diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3ffa252..41cab9e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -65,6 +65,8 @@ jobs:
           fish fish/tests/w5a-hremote.fish
           fish fish/tests/w5b-herdr-ssh.fish
           fish fish/tests/w6-agent-helpers.fish
+          fish fish/tests/w7-gentle-ai-path.fish
+          fish fish/tests/w8-linux-path.fish
 
       - name: Validate JSON configs
         shell: bash
diff --git a/fish/conf.d/10-core.fish b/fish/conf.d/10-core.fish
index 1392862..42657b2 100644
--- a/fish/conf.d/10-core.fish
+++ b/fish/conf.d/10-core.fish
@@ -49,6 +49,16 @@ else
 end
 set -gx VISUAL "$EDITOR"
 
+if test (uname) = Linux
+    # One list for every Linux host; each dir is added only if it exists.
+    # Later entries end up first (fish_add_path --move prepends).
+    for tool_bin in /usr/local/go/bin $HOME/.local/go-*/bin "$HOME/.bun/bin" "$HOME/.local/share/pnpm/bin" /nix/var/nix/profiles/default/bin "$HOME/.nix-profile/bin" "$HOME/.opencode/bin" "$HOME/.local/bin"
+        if test -d "$tool_bin"
+            fish_add_path --path --move "$tool_bin"
+        end
+    end
+end
+
 alias g git
 alias ga 'git add'
 alias gc 'git commit -m'
@@ -64,7 +74,10 @@ alias .. 'cd ..'
 alias ... 'cd ../..'
 alias .... 'cd ../../..'
 alias c clear
-alias o open
+
+if test (uname) = Darwin
+    alias o open
+end
 
 if command -q eza
     alias ll 'eza -la --icons --git'
diff --git a/fish/tests/w8-linux-path.fish b/fish/tests/w8-linux-path.fish
new file mode 100644
index 0000000..478f3e7
--- /dev/null
+++ b/fish/tests/w8-linux-path.fish
@@ -0,0 +1,51 @@
+#!/usr/bin/env fish
+# Linux hosts share one 10-core.fish: every tool directory any host uses is
+# listed once and added only when it exists, so no host edits its own copy.
+# macOS keeps the `o` alias; Linux has no `open`, so the alias is absent.
+
+set -l repo_root (cd (dirname (dirname (status filename))); and pwd)
+set -l core "$repo_root/conf.d/10-core.fish"
+set -l fish_bin (status fish-path)
+set -l ws (mktemp -d)
+
+function fail
+    printf 'FAIL: %s\n' "$argv" >&2
+    exit 1
+end
+
+set -l home "$ws/home"
+set -l fake "$ws/fake"
+mkdir -p "$fake"
+printf '#!/bin/sh\necho Linux\n' >"$fake/uname"
+chmod +x "$fake/uname"
+
+# Prefixed with $home so the test never depends on the runner's real dirs.
+set -l dirs .local/go-1.27.1/bin .bun/bin .local/share/pnpm/bin .nix-profile/bin .opencode/bin .local/bin
+for d in $dirs
+    mkdir -p "$home/$d"
+end
+
+set -l probe 'source $argv[1]; string join "|" $PATH; functions -q o; and echo o=defined; or echo o=absent'
+set -l out (env -i HOME="$home" PATH="$fake:/usr/bin:/bin" "$fish_bin" --no-config -c "$probe" "$core")
+
+# fish_add_path --move prepends in loop order: the last listed dir ends first.
+# Only entries under the fake HOME: system dirs like /nix differ per runner.
+set -l ours (string join '|' (string match -- "$home/*" (string split '|' -- $out[1])))
+set -l expected "$home/.local/bin|$home/.opencode/bin|$home/.nix-profile/bin|$home/.local/share/pnpm/bin|$home/.bun/bin|$home/.local/go-1.27.1/bin"
+test "$ours" = "$expected"; or fail "Linux PATH order (expected $expected, got $ours)"
+string match -q -- "$home/.local/bin|*" "$out[1]"; or fail "user-local bin must lead PATH ($out[1])"
+test "$out[2]" = o=absent; or fail "Linux must not define the macOS open alias ($out[2])"
+
+# Absent dirs are skipped, not added.
+set -l bare "$ws/bare"
+mkdir -p "$bare"
+set -l out_bare (env -i HOME="$bare" PATH="$fake:/usr/bin:/bin" "$fish_bin" --no-config -c "$probe" "$core")
+string match -q -- "*$bare*" "$out_bare[1]"; and fail "missing dirs were added to PATH: $out_bare[1]"
+
+# macOS keeps `o`.
+printf '#!/bin/sh\necho Darwin\n' >"$fake/uname"
+set -l out_mac (env -i HOME="$bare" PATH="$fake:/usr/bin:/bin" "$fish_bin" --no-config -c "$probe" "$core")
+test "$out_mac[2]" = o=defined; or fail "macOS must define the open alias ($out_mac[2])"
+
+rm -rf -- "$ws"
+printf 'linux path checks passed\n'