diff --git a/src/agents/tools/web-search-provider-config.ts b/src/agents/tools/web-search-provider-config.ts
index eb7f7c325ac..b1f15357d83 100644
--- a/src/agents/tools/web-search-provider-config.ts
+++ b/src/agents/tools/web-search-provider-config.ts
@@ -1,5 +1,6 @@
 import { resolvePluginWebSearchConfig } from "../../config/plugin-web-search-config.js";
 import type { OpenClawConfig } from "../../config/types.openclaw.js";
+import { isLegacyWebSearchProviderConfigKey } from "../../config/web-search-legacy-provider-keys.js";
 
 export function getTopLevelCredentialValue(searchConfig?: Record<string, unknown>): unknown {
   return searchConfig?.apiKey;
@@ -52,13 +53,22 @@ export function mergeScopedSearchConfig(
     !Array.isArray(searchConfig[key])
       ? (searchConfig[key] as Record<string, unknown>)
       : {};
-  const next: Record<string, unknown> = {
-    ...searchConfig,
-    [key]: {
+  const next: Record<string, unknown> = { ...searchConfig };
+  const existingDescriptor = searchConfig
+    ? Object.getOwnPropertyDescriptor(searchConfig, key)
+    : undefined;
+  const shouldHideRuntimeInjectedLegacyShape =
+    isLegacyWebSearchProviderConfigKey(key) && existingDescriptor === undefined;
+
+  Object.defineProperty(next, key, {
+    value: {
       ...currentScoped,
       ...pluginConfig,
     },
-  };
+    enumerable: !shouldHideRuntimeInjectedLegacyShape,
+    configurable: true,
+    writable: true,
+  });
 
   if (options?.mirrorApiKeyToTopLevel && pluginConfig.apiKey !== undefined) {
     next.apiKey = pluginConfig.apiKey;
diff --git a/src/agents/tools/web-search.test.ts b/src/agents/tools/web-search.test.ts
index 06eeafcacde..b33114e2b15 100644
--- a/src/agents/tools/web-search.test.ts
+++ b/src/agents/tools/web-search.test.ts
@@ -144,4 +144,15 @@ describe("web_search scoped config merge", () => {
       brave: { count: 5, apiKey: "brave-test-key" },
     });
   });
+
+  it("keeps newly injected legacy provider config runtime-only for validation", () => {
+    const merged = mergeScopedSearchConfig({ enabled: true, provider: "gemini" }, "perplexity", {
+      apiKey: "perplexity-test-key",
+    });
+
+    expect(merged?.perplexity).toEqual({ apiKey: "perplexity-test-key" });
+    expect(Object.keys(merged ?? {})).toEqual(["enabled", "provider"]);
+
+    expect(Object.getOwnPropertyDescriptor(merged, "perplexity")?.enumerable).toBe(false);
+  });
 });
diff --git a/src/config/web-search-codex-config.test.ts b/src/config/web-search-codex-config.test.ts
index 9151f34b3ce..4b12391075a 100644
--- a/src/config/web-search-codex-config.test.ts
+++ b/src/config/web-search-codex-config.test.ts
@@ -1,5 +1,6 @@
 import { importFreshModule } from "openclaw/plugin-sdk/test-fixtures";
 import { describe, expect, it } from "vitest";
+import { mergeScopedSearchConfig } from "../agents/tools/web-search-provider-config.js";
 import { validateConfigObjectRaw } from "./validation.js";
 
 describe("web search Codex native config validation", () => {
@@ -54,6 +55,23 @@ describe("web search Codex native config validation", () => {
     }
   });
 
+  it("accepts runtime-only legacy provider entries injected by web search merge", () => {
+    const search = mergeScopedSearchConfig({ enabled: true, provider: "gemini" }, "perplexity", {
+      apiKey: "perplexity-test-key",
+    });
+    const result = validateConfigObjectRaw({
+      tools: {
+        web: {
+          search,
+        },
+      },
+    });
+
+    expect(search?.perplexity).toEqual({ apiKey: "perplexity-test-key" });
+    expect(Object.keys(search ?? {})).toEqual(["enabled", "provider"]);
+    expect(result.ok).toBe(true);
+  });
+
   it.each(["__proto__", "prototype", "constructor"])(
     "rejects blocked tools.web.search key %s",
     (key) => {
diff --git a/src/config/web-search-legacy-provider-keys.ts b/src/config/web-search-legacy-provider-keys.ts
new file mode 100644
index 00000000000..4492d5a8477
--- /dev/null
+++ b/src/config/web-search-legacy-provider-keys.ts
@@ -0,0 +1,18 @@
+export const LEGACY_WEB_SEARCH_PROVIDER_CONFIG_KEYS = new Set([
+  "brave",
+  "duckduckgo",
+  "exa",
+  "firecrawl",
+  "gemini",
+  "grok",
+  "kimi",
+  "minimax",
+  "ollama",
+  "perplexity",
+  "searxng",
+  "tavily",
+]);
+
+export function isLegacyWebSearchProviderConfigKey(key: string): boolean {
+  return LEGACY_WEB_SEARCH_PROVIDER_CONFIG_KEYS.has(key);
+}
diff --git a/src/config/zod-schema.agent-runtime.ts b/src/config/zod-schema.agent-runtime.ts
index 5bef3b9535c..8cb70d3e7d8 100644
--- a/src/config/zod-schema.agent-runtime.ts
+++ b/src/config/zod-schema.agent-runtime.ts
@@ -10,6 +10,7 @@ import {
 } from "../shared/string-coerce.js";
 import { uniqueStrings } from "../shared/string-normalization.js";
 import { isBlockedObjectKey } from "./prototype-keys.js";
+import { LEGACY_WEB_SEARCH_PROVIDER_CONFIG_KEYS } from "./web-search-legacy-provider-keys.js";
 import { AgentModelSchema, AgentToolModelSchema } from "./zod-schema.agent-model.js";
 import {
   GroupChatSchema,
@@ -352,21 +353,6 @@ const CodexUserLocationSchema = z
   })
   .optional();
 
-const LEGACY_WEB_SEARCH_PROVIDER_CONFIG_KEYS = new Set([
-  "brave",
-  "duckduckgo",
-  "exa",
-  "firecrawl",
-  "gemini",
-  "grok",
-  "kimi",
-  "minimax",
-  "ollama",
-  "perplexity",
-  "searxng",
-  "tavily",
-]);
-
 const BLOCKED_WEB_SEARCH_KEYS_ISSUE_FIELD = "__openclawBlockedWebSearchKeys";
 
 const ToolsWebSearchSchema = z