diff --git a/extension/background.js b/extension/background.js
index 68b8400..c794baa 100644
--- a/extension/background.js
+++ b/extension/background.js
@@ -892,13 +892,7 @@ async function importSettings(file) {
 // A saved key belongs to the host it was saved for (options.js savedKeyApplies): a key whose platform row, or the
 // Obsidian address, points at another origin after an import is dropped, never sent there; the user enters it again.
 async function dropMovedKeys(before, after) {
-  const origin = (url) => {
-    try {
-      return new URL(String(url).trim()).origin;
-    } catch {
-      return "";
-    }
-  };
+  const origin = MdgSettings.urlOrigin;
   const origins = (settings) => new Map((Array.isArray(settings[AI_PROVIDERS]) ? settings[AI_PROVIDERS] : []).map((p) => [String(p?.id || "").trim(), origin(p?.baseUrl)]));
   const [was, now] = [origins(before), origins(after)];
   const keys = await loadAiProviderKeys();
@@ -912,9 +906,6 @@ async function dropMovedKeys(before, after) {
 
 const { aiApiKeys: AI_PROVIDER_KEYS_STORAGE, aiProviderList: AI_PROVIDERS } = MdgLimits.KEYS;
 
-// An AI platform's address as requests use it: no spaces, no trailing slashes.
-const trimBaseUrl = (url) => String(url || "").trim().replace(/\/+$/, "");
-
 function normalizeAiProvider(item) {
   if (!item || typeof item !== "object") return null;
   const id = String(item.id || "").trim();
@@ -923,7 +914,7 @@ function normalizeAiProvider(item) {
     id,
     presetId: String(item.presetId || "custom"),
     name: String(item.name || "").trim() || MdgErrors.LABEL.customAi,
-    baseUrl: trimBaseUrl(item.baseUrl),
+    baseUrl: MdgSettings.trimBaseUrl(item.baseUrl),
     model: String(item.model || "").trim(),
     temperature: typeof item.temperature === "number" ? item.temperature : 0.7,
     requiresKey: item.requiresKey !== false,
@@ -1264,7 +1255,7 @@ async function testAiConnection({ baseUrl, apiKey, model, requiresKey }) {
     return { ok: false, error: problem.text, code: problem.code };
   }
   return probeAiChatCompletion({
-    baseUrl: trimBaseUrl(baseUrl),
+    baseUrl: MdgSettings.trimBaseUrl(baseUrl),
     apiKey,
     model: String(model).trim()
   });
diff --git a/extension/options.js b/extension/options.js
index 8c9bc0a..1020ed5 100644
--- a/extension/options.js
+++ b/extension/options.js
@@ -513,7 +513,7 @@ function syncObsidianKeyTag() {
 // While a save or a test runs it stays disabled; setBusy(null) calls this again.
 // The result next to it is for the 地址 and Key it tested: an edit away from them clears it.
 function syncObsidianTest() {
-  const typed = { obsidianApiBaseUrl: normalizeBaseUrl(elements.obsidianApiBaseUrl.value), obsidianApiKey: MdgSettings.normalizeApiKey(elements.obsidianApiKey.value) };
+  const typed = { obsidianApiBaseUrl: MdgSettings.trimBaseUrl(elements.obsidianApiBaseUrl.value), obsidianApiKey: MdgSettings.normalizeApiKey(elements.obsidianApiKey.value) };
   if (obsidianTest && obsidianTest.target !== obsidianTarget(typed)) {
     obsidianTests.next();
     setTestResult("");
@@ -552,7 +552,7 @@ function readFormPayload() {
   const normalized = MdgSettings.normalizeSyncSettings(form);
   return {
     ...Object.fromEntries(Object.keys(form).map((k) => [k, normalized[k]])),
-    obsidianApiBaseUrl: normalizeBaseUrl(elements.obsidianApiBaseUrl.value),
+    obsidianApiBaseUrl: MdgSettings.trimBaseUrl(elements.obsidianApiBaseUrl.value),
     obsidianApiKey: MdgSettings.normalizeApiKey(elements.obsidianApiKey.value)
   };
 }
@@ -988,11 +988,6 @@ function closeAllFixedPropertyMenus() {
   });
 }
 
-function normalizeBaseUrl(value) {
-  return String(value || "").trim().replace(/\/+$/g, "");
-}
-
-
 async function testConnection() {
   clearInputErrors();
   const payload = collectFormPayload();
@@ -1118,7 +1113,7 @@ function addAiProviderRow(item = {}) {
   row.className = "ai-provider-row";
   row.dataset.providerId = id;
   row.dataset.hasSavedKey = hasSavedKey ? "1" : "0";
-  row.dataset.keyOrigin = urlOrigin(baseUrl);
+  row.dataset.keyOrigin = MdgSettings.urlOrigin(baseUrl);
   row.dataset.currentPresetId = presetId;
   row.innerHTML = `
     <select class="ai-provider-preset" name="aiProviderPreset" aria-label="平台">
@@ -1288,15 +1283,7 @@ async function testAiProviderRow(row, sync) {
 // A saved Key belongs to the host it was saved for: once 接口地址 points at another host it is neither sent nor counted as
 // filled, so switching platform asks for that platform's Key.
 function savedKeyApplies(row) {
-  return row.dataset.hasSavedKey === "1" && urlOrigin(row.querySelector(".ai-provider-baseurl").value) === row.dataset.keyOrigin;
-}
-
-function urlOrigin(url) {
-  try {
-    return new URL(String(url).trim()).origin;
-  } catch {
-    return "";
-  }
+  return row.dataset.hasSavedKey === "1" && MdgSettings.urlOrigin(row.querySelector(".ai-provider-baseurl").value) === row.dataset.keyOrigin;
 }
 
 function apiKeyPlaceholder(hasSavedKey, requiresKey) {
diff --git a/extension/options.selftest.js b/extension/options.selftest.js
index 7fa5b24..d930c0e 100644
--- a/extension/options.selftest.js
+++ b/extension/options.selftest.js
@@ -83,7 +83,7 @@ vm.runInContext(["const { escapeHtml } = MdgErrors;", fn("buildFixedPropertyValu
 for (const bad of XSS) assertInert(ctx.buildFixedPropertyValueControl("text", bad), "property value");
 
 // Obsidian's 测试连接 is disabled with the reason while the 地址 or the Key is empty, like an AI platform row's (H2).
-vm.runInContext([fn("syncObsidianTest"), fn("obsidianTarget"), fn("normalizeBaseUrl"), fn("setTestResult")].join("\n"), ctx);
+vm.runInContext([fn("syncObsidianTest"), fn("obsidianTarget"), fn("setTestResult")].join("\n"), ctx);
 const testBtn = { setAttribute() {}, removeAttribute() {} };
 Object.assign(ctx.elements, { testConnectionBtn: testBtn, obsidianApiBaseUrl: { value: "" }, obsidianApiKey: { value: " " }, obsidianTestResult: { textContent: "", dataset: {} } });
 ctx.syncObsidianTest();
@@ -110,7 +110,7 @@ ctx.obsidianTest = null;
 (async () => {
   // fn() slices from "function": testConnection is async.
   vm.runInContext([`async ${fn("testConnection")}`, "let hasUnsavedChanges = false;"].join("\n"), ctx);
-  const typed = () => ({ obsidianApiBaseUrl: ctx.normalizeBaseUrl(ctx.elements.obsidianApiBaseUrl.value), obsidianApiKey: ctx.MdgSettings.normalizeApiKey(ctx.elements.obsidianApiKey.value) });
+  const typed = () => ({ obsidianApiBaseUrl: ctx.MdgSettings.trimBaseUrl(ctx.elements.obsidianApiBaseUrl.value), obsidianApiKey: ctx.MdgSettings.normalizeApiKey(ctx.elements.obsidianApiKey.value) });
   Object.assign(ctx, { clearInputErrors() {}, collectFormPayload: typed, validateSettings: () => ({ ok: true }), applyValidationError() {}, setBusy() {}, renderSavedState() {} });
   let answer;
   ctx.chrome = { runtime: { sendMessage: () => new Promise((r) => (answer = () => r({ ok: true, service: "Obsidian" }))) } };
@@ -172,8 +172,8 @@ assert.ok(!/seenThreshold\.value = String\((readFormPayload\(\)|payload)\.seenTh
   };
   const parts = {};
   const row = { ...stub(), querySelector: (sel) => (parts[sel] ||= stub()), querySelectorAll: () => [] };
-  const page = vm.createContext({ URL, MdgErrors: ctx.MdgErrors, escapeHtml: ctx.MdgErrors.escapeHtml, AI_PRESETS: [{ id: "custom", name: "自定义", baseUrl: "", model: "" }], document: { createElement: () => row }, elements: { aiProvidersList: { appendChild() {} } }, updateAiProvidersEmptyState() {} });
-  vm.runInContext([constant("TRASH_ICON"), constant("AI_FIELD"), fn("addAiProviderRow"), fn("presetOf"), constant("PLAIN_HTTP_WARNING"), fn("plainHttpWarning"), fn("apiKeyPlaceholder"), fn("generateAiProviderId"), fn("savedKeyApplies"), fn("urlOrigin")].join("\n"), page);
+  const page = vm.createContext({ URL, MdgErrors: ctx.MdgErrors, MdgSettings: ctx.MdgSettings, escapeHtml: ctx.MdgErrors.escapeHtml, AI_PRESETS: [{ id: "custom", name: "自定义", baseUrl: "", model: "" }], document: { createElement: () => row }, elements: { aiProvidersList: { appendChild() {} } }, updateAiProvidersEmptyState() {} });
+  vm.runInContext([constant("TRASH_ICON"), constant("AI_FIELD"), fn("addAiProviderRow"), fn("presetOf"), constant("PLAIN_HTTP_WARNING"), fn("plainHttpWarning"), fn("apiKeyPlaceholder"), fn("generateAiProviderId"), fn("savedKeyApplies")].join("\n"), page);
   page.addAiProviderRow({});
   const test = parts[".ai-provider-test"];
   const type = (sel, v) => ((parts[sel].value = v), parts[sel].L.input.forEach((f) => f()));
@@ -194,7 +194,7 @@ assert.ok(!/seenThreshold\.value = String\((readFormPayload\(\)|payload)\.seenTh
 {
   const btn = (textContent) => ({ textContent, dataset: {}, setAttribute() {}, removeAttribute() {} });
   const page = vm.createContext({ MdgErrors: ctx.MdgErrors, MdgSettings: ctx.MdgSettings, busyButton: null, obsidianTest: null, elements: { saveBtn: btn("保存"), testConnectionBtn: btn("测试连接"), obsidianApiBaseUrl: { value: "http://127.0.0.1:27123" }, obsidianApiKey: { value: "" } } });
-  vm.runInContext([fn("setBusy"), fn("syncObsidianTest"), fn("normalizeBaseUrl")].join("\n"), page);
+  vm.runInContext([fn("setBusy"), fn("syncObsidianTest")].join("\n"), page);
   page.setBusy(page.elements.testConnectionBtn);
   page.elements.obsidianApiKey.value = "new key";
   page.syncObsidianTest();
@@ -247,7 +247,7 @@ assert.ok(!/seenThreshold\.value = String\((readFormPayload\(\)|payload)\.seenTh
     updateAiProvidersEmptyState() {},
     chrome: { permissions: { request: async () => true }, runtime: { sendMessage: (m) => (sent.push(m), new Promise((r) => (answer = r))) } }
   });
-  vm.runInContext([constant("TRASH_ICON"), constant("AI_FIELD"), fn("addAiProviderRow"), fn("presetOf"), constant("PLAIN_HTTP_WARNING"), fn("plainHttpWarning"), fn("apiKeyPlaceholder"), fn("generateAiProviderId"), fn("savedKeyApplies"), fn("urlOrigin"), fn("collectAiProviders"), fn("hostPermissionPattern"), fn("showAiProviderStatus"), `async ${fn("testAiProviderRow")}`].join("\n"), page);
+  vm.runInContext([constant("TRASH_ICON"), constant("AI_FIELD"), fn("addAiProviderRow"), fn("presetOf"), constant("PLAIN_HTTP_WARNING"), fn("plainHttpWarning"), fn("apiKeyPlaceholder"), fn("generateAiProviderId"), fn("savedKeyApplies"), fn("collectAiProviders"), fn("hostPermissionPattern"), fn("showAiProviderStatus"), `async ${fn("testAiProviderRow")}`].join("\n"), page);
   page.addAiProviderRow({ id: "p1", presetId: "deepseek", baseUrl: "https://api.deepseek.com/v1", model: "deepseek-flash", hasSavedKey: true });
   parts[".ai-provider-preset"].value = "deepseek";
   const type = (sel, v) => ((parts[sel].value = v), parts[sel].L.input.forEach((f) => f()));
@@ -403,11 +403,11 @@ assert.ok(!/seenThreshold\.value = String\((readFormPayload\(\)|payload)\.seenTh
   let reply;
   const row = { ...stub(), querySelector: (sel) => (parts[sel] ||= stub()), querySelectorAll: () => [], remove: () => removed++ };
   const page = vm.createContext({
-    URL, MdgErrors: ctx.MdgErrors, escapeHtml: ctx.MdgErrors.escapeHtml, AI_PRESETS: [{ id: "custom", name: "自定义", baseUrl: "", model: "", requiresKey: true }],
+    URL, MdgErrors: ctx.MdgErrors, MdgSettings: ctx.MdgSettings, escapeHtml: ctx.MdgErrors.escapeHtml, AI_PRESETS: [{ id: "custom", name: "自定义", baseUrl: "", model: "", requiresKey: true }],
     document: { createElement: () => row }, elements: { aiProvidersList: { appendChild() {} } },
     updateAiProvidersEmptyState() {}, updateSavedProviders() {}, chrome: { runtime: { sendMessage: async () => reply() } }
   });
-  vm.runInContext([constant("TRASH_ICON"), constant("AI_FIELD"), fn("addAiProviderRow"), fn("presetOf"), constant("PLAIN_HTTP_WARNING"), fn("plainHttpWarning"), fn("apiKeyPlaceholder"), fn("generateAiProviderId"), fn("savedKeyApplies"), fn("urlOrigin"), fn("showAiProviderStatus")].join("\n"), page);
+  vm.runInContext([constant("TRASH_ICON"), constant("AI_FIELD"), fn("addAiProviderRow"), fn("presetOf"), constant("PLAIN_HTTP_WARNING"), fn("plainHttpWarning"), fn("apiKeyPlaceholder"), fn("generateAiProviderId"), fn("savedKeyApplies"), fn("showAiProviderStatus")].join("\n"), page);
   page.addAiProviderRow({ id: "p1" });
   const del = parts[".ai-provider-remove"];
   const status = parts[".ai-provider-status"];
@@ -443,7 +443,7 @@ assert.ok(!/seenThreshold\.value = String\((readFormPayload\(\)|payload)\.seenTh
     chrome: { permissions: { request: async ({ origins }) => (log.push(`ask ${origins}`), allow) }, runtime: { sendMessage: async (m) => (log.push(`test ${m.baseUrl}`), { ok: true }) } }
   });
   vm.runInContext(fs.readFileSync(path.join(__dirname, "errors.js"), "utf8"), page);
-  vm.runInContext([fn("hostPermissionPattern"), fn("showAiProviderStatus"), fn("savedKeyApplies"), fn("urlOrigin"), fn("presetOf"), `async ${fn("testAiProviderRow")}`].join("\n"), page);
+  vm.runInContext([fn("hostPermissionPattern"), fn("showAiProviderStatus"), fn("savedKeyApplies"), fn("presetOf"), `async ${fn("testAiProviderRow")}`].join("\n"), page);
   // L4: the declined permission carries its code, as the background's does.
   const replies = [];
   const realText = page.MdgErrors.text;
@@ -484,7 +484,7 @@ assert.ok(!/seenThreshold\.value = String\((readFormPayload\(\)|payload)\.seenTh
     renderBiliMarks() {}, renderStorageLimits() {}, syncObsidianBody() {}, syncSeenRows() {}, syncBiliMarks() {}, renderAiProviders() {},
     renderHostPermissionBanner() {}, hostPermissionUrls() {}, markSaved() {}
   });
-  vm.runInContext([constant("DEFAULT_SETTINGS"), constant("elements"), "elements.frontmatterFields = document.querySelectorAll(\"input[name=frontmatterField]\");", constant("formKeys"), constant("SWITCH_KEYS"), constant("VALUE_KEYS"), `async ${fn("loadSettings")}`, fn("readFormPayload"), fn("normalizeBaseUrl")].join("\n"), page);
+  vm.runInContext([constant("DEFAULT_SETTINGS"), constant("elements"), "elements.frontmatterFields = document.querySelectorAll(\"input[name=frontmatterField]\");", constant("formKeys"), constant("SWITCH_KEYS"), constant("VALUE_KEYS"), `async ${fn("loadSettings")}`, fn("readFormPayload")].join("\n"), page);
   await page.loadSettings();
   const payload = page.readFormPayload();
   const keys = ["obsidianEnabled", "noteFolder", "obsidianApiBaseUrl", "obsidianApiKey", "tags", "downloadFormat", "youtubeSubtitleLang", "includeDateInFilename", "includeHotCommentsInNote", "includeCoverInNote", "includeAiChatInNote", "enablePlayerAiQuickAction", "playerAiQuickPrompt", "includeTimestampInBody", "showBiliTriageBadges", "showBiliUpTags", "showBiliVerdicts", "biliMarksOff", "seenShow", "seenThreshold", "seenStyle", "enableDebugLogs", "frontmatterFields", "fixedFrontmatterProperties", "notePlaceholderSections", "aiSystemPrompt", "aiPresetPrompts", "webAiSystemPrompt", "webAiSummaryPrompt", "webAiPresetPrompts"];
diff --git a/extension/settings.js b/extension/settings.js
index 069f64f..aa77ac0 100644
--- a/extension/settings.js
+++ b/extension/settings.js
@@ -115,6 +115,16 @@
   // A note field as stored: "bvid" was video_id's name before the site registry (the settings page and note.js both read it).
   const normalizeFrontmatterField = (value) => text(value).replace(/^bvid$/, "video_id");
   const normalizeApiKey = (value) => text(value).replace(/^Bearer\s+/i, "").trim();
+  // An address (AI platform, Obsidian) as requests use it: no spaces, no trailing slashes.
+  const trimBaseUrl = (url) => String(url || "").trim().replace(/\/+$/, "");
+  // A saved Key belongs to its address's origin (options.js savedKeyApplies, background.js dropMovedKeys); "" if not a URL.
+  const urlOrigin = (url) => {
+    try {
+      return new URL(String(url).trim()).origin;
+    } catch {
+      return "";
+    }
+  };
   const normalizeDownloadFormat = (value) => (value === "txt" ? "txt" : "srt");
   const normalizePlayerAiQuickPrompt = (value) => text(value);
   // 快捷追问: trimmed, no blanks or repeats, at most MAX_PRESET_PROMPTS.
@@ -246,6 +256,8 @@
     normalizeAiSystemPrompt,
     normalizeSeenThreshold,
     normalizeApiKey,
+    trimBaseUrl,
+    urlOrigin,
     normalizeFrontmatterField,
     normalizeDownloadFormat,
     normalizePlayerAiQuickPrompt,
diff --git a/extension/settings.selftest.js b/extension/settings.selftest.js
index 6fe9313..bd6be47 100644
--- a/extension/settings.selftest.js
+++ b/extension/settings.selftest.js
@@ -6,7 +6,7 @@ const vm = require("vm");
 const assert = require("assert");
 
 const read = (file) => fs.readFileSync(path.join(__dirname, file), "utf8");
-const ctx = vm.createContext({});
+const ctx = vm.createContext({ URL });
 ctx.globalThis = ctx;
 vm.runInContext(read("common.js"), ctx);
 vm.runInContext(read("settings.js"), ctx);
@@ -34,6 +34,9 @@ assert.deepStrictEqual(["zh-Hans", "fr", undefined].map(S.normalizeSubtitleLang)
 
 assert.strictEqual(S.normalizeApiKey("  Bearer abc "), "abc");
 assert.strictEqual(S.normalizeApiKey(undefined), "");
+// An AI platform's or Obsidian's address, and the origin its saved Key belongs to.
+assert.deepStrictEqual([" https://api.x.com/v1// ", "", undefined].map(S.trimBaseUrl), ["https://api.x.com/v1", "", ""]);
+assert.deepStrictEqual([" https://api.x.com/v1/ ", "http://127.0.0.1:27123", "api.x.com", "", undefined].map(S.urlOrigin), ["https://api.x.com", "http://127.0.0.1:27123", "", "", ""]);
 assert.strictEqual(S.normalizeDownloadFormat("txt"), "txt");
 assert.strictEqual(S.normalizeDownloadFormat("TXT"), "srt");
 // Non-strings keep their text (an imported file may carry numbers); only null and undefined are empty.