diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8279c79..4a71b91 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,10 +26,14 @@ jobs:
         with:
           configFile: commitlint.config.mjs
 
-  # Lint install.sh: POSIX-only shellcheck plus canonical shfmt formatting.
+  # Lint the shell that puts a binary on someone's PATH: POSIX-only shellcheck
+  # plus canonical shfmt formatting. Both scripts here are install-path logic
+  # guarded by D-0004 — install.sh places a released binary, dev-install.sh
+  # symlinks a build-tree one — which is why they are held to a standard the
+  # rest of the repo's shell is not.
   # Lightweight — stays on GitHub-hosted runners, same as commit-lint.
   shell-lint:
-    name: Shell Lint (install.sh)
+    name: Shell Lint (install scripts)
     runs-on: ubuntu-latest
     timeout-minutes: 5
     if: github.event.pull_request.draft == false
@@ -39,10 +43,10 @@ jobs:
         uses: taiki-e/install-action@v2
         with:
           tool: shfmt
-      - name: shellcheck -s sh install.sh
-        run: shellcheck -s sh install.sh
-      - name: shfmt -d -s -ln posix -i 2 install.sh
-        run: shfmt -d -s -ln posix -i 2 install.sh
+      - name: shellcheck -s sh install.sh dev-install.sh
+        run: shellcheck -s sh install.sh dev-install.sh
+      - name: shfmt -d -s -ln posix -i 2 install.sh dev-install.sh
+        run: shfmt -d -s -ln posix -i 2 install.sh dev-install.sh
 
   # Lint install.ps1: PSScriptAnalyzer at Warning severity, install.sh's Windows sibling.
   # Lightweight — stays on GitHub-hosted runners, same as shell-lint above. `shell: pwsh`
diff --git a/.zavet/decisions/D-0004-never-overwrite-a-development-install.md b/.zavet/decisions/D-0004-never-overwrite-a-development-install.md
index 7bace5c..603f48d 100644
--- a/.zavet/decisions/D-0004-never-overwrite-a-development-install.md
+++ b/.zavet/decisions/D-0004-never-overwrite-a-development-install.md
@@ -6,7 +6,7 @@ guards:
   - cli/dira/src/update/replace.rs
   - install.sh
   - install.ps1
-  - justfile
+  - dev-install.sh
 origin: recorded
 verified: true
 ---
@@ -20,8 +20,8 @@ only. Never a build-tree binary.
 
 ## Why
 
-`just install` symlinks `target/release/{dira,dirad}` into `~/.local/bin`, so
-a contributor's PATH entry points into their build tree. Silently replacing
+`just install` symlinks `target/release/{dira,dirad}` into `~/.local/bin` (via
+`dev-install.sh`), so a contributor's PATH entry points into their build tree. Silently replacing
 that symlink with a released binary destroys their dev loop in a way that is
 confusing to diagnose: `cargo build` keeps succeeding, the binary on PATH
 just stops changing. Overwriting a file *inside* `target/` is worse. The
@@ -47,5 +47,11 @@ sees it.
   never treat `current_exe()` as authoritative for this check.
 - Any new install-like path must reuse `discover_install` rather than
   re-deriving the rule.
+- The dev install must stay a **symlink**. `dev-install.sh` exists so that
+  rule sits in one guarded, shellcheck'd file: copying the binaries onto PATH
+  instead would leave a dev install indistinguishable from a managed one and
+  silently defeat every refusal above. This guard used to name the whole
+  `justfile`, which fired on unrelated recipes and taught readers to skim past
+  it.
 - Error text must name `just install` as the way to update a dev build, and
   give the exact commands to switch to released binaries.
diff --git a/dev-install.sh b/dev-install.sh
new file mode 100644
index 0000000..b93f088
--- /dev/null
+++ b/dev-install.sh
@@ -0,0 +1,39 @@
+#!/bin/sh
+# Create the development install: point the PATH entry at the build tree.
+#
+# Driven by `just link` (and so by `just install`); not a user-facing
+# installer. install.sh is the one contributors and users run — this is its
+# opposite number, the thing that deliberately puts a build-tree binary on
+# PATH.
+#
+# The symlink is load-bearing, not a convenience. D-0004 has install.sh and
+# `dira update` refuse to overwrite a development install, and the only thing
+# that distinguishes one is that the PATH entry is a symlink into `target/`:
+# `discover_install` reads it with `symlink_metadata`, because `current_exe()`
+# resolves symlinks on both Linux and macOS and would see an ordinary managed
+# install. Copy the binaries here instead of linking them and that detection
+# goes blind — `dira update` would overwrite a contributor's dev build and
+# `cargo build` would silently stop affecting the binary on PATH, which is the
+# exact failure D-0004 exists to prevent. Keep it a symlink.
+#
+# Idempotent: safe to re-run, and `ln -sf` re-points an existing link rather
+# than nesting one inside it.
+set -eu
+
+repo_dir="${1:?usage: dev-install.sh <repo-dir> <bin-dir>}"
+bin_dir="${2:?usage: dev-install.sh <repo-dir> <bin-dir>}"
+
+for name in dira dirad; do
+  built="$repo_dir/target/release/$name"
+  if [ ! -x "$built" ]; then
+    echo "dev-install: $built is missing — run \`just release\` first." >&2
+    exit 1
+  fi
+done
+
+mkdir -p "$bin_dir"
+for name in dira dirad; do
+  ln -sf "$repo_dir/target/release/$name" "$bin_dir/$name"
+done
+
+echo "Linked dira + dirad -> $bin_dir"
diff --git a/justfile b/justfile
index d88408f..74e0589 100644
--- a/justfile
+++ b/justfile
@@ -89,11 +89,15 @@ install: release link daemon-restart
     @echo "Installed. `dira` + `dirad` are live from {{bin_dir}} (latest build)."
 
 # Symlink dira + dirad into {{bin_dir}} (idempotent; safe to re-run).
+#
+# The symlinking itself lives in dev-install.sh rather than inline here. It is
+# install-path logic — D-0004's dev-install detection reads the PATH entry with
+# `symlink_metadata` and goes blind the moment these become copies — so it
+# belongs in a shellcheck'd script beside install.sh, under that decision's
+# guard, instead of in a recipe the guard could only reach by claiming the
+# whole justfile and every unrelated recipe in it.
 link:
-    mkdir -p "{{bin_dir}}"
-    ln -sf "{{justfile_directory()}}/target/release/dira" "{{bin_dir}}/dira"
-    ln -sf "{{justfile_directory()}}/target/release/dirad" "{{bin_dir}}/dirad"
-    @echo "Linked dira + dirad -> {{bin_dir}}"
+    sh dev-install.sh "{{justfile_directory()}}" "{{bin_dir}}"
 
 # Restart the resident daemon from the freshly built binary.
 #