diff --git a/.changeset/graceful-elks-wander.md b/.changeset/graceful-elks-wander.md
new file mode 100644
index 000000000..3cce123e4
--- /dev/null
+++ b/.changeset/graceful-elks-wander.md
@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 4034
+---
+audit-open summary counts now include the display-truncation remainder: a milestone with more than 5 open files reported counts capped at 5 because the _remainder_count display marker was counted as one item instead of the real files it records (#3817)
diff --git a/scripts/lint-test-file-count.allowlist.json b/scripts/lint-test-file-count.allowlist.json
index cb907d7be..4e6cec476 100644
--- a/scripts/lint-test-file-count.allowlist.json
+++ b/scripts/lint-test-file-count.allowlist.json
@@ -257,10 +257,11 @@
         "audit-command-cutover.test.cjs",
         "audit-fix-command.test.cjs",
         "audit-milestone-filename-guard.test.cjs",
+        "audit-open-remainder-count.test.cjs",
         "audit-uat-acknowledged.test.cjs",
         "audit-workstream-layouts.test.cjs"
       ],
-      "issue": "#3804/#3805 \u2014 audit-layout and acknowledged-marker suites drive the real audit-uat CLI against on-disk fixtures"
+      "issue": "#3804/#3805 \u2014 audit-layout and acknowledged-marker suites drive the real audit-uat CLI against on-disk fixtures | #3817 \u2014 regression suite proving countReal counts the truncation remainder marker instead of treating it as one phantom item"
     }
   }
 }
diff --git a/src/audit.cts b/src/audit.cts
index 78b0c3596..53d512a40 100644
--- a/src/audit.cts
+++ b/src/audit.cts
@@ -1337,9 +1337,17 @@ function auditOpenArtifacts(cwd: string): AuditResult {
     try { return scanDeferredItems(planDir, cwd); } catch { return { items: [{ scan_error: true, phase: '', file: '', text: '' }], acknowledged: 0 }; }
   })();
 
-  // Count real items (not scan_error sentinels)
+  // Count real items (not scan_error sentinels). #3817: a `_remainder_count`
+  // marker is not a phantom — it RECORDS real items the detail list truncated
+  // away for display, so its value counts toward the total. Truncation limits
+  // display, never counting; only scan_error (a read failure, not an item)
+  // contributes zero.
   const countReal = (arr: Array<{ scan_error?: boolean; _remainder_count?: number }>) =>
-    arr.filter(i => !i.scan_error && !i._remainder_count).length;
+    arr.reduce((sum, i) => {
+      if (i.scan_error) return sum;
+      if (typeof i._remainder_count === 'number') return sum + i._remainder_count;
+      return sum + 1;
+    }, 0);
 
   const counts: AuditCounts = {
     debug_sessions: countReal(debugSessions.items),
diff --git a/tests/audit-command-cutover.test.cjs b/tests/audit-command-cutover.test.cjs
index c240d448f..d4ee199e7 100644
--- a/tests/audit-command-cutover.test.cjs
+++ b/tests/audit-command-cutover.test.cjs
@@ -2259,7 +2259,9 @@ describe('bug #950: quick-task SUMMARY must carry status: complete', () => {
       }
 
       const before = audit(tmpDir);
-      assert.equal(before.counts.todos, 5, 'display cap: 5 of 7 shown in one scan');
+      // #3817: the display cap truncates the DETAIL list, not the count —
+      // 7 pending files means counts.todos is 7 (5 shown + remainder 2).
+      assert.equal(before.counts.todos, 7, 'counts include the truncation remainder (#3817)');
       assert.equal(before.has_open_items, true);
 
       const shown = before.items.todos.filter((i) => !i.scan_error && !i._remainder_count).map((i) => i.filename);
diff --git a/tests/audit-open-remainder-count.test.cjs b/tests/audit-open-remainder-count.test.cjs
new file mode 100644
index 000000000..621cbe65b
--- /dev/null
+++ b/tests/audit-open-remainder-count.test.cjs
@@ -0,0 +1,120 @@
+'use strict';
+
+// ─────────────────────────────────────────────────────────────────────────────
+// #3817 — audit-open's counts must include the truncation remainder.
+//
+// The todo scan truncates its detail list at 5 and pushes a synthetic
+// {_remainder_count: N} marker; the counting pass filtered that marker out
+// alongside scan_error, so counts.todos and counts.total read systematically
+// low by exactly N — the remainder existed only in the "… and N more" prose
+// (reporter: 19 pending, reported 5). Truncation limits display, never
+// counting.
+// ─────────────────────────────────────────────────────────────────────────────
+
+const { test, describe } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const { createTempProject, cleanup, runGsdTools } = require('./helpers.cjs');
+
+function runAuditOpen(cwd) {
+  const r = runGsdTools(['audit-open', '--json'], cwd);
+  assert.ok(r.success, r.error);
+  return JSON.parse(r.output);
+}
+
+describe('#3817: audit-open counts include the truncation remainder', () => {
+  test('#3817: more than 5 todo files → counts.todos counts every pending file', (t) => {
+    const tmpDir = createTempProject('gsd-3817-many-');
+    t.after(() => cleanup(tmpDir));
+    const pendingDir = path.join(tmpDir, '.planning', 'todos', 'pending');
+    fs.mkdirSync(pendingDir, { recursive: true });
+    const TOTAL = 8; // 5 shown + remainder 3
+    for (let i = 1; i <= TOTAL; i++) {
+      fs.writeFileSync(path.join(pendingDir, `todo-${String(i).padStart(2, '0')}.md`), [
+        '---',
+        'title: Fix thing ' + i,
+        'area: general',
+        'created: 2026-08-01',
+        '---',
+        '',
+        'Body ' + i,
+        '',
+      ].join('\n'));
+    }
+
+    const out = runAuditOpen(tmpDir);
+    assert.equal(
+      out.counts.todos,
+      TOTAL,
+      `#3817: counts.todos must count every pending todo file (${TOTAL}); got ${out.counts.todos}`,
+    );
+    assert.equal(
+      out.counts.total,
+      TOTAL,
+      `#3817: counts.total must include the remainder; got ${out.counts.total}`,
+    );
+    // The display contract is unchanged: at most 5 detail objects, and the
+    // prose still announces the remainder.
+    assert.ok(
+      Array.isArray(out.items && out.items.todos),
+      'todos detail list present',
+    );
+    const detailFiles = out.items.todos.filter((i) => i && i.filename);
+    assert.ok(detailFiles.length <= 5, `display stays truncated; got ${detailFiles.length}`);
+  });
+
+  test('#3817 boundary: exactly 5 files → no marker, counts exact; 6 files → remainder 1', (t) => {
+    const tmpDir = createTempProject('gsd-3817-boundary-');
+    t.after(() => cleanup(tmpDir));
+    const pendingDir = path.join(tmpDir, '.planning', 'todos', 'pending');
+    fs.mkdirSync(pendingDir, { recursive: true });
+    const seed = (n) => fs.writeFileSync(path.join(pendingDir, `todo-${n}.md`), [
+      '---',
+      'title: T ' + n,
+      'area: general',
+      'created: 2026-08-01',
+      '---',
+      '',
+      'Body',
+      '',
+    ].join('\n'));
+
+    for (let i = 1; i <= 5; i++) seed(i);
+    let out = runAuditOpen(tmpDir);
+    assert.equal(out.counts.todos, 5, 'exactly at the cap: no marker, count exact');
+    const markers5 = (out.items.todos || []).filter((i) => i && typeof i._remainder_count === 'number');
+    assert.equal(markers5.length, 0, 'no marker emitted at exactly 5');
+
+    seed(6);
+    out = runAuditOpen(tmpDir);
+    assert.equal(out.counts.todos, 6, 'one past the cap: remainder 1 counted');
+    const marker = (out.items.todos || []).find((i) => i && typeof i._remainder_count === 'number');
+    assert.ok(marker, 'marker present at 6');
+    assert.equal(marker._remainder_count, 1, 'marker records exactly the dropped count');
+  });
+
+  test('#3817 control: 5 or fewer todo files → counts unchanged', (t) => {
+    const tmpDir = createTempProject('gsd-3817-few-');
+    t.after(() => cleanup(tmpDir));
+    const pendingDir = path.join(tmpDir, '.planning', 'todos', 'pending');
+    fs.mkdirSync(pendingDir, { recursive: true });
+    for (let i = 1; i <= 3; i++) {
+      fs.writeFileSync(path.join(pendingDir, `todo-${i}.md`), [
+        '---',
+        'title: T ' + i,
+        'area: general',
+        'created: 2026-08-01',
+        '---',
+        '',
+        'Body',
+        '',
+      ].join('\n'));
+    }
+
+    const out = runAuditOpen(tmpDir);
+    assert.equal(out.counts.todos, 3, 'no truncation → counts exact');
+    assert.equal(out.counts.total, 3);
+  });
+});