diff --git a/bob.yaml b/bob.yaml
index 5f8cf4a2..ac562dbc 100644
--- a/bob.yaml
+++ b/bob.yaml
@@ -5,18 +5,22 @@ variables:
 
 build:
   build:
+    input: "*"
     cmd: go build -tags dev -ldflags="-X 'main.Version=${VERSION}'" -o ./run
     target: run
     dependson:
       - proto
 
   gomodtidy:
+    input: "*"
     cmd: go mod tidy
 
   lint:
+    input: "*"
     cmd: CGO_ENABLED=0 golangci-lint run --timeout=10m0s
 
   test:
+    input: "*"
     cmd: go test ./...
 
   proto:
diff --git a/bob/aggregate.go b/bob/aggregate.go
index f2276348..945fc2ec 100644
--- a/bob/aggregate.go
+++ b/bob/aggregate.go
@@ -217,7 +217,7 @@ func (b *B) Aggregate() (aggregate *bobfile.Bobfile, err error) {
 		aggregate.Project = aggregate.Dir()
 	}
 
-	err = aggregate.Verify()
+	err = aggregate.Verify(b.enableCaching, b.enableRedundantTargets)
 	errz.Fatal(err)
 
 	err = aggregate.BTasks.IgnoreChildTargets()
@@ -246,7 +246,7 @@ func collectDecorations(ag *bobfile.Bobfile) (_ map[string][]string, err error)
 		if !task.IsDecoration() {
 			continue
 		}
-		if !task.IsValidDecoration() {
+		if !task.IsCompoundTask() {
 			errz.Fatal(usererror.Wrap(fmt.Errorf("task `%s` modifies an imported task. It can only contain a `dependsOn` property", k)))
 		}
 		decorations[k] = task.DependsOn
diff --git a/bob/aggregate_test.go b/bob/aggregate_test.go
index 1eacb11a..b0a2211b 100644
--- a/bob/aggregate_test.go
+++ b/bob/aggregate_test.go
@@ -103,7 +103,7 @@ func benchmarkAggregate(b *testing.B, ignoredMultiplier int) {
 }
 
 // createFileSturcture creates a deep file structure.
-// `multiplier`` is the number of directorys created containing the structure.
+// `multiplier“ is the number of directorys created containing the structure.
 func createFileSturcture(dir string, multiplier int) error {
 	for i := 0; i < multiplier; i++ {
 		// create parent
@@ -142,7 +142,7 @@ func createFileSturcture(dir string, multiplier int) error {
 }
 
 // createIgnoreFileSturcture creates a deep file structure witch must be ignored by Aggregate().
-// `multiplier`` is the number of directorys created containing the structure.
+// `multiplier“ is the number of directorys created containing the structure.
 func createIgnoreFileSturcture(dir string, multiplier int) error {
 	for i := 0; i < multiplier; i++ {
 		// create parent
@@ -190,7 +190,7 @@ func TestEmptyProjectName(t *testing.T) {
 	err = os.Chdir(dir)
 	assert.Nil(t, err)
 
-	testBob, err := Bob(WithDir(dir))
+	testBob, err := Bob(WithDir(dir), WithEnableRedundantTargets())
 	assert.Nil(t, err)
 
 	err = CreatePlayground(PlaygroundOptions{Dir: dir})
@@ -213,7 +213,7 @@ func TestProjectName(t *testing.T) {
 	err = os.Chdir(dir)
 	assert.Nil(t, err)
 
-	testBob, err := Bob(WithDir(dir))
+	testBob, err := Bob(WithDir(dir), WithEnableRedundantTargets())
 	assert.Nil(t, err)
 
 	projectName := "example.com/test-user/test-project"
@@ -240,7 +240,7 @@ func TestInvalidProjectName(t *testing.T) {
 	err = os.Chdir(dir)
 	assert.Nil(t, err)
 
-	testBob, err := Bob(WithDir(dir))
+	testBob, err := Bob(WithDir(dir), WithEnableRedundantTargets())
 	assert.Nil(t, err)
 
 	projectName := "@"
@@ -333,7 +333,7 @@ func TestMultiLevelBobfileSameProjectName(t *testing.T) {
 	err = os.Chdir(dir)
 	assert.Nil(t, err)
 
-	testBob, err := Bob(WithDir(dir))
+	testBob, err := Bob(WithDir(dir), WithEnableRedundantTargets())
 	assert.Nil(t, err)
 
 	projectName := "first-level"
diff --git a/bob/bob.go b/bob/bob.go
index b2e7e6ed..7745acb4 100644
--- a/bob/bob.go
+++ b/bob/bob.go
@@ -47,6 +47,11 @@ type B struct {
 	// from the cache Default: true
 	enableCaching bool
 
+	// enableRedundantTargets option allows redundant targets on build tasks
+	// a task has redundant target when it has a `target` used in combination with `rebuild:always`
+	// by default a user error will return when a task has both `target` and `rebuild:always` defined
+	enableRedundantTargets bool
+
 	// allowInsecure uses http protocol for accessing the remote artifact store, if any
 	allowInsecure bool
 
diff --git a/bob/bobfile/verify.go b/bob/bobfile/verify.go
index e3c41563..7a4c5a56 100644
--- a/bob/bobfile/verify.go
+++ b/bob/bobfile/verify.go
@@ -5,13 +5,8 @@ import (
 )
 
 // Verify a bobfile before task runner.
-func (b *Bobfile) Verify() error {
-	return b.verifyBefore()
-}
-
-// VerifyBefore a bobfile before task runner.
-func (b *Bobfile) VerifyBefore() error {
-	return b.verifyBefore()
+func (b *Bobfile) Verify(cacheEnabled, allowRedundantTargets bool) error {
+	return b.verifyBefore(cacheEnabled, allowRedundantTargets)
 }
 
 // VerifyAfter a bobfile after task runner.
@@ -20,14 +15,17 @@ func (b *Bobfile) VerifyAfter() error {
 }
 
 // verifyBefore verifies a Bobfile before Run() is called.
-func (b *Bobfile) verifyBefore() (err error) {
+func (b *Bobfile) verifyBefore(cacheEnabled, allowRedundantTargets bool) (err error) {
 	defer errz.Recover(&err)
 
 	err = b.BTasks.VerifyDuplicateTargets()
 	errz.Fatal(err)
 
+	err = b.BTasks.VerifyMandatoryInputs()
+	errz.Fatal(err)
+
 	for _, task := range b.BTasks {
-		err = task.VerifyBefore()
+		err = task.VerifyBefore(cacheEnabled, allowRedundantTargets)
 		errz.Fatal(err)
 	}
 
diff --git a/bob/options.go b/bob/options.go
index c893ab3f..6247455a 100644
--- a/bob/options.go
+++ b/bob/options.go
@@ -52,6 +52,12 @@ func WithCachingEnabled(enabled bool) Option {
 	}
 }
 
+func WithEnableRedundantTargets() Option {
+	return func(b *B) {
+		b.enableRedundantTargets = true
+	}
+}
+
 func WithPushEnabled(enabled bool) Option {
 	return func(b *B) {
 		b.enablePush = enabled
diff --git a/bob/playbook/build_internal.go b/bob/playbook/build_internal.go
index a0f1c4fe..cc7c52e9 100644
--- a/bob/playbook/build_internal.go
+++ b/bob/playbook/build_internal.go
@@ -99,10 +99,14 @@ func (p *Playbook) build(ctx context.Context, task *bobtask.Task) (err error) {
 	}
 
 	if !rebuildRequired {
-		status := StateNoRebuildRequired
+		status := StateCached
+		t, _ := task.Target()
+		if t == nil {
+			status = StateNoRebuildRequired
+		}
 		boblog.Log.V(2).Info(fmt.Sprintf("%-*s\t%s", p.namePad, coloredName, status.Short()))
 		taskSuccessFul = true
-		return p.TaskNoRebuildRequired(task.Name())
+		return p.TaskNoRebuildRequired(task.Name(), status)
 	}
 
 	err = task.Clean()
diff --git a/bob/playbook/play.go b/bob/playbook/play.go
index 751c9538..c77eb16d 100644
--- a/bob/playbook/play.go
+++ b/bob/playbook/play.go
@@ -37,7 +37,7 @@ func (p *Playbook) play() error {
 			return err
 		}
 
-		//boblog.Log.V(3).Info(fmt.Sprintf("%-*s\t walking", p.namePad, taskname))
+		// boblog.Log.V(3).Info(fmt.Sprintf("%-*s\t walking", p.namePad, taskname))
 
 		switch task.State() {
 		case StatePending:
@@ -45,12 +45,12 @@ func (p *Playbook) play() error {
 			for _, dependentTaskName := range task.Task.DependsOn {
 				t, ok := p.Tasks[dependentTaskName]
 				if !ok {
-					//fmt.Printf("Task %s does not exist", dependentTaskName)
+					// fmt.Printf("Task %s does not exist", dependentTaskName)
 					return usererror.Wrap(boberror.ErrTaskDoesNotExistF(dependentTaskName))
 				}
 
 				state := t.State()
-				if state != StateCompleted && state != StateNoRebuildRequired {
+				if state != StateCompleted && state != StateCached && state != StateNoRebuildRequired {
 					// A dependent task is not completed.
 					// So this task is not yet ready to run.
 					return nil
@@ -60,7 +60,7 @@ func (p *Playbook) play() error {
 			return taskFailed
 		case StateCanceled:
 			return nil
-		case StateNoRebuildRequired:
+		case StateCached, StateNoRebuildRequired:
 			return nil
 		case StateCompleted:
 			return nil
diff --git a/bob/playbook/playbook.go b/bob/playbook/playbook.go
index c33160f9..5c9e4682 100644
--- a/bob/playbook/playbook.go
+++ b/bob/playbook/playbook.go
@@ -214,10 +214,10 @@ func (p *Playbook) TaskCompleted(taskname string) (err error) {
 }
 
 // TaskNoRebuildRequired sets a task's state to indicate that no rebuild is required
-func (p *Playbook) TaskNoRebuildRequired(taskname string) (err error) {
+func (p *Playbook) TaskNoRebuildRequired(taskname string, status State) (err error) {
 	defer errz.Recover(&err)
 
-	err = p.setTaskState(taskname, StateNoRebuildRequired, nil)
+	err = p.setTaskState(taskname, status, nil)
 	errz.Fatal(err)
 
 	err = p.play()
@@ -301,7 +301,7 @@ func (p *Playbook) setTaskState(taskname string, state State, taskError error) e
 
 	task.SetState(state, taskError)
 	switch state {
-	case StateCompleted, StateCanceled, StateNoRebuildRequired, StateFailed:
+	case StateCompleted, StateCanceled, StateCached, StateNoRebuildRequired, StateFailed:
 		task.SetEnd(time.Now())
 	}
 
diff --git a/bob/playbook/rebuild.go b/bob/playbook/rebuild.go
index 3bb84c50..08ec97ee 100644
--- a/bob/playbook/rebuild.go
+++ b/bob/playbook/rebuild.go
@@ -80,7 +80,7 @@ func (p *Playbook) didChildTaskChange(taskname string, namePad int, coloredName
 		}
 
 		// Check if child task changed
-		if t.State() != StateNoRebuildRequired {
+		if t.State() != StateCached && t.State() != StateNoRebuildRequired {
 			return Done
 		}
 
diff --git a/bob/playbook/state.go b/bob/playbook/state.go
index c61ccbdf..37c46570 100644
--- a/bob/playbook/state.go
+++ b/bob/playbook/state.go
@@ -12,8 +12,10 @@ func (s *State) Summary() string {
 		return "⌛       "
 	case StateCompleted:
 		return aurora.Green("✔").Bold().String() + "       "
-	case StateNoRebuildRequired:
+	case StateCached:
 		return aurora.Green("cached").String() + "  "
+	case StateNoRebuildRequired:
+		return aurora.Gray(10, "✔").Bold().String() + "       "
 	case StateFailed:
 		return aurora.Red("failed").String() + "  "
 	case StateCanceled:
@@ -29,8 +31,10 @@ func (s *State) Short() string {
 		return "pending"
 	case StateCompleted:
 		return "done"
-	case StateNoRebuildRequired:
+	case StateCached:
 		return "cached"
+	case StateNoRebuildRequired:
+		return "not-rebuild"
 	case StateFailed:
 		return "failed"
 	case StateCanceled:
@@ -43,7 +47,8 @@ func (s *State) Short() string {
 const (
 	StatePending           State = "PENDING"
 	StateCompleted         State = "COMPLETED"
-	StateNoRebuildRequired State = "CACHED"
+	StateCached            State = "CACHED"
+	StateNoRebuildRequired State = "NO-REBUILD"
 	StateFailed            State = "FAILED"
 	StateRunning           State = "RUNNING"
 	StateCanceled          State = "CANCELED"
diff --git a/bob/playbook/summary.go b/bob/playbook/summary.go
index 27fa1086..94d62bbe 100644
--- a/bob/playbook/summary.go
+++ b/bob/playbook/summary.go
@@ -11,7 +11,6 @@ import (
 
 // summary prints the tasks processing details as a summary of the playbook.
 func (p *Playbook) summary(processedTasks []*bobtask.Task) {
-
 	boblog.Log.V(1).Info("")
 	boblog.Log.V(1).Info(aurora.Bold("● ● ● ●").BrightGreen().String())
 
@@ -27,12 +26,16 @@ func (p *Playbook) summary(processedTasks []*bobtask.Task) {
 
 		execTime := ""
 		status := stat.State()
-		if status != StateNoRebuildRequired {
+		if status != StateCached && status != StateNoRebuildRequired {
 			execTime = fmt.Sprintf("\t(%s)", format.DisplayDuration(stat.ExecutionTime()))
 		}
 
 		taskName := t.Name()
-		boblog.Log.V(1).Info(fmt.Sprintf("  %-*s\t%s%s", p.namePad, taskName, status.Summary(), execTime))
+		if t.IsCompoundTask() {
+			boblog.Log.V(1).Info(fmt.Sprintf("  %-*s\t%s%s", p.namePad, taskName, "-", execTime))
+		} else {
+			boblog.Log.V(1).Info(fmt.Sprintf("  %-*s\t%s%s", p.namePad, taskName, status.Summary(), execTime))
+		}
 	}
 	boblog.Log.V(1).Info("")
 }
diff --git a/bob/playground.go b/bob/playground.go
index 4fe3610a..6ac56cee 100644
--- a/bob/playground.go
+++ b/bob/playground.go
@@ -297,7 +297,8 @@ func createPlaygroundBobfile(dir string, overwrite bool, projectName string) (er
 			"sleep 2",
 			"touch slowdone",
 		}, "\n"),
-		TargetDirty: "slowdone",
+		RebuildDirty: string(bobtask.RebuildAlways),
+		TargetDirty:  "slowdone",
 	}
 
 	// A run command to run a environment from a compose file
@@ -345,7 +346,8 @@ func createPlaygroundBobfile(dir string, overwrite bool, projectName string) (er
 	}
 
 	bobfile.BTasks["print"] = bobtask.Task{
-		CmdDirty: "echo ${HELLOWORLD}",
+		CmdDirty:     "echo ${HELLOWORLD}",
+		RebuildDirty: string(bobtask.RebuildAlways),
 	}
 
 	bobfile.BTasks["multilinetouch"] = bobtask.Task{
@@ -354,6 +356,7 @@ func createPlaygroundBobfile(dir string, overwrite bool, projectName string) (er
 			"touch \\\n\tmultilinefile1 \\\n\tmultilinefile2 \\\n\t\tmultilinefile3 \\\n        multilinefile4",
 			"touch \\\n  multilinefile5",
 		}, "\n"),
+		RebuildDirty: string(bobtask.RebuildAlways),
 	}
 
 	bobfile.BTasks["ignoredInputs"] = bobtask.Task{
@@ -369,7 +372,8 @@ func createPlaygroundBobfile(dir string, overwrite bool, projectName string) (er
 			"touch .bbuild/dirone/dirtwo/fileone",
 			"touch .bbuild/dirone/dirtwo/filetwo",
 		}, "\n"),
-		TargetDirty: ".bbuild/dirone/",
+		RebuildDirty: string(bobtask.RebuildAlways),
+		TargetDirty:  ".bbuild/dirone/",
 	}
 
 	bobfile.BTasks[SecondLevelDir+"/build2"] = bobtask.Task{
@@ -379,6 +383,7 @@ func createPlaygroundBobfile(dir string, overwrite bool, projectName string) (er
 	m := make(map[string]interface{})
 	m["image"] = BuildTargetBobTestImage
 	bobfile.BTasks[BuildTargetDockerImageName] = bobtask.Task{
+		InputDirty: "Dockerfile",
 		CmdDirty: strings.Join([]string{
 			fmt.Sprintf("docker build -t %s .", BuildTargetBobTestImage),
 		}, "\n"),
@@ -388,6 +393,7 @@ func createPlaygroundBobfile(dir string, overwrite bool, projectName string) (er
 	m = make(map[string]interface{})
 	m["image"] = BuildTargetBobTestImagePlus
 	bobfile.BTasks[BuildTargetDockerImagePlusName] = bobtask.Task{
+		InputDirty: "Dockerfile.plus",
 		CmdDirty: strings.Join([]string{
 			fmt.Sprintf("docker build -f Dockerfile.plus -t %s .", BuildTargetBobTestImagePlus),
 		}, "\n"),
@@ -444,7 +450,8 @@ func createPlaygroundBobfileThirdLevel(dir string, overwrite bool, projectName s
 	}
 
 	bobfile.BTasks["print"] = bobtask.Task{
-		CmdDirty: "echo hello-third-level",
+		CmdDirty:     "echo hello-third-level",
+		RebuildDirty: string(bobtask.RebuildAlways),
 	}
 
 	bobfile.Dependencies = []string{"docker", "go_1_18", "git"}
diff --git a/bobtask/map.go b/bobtask/map.go
index e2becd6c..f651d64f 100644
--- a/bobtask/map.go
+++ b/bobtask/map.go
@@ -235,3 +235,20 @@ func CreateErrAmbiguousTargets(tasks []string, target string) error {
 	sort.Strings(tasks)
 	return fmt.Errorf("%w,\nmultiple tasks [%s] pointing to the same target `%s`", ErrAmbigousTargets, strings.Join(tasks, " "), target)
 }
+
+// VerifyMandatoryInputs check that build tasks have `input` field set
+// input is mandatory except when task has `rebuild:always` set or is a compound task
+func (tm Map) VerifyMandatoryInputs() error {
+	for taskName, v := range tm {
+		if v.InputDirty == "" {
+			if v.Rebuild() == RebuildAlways {
+				continue
+			}
+			if v.IsCompoundTask() {
+				continue
+			}
+			return usererror.Wrap(fmt.Errorf("no input provided for task `%s`", taskName))
+		}
+	}
+	return nil
+}
diff --git a/bobtask/task.go b/bobtask/task.go
index 932bf087..572b145a 100644
--- a/bobtask/task.go
+++ b/bobtask/task.go
@@ -21,7 +21,7 @@ const (
 	RebuildOnChange RebuildType = "on-change"
 )
 
-// Hint: When adding a new *Dirty field assure to update IsValidDecoration().
+// Hint: When adding a new *Dirty field assure to update IsCompoundTask().
 type Task struct {
 	// Inputs are directories or files
 	// the task monitors for a rebuild.
@@ -30,7 +30,7 @@ type Task struct {
 	InputDirty string `yaml:"input,omitempty"`
 	// InputAdditionalIgnores is a list of ignores
 	// usually the child targets.
-	InputAdditionalIgnores []string `yaml:"input_additional_ignores,omitempty"`
+	InputAdditionalIgnores []string
 	// inputs is filtered by ignored & sanitized
 	inputs []string
 
@@ -143,19 +143,35 @@ func (t *Task) IsDecoration() bool {
 	return strings.ContainsRune(t.name, TaskPathSeparator)
 }
 
-// IsValidDecoration checks if the task is a valid decoration.
-// tasks containing a `dependsOn` node only are considered as
-// valid decoration.
+// IsCompoundTask checks if the task is a compound task
 //
-// Make sure to update IsValidDecoration() very time a new
-// *Dirty field is added to the task.
-func (t *Task) IsValidDecoration() bool {
+// tasks containing only `dependsOn` node are considered as compound task
+//
+// # Compound tasks are used when decorating a task or when grouping several tasks together
+//
+// Grouping tasks example:
+//
+//		build:
+//	    	dependsOn:
+//				- backend
+//				- frontend
+//
+// Decoration example:
+//
+//			import:
+//	 			- backend
+//			build:
+//			 	backend/hello: # the task decoration
+//	   				dependsOn:
+//	     				- generateDocs
+//	 			generateDocs:
+//	   		cmd: touch docs.md
+//
+// Make sure to update IsCompoundTask() very time a new *Dirty field is added to the task.
+func (t *Task) IsCompoundTask() bool {
 	if t.InputDirty != "" {
 		return false
 	}
-	if len(t.InputAdditionalIgnores) > 0 {
-		return false
-	}
 	if t.CmdDirty != "" {
 		return false
 	}
diff --git a/bobtask/verify.go b/bobtask/verify.go
index c4ff7a92..fd058230 100644
--- a/bobtask/verify.go
+++ b/bobtask/verify.go
@@ -8,14 +8,9 @@ import (
 	"github.com/benchkram/bob/pkg/usererror"
 )
 
-// Verify a bobfile before task runner.
-func (t *Task) Verify() error {
-	return t.verifyBefore()
-}
-
 // VerifyBefore a bobfile before task runner.
-func (t *Task) VerifyBefore() error {
-	return t.verifyBefore()
+func (t *Task) VerifyBefore(cacheEnabled, allowRedundantTargets bool) error {
+	return t.verifyBefore(cacheEnabled, allowRedundantTargets)
 }
 
 // VerifyAfter a bobfile after task runner.
@@ -23,8 +18,11 @@ func (t *Task) VerifyAfter() error {
 	return t.verifyAfter()
 }
 
-func (t *Task) verifyBefore() (err error) {
+func (t *Task) verifyBefore(cacheEnabled, allowRedundantTargets bool) (err error) {
 	if t.target != nil {
+		if !allowRedundantTargets && cacheEnabled && t.Rebuild() == RebuildAlways {
+			return usererror.Wrap(fmt.Errorf("`rebuild:always` not allowed in combination with `target` for task: `%s`", t.name))
+		}
 		for _, path := range t.target.FilesystemEntriesRawPlain() {
 			if !isValidFilesystemTarget(path) {
 				return usererror.Wrap(fmt.Errorf("invalid target `%s` for task `%s`", path, t.name))
diff --git a/test/e2e/artifacts/artifacts_extraction_test.go b/test/e2e/artifacts/artifacts_extraction_test.go
index 6ef3bd1d..540b0829 100644
--- a/test/e2e/artifacts/artifacts_extraction_test.go
+++ b/test/e2e/artifacts/artifacts_extraction_test.go
@@ -57,7 +57,7 @@ var _ = Describe("Test artifact creation and extraction", func() {
 		It("extract artifact from store on rebuild", func() {
 			state, err := buildTask(b, bob.BuildTargetwithdirsTargetName)
 			Expect(err).NotTo(HaveOccurred())
-			Expect(state.State()).To(Equal(playbook.StateNoRebuildRequired))
+			Expect(state.State()).To(Equal(playbook.StateCompleted))
 		})
 
 		It("cleanup", func() {
@@ -140,7 +140,7 @@ var _ = Describe("Test artifact creation and extraction from docker targets", fu
 		It("should extract artifact from store on rebuild", func() {
 			state, err := buildTask(b, bob.BuildTargetDockerImageName)
 			Expect(err).NotTo(HaveOccurred())
-			Expect(state.State()).To(Equal(playbook.StateNoRebuildRequired))
+			Expect(state.State()).To(Equal(playbook.StateCached))
 		})
 
 		It("should check that the docker image was created correctly", func() {
diff --git a/test/e2e/artifacts/artifacts_suite_test.go b/test/e2e/artifacts/artifacts_suite_test.go
index 751a3767..4201518f 100644
--- a/test/e2e/artifacts/artifacts_suite_test.go
+++ b/test/e2e/artifacts/artifacts_suite_test.go
@@ -86,6 +86,7 @@ var _ = BeforeSuite(func() {
 		bob.WithFilestore(artifactStore),
 		bob.WithBuildinfoStore(buildinfoStore),
 		bob.WithNixBuilder(nixBuilder),
+		bob.WithEnableRedundantTargets(),
 	)
 	Expect(err).NotTo(HaveOccurred())
 
diff --git a/test/e2e/artifacts/artifacts_test.go b/test/e2e/artifacts/artifacts_test.go
index 627e7cad..862709f5 100644
--- a/test/e2e/artifacts/artifacts_test.go
+++ b/test/e2e/artifacts/artifacts_test.go
@@ -42,7 +42,7 @@ var _ = Describe("Test artifact and target invalidation", func() {
 			err := artifactRemove(artifactID)
 			Expect(err).NotTo(HaveOccurred())
 
-			//time.Sleep(1 * time.Minute)
+			// time.Sleep(1 * time.Minute)
 
 			state, err := buildTask(b, "build")
 			Expect(err).NotTo(HaveOccurred())
@@ -57,7 +57,7 @@ var _ = Describe("Test artifact and target invalidation", func() {
 		It("should not rebuild but unpack from local artifact", func() {
 			state, err := buildTask(b, "build")
 			Expect(err).NotTo(HaveOccurred())
-			Expect(state.State()).To(Equal(playbook.StateNoRebuildRequired))
+			Expect(state.State()).To(Equal(playbook.StateCached))
 		})
 
 		// 7)
@@ -83,7 +83,7 @@ var _ = Describe("Test artifact and target invalidation", func() {
 
 			state, err := buildTask(b, "build")
 			Expect(err).NotTo(HaveOccurred())
-			Expect(state.State()).To(Equal(playbook.StateNoRebuildRequired))
+			Expect(state.State()).To(Equal(playbook.StateCached))
 
 			file.Exists(filepath.Join(dir, "run"))
 		})
@@ -102,7 +102,7 @@ var _ = Describe("Test artifact and target invalidation", func() {
 	})
 })
 
-//  docker targets
+// docker targets
 var _ = Describe("Test artifact and docker-target invalidation", func() {
 	Context("in a fresh playground", func() {
 
@@ -144,7 +144,7 @@ var _ = Describe("Test artifact and docker-target invalidation", func() {
 		It("should not rebuild but extract from local artifact", func() {
 			state, err := buildTask(b, bob.BuildTargetDockerImageName)
 			Expect(err).NotTo(HaveOccurred())
-			Expect(state.State()).To(Equal(playbook.StateNoRebuildRequired))
+			Expect(state.State()).To(Equal(playbook.StateCached))
 		})
 
 		// 7)
@@ -183,7 +183,7 @@ var _ = Describe("Test artifact and docker-target invalidation", func() {
 
 			state, err := buildTask(b, bob.BuildTargetDockerImageName)
 			Expect(err).NotTo(HaveOccurred())
-			Expect(state.State()).To(Equal(playbook.StateNoRebuildRequired))
+			Expect(state.State()).To(Equal(playbook.StateCached))
 
 			exists, err := mobyClient.ImageExists(bob.BuildTargetBobTestImage)
 			Expect(err).NotTo(HaveOccurred())
diff --git a/test/e2e/artifacts/nobuildinfo_test.go b/test/e2e/artifacts/nobuildinfo_test.go
index 3d4cef83..8d1c5ef5 100644
--- a/test/e2e/artifacts/nobuildinfo_test.go
+++ b/test/e2e/artifacts/nobuildinfo_test.go
@@ -72,7 +72,7 @@ var _ = Describe("Test artifact and target lifecycle without existing buildinfo"
 
 			state, err = buildTask(b, "build")
 			Expect(err).NotTo(HaveOccurred())
-			Expect(state.State()).To(Equal(playbook.StateNoRebuildRequired))
+			Expect(state.State()).To(Equal(playbook.StateCached))
 		})
 
 		It("clean artifacts & buildinfo", func() {
@@ -165,7 +165,7 @@ var _ = Describe("Test artifact and target lifecycle for docker images without e
 
 			state, err = buildTask(b, bob.BuildTargetDockerImageName)
 			Expect(err).NotTo(HaveOccurred())
-			Expect(state.State()).To(Equal(playbook.StateNoRebuildRequired))
+			Expect(state.State()).To(Equal(playbook.StateCached))
 		})
 
 		It("clean artifacts & buildinfo", func() {
diff --git a/test/e2e/build/build_suite_test.go b/test/e2e/build/build_suite_test.go
index b1a5e34e..2a314b06 100644
--- a/test/e2e/build/build_suite_test.go
+++ b/test/e2e/build/build_suite_test.go
@@ -32,7 +32,7 @@ var _ = BeforeSuite(func() {
 	nixBuilder, err := NixBuilder()
 	Expect(err).NotTo(HaveOccurred())
 
-	b, err = bob.BobWithBaseStoreDir(storageDir, bob.WithDir(dir), bob.WithNixBuilder(nixBuilder))
+	b, err = bob.BobWithBaseStoreDir(storageDir, bob.WithDir(dir), bob.WithNixBuilder(nixBuilder), bob.WithEnableRedundantTargets())
 	Expect(err).NotTo(HaveOccurred())
 })
 
diff --git a/test/e2e/ignore/ignore_suite_test.go b/test/e2e/ignore/ignore_suite_test.go
index 8ff4442f..17611226 100644
--- a/test/e2e/ignore/ignore_suite_test.go
+++ b/test/e2e/ignore/ignore_suite_test.go
@@ -33,7 +33,7 @@ var _ = BeforeSuite(func() {
 	nixBuilder, err := NixBuilder()
 	Expect(err).NotTo(HaveOccurred())
 
-	b, err = bob.BobWithBaseStoreDir(storageDir, bob.WithDir(dir), bob.WithNixBuilder(nixBuilder))
+	b, err = bob.BobWithBaseStoreDir(storageDir, bob.WithDir(dir), bob.WithNixBuilder(nixBuilder), bob.WithEnableRedundantTargets())
 	Expect(err).NotTo(HaveOccurred())
 })
 
diff --git a/test/e2e/multilevelbuild/multilevelbuild_suite_test.go b/test/e2e/multilevelbuild/multilevelbuild_suite_test.go
index 71805c09..ed77b31d 100644
--- a/test/e2e/multilevelbuild/multilevelbuild_suite_test.go
+++ b/test/e2e/multilevelbuild/multilevelbuild_suite_test.go
@@ -37,7 +37,7 @@ var _ = BeforeSuite(func() {
 	nixBuilder, err := NixBuilder()
 	Expect(err).NotTo(HaveOccurred())
 
-	b, err = bob.BobWithBaseStoreDir(storageDir, bob.WithDir(dir), bob.WithNixBuilder(nixBuilder))
+	b, err = bob.BobWithBaseStoreDir(storageDir, bob.WithDir(dir), bob.WithNixBuilder(nixBuilder), bob.WithEnableRedundantTargets())
 	Expect(err).NotTo(HaveOccurred())
 })
 
diff --git a/test/e2e/multilevelbuild/multilevelbuild_test.go b/test/e2e/multilevelbuild/multilevelbuild_test.go
index 62576964..90b9ce65 100644
--- a/test/e2e/multilevelbuild/multilevelbuild_test.go
+++ b/test/e2e/multilevelbuild/multilevelbuild_test.go
@@ -107,14 +107,6 @@ var _ = Describe("Test bob multilevel build", func() {
 
 		It("checks that we do not require a rebuild of any of the levels", func() {
 			fixtures := []requiresRebuildFixture{
-				{
-					taskname:        bob.BuildAllTargetName,
-					requiresRebuild: false,
-				},
-				{
-					taskname:        "second-level/build2",
-					requiresRebuild: false,
-				},
 				{
 					taskname:        "second-level/third-level/build3",
 					requiresRebuild: false,
@@ -162,14 +154,6 @@ var _ = Describe("Test bob multilevel build", func() {
 
 		It("checks that we do not require a rebuild of any of the levels", func() {
 			fixtures := []requiresRebuildFixture{
-				{
-					taskname:        bob.BuildAllTargetName,
-					requiresRebuild: false,
-				},
-				{
-					taskname:        "second-level/build2",
-					requiresRebuild: false,
-				},
 				{
 					taskname:        "second-level/third-level/build3",
 					requiresRebuild: false,
@@ -230,7 +214,7 @@ func requiresRebuildMustMatchFixtures(b *bob.B, fixtures []requiresRebuildFixtur
 	for _, f := range fixtures {
 		ts, err := pb.TaskStatus(f.taskname)
 		Expect(err).NotTo(HaveOccurred())
-		requiresRebuild := ts.State() != playbook.StateNoRebuildRequired
+		requiresRebuild := ts.State() != playbook.StateCached && ts.State() != playbook.StateNoRebuildRequired
 
 		Expect(f.requiresRebuild).To(Equal(requiresRebuild), fmt.Sprintf("task's %q rebuild requirement differ, got: %t, want: %t", f.taskname, requiresRebuild, f.requiresRebuild))
 	}
diff --git a/test/e2e/target-cleanup/with_dir_target/bob.yaml b/test/e2e/target-cleanup/with_dir_target/bob.yaml
index 5471c5a1..442cf63f 100644
--- a/test/e2e/target-cleanup/with_dir_target/bob.yaml
+++ b/test/e2e/target-cleanup/with_dir_target/bob.yaml
@@ -1,5 +1,6 @@
 build:
   build:
+    input: "*"
     cmd: |-
       mkdir sub-dir
       touch ./sub-dir/non-empty-file
diff --git a/test/e2e/target-name/with_second_level/bob.yaml b/test/e2e/target-name/with_second_level/bob.yaml
index 99439afc..8d26c956 100644
--- a/test/e2e/target-name/with_second_level/bob.yaml
+++ b/test/e2e/target-name/with_second_level/bob.yaml
@@ -3,5 +3,6 @@ import:
 
 build:
   build:
+    input: "*"
     cmd: touch hello
     target: hello
\ No newline at end of file
diff --git a/test/e2e/target-name/with_second_level/second/bob.yaml b/test/e2e/target-name/with_second_level/second/bob.yaml
index 61715466..9c07ed21 100644
--- a/test/e2e/target-name/with_second_level/second/bob.yaml
+++ b/test/e2e/target-name/with_second_level/second/bob.yaml
@@ -1,4 +1,5 @@
 build:
   build:
+    input: "*"
     cmd: touch hello
     target: hello
\ No newline at end of file
diff --git a/test/e2e/target-symlink/with_symlink/bob.yaml b/test/e2e/target-symlink/with_symlink/bob.yaml
index 8d3fae08..eb174ed2 100644
--- a/test/e2e/target-symlink/with_symlink/bob.yaml
+++ b/test/e2e/target-symlink/with_symlink/bob.yaml
@@ -1,5 +1,6 @@
 build:
   build:
+    input: "*"
     cmd: |-
       touch hello
       ln -s hello shortcut
diff --git a/test/e2e/target/target_suite_test.go b/test/e2e/target/target_suite_test.go
index 6483855c..e57aa8ea 100644
--- a/test/e2e/target/target_suite_test.go
+++ b/test/e2e/target/target_suite_test.go
@@ -47,6 +47,7 @@ var _ = BeforeSuite(func() {
 		bob.WithBuildinfoStore(buildInfoStore),
 		bob.WithDir(dir),
 		bob.WithNixBuilder(nixBuilder),
+		bob.WithEnableRedundantTargets(),
 	)
 
 	Expect(err).NotTo(HaveOccurred())
diff --git a/test/e2e/task-decoration/with_decoration/bob.yaml b/test/e2e/task-decoration/with_decoration/bob.yaml
index 94fd0b24..849e9118 100644
--- a/test/e2e/task-decoration/with_decoration/bob.yaml
+++ b/test/e2e/task-decoration/with_decoration/bob.yaml
@@ -8,6 +8,7 @@ build:
   second/build:
     dependsOn: [ before ]
   before:
+    input: "*"
     cmd: |-
       touch textfile_before
       echo "Before!" > textfile_before
diff --git a/test/e2e/task-decoration/with_decoration/second/bob.yaml b/test/e2e/task-decoration/with_decoration/second/bob.yaml
index 81394d3c..27c04b13 100644
--- a/test/e2e/task-decoration/with_decoration/second/bob.yaml
+++ b/test/e2e/task-decoration/with_decoration/second/bob.yaml
@@ -2,12 +2,14 @@ nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fff
 
 build:
   build:
+    input: "*"
     cmd: |-
       touch textfile_build
       echo "Build!" > textfile_build
     target: textfile_build
     dependsOn: [ hello ]
   hello:
+    input: "*"
     cmd: |-
       touch textfile_hello
       echo "Hello!" > textfile_hello
diff --git a/test/e2e/task-decoration/with_invalid_decoration/bob.yaml b/test/e2e/task-decoration/with_invalid_decoration/bob.yaml
index a293774a..8f85a0d7 100644
--- a/test/e2e/task-decoration/with_invalid_decoration/bob.yaml
+++ b/test/e2e/task-decoration/with_invalid_decoration/bob.yaml
@@ -7,6 +7,7 @@ build:
     cmd: echo "Hello"
     dependsOn: [ before ]
   before:
+    input: "*"
     cmd: echo "before"
   
 
diff --git a/test/e2e/task-decoration/with_invalid_decoration/second/bob.yaml b/test/e2e/task-decoration/with_invalid_decoration/second/bob.yaml
index 3933c9a4..27c04b13 100644
--- a/test/e2e/task-decoration/with_invalid_decoration/second/bob.yaml
+++ b/test/e2e/task-decoration/with_invalid_decoration/second/bob.yaml
@@ -2,15 +2,17 @@ nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fff
 
 build:
   build:
+    input: "*"
     cmd: |-
-        touch textfile_build
-        echo "Build!" > textfile_build
+      touch textfile_build
+      echo "Build!" > textfile_build
     target: textfile_build
     dependsOn: [ hello ]
   hello:
+    input: "*"
     cmd: |-
-        touch textfile_hello
-        echo "Hello!" > textfile_hello
+      touch textfile_hello
+      echo "Hello!" > textfile_hello
     target: textfile_hello
 
 
diff --git a/test/e2e/task-decoration/with_missed_decoration/bob.yaml b/test/e2e/task-decoration/with_missed_decoration/bob.yaml
index 90eaa8a1..9294ea5e 100644
--- a/test/e2e/task-decoration/with_missed_decoration/bob.yaml
+++ b/test/e2e/task-decoration/with_missed_decoration/bob.yaml
@@ -6,6 +6,7 @@ build:
   second/build:
     dependsOn: [ before ]
   before:
+    input: "*"
     cmd: echo "before"
   
 
diff --git a/test/e2e/task-decoration/with_thirdlevel_decoration/bob.yaml b/test/e2e/task-decoration/with_thirdlevel_decoration/bob.yaml
index 00442f81..1b09a317 100644
--- a/test/e2e/task-decoration/with_thirdlevel_decoration/bob.yaml
+++ b/test/e2e/task-decoration/with_thirdlevel_decoration/bob.yaml
@@ -8,6 +8,7 @@ build:
   second/third/build:
     dependsOn: [ second/hello ]
   before:
+    input: "*"
     cmd: |-
       touch textfile_before
       echo "Before!" > textfile_before
diff --git a/test/e2e/task-decoration/with_thirdlevel_decoration/second/bob.yaml b/test/e2e/task-decoration/with_thirdlevel_decoration/second/bob.yaml
index e1a66b38..3471b7b0 100644
--- a/test/e2e/task-decoration/with_thirdlevel_decoration/second/bob.yaml
+++ b/test/e2e/task-decoration/with_thirdlevel_decoration/second/bob.yaml
@@ -5,17 +5,20 @@ import:
 
 build:
   build:
+    input: "*"
     cmd: |-
       touch textfile_build2
       echo "Build!" > textfile_build2
     target: textfile_build2
     dependsOn: [ create ]
   hello:
+    input: "*"
     cmd: |-
       touch textfile_hello2
       echo "Hello!" > textfile_hello2
     target: textfile_hello2
   create:
+    input: "*"
     cmd: echo "create!"
 
 
diff --git a/test/e2e/task-decoration/with_thirdlevel_decoration/second/third/bob.yaml b/test/e2e/task-decoration/with_thirdlevel_decoration/second/third/bob.yaml
index 81394d3c..27c04b13 100644
--- a/test/e2e/task-decoration/with_thirdlevel_decoration/second/third/bob.yaml
+++ b/test/e2e/task-decoration/with_thirdlevel_decoration/second/third/bob.yaml
@@ -2,12 +2,14 @@ nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fff
 
 build:
   build:
+    input: "*"
     cmd: |-
       touch textfile_build
       echo "Build!" > textfile_build
     target: textfile_build
     dependsOn: [ hello ]
   hello:
+    input: "*"
     cmd: |-
       touch textfile_hello
       echo "Hello!" > textfile_hello
diff --git a/test/e2e/tasksemantics/compound_task/bob.yaml b/test/e2e/tasksemantics/compound_task/bob.yaml
new file mode 100644
index 00000000..6af8040c
--- /dev/null
+++ b/test/e2e/tasksemantics/compound_task/bob.yaml
@@ -0,0 +1,9 @@
+nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fffe0690fbb20.tar.gz
+build:
+  # build is a compound task because it has only dependsOn node
+  build:
+    dependsOn: [ generated ]
+  generated:
+    input: "*"
+    cmd: touch hello
+    target: hello
\ No newline at end of file
diff --git a/test/e2e/tasksemantics/no_input_no_target/bob.yaml b/test/e2e/tasksemantics/no_input_no_target/bob.yaml
new file mode 100644
index 00000000..0016651d
--- /dev/null
+++ b/test/e2e/tasksemantics/no_input_no_target/bob.yaml
@@ -0,0 +1,4 @@
+nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fffe0690fbb20.tar.gz
+build:
+  build:
+    cmd: echo Hello World
diff --git a/test/e2e/tasksemantics/no_input_no_target_rebuild_always/bob.yaml b/test/e2e/tasksemantics/no_input_no_target_rebuild_always/bob.yaml
new file mode 100644
index 00000000..5edb67bf
--- /dev/null
+++ b/test/e2e/tasksemantics/no_input_no_target_rebuild_always/bob.yaml
@@ -0,0 +1,5 @@
+nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fffe0690fbb20.tar.gz
+build:
+  build:
+    cmd: echo Hello World
+    rebuild: always
\ No newline at end of file
diff --git a/test/e2e/tasksemantics/no_input_unknown_target/bob.yaml b/test/e2e/tasksemantics/no_input_unknown_target/bob.yaml
new file mode 100644
index 00000000..f97c47df
--- /dev/null
+++ b/test/e2e/tasksemantics/no_input_unknown_target/bob.yaml
@@ -0,0 +1,4 @@
+nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fffe0690fbb20.tar.gz
+build:
+  build:
+    cmd: touch hello
\ No newline at end of file
diff --git a/test/e2e/tasksemantics/no_input_with_target/bob.yaml b/test/e2e/tasksemantics/no_input_with_target/bob.yaml
new file mode 100644
index 00000000..02c077bb
--- /dev/null
+++ b/test/e2e/tasksemantics/no_input_with_target/bob.yaml
@@ -0,0 +1,5 @@
+nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fffe0690fbb20.tar.gz
+build:
+  build:
+    cmd: touch hello
+    target: hello
\ No newline at end of file
diff --git a/test/e2e/tasksemantics/rebuild_always_with_target/bob.yaml b/test/e2e/tasksemantics/rebuild_always_with_target/bob.yaml
new file mode 100644
index 00000000..5d2e6093
--- /dev/null
+++ b/test/e2e/tasksemantics/rebuild_always_with_target/bob.yaml
@@ -0,0 +1,6 @@
+nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fffe0690fbb20.tar.gz
+build:
+  build:
+    cmd: touch content.json
+    rebuild: always
+    target: content.json
\ No newline at end of file
diff --git a/test/e2e/tasksemantics/rebuild_on_input_change/bob.yaml b/test/e2e/tasksemantics/rebuild_on_input_change/bob.yaml
new file mode 100644
index 00000000..87deb644
--- /dev/null
+++ b/test/e2e/tasksemantics/rebuild_on_input_change/bob.yaml
@@ -0,0 +1,6 @@
+nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fffe0690fbb20.tar.gz
+build:
+  build:
+    input: "*"
+    cmd: touch hello
+    target: hello
\ No newline at end of file
diff --git a/test/e2e/tasksemantics/semantics_suite_test.go b/test/e2e/tasksemantics/semantics_suite_test.go
new file mode 100644
index 00000000..6cdc047f
--- /dev/null
+++ b/test/e2e/tasksemantics/semantics_suite_test.go
@@ -0,0 +1,110 @@
+package tasksemanticstest
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/benchkram/bob/bob/bobfile"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var (
+	dir string
+
+	stdout *os.File
+	stderr *os.File
+	pr     *os.File
+	pw     *os.File
+)
+
+var _ = BeforeSuite(func() {
+	// Initialize mock bob files from local directory
+	bobFiles := []string{
+		"rebuild_on_input_change",
+		"no_input_with_target",
+		"no_input_unknown_target",
+		"no_input_no_target",
+		"with_input_no_target",
+		"no_input_no_target_rebuild_always",
+		"compound_task",
+		"rebuild_always_with_target",
+	}
+	nameToBobfile := make(map[string]*bobfile.Bobfile)
+	for _, name := range bobFiles {
+		abs, err := filepath.Abs("./" + name)
+		Expect(err).NotTo(HaveOccurred())
+		bf, err := bobfile.BobfileRead(abs)
+		Expect(err).NotTo(HaveOccurred())
+		nameToBobfile[strings.ReplaceAll(name, "/", "_")] = bf
+	}
+
+	testDir, err := ioutil.TempDir("", "bob-test-task-semantics-*")
+	Expect(err).NotTo(HaveOccurred())
+	dir = testDir
+
+	err = os.Chdir(dir)
+	Expect(err).NotTo(HaveOccurred())
+
+	// Save bob files in dir to have them available in tests
+	for name, bf := range nameToBobfile {
+		err = bf.BobfileSave(dir, name+".yaml")
+		Expect(err).NotTo(HaveOccurred())
+	}
+})
+
+var _ = AfterSuite(func() {
+	err := os.RemoveAll(dir)
+	Expect(err).NotTo(HaveOccurred())
+
+	for _, file := range tmpFiles {
+		err = os.Remove(file)
+		Expect(err).NotTo(HaveOccurred())
+	}
+})
+
+func TestBuild(t *testing.T) {
+	_, err := exec.LookPath("nix")
+	if err != nil {
+		// Allow to skip tests only locally.
+		// CI is always set to true on GitHub actions.
+		// https://docs.github.com/en/actions/learn-github-actions/environment-variables#default-environment-variables
+		if os.Getenv("CI") != "true" {
+			t.Skip("Test skipped because nix is not installed on your system")
+		}
+	}
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "task semantics suite")
+}
+
+func capture() {
+	stdout = os.Stdout
+	stderr = os.Stderr
+
+	var err error
+	pr, pw, err = os.Pipe()
+	Expect(err).NotTo(HaveOccurred())
+
+	os.Stdout = pw
+	os.Stderr = pw
+}
+
+func output() string {
+	pw.Close()
+
+	b, err := io.ReadAll(pr)
+	Expect(err).NotTo(HaveOccurred())
+
+	pr.Close()
+
+	os.Stdout = stdout
+	os.Stderr = stderr
+
+	return string(b)
+}
diff --git a/test/e2e/tasksemantics/semantics_test.go b/test/e2e/tasksemantics/semantics_test.go
new file mode 100644
index 00000000..daf22909
--- /dev/null
+++ b/test/e2e/tasksemantics/semantics_test.go
@@ -0,0 +1,225 @@
+package tasksemanticstest
+
+import (
+	"context"
+	"os"
+
+	"github.com/benchkram/bob/bob/playbook"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Testing task semantics behaviour", func() {
+	When("task has input * and a target", func() {
+		b, err := Bob()
+		Expect(err).NotTo(HaveOccurred())
+
+		It("it will first build successfully", func() {
+			useBobfile("rebuild_on_input_change")
+			defer releaseBobfile("rebuild_on_input_change")
+
+			capture()
+			ctx := context.Background()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			buildCompleted := playbook.StateCompleted
+			Expect(output()).To(ContainSubstring(buildCompleted.Summary()))
+		})
+
+		It("it will have summary cached on the second build", func() {
+			capture()
+			useBobfile("rebuild_on_input_change")
+			defer releaseBobfile("rebuild_on_input_change")
+
+			ctx := context.Background()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			buildCached := playbook.StateCached
+			Expect(output()).To(ContainSubstring(buildCached.Summary()))
+		})
+
+		It("it will be rebuilt when input * changes", func() {
+			useBobfile("rebuild_on_input_change")
+			defer releaseBobfile("rebuild_on_input_change")
+
+			// invalidate target by creating a new file
+			err := os.WriteFile("./someFile", []byte("hello\ngo\n"), 0644)
+			Expect(err).NotTo(HaveOccurred())
+
+			ctx := context.Background()
+			capture()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			buildCompleted := playbook.StateCompleted
+			Expect(output()).To(ContainSubstring(buildCompleted.Summary()))
+		})
+	})
+
+	When("task has target but no input set", func() {
+		It("it will trigger a no input provided error on aggregation", func() {
+			b, err := Bob()
+			Expect(err).NotTo(HaveOccurred())
+
+			useBobfile("no_input_with_target")
+			defer releaseBobfile("no_input_with_target")
+
+			_, err = b.Aggregate()
+			Expect(err.Error()).To(Equal("no input provided for task `build`"))
+		})
+	})
+
+	// An unknown target is a file created inside `cmd` which is not specified in `target`
+	When("task has no input and an unknown target to be created", func() {
+		It("it will trigger a no input provided error on aggregation", func() {
+			b, err := Bob()
+			Expect(err).NotTo(HaveOccurred())
+
+			useBobfile("no_input_unknown_target")
+			defer releaseBobfile("no_input_unknown_target")
+
+			_, err = b.Aggregate()
+			Expect(err.Error()).To(Equal("no input provided for task `build`"))
+		})
+	})
+
+	When("task has no input and no target defined", func() {
+		It("it will trigger a no input provided error on aggregation", func() {
+			useBobfile("no_input_no_target")
+			defer releaseBobfile("no_input_no_target")
+
+			b, err := Bob()
+			Expect(err).NotTo(HaveOccurred())
+
+			_, err = b.Aggregate()
+			Expect(err.Error()).To(Equal("no input provided for task `build`"))
+		})
+
+		It("it will not trigger a no input provided error if rebuild:always", func() {
+			useBobfile("no_input_no_target_rebuild_always")
+			defer releaseBobfile("no_input_no_target_rebuild_always")
+
+			b, err := Bob()
+			Expect(err).NotTo(HaveOccurred())
+
+			_, err = b.Aggregate()
+			Expect(err).NotTo(HaveOccurred())
+		})
+	})
+
+	When("task has input * and no target to be created", func() {
+		b, err := Bob()
+		Expect(err).NotTo(HaveOccurred())
+
+		It("it will first build successfully", func() {
+			useBobfile("with_input_no_target")
+			defer releaseBobfile("with_input_no_target")
+
+			capture()
+			ctx := context.Background()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			buildCompleted := playbook.StateCompleted
+			Expect(output()).To(ContainSubstring(buildCompleted.Summary()))
+		})
+
+		It("it will have summary no-rebuild on second build", func() {
+			useBobfile("with_input_no_target")
+			defer releaseBobfile("with_input_no_target")
+
+			ctx := context.Background()
+			capture()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			buildCached := playbook.StateNoRebuildRequired
+			Expect(output()).To(ContainSubstring(buildCached.Summary()))
+		})
+
+		It("it will be rebuilt when input * changes", func() {
+			useBobfile("with_input_no_target")
+			defer releaseBobfile("with_input_no_target")
+
+			// invalidate target by creating a new file
+			err := os.WriteFile("./someRandomFile", []byte("hello\ngo\n"), 0644)
+			Expect(err).NotTo(HaveOccurred())
+
+			ctx := context.Background()
+			capture()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			buildCompleted := playbook.StateCompleted
+			Expect(output()).To(ContainSubstring(buildCompleted.Summary()))
+		})
+	})
+
+	When("task is a compound task", func() {
+		b, err := Bob()
+		Expect(err).NotTo(HaveOccurred())
+
+		It("it will first build successfully", func() {
+			useBobfile("compound_task")
+			defer releaseBobfile("compound_task")
+
+			capture()
+			ctx := context.Background()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			buildCompleted := playbook.StateCompleted
+			Expect(output()).To(ContainSubstring(buildCompleted.Summary()))
+		})
+
+		It("it will have summary no-rebuild on second build", func() {
+			useBobfile("compound_task")
+			defer releaseBobfile("compound_task")
+
+			ctx := context.Background()
+			capture()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			// generated task is cached
+			buildCached := playbook.StateCached
+			out := output()
+			Expect(out).To(ContainSubstring(buildCached.Summary()))
+
+			// build is marked as no-rebuild and shown with -
+			Expect(out).To(ContainSubstring("-"))
+		})
+
+		It("it will be rebuilt when input * changes", func() {
+			useBobfile("compound_task")
+			defer releaseBobfile("compound_task")
+
+			// invalidate target by creating a new file
+			err := os.WriteFile("./anotherRandomFile", []byte("hello\ngo\n"), 0644)
+			Expect(err).NotTo(HaveOccurred())
+
+			ctx := context.Background()
+			capture()
+			err = b.Build(ctx, "build")
+			Expect(err).NotTo(HaveOccurred())
+
+			buildCompleted := playbook.StateCompleted
+			Expect(output()).To(ContainSubstring(buildCompleted.Summary()))
+		})
+	})
+
+	When("task has rebuild:always and target set", func() {
+		It("it will trigger an error on aggregation", func() {
+			b, err := Bob()
+			Expect(err).NotTo(HaveOccurred())
+
+			useBobfile("rebuild_always_with_target")
+			defer releaseBobfile("rebuild_always_with_target")
+
+			_, err = b.Aggregate()
+			Expect(err.Error()).To(Equal("`rebuild:always` not allowed in combination with `target` for task: `build`"))
+		})
+	})
+})
diff --git a/test/e2e/tasksemantics/setup_test.go b/test/e2e/tasksemantics/setup_test.go
new file mode 100644
index 00000000..21b24f02
--- /dev/null
+++ b/test/e2e/tasksemantics/setup_test.go
@@ -0,0 +1,55 @@
+package tasksemanticstest
+
+import (
+	"os"
+
+	"github.com/benchkram/bob/bob"
+	"github.com/benchkram/bob/pkg/nix"
+	. "github.com/onsi/gomega"
+)
+
+func Bob() (*bob.B, error) {
+	nixBuilder, err := NixBuilder()
+	if err != nil {
+		return nil, err
+	}
+	return bob.Bob(
+		bob.WithDir(dir),
+		bob.WithCachingEnabled(true),
+		bob.WithNixBuilder(nixBuilder),
+	)
+}
+
+// tmpFiles tracks temporarily created files in these tests
+// to be cleaned up at the end.
+var tmpFiles []string
+
+func NixBuilder() (*bob.NixBuilder, error) {
+	file, err := os.CreateTemp("", ".nix_cache*")
+	if err != nil {
+		return nil, err
+	}
+	name := file.Name()
+	file.Close()
+
+	tmpFiles = append(tmpFiles, name)
+
+	cache, err := nix.NewCacheStore(nix.WithPath(name))
+	if err != nil {
+		return nil, err
+	}
+
+	return bob.NewNixBuilder(bob.WithCache(cache)), nil
+}
+
+// useBobfile sets the right bobfile to be used for test
+func useBobfile(name string) {
+	err := os.Rename(name+".yaml", "bob.yaml")
+	Expect(err).NotTo(HaveOccurred())
+}
+
+// releaseBobfile will revert changes done in useBobfile
+func releaseBobfile(name string) {
+	err := os.Rename("bob.yaml", name+".yaml")
+	Expect(err).NotTo(HaveOccurred())
+}
diff --git a/test/e2e/tasksemantics/with_input_no_target/bob.yaml b/test/e2e/tasksemantics/with_input_no_target/bob.yaml
new file mode 100644
index 00000000..411fd219
--- /dev/null
+++ b/test/e2e/tasksemantics/with_input_no_target/bob.yaml
@@ -0,0 +1,5 @@
+nixpkgs: https://github.com/NixOS/nixpkgs/archive/eeefd01d4f630fcbab6588fe3e7fffe0690fbb20.tar.gz
+build:
+  build:
+    input: "*"
+    cmd: echo Hello World
\ No newline at end of file
diff --git a/test/e2e/variables/variables_suite_test.go b/test/e2e/variables/variables_suite_test.go
index 9d72883e..dcca19e4 100644
--- a/test/e2e/variables/variables_suite_test.go
+++ b/test/e2e/variables/variables_suite_test.go
@@ -33,7 +33,7 @@ var _ = BeforeSuite(func() {
 	nixBuilder, err := NixBuilder()
 	Expect(err).NotTo(HaveOccurred())
 
-	b, err = bob.BobWithBaseStoreDir(storageDir, bob.WithDir(dir), bob.WithNixBuilder(nixBuilder))
+	b, err = bob.BobWithBaseStoreDir(storageDir, bob.WithDir(dir), bob.WithNixBuilder(nixBuilder), bob.WithCachingEnabled(false))
 	Expect(err).NotTo(HaveOccurred())
 })
 
diff --git a/test/e2e/version/version_suite_test.go b/test/e2e/version/version_suite_test.go
index 6dd06c85..81bd928f 100644
--- a/test/e2e/version/version_suite_test.go
+++ b/test/e2e/version/version_suite_test.go
@@ -35,7 +35,7 @@ var _ = BeforeSuite(func() {
 	err = os.Chdir(dir)
 	Expect(err).NotTo(HaveOccurred())
 
-	b, err = bob.Bob(bob.WithDir(dir))
+	b, err = bob.Bob(bob.WithDir(dir), bob.WithCachingEnabled(false))
 	Expect(err).NotTo(HaveOccurred())
 })