diff --git a/CHANGELOG.md b/CHANGELOG.md
index e18eaeb55d3..bd7112eb8a7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -39,6 +39,7 @@ Docs: https://docs.openclaw.ai
 - Control UI/WebChat: let sidebar markdown code-block Copy buttons use the same delegated clipboard handler as chat messages. (#58709) Thanks @tikitoki.
 - Discord/streaming: only mark partial draft previews delivered after final edit or fallback delivery succeeds, so failed finalization cleanup removes stale truncated drafts instead of leaving them as the visible reply. Fixes #82035. Thanks @compoodment.
 - macOS/Gateway: surface leftover `ai.openclaw.update.*` launchd updater jobs in `openclaw gateway status --deep` and doctor so post-update launchd loops point at the stale job cleanup. Fixes #81859. Thanks @BKF-Gitty.
+- macOS/screen snapshots: reject malformed `screen.snapshot` params before capture, bound base64 results against the projected `node.invoke.result` frame, and preserve stable caller-facing errors for oversized payloads and capture failures. Fixes #68181. Thanks @shaun0927 and @BunsDev.
 - Config/doctor: rotate capped `.clobbered.*` repair snapshots by artifact timestamp so repeated repairs keep the newest forensic copy instead of preserving only the first capped set. (#82012) Thanks @Kaspre.
 - Telegram: initialize the bot before isolated polling drains spooled updates so default isolated polling no longer retries every update with `Bot not initialized` and stalls replies. Fixes #81973. (#81975) Thanks @neeravmakwana.
 - Telegram: apply method-aware Bot API request timeouts to direct message/action clients so `openclaw message delete --channel telegram` no longer waits on grammY's 500-second default when the API request wedges. Fixes #81908. Thanks @DashLabsDev.
diff --git a/apps/macos/Sources/OpenClaw/NodeMode/MacNodeRuntime.swift b/apps/macos/Sources/OpenClaw/NodeMode/MacNodeRuntime.swift
index a955c7a1b86..eb18e95d244 100644
--- a/apps/macos/Sources/OpenClaw/NodeMode/MacNodeRuntime.swift
+++ b/apps/macos/Sources/OpenClaw/NodeMode/MacNodeRuntime.swift
@@ -4,6 +4,8 @@ import OpenClawIPC
 import OpenClawKit
 
 actor MacNodeRuntime {
+    private static let maxGatewayPayloadBytes = 25 * 1024 * 1024
+    private static let maxScreenSnapshotRawBytesBeforeBase64 = (maxGatewayPayloadBytes / 4) * 3
     private let cameraCapture = CameraCaptureService()
     private let makeMainActorServices: () async -> any MacNodeRuntimeMainActorServices
     private let browserProxyRequest: @Sendable (String?) async throws -> String
@@ -363,15 +365,55 @@ actor MacNodeRuntime {
     }
 
     private func handleScreenSnapshotInvoke(_ req: BridgeInvokeRequest) async throws -> BridgeInvokeResponse {
-        let params = (try? Self.decodeParams(MacNodeScreenSnapshotParams.self, from: req.paramsJSON)) ??
-            MacNodeScreenSnapshotParams()
+        let params: MacNodeScreenSnapshotParams
+        if let paramsJSON = req.paramsJSON {
+            do {
+                params = try Self.decodeParams(MacNodeScreenSnapshotParams.self, from: paramsJSON)
+            } catch {
+                return Self.errorResponse(
+                    req,
+                    code: .invalidRequest,
+                    message: "INVALID_REQUEST: invalid screen snapshot params")
+            }
+        } else {
+            params = MacNodeScreenSnapshotParams()
+        }
         let services = await self.mainActorServices()
         let capturedAtMs = Int64(Date().timeIntervalSince1970 * 1000)
-        let res = try await services.snapshotScreen(
-            screenIndex: params.screenIndex,
-            maxWidth: params.maxWidth,
-            quality: params.quality,
-            format: params.format)
+        let res: (data: Data, format: OpenClawScreenSnapshotFormat, width: Int, height: Int)
+        do {
+            res = try await services.snapshotScreen(
+                screenIndex: params.screenIndex,
+                maxWidth: params.maxWidth,
+                quality: params.quality,
+                format: params.format)
+        } catch let error as ScreenSnapshotService.ScreenSnapshotError {
+            switch error {
+            case .noDisplays:
+                return Self.errorResponse(
+                    req,
+                    code: .invalidRequest,
+                    message: "INVALID_REQUEST: no displays available for screen snapshot")
+            case let .invalidScreenIndex(idx):
+                return Self.errorResponse(
+                    req,
+                    code: .invalidRequest,
+                    message: "INVALID_REQUEST: invalid screen index \(idx)")
+            case .captureFailed, .encodeFailed:
+                return Self.errorResponse(
+                    req,
+                    code: .unavailable,
+                    message: "UNAVAILABLE: screen snapshot failed")
+            }
+        } catch {
+            return Self.errorResponse(
+                req,
+                code: .unavailable,
+                message: "UNAVAILABLE: screen snapshot failed")
+        }
+        if res.data.count > Self.maxScreenSnapshotRawBytesBeforeBase64 {
+            return Self.screenSnapshotPayloadTooLarge(req)
+        }
         struct ScreenSnapshotPayload: Encodable {
             var format: String
             var base64: String
@@ -387,6 +429,13 @@ actor MacNodeRuntime {
             height: res.height,
             screenIndex: params.screenIndex,
             capturedAtMs: capturedAtMs))
+        if try Self.projectedOuterFrameBytes(
+            forPayloadJSON: payload,
+            requestId: req.id,
+            nodeId: req.nodeId) > Self.maxGatewayPayloadBytes
+        {
+            return Self.screenSnapshotPayloadTooLarge(req)
+        }
         return BridgeInvokeResponse(id: req.id, ok: true, payloadJSON: payload)
     }
 
@@ -1004,6 +1053,40 @@ extension MacNodeRuntime {
         return json
     }
 
+    static func projectedOuterFrameBytes(
+        forPayloadJSON payloadJSON: String,
+        requestId: String,
+        nodeId: String?) throws -> Int
+    {
+        struct InvokeResultFrame: Encodable {
+            let type = "req"
+            let id = "00000000-0000-0000-0000-000000000000"
+            let method = "node.invoke.result"
+            let params: Params
+
+            struct Params: Encodable {
+                let id: String
+                let nodeId: String
+                let ok: Bool
+                let payloadJSON: String
+            }
+        }
+
+        let frame = InvokeResultFrame(params: InvokeResultFrame.Params(
+            id: requestId,
+            nodeId: nodeId ?? "",
+            ok: true,
+            payloadJSON: payloadJSON))
+        return try JSONEncoder().encode(frame).count
+    }
+
+    private static func screenSnapshotPayloadTooLarge(_ req: BridgeInvokeRequest) -> BridgeInvokeResponse {
+        self.errorResponse(
+            req,
+            code: .unavailable,
+            message: "UNAVAILABLE: screen snapshot payload too large; reduce maxWidth or use jpeg")
+    }
+
     private nonisolated static func canvasEnabled() -> Bool {
         UserDefaults.standard.object(forKey: canvasEnabledKey) as? Bool ?? true
     }
diff --git a/apps/macos/Sources/OpenClaw/ScreenSnapshotService.swift b/apps/macos/Sources/OpenClaw/ScreenSnapshotService.swift
index 8a5b9f813e9..774c0da5717 100644
--- a/apps/macos/Sources/OpenClaw/ScreenSnapshotService.swift
+++ b/apps/macos/Sources/OpenClaw/ScreenSnapshotService.swift
@@ -63,7 +63,7 @@ final class ScreenSnapshotService {
                 contentFilter: filter,
                 configuration: config)
         } catch {
-            throw ScreenSnapshotError.captureFailed(error.localizedDescription)
+            throw ScreenSnapshotError.captureFailed("screen capture failed")
         }
 
         let bitmap = NSBitmapImageRep(cgImage: cgImage)
diff --git a/apps/macos/Tests/OpenClawIPCTests/MacNodeRuntimeTests.swift b/apps/macos/Tests/OpenClawIPCTests/MacNodeRuntimeTests.swift
index a69139f210e..55cb6a01e43 100644
--- a/apps/macos/Tests/OpenClawIPCTests/MacNodeRuntimeTests.swift
+++ b/apps/macos/Tests/OpenClawIPCTests/MacNodeRuntimeTests.swift
@@ -26,6 +26,78 @@ struct MacNodeRuntimeTests {
         }
     }
 
+    @MainActor
+    final class ScreenSnapshotProbeServices: MacNodeRuntimeMainActorServices, @unchecked Sendable {
+        typealias SnapshotResult = (
+            data: Data,
+            format: OpenClawScreenSnapshotFormat,
+            width: Int,
+            height: Int)
+
+        var snapshotCallCount = 0
+        var receivedSnapshotParams: MacNodeScreenSnapshotParams?
+        var snapshotResult: SnapshotResult
+        var snapshotError: Error?
+
+        init(
+            snapshotResult: SnapshotResult = (Data("ok".utf8), .jpeg, 10, 10),
+            snapshotError: Error? = nil)
+        {
+            self.snapshotResult = snapshotResult
+            self.snapshotError = snapshotError
+        }
+
+        func snapshotScreen(
+            screenIndex: Int?,
+            maxWidth: Int?,
+            quality: Double?,
+            format: OpenClawScreenSnapshotFormat?) async throws -> SnapshotResult
+        {
+            self.snapshotCallCount += 1
+            self.receivedSnapshotParams = MacNodeScreenSnapshotParams(
+                screenIndex: screenIndex,
+                maxWidth: maxWidth,
+                quality: quality,
+                format: format)
+            if let snapshotError {
+                throw snapshotError
+            }
+            return self.snapshotResult
+        }
+
+        func recordScreen(
+            screenIndex: Int?,
+            durationMs: Int?,
+            fps: Double?,
+            includeAudio: Bool?,
+            outPath: String?) async throws -> (path: String, hasAudio: Bool)
+        {
+            let url = FileManager().temporaryDirectory
+                .appendingPathComponent("openclaw-test-screen-record-\(UUID().uuidString).mp4")
+            try Data("ok".utf8).write(to: url)
+            return (path: url.path, hasAudio: false)
+        }
+
+        func locationAuthorizationStatus() -> CLAuthorizationStatus {
+            .authorizedAlways
+        }
+
+        func locationAccuracyAuthorization() -> CLAccuracyAuthorization {
+            .fullAccuracy
+        }
+
+        func currentLocation(
+            desiredAccuracy: OpenClawLocationAccuracy,
+            maxAgeMs: Int?,
+            timeoutMs: Int?) async throws -> CLLocation
+        {
+            _ = desiredAccuracy
+            _ = maxAgeMs
+            _ = timeoutMs
+            return CLLocation(latitude: 0, longitude: 0)
+        }
+    }
+
     @Test func `handle invoke rejects unknown command`() async {
         let runtime = MacNodeRuntime()
         let response = await runtime.handleInvoke(
@@ -298,6 +370,199 @@ struct MacNodeRuntimeTests {
         #expect(payload.capturedAtMs <= snapshotCalledAtMs!)
     }
 
+    @Test func `handle invoke screen snapshot rejects malformed params before capture`() async throws {
+        let services = await MainActor.run { ScreenSnapshotProbeServices() }
+        let runtime = MacNodeRuntime(makeMainActorServices: { services })
+
+        let response = await runtime.handleInvoke(
+            BridgeInvokeRequest(
+                id: "req-screen-snapshot-invalid",
+                command: MacNodeScreenCommand.snapshot.rawValue,
+                paramsJSON: #"{"screenIndex":"#))
+
+        #expect(response.ok == false)
+        #expect(response.error?.code == .invalidRequest)
+        #expect(response.error?.message == "INVALID_REQUEST: invalid screen snapshot params")
+        let snapshotCallCount = await MainActor.run { services.snapshotCallCount }
+        #expect(snapshotCallCount == 0)
+    }
+
+    @Test func `handle invoke screen snapshot keeps nil params as defaults`() async throws {
+        let services = await MainActor.run { ScreenSnapshotProbeServices() }
+        let runtime = MacNodeRuntime(makeMainActorServices: { services })
+
+        let response = await runtime.handleInvoke(
+            BridgeInvokeRequest(
+                id: "req-screen-snapshot-defaults",
+                command: MacNodeScreenCommand.snapshot.rawValue))
+
+        #expect(response.ok == true)
+        let received = await MainActor.run { services.receivedSnapshotParams }
+        #expect(received == MacNodeScreenSnapshotParams())
+    }
+
+    @Test func `handle invoke screen snapshot sanitizes capture failures`() async throws {
+        struct SensitiveError: LocalizedError {
+            let detail: String
+            var errorDescription: String? { detail }
+        }
+
+        let services = await MainActor.run {
+            ScreenSnapshotProbeServices(snapshotError: SensitiveError(detail: "TCC_DENIED display-id=ABC123"))
+        }
+        let runtime = MacNodeRuntime(makeMainActorServices: { services })
+
+        let response = await runtime.handleInvoke(
+            BridgeInvokeRequest(
+                id: "req-screen-snapshot-error",
+                command: MacNodeScreenCommand.snapshot.rawValue))
+
+        #expect(response.ok == false)
+        #expect(response.error?.code == .unavailable)
+        #expect(response.error?.message == "UNAVAILABLE: screen snapshot failed")
+    }
+
+    @Test func `handle invoke screen snapshot reports validation failures as invalid request`() async throws {
+        let invalidIndexServices = await MainActor.run {
+            ScreenSnapshotProbeServices(
+                snapshotError: ScreenSnapshotService.ScreenSnapshotError.invalidScreenIndex(4))
+        }
+        let invalidIndexRuntime = MacNodeRuntime(makeMainActorServices: { invalidIndexServices })
+        let invalidIndexResponse = await invalidIndexRuntime.handleInvoke(
+            BridgeInvokeRequest(
+                id: "req-screen-snapshot-bad-index",
+                command: MacNodeScreenCommand.snapshot.rawValue))
+
+        #expect(invalidIndexResponse.ok == false)
+        #expect(invalidIndexResponse.error?.code == .invalidRequest)
+        #expect(invalidIndexResponse.error?.message == "INVALID_REQUEST: invalid screen index 4")
+
+        let noDisplaysServices = await MainActor.run {
+            ScreenSnapshotProbeServices(snapshotError: ScreenSnapshotService.ScreenSnapshotError.noDisplays)
+        }
+        let noDisplaysRuntime = MacNodeRuntime(makeMainActorServices: { noDisplaysServices })
+        let noDisplaysResponse = await noDisplaysRuntime.handleInvoke(
+            BridgeInvokeRequest(
+                id: "req-screen-snapshot-no-displays",
+                command: MacNodeScreenCommand.snapshot.rawValue))
+
+        #expect(noDisplaysResponse.ok == false)
+        #expect(noDisplaysResponse.error?.code == .invalidRequest)
+        #expect(
+            noDisplaysResponse.error?.message ==
+                "INVALID_REQUEST: no displays available for screen snapshot")
+    }
+
+    @Test func `handle invoke screen snapshot rejects raw payloads above base64 ceiling`() async throws {
+        let payloadSize = 19_660_801
+        let services = await MainActor.run {
+            ScreenSnapshotProbeServices(snapshotResult: (
+                Data(repeating: 0x41, count: payloadSize),
+                .jpeg,
+                4000,
+                3000))
+        }
+        let runtime = MacNodeRuntime(makeMainActorServices: { services })
+
+        let response = await runtime.handleInvoke(
+            BridgeInvokeRequest(
+                id: "req-screen-snapshot-too-large",
+                command: MacNodeScreenCommand.snapshot.rawValue))
+
+        #expect(response.ok == false)
+        #expect(response.payloadJSON == nil)
+        #expect(response.error?.code == .unavailable)
+        #expect(
+            response.error?.message ==
+                "UNAVAILABLE: screen snapshot payload too large; reduce maxWidth or use jpeg")
+    }
+
+    @Test func `handle invoke screen snapshot rejects escaped oversized outer frames`() async throws {
+        let payloadSize = 12 * 1024 * 1024
+        let services = await MainActor.run {
+            ScreenSnapshotProbeServices(snapshotResult: (
+                Data(repeating: 0xFF, count: payloadSize),
+                .png,
+                4000,
+                3000))
+        }
+        let runtime = MacNodeRuntime(makeMainActorServices: { services })
+
+        let response = await runtime.handleInvoke(
+            BridgeInvokeRequest(
+                id: "req-screen-snapshot-slash-heavy",
+                command: MacNodeScreenCommand.snapshot.rawValue,
+                nodeId: "node-slash-heavy"))
+
+        #expect(response.ok == false)
+        #expect(response.error?.code == .unavailable)
+        #expect(
+            response.error?.message ==
+                "UNAVAILABLE: screen snapshot payload too large; reduce maxWidth or use jpeg")
+    }
+
+    @Test func `handle invoke screen snapshot accepts near-limit frames that fit`() async throws {
+        let payloadSize = 19_660_100
+        let services = await MainActor.run {
+            ScreenSnapshotProbeServices(snapshotResult: (
+                Data(repeating: 0x00, count: payloadSize),
+                .jpeg,
+                4000,
+                3000))
+        }
+        let runtime = MacNodeRuntime(makeMainActorServices: { services })
+
+        let response = await runtime.handleInvoke(
+            BridgeInvokeRequest(
+                id: "req-fit",
+                command: MacNodeScreenCommand.snapshot.rawValue,
+                nodeId: "node-fit"))
+
+        #expect(response.ok == true)
+        let payloadJSON = try #require(response.payloadJSON)
+        let projected = try MacNodeRuntime.projectedOuterFrameBytes(
+            forPayloadJSON: payloadJSON,
+            requestId: "req-fit",
+            nodeId: "node-fit")
+        #expect(projected < 25 * 1024 * 1024)
+    }
+
+    @Test func `projected outer frame bytes accounts for dynamic node id escaping`() throws {
+        let inner = "{\"format\":\"png\",\"note\":\"\u{0001}\u{0002}\n\t\\\"raw\\\"\",\"width\":1,\"height\":1,\"capturedAtMs\":0}"
+        let projected = try MacNodeRuntime.projectedOuterFrameBytes(
+            forPayloadJSON: inner,
+            requestId: "req-control",
+            nodeId: "node-\u{0001}\u{0002}\u{0003}\n\t-id")
+
+        struct Frame: Encodable {
+            let type = "req"
+            let id = "00000000-0000-0000-0000-000000000000"
+            let method = "node.invoke.result"
+            let params: Params
+
+            struct Params: Encodable {
+                let id: String
+                let nodeId: String
+                let ok: Bool
+                let payloadJSON: String
+            }
+        }
+        let serialized = try JSONEncoder().encode(Frame(params: Frame.Params(
+            id: "req-control",
+            nodeId: "node-\u{0001}\u{0002}\u{0003}\n\t-id",
+            ok: true,
+            payloadJSON: inner)))
+
+        #expect(projected == serialized.count)
+
+        let controlHeavyNodeId = String(repeating: "\u{0001}", count: 5 * 1024 * 1024)
+        let controlHeavyProjection = try MacNodeRuntime.projectedOuterFrameBytes(
+            forPayloadJSON: "{}",
+            requestId: "req-control",
+            nodeId: controlHeavyNodeId)
+        #expect(controlHeavyProjection > 25 * 1024 * 1024)
+    }
+
     @Test func `handle invoke browser proxy uses injected request`() async {
         let runtime = MacNodeRuntime(browserProxyRequest: { paramsJSON in
             #expect(paramsJSON?.contains("/tabs") == true)
diff --git a/apps/shared/OpenClawKit/Sources/OpenClawKit/BridgeFrames.swift b/apps/shared/OpenClawKit/Sources/OpenClawKit/BridgeFrames.swift
index debcec3ae87..79d1a7369e6 100644
--- a/apps/shared/OpenClawKit/Sources/OpenClawKit/BridgeFrames.swift
+++ b/apps/shared/OpenClawKit/Sources/OpenClawKit/BridgeFrames.swift
@@ -13,12 +13,20 @@ public struct BridgeInvokeRequest: Codable, Sendable {
     public let id: String
     public let command: String
     public let paramsJSON: String?
+    public let nodeId: String?
 
-    public init(type: String = "invoke", id: String, command: String, paramsJSON: String? = nil) {
+    public init(
+        type: String = "invoke",
+        id: String,
+        command: String,
+        paramsJSON: String? = nil,
+        nodeId: String? = nil)
+    {
         self.type = type
         self.id = id
         self.command = command
         self.paramsJSON = paramsJSON
+        self.nodeId = nodeId
     }
 }
 
diff --git a/apps/shared/OpenClawKit/Sources/OpenClawKit/GatewayNodeSession.swift b/apps/shared/OpenClawKit/Sources/OpenClawKit/GatewayNodeSession.swift
index 19730692846..18fd7904556 100644
--- a/apps/shared/OpenClawKit/Sources/OpenClawKit/GatewayNodeSession.swift
+++ b/apps/shared/OpenClawKit/Sources/OpenClawKit/GatewayNodeSession.swift
@@ -457,7 +457,8 @@ public actor GatewayNodeSession {
             let req = BridgeInvokeRequest(
                 id: request.id,
                 command: request.command,
-                paramsJSON: request.paramsJSON)
+                paramsJSON: request.paramsJSON,
+                nodeId: request.nodeId)
             self.logger.info("node invoke executing id=\(request.id, privacy: .public)")
             let response = await Self.invokeWithTimeout(
                 request: req,