diff --git a/.agents/skills/iterate-pr/SKILL.md b/.agents/skills/iterate-pr/SKILL.md
index 6e3ccc68..cfa1a0c2 100644
--- a/.agents/skills/iterate-pr/SKILL.md
+++ b/.agents/skills/iterate-pr/SKILL.md
@@ -131,9 +131,11 @@ that same upstream, so its expectation cannot be inflated by the parent's
 superseded commits.
 
 ```bash
-node ${CLAUDE_SKILL_ROOT}/scripts/propagate_stack.cjs --root <branch> [--dry-run] [--no-push]
+node ${CLAUDE_SKILL_ROOT}/scripts/propagate_stack.cjs --root <branch> [--dry-run] [--no-push] [--no-sign]
 ```
 
+**Every replayed commit is GPG-signed.** A rebase writes new commits, and git signs them only when told to, so a stack signed with `commit -S` comes back unsigned from a plain rebase. The script passes `--gpg-sign`, and a signing failure (usually a locked key) is reported as one, not as a conflict. `--no-sign` opts out for a repository that does not sign.
+
 **One failure path leaves the repo on another branch.** Normal completion, a
 rebase conflict, a balloon guard trip, and a push failure all `checkout` the
 branch you started on before returning. The exception is when checking out a
diff --git a/.agents/skills/iterate-pr/scripts/propagate_stack.cjs b/.agents/skills/iterate-pr/scripts/propagate_stack.cjs
index 5ca79182..632b6022 100755
--- a/.agents/skills/iterate-pr/scripts/propagate_stack.cjs
+++ b/.agents/skills/iterate-pr/scripts/propagate_stack.cjs
@@ -33,7 +33,14 @@
  *   * Push uses --force-with-lease against a freshly fetched origin; the lease
  *     is only meaningful if remote-tracking refs are current, so we fetch first.
  *
- *     node ${CLAUDE_SKILL_ROOT}/scripts/propagate_stack.cjs --root <branch> [--dry-run] [--no-push]
+ * SIGNING: every replayed commit is GPG-signed (`rebase --gpg-sign`). A rebase
+ * writes new commits, and without the flag git signs them only if
+ * `commit.gpgSign` is set, which it is not when a repository signs with an
+ * explicit `commit -S`. Measured on a six-branch stack: 21 of 25 commits came
+ * back unsigned after one propagation, every one of them signed before it.
+ * `--no-sign` opts out, for a repository that does not sign at all.
+ *
+ *     node ${CLAUDE_SKILL_ROOT}/scripts/propagate_stack.cjs --root <branch> [--dry-run] [--no-push] [--no-sign]
  */
 
 const { parseArgs } = require("node:util");
@@ -136,6 +143,7 @@ const main = ({
       "dry-run": { type: "boolean", default: false },
       "no-push": { type: "boolean", default: false },
       "max-own": { type: "string", default: "15" },
+      "no-sign": { type: "boolean", default: false },
     },
   });
 
@@ -227,10 +235,23 @@ const main = ({
     }
 
     const before = gitOut(git, "rev-parse", child);
-    const rebase = git("rebase", "--onto", parent, upstream);
+    const sign = values["no-sign"] ? [] : ["--gpg-sign"];
+    const rebase = git("rebase", ...sign, "--onto", parent, upstream);
     if (rebase.code !== 0) {
       const conflicts = gitOut(git, "diff", "--name-only", "--diff-filter=U");
       git("rebase", "--abort");
+      if (!conflicts && /failed to sign|gpg failed/i.test(rebase.stderr)) {
+        // Not a conflict, and reporting it as one sends the reader looking for
+        // files that do not exist. The key is usually just locked.
+        emit(
+          `  ✗ SIGNING FAILED rebasing ${child}; nothing was rewritten. ` +
+            "Unlock the key (`echo test | gpg --sign > /dev/null`) and run " +
+            "again, or pass --no-sign if this repository does not sign:" +
+            `\n${rebase.stderr.trim()}`
+        );
+        if (start) git("checkout", start);
+        return 7;
+      }
       emit(
         `  ✗ CONFLICT: ${child} onto ${parent} (from ${upstream.slice(0, 9)}, ` +
           `${source}). Needs manual reconcile:`
diff --git a/.agents/skills/iterate-pr/scripts/propagate_stack.test.cjs b/.agents/skills/iterate-pr/scripts/propagate_stack.test.cjs
index 5955cb9c..d1cbeae6 100644
--- a/.agents/skills/iterate-pr/scripts/propagate_stack.test.cjs
+++ b/.agents/skills/iterate-pr/scripts/propagate_stack.test.cjs
@@ -156,12 +156,14 @@ test("a grandchild is rebased from its parent's pre-rebase tip, not from the par
 
   // The fake answers `rev-parse kid` with "sha-of-kid", so that string IS kid's
   // tip as it stood before the first rebase below rewrote it.
-  const rebases = git.calls.filter((c) => c.startsWith("rebase --onto"));
+  const rebases = git.calls.filter((c) =>
+    c.startsWith("rebase --gpg-sign --onto")
+  );
   assert.deepEqual(rebases, [
-    "rebase --onto root kid-forked-at",
-    // NOT "rebase --onto kid kid" — the upstream is where grandkid forked,
+    "rebase --gpg-sign --onto root kid-forked-at",
+    // NOT "rebase --gpg-sign --onto kid kid" — the upstream is where grandkid forked,
     // which is kid's tip BEFORE the line above rewrote it.
-    "rebase --onto kid sha-of-kid",
+    "rebase --gpg-sign --onto kid sha-of-kid",
   ]);
 });
 
@@ -224,7 +226,7 @@ test("--max-own bounds a branch whose expected own-count is unknown", () => {
 test("a conflict aborts the rebase, names the files, and stops the cascade", () => {
   const git = fakeGit({
     overrides: [
-      ["rebase --onto", { code: 1, stderr: "CONFLICT" }],
+      ["rebase --gpg-sign --onto", { code: 1, stderr: "CONFLICT" }],
       ["diff --name-only", { code: 0, stdout: "src/a.ts\nsrc/b.ts" }],
     ],
   });
@@ -242,6 +244,38 @@ test("a conflict aborts the rebase, names the files, and stops the cascade", ()
   );
 });
 
+// A rebase writes new commits, and git signs them only when told to. Without
+// the flag, a stack whose commits were all signed came back 21 of 25 unsigned.
+test("every replayed commit is signed unless --no-sign is passed", () => {
+  const signed = run(["--root", "root", "--no-push"], { git: fakeGit() }).git;
+  assert.ok(signed.calls.some((c) => c.startsWith("rebase --gpg-sign --onto")));
+
+  const unsigned = run(["--root", "root", "--no-push", "--no-sign"], {
+    git: fakeGit(),
+  }).git;
+  assert.ok(unsigned.calls.some((c) => c.startsWith("rebase --onto")));
+  assert.ok(!unsigned.calls.some((c) => c.includes("--gpg-sign")));
+});
+
+test("a signing failure is reported as one, not as a conflict", () => {
+  const git = fakeGit({
+    overrides: [
+      [
+        "rebase --gpg-sign --onto",
+        { code: 1, stderr: "error: gpg failed to sign the data" },
+      ],
+    ],
+  });
+  const { code, lines } = run(["--root", "root"], { git });
+
+  assert.equal(code, 7);
+  assert.match(lines, /SIGNING FAILED rebasing child/);
+  assert.doesNotMatch(lines, /CONFLICT/);
+  assert.ok(git.calls.includes("rebase --abort"));
+  assert.ok(!git.calls.some((c) => c.startsWith("push")));
+  assert.equal(git.calls.at(-1), "checkout start");
+});
+
 // Continuing past a failed checkout would rebase and force-push whichever
 // branch happened to be checked out — the worst outcome available here.
 test("a failed checkout aborts before any rebase", () => {
@@ -275,7 +309,7 @@ test("--no-push skips the fetch and the push, but still rebases", () => {
 
   assert.equal(code, 0);
   assert.match(lines, /not pushed \(--no-push\)/);
-  assert.ok(git.calls.some((c) => c.startsWith("rebase --onto")));
+  assert.ok(git.calls.some((c) => c.startsWith("rebase --gpg-sign --onto")));
   assert.ok(!git.calls.some((c) => c.startsWith("fetch")));
   assert.ok(!git.calls.some((c) => c.startsWith("push")));
 });
@@ -346,7 +380,7 @@ test("a branch missing locally is skipped without stopping the cascade", () => {
   assert.equal(code, 0);
   assert.match(lines, /· skip gone/);
   assert.ok(
-    git.calls.includes("rebase --onto root forked-at"),
+    git.calls.includes("rebase --gpg-sign --onto root forked-at"),
     "the other branch still runs"
   );
 });
@@ -399,7 +433,7 @@ test("with no reflog knowledge of a rewrite, the guard agrees with a wrong upstr
   assert.equal(code, 0, "the run reports success");
   assert.match(lines, /rebased onto root/);
   assert.ok(
-    git.calls.includes("rebase --onto root root"),
+    git.calls.includes("rebase --gpg-sign --onto root root"),
     "the upstream fell back to the parent itself"
   );
   assert.ok(
@@ -459,7 +493,7 @@ test("a conflict on a guessed upstream says which side is the superseded one", (
   const git = fakeGit({
     overrides: [
       ["merge-base --is-ancestor", { code: 1 }],
-      ["rebase --onto", { code: 1, stderr: "CONFLICT" }],
+      ["rebase --gpg-sign --onto", { code: 1, stderr: "CONFLICT" }],
       ["diff --name-only", { code: 0, stdout: "parent.txt" }],
     ],
   });
@@ -476,7 +510,7 @@ test("a conflict on a known fork point carries no guess warning", () => {
   const git = fakeGit({
     forkPoints: { "root->child": "forked-at" },
     overrides: [
-      ["rebase --onto", { code: 1, stderr: "CONFLICT" }],
+      ["rebase --gpg-sign --onto", { code: 1, stderr: "CONFLICT" }],
       ["diff --name-only", { code: 0, stdout: "parent.txt" }],
     ],
   });
@@ -490,7 +524,7 @@ test("the conflict line names where the upstream came from", () => {
   const git = fakeGit({
     forkPoints: { "root->child": "forked-at" },
     overrides: [
-      ["rebase --onto", { code: 1, stderr: "CONFLICT" }],
+      ["rebase --gpg-sign --onto", { code: 1, stderr: "CONFLICT" }],
       ["diff --name-only", { code: 0, stdout: "a.ts" }],
     ],
   });