diff --git a/cli/e2e/e2e_test.go b/cli/e2e/e2e_test.go
new file mode 100644
index 0000000..2bc2d40
--- /dev/null
+++ b/cli/e2e/e2e_test.go
@@ -0,0 +1,63 @@
+//go:build e2e
+
+package e2e_test
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+
+	"github.com/rogpeppe/go-internal/testscript"
+)
+
+var sameBinary string
+
+func TestMain(m *testing.M) {
+	tmpDir, err := os.MkdirTemp("", "same-e2e-*")
+	if err != nil {
+		panic(err)
+	}
+
+	sameBinary = filepath.Join(tmpDir, "same")
+
+	//nolint:gosec // Building binary with static arguments, not user input
+	cmd := exec.Command("nix", "develop", "-c", "go", "build", "-o", sameBinary, "./cli/cmd/same")
+	cmd.Dir = filepath.Join("..", "..")
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
+	if err := cmd.Run(); err != nil {
+		panic("failed to build same binary: " + err.Error())
+	}
+
+	exitCode := m.Run()
+
+	_ = os.RemoveAll(tmpDir)
+
+	os.Exit(exitCode)
+}
+
+func TestScripts(t *testing.T) {
+	testscript.Run(t, testscript.Params{
+		Dir:   "testdata",
+		Setup: setupE2E,
+	})
+}
+
+func setupE2E(env *testscript.Env) error {
+	env.Setenv("NO_COLOR", "1")
+	env.Setenv("CI", "true")
+
+	binDir := filepath.Dir(sameBinary)
+	currentPath := env.Getenv("PATH")
+	env.Setenv("PATH", binDir+string(os.PathListSeparator)+currentPath)
+
+	homeDir := filepath.Join(env.WorkDir, ".home")
+	if err := os.MkdirAll(homeDir, 0o750); err != nil {
+		return err
+	}
+	env.Setenv("HOME", homeDir)
+
+	return nil
+}
diff --git a/cli/e2e/testdata/basic_execution.txtar b/cli/e2e/testdata/basic_execution.txtar
new file mode 100644
index 0000000..5ae54b6
--- /dev/null
+++ b/cli/e2e/testdata/basic_execution.txtar
@@ -0,0 +1,12 @@
+# Basic task execution test
+exec same run --ci hello
+stderr '\[hello\] Starting\.\.\.'
+stdout '\[hello\] Hello, World!'
+stderr '\[hello\] ✓ Completed'
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  hello:
+    cmd: ["echo", "Hello, World!"]
diff --git a/cli/e2e/testdata/cache_hit.txtar b/cli/e2e/testdata/cache_hit.txtar
new file mode 100644
index 0000000..feda0c1
--- /dev/null
+++ b/cli/e2e/testdata/cache_hit.txtar
@@ -0,0 +1,19 @@
+# First run builds from scratch
+exec same run --ci greet
+stderr '\[greet\] ✓ Completed'
+! stderr 'Cached'
+
+# Second run hits cache
+exec same run --ci greet
+stderr '\[greet\] ⚡ Cached'
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  greet:
+    cmd: ["echo", "Greetings!"]
+    input: ["input.txt"]
+
+-- input.txt --
+Hello
diff --git a/cli/e2e/testdata/cache_invalidation.txtar b/cli/e2e/testdata/cache_invalidation.txtar
new file mode 100644
index 0000000..04b65dd
--- /dev/null
+++ b/cli/e2e/testdata/cache_invalidation.txtar
@@ -0,0 +1,26 @@
+# First run
+exec same run --ci process
+stderr '\[process\] ✓ Completed'
+exists .same/store
+
+# Modify input
+cp data2.txt data.txt
+
+# Second run rebuilds
+exec same run --ci process
+stderr '\[process\] Starting\.\.\.'
+stderr '\[process\] ✓ Completed'
+! stderr 'Cached'
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  process:
+    input: ["data.txt"]
+    cmd: ["cat", "data.txt"]
+
+-- data.txt --
+original
+-- data2.txt --
+modified
diff --git a/cli/e2e/testdata/clean.txtar b/cli/e2e/testdata/clean.txtar
new file mode 100644
index 0000000..86e9225
--- /dev/null
+++ b/cli/e2e/testdata/clean.txtar
@@ -0,0 +1,30 @@
+# Run task to populate cache
+exec same run --ci task1
+exists .same/store
+
+# Clean build cache (default)
+exec same clean
+! exists .same/store
+
+# Verify cache directories may still exist
+# (Nix cache is managed separately)
+
+# Repopulate
+exec same run --ci task1
+exists .same/store
+
+# Clean all - removes build store and attempts to clean cache
+exec same clean --all
+! exists .same/store
+# Note: cache directory structure may remain even after clean --all
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  task1:
+    cmd: ["echo", "test"]
+    input: ["file.txt"]
+
+-- file.txt --
+content
diff --git a/cli/e2e/testdata/dependency_order.txtar b/cli/e2e/testdata/dependency_order.txtar
new file mode 100644
index 0000000..c498139
--- /dev/null
+++ b/cli/e2e/testdata/dependency_order.txtar
@@ -0,0 +1,27 @@
+# Verify topological execution order
+exec same run --ci final
+stderr '\[setup\] Starting\.\.\.'
+stderr '\[setup\] ✓ Completed'
+stderr '\[build\] Starting\.\.\.'
+stderr '\[build\] ✓ Completed'
+stderr '\[final\] Starting\.\.\.'
+stderr '\[final\] ✓ Completed'
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  setup:
+    cmd: ["sh", "-c", "echo 'Setup complete' > setup.txt"]
+    target: ["setup.txt"]
+  
+  build:
+    cmd: ["sh", "-c", "cat setup.txt && echo 'Build complete' > build.txt"]
+    input: ["setup.txt"]
+    target: ["build.txt"]
+    dependsOn: ["setup"]
+  
+  final:
+    cmd: ["sh", "-c", "cat build.txt && echo 'Final step'"]
+    input: ["build.txt"]
+    dependsOn: ["build"]
diff --git a/cli/e2e/testdata/error_circular_deps.txtar b/cli/e2e/testdata/error_circular_deps.txtar
new file mode 100644
index 0000000..11bb127
--- /dev/null
+++ b/cli/e2e/testdata/error_circular_deps.txtar
@@ -0,0 +1,17 @@
+# Circular dependency should be detected
+! exec same run --ci a
+# Command should fail with non-zero exit code
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  a:
+    cmd: ["echo", "A"]
+    dependsOn: ["b"]
+  b:
+    cmd: ["echo", "B"]
+    dependsOn: ["c"]
+  c:
+    cmd: ["echo", "C"]
+    dependsOn: ["a"]
diff --git a/cli/e2e/testdata/error_invalid_config.txtar b/cli/e2e/testdata/error_invalid_config.txtar
new file mode 100644
index 0000000..f98a966
--- /dev/null
+++ b/cli/e2e/testdata/error_invalid_config.txtar
@@ -0,0 +1,9 @@
+# Invalid config should fail with error
+! exec same run --ci task1
+stderr 'failed to load configuration'
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  invalid syntax here
diff --git a/cli/e2e/testdata/error_missing_file.txtar b/cli/e2e/testdata/error_missing_file.txtar
new file mode 100644
index 0000000..43c5848
--- /dev/null
+++ b/cli/e2e/testdata/error_missing_file.txtar
@@ -0,0 +1,3 @@
+# No same.yaml present
+! exec same run --ci anything
+stderr 'could not find samefile or workfile'
diff --git a/cli/e2e/testdata/error_unknown_task.txtar b/cli/e2e/testdata/error_unknown_task.txtar
new file mode 100644
index 0000000..ec534fa
--- /dev/null
+++ b/cli/e2e/testdata/error_unknown_task.txtar
@@ -0,0 +1,9 @@
+! exec same run --ci nonexistent
+# Command should fail with non-zero exit code
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  real:
+    cmd: ["echo", "exists"]
diff --git a/cli/e2e/testdata/hermetic_env.txtar b/cli/e2e/testdata/hermetic_env.txtar
new file mode 100644
index 0000000..5e756a5
--- /dev/null
+++ b/cli/e2e/testdata/hermetic_env.txtar
@@ -0,0 +1,22 @@
+# Set host variable
+env TEST_VAR=from_host
+
+# Task without env should not see it
+exec same run --ci no-env
+! stdout 'from_host'
+
+# Task with explicit env should see it
+exec same run --ci with-env
+stdout 'custom_value'
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  no-env:
+    cmd: ["sh", "-c", "echo TEST_VAR=${TEST_VAR:-empty}"]
+  
+  with-env:
+    cmd: ["sh", "-c", "echo TEST_VAR=$TEST_VAR"]
+    environment:
+      TEST_VAR: "custom_value"
diff --git a/cli/e2e/testdata/nix_hermetic.txtar b/cli/e2e/testdata/nix_hermetic.txtar
new file mode 100644
index 0000000..e1a14f2
--- /dev/null
+++ b/cli/e2e/testdata/nix_hermetic.txtar
@@ -0,0 +1,22 @@
+# Multiple tools in isolated environment
+# TODO: Re-enable when Nix tool resolution is fully implemented
+skip 'Nix hermetic environments not yet implemented'
+
+exec same run --ci multi-tool
+! stderr 'operation failed'
+
+-- same.work.yaml --
+version: "1"
+root: "."
+tools:
+  go: go@1.25.4
+  lint: golangci-lint@2.7.2
+projects: ["."]
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  multi-tool:
+    cmd: ["sh", "-c", "go version && golangci-lint version"]
+    tools: ["go", "lint"]
diff --git a/cli/e2e/testdata/nix_tool_resolution.txtar b/cli/e2e/testdata/nix_tool_resolution.txtar
new file mode 100644
index 0000000..c624fc1
--- /dev/null
+++ b/cli/e2e/testdata/nix_tool_resolution.txtar
@@ -0,0 +1,21 @@
+# Task requires Go tool from Nix
+# TODO: Re-enable when Nix tool resolution is fully implemented
+skip 'Nix tool resolution not yet implemented'
+
+exec same run --ci check-go
+! stderr 'operation failed'
+
+-- same.work.yaml --
+version: "1"
+root: "."
+tools:
+  go: go@1.25.4
+projects: ["."]
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  check-go:
+    cmd: ["go", "version"]
+    tools: ["go"]
diff --git a/cli/e2e/testdata/no_cache_flag.txtar b/cli/e2e/testdata/no_cache_flag.txtar
new file mode 100644
index 0000000..b5f0d61
--- /dev/null
+++ b/cli/e2e/testdata/no_cache_flag.txtar
@@ -0,0 +1,23 @@
+# First run
+exec same run --ci task
+stderr '\[task\] ✓ Completed'
+
+# Cached run
+exec same run --ci task
+stderr 'Cached'
+
+# Force rebuild with --no-cache
+exec same run --ci --no-cache task
+stderr '\[task\] Starting'
+! stderr 'Cached'
+
+-- same.yaml --
+version: "1"
+project: test
+tasks:
+  task:
+    cmd: ["echo", "running"]
+    input: ["data.txt"]
+
+-- data.txt --
+stable
diff --git a/cli/e2e/testdata/workspace.txtar b/cli/e2e/testdata/workspace.txtar
new file mode 100644
index 0000000..adee4db
--- /dev/null
+++ b/cli/e2e/testdata/workspace.txtar
@@ -0,0 +1,30 @@
+# Run task from sub-project
+cd proj1
+exec same run --ci build
+stderr '\[build\] ✓ Completed'
+
+# Run task from another project
+cd ../proj2
+exec same run --ci test
+stderr '\[test\] ✓ Completed'
+
+-- same.work.yaml --
+version: "1"
+root: "."
+projects:
+  - "proj1"
+  - "proj2"
+
+-- proj1/same.yaml --
+version: "1"
+project: proj1
+tasks:
+  build:
+    cmd: ["echo", "Building proj1"]
+
+-- proj2/same.yaml --
+version: "1"
+project: proj2
+tasks:
+  test:
+    cmd: ["echo", "Testing proj2"]
diff --git a/cli/go.mod b/cli/go.mod
index 02b4a60..32d2feb 100644
--- a/cli/go.mod
+++ b/cli/go.mod
@@ -9,6 +9,7 @@ require (
 	github.com/creack/pty v1.1.24
 	github.com/grindlemire/graft v0.2.3
 	github.com/muesli/termenv v0.16.0
+	github.com/rogpeppe/go-internal v1.14.1
 	github.com/spf13/cobra v1.10.2
 	github.com/stretchr/testify v1.11.1
 	github.com/vito/midterm v0.2.3
@@ -18,6 +19,7 @@ require (
 	go.trai.ch/zerr v0.2.1
 	go.uber.org/mock v0.6.0
 	golang.org/x/sync v0.19.0
+	golang.org/x/term v0.39.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
@@ -51,7 +53,6 @@ require (
 	go.opentelemetry.io/otel/metric v1.39.0 // indirect
 	golang.org/x/mod v0.31.0 // indirect
 	golang.org/x/sys v0.40.0 // indirect
-	golang.org/x/term v0.39.0 // indirect
 	golang.org/x/text v0.3.8 // indirect
 	golang.org/x/tools v0.40.0 // indirect
 )
diff --git a/cli/go.sum b/cli/go.sum
index d037c16..0f6002b 100644
--- a/cli/go.sum
+++ b/cli/go.sum
@@ -109,8 +109,6 @@ golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
 golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sys v0.0.0-20210809222454-d867a43fc93e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
-golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/sys v0.40.0 h1:DBZZqJ2Rkml6QMQsZywtnjnnGvHza6BTfYFWY9kjEWQ=
 golang.org/x/sys v0.40.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/term v0.39.0 h1:RclSuaJf32jOqZz74CkPA9qFuVTX7vhLlpfj/IGWlqY=
diff --git a/cli/same.yaml b/cli/same.yaml
index 30a987b..5ddb01a 100644
--- a/cli/same.yaml
+++ b/cli/same.yaml
@@ -38,3 +38,10 @@ tasks:
     target: ["bin/same"]
     tools: ["go"]
     dependsOn: ["generate"]
+
+  # Run E2E tests
+  e2e-test:
+    input: ["e2e", "cmd", "internal"]
+    cmd: ["go", "test", "-v", "-tags=e2e", "./e2e/..."]
+    tools: ["go"]
+    dependsOn: ["generate"]
diff --git a/flake.nix b/flake.nix
index 0970aa9..d83c05f 100644
--- a/flake.nix
+++ b/flake.nix
@@ -43,7 +43,7 @@
           inherit version;
 
           src = ./cli;
-          vendorHash = "sha256-dtmW7rFQfLBww7mNMPTkyG3SvkcU2En+bHY2BTA8y4w=";
+          vendorHash = "sha256-O9y+DIxt8YcqlP499Ns5ECHEWV2IENy6nAH25Leh1AI=";
 
           env.CGO_ENABLED = 0;