swung0x48 465656843b [Docs] (Disaggregated): P5f - every piece of state on the wire, and P6 is blocked until it is ...

P6's premise is that it is "only a transport swap". That premise was bought by P5c and has
expired. Measured on this head, the two roles still share state directly, so a spawned server
would have no source for it. P5f is the phase that makes the premise true, and P6 does not
start before it.

WHAT THE MEASUREMENT FOUND

- FieldOwnership.def still carries 21 BARRIER_PULLED rows over 15 distinct fields. That class
  is defined as "the server answers by reading a value the client's residual fill left in THE
  SINGLE SHARED gPipeInputs while the verb barrier holds both threads apart". Eight of those
  fields were retired by P5e for Espryt's unbarriered path only - Magma has not moved at all.
  The strict lane measures 10 live <field>@<verb> pairs today.
- gPipeInputs (MG_Backend/MGPipe/PipeInputs.h:835) is a plain process global,
  `inline PipeInputs& gPipeInputs = *new PipeInputs();` - not a shm segment. The client fills
  it (MG_Impl/Pipe/PipeFill.cpp), the backend reads it. Under spawn the two processes have
  DIFFERENT objects, the 15 BARRIER_PULLED fields have no filler in the server's copy, and
  every read is Fatal{UnmigratedPipeInput}. MG_Impl is not in the server, so "let the server
  fill it" is not available either. The header says this itself at :279 and :902.
- The twelve Server* EGL forwarders do not use the wire at all: they post a function pointer
  plus a stack-local void* through a one-slot mailbox (ServerLoop.cpp:533-568, :645). The
  SurfaceOp / SurfaceReply / WindowKind schema is defined in protocol.fbs and unused.
- Process-level statics with per-context semantics (g_syncedRenderStateParameters,
  ScopedDefaultUnpackState::s_synced) - and the full list is unknown, because this defect class
  is structurally invisible to inproc.
- MGPipeFrontendKeyedRegistryScope is still live at ~12 sites in DirectGLES.cpp, carrying
  P3b/P4b's debt: the registry is still keyed by frontend address / lifetime id.

THE SCOPE RULE

P5f takes the cross-process-blocking subset of P3b/P4b/P7/P8/P9 and nothing else. One test:
does it still hold in another address space? No -> P5f. Yes but slow or ugly -> it stays with
the phase that owns it. So Magma's nine fields and its direct writes into client storage come
here; content-addressed CSO, internal shader baking and the fixed-width rewrite stay P7's. The
reverse channel's asynchrony and ordering stay P9's; only the parts that touch client memory
move. Class C is NOT P5f's - a named refusal behaves identically in two processes.

THE CENTRAL MECHANISM: A TWO-BLOCK REHEARSAL

P5c set the same rule (rule E) and checked it by AUDIT - a human reading 59 lines. P5f checks
it by MACHINE: give each role its own PipeInputs under inproc, and its own copy of every
per-context static, behind a knob. Anything that depends on the two being the same object
becomes Fatal{UnmigratedPipeInput, "<Field>@<Verb>"} with the field and verb named.

That rehearses the process split's SEMANTICS without a second process. It matters because
today "the server read the value the client filled" and "the server read the value a record
carried" are indistinguishable at runtime - which is exactly what P6 would discover on day
one. The package order puts the mechanism (f1) BEFORE the migrations deliberately: let the red
appear first and let it be the worklist, rather than having each package declare itself done
and then looking for a criterion.

Exit gate: the two-block lane green; strict-expected-markers.txt EMPTY with its two-sided
ratchet still armed; zero BARRIER_PULLED rows; rsp reading zero per frame; Magma judged by the
same criteria as Espryt. The negative control is that turning the two-block knob OFF must move
at least one named case from green to red - otherwise the mechanism proves nothing, which is
ID-122's lesson.

ALSO IN THIS COMMIT

- ROADMAP gains the P5f row and the IPC track becomes P5e -> P5f -> P6; P6's status cell
  becomes "blocked on P5f".
- README and CURRENT_STAGE_PROGRESS gain the same, plus the file-map entry.
- Both P6 documents gain a blocked banner naming what is not true yet.

Doc citation lint: 124 citations across docs/Disaggregated/*.md, 0 problems.

2026-09-19 05:32:38 -04:00

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Disaggregated

[Docs] (Disaggregated): P5f - every piece of state on the wire, and P6 is blocked until it is

2026-09-19 05:32:38 -04:00