diff --git a/integrations/dsh/docs/environment.md b/integrations/dsh/docs/environment.md
index d8962d0b..fbbdb05d 100644
--- a/integrations/dsh/docs/environment.md
+++ b/integrations/dsh/docs/environment.md
@@ -136,7 +136,8 @@ DSH settings.
   backend, exactly as ReMe would start it.
 - A known backend written in the wrong case (`LLM_BACKEND=OpenAI`) is reported as invalid, with the spelling to
   use: ReMe's backend registry is case-sensitive and refuses that name. A backend name the plugin has never heard
-  of is still probed tolerantly — the list here is a snapshot, and ReMe may know more than the plugin does.
+  of is still probed tolerantly — the list here is a snapshot, and ReMe may know more than the plugin does. That
+  holds however the name looks: only a backend the plugin actually knows can be reported as a wrong spelling.
 - The draft, the save message and the LLM-test result belong to the workspace they were produced for: switching
   the workspace disposes the section's state, so neither a key typed for one workspace nor a success reported for
   it can be carried into another.
diff --git a/integrations/dsh/docs/environment_ZH.md b/integrations/dsh/docs/environment_ZH.md
index 4ce50c81..49394855 100644
--- a/integrations/dsh/docs/environment_ZH.md
+++ b/integrations/dsh/docs/environment_ZH.md
@@ -108,7 +108,8 @@ ReMe 在服务启动时读取 workspace 目录下的 `.env`；标签页从不把
   任何请求：此时 ReMe 启动时并没有任何后端，探测不能去测试服务根本无法使用的配置。若 `.env` 里没有这个键，
   探测会与 ReMe 一样使用默认后端。
 - 已知后端名写错了大小写（如 `LLM_BACKEND=OpenAI`）会被报告为无效，并给出正确写法：ReMe 的后端注册表区分大小写，
-  会拒绝这个名字。而插件从未听说过的后端名仍被宽容地探测——这里的列表只是一份快照，ReMe 可能认识得更多。
+  会拒绝这个名字。而插件从未听说过的后端名仍被宽容地探测——这里的列表只是一份快照，ReMe 可能认识得更多。这条规则与名字
+  长什么样无关：只有插件确实认识的后端才会被判定为大小写写错。
 - 草稿、保存提示与 LLM 测试结果都属于产生它们的 workspace：切换 workspace 会随旧区块一并丢弃，因此为某个 workspace
   输入的密钥、或属于它的一次成功提示，都不会被带到另一个。
 
diff --git a/integrations/dsh/src/environment/host/workspace.ts b/integrations/dsh/src/environment/host/workspace.ts
index ef7e622b..7aa3592b 100644
--- a/integrations/dsh/src/environment/host/workspace.ts
+++ b/integrations/dsh/src/environment/host/workspace.ts
@@ -278,6 +278,17 @@ export const LLM_PROTOCOLS: Record<string, LlmProtocol> = {
 /** The backend ReMe itself falls back to when `.env` names none. */
 export { DEFAULT_LLM_BACKEND };
 
+/**
+ * The protocol entry the table holds for `key`, if it holds one at all.
+ *
+ * Only an own entry counts: the table inherits from `Object.prototype`, so a
+ * plain lookup would hand out `Object` for a backend named `constructor` and
+ * build a malformed probe from it.
+ */
+function ownProtocol(key: string): LlmProtocol | undefined {
+  return Object.hasOwn(LLM_PROTOCOLS, key) ? LLM_PROTOCOLS[key] : undefined;
+}
+
 /**
  * The protocol a backend speaks; an unknown backend uses the OpenAI-style
  * request.
@@ -287,7 +298,7 @@ export { DEFAULT_LLM_BACKEND };
  * refused.
  */
 export function llmProtocolFor(backend: string): LlmProtocol {
-  return LLM_PROTOCOLS[llmBackendOf(backend)] ?? OPENAI_PROTOCOL;
+  return ownProtocol(llmBackendOf(backend)) ?? OPENAI_PROTOCOL;
 }
 
 /**
@@ -299,9 +310,12 @@ export function llmProtocolFor(backend: string): LlmProtocol {
  * alone: its list is a snapshot, and ReMe may know more than the plugin does.
  */
 export function backendSpellingIsWrong(name: string): boolean {
+  // Own entries only. An inherited member is not a known backend: `constructor`
+  // and `__proto__` would otherwise be reported as known backends written in
+  // the wrong case, and the message would name a spelling ReMe refuses too.
   return (
-    LLM_PROTOCOLS[name] === undefined &&
-    LLM_PROTOCOLS[name.toLowerCase()] !== undefined
+    ownProtocol(name) === undefined &&
+    ownProtocol(name.toLowerCase()) !== undefined
   );
 }
 
diff --git a/integrations/dsh/tests/env-workspace.test.mjs b/integrations/dsh/tests/env-workspace.test.mjs
index af00c43d..d38466ef 100644
--- a/integrations/dsh/tests/env-workspace.test.mjs
+++ b/integrations/dsh/tests/env-workspace.test.mjs
@@ -526,6 +526,64 @@ test("the probe refuses a known backend written in the wrong case", async (t) =>
   assert.equal(calls.length, 0, "the snippet is not run");
 });
 
+test("a backend name the plugin does not know is probed tolerantly, whatever it looks like", async (t) => {
+  // The protocol table is a plain object, so it inherits from
+  // `Object.prototype`: `constructor` and `__proto__` are not backends. A name
+  // the plugin has never heard of must be probed like any other unknown name,
+  // and must never be reported as a known backend written in the wrong case.
+  const directory = mkdtempSync(join(tmpdir(), "reme-llm-prototype-"));
+  t.after(() => rmSync(directory, { recursive: true, force: true }));
+  const names = ["constructor", "__proto__", "CONSTRUCTOR", "__PROTO__"];
+  for (const name of names) {
+    writeFileSync(
+      join(directory, ".env"),
+      [
+        `LLM_BACKEND=${name}`,
+        "LLM_MODEL_NAME=test-model",
+        "LLM_API_KEY=sk-test",
+        "LLM_BASE_URL=https://provider.invalid",
+      ].join("\n"),
+    );
+    const calls = [];
+    const result = await testLlm(
+      {
+        run: async (exe, args, options) => {
+          calls.push({ exe, args, options });
+          return {
+            code: 0,
+            stdout:
+              '{"ok": true, "status": 200, "latencyMs": 12, "error": ""}\n',
+            stderr: "",
+          };
+        },
+      },
+      { workspaceDir: directory, pythonPath: "C:\\env\\python.exe" },
+    );
+    assert.doesNotMatch(
+      result.error ?? "",
+      /lower case/,
+      `${name} is not reported as a known backend in the wrong case`,
+    );
+    assert.equal(calls.length, 1, `${name} is probed tolerantly`);
+    const snippet = String(calls[0]?.args[1] ?? "");
+    assert.match(
+      snippet,
+      /\/chat\/completions/,
+      `${name} gets the default protocol`,
+    );
+    assert.match(
+      snippet,
+      /"Authorization"/,
+      `${name} gets the default protocol`,
+    );
+    assert.doesNotMatch(
+      snippet,
+      /undefined/,
+      `${name} builds no malformed snippet`,
+    );
+  }
+});
+
 test("a .env without the backend key is probed with the default protocol", async (t) => {
   // The key is absent, so ReMe applies its default; the probe does the same.
   const directory = mkdtempSync(join(tmpdir(), "reme-llm-absent-"));