- 3rdparty/flatbuffers submodule pinned to the latest release tag v25.12.19 (7e163021). The runtime is header-only, so only 3rdparty/flatbuffers/include is ever used and no library is linked; CMake never calls add_subdirectory on it and flatc is not in the build graph (plan B section 8.1, inheriting the earlier plan's section 7.1).
- MobileGL/MG_Remote/Protocol/protocol.fbs carries the CONTROL PLANE only: SegmentRef, Hello, Welcome, CapsSnapshot, DefaultFramebufferInfo, SurfaceOp, SurfaceReply, ResyncRequest, ResyncDone, AuxRequest, Fatal, LogLine, union CtrlMsg and the CtrlEnvelope root with a file_identifier. Hot-path records are FlatBuffers structs generated from MG_Pipe/PipeCalls.def in a later package and are deliberately absent here, so record numbering never churns.
- Two deviations from the earlier plan's section 7.1 sketch, both deliberate: (a) ProgramReflection is not a union member - plan B ships program artifacts inside the create_shader_state CSO blob (section 8.2), and union tags are wire values that may only ever be appended, so reserving a tag for a message that may never exist is worse than appending one later; (b) maxComputeWorkGroupCount/Size are vectors, not [int:3] - fixed-size arrays are legal only in FlatBuffers structs, never in tables.
- scripts/gen_protocol.py resolves flatc as MOBILEGL_FLATC_EXECUTABLE, otherwise builds the pinned flatc ONCE into <repo>/../flatc-build (override with MOBILEGL_FLATC_BUILD_DIR), outside the project build graph. A flatc found on PATH is deliberately refused and a version mismatch against the pinned runtime is a hard error: the generated header static_asserts FLATBUFFERS_VERSION, so a stray flatc either fails to compile or churns the committed file on every machine. The earlier branch did the opposite - Protocol/CMakeLists.txt:22-38 add_subdirectory'd the FlatBuffers tree with FLATBUFFERS_BUILD_FLATC=ON whenever MOBILEGL_FLATC_EXECUTABLE was unset, which is exactly the NDK trap it claimed to avoid (cross-compile an arm64 flatc, then run it on the host).
- protocol_generated.h is committed with the project source header prepended by the generator, so regeneration is byte-identical: verified by running gen_protocol.py twice and by perturbing the file and regenerating it back.
- Reuse from Feat/CS-Delta-IPC: MobileGL/Protocol/mg_protocol_base.h, kept as the shared C vocabulary (result codes, byte spans, shm region, id typedefs) and keeping the structSize-first versioning discipline that section 14.2 calls the answer to risk B-R10. Dropped from it: MobileGLObjectKind / MobileGLObjectScope / MobileGLObjectHandle - plan B never puts GL object identity on the wire (the frontend allocates {slot, generation} handles in MG_Pipe, section 4.2.1), so a second identity vocabulary would be a drift surface with no reader. Added MOBILEGL_ERR_BUFFER_TOO_SMALL as an append-only code for the receive contract.
- Three P0 gates from plan B section 11, in one job that needs no build: a broken build
must not be able to hide a drifted interface.
- pipe-gen-check regenerates G1-G7 and runs git diff --exit-code over
MobileGL/MG_Pipe/generated. Since all seven generators read the same .def files, this is
what makes drift between them impossible rather than merely unlikely.
- The stdio gate refuses fprintf(stderr and printf( under MG_Backend and MG_State. Nothing
there matches today, so it lands with NO whitelist - verified with a negative control
that fprintf(stderr and std::printf both trip it while snprintf does not. Per-draw
instrumentation has been committed by accident before, once inside a mutex critical
section, and MGLOG_D is the channel these trees are allowed to use because it compiles
out in INFO builds.
- scripts/gen_pipe_dirty_surface.py reports the frontend mutation surface corollary 4
needs covered: 926 mutator calls under MG_Impl/GLImpl over 73 distinct mutators, of
which only 92 sit in a function that also reaches the backend. The other 834 are
published by the NEXT verb, which is precisely the population that needs an aggregate
generation. Informational in P0; it becomes a gate in P1 when there is a mapping file to
diff against.
- scripts/check_doc_citations.py resolves every `path:line` citation against a git
revision. It reproduces the failure that motivated it - the plan's first draft cited
SamplerObject.h:468-492 in a 160-line file - and reports 84 unresolved citations out of
1028 in docs/Disaggregated today, which is why CI runs it warning-only until those
documents settle. --strict exits 1, verified in both directions.
- Plan B section 4 makes the frontend/backend boundary explicit and gives the backend its
own state machine. This is the P0 deliverable of section 11: the whole catalogue exists
from day one, placeholders included, because the wire opcode is a call's position in
PipeCalls.def and record numbering must never churn.
- MG_Pipe/PipeCalls.def is the single source of truth: 68 unique calls as
X(Name, Payload, Class, Flags). Its header reconciles that number with the plan's
headline counts (section 4.4, appendix A), which double count - "CSO 15" names
bind_sampler_states and set_sampler_views that the "set_* 17" list also names, "screen
14" tabulates the query family that section 4.3 assigns to the context, and the
"transfer 12" row enumerates 11 calls. Each reconciliation is written down next to the
count rather than resolved silently.
- MGPipeHandles.h: the 8-byte {slot, gen} pair, dense per-kind slots, the reserved null
and default-framebuffer handles, and the ShaderCso composite band (sections 4.2, 5.6.3).
The two generations are documented as strictly separate, with the interface rule that no
call may require the client to know MGGen.
- MGPipeTypes.h: every payload of section 4.5 as a flat POD with explicit padding, a
trivial-copyability assertion and an exact sizeof assertion, because the wire records are
memcpy'd and a field silently changing width is a protocol break no test would see.
MGPCaps embeds DynamicBackendParameters by inclusion so a caps field added there needs no
second edit here; its assertion is stated as a composition because that struct still
carries SizeT. ResidualValueBlock is pinned at MGL_RESIDUAL_BLOCK_SIZE 1248, the ratchet
that only ever goes down and reaches static_assert(... == 0) in P13 (section 6.3).
- MGPipeHostSpan.h keeps the one shape that changes with the transport isolated behind one
predictable branch, with the kFromServerIndexMirror sentinel D-B7 needs.
- MGPipeCallbacks.h names the reverse channel as ten callbacks plus the forward terminator
in the context table, replacing 95 poke sites across 17 methods (section 7.1).
- scripts/gen_pipe.py runs G1-G7 off those .def files. G1 asserts each table is EXACTLY its
call count of function pointers; G3 pads every wire record to the stream's 8-byte
granularity and checks size >= sizeof && size <= remaining && size % 8 == 0 before
dispatch, fatally; G4 compares field by field (padding excluded, floats by bits) because
a comparator with false positives is one nobody reads - DirectGLES.cpp says the same
thing about its own memcmp of RenderStateParameters; G5 turns the accessor list into
per-verb poison generations rather than a written-once bitmap, which is the only version
that can see a field left over from the previous draw (section 6.2.2); G6 joins the 477
read points of the vendored backend_read_inventory.md against Coverage.def and reports
0 UNMAPPED (299 to a call, 167 signatures that become handle parameters, 6 reverse
channel, 5 client-resolved); G7 pins the pipeline subset BY MEMBER NAME from what
VulkanRenderer::ComputePipelineStateHash hashes today, computing no offsets in python.
- The generated files are committed so the build never depends on python; CI regenerates
and diffs them.
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