diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1edb0770e3a..0a9621f96da 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -165,6 +165,7 @@ Docs: https://docs.openclaw.ai
 - Auth/profile resolution: log debug details when auto-discovered auth profiles fail during provider API-key resolution, so `--debug` output surfaces the real refresh/keychain/credential-store failure instead of only the generic missing-key message. (#41271) thanks @he-yufeng.
 - ACP/cancel scoping: scope `chat.abort` and shared-session ACP event routing by `runId` so one session cannot cancel or consume another session's run when they share the same gateway session key. (#41331) Thanks @pejmanjohn.
 - SecretRef/models: harden custom/provider secret persistence and reuse across models.json snapshots, merge behavior, runtime headers, and secret audits. (#42554) Thanks @joshavant.
+- macOS/browser proxy: serialize non-GET browser proxy request bodies through `AnyCodable.foundationValue` so nested JSON bodies no longer crash the macOS app with `Invalid type in JSON write (__SwiftValue)`. (#43069) Thanks @Effet.
 
 ## 2026.3.7
 
diff --git a/apps/macos/Sources/OpenClaw/NodeMode/MacNodeBrowserProxy.swift b/apps/macos/Sources/OpenClaw/NodeMode/MacNodeBrowserProxy.swift
index 0da6510f608..367907f9fb7 100644
--- a/apps/macos/Sources/OpenClaw/NodeMode/MacNodeBrowserProxy.swift
+++ b/apps/macos/Sources/OpenClaw/NodeMode/MacNodeBrowserProxy.swift
@@ -146,8 +146,8 @@ actor MacNodeBrowserProxy {
             request.setValue(password, forHTTPHeaderField: "x-openclaw-password")
         }
 
-        if method != "GET", let body = params.body?.value {
-            request.httpBody = try JSONSerialization.data(withJSONObject: body, options: [.fragmentsAllowed])
+        if method != "GET", let body = params.body {
+            request.httpBody = try JSONSerialization.data(withJSONObject: body.foundationValue, options: [.fragmentsAllowed])
             request.setValue("application/json", forHTTPHeaderField: "Content-Type")
         }
 
diff --git a/apps/macos/Tests/OpenClawIPCTests/MacNodeBrowserProxyTests.swift b/apps/macos/Tests/OpenClawIPCTests/MacNodeBrowserProxyTests.swift
index c000f6d4241..b341263b21f 100644
--- a/apps/macos/Tests/OpenClawIPCTests/MacNodeBrowserProxyTests.swift
+++ b/apps/macos/Tests/OpenClawIPCTests/MacNodeBrowserProxyTests.swift
@@ -38,4 +38,49 @@ struct MacNodeBrowserProxyTests {
         #expect(tabs.count == 1)
         #expect(tabs[0]["id"] as? String == "tab-1")
     }
+
+    // Regression test: nested POST bodies must serialize without __SwiftValue crashes.
+    @Test func postRequestSerializesNestedBodyWithoutCrash() async throws {
+        actor BodyCapture {
+            private var body: Data?
+
+            func set(_ body: Data?) {
+                self.body = body
+            }
+
+            func get() -> Data? {
+                self.body
+            }
+        }
+
+        let capturedBody = BodyCapture()
+        let proxy = MacNodeBrowserProxy(
+            endpointProvider: {
+                MacNodeBrowserProxy.Endpoint(
+                    baseURL: URL(string: "http://127.0.0.1:18791")!,
+                    token: nil,
+                    password: nil)
+            },
+            performRequest: { request in
+                await capturedBody.set(request.httpBody)
+                let url = try #require(request.url)
+                let response = try #require(
+                    HTTPURLResponse(
+                        url: url,
+                        statusCode: 200,
+                        httpVersion: nil,
+                        headerFields: nil))
+                return (Data(#"{"ok":true}"#.utf8), response)
+            })
+
+        _ = try await proxy.request(
+            paramsJSON: #"{"method":"POST","path":"/action","body":{"nested":{"key":"val"},"arr":[1,2]}}"#)
+
+        let bodyData = try #require(await capturedBody.get())
+        let parsed = try #require(JSONSerialization.jsonObject(with: bodyData) as? [String: Any])
+        let nested = try #require(parsed["nested"] as? [String: Any])
+        #expect(nested["key"] as? String == "val")
+        let arr = try #require(parsed["arr"] as? [Any])
+        #expect(arr.count == 2)
+    }
 }