diff --git a/hooks/gsd-context-monitor.js b/hooks/gsd-context-monitor.js
index ed36374b2..5b0ae89b9 100644
--- a/hooks/gsd-context-monitor.js
+++ b/hooks/gsd-context-monitor.js
@@ -21,6 +21,7 @@
 const fs = require('fs');
 const os = require('os');
 const path = require('path');
+const { spawn } = require('child_process');
 
 const WARNING_THRESHOLD = 35;  // remaining_percentage <= 35%
 const CRITICAL_THRESHOLD = 25; // remaining_percentage <= 25%
@@ -130,16 +131,27 @@ process.stdin.on('end', () => {
 
     // On CRITICAL with active GSD project, auto-record session state as a
     // breadcrumb for /gsd-resume-work (#1974). Fire-and-forget subprocess —
-    // doesn't block the hook or the agent.
-    if (isCritical && isGsdActive) {
+    // doesn't block the hook or the agent. Fires ONCE per CRITICAL session,
+    // guarded by warnData.criticalRecorded to prevent repeated overwrites
+    // of the "crash moment" record on every debounce cycle.
+    if (isCritical && isGsdActive && !warnData.criticalRecorded) {
       try {
-        const gsdTools = path.join(process.env.HOME || '', '.claude', 'get-shit-done', 'bin', 'gsd-tools.cjs');
-        const timestamp = new Date().toISOString().split('T')[0];
-        require('child_process').spawn(
+        // Runtime-agnostic path: this hook lives at <runtime-config>/hooks/
+        // and gsd-tools.cjs lives at <runtime-config>/get-shit-done/bin/.
+        // Using __dirname makes this work on Claude Code, OpenCode, Gemini,
+        // Kilo, etc. without hardcoding ~/.claude/.
+        const gsdTools = path.join(__dirname, '..', 'get-shit-done', 'bin', 'gsd-tools.cjs');
+        // Coerce usedPct to a safe number in case bridge file is malformed
+        const safeUsedPct = Number(usedPct) || 0;
+        const stoppedAt = `context exhaustion at ${safeUsedPct}% (${new Date().toISOString().split('T')[0]})`;
+        spawn(
           process.execPath,
-          [gsdTools, 'state', 'update', 'Stopped At', `context exhaustion at ${usedPct}% (${timestamp})`],
+          [gsdTools, 'state', 'record-session', '--stopped-at', stoppedAt],
           { cwd, detached: true, stdio: 'ignore' }
         ).unref();
+        warnData.criticalRecorded = true;
+        // Persist the sentinel so subsequent debounce cycles don't re-fire
+        fs.writeFileSync(warnPath, JSON.stringify(warnData));
       } catch { /* non-critical — don't let state recording break the hook */ }
     }
 
diff --git a/tests/bug-1974-context-exhaustion-record.test.cjs b/tests/bug-1974-context-exhaustion-record.test.cjs
new file mode 100644
index 000000000..2cebdd82b
--- /dev/null
+++ b/tests/bug-1974-context-exhaustion-record.test.cjs
@@ -0,0 +1,179 @@
+/**
+ * Integration tests for gsd-context-monitor.js auto-record on CRITICAL (#1974).
+ *
+ * Verifies:
+ * 1. On CRITICAL + active GSD project, subprocess is spawned and STATE.md
+ *    receives the "Stopped At" field.
+ * 2. Subsequent CRITICAL firings within the same session do NOT re-fire
+ *    the subprocess (sentinel guard prevents repeated overwrites).
+ * 3. When no .planning/STATE.md exists, the subprocess is not spawned.
+ * 4. Path resolution uses __dirname, not hardcoded ~/.claude/.
+ */
+
+'use strict';
+
+const { test, describe, beforeEach, afterEach } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const os = require('node:os');
+const { spawnSync } = require('node:child_process');
+
+const HOOK_PATH = path.resolve(__dirname, '..', 'hooks', 'gsd-context-monitor.js');
+
+/**
+ * Run the hook with a given session id and context percentage.
+ * Writes a bridge metrics file first, then pipes the hook input via stdin.
+ * Returns after the hook exits.
+ */
+function runHook(sessionId, remainingPct, cwd) {
+  // Write the bridge metrics file the hook reads
+  const bridgePath = path.join(os.tmpdir(), `claude-ctx-${sessionId}.json`);
+  fs.writeFileSync(bridgePath, JSON.stringify({
+    session_id: sessionId,
+    remaining_percentage: remainingPct,
+    used_pct: 100 - remainingPct,
+    timestamp: Math.floor(Date.now() / 1000),
+  }));
+
+  const input = JSON.stringify({
+    session_id: sessionId,
+    cwd,
+  });
+
+  const result = spawnSync(process.execPath, [HOOK_PATH], {
+    input,
+    encoding: 'utf-8',
+    timeout: 10000,
+    env: { ...process.env, HOME: process.env.HOME },
+  });
+
+  return { exitCode: result.status, stdout: result.stdout, stderr: result.stderr };
+}
+
+/**
+ * Wait up to `ms` for a file to exist (the subprocess is fire-and-forget).
+ */
+function waitForStoppedAt(statePath, ms = 2000) {
+  const deadline = Date.now() + ms;
+  while (Date.now() < deadline) {
+    try {
+      const content = fs.readFileSync(statePath, 'utf-8');
+      if (/Stopped [Aa]t.*context exhaustion/.test(content)) return content;
+    } catch { /* file may briefly not exist during atomic write */ }
+    // Tight poll loop — subprocess should complete in <100ms
+    const start = Date.now();
+    while (Date.now() - start < 50) { /* spin */ }
+  }
+  return null;
+}
+
+describe('#1974 context exhaustion auto-record', () => {
+  let tmpDir;
+  let statePath;
+  let sessionId;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-1974-'));
+    const planningDir = path.join(tmpDir, '.planning');
+    fs.mkdirSync(planningDir, { recursive: true });
+
+    // Minimal STATE.md with Stopped At field
+    statePath = path.join(planningDir, 'STATE.md');
+    fs.writeFileSync(statePath, [
+      '# Session State',
+      '',
+      '**Current Phase:** 1',
+      '**Status:** executing',
+      '**Last session:** unset',
+      '**Last Date:** unset',
+      '**Stopped At:** None',
+      '**Resume File:** None',
+      '',
+    ].join('\n'));
+
+    // Minimal config.json required by gsd-tools
+    fs.writeFileSync(path.join(planningDir, 'config.json'), JSON.stringify({ project_code: 'TEST' }));
+
+    sessionId = `test-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+    // Clean up bridge files
+    try {
+      const warnPath = path.join(os.tmpdir(), `claude-ctx-${sessionId}-warned.json`);
+      if (fs.existsSync(warnPath)) fs.unlinkSync(warnPath);
+      const bridgePath = path.join(os.tmpdir(), `claude-ctx-${sessionId}.json`);
+      if (fs.existsSync(bridgePath)) fs.unlinkSync(bridgePath);
+    } catch { /* noop */ }
+  });
+
+  test('spawns subprocess and writes Stopped At field on CRITICAL with active GSD', () => {
+    // Trigger CRITICAL — remaining <= 25
+    const result = runHook(sessionId, 20, tmpDir);
+    assert.strictEqual(result.exitCode, 0, `hook should exit 0: ${result.stderr}`);
+
+    // Wait for fire-and-forget subprocess to write STATE.md
+    const content = waitForStoppedAt(statePath);
+    assert.ok(content, `STATE.md should contain "context exhaustion" after CRITICAL fire`);
+    assert.match(content, /context exhaustion at \d+%/);
+  });
+
+  test('does NOT spawn subprocess when .planning/STATE.md is absent', () => {
+    // Delete STATE.md to simulate non-GSD project
+    fs.unlinkSync(statePath);
+    const originalMtime = Date.now();
+
+    const result = runHook(sessionId, 20, tmpDir);
+    assert.strictEqual(result.exitCode, 0);
+
+    // Wait a bit then verify STATE.md was NOT recreated
+    const start = Date.now();
+    while (Date.now() - start < 500) { /* spin */ }
+    assert.ok(!fs.existsSync(statePath), 'STATE.md should not be recreated when absent');
+  });
+
+  test('sentinel prevents repeated firing within same session', () => {
+    // First CRITICAL fire — should record
+    runHook(sessionId, 20, tmpDir);
+    const content1 = waitForStoppedAt(statePath);
+    assert.ok(content1, 'first fire should record Stopped At');
+
+    // Extract the timestamp from first fire
+    const firstMatch = content1.match(/context exhaustion at (\d+)%/);
+    assert.ok(firstMatch, 'first fire should have numeric usedPct');
+
+    // Manually set Stopped At to a sentinel value to detect second fire
+    const modified = content1.replace(/(\*\*Stopped At:\*\*) .+/, '$1 SENTINEL_SHOULD_NOT_CHANGE');
+    fs.writeFileSync(statePath, modified);
+
+    // Second CRITICAL fire — should NOT re-fire the subprocess
+    runHook(sessionId, 18, tmpDir);
+
+    // Wait and verify the sentinel is preserved
+    const start = Date.now();
+    while (Date.now() - start < 500) { /* spin */ }
+    const content2 = fs.readFileSync(statePath, 'utf-8');
+    assert.match(
+      content2,
+      /SENTINEL_SHOULD_NOT_CHANGE/,
+      'second CRITICAL fire should not re-record (sentinel guard)'
+    );
+  });
+
+  test('hook uses __dirname-based path (runtime-agnostic)', () => {
+    // Verify the hook source references __dirname, not ~/.claude/
+    const hookSource = fs.readFileSync(HOOK_PATH, 'utf-8');
+    assert.match(
+      hookSource,
+      /path\.join\(__dirname,\s*'\.\.',\s*'get-shit-done'/,
+      'hook must use __dirname-based path resolution for gsd-tools.cjs'
+    );
+    assert.doesNotMatch(
+      hookSource,
+      /process\.env\.HOME.*\.claude.*get-shit-done.*gsd-tools\.cjs/,
+      'hook must not hardcode ~/.claude/ path'
+    );
+  });
+});