diff --git a/Cargo.lock b/Cargo.lock
index 28df02ac04..da0b463e46 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4784,9 +4784,9 @@ checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
 
 [[package]]
 name = "perex"
-version = "0.1.11"
+version = "0.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4cacad0d8fd77338345abb71e4f8372ce93bf0e9205d845940f8e789b3fc98a8"
+checksum = "86d57d56f880b3ce759f0423b632c7522e5faa05227b8785154797e749fdc9eb"
 
 [[package]]
 name = "perry"
diff --git a/Cargo.toml b/Cargo.toml
index b025d1fd1e..45a66ca780 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -401,20 +401,21 @@ regex = "1.12"
 aho-corasick = "1.1"
 memchr = "2"
 # The single regular-expression engine, through crates/perry-perex.
-# 0.1.11 carries PerryTS/perex#3 (package-shaped repeats and classes leave the
-# per-character phase loop; release commit 80845f5310, tag v0.1.11). It is
-# younger than the 7-day `global-min-publish-age` soak (.cargo/config.toml),
-# so Cargo.lock was resolved once with CARGO_RESOLVER_INCOMPATIBLE_PUBLISH_AGE=allow
-# under an owner-approved one-time publish-age override (2026-09-28), for this
-# version only; the window itself is unchanged. No public API change from
-# 0.1.10. Published 2026-09-27T21:13:35Z, sha256
-# 4cacad0d8fd77338345abb71e4f8372ce93bf0e9205d845940f8e789b3fc98a8 — the
+# 0.1.12 carries PerryTS/perex#4 (alternatives that cannot begin at the current
+# character are skipped without a frame: a first-character BRANCH, flat
+# alternation, anchoring decided at compile time; program format 14; release
+# commit b97fa7c235, tag v0.1.12). It is younger than the 7-day
+# `global-min-publish-age` soak (.cargo/config.toml), so Cargo.lock was
+# resolved once with CARGO_RESOLVER_INCOMPATIBLE_PUBLISH_AGE=allow under an
+# owner-approved one-time publish-age override (2026-10-08), for this version
+# only; the window itself is unchanged. No public API change from 0.1.11.
+# sha256 86d57d56f880b3ce759f0423b632c7522e5faa05227b8785154797e749fdc9eb — the
 # checksum Cargo.lock records, verified against
-# https://crates.io/api/v1/crates/perex/0.1.11. As with turnloop above, the
+# https://crates.io/api/v1/crates/perex/0.1.12. As with turnloop above, the
 # opt-out is a committed, reviewable change, never a silent one, and the lock
-# pins the exact artifact. The override lapses on its own on 2026-10-04, when
-# 0.1.11 clears the window.
-perex = "0.1.11"
+# pins the exact artifact. The override lapses on its own on 2026-10-15, when
+# 0.1.12 clears the window.
+perex = "0.1.12"
 # turnloop P0/P1: the per-agent event-loop wait driver and, since P1, Perry's
 # stream sockets (docs/turnloop/p0-report.md, crates/perry-runtime/src/turnloop_net).
 # 0.1.0-alpha.3 switched turnloop's own dependency requirements from exact pins
diff --git a/changelog.d/perex-0-1-12.md b/changelog.d/perex-0-1-12.md
new file mode 100644
index 0000000000..711b890f29
--- /dev/null
+++ b/changelog.d/perex-0-1-12.md
@@ -0,0 +1 @@
+perex 0.1.12 (PerryTS/perex#4): alternatives that cannot begin at the current character are skipped without a backtracking frame, so large alternations like an emoji-width regex stop backtracking through every branch. In perry, `emoji.test(c)` 3,396 -> 2,123 instructions per call, `ns.default().test(c)` 3,865 -> 2,593, Claude Code string-width per grapheme 15,161 -> 13,825; commander -0.32%, fastify -0.18%, qs parse -0.18% instructions.