diff --git a/README.md b/README.md
index 85f8428..961c1f5 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@
 ![plugin: lua](https://img.shields.io/badge/plugin-lua-000080?style=flat&logo=lua&logoColor=white)
 [![runtime: mise](https://img.shields.io/badge/runtime-mise-7c3aed?style=flat)](https://mise.jdx.dev)
 ![tests: 82 passing](https://img.shields.io/badge/tests-82%20passing-brightgreen?style=flat)
-[![shiv: v0.3.6](https://img.shields.io/badge/shiv-v0.3.6-blue?style=flat)](https://github.com/KnickKnackLabs/shiv)
+[![shiv: v0.4.0](https://img.shields.io/badge/shiv-v0.4.0-blue?style=flat)](https://github.com/KnickKnackLabs/shiv)
 [![License: MIT](https://img.shields.io/badge/License-MIT-blue?style=flat)](LICENSE)
 
 </div>
@@ -37,7 +37,7 @@ mise install "shiv:shimmer@0.0.1-alpha"
   │    list git tags + branch pseudo-version → ["main", "0.0.1-alpha"]
   │
   ├─ BackendInstall
-  │    ensure shiv is bootstrapped (pinned to v0.3.6)
+  │    ensure shiv is bootstrapped (pinned to v0.4.0)
   │    SHIV_PACKAGES_DIR=<install_path>/packages \
   │    SHIV_BIN_DIR=<install_path>/bin \
   │      mise -C <shiv> run install shimmer@v0.0.1-alpha
@@ -46,7 +46,7 @@ mise install "shiv:shimmer@0.0.1-alpha"
        PATH += <install_path>/bin
 ```
 
-The plugin maintains its own shiv clone at `~/.local/share/mise/shiv-backend/shiv/`, pinned to `v0.3.6` for reproducibility. This is separate from any user-installed shiv — the plugin's build infrastructure doesn't change unless you deliberately update it.
+The plugin maintains its own shiv clone at `~/.local/share/mise/shiv-backend/shiv/`, pinned to `v0.4.0` for reproducibility. This is separate from any user-installed shiv — the plugin's build infrastructure doesn't change unless you deliberately update it.
 
 Version isolation comes from overriding shiv's path environment variables. Each version gets its own directory under mise's installs, so project A can pin `shimmer@0.0.1-alpha` while project B tracks the newest release with `latest`.
 
@@ -80,7 +80,7 @@ VFOX_SHIV_PATH     Path to plugin's shiv clone
                    Default: ~/.local/share/mise/shiv-backend/shiv
 
 VFOX_SHIV_REF      Pinned shiv version for bootstrap
-                   Default: v0.3.6
+                   Default: v0.4.0
 
 VFOX_SHIV_REPO     Shiv repository URL
                    Default: https://github.com/KnickKnackLabs/shiv.git
diff --git a/hooks/backend_install.lua b/hooks/backend_install.lua
index 07e68df..5f26cff 100644
--- a/hooks/backend_install.lua
+++ b/hooks/backend_install.lua
@@ -362,7 +362,7 @@ function ensure_shiv()
     local shiv_path = get_shiv_path()
 
     -- Pin to a specific shiv version for reproducibility
-    local shiv_ref = os.getenv("VFOX_SHIV_REF") or "v0.3.6"
+    local shiv_ref = os.getenv("VFOX_SHIV_REF") or "v0.4.0"
     local shiv_repo = os.getenv("VFOX_SHIV_REPO") or "https://github.com/KnickKnackLabs/shiv.git"
 
     if shiv_bootstrap_ready(shiv_path, shiv_ref) then
diff --git a/test/bootstrap.bats b/test/bootstrap.bats
index 41c6846..dfe2931 100644
--- a/test/bootstrap.bats
+++ b/test/bootstrap.bats
@@ -13,7 +13,7 @@ setup() {
 
 @test "bootstrapped shiv is pinned to expected ref" {
   local shiv_path="${VFOX_SHIV_PATH:-$HOME/.local/share/mise/shiv-backend/shiv}"
-  local expected_ref="${VFOX_SHIV_REF:-v0.3.6}"
+  local expected_ref="${VFOX_SHIV_REF:-v0.4.0}"
 
   run git -C "$shiv_path" describe --tags --exact-match HEAD
   [ "$status" -eq 0 ]
diff --git a/test/helpers.bash b/test/helpers.bash
index fe2ecb4..be67f39 100644
--- a/test/helpers.bash
+++ b/test/helpers.bash
@@ -39,7 +39,7 @@ EOF
 # Triggers bootstrap by installing a lightweight package.
 ensure_bootstrap() {
   local shiv_path="${VFOX_SHIV_PATH:-$HOME/.local/share/mise/shiv-backend/shiv}"
-  local expected_ref="${VFOX_SHIV_REF:-v0.3.6}"
+  local expected_ref="${VFOX_SHIV_REF:-v0.4.0}"
   local current_ref=""
 
   if [ -d "$shiv_path/.git" ]; then
diff --git a/test/lua/backend_install_test.lua b/test/lua/backend_install_test.lua
index 44ac8fb..da0ff27 100644
--- a/test/lua/backend_install_test.lua
+++ b/test/lua/backend_install_test.lua
@@ -159,7 +159,7 @@ test("BackendInstall lets delegated dependency installs reenter lock", function(
                 return "/bin/mise\n"
             end
             if command:find("^git %-C '/tmp/shiv' describe") then
-                return "v0.3.6\n"
+                return "v0.4.0\n"
             end
             if command:find("^printf '%%s:%%s:%%s'") then
                 return "owner-token\n"