diff --git a/cmd/tag.go b/cmd/tag.go
index f392e854..7e4847c7 100644
--- a/cmd/tag.go
+++ b/cmd/tag.go
@@ -2,7 +2,11 @@ package cmd
 
 import (
 	"fmt"
+	"os"
+	"os/exec"
 	"regexp"
+	"strconv"
+	"strings"
 
 	"github.com/spf13/cobra"
 	"github.com/tta-lab/ttal-cli/internal/daemon"
@@ -14,31 +18,74 @@ import (
 // to keep validation simple — use dots as separators: v1.0.0-rc.1 not v1.0.0-rc-1).
 var semverRe = regexp.MustCompile(`^v\d+\.\d+\.\d+(-[a-zA-Z0-9]+(\.[a-zA-Z0-9]+)*)?(\+[a-zA-Z0-9]+(\.[a-zA-Z0-9]+)*)?$`)
 
+// semverBaseRe captures vMAJOR.MINOR.PATCH and optional +suffix from a tag.
+// Groups: 1=full base (v1.2.3), 2=MAJOR, 3=MINOR, 4=PATCH, 5=+suffix (including +).
+var semverBaseRe = regexp.MustCompile(`^v(\d+)\.(\d+)\.(\d+)(\+[a-zA-Z0-9]+(\.[a-zA-Z0-9]+)*)?$`)
+
 var tagCmd = &cobra.Command{
-	Use:   "tag <version> --project <alias>",
+	Use:   "tag [<version> | --bump <major|minor|patch>]",
 	Short: "Create and push a git tag via daemon (no credentials needed in worker)",
 	Long: `Creates a lightweight git tag and pushes it to origin through the daemon.
 The daemon injects credentials — workers don't need tokens in their environment.
 
-The tag must be a valid semver version prefixed with 'v' (e.g. v1.0.0, v2.1.0-rc.1).
+Resolves the project from the current working directory. No --project flag needed.
+
+With --bump, automatically bumps the largest existing version tag in the repo.
+Existing +suffix (e.g. +0.74.1) is preserved on bump.
+
+With a positional version argument, tags that exact version directly.
 
 Examples:
-  ttal tag v1.0.0 --project ttal-cli
-  ttal tag v2.1.0-rc.1 --project fn-agent
-  ttal tag v1.1.1-guion.1 --project fn-cli`,
-	Args: cobra.ExactArgs(1),
+  ttal tag --bump patch          # v1.2.3 → v1.2.4
+  ttal tag --bump minor          # v1.2.3 → v1.3.0
+  ttal tag --bump major          # v1.2.3 → v2.0.0
+  ttal tag v2.0.0                # explicit version
+  ttal tag v1.6.1+0.74.1         # explicit with +suffix`,
+	Args: cobra.MaximumNArgs(1),
 	RunE: func(cmd *cobra.Command, args []string) error {
-		tag := args[0]
-		if !semverRe.MatchString(tag) {
-			return fmt.Errorf("invalid semver tag %q — expected format: v1.0.0, v2.1.0-rc.1", tag)
+		cwd, err := os.Getwd()
+		if err != nil {
+			return fmt.Errorf("getwd: %w", err)
 		}
 
-		projectAlias, _ := cmd.Flags().GetString("project")
+		projectAlias := project.ResolveProjectAlias(cwd)
+		if projectAlias == "" {
+			return fmt.Errorf("current directory %q is not under a registered ttal project", cwd)
+		}
 		projectPath, err := project.GetProjectPath(projectAlias)
 		if err != nil {
 			return err
 		}
 
+		bump, _ := cmd.Flags().GetString("bump")
+		isBump := bump != ""
+
+		if isBump && len(args) > 0 {
+			return fmt.Errorf("--bump and a positional version are mutually exclusive")
+		}
+
+		var tag string
+
+		if isBump {
+			switch bump {
+			case bumpMajor, bumpMinor, bumpPatch:
+			default:
+				return fmt.Errorf("invalid --bump value %q — must be major, minor, or patch", bump)
+			}
+			tag, err = computeBumpedTag(projectPath, bump)
+			if err != nil {
+				return err
+			}
+		} else {
+			if len(args) == 0 {
+				return fmt.Errorf("either a version argument or --bump is required")
+			}
+			tag = args[0]
+			if !semverRe.MatchString(tag) {
+				return fmt.Errorf("invalid semver tag %q — expected format: v1.0.0, v2.1.0-rc.1", tag)
+			}
+		}
+
 		resp, err := daemon.GitTag(daemon.GitTagRequest{
 			WorkDir:      projectPath,
 			Tag:          tag,
@@ -57,7 +104,75 @@ Examples:
 }
 
 func init() {
-	tagCmd.Flags().StringP("project", "p", "", "project alias (required)")
-	_ = tagCmd.MarkFlagRequired("project")
+	tagCmd.Flags().String("bump", "", "bump version: major, minor, or patch")
 	rootCmd.AddCommand(tagCmd)
 }
+
+// latestTag returns the largest semver tag in the repo, or "" if none exist.
+func latestTag(workDir string) (string, error) {
+	cmd := exec.Command("git", "-C", workDir, "tag", "--sort=-version:refname")
+	out, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("git tag: %w", err)
+	}
+	lines := strings.Split(strings.TrimSpace(string(out)), "\n")
+	if len(lines) == 0 || lines[0] == "" {
+		return "", nil
+	}
+	return lines[0], nil
+}
+
+const (
+	initialMajor = "v1.0.0"
+	initialMinor = "v0.1.0"
+	initialPatch = "v0.0.1"
+
+	bumpMajor = "major"
+	bumpMinor = "minor"
+	bumpPatch = "patch"
+)
+
+// computeBumpedTag finds the largest tag, bumps the specified level, and returns the new tag.
+// The +suffix from the latest tag is preserved.
+func computeBumpedTag(workDir, level string) (string, error) {
+	latest, err := latestTag(workDir)
+	if err != nil {
+		return "", err
+	}
+	if latest == "" {
+		switch level {
+		case bumpMajor:
+			return initialMajor, nil
+		case bumpMinor:
+			return initialMinor, nil
+		default:
+			return initialPatch, nil
+		}
+	}
+
+	matches := semverBaseRe.FindStringSubmatch(latest)
+	if matches == nil {
+		return "", fmt.Errorf(
+			"latest tag %q is not a plain semver with optional +suffix (has pre-release: %s)",
+			latest, latest)
+	}
+
+	maj, _ := strconv.Atoi(matches[1])
+	min, _ := strconv.Atoi(matches[2])
+	pat, _ := strconv.Atoi(matches[3])
+	suffix := matches[4] // includes leading +, or "" if absent
+
+	switch level {
+	case bumpMajor:
+		maj++
+		min = 0
+		pat = 0
+	case bumpMinor:
+		min++
+		pat = 0
+	default:
+		pat++
+	}
+
+	return fmt.Sprintf("v%d.%d.%d%s", maj, min, pat, suffix), nil
+}
diff --git a/cmd/tag_test.go b/cmd/tag_test.go
index 961a450d..98fb866c 100644
--- a/cmd/tag_test.go
+++ b/cmd/tag_test.go
@@ -1,6 +1,10 @@
 package cmd
 
-import "testing"
+import (
+	"os"
+	"os/exec"
+	"testing"
+)
 
 func TestSemverRe(t *testing.T) {
 	tests := []struct {
@@ -40,3 +44,182 @@ func TestSemverRe(t *testing.T) {
 		})
 	}
 }
+
+func TestSemverBaseRe(t *testing.T) {
+	tests := []struct {
+		tag     string
+		matches bool
+		major   string
+		minor   string
+		patch   string
+		suffix  string
+	}{
+		{"v1.0.0", true, "1", "0", "0", ""},
+		{"v0.1.0", true, "0", "1", "0", ""},
+		{"v10.20.30", true, "10", "20", "30", ""},
+		{"v1.0.0+build.123", true, "1", "0", "0", "+build.123"},
+		{"v1.6.1+0.74.1", true, "1", "6", "1", "+0.74.1"},
+		{"v1.0.0-rc.1", false, "", "", "", ""}, // pre-release not matched
+		{"v1.0.0-rc.1+build.456", false, "", "", "", ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.tag, func(t *testing.T) {
+			matches := semverBaseRe.FindStringSubmatch(tt.tag)
+			if tt.matches && matches == nil {
+				t.Fatalf("semverBaseRe.FindStringSubmatch(%q) = nil, want match", tt.tag)
+			}
+			if !tt.matches && matches != nil {
+				t.Fatalf("semverBaseRe.FindStringSubmatch(%q) = %v, want no match", tt.tag, matches)
+			}
+			if matches != nil {
+				if matches[1] != tt.major {
+					t.Errorf("major: got %q, want %q", matches[1], tt.major)
+				}
+				if matches[2] != tt.minor {
+					t.Errorf("minor: got %q, want %q", matches[2], tt.minor)
+				}
+				if matches[3] != tt.patch {
+					t.Errorf("patch: got %q, want %q", matches[3], tt.patch)
+				}
+				if matches[4] != tt.suffix {
+					t.Errorf("suffix: got %q, want %q", matches[4], tt.suffix)
+				}
+			}
+		})
+	}
+}
+
+func testBumpedTag(t *testing.T, workDir, level, want string) {
+	t.Helper()
+	got, err := computeBumpedTag(workDir, level)
+	if err != nil {
+		t.Fatalf("computeBumpedTag(%q): %v", level, err)
+	}
+	if got != want {
+		t.Errorf("computeBumpedTag(%q) = %q, want %q", level, got, want)
+	}
+}
+
+func testBumpedTagError(t *testing.T, workDir, level string) {
+	t.Helper()
+	got, err := computeBumpedTag(workDir, level)
+	if err == nil {
+		t.Errorf("expected error for computeBumpedTag(%q), got %q", level, got)
+	}
+	if got != "" {
+		t.Errorf("expected empty tag on error, got %q", got)
+	}
+}
+
+func TestComputeBumpedTagNoTags(t *testing.T) {
+	dir, _ := setupBumpTestRepo(t)
+	defer func() { _ = os.RemoveAll(dir) }()
+
+	testBumpedTag(t, dir, bumpPatch, "v0.0.1")
+	testBumpedTag(t, dir, bumpMinor, "v0.1.0")
+	testBumpedTag(t, dir, bumpMajor, "v1.0.0")
+}
+
+func TestComputeBumpedTagSimple(t *testing.T) {
+	dir := setupBumpTestRepoWithTag(t, "v1.2.3")
+	defer func() { _ = os.RemoveAll(dir) }()
+
+	testBumpedTag(t, dir, bumpPatch, "v1.2.4")
+	testBumpedTag(t, dir, bumpMinor, "v1.3.0")
+	testBumpedTag(t, dir, bumpMajor, "v2.0.0")
+}
+
+func TestComputeBumpedTagSuffix(t *testing.T) {
+	dir := setupBumpTestRepoWithTag(t, "v1.6.1+0.74.1")
+	defer func() { _ = os.RemoveAll(dir) }()
+
+	testBumpedTag(t, dir, bumpPatch, "v1.6.2+0.74.1")
+	testBumpedTag(t, dir, bumpMinor, "v1.7.0+0.74.1")
+	testBumpedTag(t, dir, bumpMajor, "v2.0.0+0.74.1")
+}
+
+func TestComputeBumpedTagPreRelease(t *testing.T) {
+	dir := setupBumpTestRepoWithTag(t, "v2.0.0-rc.1")
+	defer func() { _ = os.RemoveAll(dir) }()
+
+	testBumpedTagError(t, dir, bumpPatch)
+}
+
+func TestComputeBumpedTagInvalidLevel(t *testing.T) {
+	_, err := computeBumpedTag("/tmp", "foo")
+	if err == nil {
+		t.Fatal("expected error for invalid level")
+	}
+}
+
+func setupBumpTestRepo(t *testing.T) (dir string, runGit func(...string)) {
+	dir, err := os.MkdirTemp("", "ttal-tag-test-*")
+	if err != nil {
+		t.Fatal(err)
+	}
+	runGit = func(args ...string) {
+		cmd := exec.Command("git", append([]string{"-C", dir}, args...)...)
+		out, err := cmd.CombinedOutput()
+		if err != nil {
+			t.Fatalf("git %v: %s — %v", args, string(out), err)
+		}
+	}
+	runGit("init")
+	runGit("config", "user.name", "test")
+	runGit("config", "user.email", "test@test")
+	runGit("commit", "--allow-empty", "-m", "init")
+	return dir, runGit
+}
+
+func setupBumpTestRepoWithTag(t *testing.T, tag string) string {
+	dir, runGit := setupBumpTestRepo(t)
+	runGit("tag", tag)
+	return dir
+}
+
+func TestTagCmdArgValidation(t *testing.T) {
+	// Simulate the arg validation logic from tagCmd.RunE
+
+	// Test mutex: --bump + positional arg fails
+	bump := bumpPatch
+	args := []string{"v1.0.0"}
+	isBump := bump != ""
+	if isBump && len(args) > 0 {
+		// expected error
+	} else {
+		t.Fatal("expected mutex error")
+	}
+
+	// Test no args + no bump fails
+	bump = ""
+	args = []string{}
+	isBump = bump != ""
+	if !isBump && len(args) == 0 {
+		// expected error
+	} else {
+		t.Fatal("expected error for no bump and no args")
+	}
+
+	// Test positional + no bump OK
+	bump = ""
+	args = []string{"v1.0.0"}
+	isBump = bump != ""
+	if isBump {
+		t.Fatal("should not be bump")
+	}
+	if len(args) == 0 {
+		t.Fatal("should have arg")
+	}
+
+	// Test bump only OK
+	bump = bumpPatch
+	args = []string{}
+	isBump = bump != ""
+	if !isBump {
+		t.Fatal("should be bump")
+	}
+	if len(args) > 0 {
+		t.Fatal("should not have positional")
+	}
+}