diff --git a/bin/evaluate-all b/bin/evaluate-all
index ec7ea92..0955f3e 100755
--- a/bin/evaluate-all
+++ b/bin/evaluate-all
@@ -2,7 +2,7 @@
 
 set -e
 
-ARGS="--directory ~/Code/link"
+ARGS="--directory ~/Code/link --force"
 
 bin/mosaik evaluate ${ARGS} --input tmp/structural_logical_contributor.csv --output tmp/evaluation/structural_logical_contributor.csv --statistics tmp/evaluation/structural_logical_contributor.yml
 bin/mosaik evaluate ${ARGS} --input tmp/structural_logical.csv --output tmp/evaluation/structural_logical.csv --statistics tmp/evaluation/structural_logical.yml
diff --git a/bin/extract-all b/bin/extract-all
index 8716eab..55712f6 100755
--- a/bin/extract-all
+++ b/bin/extract-all
@@ -2,6 +2,6 @@
 
 set -e
 
-ARGS="--directory ~/Code/link --output tmp/link.csv"
+ARGS="--directory ~/Code/link --output tmp/link.csv --force"
 
 bin/mosaik extract ${ARGS} --since 2023-10-27 --limit 0 --reduce --visualize --renderer neato
diff --git a/bin/identify-all b/bin/identify-all
index 6ca5076..91bf641 100755
--- a/bin/identify-all
+++ b/bin/identify-all
@@ -2,7 +2,7 @@
 
 set -e
 
-ARGS="--directory ~/Code/link --input tmp/link.csv --debug"
+ARGS="--directory ~/Code/link --input tmp/link.csv --debug --force"
 
 bin/mosaik identify ${ARGS} --structural 1 --logical 1 --contributor 1 --output tmp/structural_logical_contributor.csv
 bin/mosaik identify ${ARGS} --structural 1 --logical 1 --contributor 0 --output tmp/structural_logical.csv
diff --git a/lib/mosaik/command.rb b/lib/mosaik/command.rb
index dab44f2..e7c6227 100644
--- a/lib/mosaik/command.rb
+++ b/lib/mosaik/command.rb
@@ -13,9 +13,11 @@ def call; end
 
     ##
     # Base class for commands that output graphs
+    #
     class Graph < Command
       defaults input: "mosaik.csv",
                output: "mosaik.csv",
+               force: false,
                visualize: false,
                format: "svg",
                renderer: "dot",
@@ -25,6 +27,7 @@ class Graph < Command
 
       argument "--input FILE", "Input file for the dependency graph (default: #{defaults[:input]})"
       argument "--output FILE", "Output file for the dependency graph (default: #{defaults[:output]})"
+      argument "--force", "Overwrite the output file if it exists (default: #{defaults[:force]})"
 
       argument "--visualize", "Enable graph visualization (default: #{defaults[:visualize]})"
       argument "--format FORMAT", "Graph visualization format: svg or png (default: #{defaults[:format]})"
@@ -38,6 +41,7 @@ class Graph < Command
       def validate
         raise OptionError, "unknown format: #{options[:format]}" unless options[:format].in? ["svg", "png"]
         raise OptionError, "unknown renderer: #{options[:renderer]}" unless options[:renderer].in? ["dot", "fdp", "sfdp", "neato"]
+        raise OptionError, "output file exists: #{options[:output]}" if File.exist?(options[:output])
       end
 
       protected
diff --git a/spec/mosaik/command_spec.rb b/spec/mosaik/command_spec.rb
index 85e553d..f51f725 100644
--- a/spec/mosaik/command_spec.rb
+++ b/spec/mosaik/command_spec.rb
@@ -5,10 +5,18 @@
   describe MOSAIK::Command::Graph do
     subject(:command) { described_class.new(options, *arguments) }
 
-    let(:options) { { input: "README.md" } }
+    let(:options) { { input: "README.md", output: "doesnotexist.csv" } }
     let(:arguments) { [] }
 
     describe "#validate" do
+      describe "--output" do
+        let(:arguments) { ["--output", "README.md"] }
+
+        it "raises an error" do
+          expect { command.validate }.to raise_error MOSAIK::OptionError, "output file exists: README.md"
+        end
+      end
+
       describe "--visualize" do
         let(:arguments) { ["--visualize"] }
 
diff --git a/spec/mosaik/commands/evaluate_spec.rb b/spec/mosaik/commands/evaluate_spec.rb
index 9fb61de..38ec137 100644
--- a/spec/mosaik/commands/evaluate_spec.rb
+++ b/spec/mosaik/commands/evaluate_spec.rb
@@ -3,7 +3,7 @@
 RSpec.describe MOSAIK::Commands::Evaluate do
   subject(:command) { build(:evaluate_command, options:, arguments:) }
 
-  let(:options) { { input: "README.md" } }
+  let(:options) { { input: "README.md", output: "doesnotexist.csv" } }
   let(:arguments) { [] }
 
   describe "#validate" do
diff --git a/spec/mosaik/commands/extract_spec.rb b/spec/mosaik/commands/extract_spec.rb
index 05c7118..939bfee 100644
--- a/spec/mosaik/commands/extract_spec.rb
+++ b/spec/mosaik/commands/extract_spec.rb
@@ -3,7 +3,7 @@
 RSpec.describe MOSAIK::Commands::Extract do
   subject(:command) { build(:extract_command, options:, arguments:) }
 
-  let(:options) { { input: "README.md" } }
+  let(:options) { { input: "README.md", output: "doesnotexist.csv" } }
   let(:arguments) { [] }
 
   describe "#validate" do
diff --git a/spec/mosaik/commands/identify_spec.rb b/spec/mosaik/commands/identify_spec.rb
index f579f20..91f18f0 100644
--- a/spec/mosaik/commands/identify_spec.rb
+++ b/spec/mosaik/commands/identify_spec.rb
@@ -3,7 +3,7 @@
 RSpec.describe MOSAIK::Commands::Identify do
   subject(:command) { build(:identify_command, options:, arguments:) }
 
-  let(:options) { { input: "README.md" } }
+  let(:options) { { input: "README.md", output: "doesnotexist.csv" } }
   let(:arguments) { [] }
 
   describe "#validate" do