diff --git a/src/main/index.ts b/src/main/index.ts
index 213204e..4b6df15 100644
--- a/src/main/index.ts
+++ b/src/main/index.ts
@@ -21,20 +21,23 @@ import { getStore } from './config/store'
 import { migrateProvidersToConnections } from './config/connectionMigration'
 import { isSmokeTestRequested, runSmokeTest } from './smokeTest'
 import { isEvalRequested, runEvalCli } from './eval/run'
+import { declareDocumentScheme, registerDocumentProtocolHandler } from './protocol/documentProtocol'
 import {
-  registerDocumentProtocolHandler,
-  registerDocumentScheme
-} from './protocol/documentProtocol'
-import {
-  registerPdfjsAssetProtocolHandler,
-  registerPdfjsAssetScheme
+  declarePdfjsAssetScheme,
+  registerPdfjsAssetProtocolHandler
 } from './protocol/pdfjsAssetProtocol'
+import { applyPrivilegedSchemes } from './protocol/privilegedSchemes'
 import Logger from '../shared/utils/logger'
 
-// Scheme privileges must be registered before the app is ready, so this is a
-// module-scope call rather than part of the whenReady sequence.
-registerDocumentScheme()
-registerPdfjsAssetScheme()
+// Scheme privileges must be declared before the app is ready, so this is a
+// module-scope sequence rather than part of the whenReady flow. They are
+// submitted in one call on purpose: Electron *replaces* the privilege table
+// instead of appending to it, so a second `registerSchemesAsPrivileged()` drops
+// every scheme registered by the first - which is how `knownote-asset` silently
+// broke `knownote-doc` and the PDF reader (#135).
+declareDocumentScheme()
+declarePdfjsAssetScheme()
+applyPrivilegedSchemes()
 
 let connectionManager: ConnectionManager | null = null
 let embeddingService: EmbeddingService | null = null
diff --git a/src/main/protocol/documentProtocol.ts b/src/main/protocol/documentProtocol.ts
index 667779f..3a42337 100644
--- a/src/main/protocol/documentProtocol.ts
+++ b/src/main/protocol/documentProtocol.ts
@@ -4,13 +4,14 @@
  * 渲染进程不应拿到任意文件路径。它只知道 documentId，主进程按 id 查库、只服务
  * 这份来源自己的文件。路径永远来自数据库，不来自请求，因此不存在路径穿越。
  *
- * scheme 必须在 app ready 之前注册为 privileged；handler 在 ready 之后安装。
+ * scheme 必须在 app ready 之前声明为 privileged；handler 在 ready 之后安装。
  */
 
 import { net, protocol } from 'electron'
 import { pathToFileURL } from 'url'
 import { DOCUMENT_SCHEME, parseDocumentUrl } from '../../shared/utils/documentUrl'
 import Logger from '../../shared/utils/logger'
+import { declarePrivilegedScheme } from './privilegedSchemes'
 
 /**
  * Origins allowed to read a document. The renderer is `file://` in production
@@ -22,23 +23,21 @@ const ALLOWED_ORIGINS = new Set(['null', 'http://localhost:5173', 'http://127.0.
 
 export { DOCUMENT_SCHEME, documentUrl, parseDocumentUrl } from '../../shared/utils/documentUrl'
 
-/** 必须在 app ready 之前调用一次。 */
-export function registerDocumentScheme(): void {
-  protocol.registerSchemesAsPrivileged([
-    {
-      scheme: DOCUMENT_SCHEME,
-      privileges: {
-        standard: true,
-        secure: true,
-        supportFetchAPI: true,
-        stream: true,
-        // The renderer fetches this scheme from a different origin (`file://` in
-        // production, the dev server in development), so it is a cross-origin
-        // request and must be CORS-enabled to succeed.
-        corsEnabled: true
-      }
+/** 声明特权。只入队，提交由 `applyPrivilegedSchemes()` 在 ready 前统一完成（#135）。 */
+export function declareDocumentScheme(): void {
+  declarePrivilegedScheme({
+    scheme: DOCUMENT_SCHEME,
+    privileges: {
+      standard: true,
+      secure: true,
+      supportFetchAPI: true,
+      stream: true,
+      // The renderer fetches this scheme from a different origin (`file://` in
+      // production, the dev server in development), so it is a cross-origin
+      // request and must be CORS-enabled to succeed.
+      corsEnabled: true
     }
-  ])
+  })
 }
 
 /** 在 app ready 之后调用，安装只读的字节服务 handler。 */
diff --git a/src/main/protocol/pdfjsAssetProtocol.ts b/src/main/protocol/pdfjsAssetProtocol.ts
index 60a26b9..0febd21 100644
--- a/src/main/protocol/pdfjsAssetProtocol.ts
+++ b/src/main/protocol/pdfjsAssetProtocol.ts
@@ -5,7 +5,7 @@
  * `resources/pdfjs/{cmaps,standard_fonts,wasm}` 下的文件。路径来自这里的
  * `pdfjsAssetRoot()`，不来自请求。
  *
- * 和 `documentProtocol` 一样，scheme 必须在 app ready 之前注册为 privileged；
+ * 和 `documentProtocol` 一样，scheme 必须在 app ready 之前声明为 privileged；
  * handler 在 ready 之后安装。
  */
 
@@ -15,6 +15,7 @@ import { pathToFileURL } from 'url'
 import { PDFJS_ASSET_SCHEME, parsePdfjsAssetUrl } from '../../shared/utils/pdfjsAssets'
 import { pdfjsAssetRoot } from '../pdfjsAssetPaths'
 import Logger from '../../shared/utils/logger'
+import { declarePrivilegedScheme } from './privilegedSchemes'
 
 /**
  * Origins allowed to read an asset. Same set as `documentProtocol`: the renderer
@@ -23,23 +24,21 @@ import Logger from '../../shared/utils/logger'
  */
 const ALLOWED_ORIGINS = new Set(['null', 'http://localhost:5173', 'http://127.0.0.1:5173'])
 
-/** 必须在 app ready 之前调用一次。 */
-export function registerPdfjsAssetScheme(): void {
-  protocol.registerSchemesAsPrivileged([
-    {
-      scheme: PDFJS_ASSET_SCHEME,
-      privileges: {
-        standard: true,
-        secure: true,
-        supportFetchAPI: true,
-        stream: true,
-        // The renderer fetches this scheme from a different origin (`file://` in
-        // production, the dev server in development), so it is a cross-origin
-        // request and must be CORS-enabled to succeed.
-        corsEnabled: true
-      }
+/** 声明特权。只入队，提交由 `applyPrivilegedSchemes()` 在 ready 前统一完成（#135）。 */
+export function declarePdfjsAssetScheme(): void {
+  declarePrivilegedScheme({
+    scheme: PDFJS_ASSET_SCHEME,
+    privileges: {
+      standard: true,
+      secure: true,
+      supportFetchAPI: true,
+      stream: true,
+      // The renderer fetches this scheme from a different origin (`file://` in
+      // production, the dev server in development), so it is a cross-origin
+      // request and must be CORS-enabled to succeed.
+      corsEnabled: true
     }
-  ])
+  })
 }
 
 /** 在 app ready 之后调用，安装只读的资源 handler。 */
diff --git a/src/main/protocol/privilegedSchemes.ts b/src/main/protocol/privilegedSchemes.ts
new file mode 100644
index 0000000..da527a6
--- /dev/null
+++ b/src/main/protocol/privilegedSchemes.ts
@@ -0,0 +1,30 @@
+/**
+ * 自定义 scheme 特权的**单一提交点**。
+ *
+ * `protocol.registerSchemesAsPrivileged()` 是替换而不是追加：第二次调用会整张表覆盖
+ * 上一次。之前 `documentProtocol` 和 `pdfjsAssetProtocol` 各调了一次，后注册的
+ * `knownote-asset` 顶掉了 `knownote-doc` 的 `supportFetchAPI`，渲染进程的
+ * `fetch('knownote-doc://...')` 立刻报
+ * `URL scheme "knownote-doc" is not supported` —— PDF Reader 整个打不开（#135）。
+ *
+ * 打包 smoke 当时没发现，是因为它用主进程 `net.fetch` 检查同一个协议：`protocol.handle`
+ * 在 scheme 没有特权时照样在 main 里工作，只有 renderer 的 `fetch` 会失败。所以这里
+ * 也补了 renderer 侧检查。
+ *
+ * 协议模块只声明自己的 scheme；提交集中在 `applyPrivilegedSchemes()`，在 app ready
+ * 之前调用一次。
+ */
+
+import { protocol, type CustomScheme } from 'electron'
+
+const declaredSchemes: CustomScheme[] = []
+
+/** 声明一个 scheme 的特权。只入队，不调用 Electron API。 */
+export function declarePrivilegedScheme(scheme: CustomScheme): void {
+  declaredSchemes.push(scheme)
+}
+
+/** 在 app ready 之前调用一次，把全部声明一次提交。 */
+export function applyPrivilegedSchemes(): void {
+  protocol.registerSchemesAsPrivileged(declaredSchemes)
+}
diff --git a/src/main/smokeTest.ts b/src/main/smokeTest.ts
index 085f20b..40f0b3a 100644
--- a/src/main/smokeTest.ts
+++ b/src/main/smokeTest.ts
@@ -18,8 +18,12 @@
  * actually broke - loading every external package the main process needs, the
  * native addons, the app's own vector-store code path and the document importers
  * (PDF, DOCX, HTML) against the fixtures in test/fixtures - and then exits
- * without creating a window, so CI can gate on the exit code. It is driven by
+ * without showing a window, so CI can gate on the exit code. It is driven by
  * `scripts/smoke-packaged.mjs`, which passes `--smoke-fixtures=<dir>`.
+ *
+ * One check does create a hidden window: a custom scheme's `supportFetchAPI`
+ * privilege is only observable from a renderer, and checking it from the main
+ * process is what let #135 ship.
  */
 
 import Logger from '../shared/utils/logger'
@@ -27,7 +31,7 @@ import { readFile, readdir } from 'fs/promises'
 import { mkdtempSync, rmSync, writeFileSync } from 'fs'
 import { tmpdir } from 'os'
 import { join } from 'path'
-import { net } from 'electron'
+import { net, BrowserWindow } from 'electron'
 import { eq } from 'drizzle-orm'
 import {
   closeDatabase,
@@ -105,6 +109,39 @@ function assertThrows(run: () => unknown, message: string): void {
   throw new Error(message)
 }
 
+/**
+ * Hidden windows created for renderer-side checks. They are deliberately **not**
+ * destroyed: destroying the last window fires `window-all-closed`, and this app
+ * closes the database (and quits) on that event, which would abort every check
+ * after this one. The process exits through `app.exit()` anyway.
+ */
+const smokeWindows: BrowserWindow[] = []
+
+/**
+ * Fetch a custom-scheme URL from a real renderer.
+ *
+ * `protocol.handle` keeps working in the main process even when its scheme was
+ * never registered as privileged, so a `net.fetch` check cannot see a missing
+ * privilege. Only the renderer's `fetch` can - and that is exactly what broke
+ * when two `registerSchemesAsPrivileged()` calls replaced each other and dropped
+ * `knownote-doc`, leaving every PDF unopenable (#135).
+ */
+async function fetchFromRenderer(
+  url: string
+): Promise<{ ok: boolean; status: number; body: string }> {
+  const window = new BrowserWindow({ show: false })
+  smokeWindows.push(window)
+  await window.loadURL('data:text/html,<html><body></body></html>')
+  return (await window.webContents.executeJavaScript(`(async () => {
+    try {
+      const response = await fetch(${JSON.stringify(url)});
+      return { ok: response.ok, status: response.status, body: await response.text() };
+    } catch (error) {
+      return { ok: false, status: 0, body: String((error && error.message) || error) };
+    }
+  })()`)) as { ok: boolean; status: number; body: string }
+}
+
 /**
  * A deterministic stand-in for `EmbeddingService` so the smoke test can drive
  * the whole index lifecycle (blocks → chunks → embeddings → vectors) without
@@ -261,9 +298,17 @@ async function runChecks(): Promise<string[]> {
   const unknown = await net.fetch(documentUrl('smoke-missing-doc'))
   assert(unknown.status === 404, `an unknown document id returned ${unknown.status}, not 404`)
 
+  // And the same URL from a renderer: this is the check whose absence let #135 ship.
+  const rendererFetch = await fetchFromRenderer(documentUrl(protocolDocumentId))
+  assert(
+    rendererFetch.ok && rendererFetch.body === protocolPayload,
+    `the renderer could not fetch knownote-doc:// (status ${rendererFetch.status}: ${rendererFetch.body})`
+  )
+
   database.prepare('DELETE FROM documents WHERE id = ?').run(protocolDocumentId)
   rmSync(protocolDir, { recursive: true, force: true })
   pass('knownote-doc:// serves an owned document and 404s an unknown id')
+  pass('knownote-doc:// is fetchable from a renderer (scheme privileges registered)')
 
   const { version } = database.prepare('SELECT vec_version() AS version').get() as {
     version: string
diff --git a/test/privilegedSchemes.test.ts b/test/privilegedSchemes.test.ts
new file mode 100644
index 0000000..afa00f3
--- /dev/null
+++ b/test/privilegedSchemes.test.ts
@@ -0,0 +1,60 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { readFileSync, readdirSync, statSync } from 'node:fs'
+import { join } from 'node:path'
+
+/**
+ * 自定义 scheme 特权只能提交一次。
+ *
+ * `protocol.registerSchemesAsPrivileged()` 是**替换**而不是追加：第二个调用会把上一张
+ * 表整个覆盖。`knownote-asset` 单独注册时顶掉了 `knownote-doc` 的 `supportFetchAPI`，
+ * 渲染进程再 `fetch('knownote-doc://...')` 就报 `URL scheme ... is not supported`，
+ * PDF Reader 全挂（#135）。
+ *
+ * 这条护栏把「只能有一个提交点」钉住；真正的行为检查在 `smokeTest.ts` 里，用真实
+ * 渲染进程 fetch 两个 scheme。
+ */
+
+const SCAN_ROOT = 'src'
+
+const walk = (dir: string, files: string[] = []): string[] => {
+  for (const entry of readdirSync(dir)) {
+    const path = join(dir, entry)
+    if (statSync(path).isDirectory()) walk(path, files)
+    else if (/\.(ts|tsx|mts|cts|js|mjs|cjs)$/.test(path)) files.push(path)
+  }
+  return files
+}
+
+test('exactly one call site submits the custom-scheme privileges', () => {
+  const callSites: string[] = []
+
+  for (const file of walk(SCAN_ROOT)) {
+    const matches = readFileSync(file, 'utf8').match(/protocol\.registerSchemesAsPrivileged\s*\(/g)
+    if (matches) callSites.push(`${file} (${matches.length})`)
+  }
+
+  assert.equal(
+    callSites.length,
+    1,
+    'Electron replaces the whole privilege table on every call, so a second call drops the ' +
+      'schemes the first registered (#135). Declare schemes with `declarePrivilegedScheme()` ' +
+      `and submit them once. Found: ${callSites.join(', ') || 'none'}`
+  )
+  assert.ok(
+    callSites[0].startsWith(join(SCAN_ROOT, 'main', 'protocol', 'privilegedSchemes.ts')),
+    `the single call must live in privilegedSchemes.ts, found ${callSites[0]}`
+  )
+})
+
+test('every scheme is declared and submitted before the app is ready', () => {
+  const index = readFileSync(join(SCAN_ROOT, 'main', 'index.ts'), 'utf8')
+
+  for (const call of [
+    'declareDocumentScheme()',
+    'declarePdfjsAssetScheme()',
+    'applyPrivilegedSchemes()'
+  ]) {
+    assert.ok(index.includes(call), `index.ts stopped calling ${call}`)
+  }
+})