diff --git a/CLAUDE.md b/CLAUDE.md
index fbfff02673..33850c1792 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:** 0.5.1426
+**Current Version:** 0.5.1427
 
 
 ## TypeScript Parity Status
diff --git a/Cargo.lock b/Cargo.lock
index a34a2d893d..d68b86a9a0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5547,7 +5547,7 @@ checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
 
 [[package]]
 name = "perry"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "base64",
@@ -5607,14 +5607,14 @@ dependencies = [
 
 [[package]]
 name = "perry-api-manifest"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "perry-audio-miniaudio"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "cc",
  "libc",
@@ -5622,7 +5622,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "inkwell",
@@ -5639,7 +5639,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-arkts"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5647,7 +5647,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-glance"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5655,7 +5655,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-js"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "perry-dispatch",
@@ -5664,7 +5664,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-swiftui"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5672,7 +5672,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-wasm"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "base64",
@@ -5684,7 +5684,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-wear-tiles"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5692,7 +5692,7 @@ dependencies = [
 
 [[package]]
 name = "perry-container-compose"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -5721,14 +5721,14 @@ dependencies = [
 
 [[package]]
 name = "perry-container-e2e"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
 ]
 
 [[package]]
 name = "perry-diagnostics"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "serde",
  "serde_json",
@@ -5736,7 +5736,7 @@ dependencies = [
 
 [[package]]
 name = "perry-dispatch"
-version = "0.5.1426"
+version = "0.5.1427"
 
 [[package]]
 name = "perry-doc-fixture-my-bindings"
@@ -5747,7 +5747,7 @@ dependencies = [
 
 [[package]]
 name = "perry-doc-tests"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "clap",
@@ -5762,7 +5762,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ads"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "block2",
  "objc2",
@@ -5772,7 +5772,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-argon2"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "argon2",
  "perry-ffi",
@@ -5780,7 +5780,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-axios"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "reqwest",
@@ -5789,7 +5789,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-bcrypt"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "bcrypt",
  "perry-ffi",
@@ -5797,7 +5797,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-better-sqlite3"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "rusqlite",
@@ -5805,7 +5805,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-cheerio"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "scraper",
@@ -5813,7 +5813,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-commander"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "perry-runtime",
@@ -5821,7 +5821,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-cron"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "chrono",
  "cron",
@@ -5831,7 +5831,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-dayjs"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5839,7 +5839,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-decimal"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "rust_decimal",
@@ -5847,7 +5847,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-dotenv"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "serde_json",
@@ -5855,7 +5855,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ethers"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "rand 0.10.1",
@@ -5863,7 +5863,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-events"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "perry-runtime",
@@ -5871,14 +5871,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-exponential-backoff"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
 ]
 
 [[package]]
 name = "perry-ext-fastify"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "bytes",
  "http-body-util",
@@ -5896,7 +5896,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-fetch"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "bytes",
  "lazy_static",
@@ -5909,7 +5909,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-http"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "bytes",
  "h2",
@@ -5933,7 +5933,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ioredis"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "lazy_static",
  "perry-ffi",
@@ -5943,7 +5943,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-jsonwebtoken"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "base64",
  "jsonwebtoken",
@@ -5954,7 +5954,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-lru-cache"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "lru",
  "perry-ffi",
@@ -5963,7 +5963,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-moment"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5971,7 +5971,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-mongodb"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "bson",
  "futures-util",
@@ -5983,7 +5983,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-mysql2"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5993,7 +5993,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-nanoid"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "nanoid",
  "perry-ffi",
@@ -6002,7 +6002,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-net"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "bytes",
  "perry-ffi",
@@ -6015,7 +6015,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-node-forge"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "const-oid 0.9.6",
  "der 0.7.10",
@@ -6034,7 +6034,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-nodemailer"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "lettre",
  "perry-ffi",
@@ -6044,7 +6044,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-pdf"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "printpdf",
@@ -6052,7 +6052,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-pg"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "sqlx",
@@ -6061,7 +6061,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ratelimit"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "governor",
  "perry-ffi",
@@ -6069,7 +6069,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-sharp"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "fast_image_resize",
  "image",
@@ -6079,14 +6079,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-slugify"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
 ]
 
 [[package]]
 name = "perry-ext-streams"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "lazy_static",
  "perry-ffi",
@@ -6095,7 +6095,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-undici"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "perry-runtime",
@@ -6104,7 +6104,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-uuid"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "uuid",
@@ -6112,7 +6112,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-validator"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ffi",
  "regex",
@@ -6122,7 +6122,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ws"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "futures-util",
  "lazy_static",
@@ -6135,7 +6135,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-zlib"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "brotli",
  "flate2",
@@ -6145,7 +6145,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ffi"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "dashmap",
  "once_cell",
@@ -6154,7 +6154,7 @@ dependencies = [
 
 [[package]]
 name = "perry-hir"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "perry-api-manifest",
@@ -6172,7 +6172,7 @@ dependencies = [
 
 [[package]]
 name = "perry-parser"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "perry-diagnostics",
@@ -6184,7 +6184,7 @@ dependencies = [
 
 [[package]]
 name = "perry-runtime"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "base64",
@@ -6226,14 +6226,14 @@ dependencies = [
 
 [[package]]
 name = "perry-runtime-static"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-runtime",
 ]
 
 [[package]]
 name = "perry-stdlib"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "aes 0.8.4",
  "aes 0.9.1",
@@ -6328,14 +6328,14 @@ dependencies = [
 
 [[package]]
 name = "perry-stdlib-static"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-stdlib",
 ]
 
 [[package]]
 name = "perry-transform"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -6344,14 +6344,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ui"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ui-model",
 ]
 
 [[package]]
 name = "perry-ui-android"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "base64",
  "itoa",
@@ -6368,7 +6368,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-geisterhand"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "rand 0.10.1",
  "serde",
@@ -6378,7 +6378,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-gtk4"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "base64",
  "cairo-rs 0.22.0",
@@ -6401,7 +6401,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-ios"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "base64",
  "block2",
@@ -6417,7 +6417,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-macos"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "base64",
  "block2",
@@ -6432,7 +6432,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-model"
-version = "0.5.1426"
+version = "0.5.1427"
 
 [[package]]
 name = "perry-ui-test"
@@ -6443,11 +6443,11 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-testkit"
-version = "0.5.1426"
+version = "0.5.1427"
 
 [[package]]
 name = "perry-ui-tvos"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "base64",
  "block2",
@@ -6463,7 +6463,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-visionos"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "base64",
  "block2",
@@ -6479,7 +6479,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-watchos"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "block2",
  "libc",
@@ -6492,7 +6492,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-windows"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "base64",
  "libc",
@@ -6509,14 +6509,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-windows-winui"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "perry-ui-windows",
 ]
 
 [[package]]
 name = "perry-updater"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "anyhow",
  "base64",
@@ -6532,7 +6532,7 @@ dependencies = [
 
 [[package]]
 name = "perry-wasm-host"
-version = "0.5.1426"
+version = "0.5.1427"
 dependencies = [
  "wasmi",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 5b083490b6..13413226ad 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -315,7 +315,7 @@ codegen-units = 16
 codegen-units = 16
 
 [workspace.package]
-version = "0.5.1426"
+version = "0.5.1427"
 edition = "2021"
 license = "MIT"
 repository = "https://github.com/PerryTS/perry"
diff --git a/changelog.d/7733-retain-live-set-major-pacing.md b/changelog.d/7733-retain-live-set-major-pacing.md
new file mode 100644
index 0000000000..39bc04d779
--- /dev/null
+++ b/changelog.d/7733-retain-live-set-major-pacing.md
@@ -0,0 +1,85 @@
+### gc: a heap where nothing dies stopped being marked over and over
+
+`gc-handoff/bench/retain.ts` builds a 3 M-element array of `{a, b}` records,
+keeps every one of them live, then sums a field. **Nothing is ever garbage**,
+and Perry spent **1.26 s of a 1.31 s run inside the collector** (96%). Node
+does it in 0.13 s. Two independent causes, both measured on the pinned quiet
+M1 against `c156f8a41`.
+
+#### Two full mark-sweeps that reclaimed 4 MB between them
+
+`PERRY_GC_TRACE=1 ./n_retain` before:
+
+| cycle | kind | pause | arena in-use before → after |
+|---|---|--:|---|
+| 3 | **full** | 160.6 ms | 67 → 63 MB |
+| 6 | **full** | 483.5 ms | 204 → 204 MB |
+
+`arena_growth_full_escalation_due` escalates a minor to a full once arena
+live-bytes pass K× (K = 2) the live set measured after the last full. Its own
+doc-comment claimed that "a workload with a legitimately large *stable* live
+set (retain-style) does not over-escalate — its arena hovers near its own
+baseline". `retain`'s live set is not stable, it **grows**: every doubling
+crosses the threshold, and each resulting full marks a heap where nothing has
+died. 644 ms of pause for 4 MB, and the second full moved arena in-use by
+exactly zero.
+
+So price a full by what it reclaims. A full that shrinks arena in-use by less
+than `MAJOR_PACING_PRODUCTIVE_YIELD_PCT` (20%) shifts the next escalation
+threshold left by one — capped at 2, so the multiplier tops out at 8× — and a
+productive full resets the shift to 0 in one step. The yield is deliberately
+measured on the **same** metric the escalation gate reads, so the two cannot
+disagree about whether a full helped, and it is deliberately scoped to
+*escalated* fulls: an explicit `gc()` never moves the backoff, or a
+`gc()`-in-a-loop test would drive it straight to the cap. Old-gen garbage is
+unaffected either way — `old_reclaim_pressure_due` still forces its own full.
+
+Churn-shaped workloads reclaim most of the heap on every full, hold the shift
+at 0, and are paced exactly as before.
+
+#### Every evacuated object took a process-global mutex to hash an empty map
+
+`object_static_prototype_owner_moved` — the `ObjectOverflowFields` move hook,
+run once per moved object — took a `Mutex<HashMap<usize, u64>>` and ran a
+SipHash `remove` against the residual `Object.setPrototypeOf` registry.
+
+That registry is empty in any program that never re-prototypes a
+non-meta-capable owner, and a latch already says so: `OBJECT_PROTOTYPES_NONEMPTY`,
+stored `Release` *before* the insert, and read by both siblings
+(`object_static_prototype`, `prune_dead_object_prototype_owners`). The move
+hook was the one reader that skipped it, so a 3 M-record promotion paid 2.5 M
+lock/unlock pairs and 2.5 M hash probes against an empty map. That is why a
+single-threaded benchmark profiled with `pthread_mutex_lock` and
+`std::hash::random::RandomState` in its top ten.
+
+#### The bug this nearly shipped as
+
+The first cut recorded the pre-full arena reading at the two
+`gc_start_budgeted_cycle_for_pressure` call sites. Both correct, both the wrong
+sites: the escalation the shipped safepoint path actually takes lives in
+`gc::gc_collect_minor_with_trigger_inner`, so the reading was never recorded,
+`update_major_pacing_backoff` early-returned on every cycle, and the change
+measured **1.31 s → 1.28 s** — the mutex fix alone — with every test green and
+the decision function correct in isolation.
+
+The recording now happens **inside** `arena_growth_full_escalation_due` on the
+`true` verdict, so a call site added later is priced by construction, and the
+GC trace gained a `major_pacing` block (`baseline_bytes`, `backoff_shift`,
+`escalate_above_bytes`) so the subject can be asserted live rather than
+inferred from a green run. That block is what showed the backoff sitting at 0
+through all seven cycles.
+
+#### Not fixed here, measured and named
+
+`retain` is still ~5× Node, and the residue is one number: **~220 ns of
+per-object bookkeeping for every promoted object** (2.5 M promotions on this
+workload), spread over `arena_alloc_gc_old`, `layout_transfer`,
+`old_page_account_promoted_object`, the move hooks, and two page-generation
+classifications per visited slot. The structural answer is V8-style whole-page
+promotion — relabel a nearly-all-live Eden block as old-gen instead of
+evacuating it object by object — which needs none of that per-object work.
+Second on the list: `gc::verify::restore_surviving_dirty_coverage` walks
+**every** slot of a parent on a pre-cycle dirty page, where the scan it repairs
+(`scan_dirty_object_slots`) walks only the slots on dirty pages — 8.8% of a
+pure-retain profile, re-walking the whole 3 M-element backing store on every
+minor.
diff --git a/crates/perry-runtime/src/gc/policy.rs b/crates/perry-runtime/src/gc/policy.rs
index 8c6a43ab0a..1451183889 100644
--- a/crates/perry-runtime/src/gc/policy.rs
+++ b/crates/perry-runtime/src/gc/policy.rs
@@ -865,6 +865,26 @@ thread_local! {
     /// Total arena in-use bytes measured right after the last FULL mark-sweep —
     /// the baseline for major-GC pacing (`arena_growth_full_escalation_due`).
     pub(super) static GC_LAST_FULL_ARENA_IN_USE_BYTES: Cell<usize> = const { Cell::new(0) };
+    /// Total arena in-use bytes measured when the last FULL mark-sweep STARTED.
+    /// Paired with `GC_LAST_FULL_ARENA_IN_USE_BYTES` to price what that full
+    /// actually reclaimed — see `GC_MAJOR_PACING_BACKOFF_SHIFT`.
+    pub(super) static GC_FULL_CYCLE_PRE_IN_USE_BYTES: Cell<usize> = const { Cell::new(0) };
+    /// Yield-adaptive backoff for major-GC pacing (#7726).
+    ///
+    /// `arena_growth_full_escalation_due` escalates a minor to a full once the
+    /// arena's live bytes pass K× the last full's live set. On a workload whose
+    /// live set genuinely GROWS — every record retained, nothing to reclaim —
+    /// that gate fires on the growth itself and buys nothing: measured on
+    /// `gc-handoff/bench/retain.ts`, the two escalated fulls cost 644 ms of a
+    /// 1.31 s run and moved arena in-use by 4 MB total, the second one by zero.
+    ///
+    /// So price each full by what it reclaimed and shift K left when the answer
+    /// is "almost nothing". A churn workload's fulls reclaim most of the heap,
+    /// keep the shift at 0, and pace exactly as before. The shift is capped and
+    /// resets on the first productive full, and it does not touch the
+    /// `OldReclaim` escalation — old-gen garbage still forces a full through
+    /// `old_reclaim_pressure_due` regardless of this backoff.
+    pub(super) static GC_MAJOR_PACING_BACKOFF_SHIFT: Cell<u32> = const { Cell::new(0) };
     /// Re-entrancy guard for the #5476 direct old-gen reclaim driven from
     /// `gc_check_trigger`: the full collection must not recursively trigger
     /// another reclaim if a hook it runs allocates.
@@ -1475,10 +1495,118 @@ pub(super) fn finish_full_old_reclaim_baseline() {
     // Record the TOTAL post-full live set for major-GC pacing (young+old): the
     // full sweep is the only collection that frees forwarding stubs, so this is
     // the "clean" size the arena returns to and the base for the K× growth gate.
-    GC_LAST_FULL_ARENA_IN_USE_BYTES.with(|bytes| bytes.set(crate::arena::arena_in_use_bytes()));
+    let post_in_use = crate::arena::arena_in_use_bytes();
+    GC_LAST_FULL_ARENA_IN_USE_BYTES.with(|bytes| bytes.set(post_in_use));
+    update_major_pacing_backoff(post_in_use);
     GC_OLD_RECLAIM_PENDING.with(|pending| pending.set(false));
 }
 
+/// Percent of the pre-full live set a full must reclaim to count as productive.
+/// Below this the next arena-growth escalation is pushed out (see
+/// `GC_MAJOR_PACING_BACKOFF_SHIFT`).
+/// Deliberately low. A full that reclaims 20% of the heap is still doing real
+/// work, and pushing its successor out would carry that garbage twice as long;
+/// the shape this exists for reclaims single-digit percent (5.9% and 0.0% on
+/// `retain.ts`). Raising it trades RSS for pause time.
+const MAJOR_PACING_PRODUCTIVE_YIELD_PCT: usize = 20;
+
+/// Cap on the backoff shift: the escalation multiplier tops out at
+/// `growth_num << 2`, i.e. 8× with the default `growth_num` of 2. Bounded so a
+/// long run of low-yield fulls cannot disable arena-growth pacing outright.
+const MAJOR_PACING_BACKOFF_SHIFT_MAX: u32 = 2;
+
+/// Record what the just-finished full reclaimed and adjust the pacing backoff.
+///
+/// `pre` is the arena in-use reading captured when the full cycle started
+/// (`note_full_cycle_started`); a full that shrinks it by less than
+/// `MAJOR_PACING_PRODUCTIVE_YIELD_PCT` shifts the next escalation threshold
+/// left by one, a productive full resets the shift to 0. Deliberately measured
+/// on the SAME metric the escalation gate reads (`arena_in_use_bytes`) so the
+/// two cannot disagree about whether a full helped.
+fn update_major_pacing_backoff(post_in_use: usize) {
+    let pre_in_use = GC_FULL_CYCLE_PRE_IN_USE_BYTES.with(|bytes| bytes.get());
+    if pre_in_use == 0 {
+        // No start reading (a full driven from a path that does not announce
+        // itself): leave the shift alone rather than guess a yield.
+        return;
+    }
+    GC_FULL_CYCLE_PRE_IN_USE_BYTES.with(|bytes| bytes.set(0));
+    let reclaimed = pre_in_use.saturating_sub(post_in_use);
+    let productive =
+        reclaimed.saturating_mul(100) / pre_in_use >= MAJOR_PACING_PRODUCTIVE_YIELD_PCT;
+    GC_MAJOR_PACING_BACKOFF_SHIFT.with(|shift| {
+        if productive {
+            shift.set(0);
+        } else {
+            shift.set(
+                shift
+                    .get()
+                    .saturating_add(1)
+                    .min(MAJOR_PACING_BACKOFF_SHIFT_MAX),
+            );
+        }
+    });
+}
+
+/// Announce the start of an ESCALATED full mark-sweep so
+/// `update_major_pacing_backoff` can price what it reclaimed. Called only from
+/// `arena_growth_full_escalation_due`, so an explicit `gc()` — whose yield says
+/// nothing about arena-growth pacing, and whose repeated use would otherwise
+/// drive the shift to its cap — never moves the backoff.
+fn note_full_cycle_started() {
+    GC_FULL_CYCLE_PRE_IN_USE_BYTES.with(|bytes| bytes.set(crate::arena::arena_in_use_bytes()));
+}
+
+/// Current arena-growth escalation backoff shift.
+#[cfg(any(feature = "diagnostics", test))]
+pub(super) fn major_pacing_backoff_shift() -> u32 {
+    GC_MAJOR_PACING_BACKOFF_SHIFT.with(|shift| shift.get())
+}
+
+/// `(post-full baseline bytes, backoff shift, arena in-use bytes needed to
+/// escalate the next minor to a full)` — emitted in the GC trace so a gate can
+/// prove the backoff actually engaged rather than merely that nothing threw.
+/// A zero baseline means no full has run yet, and the threshold is reported as
+/// 0 because the `baseline == 0` clause escalates unconditionally.
+#[cfg(feature = "diagnostics")]
+pub(super) fn major_pacing_snapshot() -> (usize, u32, usize) {
+    let (_floor, growth_num) = major_pacing_config();
+    let baseline = GC_LAST_FULL_ARENA_IN_USE_BYTES.with(|bytes| bytes.get());
+    let shift = major_pacing_backoff_shift();
+    let threshold = baseline.saturating_mul(growth_num.saturating_mul(1usize << shift));
+    (baseline, shift, threshold)
+}
+
+#[cfg(test)]
+pub(super) fn test_reset_major_pacing_backoff() {
+    GC_MAJOR_PACING_BACKOFF_SHIFT.with(|shift| shift.set(0));
+    GC_FULL_CYCLE_PRE_IN_USE_BYTES.with(|bytes| bytes.set(0));
+}
+
+/// The pre-full arena reading `arena_growth_full_escalation_due` recorded, or 0
+/// if it declined to escalate. Non-zero is the proof that the escalation is
+/// PRICED — without it the backoff cannot fire and the pacing silently reverts
+/// to the unconditional K× rule.
+#[cfg(test)]
+pub(super) fn test_major_pacing_pre_in_use_bytes() -> usize {
+    GC_FULL_CYCLE_PRE_IN_USE_BYTES.with(|bytes| bytes.get())
+}
+
+#[cfg(test)]
+pub(super) fn test_set_major_pacing_baseline(bytes: usize) -> usize {
+    GC_LAST_FULL_ARENA_IN_USE_BYTES.with(|cell| {
+        let previous = cell.get();
+        cell.set(bytes);
+        previous
+    })
+}
+
+#[cfg(test)]
+pub(super) fn test_note_full_cycle_reclaimed(pre_in_use: usize, post_in_use: usize) {
+    GC_FULL_CYCLE_PRE_IN_USE_BYTES.with(|bytes| bytes.set(pre_in_use));
+    update_major_pacing_backoff(post_in_use);
+}
+
 pub(super) fn gc_bump_malloc_trigger_with_snapshot(current: usize, bytes_now: usize) -> bool {
     let step = GC_MALLOC_COUNT_STEP.with(|c| c.get());
     GC_NEXT_MALLOC_TRIGGER.with(|c| c.set(current + step));
@@ -2404,11 +2532,13 @@ pub(super) fn test_start_budgeted_minor_fallback_state_with_trace(
 /// pay for a full, and by the K× ratio so a workload with a legitimately large
 /// *stable* live set (retain-style) does not over-escalate — its arena hovers
 /// near its own baseline, well under K×.
-pub(super) fn arena_growth_full_escalation_due() -> bool {
-    // Config is parsed ONCE — this runs on the minor-GC path, so no per-call
-    // env lookup / parse / String alloc. The env vars are for tuning and
-    // measurement (read at process start); defaults chosen so churn oscillates
-    // ~baseline..2×baseline and stays below node's peak.
+/// `(floor_bytes, growth_num)` for major-GC pacing.
+///
+/// Parsed ONCE — this runs on the minor-GC path, so no per-call env lookup /
+/// parse / String alloc. The env vars are for tuning and measurement (read at
+/// process start); defaults chosen so churn oscillates ~baseline..2×baseline
+/// and stays below node's peak.
+fn major_pacing_config() -> (usize, usize) {
     use std::sync::OnceLock;
     static CONFIG: OnceLock<(usize, usize)> = OnceLock::new();
     let &(floor_bytes, growth_num) = CONFIG.get_or_init(|| {
@@ -2426,6 +2556,29 @@ pub(super) fn arena_growth_full_escalation_due() -> bool {
             .unwrap_or(DEFAULT_GROWTH_NUM);
         (floor_bytes, growth_num)
     });
+    (floor_bytes, growth_num)
+}
+
+/// Every caller acts on a `true` by running a FULL immediately, so the pre-full
+/// arena reading is recorded HERE rather than at the call sites — that is what
+/// keeps the escalation and the pricing of its result from drifting apart.
+///
+/// The first cut of #7726 wired the two `gc_start_budgeted_cycle_for_pressure`
+/// sites by hand and missed the one in `gc::gc_collect_minor_with_trigger_inner`
+/// — which is the site the shipped safepoint path actually takes. The backoff
+/// then never fired, and the whole change measured as a 30 ms no-op on
+/// `retain.ts` while every test still passed. Recording inside the predicate
+/// makes a future call site correct by construction.
+pub(super) fn arena_growth_full_escalation_due() -> bool {
+    let due = arena_growth_full_escalation_due_inner();
+    if due {
+        note_full_cycle_started();
+    }
+    due
+}
+
+fn arena_growth_full_escalation_due_inner() -> bool {
+    let (floor_bytes, growth_num) = major_pacing_config();
     if floor_bytes == 0 {
         return false; // PERRY_GC_MAJOR_PACING_FLOOR_MB=0 disables the pacing
     }
@@ -2435,7 +2588,15 @@ pub(super) fn arena_growth_full_escalation_due() -> bool {
     }
     let baseline = GC_LAST_FULL_ARENA_IN_USE_BYTES.with(|bytes| bytes.get());
     // No full yet (baseline 0): bound the initial growth once we clear the floor.
-    baseline == 0 || in_use > baseline.saturating_mul(growth_num)
+    if baseline == 0 {
+        return true;
+    }
+    // Yield-adaptive: a full that reclaimed almost nothing pushes the next
+    // escalation out (`GC_MAJOR_PACING_BACKOFF_SHIFT`). Shift the multiplier,
+    // not the baseline, so one productive full restores the original pacing.
+    let shift = GC_MAJOR_PACING_BACKOFF_SHIFT.with(|shift| shift.get());
+    let growth = growth_num.saturating_mul(1usize << shift);
+    in_use > baseline.saturating_mul(growth)
 }
 
 fn gc_start_budgeted_cycle_for_pressure(progress_kind: GcProgressKind) -> Option<BudgetedGcCycle> {
diff --git a/crates/perry-runtime/src/gc/telemetry.rs b/crates/perry-runtime/src/gc/telemetry.rs
index 61d48cc690..4271d4e54e 100644
--- a/crates/perry-runtime/src/gc/telemetry.rs
+++ b/crates/perry-runtime/src/gc/telemetry.rs
@@ -1116,6 +1116,13 @@ impl GcCycleTrace {
         let allocator_maintenance_json =
             allocator_maintenance_json(self.allocator_maintenance, self.progress_kind);
         let steps_value = steps_json(self.steps_before, steps_after);
+        let (pacing_baseline, pacing_shift, pacing_threshold) =
+            super::policy::major_pacing_snapshot();
+        let major_pacing_json = serde_json::json!({
+            "baseline_bytes": pacing_baseline,
+            "backoff_shift": pacing_shift,
+            "escalate_above_bytes": pacing_threshold,
+        });
         serde_json::json!({
             "event": "gc_cycle",
             "collection_kind": self.collection_kind.as_str(),
@@ -1148,6 +1155,7 @@ impl GcCycleTrace {
             "debt": debt_json,
             "allocator_maintenance": allocator_maintenance_json,
             "steps": steps_value,
+            "major_pacing": major_pacing_json,
         })
     }
 
diff --git a/crates/perry-runtime/src/gc/tests/triggers.rs b/crates/perry-runtime/src/gc/tests/triggers.rs
index 06642565a8..b7a81ab507 100644
--- a/crates/perry-runtime/src/gc/tests/triggers.rs
+++ b/crates/perry-runtime/src/gc/tests/triggers.rs
@@ -667,3 +667,113 @@ fn polls_default_matches_codegen_mirror() {
         );
     }
 }
+
+// ───────────────────────────────────────────────────────────────────────────
+// Yield-adaptive major-GC pacing (#7726).
+//
+// `arena_growth_full_escalation_due` escalates a minor to a FULL once arena
+// live-bytes pass K× the last full's live set. On a monotonically growing
+// all-live heap that gate fires on the growth itself and reclaims ~nothing:
+// measured on `gc-handoff/bench/retain.ts`, the two escalated fulls cost 644 ms
+// of a 1.31 s run and moved arena in-use by 4 MB total — the second by zero.
+// So price each full by what it reclaimed and push the next escalation out when
+// the answer is "almost nothing".
+//
+// These assert the DECISION FUNCTION over recorded (pre, post) pairs, which is
+// the part a benchmark cannot pin: a green retain time proves the backoff fired
+// on that one shape, not that a productive full still resets it.
+// ───────────────────────────────────────────────────────────────────────────
+#[test]
+fn major_pacing_backoff_defaults_to_zero_and_needs_a_recorded_cycle_start() {
+    use super::super::policy::{
+        major_pacing_backoff_shift, test_note_full_cycle_reclaimed, test_reset_major_pacing_backoff,
+    };
+    test_reset_major_pacing_backoff();
+    assert_eq!(
+        major_pacing_backoff_shift(),
+        0,
+        "default pacing must be exactly today's: escalate at K× the baseline"
+    );
+    // A full with no recorded start (`note_full_cycle_started` never ran — an
+    // explicit `gc()`, not an arena-growth escalation) must not move the shift:
+    // its yield says nothing about the gate this backoff paces.
+    test_note_full_cycle_reclaimed(0, 0);
+    assert_eq!(major_pacing_backoff_shift(), 0);
+    test_reset_major_pacing_backoff();
+}
+
+#[test]
+fn major_pacing_backs_off_on_futile_fulls_and_resets_on_a_productive_one() {
+    use super::super::policy::{
+        major_pacing_backoff_shift, test_note_full_cycle_reclaimed, test_reset_major_pacing_backoff,
+    };
+    const MB: usize = 1024 * 1024;
+    test_reset_major_pacing_backoff();
+
+    // retain.ts's own two fulls: 67 MB → 63 MB (5.9%) and 204 MB → 204 MB (0%).
+    test_note_full_cycle_reclaimed(67 * MB, 63 * MB);
+    assert_eq!(
+        major_pacing_backoff_shift(),
+        1,
+        "a 5.9%-yield full backs off"
+    );
+    test_note_full_cycle_reclaimed(204 * MB, 204 * MB);
+    assert_eq!(
+        major_pacing_backoff_shift(),
+        2,
+        "a 0%-yield full backs off again"
+    );
+
+    // Capped: a long run of futile fulls must not disable pacing outright.
+    test_note_full_cycle_reclaimed(400 * MB, 400 * MB);
+    test_note_full_cycle_reclaimed(800 * MB, 800 * MB);
+    assert_eq!(major_pacing_backoff_shift(), 2, "the shift is capped");
+
+    // A churn-shaped full reclaims most of the heap and restores the original
+    // pacing immediately — the backoff is not a ratchet.
+    test_note_full_cycle_reclaimed(800 * MB, 200 * MB);
+    assert_eq!(
+        major_pacing_backoff_shift(),
+        0,
+        "a productive full resets the backoff in one step"
+    );
+
+    // Exactly at the threshold counts as productive (>=, not >).
+    test_note_full_cycle_reclaimed(100 * MB, 80 * MB);
+    assert_eq!(major_pacing_backoff_shift(), 0);
+    // One percent under it does not.
+    test_note_full_cycle_reclaimed(100 * MB, 81 * MB);
+    assert_eq!(major_pacing_backoff_shift(), 1);
+    test_reset_major_pacing_backoff();
+}
+
+/// The escalation and the pricing of its result must not be separable.
+///
+/// #7726's first cut recorded the pre-full reading at the two
+/// `gc_start_budgeted_cycle_for_pressure` call sites and missed the one in
+/// `gc::gc_collect_minor_with_trigger_inner` — the site the shipped safepoint
+/// path actually takes. Every test still passed, the decision function was
+/// correct in isolation, and the change measured as a 30 ms no-op on a
+/// benchmark it should have taken 480 ms off. The recording now lives INSIDE
+/// `arena_growth_full_escalation_due`; this pins that coupling, in the one
+/// direction a unit test can force without a 32 MB heap.
+#[test]
+fn declining_to_escalate_records_no_pre_full_reading() {
+    use super::super::policy::{
+        arena_growth_full_escalation_due, test_major_pacing_pre_in_use_bytes,
+        test_reset_major_pacing_backoff, test_set_major_pacing_baseline,
+    };
+    test_reset_major_pacing_backoff();
+    // A baseline no live arena can exceed forces the verdict to `false`.
+    let previous = test_set_major_pacing_baseline(usize::MAX / 4);
+    let due = arena_growth_full_escalation_due();
+    let recorded = test_major_pacing_pre_in_use_bytes();
+    test_set_major_pacing_baseline(previous);
+    test_reset_major_pacing_backoff();
+    assert!(!due, "an unreachable baseline must not escalate");
+    assert_eq!(
+        recorded, 0,
+        "a declined escalation must leave no pre-full reading behind — a stale \
+         one would price the NEXT full against the wrong heap"
+    );
+}
diff --git a/crates/perry-runtime/src/object/prototype_chain.rs b/crates/perry-runtime/src/object/prototype_chain.rs
index 55b75730cf..575ea3b899 100644
--- a/crates/perry-runtime/src/object/prototype_chain.rs
+++ b/crates/perry-runtime/src/object/prototype_chain.rs
@@ -340,6 +340,18 @@ pub(crate) fn object_static_prototype_owner_moved(old_owner: usize, new_owner: u
     if old_owner == 0 || new_owner == 0 || old_owner == new_owner {
         return;
     }
+    // The residual registry is EMPTY until a non-meta-capable owner records a
+    // prototype, and the latch is stored (`Release`) *before* that insert — so
+    // a `false` read here proves there is no entry to migrate. Its two sibling
+    // readers (`object_static_prototype`, `prune_dead_object_prototype_owners`)
+    // already gate on it; this one did not, so every evacuated object took a
+    // process-global `Mutex<HashMap>` and paid a SipHash probe against an empty
+    // map. On a promotion-heavy workload that is one lock + one hash per moved
+    // object (2.5 M of each on `gc-handoff/bench/retain.ts`), and it showed up
+    // as `pthread_mutex_lock` + `RandomState` in a single-threaded profile.
+    if !OBJECT_PROTOTYPES_NONEMPTY.load(Ordering::Acquire) {
+        return;
+    }
     if let Ok(mut map) = get_object_prototypes().lock() {
         if let Some(proto_bits) = map.remove(&old_owner) {
             map.insert(new_owner, proto_bits);