diff --git a/CLAUDE.md b/CLAUDE.md
index 753f15bddb..73d23dfbac 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -8,7 +8,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 Perry is a native TypeScript compiler written in Rust that compiles TypeScript source code directly to native executables. It uses SWC for TypeScript parsing and LLVM for code generation.
 
-**Current Version:** 0.5.1460
+**Current Version:** 0.5.1461
 
 
 ## TypeScript Parity Status
@@ -82,7 +82,8 @@ cargo build --release                          # Build all crates
 cargo build --profile perry-dev -p perry       # Fast local dev build (#5422; perry-dev profile)
 cargo build --release -p perry-runtime -p perry-stdlib  # Rebuild runtime (MUST rebuild stdlib too!)
 cargo build --release -p perry-runtime-static -p perry-stdlib-static  # Emit libperry_{runtime,stdlib}.a (#5422: runtime/stdlib are now rlib-only; the .a comes from these wrapper crates)
-cargo test --release --workspace \
+RUST_TEST_THREADS=1 cargo test --release -p perry-runtime   # MUST be single-threaded (see below)
+cargo test --release --workspace --exclude perry-runtime \
   --exclude perry-ui-ios --exclude perry-ui-tvos --exclude perry-ui-watchos \
   --exclude perry-ui-visionos --exclude perry-ui-android --exclude perry-ui-windows \
   --exclude perry-ui-gtk4   # Run tests (exclude cross-host UI crates on macOS)
@@ -236,6 +237,7 @@ Build outputs are invisible to `git status`, so a clean tree tells you nothing a
 - **addr-class ratchet** (`scripts/addr_class_inventory.py`) — a file gaining a bare-address site fails `lint`.
 - **`conformance-smoke` shards are flaky.** Before believing a red shard, re-run it and A/B the named tests against a pristine `main` build; several are already in `test-parity/known_failures.json`.
 - **Integration suites under `crates/*/tests/*.rs` do not run per-PR** (nightly/tag only) — a regression there can land green and sit red for days. Prefer putting acceptance coverage in `cargo-test`-visible unit tests (#5960).
+- **`perry-runtime`'s tests are not parallel-safe — run them `RUST_TEST_THREADS=1`.** They share process-global side tables (#1444), and ~180 readers are not required to take the clearing lock (see `gc::tests::global_sink_isolation`'s header; #7672 is converting them to `per_test_global!` one at a time). Every CI path already pins `RUST_TEST_THREADS=1`; a local `cargo test --workspace` does NOT, which is the whole gap. Measured on the default pool: 600 full-suite runs at `--test-threads=16` (load ~90) were clean, but at `--test-threads=64` (load ~115) **2 of 320 runs failed** — in `proxy::…numeric_write_guard…` and `array::element_shape::matrix_tests::matrix_delete_revokes`, neither related to the change under test. The tell is the message: these fail on their own *fixture precondition* ("fixture must start proven, or every verdict below is vacuous"), i.e. another thread wiped the global, not a real defect in the code under test. Chasing such a failure as if it were a regression is wasted days.
 
 ### ★ Four ways a gate can be unable to fail
 
diff --git a/Cargo.lock b/Cargo.lock
index 54362bfd8c..be4d2cedf5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5547,7 +5547,7 @@ checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
 
 [[package]]
 name = "perry"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "base64",
@@ -5607,14 +5607,14 @@ dependencies = [
 
 [[package]]
 name = "perry-api-manifest"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "perry-audio-miniaudio"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "cc",
  "libc",
@@ -5622,7 +5622,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "inkwell",
@@ -5639,7 +5639,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-arkts"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5647,7 +5647,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-glance"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5655,7 +5655,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-js"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "perry-dispatch",
@@ -5664,7 +5664,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-swiftui"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5672,7 +5672,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-wasm"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "base64",
@@ -5684,7 +5684,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-wear-tiles"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5692,7 +5692,7 @@ dependencies = [
 
 [[package]]
 name = "perry-container-compose"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -5721,14 +5721,14 @@ dependencies = [
 
 [[package]]
 name = "perry-container-e2e"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
 ]
 
 [[package]]
 name = "perry-diagnostics"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "serde",
  "serde_json",
@@ -5736,7 +5736,7 @@ dependencies = [
 
 [[package]]
 name = "perry-dispatch"
-version = "0.5.1460"
+version = "0.5.1461"
 
 [[package]]
 name = "perry-doc-fixture-my-bindings"
@@ -5747,7 +5747,7 @@ dependencies = [
 
 [[package]]
 name = "perry-doc-tests"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "clap",
@@ -5762,7 +5762,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ads"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "block2",
  "objc2",
@@ -5772,7 +5772,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-argon2"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "argon2",
  "perry-ffi",
@@ -5780,7 +5780,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-axios"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "reqwest",
@@ -5789,7 +5789,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-bcrypt"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "bcrypt",
  "perry-ffi",
@@ -5797,7 +5797,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-better-sqlite3"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "rusqlite",
@@ -5805,7 +5805,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-cheerio"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "scraper",
@@ -5813,7 +5813,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-commander"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "perry-runtime",
@@ -5821,7 +5821,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-cron"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "chrono",
  "cron",
@@ -5831,7 +5831,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-dayjs"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5839,7 +5839,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-decimal"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "rust_decimal",
@@ -5847,7 +5847,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-dotenv"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "serde_json",
@@ -5855,7 +5855,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ethers"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "rand 0.10.1",
@@ -5863,7 +5863,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-events"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "perry-runtime",
@@ -5871,14 +5871,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-exponential-backoff"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
 ]
 
 [[package]]
 name = "perry-ext-fastify"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "bytes",
  "http-body-util",
@@ -5896,7 +5896,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-fetch"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "bytes",
  "lazy_static",
@@ -5909,7 +5909,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-http"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "bytes",
  "h2",
@@ -5933,7 +5933,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ioredis"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "lazy_static",
  "perry-ffi",
@@ -5943,7 +5943,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-jsonwebtoken"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "base64",
  "jsonwebtoken",
@@ -5954,7 +5954,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-lru-cache"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "lru",
  "perry-ffi",
@@ -5963,7 +5963,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-moment"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5971,7 +5971,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-mongodb"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "bson",
  "futures-util",
@@ -5983,7 +5983,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-mysql2"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5993,7 +5993,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-nanoid"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "nanoid",
  "perry-ffi",
@@ -6002,7 +6002,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-net"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "bytes",
  "perry-ffi",
@@ -6015,7 +6015,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-node-forge"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "const-oid 0.9.6",
  "der 0.7.10",
@@ -6034,7 +6034,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-nodemailer"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "lettre",
  "perry-ffi",
@@ -6044,7 +6044,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-pdf"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "printpdf",
@@ -6052,7 +6052,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-pg"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "sqlx",
@@ -6061,7 +6061,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ratelimit"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "governor",
  "perry-ffi",
@@ -6069,7 +6069,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-sharp"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "fast_image_resize",
  "image",
@@ -6079,14 +6079,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-slugify"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
 ]
 
 [[package]]
 name = "perry-ext-streams"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "lazy_static",
  "perry-ffi",
@@ -6095,7 +6095,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-undici"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "perry-runtime",
@@ -6104,7 +6104,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-uuid"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "uuid",
@@ -6112,7 +6112,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-validator"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ffi",
  "regex",
@@ -6122,7 +6122,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ws"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "futures-util",
  "lazy_static",
@@ -6135,7 +6135,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-zlib"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "brotli",
  "flate2",
@@ -6145,7 +6145,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ffi"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "dashmap",
  "once_cell",
@@ -6154,7 +6154,7 @@ dependencies = [
 
 [[package]]
 name = "perry-hir"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "perry-api-manifest",
@@ -6172,7 +6172,7 @@ dependencies = [
 
 [[package]]
 name = "perry-parser"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "perry-diagnostics",
@@ -6184,7 +6184,7 @@ dependencies = [
 
 [[package]]
 name = "perry-runtime"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "base64",
@@ -6226,14 +6226,14 @@ dependencies = [
 
 [[package]]
 name = "perry-runtime-static"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-runtime",
 ]
 
 [[package]]
 name = "perry-stdlib"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "aes 0.8.4",
  "aes 0.9.1",
@@ -6328,14 +6328,14 @@ dependencies = [
 
 [[package]]
 name = "perry-stdlib-static"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-stdlib",
 ]
 
 [[package]]
 name = "perry-transform"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -6344,14 +6344,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ui"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ui-model",
 ]
 
 [[package]]
 name = "perry-ui-android"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "base64",
  "itoa",
@@ -6368,7 +6368,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-geisterhand"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "rand 0.10.1",
  "serde",
@@ -6378,7 +6378,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-gtk4"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "base64",
  "cairo-rs 0.22.0",
@@ -6401,7 +6401,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-ios"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "base64",
  "block2",
@@ -6417,7 +6417,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-macos"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "base64",
  "block2",
@@ -6432,7 +6432,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-model"
-version = "0.5.1460"
+version = "0.5.1461"
 
 [[package]]
 name = "perry-ui-test"
@@ -6443,11 +6443,11 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-testkit"
-version = "0.5.1460"
+version = "0.5.1461"
 
 [[package]]
 name = "perry-ui-tvos"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "base64",
  "block2",
@@ -6463,7 +6463,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-visionos"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "base64",
  "block2",
@@ -6479,7 +6479,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-watchos"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "block2",
  "libc",
@@ -6492,7 +6492,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-windows"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "base64",
  "libc",
@@ -6509,14 +6509,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-windows-winui"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "perry-ui-windows",
 ]
 
 [[package]]
 name = "perry-updater"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "anyhow",
  "base64",
@@ -6532,7 +6532,7 @@ dependencies = [
 
 [[package]]
 name = "perry-wasm-host"
-version = "0.5.1460"
+version = "0.5.1461"
 dependencies = [
  "wasmi",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 431c2eb967..be1119fc8d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -315,7 +315,7 @@ codegen-units = 16
 codegen-units = 16
 
 [workspace.package]
-version = "0.5.1460"
+version = "0.5.1461"
 edition = "2021"
 license = "MIT"
 repository = "https://github.com/PerryTS/perry"
diff --git a/changelog.d/7791-perry-runtime-tests-single-threaded.md b/changelog.d/7791-perry-runtime-tests-single-threaded.md
new file mode 100644
index 0000000000..635163cf88
--- /dev/null
+++ b/changelog.d/7791-perry-runtime-tests-single-threaded.md
@@ -0,0 +1,16 @@
+Document that `perry-runtime`'s tests must run single-threaded locally, matching what every CI path already does.
+
+**Why.** `gc::tests::root_words::bare_address_in_shadow_slot_survives_a_real_collection` was reported failing on a clean `c2a96b638` with the box at load ~111, passing in isolation and passing three full-suite reruns on a lightly loaded box. It was investigated as a possible load-dependent GC bug. It is not one.
+
+**What it actually is.** `perry-runtime`'s tests share process-global side tables. `test.yml` has pinned `RUST_TEST_THREADS=1` for this crate since #1444 — the comment there says the default pool "races the GC/threading tests into intermittent SIGSEGV" — and `gc::tests::global_sink_isolation`'s header records that ~180 readers are still not required to take the clearing lock (#7672 converts them to `per_test_global!` one table at a time). The command CLAUDE.md documented for local runs, `cargo test --release --workspace`, does not pin the thread count, so it runs this crate in exactly the configuration CI exists to avoid. That divergence is the bug being fixed here.
+
+**Evidence.** Against `2e5bf4434` (release, includes #7317 so the seeded-schedule machinery is present):
+
+- 4 × 150 full-suite runs at `--test-threads=16`, sustained load ~90: **600/600 clean**, 0 vacuous.
+- 4 × 80 full-suite runs at `--test-threads=64`, load ~115: **2 failures in 320** — `proxy::tests::object_array_numeric_write_guard_requires_complete_uniform_proof` and `array::element_shape::matrix_tests::matrix_delete_revokes`. Neither is `root_words`; the failing test is simply whichever one loses the race.
+- Both failures are the crate's own vacuity guards firing ("fixture must start proven, or every verdict below is vacuous"; "one-field loops should publish one non-zero 16-bit lane") — a test finding its *precondition* destroyed by a concurrent thread, not a GC invariant violated. That distinction is what rules out the GC-bug reading.
+- `root_words` itself did not fail once in 920 parallel full-suite runs, 1500 targeted `root_words`+`global_sink_isolation` pairings, or a 40-seed `PERRY_GC_SCHEDULE_SEED` sweep (rate 25%) — it never appears in that sweep's failures.
+
+So the reported symptom is real and load-dependent, but it belongs to the test harness, not the collector. No test is `#[ignore]`d and no retry is added: the fix is to stop documenting the unsupported configuration.
+
+**Note for the seeded-schedule sweep.** `PERRY_GC_SCHEDULE_SEED` is a whole-process env var, and `scripts/gc_schedule_fuzz.sh` takes a *compiled binary*, not the unit-test suite. Setting it across `cargo test` fails 8 GC tests at every seed (several assert the unset behaviour outright, e.g. `schedule::unset_is_inert_for_evacuation_policy`). That is the tool being used outside its contract, not a defect — recorded here so the next person does not re-derive it.