diff --git a/internal/cmd/root.go b/internal/cmd/root.go
index e574cf6..dc85c47 100644
--- a/internal/cmd/root.go
+++ b/internal/cmd/root.go
@@ -1,3 +1,6 @@
+// Package cmd implements the Headjack CLI commands using Cobra.
+// It provides commands for managing isolated LLM agent instances,
+// including create, attach, stop, remove, and session management.
 package cmd
 
 import (
diff --git a/internal/config/config.go b/internal/config/config.go
index f0646b4..634a7b6 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -100,36 +100,6 @@ func (c *Config) Validate() error {
 	return nil
 }
 
-// IsValidAgent returns true if the agent name is valid.
-func (c *Config) IsValidAgent(name string) bool {
-	return validAgents[name]
-}
-
-// ValidAgentNames returns the list of valid agent names.
-func (c *Config) ValidAgentNames() []string {
-	return []string{"claude", "gemini", "codex"}
-}
-
-// IsValidMultiplexer returns true if the multiplexer name is valid.
-func (c *Config) IsValidMultiplexer(name string) bool {
-	return validMultiplexers[name]
-}
-
-// ValidMultiplexerNames returns the list of valid multiplexer names.
-func (c *Config) ValidMultiplexerNames() []string {
-	return []string{"tmux", "zellij"}
-}
-
-// IsValidRuntime returns true if the runtime name is valid.
-func (c *Config) IsValidRuntime(name string) bool {
-	return validRuntimes[name]
-}
-
-// ValidRuntimeNames returns the list of valid runtime names.
-func (c *Config) ValidRuntimeNames() []string {
-	return []string{"podman", "apple"}
-}
-
 // Loader provides configuration loading and saving.
 type Loader struct {
 	v       *viper.Viper
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index 02b21c0..e634347 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -210,19 +210,16 @@ func TestConfig_Validate(t *testing.T) {
 	})
 }
 
-func TestConfig_IsValidAgent(t *testing.T) {
-	cfg := &Config{}
-
-	assert.True(t, cfg.IsValidAgent("claude"))
-	assert.True(t, cfg.IsValidAgent("gemini"))
-	assert.True(t, cfg.IsValidAgent("codex"))
-	assert.False(t, cfg.IsValidAgent("invalid"))
-	assert.False(t, cfg.IsValidAgent(""))
+func TestIsValidAgent(t *testing.T) {
+	assert.True(t, IsValidAgent("claude"))
+	assert.True(t, IsValidAgent("gemini"))
+	assert.True(t, IsValidAgent("codex"))
+	assert.False(t, IsValidAgent("invalid"))
+	assert.False(t, IsValidAgent(""))
 }
 
-func TestConfig_ValidAgentNames(t *testing.T) {
-	cfg := &Config{}
-	names := cfg.ValidAgentNames()
+func TestValidAgentNames(t *testing.T) {
+	names := ValidAgentNames()
 
 	assert.Contains(t, names, "claude")
 	assert.Contains(t, names, "gemini")
diff --git a/internal/container/apple.go b/internal/container/apple.go
index 7a32585..a3ffb18 100644
--- a/internal/container/apple.go
+++ b/internal/container/apple.go
@@ -4,14 +4,9 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"os"
-	"os/signal"
 	"strings"
-	"syscall"
 	"time"
 
-	"golang.org/x/term"
-
 	"github.com/jmgilman/headjack/internal/exec"
 )
 
@@ -22,63 +17,35 @@ type AppleConfig struct {
 }
 
 type appleRuntime struct {
-	exec   exec.Executor
+	baseRuntime
 	config AppleConfig
 }
 
 // NewAppleRuntime creates a Runtime using Apple Containerization CLI.
 func NewAppleRuntime(e exec.Executor, cfg AppleConfig) Runtime {
-	return &appleRuntime{exec: e, config: cfg}
-}
-
-// containerError formats an error from the container CLI, including stderr if available.
-func containerError(operation string, result *exec.Result, err error) error {
-	if result != nil {
-		stderr := strings.TrimSpace(string(result.Stderr))
-		if stderr != "" {
-			return fmt.Errorf("%s: %s", operation, stderr)
-		}
+	return &appleRuntime{
+		baseRuntime: baseRuntime{
+			exec:        e,
+			binaryName:  "container",
+			execCommand: []string{"container", "exec"},
+		},
+		config: cfg,
 	}
-	return fmt.Errorf("%s: %w", operation, err)
 }
 
 func (r *appleRuntime) Run(ctx context.Context, cfg *RunConfig) (*Container, error) {
-	args := []string{"run", "--detach", "--name", cfg.Name}
-
-	// Add merged flags (image labels + config, merged by manager)
-	args = append(args, cfg.Flags...)
-
-	for _, m := range cfg.Mounts {
-		mountSpec := fmt.Sprintf("%s:%s", m.Source, m.Target)
-		if m.ReadOnly {
-			mountSpec += ":ro"
-		}
-		args = append(args, "-v", mountSpec)
-	}
-
-	for _, e := range cfg.Env {
-		args = append(args, "-e", e)
-	}
-
-	args = append(args, cfg.Image)
-
-	// Add init command (default to "sleep infinity" if not specified)
-	initCmd := cfg.Init
-	if initCmd == "" {
-		initCmd = "sleep infinity"
-	}
-	args = append(args, strings.Fields(initCmd)...)
+	args := buildRunArgs(cfg)
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "container",
+		Name: r.binaryName,
 		Args: args,
 	})
 	if err != nil {
 		stderr := string(result.Stderr)
-		if strings.Contains(stderr, "already exists") {
+		if isAlreadyExistsError(stderr) {
 			return nil, ErrAlreadyExists
 		}
-		return nil, containerError("run container", result, err)
+		return nil, cliError("run container", result, err)
 	}
 
 	// Container ID is returned on stdout
@@ -103,79 +70,23 @@ func (r *appleRuntime) Exec(ctx context.Context, id string, cfg ExecConfig) erro
 		return ErrNotRunning
 	}
 
-	args := []string{"exec"}
-
-	if cfg.Interactive {
-		args = append(args, "-it")
-	}
-
-	if cfg.Workdir != "" {
-		args = append(args, "-w", cfg.Workdir)
-	}
-
-	for _, e := range cfg.Env {
-		args = append(args, "-e", e)
-	}
-
-	args = append(args, id)
-	args = append(args, cfg.Command...)
+	args := buildExecArgs(id, cfg)
 
 	if cfg.Interactive {
 		return r.execInteractive(ctx, args)
 	}
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "container",
+		Name: r.binaryName,
 		Args: args,
 	})
 	if err != nil {
-		return containerError("exec in container", result, err)
+		return cliError("exec in container", result, err)
 	}
 
 	return nil
 }
 
-// execInteractive runs the container exec command with TTY support.
-func (r *appleRuntime) execInteractive(ctx context.Context, args []string) error {
-	stdinFd := int(os.Stdin.Fd())
-
-	// Check if stdin is a terminal
-	if !term.IsTerminal(stdinFd) {
-		// Fall back to non-interactive mode
-		_, err := r.exec.Run(ctx, &exec.RunOptions{
-			Name:   "container",
-			Args:   args,
-			Stdin:  os.Stdin,
-			Stdout: os.Stdout,
-			Stderr: os.Stderr,
-		})
-		return err
-	}
-
-	// Put terminal in raw mode
-	oldState, err := term.MakeRaw(stdinFd)
-	if err != nil {
-		return fmt.Errorf("set terminal raw mode: %w", err)
-	}
-	defer func() { _ = term.Restore(stdinFd, oldState) }()
-
-	// Handle window resize signals
-	sigCh := make(chan os.Signal, 1)
-	signal.Notify(sigCh, syscall.SIGWINCH)
-	defer signal.Stop(sigCh)
-
-	// Run the command with stdio attached
-	_, err = r.exec.Run(ctx, &exec.RunOptions{
-		Name:   "container",
-		Args:   args,
-		Stdin:  os.Stdin,
-		Stdout: os.Stdout,
-		Stderr: os.Stderr,
-	})
-
-	return err
-}
-
 func (r *appleRuntime) Stop(ctx context.Context, id string) error {
 	// Verify container exists
 	c, err := r.Get(ctx, id)
@@ -189,11 +100,11 @@ func (r *appleRuntime) Stop(ctx context.Context, id string) error {
 	}
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "container",
+		Name: r.binaryName,
 		Args: []string{"stop", id},
 	})
 	if err != nil {
-		return containerError("stop container", result, err)
+		return cliError("stop container", result, err)
 	}
 
 	return nil
@@ -212,11 +123,11 @@ func (r *appleRuntime) Start(ctx context.Context, id string) error {
 	}
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "container",
+		Name: r.binaryName,
 		Args: []string{"start", id},
 	})
 	if err != nil {
-		return containerError("start container", result, err)
+		return cliError("start container", result, err)
 	}
 
 	return nil
@@ -224,15 +135,15 @@ func (r *appleRuntime) Start(ctx context.Context, id string) error {
 
 func (r *appleRuntime) Remove(ctx context.Context, id string) error {
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "container",
+		Name: r.binaryName,
 		Args: []string{"rm", id},
 	})
 	if err != nil {
 		stderr := string(result.Stderr)
-		if strings.Contains(stderr, "not found") || strings.Contains(stderr, "no such") {
+		if isNotFoundError(stderr) {
 			return ErrNotFound
 		}
-		return containerError("remove container", result, err)
+		return cliError("remove container", result, err)
 	}
 
 	return nil
@@ -240,18 +151,18 @@ func (r *appleRuntime) Remove(ctx context.Context, id string) error {
 
 func (r *appleRuntime) Get(ctx context.Context, id string) (*Container, error) {
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "container",
+		Name: r.binaryName,
 		Args: []string{"inspect", id},
 	})
 	if err != nil {
 		stderr := string(result.Stderr)
-		if strings.Contains(stderr, "not found") || strings.Contains(stderr, "no such") {
+		if isNotFoundError(stderr) {
 			return nil, ErrNotFound
 		}
-		return nil, containerError("inspect container", result, err)
+		return nil, cliError("inspect container", result, err)
 	}
 
-	var infos []containerInspect
+	var infos []appleInspect
 	if err := json.Unmarshal(result.Stdout, &infos); err != nil {
 		return nil, fmt.Errorf("parse container info: %w", err)
 	}
@@ -271,11 +182,11 @@ func (r *appleRuntime) List(ctx context.Context, filter ListFilter) ([]Container
 	}
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "container",
+		Name: r.binaryName,
 		Args: args,
 	})
 	if err != nil {
-		return nil, containerError("list containers", result, err)
+		return nil, cliError("list containers", result, err)
 	}
 
 	// Handle empty list
@@ -284,7 +195,7 @@ func (r *appleRuntime) List(ctx context.Context, filter ListFilter) ([]Container
 		return []Container{}, nil
 	}
 
-	var items []containerListItem
+	var items []appleListItem
 	if err := json.Unmarshal(result.Stdout, &items); err != nil {
 		return nil, fmt.Errorf("parse container list: %w", err)
 	}
@@ -298,16 +209,10 @@ func (r *appleRuntime) List(ctx context.Context, filter ListFilter) ([]Container
 }
 
 func (r *appleRuntime) Build(ctx context.Context, cfg *BuildConfig) error {
-	args := []string{"build", "-t", cfg.Tag}
-
-	if cfg.Dockerfile != "" {
-		args = append(args, "-f", cfg.Dockerfile)
-	}
-
-	args = append(args, cfg.Context)
+	args := buildBuildArgs(cfg)
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "container",
+		Name: r.binaryName,
 		Args: args,
 	})
 	if err != nil {
@@ -317,8 +222,8 @@ func (r *appleRuntime) Build(ctx context.Context, cfg *BuildConfig) error {
 	return nil
 }
 
-// containerInspect represents the JSON output of `container inspect`.
-type containerInspect struct {
+// appleInspect represents the JSON output of `container inspect`.
+type appleInspect struct {
 	Status        string `json:"status"`
 	Configuration struct {
 		ID    string `json:"id"`
@@ -328,26 +233,18 @@ type containerInspect struct {
 	} `json:"configuration"`
 }
 
-func (c *containerInspect) toContainer() *Container {
-	status := StatusUnknown
-	switch strings.ToLower(c.Status) {
-	case cliStatusRunning:
-		status = StatusRunning
-	case cliStatusStopped, cliStatusExited:
-		status = StatusStopped
-	}
-
+func (c *appleInspect) toContainer() *Container {
 	return &Container{
 		ID:     c.Configuration.ID,
 		Name:   c.Configuration.ID,
 		Image:  c.Configuration.Image.Reference,
-		Status: status,
+		Status: parseContainerStatus(c.Status),
 	}
 }
 
-// containerListItem represents a single item in `container list` JSON output.
+// appleListItem represents a single item in `container list` JSON output.
 // Note: Apple container list has same format as inspect.
-type containerListItem struct {
+type appleListItem struct {
 	Status        string `json:"status"`
 	Configuration struct {
 		ID    string `json:"id"`
@@ -357,23 +254,11 @@ type containerListItem struct {
 	} `json:"configuration"`
 }
 
-func (c *containerListItem) toContainer() Container {
-	status := StatusUnknown
-	switch strings.ToLower(c.Status) {
-	case cliStatusRunning:
-		status = StatusRunning
-	case cliStatusStopped, cliStatusExited:
-		status = StatusStopped
-	}
-
+func (c *appleListItem) toContainer() Container {
 	return Container{
 		ID:     c.Configuration.ID,
 		Name:   c.Configuration.ID,
 		Image:  c.Configuration.Image.Reference,
-		Status: status,
+		Status: parseContainerStatus(c.Status),
 	}
 }
-
-func (r *appleRuntime) ExecCommand() []string {
-	return []string{"container", "exec"}
-}
diff --git a/internal/container/common.go b/internal/container/common.go
new file mode 100644
index 0000000..38cb6fd
--- /dev/null
+++ b/internal/container/common.go
@@ -0,0 +1,169 @@
+package container
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+	"strings"
+	"syscall"
+
+	"golang.org/x/term"
+
+	"github.com/jmgilman/headjack/internal/exec"
+)
+
+// baseRuntime provides shared functionality for container runtimes.
+// Concrete implementations (Podman, Apple) embed this and provide runtime-specific behavior.
+type baseRuntime struct {
+	exec        exec.Executor
+	binaryName  string
+	execCommand []string
+}
+
+// cliError formats an error from a container CLI, including stderr if available.
+func cliError(operation string, result *exec.Result, err error) error {
+	if result != nil {
+		stderr := strings.TrimSpace(string(result.Stderr))
+		if stderr != "" {
+			return fmt.Errorf("%s: %s", operation, stderr)
+		}
+	}
+	return fmt.Errorf("%s: %w", operation, err)
+}
+
+// execInteractive runs a container exec command with TTY support.
+// This is shared between runtime implementations.
+func (r *baseRuntime) execInteractive(ctx context.Context, args []string) error {
+	stdinFd := int(os.Stdin.Fd())
+
+	// Check if stdin is a terminal
+	if !term.IsTerminal(stdinFd) {
+		// Fall back to non-interactive mode
+		_, err := r.exec.Run(ctx, &exec.RunOptions{
+			Name:   r.binaryName,
+			Args:   args,
+			Stdin:  os.Stdin,
+			Stdout: os.Stdout,
+			Stderr: os.Stderr,
+		})
+		return err
+	}
+
+	// Put terminal in raw mode
+	oldState, err := term.MakeRaw(stdinFd)
+	if err != nil {
+		return fmt.Errorf("set terminal raw mode: %w", err)
+	}
+	defer func() { _ = term.Restore(stdinFd, oldState) }()
+
+	// Handle window resize signals
+	sigCh := make(chan os.Signal, 1)
+	signal.Notify(sigCh, syscall.SIGWINCH)
+	defer signal.Stop(sigCh)
+
+	// Run the command with stdio attached
+	_, err = r.exec.Run(ctx, &exec.RunOptions{
+		Name:   r.binaryName,
+		Args:   args,
+		Stdin:  os.Stdin,
+		Stdout: os.Stdout,
+		Stderr: os.Stderr,
+	})
+
+	return err
+}
+
+// ExecCommand returns the command prefix for executing commands in a container.
+func (r *baseRuntime) ExecCommand() []string {
+	return r.execCommand
+}
+
+// buildRunArgs constructs the common container run arguments.
+func buildRunArgs(cfg *RunConfig) []string {
+	args := []string{"run", "--detach", "--name", cfg.Name}
+
+	// Add merged flags (image labels + config, merged by manager)
+	args = append(args, cfg.Flags...)
+
+	for _, m := range cfg.Mounts {
+		mountSpec := fmt.Sprintf("%s:%s", m.Source, m.Target)
+		if m.ReadOnly {
+			mountSpec += ":ro"
+		}
+		args = append(args, "-v", mountSpec)
+	}
+
+	for _, e := range cfg.Env {
+		args = append(args, "-e", e)
+	}
+
+	args = append(args, cfg.Image)
+
+	// Add init command (default to "sleep infinity" if not specified)
+	initCmd := cfg.Init
+	if initCmd == "" {
+		initCmd = "sleep infinity"
+	}
+	args = append(args, strings.Fields(initCmd)...)
+
+	return args
+}
+
+// buildExecArgs constructs the common container exec arguments.
+func buildExecArgs(id string, cfg ExecConfig) []string {
+	args := []string{"exec"}
+
+	if cfg.Interactive {
+		args = append(args, "-it")
+	}
+
+	if cfg.Workdir != "" {
+		args = append(args, "-w", cfg.Workdir)
+	}
+
+	for _, e := range cfg.Env {
+		args = append(args, "-e", e)
+	}
+
+	args = append(args, id)
+	args = append(args, cfg.Command...)
+
+	return args
+}
+
+// buildBuildArgs constructs the common image build arguments.
+func buildBuildArgs(cfg *BuildConfig) []string {
+	args := []string{"build", "-t", cfg.Tag}
+
+	if cfg.Dockerfile != "" {
+		args = append(args, "-f", cfg.Dockerfile)
+	}
+
+	args = append(args, cfg.Context)
+	return args
+}
+
+// parseContainerStatus converts CLI status strings to Status constants.
+func parseContainerStatus(cliStatus string) Status {
+	switch strings.ToLower(cliStatus) {
+	case cliStatusRunning:
+		return StatusRunning
+	case cliStatusStopped, cliStatusExited, cliStatusCreated:
+		return StatusStopped
+	default:
+		return StatusUnknown
+	}
+}
+
+// isAlreadyExistsError checks if stderr indicates container already exists.
+func isAlreadyExistsError(stderr string) bool {
+	return strings.Contains(stderr, "already in use") || strings.Contains(stderr, "already exists")
+}
+
+// isNotFoundError checks if stderr indicates container not found.
+func isNotFoundError(stderr string) bool {
+	return strings.Contains(stderr, "no such") ||
+		strings.Contains(stderr, "no container") ||
+		strings.Contains(stderr, "not found")
+}
diff --git a/internal/container/podman.go b/internal/container/podman.go
index c12797b..83b45dc 100644
--- a/internal/container/podman.go
+++ b/internal/container/podman.go
@@ -4,14 +4,9 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"os"
-	"os/signal"
 	"strings"
-	"syscall"
 	"time"
 
-	"golang.org/x/term"
-
 	"github.com/jmgilman/headjack/internal/exec"
 )
 
@@ -22,63 +17,35 @@ type PodmanConfig struct {
 }
 
 type podmanRuntime struct {
-	exec   exec.Executor
+	baseRuntime
 	config PodmanConfig
 }
 
 // NewPodmanRuntime creates a Runtime using Podman CLI.
 func NewPodmanRuntime(e exec.Executor, cfg PodmanConfig) Runtime {
-	return &podmanRuntime{exec: e, config: cfg}
-}
-
-// podmanError formats an error from the podman CLI, including stderr if available.
-func podmanError(operation string, result *exec.Result, err error) error {
-	if result != nil {
-		stderr := strings.TrimSpace(string(result.Stderr))
-		if stderr != "" {
-			return fmt.Errorf("%s: %s", operation, stderr)
-		}
+	return &podmanRuntime{
+		baseRuntime: baseRuntime{
+			exec:        e,
+			binaryName:  "podman",
+			execCommand: []string{"podman", "exec"},
+		},
+		config: cfg,
 	}
-	return fmt.Errorf("%s: %w", operation, err)
 }
 
 func (r *podmanRuntime) Run(ctx context.Context, cfg *RunConfig) (*Container, error) {
-	args := []string{"run", "--detach", "--name", cfg.Name}
-
-	// Add merged flags (image labels + config, merged by manager)
-	args = append(args, cfg.Flags...)
-
-	for _, m := range cfg.Mounts {
-		mountSpec := fmt.Sprintf("%s:%s", m.Source, m.Target)
-		if m.ReadOnly {
-			mountSpec += ":ro"
-		}
-		args = append(args, "-v", mountSpec)
-	}
-
-	for _, e := range cfg.Env {
-		args = append(args, "-e", e)
-	}
-
-	args = append(args, cfg.Image)
-
-	// Add init command (default to "sleep infinity" if not specified)
-	initCmd := cfg.Init
-	if initCmd == "" {
-		initCmd = "sleep infinity"
-	}
-	args = append(args, strings.Fields(initCmd)...)
+	args := buildRunArgs(cfg)
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "podman",
+		Name: r.binaryName,
 		Args: args,
 	})
 	if err != nil {
 		stderr := string(result.Stderr)
-		if strings.Contains(stderr, "already in use") || strings.Contains(stderr, "already exists") {
+		if isAlreadyExistsError(stderr) {
 			return nil, ErrAlreadyExists
 		}
-		return nil, podmanError("run container", result, err)
+		return nil, cliError("run container", result, err)
 	}
 
 	// Container ID is returned on stdout
@@ -103,79 +70,23 @@ func (r *podmanRuntime) Exec(ctx context.Context, id string, cfg ExecConfig) err
 		return ErrNotRunning
 	}
 
-	args := []string{"exec"}
-
-	if cfg.Interactive {
-		args = append(args, "-it")
-	}
-
-	if cfg.Workdir != "" {
-		args = append(args, "-w", cfg.Workdir)
-	}
-
-	for _, e := range cfg.Env {
-		args = append(args, "-e", e)
-	}
-
-	args = append(args, id)
-	args = append(args, cfg.Command...)
+	args := buildExecArgs(id, cfg)
 
 	if cfg.Interactive {
 		return r.execInteractive(ctx, args)
 	}
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "podman",
+		Name: r.binaryName,
 		Args: args,
 	})
 	if err != nil {
-		return podmanError("exec in container", result, err)
+		return cliError("exec in container", result, err)
 	}
 
 	return nil
 }
 
-// execInteractive runs the podman exec command with TTY support.
-func (r *podmanRuntime) execInteractive(ctx context.Context, args []string) error {
-	stdinFd := int(os.Stdin.Fd())
-
-	// Check if stdin is a terminal
-	if !term.IsTerminal(stdinFd) {
-		// Fall back to non-interactive mode
-		_, err := r.exec.Run(ctx, &exec.RunOptions{
-			Name:   "podman",
-			Args:   args,
-			Stdin:  os.Stdin,
-			Stdout: os.Stdout,
-			Stderr: os.Stderr,
-		})
-		return err
-	}
-
-	// Put terminal in raw mode
-	oldState, err := term.MakeRaw(stdinFd)
-	if err != nil {
-		return fmt.Errorf("set terminal raw mode: %w", err)
-	}
-	defer func() { _ = term.Restore(stdinFd, oldState) }()
-
-	// Handle window resize signals
-	sigCh := make(chan os.Signal, 1)
-	signal.Notify(sigCh, syscall.SIGWINCH)
-	defer signal.Stop(sigCh)
-
-	// Run the command with stdio attached
-	_, err = r.exec.Run(ctx, &exec.RunOptions{
-		Name:   "podman",
-		Args:   args,
-		Stdin:  os.Stdin,
-		Stdout: os.Stdout,
-		Stderr: os.Stderr,
-	})
-
-	return err
-}
-
 func (r *podmanRuntime) Stop(ctx context.Context, id string) error {
 	// Verify container exists
 	c, err := r.Get(ctx, id)
@@ -189,11 +100,11 @@ func (r *podmanRuntime) Stop(ctx context.Context, id string) error {
 	}
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "podman",
+		Name: r.binaryName,
 		Args: []string{"stop", id},
 	})
 	if err != nil {
-		return podmanError("stop container", result, err)
+		return cliError("stop container", result, err)
 	}
 
 	return nil
@@ -212,11 +123,11 @@ func (r *podmanRuntime) Start(ctx context.Context, id string) error {
 	}
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "podman",
+		Name: r.binaryName,
 		Args: []string{"start", id},
 	})
 	if err != nil {
-		return podmanError("start container", result, err)
+		return cliError("start container", result, err)
 	}
 
 	return nil
@@ -224,15 +135,15 @@ func (r *podmanRuntime) Start(ctx context.Context, id string) error {
 
 func (r *podmanRuntime) Remove(ctx context.Context, id string) error {
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "podman",
+		Name: r.binaryName,
 		Args: []string{"rm", id},
 	})
 	if err != nil {
 		stderr := string(result.Stderr)
-		if strings.Contains(stderr, "no such") || strings.Contains(stderr, "no container") {
+		if isNotFoundError(stderr) {
 			return ErrNotFound
 		}
-		return podmanError("remove container", result, err)
+		return cliError("remove container", result, err)
 	}
 
 	return nil
@@ -240,15 +151,15 @@ func (r *podmanRuntime) Remove(ctx context.Context, id string) error {
 
 func (r *podmanRuntime) Get(ctx context.Context, id string) (*Container, error) {
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "podman",
+		Name: r.binaryName,
 		Args: []string{"inspect", id},
 	})
 	if err != nil {
 		stderr := string(result.Stderr)
-		if strings.Contains(stderr, "no such") || strings.Contains(stderr, "no container") {
+		if isNotFoundError(stderr) {
 			return nil, ErrNotFound
 		}
-		return nil, podmanError("inspect container", result, err)
+		return nil, cliError("inspect container", result, err)
 	}
 
 	var infos []podmanInspect
@@ -271,11 +182,11 @@ func (r *podmanRuntime) List(ctx context.Context, filter ListFilter) ([]Containe
 	}
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "podman",
+		Name: r.binaryName,
 		Args: args,
 	})
 	if err != nil {
-		return nil, podmanError("list containers", result, err)
+		return nil, cliError("list containers", result, err)
 	}
 
 	// Handle empty list
@@ -298,16 +209,10 @@ func (r *podmanRuntime) List(ctx context.Context, filter ListFilter) ([]Containe
 }
 
 func (r *podmanRuntime) Build(ctx context.Context, cfg *BuildConfig) error {
-	args := []string{"build", "-t", cfg.Tag}
-
-	if cfg.Dockerfile != "" {
-		args = append(args, "-f", cfg.Dockerfile)
-	}
-
-	args = append(args, cfg.Context)
+	args := buildBuildArgs(cfg)
 
 	result, err := r.exec.Run(ctx, &exec.RunOptions{
-		Name: "podman",
+		Name: r.binaryName,
 		Args: args,
 	})
 	if err != nil {
@@ -332,13 +237,7 @@ type podmanInspect struct {
 }
 
 func (p *podmanInspect) toContainer() *Container {
-	status := StatusUnknown
-	switch strings.ToLower(p.State.Status) {
-	case cliStatusRunning:
-		status = StatusRunning
-	case cliStatusStopped, cliStatusExited, cliStatusCreated:
-		status = StatusStopped
-	}
+	status := parseContainerStatus(p.State.Status)
 
 	// Remove leading "/" from name if present
 	name := strings.TrimPrefix(p.Name, "/")
@@ -377,13 +276,7 @@ type podmanListItem struct {
 }
 
 func (p *podmanListItem) toContainer() Container {
-	status := StatusUnknown
-	switch strings.ToLower(p.State) {
-	case cliStatusRunning:
-		status = StatusRunning
-	case cliStatusStopped, cliStatusExited, cliStatusCreated:
-		status = StatusStopped
-	}
+	status := parseContainerStatus(p.State)
 
 	name := ""
 	if len(p.Names) > 0 {
@@ -398,7 +291,3 @@ func (p *podmanListItem) toContainer() Container {
 		CreatedAt: time.Unix(p.Created, 0),
 	}
 }
-
-func (r *podmanRuntime) ExecCommand() []string {
-	return []string{"podman", "exec"}
-}
diff --git a/internal/git/git.go b/internal/git/git.go
index 3e8dd90..b586245 100644
--- a/internal/git/git.go
+++ b/internal/git/git.go
@@ -4,6 +4,10 @@ package git
 import (
 	"context"
 	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/jmgilman/headjack/internal/exec"
 )
 
 // Sentinel errors for git operations.
@@ -15,6 +19,17 @@ var (
 	ErrWorktreeNotFound = errors.New("worktree not found")
 )
 
+// gitError formats an error from a git command, including stderr if available.
+func gitError(operation string, result *exec.Result, err error) error {
+	if result != nil {
+		stderr := strings.TrimSpace(string(result.Stderr))
+		if stderr != "" {
+			return fmt.Errorf("%s: %s", operation, stderr)
+		}
+	}
+	return fmt.Errorf("%s: %w", operation, err)
+}
+
 // Worktree represents a git worktree.
 type Worktree struct {
 	Path   string // Filesystem path to the worktree
diff --git a/internal/git/opener.go b/internal/git/opener.go
index d211593..8483e3e 100644
--- a/internal/git/opener.go
+++ b/internal/git/opener.go
@@ -10,17 +10,6 @@ import (
 	"github.com/jmgilman/headjack/internal/exec"
 )
 
-// openerGitError formats an error from a git command in the opener, including stderr if available.
-func openerGitError(operation string, result *exec.Result, err error) error {
-	if result != nil {
-		stderr := strings.TrimSpace(string(result.Stderr))
-		if stderr != "" {
-			return fmt.Errorf("%s: %s", operation, stderr)
-		}
-	}
-	return fmt.Errorf("%s: %w", operation, err)
-}
-
 type opener struct {
 	exec exec.Executor
 }
@@ -65,7 +54,7 @@ func (o *opener) getRepoRoot(ctx context.Context, path string) (string, error) {
 				return "", ErrNotRepository
 			}
 		}
-		return "", openerGitError("get repository root", result, err)
+		return "", gitError("get repository root", result, err)
 	}
 
 	return strings.TrimSpace(string(result.Stdout)), nil
@@ -81,7 +70,7 @@ func (o *opener) generateIdentifier(ctx context.Context, root string) (string, e
 		Dir:  root,
 	})
 	if err != nil {
-		return "", openerGitError("get initial commit", result, err)
+		return "", gitError("get initial commit", result, err)
 	}
 
 	// Take first line (in case of multiple roots) and first 7 chars
diff --git a/internal/git/repository.go b/internal/git/repository.go
index 7e71865..e55c80c 100644
--- a/internal/git/repository.go
+++ b/internal/git/repository.go
@@ -9,17 +9,6 @@ import (
 	"github.com/jmgilman/headjack/internal/exec"
 )
 
-// gitError formats an error from a git command, including stderr if available.
-func gitError(operation string, result *exec.Result, err error) error {
-	if result != nil {
-		stderr := strings.TrimSpace(string(result.Stderr))
-		if stderr != "" {
-			return fmt.Errorf("%s: %s", operation, stderr)
-		}
-	}
-	return fmt.Errorf("%s: %w", operation, err)
-}
-
 type repository struct {
 	root       string
 	identifier string
diff --git a/internal/instance/manager.go b/internal/instance/manager.go
index fc21b0c..9edb318 100644
--- a/internal/instance/manager.go
+++ b/internal/instance/manager.go
@@ -298,7 +298,7 @@ func (m *Manager) Create(ctx context.Context, repoPath string, cfg CreateConfig)
 func (m *Manager) Get(ctx context.Context, id string) (*Instance, error) {
 	entry, err := m.catalog.Get(ctx, id)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return nil, ErrNotFound
 		}
 		return nil, fmt.Errorf("get catalog entry: %w", err)
@@ -316,7 +316,7 @@ func (m *Manager) GetByBranch(ctx context.Context, repoPath, branch string) (*In
 
 	entry, err := m.catalog.GetByRepoBranch(ctx, repo.Identifier(), branch)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return nil, ErrNotFound
 		}
 		return nil, fmt.Errorf("get catalog entry: %w", err)
@@ -326,6 +326,8 @@ func (m *Manager) GetByBranch(ctx context.Context, repoPath, branch string) (*In
 }
 
 // List returns all instances matching the filter.
+// Instances with degraded containers (e.g., container not found) are silently
+// skipped to ensure the list operation completes even if some instances have issues.
 func (m *Manager) List(ctx context.Context, filter ListFilter) ([]Instance, error) {
 	entries, err := m.catalog.List(ctx, catalog.ListFilter{
 		RepoID: filter.RepoID,
@@ -339,7 +341,8 @@ func (m *Manager) List(ctx context.Context, filter ListFilter) ([]Instance, erro
 	for i := range entries {
 		inst, err := m.entryToInstance(ctx, &entries[i])
 		if err != nil {
-			// Log and continue on individual failures
+			// Skip degraded instances (e.g., container not found) to ensure
+			// the list operation completes successfully
 			continue
 		}
 		instances = append(instances, *inst)
@@ -352,7 +355,7 @@ func (m *Manager) List(ctx context.Context, filter ListFilter) ([]Instance, erro
 func (m *Manager) Stop(ctx context.Context, id string) error {
 	entry, err := m.catalog.Get(ctx, id)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return ErrNotFound
 		}
 		return fmt.Errorf("get catalog entry: %w", err)
@@ -374,7 +377,7 @@ func (m *Manager) Stop(ctx context.Context, id string) error {
 func (m *Manager) Start(ctx context.Context, id string) error {
 	entry, err := m.catalog.Get(ctx, id)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return ErrNotFound
 		}
 		return fmt.Errorf("get catalog entry: %w", err)
@@ -533,7 +536,7 @@ func (m *Manager) stopContainerWithRetry(ctx context.Context, containerID string
 func (m *Manager) Remove(ctx context.Context, id string) error {
 	entry, err := m.catalog.Get(ctx, id)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return ErrNotFound
 		}
 		return fmt.Errorf("get catalog entry: %w", err)
@@ -576,7 +579,7 @@ func (m *Manager) Remove(ctx context.Context, id string) error {
 func (m *Manager) Recreate(ctx context.Context, id, image string) (*Instance, error) {
 	entry, err := m.catalog.Get(ctx, id)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return nil, ErrNotFound
 		}
 		return nil, fmt.Errorf("get catalog entry: %w", err)
@@ -634,7 +637,7 @@ func (m *Manager) Recreate(ctx context.Context, id, image string) (*Instance, er
 func (m *Manager) Attach(ctx context.Context, id string, cfg AttachConfig) error {
 	entry, err := m.catalog.Get(ctx, id)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return ErrNotFound
 		}
 		return fmt.Errorf("get catalog entry: %w", err)
@@ -914,7 +917,7 @@ echo '{"security":{"auth":{"selectedType":"oauth-personal"}}}' > ~/.gemini/setti
 func (m *Manager) getRunningInstance(ctx context.Context, instanceID string) (*catalog.Entry, error) {
 	entry, err := m.catalog.Get(ctx, instanceID)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return nil, ErrNotFound
 		}
 		return nil, fmt.Errorf("get catalog entry: %w", err)
@@ -940,7 +943,7 @@ func (m *Manager) getRunningInstance(ctx context.Context, instanceID string) (*c
 func (m *Manager) GetSession(ctx context.Context, instanceID, sessionName string) (*Session, error) {
 	entry, err := m.catalog.Get(ctx, instanceID)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return nil, ErrNotFound
 		}
 		return nil, fmt.Errorf("get catalog entry: %w", err)
@@ -966,7 +969,7 @@ func (m *Manager) GetSession(ctx context.Context, instanceID, sessionName string
 func (m *Manager) ListSessions(ctx context.Context, instanceID string) ([]Session, error) {
 	entry, err := m.catalog.Get(ctx, instanceID)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return nil, ErrNotFound
 		}
 		return nil, fmt.Errorf("get catalog entry: %w", err)
@@ -991,7 +994,7 @@ func (m *Manager) ListSessions(ctx context.Context, instanceID string) ([]Sessio
 func (m *Manager) KillSession(ctx context.Context, instanceID, sessionName string) error {
 	entry, err := m.catalog.Get(ctx, instanceID)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return ErrNotFound
 		}
 		return fmt.Errorf("get catalog entry: %w", err)
@@ -1036,7 +1039,7 @@ func (m *Manager) KillSession(ctx context.Context, instanceID, sessionName strin
 func (m *Manager) AttachSession(ctx context.Context, instanceID, sessionName string) error {
 	entry, err := m.catalog.Get(ctx, instanceID)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return ErrNotFound
 		}
 		return fmt.Errorf("get catalog entry: %w", err)
@@ -1110,7 +1113,7 @@ func (m *Manager) cleanupExitedSession(ctx context.Context, instanceID, sessionN
 func (m *Manager) GetMRUSession(ctx context.Context, instanceID string) (*Session, error) {
 	entry, err := m.catalog.Get(ctx, instanceID)
 	if err != nil {
-		if err == catalog.ErrNotFound {
+		if errors.Is(err, catalog.ErrNotFound) {
 			return nil, ErrNotFound
 		}
 		return nil, fmt.Errorf("get catalog entry: %w", err)
@@ -1138,10 +1141,12 @@ func (m *Manager) GetMRUSession(ctx context.Context, instanceID string) (*Sessio
 	}, nil
 }
 
-// GlobalMRUSession represents a session with its instance context.
+// GlobalMRUSession represents the most recently used session along with
+// its containing instance information. This is returned by GetGlobalMRUSession
+// to provide context about which instance owns the session.
 type GlobalMRUSession struct {
-	InstanceID string
-	Session    Session
+	InstanceID string  // ID of the instance containing the session
+	Session    Session // The most recently used session
 }
 
 // GetGlobalMRUSession returns the most recently used session across all instances.
diff --git a/internal/instance/manager_test.go b/internal/instance/manager_test.go
index 4c036b3..2fe464a 100644
--- a/internal/instance/manager_test.go
+++ b/internal/instance/manager_test.go
@@ -651,6 +651,10 @@ func TestManager_Attach(t *testing.T) {
 	})
 }
 
+// TestSanitizeBranch tests the branch name sanitization logic used for
+// generating container names and worktree paths. This is tested directly
+// because the behavior is critical for naming consistency and hard to verify
+// through the public API without creating actual containers.
 func TestSanitizeBranch(t *testing.T) {
 	tests := []struct {
 		input    string
diff --git a/internal/keychain/keychain_darwin.go b/internal/keychain/keychain_darwin.go
index 6312cdf..091c9d4 100644
--- a/internal/keychain/keychain_darwin.go
+++ b/internal/keychain/keychain_darwin.go
@@ -2,7 +2,11 @@
 
 package keychain
 
-import gokeychain "github.com/keybase/go-keychain"
+import (
+	"errors"
+
+	gokeychain "github.com/keybase/go-keychain"
+)
 
 // serviceName is the service identifier used for all headjack credentials.
 const serviceName = "com.headjack.cli"
@@ -40,7 +44,7 @@ func (k *keychain) Get(account string) (string, error) {
 	query.SetReturnData(true)
 
 	results, err := gokeychain.QueryItem(query)
-	if err == gokeychain.ErrorItemNotFound {
+	if errors.Is(err, gokeychain.ErrorItemNotFound) {
 		return "", ErrNotFound
 	}
 	if err != nil {
@@ -60,7 +64,7 @@ func (k *keychain) Delete(account string) error {
 	item.SetAccount(account)
 
 	err := gokeychain.DeleteItem(item)
-	if err == gokeychain.ErrorItemNotFound {
+	if errors.Is(err, gokeychain.ErrorItemNotFound) {
 		return nil
 	}
 	return err