feat(settings): report which saved keys need a restart

Every settings update answered with a bare success, so the console could not
tell a change that took effect at once from one written to the file that the
running program would keep ignoring until it was restarted — the listener
address, the storage paths, the Komari dashboard URL.

Classify the patch instead. config.RestartRequiredKeys expands a patch into the
dot-separated paths of its leaves and intersects them with the settings main
reads before it starts serving, and the settings endpoint returns that list as
data.restartRequired. It is a pure function of the patch, so UpdateSettings
keeps its signature and nothing else has to change; the write succeeds either
way, and the field only says which edits are not live.

Matching is by overlap rather than equality, so a patch that names a section —
replacing it, or deleting it with a null — reports the startup-only keys inside
it, while a sibling subtree like webhook.endpoints is not mistaken for
webhook.enabled.

The result is never nil, so an update with nothing to report serializes as []
rather than null and a client can iterate it without a guard.

The console reads the field in ConfigSection and warns instead of confirming,
naming the keys that are pending; Settings.vue's hints for the Komari URL, the
listen address and the storage paths now say which of their fields is affected
rather than labelling the whole card.

README.md

@@ -294,6 +294,18 @@ Admins and trusted groups are defined **per bot channel** and map a member ID to
 | `{{ list.offlineServers }}` | Formatted list of offline servers |
 | `{{ softwareVersion }}`, `{{ softwareBuildVer }}`, `{{ softwareCommitHash }}`, `{{ softwareBuildType }}`, `{{ softwareBuildTime }}`, `{{ softwareDeveloper }}`, `{{ softwareDescription }}` | Build metadata (commit hash and build time are injected at compile time) |
 
+### What applies without a restart
+
+Saving settings applies most of them immediately. How each group takes effect:
+
+| Settings | How it applies |
+|---|---|
+| `controllerMethod` (all five channels) | Every channel is **rebuilt**: the running controllers are stopped and a fresh set is built from the new settings. A channel that owns a connection reconnects — Telegram re-runs its `getMe` handshake, NapCat opens a new WebSocket — so notifications sent during the swap are lost. The rebuild only happens when this section actually changed; saving a message template does not disturb the channels. |
+| `controllerMessage`, `debug`, `bot_user_config.json`, `bot_node_config.json`, `webhook.endpoints` | Picked up as they are used; nothing is restarted. |
+| `system.debugMode` | Applies to both behavior and log filtering. |
+| `system.networkProxy` | Read on every request and every dial, so a new address reaches channels that are already running. Only the per-channel `networkUseProxy` opt-in is fixed when a channel is built, so toggling that still needs the rebuild above. |
+| `system.listenAddr` / `listenPort`, `webhook.enabled` / `listenAddr` / `listenPort`, `dataPath`, `dbPath`, `komari.dashboardURL` | **Applied at startup only.** Saving them changes the file and the in-memory configuration but not the running listener, database or Komari client — restart to apply. |
+
 ## API
 
 Success responses follow the envelope `{"success": true, "message": "...", "data": {...}}`, with the payload nested under a single `data` key. Error responses use `{"success": false, "message": "..."}`. `message` may be omitted on success when there is nothing to report.
@@ -322,7 +334,7 @@ Browser WebSocket handshakes cannot carry custom headers, so `/api/system/getLog
 | `/api/server/getStatus` | GET | admin | Live server status (mirrors the Bot's `/status`). Query `?uuid=<uuid>` (or `all`). Returns `data: {<uuid>: {uuid, name, online, report}}`; `report` is `null` when the node has not reported yet. `404` for an unknown single uuid. |
 | `/api/server/exec` | POST | bot / admin | Execute a command. Body `{uuid: [<uuid>...], command}`. Dispatches a Komari task and polls until completion (or timeout). Returns `data: {taskID, results}`. |
 | `/api/settings/get` | GET | admin | `?type=global\|bot_user_config\|bot_node_config` | Returns `data: {config}`, where `config` is the selected config file's content (same layout as the JSON file). |
-| `/api/settings/set` | POST | admin | `?type=<same types>` + JSON body of partial updates, e.g. `{"system":{"debugMode":true}}` | Deep-merges the body into the selected config file, persists it, and reloads it in memory. Only the given keys change; arrays replace. |
+| `/api/settings/set` | POST | admin | `?type=<same types>` + JSON body of partial updates, e.g. `{"system":{"debugMode":true}}` | Deep-merges the body into the selected config file, persists it, and reloads it in memory. Only the given keys change; arrays replace. Returns `data: {type, restartRequired}`, where `restartRequired` lists the keys the update changed that are only read at startup (see [What applies without a restart](#what-applies-without-a-restart)) — the write succeeds regardless, this only says which edits are not live yet. Always an array, empty when everything took effect. |
 | `/api/webhook/add` | POST | admin | Add an incoming webhook endpoint. Body `{name, enabled?, token?, notifyPipes?}` — only the fields given are stored, the rest start at their defaults. `409` when the name is already configured. |
 | `/api/webhook/modify` | POST | admin | Change an existing endpoint. Body `{name, ...}` — the fields given are the fields that change (same partial-update rule as `/api/settings/set`, but scoped to one endpoint). `404` for an unknown name, `400` when no other field is given. |
 | `/api/webhook/delete` | POST | admin | Remove an endpoint. Body `{name}`. `404` for an unknown name. |

config/reload.go

@@ -0,0 +1,81 @@
+package config
+
+import (
+	"fmt"
+	"sync"
+
+	"nukumizu-backend/postLog"
+)
+
+// reloadHooks are the callbacks run after the global configuration has been
+// reloaded, i.e. after every settings update that touches config.json.
+//
+// They exist so that packages which already depend on config — the controller
+// manager, the logger — can react to an update without config importing them,
+// which would be an import cycle. Everything a hook needs is passed in.
+var (
+	reloadHooksMu sync.Mutex
+	reloadHooks   []func(*Config)
+
+	// reloadRunMu serializes hook execution. A hook mutates process-wide state
+	// — the logger's debug flag, the controller registry — so two overlapping
+	// settings updates must not run them at the same time, or both would decide
+	// to rebuild the controllers from their own view of what was applied.
+	reloadRunMu sync.Mutex
+)
+
+// OnReload registers a hook to run after every reload of the global
+// configuration, receiving the configuration now in effect. Hooks run in
+// registration order.
+//
+// Register once, at startup, before the first settings update can arrive: a
+// hook registered later has already missed the updates that came before it, and
+// the configuration it would have seen is not replayed.
+//
+// A hook runs on the goroutine serving /api/settings/set, so it must not block
+// for long. It may be called concurrently by two overlapping updates.
+func OnReload(hook func(*Config)) {
+	reloadHooksMu.Lock()
+	defer reloadHooksMu.Unlock()
+	reloadHooks = append(reloadHooks, hook)
+}
+
+// notifyReload runs every registered hook with cfg. A nil cfg is the signal
+// that the update touched one of the other settings files, which have no
+// hook-visible reload, and it is ignored.
+//
+// A panicking hook is logged and skipped rather than allowed to unwind through
+// UpdateSettings: by the time hooks run the new configuration is already on
+// disk and published in memory, so reporting the write as failed would be a
+// lie, and the hooks registered after the broken one must still run.
+func notifyReload(cfg *Config) {
+	if cfg == nil {
+		return
+	}
+
+	// Copy under the registry lock, then release it before running anything: a
+	// hook is free to register another hook without deadlocking.
+	reloadHooksMu.Lock()
+	hooks := make([]func(*Config), len(reloadHooks))
+	copy(hooks, reloadHooks)
+	reloadHooksMu.Unlock()
+
+	reloadRunMu.Lock()
+	defer reloadRunMu.Unlock()
+	for _, hook := range hooks {
+		runReloadHook(hook, cfg)
+	}
+}
+
+// runReloadHook runs one hook, isolating a panic to that hook. Recovering in a
+// separate function rather than inline is deliberate: a deferred recover placed
+// in the loop body would not run until notifyReload itself returned, which
+// would abandon the remaining hooks.
+func runReloadHook(hook func(*Config), cfg *Config) {
+	defer func() {
+		if r := recover(); r != nil {
+			postLog.Error(fmt.Sprintf("Configuration reload hook panicked: %v", r))
+		}
+	}()
+	hook(cfg)
+}

config/reload_test.go

@@ -0,0 +1,173 @@
+package config
+
+import (
+	"reflect"
+	"testing"
+
+	"nukumizu-backend/global"
+)
+
+// swapReloadHooks replaces the registered reload hooks for the duration of a
+// test and restores the previous set afterwards, so the package-level registry
+// cannot leak into another test.
+func swapReloadHooks(t *testing.T, hooks ...func(*Config)) {
+	t.Helper()
+
+	reloadHooksMu.Lock()
+	original := reloadHooks
+	reloadHooks = hooks
+	reloadHooksMu.Unlock()
+
+	t.Cleanup(func() {
+		reloadHooksMu.Lock()
+		reloadHooks = original
+		reloadHooksMu.Unlock()
+	})
+}
+
+func TestReloadHookRunsOnlyForGlobalSettings(t *testing.T) {
+	writeTempConfig(t, &global.ConfigPath.Global, `{"system":{"debugMode":false}}`)
+	writeTempConfig(t, &global.ConfigPath.BotUserConfig, `{}`)
+	writeTempConfig(t, &global.ConfigPath.BotNodeConfig, `{}`)
+
+	var seen []bool
+	swapReloadHooks(t, func(cfg *Config) {
+		seen = append(seen, cfg.System.DebugMode)
+	})
+
+	// A config.json update runs the hook, with the values just written.
+	if err := UpdateSettings(SettingGlobal, map[string]interface{}{
+		"system": map[string]interface{}{"debugMode": true},
+	}); err != nil {
+		t.Fatalf("UpdateSettings(global): %v", err)
+	}
+
+	if len(seen) != 1 {
+		t.Fatalf("hook ran %d times for a config.json update, want 1", len(seen))
+	}
+	if !seen[0] {
+		t.Error("hook received a configuration without the updated debugMode")
+	}
+
+	// The other two files reload a singleton that callers read at the point of
+	// use, so they have nothing to notify.
+	for _, settingsType := range []string{SettingBotUserConfig, SettingBotNodeConfig} {
+		if err := UpdateSettings(settingsType, map[string]interface{}{
+			"unused": map[string]interface{}{"event_reply": true},
+		}); err != nil {
+			t.Fatalf("UpdateSettings(%s): %v", settingsType, err)
+		}
+	}
+
+	if len(seen) != 1 {
+		t.Errorf("hook ran %d times after updates to the other settings files, want 1", len(seen))
+	}
+}
+
+func TestReloadHookIsolatesPanic(t *testing.T) {
+	writeTempConfig(t, &global.ConfigPath.Global, `{"system":{"debugMode":false}}`)
+
+	reached := false
+	swapReloadHooks(t,
+		func(*Config) { panic("hook under test") },
+		func(*Config) { reached = true },
+	)
+
+	// The configuration is already on disk and published by the time hooks run,
+	// so a broken hook must not turn a successful write into a failed request.
+	if err := UpdateSettings(SettingGlobal, map[string]interface{}{
+		"system": map[string]interface{}{"debugMode": true},
+	}); err != nil {
+		t.Fatalf("a panicking hook must not fail the settings write: %v", err)
+	}
+	if !reached {
+		t.Error("a panicking hook stopped the hooks registered after it")
+	}
+
+	// The write itself must still have landed.
+	cfg := Current()
+	if cfg == nil || !cfg.System.DebugMode {
+		t.Error("the settings write did not take effect")
+	}
+}
+
+// TestUnrelatedUpdateLeavesControllerMethodAlone guards the trigger for a
+// controller rebuild. Whether to rebuild is decided by comparing the whole
+// controllerMethod section with the one the running controllers were built
+// from, so reloading the file has to reproduce that section byte for byte. A
+// default applied inconsistently — a nil recipient slice turned into an empty
+// one on the second load, say — would make every settings edit look like a
+// controller change and tear down every channel on each save.
+func TestUnrelatedUpdateLeavesControllerMethodAlone(t *testing.T) {
+	writeTempConfig(t, &global.ConfigPath.Global, `{
+    "controllerMethod": {
+        "qq(napcat)": { "enabled": false },
+        "email": { "enabled": false, "to": [] },
+        "webhook": { "enabled": false, "headers": {} }
+    }
+}`)
+
+	first, err := LoadGlobalConfig(global.ConfigPath.Global)
+	if err != nil {
+		t.Fatalf("LoadGlobalConfig: %v", err)
+	}
+	before := first.ControllerMethod
+
+	if err := UpdateSettings(SettingGlobal, map[string]interface{}{
+		"controllerMessage": map[string]interface{}{"BOT_STARTED": "hello"},
+	}); err != nil {
+		t.Fatalf("UpdateSettings: %v", err)
+	}
+
+	after := Current().ControllerMethod
+	if !reflect.DeepEqual(before, after) {
+		t.Errorf("an unrelated update changed the controllerMethod section:\nbefore: %+v\nafter:  %+v", before, after)
+	}
+}
+
+// TestReloadHookSeesEveryWriterPath pins the invariant that each writer of
+// config.json notifies, not just /api/settings/set: the webhook endpoint
+// helpers go through the same channel.
+func TestReloadHookSeesEveryWriterPath(t *testing.T) {
+	writeTempConfig(t, &global.ConfigPath.Global, `{
+    "webhook": { "endpoints": {} }
+}`)
+
+	var seen int
+	swapReloadHooks(t, func(*Config) { seen++ })
+
+	if err := AddWebhookEndpoint("example", map[string]interface{}{
+		"enabled":     true,
+		"token":       "secret",
+		"notifyPipes": []interface{}{"ntfy"},
+	}); err != nil {
+		t.Fatalf("AddWebhookEndpoint: %v", err)
+	}
+	if seen != 1 {
+		t.Errorf("hook ran %d times after adding an endpoint, want 1", seen)
+	}
+
+	if err := ModifyWebhookEndpoint("example", map[string]interface{}{
+		"enabled": false,
+	}); err != nil {
+		t.Fatalf("ModifyWebhookEndpoint: %v", err)
+	}
+	if seen != 2 {
+		t.Errorf("hook ran %d times after modifying an endpoint, want 2", seen)
+	}
+
+	if err := DeleteWebhookEndpoint("example"); err != nil {
+		t.Fatalf("DeleteWebhookEndpoint: %v", err)
+	}
+	if seen != 3 {
+		t.Errorf("hook ran %d times after deleting an endpoint, want 3", seen)
+	}
+
+	// A rejected write changes nothing, so it must not notify either.
+	if err := DeleteWebhookEndpoint("ghost"); err == nil {
+		t.Error("deleting an unknown endpoint should fail")
+	}
+	if seen != 3 {
+		t.Errorf("hook ran for a rejected write (%d notifications, want 3)", seen)
+	}
+}

config/settings.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"sync"
 
 	"nukumizu-backend/global"
@@ -23,6 +24,89 @@ const (
 // accepted constants above.
 var ErrUnsupportedSettingsType = errors.New("unsupported settings type")
 
+// startupOnlySettings are the config.json keys that are read once before the
+// program starts serving and never again: the listener addresses, the paths the
+// databases are opened from, and the Komari dashboard its client is built
+// against. Editing one writes the file and replaces the in-memory
+// configuration, but the running program keeps the old value, so an update that
+// touches one is reported back to the caller instead of being silently
+// accepted.
+//
+// Keep this in step with main: these are exactly the settings main reads before
+// the HTTP server comes up. Everything else — controllerMethod, networkProxy,
+// the message templates, the debug switches — is picked up at runtime.
+var startupOnlySettings = []string{
+	"system.listenAddr",
+	"system.listenPort",
+	"webhook.enabled",
+	"webhook.listenAddr",
+	"webhook.listenPort",
+	"komari.dashboardURL",
+	"dataPath",
+	"dbPath",
+}
+
+// RestartRequiredKeys lists the settings in patch that only take effect at
+// startup, as dot-separated paths, in the order startupOnlySettings declares
+// them. Only config.json carries such settings; an update to one of the other
+// files always reports nothing.
+//
+// The write itself succeeds either way — this is advice for the user, not a
+// rejection. The result is never nil, so a caller can put it straight into a
+// JSON response and get [] rather than null.
+func RestartRequiredKeys(settingsType string, patch map[string]interface{}) []string {
+	keys := []string{}
+	if settingsType != SettingGlobal {
+		return keys
+	}
+
+	patched := patchPaths(patch)
+	for _, watched := range startupOnlySettings {
+		for _, path := range patched {
+			if pathsOverlap(path, watched) {
+				keys = append(keys, watched)
+				break
+			}
+		}
+	}
+	return keys
+}
+
+// patchPaths expands a nested settings patch into the dot-separated paths of its
+// leaves. An object is descended into rather than reported, so a patch that only
+// names sections still resolves to the keys it changes, and a JSON null is a
+// leaf because it deletes the key it names.
+func patchPaths(patch map[string]interface{}) []string {
+	paths := []string{}
+	var walk func(prefix string, node map[string]interface{})
+	walk = func(prefix string, node map[string]interface{}) {
+		for key, value := range node {
+			path := key
+			if prefix != "" {
+				path = prefix + "." + key
+			}
+			if nested, ok := value.(map[string]interface{}); ok && nested != nil {
+				walk(path, nested)
+				continue
+			}
+			paths = append(paths, path)
+		}
+	}
+	walk("", patch)
+	return paths
+}
+
+// pathsOverlap reports whether a patched path and a watched setting can affect
+// each other: they are the same key, the patch names something inside the
+// watched setting, or the patch names a section the watched setting lives in.
+// The last case matters because a patch may replace a whole section, which
+// changes every key under it.
+func pathsOverlap(patched, watched string) bool {
+	return patched == watched ||
+		strings.HasPrefix(patched, watched+".") ||
+		strings.HasPrefix(watched, patched+".")
+}
+
 // settingsLock serializes read-modify-write access to the on-disk configuration
 // files so concurrent admin edits (UpdateSettings) and the node tracker's
 // background save (SaveBotNodeConfig) cannot lose each other's updates.
@@ -82,19 +166,45 @@ func GetSettings(settingsType string) ([]byte, error) {
 // written the matching in-memory singleton is reloaded so runtime code observes
 // the new values.
 func UpdateSettings(settingsType string, patch map[string]interface{}) error {
-	settingsLock.Lock()
+	return runSettingsUpdate(func() (*Config, error) {
-	defer settingsLock.Unlock()
+		return updateSettingsLocked(settingsType, patch)
+	})
+}
 
-	return updateSettingsLocked(settingsType, patch)
+// runSettingsUpdate runs fn under settingsLock and then, once the lock is
+// released, runs the reload hooks with whatever configuration fn reports (nil
+// when the update did not touch config.json).
+//
+// The hooks deliberately run outside settingsLock. A hook rebuilds controllers,
+// which can wait on a network call, while settingsLock is also held by the node
+// tracker's background save (SaveBotNodeConfig); holding it across a hook would
+// stall node registration behind an unrelated settings edit.
+func runSettingsUpdate(fn func() (*Config, error)) error {
+	cfg, err := func() (*Config, error) {
+		settingsLock.Lock()
+		defer settingsLock.Unlock()
+		return fn()
+	}()
+	if err != nil {
+		return err
+	}
+
+	notifyReload(cfg)
+	return nil
 }
 
 // updateSettingsLocked is UpdateSettings without the locking, for callers that
 // need to inspect the loaded configuration and write in one critical section
 // (see the incoming webhook endpoint helpers). Callers must hold settingsLock.
-func updateSettingsLocked(settingsType string, patch map[string]interface{}) error {
+//
+// It returns the freshly loaded global configuration, or nil when the settings
+// type is one of the other files. The caller is responsible for handing that
+// value to notifyReload once settingsLock is released — which runSettingsUpdate
+// does for every writer.
+func updateSettingsLocked(settingsType string, patch map[string]interface{}) (*Config, error) {
 	path, err := settingsPath(settingsType)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	// Start from whatever is already on disk so nothing is dropped. A missing or
@@ -104,23 +214,23 @@ func updateSettingsLocked(settingsType string, patch map[string]interface{}) err
 	if err == nil {
 		if len(bytes.TrimSpace(data)) > 0 {
 			if err := json.Unmarshal(data, &current); err != nil {
-				return fmt.Errorf("failed to parse existing %s settings file %s: %w", settingsType, path, err)
+				return nil, fmt.Errorf("failed to parse existing %s settings file %s: %w", settingsType, path, err)
 			}
 		}
 	} else if !os.IsNotExist(err) {
-		return fmt.Errorf("failed to read existing %s settings file %s: %w", settingsType, path, err)
+		return nil, fmt.Errorf("failed to read existing %s settings file %s: %w", settingsType, path, err)
 	}
 
 	deepMergeSettings(current, patch)
 
 	data, err = json.MarshalIndent(current, "", "    ")
 	if err != nil {
-		return fmt.Errorf("failed to marshal %s settings: %w", settingsType, err)
+		return nil, fmt.Errorf("failed to marshal %s settings: %w", settingsType, err)
 	}
 	data = append(data, '\n')
 
 	if err := os.WriteFile(path, data, 0o644); err != nil {
-		return fmt.Errorf("failed to write %s settings file %s: %w", settingsType, path, err)
+		return nil, fmt.Errorf("failed to write %s settings file %s: %w", settingsType, path, err)
 	}
 
 	return reloadSettings(settingsType, path)
@@ -151,18 +261,19 @@ func deepMergeSettings(dst, src map[string]interface{}) {
 }
 
 // reloadSettings refreshes the in-memory singleton for the given settings type
-// so the running program observes the values just persisted to disk.
+// so the running program observes the values just persisted to disk. Only
-func reloadSettings(settingsType, path string) error {
+// config.json has a hook-visible reload, so for SettingGlobal it returns the
+// configuration now in effect and for the other types it returns nil.
+func reloadSettings(settingsType, path string) (*Config, error) {
 	switch settingsType {
 	case SettingGlobal:
-		_, err := LoadGlobalConfig(path)
+		return LoadGlobalConfig(path)
-		return err
 	case SettingBotUserConfig:
 		_, err := LoadBotUserConfig(path)
-		return err
+		return nil, err
 	case SettingBotNodeConfig:
-		return LoadBotNodeConfig(path)
+		return nil, LoadBotNodeConfig(path)
 	default:
-		return ErrUnsupportedSettingsType
+		return nil, ErrUnsupportedSettingsType
 	}
 }

config/settings_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+	"reflect"
 	"strings"
 	"testing"
 
@@ -148,6 +149,162 @@ func TestUpdateSettingsReplacesArraysAndKeepsNumbers(t *testing.T) {
 	}
 }
 
+func TestRestartRequiredKeys(t *testing.T) {
+	cases := []struct {
+		name         string
+		settingsType string
+		patch        map[string]interface{}
+		want         []string
+	}{
+		{
+			name:         "a runtime switch needs no restart",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"system": map[string]interface{}{"debugMode": true}},
+			want:         []string{},
+		},
+		{
+			name:         "the listen port does",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"system": map[string]interface{}{"listenPort": "9090"}},
+			want:         []string{"system.listenPort"},
+		},
+		{
+			name:         "only the startup key of a mixed patch is reported",
+			settingsType: SettingGlobal,
+			patch: map[string]interface{}{
+				"system": map[string]interface{}{"listenPort": "9090", "debugMode": true},
+			},
+			want: []string{"system.listenPort"},
+		},
+		{
+			name:         "a top-level path is reported",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"dataPath": "/srv/data"},
+			want:         []string{"dataPath"},
+		},
+		{
+			name:         "results follow the declared order, not the patch order",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"dbPath": "/srv/db", "dataPath": "/srv/data"},
+			want:         []string{"dataPath", "dbPath"},
+		},
+		{
+			name:         "deleting a startup key with null is reported",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"system": map[string]interface{}{"listenPort": nil}},
+			want:         []string{"system.listenPort"},
+		},
+		{
+			name:         "replacing a whole section reports the startup keys inside it",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"webhook": map[string]interface{}{"listenAddr": "127.0.0.1"}},
+			want:         []string{"webhook.listenAddr"},
+		},
+		{
+			// Deleting the section resets the URL to its built-in default.
+			name:         "deleting a section the startup key lives in reports it",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"komari": nil},
+			want:         []string{"komari.dashboardURL"},
+		},
+		{
+			name:         "deleting a section reports every startup key inside it",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"webhook": nil},
+			want:         []string{"webhook.enabled", "webhook.listenAddr", "webhook.listenPort"},
+		},
+		{
+			// An empty object merges nothing, so it changes no key and needs no
+			// restart — surprising enough to pin.
+			name:         "an empty object changes nothing",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{"komari": map[string]interface{}{}},
+			want:         []string{},
+		},
+		{
+			// webhook.endpoints must not be mistaken for webhook.enabled.
+			name:         "a sibling subtree is not mistaken for the startup key",
+			settingsType: SettingGlobal,
+			patch: map[string]interface{}{
+				"webhook": map[string]interface{}{
+					"endpoints": map[string]interface{}{"example": map[string]interface{}{"enabled": true}},
+				},
+			},
+			want: []string{},
+		},
+		{
+			// The Komari credentials are re-read on the next login, so only the
+			// dashboard URL is startup-only.
+			name:         "komari credentials are not startup-only",
+			settingsType: SettingGlobal,
+			patch: map[string]interface{}{
+				"komari": map[string]interface{}{
+					"account": map[string]interface{}{"username": "admin", "password": "x"},
+				},
+			},
+			want: []string{},
+		},
+		{
+			name:         "controller settings are not startup-only",
+			settingsType: SettingGlobal,
+			patch: map[string]interface{}{
+				"controllerMethod": map[string]interface{}{
+					"telegram": map[string]interface{}{"enabled": true, "botToken": "t"},
+				},
+			},
+			want: []string{},
+		},
+		{
+			name:         "an empty patch reports nothing",
+			settingsType: SettingGlobal,
+			patch:        map[string]interface{}{},
+			want:         []string{},
+		},
+		{
+			// Only config.json has settings that are read once at startup.
+			name:         "the other settings files never need a restart",
+			settingsType: SettingBotUserConfig,
+			patch:        map[string]interface{}{"dataPath": "/srv/data"},
+			want:         []string{},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := RestartRequiredKeys(tc.settingsType, tc.patch)
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("RestartRequiredKeys() = %v, want %v", got, tc.want)
+			}
+			if got == nil {
+				t.Error("the result must never be nil, so it serializes as [] rather than null")
+			}
+		})
+	}
+}
+
+// TestRestartRequiredKeysIsAdvisory pins that reporting a startup-only key does
+// not stop the write: the caller is told, the file is still updated.
+func TestRestartRequiredKeysIsAdvisory(t *testing.T) {
+	writeTempConfig(t, &global.ConfigPath.Global, `{"system":{"listenPort":"8080"}}`)
+
+	keys := RestartRequiredKeys(SettingGlobal, map[string]interface{}{
+		"system": map[string]interface{}{"listenPort": "9090"},
+	})
+	if len(keys) != 1 {
+		t.Fatalf("expected the listen port to be reported, got %v", keys)
+	}
+
+	if err := UpdateSettings(SettingGlobal, map[string]interface{}{
+		"system": map[string]interface{}{"listenPort": "9090"},
+	}); err != nil {
+		t.Fatalf("UpdateSettings: %v", err)
+	}
+
+	if got := Current().System.ListenPort; got != "9090" {
+		t.Errorf("the update was not applied: listenPort = %q", got)
+	}
+}
+
 func TestSettingsTypeValidation(t *testing.T) {
 	for _, valid := range []string{SettingGlobal, SettingBotUserConfig, SettingBotNodeConfig} {
 		if !IsValidSettingsType(valid) {

config/webhook.go

@@ -60,13 +60,12 @@ func AddWebhookEndpoint(name string, fields map[string]interface{}) error {
 		return err
 	}
 
-	settingsLock.Lock()
+	return runSettingsUpdate(func() (*Config, error) {
-	defer settingsLock.Unlock()
+		if _, exists := webhookEndpoint(name); exists {
-
+			return nil, fmt.Errorf("%w: %s", ErrWebhookEndpointExists, name)
-	if _, exists := webhookEndpoint(name); exists {
+		}
-		return fmt.Errorf("%w: %s", ErrWebhookEndpointExists, name)
+		return updateSettingsLocked(SettingGlobal, webhookEndpointsPatch(name, patch))
-	}
+	})
-	return updateSettingsLocked(SettingGlobal, webhookEndpointsPatch(name, patch))
 }
 
 // ModifyWebhookEndpoint updates an existing incoming webhook endpoint. Only the
@@ -84,27 +83,24 @@ func ModifyWebhookEndpoint(name string, fields map[string]interface{}) error {
 		return fmt.Errorf("%w: no fields to update", ErrWebhookEndpointInvalid)
 	}
 
-	settingsLock.Lock()
+	return runSettingsUpdate(func() (*Config, error) {
-	defer settingsLock.Unlock()
+		if _, exists := webhookEndpoint(name); !exists {
-
+			return nil, fmt.Errorf("%w: %s", ErrWebhookEndpointNotFound, name)
-	if _, exists := webhookEndpoint(name); !exists {
+		}
-		return fmt.Errorf("%w: %s", ErrWebhookEndpointNotFound, name)
+		return updateSettingsLocked(SettingGlobal, webhookEndpointsPatch(name, patch))
-	}
+	})
-	return updateSettingsLocked(SettingGlobal, webhookEndpointsPatch(name, patch))
 }
 
 // DeleteWebhookEndpoint removes the incoming webhook endpoint registered under
 // name. The endpoint stops accepting requests as soon as the configuration is
 // reloaded.
 func DeleteWebhookEndpoint(name string) error {
-	settingsLock.Lock()
+	return runSettingsUpdate(func() (*Config, error) {
-	defer settingsLock.Unlock()
+		if _, exists := webhookEndpoint(name); !exists {
-
+			return nil, fmt.Errorf("%w: %s", ErrWebhookEndpointNotFound, name)
-	if _, exists := webhookEndpoint(name); !exists {
+		}
-		return fmt.Errorf("%w: %s", ErrWebhookEndpointNotFound, name)
+		return updateSettingsLocked(SettingGlobal, webhookEndpointDeletePatch(name))
-	}
+	})
-
-	return updateSettingsLocked(SettingGlobal, webhookEndpointDeletePatch(name))
 }
 
 // webhookEndpoint returns the named endpoint held by the loaded configuration.

frontend/src/api/index.js

@@ -13,6 +13,10 @@ export const serverApi = {
 
 // /api/settings/get?type=… / /api/settings/set?type=…
 // get → { success, message, data: { config } }.
+// set → { success, message, data: { type, restartRequired } }, where
+//       restartRequired lists the keys the update changed that are only read at
+//       startup, so the caller can say which edits are not live yet. It is
+//       always an array, empty when the whole update took effect.
 // `type` is one of global | bot_user_config | bot_node_config.
 // For set, pass a partial object; a JSON null value removes that key.
 export const settingsApi = {

frontend/src/components/ConfigSection.vue

@@ -133,8 +133,15 @@ async function save() {
     const patch = wrapRoot(props.section, nest(obj));
     saving.value = true;
     try {
-        await settingsApi.set('global', patch);
+        const res = await settingsApi.set('global', patch);
-        toast.success(`${props.section.title} saved`);
+        // The backend reports the keys it wrote that are only read at startup.
+        // A plain "saved" would suggest those are live too.
+        const pending = (res && res.data && res.data.restartRequired) || [];
+        if (pending.length) {
+            toast.warn(`${props.section.title} saved — restart to apply: ${pending.join(', ')}`, 7000);
+        } else {
+            toast.success(`${props.section.title} saved`);
+        }
         emit('saved');
     } catch (e) {
         toast.error('Failed to save: ' + e.message);

frontend/src/views/Settings.vue

@@ -11,7 +11,7 @@ const sections = [
     {
         id: 'system',
         title: 'System',
-        hint: 'HTTP listener and global runtime switches.',
+        hint: 'HTTP listener and global runtime switches. A changed listen address or port applies on restart.',
         root: ['system'],
         fields: [
             { key: 'debugMode', type: 'bool', label: 'Debug mode', help: 'Skipped X-Timestamp checks and verbose debug logging.' },
@@ -37,7 +37,7 @@ const sections = [
     {
         id: 'komari',
         title: 'Komari dashboard',
-        hint: 'Connection the monitor reads node data from. Takes effect on restart.',
+        hint: 'Connection the monitor reads node data from. The URL applies on restart; the account is re-read on the next login.',
         root: ['komari'],
         fields: [
             { key: 'dashboardURL', type: 'text', label: 'Dashboard URL' },

handler/settings.go

@@ -47,6 +47,10 @@ func SettingsGetHandler(w http.ResponseWriter, r *http.Request) {
 //	{"system": {"debugMode": true}}
 //
 // Multiple entries may be given at once; only the provided keys are changed.
+//
+// The response carries data.restartRequired: the keys the update changed that
+// are only read at startup, so the caller can say which edits are not live yet.
+// It is empty for an update that took effect in full.
 func SettingsSetHandler(w http.ResponseWriter, r *http.Request) {
 	if !utils.Auth(w, r, "POST", "admin") {
 		return
@@ -80,7 +84,10 @@ func SettingsSetHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// The write landed either way. This only tells the caller which of the keys
+	// it changed will not be live until the program is restarted.
 	utils.SendSuccessResponse(w, "settings updated successfully", map[string]interface{}{
-		"type": settingsType,
+		"type":            settingsType,
+		"restartRequired": config.RestartRequiredKeys(settingsType, patch),
 	})
 }

handler/settings_test.go

@@ -0,0 +1,128 @@
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"nukumizu-backend/config"
+	"nukumizu-backend/global"
+)
+
+// tempConfigFile points one of the settings paths at a throwaway file, so a
+// test can drive the settings API without touching the config files in the
+// working directory.
+func tempConfigFile(t *testing.T, field *string, content string) {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatalf("write temp config: %v", err)
+	}
+	original := *field
+	*field = path
+	t.Cleanup(func() { *field = original })
+}
+
+// settingsSetRequest builds an authenticated POST for the settings endpoint.
+func settingsSetRequest(t *testing.T, settingsType, body string) *http.Request {
+	t.Helper()
+	req := httptest.NewRequest(
+		http.MethodPost,
+		"/api/settings/set?type="+settingsType,
+		strings.NewReader(body),
+	)
+	req.Header.Set("X-Token", "test-admin-token")
+	req.Header.Set("X-Timestamp", strconv.FormatInt(time.Now().Unix(), 10))
+	return req
+}
+
+// settingsSetResponse is the envelope /api/settings/set answers with.
+type settingsSetResponse struct {
+	Success bool `json:"success"`
+	Data    struct {
+		Type            string   `json:"type"`
+		RestartRequired []string `json:"restartRequired"`
+	} `json:"data"`
+}
+
+func decodeSettingsSetResponse(t *testing.T, w *httptest.ResponseRecorder) settingsSetResponse {
+	t.Helper()
+	var body settingsSetResponse
+	if err := json.Unmarshal(w.Body.Bytes(), &body); err != nil {
+		t.Fatalf("decode response: %v; body=%s", err, w.Body.String())
+	}
+	return body
+}
+
+// TestSettingsSetReportsStartupOnlyKeys covers the field the console reads to
+// tell the user which of their edits are not live yet.
+func TestSettingsSetReportsStartupOnlyKeys(t *testing.T) {
+	setupAdminToken()
+	tempConfigFile(t, &global.ConfigPath.Global, `{"system":{"debugMode":false,"listenPort":"8080"}}`)
+
+	w := httptest.NewRecorder()
+	SettingsSetHandler(w, settingsSetRequest(t, "global",
+		`{"system":{"listenPort":"9090","debugMode":true}}`))
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("status = %d, body = %s", w.Code, w.Body.String())
+	}
+	body := decodeSettingsSetResponse(t, w)
+	if !body.Success {
+		t.Fatalf("not a success envelope: %s", w.Body.String())
+	}
+	if body.Data.Type != "global" {
+		t.Errorf("data.type = %q, want global", body.Data.Type)
+	}
+	if len(body.Data.RestartRequired) != 1 || body.Data.RestartRequired[0] != "system.listenPort" {
+		t.Errorf("restartRequired = %v, want [system.listenPort]", body.Data.RestartRequired)
+	}
+
+	// Being reported as startup-only must not stop the write.
+	data, err := config.GetSettings(config.SettingGlobal)
+	if err != nil {
+		t.Fatalf("GetSettings: %v", err)
+	}
+	for _, want := range []string{`"listenPort": "9090"`, `"debugMode": true`} {
+		if !strings.Contains(string(data), want) {
+			t.Errorf("the patch was not applied, missing %s:\n%s", want, data)
+		}
+	}
+}
+
+// TestSettingsSetRestartRequiredIsAlwaysAnArray pins the shape a client
+// iterates over: an update with nothing to report must answer [] and not null.
+func TestSettingsSetRestartRequiredIsAlwaysAnArray(t *testing.T) {
+	setupAdminToken()
+	tempConfigFile(t, &global.ConfigPath.Global, `{"system":{"debugMode":false}}`)
+
+	w := httptest.NewRecorder()
+	SettingsSetHandler(w, settingsSetRequest(t, "global", `{"system":{"debugMode":true}}`))
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("status = %d, body = %s", w.Code, w.Body.String())
+	}
+	if !strings.Contains(w.Body.String(), `"restartRequired":[]`) {
+		t.Errorf("restartRequired should serialize as an empty array: %s", w.Body.String())
+	}
+}
+
+// TestSettingsSetRejectsUnknownType keeps the failure path intact now that the
+// success path computes an extra field.
+func TestSettingsSetRejectsUnknownType(t *testing.T) {
+	setupAdminToken()
+	tempConfigFile(t, &global.ConfigPath.Global, `{}`)
+
+	w := httptest.NewRecorder()
+	SettingsSetHandler(w, settingsSetRequest(t, "nonsense", `{}`))
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("status = %d, want 400", w.Code)
+	}
+}

internal/controller/controller.go

@@ -3,8 +3,10 @@ package controller
 import (
 	"errors"
 	"fmt"
+	"reflect"
 	"strings"
 	"sync"
+	"sync/atomic"
 
 	"nukumizu-backend/config"
 	"nukumizu-backend/internal/node"
@@ -109,6 +111,12 @@ type BotController interface {
 type Manager struct {
 	mu          sync.RWMutex
 	controllers map[string]Controller
+
+	// builtFrom records the controllerMethod section the registered controllers
+	// were built from, so a settings update that concerns them can be told apart
+	// from one that does not. It is read on the settings-update goroutine and
+	// written when the set is replaced.
+	builtFrom atomic.Pointer[config.ControllerMethodConfig]
 }
 
 var globalManager *Manager
@@ -126,12 +134,70 @@ func GetManager() *Manager {
 	return globalManager
 }
 
-// Register adds a controller to the manager.
+// NeedsRebuild reports whether next differs from the controllerMethod section
-func (m *Manager) Register(c Controller) {
+// the registered controllers were built from. A manager with no controllers yet
+// always reports true, so the first call installs the initial set.
+//
+// Controllers are rebuilt wholesale rather than reconfigured in place: each one
+// reads its settings into fields at construction, and two of them own
+// connections that cannot be re-pointed (the NapCat WebSocket listener is
+// stopped through a sync.Once, the Telegram polling context is created with the
+// controller). Replacing the set keeps every channel on the same footing.
+func (m *Manager) NeedsRebuild(next config.ControllerMethodConfig) bool {
+	built := m.builtFrom.Load()
+	if built == nil {
+		return true
+	}
+	// The section carries a header map and a recipient slice, so it is not
+	// comparable with ==.
+	return !reflect.DeepEqual(*built, next)
+}
+
+// ReplaceAll stops every registered controller and swaps in next, which the
+// caller built from method. It is the only way controllers are installed, at
+// startup and after a settings change alike.
+//
+// The swap happens under the registry lock so routing flips to the new set
+// atomically; stopping and starting happen outside it. Both can block — Stop
+// closes sockets, Start performs a handshake — and holding m.mu across them
+// would stall every notification for the duration.
+func (m *Manager) ReplaceAll(next []Controller, method config.ControllerMethodConfig) {
 	m.mu.Lock()
-	defer m.mu.Unlock()
+	previous := m.controllers
-	m.controllers[c.Name()] = c
+	m.controllers = make(map[string]Controller, len(next))
-	postLog.Info("Controller registered: " + c.Name())
+	for _, ctrl := range next {
+		m.controllers[ctrl.Name()] = ctrl
+	}
+	m.mu.Unlock()
+
+	m.builtFrom.Store(&method)
+
+	names := make([]string, 0, len(next))
+	for _, ctrl := range next {
+		names = append(names, ctrl.Name())
+	}
+	postLog.Info("Controller set installed: " + strings.Join(names, ", "))
+
+	for _, ctrl := range previous {
+		ctrl.Stop()
+	}
+
+	// Start off the calling goroutine, the way startup does: Telegram's getMe
+	// and the NapCat WebSocket handshake would otherwise hold the settings
+	// request open for as long as they take. The new controllers are already
+	// routable, and each one can send before Start returns.
+	for _, ctrl := range next {
+		go func(ctrl Controller) {
+			defer func() {
+				if r := recover(); r != nil {
+					postLog.Error(fmt.Sprintf("Controller %s panicked on start: %v", ctrl.Name(), r))
+				}
+			}()
+			if err := ctrl.Start(); err != nil {
+				postLog.Error(fmt.Sprintf("Failed to start controller %s: %v", ctrl.Name(), err))
+			}
+		}(ctrl)
+	}
 }
 
 // ShowBotInitMessage sends the bot initialization message to all enabled

internal/controller/controller_test.go

@@ -0,0 +1,222 @@
+package controller
+
+import (
+	"sync"
+	"testing"
+	"time"
+
+	"nukumizu-backend/config"
+	"nukumizu-backend/internal/node"
+)
+
+// fakeController records the lifecycle calls it receives so a test can assert
+// what ReplaceAll did to it. Start signals on started, because ReplaceAll starts
+// controllers off the calling goroutine.
+type fakeController struct {
+	name    string
+	started chan struct{}
+
+	mu     sync.Mutex
+	starts int
+	stops  int
+}
+
+func newFake(name string) *fakeController {
+	return &fakeController{name: name, started: make(chan struct{}, 4)}
+}
+
+func (f *fakeController) Name() string     { return f.name }
+func (f *fakeController) IsEnabled() bool  { return true }
+func (f *fakeController) IsMarkdown() bool { return false }
+
+func (f *fakeController) Start() error {
+	f.mu.Lock()
+	f.starts++
+	f.mu.Unlock()
+	select {
+	case f.started <- struct{}{}:
+	default:
+	}
+	return nil
+}
+
+func (f *fakeController) Stop() {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.stops++
+}
+
+func (f *fakeController) lifecycle() (starts, stops int) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return f.starts, f.stops
+}
+
+func (f *fakeController) SendStatusChange(node.StatusChange) error               { return nil }
+func (f *fakeController) SendServerList(string, string) error                    { return nil }
+func (f *fakeController) SendExecuteResult(string, string, string, string) error { return nil }
+func (f *fakeController) SendAlert(Alert) error                                  { return nil }
+
+// waitStarted blocks until the controller's Start has run.
+func (f *fakeController) waitStarted(t *testing.T) {
+	t.Helper()
+	select {
+	case <-f.started:
+	case <-time.After(5 * time.Second):
+		t.Fatalf("controller %s was never started", f.name)
+	}
+}
+
+func newTestManager() *Manager {
+	return &Manager{controllers: make(map[string]Controller)}
+}
+
+// routedTo returns the controller the manager currently routes the given name
+// to.
+func (m *Manager) routedTo(name string) Controller {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.controllers[name]
+}
+
+func TestReplaceAllInstallsAndStarts(t *testing.T) {
+	m := newTestManager()
+	alpha, beta := newFake("alpha"), newFake("beta")
+
+	m.ReplaceAll([]Controller{alpha, beta}, config.ControllerMethodConfig{})
+
+	alpha.waitStarted(t)
+	beta.waitStarted(t)
+
+	if got := m.routedTo("alpha"); got != Controller(alpha) {
+		t.Errorf("alpha is not routable after ReplaceAll: %v", got)
+	}
+	if got := m.routedTo("beta"); got != Controller(beta) {
+		t.Errorf("beta is not routable after ReplaceAll: %v", got)
+	}
+}
+
+// TestReplaceAllStopsTheOutgoingSet is the invariant the rebuild relies on: the
+// old controllers must be shut down, or a rebuilt NapCat or Telegram controller
+// would leave its previous connection running.
+func TestReplaceAllStopsTheOutgoingSet(t *testing.T) {
+	m := newTestManager()
+	outgoing := newFake("alpha")
+	m.ReplaceAll([]Controller{outgoing}, config.ControllerMethodConfig{})
+	outgoing.waitStarted(t)
+
+	incoming := newFake("alpha")
+	m.ReplaceAll([]Controller{incoming}, config.ControllerMethodConfig{})
+	incoming.waitStarted(t)
+
+	if starts, stops := outgoing.lifecycle(); starts != 1 || stops != 1 {
+		t.Errorf("outgoing controller lifecycle = %d starts / %d stops, want 1/1", starts, stops)
+	}
+	if _, stops := incoming.lifecycle(); stops != 0 {
+		t.Errorf("incoming controller was stopped %d times", stops)
+	}
+	if got := m.routedTo("alpha"); got != Controller(incoming) {
+		t.Error("routing still points at the outgoing controller")
+	}
+}
+
+func TestReplaceAllDropsChannelsLeftOut(t *testing.T) {
+	m := newTestManager()
+	m.ReplaceAll([]Controller{newFake("alpha"), newFake("beta")}, config.ControllerMethodConfig{})
+
+	m.ReplaceAll([]Controller{newFake("beta")}, config.ControllerMethodConfig{})
+
+	if got := m.routedTo("alpha"); got != nil {
+		t.Errorf("a channel missing from the new set is still routable: %v", got)
+	}
+	if got := m.routedTo("beta"); got == nil {
+		t.Error("the surviving channel is not routable")
+	}
+}
+
+func TestNeedsRebuild(t *testing.T) {
+	m := newTestManager()
+	base := config.ControllerMethodConfig{
+		Email: config.EmailConfig{Enabled: true, SMTPPort: 587, To: []string{"a@example.com"}},
+	}
+
+	if !m.NeedsRebuild(base) {
+		t.Error("a manager with nothing installed must report that a rebuild is needed")
+	}
+
+	m.ReplaceAll(nil, base)
+	if m.NeedsRebuild(base) {
+		t.Error("the settings the set was built from must not ask for another rebuild")
+	}
+
+	changed := base
+	changed.Email.Enabled = false
+	if !m.NeedsRebuild(changed) {
+		t.Error("a changed email setting must ask for a rebuild")
+	}
+
+	// The section carries maps and slices, so it is compared by value rather
+	// than by identity: equal content must not trigger a rebuild.
+	withHeaders := config.ControllerMethodConfig{
+		Webhook: config.WebhookConfig{Headers: map[string]string{"X-Token": "t"}},
+	}
+	m.ReplaceAll(nil, withHeaders)
+	equalHeaders := config.ControllerMethodConfig{
+		Webhook: config.WebhookConfig{Headers: map[string]string{"X-Token": "t"}},
+	}
+	if m.NeedsRebuild(equalHeaders) {
+		t.Error("equal header maps must not ask for a rebuild")
+	}
+
+	differentHeaders := config.ControllerMethodConfig{
+		Webhook: config.WebhookConfig{Headers: map[string]string{"X-Token": "other"}},
+	}
+	if !m.NeedsRebuild(differentHeaders) {
+		t.Error("a changed header must ask for a rebuild")
+	}
+}
+
+// TestReplaceAllDuringNotification drives ReplaceAll while notifications are
+// being routed. Run with -race: the swap replaces the map the routing path
+// reads, which is what the registry lock exists to make safe.
+func TestReplaceAllDuringNotification(t *testing.T) {
+	m := newTestManager()
+	m.ReplaceAll([]Controller{newFake("alpha")}, config.ControllerMethodConfig{})
+
+	var readers, writers sync.WaitGroup
+	stop := make(chan struct{})
+
+	for i := 0; i < 3; i++ {
+		readers.Add(1)
+		go func() {
+			defer readers.Done()
+			for {
+				select {
+				case <-stop:
+					return
+				default:
+				}
+				m.NotifyStatusChange(node.StatusChange{UUID: "u1", Name: "alpha", Event: "Online"})
+				_ = m.IsMarkdown("alpha")
+			}
+		}()
+	}
+
+	writers.Add(1)
+	go func() {
+		defer writers.Done()
+		for i := 0; i < 20; i++ {
+			m.ReplaceAll([]Controller{newFake("alpha"), newFake("beta")}, config.ControllerMethodConfig{})
+		}
+	}()
+
+	// Let the writer finish, then release the readers: they only return once
+	// stop is closed.
+	writers.Wait()
+	close(stop)
+	readers.Wait()
+
+	if got := m.routedTo("beta"); got == nil {
+		t.Error("the last installed set is not routable")
+	}
+}

internal/controller/pipes/email.go

@@ -2,6 +2,7 @@ package pipes
 
 import (
 	"fmt"
+	"net"
 
 	gomail "gopkg.in/mail.v2"
 
@@ -14,22 +15,34 @@ import (
 )
 
 // EmailController handles email notifications via SMTP.
+//
+// cfg is written once, by the constructor, and never again: a controller that
+// needs different settings is replaced wholesale by the manager rather than
+// reconfigured in place, so the send methods can read it without locking.
 type EmailController struct {
 	cfg config.EmailConfig
 }
 
 // NewEmailController creates a new Email controller.
 func NewEmailController(cfg config.EmailConfig) *EmailController {
-	if cfg.NetworkUseProxy {
+	applyEmailProxy(cfg.NetworkUseProxy)
-		// Route SMTP through the HTTP CONNECT proxy. NetDialTimeout is
-		// gomail's documented hook for overriding how the SMTP connection is
-		// dialed. There is a single global email channel, so overriding it
-		// unconditionally when the flag is set is safe.
-		gomail.NetDialTimeout = netproxy.DialWithTimeout(true)
-	}
 	return &EmailController{cfg: cfg}
 }
 
+// applyEmailProxy routes SMTP through the HTTP CONNECT proxy, or restores a
+// direct dial. gomail exposes the dial path as the package-level
+// NetDialTimeout, whose own default is net.DialTimeout, so turning the proxy
+// off has to put that back rather than leave the hook in place. There is a
+// single global email channel, so setting a package-level hook here is
+// unambiguous.
+func applyEmailProxy(useProxy bool) {
+	if useProxy {
+		gomail.NetDialTimeout = netproxy.DialWithTimeout(true)
+		return
+	}
+	gomail.NetDialTimeout = net.DialTimeout
+}
+
 // Name returns the controller name.
 func (e *EmailController) Name() string {
 	return "email"

internal/controller/pipes/email_proxy_test.go

@@ -0,0 +1,54 @@
+package pipes
+
+import (
+	"net"
+	"reflect"
+	"testing"
+
+	gomail "gopkg.in/mail.v2"
+
+	"nukumizu-backend/config"
+)
+
+// dialerIsDefault reports whether gomail still dials directly. Function values
+// are not comparable in Go, so the code pointers are compared instead.
+func dialerIsDefault() bool {
+	return reflect.ValueOf(gomail.NetDialTimeout).Pointer() ==
+		reflect.ValueOf(net.DialTimeout).Pointer()
+}
+
+// TestApplyEmailProxyRestoresDefaultDialer covers the case the constructor used
+// to get wrong. gomail exposes its dial hook as a package-level variable with no
+// unset, and the code only installed the proxy dialer when the flag was set, so
+// turning networkUseProxy back off left SMTP tunnelled through a proxy nobody
+// had asked for — with no way to undo it short of a restart.
+func TestApplyEmailProxyRestoresDefaultDialer(t *testing.T) {
+	t.Cleanup(func() { gomail.NetDialTimeout = net.DialTimeout })
+
+	applyEmailProxy(true)
+	if dialerIsDefault() {
+		t.Fatal("applyEmailProxy(true) did not install the proxy dialer")
+	}
+
+	applyEmailProxy(false)
+	if !dialerIsDefault() {
+		t.Error("applyEmailProxy(false) left the proxy dialer in place")
+	}
+}
+
+// TestNewEmailControllerAppliesProxySetting pins that the dialer follows the
+// settings a controller is built with, which is what makes a rebuilt controller
+// pick up a changed proxy flag.
+func TestNewEmailControllerAppliesProxySetting(t *testing.T) {
+	t.Cleanup(func() { gomail.NetDialTimeout = net.DialTimeout })
+
+	NewEmailController(config.EmailConfig{NetworkUseProxy: true})
+	if dialerIsDefault() {
+		t.Error("a controller built with networkUseProxy: true did not install the proxy dialer")
+	}
+
+	NewEmailController(config.EmailConfig{NetworkUseProxy: false})
+	if !dialerIsDefault() {
+		t.Error("a controller rebuilt with networkUseProxy: false left the proxy dialer in place")
+	}
+}

internal/controller/pipes/ntfy.go

@@ -15,6 +15,11 @@ import (
 )
 
 // NtfyController handles notifications via ntfy.sh or a self-hosted ntfy server.
+//
+// cfg and httpClient are written once, by the constructor, and never again: a
+// controller that needs different settings is replaced wholesale by the manager
+// rather than reconfigured in place, so the send methods can read them without
+// locking.
 type NtfyController struct {
 	cfg        config.NtfyConfig
 	httpClient *http.Client

internal/controller/pipes/webhook.go

@@ -16,6 +16,11 @@ import (
 )
 
 // WebhookController handles notifications via generic HTTP webhooks.
+//
+// cfg and httpClient are written once, by the constructor, and never again: a
+// controller that needs different settings is replaced wholesale by the manager
+// rather than reconfigured in place, so the send methods can read them without
+// locking.
 type WebhookController struct {
 	cfg        config.WebhookConfig
 	httpClient *http.Client

internal/netproxy/netproxy.go

@@ -2,6 +2,10 @@
 // network proxy configured in the system config. Each caller decides whether
 // to use the proxy by passing its own useProxy flag (the per-channel
 // networkUseProxy setting), so proxying is opt-in per channel.
+//
+// The opt-in is captured when a client is built, but the proxy address is not:
+// it is read again on every request and every dial, so editing
+// system.networkProxy takes effect on clients that already exist.
 package netproxy
 
 import (
@@ -39,19 +43,23 @@ func proxyURL() *url.URL {
 }
 
 // ProxyFunc returns a transport proxy function that routes requests through
-// the configured network proxy when enabled. It returns nil when the caller
+// the configured network proxy when enabled, and nil when the caller opts out
-// opts out or no proxy is configured, meaning direct connection. The returned
+// of proxying entirely. The returned function is compatible with both
-// function is compatible with both http.Transport.Proxy and
+// http.Transport.Proxy and websocket.Dialer.Proxy.
-// websocket.Dialer.Proxy.
+//
+// The proxy address is resolved on every call rather than once here, so a
+// settings update that changes system.networkProxy reaches a client that was
+// already built. That is also why opting out is the only case that returns nil:
+// a function resolved to nothing at construction time would pin its client to
+// whatever was configured then. A nil URL from the returned function means no
+// proxy is configured and the request goes direct.
 func ProxyFunc(useProxy bool) func(*http.Request) (*url.URL, error) {
 	if !useProxy {
 		return nil
 	}
-	u := proxyURL()
+	return func(*http.Request) (*url.URL, error) {
-	if u == nil {
+		return proxyURL(), nil
-		return nil
 	}
-	return http.ProxyURL(u)
 }
 
 // HTTPClient builds an http.Client that sends traffic through the configured
@@ -71,10 +79,16 @@ func HTTPClient(useProxy bool, timeout time.Duration) *http.Client {
 // through the configured HTTP CONNECT proxy when enabled. Its signature
 // matches net.DialTimeout so it can be plugged into gomail's NetDialTimeout
 // to send SMTP over the proxy.
+//
+// Like ProxyFunc it reads the proxy address per dial, so clearing or changing
+// system.networkProxy reaches a dialer that already exists.
 func DialWithTimeout(useProxy bool) func(network, addr string, timeout time.Duration) (net.Conn, error) {
-	u := proxyURL()
 	return func(network, addr string, timeout time.Duration) (net.Conn, error) {
-		if !useProxy || u == nil {
+		if !useProxy {
+			return net.DialTimeout(network, addr, timeout)
+		}
+		u := proxyURL()
+		if u == nil {
 			return net.DialTimeout(network, addr, timeout)
 		}
 		return dialViaProxy(u, addr, timeout)

internal/netproxy/netproxy_test.go

@@ -0,0 +1,133 @@
+package netproxy
+
+import (
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"nukumizu-backend/config"
+)
+
+// publishConfig writes a config.json and makes it the configuration in effect,
+// which is what a settings update does.
+func publishConfig(t *testing.T, body string) {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
+		t.Fatalf("write temp config: %v", err)
+	}
+	if _, err := config.LoadGlobalConfig(path); err != nil {
+		t.Fatalf("LoadGlobalConfig: %v", err)
+	}
+}
+
+// resolve runs a proxy function and returns the URL it chose, or "" when it
+// chose a direct connection.
+func resolve(t *testing.T, proxy func(*http.Request) (*url.URL, error)) string {
+	t.Helper()
+	req, err := http.NewRequest(http.MethodGet, "https://example.com/", nil)
+	if err != nil {
+		t.Fatalf("NewRequest: %v", err)
+	}
+	u, err := proxy(req)
+	if err != nil {
+		t.Fatalf("proxy function: %v", err)
+	}
+	if u == nil {
+		return ""
+	}
+	return u.String()
+}
+
+// TestProxyFuncResolvesPerCall is the property that makes system.networkProxy
+// hot-reloadable: the function handed to a transport keeps reading the live
+// configuration instead of the address that was configured when it was built.
+func TestProxyFuncResolvesPerCall(t *testing.T) {
+	publishConfig(t, `{"system":{"networkProxy":"http://127.0.0.1:7890"}}`)
+
+	proxy := ProxyFunc(true)
+	if proxy == nil {
+		t.Fatal("ProxyFunc(true) returned nil, so the channel would never proxy")
+	}
+	if got := resolve(t, proxy); got != "http://127.0.0.1:7890" {
+		t.Errorf("first resolution = %q", got)
+	}
+
+	// The same function must follow a settings update.
+	publishConfig(t, `{"system":{"networkProxy":"http://127.0.0.1:8888"}}`)
+	if got := resolve(t, proxy); got != "http://127.0.0.1:8888" {
+		t.Errorf("after a settings update the same function resolved %q", got)
+	}
+
+	// Clearing the proxy falls back to a direct connection.
+	publishConfig(t, `{"system":{"networkProxy":""}}`)
+	if got := resolve(t, proxy); got != "" {
+		t.Errorf("a cleared proxy still resolved %q", got)
+	}
+}
+
+func TestProxyFuncOptOutReturnsNil(t *testing.T) {
+	publishConfig(t, `{"system":{"networkProxy":"http://127.0.0.1:7890"}}`)
+
+	// A channel with networkUseProxy off must not be handed a function at all,
+	// so its transport keeps the default direct dialing.
+	if ProxyFunc(false) != nil {
+		t.Error("ProxyFunc(false) must return nil")
+	}
+}
+
+func TestProxyFuncNormalizesMissingScheme(t *testing.T) {
+	publishConfig(t, `{"system":{"networkProxy":"127.0.0.1:7890"}}`)
+
+	if got := resolve(t, ProxyFunc(true)); got != "http://127.0.0.1:7890" {
+		t.Errorf("resolved %q, want the http:// prefix added", got)
+	}
+}
+
+func TestProxyFuncIgnoresUnusableProxy(t *testing.T) {
+	// A value that cannot be parsed must leave the client dialing directly
+	// rather than failing every request.
+	publishConfig(t, `{"system":{"networkProxy":"://missing-scheme"}}`)
+
+	if got := resolve(t, ProxyFunc(true)); got != "" {
+		t.Errorf("an unparseable proxy resolved %q, want a direct connection", got)
+	}
+}
+
+// TestDialWithTimeoutDialsDirectlyWithoutProxy covers the path a cleared
+// system.networkProxy takes: the dialer was built while a proxy was configured,
+// and must fall back to a direct dial once there is none.
+func TestDialWithTimeoutDialsDirectlyWithoutProxy(t *testing.T) {
+	publishConfig(t, `{"system":{"networkProxy":"http://127.0.0.1:7890"}}`)
+
+	dial := DialWithTimeout(true)
+	if dial == nil {
+		t.Fatal("DialWithTimeout(true) returned nil")
+	}
+
+	// No proxy is listening on that address, so a dial attempted now would
+	// fail; clearing the setting is what makes the direct path reachable.
+	publishConfig(t, `{"system":{"networkProxy":""}}`)
+
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	defer ln.Close()
+	go func() {
+		conn, err := ln.Accept()
+		if err == nil {
+			conn.Close()
+		}
+	}()
+
+	conn, err := dial("tcp", ln.Addr().String(), 5*time.Second)
+	if err != nil {
+		t.Fatalf("dial through a cleared proxy: %v", err)
+	}
+	conn.Close()
+}

main.go

@@ -58,6 +58,27 @@ func main() {
 	postLog.SetDebugMode(cfg.System.DebugMode)
 	postLog.InitLogBroadcaster()
 
+	// A settings update replaces the configuration in memory; these hooks push
+	// the new values into the state that was derived from the old one. The
+	// logger's debug flag is process-wide rather than read at every log call,
+	// and each controller holds its own copy of its channel settings plus the
+	// clients built from them.
+	config.OnReload(func(updated *config.Config) {
+		postLog.SetDebugMode(updated.System.DebugMode)
+
+		mgr := controller.GetManager()
+		if mgr == nil || !mgr.NeedsRebuild(updated.ControllerMethod) {
+			return
+		}
+
+		// Controller settings changed. Each controller reads its settings into
+		// fields when it is built, and the NapCat and Telegram ones own
+		// connections that cannot be re-pointed, so the change is applied by
+		// replacing the whole set rather than reconfiguring it in place.
+		postLog.Info("Controller settings changed; rebuilding every channel")
+		mgr.ReplaceAll(buildControllers(updated), updated.ControllerMethod)
+	})
+
 	dbPath := cfg.DBPath
 
 	if err := postLog.InitLogsDatabase(fmt.Sprintf("%s/log.db", dbPath)); err != nil {
@@ -199,83 +220,28 @@ func startWebhookServer(cfg *config.Config) {
 	}()
 }
 
-// initControllers initializes and starts all configured controllers.
+// buildControllers constructs one controller per channel from the given
+// configuration. The set is built fresh whenever controller settings change,
+// because a controller reads its settings once at construction and two of them
+// own connections that cannot be re-pointed.
+func buildControllers(cfg *config.Config) []controller.Controller {
+	return []controller.Controller{
+		qq_napcat.NewQQController(cfg.ControllerMethod.QQ),
+		telegram.NewTelegramController(cfg.ControllerMethod.Telegram),
+		pipes.NewEmailController(cfg.ControllerMethod.Email),
+		pipes.NewNtfyController(cfg.ControllerMethod.Ntfy),
+		pipes.NewWebhookController(cfg.ControllerMethod.Webhook),
+	}
+}
+
+// initControllers installs the initial controller set.
 func initControllers() {
 	cfg := config.Current()
 	mgr := controller.GetManager()
-	if mgr == nil {
+	if mgr == nil || cfg == nil {
 		return
 	}
-
+	mgr.ReplaceAll(buildControllers(cfg), cfg.ControllerMethod)
-	// QQ (Napcat) controller.
-	qqCtrl := qq_napcat.NewQQController(cfg.ControllerMethod.QQ)
-	mgr.Register(qqCtrl)
-	go func() {
-		defer func() {
-			if r := recover(); r != nil {
-				postLog.Error(fmt.Sprintf("QQ controller panic: %v", r))
-			}
-		}()
-		if err := qqCtrl.Start(); err != nil {
-			postLog.Error("Failed to start QQ controller: " + err.Error())
-		}
-	}()
-
-	// Telegram controller.
-	tgCtrl := telegram.NewTelegramController(cfg.ControllerMethod.Telegram)
-	mgr.Register(tgCtrl)
-	go func() {
-		defer func() {
-			if r := recover(); r != nil {
-				postLog.Error(fmt.Sprintf("Telegram controller panic: %v", r))
-			}
-		}()
-		if err := tgCtrl.Start(); err != nil {
-			postLog.Error("Failed to start Telegram controller: " + err.Error())
-		}
-	}()
-
-	// Email controller (status-only).
-	emailCtrl := pipes.NewEmailController(cfg.ControllerMethod.Email)
-	mgr.Register(emailCtrl)
-	go func() {
-		defer func() {
-			if r := recover(); r != nil {
-				postLog.Error(fmt.Sprintf("Email controller panic: %v", r))
-			}
-		}()
-		if err := emailCtrl.Start(); err != nil {
-			postLog.Error("Failed to start Email controller: " + err.Error())
-		}
-	}()
-
-	// Ntfy controller (status-only).
-	ntfyCtrl := pipes.NewNtfyController(cfg.ControllerMethod.Ntfy)
-	mgr.Register(ntfyCtrl)
-	go func() {
-		defer func() {
-			if r := recover(); r != nil {
-				postLog.Error(fmt.Sprintf("Ntfy controller panic: %v", r))
-			}
-		}()
-		if err := ntfyCtrl.Start(); err != nil {
-			postLog.Error("Failed to start Ntfy controller: " + err.Error())
-		}
-	}()
-
-	// Webhook controller (status-only).
-	webhookCtrl := pipes.NewWebhookController(cfg.ControllerMethod.Webhook)
-	mgr.Register(webhookCtrl)
-	go func() {
-		defer func() {
-			if r := recover(); r != nil {
-				postLog.Error(fmt.Sprintf("Webhook controller panic: %v", r))
-			}
-		}()
-		if err := webhookCtrl.Start(); err != nil {
-			postLog.Error("Failed to start Webhook controller: " + err.Error())
-		}
-	}()
 }
 
 // startBackgroundTasks starts periodic background goroutines.