diff --git a/cmd/opencodereview/main.go b/cmd/opencodereview/main.go
index cf3e4ddc..fd47e9e1 100644
--- a/cmd/opencodereview/main.go
+++ b/cmd/opencodereview/main.go
@@ -5,10 +5,12 @@ package main
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"time"
 
+	"github.com/alibaba/open-code-review/internal/gitcmd"
 	"github.com/alibaba/open-code-review/internal/llm"
 	"github.com/alibaba/open-code-review/internal/telemetry"
 )
@@ -22,6 +24,12 @@ func main() {
 		defer telemetry.ShutdownWithTimeout(ctx, 5*time.Second)
 	}
 
+	if _, err := gitcmd.CheckGitVersion(); err != nil {
+		if !errors.Is(err, gitcmd.ErrGitVersionTooOld) {
+			fmt.Fprintf(os.Stderr, "warning: %v\n", err)
+		}
+	}
+
 	if err := rootCmd.Execute(); err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
 		os.Exit(1)
diff --git a/internal/gitcmd/version.go b/internal/gitcmd/version.go
new file mode 100644
index 00000000..f6555cab
--- /dev/null
+++ b/internal/gitcmd/version.go
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright 2026 alibaba/open-code-review Contributors
+
+package gitcmd
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+type GitVersion struct {
+	Major int
+	Minor int
+	Patch int
+}
+
+var gitVersionMin = GitVersion{Major: 2, Minor: 41, Patch: 0}
+
+var ErrGitVersionTooOld = errors.New("git version below minimum supported")
+
+func (v GitVersion) String() string {
+	return fmt.Sprintf("%d.%d.%d", v.Major, v.Minor, v.Patch)
+}
+
+func (v GitVersion) AtLeast(o GitVersion) bool {
+	switch {
+	case v.Major != o.Major:
+		return v.Major > o.Major
+	case v.Minor != o.Minor:
+		return v.Minor > o.Minor
+	default:
+		return v.Patch >= o.Patch
+	}
+}
+
+// ParseGitVersion extracts a MAJOR.MINOR.PATCH version from a git --version
+func ParseGitVersion(s string) (GitVersion, error) {
+	i := 0
+	for i < len(s) && (s[i] < '0' || s[i] > '9') {
+		i++
+	}
+	if i == len(s) {
+		return GitVersion{}, fmt.Errorf("unrecognized git version %q", strings.TrimSpace(s))
+	}
+	var v GitVersion
+	n, err := fmt.Sscanf(s[i:], "%d.%d.%d", &v.Major, &v.Minor, &v.Patch)
+	if err != nil || n < 3 {
+		return GitVersion{}, fmt.Errorf("unrecognized git version %q", strings.TrimSpace(s))
+	}
+	return v, nil
+}
+
+func versionWarning(current GitVersion) (string, bool) {
+	if current.AtLeast(gitVersionMin) {
+		return "", false
+	}
+	return fmt.Sprintf(
+		"warning: git %s is older than the minimum supported version %s. "+
+			"Some commands may not work correctly; consider upgrading git.\n",
+		current, gitVersionMin,
+	), true
+}
+
+func CheckGitVersion() (string, error) {
+	return checkGitVersion(os.Stderr, func() ([]byte, error) {
+		return exec.Command("git", "--version").Output()
+	})
+}
+
+func checkGitVersion(w io.Writer, getVersion func() ([]byte, error)) (string, error) {
+	out, err := getVersion()
+	if err != nil {
+		return "", fmt.Errorf("running git --version: %w", err)
+	}
+	v, err := ParseGitVersion(string(out))
+	if err != nil {
+		return "", err
+	}
+	if msg, ok := versionWarning(v); ok {
+		fmt.Fprint(w, msg)
+		return v.String(), fmt.Errorf("%w: %s", ErrGitVersionTooOld, v.String())
+	}
+	return v.String(), nil
+}
diff --git a/internal/gitcmd/version_test.go b/internal/gitcmd/version_test.go
new file mode 100644
index 00000000..6cd7ca55
--- /dev/null
+++ b/internal/gitcmd/version_test.go
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright 2026 alibaba/open-code-review Contributors
+
+package gitcmd
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+	"testing"
+)
+
+func TestParseGitVersion(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   string
+		want    GitVersion
+		wantErr bool
+	}{
+		{name: "plain", input: "git version 2.41.0\n", want: GitVersion{2, 41, 0}},
+		{name: "apple suffix", input: "git version 2.39.2 (Apple Git-145)\n", want: GitVersion{2, 39, 2}},
+		{name: "windows suffix", input: "git version 2.41.0.windows.1\n", want: GitVersion{2, 41, 0}},
+		{name: "no trailing newline", input: "git version 2.45.2", want: GitVersion{2, 45, 2}},
+		{name: "no prefix", input: "2.41.0", want: GitVersion{2, 41, 0}},
+		{name: "minor 10", input: "git version 2.10.0\n", want: GitVersion{2, 10, 0}},
+		{name: "newer major", input: "git version 3.0.0\n", want: GitVersion{3, 0, 0}},
+		{name: "empty", input: "", wantErr: true},
+		{name: "garbage", input: "banana", wantErr: true},
+		{name: "two component", input: "git version 2.41\n", wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := ParseGitVersion(tt.input)
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("expected error for input %q, got %v", tt.input, got)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error for %q: %v", tt.input, err)
+			}
+			if got != tt.want {
+				t.Errorf("got %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestGitVersion_AtLeast(t *testing.T) {
+	min := GitVersion{2, 41, 0}
+	tests := []struct {
+		v    GitVersion
+		want bool
+	}{
+		{GitVersion{2, 41, 0}, true},
+		{GitVersion{2, 41, 1}, true},
+		{GitVersion{2, 42, 0}, true},
+		{GitVersion{3, 0, 0}, true},
+		{GitVersion{2, 40, 0}, false},
+		{GitVersion{2, 39, 99}, false},
+		{GitVersion{1, 99, 99}, false},
+		{GitVersion{2, 40, 1}, false},
+		{GitVersion{2, 41, 0}, true}, // duplicate to be explicit
+	}
+
+	for _, tt := range tests {
+		t.Run(fmt.Sprintf("%s>=%s=%v", tt.v, min, tt.want), func(t *testing.T) {
+			if got := tt.v.AtLeast(min); got != tt.want {
+				t.Errorf("%s.AtLeast(%s) = %v, want %v", tt.v, min, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestVersionWarning(t *testing.T) {
+	tests := []struct {
+		v       GitVersion
+		wantOk  bool
+		contain []string
+	}{
+		{GitVersion{2, 30, 0}, true, []string{"warning:", "2.30.0", "2.41.0", "upgrading git"}},
+		{GitVersion{2, 41, 0}, false, nil},
+		{GitVersion{2, 41, 1}, false, nil},
+		{GitVersion{3, 0, 0}, false, nil},
+	}
+
+	for _, tt := range tests {
+		t.Run(fmt.Sprintf("v=%s", tt.v), func(t *testing.T) {
+			msg, ok := versionWarning(tt.v)
+			if ok != tt.wantOk {
+				t.Errorf("versionWarning(%s) ok=%v, want %v", tt.v, ok, tt.wantOk)
+			}
+			if tt.wantOk {
+				for _, want := range tt.contain {
+					if !strings.Contains(msg, want) {
+						t.Errorf("message %q does not contain %q", msg, want)
+					}
+				}
+			} else if msg != "" {
+				t.Errorf("expected empty message, got %q", msg)
+			}
+		})
+	}
+}
+
+func TestCheckGitVersion(t *testing.T) {
+	t.Run("happy path", func(t *testing.T) {
+		var buf bytes.Buffer
+		getVersion := func() ([]byte, error) {
+			return []byte("git version 2.45.2\n"), nil
+		}
+		ver, err := checkGitVersion(&buf, getVersion)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if ver != "2.45.2" {
+			t.Errorf("version = %q, want %q", ver, "2.45.2")
+		}
+		if buf.Len() != 0 {
+			t.Errorf("expected no warning, got %q", buf.String())
+		}
+	})
+
+	t.Run("old git warns", func(t *testing.T) {
+		var buf bytes.Buffer
+		getVersion := func() ([]byte, error) {
+			return []byte("git version 2.30.0\n"), nil
+		}
+		ver, err := checkGitVersion(&buf, getVersion)
+		if err == nil {
+			t.Fatal("expected ErrGitVersionTooOld, got nil")
+		}
+		if !errors.Is(err, ErrGitVersionTooOld) {
+			t.Errorf("expected ErrGitVersionTooOld, got %v", err)
+		}
+		if ver != "2.30.0" {
+			t.Errorf("version = %q, want %q", ver, "2.30.0")
+		}
+		msg := buf.String()
+		if !strings.Contains(msg, "warning:") || !strings.Contains(msg, "2.41.0") {
+			t.Errorf("expected warning with version, got %q", msg)
+		}
+	})
+
+	t.Run("getVersion error", func(t *testing.T) {
+		var buf bytes.Buffer
+		getVersion := func() ([]byte, error) {
+			return nil, errors.New("git not found")
+		}
+		_, err := checkGitVersion(&buf, getVersion)
+		if err == nil {
+			t.Fatal("expected error, got nil")
+		}
+		if buf.Len() != 0 {
+			t.Errorf("expected no warning, got %q", buf.String())
+		}
+	})
+
+	t.Run("garbage output", func(t *testing.T) {
+		var buf bytes.Buffer
+		getVersion := func() ([]byte, error) {
+			return []byte("banana\n"), nil
+		}
+		_, err := checkGitVersion(&buf, getVersion)
+		if err == nil {
+			t.Fatal("expected parse error, got nil")
+		}
+		if buf.Len() != 0 {
+			t.Errorf("expected no warning, got %q", buf.String())
+		}
+	})
+}
+
+func TestCheckGitVersion_Real(t *testing.T) {
+	if _, err := exec.LookPath("git"); err != nil {
+		t.Skip("git not found in PATH")
+	}
+	ver, err := CheckGitVersion()
+	if errors.Is(err, ErrGitVersionTooOld) {
+		// Allowed: installed git is older than minimum. Version string must
+		// still be populated so the caller can inspect it.
+		if ver == "" {
+			t.Error("expected non-empty version string even when too old")
+		}
+		return
+	}
+	if err != nil {
+		t.Fatalf("CheckGitVersion() error: %v", err)
+	}
+	if ver == "" {
+		t.Error("expected non-empty version string")
+	}
+	if !strings.Contains(ver, ".") {
+		t.Errorf("version %q does not look like a semver", ver)
+	}
+}