diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9006b2a..6ccefe9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+## [4.0.4] - 2026-10-22
+
 ### Changed
 
 - Rewrite the README and crate-root docs around a short example, a table of contents, and
diff --git a/Cargo.toml b/Cargo.toml
index 80085cd..eb125d7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "cached"
-version = "4.0.3"
+version = "4.0.4"
 authors = ["James Kominick <james@kominick.com>"]
 description = "Generic cache implementations and simplified function memoization"
 repository = "https://github.com/jaemk/cached"
diff --git a/docs/migrations/4.0.3-to-4.0.4.md b/docs/migrations/4.0.3-to-4.0.4.md
new file mode 100644
index 0000000..ef94b1e
--- /dev/null
+++ b/docs/migrations/4.0.3-to-4.0.4.md
@@ -0,0 +1,39 @@
+# cached 4.0.3 -> 4.0.4 Migration (Agent Instructions)
+
+Versions: `cached 4.0.3` -> `cached 4.0.4`
+
+`cached_proc_macro` and `cached_proc_macro_types` did not change; leave them pinned at
+`3.0.1` and `3.0.0` respectively if pinned directly.
+
+## Breaking changes
+
+None. This release only reorganizes documentation: the README and crate-root docs are
+rewritten, and the reference material moves to the `stores` and `macros` module docs. No public
+API or runtime behavior changed.
+
+## New APIs
+
+None.
+
+## Detection
+
+Nothing to detect. No existing call site changes meaning.
+
+## Required Cargo.toml change
+
+```toml
+# Before
+cached = "4.0.3"
+
+# After
+cached = "4.0.4"
+```
+
+## VERIFY
+
+```
+cargo build
+cargo test
+```
+
+No new compile errors are expected from the version bump.