diff --git a/.gitignore b/.gitignore
index 02ef18d1f..977eb0b5b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -47,3 +47,4 @@ dist/
 
 # Windows Application Icon/Resource
 *.syso
+AGENTS.md
diff --git a/go.mod b/go.mod
index c1172937c..6fa3a900c 100644
--- a/go.mod
+++ b/go.mod
@@ -11,6 +11,7 @@ require (
 	github.com/gdamore/tcell/v2 v2.13.8
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/websocket v1.5.3
+	github.com/h2non/filetype v1.1.3
 	github.com/larksuite/oapi-sdk-go/v3 v3.5.3
 	github.com/mdp/qrterminal/v3 v3.2.1
 	github.com/modelcontextprotocol/go-sdk v1.3.0
@@ -37,8 +38,6 @@ require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/elliotchance/orderedmap/v3 v3.1.0 // indirect
 	github.com/gdamore/encoding v1.0.1 // indirect
-	github.com/gdamore/tcell/v2 v2.13.8 // indirect
-	github.com/h2non/filetype v1.1.3 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/lucasb-eyer/go-colorful v1.3.0 // indirect
 	github.com/mattn/go-colorable v0.1.14 // indirect
diff --git a/pkg/agent/instance.go b/pkg/agent/instance.go
index ed25f537f..64cf83797 100644
--- a/pkg/agent/instance.go
+++ b/pkg/agent/instance.go
@@ -113,7 +113,38 @@ func NewAgentInstance(
 		summarizeTokenPercent = 75
 	}
 
-	// Resolve fallback candidates
+	candidates := ResolveCandidatesForModel(cfg, defaults.Provider, model, fallbacks)
+
+	return &AgentInstance{
+		ID:                        agentID,
+		Name:                      agentName,
+		Model:                     model,
+		Fallbacks:                 fallbacks,
+		Workspace:                 workspace,
+		MaxIterations:             maxIter,
+		MaxTokens:                 maxTokens,
+		Temperature:               temperature,
+		ContextWindow:             maxTokens,
+		SummarizeMessageThreshold: summarizeMessageThreshold,
+		SummarizeTokenPercent:     summarizeTokenPercent,
+		Provider:                  provider,
+		Sessions:                  sessionsManager,
+		ContextBuilder:            contextBuilder,
+		Tools:                     toolsRegistry,
+		Subagents:                 subagents,
+		SkillsFilter:              skillsFilter,
+		Candidates:                candidates,
+	}
+}
+
+// ResolveCandidatesForModel resolves fallback candidates using the same lookup
+// behavior as AgentInstance construction. It is reused by model hot-switch paths.
+func ResolveCandidatesForModel(
+	cfg *config.Config,
+	defaultProvider string,
+	model string,
+	fallbacks []string,
+) []providers.FallbackCandidate {
 	modelCfg := providers.ModelConfig{
 		Primary:   model,
 		Fallbacks: fallbacks,
@@ -158,28 +189,7 @@ func NewAgentInstance(
 		return "", false
 	}
 
-	candidates := providers.ResolveCandidatesWithLookup(modelCfg, defaults.Provider, resolveFromModelList)
-
-	return &AgentInstance{
-		ID:                        agentID,
-		Name:                      agentName,
-		Model:                     model,
-		Fallbacks:                 fallbacks,
-		Workspace:                 workspace,
-		MaxIterations:             maxIter,
-		MaxTokens:                 maxTokens,
-		Temperature:               temperature,
-		ContextWindow:             maxTokens,
-		SummarizeMessageThreshold: summarizeMessageThreshold,
-		SummarizeTokenPercent:     summarizeTokenPercent,
-		Provider:                  provider,
-		Sessions:                  sessionsManager,
-		ContextBuilder:            contextBuilder,
-		Tools:                     toolsRegistry,
-		Subagents:                 subagents,
-		SkillsFilter:              skillsFilter,
-		Candidates:                candidates,
-	}
+	return providers.ResolveCandidatesWithLookup(modelCfg, defaultProvider, resolveFromModelList)
 }
 
 // resolveAgentWorkspace determines the workspace directory for an agent.
diff --git a/pkg/agent/loop.go b/pkg/agent/loop.go
index db9efa2cf..752746279 100644
--- a/pkg/agent/loop.go
+++ b/pkg/agent/loop.go
@@ -37,6 +37,7 @@ type AgentLoop struct {
 	bus            *bus.MessageBus
 	cfg            *config.Config
 	registry       *AgentRegistry
+	modelSwitch    *ModelSwitchManager
 	state          *state.Manager
 	running        atomic.Bool
 	summarizing    sync.Map
@@ -66,6 +67,7 @@ func NewAgentLoop(
 	provider providers.LLMProvider,
 ) *AgentLoop {
 	registry := NewAgentRegistry(cfg, provider)
+	modelSwitch := NewModelSwitchManager(cfg, registry)
 
 	// Register shared tools to all agents
 	registerSharedTools(cfg, msgBus, registry, provider)
@@ -85,6 +87,7 @@ func NewAgentLoop(
 		bus:         msgBus,
 		cfg:         cfg,
 		registry:    registry,
+		modelSwitch: modelSwitch,
 		state:       stateManager,
 		summarizing: sync.Map{},
 		fallback:    fallbackChain,
@@ -1459,7 +1462,9 @@ func (al *AgentLoop) handleCommand(ctx context.Context, msg bus.InboundMessage)
 				return "No default agent configured", true
 			}
 			oldModel := defaultAgent.Model
-			defaultAgent.Model = value
+			if err := al.modelSwitch.SwitchModel("", value); err != nil {
+				return fmt.Sprintf("Failed to switch model: %v", err), true
+			}
 			return fmt.Sprintf("Switched model from %s to %s", oldModel, value), true
 		case "channel":
 			if al.channelManager == nil {
diff --git a/pkg/agent/model_switch.go b/pkg/agent/model_switch.go
new file mode 100644
index 000000000..430e40d37
--- /dev/null
+++ b/pkg/agent/model_switch.go
@@ -0,0 +1,110 @@
+package agent
+
+import (
+	"fmt"
+	"sync"
+
+	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/providers"
+)
+
+// ModelSwitchManager handles dynamic model switching at runtime.
+type ModelSwitchManager struct {
+	config   *config.Config
+	registry *AgentRegistry
+	mu       sync.RWMutex
+}
+
+// NewModelSwitchManager creates a new model switch manager.
+func NewModelSwitchManager(cfg *config.Config, registry *AgentRegistry) *ModelSwitchManager {
+	return &ModelSwitchManager{
+		config:   cfg,
+		registry: registry,
+	}
+}
+
+// SwitchModel switches the model for a given session.
+// If sessionKey is empty, it updates the global default model.
+func (m *ModelSwitchManager) SwitchModel(sessionKey, modelName string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// Validate model exists in config
+	if _, err := m.config.GetModelConfig(modelName); err != nil {
+		return fmt.Errorf("model %q not found. Available models: %v", modelName, m.listAvailableModels())
+	}
+
+	// Session-scoped override is not implemented yet.
+	if sessionKey != "" {
+		return fmt.Errorf("session-scoped model switch is not supported yet")
+	}
+
+	oldModel := m.config.Agents.Defaults.GetModelName()
+	if oldModel == modelName {
+		return nil
+	}
+
+	if err := m.config.SetDefaultModel(modelName); err != nil {
+		return fmt.Errorf("failed to set default model: %w", err)
+	}
+
+	newProvider, _, err := providers.CreateProvider(m.config)
+	if err != nil {
+		// Roll back config on provider creation failure.
+		_ = m.config.SetDefaultModel(oldModel)
+		return fmt.Errorf("failed to create provider for model switch: %w", err)
+	}
+
+	if err := m.registry.SwitchModel(m.config, oldModel, modelName, newProvider); err != nil {
+		_ = m.config.SetDefaultModel(oldModel)
+		if cp, ok := newProvider.(providers.StatefulProvider); ok {
+			cp.Close()
+		}
+		return fmt.Errorf("failed to apply hot model switch: %w", err)
+	}
+
+	return nil
+}
+
+// GetCurrentModel returns the current model for a session.
+// If session-specific override exists, returns that. Otherwise returns global default.
+func (m *ModelSwitchManager) GetCurrentModel(sessionKey string) string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	// For now, always return the global default model
+	// Session-scoped overrides can be added later
+	return m.config.Agents.Defaults.GetModelName()
+}
+
+// ValidateModel validates if a model exists in the configuration.
+func (m *ModelSwitchManager) ValidateModel(modelName string) (*config.ModelConfig, error) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	return m.config.GetModelConfig(modelName)
+}
+
+// listAvailableModels returns a slice of all available model names.
+func (m *ModelSwitchManager) listAvailableModels() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	models := make([]string, 0, len(m.config.ModelList))
+	for _, mc := range m.config.ModelList {
+		if mc.ModelName != "" {
+			models = append(models, mc.ModelName)
+		}
+	}
+	return models
+}
+
+// GetModelInfo returns formatted information about the current model.
+func (m *ModelSwitchManager) GetModelInfo(sessionKey string) (string, string) {
+	currentModel := m.GetCurrentModel(sessionKey)
+	if mc, err := m.config.GetModelConfig(currentModel); err == nil {
+		return currentModel, mc.Model
+	}
+
+	return currentModel, "unknown"
+}
diff --git a/pkg/agent/model_switch_test.go b/pkg/agent/model_switch_test.go
new file mode 100644
index 000000000..c2e4c7234
--- /dev/null
+++ b/pkg/agent/model_switch_test.go
@@ -0,0 +1,120 @@
+package agent
+
+import (
+	"context"
+	"testing"
+
+	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/providers"
+)
+
+type statefulMockProvider struct {
+	closed bool
+}
+
+func (m *statefulMockProvider) Chat(
+	ctx context.Context,
+	messages []providers.Message,
+	tools []providers.ToolDefinition,
+	model string,
+	options map[string]any,
+) (*providers.LLMResponse, error) {
+	return &providers.LLMResponse{Content: "ok"}, nil
+}
+
+func (m *statefulMockProvider) GetDefaultModel() string { return "mock" }
+func (m *statefulMockProvider) Close()                  { m.closed = true }
+
+func testSwitchConfig() *config.Config {
+	return &config.Config{
+		Agents: config.AgentsConfig{
+			Defaults: config.AgentDefaults{
+				Workspace:         "/tmp/picoclaw-switch-test",
+				ModelName:         "model-a",
+				MaxTokens:         4096,
+				MaxToolIterations: 10,
+			},
+			List: []config.AgentConfig{
+				{ID: "main", Default: true},
+				{ID: "worker", Model: &config.AgentModelConfig{Primary: "fixed-model"}},
+			},
+		},
+		ModelList: []config.ModelConfig{
+			{ModelName: "model-a", Model: "codex-cli/codex"},
+			{ModelName: "model-b", Model: "claude-cli/claude"},
+			{ModelName: "fixed-model", Model: "codex-cli/fixed"},
+			{ModelName: "broken-model", Model: "openai/gpt-bad"},
+		},
+	}
+}
+
+func TestModelSwitchManager_SwitchModelSuccess(t *testing.T) {
+	cfg := testSwitchConfig()
+	initialProvider := &statefulMockProvider{}
+	registry := NewAgentRegistry(cfg, initialProvider)
+	manager := NewModelSwitchManager(cfg, registry)
+
+	if err := manager.SwitchModel("", "model-b"); err != nil {
+		t.Fatalf("SwitchModel() error = %v", err)
+	}
+
+	if got := cfg.Agents.Defaults.GetModelName(); got != "model-b" {
+		t.Fatalf("default model = %q, want %q", got, "model-b")
+	}
+
+	mainAgent, ok := registry.GetAgent("main")
+	if !ok {
+		t.Fatal("main agent not found")
+	}
+	if mainAgent.Model != "model-b" {
+		t.Fatalf("main agent model = %q, want %q", mainAgent.Model, "model-b")
+	}
+	if len(mainAgent.Candidates) == 0 || mainAgent.Candidates[0].Provider != "claude-cli" {
+		t.Fatalf("main candidates not refreshed: %+v", mainAgent.Candidates)
+	}
+
+	worker, ok := registry.GetAgent("worker")
+	if !ok {
+		t.Fatal("worker agent not found")
+	}
+	if worker.Model != "fixed-model" {
+		t.Fatalf("worker model should remain fixed-model, got %q", worker.Model)
+	}
+	if worker.Provider == initialProvider {
+		t.Fatal("worker provider should be hot-swapped to new provider")
+	}
+
+	if !initialProvider.closed {
+		t.Fatal("old stateful provider should be closed after switch")
+	}
+}
+
+func TestModelSwitchManager_SwitchModelRollbackOnProviderCreateFailure(t *testing.T) {
+	cfg := testSwitchConfig()
+	initialProvider := &statefulMockProvider{}
+	registry := NewAgentRegistry(cfg, initialProvider)
+	manager := NewModelSwitchManager(cfg, registry)
+
+	err := manager.SwitchModel("", "broken-model")
+	if err == nil {
+		t.Fatal("expected error for broken-model provider creation")
+	}
+
+	if got := cfg.Agents.Defaults.GetModelName(); got != "model-a" {
+		t.Fatalf("default model should roll back to model-a, got %q", got)
+	}
+
+	mainAgent, ok := registry.GetAgent("main")
+	if !ok {
+		t.Fatal("main agent not found")
+	}
+	if mainAgent.Model != "model-a" {
+		t.Fatalf("main model should remain model-a, got %q", mainAgent.Model)
+	}
+	if mainAgent.Provider != initialProvider {
+		t.Fatal("provider should remain unchanged on failure")
+	}
+	if initialProvider.closed {
+		t.Fatal("old provider should not be closed when switch fails")
+	}
+}
diff --git a/pkg/agent/registry.go b/pkg/agent/registry.go
index 77b846832..c89371c20 100644
--- a/pkg/agent/registry.go
+++ b/pkg/agent/registry.go
@@ -1,6 +1,8 @@
 package agent
 
 import (
+	"fmt"
+	"slices"
 	"sync"
 
 	"github.com/sipeed/picoclaw/pkg/config"
@@ -11,9 +13,10 @@ import (
 
 // AgentRegistry manages multiple agent instances and routes messages to them.
 type AgentRegistry struct {
-	agents   map[string]*AgentInstance
-	resolver *routing.RouteResolver
-	mu       sync.RWMutex
+	agents         map[string]*AgentInstance
+	resolver       *routing.RouteResolver
+	defaultAgentID string
+	mu             sync.RWMutex
 }
 
 // NewAgentRegistry creates a registry from config, instantiating all agents.
@@ -34,6 +37,7 @@ func NewAgentRegistry(
 		}
 		instance := NewAgentInstance(implicitAgent, &cfg.Agents.Defaults, cfg, provider)
 		registry.agents["main"] = instance
+		registry.defaultAgentID = "main"
 		logger.InfoCF("agent", "Created implicit main agent (no agents.list configured)", nil)
 	} else {
 		for i := range agentConfigs {
@@ -41,6 +45,9 @@ func NewAgentRegistry(
 			id := routing.NormalizeAgentID(ac.ID)
 			instance := NewAgentInstance(ac, &cfg.Agents.Defaults, cfg, provider)
 			registry.agents[id] = instance
+			if ac.Default && registry.defaultAgentID == "" {
+				registry.defaultAgentID = id
+			}
 			logger.InfoCF("agent", "Registered agent",
 				map[string]any{
 					"agent_id":  id,
@@ -51,6 +58,17 @@ func NewAgentRegistry(
 		}
 	}
 
+	if registry.defaultAgentID == "" {
+		ids := make([]string, 0, len(registry.agents))
+		for id := range registry.agents {
+			ids = append(ids, id)
+		}
+		slices.Sort(ids)
+		if len(ids) > 0 {
+			registry.defaultAgentID = ids[0]
+		}
+	}
+
 	return registry
 }
 
@@ -104,11 +122,61 @@ func (r *AgentRegistry) CanSpawnSubagent(parentAgentID, targetAgentID string) bo
 func (r *AgentRegistry) GetDefaultAgent() *AgentInstance {
 	r.mu.RLock()
 	defer r.mu.RUnlock()
+	if r.defaultAgentID != "" {
+		if agent, ok := r.agents[r.defaultAgentID]; ok {
+			return agent
+		}
+	}
 	if agent, ok := r.agents["main"]; ok {
 		return agent
 	}
-	for _, agent := range r.agents {
-		return agent
+	ids := make([]string, 0, len(r.agents))
+	for id := range r.agents {
+		ids = append(ids, id)
+	}
+	slices.Sort(ids)
+	if len(ids) > 0 {
+		return r.agents[ids[0]]
 	}
 	return nil
 }
+
+// SwitchModel hot-swaps provider and effective model at runtime.
+// It updates all agents that currently use oldModel to newModel, and refreshes
+// provider + fallback candidates atomically by replacing agent pointers.
+func (r *AgentRegistry) SwitchModel(
+	cfg *config.Config,
+	oldModel string,
+	newModel string,
+	newProvider providers.LLMProvider,
+) error {
+	r.mu.Lock()
+	if len(r.agents) == 0 {
+		r.mu.Unlock()
+		return fmt.Errorf("no agents registered")
+	}
+
+	var oldProvider providers.LLMProvider
+	for id, agent := range r.agents {
+		if oldProvider == nil {
+			oldProvider = agent.Provider
+		}
+
+		updated := *agent
+		if updated.Model == oldModel {
+			updated.Model = newModel
+		}
+		updated.Provider = newProvider
+		updated.Candidates = ResolveCandidatesForModel(cfg, cfg.Agents.Defaults.Provider, updated.Model, updated.Fallbacks)
+		r.agents[id] = &updated
+	}
+	r.mu.Unlock()
+
+	if oldProvider != nil && oldProvider != newProvider {
+		if cp, ok := oldProvider.(providers.StatefulProvider); ok {
+			cp.Close()
+		}
+	}
+
+	return nil
+}
diff --git a/pkg/agent/registry_test.go b/pkg/agent/registry_test.go
index 518bb441f..a7ed4eaff 100644
--- a/pkg/agent/registry_test.go
+++ b/pkg/agent/registry_test.go
@@ -104,11 +104,29 @@ func TestAgentRegistry_GetDefaultAgent(t *testing.T) {
 	})
 	registry := NewAgentRegistry(cfg, &mockRegistryProvider{})
 
-	// GetDefaultAgent first checks for "main", then returns any
 	agent := registry.GetDefaultAgent()
 	if agent == nil {
 		t.Fatal("expected a default agent")
 	}
+	if agent.ID != "beta" {
+		t.Fatalf("default agent ID = %q, want %q", agent.ID, "beta")
+	}
+}
+
+func TestAgentRegistry_GetDefaultAgent_FallbackDeterministic(t *testing.T) {
+	cfg := testCfg([]config.AgentConfig{
+		{ID: "zeta"},
+		{ID: "alpha"},
+	})
+	registry := NewAgentRegistry(cfg, &mockRegistryProvider{})
+
+	agent := registry.GetDefaultAgent()
+	if agent == nil {
+		t.Fatal("expected a default agent")
+	}
+	if agent.ID != "alpha" {
+		t.Fatalf("default agent fallback should be deterministic sorted first, got %q", agent.ID)
+	}
 }
 
 func TestAgentRegistry_CanSpawnSubagent(t *testing.T) {
diff --git a/pkg/channels/base.go b/pkg/channels/base.go
index 063a66523..44c406cf1 100644
--- a/pkg/channels/base.go
+++ b/pkg/channels/base.go
@@ -111,6 +111,12 @@ func NewBaseChannel(
 	return bc
 }
 
+// Config returns the underlying config object passed when constructing
+// the BaseChannel. Callers must perform an appropriate type assertion.
+func (c *BaseChannel) Config() any {
+	return c.config
+}
+
 // MaxMessageLength returns the maximum message length (in runes) for this channel.
 // A value of 0 means no limit.
 func (c *BaseChannel) MaxMessageLength() int {
diff --git a/pkg/channels/discord/discord.go b/pkg/channels/discord/discord.go
index 1de910c83..e09f67a65 100644
--- a/pkg/channels/discord/discord.go
+++ b/pkg/channels/discord/discord.go
@@ -29,35 +29,37 @@ const (
 type DiscordChannel struct {
 	*channels.BaseChannel
 	session    *discordgo.Session
-	config     config.DiscordConfig
 	ctx        context.Context
 	cancel     context.CancelFunc
 	typingMu   sync.Mutex
 	typingStop map[string]chan struct{} // chatID → stop signal
 	botUserID  string                   // stored for mention checking
+	commands   DiscordCommander         // Discord command handler
 }
 
-func NewDiscordChannel(cfg config.DiscordConfig, bus *bus.MessageBus) (*DiscordChannel, error) {
-	session, err := discordgo.New("Bot " + cfg.Token)
+func NewDiscordChannel(cfg *config.Config, bus *bus.MessageBus) (*DiscordChannel, error) {
+	session, err := discordgo.New("Bot " + cfg.Channels.Discord.Token)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create discord session: %w", err)
 	}
 
-	if err := applyDiscordProxy(session, cfg.Proxy); err != nil {
+	if err := applyDiscordProxy(session, cfg.Channels.Discord.Proxy); err != nil {
 		return nil, err
 	}
-	base := channels.NewBaseChannel("discord", cfg, bus, cfg.AllowFrom,
+	base := channels.NewBaseChannel("discord", cfg, bus, cfg.Channels.Discord.AllowFrom,
 		channels.WithMaxMessageLength(2000),
-		channels.WithGroupTrigger(cfg.GroupTrigger),
-		channels.WithReasoningChannelID(cfg.ReasoningChannelID),
+		channels.WithGroupTrigger(cfg.Channels.Discord.GroupTrigger),
+		channels.WithReasoningChannelID(cfg.Channels.Discord.ReasoningChannelID),
 	)
 
+	commands := NewDiscordCommands(session, cfg, bus)
+
 	return &DiscordChannel{
 		BaseChannel: base,
 		session:     session,
-		config:      cfg,
 		ctx:         context.Background(),
 		typingStop:  make(map[string]chan struct{}),
+		commands:    commands,
 	}, nil
 }
 
@@ -235,11 +237,20 @@ func (c *DiscordChannel) EditMessage(ctx context.Context, chatID string, message
 // It sends a placeholder message that will later be edited to the actual
 // response via EditMessage (channels.MessageEditor).
 func (c *DiscordChannel) SendPlaceholder(ctx context.Context, chatID string) (string, error) {
-	if !c.config.Placeholder.Enabled {
+	// Placeholder configuration is stored in the Discord channel config
+	// under the global config passed to BaseChannel.
+	cfgAny := c.BaseChannel.Config()
+	cfg, ok := cfgAny.(*config.Config)
+	if !ok {
 		return "", nil
 	}
 
-	text := c.config.Placeholder.Text
+	phCfg := cfg.Channels.Discord.Placeholder
+	if !phCfg.Enabled {
+		return "", nil
+	}
+
+	text := phCfg.Text
 	if text == "" {
 		text = "Thinking... 💭"
 	}
@@ -314,6 +325,16 @@ func (c *DiscordChannel) handleMessage(s *discordgo.Session, m *discordgo.Messag
 
 	content := m.Content
 
+	// Check for slash commands first
+	if strings.HasPrefix(strings.TrimSpace(content), "/") {
+		if err := c.handleSlashCommand(c.ctx, s, m); err != nil {
+			logger.DebugCF("discord", "Command error", map[string]any{
+				"error": err.Error(),
+			})
+		}
+		return
+	}
+
 	// In guild (group) channels, apply unified group trigger filtering
 	// DMs (GuildID is empty) always get a response
 	if m.GuildID != "" {
@@ -519,3 +540,34 @@ func (c *DiscordChannel) stripBotMention(text string) string {
 	text = strings.ReplaceAll(text, fmt.Sprintf("<@!%s>", c.botUserID), "")
 	return strings.TrimSpace(text)
 }
+
+// handleSlashCommand processes slash commands and forwards to appropriate handler.
+func (c *DiscordChannel) handleSlashCommand(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error {
+	content := strings.TrimSpace(m.Content)
+	if !strings.HasPrefix(content, "/") {
+		return nil
+	}
+
+	parts := strings.Fields(content)
+	if len(parts) == 0 {
+		return nil
+	}
+
+	cmd := strings.TrimPrefix(parts[0], "/")
+
+	switch cmd {
+	case "help":
+		return c.commands.Help(ctx, s, m)
+	case "start":
+		return c.commands.Help(ctx, s, m) // Start uses same help message
+	case "show":
+		return c.commands.Show(ctx, s, m)
+	case "list":
+		return c.commands.List(ctx, s, m)
+	case "switch":
+		return c.commands.Switch(ctx, s, m)
+	default:
+		// Unknown command - let it fall through to normal message handling
+		return nil
+	}
+}
diff --git a/pkg/channels/discord/discord_commands.go b/pkg/channels/discord/discord_commands.go
new file mode 100644
index 000000000..ce01d0276
--- /dev/null
+++ b/pkg/channels/discord/discord_commands.go
@@ -0,0 +1,268 @@
+package discord
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/bwmarrin/discordgo"
+
+	"github.com/sipeed/picoclaw/pkg/bus"
+	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/identity"
+)
+
+type DiscordCommander interface {
+	Help(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error
+	Show(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error
+	List(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error
+	Switch(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error
+}
+
+type cmd struct {
+	session *discordgo.Session
+	config  *config.Config
+	bus     *bus.MessageBus
+}
+
+func NewDiscordCommands(session *discordgo.Session, cfg *config.Config, bus *bus.MessageBus) DiscordCommander {
+	return &cmd{
+		session: session,
+		config:  cfg,
+		bus:     bus,
+	}
+}
+
+// parseCommand extracts the command and arguments from message content.
+func parseCommand(content string) (string, string) {
+	content = strings.TrimSpace(content)
+	if !strings.HasPrefix(content, "/") {
+		return "", ""
+	}
+
+	parts := strings.SplitN(content, " ", 2)
+	cmd := strings.TrimPrefix(parts[0], "/")
+
+	if len(parts) < 2 {
+		return cmd, ""
+	}
+
+	return cmd, strings.TrimSpace(parts[1])
+}
+
+func (c *cmd) Help(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error {
+	msg := `**PicoClaw Commands**
+
+/start - Start the bot
+/help - Show this help message
+/show [model|channel] - Show current configuration
+/list [models|channels] - List available options
+/switch model <name> - Switch to a different model
+
+**Examples:**
+/switch model gpt-4
+/switch model claude-sonnet-4.6
+
+Use /list models to see all available models.
+`
+
+	_, err := s.ChannelMessageSend(m.ChannelID, msg)
+	return err
+}
+
+func (c *cmd) Show(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error {
+	cmd, args := parseCommand(m.Content)
+	if cmd != "show" {
+		return fmt.Errorf("invalid command format")
+	}
+
+	if args == "" {
+		_, err := s.ChannelMessageSend(m.ChannelID, "Usage: /show [model|channel]")
+		return err
+	}
+
+	var response string
+	switch args {
+	case "model":
+		currentModel := c.config.Agents.Defaults.GetModelName()
+		provider := c.config.Agents.Defaults.Provider
+		response = fmt.Sprintf("**Current Model:** %s\n**Provider:** %s", currentModel, provider)
+	case "channel":
+		response = "**Current Channel:** discord"
+	default:
+		response = fmt.Sprintf("Unknown parameter: %s. Try 'model' or 'channel'.", args)
+	}
+
+	_, err := s.ChannelMessageSend(m.ChannelID, response)
+	return err
+}
+
+func (c *cmd) List(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error {
+	cmd, args := parseCommand(m.Content)
+	if cmd != "list" {
+		return fmt.Errorf("invalid command format")
+	}
+
+	if args == "" {
+		_, err := s.ChannelMessageSend(m.ChannelID, "Usage: /list [models|channels]")
+		return err
+	}
+
+	var response string
+	switch args {
+	case "models":
+		response = c.formatModelsList()
+	case "channels":
+		response = c.formatChannelsList()
+	default:
+		response = fmt.Sprintf("Unknown parameter: %s. Try 'models' or 'channels'.", args)
+	}
+
+	_, err := s.ChannelMessageSend(m.ChannelID, response)
+	return err
+}
+
+func (c *cmd) Switch(ctx context.Context, s *discordgo.Session, m *discordgo.MessageCreate) error {
+	cmd, args := parseCommand(m.Content)
+	if cmd != "switch" {
+		return fmt.Errorf("invalid command format")
+	}
+
+	if args == "" {
+		_, err := s.ChannelMessageSend(m.ChannelID, "Usage: /switch model <name>\nUse /list models to see available models.")
+		return err
+	}
+
+	// Parse "model <name>" format
+	parts := strings.SplitN(args, " ", 2)
+	if len(parts) < 2 || parts[0] != "model" {
+		_, err := s.ChannelMessageSend(m.ChannelID, "Usage: /switch model <name>\nUse /list models to see available models.")
+		return err
+	}
+
+	modelName := strings.TrimSpace(parts[1])
+
+	// Optional: validate model exists to provide immediate feedback
+	if _, err := c.config.GetModelConfig(modelName); err != nil {
+		available := c.formatModelsList()
+		_, sendErr := c.session.ChannelMessageSend(
+			m.ChannelID,
+			fmt.Sprintf("❌ Model not found: %s\n\n**Available models:**\n%s", modelName, available),
+		)
+		return sendErr
+	}
+
+	if c.bus == nil {
+		_, err := c.session.ChannelMessageSend(m.ChannelID, "❌ Internal error: message bus not initialized")
+		return err
+	}
+
+	// Forward a normalized switch command to the agent loop via the message bus
+	// so that the agent can apply the change and persist any in-memory state.
+	inbound := bus.InboundMessage{
+		Channel:  "discord",
+		SenderID: m.Author.ID,
+		Sender: bus.SenderInfo{
+			Platform:    "discord",
+			PlatformID:  m.Author.ID,
+			CanonicalID: identity.BuildCanonicalID("discord", m.Author.ID),
+			Username:    m.Author.Username,
+			DisplayName: m.Author.Username,
+		},
+		ChatID:    m.ChannelID,
+		Content:   fmt.Sprintf("/switch model to %s", modelName),
+		MessageID: m.ID,
+		Metadata: map[string]string{
+			"guild_id":   m.GuildID,
+			"channel_id": m.ChannelID,
+		},
+	}
+
+	if err := c.bus.PublishInbound(ctx, inbound); err != nil {
+		_, sendErr := c.session.ChannelMessageSend(m.ChannelID, fmt.Sprintf("❌ Failed to switch model: %v", err))
+		return sendErr
+	}
+
+	// The agent will respond via the normal outbound flow; no immediate reply here.
+	return nil
+}
+
+func (c *cmd) formatModelsList() string {
+	if len(c.config.ModelList) == 0 {
+		return "No models configured. Please check your configuration."
+	}
+
+	currentModel := c.config.Agents.Defaults.GetModelName()
+
+	var sb strings.Builder
+	sb.WriteString("**Available Models:**\n\n")
+
+	for _, mc := range c.config.ModelList {
+		if mc.ModelName == "" {
+			continue
+		}
+
+		prefix := "  "
+		if mc.ModelName == currentModel {
+			prefix = "✓ "
+		}
+
+		provider := "openai"
+		if strings.Contains(mc.Model, "/") {
+			protocolParts := strings.SplitN(mc.Model, "/", 2)
+			if len(protocolParts) > 0 {
+				provider = protocolParts[0]
+			}
+		}
+
+		sb.WriteString(fmt.Sprintf("%s**%s** - %s (%s)\n", prefix, mc.ModelName, mc.Model, provider))
+	}
+
+	return sb.String()
+}
+
+func (c *cmd) formatChannelsList() string {
+	var enabled []string
+	if c.config.Channels.Telegram.Enabled {
+		enabled = append(enabled, "telegram")
+	}
+	if c.config.Channels.WhatsApp.Enabled {
+		enabled = append(enabled, "whatsapp")
+	}
+	if c.config.Channels.Feishu.Enabled {
+		enabled = append(enabled, "feishu")
+	}
+	if c.config.Channels.Discord.Enabled {
+		enabled = append(enabled, "discord")
+	}
+	if c.config.Channels.Slack.Enabled {
+		enabled = append(enabled, "slack")
+	}
+	if c.config.Channels.LINE.Enabled {
+		enabled = append(enabled, "line")
+	}
+	if c.config.Channels.QQ.Enabled {
+		enabled = append(enabled, "qq")
+	}
+	if c.config.Channels.OneBot.Enabled {
+		enabled = append(enabled, "onebot")
+	}
+	if c.config.Channels.WeCom.Enabled {
+		enabled = append(enabled, "wecom")
+	}
+	if c.config.Channels.WeComApp.Enabled {
+		enabled = append(enabled, "wecom_app")
+	}
+	if c.config.Channels.WeComAIBot.Enabled {
+		enabled = append(enabled, "wecom_aibot")
+	}
+	if c.config.Channels.Pico.Enabled {
+		enabled = append(enabled, "pico")
+	}
+
+	if len(enabled) == 0 {
+		return "No channels enabled."
+	}
+
+	return fmt.Sprintf("Enabled channels:\n- %s", strings.Join(enabled, "\n- "))
+}
diff --git a/pkg/channels/discord/init.go b/pkg/channels/discord/init.go
index 15a539804..6e538bd1e 100644
--- a/pkg/channels/discord/init.go
+++ b/pkg/channels/discord/init.go
@@ -8,6 +8,6 @@ import (
 
 func init() {
 	channels.RegisterFactory("discord", func(cfg *config.Config, b *bus.MessageBus) (channels.Channel, error) {
-		return NewDiscordChannel(cfg.Channels.Discord, b)
+		return NewDiscordChannel(cfg, b)
 	})
 }
diff --git a/pkg/channels/telegram/telegram.go b/pkg/channels/telegram/telegram.go
index f328f32b8..14752e1cf 100644
--- a/pkg/channels/telegram/telegram.go
+++ b/pkg/channels/telegram/telegram.go
@@ -93,7 +93,7 @@ func NewTelegramChannel(cfg *config.Config, bus *bus.MessageBus) (*TelegramChann
 
 	return &TelegramChannel{
 		BaseChannel: base,
-		commands:    NewTelegramCommands(bot, cfg),
+		commands:    NewTelegramCommands(bot, cfg, bus),
 		bot:         bot,
 		config:      cfg,
 		chatIDs:     make(map[string]int64),
@@ -141,6 +141,10 @@ func (c *TelegramChannel) Start(ctx context.Context) error {
 		return c.commands.List(ctx, message)
 	}, th.CommandEqual("list"))
 
+	bh.HandleMessage(func(ctx *th.Context, message telego.Message) error {
+		return c.commands.Switch(ctx, message)
+	}, th.CommandEqual("switch"))
+
 	bh.HandleMessage(func(ctx *th.Context, message telego.Message) error {
 		return c.handleMessage(ctx, &message)
 	}, th.AnyMessage())
@@ -203,6 +207,10 @@ func (c *TelegramChannel) initBotCommands(ctx context.Context) error {
 			Command:     "list",
 			Description: "List available options",
 		},
+		{
+			Command:     "switch",
+			Description: "Switch to a different model",
+		},
 	}
 
 	// Setting commands on each start will hit the rate limit very quickly, that's why we check if an update is needed
diff --git a/pkg/channels/telegram/telegram_commands.go b/pkg/channels/telegram/telegram_commands.go
index 496fc5e4f..149d48f79 100644
--- a/pkg/channels/telegram/telegram_commands.go
+++ b/pkg/channels/telegram/telegram_commands.go
@@ -7,7 +7,9 @@ import (
 
 	"github.com/mymmrac/telego"
 
+	"github.com/sipeed/picoclaw/pkg/bus"
 	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/identity"
 )
 
 type TelegramCommander interface {
@@ -15,17 +17,20 @@ type TelegramCommander interface {
 	Start(ctx context.Context, message telego.Message) error
 	Show(ctx context.Context, message telego.Message) error
 	List(ctx context.Context, message telego.Message) error
+	Switch(ctx context.Context, message telego.Message) error
 }
 
 type cmd struct {
 	bot    *telego.Bot
 	config *config.Config
+	bus    *bus.MessageBus
 }
 
-func NewTelegramCommands(bot *telego.Bot, cfg *config.Config) TelegramCommander {
+func NewTelegramCommands(bot *telego.Bot, cfg *config.Config, bus *bus.MessageBus) TelegramCommander {
 	return &cmd{
 		bot:    bot,
 		config: cfg,
+		bus:    bus,
 	}
 }
 
@@ -37,12 +42,31 @@ func commandArgs(text string) string {
 	return strings.TrimSpace(parts[1])
 }
 
+func isTelegramSwitchAllowed(allowFrom config.FlexibleStringSlice, sender bus.SenderInfo) bool {
+	if len(allowFrom) == 0 {
+		return true
+	}
+	for _, allowedEntry := range allowFrom {
+		if identity.MatchAllowed(sender, allowedEntry) {
+			return true
+		}
+	}
+	return false
+}
+
 func (c *cmd) Help(ctx context.Context, message telego.Message) error {
 	msg := `/start - Start the bot
 /help - Show this help message
 /show [model|channel] - Show current configuration
 /list [models|channels] - List available options
-	`
+/switch model <name> - Switch to a different model
+
+**Examples:**
+/switch model gpt-4
+/switch model claude-sonnet-4.6
+
+Use /list models to see all available models.
+`
 	_, err := c.bot.SendMessage(ctx, &telego.SendMessageParams{
 		ChatID: telego.ChatID{ID: message.Chat.ID},
 		Text:   msg,
@@ -80,9 +104,10 @@ func (c *cmd) Show(ctx context.Context, message telego.Message) error {
 	var response string
 	switch args {
 	case "model":
+		currentModel := c.config.Agents.Defaults.GetModelName()
+		provider := c.config.Agents.Defaults.Provider
 		response = fmt.Sprintf("Current Model: %s (Provider: %s)",
-			c.config.Agents.Defaults.GetModelName(),
-			c.config.Agents.Defaults.Provider)
+			currentModel, provider)
 	case "channel":
 		response = "Current Channel: telegram"
 	default:
@@ -115,12 +140,7 @@ func (c *cmd) List(ctx context.Context, message telego.Message) error {
 	var response string
 	switch args {
 	case "models":
-		provider := c.config.Agents.Defaults.Provider
-		if provider == "" {
-			provider = "configured default"
-		}
-		response = fmt.Sprintf("Configured Model: %s\nProvider: %s\n\nTo change models, update config.json",
-			c.config.Agents.Defaults.GetModelName(), provider)
+		response = c.formatModelsList()
 
 	case "channels":
 		var enabled []string
@@ -154,3 +174,146 @@ func (c *cmd) List(ctx context.Context, message telego.Message) error {
 	})
 	return err
 }
+
+func (c *cmd) Switch(ctx context.Context, message telego.Message) error {
+	if message.From == nil {
+		_, err := c.bot.SendMessage(ctx, &telego.SendMessageParams{
+			ChatID: telego.ChatID{ID: message.Chat.ID},
+			Text:   "❌ Cannot determine sender",
+			ReplyParameters: &telego.ReplyParameters{
+				MessageID: message.MessageID,
+			},
+		})
+		return err
+	}
+
+	platformID := fmt.Sprintf("%d", message.From.ID)
+	sender := bus.SenderInfo{
+		Platform:    "telegram",
+		PlatformID:  platformID,
+		CanonicalID: identity.BuildCanonicalID("telegram", platformID),
+		Username:    message.From.Username,
+		DisplayName: message.From.FirstName,
+	}
+	if !isTelegramSwitchAllowed(c.config.Channels.Telegram.AllowFrom, sender) {
+		_, err := c.bot.SendMessage(ctx, &telego.SendMessageParams{
+			ChatID: telego.ChatID{ID: message.Chat.ID},
+			Text:   "❌ You are not allowed to use this command.",
+			ReplyParameters: &telego.ReplyParameters{
+				MessageID: message.MessageID,
+			},
+		})
+		return err
+	}
+
+	content := strings.TrimSpace(message.Text)
+	content = strings.TrimPrefix(content, "/switch")
+	content = strings.TrimSpace(content)
+
+	parts := strings.SplitN(content, " ", 2)
+	if len(parts) < 2 || parts[0] != "model" {
+		_, err := c.bot.SendMessage(ctx, &telego.SendMessageParams{
+			ChatID: telego.ChatID{ID: message.Chat.ID},
+			Text:   "Usage: /switch model <name>\nUse /list models to see available models.",
+			ReplyParameters: &telego.ReplyParameters{
+				MessageID: message.MessageID,
+			},
+		})
+		return err
+	}
+
+	modelName := strings.TrimSpace(parts[1])
+	if modelName == "" {
+		_, err := c.bot.SendMessage(ctx, &telego.SendMessageParams{
+			ChatID: telego.ChatID{ID: message.Chat.ID},
+			Text:   "Usage: /switch model <name>\nUse /list models to see available models.",
+			ReplyParameters: &telego.ReplyParameters{
+				MessageID: message.MessageID,
+			},
+		})
+		return err
+	}
+
+	// Optional: validate model exists to provide immediate feedback
+	if _, err := c.config.GetModelConfig(modelName); err != nil {
+		_, sendErr := c.bot.SendMessage(ctx, &telego.SendMessageParams{
+			ChatID: telego.ChatID{ID: message.Chat.ID},
+			Text:   fmt.Sprintf("❌ Model not found: %s\n\n%s", modelName, c.formatModelsList()),
+			ReplyParameters: &telego.ReplyParameters{
+				MessageID: message.MessageID,
+			},
+		})
+		return sendErr
+	}
+
+	if c.bus == nil {
+		_, err := c.bot.SendMessage(ctx, &telego.SendMessageParams{
+			ChatID: telego.ChatID{ID: message.Chat.ID},
+			Text:   "❌ Internal error: message bus not initialized",
+			ReplyParameters: &telego.ReplyParameters{
+				MessageID: message.MessageID,
+			},
+		})
+		return err
+	}
+
+	inbound := bus.InboundMessage{
+		Channel:   "telegram",
+		SenderID:  platformID,
+		Sender:    sender,
+		ChatID:    fmt.Sprintf("%d", message.Chat.ID),
+		Content:   fmt.Sprintf("/switch model to %s", modelName),
+		MessageID: fmt.Sprintf("%d", message.MessageID),
+		Metadata: map[string]string{
+			"is_group": fmt.Sprintf("%t", message.Chat.Type != "private"),
+		},
+	}
+
+	if err := c.bus.PublishInbound(ctx, inbound); err != nil {
+		_, sendErr := c.bot.SendMessage(ctx, &telego.SendMessageParams{
+			ChatID: telego.ChatID{ID: message.Chat.ID},
+			Text:   fmt.Sprintf("❌ Failed to switch model: %v", err),
+			ReplyParameters: &telego.ReplyParameters{
+				MessageID: message.MessageID,
+			},
+		})
+		return sendErr
+	}
+
+	// The agent will respond via the normal outbound flow; no immediate reply here.
+	return nil
+}
+
+func (c *cmd) formatModelsList() string {
+	if len(c.config.ModelList) == 0 {
+		return "No models configured. Please check your configuration."
+	}
+
+	currentModel := c.config.Agents.Defaults.GetModelName()
+
+	var sb strings.Builder
+	sb.WriteString("*Available Models:*\n\n")
+
+	for _, mc := range c.config.ModelList {
+		if mc.ModelName == "" {
+			continue
+		}
+
+		prefix := "  "
+		if mc.ModelName == currentModel {
+			prefix = "✓ "
+		}
+
+		providerStr := "openai"
+		if strings.Contains(mc.Model, "/") {
+			protocolParts := strings.SplitN(mc.Model, "/", 2)
+			if len(protocolParts) > 0 {
+				providerStr = protocolParts[0]
+			}
+		}
+
+		sb.WriteString(fmt.Sprintf("%s%s - %s (%s)\n", prefix, mc.ModelName, mc.Model, providerStr))
+	}
+
+	return sb.String()
+}
diff --git a/pkg/channels/telegram/telegram_commands_test.go b/pkg/channels/telegram/telegram_commands_test.go
new file mode 100644
index 000000000..fc2a64225
--- /dev/null
+++ b/pkg/channels/telegram/telegram_commands_test.go
@@ -0,0 +1,115 @@
+package telegram
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/mymmrac/telego"
+
+	"github.com/sipeed/picoclaw/pkg/bus"
+	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/identity"
+)
+
+func TestIsTelegramSwitchAllowed(t *testing.T) {
+	sender := bus.SenderInfo{
+		Platform:    "telegram",
+		PlatformID:  "123",
+		CanonicalID: identity.BuildCanonicalID("telegram", "123"),
+		Username:    "alice",
+	}
+
+	tests := []struct {
+		name      string
+		allowFrom config.FlexibleStringSlice
+		want      bool
+	}{
+		{
+			name:      "empty allowlist allows all",
+			allowFrom: config.FlexibleStringSlice{},
+			want:      true,
+		},
+		{
+			name:      "matches raw platform id",
+			allowFrom: config.FlexibleStringSlice{"123"},
+			want:      true,
+		},
+		{
+			name:      "matches canonical id",
+			allowFrom: config.FlexibleStringSlice{"telegram:123"},
+			want:      true,
+		},
+		{
+			name:      "non matching denied",
+			allowFrom: config.FlexibleStringSlice{"999"},
+			want:      false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := isTelegramSwitchAllowed(tt.allowFrom, sender)
+			if got != tt.want {
+				t.Fatalf("isTelegramSwitchAllowed() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestSwitchPublishesNormalizedCommand(t *testing.T) {
+	msgBus := bus.NewMessageBus()
+	t.Cleanup(msgBus.Close)
+
+	cfg := &config.Config{
+		Agents: config.AgentsConfig{
+			Defaults: config.AgentDefaults{
+				ModelName: "model-a",
+			},
+		},
+		Channels: config.ChannelsConfig{
+			Telegram: config.TelegramConfig{
+				AllowFrom: config.FlexibleStringSlice{},
+			},
+		},
+		ModelList: []config.ModelConfig{
+			{ModelName: "model-a", Model: "codex-cli/codex"},
+		},
+	}
+
+	commander := &cmd{
+		config: cfg,
+		bus:    msgBus,
+		// bot is intentionally nil: success path should not call SendMessage
+	}
+
+	message := telego.Message{
+		MessageID: 7,
+		Text:      "/switch model model-a",
+		Chat: telego.Chat{
+			ID: 42,
+		},
+		From: &telego.User{
+			ID:        123,
+			Username:  "alice",
+			FirstName: "Alice",
+		},
+	}
+
+	if err := commander.Switch(context.Background(), message); err != nil {
+		t.Fatalf("Switch() error = %v", err)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
+	defer cancel()
+	got, ok := msgBus.ConsumeInbound(ctx)
+	if !ok {
+		t.Fatal("expected inbound switch command")
+	}
+	if got.Content != "/switch model to model-a" {
+		t.Fatalf("inbound content = %q, want %q", got.Content, "/switch model to model-a")
+	}
+	if got.Channel != "telegram" || got.ChatID != "42" {
+		t.Fatalf("unexpected inbound routing: channel=%q chat=%q", got.Channel, got.ChatID)
+	}
+}
diff --git a/pkg/config/config.go b/pkg/config/config.go
index f40e05e1c..3dcd94abe 100644
--- a/pkg/config/config.go
+++ b/pkg/config/config.go
@@ -832,3 +832,17 @@ func (c *Config) ValidateModelList() error {
 	}
 	return nil
 }
+
+// SetDefaultModel sets the default model for all agents.
+// It validates the model exists in ModelList before updating.
+func (c *Config) SetDefaultModel(modelName string) error {
+	// Validate model exists
+	if _, err := c.GetModelConfig(modelName); err != nil {
+		return fmt.Errorf("model %q not found: %w", modelName, err)
+	}
+
+	// Update the default model name
+	c.Agents.Defaults.ModelName = modelName
+
+	return nil
+}