diff --git a/src/cli/command-secret-gateway.ts b/src/cli/command-secret-gateway.ts
index b61f1af7284..5228ce0baec 100644
--- a/src/cli/command-secret-gateway.ts
+++ b/src/cli/command-secret-gateway.ts
@@ -393,7 +393,7 @@ function collectInactiveSurfacePathsFromDiagnostics(diagnostics: string[]): Set<
 }
 
 function isUnsupportedSecretsResolveError(err: unknown): boolean {
-  const message = formatErrorMessage(err).toLowerCase();
+  const message = normalizeLowercaseStringOrEmpty(formatErrorMessage(err));
   if (!message.includes("secrets.resolve")) {
     return false;
   }
diff --git a/src/cli/completion-cli.ts b/src/cli/completion-cli.ts
index 08875a7f327..565597b9763 100644
--- a/src/cli/completion-cli.ts
+++ b/src/cli/completion-cli.ts
@@ -4,6 +4,7 @@ import path from "node:path";
 import { Command, Option } from "commander";
 import { resolveStateDir } from "../config/paths.js";
 import { routeLogsToStderr } from "../logging/console.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { formatDocsLink } from "../terminal/links.js";
 import { theme } from "../terminal/theme.js";
 import { pathExists } from "../utils.js";
@@ -24,7 +25,7 @@ function isCompletionShell(value: string): value is CompletionShell {
 
 export function resolveShellFromEnv(env: NodeJS.ProcessEnv = process.env): CompletionShell {
   const shellPath = env.SHELL?.trim() ?? "";
-  const shellName = shellPath ? path.basename(shellPath).toLowerCase() : "";
+  const shellName = shellPath ? normalizeLowercaseStringOrEmpty(path.basename(shellPath)) : "";
   if (shellName === "zsh") {
     return "zsh";
   }
diff --git a/src/cli/cron-cli/register.cron-add.ts b/src/cli/cron-cli/register.cron-add.ts
index 4aed799e61a..c1bd62f454c 100644
--- a/src/cli/cron-cli/register.cron-add.ts
+++ b/src/cli/cron-cli/register.cron-add.ts
@@ -2,7 +2,10 @@ import type { Command } from "commander";
 import type { CronJob } from "../../cron/types.js";
 import { sanitizeAgentId } from "../../routing/session-key.js";
 import { defaultRuntime } from "../../runtime.js";
-import { normalizeOptionalString } from "../../shared/string-coerce.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeOptionalString,
+} from "../../shared/string-coerce.js";
 import type { GatewayRpcOpts } from "../gateway-rpc.js";
 import { addGatewayClientOptions, callGatewayFromCli } from "../gateway-rpc.js";
 import { parsePositiveIntOrUndefined } from "../program/helpers.js";
@@ -170,7 +173,7 @@ export function registerCronAddCommand(cron: Command) {
           const sessionTarget =
             sessionSource === "cli" ? sessionTargetRaw || "" : inferredSessionTarget;
           const isCustomSessionTarget =
-            sessionTarget.toLowerCase().startsWith("session:") &&
+            normalizeLowercaseStringOrEmpty(sessionTarget).startsWith("session:") &&
             sessionTarget.slice(8).trim().length > 0;
           const isIsolatedLikeSessionTarget =
             sessionTarget === "isolated" || sessionTarget === "current" || isCustomSessionTarget;
diff --git a/src/cli/cron-cli/shared.ts b/src/cli/cron-cli/shared.ts
index f9d0c6d5af2..d1160fde747 100644
--- a/src/cli/cron-cli/shared.ts
+++ b/src/cli/cron-cli/shared.ts
@@ -9,6 +9,7 @@ import {
   parseOffsetlessIsoDateTimeInTimeZone,
 } from "../../infra/format-time/parse-offsetless-zoned-datetime.js";
 import { defaultRuntime, type RuntimeEnv } from "../../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { colorize, isRich, theme } from "../../terminal/theme.js";
 import type { GatewayRpcOpts } from "../gateway-rpc.js";
 import { callGatewayFromCli } from "../gateway-rpc.js";
@@ -67,7 +68,7 @@ export function parseDurationMs(input: string): number | null {
   if (!Number.isFinite(n) || n <= 0) {
     return null;
   }
-  const unit = (match[2] ?? "").toLowerCase();
+  const unit = normalizeLowercaseStringOrEmpty(match[2] ?? "");
   const factor =
     unit === "ms"
       ? 1
diff --git a/src/cli/daemon-cli/restart-health.ts b/src/cli/daemon-cli/restart-health.ts
index c73d99c03e8..b326f01af38 100644
--- a/src/cli/daemon-cli/restart-health.ts
+++ b/src/cli/daemon-cli/restart-health.ts
@@ -8,7 +8,10 @@ import {
   type PortUsage,
 } from "../../infra/ports.js";
 import { killProcessTree } from "../../process/kill-tree.js";
-import { normalizeOptionalString } from "../../shared/string-coerce.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeOptionalString,
+} from "../../shared/string-coerce.js";
 import { sleep } from "../../utils.js";
 
 export const DEFAULT_RESTART_HEALTH_TIMEOUT_MS = 60_000;
@@ -56,7 +59,7 @@ function looksLikeAuthClose(code: number | undefined, reason: string | undefined
   if (code !== 1008) {
     return false;
   }
-  const normalized = (reason ?? "").toLowerCase();
+  const normalized = normalizeLowercaseStringOrEmpty(reason);
   return (
     normalized.includes("auth") ||
     normalized.includes("token") ||
diff --git a/src/cli/mcp-cli.ts b/src/cli/mcp-cli.ts
index 2e6a4702a9d..013ec1c8935 100644
--- a/src/cli/mcp-cli.ts
+++ b/src/cli/mcp-cli.ts
@@ -8,6 +8,7 @@ import {
 } from "../config/mcp-config.js";
 import { serveOpenClawChannelMcp } from "../mcp/channel-server.js";
 import { defaultRuntime } from "../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { normalizeOptionalString } from "../shared/string-coerce.js";
 
 function fail(message: string): never {
@@ -83,9 +84,9 @@ export function registerMcpCli(program: Command) {
         if (opts.password) {
           warnSecretCliFlag("--password");
         }
-        const claudeChannelMode = String(opts.claudeChannelMode ?? "auto")
-          .trim()
-          .toLowerCase();
+        const claudeChannelMode = normalizeLowercaseStringOrEmpty(
+          String(opts.claudeChannelMode ?? "auto").trim(),
+        );
         if (
           claudeChannelMode !== "auto" &&
           claudeChannelMode !== "on" &&
diff --git a/src/cli/nodes-cli/register.camera.ts b/src/cli/nodes-cli/register.camera.ts
index de6b0791a3c..a44d01b80d7 100644
--- a/src/cli/nodes-cli/register.camera.ts
+++ b/src/cli/nodes-cli/register.camera.ts
@@ -1,5 +1,6 @@
 import type { Command } from "commander";
 import { defaultRuntime } from "../../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { getTerminalTableWidth, renderTable } from "../../terminal/table.js";
 import { shortenHomePath } from "../../utils.js";
 import {
@@ -22,9 +23,7 @@ import {
 import type { NodesRpcOpts } from "./types.js";
 
 const parseFacing = (value: string): CameraFacing => {
-  const v = String(value ?? "")
-    .trim()
-    .toLowerCase();
+  const v = normalizeLowercaseStringOrEmpty(String(value ?? "").trim());
   if (v === "front" || v === "back") {
     return v;
   }
@@ -115,9 +114,7 @@ export function registerNodesCameraCommands(nodes: Command) {
         await runNodesCommand("camera snap", async () => {
           const node = await resolveNode(opts, String(opts.node ?? ""));
           const nodeId = node.nodeId;
-          const facingOpt = String(opts.facing ?? "both")
-            .trim()
-            .toLowerCase();
+          const facingOpt = normalizeLowercaseStringOrEmpty(String(opts.facing ?? "both").trim());
           const facings: CameraFacing[] =
             facingOpt === "both"
               ? ["front", "back"]
diff --git a/src/cli/nodes-cli/register.canvas.ts b/src/cli/nodes-cli/register.canvas.ts
index 79b6e9f7ce3..0a89b52059e 100644
--- a/src/cli/nodes-cli/register.canvas.ts
+++ b/src/cli/nodes-cli/register.canvas.ts
@@ -1,6 +1,7 @@
 import fs from "node:fs/promises";
 import type { Command } from "commander";
 import { defaultRuntime } from "../../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { shortenHomePath } from "../../utils.js";
 import { writeBase64ToFile } from "../nodes-camera.js";
 import { canvasSnapshotTempPath, parseCanvasSnapshotPayload } from "../nodes-canvas.js";
@@ -41,9 +42,7 @@ export function registerNodesCanvasCommands(nodes: Command) {
       .option("--invoke-timeout <ms>", "Node invoke timeout in ms (default 20000)", "20000")
       .action(async (opts: NodesRpcOpts) => {
         await runNodesCommand("canvas snapshot", async () => {
-          const formatOpt = String(opts.format ?? "jpg")
-            .trim()
-            .toLowerCase();
+          const formatOpt = normalizeLowercaseStringOrEmpty(String(opts.format ?? "jpg").trim());
           const formatForParams =
             formatOpt === "jpg" ? "jpeg" : formatOpt === "jpeg" ? "jpeg" : "png";
           if (formatForParams !== "png" && formatForParams !== "jpeg") {
diff --git a/src/cli/nodes-cli/register.invoke.ts b/src/cli/nodes-cli/register.invoke.ts
index e663fd90075..3af69166496 100644
--- a/src/cli/nodes-cli/register.invoke.ts
+++ b/src/cli/nodes-cli/register.invoke.ts
@@ -1,6 +1,7 @@
 import type { Command } from "commander";
 import { randomIdempotencyKey } from "../../gateway/call.js";
 import { defaultRuntime } from "../../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { getNodesTheme, runNodesCommand } from "./cli-utils.js";
 import { callGatewayCli, nodesCallOpts, resolveNodeId } from "./rpc.js";
 import type { NodesRpcOpts } from "./types.js";
@@ -27,7 +28,7 @@ export function registerNodesInvokeCommands(nodes: Command) {
             defaultRuntime.exit(1);
             return;
           }
-          if (BLOCKED_NODE_INVOKE_COMMANDS.has(command.toLowerCase())) {
+          if (BLOCKED_NODE_INVOKE_COMMANDS.has(normalizeLowercaseStringOrEmpty(command))) {
             throw new Error(
               `command "${command}" is reserved for shell execution; use the exec tool with host=node instead`,
             );
diff --git a/src/cli/nodes-cli/register.status.ts b/src/cli/nodes-cli/register.status.ts
index 5139df03a67..36030450428 100644
--- a/src/cli/nodes-cli/register.status.ts
+++ b/src/cli/nodes-cli/register.status.ts
@@ -3,6 +3,7 @@ import { formatErrorMessage } from "../../infra/errors.js";
 import { formatTimeAgo } from "../../infra/format-time/format-relative.ts";
 import { defaultRuntime } from "../../runtime.js";
 import {
+  normalizeLowercaseStringOrEmpty,
   normalizeOptionalLowercaseString,
   normalizeOptionalString,
 } from "../../shared/string-coerce.js";
@@ -20,7 +21,7 @@ function formatVersionLabel(raw: string) {
   if (!trimmed) {
     return raw;
   }
-  if (trimmed.toLowerCase().startsWith("v")) {
+  if (normalizeLowercaseStringOrEmpty(trimmed).startsWith("v")) {
     return trimmed;
   }
   return /^\d/.test(trimmed) ? `v${trimmed}` : trimmed;
diff --git a/src/cli/nodes-cli/rpc.ts b/src/cli/nodes-cli/rpc.ts
index a3c71145861..a8bbbe7d7c4 100644
--- a/src/cli/nodes-cli/rpc.ts
+++ b/src/cli/nodes-cli/rpc.ts
@@ -1,6 +1,7 @@
 import { randomUUID } from "node:crypto";
 import type { Command } from "commander";
 import { resolveNodeFromNodeList } from "../../shared/node-resolve.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { parseNodeList, parsePairingList } from "./format.js";
 import type { NodeListNode, NodesRpcOpts } from "./types.js";
 
@@ -50,7 +51,7 @@ export function buildNodeInvokeParams(params: {
 }
 
 export function unauthorizedHintForMessage(message: string): string | null {
-  const haystack = message.toLowerCase();
+  const haystack = normalizeLowercaseStringOrEmpty(message);
   if (
     haystack.includes("unauthorizedclient") ||
     haystack.includes("bridge client is not authorized") ||
diff --git a/src/cli/outbound-send-mapping.ts b/src/cli/outbound-send-mapping.ts
index e6dcd8f4228..cdcd6ff7ffb 100644
--- a/src/cli/outbound-send-mapping.ts
+++ b/src/cli/outbound-send-mapping.ts
@@ -1,5 +1,6 @@
 import { normalizeAnyChannelId } from "../channels/registry.js";
 import type { OutboundSendDeps } from "../infra/outbound/deliver.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 
 /**
  * CLI-internal send function sources, keyed by channel ID.
@@ -8,12 +9,13 @@ import type { OutboundSendDeps } from "../infra/outbound/deliver.js";
 export type CliOutboundSendSource = { [channelId: string]: unknown };
 
 function normalizeLegacyChannelStem(raw: string): string {
-  return raw
-    .replace(/([a-z0-9])([A-Z])/g, "$1-$2")
-    .replace(/_/g, "-")
-    .trim()
-    .toLowerCase()
-    .replace(/-/g, "");
+  const normalized = normalizeLowercaseStringOrEmpty(
+    raw
+      .replace(/([a-z0-9])([A-Z])/g, "$1-$2")
+      .replace(/_/g, "-")
+      .trim(),
+  );
+  return normalized.replace(/-/g, "");
 }
 
 function resolveChannelIdFromLegacySourceKey(key: string): string | undefined {
diff --git a/src/cli/pairing-cli.ts b/src/cli/pairing-cli.ts
index b106f45fc0c..eaf0a8f72fe 100644
--- a/src/cli/pairing-cli.ts
+++ b/src/cli/pairing-cli.ts
@@ -9,6 +9,7 @@ import {
   type PairingChannel,
 } from "../pairing/pairing-store.js";
 import { defaultRuntime } from "../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { formatDocsLink } from "../terminal/links.js";
 import { getTerminalTableWidth, renderTable } from "../terminal/table.js";
 import { theme } from "../terminal/theme.js";
@@ -16,15 +17,14 @@ import { formatCliCommand } from "./command-format.js";
 
 /** Parse channel, allowing extension channels not in core registry. */
 function parseChannel(raw: unknown, channels: PairingChannel[]): PairingChannel {
-  const value = (
-    typeof raw === "string"
+  const value = normalizeLowercaseStringOrEmpty(
+    (typeof raw === "string"
       ? raw
       : typeof raw === "number" || typeof raw === "boolean"
         ? String(raw)
         : ""
-  )
-    .trim()
-    .toLowerCase();
+    ).trim(),
+  );
   if (!value) {
     throw new Error("Channel required");
   }
diff --git a/src/cli/parse-bytes.ts b/src/cli/parse-bytes.ts
index db993a292f7..cb48a18c324 100644
--- a/src/cli/parse-bytes.ts
+++ b/src/cli/parse-bytes.ts
@@ -1,3 +1,5 @@
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
+
 export type BytesParseOptions = {
   defaultUnit?: "b" | "kb" | "mb" | "gb" | "tb";
 };
@@ -15,9 +17,7 @@ const UNIT_MULTIPLIERS: Record<string, number> = {
 };
 
 export function parseByteSize(raw: string, opts?: BytesParseOptions): number {
-  const trimmed = String(raw ?? "")
-    .trim()
-    .toLowerCase();
+  const trimmed = normalizeLowercaseStringOrEmpty(String(raw ?? "").trim());
   if (!trimmed) {
     throw new Error("invalid byte size (empty)");
   }
@@ -32,7 +32,7 @@ export function parseByteSize(raw: string, opts?: BytesParseOptions): number {
     throw new Error(`invalid byte size: ${raw}`);
   }
 
-  const unit = (m[2] ?? opts?.defaultUnit ?? "b").toLowerCase();
+  const unit = normalizeLowercaseStringOrEmpty(m[2] ?? opts?.defaultUnit ?? "b");
   const multiplier = UNIT_MULTIPLIERS[unit];
   if (!multiplier) {
     throw new Error(`invalid byte size unit: ${raw}`);
diff --git a/src/cli/parse-duration.ts b/src/cli/parse-duration.ts
index 4ad673fb39c..ab9cb6f5ef7 100644
--- a/src/cli/parse-duration.ts
+++ b/src/cli/parse-duration.ts
@@ -1,3 +1,5 @@
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
+
 export type DurationMsParseOptions = {
   defaultUnit?: "ms" | "s" | "m" | "h" | "d";
 };
@@ -11,9 +13,7 @@ const DURATION_MULTIPLIERS: Record<string, number> = {
 };
 
 export function parseDurationMs(raw: string, opts?: DurationMsParseOptions): number {
-  const trimmed = String(raw ?? "")
-    .trim()
-    .toLowerCase();
+  const trimmed = normalizeLowercaseStringOrEmpty(String(raw ?? "").trim());
   if (!trimmed) {
     throw new Error("invalid duration (empty)");
   }
diff --git a/src/cli/plugins-command-helpers.ts b/src/cli/plugins-command-helpers.ts
index ef842c6c913..9540f52eb9c 100644
--- a/src/cli/plugins-command-helpers.ts
+++ b/src/cli/plugins-command-helpers.ts
@@ -6,6 +6,7 @@ import { CLAWHUB_INSTALL_ERROR_CODE } from "../plugins/clawhub.js";
 import { applyExclusiveSlotSelection } from "../plugins/slots.js";
 import { buildPluginDiagnosticsReport } from "../plugins/status.js";
 import { defaultRuntime } from "../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { theme } from "../terminal/theme.js";
 
 type HookInternalEntryLike = Record<string, unknown> & { enabled?: boolean };
@@ -14,7 +15,7 @@ export function resolveFileNpmSpecToLocalPath(
   raw: string,
 ): { ok: true; path: string } | { ok: false; error: string } | null {
   const trimmed = raw.trim();
-  if (!trimmed.toLowerCase().startsWith("file:")) {
+  if (!normalizeLowercaseStringOrEmpty(trimmed).startsWith("file:")) {
     return null;
   }
   const rest = trimmed.slice("file:".length);
diff --git a/src/cli/profile-utils.ts b/src/cli/profile-utils.ts
index 2e89a8243fd..2ad1ee9910e 100644
--- a/src/cli/profile-utils.ts
+++ b/src/cli/profile-utils.ts
@@ -1,3 +1,5 @@
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
+
 const PROFILE_NAME_RE = /^[a-z0-9][a-z0-9_-]{0,63}$/i;
 
 export function isValidProfileName(value: string): boolean {
@@ -13,7 +15,7 @@ export function normalizeProfileName(raw?: string | null): string | null {
   if (!profile) {
     return null;
   }
-  if (profile.toLowerCase() === "default") {
+  if (normalizeLowercaseStringOrEmpty(profile) === "default") {
     return null;
   }
   if (!isValidProfileName(profile)) {
diff --git a/src/cli/profile.ts b/src/cli/profile.ts
index 189eacf046d..9881a25c16e 100644
--- a/src/cli/profile.ts
+++ b/src/cli/profile.ts
@@ -2,6 +2,7 @@ import os from "node:os";
 import path from "node:path";
 import { FLAG_TERMINATOR } from "../infra/cli-root-options.js";
 import { resolveRequiredHomeDir } from "../infra/home-dir.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { resolveCliArgvInvocation } from "./argv-invocation.js";
 import { isValidProfileName } from "./profile-utils.js";
 import { forwardConsumedCliRootOption } from "./root-option-forward.js";
@@ -83,7 +84,7 @@ function resolveProfileStateDir(
   env: Record<string, string | undefined>,
   homedir: () => string,
 ): string {
-  const suffix = profile.toLowerCase() === "default" ? "" : `-${profile}`;
+  const suffix = normalizeLowercaseStringOrEmpty(profile) === "default" ? "" : `-${profile}`;
   return path.join(resolveRequiredHomeDir(env as NodeJS.ProcessEnv, homedir), `.openclaw${suffix}`);
 }
 
diff --git a/src/cli/program/register.agent.ts b/src/cli/program/register.agent.ts
index e5847f3c164..c5cfebfdb84 100644
--- a/src/cli/program/register.agent.ts
+++ b/src/cli/program/register.agent.ts
@@ -11,6 +11,7 @@ import {
 } from "../../commands/agents.js";
 import { setVerbose } from "../../globals.js";
 import { defaultRuntime } from "../../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { formatDocsLink } from "../../terminal/links.js";
 import { theme } from "../../terminal/theme.js";
 import { runCommandWithRuntime } from "../cli-utils.js";
@@ -73,7 +74,8 @@ ${formatHelpExamples([
 ${theme.muted("Docs:")} ${formatDocsLink("/cli/agent", "docs.openclaw.ai/cli/agent")}`,
     )
     .action(async (opts) => {
-      const verboseLevel = typeof opts.verbose === "string" ? opts.verbose.toLowerCase() : "";
+      const verboseLevel =
+        typeof opts.verbose === "string" ? normalizeLowercaseStringOrEmpty(opts.verbose) : "";
       setVerbose(verboseLevel === "on");
       // Build default deps (keeps parity with other commands; future-proofing).
       const deps = createDefaultDeps();
diff --git a/src/cli/update-cli/progress.ts b/src/cli/update-cli/progress.ts
index 676231a0e7f..1a0c13676a9 100644
--- a/src/cli/update-cli/progress.ts
+++ b/src/cli/update-cli/progress.ts
@@ -6,6 +6,7 @@ import type {
   UpdateStepProgress,
 } from "../../infra/update-runner.js";
 import { defaultRuntime } from "../../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { theme } from "../../terminal/theme.js";
 import type { UpdateCommandOptions } from "./shared.js";
 
@@ -72,7 +73,7 @@ export function inferUpdateFailureHints(result: UpdateRunResult): string[] {
     return [];
   }
 
-  const stderr = (failedStep.stderrTail ?? "").toLowerCase();
+  const stderr = normalizeLowercaseStringOrEmpty(failedStep.stderrTail);
   const hints: string[] = [];
 
   if (failedStep.name.startsWith("global update") && stderr.includes("eacces")) {
diff --git a/src/cli/update-cli/shared.ts b/src/cli/update-cli/shared.ts
index 3f2046b870b..8efbee06739 100644
--- a/src/cli/update-cli/shared.ts
+++ b/src/cli/update-cli/shared.ts
@@ -19,6 +19,7 @@ import {
 import type { UpdateStepProgress, UpdateStepResult } from "../../infra/update-runner.js";
 import { runCommandWithTimeout } from "../../process/exec.js";
 import { defaultRuntime } from "../../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { theme } from "../../terminal/theme.js";
 import { pathExists } from "../../utils.js";
 
@@ -129,7 +130,7 @@ function resolveDefaultGitDir(): string {
 }
 
 export function resolveNodeRunner(): string {
-  const base = path.basename(process.execPath).toLowerCase();
+  const base = normalizeLowercaseStringOrEmpty(path.basename(process.execPath));
   if (base === "node" || base === "node.exe") {
     return process.execPath;
   }
diff --git a/src/cli/windows-argv.ts b/src/cli/windows-argv.ts
index 14c1645b665..b7f9b70bb4b 100644
--- a/src/cli/windows-argv.ts
+++ b/src/cli/windows-argv.ts
@@ -1,5 +1,6 @@
 import fs from "node:fs";
 import path from "node:path";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 
 export function normalizeWindowsArgv(argv: string[]): string[] {
   if (process.platform !== "win32") {
@@ -28,8 +29,8 @@ export function normalizeWindowsArgv(argv: string[]): string[] {
     normalizeArg(value).replace(/^\\\\\\?\\/, "");
 
   const execPath = normalizeCandidate(process.execPath);
-  const execPathLower = execPath.toLowerCase();
-  const execBase = path.basename(execPath).toLowerCase();
+  const execPathLower = normalizeLowercaseStringOrEmpty(execPath);
+  const execBase = normalizeLowercaseStringOrEmpty(path.basename(execPath));
   const isExecPath = (value: string | undefined): boolean => {
     if (!value) {
       return false;
@@ -38,7 +39,7 @@ export function normalizeWindowsArgv(argv: string[]): string[] {
     if (!normalized) {
       return false;
     }
-    const lower = normalized.toLowerCase();
+    const lower = normalizeLowercaseStringOrEmpty(normalized);
     return (
       lower === execPathLower ||
       path.basename(lower) === execBase ||
diff --git a/src/infra/dispatch-wrapper-resolution.ts b/src/infra/dispatch-wrapper-resolution.ts
index a75f625ac6d..5a946492767 100644
--- a/src/infra/dispatch-wrapper-resolution.ts
+++ b/src/infra/dispatch-wrapper-resolution.ts
@@ -1,3 +1,4 @@
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { normalizeExecutableToken } from "./exec-wrapper-tokens.js";
 
 export const MAX_DISPATCH_WRAPPER_DEPTH = 4;
@@ -128,7 +129,7 @@ function scanWrapperInvocation(
       idx += 1;
       break;
     }
-    const directive = params.onToken(token, token.toLowerCase());
+    const directive = params.onToken(token, normalizeLowercaseStringOrEmpty(token));
     if (directive === "stop") {
       break;
     }
@@ -197,7 +198,7 @@ function envInvocationUsesModifiers(argv: string[]): boolean {
     if (!token.startsWith("-") || token === "-") {
       break;
     }
-    const lower = token.toLowerCase();
+    const lower = normalizeLowercaseStringOrEmpty(token);
     const [flag] = lower.split("=", 2);
     if (ENV_FLAG_OPTIONS.has(flag)) {
       return true;
diff --git a/src/infra/restart-stale-pids.ts b/src/infra/restart-stale-pids.ts
index fa06729c878..b8ce4ad9b48 100644
--- a/src/infra/restart-stale-pids.ts
+++ b/src/infra/restart-stale-pids.ts
@@ -2,6 +2,7 @@ import { spawnSync } from "node:child_process";
 import path from "node:path";
 import { resolveGatewayPort } from "../config/paths.js";
 import { createSubsystemLogger } from "../logging/subsystem.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { isGatewayArgv } from "./gateway-process-argv.js";
 import { resolveLsofCommandSync } from "./ports-lsof.js";
 import {
@@ -70,7 +71,11 @@ function parsePidsFromLsofOutput(stdout: string): number[] {
   let currentCmd: string | undefined;
   for (const line of stdout.split(/\r?\n/).filter(Boolean)) {
     if (line.startsWith("p")) {
-      if (currentPid != null && currentCmd && currentCmd.toLowerCase().includes("openclaw")) {
+      if (
+        currentPid != null &&
+        currentCmd &&
+        normalizeLowercaseStringOrEmpty(currentCmd).includes("openclaw")
+      ) {
         pids.push(currentPid);
       }
       const parsed = Number.parseInt(line.slice(1), 10);
@@ -80,7 +85,11 @@ function parsePidsFromLsofOutput(stdout: string): number[] {
       currentCmd = line.slice(1);
     }
   }
-  if (currentPid != null && currentCmd && currentCmd.toLowerCase().includes("openclaw")) {
+  if (
+    currentPid != null &&
+    currentCmd &&
+    normalizeLowercaseStringOrEmpty(currentCmd).includes("openclaw")
+  ) {
     pids.push(currentPid);
   }
   // Deduplicate: dual-stack listeners (IPv4 + IPv6) cause lsof to emit the
diff --git a/src/plugin-sdk/bluebubbles.ts b/src/plugin-sdk/bluebubbles.ts
index bbaf2cfb783..3fd81753e5b 100644
--- a/src/plugin-sdk/bluebubbles.ts
+++ b/src/plugin-sdk/bluebubbles.ts
@@ -1,5 +1,6 @@
 import type { ChannelStatusIssue } from "../channels/plugins/types.js";
 import type { OpenClawConfig } from "../config/config.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import {
   parseChatTargetPrefixesOrThrow,
   resolveServicePrefixedTarget,
@@ -83,7 +84,7 @@ function stripBlueBubblesPrefix(value: string): string {
   if (!trimmed) {
     return "";
   }
-  if (!trimmed.toLowerCase().startsWith("bluebubbles:")) {
+  if (!normalizeLowercaseStringOrEmpty(trimmed).startsWith("bluebubbles:")) {
     return trimmed;
   }
   return trimmed.slice("bluebubbles:".length).trim();
@@ -135,7 +136,7 @@ function normalizeBlueBubblesHandle(raw: string): string {
   if (!trimmed) {
     return "";
   }
-  const lowered = trimmed.toLowerCase();
+  const lowered = normalizeLowercaseStringOrEmpty(trimmed);
   if (lowered.startsWith("imessage:")) {
     return normalizeBlueBubblesHandle(trimmed.slice(9));
   }
@@ -146,7 +147,7 @@ function normalizeBlueBubblesHandle(raw: string): string {
     return normalizeBlueBubblesHandle(trimmed.slice(5));
   }
   if (trimmed.includes("@")) {
-    return trimmed.toLowerCase();
+    return normalizeLowercaseStringOrEmpty(trimmed);
   }
   return trimmed.replace(/\s+/g, "");
 }
@@ -167,7 +168,7 @@ function parseBlueBubblesTarget(raw: string): BlueBubblesTarget {
   if (!trimmed) {
     throw new Error("BlueBubbles target is required");
   }
-  const lower = trimmed.toLowerCase();
+  const lower = normalizeLowercaseStringOrEmpty(trimmed);
 
   const servicePrefixed = resolveServicePrefixedTarget({
     trimmed,
diff --git a/src/plugin-sdk/channel-entry-contract.ts b/src/plugin-sdk/channel-entry-contract.ts
index 907bf58d068..8e4323f2667 100644
--- a/src/plugin-sdk/channel-entry-contract.ts
+++ b/src/plugin-sdk/channel-entry-contract.ts
@@ -13,6 +13,7 @@ import {
   resolvePluginLoaderJitiConfig,
 } from "../plugins/sdk-alias.js";
 import type { AnyAgentTool, OpenClawPluginApi, PluginCommandContext } from "../plugins/types.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 
 export type { AnyAgentTool, OpenClawPluginApi, PluginCommandContext };
 
@@ -68,7 +69,7 @@ const jitiLoaders = new Map<string, ReturnType<typeof createJiti>>();
 const loadedModuleExports = new Map<string, unknown>();
 
 function resolveSpecifierCandidates(modulePath: string): string[] {
-  const ext = path.extname(modulePath).toLowerCase();
+  const ext = normalizeLowercaseStringOrEmpty(path.extname(modulePath));
   if (ext === ".js") {
     return [modulePath, modulePath.slice(0, -3) + ".ts"];
   }
@@ -279,7 +280,7 @@ function loadBundledEntryModuleSync(importMetaUrl: string, specifier: string): u
   if (
     process.platform === "win32" &&
     modulePath.includes(`${path.sep}dist${path.sep}`) &&
-    [".js", ".mjs", ".cjs"].includes(path.extname(modulePath).toLowerCase())
+    [".js", ".mjs", ".cjs"].includes(normalizeLowercaseStringOrEmpty(path.extname(modulePath)))
   ) {
     try {
       loaded = nodeRequire(modulePath);
diff --git a/src/plugin-sdk/core.ts b/src/plugin-sdk/core.ts
index 81128579541..4d9b1945b12 100644
--- a/src/plugin-sdk/core.ts
+++ b/src/plugin-sdk/core.ts
@@ -25,6 +25,7 @@ import { buildOutboundBaseSessionKey } from "../infra/outbound/base-session-key.
 import type { OutboundDeliveryResult } from "../infra/outbound/deliver.js";
 import type { PluginRuntime } from "../plugins/runtime/types.js";
 import type { OpenClawPluginApi } from "../plugins/types.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 
 export type {
   AnyAgentTool,
@@ -237,8 +238,8 @@ export function getChatChannelMeta(id: ChatChannelId): ChannelMeta {
 export function stripChannelTargetPrefix(raw: string, ...providers: string[]): string {
   const trimmed = raw.trim();
   for (const provider of providers) {
-    const prefix = `${provider.toLowerCase()}:`;
-    if (trimmed.toLowerCase().startsWith(prefix)) {
+    const prefix = `${normalizeLowercaseStringOrEmpty(provider)}:`;
+    if (normalizeLowercaseStringOrEmpty(trimmed).startsWith(prefix)) {
       return trimmed.slice(prefix.length).trim();
     }
   }
diff --git a/src/plugin-sdk/speech.ts b/src/plugin-sdk/speech.ts
index 8320ab22d29..3115da936f1 100644
--- a/src/plugin-sdk/speech.ts
+++ b/src/plugin-sdk/speech.ts
@@ -1,4 +1,5 @@
 import { rmSync } from "node:fs";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 
 // Public speech helpers for bundled or third-party plugins.
 //
@@ -55,7 +56,7 @@ export function normalizeLanguageCode(code?: string): string | undefined {
   if (!trimmed) {
     return undefined;
   }
-  const normalized = trimmed.toLowerCase();
+  const normalized = normalizeLowercaseStringOrEmpty(trimmed);
   if (!/^[a-z]{2}$/.test(normalized)) {
     throw new Error("languageCode must be a 2-letter ISO 639-1 code (e.g. en, de, fr)");
   }
@@ -67,7 +68,7 @@ export function normalizeApplyTextNormalization(mode?: string): "auto" | "on" |
   if (!trimmed) {
     return undefined;
   }
-  const normalized = trimmed.toLowerCase();
+  const normalized = normalizeLowercaseStringOrEmpty(trimmed);
   if (normalized === "auto" || normalized === "on" || normalized === "off") {
     return normalized;
   }