diff --git a/.devcontainer/compose.yml b/.devcontainer/compose.yml
index b4eed1e..362818b 100644
--- a/.devcontainer/compose.yml
+++ b/.devcontainer/compose.yml
@@ -5,7 +5,7 @@ services:
       dockerfile: Dockerfile
       args:
         # Elixir Version: 1.9, 1.10, 1.10.4, ...
-        VARIANT: "1.19.5"
+        VARIANT: "1.20.0-rc.4"
         # Phoenix Version: 1.4.17, 1.5.4, ...
         PHOENIX_VERSION: "1.7.21"
         # Node Version: 12, 14, ...
diff --git a/.tool-versions b/.tool-versions
index c9c7f48..9861782 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1,2 +1,2 @@
-elixir 1.19.5-otp-28
-erlang 28.4.3
+elixir 1.20.0-rc.4-otp-29
+erlang 29.0-rc3
diff --git a/Dockerfile b/Dockerfile
index 9b2ccad..55afe41 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -13,8 +13,8 @@
 #   - https://pkgs.org/ - resource for finding needed packages
 #   - Ex: hexpm/elixir:1.15.4-erlang-26.0.2-debian-bullseye-20230612-slim
 #
-ARG ELIXIR_VERSION=1.19.5
-ARG OTP_VERSION=28.4.3
+ARG ELIXIR_VERSION=1.20.0-rc.4
+ARG OTP_VERSION=29.0-rc3
 ARG DEBIAN_VERSION=bullseye-20260421-slim
 
 ARG BUILDER_IMAGE="hexpm/elixir:${ELIXIR_VERSION}-erlang-${OTP_VERSION}-debian-${DEBIAN_VERSION}"
diff --git a/mix.exs b/mix.exs
index f67d8cc..526d900 100644
--- a/mix.exs
+++ b/mix.exs
@@ -5,7 +5,7 @@ defmodule ZeroPhoenix.Mixfile do
     [
       app: :zero_phoenix,
       version: "3.6.0",
-      elixir: "~> 1.19.5",
+      elixir: "~> 1.20.0-rc.4",
       elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),