diff --git a/.claude/CLAUDE.md b/.claude/CLAUDE.md
index 791c26bc..12db728d 100644
--- a/.claude/CLAUDE.md
+++ b/.claude/CLAUDE.md
@@ -125,25 +125,31 @@ items 8-9. Run on **BOTH Mac AND Ubuntu x86_64**. No skipping.
 9. **versions.lock ↔ flake.nix consistency**: `bash scripts/sync-versions.sh`
    exits 0. Run automatically by `gate-merge.sh` and by the CI
    `versions-lock-sync` job.
-10. **Local bench record on Mac, every merge**: after the PR is squash-merged
+10. **Local bench record, every merge**: after the PR is squash-merged
     and main is checked out (`git checkout main && git pull --ff-only`),
     `bash scripts/record-merge-bench.sh` appends one row to
-    `bench/history.yaml` keyed on the merge commit SHA. Always full
-    hyperfine (5 runs + 3 warmup, ~5 min) — `bench/history.yaml` is the
-    canonical Mac M4 Pro absolute-time baseline used at tag time, so
-    every entry must be measurement-grade. Lower run/warmup counts are
-    only for `bench/run_bench.sh --quick`'s interactive smoke tests, not
-    for durable history. Skipped automatically on Linux/Windows because
-    the file's `env:` block is Darwin-only. Commit the resulting
+    `bench/history.yaml` keyed on the (merge SHA, target triple) pair.
+    Always full hyperfine (5 runs + 3 warmup, ~5 min) —
+    `bench/history.yaml` is the canonical absolute-time baseline used
+    at tag time, so every entry must be measurement-grade. Lower
+    run/warmup counts are only for `bench/run_bench.sh --quick`'s
+    interactive smoke tests, not for durable history. Multi-arch
+    (C-g, 2026-04-29): the script auto-detects `aarch64-darwin` /
+    `x86_64-linux` / `x86_64-windows` from `uname -s -m` and tags the
+    entry's `arch:` field accordingly; aarch64-darwin remains the
+    primary tag-time baseline, but Linux/Windows rows are encouraged
+    so cross-platform regressions surface early. Commit the resulting
     `history.yaml` change directly to main as a follow-up
-    `Record benchmark for <subject>` commit; CI runs but is not gating
-    for that small commit.
+    `Record benchmark for <subject>` commit; CI runs but is not
+    gating for that small commit.
 
 CI Linux runners separately enforce a soft regression check
 (`bench/ci_compare.sh --base=origin/main --threshold=20 --runs=3
---warmup=1` on PR, `continue-on-error: true`) — Ubuntu-vs-Ubuntu, never
-mixed with the Mac history. Treat the two baselines as independent
-artefacts, not as values to compare against each other.
+--warmup=1` on PR, `continue-on-error: true`) — Ubuntu-vs-Ubuntu only,
+the comparison is fresh-measured on the same runner. Compare entries
+in `bench/history.yaml` only within a single `arch:` series; the three
+target triples are independent artefacts, not values to compare
+against each other.
 
 Items 1-6 must pass on BOTH platforms before merge. Run them in parallel:
 Mac items can run locally, Ubuntu items via `orb run -m my-ubuntu-amd64`.
diff --git a/bench/history.yaml b/bench/history.yaml
index c97febc4..0f506d5e 100644
--- a/bench/history.yaml
+++ b/bench/history.yaml
@@ -6,11 +6,13 @@ env:
   ram: 48 GB
   os: Darwin 25.2.0
   tool: hyperfine
+  arch: aarch64-darwin
 entries:
   - id: "3.6"
     date: "2026-02-11"
     reason: "Baseline with all shootout (excl ed25519)"
     commit: "634f6e0"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 430.2}
@@ -33,6 +35,7 @@ entries:
     date: "2026-02-11"
     reason: "ARM64 function-level JIT: division, memory, rotation, CLZ/CTZ, select, sign-ext"
     commit: "cb82f94"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 338.8}
@@ -55,6 +58,7 @@ entries:
     date: "2026-02-11"
     reason: "Tiered execution: back-edge counting + lower call threshold"
     commit: "2e9fb74"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 331.0}
@@ -77,6 +81,7 @@ entries:
     date: "2026-02-11"
     reason: "JIT call optimization: fast JIT-to-JIT path"
     commit: "d6fecb7"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 234.4}
@@ -99,6 +104,7 @@ entries:
     date: "2026-02-11"
     reason: "JIT code quality: direct dest reg, selective reload, shared error epilogue"
     commit: "8e47ed0"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 223.6}
@@ -121,6 +127,7 @@ entries:
     date: "2026-02-11"
     reason: "Inline self-call with cached reg_ptr addr"
     commit: "377a73e"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 119.3}
@@ -143,6 +150,7 @@ entries:
     date: "2026-02-11"
     reason: "Spill-only-needed: caller-saved + arg vregs only"
     commit: "6db9491"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 103.0}
@@ -165,6 +173,7 @@ entries:
     date: "2026-02-11"
     reason: "Inline self-call for memory functions"
     commit: "a3722b1"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 102.7}
@@ -187,6 +196,7 @@ entries:
     date: "2026-02-11"
     reason: "doCallDirectIR regIR/JIT fast path for shootout callees"
     commit: "f5cc138"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 103.2}
@@ -209,6 +219,7 @@ entries:
     date: "2026-02-11"
     reason: "f64 ARM64 JIT codegen"
     commit: "24b3820"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 103.3}
@@ -231,6 +242,7 @@ entries:
     date: "2026-02-11"
     reason: "Stage 5 final — f64 JIT, regIR expansion"
     commit: "4dbb26e"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 115.8}
@@ -253,6 +265,7 @@ entries:
     date: "2026-02-11"
     reason: "Benchmark expansion (21 benchmarks)"
     commit: "9863277"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 110.5}
@@ -280,6 +293,7 @@ entries:
     date: "2026-02-12"
     reason: "Reg reuse, 14 phys regs, const-addr elision, write-tracked spills"
     commit: "093c524"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 98.4}
@@ -307,6 +321,7 @@ entries:
     date: "2026-02-12"
     reason: "SCRATCH/FP caches, inline call opts, peephole"
     commit: "6e9568a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 97.2}
@@ -334,6 +349,7 @@ entries:
     date: "2026-02-12"
     reason: "Stage 7 start: limits i64 decoding"
     commit: "b80674c"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 95.2}
@@ -361,6 +377,7 @@ entries:
     date: "2026-02-12"
     reason: "Stage 7 complete: memory64 table operations"
     commit: "b081800"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 94.1}
@@ -388,6 +405,7 @@ entries:
     date: "2026-02-12"
     reason: "Stage 12 complete: WAT parser + validateBodyEnd + E2E 100%"
     commit: "c467105"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 97.7}
@@ -415,6 +433,7 @@ entries:
     date: "2026-02-12"
     reason: "Stage 13 complete"
     commit: "76c0540"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 97.0}
@@ -442,6 +461,7 @@ entries:
     date: "2026-02-12"
     reason: "Stage 14 complete"
     commit: "ece72a9"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 96.9}
@@ -469,6 +489,7 @@ entries:
     date: "2026-02-12"
     reason: "Stage 15 baseline (multi-memory)"
     commit: "c886849"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 93.9}
@@ -496,6 +517,7 @@ entries:
     date: "2026-02-12"
     reason: "Stage 15 complete (multi-memory)"
     commit: "accb90c"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 94.3}
@@ -523,6 +545,7 @@ entries:
     date: "2026-02-12"
     reason: "Stage 16 relaxed SIMD complete"
     commit: "5054aee"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 95.9}
@@ -550,6 +573,7 @@ entries:
     date: "2026-02-12"
     reason: "Release v0.13.0"
     commit: "c383d45"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 90.9}
@@ -577,6 +601,7 @@ entries:
     date: "2026-02-13"
     reason: "Stage 16V complete: spec validation coverage"
     commit: "2c1011f"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 88.4}
@@ -604,6 +629,7 @@ entries:
     date: "2026-02-13"
     reason: "Stage 17 (Function References) complete"
     commit: "9b7a6be"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 92.9}
@@ -631,6 +657,7 @@ entries:
     date: "2026-02-13"
     reason: "Stage 18 GC complete"
     commit: "1dd02fe"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 95.6}
@@ -658,6 +685,7 @@ entries:
     date: "2026-02-13"
     reason: "Pre-v0.1.0 full benchmark"
     commit: "bf326f0"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 88.7}
@@ -685,6 +713,7 @@ entries:
     date: "2026-02-14"
     reason: "Stage 22 complete"
     commit: "f2a6dc0"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 96.4}
@@ -712,6 +741,7 @@ entries:
     date: "2026-02-14"
     reason: "Pre-v0.2.0 tag: Stages 20-22 complete"
     commit: "58cbb58"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 93.0}
@@ -739,6 +769,7 @@ entries:
     date: "2026-02-14"
     reason: "Liveness-aware spill/reload"
     commit: "6efe779"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 93.4}
@@ -766,6 +797,7 @@ entries:
     date: "2026-02-14"
     reason: "Guard pages for bounds check elimination"
     commit: "853fbe3"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 96.1}
@@ -793,6 +825,7 @@ entries:
     date: "2026-02-14"
     reason: "Stage 23.5 measure and tune complete"
     commit: "16f9a18"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 90.6}
@@ -820,6 +853,7 @@ entries:
     date: "2026-02-14"
     reason: "lightweight self-call"
     commit: "5effc85"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 57.5}
@@ -847,6 +881,7 @@ entries:
     date: "2026-02-15"
     reason: "Stage 26 peephole (fusion+MOVN, OP_MOV reverted)"
     commit: "162d84c"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 59.0}
@@ -874,6 +909,7 @@ entries:
     date: "2026-02-16"
     reason: "Stage 28 complete: spec fix batch + x86 JIT call spill"
     commit: "086779c"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 54.7}
@@ -901,6 +937,7 @@ entries:
     date: "2026-02-16"
     reason: "Stage 29 complete: threads"
     commit: "8dcc1f3"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 54.0}
@@ -928,6 +965,7 @@ entries:
     date: "2026-02-16"
     reason: "Stage 30 complete: perf gap analysis + u16 regs + MAX_PHYS_REGS 23"
     commit: "90de63e"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 54.1}
@@ -955,6 +993,7 @@ entries:
     date: "2026-02-16"
     reason: "Add GC benchmarks (gc_alloc, gc_tree)"
     commit: "97b2332"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 53.5}
@@ -984,6 +1023,7 @@ entries:
     date: "2026-02-16"
     reason: "GC arena + adaptive threshold (D121)"
     commit: "87f3a1f"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 54.1}
@@ -1013,6 +1053,7 @@ entries:
     date: "2026-02-16"
     reason: "v1.0.0 release baseline"
     commit: "1f4b215"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 53.9}
@@ -1042,6 +1083,7 @@ entries:
     date: "2026-02-18"
     reason: "Stage 44 complete"
     commit: "3784802"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 54.2}
@@ -1071,6 +1113,7 @@ entries:
     date: "2026-02-18"
     reason: "Stage 45 complete: SIMD performance engineering"
     commit: "1b90d00"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 50.9}
@@ -1100,6 +1143,7 @@ entries:
     date: "2026-02-18"
     reason: "v1.1.0 release"
     commit: "318365a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 52.7}
@@ -1129,6 +1173,7 @@ entries:
     date: "2026-02-26"
     reason: "Add real-world benchmark layer and fair benchmark defaults"
     commit: "b39b828"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 59.7}
@@ -1164,6 +1209,7 @@ entries:
     date: "2026-02-26"
     reason: "Revise reliability plan: zero tolerance, experiment-first, context efficiency"
     commit: "7531200"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 55.1}
@@ -1199,6 +1245,7 @@ entries:
     date: "2026-02-26"
     reason: "Add validation + import type checking to E2E runner (I.1, I.2)"
     commit: "b658a41"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 60.1}
@@ -1234,6 +1281,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix memory64 bulk ops and import is_64 checking (I.3, I.6)"
     commit: "eec6fa4"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 64.3}
@@ -1269,6 +1317,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix GC array alloc limit and externref encoding in E2E runner (I.4, I.5)"
     commit: "589a4db"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 59.3}
@@ -1304,6 +1353,7 @@ entries:
     date: "2026-02-26"
     reason: "Add thread/wait command support to E2E runner (I.7)"
     commit: "9dc57c0"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 57.2}
@@ -1339,6 +1389,7 @@ entries:
     date: "2026-02-26"
     reason: "Update handover: I.1-I.7 complete, E2E 792/792 (100%)"
     commit: "6752fde"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 57.6}
@@ -1374,6 +1425,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix JIT FP precision: getOrLoad must check dirty FP cache first (I.0)"
     commit: "be466a0"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 59.9}
@@ -1409,6 +1461,7 @@ entries:
     date: "2026-02-26"
     reason: "Update handover: Phase I complete, FP precision fixed"
     commit: "465146a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 56.6}
@@ -1444,6 +1497,7 @@ entries:
     date: "2026-02-26"
     reason: "Add x86 JIT division safety: zero check, overflow, signed rem fixup"
     commit: "61e1c4d"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 57.1}
@@ -1479,6 +1533,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix x86 JIT register clobbering in division and ABI call setup"
     commit: "a93d4ab"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 61.1}
@@ -1514,6 +1569,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix x86 JIT SCRATCH2/vreg10 register alias: reserve R11 for scratch only"
     commit: "9ec9434"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 60.5}
@@ -1549,6 +1605,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix call liveness analysis: treat rd as USE for return/store/branch"
     commit: "bad86de"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 59.5}
@@ -1584,6 +1641,7 @@ entries:
     date: "2026-02-26"
     reason: "Update handover: Phase J complete, all x86 JIT bugs fixed"
     commit: "be29897"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 56.1}
@@ -1619,6 +1677,7 @@ entries:
     date: "2026-02-26"
     reason: "Add select, br_table, trunc_sat JIT opcodes for ARM64 and x86_64"
     commit: "22859e2"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 62.2}
@@ -1654,6 +1713,7 @@ entries:
     date: "2026-02-26"
     reason: "Clarify W34 reentry guard comment: needs OSR for optimization"
     commit: "c01aa39"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 60.6}
@@ -1689,6 +1749,7 @@ entries:
     date: "2026-02-26"
     reason: "Add ARM64 JIT optimizations: FP-direct load/store, const-folded ADD/SUB"
     commit: "bf56424"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 61.5}
@@ -1724,6 +1785,7 @@ entries:
     date: "2026-02-26"
     reason: "Add ARM64 JIT div/rem-by-constant optimization (UMULL+LSR)"
     commit: "9261dbe"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 61.3}
@@ -1759,6 +1821,7 @@ entries:
     date: "2026-02-26"
     reason: "Update Phase K progress: div-by-constant done, gaps documented"
     commit: "a8db014"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 57.5}
@@ -1794,6 +1857,7 @@ entries:
     date: "2026-02-26"
     reason: "Optimize self-call setup: bypass shared prologue for self-call entry"
     commit: "26523a2"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 52.4}
@@ -1829,6 +1893,7 @@ entries:
     date: "2026-02-26"
     reason: "Update Phase K progress: self-call setup optimization results"
     commit: "9b54765"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 54.8}
@@ -1864,6 +1929,7 @@ entries:
     date: "2026-02-26"
     reason: "Eliminate redundant reg_ptr overflow check for self-call-only functions"
     commit: "9655e97"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 54.8}
@@ -1899,6 +1965,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix trunc_sat edge cases in x86_64 JIT and interpreter"
     commit: "a1acec0"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 49.8}
@@ -1934,6 +2001,7 @@ entries:
     date: "2026-02-26"
     reason: "Record K.5 benchmark results, update Phase H Gate status"
     commit: "999dfb3"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 49.0}
@@ -1969,6 +2037,7 @@ entries:
     date: "2026-02-26"
     reason: "Add x86_64 JIT self-call optimization"
     commit: "ced7c48"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 54.9}
@@ -2004,6 +2073,7 @@ entries:
     date: "2026-02-26"
     reason: "Add x86_64 JIT div-by-constant optimization"
     commit: "d010830"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 51.7}
@@ -2039,6 +2109,7 @@ entries:
     date: "2026-02-26"
     reason: "Update handover: x86_64 self-call and div-by-constant complete"
     commit: "fd30f76"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 48.8}
@@ -2074,6 +2145,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix ARM64 JIT: OSR support, FP cache self-clobber, globalGet x0 clobber"
     commit: "ee5f585"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 53.3}
@@ -2108,6 +2180,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix rw_c_string hang: skip back-edge JIT for reentry guard functions"
     commit: "b380c57"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 47.9}
@@ -2143,6 +2216,7 @@ entries:
     date: "2026-02-26"
     reason: "Fix nbody FP cache: expand D-reg cache D2-D15, FP-aware MOV"
     commit: "c34454a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 53.0}
@@ -2178,6 +2252,7 @@ entries:
     date: "2026-02-26"
     reason: "Re-measure rw_c_math: accept as regalloc limit (136 regs, 4.92x)"
     commit: "515c383"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.4}
@@ -2213,6 +2288,7 @@ entries:
     date: "2026-02-27"
     reason: "P4: GC JIT implementation (struct.new/get/set + ref.null/is_null)"
     commit: "244f2bf"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 47.8}
@@ -2248,6 +2324,7 @@ entries:
     date: "2026-02-27"
     reason: "R6: OSR for back-edge JIT — st_sieve 0.97x restored"
     commit: "6905eb7"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 49.5}
@@ -2283,6 +2360,7 @@ entries:
     date: "2026-02-27"
     reason: "Release v1.2.0"
     commit: "93d4a9e"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 52.1}
@@ -2318,6 +2396,7 @@ entries:
     date: "2026-03-02"
     reason: "Phase 1: guard pages + module cache (v1.3.0 candidate)"
     commit: "4de317d"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 50.8}
@@ -2353,6 +2432,7 @@ entries:
     date: "2026-03-02"
     reason: "Phase 1 with cache variants baseline"
     commit: "0176572"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 53.1}
@@ -2417,6 +2497,7 @@ entries:
     date: "2026-03-02"
     reason: "Release v1.3.0"
     commit: "3812372"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 52.4}
@@ -2481,6 +2562,7 @@ entries:
     date: "2026-03-03"
     reason: "Phase 8 merge: 5 JIT codegen fixes + 50 real-world programs"
     commit: "03a16fe"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 85.7}
@@ -2545,6 +2627,7 @@ entries:
     date: "2026-03-11"
     reason: "Suppress JIT when fuel metering active (no perf impact on normal execution)"
     commit: "83d1a33"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 49.6}
@@ -2609,6 +2692,7 @@ entries:
     date: "2026-03-11"
     reason: "Add timeout support (PR#6 + CLI + JIT deadline suppression)"
     commit: "c333873"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 50.5}
@@ -2673,6 +2757,7 @@ entries:
     date: "2026-03-15"
     reason: "PR #8 Windows first-class support + review fixes"
     commit: "6528ce4"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 47.5}
@@ -2737,6 +2822,7 @@ entries:
     date: "2026-03-22"
     reason: "W35 fix: emitGlobalSet ABI clobber + --interp + i32.store16"
     commit: "1429f81"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 51.5}
@@ -2801,6 +2887,7 @@ entries:
     date: "2026-03-23"
     reason: "198/256 SIMD opcodes native NEON (77% coverage)"
     commit: "f5e8a34"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 50.7}
@@ -2865,6 +2952,7 @@ entries:
     date: "2026-03-23"
     reason: "235/256 SIMD native (92%), all non-relaxed except shuffle"
     commit: "1c52db8"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 53.5}
@@ -2929,6 +3017,7 @@ entries:
     date: "2026-03-23"
     reason: "Phase 13.7: SIMD JIT benchmarks & wasmtime comparison"
     commit: "5ade595"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 50.8}
@@ -2993,6 +3082,7 @@ entries:
     date: "2026-03-23"
     reason: "W40 epoch JIT timeout + W37 contiguous v128 + W39 multi-value return"
     commit: "a3211ac"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 53.0}
@@ -3057,6 +3147,7 @@ entries:
     date: "2026-03-24"
     reason: "W38: HOT_THRESHOLD 10→3, extract_lane fix, back_edge_bailed"
     commit: "98a2827"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 50.8}
@@ -3121,6 +3212,7 @@ entries:
     date: "2026-03-24"
     reason: "W38 final: threshold=3 + all fixes"
     commit: "8085bab"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 57.0}
@@ -3185,6 +3277,7 @@ entries:
     date: "2026-03-25"
     reason: "Phase 20: written_vregs pre-scan fix — correctness fix, no perf change expected"
     commit: "126fa91"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.6}
@@ -3249,6 +3342,7 @@ entries:
     date: "2026-03-25"
     reason: "Phase 20 complete: remainder aliasing fix, Mac+Ubuntu 50/50"
     commit: "65db814"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 48.4}
@@ -3313,6 +3407,7 @@ entries:
     date: "2026-03-26"
     reason: "W44 SIMD register class: Q16-Q31 (ARM64) + XMM6-XMM15 (x86) cache for v128"
     commit: "e8d0317"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 47.3}
@@ -3377,6 +3472,7 @@ entries:
     date: "2026-03-26"
     reason: "Post W44+SIMD bench: verify no scalar regression"
     commit: "a642ae3"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.9}
@@ -3441,6 +3537,7 @@ entries:
     date: "2026-03-26"
     reason: "W45: SIMD Q-reg loop persistence (pre-header + flush stubs)"
     commit: "1e406db"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 48.6}
@@ -3505,6 +3602,7 @@ entries:
     date: "2026-04-15"
     reason: "Baseline after PR #32 (force_interpreter persistence) + #33 (spec-sha bump) + #35 (doc URL fix); reference for upcoming PR #30/#28 work"
     commit: "201d13c"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 48.5}
@@ -3569,6 +3667,7 @@ entries:
     date: "2026-04-21"
     reason: "Release v1.8.0 — Config-based module loading API"
     commit: "924c043"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 47.7}
@@ -3633,6 +3732,7 @@ entries:
     date: "2026-04-24"
     reason: "execution cancellation API (D134)"
     commit: "3bad07a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 48.8}
@@ -3697,6 +3797,7 @@ entries:
     date: "2026-04-24"
     reason: "Release v1.9.0 baseline"
     commit: "231c7ca"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 55.0}
@@ -3761,6 +3862,7 @@ entries:
     date: "2026-04-24"
     reason: "Release v1.9.1 baseline"
     commit: "078f8f2"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 48.2}
@@ -3825,6 +3927,7 @@ entries:
     date: "2026-04-24"
     reason: "Zig 0.16.0 migration baseline"
     commit: "1df937b"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 51.7}
@@ -3889,6 +3992,7 @@ entries:
     date: "2026-04-25"
     reason: "W46 Phase 2: route std.c.* through platform helpers"
     commit: "b168570"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 48.7}
@@ -3953,6 +4057,7 @@ entries:
     date: "2026-04-25"
     reason: "W48: panic handler trim + segfault disable + u8 main return"
     commit: "68a7067"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.2}
@@ -4017,6 +4122,7 @@ entries:
     date: "2026-04-26"
     reason: "loadCore errdefer for export_fns/cached_fns (issue #42)"
     commit: "dd7b43a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 44.9}
@@ -4081,6 +4187,7 @@ entries:
     date: "2026-04-26"
     reason: "Release v1.11.0"
     commit: "2386f22"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 44.0}
@@ -4145,6 +4252,7 @@ entries:
     date: "2026-04-29"
     reason: "docs: fresh-session simulation findings + Japanese strip"
     commit: "f9eb775"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.5}
@@ -4209,6 +4317,7 @@ entries:
     date: "2026-04-29"
     reason: "ci(windows): drop shared-lib guard — Plan C-a (#68)"
     commit: "8a3370c"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 47.0}
@@ -4273,6 +4382,7 @@ entries:
     date: "2026-04-29"
     reason: "ci(windows): drop static-lib + static-link guards — Plan C-d (#69)"
     commit: "8fd36ab"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.7}
@@ -4337,6 +4447,7 @@ entries:
     date: "2026-04-29"
     reason: "ci(windows): drop Rust example dynamic guard — Plan C-c (#71)"
     commit: "306c838"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.7}
@@ -4401,6 +4512,7 @@ entries:
     date: "2026-04-29"
     reason: "ci(windows): cross-platform binary size via -Dstrip=true — Plan C-e + C-f (#70)"
     commit: "8b17991"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.5}
@@ -4465,6 +4577,7 @@ entries:
     date: "2026-04-29"
     reason: "ci(windows): port FFI tests to Win32 — Plan C-b (#72)"
     commit: "29ba78a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.9}
@@ -4529,6 +4642,7 @@ entries:
     date: "2026-04-29"
     reason: "docs(decisions): D137 — cross-platform stripping + per-OS size ceilings (#73)"
     commit: "0d3b8f6"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.3}
@@ -4593,6 +4707,7 @@ entries:
     date: "2026-04-29"
     reason: "feat(windows): install-tools.ps1 — Rust / Go / TinyGo (W52) (#74)"
     commit: "6b89d0c"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.7}
@@ -4657,6 +4772,7 @@ entries:
     date: "2026-04-29"
     reason: "docs: align Merge Gate / runner forms / per-OS size ceilings (#75)"
     commit: "b742f51"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.2}
@@ -4721,6 +4837,7 @@ entries:
     date: "2026-04-29"
     reason: "docs: drop obsolete .dev/checklist-jit-fuel-timeout.md (#76)"
     commit: "2083573"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.3}
@@ -4785,6 +4902,7 @@ entries:
     date: "2026-04-29"
     reason: "docs: changelog [Unreleased] PR-tags + D137 + memo.md current-task refresh (#77)"
     commit: "09e890a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.4}
@@ -4849,6 +4967,7 @@ entries:
     date: "2026-04-29"
     reason: "docs(readme): W52 status + per-OS size ceilings (D137) (#78)"
     commit: "eb45994"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.4}
@@ -4913,6 +5032,7 @@ entries:
     date: "2026-04-29"
     reason: "docs+ci: trailing cleanup after #75..#78 (#79)"
     commit: "f7897fb"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.9}
@@ -4977,6 +5097,7 @@ entries:
     date: "2026-04-29"
     reason: "feat(flake): explicit URL+sha256 pins for wasm-tools + wasmtime (W50 PR-A) (#80)"
     commit: "5768928"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 47.7}
@@ -5041,6 +5162,7 @@ entries:
     date: "2026-04-29"
     reason: "ci: add test-nix Linux job using Nix devshell (W50 PR-B) (#81)"
     commit: "b23a013"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 45.3}
@@ -5105,6 +5227,7 @@ entries:
     date: "2026-04-29"
     reason: "ci: extend test-nix to macos-latest (W50 PR-C) (#82)"
     commit: "bb06753"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.6}
@@ -5169,6 +5292,7 @@ entries:
     date: "2026-04-29"
     reason: "ci: complete W50 — Windows install-tools.ps1 + restore extras (W50 PR-D) (#83)"
     commit: "3a9c47a"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.6}
@@ -5233,6 +5357,7 @@ entries:
     date: "2026-04-29"
     reason: "docs(w47): investigation note — variance dominates the +24 % signal (#84)"
     commit: "f087bab"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.0}
@@ -5297,6 +5422,7 @@ entries:
     date: "2026-04-29"
     reason: "fix(w53): route rustup-init stdout through Out-Host (#85)"
     commit: "52c7ce4"
+    arch: aarch64-darwin
     build: ReleaseSafe
     results:
       fib: {time_ms: 46.5}
diff --git a/bench/record.sh b/bench/record.sh
index 6014bd83..45e5da9c 100755
--- a/bench/record.sh
+++ b/bench/record.sh
@@ -28,6 +28,8 @@ RUNS=5
 WARMUP=3
 TIMEOUT=60  # per-benchmark timeout in seconds
 NO_CACHE=false
+# Auto-detected target triple. Resolved below; --arch=... overrides it.
+ARCH=""
 
 # --- Benchmark definitions: name:wasm:function:args:type ---
 # Keep in sync with run_bench.sh
@@ -85,6 +87,7 @@ for arg in "$@"; do
     --warmup=*)   WARMUP="${arg#--warmup=}" ;;
     --timeout=*)  TIMEOUT="${arg#--timeout=}" ;;
     --no-cache)   NO_CACHE=true ;;
+    --arch=*)     ARCH="${arg#--arch=}" ;;
     -h|--help)
       echo "Usage: bash bench/record.sh --id=ID --reason=REASON [OPTIONS]"
       echo ""
@@ -100,6 +103,8 @@ for arg in "$@"; do
       echo "  --warmup=N        Number of warmup runs (default: 3)"
       echo "  --timeout=SEC     Per-benchmark timeout (default: 60)"
       echo "  --no-cache        Skip cached variant measurements"
+      echo "  --arch=TRIPLE     Override the auto-detected target triple"
+      echo "                    (e.g. aarch64-darwin, x86_64-linux, x86_64-windows)"
       echo "  -h, --help        Show this help"
       exit 0
       ;;
@@ -134,11 +139,33 @@ if [[ -z "$ID" || -z "$REASON" ]]; then
   exit 1
 fi
 
-# --- Check for duplicate id ---
+# Resolve the target triple if the caller did not pass --arch=...
+if [[ -z "$ARCH" ]]; then
+  case "$(uname -s)-$(uname -m)" in
+    Darwin-arm64)        ARCH="aarch64-darwin" ;;
+    Darwin-x86_64)       ARCH="x86_64-darwin" ;;
+    Linux-x86_64)        ARCH="x86_64-linux" ;;
+    Linux-aarch64)       ARCH="aarch64-linux" ;;
+    MINGW*-x86_64|MSYS*-x86_64|CYGWIN*-x86_64) ARCH="x86_64-windows" ;;
+    *)
+      echo "Error: cannot auto-detect target triple ($(uname -s)/$(uname -m))." >&2
+      echo "       Pass --arch=<triple> explicitly." >&2
+      exit 1
+      ;;
+  esac
+fi
+
+# --- Check for duplicate (id, arch) ---
+# An entry is identified by the (id, arch) tuple — the same merge SHA
+# can be recorded once per target triple. Older entries that predate
+# the multi-arch schema have an explicit `arch: aarch64-darwin` after
+# the C-g migration; we still default-fill aarch64-darwin in the
+# select below as a safety net for any hand-edited rows that omit
+# the field.
 if [[ -f "$HISTORY_FILE" ]] && ! $OVERWRITE; then
-  existing=$(yq ".entries[] | select(.id == \"$ID\") | .id" "$HISTORY_FILE" 2>/dev/null || echo "")
+  existing=$(yq ".entries[] | select(.id == \"$ID\" and (.arch // \"aarch64-darwin\") == \"$ARCH\") | .id" "$HISTORY_FILE" 2>/dev/null || echo "")
   if [[ -n "$existing" ]]; then
-    echo "Error: Entry '$ID' already exists. Use --overwrite to replace." >&2
+    echo "Error: Entry '$ID' already exists for arch '$ARCH'. Use --overwrite to replace." >&2
     exit 1
   fi
 fi
@@ -310,9 +337,10 @@ entries: []
 INITEOF
 fi
 
-# Remove existing entry if overwriting
+# Remove existing entry if overwriting (scoped to the current arch so
+# --overwrite never wipes a sibling row recorded on a different host).
 if $OVERWRITE; then
-  yq -i "del(.entries[] | select(.id == \"$ID\"))" "$HISTORY_FILE"
+  yq -i "del(.entries[] | select(.id == \"$ID\" and (.arch // \"aarch64-darwin\") == \"$ARCH\"))" "$HISTORY_FILE"
 fi
 
 # Build YAML entry fragment
@@ -322,6 +350,7 @@ id: "$ID"
 date: "$DATE"
 reason: "$REASON"
 commit: "$COMMIT"
+arch: $ARCH
 build: ReleaseSafe
 results:
 ENTRYEOF
diff --git a/scripts/record-merge-bench.sh b/scripts/record-merge-bench.sh
index a77411de..a903ed8e 100755
--- a/scripts/record-merge-bench.sh
+++ b/scripts/record-merge-bench.sh
@@ -2,29 +2,33 @@
 # scripts/record-merge-bench.sh — append a benchmark row to
 # bench/history.yaml for the current commit.
 #
-# Project policy: every merge to main gets one row. Run this after the
-# PR is merged and main is checked out locally, NOT before — the row
-# should reference the merge commit, not the branch tip.
+# Project policy: every merge to main gets one row per platform the
+# user has access to. Run this after the PR is merged and main is
+# checked out locally, NOT before — the row should reference the
+# merge commit, not the branch tip.
 #
-# Mac-only by design. bench/history.yaml's env block declares
-# `os: Darwin <version>` so cross-host entries would be misleading.
-# On Linux/Windows the script logs and exits 0 so it can sit in a
-# scripted post-merge flow without breaking it.
+# Multi-arch (C-g, 2026-04-29): bench/history.yaml stores entries for
+# every target triple side by side; each row carries `arch:`
+# (auto-detected from `uname -s -m`, override with --arch=...). Mac
+# aarch64-darwin remains the canonical absolute-time baseline used at
+# tag time, but x86_64-linux and x86_64-windows rows are encouraged
+# so that cross-platform regressions surface early.
 #
 # Usage:
-#   bash scripts/record-merge-bench.sh                 # full record (5 runs + 3 warmup)
-#   bash scripts/record-merge-bench.sh --reason="..."  # override default reason
+#   bash scripts/record-merge-bench.sh                       # full record (5 runs + 3 warmup)
+#   bash scripts/record-merge-bench.sh --reason="..."        # override default reason
+#   bash scripts/record-merge-bench.sh --arch=x86_64-linux   # explicit triple
 #
 # All arguments after the script are passed straight to
-# bench/record.sh. --id and --reason are auto-filled from the current
-# HEAD commit if you do not pass them explicitly.
+# bench/record.sh. --id, --reason, and --arch are auto-filled when
+# the caller does not pass them explicitly.
 #
 # Always use the default 5 runs + 3 warmup. bench/history.yaml is the
-# canonical Mac M4 Pro absolute-time baseline used at tag time; lower
-# run/warmup counts produce noisy / cold-cache-biased numbers that
-# distort the long-term trend graph. `bench/run_bench.sh --quick`
-# exists for interactive smoke tests — use that, not record.sh, when
-# you just want a fast local check.
+# canonical absolute-time baseline used at tag time; lower run/warmup
+# counts produce noisy / cold-cache-biased numbers that distort the
+# long-term trend graph. `bench/run_bench.sh --quick` exists for
+# interactive smoke tests — use that, not record.sh, when you just
+# want a fast local check.
 
 set -euo pipefail
 
@@ -34,20 +38,16 @@ source "$SCRIPT_DIR/lib/versions.sh"
 
 cd "$ZWASM_REPO_ROOT"
 
-if [ "$(uname)" != "Darwin" ]; then
-    echo "record-merge-bench: bench/history.yaml is Mac-specific (env: Darwin)." >&2
-    echo "                    Skipping on $(uname)." >&2
-    exit 0
-fi
-
-# Allow caller to override --id / --reason. We default-fill them from
-# git only when the caller did not pass either flag.
+# Allow caller to override --id / --reason / --arch. We default-fill
+# them from git / `uname` only when the caller did not pass them.
 have_id=false
 have_reason=false
+have_arch=false
 for arg in "$@"; do
     case "$arg" in
         --id=*)     have_id=true ;;
         --reason=*) have_reason=true ;;
+        --arch=*)   have_arch=true ;;
     esac
 done
 
@@ -58,6 +58,20 @@ fi
 if ! $have_reason; then
     extra_args+=("--reason=$(git log -1 --pretty=%s)")
 fi
+if ! $have_arch; then
+    case "$(uname -s)-$(uname -m)" in
+        Darwin-arm64)        extra_args+=("--arch=aarch64-darwin") ;;
+        Darwin-x86_64)       extra_args+=("--arch=x86_64-darwin") ;;
+        Linux-x86_64)        extra_args+=("--arch=x86_64-linux") ;;
+        Linux-aarch64)       extra_args+=("--arch=aarch64-linux") ;;
+        MINGW*-x86_64|MSYS*-x86_64|CYGWIN*-x86_64) extra_args+=("--arch=x86_64-windows") ;;
+        *)
+            echo "record-merge-bench: cannot auto-detect target triple ($(uname -s)/$(uname -m))." >&2
+            echo "                    Pass --arch=<triple> explicitly." >&2
+            exit 1
+            ;;
+    esac
+fi
 
 # Idempotent: if the auto-derived id already exists, the inner
 # bench/record.sh will refuse without --overwrite. That's intentional