diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,13 @@
 
 ## Unreleased
 
+## 0.2.1.2 — 2026-08-07
+
+### Changed
+
+- Upgraded the `baikai` dependency to the `0.5` series (`>=0.5 && <0.6`).
+  Dependency bounds only — no changes to the exported API.
+
 ## 0.2.1.1 - 2026-07-20
 
 ### Changed
diff --git a/shikumi-optimize.cabal b/shikumi-optimize.cabal
--- a/shikumi-optimize.cabal
+++ b/shikumi-optimize.cabal
@@ -1,6 +1,6 @@
 cabal-version:   3.4
 name:            shikumi-optimize
-version:         0.2.1.1
+version:         0.2.1.2
 synopsis:        The optimizer framework for shikumi LM programs (EP-10)
 category:        AI
 description:
@@ -98,7 +98,7 @@
 
   build-depends:
     , aeson
-    , baikai            >=0.4      && <0.5
+    , baikai            >=0.5      && <0.6
     , base
     , containers
     , effectful