multitier_100k: 335k scenarios @ 1,115/sec against 100k corpus, 4/6 at 0% fail

J asked for a much more sophisticated test using the 100k corpus from
the Rust legacy database. This commit ships:

scripts/cutover/multitier/main.go — 6-scenario harness with weighted
random selection per goroutine. Mixes search, email/SMS/fill
validators (in-process via internal/validator), profile swap with
ExcludeIDs, repeat-cache exercise, and playbook record/replay.

Scenarios + weights (cumulative scenario fractions):
  35% cold_search_email      — search + email outreach + EmailValidator
  15% surge_fill_validate    — search + fill proposal + FillValidator + record
  15% profile_swap           — original search + ExcludeIDs swap + no-overlap check
  15% repeat_cache           — same query × 5 (cache effectiveness)
  10% sms_validate           — SMS draft (≤160 chars, phone for SSN-FP guard)
  10% playbook_record_replay — cold → record → warm w/ use_playbook=true

Test results (5-min sustained, conc=50, 100k workers indexed):
  TOTAL 335,257 scenarios @ 1,115/sec
  cold_search_email     117k @ 0.0% fail · p50 2.2ms · p99 8.6ms
  surge_fill_validate    50k @ 98.8% fail (substrate bug below)
  profile_swap           50k @ 0.0% fail · p50 4.5ms · ExcludeIDs verified
  repeat_cache           50k × 5 = 252k searches @ 0.0% fail · p50 11.7ms
  sms_validate           33k @ 0.0% fail · phone-pattern guard works
  playbook_record_replay 33k @ 96.8% fail (substrate bug below)
  Total successful workflows: ~250k+

Validator integration verified at load:
  150,930 EmailValidator passes across cold_search_email + sms_validate
  35 + 1,061 successful FillValidator + playbook_record (where the bug
    didn't fire)
  zero false positives on the SSN-pattern guard against phone numbers

Resource footprint at 100k:
  vectord 1.23GB RSS (linear with 100k vectors)
  matrixd 26MB, 75% CPU (1-core saturated at conc=50)
  Total across 11 daemons: 1.7GB
  Compare to Rust at 14.9GB — ~10× less even at 100k.

SUBSTRATE BUG SURFACED: coder/hnsw v0.6.1 nil-deref in
layerNode.search at graph.go:95. Triggers on /v1/matrix/playbooks/record
under sustained writes to the small playbook_memory index. Both Add
and Search paths can panic.

Workaround applied (this commit) in internal/vectord/index.go
BatchAdd: recover() guard converts panic to error; daemon stays up
instead of crashing the request handler.

Operator recovery procedure (also documented in the report):
  curl -X DELETE http://localhost:4215/vectors/index/playbook_memory
Next record recreates the index fresh.

Real fix DEFERRED — open in docs/ARCHITECTURE_COMPARISON.md
Decisions tracker. Three options:
  a) upstream patch to coder/hnsw
  b) custom small-index Add path that always rebuilds when len < threshold
  c) alternate store for playbook_memory (Lance? in-memory map?)

Evidence: reports/cutover/multitier_100k.md (full methodology +
results + repro + bug analysis). docs/ARCHITECTURE_COMPARISON.md
Decisions tracker updated.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

reports/cutover/SUMMARY.md

@@ -16,6 +16,7 @@ what's safe to flip. Append a row when a new endpoint clears parity.
 | **5-loop live through cutover slice** | 2026-05-01 | (none — pure substrate) | Bun `/_go/v1/matrix/search` + `/_go/v1/matrix/playbooks/record` | ✅ Math + Gate verified | First end-to-end learning loop through real Bun-frontend traffic. Cold dist 0.4449 → warm dist 0.2224 (BoostFactor=0.5 for score=1.0; 0.4449×0.5=0.2225 expected, 0.2224 observed — 4-decimal exact). Cross-role gate: Forklift recording does NOT bleed onto CNC Operator query (boosted=0, injected=0). Both substrate properties (Shape A boost + role gate) hold through 3 HTTP hops (Bun → gateway → matrixd). See `g5_first_loop_live.md`. |
 | **Production load test** | 2026-05-01 | (none — pure load probe) | Bun `/_go/v1/matrix/search` + direct Go `:4110` | ✅ 0 errors / 101k req | Three runs, **zero correctness errors**. Direct-to-Go: 2,772 RPS @ p50 2.5ms / p99 8.5ms (production-grade). Via Bun: 484 RPS @ p50 4.6ms / p99 92ms (Bun event-loop is the bottleneck — 5.7× RPS hit, 11× p99 inflation; substrate itself is fine). For staffing-domain demand (<1 RPS typical), Bun-fronted has 480× headroom. See `g5_load_test.md`. |
 | **Big load test (5K corpus, 200 bodies)** | 2026-05-01 | (none — pure load probe) | Direct Go `:4110/v1/matrix/search` + `:4110/v1/embed` | ✅ **0 errors / 5.87M req** | Concurrency sweep (10/50/100/200) + mixed embed+search workload. Peak: 8,114 RPS @ conc=200 (search). Mixed: 16,889 RPS combined. Saturation at conc=100+ — matrixd pegs 1 CPU core. **Total RSS ~370MB** across 11 daemons (40× lower than Rust 14.9G). matrixd identified as horizontal-scale target. See `g5_load_test_big.md`. |
+| **Multi-tier 100k (6 scenarios + validators)** | 2026-05-01 | (none — pure substrate probe) | Direct Go `:4110` mixed scenarios | ✅ 4/6 scenarios 0% fail · ⚠ 2/6 hit substrate bug | 335,257 scenarios in 5 min @ conc=50 (1,115/sec) against 100k corpus. **Validators integrated**: 150,930 EmailValidator passes (cold_search_email + sms_validate). 4 scenarios at 0% fail: cold_search_email (117k), profile_swap (50k, ExcludeIDs no-overlap verified), repeat_cache (50k × 5 = 252k cached searches), sms_validate (33k, phone-pattern guard works). 2 scenarios fail at `/v1/matrix/playbooks/record`: **coder/hnsw v0.6.1 nil-deref in `layerNode.search` on small playbook_memory index** under sustained writes. Recover guard added in vectord BatchAdd. Total RSS at 100k: 1.7GB (vs Rust 14.9GB — still ~10× lower). See `multitier_100k.md`. |
 
 ## Wire-format drift catalog