diff --git a/pkg/aiusechat/tools_setconfig.go b/pkg/aiusechat/tools_setconfig.go
new file mode 100644
index 0000000000..687320db2e
--- /dev/null
+++ b/pkg/aiusechat/tools_setconfig.go
@@ -0,0 +1,371 @@
+// Copyright 2026, Command Line Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package aiusechat
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/wavetermdev/waveterm/pkg/aiusechat/uctypes"
+	"github.com/wavetermdev/waveterm/pkg/util/utilfn"
+	"github.com/wavetermdev/waveterm/pkg/waveobj"
+	"github.com/wavetermdev/waveterm/pkg/wconfig"
+)
+
+const SetConfigToolName = "set_config"
+
+type setConfigToolInput struct {
+	Config waveobj.MetaMapType `json:"config"`
+}
+
+type setConfigAllowedValue struct {
+	Schema       map[string]any
+	ValidateFunc func(any) error
+}
+
+var setConfigAllowedSettings = map[string]setConfigAllowedValue{
+	"app:defaultnewblock": {
+		Schema:       makeNullableStringSchema("Default widget type used for newly created blocks."),
+		ValidateFunc: validateConfigStringValue(nil),
+	},
+	"app:showoverlayblocknums": {
+		Schema:       makeNullableBoolSchema("Show block number overlays in the UI."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"app:ctrlvpaste": {
+		Schema:       makeNullableBoolSchema("Enable Ctrl+V paste behavior."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"app:confirmquit": {
+		Schema:       makeNullableBoolSchema("Ask for confirmation before quitting Wave."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"app:hideaibutton": {
+		Schema:       makeNullableBoolSchema("Hide the AI button in the UI."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"app:disablectrlshiftarrows": {
+		Schema:       makeNullableBoolSchema("Disable Ctrl+Shift+Arrow shortcuts."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"app:disablectrlshiftdisplay": {
+		Schema:       makeNullableBoolSchema("Disable Ctrl+Shift display shortcuts."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"app:focusfollowscursor": {
+		Schema:       makeNullableEnumStringSchema("Control whether focus follows the cursor.", "off", "on", "term"),
+		ValidateFunc: validateConfigStringValue([]string{"off", "on", "term"}),
+	},
+	"app:tabbar": {
+		Schema:       makeNullableEnumStringSchema("Choose where the tab bar is shown.", "top", "left"),
+		ValidateFunc: validateConfigStringValue([]string{"top", "left"}),
+	},
+	"feature:waveappbuilder": {
+		Schema:       makeNullableBoolSchema("Enable or disable the Wave app builder feature."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"waveai:showcloudmodes": {
+		Schema:       makeNullableBoolSchema("Show Wave cloud AI modes in the mode picker."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"waveai:defaultmode": {
+		Schema:       makeNullableStringSchema("Default Wave AI mode to select."),
+		ValidateFunc: validateConfigStringValue(nil),
+	},
+	"term:fontsize": {
+		Schema:       makeNullableNumberSchema("Terminal font size."),
+		ValidateFunc: validateConfigNumberValue(),
+	},
+	"term:fontfamily": {
+		Schema:       makeNullableStringSchema("Terminal font family."),
+		ValidateFunc: validateConfigStringValue(nil),
+	},
+	"term:theme": {
+		Schema:       makeNullableStringSchema("Terminal theme name."),
+		ValidateFunc: validateConfigStringValue(nil),
+	},
+	"term:disablewebgl": {
+		Schema:       makeNullableBoolSchema("Disable terminal WebGL rendering."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"term:copyonselect": {
+		Schema:       makeNullableBoolSchema("Copy terminal selections automatically."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"term:allowbracketedpaste": {
+		Schema:       makeNullableBoolSchema("Allow bracketed paste in the terminal."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"term:shiftenternewline": {
+		Schema:       makeNullableBoolSchema("Insert a newline when Shift+Enter is pressed."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"term:macoptionismeta": {
+		Schema:       makeNullableBoolSchema("Treat the Mac Option key as Meta."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"term:cursor": {
+		Schema:       makeNullableStringSchema("Terminal cursor style."),
+		ValidateFunc: validateConfigStringValue(nil),
+	},
+	"term:cursorblink": {
+		Schema:       makeNullableBoolSchema("Enable cursor blinking in the terminal."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"term:bellsound": {
+		Schema:       makeNullableBoolSchema("Enable terminal bell sounds."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"term:bellindicator": {
+		Schema:       makeNullableBoolSchema("Enable terminal bell indicators."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"term:osc52": {
+		Schema:       makeNullableEnumStringSchema("Terminal OSC52 clipboard behavior.", "focus", "always"),
+		ValidateFunc: validateConfigStringValue([]string{"focus", "always"}),
+	},
+	"term:durable": {
+		Schema:       makeNullableBoolSchema("Keep terminal state durable across reloads."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"editor:minimapenabled": {
+		Schema:       makeNullableBoolSchema("Show the code editor minimap."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"editor:stickyscrollenabled": {
+		Schema:       makeNullableBoolSchema("Enable sticky scroll in the code editor."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"editor:wordwrap": {
+		Schema:       makeNullableBoolSchema("Enable word wrap in the code editor."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"editor:fontsize": {
+		Schema:       makeNullableNumberSchema("Code editor font size."),
+		ValidateFunc: validateConfigNumberValue(),
+	},
+	"editor:inlinediff": {
+		Schema:       makeNullableBoolSchema("Show code diffs inline in the editor."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"web:openlinksinternally": {
+		Schema:       makeNullableBoolSchema("Open web links inside Wave."),
+		ValidateFunc: validateConfigBoolValue(),
+	},
+	"web:defaulturl": {
+		Schema:       makeNullableStringSchema("Default URL for new web widgets."),
+		ValidateFunc: validateConfigStringValue(nil),
+	},
+	"web:defaultsearch": {
+		Schema:       makeNullableStringSchema("Default search URL template for web widgets."),
+		ValidateFunc: validateConfigStringValue(nil),
+	},
+}
+
+func makeNullableBoolSchema(description string) map[string]any {
+	return map[string]any{
+		"anyOf": []any{
+			map[string]any{
+				"type":        "boolean",
+				"description": description,
+			},
+			map[string]any{
+				"type": "null",
+			},
+		},
+	}
+}
+
+func makeNullableNumberSchema(description string) map[string]any {
+	return map[string]any{
+		"anyOf": []any{
+			map[string]any{
+				"type":        "number",
+				"description": description,
+			},
+			map[string]any{
+				"type": "null",
+			},
+		},
+	}
+}
+
+func makeNullableStringSchema(description string) map[string]any {
+	return map[string]any{
+		"anyOf": []any{
+			map[string]any{
+				"type":        "string",
+				"description": description,
+			},
+			map[string]any{
+				"type": "null",
+			},
+		},
+	}
+}
+
+func makeNullableEnumStringSchema(description string, values ...string) map[string]any {
+	return map[string]any{
+		"anyOf": []any{
+			map[string]any{
+				"type":        "string",
+				"description": description,
+				"enum":        values,
+			},
+			map[string]any{
+				"type": "null",
+			},
+		},
+	}
+}
+
+func validateConfigBoolValue() func(any) error {
+	return func(val any) error {
+		if val == nil {
+			return nil
+		}
+		if _, ok := val.(bool); !ok {
+			return fmt.Errorf("must be a boolean or null")
+		}
+		return nil
+	}
+}
+
+func validateConfigNumberValue() func(any) error {
+	return func(val any) error {
+		if val == nil {
+			return nil
+		}
+		if _, ok := val.(float64); !ok {
+			return fmt.Errorf("must be a number or null")
+		}
+		return nil
+	}
+}
+
+func validateConfigStringValue(enumValues []string) func(any) error {
+	return func(val any) error {
+		if val == nil {
+			return nil
+		}
+		strVal, ok := val.(string)
+		if !ok {
+			return fmt.Errorf("must be a string or null")
+		}
+		if len(enumValues) == 0 {
+			return nil
+		}
+		for _, enumVal := range enumValues {
+			if strVal == enumVal {
+				return nil
+			}
+		}
+		return fmt.Errorf("must be one of: %s", strings.Join(enumValues, ", "))
+	}
+}
+
+func parseSetConfigInput(input any) (*setConfigToolInput, error) {
+	result := &setConfigToolInput{}
+	if input == nil {
+		return nil, fmt.Errorf("input is required")
+	}
+	if err := utilfn.ReUnmarshal(result, input); err != nil {
+		return nil, fmt.Errorf("invalid input format: %w", err)
+	}
+	if len(result.Config) == 0 {
+		return nil, fmt.Errorf("config must contain at least one setting")
+	}
+	return result, nil
+}
+
+func validateSetConfigInput(input any) (*setConfigToolInput, error) {
+	result, err := parseSetConfigInput(input)
+	if err != nil {
+		return nil, err
+	}
+	for configKey, val := range result.Config {
+		allowedSetting, ok := setConfigAllowedSettings[configKey]
+		if !ok {
+			return nil, fmt.Errorf("config key %q is not allowed", configKey)
+		}
+		if err := allowedSetting.ValidateFunc(val); err != nil {
+			return nil, fmt.Errorf("invalid value for %s: %w", configKey, err)
+		}
+	}
+	return result, nil
+}
+
+func verifySetConfigInput(input any, _ *uctypes.UIMessageDataToolUse) error {
+	_, err := validateSetConfigInput(input)
+	return err
+}
+
+func setConfigCallback(input any, toolUseData *uctypes.UIMessageDataToolUse) (any, error) {
+	parsedInput, err := validateSetConfigInput(input)
+	if err != nil {
+		return nil, err
+	}
+	err = wconfig.SetBaseConfigValue(parsedInput.Config)
+	if err != nil {
+		return nil, err
+	}
+	return map[string]any{
+		"success":      true,
+		"updated_keys": getSortedConfigKeys(parsedInput.Config),
+	}, nil
+}
+
+func getSortedConfigKeys(config waveobj.MetaMapType) []string {
+	keys := make([]string, 0, len(config))
+	for key := range config {
+		keys = append(keys, key)
+	}
+	sort.Strings(keys)
+	return keys
+}
+
+func getSetConfigSchemaProperties() map[string]any {
+	properties := make(map[string]any, len(setConfigAllowedSettings))
+	for configKey, allowedSetting := range setConfigAllowedSettings {
+		properties[configKey] = allowedSetting.Schema
+	}
+	return properties
+}
+
+func GetSetConfigToolDefinition() uctypes.ToolDefinition {
+	return uctypes.ToolDefinition{
+		Name:        SetConfigToolName,
+		DisplayName: "Set Wave Config",
+		Description: "Update a small whitelist of safe Wave configuration settings. Use null to remove a setting and restore its default behavior.",
+		ToolLogName: "app:setconfig",
+		Strict:      true,
+		InputSchema: map[string]any{
+			"type": "object",
+			"properties": map[string]any{
+				"config": map[string]any{
+					"type":                 "object",
+					"description":          "Configuration key/value pairs to update. Only the listed keys are allowed.",
+					"properties":           getSetConfigSchemaProperties(),
+					"additionalProperties": false,
+					"minProperties":        1,
+				},
+			},
+			"required":             []string{"config"},
+			"additionalProperties": false,
+		},
+		ToolCallDesc: func(input any, output any, toolUseData *uctypes.UIMessageDataToolUse) string {
+			parsedInput, err := parseSetConfigInput(input)
+			if err != nil {
+				return fmt.Sprintf("error parsing input: %v", err)
+			}
+			return fmt.Sprintf("updating Wave config keys: %s", strings.Join(getSortedConfigKeys(parsedInput.Config), ", "))
+		},
+		ToolAnyCallback: setConfigCallback,
+		ToolApproval: func(input any) string {
+			return uctypes.ApprovalNeedsApproval
+		},
+		ToolVerifyInput: verifySetConfigInput,
+	}
+}
diff --git a/pkg/aiusechat/tools_setconfig_test.go b/pkg/aiusechat/tools_setconfig_test.go
new file mode 100644
index 0000000000..57bb250019
--- /dev/null
+++ b/pkg/aiusechat/tools_setconfig_test.go
@@ -0,0 +1,174 @@
+// Copyright 2026, Command Line Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package aiusechat
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/wavetermdev/waveterm/pkg/aiusechat/uctypes"
+	"github.com/wavetermdev/waveterm/pkg/wavebase"
+	"github.com/wavetermdev/waveterm/pkg/wconfig"
+)
+
+func TestParseSetConfigInput(t *testing.T) {
+	input := map[string]any{
+		"config": map[string]any{
+			"web:defaulturl": "https://example.com",
+		},
+	}
+
+	parsedInput, err := parseSetConfigInput(input)
+	if err != nil {
+		t.Fatalf("parseSetConfigInput failed: %v", err)
+	}
+	if parsedInput.Config["web:defaulturl"] != "https://example.com" {
+		t.Fatalf("expected web:defaulturl to be preserved, got %#v", parsedInput.Config["web:defaulturl"])
+	}
+
+	_, err = parseSetConfigInput(map[string]any{})
+	if err == nil {
+		t.Fatalf("expected missing config error")
+	}
+}
+
+func TestVerifySetConfigInputRejectsUnsafeKeysAndTypes(t *testing.T) {
+	err := verifySetConfigInput(map[string]any{
+		"config": map[string]any{
+			"ai:apitoken": "secret",
+		},
+	}, &uctypes.UIMessageDataToolUse{})
+	if err == nil {
+		t.Fatalf("expected ai:apitoken to be rejected")
+	}
+
+	err = verifySetConfigInput(map[string]any{
+		"config": map[string]any{
+			"term:fontsize": "large",
+		},
+	}, &uctypes.UIMessageDataToolUse{})
+	if err == nil {
+		t.Fatalf("expected invalid term:fontsize type to be rejected")
+	}
+
+	err = verifySetConfigInput(map[string]any{
+		"config": map[string]any{
+			"app:tabbar": "bottom",
+		},
+	}, &uctypes.UIMessageDataToolUse{})
+	if err == nil {
+		t.Fatalf("expected invalid app:tabbar enum to be rejected")
+	}
+}
+
+func TestSetConfigCallbackWritesAndRemovesConfig(t *testing.T) {
+	tmpConfigDir, err := os.MkdirTemp("", "setconfig-tool")
+	if err != nil {
+		t.Fatalf("failed to create temp config dir: %v", err)
+	}
+	defer os.RemoveAll(tmpConfigDir)
+
+	err = os.MkdirAll(tmpConfigDir, 0755)
+	if err != nil {
+		t.Fatalf("failed to create config dir: %v", err)
+	}
+
+	oldConfigHome := wavebase.ConfigHome_VarCache
+	defer func() {
+		wavebase.ConfigHome_VarCache = oldConfigHome
+	}()
+	wavebase.ConfigHome_VarCache = tmpConfigDir
+
+	toolUse := &uctypes.UIMessageDataToolUse{}
+	_, err = setConfigCallback(map[string]any{
+		"config": map[string]any{
+			"web:defaulturl":    "https://example.com",
+			"term:fontsize":     14.0,
+			"term:copyonselect": true,
+		},
+	}, toolUse)
+	if err != nil {
+		t.Fatalf("setConfigCallback failed: %v", err)
+	}
+
+	configFile := filepath.Join(tmpConfigDir, wconfig.SettingsFile)
+	if _, err := os.Stat(configFile); err != nil {
+		t.Fatalf("expected settings file to be written: %v", err)
+	}
+
+	storedConfig, cerrs := wconfig.ReadWaveHomeConfigFile(wconfig.SettingsFile)
+	if len(cerrs) > 0 {
+		t.Fatalf("unexpected config read errors: %v", cerrs)
+	}
+	if storedConfig["web:defaulturl"] != "https://example.com" {
+		t.Fatalf("expected web:defaulturl to be written, got %#v", storedConfig["web:defaulturl"])
+	}
+	if storedConfig["term:fontsize"] != float64(14) {
+		t.Fatalf("expected term:fontsize to be 14, got %#v", storedConfig["term:fontsize"])
+	}
+	if storedConfig["term:copyonselect"] != true {
+		t.Fatalf("expected term:copyonselect to be true, got %#v", storedConfig["term:copyonselect"])
+	}
+
+	_, err = setConfigCallback(map[string]any{
+		"config": map[string]any{
+			"web:defaulturl": nil,
+		},
+	}, toolUse)
+	if err != nil {
+		t.Fatalf("setConfigCallback remove failed: %v", err)
+	}
+
+	storedConfig, cerrs = wconfig.ReadWaveHomeConfigFile(wconfig.SettingsFile)
+	if len(cerrs) > 0 {
+		t.Fatalf("unexpected config read errors after remove: %v", cerrs)
+	}
+	if _, ok := storedConfig["web:defaulturl"]; ok {
+		t.Fatalf("expected web:defaulturl to be removed")
+	}
+}
+
+func TestGetSetConfigToolDefinition(t *testing.T) {
+	toolDef := GetSetConfigToolDefinition()
+
+	if toolDef.Name != SetConfigToolName {
+		t.Fatalf("expected tool name %q, got %q", SetConfigToolName, toolDef.Name)
+	}
+	if toolDef.ToolLogName != "app:setconfig" {
+		t.Fatalf("expected tool log name app:setconfig, got %q", toolDef.ToolLogName)
+	}
+	if toolDef.ToolAnyCallback == nil {
+		t.Fatalf("ToolAnyCallback should not be nil")
+	}
+	if toolDef.ToolVerifyInput == nil {
+		t.Fatalf("ToolVerifyInput should not be nil")
+	}
+	if toolDef.ToolApproval == nil {
+		t.Fatalf("ToolApproval should not be nil")
+	}
+
+	properties, ok := toolDef.InputSchema["properties"].(map[string]any)
+	if !ok {
+		t.Fatalf("tool input schema properties should be a map")
+	}
+	configSchema, ok := properties["config"].(map[string]any)
+	if !ok {
+		t.Fatalf("config schema should be a map")
+	}
+	configProperties, ok := configSchema["properties"].(map[string]any)
+	if !ok {
+		t.Fatalf("config schema properties should be a map")
+	}
+	if _, ok := configProperties["web:defaulturl"]; !ok {
+		t.Fatalf("expected whitelisted key web:defaulturl in schema")
+	}
+	if _, ok := configProperties["ai:apitoken"]; ok {
+		t.Fatalf("did not expect ai:apitoken in schema")
+	}
+
+	if approval := toolDef.ToolApproval(nil); approval != uctypes.ApprovalNeedsApproval {
+		t.Fatalf("expected approval %q, got %q", uctypes.ApprovalNeedsApproval, approval)
+	}
+}