fix: drop /root/repo fallback in vm exec for unbound VMs

vm exec defaulted execGuestPath to /root/repo whenever the VM had no
recorded workspace, so running it against a plain VM (one that never
had vm workspace prepare / vm run ./repo) blew up with
'cd: /root/repo: No such file or directory' — surfaced via the login
shell's mise activate hook because bash -lc sources profile.d before
the explicit cd. Now auto-cd only fires when --guest-path is passed
or the VM actually has a workspace recorded; otherwise the command
runs from root's home. Mise wrapping unchanged — without a .mise.toml
it's a no-op.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -10,6 +10,26 @@ changed between versions.
 
 ## [Unreleased]
 
+### Fixed
+
+- `vm exec` no longer falls back to `cd /root/repo` on VMs that have
+  no recorded workspace. Previously, running `vm exec` against a plain
+  VM (one that never had `vm workspace prepare` / `vm run ./repo`)
+  blew up with `cd: /root/repo: No such file or directory` — surfaced
+  via the login shell's mise activate hook because `bash -lc` sources
+  profile.d before the explicit cd. Now the auto-cd only fires when
+  the user passes `--guest-path` or the VM actually has a workspace
+  recorded; otherwise the command runs from root's home. Mise wrapping
+  is unchanged — without a `.mise.toml` it's a no-op.
+
+### Changed
+
+- `vm exec --guest-path` default in `--help` now reads "from last
+  workspace prepare; otherwise root's home" (was "or /root/repo").
+  Anyone who relied on the implicit `/root/repo` default for a VM that
+  has a repo there but no workspace record must now pass
+  `--guest-path /root/repo` explicitly.
+
 ## [v0.1.8] - 2026-05-01
 
 ### Fixed

internal/cli/vm_exec.go

@@ -21,13 +21,14 @@ func (d *deps) newVMExecCommand() *cobra.Command {
 		Use:   "exec <id-or-name> -- <command> [args...]",
 		Short: "Run a command in the VM workspace with the repo toolchain",
 		Long: strings.TrimSpace(`
-Run a command inside a persistent VM, automatically cd-ing into the
-prepared workspace and wrapping the command with 'mise exec' so all
-mise-managed tools (Go, Node, Python, etc.) are on PATH.
+Run a command inside a persistent VM, wrapping it with 'mise exec' so
+all mise-managed tools (Go, Node, Python, etc.) are on PATH.
 
-The workspace path comes from the last 'vm workspace prepare' or
-'vm run ./repo' on this VM. If the host repo has advanced since then,
-banger warns; pass --auto-prepare to re-sync the workspace first.
+If the VM has a prepared workspace (from 'vm workspace prepare' or
+'vm run ./repo'), the command runs from that directory and a stale-
+workspace warning is printed when the host repo has advanced since the
+last prepare; pass --auto-prepare to re-sync first. Otherwise the
+command runs from root's home directory. --guest-path overrides both.
 
 Exit code of the guest command is propagated verbatim.
 `),
@@ -76,13 +77,14 @@ Exit code of the guest command is propagated verbatim.
 				return fmt.Errorf("vm %q is not running (state: %s)", vm.Name, vm.State)
 			}
 
-			// Resolve effective guest workspace path.
+			// Resolve effective guest workspace path. Empty means "no
+			// cd": run from the SSH session's default cwd ($HOME). We
+			// only auto-cd when the user explicitly passed --guest-path
+			// or the VM actually has a recorded workspace — otherwise
+			// arbitrary VMs (no repo) would fail with cd errors.
 			execGuestPath := strings.TrimSpace(guestPath)
 			if execGuestPath == "" {
-				execGuestPath = vm.Workspace.GuestPath
-			}
-			if execGuestPath == "" {
-				execGuestPath = "/root/repo"
+				execGuestPath = strings.TrimSpace(vm.Workspace.GuestPath)
 			}
 
 			// Dirty-workspace check: compare stored HEAD with current host HEAD.
@@ -130,15 +132,18 @@ Exit code of the guest command is propagated verbatim.
 			return nil
 		},
 	}
-	cmd.Flags().StringVar(&guestPath, "guest-path", "", "workspace directory in the guest (default: from last workspace prepare, or /root/repo)")
+	cmd.Flags().StringVar(&guestPath, "guest-path", "", "workspace directory in the guest (default: from last workspace prepare; otherwise root's home)")
 	cmd.Flags().BoolVar(&autoPrepare, "auto-prepare", false, "re-sync the workspace from the host repo before running if it's stale")
 	_ = cmd.RegisterFlagCompletionFunc("guest-path", cobra.NoFileCompletions)
 	return cmd
 }
 
-// buildVMExecScript returns the bash -lc argument that cd's into the
-// workspace and runs the command through mise exec when mise is
-// available, falling back to a plain exec if it's not. Each command
+// buildVMExecScript returns the bash -lc argument that runs the
+// command through mise exec when mise is available, falling back to a
+// plain exec if it's not. When guestPath is non-empty, the script
+// cd's into it first (workspace mode); when empty, the command runs
+// from the SSH session's default cwd so VMs without a prepared
+// workspace don't blow up on a non-existent /root/repo. Each command
 // argument is shell-quoted so spaces and special characters survive
 // the bash re-parse inside the -lc string.
 func buildVMExecScript(guestPath string, command []string) string {
@@ -147,12 +152,15 @@ func buildVMExecScript(guestPath string, command []string) string {
 		parts[i] = shellQuote(a)
 	}
 	quotedCmd := strings.Join(parts, " ")
-	return fmt.Sprintf(
-		"cd %s && if command -v mise >/dev/null 2>&1; then mise exec -- %s; else %s; fi",
-		shellQuote(guestPath),
+	body := fmt.Sprintf(
+		"if command -v mise >/dev/null 2>&1; then mise exec -- %s; else %s; fi",
 		quotedCmd,
 		quotedCmd,
 	)
+	if guestPath == "" {
+		return body
+	}
+	return fmt.Sprintf("cd %s && %s", shellQuote(guestPath), body)
 }
 
 // vmExecDirtyCheck compares the HEAD commit stored in the VM's

internal/cli/vm_exec_test.go

@@ -0,0 +1,35 @@
+package cli
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestBuildVMExecScriptWithGuestPath(t *testing.T) {
+	got := buildVMExecScript("/root/repo", []string{"make", "test"})
+	want := "cd '/root/repo' && if command -v mise >/dev/null 2>&1; then mise exec -- 'make' 'test'; else 'make' 'test'; fi"
+	if got != want {
+		t.Fatalf("buildVMExecScript with path:\n got:  %q\n want: %q", got, want)
+	}
+}
+
+func TestBuildVMExecScriptWithoutGuestPath(t *testing.T) {
+	got := buildVMExecScript("", []string{"whoami"})
+	want := "if command -v mise >/dev/null 2>&1; then mise exec -- 'whoami'; else 'whoami'; fi"
+	if got != want {
+		t.Fatalf("buildVMExecScript without path:\n got:  %q\n want: %q", got, want)
+	}
+	if strings.Contains(got, "cd ") {
+		t.Fatalf("expected no cd when guestPath is empty, got: %q", got)
+	}
+}
+
+func TestBuildVMExecScriptShellQuotesPathWithSpaces(t *testing.T) {
+	got := buildVMExecScript("/tmp/with space", []string{"echo", "a b"})
+	if !strings.Contains(got, "cd '/tmp/with space'") {
+		t.Fatalf("expected guest path to be shell-quoted, got: %q", got)
+	}
+	if !strings.Contains(got, "mise exec -- 'echo' 'a b'") {
+		t.Fatalf("expected command args to be shell-quoted, got: %q", got)
+	}
+}