diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7f6f53d..69a10eb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@ this crate adheres to [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+## [0.4.0] — 2026-09-07
+
 ### Changed
 
 - **`alkcall` dependency bumped to 0.7.0** (CF-005/006/007 — the
@@ -31,7 +33,9 @@ this crate adheres to [Semantic Versioning](https://semver.org/).
   (`from_wss`'s pending-call fail-all is retryable
   `CONNECTION_CLOSED`). The code is `retryable: true`, so the existing
   `retry_after` details path applies on 503. Tests pin the mapping and
-  the `Retry-After` passthrough.
+  the `Retry-After` passthrough. Behavioral break for HTTP callers
+  matching on the 500 previously emitted for this code — hence a minor
+  bump, not a patch.
 
 ## [0.3.0] — 2026-09-07
 
diff --git a/Cargo.lock b/Cargo.lock
index e61f565..db51474 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -48,7 +48,7 @@ dependencies = [
 
 [[package]]
 name = "alkhttp"
-version = "0.3.0"
+version = "0.4.0"
 dependencies = [
  "alkcall",
  "arc-swap",
diff --git a/Cargo.toml b/Cargo.toml
index 6fdc487..1943140 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "alkhttp"
-version = "0.3.0"
+version = "0.4.0"
 edition = "2021"
 rust-version = "1.85"
 license = "MIT OR Apache-2.0"
diff --git a/README.md b/README.md
index cfd5ea3..b78e330 100644
--- a/README.md
+++ b/README.md
@@ -161,7 +161,7 @@ A lean single-side build takes `default-features = false` plus the side
 it needs:
 
 ```toml
-alkhttp = { version = "0.3", default-features = false, features = ["server"] }
+alkhttp = { version = "0.4", default-features = false, features = ["server"] }
 ```
 
 ## Security posture