diff --git a/packages/node/src/sdk/client.ts b/packages/node/src/sdk/client.ts
index 76a4323f3f75..01de1b58fd82 100644
--- a/packages/node/src/sdk/client.ts
+++ b/packages/node/src/sdk/client.ts
@@ -17,6 +17,7 @@ import {
   type SentryTracerProvider,
   setOpenTelemetryContextAsyncContextStrategy,
 } from '@sentry/opentelemetry';
+import { registerDiagnosticsChannelInjection } from '@sentry/server-runtime-injection/register';
 import { setAsyncLocalStorageAsyncContextStrategy } from '@sentry/server-utils';
 import { isMainThread, threadId } from 'worker_threads';
 import { DEBUG_BUILD } from '../debug-build';
@@ -24,6 +25,10 @@ import type { NodeClientOptions } from '../types';
 
 const DEFAULT_CLIENT_REPORT_FLUSH_INTERVAL_MS = 60_000; // 60s was chosen arbitrarily
 
+// Treeshakable guard to remove all code related to runtime diagnostics-channel injection. Set to
+// `false` at build time by the Sentry bundler plugins' `bundleSizeOptimizations.excludeChannelInjection`.
+declare const __SENTRY_CHANNEL_INJECTION__: boolean | undefined;
+
 /** A client for using Sentry with Node & OpenTelemetry. */
 export class NodeClient extends ServerRuntimeClient<NodeClientOptions> {
   public traceProvider: SentryTracerProvider | undefined;
@@ -82,6 +87,21 @@ export class NodeClient extends ServerRuntimeClient<NodeClientOptions> {
     // Same constructor anchoring as above: every client must continue incoming (remote) traces,
     // also manually constructed ones that never run `initOtel`.
     registerPrepareSpanScope(this);
+
+    // Install the channel-based (orchestrion diagnostics-channel) instrumentation hooks here, in the
+    // constructor, so that every client installs them — not only the one built by the Node SDK's
+    // `init()`. Downstream SDKs construct a client without going through that path, and would
+    // otherwise never install the hooks. Registration is idempotent (a global marker guards it), so
+    // a second construction is harmless. The channel integrations capture errors as well as spans,
+    // so this is independent of tracing. Opt out at runtime with `enableRuntimeChannelInjection:
+    // false`, or at build time via the bundler plugins'
+    // `bundleSizeOptimizations.excludeChannelInjection` (which tree-shakes this whole block away).
+    if (
+      (typeof __SENTRY_CHANNEL_INJECTION__ === 'undefined' || __SENTRY_CHANNEL_INJECTION__) &&
+      options.enableRuntimeChannelInjection !== false
+    ) {
+      registerDiagnosticsChannelInjection();
+    }
   }
 
   /** @inheritDoc */
diff --git a/packages/node/src/sdk/index.ts b/packages/node/src/sdk/index.ts
index d98b800c8abb..6f7d96a22f42 100644
--- a/packages/node/src/sdk/index.ts
+++ b/packages/node/src/sdk/index.ts
@@ -17,7 +17,6 @@ import {
 } from '@sentry/core';
 import { isMainThread, parentPort } from 'node:worker_threads';
 import { detectOrchestrionSetup, getErrorIntegrations, getTracingIntegrations } from '@sentry/server-utils';
-import { registerDiagnosticsChannelInjection } from '@sentry/server-runtime-injection/register';
 import { DEBUG_BUILD } from '../debug-build';
 import { childProcessIntegration } from '../integrations/childProcess';
 import { consoleIntegration } from '../integrations/console';
@@ -41,10 +40,6 @@ import { defaultStackParser, getSentryRelease } from './api';
 import { NodeClient } from './client';
 import { initOpenTelemetry } from './initOtel';
 
-// Treeshakable guard to remove all code related to runtime diagnostics-channel injection. Set to
-// `false` at build time by the Sentry bundler plugins' `bundleSizeOptimizations.excludeChannelInjection`.
-declare const __SENTRY_CHANNEL_INJECTION__: boolean | undefined;
-
 /**
  * Get the base default integrations shared by all Node SDK default-integration sets.
  */
@@ -134,9 +129,10 @@ function _init(
 
   applySdkMetadata(options, 'node');
 
-  // Enable debug logging before channel-injection registration below, so its failure modes (e.g. no
-  // available Node hook API, dep-resolution errors) actually surface. `getClientOptions` resolves
-  // `debug` the same way for the client; resolving it here as well keeps the two in agreement.
+  // Enable debug logging before the client is created, so failure modes during setup (e.g. the
+  // channel-injection registration finding no available Node hook API, or dep-resolution errors)
+  // actually surface. `getClientOptions` resolves `debug` the same way for the client; resolving it
+  // here as well keeps the two in agreement.
   if (envToBool(options.debug ?? process.env.SENTRY_DEBUG)) {
     if (DEBUG_BUILD) {
       debug.enable();
@@ -158,18 +154,6 @@ function _init(
     tracesSampleRate: getTracesSampleRate(options.tracesSampleRate),
   };
 
-  // Install the channel-based (orchestrion diagnostics-channel) instrumentation hooks by default,
-  // independent of tracing — the channel integrations also capture errors, not just spans. Opt out at
-  // runtime with `enableRuntimeChannelInjection: false`, or at build time via the bundler plugins'
-  // `bundleSizeOptimizations.excludeChannelInjection` (which tree-shakes this whole block away).
-  // Install as early as possible, before the app imports its instrumented modules.
-  if (
-    (typeof __SENTRY_CHANNEL_INJECTION__ === 'undefined' || __SENTRY_CHANNEL_INJECTION__) &&
-    options.enableRuntimeChannelInjection !== false
-  ) {
-    registerDiagnosticsChannelInjection();
-  }
-
   // Only use Node SDK defaults if none provided.
   const defaultIntegrations = options.defaultIntegrations ?? getDefaultIntegrationsImpl(optionsWithResolvedTracing);
 
diff --git a/packages/node/test/sdk/diagnosticsChannelInjection.test.ts b/packages/node/test/sdk/diagnosticsChannelInjection.test.ts
index fab55e968706..c90d467da20f 100644
--- a/packages/node/test/sdk/diagnosticsChannelInjection.test.ts
+++ b/packages/node/test/sdk/diagnosticsChannelInjection.test.ts
@@ -14,7 +14,9 @@ vi.mock('@sentry/server-utils', async importOriginal => {
   return { ...actual, detectOrchestrionSetup };
 });
 
+import { NodeClient } from '../../src/sdk/client';
 import { init } from '../../src/sdk';
+import { getDefaultNodeClientOptions } from '../helpers/getDefaultNodeClientOptions';
 import { cleanupOtel, resetGlobals } from '../helpers/mockSdkInit';
 
 // eslint-disable-next-line no-var
@@ -83,3 +85,44 @@ describe('diagnostics-channel injection', () => {
     }
   });
 });
+
+// The registration lives in the `NodeClient` constructor, so downstream SDKs that build a client
+// directly (without going through the Node SDK's `init()`) still install the injection hooks.
+describe('diagnostics-channel injection on direct client construction', () => {
+  beforeEach(() => {
+    global.__SENTRY__ = {};
+    vi.spyOn(debug, 'enable').mockImplementation(() => undefined);
+  });
+
+  afterEach(() => {
+    cleanupOtel();
+    resetGlobals();
+    vi.clearAllMocks();
+  });
+
+  it('registers the injection hooks when a NodeClient is constructed directly', () => {
+    new NodeClient(getDefaultNodeClientOptions({ enableOpenTelemetrySetup: false }));
+
+    expect(registerDiagnosticsChannelInjection).toHaveBeenCalledTimes(1);
+  });
+
+  it('does not register the injection hooks when `enableRuntimeChannelInjection` is false', () => {
+    new NodeClient(
+      getDefaultNodeClientOptions({ enableRuntimeChannelInjection: false, enableOpenTelemetrySetup: false }),
+    );
+
+    expect(registerDiagnosticsChannelInjection).not.toHaveBeenCalled();
+  });
+
+  it('does not register the injection hooks when the `__SENTRY_CHANNEL_INJECTION__` build flag is false', () => {
+    vi.stubGlobal('__SENTRY_CHANNEL_INJECTION__', false);
+
+    try {
+      new NodeClient(getDefaultNodeClientOptions({ enableOpenTelemetrySetup: false }));
+
+      expect(registerDiagnosticsChannelInjection).not.toHaveBeenCalled();
+    } finally {
+      vi.unstubAllGlobals();
+    }
+  });
+});