plan(vm): define wide local bytecode

plans/2026-08-09_architecture-plan-index.md

@@ -16,6 +16,7 @@
 | Compiler correctness | UTF-8 rewrite, parent-path normalization, nested source diagnostics, public entry-point parity | `2026-08-09_nested-module-correctness.md` | none |
 | Compiler architecture | Text rewrite, synthetic preludes, flat global symbols, basename identity, source ownership | `2026-08-09_semantic-module-system.md` | nested correctness |
 | Compiler/runtime correctness | Named script calls count separate callee frames as caller-live locals; aggregate overflow reports a sentinel; direct-only functions reserve hidden callable slots | `2026-08-11_frame-aware-local-allocation.md` | real script call frames; semantic module identities for cross-module use classification |
+| Bytecode/wire capacity | Genuine same-frame local pressure above 256 cannot be encoded or consumed consistently | `2026-08-11_wide-local-bytecode.md` | frame-aware local allocation and callable slot reduction |
 | VM ownership | Monolithic VM mixes engine/program/instance/run/host state | `2026-08-09_vm-runtime-decomposition.md` | static IDs |
 | Host lifecycle | Generic resource/operation code unused; IO/HTTP/SQLite duplicate lifecycle/cancellation | `2026-08-09_unified-host-lifecycle.md` | VM decomposition |
 | Execution contract | Return/event ambiguity, buffered-only events, string errors, fragmented terminal state | `2026-08-09_run-outcome-event-error-contract.md` | RunContext; host lifecycle for final cancellation integration |
@@ -69,21 +70,23 @@ Can run in parallel after their dependencies:
 3. Backend semantic convergence.
 4. Agent run lifecycle and durable state integration.
 
-### Local-slot correction route
+### Local-slot correction and capacity route
 
 This route is ordered independently of the host-lifecycle waves:
 
 1. Execute `2026-08-11_frame-aware-local-allocation.md` first. Land named-call frame-aware liveness and real-count diagnostics before direct-call/selective callable materialization.
 2. Verify the storage-shaped dispatch fixture stays below the short-bytecode ceiling and the true same-frame 257-local control still fails for the declared capacity reason.
+3. Execute `2026-08-11_wide-local-bytecode.md` only for genuine same-frame pressure. Preserve short opcode bytes and add VMBC/debug/backend support as one declared compatibility change.
 
-Exit gate: separate frames reuse relative slots, direct-only named functions do not require hidden callable locals, and aggregate diagnostics report actual counts.
+Exit gate: separate frames reuse relative slots, direct-only named functions do not require hidden callable locals, aggregate diagnostics report actual counts, and every runtime/tooling consumer agrees on short and wide local operands.
 
 ## Scope boundary
 
 - No plan adds compatibility decoding for pre-static-ID VMBC.
 - No plan adds agent/provider/platform policy to `rustscript`.
 - No agent plan defines VM internal implementation.
 - Correctness plans do not wait for structural refactors.
+- Wide-local capacity does not compensate for cross-frame liveness over-allocation; the frame-aware plan is a hard dependency.
 - Structural plans remove superseded transitional paths after migration; they do not retain dual long-term architectures.
 - New generic host functions require their own implementation plans; this index covers the architecture findings already identified.
 - Async host futures are driven by the embedding host. VM, HTTP, and IO do not own a private executor or synchronous polling scheduler.