diff --git a/Runfile b/Runfile
index bac19fe..70349b0 100644
--- a/Runfile
+++ b/Runfile
@@ -24,3 +24,9 @@ action :schema do
   end
 end
 
+help   'Run preconfigured shfmt on any script'
+usage  'shfmt SCRIPT'
+action :shfmt do |args|
+  system "shfmt -d -i 2 -ci #{args['SCRIPT']}"
+  say $?.success? ? 'g`PASS`' : 'r`FAIL`'
+end
diff --git a/lib/completely/installer.rb b/lib/completely/installer.rb
index ae80323..f4eebdf 100644
--- a/lib/completely/installer.rb
+++ b/lib/completely/installer.rb
@@ -4,8 +4,8 @@ class << self
       def from_io(program:, io: nil)
         io ||= $stdin
 
-        raise InstallError, "io must respond to #read" unless io.respond_to?(:read)
-        raise InstallError, "io is closed" if io.respond_to?(:closed?) && io.closed?
+        raise InstallError, 'io must respond to #read' unless io.respond_to?(:read)
+        raise InstallError, 'io is closed' if io.respond_to?(:closed?) && io.closed?
 
         from_string program:, string: io.read
       end
@@ -23,7 +23,7 @@ def from_string(program:, string:)
       end
 
       def create_tempfile
-        tempfile = Tempfile.new ["completely-", '.bash']
+        tempfile = Tempfile.new ['completely-', '.bash']
         tempfiles.push tempfile
         tempfile
       end
diff --git a/lib/completely/templates/template.erb b/lib/completely/templates/template.erb
index 53d097c..b5dfbe4 100644
--- a/lib/completely/templates/template.erb
+++ b/lib/completely/templates/template.erb
@@ -9,24 +9,46 @@
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 <%= function_name %>() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
 % if ENV['COMPLETELY_DEBUG']
   if [[ -n "$COMPLETELY_DEBUG" ]]; then
     echo "compline: '$compline'" > 'completely-debug.txt'
diff --git a/spec/approvals/cli/generated-script b/spec/approvals/cli/generated-script
index 5b866d8..94e256e 100644
--- a/spec/approvals/cli/generated-script
+++ b/spec/approvals/cli/generated-script
@@ -9,24 +9,46 @@ _mygit_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _mygit_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     'status'*'--branch')
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "$(git branch --format='%(refname:short)' 2>/dev/null)")" -- "$cur")
diff --git a/spec/approvals/cli/generated-script-alt b/spec/approvals/cli/generated-script-alt
index 789149f..217aae4 100644
--- a/spec/approvals/cli/generated-script-alt
+++ b/spec/approvals/cli/generated-script-alt
@@ -9,24 +9,46 @@ _mycomps_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _mycomps() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     'status'*'--branch')
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mycomps_filter "$(git branch --format='%(refname:short)' 2>/dev/null)")" -- "$cur")
diff --git a/spec/approvals/cli/generated-wrapped-script b/spec/approvals/cli/generated-wrapped-script
index a788dd1..e37ade0 100644
--- a/spec/approvals/cli/generated-wrapped-script
+++ b/spec/approvals/cli/generated-wrapped-script
@@ -10,24 +10,46 @@ give_comps() {
   echo $'  local cur=${COMP_WORDS[COMP_CWORD]}'
   echo $'  local result=()'
   echo $''
+  echo $'  # words the user already typed (excluding the command itself)'
+  echo $'  local used=()'
+  echo $'  if ((COMP_CWORD > 1)); then'
+  echo $'    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")'
+  echo $'  fi'
+  echo $''
   echo $'  if [[ "${cur:0:1}" == "-" ]]; then'
+  echo $'    # Completing an option: offer everything (including options)'
   echo $'    echo "$words"'
   echo $''
   echo $'  else'
+  echo $'    # Completing a non-option: offer only non-options,'
+  echo $'    # and don\'t re-offer ones already used earlier in the line.'
   echo $'    for word in $words; do'
-  echo $'      [[ "${word:0:1}" != "-" ]] && result+=("$word")'
+  echo $'      [[ "${word:0:1}" == "-" ]] && continue'
+  echo $''
+  echo $'      local seen=0'
+  echo $'      for u in "${used[@]}"; do'
+  echo $'        if [[ "$u" == "$word" ]]; then'
+  echo $'          seen=1'
+  echo $'          break'
+  echo $'        fi'
+  echo $'      done'
+  echo $'      ((!seen)) && result+=("$word")'
   echo $'    done'
   echo $''
   echo $'    echo "${result[*]}"'
-  echo $''
   echo $'  fi'
   echo $'}'
   echo $''
   echo $'_mygit_completions() {'
   echo $'  local cur=${COMP_WORDS[COMP_CWORD]}'
-  echo $'  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")'
+  echo $'  local compwords=()'
+  echo $'  if ((COMP_CWORD > 0)); then'
+  echo $'    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")'
+  echo $'  fi'
   echo $'  local compline="${compwords[*]}"'
   echo $''
+  echo $'  COMPREPLY=()'
+  echo $''
   echo $'  case "$compline" in'
   echo $'    \'status\'*\'--branch\')'
   echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "$(git branch --format=\'%(refname:short)\' 2>/dev/null)")" -- "$cur")'
diff --git a/spec/approvals/cli/test/completely-tester-1.sh b/spec/approvals/cli/test/completely-tester-1.sh
index b538012..50d5b48 100644
--- a/spec/approvals/cli/test/completely-tester-1.sh
+++ b/spec/approvals/cli/test/completely-tester-1.sh
@@ -17,24 +17,46 @@ _mygit_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _mygit_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     'status'*'--branch')
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "$(git branch --format='%(refname:short)' 2>/dev/null)")" -- "$cur")
diff --git a/spec/approvals/cli/test/completely-tester-2.sh b/spec/approvals/cli/test/completely-tester-2.sh
index 4d7f4d5..a0fb1e3 100644
--- a/spec/approvals/cli/test/completely-tester-2.sh
+++ b/spec/approvals/cli/test/completely-tester-2.sh
@@ -17,24 +17,46 @@ _mygit_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _mygit_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     'status'*'--branch')
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "$(git branch --format='%(refname:short)' 2>/dev/null)")" -- "$cur")
diff --git a/spec/approvals/cli/test/completely-tester.sh b/spec/approvals/cli/test/completely-tester.sh
index 2633b8b..108dbf9 100644
--- a/spec/approvals/cli/test/completely-tester.sh
+++ b/spec/approvals/cli/test/completely-tester.sh
@@ -17,24 +17,46 @@ _mygit_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _mygit_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     'status'*'--branch')
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "$(git branch --format='%(refname:short)' 2>/dev/null)")" -- "$cur")
diff --git a/spec/approvals/completions/function b/spec/approvals/completions/function
index 9c62787..1b31b34 100644
--- a/spec/approvals/completions/function
+++ b/spec/approvals/completions/function
@@ -10,24 +10,46 @@ send_completions() {
   echo $'  local cur=${COMP_WORDS[COMP_CWORD]}'
   echo $'  local result=()'
   echo $''
+  echo $'  # words the user already typed (excluding the command itself)'
+  echo $'  local used=()'
+  echo $'  if ((COMP_CWORD > 1)); then'
+  echo $'    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")'
+  echo $'  fi'
+  echo $''
   echo $'  if [[ "${cur:0:1}" == "-" ]]; then'
+  echo $'    # Completing an option: offer everything (including options)'
   echo $'    echo "$words"'
   echo $''
   echo $'  else'
+  echo $'    # Completing a non-option: offer only non-options,'
+  echo $'    # and don\'t re-offer ones already used earlier in the line.'
   echo $'    for word in $words; do'
-  echo $'      [[ "${word:0:1}" != "-" ]] && result+=("$word")'
+  echo $'      [[ "${word:0:1}" == "-" ]] && continue'
+  echo $''
+  echo $'      local seen=0'
+  echo $'      for u in "${used[@]}"; do'
+  echo $'        if [[ "$u" == "$word" ]]; then'
+  echo $'          seen=1'
+  echo $'          break'
+  echo $'        fi'
+  echo $'      done'
+  echo $'      ((!seen)) && result+=("$word")'
   echo $'    done'
   echo $''
   echo $'    echo "${result[*]}"'
-  echo $''
   echo $'  fi'
   echo $'}'
   echo $''
   echo $'_completely_completions() {'
   echo $'  local cur=${COMP_WORDS[COMP_CWORD]}'
-  echo $'  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")'
+  echo $'  local compwords=()'
+  echo $'  if ((COMP_CWORD > 0)); then'
+  echo $'    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")'
+  echo $'  fi'
   echo $'  local compline="${compwords[*]}"'
   echo $''
+  echo $'  COMPREPLY=()'
+  echo $''
   echo $'  case "$compline" in'
   echo $'    \'generate\'*)'
   echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help --force")" -- "$cur")'
diff --git a/spec/approvals/completions/script b/spec/approvals/completions/script
index 32b7da3..cba794b 100644
--- a/spec/approvals/completions/script
+++ b/spec/approvals/completions/script
@@ -9,24 +9,46 @@ _completely_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _completely_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     'generate'*)
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help --force")" -- "$cur")
diff --git a/spec/approvals/completions/script-complete-options b/spec/approvals/completions/script-complete-options
index df0c962..a0dff27 100644
--- a/spec/approvals/completions/script-complete-options
+++ b/spec/approvals/completions/script-complete-options
@@ -9,24 +9,46 @@ _mygit_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _mygit_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     *)
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "status commit")" -- "$cur")
diff --git a/spec/approvals/completions/script-only-spaces b/spec/approvals/completions/script-only-spaces
index 65df1dc..44695a6 100644
--- a/spec/approvals/completions/script-only-spaces
+++ b/spec/approvals/completions/script-only-spaces
@@ -9,24 +9,46 @@ _completely_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _completely_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     'generate'*)
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help --force")" -- "$cur")
diff --git a/spec/approvals/completions/script-with-debug b/spec/approvals/completions/script-with-debug
index 14c9911..afc0053 100644
--- a/spec/approvals/completions/script-with-debug
+++ b/spec/approvals/completions/script-with-debug
@@ -9,24 +9,46 @@ _completely_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _completely_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   if [[ -n "$COMPLETELY_DEBUG" ]]; then
     echo "compline: '$compline'" > 'completely-debug.txt'
     echo "cur:      '$cur'" >> 'completely-debug.txt'
diff --git a/spec/completely/installer_spec.rb b/spec/completely/installer_spec.rb
index 9c78caf..f74f6fc 100644
--- a/spec/completely/installer_spec.rb
+++ b/spec/completely/installer_spec.rb
@@ -14,18 +14,20 @@
   end
 
   describe '::from_io' do
-    let(:io) { StringIO.new 'dummy data' }
     subject { described_class.from_io program:, io: }
 
+    let(:io) { StringIO.new 'dummy data' }
+
     it 'reads the script from io and writes it to a temp file' do
       expect(File.read subject.script_path).to eq 'dummy data'
     end
   end
 
   describe '::from_string' do
-    let(:string) { 'dummy data' }
     subject { described_class.from_string program:, string: }
 
+    let(:string) { 'dummy data' }
+
     it 'reads the script from io and writes it to a temp file' do
       expect(File.read subject.script_path).to eq 'dummy data'
     end
diff --git a/spec/fixtures/tester/default.bash b/spec/fixtures/tester/default.bash
index 0fa0814..a5a878f 100644
--- a/spec/fixtures/tester/default.bash
+++ b/spec/fixtures/tester/default.bash
@@ -9,24 +9,46 @@ _cli_completions_filter() {
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
 
+  # words the user already typed (excluding the command itself)
+  local used=()
+  if ((COMP_CWORD > 1)); then
+    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
+
   if [[ "${cur:0:1}" == "-" ]]; then
+    # Completing an option: offer everything (including options)
     echo "$words"
 
   else
+    # Completing a non-option: offer only non-options,
+    # and don't re-offer ones already used earlier in the line.
     for word in $words; do
-      [[ "${word:0:1}" != "-" ]] && result+=("$word")
+      [[ "${word:0:1}" == "-" ]] && continue
+
+      local seen=0
+      for u in "${used[@]}"; do
+        if [[ "$u" == "$word" ]]; then
+          seen=1
+          break
+        fi
+      done
+      ((!seen)) && result+=("$word")
     done
 
     echo "${result[*]}"
-
   fi
 }
 
 _cli_completions() {
   local cur=${COMP_WORDS[COMP_CWORD]}
-  local compwords=("${COMP_WORDS[@]:1:$COMP_CWORD-1}")
+  local compwords=()
+  if ((COMP_CWORD > 0)); then
+    compwords=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
+  fi
   local compline="${compwords[*]}"
 
+  COMPREPLY=()
+
   case "$compline" in
     'command childcommand'*)
       while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "--quiet --verbose -q -v")" -- "$cur")