diff --git a/src/respawn-controller.ts b/src/respawn-controller.ts
index 31289e11..0b9419e0 100644
--- a/src/respawn-controller.ts
+++ b/src/respawn-controller.ts
@@ -2078,6 +2078,15 @@ export class RespawnController extends EventEmitter {
       return;
     }
 
+    // Check for active child processes (bash tools, test suites, builds, etc.)
+    const activeProcesses = this.session.getActiveChildProcesses();
+    if (activeProcesses.length > 0) {
+      const names = activeProcesses.map((p) => p.command).join(', ');
+      this.log(`Skipping AI check - ${activeProcesses.length} active child process(es): ${names}`);
+      this.logAction('detection', `Skipped AI check: child processes running (${names})`);
+      return;
+    }
+
     // If AI check is disabled or errored out, fall back to direct idle confirmation
     if (!this.config.aiIdleCheckEnabled || this.aiChecker.status === 'disabled') {
       this.log(`AI check unavailable (${this.aiChecker.status}), confirming idle directly via: ${reason}`);
@@ -2682,6 +2691,18 @@ export class RespawnController extends EventEmitter {
       return;
     }
 
+    // Safety check: if child processes are running (bash tools, test suites, builds, etc.)
+    const activeProcesses = this.session.getActiveChildProcesses();
+    if (activeProcesses.length > 0) {
+      const names = activeProcesses.map((p) => p.command).join(', ');
+      this.log(`Idle confirmation rejected - ${activeProcesses.length} active child process(es): ${names}`);
+      this.logAction('detection', `Rejected: child processes running (${names})`);
+      this.setState('watching');
+      this.startNoOutputTimer();
+      this.startPreFilterTimer();
+      return;
+    }
+
     this.log(`Idle confirmed via: ${reason}`);
     const status = this.getDetectionStatus();
     this.log(
diff --git a/src/session.ts b/src/session.ts
index 7c4a872a..4f4b2b48 100644
--- a/src/session.ts
+++ b/src/session.ts
@@ -29,6 +29,7 @@
  */
 
 import { EventEmitter } from 'node:events';
+import { execSync } from 'node:child_process';
 import { v4 as uuidv4 } from 'uuid';
 import * as pty from 'node-pty';
 import {
@@ -65,6 +66,7 @@ import {
   MAX_MESSAGES,
   MAX_LINE_BUFFER_SIZE,
 } from './config/buffer-limits.js';
+import { EXEC_TIMEOUT_MS } from './config/exec-timeout.js';
 import {
   buildInteractiveArgs,
   buildPromptArgs,
@@ -539,6 +541,77 @@ export class Session extends EventEmitter {
     return this._isWorking;
   }
 
+  /**
+   * Check if the Claude CLI process inside this session's tmux pane has active child processes.
+   * This detects running bash tools, test suites, builds, servers, etc. that Claude spawned.
+   *
+   * Returns an array of {pid, command} for each child process, or empty array if none.
+   * Returns empty array if no mux session or on error (fail-open to avoid blocking respawn).
+   */
+  getActiveChildProcesses(): { pid: number; command: string }[] {
+    if (!this._muxSession) return [];
+
+    try {
+      // Get direct children of the pane PID (typically just the claude process)
+      const panePid = this._muxSession.pid;
+      const claudeChildren = execSync(`pgrep -P ${panePid}`, {
+        encoding: 'utf-8',
+        timeout: EXEC_TIMEOUT_MS,
+      }).trim();
+      if (!claudeChildren) return [];
+
+      const claudePids = claudeChildren
+        .split('\n')
+        .map((p) => parseInt(p, 10))
+        .filter((p) => !Number.isNaN(p));
+
+      // For each Claude process, check for its children (the actual running tools/processes)
+      const activeProcesses: { pid: number; command: string }[] = [];
+      for (const claudePid of claudePids) {
+        try {
+          const toolChildren = execSync(`pgrep -P ${claudePid}`, {
+            encoding: 'utf-8',
+            timeout: EXEC_TIMEOUT_MS,
+          }).trim();
+          if (!toolChildren) continue;
+
+          const toolPids = toolChildren
+            .split('\n')
+            .map((p) => parseInt(p, 10))
+            .filter((p) => !Number.isNaN(p));
+
+          if (toolPids.length === 0) continue;
+
+          // Get command names for the child processes in a single ps call
+          try {
+            const psOutput = execSync(`ps -o pid=,comm= -p ${toolPids.join(',')} 2>/dev/null`, {
+              encoding: 'utf-8',
+              timeout: EXEC_TIMEOUT_MS,
+            }).trim();
+            for (const line of psOutput.split('\n')) {
+              const match = line.trim().match(/^(\d+)\s+(.+)/);
+              if (match) {
+                activeProcesses.push({ pid: parseInt(match[1], 10), command: match[2].trim() });
+              }
+            }
+          } catch {
+            // ps failed — just record PIDs without command names
+            for (const pid of toolPids) {
+              activeProcesses.push({ pid, command: 'unknown' });
+            }
+          }
+        } catch {
+          // No children for this Claude process
+        }
+      }
+
+      return activeProcesses;
+    } catch {
+      // pgrep fails with exit code 1 when no matches — that's normal (no children)
+      return [];
+    }
+  }
+
   get lastPromptTime(): number {
     return this._lastPromptTime;
   }
diff --git a/test/mocks/mock-session.ts b/test/mocks/mock-session.ts
index e1337532..12189665 100644
--- a/test/mocks/mock-session.ts
+++ b/test/mocks/mock-session.ts
@@ -17,6 +17,7 @@ export class MockSession extends EventEmitter {
   status: 'idle' | 'working' = 'idle';
   pid: number = 12345;
   isWorking: boolean = false;
+  private _activeChildProcesses: { pid: number; command: string }[] = [];
   ralphTracker: null = null;
   writeBuffer: string[] = [];
   terminalBuffer: string = '';
@@ -52,9 +53,7 @@ export class MockSession extends EventEmitter {
 
   /** Check if a specific command was written */
   hasWritten(pattern: string | RegExp): boolean {
-    return this.writeBuffer.some((data) =>
-      typeof pattern === 'string' ? data.includes(pattern) : pattern.test(data),
-    );
+    return this.writeBuffer.some((data) => (typeof pattern === 'string' ? data.includes(pattern) : pattern.test(data)));
   }
 
   // ========== Terminal Output Simulation ==========
@@ -113,10 +112,7 @@ export class MockSession extends EventEmitter {
    */
   simulatePlanModePrompt(): void {
     this.simulateTerminalOutput(
-      'Would you like to proceed with this plan?\n' +
-        '\u276f 1. Yes\n' +
-        '  2. No\n' +
-        '  3. Type your own\n',
+      'Would you like to proceed with this plan?\n' + '\u276f 1. Yes\n' + '  2. No\n' + '  3. Type your own\n'
     );
   }
 
@@ -131,11 +127,7 @@ export class MockSession extends EventEmitter {
   /** Simulate token count display */
   simulateTokenCount(tokens: number | string): void {
     const formatted =
-      typeof tokens === 'number'
-        ? tokens >= 1000
-          ? `${(tokens / 1000).toFixed(1)}k`
-          : String(tokens)
-        : tokens;
+      typeof tokens === 'number' ? (tokens >= 1000 ? `${(tokens / 1000).toFixed(1)}k` : String(tokens)) : tokens;
     this.simulateTerminalOutput(`${formatted} tokens used`);
   }
 
@@ -167,6 +159,16 @@ export class MockSession extends EventEmitter {
     return this._muxName;
   }
 
+  /** Check for active child processes (mock returns configurable list) */
+  getActiveChildProcesses(): { pid: number; command: string }[] {
+    return this._activeChildProcesses;
+  }
+
+  /** Set active child processes for testing */
+  setActiveChildProcesses(processes: { pid: number; command: string }[]): void {
+    this._activeChildProcesses = processes;
+  }
+
   // ========== Route-test conveniences ==========
 
   /** Session display name */