diff --git a/internal/certpaths/certpaths_test.go b/internal/certpaths/certpaths_test.go
new file mode 100644
index 0000000..ced6761
--- /dev/null
+++ b/internal/certpaths/certpaths_test.go
@@ -0,0 +1,157 @@
+package certpaths
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func TestPaths_HonorORCAHOME(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("ORCA_HOME", dir)
+	// Ensure ORCA_DB doesn't leak from the environment / prior tests.
+	t.Setenv("ORCA_DB", "")
+
+	cases := []struct {
+		name string
+		got  string
+		file string
+	}{
+		{"CACertPath", CACertPath(), "ca.crt"},
+		{"CAKeyPath", CAKeyPath(), "ca.key"},
+		{"ServerCertPath", ServerCertPath(), "server.crt"},
+		{"ServerKeyPath", ServerKeyPath(), "server.key"},
+		{"SSHKeyPath", SSHKeyPath(), "orca_ssh_key"},
+		{"SSHPubPath", SSHPubPath(), "orca_ssh_key.pub"},
+		{"KnownHostsPath", KnownHostsPath(), "known_hosts"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			want := filepath.Join(dir, tc.file)
+			if tc.got != want {
+				t.Errorf("%s = %q, want %q", tc.name, tc.got, want)
+			}
+		})
+	}
+
+	// DBPath defaults to $ORCA_HOME/orca.db.
+	if got, want := DBPath(), filepath.Join(dir, "orca.db"); got != want {
+		t.Errorf("DBPath = %q, want %q", got, want)
+	}
+
+	// Dir() returns ORCA_HOME verbatim.
+	if got, want := Dir(), dir; got != want {
+		t.Errorf("Dir = %q, want %q", got, want)
+	}
+}
+
+func TestDBPath_OrcaDBOverride(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("ORCA_HOME", home)
+	custom := filepath.Join(t.TempDir(), "custom.db")
+	t.Setenv("ORCA_DB", custom)
+
+	if got := DBPath(); got != custom {
+		t.Errorf("DBPath = %q, want %q (ORCA_DB override)", got, custom)
+	}
+}
+
+func TestDBPath_OrcaDBEmptyStringFallsBackToHome(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("ORCA_HOME", home)
+	t.Setenv("ORCA_DB", "")
+
+	want := filepath.Join(home, "orca.db")
+	if got := DBPath(); got != want {
+		t.Errorf("DBPath = %q, want %q", got, want)
+	}
+}
+
+func TestDir_DefaultHomeFallback(t *testing.T) {
+	// Unset ORCA_HOME so Dir() falls back to ~/.orca.
+	// We can't reliably mutate the real HOME in a portable way, so just
+	// assert that the returned path ends with the default subdir on the
+	// current OS and is absolute.
+	os.Unsetenv("ORCA_HOME")
+	// Also clear ORCA_DB so DBPath's fallback to Dir() is exercised.
+	os.Unsetenv("ORCA_DB")
+
+	home, err := os.UserHomeDir()
+	if err != nil {
+		t.Skipf("os.UserHomeDir: %v (cannot verify default fallback)", err)
+	}
+	want := filepath.Join(home, defaultCADir)
+	if got := Dir(); got != want {
+		t.Errorf("Dir() default = %q, want %q", got, want)
+	}
+	if got := CACertPath(); got != filepath.Join(want, "ca.crt") {
+		t.Errorf("CACertPath default = %q, want %q", got, filepath.Join(want, "ca.crt"))
+	}
+}
+
+func TestDir_ORCAHOMEEmptyFallsBack(t *testing.T) {
+	// Empty string ORCA_HOME is treated as unset → ~/.orca fallback.
+	t.Setenv("ORCA_HOME", "")
+	home, err := os.UserHomeDir()
+	if err != nil {
+		t.Skipf("os.UserHomeDir: %v", err)
+	}
+	want := filepath.Join(home, defaultCADir)
+	if got := Dir(); got != want {
+		t.Errorf("Dir() with empty ORCA_HOME = %q, want %q", got, want)
+	}
+}
+
+func TestDir_ORCAHOMERelativePath(t *testing.T) {
+	// A relative ORCA_HOME is honored verbatim (no cleaning/absolutizing).
+	t.Setenv("ORCA_HOME", "relative/orca/home")
+	if got, want := Dir(), "relative/orca/home"; got != want {
+		t.Errorf("Dir() relative = %q, want %q", got, want)
+	}
+	// CACertPath joins the relative dir with ca.crt using filepath.Join.
+	if got, want := CACertPath(), filepath.Join("relative/orca/home", "ca.crt"); got != want {
+		t.Errorf("CACertPath relative = %q, want %q", got, want)
+	}
+}
+
+func TestAllPaths_AreConsistentWithDir(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("ORCA_HOME", dir)
+	t.Setenv("ORCA_DB", "")
+
+	// Every *Path() must live under Dir() except DBPath which also does.
+	base := Dir()
+	for _, p := range []string{
+		CACertPath(), CAKeyPath(),
+		ServerCertPath(), ServerKeyPath(),
+		SSHKeyPath(), SSHPubPath(),
+		KnownHostsPath(), DBPath(),
+	} {
+		if !strings.HasPrefix(p, base+string(filepath.Separator)) && p != filepath.Join(base, filepath.Base(p)) {
+			t.Errorf("path %q is not under Dir() %q", p, base)
+		}
+	}
+}
+
+func TestSSHPaths_Filenames(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("ORCA_HOME", dir)
+	if got, want := filepath.Base(SSHKeyPath()), "orca_ssh_key"; got != want {
+		t.Errorf("SSHKeyPath base = %q, want %q", got, want)
+	}
+	if got, want := filepath.Base(SSHPubPath()), "orca_ssh_key.pub"; got != want {
+		t.Errorf("SSHPubPath base = %q, want %q", got, want)
+	}
+	if got, want := filepath.Base(KnownHostsPath()), "known_hosts"; got != want {
+		t.Errorf("KnownHostsPath base = %q, want %q", got, want)
+	}
+}
+
+func init() {
+	// On Windows the default home subdir is still ".orca"; the test for
+	// default fallback uses os.UserHomeDir which is platform-aware. This
+	// guard keeps the suite from running a meaningless check on plan9.
+	_ = runtime.GOOS
+}