diff --git a/src/daemon/launchd.ts b/src/daemon/launchd.ts
index 9f0a4de5cb1..a3312aad513 100644
--- a/src/daemon/launchd.ts
+++ b/src/daemon/launchd.ts
@@ -2,6 +2,7 @@ import fs from "node:fs/promises";
 import path from "node:path";
 import { parseStrictInteger, parseStrictPositiveInteger } from "../infra/parse-finite-number.js";
 import { cleanStaleGatewayProcessesSync } from "../infra/restart-stale-pids.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import {
   GATEWAY_LAUNCH_AGENT_LABEL,
   resolveGatewayServiceDescription,
@@ -301,7 +302,7 @@ export async function readLaunchAgentRuntime(
   }
   const parsed = parseLaunchctlPrint(res.stdout || res.stderr || "");
   const plistExists = await launchAgentPlistExists(env);
-  const state = parsed.state?.toLowerCase();
+  const state = normalizeLowercaseStringOrEmpty(parsed.state);
   const status = state === "running" || parsed.pid ? "running" : state ? "stopped" : "unknown";
   return {
     status,
@@ -331,7 +332,7 @@ export async function repairLaunchAgentBootstrap(args: {
   let repairStatus: LaunchAgentBootstrapRepairResult["status"] = "repaired";
   if (boot.code !== 0) {
     const detail = (boot.stderr || boot.stdout).trim();
-    const normalized = detail.toLowerCase();
+    const normalized = normalizeLowercaseStringOrEmpty(detail);
     const alreadyLoaded = boot.code === 130 || normalized.includes("already exists in domain");
     if (!alreadyLoaded) {
       return { ok: false, status: "bootstrap-failed", detail: detail || undefined };
@@ -447,7 +448,7 @@ export async function uninstallLaunchAgent({
 }
 
 function isLaunchctlNotLoaded(res: { stdout: string; stderr: string; code: number }): boolean {
-  const detail = (res.stderr || res.stdout).toLowerCase();
+  const detail = normalizeLowercaseStringOrEmpty(res.stderr || res.stdout);
   return (
     detail.includes("no such process") ||
     detail.includes("could not find service") ||
@@ -456,7 +457,7 @@ function isLaunchctlNotLoaded(res: { stdout: string; stderr: string; code: numbe
 }
 
 function isUnsupportedGuiDomain(detail: string): boolean {
-  const normalized = detail.toLowerCase();
+  const normalized = normalizeLowercaseStringOrEmpty(detail);
   return (
     normalized.includes("domain does not support specified action") ||
     normalized.includes("bootstrap failed: 125")
diff --git a/src/daemon/runtime-binary.ts b/src/daemon/runtime-binary.ts
index 794fe872bad..b5ade2570ae 100644
--- a/src/daemon/runtime-binary.ts
+++ b/src/daemon/runtime-binary.ts
@@ -1,10 +1,12 @@
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
+
 const NODE_VERSIONED_PATTERN = /^node(?:-\d+|\d+)(?:\.\d+)*(?:\.exe)?$/;
 
 function normalizeRuntimeBasename(execPath: string): string {
   const trimmed = execPath.trim().replace(/^["']|["']$/g, "");
   const lastSlash = Math.max(trimmed.lastIndexOf("/"), trimmed.lastIndexOf("\\"));
   const basename = lastSlash === -1 ? trimmed : trimmed.slice(lastSlash + 1);
-  return basename.toLowerCase();
+  return normalizeLowercaseStringOrEmpty(basename);
 }
 
 export function isNodeRuntime(execPath: string): boolean {
diff --git a/src/daemon/runtime-paths.ts b/src/daemon/runtime-paths.ts
index e55e2fe47af..798ceecdca0 100644
--- a/src/daemon/runtime-paths.ts
+++ b/src/daemon/runtime-paths.ts
@@ -5,6 +5,7 @@ import { promisify } from "node:util";
 import { isSupportedNodeVersion } from "../infra/runtime-guard.js";
 import { resolveStableNodePath } from "../infra/stable-node-path.js";
 import { getWindowsProgramFilesRoots } from "../infra/windows-install-roots.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 
 const VERSION_MANAGER_MARKERS = [
   "/.nvm/",
@@ -23,7 +24,7 @@ function getPathModule(platform: NodeJS.Platform) {
 
 function isNodeExecPath(execPath: string, platform: NodeJS.Platform): boolean {
   const pathModule = getPathModule(platform);
-  const base = pathModule.basename(execPath).toLowerCase();
+  const base = normalizeLowercaseStringOrEmpty(pathModule.basename(execPath));
   return base === "node" || base === "node.exe";
 }
 
@@ -31,7 +32,7 @@ function normalizeForCompare(input: string, platform: NodeJS.Platform): string {
   const pathModule = getPathModule(platform);
   const normalized = pathModule.normalize(input).replaceAll("\\", "/");
   if (platform === "win32") {
-    return normalized.toLowerCase();
+    return normalizeLowercaseStringOrEmpty(normalized);
   }
   return normalized;
 }
diff --git a/src/daemon/service-audit.ts b/src/daemon/service-audit.ts
index 4965005eac0..aafa85349e9 100644
--- a/src/daemon/service-audit.ts
+++ b/src/daemon/service-audit.ts
@@ -1,6 +1,9 @@
 import fs from "node:fs/promises";
 import path from "node:path";
-import { normalizeOptionalString } from "../shared/string-coerce.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeOptionalString,
+} from "../shared/string-coerce.js";
 import { resolveLaunchAgentPlistPath } from "./launchd.js";
 import { isBunRuntime, isNodeRuntime } from "./runtime-binary.js";
 import {
@@ -252,7 +255,7 @@ function normalizePathEntry(entry: string, platform: NodeJS.Platform): string {
   const pathModule = getPathModule(platform);
   const normalized = pathModule.normalize(entry).replaceAll("\\", "/");
   if (platform === "win32") {
-    return normalized.toLowerCase();
+    return normalizeLowercaseStringOrEmpty(normalized);
   }
   return normalized;
 }
diff --git a/src/daemon/systemd.ts b/src/daemon/systemd.ts
index 42cf263797f..f9b052e4c74 100644
--- a/src/daemon/systemd.ts
+++ b/src/daemon/systemd.ts
@@ -3,6 +3,7 @@ import os from "node:os";
 import path from "node:path";
 import { formatErrorMessage } from "../infra/errors.js";
 import { parseStrictInteger, parseStrictPositiveInteger } from "../infra/parse-finite-number.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { splitArgsPreservingQuotes } from "./arg-split.js";
 import {
   LEGACY_GATEWAY_SYSTEMD_SERVICE_NAMES,
@@ -277,7 +278,7 @@ function isSystemdUnitNotEnabled(detail: string): boolean {
   if (!detail) {
     return false;
   }
-  const normalized = detail.toLowerCase();
+  const normalized = normalizeLowercaseStringOrEmpty(detail);
   return (
     normalized.includes("disabled") ||
     normalized.includes("static") ||
@@ -317,7 +318,7 @@ export function isNonFatalSystemdInstallProbeError(error: unknown): boolean {
   if (!detail) {
     return false;
   }
-  const normalized = detail.toLowerCase();
+  const normalized = normalizeLowercaseStringOrEmpty(detail);
   return isSystemctlBusUnavailable(normalized) || isGenericSystemctlIsEnabledFailure(normalized);
 }
 
@@ -628,7 +629,7 @@ export async function readSystemdServiceRuntime(
   ]);
   if (res.code !== 0) {
     const detail = (res.stderr || res.stdout).trim();
-    const missing = detail.toLowerCase().includes("not found");
+    const missing = normalizeLowercaseStringOrEmpty(detail).includes("not found");
     return {
       status: missing ? "stopped" : "unknown",
       detail: detail || undefined,
@@ -636,7 +637,7 @@ export async function readSystemdServiceRuntime(
     };
   }
   const parsed = parseSystemdShow(res.stdout || "");
-  const activeState = parsed.activeState?.toLowerCase();
+  const activeState = normalizeLowercaseStringOrEmpty(parsed.activeState);
   const status = activeState === "active" ? "running" : activeState ? "stopped" : "unknown";
   return {
     status,
@@ -713,4 +714,3 @@ export async function uninstallLegacySystemdUnits({
 
   return units;
 }
-import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
diff --git a/src/logging/subsystem.ts b/src/logging/subsystem.ts
index f64b1045c10..c7769c18263 100644
--- a/src/logging/subsystem.ts
+++ b/src/logging/subsystem.ts
@@ -2,6 +2,7 @@ import { Chalk } from "chalk";
 import type { Logger as TsLogger } from "tslog";
 import { isVerbose } from "../global-state.js";
 import { defaultRuntime, type OutputRuntimeEnv, type RuntimeEnv } from "../runtime.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { clearActiveProgressLine } from "../terminal/progress-line.js";
 import { normalizeMessageChannel } from "../utils/message-channel.js";
 import {
@@ -73,7 +74,7 @@ function formatRuntimeArg(arg: unknown): string {
 }
 
 function isRichConsoleEnv(): boolean {
-  const term = (process.env.TERM ?? "").toLowerCase();
+  const term = normalizeLowercaseStringOrEmpty(process.env.TERM);
   if (process.env.COLORTERM || process.env.TERM_PROGRAM) {
     return true;
   }
@@ -151,7 +152,10 @@ export function stripRedundantSubsystemPrefixForConsole(
     const closeIdx = message.indexOf("]");
     if (closeIdx > 1) {
       const bracketTag = message.slice(1, closeIdx);
-      if (bracketTag.toLowerCase() === displaySubsystem.toLowerCase()) {
+      if (
+        normalizeLowercaseStringOrEmpty(bracketTag) ===
+        normalizeLowercaseStringOrEmpty(displaySubsystem)
+      ) {
         let i = closeIdx + 1;
         while (message[i] === " ") {
           i += 1;
@@ -162,7 +166,9 @@ export function stripRedundantSubsystemPrefixForConsole(
   }
 
   const prefix = message.slice(0, displaySubsystem.length);
-  if (prefix.toLowerCase() !== displaySubsystem.toLowerCase()) {
+  if (
+    normalizeLowercaseStringOrEmpty(prefix) !== normalizeLowercaseStringOrEmpty(displaySubsystem)
+  ) {
     return message;
   }
 
diff --git a/src/mcp/channel-bridge.ts b/src/mcp/channel-bridge.ts
index 13da5f16912..621f151a029 100644
--- a/src/mcp/channel-bridge.ts
+++ b/src/mcp/channel-bridge.ts
@@ -6,6 +6,10 @@ import { GatewayClient } from "../gateway/client.js";
 import { APPROVALS_SCOPE, READ_SCOPE, WRITE_SCOPE } from "../gateway/method-scopes.js";
 import type { EventFrame } from "../gateway/protocol/index.js";
 import { extractFirstTextBlock } from "../shared/chat-message-content.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeOptionalLowercaseString,
+} from "../shared/string-coerce.js";
 import { GATEWAY_CLIENT_MODES, GATEWAY_CLIENT_NAMES } from "../utils/message-channel.js";
 import { VERSION } from "../version.js";
 import type {
@@ -161,12 +165,14 @@ export class OpenClawChannelBridge {
       includeDerivedTitles: params?.includeDerivedTitles ?? true,
       includeLastMessage: params?.includeLastMessage ?? true,
     });
-    const requestedChannel = toText(params?.channel)?.toLowerCase();
+    const requestedChannel = normalizeOptionalLowercaseString(params?.channel);
     return (response.sessions ?? [])
       .map(toConversation)
       .filter((conversation): conversation is ConversationDescriptor => Boolean(conversation))
       .filter((conversation) =>
-        requestedChannel ? conversation.channel.toLowerCase() === requestedChannel : true,
+        requestedChannel
+          ? normalizeLowercaseStringOrEmpty(conversation.channel) === requestedChannel
+          : true,
       );
   }
 
@@ -448,14 +454,16 @@ export class OpenClawChannelBridge {
     const text = extractFirstTextBlock(payload.message);
     const permissionMatch = text ? CLAUDE_PERMISSION_REPLY_RE.exec(text) : null;
     if (permissionMatch) {
-      const requestId = permissionMatch[2]?.toLowerCase();
+      const requestId = normalizeOptionalLowercaseString(permissionMatch[2]);
       if (requestId && this.pendingClaudePermissions.has(requestId)) {
         this.pendingClaudePermissions.delete(requestId);
         await this.sendNotification({
           method: "notifications/claude/channel/permission",
           params: {
             request_id: requestId,
-            behavior: permissionMatch[1]?.toLowerCase().startsWith("y") ? "allow" : "deny",
+            behavior: normalizeLowercaseStringOrEmpty(permissionMatch[1]).startsWith("y")
+              ? "allow"
+              : "deny",
           },
         });
         return;
diff --git a/src/memory-host-sdk/dreaming.ts b/src/memory-host-sdk/dreaming.ts
index 95297881e05..be7624d3405 100644
--- a/src/memory-host-sdk/dreaming.ts
+++ b/src/memory-host-sdk/dreaming.ts
@@ -231,7 +231,7 @@ function normalizeStringArray<T extends string>(
   const allowedSet = new Set(allowed);
   const normalized: T[] = [];
   for (const entry of value) {
-    const normalizedEntry = normalizeTrimmedString(entry)?.toLowerCase();
+    const normalizedEntry = normalizeOptionalLowercaseString(entry);
     if (!normalizedEntry || !allowedSet.has(normalizedEntry as T)) {
       continue;
     }
@@ -243,7 +243,7 @@ function normalizeStringArray<T extends string>(
 }
 
 function normalizeStorageMode(value: unknown): MemoryDreamingStorageMode {
-  const normalized = normalizeTrimmedString(value)?.toLowerCase();
+  const normalized = normalizeOptionalLowercaseString(value);
   if (normalized === "inline" || normalized === "separate" || normalized === "both") {
     return normalized;
   }
@@ -251,7 +251,7 @@ function normalizeStorageMode(value: unknown): MemoryDreamingStorageMode {
 }
 
 function normalizeSpeed(value: unknown): MemoryDreamingSpeed | undefined {
-  const normalized = normalizeTrimmedString(value)?.toLowerCase();
+  const normalized = normalizeOptionalLowercaseString(value);
   if (normalized === "fast" || normalized === "balanced" || normalized === "slow") {
     return normalized;
   }
@@ -259,7 +259,7 @@ function normalizeSpeed(value: unknown): MemoryDreamingSpeed | undefined {
 }
 
 function normalizeThinking(value: unknown): MemoryDreamingThinking | undefined {
-  const normalized = normalizeTrimmedString(value)?.toLowerCase();
+  const normalized = normalizeOptionalLowercaseString(value);
   if (normalized === "low" || normalized === "medium" || normalized === "high") {
     return normalized;
   }
@@ -267,7 +267,7 @@ function normalizeThinking(value: unknown): MemoryDreamingThinking | undefined {
 }
 
 function normalizeBudget(value: unknown): MemoryDreamingBudget | undefined {
-  const normalized = normalizeTrimmedString(value)?.toLowerCase();
+  const normalized = normalizeOptionalLowercaseString(value);
   if (normalized === "cheap" || normalized === "medium" || normalized === "expensive") {
     return normalized;
   }
@@ -320,7 +320,7 @@ export function resolveMemoryDreamingPluginId(
   const plugins = asNullableRecord(root?.plugins);
   const slots = asNullableRecord(plugins?.slots);
   const configuredSlot = normalizeTrimmedString(slots?.memory);
-  if (configuredSlot && configuredSlot.toLowerCase() !== "none") {
+  if (configuredSlot && normalizeLowercaseStringOrEmpty(configuredSlot) !== "none") {
     return configuredSlot;
   }
   return DEFAULT_MEMORY_DREAMING_PLUGIN_ID;
diff --git a/src/memory-host-sdk/host/backend-config.ts b/src/memory-host-sdk/host/backend-config.ts
index b5a9db26741..1be34cbc6a4 100644
--- a/src/memory-host-sdk/host/backend-config.ts
+++ b/src/memory-host-sdk/host/backend-config.ts
@@ -13,6 +13,7 @@ import type {
   MemoryQmdSearchMode,
 } from "../../config/types.memory.js";
 import { normalizeAgentId } from "../../routing/session-key.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { resolveUserPath } from "../../utils.js";
 import { splitShellArgs } from "../../utils/shell-argv.js";
 
@@ -107,7 +108,7 @@ const DEFAULT_QMD_SCOPE: SessionSendPolicyConfig = {
 };
 
 function sanitizeName(input: string): string {
-  const lower = input.toLowerCase().replace(/[^a-z0-9-]+/g, "-");
+  const lower = normalizeLowercaseStringOrEmpty(input).replace(/[^a-z0-9-]+/g, "-");
   const trimmed = lower.replace(/^-+|-+$/g, "");
   return trimmed || "collection";
 }
diff --git a/src/memory-host-sdk/host/embedding-model-limits.ts b/src/memory-host-sdk/host/embedding-model-limits.ts
index 0819686b905..00766748848 100644
--- a/src/memory-host-sdk/host/embedding-model-limits.ts
+++ b/src/memory-host-sdk/host/embedding-model-limits.ts
@@ -1,3 +1,4 @@
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import type { EmbeddingProvider } from "./embeddings.js";
 
 const DEFAULT_EMBEDDING_MAX_INPUT_TOKENS = 8192;
@@ -22,7 +23,7 @@ export function resolveEmbeddingMaxInputTokens(provider: EmbeddingProvider): num
 
   // Provider/model mapping is best-effort; different providers use different
   // limits and we prefer to be conservative when we don't know.
-  const key = `${provider.id}:${provider.model}`.toLowerCase();
+  const key = normalizeLowercaseStringOrEmpty(`${provider.id}:${provider.model}`);
   const known = KNOWN_EMBEDDING_MAX_INPUT_TOKENS[key];
   if (typeof known === "number") {
     return known;
@@ -30,10 +31,10 @@ export function resolveEmbeddingMaxInputTokens(provider: EmbeddingProvider): num
 
   // Provider-specific conservative fallbacks. This prevents us from accidentally
   // using the OpenAI default for providers with much smaller limits.
-  if (provider.id.toLowerCase() === "gemini") {
+  if (normalizeLowercaseStringOrEmpty(provider.id) === "gemini") {
     return 2048;
   }
-  if (provider.id.toLowerCase() === "local") {
+  if (normalizeLowercaseStringOrEmpty(provider.id) === "local") {
     return DEFAULT_LOCAL_EMBEDDING_MAX_INPUT_TOKENS;
   }
 
diff --git a/src/memory-host-sdk/host/embeddings-bedrock.ts b/src/memory-host-sdk/host/embeddings-bedrock.ts
index c536cf22ca5..4c40eb1b218 100644
--- a/src/memory-host-sdk/host/embeddings-bedrock.ts
+++ b/src/memory-host-sdk/host/embeddings-bedrock.ts
@@ -1,3 +1,4 @@
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { sanitizeAndNormalizeEmbedding } from "./embedding-vectors.js";
 import { debugEmbeddingsLog } from "./embeddings-debug.js";
 import type { EmbeddingProvider, EmbeddingProviderOptions } from "./embeddings.js";
@@ -73,7 +74,7 @@ function resolveSpec(modelId: string): ModelSpec | undefined {
 
 /** Infer family from model ID prefix when not in catalog. */
 function inferFamily(modelId: string): Family {
-  const id = modelId.toLowerCase();
+  const id = normalizeLowercaseStringOrEmpty(modelId);
   if (id.startsWith("amazon.titan-embed-text-v2")) {
     return "titan-v2";
   }
diff --git a/src/memory-host-sdk/host/qmd-scope.ts b/src/memory-host-sdk/host/qmd-scope.ts
index 7eb522dd55c..3b2a350d2bd 100644
--- a/src/memory-host-sdk/host/qmd-scope.ts
+++ b/src/memory-host-sdk/host/qmd-scope.ts
@@ -80,7 +80,7 @@ function parseQmdSessionScope(key?: string): ParsedQmdSessionScope {
     }
     return {
       normalizedKey: normalized,
-      channel: parts[0]?.toLowerCase(),
+      channel: normalizeOptionalLowercaseString(parts[0]),
       chatType: chatType ?? "direct",
     };
   }
@@ -102,7 +102,7 @@ function normalizeQmdSessionKey(key?: string): string | undefined {
     return undefined;
   }
   const parsed = parseAgentSessionKey(trimmed);
-  const normalized = (parsed?.rest ?? trimmed).toLowerCase();
+  const normalized = normalizeLowercaseStringOrEmpty(parsed?.rest ?? trimmed);
   if (normalized.startsWith("subagent:")) {
     return undefined;
   }
diff --git a/src/node-host/invoke-system-run-plan.ts b/src/node-host/invoke-system-run-plan.ts
index 3dde93a6661..abc2ff33f93 100644
--- a/src/node-host/invoke-system-run-plan.ts
+++ b/src/node-host/invoke-system-run-plan.ts
@@ -19,7 +19,10 @@ import {
   resolveInlineCommandMatch,
 } from "../infra/shell-inline-command.js";
 import { formatExecCommand, resolveSystemRunCommandRequest } from "../infra/system-run-command.js";
-import { normalizeNullableString } from "../shared/string-coerce.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeNullableString,
+} from "../shared/string-coerce.js";
 import { splitShellArgs } from "../utils/shell-argv.js";
 
 export type ApprovedCwdSnapshot = {
@@ -138,6 +141,10 @@ const NODE_OPTIONS_WITH_FILE_VALUE = new Set([
 const RUBY_UNSAFE_APPROVAL_FLAGS = new Set(["-I", "-r", "--require"]);
 const PERL_UNSAFE_APPROVAL_FLAGS = new Set(["-I", "-M", "-m"]);
 
+function normalizeOptionFlag(token: string): string {
+  return normalizeLowercaseStringOrEmpty(token.split("=", 1)[0]);
+}
+
 const POSIX_SHELL_OPTIONS_WITH_VALUE = new Set([
   "--init-file",
   "--rcfile",
@@ -353,7 +360,7 @@ function unwrapPnpmExecInvocation(argv: string[]): string[] | null {
       }
       return null;
     }
-    const [flag] = token.toLowerCase().split("=", 2);
+    const flag = normalizeOptionFlag(token);
     if (PNPM_OPTIONS_WITH_VALUE.has(flag) || PNPM_DLX_OPTIONS_WITH_VALUE.has(flag)) {
       idx += token.includes("=") ? 1 : 2;
       continue;
@@ -384,7 +391,7 @@ function unwrapPnpmDlxInvocation(argv: string[]): string[] | null {
       // package binary pnpm will execute inside the temporary environment.
       return argv.slice(idx);
     }
-    const [flag] = token.toLowerCase().split("=", 2);
+    const flag = normalizeOptionFlag(token);
     if (flag === "-c" || flag === "--shell-mode") {
       return null;
     }
@@ -412,7 +419,7 @@ function unwrapDirectPackageExecInvocation(argv: string[]): string[] | null {
     if (!token.startsWith("-")) {
       return argv.slice(idx);
     }
-    const [flag] = token.toLowerCase().split("=", 2);
+    const flag = normalizeOptionFlag(token);
     if (flag === "-c" || flag === "--call") {
       return null;
     }
@@ -488,7 +495,7 @@ function resolvePosixShellScriptOperandIndex(argv: string[]): number | null {
       return null;
     }
     if (!afterDoubleDash && token.startsWith("-")) {
-      const [flag] = token.toLowerCase().split("=", 2);
+      const flag = normalizeOptionFlag(token);
       if (POSIX_SHELL_OPTIONS_WITH_VALUE.has(flag)) {
         if (!token.includes("=")) {
           i += 1;
@@ -595,7 +602,7 @@ function collectExistingFileOperandIndexes(params: {
     }
     if (token.startsWith("-")) {
       const [flag, inlineValue] = token.split("=", 2);
-      if (params.optionsWithFileValue?.has(flag.toLowerCase())) {
+      if (params.optionsWithFileValue?.has(normalizeLowercaseStringOrEmpty(flag))) {
         if (inlineValue && resolvesToExistingFileSync(inlineValue, params.cwd)) {
           hits.push(i);
           return { hits, sawOptionValueFile: true };
@@ -697,7 +704,7 @@ function hasRubyUnsafeApprovalFlag(argv: string[]): boolean {
     if (token.startsWith("-I") || token.startsWith("-r")) {
       return true;
     }
-    if (RUBY_UNSAFE_APPROVAL_FLAGS.has(token.toLowerCase())) {
+    if (RUBY_UNSAFE_APPROVAL_FLAGS.has(normalizeLowercaseStringOrEmpty(token))) {
       return true;
     }
   }
@@ -851,7 +858,7 @@ function pnpmDlxInvocationNeedsFailClosedBinding(argv: string[], cwd: string | u
       }
       return pnpmDlxTailNeedsFailClosedBinding(argv.slice(idx + 1), cwd);
     }
-    const [flag] = token.toLowerCase().split("=", 2);
+    const flag = normalizeOptionFlag(token);
     if (PNPM_OPTIONS_WITH_VALUE.has(flag) || PNPM_DLX_OPTIONS_WITH_VALUE.has(flag)) {
       idx += token.includes("=") ? 1 : 2;
       continue;
@@ -880,7 +887,7 @@ function pnpmDlxTailNeedsFailClosedBinding(argv: string[], cwd: string | undefin
     if (!token.startsWith("-")) {
       return pnpmDlxTailMayNeedStableBinding(argv.slice(idx), cwd);
     }
-    const [flag] = token.toLowerCase().split("=", 2);
+    const flag = normalizeOptionFlag(token);
     if (flag === "-c" || flag === "--shell-mode") {
       return false;
     }
diff --git a/src/tui/commands.ts b/src/tui/commands.ts
index ae277a23921..21907921c99 100644
--- a/src/tui/commands.ts
+++ b/src/tui/commands.ts
@@ -2,6 +2,7 @@ import type { SlashCommand } from "@mariozechner/pi-tui";
 import { listChatCommands, listChatCommandsForConfig } from "../auto-reply/commands-registry.js";
 import { formatThinkingLevels, listThinkingLevelLabels } from "../auto-reply/thinking.js";
 import type { OpenClawConfig } from "../config/types.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 
 const VERBOSE_LEVELS = ["on", "off"];
 const FAST_LEVELS = ["status", "on", "off"];
@@ -31,7 +32,7 @@ function createLevelCompletion(
 ): NonNullable<SlashCommand["getArgumentCompletions"]> {
   return (prefix) =>
     levels
-      .filter((value) => value.startsWith(prefix.toLowerCase()))
+      .filter((value) => value.startsWith(normalizeLowercaseStringOrEmpty(prefix)))
       .map((value) => ({
         value,
         label: value,
@@ -44,7 +45,7 @@ export function parseCommand(input: string): ParsedCommand {
     return { name: "", args: "" };
   }
   const [name, ...rest] = trimmed.split(/\s+/);
-  const normalized = name.toLowerCase();
+  const normalized = normalizeLowercaseStringOrEmpty(name);
   return {
     name: COMMAND_ALIASES[normalized] ?? normalized,
     args: rest.join(" ").trim(),
@@ -77,7 +78,7 @@ export function getSlashCommands(options: SlashCommandOptions = {}): SlashComman
       description: "Set thinking level",
       getArgumentCompletions: (prefix) =>
         thinkLevels
-          .filter((v) => v.startsWith(prefix.toLowerCase()))
+          .filter((v) => v.startsWith(normalizeLowercaseStringOrEmpty(prefix)))
           .map((value) => ({ value, label: value })),
     },
     {
diff --git a/src/tui/components/filterable-select-list.ts b/src/tui/components/filterable-select-list.ts
index 8c8e41672c7..ca39098e790 100644
--- a/src/tui/components/filterable-select-list.ts
+++ b/src/tui/components/filterable-select-list.ts
@@ -7,6 +7,7 @@ import {
   type SelectListTheme,
 } from "@mariozechner/pi-tui";
 import chalk from "chalk";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { fuzzyFilterLower, prepareSearchItems } from "./fuzzy-filter.js";
 
 export interface FilterableSelectItem extends SelectItem {
@@ -44,7 +45,7 @@ export class FilterableSelectList implements Component {
   }
 
   private applyFilter(): void {
-    const queryLower = this.filterText.toLowerCase();
+    const queryLower = normalizeLowercaseStringOrEmpty(this.filterText);
     if (!queryLower.trim()) {
       this.selectList = new SelectList(this.allItems, this.maxVisible, this.theme);
       return;
diff --git a/src/tui/components/fuzzy-filter.ts b/src/tui/components/fuzzy-filter.ts
index 7fea774223a..5bb8a793fc7 100644
--- a/src/tui/components/fuzzy-filter.ts
+++ b/src/tui/components/fuzzy-filter.ts
@@ -2,6 +2,8 @@
  * Shared fuzzy filtering utilities for select list components.
  */
 
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
+
 /**
  * Word boundary characters for matching.
  */
@@ -22,8 +24,8 @@ export function findWordBoundaryIndex(text: string, query: string): number | nul
   if (!query) {
     return null;
   }
-  const textLower = text.toLowerCase();
-  const queryLower = query.toLowerCase();
+  const textLower = normalizeLowercaseStringOrEmpty(text);
+  const queryLower = normalizeLowercaseStringOrEmpty(query);
   const maxIndex = textLower.length - queryLower.length;
   if (maxIndex < 0) {
     return null;
@@ -133,6 +135,6 @@ export function prepareSearchItems<
     if (item.searchText) {
       parts.push(item.searchText);
     }
-    return { ...item, searchTextLower: parts.join(" ").toLowerCase() };
+    return { ...item, searchTextLower: normalizeLowercaseStringOrEmpty(parts.join(" ")) };
   });
 }
diff --git a/src/tui/components/searchable-select-list.ts b/src/tui/components/searchable-select-list.ts
index 43db6d4d990..678efadb318 100644
--- a/src/tui/components/searchable-select-list.ts
+++ b/src/tui/components/searchable-select-list.ts
@@ -7,6 +7,7 @@ import {
   type SelectListTheme,
   truncateToWidth,
 } from "@mariozechner/pi-tui";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 import { stripAnsi, visibleWidth } from "../../terminal/ansi.js";
 import { findWordBoundaryIndex, fuzzyFilterLower } from "./fuzzy-filter.js";
 
@@ -80,7 +81,7 @@ export class SearchableSelectList implements Component {
    * 4. Fuzzy match (lowest priority)
    */
   private smartFilter(query: string): SelectItem[] {
-    const q = query.toLowerCase();
+    const q = normalizeLowercaseStringOrEmpty(query);
     type ScoredItem = { item: SelectItem; tier: number; score: number };
     type FuzzyCandidate = { item: SelectItem; searchTextLower: string };
     const scoredItems: ScoredItem[] = [];
@@ -89,8 +90,8 @@ export class SearchableSelectList implements Component {
     for (const item of this.items) {
       const rawLabel = this.getItemLabel(item);
       const rawDesc = item.description ?? "";
-      const label = stripAnsi(rawLabel).toLowerCase();
-      const desc = stripAnsi(rawDesc).toLowerCase();
+      const label = normalizeLowercaseStringOrEmpty(stripAnsi(rawLabel));
+      const desc = normalizeLowercaseStringOrEmpty(stripAnsi(rawDesc));
 
       // Tier 1: Exact substring in label
       const labelIndex = label.indexOf(q);
@@ -114,11 +115,12 @@ export class SearchableSelectList implements Component {
       const searchText = (item as { searchText?: string }).searchText ?? "";
       fuzzyCandidates.push({
         item,
-        searchTextLower: [rawLabel, rawDesc, searchText]
-          .map((value) => stripAnsi(value))
-          .filter(Boolean)
-          .join(" ")
-          .toLowerCase(),
+        searchTextLower: normalizeLowercaseStringOrEmpty(
+          [rawLabel, rawDesc, searchText]
+            .map((value) => stripAnsi(value))
+            .filter(Boolean)
+            .join(" "),
+        ),
       });
     }
 
@@ -171,7 +173,7 @@ export class SearchableSelectList implements Component {
     const tokens = query
       .trim()
       .split(/\s+/)
-      .map((token) => token.toLowerCase())
+      .map((token) => normalizeLowercaseStringOrEmpty(token))
       .filter((token) => token.length > 0);
     if (tokens.length === 0) {
       return text;
diff --git a/src/tui/tui-submit.ts b/src/tui/tui-submit.ts
index 81cb1abe593..f048217102a 100644
--- a/src/tui/tui-submit.ts
+++ b/src/tui/tui-submit.ts
@@ -1,3 +1,5 @@
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
+
 export function createEditorSubmitHandler(params: {
   editor: {
     setText: (value: string) => void;
@@ -44,7 +46,7 @@ export function shouldEnableWindowsGitBashPasteFallback(params?: {
 }): boolean {
   const platform = params?.platform ?? process.platform;
   const env = params?.env ?? process.env;
-  const termProgram = (env.TERM_PROGRAM ?? "").toLowerCase();
+  const termProgram = normalizeLowercaseStringOrEmpty(env.TERM_PROGRAM);
 
   // Some macOS terminals emit multiline paste as rapid single-line submits.
   // Enable burst coalescing so pasted blocks stay as one user message.
@@ -64,7 +66,7 @@ export function shouldEnableWindowsGitBashPasteFallback(params?: {
   if (msystem.startsWith("MINGW") || msystem.startsWith("MSYS")) {
     return true;
   }
-  if (shell.toLowerCase().includes("bash")) {
+  if (normalizeLowercaseStringOrEmpty(shell).includes("bash")) {
     return true;
   }
   return termProgram.includes("mintty");
diff --git a/src/tui/tui.ts b/src/tui/tui.ts
index 1fa01dcc890..83b063f6d88 100644
--- a/src/tui/tui.ts
+++ b/src/tui/tui.ts
@@ -16,6 +16,7 @@ import {
   normalizeMainKey,
   parseAgentSessionKey,
 } from "../routing/session-key.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { getSlashCommands } from "./commands.js";
 import { ChatLog } from "./components/chat-log.js";
 import { CustomEditor } from "./components/custom-editor.js";
@@ -69,9 +70,9 @@ export function resolveTuiSessionKey(params: {
     return trimmed;
   }
   if (trimmed.startsWith("agent:")) {
-    return trimmed.toLowerCase();
+    return normalizeLowercaseStringOrEmpty(trimmed);
   }
-  return `agent:${params.currentAgentId}:${trimmed.toLowerCase()}`;
+  return `agent:${params.currentAgentId}:${normalizeLowercaseStringOrEmpty(trimmed)}`;
 }
 
 export function resolveInitialTuiAgentId(params: {