diff --git a/dotfiles/lib/shellenv.sh b/dotfiles/lib/shellenv.sh
index 9ff8a5b0..de7e2be0 100644
--- a/dotfiles/lib/shellenv.sh
+++ b/dotfiles/lib/shellenv.sh
@@ -1,58 +1,73 @@
 source ~/.lib/shellenv/functions.sh
+command -v greadlink > /dev/null && alias readlink="greadlink"
 
-add_to_back_of_path "$HOME/.local/lib/python2.6/site-packages"
-add_to_back_of_path "$HOME/.rvm/bin"
-add_to_front_of_path "$HOME/bin"
-hash brew 2>/dev/null && add_to_front_of_path "$(brew --prefix coreutils)/libexec/gnubin"
-add_to_front_of_path "/usr/local/bin"
-
-if is_osx; then
-    export CFLAGS=-Qunused-arguments
-    export CPPFLAGS=-Qunused-arguments
-    add_to_back_of_path "/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources"
-    local JDK_LOCATION="$(find /Library/Java/JavaVirtualMachines -depth 1 | head -n 1)"
-    export JAVA_HOME="$JDK_LOCATION/Contents/Home"
-    export STUDIO_JDK=$JDK_LOCATION
-    export GRADLE_HOME="$(brew --prefix gradle)"
-    export ANDROID_HOME="$(brew --prefix android-sdk)"
-    add_to_back_of_path "$ANDROID_HOME"
-    
-    # Access gnu man pages.
-    hash brew 2> /dev/null && export MANPATH="$(brew --prefix)/opt/coreutils/libexec/gnuman:$MANPATH"
-else 
-    export JAVA_HOME="$(update-alternatives --config java | get_cols ' -1' | head -n 1)"
-    is_osx && export VISUAL="which emacsclient -c -n"
-fi
-
-add_to_front_of_path "$JAVA_HOME/bin"
-
-add_to_back_of_path "$(dotfiles_directory)/resources/python"
-add_to_back_of_path "/usr/local/sbin"
-
-# Load RVM into a shell session *as a function*
-[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"
-
-for filename in ~/.lib/shellenv/*; do
-    source $filename
-done
-
-function with_shellrc {
-    zsh -c "source ~/.zshrc && ""$@"
+function _source_shellenv_files {
+    for filename in ~/.lib/shellenv/*; do
+        source $filename
+    done
 }
 
-# Travis completion
-[ -f "$HOME/.travis/travis.sh" ] && source "$HOME/.travis/travis.sh"
+function _setup_env {
+    idem_add_to_back_of_path "$HOME/.local/lib/python2.6/site-packages"
+    idem_add_to_back_of_path "$HOME/.rvm/bin"
+    idem_add_to_front_of_path "$HOME/bin"
+    hash brew 2>/dev/null && idem_add_to_front_of_path "$(brew --prefix coreutils)/libexec/gnubin"
+    idem_add_to_front_of_path "/usr/local/bin"
 
-test -e /usr/libexec/path_helper && eval `/usr/libexec/path_helper -s`
+    if is_osx; then
+        export CFLAGS=-Qunused-arguments
+        export CPPFLAGS=-Qunused-arguments
+        idem_add_to_back_of_path "/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources"
+        local JDK_LOCATION="$(find /Library/Java/JavaVirtualMachines -depth 1 | head -n 1)"
+        export JAVA_HOME="$JDK_LOCATION/Contents/Home"
+        export STUDIO_JDK=$JDK_LOCATION
+        export GRADLE_HOME="$(brew --prefix gradle)"
+        export ANDROID_HOME="$(brew --prefix android-sdk)"
+        idem_add_to_back_of_path "$ANDROID_HOME"
+        
+        # Access gnu man pages.
+        hash brew 2> /dev/null && export MANPATH="$(brew --prefix)/opt/coreutils/libexec/gnuman:$MANPATH"
+    else 
+        export JAVA_HOME="$(update-alternatives --config java | get_cols ' -1' | head -n 1)"
+        is_osx && export VISUAL="which emacsclient -c -n"
+    fi
+
+    idem_add_to_front_of_path "$JAVA_HOME/bin"
+
+    idem_add_to_back_of_path "$(dotfiles_directory)/resources/python"
+    idem_add_to_back_of_path "/usr/local/sbin"
+
+    # Load RVM into a shell session *as a function*
+    [[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"
+
+    _source_shellenv_files
+
+    function with_shellrc {
+        zsh -c "source ~/.zshrc && ""$@"
+    }
+
+    # Travis completion
+    [ -f "$HOME/.travis/travis.sh" ] && source "$HOME/.travis/travis.sh"
+
+    test -e /usr/libexec/path_helper && eval `/usr/libexec/path_helper -s`
 
 
-export NVM_DIR="/Users/imalison/.nvm"
-[ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"  # This loads nvm
-export NODE_PATH="/usr/local/lib/node_modules/"
+    export NVM_DIR="/Users/imalison/.nvm"
+    [ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"  # This loads nvm
+    export NODE_PATH="/usr/local/lib/node_modules/"
 
-add_to_front_of_path "$HOME/.lib/python" 'PYTHONPATH'
+    idem_add_to_front_of_path "$HOME/.local/bin"
+    idem_add_to_front_of_path "$HOME/.lib/python" 'PYTHONPATH'
 
-export RBENV_ROOT=/usr/local/var/rbenv
-add_to_front_of_path "$HOME/.rbenv/bin"
-hash rbenv 2> /dev/null && eval "$(rbenv init -)"
-hash brew 2>/dev/null && add_to_front_of_path "$(brew --prefix coreutils)/libexec/gnubin"
+    export RBENV_ROOT=/usr/local/var/rbenv
+    idem_add_to_front_of_path "$HOME/.rbenv/bin"
+    hash rbenv 2> /dev/null && eval "$(rbenv init -)"
+    hash brew 2>/dev/null && idem_add_to_front_of_path "$(brew --prefix coreutils)/libexec/gnubin"
+    export ENVIRONMENT_SETUP_DONE="$(date)"
+}
+
+if [ -z ${ENVIRONMENT_SETUP_DONE+x} ]; then
+    _setup_env
+else
+    _source_shellenv_files
+fi
diff --git a/dotfiles/lib/shellenv/functions.sh b/dotfiles/lib/shellenv/functions.sh
index 30187fee..bf3e29c7 100644
--- a/dotfiles/lib/shellenv/functions.sh
+++ b/dotfiles/lib/shellenv/functions.sh
@@ -33,6 +33,32 @@ function add_to_back_of_path {
 	export $target="$(_add_to_back_of_path_lines $1 $target | tr '\n' ':' | remove_trailing_colon)"
 }
 
+function idem_add_to_front_of_path {
+    target=${2-PATH}
+    exists_in_path_var $1 $target || add_to_front_of_path $1 $target
+}
+
+function idem_add_to_back_of_path {
+    target=${2-PATH}
+    exists_in_path_var $1 $target || add_to_back_of_path $1 $target
+}
+
+function indirect_expand {
+    eval "value=\"\${$1}\""
+    echo $value
+}
+
+function environment_variable_exists {
+    eval "value=\"\${$1+x}\""
+    [ ! -z $value ]
+}
+
+function exists_in_path_var {
+    target=${2-PATH}
+    local path_contents="$(indirect_expand $target)"
+    [[ ":$path_contents:" == *":$1:"* ]]
+}
+
 function split_into_vars () {
     local string IFS
     
@@ -347,6 +373,7 @@ function parse_timestamp {
 }
 
 function refresh_config {
+    unset ENVIRONMENT_SETUP_DONE
     source ~/.zshenv
     source ~/.zshrc
 }
diff --git a/dotfiles/lib/shellenv/uber.sh b/dotfiles/lib/shellenv/uber.sh
index 264181ce..a5bf4650 100644
--- a/dotfiles/lib/shellenv/uber.sh
+++ b/dotfiles/lib/shellenv/uber.sh
@@ -4,7 +4,6 @@ export UBER_OWNER="imalison@uber.com"
 [ -z "$GIT_SSH" ] || export GIT_SSH="$HOME/.lib/git-ssh.sh"
 export VAGRANT_DEFAULT_PROVIDER=aws
 [ -s "/usr/local/bin/virtualenvwrapper.sh" ] && . /usr/local/bin/virtualenvwrapper.sh
-[ -s "$HOME/.nvm/nvm.sh" ] && . $HOME/.nvm/nvm.sh
 
 cdsync () {
     cd $(boxer sync_dir $@)
diff --git a/dotfiles/zshenv b/dotfiles/zshenv
index 21fe1f91..d7accd59 100644
--- a/dotfiles/zshenv
+++ b/dotfiles/zshenv
@@ -1 +1,11 @@
-source ~/.lib/shellenv.sh
\ No newline at end of file
+function init_profile {
+	zmodload zsh/datetime
+	setopt promptsubst
+	PS4='+$EPOCHREALTIME %N:%i> '
+	# save file stderr to file descriptor 3 and redirect stderr (including trace 
+	# output) to a file with the script's PID as an extension
+	exec 3>&2 2>/tmp/startlog.$$
+	# set options to turn on tracing and expansion of commands contained in the prompt
+	setopt xtrace prompt_subst
+}
+source ~/.lib/shellenv.sh