diff --git a/README.md b/README.md
index 3492d91..088e2ca 100644
--- a/README.md
+++ b/README.md
@@ -78,14 +78,18 @@ Installs to `$(go env GOPATH)/bin`, which must be on your `PATH`.
 anvil detect                       # identify the project and its stack
 anvil build                        # deps, analyze, test, build (guided)
 anvil build --release --flavor prod
+anvil build --until analyze        # deps, then analyze
+anvil build --only test            # test phase only
 anvil sign                         # set up Android or iOS signing
 anvil build --sign                 # build and sign
 anvil upload                       # dry-run by default, pass --yes to perform
 ```
 
 Useful flags: `--path` (project directory), `--target` (android or ios),
-`--flavor`, `--release`, `--dry-run` (print the plan without running it), and
-`--plain` (no TUI, for CI). Every command has `--help`.
+`--flavor`, `--release`, `--until` (inclusive lifecycle prefix), `--only` (one
+lifecycle phase), `--dry-run` (print the plan without running it), and `--plain`
+(no TUI, for CI). `--until` and `--only` are mutually exclusive. Every command
+has `--help`.
 
 anvil never puts secrets on the command line or in the repo. Keystore and store
 credentials come from a prompt or an environment variable, and a credential
diff --git a/cmd/build.go b/cmd/build.go
index 74a7466..798bdc6 100644
--- a/cmd/build.go
+++ b/cmd/build.go
@@ -26,6 +26,8 @@ var (
 	buildSign    bool
 	buildDryRun  bool
 	buildPlain   bool
+	buildUntil   string
+	buildOnly    string
 )
 
 var buildCmd = &cobra.Command{
@@ -43,10 +45,16 @@ func init() {
 	buildCmd.Flags().BoolVar(&buildSign, "sign", false, "set up signing and produce a signed artifact")
 	buildCmd.Flags().BoolVar(&buildDryRun, "dry-run", false, "print the steps without running them")
 	buildCmd.Flags().BoolVar(&buildPlain, "plain", false, "plain line output instead of the interactive view")
+	buildCmd.Flags().StringVar(&buildUntil, "until", "", "run through this lifecycle phase")
+	buildCmd.Flags().StringVar(&buildOnly, "only", "", "run only this lifecycle phase")
 	rootCmd.AddCommand(buildCmd)
 }
 
 func runBuild(cmd *cobra.Command, _ []string) error {
+	if buildUntil != "" && buildOnly != "" {
+		return errors.New("--until and --only cannot be used together")
+	}
+
 	chosen, err := resolveProject(cmd, buildPath)
 	if err != nil {
 		return err
@@ -68,6 +76,11 @@ func runBuild(cmd *cobra.Command, _ []string) error {
 		phases = append(append([]driver.Phase{}, driver.Phases...), extra...)
 	}
 
+	phases, err = selectBuildPhases(phases, buildUntil, buildOnly)
+	if err != nil {
+		return err
+	}
+
 	if buildDryRun {
 		printPlan(cmd, chosen, d, opts, phases)
 		return nil
@@ -75,6 +88,35 @@ func runBuild(cmd *cobra.Command, _ []string) error {
 	return runPipeline(cmd, chosen.Path, d, opts, phases)
 }
 
+func selectBuildPhases(available []driver.Phase, until, only string) ([]driver.Phase, error) {
+	if until != "" && only != "" {
+		return nil, errors.New("--until and --only cannot be used together")
+	}
+	if until == "" && only == "" {
+		return append([]driver.Phase{}, available...), nil
+	}
+
+	selected := only
+	if selected == "" {
+		selected = until
+	}
+	for idx, phase := range available {
+		if phase.String() != selected {
+			continue
+		}
+		if only != "" {
+			return []driver.Phase{phase}, nil
+		}
+		return append([]driver.Phase{}, available[:idx+1]...), nil
+	}
+
+	names := make([]string, len(available))
+	for idx, phase := range available {
+		names[idx] = phase.String()
+	}
+	return nil, fmt.Errorf("unknown phase %q; available phases: %s", selected, strings.Join(names, ", "))
+}
+
 func resolveProject(cmd *cobra.Command, path string) (detect.Project, error) {
 	root, err := filepath.Abs(path)
 	if err != nil {
diff --git a/cmd/build_test.go b/cmd/build_test.go
new file mode 100644
index 0000000..f962585
--- /dev/null
+++ b/cmd/build_test.go
@@ -0,0 +1,57 @@
+package cmd
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/openforge-oss/anvil/internal/driver"
+)
+
+func TestSelectBuildPhases(t *testing.T) {
+	available := []driver.Phase{driver.Deps, driver.Analyze, driver.Test, driver.Build}
+
+	tests := []struct {
+		name    string
+		until   string
+		only    string
+		want    []driver.Phase
+		wantErr string
+	}{
+		{name: "all phases by default", want: available},
+		{name: "inclusive prefix", until: "analyze", want: []driver.Phase{driver.Deps, driver.Analyze}},
+		{name: "one phase", only: "test", want: []driver.Phase{driver.Test}},
+		{name: "conflicting selectors", until: "test", only: "analyze", wantErr: "cannot be used together"},
+		{name: "unknown phase", only: "sign", wantErr: "available phases: deps, analyze, test, build"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := selectBuildPhases(available, tt.until, tt.only)
+			if tt.wantErr != "" {
+				if err == nil || !strings.Contains(err.Error(), tt.wantErr) {
+					t.Fatalf("error = %v, want substring %q", err, tt.wantErr)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("selectBuildPhases() error = %v", err)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Fatalf("phases = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestSelectBuildPhasesIncludesOptionalSign(t *testing.T) {
+	available := append(append([]driver.Phase{}, driver.Phases...), driver.Sign)
+
+	got, err := selectBuildPhases(available, "", "sign")
+	if err != nil {
+		t.Fatalf("selectBuildPhases() error = %v", err)
+	}
+	if !reflect.DeepEqual(got, []driver.Phase{driver.Sign}) {
+		t.Fatalf("phases = %v, want [sign]", got)
+	}
+}
diff --git a/tasks/todo.md b/tasks/todo.md
index b093db1..53cab49 100644
--- a/tasks/todo.md
+++ b/tasks/todo.md
@@ -106,3 +106,17 @@ and `scoop-bucket` repos plus a `HOMEBREW_TAP_TOKEN` secret before the first
 release tag. Deferred: App Store submission metadata, Play staged rollout,
 fastlane back-ends, `anvil build --upload`, npm OIDC. This completes the core
 detect -> build -> sign -> upload pipeline.
+
+## Issue 9: lifecycle phase selection
+
+- [x] Add mutually exclusive `anvil build --until <phase>` and `--only <phase>` flags.
+- [x] Validate phase names and filter the selected driver's plan before dry-run or execution.
+- [x] Cover inclusive prefix selection, single-phase selection, invalid values, and conflicting flags.
+- [x] Run `./check`, review the focused diff, and open a pull request into `develop`.
+
+### Review, Issue 9
+
+Phase selection is validated once at the command boundary and feeds both dry-run output and real
+execution. Focused tests cover prefixes, single phases, invalid values, conflicts, and optional
+signing. `./check`, the binary build, staticcheck, and direct CLI dry runs pass. Pull request #20
+targets `develop`.