diff --git a/extensions/anthropic-vertex/region.ts b/extensions/anthropic-vertex/region.ts
index d7407ba2c91..ca4e322093d 100644
--- a/extensions/anthropic-vertex/region.ts
+++ b/extensions/anthropic-vertex/region.ts
@@ -2,6 +2,7 @@ import { readFileSync } from "node:fs";
 import { homedir, platform } from "node:os";
 import { join } from "node:path";
 import { resolveProviderEndpoint } from "openclaw/plugin-sdk/provider-http";
+import { normalizeLowercaseStringOrEmpty } from "openclaw/plugin-sdk/text-runtime";
 
 const ANTHROPIC_VERTEX_DEFAULT_REGION = "global";
 const ANTHROPIC_VERTEX_REGION_RE = /^[a-z0-9-]+$/;
@@ -64,7 +65,10 @@ export function resolveAnthropicVertexClientRegion(params?: {
 
 function hasAnthropicVertexMetadataServerAdc(env: NodeJS.ProcessEnv = process.env): boolean {
   const explicitMetadataOptIn = normalizeOptionalSecretInput(env.ANTHROPIC_VERTEX_USE_GCP_METADATA);
-  return explicitMetadataOptIn === "1" || explicitMetadataOptIn?.toLowerCase() === "true";
+  return (
+    explicitMetadataOptIn === "1" ||
+    normalizeLowercaseStringOrEmpty(explicitMetadataOptIn) === "true"
+  );
 }
 
 function resolveAnthropicVertexDefaultAdcPath(env: NodeJS.ProcessEnv = process.env): string {
diff --git a/extensions/discord/src/media-detection.ts b/extensions/discord/src/media-detection.ts
index aef9f64bfda..9afa48bd2f8 100644
--- a/extensions/discord/src/media-detection.ts
+++ b/extensions/discord/src/media-detection.ts
@@ -1,3 +1,5 @@
+import { normalizeLowercaseStringOrEmpty } from "openclaw/plugin-sdk/text-runtime";
+
 const DISCORD_VIDEO_MEDIA_EXTENSIONS = new Set([".avi", ".m4v", ".mkv", ".mov", ".mp4", ".webm"]);
 
 function normalizeMediaPathForExtension(mediaUrl: string): string {
@@ -7,11 +9,11 @@ function normalizeMediaPathForExtension(mediaUrl: string): string {
   }
   try {
     const parsed = new URL(trimmed);
-    return parsed.pathname.toLowerCase();
+    return normalizeLowercaseStringOrEmpty(parsed.pathname);
   } catch {
     const withoutHash = trimmed.split("#", 1)[0] ?? trimmed;
     const withoutQuery = withoutHash.split("?", 1)[0] ?? withoutHash;
-    return withoutQuery.toLowerCase();
+    return normalizeLowercaseStringOrEmpty(withoutQuery);
   }
 }
 
diff --git a/src/agents/model-ref-shared.ts b/src/agents/model-ref-shared.ts
index 91fda4a8022..09d1a7466d7 100644
--- a/src/agents/model-ref-shared.ts
+++ b/src/agents/model-ref-shared.ts
@@ -2,6 +2,7 @@ import {
   normalizeGooglePreviewModelId,
   normalizeNativeXaiModelId,
 } from "../plugin-sdk/provider-model-id-normalize.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { normalizeProviderId } from "./provider-id.js";
 
 export type StaticModelRef = {
@@ -18,7 +19,9 @@ export function modelKey(provider: string, model: string): string {
   if (!modelId) {
     return providerId;
   }
-  return modelId.toLowerCase().startsWith(`${providerId.toLowerCase()}/`)
+  return normalizeLowercaseStringOrEmpty(modelId).startsWith(
+    `${normalizeLowercaseStringOrEmpty(providerId)}/`,
+  )
     ? modelId
     : `${providerId}/${modelId}`;
 }
@@ -28,7 +31,7 @@ export function normalizeAnthropicModelId(model: string): string {
   if (!trimmed) {
     return trimmed;
   }
-  switch (trimmed.toLowerCase()) {
+  switch (normalizeLowercaseStringOrEmpty(trimmed)) {
     case "opus-4.6":
       return "claude-opus-4-6";
     case "opus-4.5":
@@ -48,7 +51,9 @@ function normalizeHuggingfaceModelId(model: string): string {
     return trimmed;
   }
   const prefix = "huggingface/";
-  return trimmed.toLowerCase().startsWith(prefix) ? trimmed.slice(prefix.length) : trimmed;
+  return normalizeLowercaseStringOrEmpty(trimmed).startsWith(prefix)
+    ? trimmed.slice(prefix.length)
+    : trimmed;
 }
 
 export function normalizeStaticProviderModelId(provider: string, model: string): string {
diff --git a/src/channels/plugins/module-loader.ts b/src/channels/plugins/module-loader.ts
index cb246a4ef6f..44a4af7faa0 100644
--- a/src/channels/plugins/module-loader.ts
+++ b/src/channels/plugins/module-loader.ts
@@ -7,6 +7,7 @@ import {
   buildPluginLoaderJitiOptions,
   resolvePluginLoaderJitiConfig,
 } from "../../plugins/sdk-alias.js";
+import { normalizeLowercaseStringOrEmpty } from "../../shared/string-coerce.js";
 
 const nodeRequire = createRequire(import.meta.url);
 
@@ -36,7 +37,9 @@ function createModuleLoader() {
 let loadModule = createModuleLoader();
 
 export function isJavaScriptModulePath(modulePath: string): boolean {
-  return [".js", ".mjs", ".cjs"].includes(path.extname(modulePath).toLowerCase());
+  return [".js", ".mjs", ".cjs"].includes(
+    normalizeLowercaseStringOrEmpty(path.extname(modulePath)),
+  );
 }
 
 export function resolveCompiledBundledModulePath(modulePath: string): string {
diff --git a/src/plugin-sdk/anthropic-vertex-auth-presence.ts b/src/plugin-sdk/anthropic-vertex-auth-presence.ts
index 4a3d2e068a0..79d72e5f6cb 100644
--- a/src/plugin-sdk/anthropic-vertex-auth-presence.ts
+++ b/src/plugin-sdk/anthropic-vertex-auth-presence.ts
@@ -1,7 +1,10 @@
 import { readFileSync } from "node:fs";
 import { homedir, platform } from "node:os";
 import { join } from "node:path";
-import { normalizeOptionalString } from "../shared/string-coerce.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeOptionalString,
+} from "../shared/string-coerce.js";
 import { normalizeOptionalSecretInput } from "../utils/normalize-secret-input.js";
 
 const GCLOUD_DEFAULT_ADC_PATH = join(
@@ -13,7 +16,10 @@ const GCLOUD_DEFAULT_ADC_PATH = join(
 
 function hasAnthropicVertexMetadataServerAdc(env: NodeJS.ProcessEnv = process.env): boolean {
   const explicitMetadataOptIn = normalizeOptionalSecretInput(env.ANTHROPIC_VERTEX_USE_GCP_METADATA);
-  return explicitMetadataOptIn === "1" || explicitMetadataOptIn?.toLowerCase() === "true";
+  return (
+    explicitMetadataOptIn === "1" ||
+    normalizeLowercaseStringOrEmpty(explicitMetadataOptIn) === "true"
+  );
 }
 
 function resolveAnthropicVertexDefaultAdcPath(env: NodeJS.ProcessEnv = process.env): string {
diff --git a/src/plugin-sdk/windows-spawn.ts b/src/plugin-sdk/windows-spawn.ts
index 688d708a3be..735c6931ef4 100644
--- a/src/plugin-sdk/windows-spawn.ts
+++ b/src/plugin-sdk/windows-spawn.ts
@@ -1,6 +1,9 @@
 import { readFileSync, statSync } from "node:fs";
 import path from "node:path";
-import { normalizeOptionalString } from "../shared/string-coerce.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeOptionalString,
+} from "../shared/string-coerce.js";
 
 export type WindowsSpawnResolution =
   | "direct"
@@ -82,7 +85,9 @@ export function resolveWindowsExecutablePath(command: string, env: NodeJS.Proces
 
   for (const dir of pathEntries) {
     for (const ext of pathExt) {
-      for (const candidateExt of [ext, ext.toLowerCase(), ext.toUpperCase()]) {
+      const normalizedExt = normalizeLowercaseStringOrEmpty(ext);
+      const uppercaseExt = ext.toUpperCase();
+      for (const candidateExt of [ext, normalizedExt, uppercaseExt]) {
         const candidate = path.join(dir, `${command}${candidateExt}`);
         if (isFilePath(candidate)) {
           return candidate;
@@ -116,7 +121,7 @@ function resolveEntrypointFromCmdShim(wrapperPath: string): string | null {
       }
     }
     const nonNode = candidates.find((candidate) => {
-      const base = path.basename(candidate).toLowerCase();
+      const base = normalizeLowercaseStringOrEmpty(path.basename(candidate));
       return base !== "node.exe" && base !== "node";
     });
     return nonNode ?? null;
@@ -211,7 +216,7 @@ export function resolveWindowsSpawnProgramCandidate(
   }
 
   const resolvedCommand = resolveWindowsExecutablePath(params.command, env);
-  const ext = path.extname(resolvedCommand).toLowerCase();
+  const ext = normalizeLowercaseStringOrEmpty(path.extname(resolvedCommand));
   if (ext === ".js" || ext === ".cjs" || ext === ".mjs") {
     return {
       command: execPath,
@@ -226,7 +231,7 @@ export function resolveWindowsSpawnProgramCandidate(
       resolveEntrypointFromCmdShim(resolvedCommand) ??
       resolveEntrypointFromPackageJson(resolvedCommand, params.packageName);
     if (entrypoint) {
-      const entryExt = path.extname(entrypoint).toLowerCase();
+      const entryExt = normalizeLowercaseStringOrEmpty(path.extname(entrypoint));
       if (entryExt === ".exe") {
         return {
           command: entrypoint,
diff --git a/src/process/exec.ts b/src/process/exec.ts
index ae22ecf4ea1..263dd76493c 100644
--- a/src/process/exec.ts
+++ b/src/process/exec.ts
@@ -6,6 +6,7 @@ import { promisify } from "node:util";
 import { danger, shouldLogVerbose } from "../globals.js";
 import { markOpenClawExecEnv } from "../infra/openclaw-exec-env.js";
 import { logDebug, logError } from "../logger.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { resolveCommandStdio } from "./spawn-utils.js";
 import { resolveWindowsCommandShim } from "./windows-command.js";
 
@@ -17,7 +18,7 @@ function isWindowsBatchCommand(resolvedCommand: string): boolean {
   if (process.platform !== "win32") {
     return false;
   }
-  const ext = path.extname(resolvedCommand).toLowerCase();
+  const ext = normalizeLowercaseStringOrEmpty(path.extname(resolvedCommand));
   return ext === ".cmd" || ext === ".bat";
 }
 
@@ -49,10 +50,10 @@ function resolveNpmArgvForWindows(argv: string[]): string[] | null {
   if (process.platform !== "win32" || argv.length === 0) {
     return null;
   }
-  const basename = path
-    .basename(argv[0])
-    .toLowerCase()
-    .replace(/\.(cmd|exe|bat)$/, "");
+  const basename = normalizeLowercaseStringOrEmpty(path.basename(argv[0])).replace(
+    /\.(cmd|exe|bat)$/,
+    "",
+  );
   const cliName = basename === "npx" ? "npx-cli.js" : basename === "npm" ? "npm-cli.js" : null;
   if (!cliName) {
     return null;
@@ -64,7 +65,7 @@ function resolveNpmArgvForWindows(argv: string[]): string[] | null {
     // Fall back to npm.cmd/npx.cmd so we still route through cmd wrapper
     // (avoids direct .cmd spawn EINVAL on patched Node).
     const command = argv[0] ?? "";
-    const ext = path.extname(command).toLowerCase();
+    const ext = normalizeLowercaseStringOrEmpty(path.extname(command));
     const shimmedCommand = ext ? command : `${command}.cmd`;
     return [shimmedCommand, ...argv.slice(1)];
   }
diff --git a/src/process/windows-command.ts b/src/process/windows-command.ts
index c8e5981e2ef..6226c25529c 100644
--- a/src/process/windows-command.ts
+++ b/src/process/windows-command.ts
@@ -1,5 +1,6 @@
 import path from "node:path";
 import process from "node:process";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 
 export function resolveWindowsCommandShim(params: {
   command: string;
@@ -9,7 +10,7 @@ export function resolveWindowsCommandShim(params: {
   if ((params.platform ?? process.platform) !== "win32") {
     return params.command;
   }
-  const basename = path.basename(params.command).toLowerCase();
+  const basename = normalizeLowercaseStringOrEmpty(path.basename(params.command));
   if (path.extname(basename)) {
     return params.command;
   }