+  "https://5215134cd78d5e6c199e29300b8425af@o4509530546634752.ingest.de.sentry.io/4511102546608208";
+const sentryDsn = process.env.SENTRY_DSN ?? FLAGSHIP_PLANNER_SENTRY_DSN;
+if (process.env.SENTRY_DISABLED !== "true" && sentryDsn !== "") {
+  Sentry.init({
+    dsn: sentryDsn,
+    ...nodeSentryConfig("planner server"),
+    beforeSend: drop404s,
+  });
+}
 
 const port = Number(process.env.PORT ?? 3001);
 const CLIENT_DIR = resolve(import.meta.dirname, "build", "client");