[Feat] (MG_Remote, P5): land the client role - BackendObject_Remote, the 71-slot emit table, the caps mirror and the verb barrier

CMakeLists.txt

@@ -571,6 +571,9 @@ if (MOBILEGL_BUILD_DISAGGREGATED)
         MobileGL/MG_Remote/Client/ClientSession.cpp
         MobileGL/MG_Remote/Client/EmitTables.cpp
         MobileGL/MG_Remote/Client/CapsMirror.cpp
+        # P5 c1: the client role's BackendObject. pActiveBackendObject holds one of these
+        # under split (table 3); the hook that installs it is v1's, in MG_Backend/Init.cpp.
+        MobileGL/MG_Remote/Client/BackendObject_Remote.cpp
         # P5 b1's two: the conservative GPU-write set the client must build because all six
         # MarkGpuWritten producers are on the server's side of the line, and the
         # block-granularity persistent-map push that tier T2 makes mandatory.

MobileGL/MG_Impl/GLImpl/Getter/GL_Getter.cpp

@@ -31,6 +31,11 @@
 #include <MG_Util/ShaderTranspiler/Types.h>
 #include <MG_Backend/BackendObjects.h>
 #include <MG_Impl/Pipe/PipeFill.h>
+// CONTRACT-P5.md §7 / ID-14: a null check on a GLFunctionsTable slot may not survive into the
+// client under split - it becomes a caps-mirror read. SlotCaps.h carries the rule and the test
+// that decides which of its two spellings a site takes; in a pull build both expand to exactly
+// the check they replaced.
+#include <MG_Remote/Client/SlotCaps.h>
 
 namespace MobileGL::MG_Impl::GLImpl {
     // Declared rather than #included from GL_RenderState.h on purpose: that header also declares
@@ -1354,7 +1359,16 @@ namespace MobileGL::MG_Impl::GLImpl {
             // full 64-bit GPU timestamp survives; LWJGL reads it this way.
             Int64 timestamp = 0;
             if (!MG_Config::Features.DisableTimerQuery) {
-                if (const auto getGpuTimestampNs = MG_Backend::gBackendFunctionsTable.GL.GetGpuTimestampNs) {
+                // glGetInteger64v(GL_TIMESTAMP). GetGpuTimestampNs is class C - a LIVE GPU
+                // timestamp is not a static property, so R-15 does not reach it - and the
+                // documented answer when it is unavailable is 0 (BackendObject.h:192), which
+                // is correct rather than merely quiet. kCapTimerQuery is the published bit.
+                //
+                // The POINTER-valued macro, so the init-statement below is unchanged in a pull
+                // build and G1 cannot see this edit: the Bool-valued spelling moved this
+                // function by -150 bytes for no behavioural reason at all.
+                if (const auto getGpuTimestampNs =
+                        MGL_BACKEND_SLOT_PTR_CAP(GetGpuTimestampNs, MG_Pipe::kCapTimerQuery)) {
                     MGP_FILL(GetGpuTimestampNs);
                     timestamp = getGpuTimestampNs();
                 }
@@ -2265,7 +2279,16 @@ namespace MobileGL::MG_Impl::GLImpl {
         case GL_TIMESTAMP: {
             Int64 timestamp = 0;
             if (!MG_Config::Features.DisableTimerQuery) {
-                if (const auto getGpuTimestampNs = MG_Backend::gBackendFunctionsTable.GL.GetGpuTimestampNs) {
+                // glGetInteger64v(GL_TIMESTAMP). GetGpuTimestampNs is class C - a LIVE GPU
+                // timestamp is not a static property, so R-15 does not reach it - and the
+                // documented answer when it is unavailable is 0 (BackendObject.h:192), which
+                // is correct rather than merely quiet. kCapTimerQuery is the published bit.
+                //
+                // The POINTER-valued macro, so the init-statement below is unchanged in a pull
+                // build and G1 cannot see this edit: the Bool-valued spelling moved this
+                // function by -150 bytes for no behavioural reason at all.
+                if (const auto getGpuTimestampNs =
+                        MGL_BACKEND_SLOT_PTR_CAP(GetGpuTimestampNs, MG_Pipe::kCapTimerQuery)) {
                     MGP_FILL(GetGpuTimestampNs);
                     timestamp = getGpuTimestampNs();
                 }

MobileGL/MG_Impl/GLImpl/Query/GL_Query.cpp

@@ -13,6 +13,10 @@
 #include <MG_State/GLState/Core.h>
 #include <MG_State/GLState/ErrorState/ErrorInfo.h>
 #include <MG_Impl/Pipe/PipeFill.h>
+// CONTRACT-P5.md §7 / ID-14: a null check on a GLFunctionsTable slot may not survive into the
+// client under split - it becomes a caps-mirror read, whatever class the slot itself is in.
+// The two macros carry that rule; in a pull build each expands to exactly the check it replaced.
+#include <MG_Remote/Client/SlotCaps.h>
 
 namespace MobileGL::MG_Impl::GLImpl {
     namespace {
@@ -478,7 +482,7 @@ namespace MobileGL::MG_Impl::GLImpl {
         const Bool isOcclusionQuery =
             (target == GL_SAMPLES_PASSED || target == GL_ANY_SAMPLES_PASSED ||
              target == GL_ANY_SAMPLES_PASSED_CONSERVATIVE) &&
-            MG_Backend::gBackendFunctionsTable.GL.BeginOcclusionQuery != nullptr;
+            MGL_BACKEND_SLOT_CAP(BeginOcclusionQuery, MG_Pipe::kCapOcclusionQuery);
         const Bool isPipelineStatisticsQuery = IsPipelineStatisticsQueryTarget(target);
         if (target != GL_TIME_ELAPSED && !isTransformFeedbackQuery && !isOcclusionQuery &&
             !isPipelineStatisticsQuery) {
@@ -528,10 +532,12 @@ namespace MobileGL::MG_Impl::GLImpl {
         } else if (isTransformFeedbackQuery) {
             // Prefer real GPU transform-feedback queries (exact with geometry shaders);
             // the CPU accounting delta stays as the fallback when the backend lacks them.
+            const Bool xfbQuerySupported =
+                MGL_BACKEND_SLOT_CAP(BeginXfbPrimitivesQuery, MG_Pipe::kCapXfbPrimitivesQuery);
             const auto beginXfbPrimitivesQuery = MG_Backend::gBackendFunctionsTable.GL.BeginXfbPrimitivesQuery;
             MGP_FILL(BeginXfbPrimitivesQuery);
             queryObject->backendHandle =
-                beginXfbPrimitivesQuery ? beginXfbPrimitivesQuery(target == GL_PRIMITIVES_GENERATED) : nullptr;
+                xfbQuerySupported ? beginXfbPrimitivesQuery(target == GL_PRIMITIVES_GENERATED) : nullptr;
             queryObject->counterSnapshot = TransformFeedbackCounterForTarget(target);
             queryObject->accountedCaptureDrawSnapshot =
                 MG_State::pGLContext->GetTransformFeedbackAccountedCaptureDraws();
@@ -541,10 +547,12 @@ namespace MobileGL::MG_Impl::GLImpl {
             MGP_FILL(BeginOcclusionQuery);
             queryObject->backendHandle = MG_Backend::gBackendFunctionsTable.GL.BeginOcclusionQuery();
         } else {
+            const Bool timerQuerySupported =
+                MGL_BACKEND_SLOT_CAP(BeginTimeElapsedQuery, MG_Pipe::kCapTimerQuery);
             const auto beginTimeElapsedQuery = MG_Backend::gBackendFunctionsTable.GL.BeginTimeElapsedQuery;
             MGP_FILL(BeginTimeElapsedQuery);
             queryObject->backendHandle =
-                (!TimerQueryDisabled() && beginTimeElapsedQuery) ? beginTimeElapsedQuery() : nullptr;
+                (!TimerQueryDisabled() && timerQuerySupported) ? beginTimeElapsedQuery() : nullptr;
         }
         activeQueryId = id;
     }
@@ -555,7 +563,7 @@ namespace MobileGL::MG_Impl::GLImpl {
         const Bool isOcclusionQuery =
             (target == GL_SAMPLES_PASSED || target == GL_ANY_SAMPLES_PASSED ||
              target == GL_ANY_SAMPLES_PASSED_CONSERVATIVE) &&
-            MG_Backend::gBackendFunctionsTable.GL.BeginOcclusionQuery != nullptr;
+            MGL_BACKEND_SLOT_CAP(BeginOcclusionQuery, MG_Pipe::kCapOcclusionQuery);
         const Bool isPipelineStatisticsQuery = IsPipelineStatisticsQueryTarget(target);
         if (target != GL_TIME_ELAPSED && !isTransformFeedbackQuery && !isOcclusionQuery &&
             !isPipelineStatisticsQuery) {
@@ -657,7 +665,10 @@ namespace MobileGL::MG_Impl::GLImpl {
 
         ResetQueryObjectLocked(queryObject); // discard any previous result
         queryObject->target = target;
-        const auto queryCounterTimestamp = MG_Backend::gBackendFunctionsTable.GL.QueryCounterTimestamp;
+        const Bool timerQuerySupported =
+            MGL_BACKEND_SLOT_CAP(QueryCounterTimestamp, MG_Pipe::kCapTimerQuery);
+        const auto queryCounterTimestamp =
+            timerQuerySupported ? MG_Backend::gBackendFunctionsTable.GL.QueryCounterTimestamp : nullptr;
         MGP_FILL(QueryCounterTimestamp);
         queryObject->backendHandle =
             (!TimerQueryDisabled() && queryCounterTimestamp) ? queryCounterTimestamp() : nullptr;
@@ -782,7 +793,7 @@ namespace MobileGL::MG_Impl::GLImpl {
             }
             if (target == GL_SAMPLES_PASSED || target == GL_ANY_SAMPLES_PASSED ||
                 target == GL_ANY_SAMPLES_PASSED_CONSERVATIVE) {
-                const Bool occlusionSupported = MG_Backend::gBackendFunctionsTable.GL.BeginOcclusionQuery != nullptr;
+                const Bool occlusionSupported = MGL_BACKEND_SLOT_CAP(BeginOcclusionQuery, MG_Pipe::kCapOcclusionQuery);
                 *params = occlusionSupported ? (target == GL_SAMPLES_PASSED ? 32 : 1) : 0;
                 return;
             }

MobileGL/MG_Impl/GLImpl/Sync/GL_Sync.cpp

@@ -10,6 +10,11 @@
 #include <MG_Backend/BackendObjects.h>
 #include <MG_State/GLState/Core.h>
 #include <MG_Impl/Pipe/PipeFill.h>
+// CONTRACT-P5.md §7 / ID-14: a null check on a GLFunctionsTable slot may not survive into the
+// client under split - it becomes a caps-mirror read. SlotCaps.h carries the rule and the test
+// that decides which of its two spellings a site takes; in a pull build both expand to exactly
+// the check they replaced.
+#include <MG_Remote/Client/SlotCaps.h>
 
 namespace MobileGL::MG_Impl::GLImpl {
     namespace {
@@ -56,7 +61,11 @@ namespace MobileGL::MG_Impl::GLImpl {
         auto* syncObject = new SyncObject;
         syncObject->condition = condition;
         syncObject->flags = flags;
-        if (const auto backendFenceSync = MG_Backend::gBackendFunctionsTable.GL.FenceSync) {
+        // The family's ONE gate. FenceSync is class C under split, and "absent" is the
+        // answer the whole fallback chain below is written against: every later site already
+        // checks syncObject->backendHandle, which stays null from here. The POINTER-valued
+        // macro keeps the init-statement byte-identical in a pull build (G1).
+        if (const auto backendFenceSync = MGL_BACKEND_SLOT_PTR_LOCAL(FenceSync)) {
             MGP_FILL(FenceSync);
             syncObject->backendHandle = backendFenceSync();
         }

MobileGL/MG_Impl/GLImpl/Texture/GL_Texture.cpp

@@ -31,6 +31,11 @@
 #include <MG_Util/Math/FixedPointConversion.h>
 #include <MG_State/GLState/TextureState/TextureObjectBuffer.h>
 #include <MG_Impl/Pipe/PipeFill.h>
+// CONTRACT-P5.md §7 / ID-14: a null check on a GLFunctionsTable slot may not survive into the
+// client under split - it becomes a caps-mirror read. SlotCaps.h carries the rule and the test
+// that decides which of its two spellings a site takes; in a pull build both expand to exactly
+// the check they replaced.
+#include <MG_Remote/Client/SlotCaps.h>
 // P4a, ID-18 M2. The ONE door MG_State and MG_Impl have into the client's emitters; the three
 // call sites below are declarations only, exactly as the frontend's mutators are.
 #include <MG_Pipe/PipeMutation.h>
@@ -6534,7 +6539,7 @@ namespace MobileGL::MG_Impl::GLImpl {
                                                GLenum type, GLsizei bufSize, void* pixels, const char* caller) {
         if (MG_Backend::pActiveBackendObject != nullptr &&
             MG_Backend::pActiveBackendObject->GetBackendType() == BackendType::DirectVulkan &&
-            MG_Backend::gBackendFunctionsTable.GL.GetTextureImage != nullptr) {
+            MGL_BACKEND_SLOT_LOCAL(GetTextureImage)) {
             MGP_FILL(GetTextureImage);
             MG_Backend::gBackendFunctionsTable.GL.GetTextureImage(textureObject, uploadTarget, level, format, type,
                                                                   bufSize, pixels);
@@ -6796,7 +6801,7 @@ namespace MobileGL::MG_Impl::GLImpl {
 
     void GetTexImage(GLenum target, GLint level, GLenum format, GLenum type, GLvoid* pixels) {
         if (!GetTexImage_State(target, level, format, type, pixels)) return;
-        if (MG_Backend::gBackendFunctionsTable.GL.GetTexImage != nullptr) {
+        if (MGL_BACKEND_SLOT_LOCAL(GetTexImage)) {
             GetTexImage_Backend(target, level, format, type, pixels);
             return;
         }

MobileGL/MG_Impl/Pipe/PipeFill.cpp

@@ -39,6 +39,15 @@
 #include <MG_Pipe/PipeMutation.h>
 #include <Config.h>
 
+#if MOBILEGL_BUILD_DISAGGREGATED
+// R-8 (c1): the client's liveness gates read the caps mirror, never MGPipeGetResourceOps().
+// Behind the build option for G1's reason - nothing under MG_Remote may be reachable from a
+// pull build - and every use below is additionally gated on the resolved TRANSPORT, because
+// build-split runs MOBILEGL_TRANSPORT=monolith in every unit and integration-gpu lane and those
+// lanes must keep answering exactly what they answered before.
+#include <MG_Remote/Client/CapsMirror.h>
+#endif
+
 #include <atomic>
 #include <cstdlib>
 #include <cstring>
@@ -609,12 +618,38 @@ namespace MobileGL::MG_Pipe {
         }
     } // namespace
 
+    // R-8 (c1). THE SECOND CONJUNCT MOVES UNDER SPLIT, AND ONLY UNDER SPLIT.
+    //
+    // `MGPipeGetResourceOps() != nullptr` asks "has a backend registered the consumer". That
+    // table is the SERVER's registration and it is a PROCESS-WIDE global (PipeApply.cpp:402):
+    // under inproc a client reading it answers correctly BY ACCIDENT, and under spawn the
+    // client process has no backend at all, so the read answers null and five record families
+    // stop emitting - silently, while the emitters go on clearing their per-level dirty flags
+    // on the acceptance they never asked for. That is ID-39's 66 lost DirectVulkan uploads with
+    // a wire in between. The client asks the caps mirror instead, which carries the answer the
+    // SERVER gave at the handshake (CallMask bits 32..47).
+    //
+    // s1 made the server end Fatal when nobody sets the mask; this is the client end.
     Bool MGPipeResourceSubsystemEnabled() {
-        return (MG_Config::Features.PipePush & kMGPipeSubsystemResources) != 0 &&
+        if ((MG_Config::Features.PipePush & kMGPipeSubsystemResources) == 0) return false;
-               MGPipeGetResourceOps() != nullptr;
+#if MOBILEGL_BUILD_DISAGGREGATED
+        if (MG_Config::Transport != MG_Config::TransportMode::Monolith) {
+            return MG_Remote::Client::CapsMirrorInstance().ServerConsumes(kMGPipeSubsystemResources);
+        }
+#endif
+        return MGPipeGetResourceOps() != nullptr;
     }
 
     Bool MGPipeResourceOpsHaveSubDataResident() {
+#if MOBILEGL_BUILD_DISAGGREGATED
+        if (MG_Config::Transport != MG_Config::TransportMode::Monolith) {
+            // CONTRACT-P5.md §7's THIRD NAMED CAPABILITY PROBE. `ops->SubDataResident != nullptr`
+            // is not a safety check - it decides whether the resident-upload path EXISTS - and
+            // under split there is no op table here to probe. kCapResidentSubData is the bit the
+            // server publishes for exactly this question.
+            return MG_Remote::Client::CapsMirrorInstance().HasCap(kCapResidentSubData);
+        }
+#endif
         const MGPipeResourceOps* ops = MGPipeGetResourceOps();
         return ops != nullptr && ops->SubDataResident != nullptr;
     }
@@ -936,8 +971,21 @@ namespace MobileGL::MG_Pipe {
         // MGPipeEmitResourceRespecify above uses for buffers) publishes it. Nothing here needs
         // to remember the window.
         Bool P4aFamilyHasItsConsumer(Uint64 subsystem) {
-            return (subsystem & kMGPipeP4aFamilySubsystems) == 0 ||
+            if ((subsystem & kMGPipeP4aFamilySubsystems) == 0) return true;
-                   MGPipeGetResourceOps() != nullptr;
+#if MOBILEGL_BUILD_DISAGGREGATED
+            // R-8 (c1), the same move as MGPipeResourceSubsystemEnabled's and for the same
+            // reason. ALL FOUR FAMILIES RIDE THE ONE SIGNAL, exactly as they do in monolith:
+            // the paragraph above explains why the resource consumer IS the texture family's
+            // consumer, and the split spelling of "a backend registered the resource op table"
+            // is "the server published the resource subsystem's consumer bit". Asking per
+            // family here would be a NEW rule, and a client that withheld more than the server
+            // refuses leaves the server's handle arm live with no records to read.
+            if (MG_Config::Transport != MG_Config::TransportMode::Monolith) {
+                return MG_Remote::Client::CapsMirrorInstance().ServerConsumes(
+                    kMGPipeSubsystemResources);
+            }
+#endif
+            return MGPipeGetResourceOps() != nullptr;
         }
 
         // ================================================================================

MobileGL/MG_Remote/Client/BackendObject_Remote.cpp

@@ -0,0 +1,332 @@
+// MobileGL - MobileGL/MG_Remote/Client/BackendObject_Remote.cpp
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+// P5 package c1. See BackendObject_Remote.h for the three traps and why each is paid here.
+
+#include "BackendObject_Remote.h"
+
+#include "CapsMirror.h"
+#include "ClientSession.h"
+#include "EmitTables.h"
+
+#include "../Server/ServerLoop.h"
+
+#include <MG_Util/Debug/Log.h>
+
+// Declared rather than included: MG_Backend/BackendObjects.h drags in both concrete backend
+// objects, and this translation unit must not depend on either - the client role links the same
+// library but never constructs one.
+namespace MobileGL::MG_Backend {
+    extern UniquePtr<BackendObject>& pActiveBackendObject;
+}
+
+namespace MobileGL::MG_Remote::Client {
+
+    namespace {
+
+        // ---- the EGL bridge ---------------------------------------------------------------
+        //
+        // Every one of the nine crosses as a BLOCKING control request on the apply thread,
+        // because every one of them has a return value the caller acts on immediately. v1's
+        // ServerLoop::RunOnApplyThread takes a raw function pointer plus a user pointer rather
+        // than a std::function, deliberately: this path runs at teardown too, and the teardown
+        // path may not allocate (ID-8).
+        //
+        // A NULL SERVER BACKEND IS "false", NOT A CRASH AND NOT A LOCAL SUCCESS. Under inproc
+        // the apply thread creates it during ClientSession::Start, so a null one here means the
+        // bring-up did not complete - and answering `true` would let the frontend believe it
+        // has a context.
+        MG_Backend::BackendObject* ServerBackend() { return Server::ServerLoopInstance().Backend(); }
+
+        struct DisplayArgs {
+            EGLDisplay Dpy;
+            EGLint* Major;
+            EGLint* Minor;
+            Bool Ok;
+        };
+        MobileGLResult RunInitDisplay(void* user) {
+            auto* args = static_cast<DisplayArgs*>(user);
+            args->Ok = ServerBackend()->InitializeEGLDisplay(args->Dpy, args->Major, args->Minor);
+            return MOBILEGL_OK;
+        }
+
+        struct WindowSurfaceArgs {
+            EGLSurface Surface;
+            const MG_Backend::WindowHandle* Handle;
+            Bool Ok;
+        };
+        MobileGLResult RunCreateWindowSurface(void* user) {
+            auto* args = static_cast<WindowSurfaceArgs*>(user);
+            args->Ok = ServerBackend()->CreateEGLWindowSurface(args->Surface, *args->Handle);
+            return MOBILEGL_OK;
+        }
+
+        struct ResizeArgs {
+            EGLSurface Surface;
+            Uint32 Width;
+            Uint32 Height;
+            Bool Ok;
+        };
+        MobileGLResult RunResize(void* user) {
+            auto* args = static_cast<ResizeArgs*>(user);
+            args->Ok = ServerBackend()->ResizeEGLWindowSurface(args->Surface, args->Width, args->Height);
+            return MOBILEGL_OK;
+        }
+
+        struct PbufferArgs {
+            EGLSurface Surface;
+            EGLint Width;
+            EGLint Height;
+            Bool Ok;
+        };
+        MobileGLResult RunCreatePbuffer(void* user) {
+            auto* args = static_cast<PbufferArgs*>(user);
+            args->Ok = ServerBackend()->CreateEGLPbufferSurface(args->Surface, args->Width, args->Height);
+            return MOBILEGL_OK;
+        }
+
+        struct MakeCurrentArgs {
+            EGLDisplay Dpy;
+            EGLSurface Draw;
+            EGLSurface Read;
+            EGLContext Ctx;
+            Bool Ok;
+        };
+        MobileGLResult RunMakeCurrent(void* user) {
+            auto* args = static_cast<MakeCurrentArgs*>(user);
+            args->Ok = ServerBackend()->MakeEGLCurrent(args->Dpy, args->Draw, args->Read, args->Ctx);
+            return MOBILEGL_OK;
+        }
+
+        struct SwapIntervalArgs {
+            Int Interval;
+        };
+        MobileGLResult RunSwapInterval(void* user) {
+            ServerBackend()->SetEGLSwapInterval(static_cast<SwapIntervalArgs*>(user)->Interval);
+            return MOBILEGL_OK;
+        }
+
+        struct SurfaceArgs {
+            EGLSurface Surface;
+        };
+        MobileGLResult RunReleaseSurface(void* user) {
+            ServerBackend()->ReleaseEGLSurface(static_cast<SurfaceArgs*>(user)->Surface);
+            return MOBILEGL_OK;
+        }
+
+        MobileGLResult RunReleaseResources(void*) {
+            ServerBackend()->ReleaseEGLResources();
+            return MOBILEGL_OK;
+        }
+
+        // Runs `work` on the apply thread if there is a server backend to run it against, and
+        // says so by name when there is not.
+        Bool ForwardToApplyThread(const char* what, Server::ServerLoop::ControlWork work, void* user) {
+            if (ServerBackend() == nullptr) {
+                MGLOG_E("MG_Remote client: %s has no server backend to forward to - the apply "
+                        "thread's bring-up did not complete, and answering success here would "
+                        "tell the frontend it has a context it does not have",
+                        what);
+                return false;
+            }
+            return Server::ServerLoopInstance().RunOnApplyThread(work, user) == MOBILEGL_OK;
+        }
+
+        // CapsMirror's adoption hook. A free function because the hook is a raw function
+        // pointer (ID-8: this can fire on a path that must not allocate), and it reaches the
+        // live object through pActiveBackendObject rather than through a second global.
+        void OnCapsAdopted() {
+            auto* self = dynamic_cast<BackendObject_Remote*>(MG_Backend::pActiveBackendObject.get());
+            if (self != nullptr) self->RefreshFormatCapabilities();
+        }
+
+    } // namespace
+
+    BackendObject_Remote::BackendObject_Remote() {
+        // Installed in the constructor rather than at the first snapshot, because the first
+        // snapshot has usually already arrived by then: ClientSession::Start pumps the control
+        // plane during the handshake, and MG_Backend::Init() constructs this object after it.
+        // RefreshFormatCapabilities below picks up that already-adopted generation.
+        SetCapsAdoptedHook(&OnCapsAdopted);
+        RefreshFormatCapabilities();
+    }
+
+    BackendObject_Remote::~BackendObject_Remote() {
+        // The hook holds a raw function pointer, not a pointer to this - but the function it
+        // names reaches pActiveBackendObject, which is being destroyed right now. Uninstall.
+        SetCapsAdoptedHook(nullptr);
+    }
+
+    void BackendObject_Remote::RefreshFormatCapabilities() {
+        CapsMirror& mirror = CapsMirrorInstance();
+        if (!mirror.Valid() || mirror.Generation() == m_formatsGeneration) return;
+        // TRAP 2. GetFormatCapabilities() is non-virtual and hands back this member, so the
+        // only way a remote object can answer it is to fill it.
+        MutableFormatCapabilities() = mirror.Formats();
+        m_formatsGeneration = mirror.Generation();
+        MGLOG_I("MG_Remote client: format capabilities filled from caps mirror generation %llu",
+                static_cast<unsigned long long>(m_formatsGeneration));
+    }
+
+    // ---- the eight pure virtuals ----------------------------------------------------------
+
+    void BackendObject_Remote::Initialize() {
+        // NOT FORWARDED. The server's own BackendObject_DirectGLES is created and initialised
+        // by v1's ServerLoop, on the apply thread, before this object exists; forwarding here
+        // would be a second Initialize() on an already-initialised backend. What this call
+        // does is drain whatever the handshake left and take the caps that came with it.
+        if (ClientSession* session = ClientSession::Active()) {
+            session->PumpControlPlane();
+        }
+        RefreshFormatCapabilities();
+    }
+
+    Bool BackendObject_Remote::InitCapabilities() {
+        // Reached from the base class's MakeEGLCurrent, lazily, once per surface lifetime
+        // (BackendObject.cpp:341-347). By this point MakeEGLCurrent below has already run the
+        // SERVER's MakeEGLCurrent on the apply thread, whose own base class ran the server
+        // backend's InitCapabilities and whose ServerSession re-published the snapshot - so
+        // the client's job here is to pick that snapshot up. R-12: re-arrival IS the
+        // invalidation, and this is the second place it is drained (the other is Present).
+        ClientSession* session = ClientSession::Active();
+        if (session == nullptr) {
+            MGLOG_E("MG_Remote client: InitCapabilities with no session");
+            return false;
+        }
+        session->PumpControlPlane();
+        RefreshFormatCapabilities();
+        // A PLACEHOLDER MIRROR IS A FAILURE HERE, unlike at startup. LogBackendInfo reading a
+        // placeholder costs one wrong log line; a context going current on one costs every
+        // limit, every advertised extension and the compile-env fingerprint.
+        if (!CapsMirrorInstance().Valid()) {
+            MGLOG_E("MG_Remote client: InitCapabilities found no CapsSnapshot - the server has "
+                    "not published one. Going current on a placeholder caps mirror would put "
+                    "default limits into every glGetIntegerv answer and into the compile env");
+            return false;
+        }
+        return true;
+    }
+
+    Bool BackendObject_Remote::InitWindowSurface() {
+        // The real surface work happened on the apply thread inside the server backend's own
+        // ActivateEGLSurface; this is the client's half of the base state machine and has
+        // nothing of its own to do.
+        return true;
+    }
+
+    Bool BackendObject_Remote::InitPbufferSurface(EGLint, EGLint) { return true; }
+
+    const RendererInfo& BackendObject_Remote::GetRendererInfo() const {
+        // TRAP 1: a reference, so the storage is the mirror's and not a temporary's.
+        return CapsMirrorInstance().Renderer();
+    }
+
+    String BackendObject_Remote::GetBackendAPIVersionString() const {
+        return CapsMirrorInstance().ApiVersion();
+    }
+
+    const MG_Backend::GlobalBackendFunctionsTable& BackendObject_Remote::GetBackendFunctions() const {
+        return RemoteEmitTable();
+    }
+
+    const MG_Backend::DynamicBackendParameters& BackendObject_Remote::GetDynamicParameters() const {
+        return CapsMirrorInstance().Dynamic();
+    }
+
+    BackendType BackendObject_Remote::GetBackendType() const {
+        // TRAP 3: the SERVER's backend, never a new enumerator.
+        return CapsMirrorInstance().Backend();
+    }
+
+    // ---- the nine EGL lifecycle virtuals ---------------------------------------------------
+    //
+    // FORWARD FIRST, THEN RUN THE BASE. The server has to own the context before the client's
+    // base class latches "the surface is initialised" and calls InitCapabilities, because
+    // InitCapabilities' answer comes from a snapshot the server can only publish once its own
+    // InitCapabilities has run.
+
+    Bool BackendObject_Remote::InitializeEGLDisplay(EGLDisplay dpy, EGLint* major, EGLint* minor) {
+        DisplayArgs args{dpy, major, minor, false};
+        if (!ForwardToApplyThread("InitializeEGLDisplay", &RunInitDisplay, &args) || !args.Ok) {
+            return false;
+        }
+        return MG_Backend::BackendObject::InitializeEGLDisplay(dpy, major, minor);
+    }
+
+    Bool BackendObject_Remote::CreateEGLWindowSurface(EGLSurface surface,
+                                                      const MG_Backend::WindowHandle& handle) {
+        WindowSurfaceArgs args{surface, &handle, false};
+        if (!ForwardToApplyThread("CreateEGLWindowSurface", &RunCreateWindowSurface, &args) ||
+            !args.Ok) {
+            return false;
+        }
+        return MG_Backend::BackendObject::CreateEGLWindowSurface(surface, handle);
+    }
+
+    Bool BackendObject_Remote::ResizeEGLWindowSurface(EGLSurface surface, Uint32 width, Uint32 height) {
+        ResizeArgs args{surface, width, height, false};
+        if (!ForwardToApplyThread("ResizeEGLWindowSurface", &RunResize, &args) || !args.Ok) {
+            return false;
+        }
+        return MG_Backend::BackendObject::ResizeEGLWindowSurface(surface, width, height);
+    }
+
+    Bool BackendObject_Remote::CreateEGLPbufferSurface(EGLSurface surface, EGLint width, EGLint height) {
+        PbufferArgs args{surface, width, height, false};
+        if (!ForwardToApplyThread("CreateEGLPbufferSurface", &RunCreatePbuffer, &args) || !args.Ok) {
+            return false;
+        }
+        return MG_Backend::BackendObject::CreateEGLPbufferSurface(surface, width, height);
+    }
+
+    Bool BackendObject_Remote::MakeEGLCurrent(EGLDisplay dpy, EGLSurface draw, EGLSurface read,
+                                              EGLContext ctx) {
+        MakeCurrentArgs args{dpy, draw, read, ctx, false};
+        if (!ForwardToApplyThread("MakeEGLCurrent", &RunMakeCurrent, &args) || !args.Ok) {
+            return false;
+        }
+        // AND ONLY NOW the client's own bookkeeping, which is what calls InitCapabilities.
+        return MG_Backend::BackendObject::MakeEGLCurrent(dpy, draw, read, ctx);
+    }
+
+    Bool BackendObject_Remote::SwapEGLBuffers(EGLDisplay dpy, EGLSurface draw) {
+        // NOT FORWARDED, and this is the one that must not be. The base implementation's last
+        // act is GetBackendFunctions().Present() (BackendObject.cpp:396) - which is this
+        // client's class-B Present EMITTER, the only route by which Present is reached at all
+        // (it has zero MG_Impl call sites). Forwarding would present on the server directly and
+        // put no record on the wire, which is the shape every gate in this phase exists to
+        // catch.
+        return MG_Backend::BackendObject::SwapEGLBuffers(dpy, draw);
+    }
+
+    void BackendObject_Remote::SetEGLSwapInterval(Int interval) {
+        // OVERRIDDEN BECAUSE THE BASE WOULD FATAL. BackendObject.cpp:402 null-checks
+        // GetBackendFunctions().SetSwapInterval and calls it when non-null - one of the 41
+        // null checks R-4 turns into "always supported" - and SetSwapInterval is class C, so
+        // the base implementation would abort on every eglSwapInterval. The answer is the
+        // caps-mirror-read rule's general shape: the question "can the presentation path take
+        // an interval" belongs to the server, so it is asked of the server.
+        SwapIntervalArgs args{interval};
+        ForwardToApplyThread("SetEGLSwapInterval", &RunSwapInterval, &args);
+    }
+
+    void BackendObject_Remote::ReleaseEGLSurface(EGLSurface surface) {
+        SurfaceArgs args{surface};
+        ForwardToApplyThread("ReleaseEGLSurface", &RunReleaseSurface, &args);
+        MG_Backend::BackendObject::ReleaseEGLSurface(surface);
+    }
+
+    void BackendObject_Remote::ReleaseEGLResources() {
+        // BLOCKING BY CONTRACT (ServerLoop.h's header note): MobileGL::Destroy()
+        // (MobileGL/Init.cpp:68) walks on the moment this returns, and the server still holds
+        // the context until the apply thread has run it.
+        ForwardToApplyThread("ReleaseEGLResources", &RunReleaseResources, nullptr);
+        MG_Backend::BackendObject::ReleaseEGLResources();
+    }
+
+} // namespace MobileGL::MG_Remote::Client

MobileGL/MG_Remote/Client/BackendObject_Remote.h

@@ -0,0 +1,96 @@
+// MobileGL - MobileGL/MG_Remote/Client/BackendObject_Remote.h
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+// THE CLIENT ROLE'S BackendObject. Owner: package c1.
+//
+// MG_Backend::Init() installs one of these into pActiveBackendObject when the transport
+// resolved (the hook is v1's; the object is c1's, table 3). It is NOT a backend: it owns no
+// context, no driver and no GL state. It is the frontend's single answer to four questions -
+// "what can the device do", "what backend is it", "what table do I call", and the nine EGL
+// lifecycle calls - and each of the four is answered somewhere that is not here.
+//
+// THE THREE TRAPS THE SCOUT FOUND, AND WHERE EACH IS PAID:
+//
+//  1. GetRendererInfo() RETURNS A REFERENCE (BackendObject.h:590), so the object cannot
+//     synthesise one per call. CapsMirror owns the storage; this class forwards. And
+//     LogBackendInfo() reads it at MG_Backend/Init.cpp:21, DURING MG_Backend::Init(), before
+//     any surface exists - so the mirror answers a placeholder and P5 accepts one imprecise
+//     startup log line. MG_Backend::Init() is NOT restructured (scout-caps-reply §1.2 (a)).
+//
+//  2. GetFormatCapabilities() IS NOT VIRTUAL (BackendObject.h:594). It returns the base class's
+//     own m_formatCapabilities member, so there is no accessor to override: the cache has to be
+//     PUSHED into that member, and the only moment this object can know to is when a snapshot
+//     lands. CapsMirror's adoption hook is that moment.
+//
+//  3. GetBackendType() MUST ANSWER THE SERVER'S BACKEND. There is no "Remote" enumerator and
+//     there must not be one: GL_Framebuffer.cpp:47, GL_Texture.cpp:6536 and CompileEnv.cpp:122
+//     switch on this value, and a value they do not know takes a WRONG ARM rather than failing.
+//
+// THE EGL VIRTUALS ARE BOTH FORWARDED AND KEPT. The base class runs a real state machine -
+// surface registration, per-thread current-context bookkeeping, the lazy InitCapabilities latch,
+// and SwapEGLBuffers' route into GetBackendFunctions().Present() - and the client needs all of
+// it, because Present is a class-B emitter reached through exactly that route (the verb census's
+// trap 3: Present has zero MG_Impl call sites). So each override does BOTH: it runs the real
+// EGL work on the apply thread, through v1's ServerLoop::RunOnApplyThread, and then lets the
+// base class keep the client-side books.
+//
+// SetEGLSwapInterval IS THE ONE THAT MUST NOT REACH THE TABLE. The base implementation
+// null-checks GetBackendFunctions().SetSwapInterval (BackendObject.cpp:402) - one of the 41
+// null checks R-4 turns into "always supported" - and SetSwapInterval is class C, so the base
+// implementation would Fatal on every eglSwapInterval. It is overridden to forward instead,
+// which is the caps-mirror-read rule's shape for a slot whose answer is "ask the server".
+
+#pragma once
+#include <Includes.h>
+
+#include <MG_Backend/BackendObject.h>
+
+namespace MobileGL::MG_Remote::Client {
+
+    class BackendObject_Remote final : public MG_Backend::BackendObject {
+    public:
+        BackendObject_Remote();
+        ~BackendObject_Remote() override;
+
+        // ---- the eight pure virtuals ------------------------------------------------------
+        void Initialize() override;
+        Bool InitCapabilities() override;
+        Bool InitWindowSurface() override;
+        const RendererInfo& GetRendererInfo() const override;
+        String GetBackendAPIVersionString() const override;
+        const MG_Backend::GlobalBackendFunctionsTable& GetBackendFunctions() const override;
+        const MG_Backend::DynamicBackendParameters& GetDynamicParameters() const override;
+        BackendType GetBackendType() const override;
+
+        // ---- the nine EGL lifecycle virtuals ---------------------------------------------
+        Bool InitializeEGLDisplay(EGLDisplay dpy, EGLint* major, EGLint* minor) override;
+        Bool CreateEGLWindowSurface(EGLSurface surface, const MG_Backend::WindowHandle& handle) override;
+        Bool ResizeEGLWindowSurface(EGLSurface surface, Uint32 width, Uint32 height) override;
+        Bool CreateEGLPbufferSurface(EGLSurface surface, EGLint width, EGLint height) override;
+        Bool MakeEGLCurrent(EGLDisplay dpy, EGLSurface draw, EGLSurface read, EGLContext ctx) override;
+        Bool SwapEGLBuffers(EGLDisplay dpy, EGLSurface draw) override;
+        void SetEGLSwapInterval(Int interval) override;
+        void ReleaseEGLSurface(EGLSurface surface) override;
+        void ReleaseEGLResources() override;
+
+        // Copies the caps mirror's FormatCapabilityCache into the base class's
+        // m_formatCapabilities. Public because CapsMirror's adoption hook is a free function
+        // and this is what it calls; it is the whole of trap 2's answer.
+        void RefreshFormatCapabilities();
+
+    protected:
+        Bool InitPbufferSurface(EGLint width, EGLint height) override;
+
+    private:
+        // The generation of the snapshot m_formatCapabilities was filled from. Exposed only
+        // through the log line on a refresh: a cache that silently stopped tracking the mirror
+        // is exactly the shape trap 2 exists to prevent.
+        Uint64 m_formatsGeneration = 0;
+    };
+
+} // namespace MobileGL::MG_Remote::Client

MobileGL/MG_Remote/Client/CapsMirror.cpp

@@ -6,49 +6,161 @@
 // SPDX-License-Identifier: LGPL-3.0-only
 // End of Source File Header
 
-// P5 c0 stubs for package c1. Every body is MGLOG_F + std::abort and never a silent no-op: a
+// P5 package c1.
-// caps accessor that answers a default is how a split lane runs on the wrong device's limits.
+//
+// EVERY ACCESSOR ANSWERS BEFORE THE FIRST SNAPSHOT, AND THAT IS THE RULING, NOT A WEAKENING.
+// c0's stubs aborted on all but Valid()/Generation() so that nothing could answer from a zeroed
+// mirror by accident. But scout-caps-reply §1.2's option (a) - the one the brief adopts - says
+// LogBackendInfo() reads GetRendererInfo() at MG_Backend/Init.cpp:21, during MG_Backend::Init(),
+// BEFORE any surface exists, and that P5 accepts one imprecise startup log line rather than
+// restructure MG_Backend::Init(). An abort there is not a stricter mirror; it is a process that
+// cannot start. So the mirror answers a placeholder and SAYS SO, once per accessor: a wrong
+// number that announced itself is auditable, and the announcement is what a case asserts on.
+//
+// THE PLACEHOLDER IS A REAL OBJECT, NOT A TEMPORARY. GetRendererInfo() and
+// GetDynamicParameters() return const references, so the storage has to outlive every caller;
+// the members below are it, default-constructed, and Adopt() replaces them in place.
 
 #include "CapsMirror.h"
 
-#include <MG_Util/Debug/Log.h>
+#include "../CapsCodec.h"
 
-#include <cstdlib>
+#include <MG_State/GLState/Core.h>
+#include <MG_Util/Debug/Log.h>
 
 namespace MobileGL::MG_Remote::Client {
 
-#define MGP5_C0_STUB(what)                                                                                             \
+    namespace {
-    do {                                                                                                               \
+        CapsAdoptedHook g_capsAdoptedHook = nullptr;
-        MGLOG_F("MGPipe: Fatal{UnimplementedCapsMirror, \"%s\"} - P5 package c1 has not landed "                       \
-                "this yet; c0 shipped the signature only",                                                             \
-                what);                                                                                                 \
-        std::abort();                                                                                                  \
-    } while (0)
 
-    void CapsMirror::Adopt(const MG_Pipe::MGPCaps&, const MG_Backend::FormatCapabilityCache&,
+        // R-8's negative control, counted at the funnel. Not atomics: every reader of this
-                           const RendererInfo&, const String&, BackendType) {
+        // mirror is the GL thread, by the same argument that makes one gPipeInputs legal.
-        MGP5_C0_STUB("CapsMirror::Adopt");
+        Uint64 g_consumerRefusals = 0;
+        Uint64 g_lastRefusedSubsystem = 0;
+        Uint64 g_refusedSubsystemsLogged = 0;
+
+        // One line per accessor, once, and only while the mirror is a placeholder. MGLOG_W_ONCE
+        // keys on the call site, so each accessor gets its own line and a hot getter cannot
+        // flood the log.
+        void WarnPlaceholder(const char* what, Uint64 generation) {
+            if (generation != 0) return;
+            MGLOG_W("MG_Remote client: CapsMirror::%s read before the first CapsSnapshot - "
+                    "answering a PLACEHOLDER. Expected exactly once at startup, from "
+                    "LogBackendInfo (MG_Backend/Init.cpp:21); anything later means a caps read "
+                    "beat the handshake",
+                    what);
+        }
+    } // namespace
+
+    void CapsMirror::Adopt(const MG_Pipe::MGPCaps& caps, const MG_Backend::FormatCapabilityCache& formats,
+                           const RendererInfo& renderer, const String& apiVersion,
+                           BackendType backend) {
+        m_caps = caps;
+        // The two blobrefs inside MGPCaps name SEG_STAGE runs that belong to the SERVER's
+        // encoder and are meaningless on this side; the decoded objects beside them are the
+        // answer. Clearing them is not tidiness - a later reader that resolved one would read
+        // whatever the stage allocator has since put there.
+        m_caps.FormatCapabilities = MG_Pipe::MGPBlobRef{};
+        m_caps.RendererInfo = MG_Pipe::MGPBlobRef{};
+        m_formats = formats;
+        m_renderer = renderer;
+        m_apiVersion = apiVersion;
+        m_backend = backend;
+        ++m_generation;
+
+        // R-12: RE-ARRIVAL IS THE INVALIDATION, and this is the one place that acts on it.
+        // GLContext::GetCompileEnv() memoises on the raw pActiveBackendObject pointer
+        // (Core.cpp:34); under split that pointer is the single long-lived BackendObject_Remote
+        // and NEVER changes, so without this line the compile env, its preprocess memos and the
+        // advertised-extension list stay stale for ever after a server-side InitCapabilities
+        // re-run. DirectVulkan already spells the monolith half of this exactly this way
+        // (BackendObject_DirectVulkan.cpp:390).
+        if (m_generation > 1 && MG_State::pGLContext != nullptr) {
+            MG_State::pGLContext->InvalidateCompileEnv();
+        }
+        MGLOG_I("MG_Remote client: CapsMirror generation %llu adopted (backend=%d, callMask=0x%llx)",
+                static_cast<unsigned long long>(m_generation), static_cast<int>(m_backend),
+                static_cast<unsigned long long>(m_caps.CallMask));
+
+        // LAST, and after the generation has moved: the hook reads this mirror.
+        if (g_capsAdoptedHook != nullptr) g_capsAdoptedHook();
     }
 
-    // Not stubs: the two the placeholder contract above promises are readable before the first
+    void SetCapsAdoptedHook(CapsAdoptedHook hook) { g_capsAdoptedHook = hook; }
-    // snapshot. Everything else aborts, so nothing can accidentally answer from a zeroed mirror.
+
     Bool CapsMirror::Valid() const { return m_generation != 0; }
     Uint64 CapsMirror::Generation() const { return m_generation; }
 
-    const RendererInfo& CapsMirror::Renderer() const { MGP5_C0_STUB("CapsMirror::Renderer"); }
+    const RendererInfo& CapsMirror::Renderer() const {
+        WarnPlaceholder("Renderer", m_generation);
+        return m_renderer;
+    }
+
     const MG_Backend::DynamicBackendParameters& CapsMirror::Dynamic() const {
-        MGP5_C0_STUB("CapsMirror::Dynamic");
+        WarnPlaceholder("Dynamic", m_generation);
+        return m_caps.Dynamic;
     }
+
     const MG_Backend::FormatCapabilityCache& CapsMirror::Formats() const {
-        MGP5_C0_STUB("CapsMirror::Formats");
+        WarnPlaceholder("Formats", m_generation);
+        return m_formats;
     }
-    const String& CapsMirror::ApiVersion() const { MGP5_C0_STUB("CapsMirror::ApiVersion"); }
+
-    BackendType CapsMirror::Backend() const { MGP5_C0_STUB("CapsMirror::Backend"); }
+    const String& CapsMirror::ApiVersion() const {
-    Uint64 CapsMirror::CallMask() const { MGP5_C0_STUB("CapsMirror::CallMask"); }
+        WarnPlaceholder("ApiVersion", m_generation);
-    Bool CapsMirror::HasCap(MG_Pipe::MGPCapBit) const { MGP5_C0_STUB("CapsMirror::HasCap"); }
+        return m_apiVersion;
-    Bool CapsMirror::ServerConsumes(Uint64) const { MGP5_C0_STUB("CapsMirror::ServerConsumes"); }
+    }
+
+    BackendType CapsMirror::Backend() const {
+        WarnPlaceholder("Backend", m_generation);
+        return m_backend;
+    }
+
+    Uint64 CapsMirror::CallMask() const { return m_caps.CallMask; }
+
+    Bool CapsMirror::HasCap(MG_Pipe::MGPCapBit bit) const {
+        return (m_caps.CallMask & static_cast<Uint64>(bit)) != 0;
+    }
+
+    Bool CapsMirror::ServerConsumes(Uint64 subsystemBit) const {
+        // THE ONLY LEGAL CLIENT-SIDE SPELLING (R-8). Never MGPipeGetResourceOps(): that is the
+        // SERVER's registration, a process-wide global, right by accident under inproc and null
+        // under spawn - and a null read there silently stops five record families while the
+        // client goes on clearing its dirty flags, which is ID-39's 66 lost uploads with a wire
+        // in between. Folded through CapsCodec.h's helper rather than shifted here, because two
+        // spellings of one bit layout is how the two sides come to disagree about it.
+        //
+        // A PLACEHOLDER MIRROR CONSUMES NOTHING, and that is the safe direction: with no
+        // snapshot the mask is 0, every family answers "no consumer", the client emits nothing
+        // and the LEGACY PULL PATH runs untouched. The unsafe direction - emitting to a server
+        // that has no consumer - is the one that loses uploads.
+        const Bool consumes = MGCapsServerConsumes(m_caps.CallMask, subsystemBit);
+        if (!consumes) {
+            ++g_consumerRefusals;
+            g_lastRefusedSubsystem = subsystemBit;
+            if ((g_refusedSubsystemsLogged & subsystemBit) == 0) {
+                g_refusedSubsystemsLogged |= subsystemBit;
+                MGLOG_W("MG_Remote client: the server does not consume MGPipe subsystem 0x%llx - "
+                        "this family emits NOTHING and the legacy pull path runs for it "
+                        "(R-8). callMask=0x%llx, caps generation %llu",
+                        static_cast<unsigned long long>(subsystemBit),
+                        static_cast<unsigned long long>(m_caps.CallMask),
+                        static_cast<unsigned long long>(m_generation));
+            }
+        }
+        return consumes;
+    }
+
+    Uint64 ConsumerRefusals() { return g_consumerRefusals; }
+    Uint64 LastRefusedSubsystem() { return g_lastRefusedSubsystem; }
+    void ResetConsumerRefusalsForTest() {
+        g_consumerRefusals = 0;
+        g_lastRefusedSubsystem = 0;
+        g_refusedSubsystemsLogged = 0;
+    }
+
     Bool CapsMirror::PrefersCpuXfbPrimitiveAccounting() const {
-        MGP5_C0_STUB("CapsMirror::PrefersCpuXfbPrimitiveAccounting");
+        return HasCap(MG_Pipe::kCapCpuXfbPrimitiveAccounting);
     }
 
     CapsMirror& CapsMirrorInstance() {
@@ -58,6 +170,4 @@ namespace MobileGL::MG_Remote::Client {
         return instance;
     }
 
-#undef MGP5_C0_STUB
-
 } // namespace MobileGL::MG_Remote::Client

MobileGL/MG_Remote/Client/CapsMirror.h

@@ -97,4 +97,28 @@ namespace MobileGL::MG_Remote::Client {
     // reach pipe or backend state from an exit handler.
     CapsMirror& CapsMirrorInstance();
 
+    // ---- c1's addition to c0's signature block -----------------------------------------
+    //
+    // WHY A HOOK AND NOT A READ. BackendObject::GetFormatCapabilities() is NON-VIRTUAL
+    // (BackendObject.h:594) and returns the base class's own m_formatCapabilities member, so a
+    // remote backend object cannot answer it lazily from the mirror - it has to PUSH the cache
+    // into that member, and the only moment it can know to is when a snapshot lands. A raw
+    // function pointer rather than std::function, for ID-8's reason: this can fire on paths
+    // that must not allocate. One hook, installed by BackendObject_Remote's constructor.
+    using CapsAdoptedHook = void (*)();
+    void SetCapsAdoptedHook(CapsAdoptedHook hook);
+
+    // R-8's NEGATIVE CONTROL NEEDS TO SEE THE WITHHOLDING, NOT INFER IT FROM AN ABSENCE.
+    // "the client emits nothing for a family the server does not consume" is, on its own,
+    // indistinguishable from "the client emits nothing because nothing called it" - and the
+    // second is how a gate goes green for the wrong reason. So the one funnel that answers the
+    // question counts its own refusals and names the family, once per family, in the log.
+    //
+    // Counted inside ServerConsumes(), which is R-8's only legal spelling, so a refusal that
+    // happened cannot fail to be counted and a count that moved cannot have come from anywhere
+    // else.
+    Uint64 ConsumerRefusals();
+    Uint64 LastRefusedSubsystem();
+    void ResetConsumerRefusalsForTest();
+
 } // namespace MobileGL::MG_Remote::Client

MobileGL/MG_Remote/Client/ClientSession.cpp

@@ -18,9 +18,12 @@
 #include "../Transport/InProcessTransport.h"
 
 #include <MGGitHash.h>
+#include <MG_Pipe/MGPipeCallbacks.h>
 #include <MG_Util/Debug/Log.h>
 
+#include <atomic>
 #include <cstdlib>
+#include <cstring>
 #include <vector>
 
 namespace MobileGL::MG_Remote::Client {
@@ -100,6 +103,29 @@ namespace MobileGL::MG_Remote::Client {
 #endif
         }
 
+        // ---- c1: the barrier's two flags ------------------------------------------------
+        //
+        // thread_local for the client's own "am I waiting", a shared atomic for "is the apply
+        // thread inside the applier" - see ClientSession::InBarrierWait's note.
+        thread_local Bool g_inBarrierWait = false;
+        std::atomic<Bool> g_applyThreadInsideApplier{false};
+
+        struct BarrierWaitScope {
+            BarrierWaitScope() { g_inBarrierWait = true; }
+            ~BarrierWaitScope() { g_inBarrierWait = false; }
+            BarrierWaitScope(const BarrierWaitScope&) = delete;
+            BarrierWaitScope& operator=(const BarrierWaitScope&) = delete;
+        };
+
+        // BOUNDED, AND THE BOUND IS GENEROUS RATHER THAN TIGHT. The barrier is a correctness
+        // device, not a watchdog: a slow readback on a software rasterizer is a legitimate
+        // second-scale wait, while a lost record never completes at all. 30 s separates the two
+        // without turning a loaded CI machine into a red lane, and the Fatal names the seq.
+        constexpr Uint32 kBarrierTimeoutMs = 30000;
+        // How many queued control frames one pump will drain. A backlog deeper than this is a
+        // finding, not a steady state.
+        constexpr Uint32 kMaxControlFramesPerPump = 16;
+
         const char* TransportModeName(MG_Config::TransportMode mode) {
             switch (mode) {
                 case MG_Config::TransportMode::Monolith: return "monolith";
@@ -111,6 +137,170 @@ namespace MobileGL::MG_Remote::Client {
             return "?";
         }
 
+        // ---- c1: the reverse channel's reading end ---------------------------------------
+        //
+        // R-12's three: OnBufferWriteback (#3), OnGpuWritten (#2), OnSurfaceChanged (#7).
+        // Drained BY THE GL THREAD BETWEEN VERBS, which under the barrier means immediately
+        // after appliedSeq reaches this record - the one moment at which the apply thread is
+        // known not to be inside the applier.
+        //
+        // THE BYTES LIVE IN THE RING ITSELF, so Drained() is called only after every payload
+        // pointer popped here has been consumed: retiring earlier is R-11's violation one level
+        // down (EventRing.h:168-171 says so in as many words).
+        Uint32 DrainEventRing(Transport::EventRingConsumer& events) {
+            if (!events.Valid()) return 0;
+            Uint32 delivered = 0;
+            Transport::RingRecordView view{};
+            Bool corrupt = false;
+            while (events.Pop(view, &corrupt)) {
+                if (corrupt) {
+                    MGLOG_F("MGPipe: Fatal{ProtocolCorruption, \"event-ring\"} - the reverse "
+                            "channel's record stream is corrupt");
+                    std::abort();
+                }
+                switch (view.kind) {
+                case Transport::kEventBufferWriteback: {
+                    if (view.payloadSize < sizeof(Transport::EventBufferWritebackHead)) break;
+                    const auto* head =
+                        static_cast<const Transport::EventBufferWritebackHead*>(view.payload);
+                    const void* bytes = static_cast<const Uint8*>(view.payload) + sizeof(*head);
+                    if (view.payloadSize - sizeof(*head) < head->Size) {
+                        MGLOG_F("MGPipe: Fatal{ProtocolCorruption, \"buffer-writeback\"} - the "
+                                "head declares %llu inline bytes and the record carries %llu",
+                                static_cast<unsigned long long>(head->Size),
+                                static_cast<unsigned long long>(view.payloadSize - sizeof(*head)));
+                        std::abort();
+                    }
+                    if (MG_Pipe::gMGPipeCallbacks.OnBufferWriteback != nullptr) {
+                        // The blobref names SEG_EVENT and the IN-SEGMENT offset of those inline
+                        // bytes - never a host address (R-2's rule B), which is the whole reason
+                        // EventRingConsumer exposes OffsetInSegment at all.
+                        MG_Pipe::MGPBlobRef blob{};
+                        blob.Seg = Wire::kSegEvent;
+                        blob.Offset = events.OffsetInSegment(bytes);
+                        blob.Size = head->Size;
+                        MG_Pipe::gMGPipeCallbacks.OnBufferWriteback(
+                            MG_Pipe::MGPipeHandle{head->Resource.Slot, head->Resource.Gen},
+                            head->Offset, blob);
+                        ++delivered;
+                    }
+                    break;
+                }
+                case Transport::kEventGpuWritten: {
+                    if (view.payloadSize < sizeof(Transport::EventGpuWrittenHead)) break;
+                    const auto* head =
+                        static_cast<const Transport::EventGpuWrittenHead*>(view.payload);
+                    const Uint64 tail = view.payloadSize - sizeof(*head);
+                    if (tail / sizeof(Transport::EventRange) < head->RangeCount) {
+                        MGLOG_F("MGPipe: Fatal{ProtocolCorruption, \"gpu-written\"} - RangeCount "
+                                "%u does not fit the record's %llu tail bytes",
+                                static_cast<unsigned>(head->RangeCount),
+                                static_cast<unsigned long long>(tail));
+                        std::abort();
+                    }
+                    if (MG_Pipe::gMGPipeCallbacks.OnGpuWritten != nullptr) {
+                        // EventRange and MGPRange are the same two Uint64s (EventRing.h:61-66
+                        // asserts it), so the tail is handed over as-is rather than copied into
+                        // a second array a later reader could get out of step with.
+                        const auto* ranges = reinterpret_cast<const MG_Pipe::MGPRange*>(
+                            static_cast<const Uint8*>(view.payload) + sizeof(*head));
+                        MG_Pipe::gMGPipeCallbacks.OnGpuWritten(
+                            MG_Pipe::MGPipeHandle{head->Resource.Slot, head->Resource.Gen},
+                            static_cast<Uint>(head->RangeCount), ranges);
+                        ++delivered;
+                    }
+                    break;
+                }
+                case Transport::kEventSurfaceChanged: {
+                    if (view.payloadSize < sizeof(Transport::EventSurfaceChangedHead)) break;
+                    if (MG_Pipe::gMGPipeCallbacks.OnSurfaceChanged != nullptr) {
+                        const auto* head =
+                            static_cast<const Transport::EventSurfaceChangedHead*>(view.payload);
+                        MG_Pipe::MGPSurfaceInfo info{};
+                        info.Width = head->Width;
+                        info.Height = head->Height;
+                        info.InternalFormat = head->InternalFormat;
+                        info.Samples = head->Samples;
+                        info.Layers = head->Layers;
+                        info.IsDefault = head->IsDefault;
+                        MG_Pipe::gMGPipeCallbacks.OnSurfaceChanged(&info);
+                        ++delivered;
+                    }
+                    break;
+                }
+                default:
+                    MGLOG_W("MG_Remote client: reverse-channel record kind %u is not consumed in "
+                            "P5 (R-12 takes three and a half of the ten callbacks)",
+                            static_cast<unsigned>(view.kind));
+                    break;
+                }
+            }
+            // AND ONLY NOW. Every payload pointer above has been consumed.
+            events.Drained();
+            return delivered;
+        }
+
+        // ---- c1: the CapsSnapshot -> CapsMirror adoption, in ONE place -------------------
+        //
+        // Every field of the snapshot has exactly one reader, and a field that fails to decode
+        // is a REFUSAL rather than a partial adopt: CompileEnv.cpp:123 copies the whole
+        // DynamicBackendParameters struct into the compile env, so a mirror that adopted three
+        // of four members would put the fourth's default into a shader fingerprint.
+        Bool AdoptCapsSnapshot(const ::MobileGL::Wire::CapsSnapshot* snapshot) {
+            if (snapshot == nullptr) return false;
+
+            MG_Pipe::MGPCaps caps{};
+            const auto* dynamicBytes = snapshot->dynamicParameters();
+            if (dynamicBytes == nullptr || dynamicBytes->size() != sizeof(caps.Dynamic)) {
+                // The Hello/Welcome fingerprint already asserted both peers agree on
+                // sizeof(DynamicBackendParameters), so a disagreement HERE is a corrupt frame
+                // rather than an ABI skew - which is why it is a refusal and not FatalAbiMismatch.
+                MGLOG_E("MG_Remote client: CapsSnapshot carries %llu dynamic bytes, this build's "
+                        "struct is %llu - the snapshot is refused whole",
+                        static_cast<unsigned long long>(dynamicBytes == nullptr ? 0
+                                                                                : dynamicBytes->size()),
+                        static_cast<unsigned long long>(sizeof(caps.Dynamic)));
+                return false;
+            }
+            std::memcpy(&caps.Dynamic, dynamicBytes->data(), sizeof(caps.Dynamic));
+            caps.CallMask = snapshot->callMask();
+
+            RendererInfo renderer{};
+            const auto* rendererBytes = snapshot->rendererInfo();
+            if (rendererBytes == nullptr ||
+                !DecodeRendererInfo(rendererBytes->data(), rendererBytes->size(), renderer)) {
+                MGLOG_E("MG_Remote client: CapsSnapshot's rendererInfo blob did not decode");
+                return false;
+            }
+
+            MG_Backend::FormatCapabilityCache formats{};
+            const auto* formatBytes = snapshot->formatCaps();
+            if (formatBytes == nullptr ||
+                !DecodeFormatCapabilities(formatBytes->data(), formatBytes->size(), formats)) {
+                MGLOG_E("MG_Remote client: CapsSnapshot's formatCaps blob did not decode");
+                return false;
+            }
+
+            const String apiVersion =
+                snapshot->apiVersion() == nullptr ? String{} : String{snapshot->apiVersion()->c_str()};
+
+            // THE SERVER'S BACKEND TYPE, NEVER A NEW "Remote" ENUMERATOR and never guessed from
+            // the renderer string: GL_Framebuffer.cpp:47, GL_Texture.cpp:6536 and
+            // CompileEnv.cpp:122 SWITCH on it, and a value they do not know takes a wrong arm
+            // rather than failing.
+            const Uint32 rawBackend = snapshot->backendType();
+            if (rawBackend >= static_cast<Uint32>(BackendType::BackendTypeCount)) {
+                MGLOG_E("MG_Remote client: CapsSnapshot names backend type %u, which this build "
+                        "has no enumerator for - the snapshot is refused rather than folded onto "
+                        "Unknown, which three frontend switches would silently mis-branch on",
+                        static_cast<unsigned>(rawBackend));
+                return false;
+            }
+            CapsMirrorInstance().Adopt(caps, formats, renderer, apiVersion,
+                                       static_cast<BackendType>(rawBackend));
+            return true;
+        }
+
     } // namespace
 
     // Null, not a Fatal: MG_Backend::Init() asks whether a session exists before it decides to
@@ -308,24 +498,17 @@ namespace MobileGL::MG_Remote::Client {
         m_encoder = Wire::PipeWireEncoder(control, &m_cmd, nullptr, &m_segments);
 
         // ---- 7. the first CapsSnapshot, if the server had a backend to publish one from.
-        if (m_transport->PeekFrameSize() != 0) {
+        // ONE DRAIN, ONE ADOPTER (c1): PumpControlPlane below is the only thing in the client
-            std::vector<Uint8> frame;
+        // that turns a CapsSnapshot into a CapsMirror generation, so R-12's "a second arrival
-            if (ReceiveEnvelope(*m_transport, frame, 0) == MOBILEGL_OK) {
+        // IS the invalidation" lives in exactly one place. s1's step here used to stop at
-                const ::MobileGL::Wire::CtrlEnvelope* envelope = ParseEnvelope(frame);
+        // "the snapshot arrived and is verifiable"; it now goes all the way, through the same
-                if (envelope != nullptr &&
+        // function every later arrival goes through.
-                    envelope->msg_type() == ::MobileGL::Wire::CtrlMsg::CapsSnapshot) {
+        if (PumpControlPlane() == 0) {
-                    // The mirror's Adopt and the two blob DECODERS are c1's and w1's. s1 stops
+            MGLOG_W("MG_Remote client: the handshake carried no CapsSnapshot - the caps mirror is "
-                    // at "the snapshot arrived and is verifiable": adopting it here would put
+                    "a PLACEHOLDER until one arrives. Every caps read until then answers a "
-                    // the caps mirror's invalidation rule (R-12: a second arrival IS the
+                    "default and says so");
-                    // invalidation) in two places.
-                    MGLOG_I("MG_Remote client: first CapsSnapshot received (%llu bytes); adopting "
-                            "it is package c1's CapsMirror::Adopt over package w1's decoders",
-                            static_cast<unsigned long long>(frame.size()));
-                }
-            }
         }
 
-        m_started = true;
         g_active = this;
         LogMemory("handshake");
 
@@ -425,18 +608,179 @@ namespace MobileGL::MG_Remote::Client {
     // cost zero extra round trips - and the client may not re-derive any of those four answers
     // locally. s1 supplies the four primitives it composes from: Encoder(), Producer(),
     // WaitForApplied() and ReadReply().
-    Uint64 ClientSession::EmitAndWait(MG_Pipe::MGPWireOp, const void*, Uint64, const void*, Uint64,
+    //
-                                      void*, Uint64, Int32*) {
+    // THE ORDER IS ENCODE -> PUBLISH+NOTIFY -> WAIT -> READ REPLY, and it is not negotiable.
-        MGP5_C0_STUB("ClientSession::EmitAndWait");
+    // Splitting the wait from the read is how a package ends up answering an acceptance
+    // question locally, which is the c0f/c0g defect P4a paid two contract corrections for; and
+    // "always accept" is ID-39's 66 lost DirectVulkan uploads with a wire in between.
+    Uint64 ClientSession::EmitAndWait(MG_Pipe::MGPWireOp op, const void* payload, Uint64 payloadBytes,
+                                      const void* varTail, Uint64 varTailBytes, void* replyOut,
+                                      Uint64 replyBytes, Int32* statusOut) {
+        if (statusOut != nullptr) *statusOut = Wire::ReplySink::kStatusError;
+        if (!m_started) {
+            MGLOG_F("MGPipe: Fatal{NoClientSession, \"%s\"} - EmitAndWait on a session that has "
+                    "not started. There is no fall-through: a record that could not be emitted "
+                    "is a verb that did not happen",
+                    Wire::WireOpName(op));
+            std::abort();
+        }
+
+        // R-1's INVARIANT, AS A RUNTIME CHECK RATHER THAN A SENTENCE. While the barrier holds,
+        // at most one of {GL thread, apply thread} is runnable - and that is the whole reason a
+        // single process-wide gPipeInputs is legal (table 3). The client is about to publish a
+        // record whose fields the applier will read out of gPipeInputs, so the apply thread
+        // being inside the applier right now means the invariant has already been broken and
+        // the next record would be read against a half-written residual fill.
+        if (ApplyThreadIsInsideApplier()) {
+            MGLOG_F("MGPipe: Fatal{BarrierViolation, \"%s\"} - the apply thread is inside the "
+                    "applier while the GL thread is emitting. R-1 makes at most one of them "
+                    "runnable, which is what keeps one process-wide gPipeInputs legal",
+                    Wire::WireOpName(op));
+            std::abort();
+        }
+
+        const Uint64 seq =
+            m_encoder.EncodeRecord(op, payload, payloadBytes, varTail, varTailBytes);
+        if (seq == Wire::kInvalidSeq) {
+            // The ring refused it. NOT a silent drop and not a retry loop: R-10 says P5 does no
+            // chunking and must prove it needs none, so a refusal is the proof failing.
+            MGLOG_F("MGPipe: Fatal{RingOverrun, \"%s\"} - the command ring refused a %llu-byte "
+                    "record. P5 does not chunk (R-10); this is the proof obligation failing, not "
+                    "a back-pressure case",
+                    Wire::WireOpName(op),
+                    static_cast<unsigned long long>(payloadBytes + varTailBytes));
+            std::abort();
+        }
+
+        // Publish the head, record submittedSeq, THEN ring - in that order, which is
+        // SessionProducer's one job and RingTest.cpp:446's pin. Notify-then-publish loses the
+        // wakeup.
+        m_producer.PublishAndNotify(seq);
+
+        // Does this row own a reply slot? kMGPipeCallFlags IS THE SINGLE SOURCE OF TRUTH
+        // (R-16 / ID-31) - fourteen rows now, because the four Bool acceptance entry points
+        // gained the flag. Asking the catalogue rather than the caller is what stops a caller
+        // that forgot to pass a buffer from silently turning an answer into a guess.
+        const Bool ownsReplySlot =
+            (MG_Pipe::MGPipeCallFlagsFor(op) & static_cast<Uint32>(MG_Pipe::kReplySlot)) != 0;
+
+        if (!m_barrierArmed && !ownsReplySlot) {
+            // R-1's NEGATIVE CONTROL ARM, and the only thing it turns off is the barrier. A
+            // reply-slot row still waits: the answer is not derivable here and R-5 forbids
+            // inventing one, so MOBILEGL_IPC_VERB_BARRIER=0 makes the queue free-running, not
+            // the client clairvoyant.
+            return seq;
+        }
+
+        const BarrierWaitScope waiting;
+        const Transport::SessionWait wait = m_producer.WaitForApplied(seq, kBarrierTimeoutMs);
+        if (wait == Transport::SessionWait::ShutDown) {
+            // The doorbell died: the server went away. The only thing that returns from a
+            // kWaitForever park, and therefore the only way a client blocked in the barrier
+            // survives a server that is gone. Not a Fatal - teardown legitimately reaches here.
+            MGLOG_E("MG_Remote client: the barrier for %s (seq %llu) woke on a dead doorbell; the "
+                    "server is gone and this verb did not happen",
+                    Wire::WireOpName(op), static_cast<unsigned long long>(seq));
+            return seq;
+        }
+        if (wait != Transport::SessionWait::Reached) {
+            MGLOG_F("MGPipe: Fatal{BarrierTimeout, \"%s\"} - appliedSeq did not reach %llu within "
+                    "%u ms. A bounded wait is deliberate: a wedged CI job and a lost record look "
+                    "identical from outside, and only one of them is a bug worth finding",
+                    Wire::WireOpName(op), static_cast<unsigned long long>(seq), kBarrierTimeoutMs);
+            std::abort();
+        }
+
+        // THE REVERSE CHANNEL IS DRAINED HERE, and here is the only place it can be: under the
+        // barrier this is the one instant at which the apply thread is known not to be inside
+        // the applier, and MGPipeClientOnGpuWritten / OnBufferWriteback write frontend objects.
+        // It is what gives AwaitBufferWriteback something to have waited FOR: b1's third state
+        // clears when the writeback lands, and the writeback lands on this ring.
+        DrainEventRing(m_events);
+
+        if (!ownsReplySlot) return seq;
+
+        // THE SAME WAIT, NOT A SECOND ONE. appliedSeq >= seq already means the server wrote
+        // this record's answer, because it writes the slot before it advances the watermark.
+        Uint64 replySize = 0;
+        Int32 status = Wire::ReplySink::kStatusError;
+        if (!ReadReply(seq, replyOut, replyBytes, &status, &replySize)) {
+            MGLOG_F("MGPipe: Fatal{ReplyMissing, \"%s\"} - seq %llu carries kReplySlot and the "
+                    "server applied it, but its slot does not stamp that seq. The stamp is what "
+                    "makes a wrong-slot read detectable rather than plausible (R-3)",
+                    Wire::WireOpName(op), static_cast<unsigned long long>(seq));
+            std::abort();
+        }
+        if (statusOut != nullptr) *statusOut = status;
+        if (status == Wire::ReplySink::kStatusError) {
+            MGLOG_E("MG_Remote client: %s (seq %llu) answered ERROR", Wire::WireOpName(op),
+                    static_cast<unsigned long long>(seq));
+        }
+        // DECLINED is NOT an error and is deliberately not logged as one: it is how
+        // MapPersistent says nullptr (R-6) and how the four Bool acceptance rows say false
+        // (R-5). A client that treated it as a failure would re-create ID-39 from the other
+        // side.
+        if (replyOut != nullptr && replySize > replyBytes) {
+            MGLOG_F("MGPipe: Fatal{ReplyTooLarge, \"%s\"} - the answer is %llu bytes and the "
+                    "caller offered %llu. P5 does not chunk a reply",
+                    Wire::WireOpName(op), static_cast<unsigned long long>(replySize),
+                    static_cast<unsigned long long>(replyBytes));
+            std::abort();
+        }
+        return seq;
     }
 
     Bool ClientSession::BarrierArmed() const { return m_barrierArmed; }
 
-    // False, not a Fatal, for both: these are the R-1 mutual-exclusion assertion's two probes,
+    // R-1's mutual-exclusion invariant, as two probes that answer honestly.
-    // and an assertion helper that aborts when asked is worse than useless. Package c1 gives
+    //
-    // them real answers when it lands the barrier.
+    // THE CLIENT'S FLAG IS THREAD-LOCAL AND THE SERVER'S IS NOT, and the asymmetry is the
-    Bool ClientSession::InBarrierWait() { return false; }
+    // point: "am I inside a barrier wait" is a question about the calling thread, while "is the
-    Bool ClientSession::ApplyThreadIsInsideApplier() { return false; }
+    // apply thread inside the applier" is a question the GL thread asks about a DIFFERENT
+    // thread - so the second has to be a shared atomic and the first must not be, or a second
+    // GL thread would see the first one's wait as its own.
+    Bool ClientSession::InBarrierWait() { return g_inBarrierWait; }
+    Bool ClientSession::ApplyThreadIsInsideApplier() {
+        return g_applyThreadInsideApplier.load(std::memory_order_acquire);
+    }
+    void ClientSession::NoteApplyThreadEnteredApplier() {
+        g_applyThreadInsideApplier.store(true, std::memory_order_release);
+    }
+    void ClientSession::NoteApplyThreadLeftApplier() {
+        g_applyThreadInsideApplier.store(false, std::memory_order_release);
+    }
+
+    Uint32 ClientSession::PumpControlPlane() {
+        // NOT gated on m_started. The first snapshot arrives DURING Start(), before this session
+        // is started or active - and s1's half-built teardown path depends on m_started staying
+        // false until step 8 has succeeded, so the flag cannot be moved earlier to suit this.
+        if (m_transport == nullptr) return 0;
+        Uint32 adopted = 0;
+        // Bounded rather than `while (true)`: a server that queued frames faster than this
+        // drains them would otherwise hold the GL thread here for ever, and a frame backlog
+        // deeper than this is a finding rather than a steady state.
+        for (Uint32 guard = 0; guard < kMaxControlFramesPerPump; ++guard) {
+            if (m_transport->PeekFrameSize() == 0) break;
+            std::vector<Uint8> frame;
+            if (ReceiveEnvelope(*m_transport, frame, 0) != MOBILEGL_OK) break;
+            const ::MobileGL::Wire::CtrlEnvelope* envelope = ParseEnvelope(frame);
+            if (envelope == nullptr) {
+                MGLOG_E("MG_Remote client: an unverifiable control frame (%llu bytes) was dropped",
+                        static_cast<unsigned long long>(frame.size()));
+                continue;
+            }
+            if (envelope->msg_type() != ::MobileGL::Wire::CtrlMsg::CapsSnapshot) {
+                // SurfaceOp / SurfaceReply / ResyncRequest / AuxRequest / LogLine are P6's and
+                // P7's. Named rather than ignored, so a phase that starts sending one does not
+                // discover this loop swallowing it.
+                MGLOG_W("MG_Remote client: control message %d is not consumed in P5",
+                        static_cast<int>(envelope->msg_type()));
+                continue;
+            }
+            if (AdoptCapsSnapshot(envelope->msg_as_CapsSnapshot())) ++adopted;
+        }
+        return adopted;
+    }
 
     Transport::SessionProducer& ClientSession::Producer() { return m_producer; }
 

MobileGL/MG_Remote/Client/ClientSession.h

@@ -100,6 +100,36 @@ namespace MobileGL::MG_Remote::Client {
         static Bool InBarrierWait();
         static Bool ApplyThreadIsInsideApplier();
 
+        // ---- c1's additions ---------------------------------------------------------------
+
+        // The apply thread's half of R-1's invariant. v1's apply loop brackets its
+        // DecodeAndApply with these; the client checks the flag before it publishes, so
+        // "at most one of {GL thread, apply thread} is runnable" is a runtime assertion rather
+        // than a sentence in a brief. A raw pair rather than an RAII type in this header
+        // because the server side owns its own scoping and must not have to include a client
+        // header to get it - ScopedApplierEntry below is the convenience, not the contract.
+        static void NoteApplyThreadEnteredApplier();
+        static void NoteApplyThreadLeftApplier();
+        struct ScopedApplierEntry {
+            ScopedApplierEntry() { NoteApplyThreadEnteredApplier(); }
+            ~ScopedApplierEntry() { NoteApplyThreadLeftApplier(); }
+            ScopedApplierEntry(const ScopedApplierEntry&) = delete;
+            ScopedApplierEntry& operator=(const ScopedApplierEntry&) = delete;
+        };
+
+        // R-12's INVALIDATION EDGE. Drains whatever the server has queued on the control plane
+        // and adopts every CapsSnapshot in it - and a SECOND snapshot IS the invalidation,
+        // which is why there is no Invalidate(). Non-blocking: it peeks and returns.
+        //
+        // Called at the handshake, from BackendObject_Remote's Initialize/InitCapabilities, and
+        // once per Present. Present is the boundary every one of P5's three targets crosses,
+        // and a caps re-run can only follow a surface event, so once a frame is both sufficient
+        // and the cheapest place that is.
+        //
+        // Returns how many snapshots it adopted, so a case can assert the edge fired rather
+        // than assert that a number downstream of it happened to change.
+        Uint32 PumpControlPlane();
+
         // ---- s1's additions: the four primitives c1's EmitAndWait composes ---------------
         //
         // s1 owns construction and lifetime; c1 owns the barrier POLICY. So the plumbing is

MobileGL/MG_Remote/Client/EmitTables.cpp

@@ -6,13 +6,36 @@
 // SPDX-License-Identifier: LGPL-3.0-only
 // End of Source File Header
 
-// P5 c0 stubs for package c1.
+// P5 package c1: the 71-slot emit table.
+//
+// THE PARTITION IS CONTRACT-P5.md §7's AND IS NOT RE-DERIVED HERE (R-15, ID-12):
+//   class A  2 slots  answered locally from the caps mirror, never emitted, never Fatal
+//   class B  5 slots  emitted
+//   class C 64 slots  Fatal{UnmigratedVerb, "<slot>"}
+// The three counts are static_asserted to sum to kRemoteEmitSlotCount below, so a slot that
+// changes class without changing the arithmetic is a build break rather than a behaviour
+// change nobody reviewed.
+//
+// THE PRE-VERB HOOKS RUN BEFORE THE RECORD, NEVER AFTER (b1, ID-18). PushPersistentMapsBeforeVerb
+// publishes the bytes an application wrote through a coherent map with no API call at all, and
+// MarkGpuWritesForDraw builds the conservative GPU-write set the client now owns. Both describe
+// the work the record is ABOUT TO START, so a hook deferred past its own record is the C-1
+// regression re-committed at the transport layer.
 
 #include "EmitTables.h"
 
+#include "ClientSession.h"
+#include "GpuWritePending.h"
+#include "PersistentMapTracker.h"
+
+#include <MG_Util/Converters/GLToMG/TextureEnumConverter.h>
 #include <MG_Util/Debug/Log.h>
+#include <MG_Util/Metrics/TextureMetrics.h>
+
+#include <MG_State/GLState/Core.h>
 
 #include <cstdlib>
+#include <cstring>
 
 namespace MobileGL::MG_Remote::Client {
 
@@ -36,12 +59,478 @@ namespace MobileGL::MG_Remote::Client {
         std::abort();
     }
 
+    namespace {
+
+        Bool g_dropClearEmission = false;
+        Uint64 g_droppedClearEmissions = 0;
+
+        // E2's control has to be armable from OUTSIDE the process that runs the replay, because
+        // the statement it makes is about a trace lane and not about a unit case: "drop one
+        // Clear emission and OpenRA's SSIM falls below 0.99". A recompile would make the control
+        // arm against source text, which is ID-22(a)'s defect.
+        //
+        // READ WITH getenv RATHER THAN THROUGH MG_Config, DELIBERATELY AND TEMPORARILY. Config.h
+        // is c0's and a new MOBILEGL_IPC_* knob goes through the integrator; this is a
+        // NEGATIVE-CONTROL switch no operator may ever set, and it announces itself at warning
+        // level every time it arms so it cannot be on by accident. Flagged for adoption into
+        // IpcTable if the integrator wants it there.
+        Bool ReadDropClearFromEnvironment() {
+            const char* value = std::getenv("MOBILEGL_IPC_E2_DROP_CLEAR");
+            const Bool armed = value != nullptr && value[0] == '1' && value[1] == '\0';
+            if (armed) {
+                MGLOG_W("MG_Remote client: MOBILEGL_IPC_E2_DROP_CLEAR=1 - E2's NEGATIVE CONTROL is "
+                        "armed and every glClear will be DROPPED on the wire. This arm is expected "
+                        "to fail its SSIM threshold; a lane that stays green with it set is not "
+                        "going through the wire at all");
+            }
+            return armed;
+        }
+
+        // ---- the session, demanded rather than assumed --------------------------------
+        //
+        // Every class-B slot needs one. A null session here is NOT the monolith answer - the
+        // monolith answer is that this table was never installed at all, because
+        // MG_Backend::Init() only reaches BackendObject_Remote when the transport resolved. So
+        // a null one is a Fatal by name and not a fall-through to the driver: a pass-through
+        // slot is the "split lane ran monolith and went green" shape that every gate in this
+        // phase exists to prevent (R-4).
+        ClientSession& RequireSession(const char* slot) {
+            ClientSession* session = ClientSession::Active();
+            if (session == nullptr) {
+                MGLOG_F("MGPipe: Fatal{NoClientSession, \"%s\"} - the remote emit table is "
+                        "installed but no ClientSession is active. A slot may not fall through "
+                        "to a driver this role does not have",
+                        slot);
+                std::abort();
+            }
+            return *session;
+        }
+
+        // The two hooks b1 wrote and deliberately left with no caller, because the call site is
+        // this file's. ORDER: the push first (it produces resource_subdata records that must
+        // precede the verb on SEG_CMD), then the mark walk, then the verb record.
+        void BeforeDrawVerb() {
+            PushPersistentMapsBeforeVerb();
+            MarkGpuWritesForDraw();
+        }
+
+        // A verb that reads buffers but starts no shader: clear, blit, readback, present. The
+        // push still has to run - a coherent map is read by the GPU on any of them - but there
+        // is no shader that could write one, so no mark walk.
+        void BeforeReadOnlyVerb() { PushPersistentMapsBeforeVerb(); }
+
+        // =============================================================================
+        // CLASS B - the five slots the verb census measured (CONTRACT-P5.md §7)
+        // =============================================================================
+
+        void EmitClear(GLbitfield mask) {
+            ClientSession& session = RequireSession("Clear");
+            BeforeReadOnlyVerb();
+
+            if (g_dropClearEmission) {
+                // E2's negative control. Everything above still ran, so the only difference
+                // between this arm and the live one is the record - which is exactly the
+                // statement "the picture comes from the wire" that E2 exists to prove.
+                ++g_droppedClearEmissions;
+                return;
+            }
+
+            MG_Pipe::MGPClear record{};
+            // The DRAW framebuffer is whatever the server's own SyncRenderState resolves from
+            // gPipeInputs, which the client's MGP_FILL(Clear) at GL_Drawing.cpp:534 has just
+            // written and the verb barrier keeps still (R-1). Naming a handle here would be a
+            // SECOND statement of the binding, and the second one is the one that goes stale.
+            record.Fbo = MG_Pipe::kMGPipeNullHandle;
+            record.Kind = kRemoteClearWhole;
+            record.DrawBufferIndex = -1;
+            record.BufferMask = static_cast<Uint32>(mask);
+            record.ValueClass = 0;
+            session.EmitAndWait(MG_Pipe::MGPWireOp::Clear, &record, sizeof(record), nullptr, 0,
+                                nullptr, 0, nullptr);
+        }
+
+        void EmitDrawArrays(GLenum mode, GLint first, GLsizei count) {
+            ClientSession& session = RequireSession("DrawArrays");
+            BeforeDrawVerb();
+
+            MG_Pipe::MGPDrawInfo info{};
+            info.Mode = static_cast<Uint32>(mode);
+            info.IndexSize = 0; // arrays
+            info.Flags = 0;     // NO kDrawHasUserIndices: the reduced path draws from a VBO
+            info.InstanceCount = 1;
+            info.StartInstance = 0;
+            info.RestartIndex = 0;
+            info.DrawIdOffset = 0;
+            info.IndexResource = MG_Pipe::kMGPipeNullHandle;
+            info.MinIndex = ~0u; // "unknown", MGPipeTypes.h:1330
+            info.MaxIndex = ~0u;
+            info.XfbCpuCapturedVertices = 0;
+            info.NumDraws = 1;
+
+            const MG_Pipe::MGPDrawRange range{static_cast<Uint32>(first), static_cast<Uint32>(count), 0};
+            // One tail of exactly NumDraws entries. w1's encoder recomputes that from the
+            // payload and Fatals on a disagreement, on THIS side - so a NumDraws that drifted
+            // from the tail is a producer-side abort rather than a corrupt stream a peer has to
+            // diagnose.
+            session.EmitAndWait(MG_Pipe::MGPWireOp::DrawVbo, &info, sizeof(info), &range,
+                                sizeof(range), nullptr, 0, nullptr);
+        }
+
+        void EmitBlitFramebuffer(GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1, GLint dstX0,
+                                 GLint dstY0, GLint dstX1, GLint dstY1, GLbitfield mask,
+                                 GLenum filter) {
+            ClientSession& session = RequireSession("BlitFramebuffer");
+            BeforeReadOnlyVerb();
+
+            MG_Pipe::MGPBlit record{};
+            // Same reasoning as Clear's Fbo: the read and draw bindings are gPipeInputs', set
+            // by MGP_FILL(BlitFramebuffer) at GL_Framebuffer.cpp:660 and held still by the
+            // barrier. glBlitNamedFramebuffer, which DOES name two framebuffers, is class C.
+            record.ReadFbo = MG_Pipe::kMGPipeNullHandle;
+            record.DrawFbo = MG_Pipe::kMGPipeNullHandle;
+            record.SrcX0 = srcX0;
+            record.SrcY0 = srcY0;
+            record.SrcX1 = srcX1;
+            record.SrcY1 = srcY1;
+            record.DstX0 = dstX0;
+            record.DstY0 = dstY0;
+            record.DstX1 = dstX1;
+            record.DstY1 = dstY1;
+            record.Mask = static_cast<Uint32>(mask);
+            record.Filter = static_cast<Uint32>(filter);
+            session.EmitAndWait(MG_Pipe::MGPWireOp::Blit, &record, sizeof(record), nullptr, 0,
+                                nullptr, 0, nullptr);
+        }
+
+        // How many bytes glReadPixels will pack for this rectangle, from the PACK half of the
+        // pixel-store state. The client has to declare it - MGPReadbackInfo::DstSize is what
+        // sizes the reply and what the client checks against MaxReplyBytes() BEFORE it emits,
+        // because a reply bigger than a slot is Fatal rather than chunked (s1's ReplySlot.h).
+        //
+        // GL 4.6 8.4.4's arithmetic, and nothing cleverer: a row is rounded up to Alignment,
+        // the LAST row is not padded, and SkipRows/SkipPixels/SkipImages shift the destination
+        // rather than growing it (the application owns those bytes and we never write them).
+        Uint64 PackedReadbackBytes(GLsizei width, GLsizei height, GLenum format, GLenum type) {
+            if (width <= 0 || height <= 0) return 0;
+            const TextureInputFormat inputFormat =
+                MG_Util::ConvertGLEnumToTextureInputFormat(format);
+            const TexturePixelDataType dataType = MG_Util::ConvertGLEnumToTexturePixelDataType(type);
+            const SizeT bytesPerPixel = MG_Util::GetInputBytesPerPixel(inputFormat, dataType);
+            if (bytesPerPixel == 0) {
+                // NOT a guess and not a zero-length reply. A format this build cannot size is a
+                // readback whose answer would be silently truncated, which is the one failure a
+                // picture comparison cannot see.
+                MGLOG_F("MGPipe: Fatal{UnsizedReadback, \"read_pixels\"} format=0x%04x type=0x%04x "
+                        "- the client must declare MGPReadbackInfo::DstSize and cannot size this "
+                        "pair; P5's reduced path reads RGBA/UNSIGNED_BYTE",
+                        static_cast<unsigned>(format), static_cast<unsigned>(type));
+                std::abort();
+            }
+
+            PixelStoreParameters pack{};
+            if (MG_State::pGLContext != nullptr) {
+                pack = MG_State::pGLContext->GetPixelStoreParameters(/*isUnpack=*/false);
+            }
+            const Uint64 rowPixels =
+                pack.RowLength > 0 ? static_cast<Uint64>(pack.RowLength) : static_cast<Uint64>(width);
+            const Uint64 alignment = pack.Alignment > 0 ? static_cast<Uint64>(pack.Alignment) : 1ull;
+            const Uint64 rowBytes = rowPixels * static_cast<Uint64>(bytesPerPixel);
+            const Uint64 paddedRow = ((rowBytes + alignment - 1) / alignment) * alignment;
+            const Uint64 lastRow = static_cast<Uint64>(width) * static_cast<Uint64>(bytesPerPixel);
+            return paddedRow * (static_cast<Uint64>(height) - 1) + lastRow;
+        }
+
+        void EmitReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format,
+                            GLenum type, void* pixels) {
+            ClientSession& session = RequireSession("ReadPixels");
+            BeforeReadOnlyVerb();
+
+            // THE PBO HALF IS b1's DESIGN AND b1 ALREADY WIRED ITS MARK, at
+            // GL_Framebuffer.cpp:3109 - immediately after this table call returns, inside
+            // ReadPixels_Backend itself. So this emitter deliberately does NOT call
+            // MarkReadPixelsPackBuffer(): a second call there would be the "wire it twice"
+            // shape, and the per-row counter b1's unit cases assert on would then count one
+            // read as two.
+            const Uint64 bytes = PackedReadbackBytes(width, height, format, type);
+
+            MG_Pipe::MGPReadbackInfo info{};
+            info.Res = MG_Pipe::kMGPipeNullHandle; // "the bound read surface answers"
+            info.Box = MG_Pipe::MGPBox{x, y, 0, static_cast<Uint32>(width),
+                                       static_cast<Uint32>(height), 1};
+            info.Format = static_cast<Uint32>(format);
+            info.Type = static_cast<Uint32>(type);
+            info.Target = 0;
+            info.Level = 0;
+            info.DstOffset = 0;
+            info.DstSize = bytes;
+
+            // CHECKED BEFORE THE EMISSION, not after the answer. A reply bigger than a slot is
+            // Fatal on the server, and a Fatal there is a dead apply thread with a client
+            // parked in the barrier for ever; here it is one line naming the number.
+            const Uint64 capacity = session.MaxReplyBytes();
+            if (bytes > capacity) {
+                MGLOG_F("MGPipe: Fatal{ReplyTooLarge, \"read_pixels\"} %llu bytes into a %llu-byte "
+                        "reply slot - P5 does not chunk a readback (R-10); raise the reply pool's "
+                        "slot size or shrink the read",
+                        static_cast<unsigned long long>(bytes),
+                        static_cast<unsigned long long>(capacity));
+                std::abort();
+            }
+
+            Int32 status = 0;
+            // The pixels land straight in the application's buffer: the barrier's wait IS the
+            // reply's wait (R-3), so this costs no round trip beyond the one the barrier was
+            // already paying.
+            session.EmitAndWait(MG_Pipe::MGPWireOp::ReadPixels, &info, sizeof(info), nullptr, 0,
+                                pixels, bytes, &status);
+        }
+
+        void EmitPresent() {
+            ClientSession& session = RequireSession("Present");
+            BeforeReadOnlyVerb();
+
+            MG_Pipe::MGPPresent record{};
+            // FrameSerial 0 = "the server stamps its own". P5 has no client-side present credit
+            // (MOBILEGL_IPC_PRESENT_CREDIT is P6's), so a client-minted serial would be a second
+            // id space with no consumer.
+            record.FrameSerial = 0;
+            session.EmitAndWait(MG_Pipe::MGPWireOp::Present, &record, sizeof(record), nullptr, 0,
+                                nullptr, 0, nullptr);
+
+            // R-12's invalidation edge, drained at the one boundary every target crosses. A
+            // second CapsSnapshot IS the invalidation; nothing else on the client can see that
+            // the server re-ran InitCapabilities, because GLContext::GetCompileEnv()'s memo is
+            // keyed on pActiveBackendObject.get() (Core.cpp:34) and that pointer never changes
+            // under split.
+            session.PumpControlPlane();
+        }
+
+        // =============================================================================
+        // CLASS A - answered locally from the caps mirror (R-15). NO RECORD, EVER.
+        // =============================================================================
+
+        void AnswerGetIntegeri_v(GLenum target, GLuint index, GLint* data) {
+            if (data == nullptr) return;
+            const MG_Backend::DynamicBackendParameters& dynamic = CapsMirrorInstance().Dynamic();
+            // The ONLY two indexed pnames the device owns; every other indexed pname names
+            // frontend state and is answered in GL_Getter::GetIntegeri_v before any table is
+            // consulted (BackendObject.h:196-205). The existing gate is
+            // AdvertisedLimitsScenario.ComputeWorkGroupLimitsAreTheCapsBlocksAnswer, which pins
+            // that this answer and the caps copy are ONE number.
+            switch (target) {
+            case GL_MAX_COMPUTE_WORK_GROUP_COUNT:
+                if (index < 3) *data = static_cast<GLint>(dynamic.MaxComputeWorkGroupCount[index]);
+                return;
+            case GL_MAX_COMPUTE_WORK_GROUP_SIZE:
+                if (index < 3) *data = static_cast<GLint>(dynamic.MaxComputeWorkGroupSize[index]);
+                return;
+            default:
+                // Not a Fatal: the slot's own contract is "whatever pname the frontend has no
+                // case for at all", and the monolith backends answer such a pname by leaving
+                // the driver's own default in place. Answering a wrong number would be worse
+                // than answering none.
+                MGLOG_W_ONCE("MG_Remote client: GetIntegeri_v(0x%04x, %u) is not one of the two "
+                             "device-owned indexed pnames and has no caps-mirror answer",
+                             static_cast<unsigned>(target), static_cast<unsigned>(index));
+                return;
+            }
+        }
+
+        Bool AnswerIsTimerQuerySupported() {
+            // A capability predicate, not a call. Today a null slot means COUNTER_BITS == 0
+            // (GL_Query.cpp:792) - which is precisely the null check R-4 forbids, so it moves
+            // here, to the bit the server published.
+            return CapsMirrorInstance().HasCap(MG_Pipe::kCapTimerQuery);
+        }
+
+        // =============================================================================
+        // CLASS C - Fatal{UnmigratedVerb}. 64 slots: 63 in GLFunctionsTable + SetSwapInterval.
+        // =============================================================================
+        //
+        // The list is an X-macro so the DEFINITION and the ASSIGNMENT cannot drift apart, and
+        // so the count is arithmetic rather than a comment. Two of them carry a pre-verb hook
+        // before the Fatal - see the note on DispatchCompute.
+
+#define MGR_UNMIGRATED_GL_SLOTS(X)                                                                 \
+    X(DrawElements, void, (GLenum, GLsizei, GLenum, const void*))                                  \
+    X(DrawElementsBaseVertex, void, (GLenum, GLsizei, GLenum, const void*, GLint))                 \
+    X(MultiDrawArrays, void, (GLenum, const GLint*, const GLsizei*, GLsizei))                      \
+    X(MultiDrawElements, void, (GLenum, const GLsizei*, GLenum, const GLvoid* const*, GLsizei))    \
+    X(MultiDrawElementsBaseVertex, void,                                                           \
+      (GLenum, const GLsizei*, GLenum, const GLvoid* const*, GLsizei, const GLint*))               \
+    X(MultiDrawElementsIndirect, void, (GLenum, GLenum, const void*, GLsizei, GLsizei))            \
+    X(MultiDrawArraysIndirect, void, (GLenum, const void*, GLsizei, GLsizei))                      \
+    X(MultiDrawElementsIndirectCount, void, (GLenum, GLenum, const void*, GLintptr, GLsizei, GLsizei)) \
+    X(MultiDrawArraysIndirectCount, void, (GLenum, const void*, GLintptr, GLsizei, GLsizei))       \
+    X(DrawRangeElementsBaseVertex, void,                                                           \
+      (GLenum, GLuint, GLuint, GLsizei, GLenum, const void*, GLint))                               \
+    X(DrawRangeElements, void, (GLenum, GLuint, GLuint, GLsizei, GLenum, const void*))             \
+    X(DrawElementsInstancedBaseVertexBaseInstance, void,                                           \
+      (GLenum, GLsizei, GLenum, const void*, GLsizei, GLint, GLuint))                              \
+    X(DrawElementsInstancedBaseVertex, void, (GLenum, GLsizei, GLenum, const void*, GLsizei, GLint)) \
+    X(DrawElementsInstancedBaseInstance, void,                                                     \
+      (GLenum, GLsizei, GLenum, const void*, GLsizei, GLuint))                                     \
+    X(DrawElementsInstanced, void, (GLenum, GLsizei, GLenum, const void*, GLsizei))                \
+    X(DrawArraysInstancedBaseInstance, void, (GLenum, GLint, GLsizei, GLsizei, GLuint))            \
+    X(DrawArraysInstanced, void, (GLenum, GLint, GLsizei, GLsizei))                                \
+    X(DrawElementsIndirect, void, (GLenum, GLenum, const void*))                                   \
+    X(DrawArraysIndirect, void, (GLenum, const void*))                                             \
+    X(ClearBufferfi, void, (GLenum, GLint, GLfloat, GLint))                                        \
+    X(ClearBufferfv, void, (GLenum, GLint, const GLfloat*))                                        \
+    X(ClearBufferuiv, void, (GLenum, GLint, const GLuint*))                                        \
+    X(ClearBufferiv, void, (GLenum, GLint, const GLint*))                                          \
+    X(ClearNamedFramebufferfv, void,                                                               \
+      (const SharedPtr<MG_State::GLState::FramebufferObject>&, GLenum, GLint, const GLfloat*))     \
+    X(ClearNamedFramebufferfi, void,                                                               \
+      (const SharedPtr<MG_State::GLState::FramebufferObject>&, GLenum, GLint, GLfloat, GLint))     \
+    X(ClearNamedFramebufferiv, void,                                                               \
+      (const SharedPtr<MG_State::GLState::FramebufferObject>&, GLenum, GLint, const GLint*))       \
+    X(ClearNamedFramebufferuiv, void,                                                              \
+      (const SharedPtr<MG_State::GLState::FramebufferObject>&, GLenum, GLint, const GLuint*))      \
+    X(BlitNamedFramebuffer, void,                                                                  \
+      (const SharedPtr<MG_State::GLState::FramebufferObject>&,                                     \
+       const SharedPtr<MG_State::GLState::FramebufferObject>&, GLint, GLint, GLint, GLint, GLint,  \
+       GLint, GLint, GLint, GLbitfield, GLenum))                                                   \
+    X(CopyTexImage2D, void, (GLenum, GLint, GLenum, GLint, GLint, GLsizei, GLsizei, GLint))        \
+    X(CopyTexSubImage2D, void, (GLenum, GLint, GLint, GLint, GLint, GLint, GLsizei, GLsizei))      \
+    X(CopyImageSubData, void,                                                                      \
+      (const MG_Backend::CopyImageEndpoint&, GLenum, GLint, GLint, GLint, GLint,                   \
+       const MG_Backend::CopyImageEndpoint&, GLenum, GLint, GLint, GLint, GLint, GLsizei, GLsizei, \
+       GLsizei))                                                                                   \
+    X(GenerateMipmap, void, (GLenum))                                                              \
+    X(GetTexImage, void, (GLenum, GLint, GLenum, GLenum, GLvoid*))                                 \
+    X(GetTextureImage, void,                                                                       \
+      (const SharedPtr<MG_State::GLState::ITextureObject>&, TextureUploadTarget, GLint, GLenum,    \
+       GLenum, GLsizei, GLvoid*))                                                                  \
+    X(MemoryBarrier, void, (GLbitfield))                                                           \
+    X(MemoryBarrierByRegion, void, (GLbitfield))                                                   \
+    X(BindImageTexture, void, (GLuint, GLuint, GLint, GLboolean, GLint, GLenum, GLenum))           \
+    X(ShaderStorageBlockBinding, void, (GLuint, const GLchar*, GLuint))                            \
+    X(WaitSync, void, (MG_Backend::BackendSyncHandle, GLbitfield, GLuint64))                       \
+    X(DeleteSync, void, (MG_Backend::BackendSyncHandle))                                           \
+    X(EndTimeElapsedQuery, void, (MG_Backend::BackendQueryHandle))                                  \
+    X(DeleteBackendQuery, void, (MG_Backend::BackendQueryHandle))                                   \
+    X(EndOcclusionQuery, void, (MG_Backend::BackendQueryHandle))                                    \
+    X(EndXfbPrimitivesQuery, void, (MG_Backend::BackendQueryHandle))                                \
+    X(PatchParameteri, void, (GLenum, GLint))                                                      \
+    X(BeginTransformFeedback, void, (GLenum))                                                      \
+    X(EndTransformFeedback, void, ())                                                              \
+    X(PauseTransformFeedback, void, ())                                                            \
+    X(ResumeTransformFeedback, void, ())                                                           \
+    X(BindTransformFeedback, void, (GLuint))                                                       \
+    X(DeleteTransformFeedback, void, (GLuint))
+
+        // The non-void ones, kept apart only because the macro body differs: a [[noreturn]]
+        // call is a complete body for a void slot and for a value-returning one alike, but a
+        // compiler that does not see UnmigratedVerbFatal's attribute through the macro would
+        // warn on the second. It does see it; they are split for readability.
+#define MGR_UNMIGRATED_GL_VALUE_SLOTS(X)                                                           \
+    X(FenceSync, MG_Backend::BackendSyncHandle, ())                                                \
+    X(ClientWaitSync, GLenum, (MG_Backend::BackendSyncHandle, GLbitfield, GLuint64))               \
+    X(GetSyncStatus, Bool, (MG_Backend::BackendSyncHandle))                                        \
+    X(BeginTimeElapsedQuery, MG_Backend::BackendQueryHandle, ())                                   \
+    X(QueryCounterTimestamp, MG_Backend::BackendQueryHandle, ())                                   \
+    X(IsQueryResultAvailable, Bool, (MG_Backend::BackendQueryHandle))                               \
+    X(GetQueryResult64, Bool, (MG_Backend::BackendQueryHandle, Bool, Uint64*))                      \
+    X(BeginOcclusionQuery, MG_Backend::BackendQueryHandle, ())                                      \
+    X(BeginXfbPrimitivesQuery, MG_Backend::BackendQueryHandle, (Bool))                              \
+    X(GetGpuTimestampNs, Int64, ())
+
+#define MGR_DEFINE_UNMIGRATED(Name, Ret, Sig)                                                      \
+    Ret Name##_Unmigrated Sig { UnmigratedVerbFatal(#Name); }
+
+        MGR_UNMIGRATED_GL_SLOTS(MGR_DEFINE_UNMIGRATED)
+        MGR_UNMIGRATED_GL_VALUE_SLOTS(MGR_DEFINE_UNMIGRATED)
+#undef MGR_DEFINE_UNMIGRATED
+
+        // THE TWO COMPUTE SLOTS CARRY b1's DISPATCH HOOK BEFORE THE FATAL, and this is stated
+        // rather than hidden. MarkGpuWritesForDispatch() belongs immediately before the
+        // dispatch record, and the dispatch record is class C in P5 - so the call site is here,
+        // in the right place, and is UNREACHABLE-IN-EFFECT: the abort follows it. There is no
+        // gate on it and this file says so; the phase that moves DispatchCompute into class B
+        // replaces the Fatal and inherits a call site that is already correct rather than
+        // discovering that the mark walk was never wired.
+        void DispatchCompute_Unmigrated(GLuint, GLuint, GLuint) {
+            PushPersistentMapsBeforeVerb();
+            MarkGpuWritesForDispatch();
+            UnmigratedVerbFatal("DispatchCompute");
+        }
+        void DispatchComputeIndirect_Unmigrated(GLintptr) {
+            PushPersistentMapsBeforeVerb();
+            MarkGpuWritesForDispatch();
+            UnmigratedVerbFatal("DispatchComputeIndirect");
+        }
+
+        void SetSwapInterval_Unmigrated(Int) { UnmigratedVerbFatal("SetSwapInterval"); }
+
+        // The counts, as arithmetic. MGR_COUNT_ONE expands to `+ 1` per row.
+#define MGR_COUNT_ONE(Name, Ret, Sig) +1
+        constexpr Uint32 kUnmigratedListedSlots =
+            0 MGR_UNMIGRATED_GL_SLOTS(MGR_COUNT_ONE) MGR_UNMIGRATED_GL_VALUE_SLOTS(MGR_COUNT_ONE);
+#undef MGR_COUNT_ONE
+        // + DispatchCompute, DispatchComputeIndirect, SetSwapInterval, written out by hand
+        // because they carry a body the macro cannot.
+        constexpr Uint32 kUnmigratedSlots = kUnmigratedListedSlots + 3;
+        constexpr Uint32 kLocallyAnsweredSlots = 2; // GetIntegeri_v, IsTimerQuerySupported
+        constexpr Uint32 kEmittedSlots = 5;         // Clear, DrawArrays, ReadPixels, Blit, Present
+
+        static_assert(kUnmigratedSlots == 64, "CONTRACT-P5.md §7 class C is 64 slots");
+        static_assert(kLocallyAnsweredSlots + kEmittedSlots + kUnmigratedSlots == kRemoteEmitSlotCount,
+                      "the three classes no longer partition the 71 slots");
+
+        MG_Backend::GlobalBackendFunctionsTable BuildRemoteEmitTable() {
+            g_dropClearEmission = ReadDropClearFromEnvironment();
+            MG_Backend::GlobalBackendFunctionsTable table{};
+
+            // ---- class C first, so that a slot forgotten below stays Fatal rather than null.
+            // Order matters for exactly this reason: if class B's assignment were first, a
+            // typo in class C would leave a NULL slot, and a null slot is 91 potential null
+            // calls with no diagnostic. This way the worst a mistake can do is name a verb
+            // that was supposed to be emitted, loudly.
+#define MGR_ASSIGN_UNMIGRATED(Name, Ret, Sig) table.GL.Name = &Name##_Unmigrated;
+            MGR_UNMIGRATED_GL_SLOTS(MGR_ASSIGN_UNMIGRATED)
+            MGR_UNMIGRATED_GL_VALUE_SLOTS(MGR_ASSIGN_UNMIGRATED)
+#undef MGR_ASSIGN_UNMIGRATED
+            table.GL.DispatchCompute = &DispatchCompute_Unmigrated;
+            table.GL.DispatchComputeIndirect = &DispatchComputeIndirect_Unmigrated;
+            table.SetSwapInterval = &SetSwapInterval_Unmigrated;
+
+            // ---- class A
+            table.GL.GetIntegeri_v = &AnswerGetIntegeri_v;
+            table.GL.IsTimerQuerySupported = &AnswerIsTimerQuerySupported;
+            // NOT A SLOT and not a verb: a Bool member of the table, whose one non-test client
+            // reader is GL_Query.cpp:221. It does NOT ride inside MGPCaps::Dynamic - it is a
+            // member of GLFunctionsTable, which is exactly the thing a split client never
+            // receives - so it is answered from kCapCpuXfbPrimitiveAccounting.
+            table.GL.PrefersCpuXfbPrimitiveAccounting =
+                CapsMirrorInstance().PrefersCpuXfbPrimitiveAccounting();
+
+            // ---- class B
+            table.GL.Clear = &EmitClear;
+            table.GL.DrawArrays = &EmitDrawArrays;
+            table.GL.ReadPixels = &EmitReadPixels;
+            table.GL.BlitFramebuffer = &EmitBlitFramebuffer;
+            table.Present = &EmitPresent;
+
+            return table;
+        }
+
+    } // namespace
+
     const MG_Backend::GlobalBackendFunctionsTable& RemoteEmitTable() {
-        MGLOG_F("MGPipe: Fatal{UnimplementedEmitTable, \"RemoteEmitTable\"} - P5 package c1 has "
+        // Leaked at exit like every other MG_Remote singleton (ID-8): MG_Backend::Init()
-                "not landed this yet; c0 shipped the signature only");
+        // copies it into gBackendFunctionsTable and MobileGL::Destroy() clears that copy from
-        std::abort();
+        // an exit handler, by which point a static destructor here would already have run.
+        static const MG_Backend::GlobalBackendFunctionsTable& table =
+            *new MG_Backend::GlobalBackendFunctionsTable{BuildRemoteEmitTable()};
+        return table;
     }
 
-    Uint32 ImplementedVerbCount() { return 0; }
+    Uint32 ImplementedVerbCount() { return kEmittedSlots; }
+    Uint32 LocallyAnsweredSlotCount() { return kLocallyAnsweredSlots; }
+    Uint32 UnmigratedSlotCount() { return kUnmigratedSlots; }
+
+    void SetDropClearEmissionForNegativeControl(Bool drop) { g_dropClearEmission = drop; }
+    Uint64 DroppedClearEmissions() { return g_droppedClearEmissions; }
 
 } // namespace MobileGL::MG_Remote::Client

MobileGL/MG_Remote/Client/EmitTables.h

@@ -60,6 +60,22 @@
 
 namespace MobileGL::MG_Remote::Client {
 
+    // MGPClear::Kind. MGPipeTypes.h:1273 states the list as a COMMENT - "Whole | Color | Depth
+    // | Stencil | DepthStencil" - and mints no enumerator, because until P5 the record had no
+    // producer. These are the values, in that comment's own order, and they are here rather
+    // than in MGPipeTypes.h because that file is c0's and this phase produces exactly ONE of
+    // them: glClear is the only entry point that reaches the Clear slot (the four
+    // glClearBuffer* and the four glClearNamedFramebuffer* are class C). v1's
+    // WireVerbSink::OnClear must therefore Fatal on anything but Whole rather than guess, and
+    // the phase that migrates the other eight moves these into the contract.
+    enum MGRemoteClearKind : Uint32 {
+        kRemoteClearWhole = 0,
+        kRemoteClearColor = 1,
+        kRemoteClearDepth = 2,
+        kRemoteClearStencil = 3,
+        kRemoteClearDepthStencil = 4,
+    };
+
     // The table MG_Backend::Init() installs into gBackendFunctionsTable for the remote role.
     // A reference to a never-destroyed block, like every other MG_Remote singleton (ID-8).
     const MG_Backend::GlobalBackendFunctionsTable& RemoteEmitTable();
@@ -77,4 +93,25 @@ namespace MobileGL::MG_Remote::Client {
     // a slot added to GLFunctionsTable without a decision here is a build break.
     inline constexpr Uint32 kRemoteEmitSlotCount = 71;
 
+    // The other two thirds of the census, so a case can assert the WHOLE partition rather than
+    // only the half that emits. CONTRACT-P5.md §7's three classes are 2 + 5 + 64, and
+    // EmitTables.cpp static_asserts that they sum to kRemoteEmitSlotCount: a slot that quietly
+    // changes class shows up as a build break in the sum, not as a silent behaviour change.
+    Uint32 LocallyAnsweredSlotCount(); // class A - answered from the caps mirror, R-15
+    Uint32 UnmigratedSlotCount();      // class C - Fatal{UnmigratedVerb}
+
+    // THE E2 NEGATIVE CONTROL (t1's debt against c1, BRIEF §7). When set, the Clear emitter
+    // SKIPS its record - it still runs the pre-verb hooks and still returns - so a replay that
+    // is really going through the wire loses one clear per frame and its SSIM falls below the
+    // 0.99 threshold, while a replay that fell through to the driver is unaffected. It is a
+    // function rather than a knob in Config.h for two reasons: the control has to be settable
+    // from a test process that has already started, and a knob would be a
+    // MOBILEGL_IPC_-shaped name for something no operator may ever set.
+    //
+    // Emissions actually skipped, so the control can assert that it DID something rather than
+    // that a picture changed - a control that silently never fired is the third shape of R-16's
+    // "a gate that cannot go red for its own reason".
+    void SetDropClearEmissionForNegativeControl(Bool drop);
+    Uint64 DroppedClearEmissions();
+
 } // namespace MobileGL::MG_Remote::Client

MobileGL/MG_Remote/Client/SlotCaps.h

@@ -0,0 +1,135 @@
+// MobileGL - MobileGL/MG_Remote/Client/SlotCaps.h
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+// THE 41 NULL CHECKS. Owner: package c1 (CONTRACT-P5.md §7, ID-14).
+//
+// FORTY-ONE OF THE SIXTY-NINE GLFunctionsTable SLOTS ARE NULL-CHECKED AT THEIR CALL SITE, AND
+// SEVERAL OF THOSE CHECKS ARE CAPABILITY PROBES RATHER THAN SAFETY CHECKS. R-4 forbids a null
+// slot in the client's emit table - so in that table every one of those probes would answer
+// "supported", and whatever fallback sits behind it would silently disappear. That is not a
+// theoretical risk: it is how a split lane produces a plausible picture for the wrong reason.
+// ARCHITECTURE.md:114 already said what replaces the probe - "CallMask replaces 'is this table
+// slot null' as the implicit capability probe" - and this header is the concrete list.
+//
+// TWO SPELLINGS, AND WHICH ONE A SITE TAKES IS DECIDED BY THE SLOT'S CLASS, NOT BY TASTE:
+//
+//   MGL_BACKEND_SLOT_CAP(Slot, CapBit)
+//       The capability has a published bit. Under split the answer is the SERVER's bit;
+//       under monolith it is exactly today's null check, character for character.
+//       The three cases CONTRACT-P5.md §7 names by hand are all of this shape:
+//         GL_Query.cpp:481 / :558 / :785  BeginOcclusionQuery   -> kCapOcclusionQuery
+//         GL_Query.cpp:534                BeginXfbPrimitivesQuery -> kCapXfbPrimitivesQuery
+//         PipeFill.cpp                    SubDataResident        -> kCapResidentSubData
+//       (the third is not a GLFunctionsTable slot but an op-table one, so it reads the bit
+//        directly in PipeFill.cpp rather than through this header).
+//
+//   MGL_BACKEND_SLOT_LOCAL(Slot)
+//       The capability has NO published bit and the slot is CONTRACT-P5.md §7 class C -
+//       Fatal{UnmigratedVerb} in the client's table. Under split the honest answer is
+//       "absent", which is precisely what the monolith nullptr meant, so every fallback the
+//       site already has survives instead of being replaced by an abort. Under monolith it is
+//       again today's null check.
+//
+// WHY "ABSENT" AND NOT "LET IT FATAL". A Fatal is loud, and for the 28 UNGUARDED slots it is
+// strictly better than today (a null there is already an immediate crash with no diagnostic).
+// But a guarded site is guarded because the frontend has a real answer for the absent case -
+// always-signaled syncs, a CPU readback, CPU primitive accounting - and turning that answer
+// into an abort is a behaviour change nobody asked for, in the direction that stops a lane
+// dead. The class-C slot IS absent from this client; saying so is the accurate answer, not a
+// weakening of R-4.
+//
+// THE TEST THAT DECIDES WHETHER A GUARDED SITE IS CONVERTED AT ALL, and it is the half of the
+// walk the contract leaves to whoever does it: A PROBE MOVES ONLY WHERE "ABSENT" IS A CORRECT
+// AND SUFFICIENT ANSWER. Where the fallback behind the probe produces a RIGHT result, "absent"
+// is the accurate description of a client that does not have the slot, and converting keeps
+// the lane running. Where the fallback produces a SILENTLY WRONG result, converting would
+// manufacture exactly the defect R-4 exists to prevent, and the probe is left alone so the
+// class-C slot Fatals by name instead.
+//
+// Converted, because the fallback is right:
+//   GL_Sync.cpp:59    FenceSync              -> always-signaled syncs, which the table's own
+//                                               header documents as the fallback and which GL
+//                                               permits; every other sync site is already
+//                                               guarded on syncObject->backendHandle, so this
+//                                               one gate carries the whole family.
+//   GL_Texture.cpp:6537 GetTextureImage      -> the frontend's own CPU readback, which is exact
+//   GL_Texture.cpp:6799 GetTexImage          -> the same
+//   GL_Getter.cpp x2  GetGpuTimestampNs      -> 0, which BackendObject.h:192 already names as
+//                                               the unsupported answer
+//   GL_Query.cpp      the four query probes   -> CPU primitive accounting / target rejection /
+//                                               COUNTER_BITS 0, all of them spec answers
+//
+// NOT converted, deliberately, because "absent" would be wrong rather than quiet:
+//   GL_Drawing.cpp:1274/:1371/:1420/:1435/:1641/:1673  the transform-feedback span family. The
+//       frontend reads a null EndTransformFeedback as "this backend does NOT own the capture,
+//       so reorder the captured records for it" (FixupGsStripCaptureOrder, :1290). Under split
+//       the server's backend DOES own it, so answering "absent" would reorder a capture that
+//       was already in GL order - a silently corrupt buffer. Transform feedback is off P5's
+//       reduced path (BRIEF §4's exclusion list) and its slots are class C, so the first XFB
+//       call aborts by name, which is the outcome R-4 asks for.
+//   GL_Drawing.cpp:844  PatchParameteri. "Absent" means the patch size is never set and every
+//       tessellation draw silently uses the previous one. Class C; it aborts by name.
+//
+// WHAT THIS HEADER DELIBERATELY DOES NOT DO. It does not touch the 28 unguarded slots: those
+// have no probe to convert, and calling one reaches Fatal{UnmigratedVerb, "<slot>"} by name,
+// which is R-4's intent. And it does not invent a cap bit - a new MGPCapBit is an
+// MGPipeTypes.h edit and that file is c0's, so a family that needs one goes through the
+// integrator (the XFB span family is the first that will).
+//
+// G1: in a build without MOBILEGL_BUILD_DISAGGREGATED both macros expand to the null check the
+// site already had, so the pull build's code generation is unchanged.
+
+#pragma once
+#include <Includes.h>
+
+#include <Config.h>
+
+#if MOBILEGL_BUILD_DISAGGREGATED
+#include <MG_Pipe/MGPipeTypes.h>
+#include <MG_Remote/Client/CapsMirror.h>
+
+#define MGL_BACKEND_SLOT_CAP(Slot, CapBit)                                                         \
+    (::MobileGL::MG_Config::Transport != ::MobileGL::MG_Config::TransportMode::Monolith             \
+         ? ::MobileGL::MG_Remote::Client::CapsMirrorInstance().HasCap(CapBit)                       \
+         : ::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot != nullptr)
+
+#define MGL_BACKEND_SLOT_LOCAL(Slot)                                                               \
+    (::MobileGL::MG_Config::Transport == ::MobileGL::MG_Config::TransportMode::Monolith &&          \
+     ::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot != nullptr)
+
+// The POINTER-valued forms, for the several sites shaped `if (const auto f = TABLE.GL.Slot)`.
+// They exist for G1 and for nothing else: a site rewritten from that shape into
+// `if (MGL_BACKEND_SLOT_CAP(...)) { const auto f = TABLE.GL.Slot; ... }` is semantically the
+// same and generated DIFFERENT CODE - the first measurement of this change moved
+// GL_Getter.cpp's GetInteger64v by -150 bytes and GetIntegerv by +2, which is two "resized"
+// symbols and a red G1. In a pull build these two expand to the slot expression ITSELF, so the
+// init-statement survives verbatim and the pull build's code generation cannot move.
+#define MGL_BACKEND_SLOT_PTR_CAP(Slot, CapBit)                                                     \
+    (::MobileGL::MG_Config::Transport != ::MobileGL::MG_Config::TransportMode::Monolith             \
+         ? (::MobileGL::MG_Remote::Client::CapsMirrorInstance().HasCap(CapBit)                      \
+                ? ::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot                            \
+                : nullptr)                                                                          \
+         : ::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot)
+
+#define MGL_BACKEND_SLOT_PTR_LOCAL(Slot)                                                           \
+    (::MobileGL::MG_Config::Transport != ::MobileGL::MG_Config::TransportMode::Monolith             \
+         ? nullptr                                                                                  \
+         : ::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot)
+
+#else
+
+#define MGL_BACKEND_SLOT_CAP(Slot, CapBit)                                                         \
+    (::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot != nullptr)
+#define MGL_BACKEND_SLOT_LOCAL(Slot)                                                               \
+    (::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot != nullptr)
+#define MGL_BACKEND_SLOT_PTR_CAP(Slot, CapBit)                                                     \
+    (::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot)
+#define MGL_BACKEND_SLOT_PTR_LOCAL(Slot)                                                           \
+    (::MobileGL::MG_Backend::gBackendFunctionsTable.GL.Slot)
+
+#endif

MobileGL/MG_Test/SanityTest.cpp

@@ -41,6 +41,13 @@
 #include <MG_Util/ShaderTranspiler/CompileEnv.h>
 #include <MG_Util/ShaderTranspiler/ShaderSourceProcessor.h>
 #include <MG_Util/Debug/Log.h>
+
+#if MOBILEGL_BUILD_DISAGGREGATED
+// P5 c1 / R-8: the client's liveness gates read the caps mirror's consumer mask under split, so
+// a split-armed case has to arm that half too - registering an op table is the SERVER's arming.
+#include <MG_Remote/CapsCodec.h>
+#include <MG_Remote/Client/CapsMirror.h>
+#endif
 #include <MG_Util/BackendLoaders/OpenGL/Loader.h>
 #include <MG_Util/Types.h>
 #include <Config.h>
@@ -4695,6 +4702,21 @@ TEST(DirectGLESBufferDrawProbe, UnderSplitTheRecordAloneAnswersTheLiveHostMapQue
     MG_Pipe::MGPipeSetResourceOps(&ops);
     MG_Config::Transport = MG_Config::TransportMode::InProcess;
     MG_Config::Ipc.PersistentBlockKb = 64;
+    // P5 c1 / R-8: UNDER SPLIT THE OP TABLE IS NO LONGER THE ARMING CONDITION, and this case is
+    // the first place that shows. `MGPipeSetResourceOps(&ops)` is the SERVER's registration; the
+    // client's liveness gate now reads the caps mirror's consumer mask instead, because under a
+    // spawn the client process has no op table at all and reading one would silently stop five
+    // record families. So the probe has to arm BOTH halves - and the fact that it did not is the
+    // defect R-8 exists to catch, reproduced here by a change rather than argued about.
+    const Uint64 previousCapsGeneration = MG_Remote::Client::CapsMirrorInstance().Generation();
+    {
+        MG_Pipe::MGPCaps caps{};
+        caps.CallMask = MG_Remote::MGCapsConsumerBits(MG_Pipe::kMGPipeSubsystemResources);
+        MG_Remote::Client::CapsMirrorInstance().Adopt(caps, MG_Backend::FormatCapabilityCache{},
+                                                      RendererInfo{}, String{},
+                                                      BackendType::DirectGLES);
+    }
+    (void)previousCapsGeneration;
 
     {
         // The constructor mints the handle and emits resource_create; Respecify emits the

MobileGL/MG_Test/Wire/CMakeLists.txt

@@ -65,3 +65,30 @@ if (MSVC)
 endif ()
 
 gtest_discover_tests(PipeWireCodecTest DISCOVERY_TIMEOUT 30 PROPERTIES LABELS unit)
+
+# P5 c1's suite: the 71-slot emit table, the caps mirror and R-8's liveness gates. Registered
+# on its own for PipeWireCodecTest's reason - MGLOG_F writes to stdout and to a named file and
+# NEVER to stderr, so a Fatal arm can only be asserted by forking and reading that file back,
+# which needs a main() of its own.
+add_executable(RemoteClientTest RemoteClientTest.cpp)
+
+target_include_directories(RemoteClientTest PRIVATE
+        ${MGL_ROOT}/include
+        ${MGL_ROOT}/MobileGL
+        ${MGL_ROOT}/MobileGL/MG_Pipe
+        ${MGL_ROOT}/3rdparty/flatbuffers/include
+        ${MGL_ROOT}/3rdparty/xxHash
+        ${MGL_ROOT}/3rdparty/Vulkan-Headers/include
+        ${MGL_ROOT}/3rdparty/SPIRV-Reflect
+)
+
+target_link_libraries(RemoteClientTest PRIVATE
+        GTest::gtest
+        ${LINK_LIBRARIES}
+)
+
+if (MSVC)
+    target_compile_options(RemoteClientTest PRIVATE /Zc:preprocessor)
+endif ()
+
+gtest_discover_tests(RemoteClientTest DISCOVERY_TIMEOUT 30 PROPERTIES LABELS unit)

MobileGL/MG_Test/Wire/RemoteClientTest.cpp

@@ -0,0 +1,419 @@
+// MobileGL - MobileGL/MG_Test/Wire/RemoteClientTest.cpp
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+// P5 package c1's suite: the 71-slot emit table, the caps mirror and R-8's liveness gates. No
+// session, no transport and no thread - s1's SessionTest owns those and w1's PipeWireCodecTest
+// owns the bytes.
+//
+// IT LINKS gtest RATHER THAN gtest_main AND CARRIES ITS OWN main(), for PipeWireCodecTest's and
+// PipeInputsTest's reason: the Fatal arms report through MGLOG_F + std::abort, and MGLOG_F
+// writes to STDOUT and to a named file, NEVER to stderr - so EXPECT_DEATH's stderr regex could
+// only ever match the empty string. A case that drives one FORKS and reads the Fatal line back
+// out of a log file this process names before anything logs. That is what makes each control
+// assert ITS OWN failure string (R-16) instead of asserting that something, somewhere, died.
+
+#include <gtest/gtest.h>
+
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <filesystem>
+#include <fstream>
+#include <sstream>
+#include <string>
+
+#include "Includes.h"
+
+#include <Config.h>
+#include <MG_Pipe/MGPipe.h>
+#include <MG_Remote/CapsCodec.h>
+#include <MG_Remote/Client/CapsMirror.h>
+#include <MG_Remote/Client/EmitTables.h>
+
+#if !defined(_WIN32)
+#include <csignal>
+#include <sys/wait.h>
+#include <unistd.h>
+#define MGTEST_HAVE_FORK 1
+#else
+#define MGTEST_HAVE_FORK 0
+#endif
+
+using namespace MobileGL;
+using namespace MobileGL::MG_Pipe;
+using namespace MobileGL::MG_Remote;
+using namespace MobileGL::MG_Remote::Client;
+
+namespace {
+
+    std::string g_logPath;
+
+    std::string ReadLog() {
+        std::ifstream in(g_logPath, std::ios::binary);
+        if (!in) return {};
+        std::ostringstream out;
+        out << in.rdbuf();
+        return out.str();
+    }
+
+    int ProcessId() {
+#if defined(_WIN32)
+        return static_cast<int>(::_getpid());
+#else
+        return static_cast<int>(::getpid());
+#endif
+    }
+
+    // A caps snapshot the client could plausibly have received, with every field distinct from
+    // its default so a mirror that answered from a zeroed struct cannot look like one that
+    // adopted. THIS IS NOT THE STATE UNDER TEST - it is the INPUT to Adopt(), which is the
+    // producer; the assertions below read what the mirror hands the frontend's own accessors
+    // back, never what this function wrote (R-16).
+    struct Snapshot {
+        MGPCaps Caps{};
+        MG_Backend::FormatCapabilityCache Formats{};
+        RendererInfo Renderer{};
+        String ApiVersion;
+        BackendType Backend = BackendType::DirectGLES;
+    };
+
+    Snapshot MakeSnapshot(Uint64 consumedSubsystems, Uint64 capBits) {
+        Snapshot s;
+        s.Caps.CallMask = capBits | MGCapsConsumerBits(consumedSubsystems);
+        s.Caps.Dynamic.MaxComputeWorkGroupCount[0] = 65531;
+        s.Caps.Dynamic.MaxComputeWorkGroupCount[1] = 65532;
+        s.Caps.Dynamic.MaxComputeWorkGroupCount[2] = 65533;
+        s.Caps.Dynamic.MaxComputeWorkGroupSize[0] = 1021;
+        s.Caps.Dynamic.MaxComputeWorkGroupSize[1] = 1022;
+        s.Caps.Dynamic.MaxComputeWorkGroupSize[2] = 1023;
+        s.Caps.Dynamic.UniformBufferOffsetAlignment = 64;
+        s.Renderer.RendererName = "MobileGL Remote Test Renderer";
+        s.Renderer.BackendName = "Espryt";
+        s.Renderer.ExtraVendor = String{"c1"};
+        s.Renderer.RendererGLInfo.TargetGLVersion = Version{4, 6, 0, {}, {}};
+        s.Renderer.RendererGLInfo.TargetGLSLVersion = Version{4, 6, 0, {}, {}};
+        s.ApiVersion = "4.6";
+        return s;
+    }
+
+    void AdoptSnapshot(const Snapshot& s) {
+        CapsMirrorInstance().Adopt(s.Caps, s.Formats, s.Renderer, s.ApiVersion, s.Backend);
+    }
+
+#if MGTEST_HAVE_FORK
+    struct ChildResult {
+        int Status = -1;
+        std::string Log;
+    };
+
+    template <class Body>
+    ChildResult RunInChild(Body body) {
+        ChildResult result;
+        // TRUNCATE, RATHER THAN REMEMBER AN OFFSET, and the difference is not cosmetic: this
+        // parent never logs, so MG_Util::Debug's FILE* is opened FOR THE FIRST TIME by each
+        // child - with "w", which truncates. An offset taken before the fork therefore points
+        // past the end of the child's own log, and `substr` hands back the tail of a DIFFERENT
+        // child's output. That is how the second death case in this file came to see the first
+        // one's slot name and assert on it: a control reading another control's message, which
+        // is one of the three shapes R-16 was written after.
+        { std::ofstream truncate(g_logPath, std::ios::trunc | std::ios::binary); }
+        std::fflush(nullptr);
+        const pid_t pid = ::fork();
+        if (pid < 0) return result;
+        if (pid == 0) {
+            body();
+            ::_exit(0);
+        }
+        int status = 0;
+        if (::waitpid(pid, &status, 0) != pid) return result;
+        result.Status = status;
+        result.Log = ReadLog();
+        return result;
+    }
+
+    bool DiedOfAbort(const ChildResult& r) {
+        return WIFSIGNALED(r.Status) && WTERMSIG(r.Status) == SIGABRT;
+    }
+    std::string DescribeStatus(const ChildResult& r) {
+        if (r.Status < 0) return "fork/waitpid failed";
+        if (WIFEXITED(r.Status)) return "exited " + std::to_string(WEXITSTATUS(r.Status));
+        if (WIFSIGNALED(r.Status)) return "signal " + std::to_string(WTERMSIG(r.Status));
+        return "status " + std::to_string(r.Status);
+    }
+#endif
+
+} // namespace
+
+// =====================================================================================
+// The emit table: the partition, and that no slot is null
+// =====================================================================================
+
+TEST(RemoteEmitTable, TheThreeClassesPartitionAllSeventyOneSlots) {
+    // CONTRACT-P5.md §7: 2 answered locally + 5 emitted + 64 Fatal. Read from the functions the
+    // table itself reports with - which is also what t1's arming condition reads - rather than
+    // recomputed here, so a table that lost an emitter cannot look like one that never had it.
+    EXPECT_EQ(LocallyAnsweredSlotCount(), 2u);
+    EXPECT_EQ(ImplementedVerbCount(), 5u);
+    EXPECT_EQ(UnmigratedSlotCount(), 64u);
+    EXPECT_EQ(LocallyAnsweredSlotCount() + ImplementedVerbCount() + UnmigratedSlotCount(),
+              kRemoteEmitSlotCount);
+}
+
+TEST(RemoteEmitTable, NoSlotIsNull) {
+    // R-4's whole rule, asserted over the STRUCT rather than over the list that built it. 91
+    // MG_Impl sites call through this table directly; a null slot is 91 potential null calls,
+    // and the one thing a list-driven check could not catch is a slot the list forgot to name.
+    //
+    // Walked as a block of function pointers because that is exactly what the struct is - the
+    // static_asserts in EmitTables.cpp pin that shape - so a slot ADDED to GLFunctionsTable is
+    // covered here on the day it appears, without this file being edited.
+    const MG_Backend::GlobalBackendFunctionsTable& table = RemoteEmitTable();
+    const void* const* cells = reinterpret_cast<const void* const*>(&table);
+    const SizeT cellCount = sizeof(table) / sizeof(void*);
+    // The struct is 71 function pointers plus ONE cell holding the packed Bool
+    // PrefersCpuXfbPrimitiveAccounting and its padding (EmitTables.cpp static_asserts exactly
+    // that shape). That Bool is legitimately zero when the server did not publish
+    // kCapCpuXfbPrimitiveAccounting, so at most one cell may read null - and this is stated as
+    // a bound rather than an index, because an index would drift the day a slot is inserted.
+    SizeT nullCells = 0;
+    for (SizeT i = 0; i < cellCount; ++i) {
+        if (cells[i] == nullptr) ++nullCells;
+    }
+    EXPECT_LE(nullCells, 1u)
+        << "a slot in the remote emit table is null (" << nullCells << " null cells out of "
+        << cellCount
+        << "). R-4 forbids it: 91 MG_Impl sites call through this table with no null check at all";
+}
+
+TEST(RemoteEmitTable, TheFiveEmittersAreTheOnesTheCensusMeasured) {
+    const MG_Backend::GlobalBackendFunctionsTable& table = RemoteEmitTable();
+    // Named, so that a table which emitted a DIFFERENT five would be red rather than merely
+    // counted. The census's answer is Clear, DrawArrays, ReadPixels, BlitFramebuffer, Present.
+    EXPECT_NE(table.GL.Clear, nullptr);
+    EXPECT_NE(table.GL.DrawArrays, nullptr);
+    EXPECT_NE(table.GL.ReadPixels, nullptr);
+    EXPECT_NE(table.GL.BlitFramebuffer, nullptr);
+    EXPECT_NE(table.Present, nullptr);
+    // And the two R-15 answers them locally, so they are not the same pointer as any Fatal one.
+    EXPECT_NE(table.GL.GetIntegeri_v, nullptr);
+    EXPECT_NE(table.GL.IsTimerQuerySupported, nullptr);
+    EXPECT_NE(reinterpret_cast<const void*>(table.GL.DrawArrays),
+              reinterpret_cast<const void*>(table.GL.DrawElements))
+        << "DrawArrays is class B and DrawElements is class C; they cannot share a thunk";
+}
+
+#if MGTEST_HAVE_FORK
+TEST(RemoteEmitTable, AnUnmigratedSlotAbortsAndNamesItself) {
+    // THE DEATH TEST ON THE UnmigratedVerbFatal ARM. It asserts the exact wording, not merely
+    // that the child died: a control that trips on any abort is satisfied by the wrong abort,
+    // which is one of the three shapes R-16 was written after.
+    const ChildResult r = RunInChild([] {
+        RemoteEmitTable().GL.DrawElements(0x0004 /*GL_TRIANGLES*/, 3, 0x1405 /*GL_UNSIGNED_INT*/,
+                                          nullptr);
+    });
+    ASSERT_TRUE(DiedOfAbort(r)) << DescribeStatus(r) << "\n" << r.Log;
+    EXPECT_NE(r.Log.find("Fatal{UnmigratedVerb, \"DrawElements\"}"), std::string::npos) << r.Log;
+}
+
+TEST(RemoteEmitTable, EachUnmigratedSlotNamesItsOwnSlot) {
+    // The half the case above cannot state on its own: that the name in the message is the
+    // slot's and not a constant. Two different slots, two different names.
+    const ChildResult r = RunInChild([] { RemoteEmitTable().GL.GenerateMipmap(0x0DE1); });
+    ASSERT_TRUE(DiedOfAbort(r)) << DescribeStatus(r) << "\n" << r.Log;
+    EXPECT_NE(r.Log.find("Fatal{UnmigratedVerb, \"GenerateMipmap\"}"), std::string::npos) << r.Log;
+    EXPECT_EQ(r.Log.find("DrawElements"), std::string::npos)
+        << "the Fatal message names a slot other than the one that was called:\n"
+        << r.Log;
+}
+
+TEST(RemoteEmitTable, SetSwapIntervalIsClassCAndSaysSo) {
+    // The slot the verb census found by NOT mirroring GLImpl: SetSwapInterval has zero MG_Impl
+    // call sites and is reached only through the EGL path, so a table built from the 89 GLImpl
+    // sites would have left it null.
+    const ChildResult r = RunInChild([] { RemoteEmitTable().SetSwapInterval(1); });
+    ASSERT_TRUE(DiedOfAbort(r)) << DescribeStatus(r) << "\n" << r.Log;
+    EXPECT_NE(r.Log.find("Fatal{UnmigratedVerb, \"SetSwapInterval\"}"), std::string::npos) << r.Log;
+}
+
+TEST(RemoteEmitTable, AClassBSlotWithNoSessionAbortsRatherThanFallingThrough) {
+    // The other half of "no slot may fall through to the driver". With no ClientSession the
+    // emitter has nowhere to put the record, and the one thing it may not do is return quietly:
+    // that is the split lane running monolith and going green.
+    const ChildResult r = RunInChild([] { RemoteEmitTable().GL.Clear(0x4000 /*COLOR_BUFFER_BIT*/); });
+    ASSERT_TRUE(DiedOfAbort(r)) << DescribeStatus(r) << "\n" << r.Log;
+    EXPECT_NE(r.Log.find("Fatal{NoClientSession, \"Clear\"}"), std::string::npos) << r.Log;
+}
+#endif // MGTEST_HAVE_FORK
+
+// =====================================================================================
+// The caps mirror: the three read paths the acceptance names
+// =====================================================================================
+
+TEST(CapsMirrorTest, GlGetStringReadsTheRendererStringsBackOutOfTheMirror) {
+    // glGetString's path is GL_Getter.cpp:596 -> pActiveBackendObject->GetRendererInfo(), which
+    // BackendObject_Remote answers from this mirror BY REFERENCE - so the test reads the
+    // reference, holds it across a second adoption, and requires it to follow. A mirror that
+    // handed back a temporary would pass an equality check and dangle here.
+    const Snapshot first = MakeSnapshot(kMGPipeSubsystemResources, 0);
+    AdoptSnapshot(first);
+    const RendererInfo& bound = CapsMirrorInstance().Renderer();
+    EXPECT_EQ(bound.RendererName, "MobileGL Remote Test Renderer");
+    EXPECT_EQ(bound.BackendName, "Espryt");
+    ASSERT_TRUE(bound.ExtraVendor.has_value());
+    EXPECT_EQ(*bound.ExtraVendor, "c1");
+
+    Snapshot second = MakeSnapshot(kMGPipeSubsystemResources, 0);
+    second.Renderer.RendererName = "A Different Device";
+    AdoptSnapshot(second);
+    EXPECT_EQ(bound.RendererName, "A Different Device")
+        << "GetRendererInfo() returns a reference, so a re-arrival must be visible through a "
+           "reference a caller already holds";
+}
+
+TEST(CapsMirrorTest, GlGetIntegervReadsTheDynamicParametersBackOutOfTheMirror) {
+    // glGetIntegerv's limit family is GL_Getter.cpp:2400 -> GetDynamicParameters(), which binds
+    // a reference and then reads many members - which is why a partial snapshot is not an
+    // option and why the whole struct crosses.
+    AdoptSnapshot(MakeSnapshot(kMGPipeSubsystemResources, 0));
+    const MG_Backend::DynamicBackendParameters& dynamic = CapsMirrorInstance().Dynamic();
+    EXPECT_EQ(dynamic.MaxComputeWorkGroupCount[0], 65531);
+    EXPECT_EQ(dynamic.MaxComputeWorkGroupCount[2], 65533);
+    EXPECT_EQ(dynamic.MaxComputeWorkGroupSize[1], 1022);
+    EXPECT_EQ(dynamic.UniformBufferOffsetAlignment, 64u);
+}
+
+TEST(CapsMirrorTest, GlGetStringiReadsTheAdvertisedExtensionListBackOutOfTheMirror) {
+    // glGetStringi(GL_EXTENSIONS) is GL_Getter.cpp:654 -> GetRendererInfo().RendererGLInfo, the
+    // same list CompileEnv.cpp:124 copies into the compile env.
+    Snapshot s = MakeSnapshot(kMGPipeSubsystemResources, 0);
+    s.Renderer.RendererGLInfo.Extensions.push_back(E_GL_ARB_timer_query);
+    AdoptSnapshot(s);
+    const auto& extensions = CapsMirrorInstance().Renderer().RendererGLInfo.Extensions;
+    ASSERT_EQ(extensions.size(), 1u);
+    EXPECT_EQ(extensions[0], E_GL_ARB_timer_query);
+    EXPECT_EQ(CapsMirrorInstance().Renderer().RendererGLInfo.TargetGLVersion.Major, 4);
+}
+
+TEST(CapsMirrorTest, ReArrivalIsTheInvalidationAndMovesTheGeneration) {
+    // R-12 has no Invalidate(), so Generation() is the ONLY thing on the client that can see a
+    // server context death - and a client memo has to key on it.
+    const Uint64 before = CapsMirrorInstance().Generation();
+    AdoptSnapshot(MakeSnapshot(kMGPipeSubsystemResources, 0));
+    const Uint64 after = CapsMirrorInstance().Generation();
+    EXPECT_EQ(after, before + 1);
+    AdoptSnapshot(MakeSnapshot(kMGPipeSubsystemResources, 0));
+    EXPECT_EQ(CapsMirrorInstance().Generation(), after + 1);
+    EXPECT_TRUE(CapsMirrorInstance().Valid());
+}
+
+TEST(CapsMirrorTest, TheBackendTypeIsTheServersAndNeverANewEnumerator) {
+    Snapshot s = MakeSnapshot(kMGPipeSubsystemResources, 0);
+    s.Backend = BackendType::DirectVulkan;
+    AdoptSnapshot(s);
+    EXPECT_EQ(CapsMirrorInstance().Backend(), BackendType::DirectVulkan);
+    s.Backend = BackendType::DirectGLES;
+    AdoptSnapshot(s);
+    EXPECT_EQ(CapsMirrorInstance().Backend(), BackendType::DirectGLES);
+}
+
+TEST(CapsMirrorTest, ThePrefersCpuXfbAnswerComesFromTheCapBitAndNotFromTheTable) {
+    // GLFunctionsTable::PrefersCpuXfbPrimitiveAccounting is a member of the FUNCTION TABLE,
+    // which is exactly the thing a split client never receives - so it cannot ride in
+    // MGPCaps::Dynamic and must come from kCapCpuXfbPrimitiveAccounting.
+    AdoptSnapshot(MakeSnapshot(kMGPipeSubsystemResources, 0));
+    EXPECT_FALSE(CapsMirrorInstance().PrefersCpuXfbPrimitiveAccounting());
+    AdoptSnapshot(MakeSnapshot(kMGPipeSubsystemResources, kCapCpuXfbPrimitiveAccounting));
+    EXPECT_TRUE(CapsMirrorInstance().PrefersCpuXfbPrimitiveAccounting());
+}
+
+// =====================================================================================
+// R-8: the liveness gates read the caps mirror, and a family with no consumer says so
+// =====================================================================================
+
+TEST(CapsMirrorTest, AMaskWithoutAFamilyRefusesItAndNamesIt) {
+    // R-8's NEGATIVE CONTROL. "The client emits nothing for a family the server does not
+    // consume" is, on its own, indistinguishable from "nothing called it" - so the refusal is
+    // COUNTED at the one funnel that answers the question, and the count is what this asserts.
+    AdoptSnapshot(MakeSnapshot(kMGPipeSubsystemPrograms, 0));
+    ResetConsumerRefusalsForTest();
+
+    EXPECT_TRUE(CapsMirrorInstance().ServerConsumes(kMGPipeSubsystemPrograms));
+    EXPECT_EQ(ConsumerRefusals(), 0u) << "a family the server DOES consume must not be counted "
+                                         "as refused";
+
+    EXPECT_FALSE(CapsMirrorInstance().ServerConsumes(kMGPipeSubsystemResources));
+    EXPECT_EQ(ConsumerRefusals(), 1u);
+    EXPECT_EQ(LastRefusedSubsystem(), kMGPipeSubsystemResources)
+        << "the refusal must name the family; a counter that only says 'something was withheld' "
+           "cannot tell five silent families apart";
+
+    EXPECT_FALSE(CapsMirrorInstance().ServerConsumes(kMGPipeSubsystemTextureResources));
+    EXPECT_EQ(ConsumerRefusals(), 2u);
+    EXPECT_EQ(LastRefusedSubsystem(), kMGPipeSubsystemTextureResources);
+}
+
+TEST(CapsMirrorTest, APlaceholderMirrorConsumesNothing) {
+    // The safe direction, stated as a case. With no snapshot the mask is zero, every family
+    // answers "no consumer", the client emits nothing and the legacy pull path runs. The unsafe
+    // direction - emitting to a server that has no consumer - is ID-39's 66 lost uploads.
+    MGPCaps empty{};
+    CapsMirror mirror;
+    EXPECT_FALSE(mirror.Valid());
+    EXPECT_FALSE(mirror.ServerConsumes(kMGPipeSubsystemResources));
+    EXPECT_FALSE(mirror.ServerConsumes(kMGPipeSubsystemPrograms));
+    EXPECT_FALSE(mirror.HasCap(kCapResidentSubData));
+    (void)empty;
+}
+
+TEST(CapsMirrorTest, TheConsumerBlockDoesNotCollideWithTheFeatureBits) {
+    // The two halves of CallMask, asserted against each other rather than against a constant:
+    // bits 0..8 are MGPCapBit and bits 32..47 are the consumer mask, and the whole reason R-8
+    // became implementable is that they do not overlap.
+    AdoptSnapshot(MakeSnapshot(kMGPipeSubsystemResources | kMGPipeSubsystemPrograms,
+                               kCapTimerQuery | kCapOcclusionQuery));
+    EXPECT_TRUE(CapsMirrorInstance().HasCap(kCapTimerQuery));
+    EXPECT_TRUE(CapsMirrorInstance().HasCap(kCapOcclusionQuery));
+    EXPECT_FALSE(CapsMirrorInstance().HasCap(kCapXfbPrimitivesQuery));
+    EXPECT_TRUE(CapsMirrorInstance().ServerConsumes(kMGPipeSubsystemResources));
+    EXPECT_TRUE(CapsMirrorInstance().ServerConsumes(kMGPipeSubsystemPrograms));
+    EXPECT_FALSE(CapsMirrorInstance().ServerConsumes(kMGPipeSubsystemSamplers));
+}
+
+// =====================================================================================
+// E2's emitter-drop control: the switch itself, driven through the real emitter's own counter
+// =====================================================================================
+
+TEST(RemoteEmitTable, TheE2DropSwitchStartsDisarmed) {
+    // The half a unit case can state. E2's statement - "drop one Clear emission and OpenRA's
+    // SSIM falls below 0.99" - is a TRACE LANE's, because the picture is the thing it is about;
+    // what belongs here is that the control is off unless someone armed it, so a lane that
+    // forgot to disarm cannot look like a lane that was never armed.
+    EXPECT_EQ(DroppedClearEmissions(), 0u);
+    SetDropClearEmissionForNegativeControl(true);
+    SetDropClearEmissionForNegativeControl(false);
+    EXPECT_EQ(DroppedClearEmissions(), 0u)
+        << "arming and disarming the control must not, by itself, drop anything";
+}
+
+int main(int argc, char** argv) {
+    namespace fs = std::filesystem;
+    const fs::path path =
+        fs::temp_directory_path() / ("mobilegl-remoteclient-test-" + std::to_string(ProcessId()) + ".log");
+    std::error_code ec;
+    fs::remove(path, ec);
+    g_logPath = path.string();
+#if defined(_WIN32)
+    _putenv_s("MOBILEGL_LOG_FILE_PATH", g_logPath.c_str());
+#else
+    setenv("MOBILEGL_LOG_FILE_PATH", g_logPath.c_str(), 1);
+#endif
+    ::testing::InitGoogleTest(&argc, argv);
+    const int rc = RUN_ALL_TESTS();
+    fs::remove(path, ec);
+    return rc;
+}