chore(backlog): TASK-42 acceptance criteria checked + implementation notes

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: ahrzb

backlog/tasks/task-42 - Specializer-M-interp-closure-compiled-IR-interpreter-the-oracle-backend.md

@@ -4,7 +4,7 @@ title: 'Specializer M-interp: closure-compiled IR interpreter (the oracle backen
 status: In Progress
 assignee: []
 created_date: '2026-07-25 02:31'
-updated_date: '2026-07-25 18:42'
+updated_date: '2026-07-25 19:18'
 labels: []
 milestone: m-7
 dependencies:
@@ -23,10 +23,10 @@ Implement the interpreter backend over the imperative IR (design doc §7): one p
 
 ## Acceptance Criteria
 <!-- AC:BEGIN -->
-- [ ] #1 Every IR instruction executes; the M-ir fixture programs all produce expected outputs
-- [ ] #2 Runs only verifier-accepted IR; rejects unverified programs
-- [ ] #3 No allocation during execution (arena-only for varlen), asserted by a test
-- [ ] #4 mise gate-specializer green
+- [x] #1 Every IR instruction executes; the M-ir fixture programs all produce expected outputs
+- [x] #2 Runs only verifier-accepted IR; rejects unverified programs
+- [x] #3 No allocation during execution (arena-only for varlen), asserted by a test
+- [x] #4 mise gate-specializer green
 <!-- AC:END -->
 
 ## Implementation Plan
@@ -38,3 +38,9 @@ Implement the interpreter backend over the imperative IR (design doc §7): one p
 4. Tests: all 5 M-ir fixtures executed against hand-computed inputs/statics/outputs; unverified-program rejection; counting global allocator asserts zero heap allocs on a warmed second run (arena/regs/builders reused); executor fuzz over gen::gen_program seeds with random inputs (no panics, |out| <= |in|, deterministic).
 5. Adversarial workflow (semantics vs spec, alloc discipline, trap/edge paths, fuzz), fix confirmed findings; gate green; stacked PR onto claude/duckdb-native-interpreter-36d016.
 <!-- SECTION:PLAN:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+Implemented in src/specializer/exec/ (mod.rs substrate + interp.rs + tests.rs). compile() verifies first; closures built in one pre-traversal; terminators interpreted as a small enum in the row loop; register slots densely remapped at compile. Semantics pins documented and every one tested. Adversarial pass (6 agents) found and I fixed: u32 arena-span wrap silently corrupting output past 4 GiB (offsets now usize), store.opt false-flag storing the live register instead of the pinned type default, unvalidated validity-lane length, sparse value ids inflating the register frame, and an overbroad zero-allocation claim (restated: warmth is per content profile, growth one-time+monotone). RunState.emitted added. cargo 65 tests; alloc-free steady state asserted via thread-local counting global allocator; 150-seed executor fuzz deterministic.
+<!-- SECTION:NOTES:END -->