debugger: defer probe pause handling until startup

Keep the initial --inspect-brk pause held until probe breakpoints are
bound and probe mode explicitly releases the target. This prevents the
generic pause handler from resuming user code before probes are ready.

Refs: https://github.com/nodejs/node/actions/runs/26482141780/job/77981519238

Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: openai:gpt-5.5
PR-URL: #63608
Refs: https://github.com/nodejs/node/actions/runs/26482141780/job/77981519238
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>

Author: trivikr

lib/internal/debugger/inspect_probe.js

@@ -491,6 +491,10 @@ class ProbeInspectorSession {
 
   async handlePaused(params) {
     if (this.finished) { return; }
+    // Ignore pauses that arrive before breakpoint setup is complete. Once
+    // startup is marked complete, `Runtime.runIfWaitingForDebugger` may surface
+    // the initial --inspect-brk pause, which the normal resume path handles.
+    if (!this.started) { return; }
 
     const hitBreakpoints = params.hitBreakpoints;
     if (hitBreakpoints === undefined || hitBreakpoints.length === 0) {
@@ -723,5 +727,6 @@ async function runProbeMode(stdout, probeOptions) {
 
 module.exports = {
   parseProbeTokens,
+  ProbeInspectorSession,
   runProbeMode,
 };

test/parallel/test-debugger-probe-startup-pause.js

@@ -0,0 +1,32 @@
+// Flags: --expose-internals
+// This tests that probe mode ignores pauses until startup has finished binding
+// breakpoints.
+'use strict';
+
+const common = require('../common');
+common.skipIfInspectorDisabled();
+
+const assert = require('assert');
+const { ProbeInspectorSession } = require('internal/debugger/inspect_probe');
+
+const session = new ProbeInspectorSession({
+  probes: [],
+});
+
+const cdpCalls = [];
+session.client = {
+  callMethod: common.mustCall(async (method) => {
+    cdpCalls.push(method);
+  }),
+};
+
+async function testStartupPauseHandling() {
+  await session.handlePaused({});
+  assert.deepStrictEqual(cdpCalls, []);
+
+  session.started = true;
+  await session.handlePaused({});
+  assert.deepStrictEqual(cdpCalls, ['Debugger.resume']);
+}
+
+testStartupPauseHandling().then(common.mustCall());