diff --git a/src/headless.ts b/src/headless.ts
index 503ca9afd..cd0d86124 100644
--- a/src/headless.ts
+++ b/src/headless.ts
@@ -259,7 +259,9 @@ async function runHeadlessOnce(options: HeadlessOptions, restartCount: number):
   // per-unit timeout via auto-supervisor. Disable the overall timeout unless the
   // user explicitly set --timeout.
   const isAutoMode = options.command === 'auto'
-  const isMultiTurnCommand = options.command === 'auto' || options.command === 'next'
+  // discuss and plan are multi-turn: they involve multiple question rounds,
+  // codebase scanning, and artifact writing before the workflow completes (#3547).
+  const isMultiTurnCommand = options.command === 'auto' || options.command === 'next' || options.command === 'discuss' || options.command === 'plan'
   if (isAutoMode && options.timeout === 300_000) {
     options.timeout = 0
   }
diff --git a/src/tests/headless-multi-turn.test.ts b/src/tests/headless-multi-turn.test.ts
new file mode 100644
index 000000000..19cb1b9bb
--- /dev/null
+++ b/src/tests/headless-multi-turn.test.ts
@@ -0,0 +1,19 @@
+/**
+ * Regression test for #3547: discuss and plan must be classified as
+ * multi-turn commands in headless mode.
+ */
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+test("headless.ts classifies discuss as multi-turn (#3547)", () => {
+  const src = readFileSync(join(__dirname, "..", "headless.ts"), "utf-8");
+  const multiTurnLine = src.match(/isMultiTurnCommand\s*=\s*[^;]+/);
+  assert.ok(multiTurnLine, "isMultiTurnCommand must be defined");
+  assert.ok(multiTurnLine![0].includes("discuss"), "discuss must be in multi-turn list");
+  assert.ok(multiTurnLine![0].includes("plan"), "plan must be in multi-turn list");
+});