diff --git a/gui/src/pages/claude-manual-env.ts b/gui/src/pages/claude-manual-env.ts
index bb0c2970d..690d0c6e4 100644
--- a/gui/src/pages/claude-manual-env.ts
+++ b/gui/src/pages/claude-manual-env.ts
@@ -5,7 +5,7 @@
  */
 
 export type SidecarBackend = "openai" | "anthropic";
-export interface SidecarOverride { backend?: SidecarBackend; model?: string }
+export interface SidecarOverride { backend?: SidecarBackend | null; model?: string }
 
 export interface ClaudeManualEnvState {
   /**
diff --git a/src/server/claude-messages.ts b/src/server/claude-messages.ts
index 5e3074bec..5ee6a9656 100644
--- a/src/server/claude-messages.ts
+++ b/src/server/claude-messages.ts
@@ -53,15 +53,25 @@ function isRec(v: unknown): v is Rec {
 
 /** Resolve Claude-only sidecar overrides without mutating the shared server config. */
 export function buildClaudeReplayConfig(config: OcxConfig): OcxConfig {
+  const webSearchOverride = config.claudeCode?.webSearchSidecar;
+  const visionOverride = config.claudeCode?.visionSidecar;
+  const { backend: webSearchBackend, ...webSearchFields } = webSearchOverride ?? {};
+  const { backend: visionBackend, ...visionFields } = visionOverride ?? {};
   return {
     ...config,
     webSearchSidecar: {
       ...config.webSearchSidecar,
-      ...config.claudeCode?.webSearchSidecar,
+      ...webSearchFields,
+      ...(webSearchOverride && "backend" in webSearchOverride
+        ? { backend: webSearchBackend ?? undefined }
+        : {}),
     },
     visionSidecar: {
       ...config.visionSidecar,
-      ...config.claudeCode?.visionSidecar,
+      ...visionFields,
+      ...(visionOverride && "backend" in visionOverride
+        ? { backend: visionBackend ?? undefined }
+        : {}),
     },
   };
 }
diff --git a/src/server/management/agent-settings-routes.ts b/src/server/management/agent-settings-routes.ts
index 17f7c00b3..5783de0d9 100644
--- a/src/server/management/agent-settings-routes.ts
+++ b/src/server/management/agent-settings-routes.ts
@@ -1021,8 +1021,7 @@ export async function handleAgentSettingsRoutes(ctx: ManagementContext): Promise
       }
       const requested = section as { backend?: "openai" | "anthropic" | null; model?: string };
       const override: NonNullable<OcxClaudeCodeConfig[typeof field]> = { ...next[field] };
-      if (requested.backend === null) delete override.backend;
-      else if (requested.backend !== undefined) override.backend = requested.backend;
+      if (requested.backend !== undefined) override.backend = requested.backend;
       if (requested.model === "") delete override.model;
       else if (requested.model !== undefined) override.model = requested.model;
       if (Object.keys(override).length > 0) next[field] = override;
diff --git a/src/types.ts b/src/types.ts
index 481c15a4b..8a67276b8 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -476,10 +476,10 @@ export interface OcxClaudeCodeConfig {
    * definition. Unset inherits the parent session effort.
    */
   subagentEffort?: "low" | "medium" | "high" | "xhigh" | "max";
-  /** Claude-originated web-search override. Unset fields inherit the global sidecar settings. */
-  webSearchSidecar?: { backend?: "openai" | "anthropic"; model?: string };
-  /** Claude-originated vision override. Unset fields inherit the global sidecar settings. */
-  visionSidecar?: { backend?: "openai" | "anthropic"; model?: string };
+  /** Claude-originated web-search override. Null backend means Auto; an absent field inherits global. */
+  webSearchSidecar?: { backend?: "openai" | "anthropic" | null; model?: string };
+  /** Claude-originated vision override. Null backend means Auto; an absent field inherits global. */
+  visionSidecar?: { backend?: "openai" | "anthropic" | null; model?: string };
   /** Persisted Claude Desktop four-family routing profile. */
   desktopProfile?: OcxClaudeDesktopProfile;
   /** Auto-reconcile Desktop 3P config when provider catalog changes. Default: enabled. */
diff --git a/tests/claude-management-api.test.ts b/tests/claude-management-api.test.ts
index 4286deeac..169b477c1 100644
--- a/tests/claude-management-api.test.ts
+++ b/tests/claude-management-api.test.ts
@@ -329,17 +329,17 @@ test("Claude sidecar overrides round-trip, partially update, clear, and reject u
     expect(loadConfig().claudeCode?.webSearchSidecar).toEqual({ backend: "anthropic", model: "claude-search-2" });
     expect(loadConfig().claudeCode?.visionSidecar).toEqual({ backend: "openai", model: "gpt-vision" });
 
-    // null backend is the explicit Auto/inherit transition; empty model deletes only model.
+    // null backend is explicit Auto; empty model deletes only model.
     response = await put({
       webSearchSidecar: { backend: null },
       visionSidecar: { backend: null, model: "" },
     });
     expect(response.status).toBe(200);
-    expect(loadConfig().claudeCode?.webSearchSidecar).toEqual({ model: "claude-search-2" });
-    expect(loadConfig().claudeCode?.visionSidecar).toBeUndefined();
+    expect(loadConfig().claudeCode?.webSearchSidecar).toEqual({ backend: null, model: "claude-search-2" });
+    expect(loadConfig().claudeCode?.visionSidecar).toEqual({ backend: null });
     get = await fetch(new URL("/api/claude-code", server.url)).then(r => r.json()) as Record<string, unknown>;
-    expect(get.webSearchSidecar).toEqual({ model: "claude-search-2" });
-    expect(get.visionSidecar).toBeUndefined();
+    expect(get.webSearchSidecar).toEqual({ backend: null, model: "claude-search-2" });
+    expect(get.visionSidecar).toEqual({ backend: null });
 
     // null and empty sections both clear the whole override.
     response = await put({ webSearchSidecar: null, visionSidecar: {} });
diff --git a/tests/claude-sidecar-override.test.ts b/tests/claude-sidecar-override.test.ts
index 17130e547..6cc41b29c 100644
--- a/tests/claude-sidecar-override.test.ts
+++ b/tests/claude-sidecar-override.test.ts
@@ -124,3 +124,21 @@ test("unset Claude overrides inherit the global sidecar backend and model", () =
     settings: { model: "global-vision" },
   });
 });
+
+test("explicit Claude Auto backends do not inherit global backend choices", () => {
+  const config: OcxConfig = {
+    port: 10100,
+    defaultProvider: "routed",
+    providers: { routed, forward },
+    webSearchSidecar: { backend: "openai", model: "global-search" },
+    visionSidecar: { backend: "openai", model: "global-vision" },
+    claudeCode: {
+      webSearchSidecar: { backend: null, model: "claude-search" },
+      visionSidecar: { backend: null, model: "claude-vision" },
+    },
+  };
+
+  const effective = buildClaudeReplayConfig(config);
+  expect(effective.webSearchSidecar).toEqual({ backend: undefined, model: "claude-search" });
+  expect(effective.visionSidecar).toEqual({ backend: undefined, model: "claude-vision" });
+});