diff --git a/frameworks/zix/Dockerfile b/frameworks/zix/Dockerfile
index 380552a68..692929f64 100644
--- a/frameworks/zix/Dockerfile
+++ b/frameworks/zix/Dockerfile
@@ -5,7 +5,7 @@ ARG RETRY=6
 ARG TARGETARCH
 ARG RETRY_DELAY=3
 ARG ZIG_VERSION=0.16.0
-ARG ZIX_VERSION=0.4.x
+ARG ZIX_VERSION=0.4.x-rc3
 RUN apk add --no-cache ca-certificates curl git tar xz
 
 RUN set -eu; \
@@ -19,9 +19,9 @@ RUN set -eu; \
     mv "/opt/zig-${ZIG_ARCH}-linux-${ZIG_VERSION}" /opt/zig
 ENV PATH="/opt/zig:${PATH}"
 
-# Vendor zix 0.4.x, separate layer so source-only rebuilds skip the fetch.
+# Vendor zix X.Y.Z, separate layer so source-only rebuilds skip the fetch.
 # The Http1 raw engine work this image needs (large-body drain plus the per-worker
-# response cache used by the /json endpoint) must be present on the 0.4.x branch.
+# response cache used by the /json endpoint) must be present on the X.Y.Z branch.
 # Four ordered attempts before giving up: curl the archive tarball from github then
 # codeberg, then a shallow git clone from github then codeberg. The github archive
 # redirects to codeload.github.com (which the benchmark runner may not resolve), so
diff --git a/frameworks/zix/meta.json b/frameworks/zix/meta.json
index e1f44d26d..b031b6910 100644
--- a/frameworks/zix/meta.json
+++ b/frameworks/zix/meta.json
@@ -3,7 +3,7 @@
   "language": "Zig",
   "type": "engine",
   "engine": "zix",
-  "description": "Zig HTTP/1.1 server on the zix.Http1 raw engine (no std.http). Shared-nothing: each worker runs its own SO_REUSEPORT accept plus level-triggered epoll loop and owns its connections. The /json endpoint serves from the per-worker response cache, and request bodies larger than the read buffer are drained rather than buffered.",
+  "description": "Zig HTTP/1.1 server on the zix.Http1 raw engine (no std.http). Shared-nothing: each worker runs its own SO_REUSEPORT multishot accept plus io_uring completion loop and owns its connections. The /json endpoint serves from the per-worker response cache, and request bodies larger than the read buffer are drained rather than buffered.",
   "repo": "https://github.com/prothegee/zix",
   "enabled": true,
   "tests": [
diff --git a/frameworks/zix/src/dataset.zig b/frameworks/zix/src/dataset.zig
index 9b0b8999e..4d12be803 100644
--- a/frameworks/zix/src/dataset.zig
+++ b/frameworks/zix/src/dataset.zig
@@ -1,5 +1,4 @@
 //! HttpArena: zix
-//! zix version: 0.4.x
 //!
 //! Dataset loader for the /json endpoint.
 //!
diff --git a/frameworks/zix/src/main.zig b/frameworks/zix/src/main.zig
index 093e37c91..90fe1bd22 100644
--- a/frameworks/zix/src/main.zig
+++ b/frameworks/zix/src/main.zig
@@ -1,13 +1,12 @@
 //! HttpArena: zix
-//! zix version: 0.4.x
 //!
 //! zix HttpArena HTTP/1.1 entry point.
 //!
-//! Intent: demonstrate zix.Http1 (URING dispatch model) against the HttpArena
+//! Intent: demonstrate zix.Http1 (EPOLL dispatch model) against the HttpArena
 //! HTTP/1.1 benchmark suite (baseline, pipelined, short-lived).
 //!
 //! Design choices:
-//! - rawIntercept: called before any header parsing for each URING request.
+//! - rawIntercept: called before any header parsing for each EPOLL request.
 //!   Handles /pipeline with zero parse overhead (direct byte-match + sink write),
 //!   direct byte-match before any parsing, avoiding the header scan loop. Routes that fall
 //!   through are handled by the Router dispatch with full parsing.
@@ -23,14 +22,25 @@ const dataset = @import("dataset.zig");
 
 const PORT: u16 = 8080;
 const LISTEN_IP: []const u8 = "::";
-const DISPATCH_MODEL: zix.Http1.DispatchModel = .EPOLL;
+const DISPATCH_MODEL: zix.Http1.DispatchModel = .URING;
 const KERNEL_BACKLOG: u31 = 16 * 1024;
-/// 4 KiB per-connection recv buffer (heap-allocated once at accept time).
-/// Benchmark requests are under 300 bytes. Halving from 16 KiB cuts the
-/// working set from 64 MiB to 16 MiB at 4096c, reducing cache pressure.
-/// Large upload bodies are drained by the engine in chunks, so headers
-/// (always < 4 KiB) are the only part that needs to fit.
-const MAX_RECV_BUF: usize = 4 * 1024;
+/// Per-machine tuning profile (ADR-041 increment 5). The dev box is 12 threads
+/// / 32 GB (lean, memory-bound), the competition box is 64 cores / 251 GB
+/// (throughput, RAM-abundant). Only the recv buffer differs: workers auto-scale
+/// (WORKERS = 0), and the backlog and cache are already sized for both. Select
+/// .throughput for the 64-core deployment.
+const Profile = enum { lean, throughput };
+const PROFILE: Profile = .lean;
+
+/// Per-connection recv buffer, heap-allocated once at accept time. .lean keeps
+/// 4 KiB to hold the working set small (benchmark requests are under 300 bytes,
+/// and large upload bodies are drained by the engine in chunks, so only headers,
+/// always < 4 KiB, must fit). .throughput raises it to 16 KiB for deeper
+/// pipelined batches per recv, which the RAM-abundant box absorbs.
+const MAX_RECV_BUF: usize = switch (PROFILE) {
+    .lean => 4 * 1024,
+    .throughput => 16 * 1024,
+};
 const MAX_HEADERS: u8 = 16;
 const WORKERS: usize = 0;
 
@@ -99,7 +109,7 @@ fn pipelineHandler(head: *const zix.Http1.ParsedHead, body: []const u8, fd: std.
     zix.Http1.fdWriteAll(fd, PIPELINE_RESP) catch {};
 }
 
-// Raw-request interceptor for the URING dispatch model. Called before any header
+// Raw-request interceptor for the EPOLL dispatch model. Called before any header
 // parsing on each inbound request. Handles /pipeline with zero parse overhead:
 // byte-matches the path directly on rem, then appends PIPELINE_RESP to the
 // coalescing RespSink. Unknown
diff --git a/site/data/baseline-4096.json b/site/data/baseline-4096.json
index 9e745ccb9..f55cc9a2d 100644
--- a/site/data/baseline-4096.json
+++ b/site/data/baseline-4096.json
@@ -1627,19 +1627,19 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 3654683,
-    "avg_latency": "1.12ms",
-    "p99_latency": "2.36ms",
-    "cpu": "6610.8%",
-    "memory": "395MiB",
+    "rps": 4492613,
+    "avg_latency": "911us",
+    "p99_latency": "1.19ms",
+    "cpu": "6413.1%",
+    "memory": "186MiB",
     "connections": 4096,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "229.97MB/s",
-    "input_bw": "282.32MB/s",
+    "bandwidth": "282.68MB/s",
+    "input_bw": "347.04MB/s",
     "reconnects": 0,
-    "status_2xx": 18273419,
+    "status_2xx": 22463065,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/baseline-512.json b/site/data/baseline-512.json
index b33c30c49..21f63b8ee 100644
--- a/site/data/baseline-512.json
+++ b/site/data/baseline-512.json
@@ -1627,19 +1627,19 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 3670251,
-    "avg_latency": "138us",
-    "p99_latency": "371us",
-    "cpu": "6426.7%",
-    "memory": "342MiB",
+    "rps": 4217982,
+    "avg_latency": "120us",
+    "p99_latency": "231us",
+    "cpu": "6348.6%",
+    "memory": "130MiB",
     "connections": 512,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "230.95MB/s",
-    "input_bw": "283.52MB/s",
+    "bandwidth": "265.42MB/s",
+    "input_bw": "325.83MB/s",
     "reconnects": 0,
-    "status_2xx": 18351256,
+    "status_2xx": 21089911,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/frameworks.json b/site/data/frameworks.json
index 6aa6c75da..6ae2d0cb5 100644
--- a/site/data/frameworks.json
+++ b/site/data/frameworks.json
@@ -915,7 +915,7 @@
   },
   "zix": {
     "dir": "zix",
-    "description": "Zig HTTP/1.1 server on the zix.Http1 raw engine (no std.http). Shared-nothing: each worker runs its own SO_REUSEPORT accept plus level-triggered epoll loop and owns its connections. The /json endpoint serves from the per-worker response cache, and request bodies larger than the read buffer are drained rather than buffered.",
+    "description": "Zig HTTP/1.1 server on the zix.Http1 raw engine (no std.http). Shared-nothing: each worker runs its own SO_REUSEPORT multishot accept plus io_uring completion loop and owns its connections. The /json endpoint serves from the per-worker response cache, and request bodies larger than the read buffer are drained rather than buffered.",
     "repo": "https://github.com/prothegee/zix",
     "type": "engine",
     "engine": "zix"
diff --git a/site/data/json-4096.json b/site/data/json-4096.json
index c4903c76d..85aae891e 100644
--- a/site/data/json-4096.json
+++ b/site/data/json-4096.json
@@ -1375,19 +1375,19 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 2396373,
-    "avg_latency": "865us",
-    "p99_latency": "3.70ms",
-    "cpu": "6464.5%",
-    "memory": "1.2GiB",
+    "rps": 2348626,
+    "avg_latency": "614us",
+    "p99_latency": "2.75ms",
+    "cpu": "5365.1%",
+    "memory": "290MiB",
     "connections": 4096,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "8.02GB/s",
-    "input_bw": "114.27MB/s",
-    "reconnects": 478596,
-    "status_2xx": 11981868,
+    "bandwidth": "7.86GB/s",
+    "input_bw": "111.99MB/s",
+    "reconnects": 468990,
+    "status_2xx": 11743130,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/limited-conn-4096.json b/site/data/limited-conn-4096.json
index 4a7bc63de..ea98cd9ee 100644
--- a/site/data/limited-conn-4096.json
+++ b/site/data/limited-conn-4096.json
@@ -1627,19 +1627,19 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 2748274,
-    "avg_latency": "1.38ms",
-    "p99_latency": "2.75ms",
-    "cpu": "6224.6%",
-    "memory": "1.5GiB",
+    "rps": 2751069,
+    "avg_latency": "1.35ms",
+    "p99_latency": "1.89ms",
+    "cpu": "5783.9%",
+    "memory": "237MiB",
     "connections": 4096,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "172.91MB/s",
-    "input_bw": "212.30MB/s",
-    "reconnects": 1374498,
-    "status_2xx": 13741371,
+    "bandwidth": "173.09MB/s",
+    "input_bw": "212.51MB/s",
+    "reconnects": 1375655,
+    "status_2xx": 13755345,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/limited-conn-512.json b/site/data/limited-conn-512.json
index 8f33957dc..580b731e3 100644
--- a/site/data/limited-conn-512.json
+++ b/site/data/limited-conn-512.json
@@ -1627,19 +1627,19 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 2535229,
-    "avg_latency": "187us",
-    "p99_latency": "687us",
-    "cpu": "5722.1%",
-    "memory": "482MiB",
+    "rps": 2740199,
+    "avg_latency": "170us",
+    "p99_latency": "403us",
+    "cpu": "5474.7%",
+    "memory": "150MiB",
     "connections": 512,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "159.53MB/s",
-    "input_bw": "195.84MB/s",
-    "reconnects": 1267619,
-    "status_2xx": 12676149,
+    "bandwidth": "172.36MB/s",
+    "input_bw": "211.67MB/s",
+    "reconnects": 1369714,
+    "status_2xx": 13700995,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/pipelined-4096.json b/site/data/pipelined-4096.json
index 4ca6975e5..a3a21860d 100644
--- a/site/data/pipelined-4096.json
+++ b/site/data/pipelined-4096.json
@@ -1598,18 +1598,18 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 49553494,
-    "avg_latency": "1.32ms",
-    "p99_latency": "2.80ms",
-    "cpu": "6562.4%",
-    "memory": "396MiB",
+    "rps": 55979164,
+    "avg_latency": "1.17ms",
+    "p99_latency": "1.79ms",
+    "cpu": "6454.4%",
+    "memory": "186MiB",
     "connections": 4096,
     "threads": 64,
     "duration": "5s",
     "pipeline": 16,
-    "bandwidth": "3.04GB/s",
+    "bandwidth": "3.44GB/s",
     "reconnects": 0,
-    "status_2xx": 247767474,
+    "status_2xx": 279895824,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/pipelined-512.json b/site/data/pipelined-512.json
index fd782d457..8284542a7 100644
--- a/site/data/pipelined-512.json
+++ b/site/data/pipelined-512.json
@@ -1598,18 +1598,18 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 49538550,
-    "avg_latency": "164us",
-    "p99_latency": "457us",
-    "cpu": "6412.0%",
-    "memory": "341MiB",
+    "rps": 53609380,
+    "avg_latency": "152us",
+    "p99_latency": "344us",
+    "cpu": "6399.9%",
+    "memory": "134MiB",
     "connections": 512,
     "threads": 64,
     "duration": "5s",
     "pipeline": 16,
-    "bandwidth": "3.04GB/s",
+    "bandwidth": "3.29GB/s",
     "reconnects": 0,
-    "status_2xx": 247692752,
+    "status_2xx": 268046903,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/static-1024.json b/site/data/static-1024.json
index f669a94b4..acbb53499 100644
--- a/site/data/static-1024.json
+++ b/site/data/static-1024.json
@@ -1255,18 +1255,18 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 2035469,
-    "avg_latency": "301.89us",
-    "p99_latency": "4.40ms",
-    "cpu": "5618.5%",
-    "memory": "351MiB",
+    "rps": 2025521,
+    "avg_latency": "300.92us",
+    "p99_latency": "3.21ms",
+    "cpu": "5488.4%",
+    "memory": "140MiB",
     "connections": 1024,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "31.01GB",
+    "bandwidth": "30.86GB",
     "reconnects": 0,
-    "status_2xx": 10380866,
+    "status_2xx": 10331115,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/static-4096.json b/site/data/static-4096.json
index 812992aaf..03ed9c3c4 100644
--- a/site/data/static-4096.json
+++ b/site/data/static-4096.json
@@ -1255,18 +1255,18 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 2036430,
-    "avg_latency": "1.06ms",
-    "p99_latency": "5.02ms",
-    "cpu": "5600.2%",
-    "memory": "417MiB",
+    "rps": 2036680,
+    "avg_latency": "1.05ms",
+    "p99_latency": "7.16ms",
+    "cpu": "5503.2%",
+    "memory": "195MiB",
     "connections": 4096,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "31.02GB",
+    "bandwidth": "31.03GB",
     "reconnects": 0,
-    "status_2xx": 10385893,
+    "status_2xx": 10386093,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/static-6800.json b/site/data/static-6800.json
index 9eab3178b..b23eaf756 100644
--- a/site/data/static-6800.json
+++ b/site/data/static-6800.json
@@ -1255,18 +1255,18 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 1984205,
-    "avg_latency": "1.77ms",
-    "p99_latency": "8.72ms",
-    "cpu": "5282.5%",
-    "memory": "496MiB",
+    "rps": 1986456,
+    "avg_latency": "1.75ms",
+    "p99_latency": "5.18ms",
+    "cpu": "5269.1%",
+    "memory": "241MiB",
     "connections": 6800,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "30.23GB",
+    "bandwidth": "30.26GB",
     "reconnects": 0,
-    "status_2xx": 10104695,
+    "status_2xx": 10111205,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/upload-256.json b/site/data/upload-256.json
index 9759686ff..8cc85c85b 100644
--- a/site/data/upload-256.json
+++ b/site/data/upload-256.json
@@ -1201,19 +1201,19 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 6701,
-    "avg_latency": "37.98ms",
-    "p99_latency": "44.40ms",
-    "cpu": "889.6%",
-    "memory": "380MiB",
+    "rps": 6661,
+    "avg_latency": "38.12ms",
+    "p99_latency": "45.10ms",
+    "cpu": "943.2%",
+    "memory": "130MiB",
     "connections": 256,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "466.17KB/s",
-    "input_bw": "53.15GB/s",
-    "reconnects": 6760,
-    "status_2xx": 33644,
+    "bandwidth": "463.46KB/s",
+    "input_bw": "52.83GB/s",
+    "reconnects": 6688,
+    "status_2xx": 33441,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0
diff --git a/site/data/upload-32.json b/site/data/upload-32.json
index da662a4e5..3c31ca373 100644
--- a/site/data/upload-32.json
+++ b/site/data/upload-32.json
@@ -1201,19 +1201,19 @@
   {
     "framework": "zix",
     "language": "Zig",
-    "rps": 8390,
-    "avg_latency": "3.78ms",
-    "p99_latency": "10.70ms",
-    "cpu": "1060.2%",
-    "memory": "337MiB",
+    "rps": 8185,
+    "avg_latency": "3.88ms",
+    "p99_latency": "10.90ms",
+    "cpu": "1065.4%",
+    "memory": "124MiB",
     "connections": 32,
     "threads": 64,
     "duration": "5s",
     "pipeline": 1,
-    "bandwidth": "584.22KB/s",
-    "input_bw": "66.55GB/s",
-    "reconnects": 8401,
-    "status_2xx": 42037,
+    "bandwidth": "569.93KB/s",
+    "input_bw": "64.92GB/s",
+    "reconnects": 8199,
+    "status_2xx": 41007,
     "status_3xx": 0,
     "status_4xx": 0,
     "status_5xx": 0