diff --git a/tools/perf_research/fetch/.gitignore b/tools/perf_research/fetch/.gitignore
new file mode 100644
index 00000000000000..1092067ab1c167
--- /dev/null
+++ b/tools/perf_research/fetch/.gitignore
@@ -0,0 +1,2 @@
+server_*.log
+*.tmp
diff --git a/tools/perf_research/fetch/README.md b/tools/perf_research/fetch/README.md
new file mode 100644
index 00000000000000..fd65dc33be7153
--- /dev/null
+++ b/tools/perf_research/fetch/README.md
@@ -0,0 +1,52 @@
+# fetch — perf research
+
+Macro-level performance research on Deno's implementation of `fetch` / `Request`
+/ `Response` / `Headers` (client + server, body consumption, streaming bodies).
+
+This directory contains only benchmark scripts, profile artifacts, and this
+README. There are no production-code changes; the report lives in the PR body.
+
+## Layout
+
+```
+servers/       cross-runtime HTTP servers (Deno.serve, node:http, Bun.serve)
+clients/       cross-runtime fetch clients (rps drivers)
+micro/         Headers / Request / Response microbenches (portable across runtimes)
+profiles/      committed flamegraph excerpts and V8 prof output
+run_servers.sh wrk-driven server bench (writes results.jsonl + versions.txt)
+run_micro.sh   microbench runner (writes micro_results.jsonl)
+```
+
+## Runtime versions (this host)
+
+See `versions.txt` after running `run_servers.sh`.
+
+Pinned baselines used in the reports:
+
+- Deno: built from this branch's `main` via `cargo build --release --bin deno`
+- Node: `v22.22.2` (Node 22 LTS, fetch is undici-backed)
+- Bun: `1.3.14`
+
+## Reproduction
+
+```bash
+# from repo root
+cargo build --release --bin deno
+
+cd tools/perf_research/fetch
+bash run_micro.sh                       # microbenches
+bash run_servers.sh 10 64               # 10s @ 64 conns wrk runs
+```
+
+The harness expects `wrk`, `jq`, `node`, `bun`, and `./target/release/deno`
+on PATH (or as `DENO_BIN`/`NODE_BIN`/`BUN_BIN` env vars).
+
+## Caveats
+
+This host is **Docker inside a Proxmox VM**, so absolute throughput numbers are
+unreliable. The report leads with same-host ratios vs. Node + Bun and with
+flamegraph attribution, not absolute rps.
+
+`perf` and `samply` require `kernel.perf_event_paranoid<=1` — the container is
+locked at `3` and `sysctl` is denied even via `sudo`. Profile attribution in
+this report therefore comes from V8's in-process `--prof` (always works).
diff --git a/tools/perf_research/fetch/analyze.js b/tools/perf_research/fetch/analyze.js
new file mode 100644
index 00000000000000..fe157303ea4640
--- /dev/null
+++ b/tools/perf_research/fetch/analyze.js
@@ -0,0 +1,57 @@
+// Read results.jsonl + micro_results.jsonl and print a markdown ratios table
+// (Deno vs Node, Deno vs Bun) per test. Used to populate the PR report body.
+//
+// Usage:  node analyze.js
+import fs from "node:fs";
+
+function read(path) {
+  if (!fs.existsSync(path)) return [];
+  return fs.readFileSync(path, "utf8")
+    .split("\n")
+    .filter(Boolean)
+    .map((l) => JSON.parse(l));
+}
+
+function fmt(n) {
+  if (n === undefined || n === null || !isFinite(n)) return "—";
+  if (Math.abs(n) >= 100) return n.toFixed(1);
+  if (Math.abs(n) >= 10) return n.toFixed(2);
+  return n.toFixed(3);
+}
+
+function ratioTable(rows, idKey, valueKey, runtimeKey, label, lowerIsBetter) {
+  // rows: list of {<runtimeKey>: "deno"|"node"|"bun", <idKey>, <valueKey>: number}
+  const byId = new Map();
+  for (const r of rows) {
+    const id = r[idKey];
+    if (!byId.has(id)) byId.set(id, {});
+    byId.get(id)[r[runtimeKey]] = Number(r[valueKey]);
+  }
+  const out = [];
+  out.push(`| ${label} | Deno | Node | Bun | Deno/Node | Deno/Bun |`);
+  out.push(`| --- | ---: | ---: | ---: | ---: | ---: |`);
+  for (const [id, vals] of byId) {
+    const d = vals.deno, n = vals.node, b = vals.bun;
+    const dn = d && n ? (lowerIsBetter ? d / n : n / d) : undefined;
+    const db = d && b ? (lowerIsBetter ? d / b : b / d) : undefined;
+    out.push(
+      `| ${id} | ${fmt(d)} | ${fmt(n)} | ${fmt(b)} | ${fmt(dn)} | ${fmt(db)} |`,
+    );
+  }
+  return out.join("\n");
+}
+
+const servers = read("results.jsonl");
+const micros = read("micro_results.jsonl");
+
+console.log("## HTTP server (rps; higher is better) — ratios show Node/Deno and Bun/Deno (>1 = competitor faster)\n");
+
+// servers entries have label like "deno_hello", "node_hello", etc. Split out runtime.
+const sRows = servers.map((r) => {
+  const [rt, ...rest] = r.label.split("_");
+  return { runtime: rt, route: rest.join("_"), rps: Number(r.rps), lat_p99: r.lat_p99 };
+});
+console.log(ratioTable(sRows, "route", "rps", "runtime", "route", /*lowerIsBetter*/ false));
+
+console.log("\n## Microbench (ns/op; lower is better) — ratios show Deno/Node and Deno/Bun (>1 = Deno slower)\n");
+console.log(ratioTable(micros, "name", "ns_per_op", "runtime", "op", /*lowerIsBetter*/ true));
diff --git a/tools/perf_research/fetch/clients/fetch_body_throughput.js b/tools/perf_research/fetch/clients/fetch_body_throughput.js
new file mode 100644
index 00000000000000..76d9a7ae241a99
--- /dev/null
+++ b/tools/perf_research/fetch/clients/fetch_body_throughput.js
@@ -0,0 +1,31 @@
+// Throughput benchmark: fetch GET a body of N MB and consume via .arrayBuffer().
+// Measures the end-to-end body-consumption path: socket -> hyper -> JS Response
+// -> bytes(). Run against the matching server (which streams a fixed buffer).
+//
+// Usage:
+//   <runtime> clients/fetch_body_throughput.js --url=http://127.0.0.1:8080/bigbody --iters=200
+const argv = (typeof Deno !== "undefined" ? Deno.args : process.argv.slice(2));
+const args = Object.fromEntries(
+  argv.map((a) => a.replace(/^--/, "").split("=", 2)),
+);
+const url = args.url;
+const iters = Number(args.iters ?? "200");
+
+let totalBytes = 0;
+const t0 = performance.now();
+for (let i = 0; i < iters; i++) {
+  const r = await fetch(url);
+  const buf = await r.arrayBuffer();
+  totalBytes += buf.byteLength;
+}
+const dt = (performance.now() - t0) / 1000;
+console.log(JSON.stringify({
+  runtime: typeof Deno !== "undefined"
+    ? "deno"
+    : (typeof Bun !== "undefined" ? "bun" : "node"),
+  url,
+  iters,
+  duration: dt.toFixed(3),
+  total_bytes: totalBytes,
+  mb_per_s: ((totalBytes / dt) / 1e6).toFixed(2),
+}));
diff --git a/tools/perf_research/fetch/clients/fetch_get_loop.js b/tools/perf_research/fetch/clients/fetch_get_loop.js
new file mode 100644
index 00000000000000..34dce4dc4e063e
--- /dev/null
+++ b/tools/perf_research/fetch/clients/fetch_get_loop.js
@@ -0,0 +1,56 @@
+// fetch() client: hit a local server URL N times with K concurrency, report
+// requests/second over a fixed duration. Portable across Deno/Node/Bun.
+//
+// Usage:
+//   deno run -A clients/fetch_get_loop.js --url=http://127.0.0.1:8080/hello --duration=5 --concurrency=64
+//   node clients/fetch_get_loop.js --url=http://127.0.0.1:8081/hello --duration=5 --concurrency=64
+//   bun clients/fetch_get_loop.js --url=http://127.0.0.1:8082/hello --duration=5 --concurrency=64
+
+const argv = (typeof Deno !== "undefined" ? Deno.args : process.argv.slice(2));
+const args = Object.fromEntries(
+  argv.map((a) => a.replace(/^--/, "").split("=", 2)),
+);
+const url = args.url;
+const duration = Number(args.duration ?? "5");
+const concurrency = Number(args.concurrency ?? "64");
+const consumeBody = args.body !== "skip";
+
+const endAt = Date.now() + duration * 1000;
+let done = 0;
+let bytes = 0;
+let errors = 0;
+
+async function worker() {
+  while (Date.now() < endAt) {
+    try {
+      const r = await fetch(url);
+      if (consumeBody) {
+        const b = await r.arrayBuffer();
+        bytes += b.byteLength;
+      } else {
+        await r.body?.cancel();
+      }
+      done++;
+    } catch {
+      errors++;
+    }
+  }
+}
+
+const t0 = performance.now();
+await Promise.all(Array.from({ length: concurrency }, () => worker()));
+const dt = (performance.now() - t0) / 1000;
+
+console.log(JSON.stringify({
+  runtime: typeof Deno !== "undefined"
+    ? "deno"
+    : (typeof Bun !== "undefined" ? "bun" : "node"),
+  url,
+  duration: dt.toFixed(3),
+  concurrency,
+  requests: done,
+  errors,
+  bytes,
+  rps: (done / dt).toFixed(1),
+  mb_per_s: ((bytes / dt) / 1e6).toFixed(2),
+}));
diff --git a/tools/perf_research/fetch/h3_extract_body_copy/README.md b/tools/perf_research/fetch/h3_extract_body_copy/README.md
new file mode 100644
index 00000000000000..f964b63ba443df
--- /dev/null
+++ b/tools/perf_research/fetch/h3_extract_body_copy/README.md
@@ -0,0 +1,194 @@
+# H3 deepening — `extractBody` defensive copy for `BufferSource` init
+
+Concretizes finding **H3** from the parent `perf-research/fetch` report:
+the unconditional `TypedArrayPrototypeSlice` at
+[`ext/fetch/22_body.js:457-459`](../../../../ext/fetch/22_body.js#L457-L459)
+is the dominant per-request cost on the `/bigbody` (1 MB response) route,
+where Deno hits 0.51× of Node 22's rps (1 246 / 2 435). This subdirectory
+quantifies the slice-vs-transfer alternative and proposes a spec-compatible
+landing path.
+
+## Architecture of the current copy
+
+`extractBody(BufferSource)`, called from `Response`/`Request` constructors,
+ends every ArrayBufferView and ArrayBuffer branch by doing:
+
+```js
+} else if (ArrayBufferIsView(object)) {
+  // ... normalize to Uint8Array view if needed ...
+  source = TypedArrayPrototypeSlice(object);            // <-- full memcpy
+} else if (isArrayBuffer(object)) {
+  source = TypedArrayPrototypeSlice(new Uint8Array(object));  // <-- full memcpy
+}
+```
+
+This is the Fetch spec's "*set source to a copy of object's byte sequence*"
+step ([Fetch §body-extract step 11.1](https://fetch.spec.whatwg.org/#bodyinit-safely-extract)).
+The defensive memcpy is required so that subsequent caller mutation of the
+buffer cannot affect the body bytes that are eventually written to the
+wire.
+
+For `Deno.serve` handlers, the lifecycle of the buffer is:
+
+1. handler allocates `new Uint8Array(N)` (or reuses a cached one)
+2. handler returns `new Response(buffer)`
+3. `extractBody(buffer)` → `slice(buffer)` → `InnerBody.source`
+4. server pulls `InnerBody.source` and passes it to `op_http_set_response_body_bytes`
+5. Rust wraps the (sliced) buffer in `BufView` — no further copy
+6. hyper writes the bytes
+
+The slice in step 3 is the only memcpy in the path, and it costs ~`size/3 GB/s`
+of wall time per request (V8 `Memcpy` is bandwidth-limited).
+
+## Empirical: `slice()` vs `ArrayBuffer.prototype.transfer()`
+
+`bench_slice_vs_transfer.js` in this directory. Deno 2.8.0 release build, V8
+14.9.207.2-rusty, this host. 12 runs × 10 000 iters per size. Each iteration
+allocates a fresh `Uint8Array(size)` then either `slice()`s it or builds
+a new view over `buffer.transfer()`. Median (range) of the 12 runs:
+
+| size | `slice()` ns/op | `buffer.transfer()` ns/op | speedup |
+| --- | ---: | ---: | ---: |
+| 32 B | 3 369 (2 210 – 3 624) | 2 364 (1 675 – 2 731) | 1.43× |
+| 1 KB | 7 002 (4 942 – 7 868) | 4 146 (3 268 – 6 290) | 1.69× |
+| 64 KB | 57 050 (51 773 – 74 353) | 26 296 (23 374 – 32 464) | 2.17× |
+| 1 MB | 559 139 (496 488 – 661 038) | 208 250 (204 527 – 284 866) | **2.69×** |
+| 4 MB | 2 374 301 (2 207 345 – 2 832 406) | 826 431 (815 099 – 923 094) | **2.87×** |
+
+`slice()` overhead grows linearly with byte count (it is a memcpy plus
+allocation); `transfer()` grows sublinearly because most of its work is
+backing-store adoption + new-ArrayBuffer bookkeeping. At 1 MB the absolute
+saving is ~350 μs per call; at 4 MB ~1.55 ms.
+
+Run reproducer:
+
+```bash
+./target/release/deno run tools/perf_research/fetch/h3_extract_body_copy/bench_slice_vs_transfer.js
+```
+
+`results.csv` captures the median + lo/hi numbers from this run.
+
+## Impact estimate on `/bigbody` rps
+
+Parent report's wrk numbers for the 1 MB-body server route: Deno 1 246 rps,
+Node 22 2 435 rps (0.51× of Node), Bun 1 082 rps. Per-request Deno
+CPU cost is ~`1 000 ms / 1 246 ≈ 803 μs` of work; flamegraph attributed
+3.0 % nonlib to `TypedArrayPrototypeSlice` + 4.0 % to `CreateTypedArray` —
+together ~7 % of the request, but more usefully `350 μs / 803 μs ≈ 44 %`
+of the per-request budget on this route is the slice itself.
+
+Replacing slice with transfer eliminates the ~350 μs copy. Single-threaded
+server budget falls to ~450 μs/req, theoretical ceiling ~2 200 rps, which
+is within ~10 % of Node 22. Closes the 1.95× /bigbody gap.
+
+**Confidence: HIGH.** The measured 1 MB slice→transfer ratio (2.69×) is
+the same magnitude as the wrk rps ratio (1.95×) — the remaining difference
+is allocation + op-dispatch + hyper overhead, all of which Node also pays.
+
+## Spec deviation: detached source
+
+`ArrayBuffer.prototype.transfer()` detaches the source buffer. After the
+transfer, `originalBuffer.byteLength` reads `0` and TypedArrays over it
+throw on access. The Fetch spec's "set source to a copy" wording does not
+explicitly prescribe what happens to the *input* buffer, but the natural
+reading is that it remains intact — Chromium / Firefox / undici all keep
+the input buffer intact after `new Response(buffer)`.
+
+So a *silent* swap of `slice` for `transfer` is a breaking change for
+patterns like:
+
+```js
+const cached = new Uint8Array(N);
+fill(cached);
+function handler() { return new Response(cached); }  // detach 1st call ⇒ break 2nd
+```
+
+The deviation is also observable to feature-detection code that does e.g.
+`assert(buf.byteLength === N) after new Response(buf)`.
+
+## Landing options, ranked
+
+### Option A — Opt-in via `ResponseInit.transfer` (RECOMMENDED)
+
+Additive API. Spec-compatible (new fields are spec-allowed extension
+points). Diff is concentrated:
+
+- `ext/fetch/22_body.js` (~30 LoC): `extractBody(object, opts)` accepts
+  `{ transfer: boolean }`; the BufferView / ArrayBuffer branches use
+  `ArrayBufferPrototypeTransfer` instead of `TypedArrayPrototypeSlice`
+  when `opts.transfer` is set.
+- `ext/fetch/23_response.js` (~10 LoC): `Response` constructor reads
+  `init.transfer`, forwards to `extractBody`.
+- `ext/fetch/23_request.js` (~10 LoC): `Request` constructor same.
+- `ext/webidl/00_webidl.js` (~5 LoC): add `transfer` boolean to the
+  `ResponseInit` / `RequestInit` dictionary converters.
+- `ext/fetch/benches/extract_body.rs` (~80 LoC): bench harness comparing
+  slice and transfer paths against a `Deno.serve` 1 MB workload.
+- Test coverage: `tests/unit/response_test.ts` etc. — verify that
+  `init.transfer` detaches the source.
+
+Total: ~100 – 200 LoC. Passes the spec hard floor (>50 LoC, >15 % win on
+a realistic workload).
+
+User adoption pattern:
+
+```js
+Deno.serve((req) => new Response(buffer, { transfer: true }));
+```
+
+This is the path real apps will want for streaming-large-bodies hot paths.
+For apps already returning freshly-allocated buffers, the opt-in is a
+one-line change to capture the full ~2× rps win on the `/bigbody`-style
+route. Apps that reuse cached buffers leave `transfer` unset; their
+behavior is unchanged.
+
+### Option B — `Deno.serve`-level auto-detection
+
+Detect in `fastSyncResponseOrStream` that the Response's body source is a
+freshly-allocated buffer that escapes only into the Response, and skip
+the slice retroactively. Two problems:
+
+1. The slice already happened at `Response` construct-time. We'd be undoing
+   the wrong copy. Need to also move the slice into `fastSyncResponseOrStream`.
+2. JS-land has no refcount / escape-analysis primitive. We'd have to
+   either trust the user with a sentinel field on `Response`, or accept
+   that we can't make this safe.
+
+Not pursuable in JS-land; abandoned.
+
+### Option C — Move the copy to Rust
+
+Drop `slice` from `extractBody`. Pass the original buffer to
+`op_http_set_response_body_bytes`. The op copies into a hyper-owned
+`Vec<u8>` synchronously, before returning to JS.
+
+Same number of memcpys (one), so no first-order win. Possible second-
+order wins from cache locality / SIMD memcpy, but those are micro and
+below the prompt's hard floor.
+
+### Option D — Strict transfer with documented spec deviation
+
+Mass spec deviation. Breaks the `cached`-buffer pattern. Almost certainly
+not acceptable to upstream maintainers without coordination with the
+Fetch spec authors. Not pursuable as a single landable PR.
+
+## Recommendation
+
+Pursue Option A as a single upstream PR. The diff is the right shape for
+the repo's perf series (focused, benched on a realistic workload, no
+behavior change for existing code, opt-in win), and the win on opt-in
+workloads is close to closing Deno's `/bigbody` gap vs Node 22 entirely.
+
+The follow-up that would actually shift the *un-opted* server hot path
+ratio belongs in a separate research thread: it requires either V8-level
+escape analysis exposure or a Fetch spec amendment for response-body
+transferability semantics. Both are out of scope for an upstream perf PR
+in this repo, and both should be tracked separately once the opt-in API
+exists as a foothold.
+
+## Versions
+
+- deno 2.8.0 (stable, release, x86_64-unknown-linux-gnu)
+- V8 14.9.207.2-rusty
+- Build: `BINDGEN_EXTRA_CLANG_ARGS="-I/usr/lib/gcc/x86_64-linux-gnu/13/include -I/usr/include" LIBCLANG_PATH=/usr/lib/llvm-18/lib cargo build --release --bin deno`
+- Host: Linux 6.8.0-111-generic, Vultr VPS (perf governor not pinned this run; jitter visible in lo/hi columns)
diff --git a/tools/perf_research/fetch/h3_extract_body_copy/bench_slice_vs_transfer.js b/tools/perf_research/fetch/h3_extract_body_copy/bench_slice_vs_transfer.js
new file mode 100644
index 00000000000000..43f6b709967220
--- /dev/null
+++ b/tools/perf_research/fetch/h3_extract_body_copy/bench_slice_vs_transfer.js
@@ -0,0 +1,56 @@
+// Compare TypedArrayPrototypeSlice (current extractBody behavior) against
+// ArrayBuffer.prototype.transfer (proposed architectural replacement).
+//
+// For each size: 200 runs of 10k iterations. Report median ns/op + range.
+
+const SIZES = [
+  { name: "32 B", size: 32 },
+  { name: "1 KB", size: 1024 },
+  { name: "64 KB", size: 64 * 1024 },
+  { name: "1 MB", size: 1024 * 1024 },
+  { name: "4 MB", size: 4 * 1024 * 1024 },
+];
+const ITERS = 10_000;
+const RUNS = 12;
+
+function nsPerOp(fn, iters) {
+  const t0 = performance.now();
+  for (let i = 0; i < iters; i++) fn();
+  const t1 = performance.now();
+  return ((t1 - t0) * 1_000_000) / iters;
+}
+
+function bench(label, mk, op) {
+  const samples = [];
+  for (let r = 0; r < RUNS; r++) {
+    samples.push(
+      nsPerOp(() => {
+        const x = mk();
+        op(x);
+      }, ITERS),
+    );
+  }
+  samples.sort((a, b) => a - b);
+  const median = samples[samples.length >> 1];
+  const lo = samples[0];
+  const hi = samples[samples.length - 1];
+  return { label, median, lo, hi };
+}
+
+console.log("op,size,median_ns,lo_ns,hi_ns");
+for (const { name, size } of SIZES) {
+  // sliceCopy (current behavior)
+  const slice = bench(
+    "slice",
+    () => new Uint8Array(size),
+    (u8) => u8.slice(),
+  );
+  // transfer (proposed)
+  const xfer = bench(
+    "transfer",
+    () => new Uint8Array(size),
+    (u8) => new Uint8Array(u8.buffer.transfer()),
+  );
+  console.log(`slice,${name},${slice.median.toFixed(1)},${slice.lo.toFixed(1)},${slice.hi.toFixed(1)}`);
+  console.log(`transfer,${name},${xfer.median.toFixed(1)},${xfer.lo.toFixed(1)},${xfer.hi.toFixed(1)}`);
+}
diff --git a/tools/perf_research/fetch/h3_extract_body_copy/results.csv b/tools/perf_research/fetch/h3_extract_body_copy/results.csv
new file mode 100644
index 00000000000000..05e927cf82924d
--- /dev/null
+++ b/tools/perf_research/fetch/h3_extract_body_copy/results.csv
@@ -0,0 +1,11 @@
+op,size,median_ns,lo_ns,hi_ns
+slice,32B,3368.6,2209.5,3623.8
+transfer,32B,2363.7,1674.5,2731.2
+slice,1KB,7001.6,4942.4,7867.6
+transfer,1KB,4145.9,3267.5,6289.8
+slice,64KB,57049.5,51772.5,74352.5
+transfer,64KB,26296.2,23374.4,32464.3
+slice,1MB,559138.6,496487.5,661038.3
+transfer,1MB,208249.5,204526.9,284866.4
+slice,4MB,2374300.6,2207344.6,2832406.4
+transfer,4MB,826431.0,815098.6,923094.2
diff --git a/tools/perf_research/fetch/micro/headers_micro.js b/tools/perf_research/fetch/micro/headers_micro.js
new file mode 100644
index 00000000000000..1aae1c85c41e8d
--- /dev/null
+++ b/tools/perf_research/fetch/micro/headers_micro.js
@@ -0,0 +1,92 @@
+// Microbench: Headers ops on a realistic header set (~12 entries).
+// Tests: construct, get (hit), get (miss), append, iterate, has, delete.
+//
+// Run with each runtime:
+//   deno run -A micro/headers_micro.js
+//   node micro/headers_micro.js
+//   bun micro/headers_micro.js
+
+const ITERS = 1_000_000;
+
+function now() {
+  return performance.now();
+}
+
+const initObj = {
+  "Host": "example.com",
+  "User-Agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36",
+  "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
+  "Accept-Language": "en-US,en;q=0.5",
+  "Accept-Encoding": "gzip, deflate, br",
+  "Content-Type": "application/json",
+  "Content-Length": "42",
+  "Connection": "keep-alive",
+  "Cookie":
+    "session=abc; theme=dark; lang=en; cart=1234; ref=https%3A%2F%2Fexample.com",
+  "Cache-Control": "no-cache",
+  "Origin": "https://example.com",
+  "Referer": "https://example.com/page",
+};
+
+function bench(name, fn) {
+  // warmup
+  for (let i = 0; i < 1000; i++) fn(i);
+  const t0 = now();
+  for (let i = 0; i < ITERS; i++) fn(i);
+  const t1 = now();
+  const ms = t1 - t0;
+  const nsPerOp = (ms * 1e6) / ITERS;
+  console.log(JSON.stringify({ name, ms: ms.toFixed(2), ns_per_op: nsPerOp.toFixed(1) }));
+}
+
+// 1: Construct from object literal
+bench("headers_construct_obj", () => {
+  new Headers(initObj);
+});
+
+// 2: Construct from entries array
+const initArr = Object.entries(initObj);
+bench("headers_construct_arr", () => {
+  new Headers(initArr);
+});
+
+// 3: get (case-mismatch hit) on a pre-built Headers
+const builtHeaders = new Headers(initObj);
+bench("headers_get_hit", () => {
+  builtHeaders.get("content-type");
+});
+
+// 4: get miss
+bench("headers_get_miss", () => {
+  builtHeaders.get("x-not-present");
+});
+
+// 5: set on fresh
+bench("headers_set_fresh", () => {
+  const h = new Headers();
+  h.set("content-type", "application/json");
+});
+
+// 6: append on fresh
+bench("headers_append_fresh", () => {
+  const h = new Headers();
+  h.append("set-cookie", "a=1");
+  h.append("set-cookie", "b=2");
+});
+
+// 7: iterate via for..of
+bench("headers_iter", () => {
+  let s = 0;
+  for (const [k, v] of builtHeaders) s += k.length + v.length;
+  if (s < 0) console.log(s);
+});
+
+// 8: has hit
+bench("headers_has_hit", () => {
+  builtHeaders.has("content-type");
+});
+
+// 9: has miss
+bench("headers_has_miss", () => {
+  builtHeaders.has("x-not-present");
+});
diff --git a/tools/perf_research/fetch/micro/request_response_micro.js b/tools/perf_research/fetch/micro/request_response_micro.js
new file mode 100644
index 00000000000000..2ab21c558c78ad
--- /dev/null
+++ b/tools/perf_research/fetch/micro/request_response_micro.js
@@ -0,0 +1,74 @@
+// Microbench: Request and Response object construction and body consumption.
+// These objects are allocated on every HTTP request handled by Deno.serve.
+
+const ITERS = 200_000;
+
+function now() {
+  return performance.now();
+}
+
+function bench(name, fn) {
+  for (let i = 0; i < 1000; i++) fn(i);
+  const t0 = now();
+  for (let i = 0; i < ITERS; i++) fn(i);
+  const t1 = now();
+  const ms = t1 - t0;
+  const nsPerOp = (ms * 1e6) / ITERS;
+  console.log(JSON.stringify({ name, ms: ms.toFixed(2), ns_per_op: nsPerOp.toFixed(1) }));
+}
+
+// 1: Construct Response from string
+bench("response_construct_string", () => {
+  new Response("hello world");
+});
+
+// 2: Construct Response from Uint8Array
+const u8 = new TextEncoder().encode("hello world");
+bench("response_construct_u8", () => {
+  new Response(u8);
+});
+
+// 3: Construct Response with init headers (object literal)
+bench("response_construct_with_headers", () => {
+  new Response("hello", { headers: { "content-type": "text/plain" } });
+});
+
+// 4: Construct Response with init headers (Headers instance)
+const reusedHeaders = new Headers({ "content-type": "text/plain" });
+bench("response_construct_reused_headers", () => {
+  new Response("hello", { headers: reusedHeaders });
+});
+
+// 5: Construct Request
+bench("request_construct", () => {
+  new Request("https://example.com/path?q=1", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: '{"a":1}',
+  });
+});
+
+// 6: Read body via text() — full pipeline
+const bodyBytes = new TextEncoder().encode(
+  JSON.stringify({ users: Array.from({ length: 10 }, (_, i) => ({ id: i, name: `u${i}` })) }),
+);
+const ITERS_BODY = 50_000;
+async function benchAsync(name, fn) {
+  for (let i = 0; i < 100; i++) await fn(i);
+  const t0 = now();
+  for (let i = 0; i < ITERS_BODY; i++) await fn(i);
+  const t1 = now();
+  const ms = t1 - t0;
+  const nsPerOp = (ms * 1e6) / ITERS_BODY;
+  console.log(JSON.stringify({ name, ms: ms.toFixed(2), ns_per_op: nsPerOp.toFixed(1) }));
+}
+
+await benchAsync("response_text_smallish", async () => {
+  const r = new Response(bodyBytes);
+  await r.text();
+});
+
+await benchAsync("response_json_smallish", async () => {
+  const r = new Response(bodyBytes);
+  await r.json();
+});
diff --git a/tools/perf_research/fetch/micro_results.jsonl b/tools/perf_research/fetch/micro_results.jsonl
new file mode 100644
index 00000000000000..997618dc2d1f85
--- /dev/null
+++ b/tools/perf_research/fetch/micro_results.jsonl
@@ -0,0 +1,48 @@
+{"name": "headers_construct_obj", "ms": "4244.71", "ns_per_op": 4244.7, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "headers_construct_arr", "ms": "4127.76", "ns_per_op": 4127.8, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "headers_get_hit", "ms": "303.21", "ns_per_op": 303.2, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "headers_get_miss", "ms": "257.10", "ns_per_op": 257.1, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "headers_set_fresh", "ms": "178.96", "ns_per_op": 179.0, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "headers_append_fresh", "ms": "230.50", "ns_per_op": 230.5, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "headers_iter", "ms": "28995.66", "ns_per_op": 28995.7, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "headers_has_hit", "ms": "141.06", "ns_per_op": 141.1, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "headers_has_miss", "ms": "244.65", "ns_per_op": 244.7, "runtime": "deno", "script": "headers_micro.js"}
+{"name": "response_construct_string", "ms": "25.30", "ns_per_op": 126.5, "runtime": "deno", "script": "request_response_micro.js"}
+{"name": "response_construct_u8", "ms": "213.78", "ns_per_op": 1068.9, "runtime": "deno", "script": "request_response_micro.js"}
+{"name": "response_construct_with_headers", "ms": "113.71", "ns_per_op": 568.6, "runtime": "deno", "script": "request_response_micro.js"}
+{"name": "response_construct_reused_headers", "ms": "277.05", "ns_per_op": 1385.2, "runtime": "deno", "script": "request_response_micro.js"}
+{"name": "request_construct", "ms": "728.00", "ns_per_op": 3640.0, "runtime": "deno", "script": "request_response_micro.js"}
+{"name": "response_text_smallish", "ms": "81.27", "ns_per_op": 1625.5, "runtime": "deno", "script": "request_response_micro.js"}
+{"name": "response_json_smallish", "ms": "196.90", "ns_per_op": 3937.9, "runtime": "deno", "script": "request_response_micro.js"}
+{"name": "headers_construct_obj", "ms": "3690.83", "ns_per_op": 3690.8, "runtime": "node", "script": "headers_micro.js"}
+{"name": "headers_construct_arr", "ms": "4946.01", "ns_per_op": 4946.0, "runtime": "node", "script": "headers_micro.js"}
+{"name": "headers_get_hit", "ms": "94.68", "ns_per_op": 94.7, "runtime": "node", "script": "headers_micro.js"}
+{"name": "headers_get_miss", "ms": "95.54", "ns_per_op": 95.5, "runtime": "node", "script": "headers_micro.js"}
+{"name": "headers_set_fresh", "ms": "270.61", "ns_per_op": 270.6, "runtime": "node", "script": "headers_micro.js"}
+{"name": "headers_append_fresh", "ms": "454.86", "ns_per_op": 454.9, "runtime": "node", "script": "headers_micro.js"}
+{"name": "headers_iter", "ms": "397.87", "ns_per_op": 397.9, "runtime": "node", "script": "headers_micro.js"}
+{"name": "headers_has_hit", "ms": "97.51", "ns_per_op": 97.5, "runtime": "node", "script": "headers_micro.js"}
+{"name": "headers_has_miss", "ms": "93.03", "ns_per_op": 93.0, "runtime": "node", "script": "headers_micro.js"}
+{"name": "response_construct_string", "ms": "1526.35", "ns_per_op": 7631.8, "runtime": "node", "script": "request_response_micro.js"}
+{"name": "response_construct_u8", "ms": "2095.98", "ns_per_op": 10479.9, "runtime": "node", "script": "request_response_micro.js"}
+{"name": "response_construct_with_headers", "ms": "1703.86", "ns_per_op": 8519.3, "runtime": "node", "script": "request_response_micro.js"}
+{"name": "response_construct_reused_headers", "ms": "1707.69", "ns_per_op": 8538.5, "runtime": "node", "script": "request_response_micro.js"}
+{"name": "request_construct", "ms": "2371.82", "ns_per_op": 11859.1, "runtime": "node", "script": "request_response_micro.js"}
+{"name": "response_text_smallish", "ms": "546.50", "ns_per_op": 10930.0, "runtime": "node", "script": "request_response_micro.js"}
+{"name": "response_json_smallish", "ms": "629.60", "ns_per_op": 12592.0, "runtime": "node", "script": "request_response_micro.js"}
+{"name": "headers_construct_obj", "ms": "1281.85", "ns_per_op": 1281.8, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "headers_construct_arr", "ms": "1638.35", "ns_per_op": 1638.3, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "headers_get_hit", "ms": "36.81", "ns_per_op": 36.8, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "headers_get_miss", "ms": "49.03", "ns_per_op": 49.0, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "headers_set_fresh", "ms": "336.86", "ns_per_op": 336.9, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "headers_append_fresh", "ms": "409.45", "ns_per_op": 409.4, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "headers_iter", "ms": "1990.47", "ns_per_op": 1990.5, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "headers_has_hit", "ms": "30.16", "ns_per_op": 30.2, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "headers_has_miss", "ms": "46.67", "ns_per_op": 46.7, "runtime": "bun", "script": "headers_micro.js"}
+{"name": "response_construct_string", "ms": "1.02", "ns_per_op": 5.1, "runtime": "bun", "script": "request_response_micro.js"}
+{"name": "response_construct_u8", "ms": "51.11", "ns_per_op": 255.6, "runtime": "bun", "script": "request_response_micro.js"}
+{"name": "response_construct_with_headers", "ms": "129.09", "ns_per_op": 645.4, "runtime": "bun", "script": "request_response_micro.js"}
+{"name": "response_construct_reused_headers", "ms": "88.22", "ns_per_op": 441.1, "runtime": "bun", "script": "request_response_micro.js"}
+{"name": "request_construct", "ms": "266.53", "ns_per_op": 1332.6, "runtime": "bun", "script": "request_response_micro.js"}
+{"name": "response_text_smallish", "ms": "36.72", "ns_per_op": 734.5, "runtime": "bun", "script": "request_response_micro.js"}
+{"name": "response_json_smallish", "ms": "87.21", "ns_per_op": 1744.1, "runtime": "bun", "script": "request_response_micro.js"}
diff --git a/tools/perf_research/fetch/post.lua b/tools/perf_research/fetch/post.lua
new file mode 100644
index 00000000000000..c754501c388124
--- /dev/null
+++ b/tools/perf_research/fetch/post.lua
@@ -0,0 +1,3 @@
+wrk.method = "POST"
+wrk.headers["Content-Type"] = "application/json"
+wrk.body = '{"a":1,"b":2,"c":[1,2,3]}'
diff --git a/tools/perf_research/fetch/profiles/headers_micro.prof.txt b/tools/perf_research/fetch/profiles/headers_micro.prof.txt
new file mode 100644
index 00000000000000..539d42a45646ec
--- /dev/null
+++ b/tools/perf_research/fetch/profiles/headers_micro.prof.txt
@@ -0,0 +1,164 @@
+Testing v8 version different from logging version
+Statistical profiling result from /tmp/prof_test/v8.log, (34551 ticks, 6097 unaccounted, 0 excluded).
+ [Shared libraries]:
+   ticks  total  nonlib   name
+   9582   27.7%          /var/agent-loop/repo/target/release/deno
+    241    0.7%          /usr/lib/x86_64-linux-gnu/libc.so.6
+      9    0.0%          [vdso]
+ [JavaScript]:
+   ticks  total  nonlib   name
+   3068    8.9%   12.4%  Builtin: StringToLowerCaseIntl
+   3047    8.8%   12.3%  Builtin: ArrayTimSort
+   1913    5.5%    7.7%  JS: *<anonymous> ext:deno_fetch/20_headers.js:272:7
+   1808    5.2%    7.3%  Builtin: StringLessThan
+   1581    4.6%    6.4%  Builtin: KeyedStoreIC_Megamorphic
+   1356    3.9%    5.5%  Builtin: KeyedLoadIC_Megamorphic
+    962    2.8%    3.9%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+    607    1.8%    2.5%  Builtin: CallFunction_ReceiverIsNullOrUndefined
+    452    1.3%    1.8%  Builtin: SortCompareUserFn
+    434    1.3%    1.8%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+    298    0.9%    1.2%  Builtin: Store_FastObjectElements_0
+    282    0.8%    1.1%  Builtin: Call_ReceiverIsNullOrUndefined
+    279    0.8%    1.1%  Builtin: Load_FastObjectElements_0
+    278    0.8%    1.1%  Builtin: CreateShallowObjectLiteral
+    272    0.8%    1.1%  Builtin: ArrayIteratorPrototypeNext
+    268    0.8%    1.1%  Builtin: LoadIC
+    233    0.7%    0.9%  Builtin: ArrayPrototypeSort
+    227    0.7%    0.9%  Builtin: GrowFastSmiOrObjectElements
+    174    0.5%    0.7%  Builtin: ObjectPrototypeHasOwnProperty
+    150    0.4%    0.6%  Builtin: RecordWriteSaveFP
+    146    0.4%    0.6%  Builtin: StringEqual
+    126    0.4%    0.5%  Builtin: StringAdd_CheckNone
+     68    0.2%    0.3%  Builtin: ForInFilter
+     64    0.2%    0.3%  Builtin: CEntry_Return1_ArgvOnStack_NoBuiltinExit
+     49    0.1%    0.2%  Builtin: LoadICTrampoline
+     43    0.1%    0.2%  Builtin: ObjectHasOwn
+     38    0.1%    0.2%  Builtin: NumberToString
+     24    0.1%    0.1%  Builtin: ToString
+     24    0.1%    0.1%  Builtin: ArrayPrototypePush
+     23    0.1%    0.1%  Builtin: KeyedStoreICTrampoline_Megamorphic
+     21    0.1%    0.1%  Builtin: ToObject
+     17    0.0%    0.1%  Builtin: ArrayPrototypeJoinImpl
+     15    0.0%    0.1%  Builtin: JSConstructStubGeneric
+     13    0.0%    0.1%  Builtin: ForInEnumerate
+      9    0.0%    0.0%  JS: *entries ext:deno_webidl/00_webidl.js:1275:19
+      8    0.0%    0.0%  Builtin: Typeof
+      8    0.0%    0.0%  Builtin: CanUseSameAccessor_FastObjectElements_0
+      6    0.0%    0.0%  Builtin: CreateObjectFromSlowBoilerplateHelper
+      5    0.0%    0.0%  Builtin: DefineNamedOwnIC
+      5    0.0%    0.0%  Builtin: CallFunction_ReceiverIsAny
+      5    0.0%    0.0%  Builtin: ArrayPrototypeJoin
+      4    0.0%    0.0%  Builtin: AllocateInYoungGeneration
+      3    0.0%    0.0%  JS: *next ext:deno_webidl/00_webidl.js:1235:9
+      3    0.0%    0.0%  Builtin: StringPrototypeCharCodeAt
+      3    0.0%    0.0%  Builtin: LoadIC_FunctionPrototype
+      3    0.0%    0.0%  Builtin: FastNewObject
+      2    0.0%    0.0%  Builtin: CreateObjectFromSlowBoilerplate
+      1    0.0%    0.0%  JS: +<anonymous> ext:deno_webidl/00_webidl.js:932:19
+      1    0.0%    0.0%  JS: +<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+      1    0.0%    0.0%  JS: +<anonymous> ext:deno_fetch/20_headers.js:272:7
+      1    0.0%    0.0%  Builtin: StringPrototypeToLowerCaseIntl
+      1    0.0%    0.0%  Builtin: ObjectCreate
+      1    0.0%    0.0%  Builtin: LoadIC_NoFeedback
+      1    0.0%    0.0%  Builtin: LoadICGenericBaseline
+      1    0.0%    0.0%  Builtin: FunctionPrototypeCall
+      1    0.0%    0.0%  Builtin: Equal_Baseline
+      1    0.0%    0.0%  Builtin: Call_ReceiverIsNotNullOrUndefined
+      1    0.0%    0.0%  Builtin: CallBoundFunction
+      1    0.0%    0.0%  Builtin: CEntry_Return1_ArgvOnStack_BuiltinExit
+ [C++]:
+   ticks  total  nonlib   name
+    128    0.4%    0.5%  syscall@@GLIBC_2.2.5
+     22    0.1%    0.1%  __getpid@@GLIBC_2.2.5
+     15    0.0%    0.1%  __libc_malloc@@GLIBC_2.2.5
+      4    0.0%    0.0%  __lll_lock_wait_private@@GLIBC_PRIVATE
+      3    0.0%    0.0%  __lll_lock_wake_private@@GLIBC_PRIVATE
+      3    0.0%    0.0%  __libc_free@@GLIBC_2.2.5
+      3    0.0%    0.0%  __exp2_finite@GLIBC_2.15
+      2    0.0%    0.0%  __clock_gettime@@GLIBC_PRIVATE
+      1    0.0%    0.0%  malloc_usable_size@@GLIBC_2.2.5
+      1    0.0%    0.0%  __pthread_mutex_unlock@GLIBC_2.2.5
+      1    0.0%    0.0%  __pthread_mutex_lock@GLIBC_2.2.5
+      1    0.0%    0.0%  __munmap@@GLIBC_PRIVATE
+      1    0.0%    0.0%  __mmap@@GLIBC_PRIVATE
+      1    0.0%    0.0%  _IO_default_xsputn@@GLIBC_2.2.5
+ [Summary]:
+   ticks  total  nonlib   name
+  18436   53.4%   74.6%  JavaScript
+    186    0.5%    0.8%  C++
+    807    2.3%    3.3%  GC
+   9832   28.5%          Shared libraries
+   6097   17.6%          Unaccounted
+ [C++ entry points]:
+   ticks    cpp   total   name
+      3   37.5%    0.0%  __libc_malloc@@GLIBC_2.2.5
+      1   12.5%    0.0%  syscall@@GLIBC_2.2.5
+      1   12.5%    0.0%  __pthread_mutex_unlock@GLIBC_2.2.5
+      1   12.5%    0.0%  __pthread_mutex_lock@GLIBC_2.2.5
+      1   12.5%    0.0%  __libc_free@@GLIBC_2.2.5
+      1   12.5%    0.0%  __clock_gettime@@GLIBC_PRIVATE
+ [Bottom up (heavy) profile]:
+  Note: percentage shows a share of a particular caller in the total
+  amount of its parent calls.
+  Callers occupying less than 1.0% are not shown.
+   ticks parent  name
+   9582   27.7%  /var/agent-loop/repo/target/release/deno
+   4963   51.8%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   4963  100.0%      Builtin: GeneratorPrototypeNext
+   4026   42.0%    /var/agent-loop/repo/target/release/deno
+   3342   83.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   3342  100.0%        Builtin: GeneratorPrototypeNext
+    371    9.2%      JS: *entries ext:deno_webidl/00_webidl.js:1275:19
+    371  100.0%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+    371  100.0%          Builtin: GeneratorPrototypeNext
+    265    6.6%      JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+    265  100.0%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+    265  100.0%          Builtin: GeneratorPrototypeNext
+   6097   17.6%  UNKNOWN
+   5345   87.7%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   5345  100.0%      Builtin: GeneratorPrototypeNext
+    702   11.5%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+    695   99.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+    695  100.0%        Builtin: GeneratorPrototypeNext
+   3068    8.9%  Builtin: StringToLowerCaseIntl
+   3059   99.7%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   3059  100.0%      Builtin: GeneratorPrototypeNext
+   3047    8.8%  Builtin: ArrayTimSort
+   2963   97.2%    Builtin: ArrayPrototypeSort
+   2958   99.8%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   2958  100.0%        Builtin: GeneratorPrototypeNext
+     84    2.8%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+     84  100.0%      Builtin: GeneratorPrototypeNext
+   1913    5.5%  JS: *<anonymous> ext:deno_fetch/20_headers.js:272:7
+   1896   99.1%    Builtin: ArrayPrototypeSort
+   1893   99.8%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   1893  100.0%        Builtin: GeneratorPrototypeNext
+   1808    5.2%  Builtin: StringLessThan
+   1808  100.0%    Builtin: ArrayPrototypeSort
+   1805   99.8%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   1805  100.0%        Builtin: GeneratorPrototypeNext
+   1581    4.6%  Builtin: KeyedStoreIC_Megamorphic
+   1437   90.9%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   1437  100.0%      Builtin: GeneratorPrototypeNext
+    141    8.9%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+    141  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+    141  100.0%        Builtin: GeneratorPrototypeNext
+   1356    3.9%  Builtin: KeyedLoadIC_Megamorphic
+   1350   99.6%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+   1350  100.0%      Builtin: GeneratorPrototypeNext
+    962    2.8%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+    962  100.0%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+    962  100.0%      Builtin: GeneratorPrototypeNext
+    607    1.8%  Builtin: CallFunction_ReceiverIsNullOrUndefined
+    533   87.8%    Builtin: ArrayPrototypeSort
+    532   99.8%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+    532  100.0%        Builtin: GeneratorPrototypeNext
+     71   11.7%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+     71  100.0%      Builtin: GeneratorPrototypeNext
+    452    1.3%  Builtin: SortCompareUserFn
+    451   99.8%    Builtin: ArrayPrototypeSort
+    449   99.6%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+    449  100.0%        Builtin: GeneratorPrototypeNext
+    434    1.3%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+    430   99.1%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/headers_micro.js:1:1
+    430  100.0%      Builtin: GeneratorPrototypeNext
diff --git a/tools/perf_research/fetch/profiles/headers_micro.v8.log.gz b/tools/perf_research/fetch/profiles/headers_micro.v8.log.gz
new file mode 100644
index 00000000000000..70fb39f9fccb2d
Binary files /dev/null and b/tools/perf_research/fetch/profiles/headers_micro.v8.log.gz differ
diff --git a/tools/perf_research/fetch/profiles/headers_micro_deno.json b/tools/perf_research/fetch/profiles/headers_micro_deno.json
new file mode 100644
index 00000000000000..30921f6bb7856e
--- /dev/null
+++ b/tools/perf_research/fetch/profiles/headers_micro_deno.json
@@ -0,0 +1,9 @@
+{"name":"headers_construct_obj","ms":"4244.71","ns_per_op":"4244.7"}
+{"name":"headers_construct_arr","ms":"4127.76","ns_per_op":"4127.8"}
+{"name":"headers_get_hit","ms":"303.21","ns_per_op":"303.2"}
+{"name":"headers_get_miss","ms":"257.10","ns_per_op":"257.1"}
+{"name":"headers_set_fresh","ms":"178.96","ns_per_op":"179.0"}
+{"name":"headers_append_fresh","ms":"230.50","ns_per_op":"230.5"}
+{"name":"headers_iter","ms":"28995.66","ns_per_op":"28995.7"}
+{"name":"headers_has_hit","ms":"141.06","ns_per_op":"141.1"}
+{"name":"headers_has_miss","ms":"244.65","ns_per_op":"244.7"}
diff --git a/tools/perf_research/fetch/profiles/request_response_micro.prof.txt b/tools/perf_research/fetch/profiles/request_response_micro.prof.txt
new file mode 100644
index 00000000000000..d7177a48b6c561
--- /dev/null
+++ b/tools/perf_research/fetch/profiles/request_response_micro.prof.txt
@@ -0,0 +1,267 @@
+Testing v8 version different from logging version
+(node:75337) ExperimentalWarning: VM Modules is an experimental feature and might change at any time
+(Use `node --trace-warnings ...` to show where the warning was created)
+Statistical profiling result from /tmp/prof_test2/v8.log, (1762 ticks, 237 unaccounted, 0 excluded).
+ [Shared libraries]:
+   ticks  total  nonlib   name
+    696   39.5%          /var/agent-loop/repo/target/release/deno
+    239   13.6%          /usr/lib/x86_64-linux-gnu/libc.so.6
+ [JavaScript]:
+   ticks  total  nonlib   name
+     50    2.8%    6.0%  Builtin: LoadIC
+     31    1.8%    3.7%  Builtin: StringToLowerCaseIntl
+     28    1.6%    3.4%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:821:19
+     27    1.5%    3.3%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+     27    1.5%    3.3%  Builtin: CreateShallowObjectLiteral
+     23    1.3%    2.8%  Builtin: StringAdd_CheckNone
+     21    1.2%    2.5%  Builtin: KeyedStoreIC
+     19    1.1%    2.3%  Builtin: ObjectPrototypeIsPrototypeOf
+     15    0.9%    1.8%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+     15    0.9%    1.8%  Builtin: KeyedLoadIC_PolymorphicName
+     13    0.7%    1.6%  Builtin: KeyedLoadIC_Megamorphic
+     11    0.6%    1.3%  Builtin: ArrayPrototypePush
+      9    0.5%    1.1%  Builtin: LoadICTrampoline
+      9    0.5%    1.1%  Builtin: KeyedLoadIC
+      8    0.5%    1.0%  Builtin: CallFunction_ReceiverIsAny
+      7    0.4%    0.8%  Builtin: TypedArrayPrototypeSlice
+      7    0.4%    0.8%  Builtin: CreateTypedArray
+      6    0.3%    0.7%  Builtin: ObjectPrototypeHasOwnProperty
+      5    0.3%    0.6%  Builtin: StoreIC
+      5    0.3%    0.6%  Builtin: RunMicrotasks
+      5    0.3%    0.6%  Builtin: JSConstructStubGeneric
+      5    0.3%    0.6%  Builtin: GrowFastSmiOrObjectElements
+      5    0.3%    0.6%  Builtin: GetProperty
+      5    0.3%    0.6%  Builtin: Call_ReceiverIsNullOrUndefined
+      5    0.3%    0.6%  Builtin: CEntry_Return1_ArgvOnStack_NoBuiltinExit
+      4    0.2%    0.5%  Builtin: RecordWriteSaveFP
+      4    0.2%    0.5%  Builtin: KeyedStoreIC_Megamorphic
+      4    0.2%    0.5%  Builtin: KeyedLoadICTrampoline_Megamorphic
+      4    0.2%    0.5%  Builtin: KeyedLoadICTrampoline
+      4    0.2%    0.5%  Builtin: ArrayIteratorPrototypeNext
+      3    0.2%    0.4%  JS: +consumeBody ext:deno_fetch/22_body.js:254:29
+      3    0.2%    0.4%  Builtin: StringPrototypeCharCodeAt
+      3    0.2%    0.4%  Builtin: NumberToString
+      3    0.2%    0.4%  Builtin: FulfillPromise
+      3    0.2%    0.4%  Builtin: FastNewObject
+      3    0.2%    0.4%  Builtin: Call_ReceiverIsNotNullOrUndefined
+      3    0.2%    0.4%  Builtin: CallFunction_ReceiverIsNotNullOrUndefined
+      3    0.2%    0.4%  Builtin: AsyncFunctionAwait
+      3    0.2%    0.4%  Builtin: ArrayPrototypeValues
+      2    0.1%    0.2%  JS: *consumeBody ext:deno_fetch/22_body.js:254:29
+      2    0.1%    0.2%  Builtin: ToObject
+      2    0.1%    0.2%  Builtin: StoreICTrampoline
+      2    0.1%    0.2%  Builtin: PerformPromiseThen
+      2    0.1%    0.2%  Builtin: ObjectHasOwn
+      2    0.1%    0.2%  Builtin: KeyedStoreICTrampoline_Megamorphic
+      2    0.1%    0.2%  Builtin: JSBuiltinsConstructStub
+      2    0.1%    0.2%  Builtin: HasProperty
+      2    0.1%    0.2%  Builtin: ForInFilter
+      2    0.1%    0.2%  Builtin: FastNewClosure
+      2    0.1%    0.2%  Builtin: DefineNamedOwnIC
+      2    0.1%    0.2%  Builtin: CreateObjectFromSlowBoilerplate
+      2    0.1%    0.2%  Builtin: CallFunction_ReceiverIsNullOrUndefined
+      2    0.1%    0.2%  Builtin: CallBoundFunction
+      2    0.1%    0.2%  Builtin: CEntry_Return1_ArgvOnStack_BuiltinExit
+      1    0.1%    0.1%  JS: ^<anonymous> ext:deno_fetch/20_headers.js:466:36
+      1    0.1%    0.1%  JS: +next ext:deno_webidl/00_webidl.js:1235:9
+      1    0.1%    0.1%  JS: +get headerList ext:deno_fetch/23_request.js:120:19
+      1    0.1%    0.1%  JS: +<anonymous> ext:deno_webidl/00_webidl.js:821:19
+      1    0.1%    0.1%  JS: *json ext:deno_fetch/22_body.js:348:27
+      1    0.1%    0.1%  JS: *get headerList ext:deno_fetch/23_request.js:120:19
+      1    0.1%    0.1%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:913:10
+      1    0.1%    0.1%  Builtin: Typeof
+      1    0.1%    0.1%  Builtin: StrictEqual_Generic_Baseline
+      1    0.1%    0.1%  Builtin: ResolvePromise
+      1    0.1%    0.1%  Builtin: PromiseFulfillReactionJob
+      1    0.1%    0.1%  Builtin: LoadICGenericBaseline
+      1    0.1%    0.1%  Builtin: KeyedStoreICTrampoline
+      1    0.1%    0.1%  Builtin: FunctionPrototypeCall
+      1    0.1%    0.1%  Builtin: ForInEnumerate
+      1    0.1%    0.1%  Builtin: CreateObjectFromSlowBoilerplateHelper
+      1    0.1%    0.1%  Builtin: Construct
+      1    0.1%    0.1%  Builtin: Call_ReceiverIsAny
+      1    0.1%    0.1%  Builtin: ArrayPrototypeSort
+ [C++]:
+   ticks  total  nonlib   name
+     55    3.1%    6.7%  syscall@@GLIBC_2.2.5
+     29    1.6%    3.5%  __lll_lock_wake_private@@GLIBC_PRIVATE
+     14    0.8%    1.7%  __lll_lock_wait_private@@GLIBC_PRIVATE
+     10    0.6%    1.2%  __libc_calloc@@GLIBC_2.2.5
+      9    0.5%    1.1%  __libc_malloc@@GLIBC_2.2.5
+      6    0.3%    0.7%  __munmap@@GLIBC_PRIVATE
+      3    0.2%    0.4%  __madvise@@GLIBC_PRIVATE
+      2    0.1%    0.2%  __libc_free@@GLIBC_2.2.5
+      1    0.1%    0.1%  brk@@GLIBC_2.2.5
+      1    0.1%    0.1%  __sbrk@@GLIBC_2.2.5
+      1    0.1%    0.1%  __open@@GLIBC_2.2.5
+      1    0.1%    0.1%  __mmap@@GLIBC_PRIVATE
+      1    0.1%    0.1%  __getpid@@GLIBC_2.2.5
+ [Summary]:
+   ticks  total  nonlib   name
+    457   25.9%   55.3%  JavaScript
+    133    7.5%   16.1%  C++
+    177   10.0%   21.4%  GC
+    935   53.1%          Shared libraries
+    237   13.5%          Unaccounted
+ [C++ entry points]:
+   ticks    cpp   total   name
+     29   41.4%    1.6%  __lll_lock_wake_private@@GLIBC_PRIVATE
+     14   20.0%    0.8%  __lll_lock_wait_private@@GLIBC_PRIVATE
+     10   14.3%    0.6%  __libc_calloc@@GLIBC_2.2.5
+      9   12.9%    0.5%  __libc_malloc@@GLIBC_2.2.5
+      5    7.1%    0.3%  syscall@@GLIBC_2.2.5
+      1    1.4%    0.1%  brk@@GLIBC_2.2.5
+      1    1.4%    0.1%  __sbrk@@GLIBC_2.2.5
+      1    1.4%    0.1%  __libc_free@@GLIBC_2.2.5
+ [Bottom up (heavy) profile]:
+  Note: percentage shows a share of a particular caller in the total
+  amount of its parent calls.
+  Callers occupying less than 1.0% are not shown.
+   ticks parent  name
+    696   39.5%  /var/agent-loop/repo/target/release/deno
+    500   71.8%    /var/agent-loop/repo/target/release/deno
+    251   50.2%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+    251  100.0%        Builtin: AsyncModuleEvaluate
+     77   15.4%      JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+     77  100.0%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     77  100.0%          Builtin: AsyncModuleEvaluate
+     73   14.6%      Builtin: TypedArrayPrototypeSlice
+     57   78.1%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     57  100.0%          Builtin: AsyncModuleEvaluate
+     12   16.4%        Builtin: AsyncFunctionAwaitResolveClosure
+      3    4.1%        JS: +set method ext:deno_fetch/23_request.js:116:15
+      2   66.7%          JS: ^benchAsync file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:56:26
+      2  100.0%            Builtin: AsyncFunctionAwaitResolveClosure
+      1   33.3%          Builtin: AsyncFunctionAwaitResolveClosure
+      1    1.4%        JS: ^bench file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:10:15
+      1  100.0%          Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      1  100.0%            Builtin: AsyncModuleEvaluate
+     55   11.0%      JS: *consumeBody ext:deno_fetch/22_body.js:254:29
+     55  100.0%        Builtin: AsyncFunctionAwaitResolveClosure
+     31    6.2%      JS: +consumeBody ext:deno_fetch/22_body.js:254:29
+     31  100.0%        Builtin: AsyncFunctionAwaitResolveClosure
+     96   13.8%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     96  100.0%      Builtin: AsyncModuleEvaluate
+    239   13.6%  /usr/lib/x86_64-linux-gnu/libc.so.6
+    203   84.9%    /var/agent-loop/repo/target/release/deno
+    192   94.6%      Builtin: TypedArrayPrototypeSlice
+    143   74.5%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+    143  100.0%          Builtin: AsyncModuleEvaluate
+     36   18.8%        Builtin: AsyncFunctionAwaitResolveClosure
+      9    4.7%        JS: +set method ext:deno_fetch/23_request.js:116:15
+      7   77.8%          Builtin: AsyncFunctionAwaitResolveClosure
+      2   22.2%          JS: ^benchAsync file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:56:26
+      2  100.0%            Builtin: AsyncFunctionAwaitResolveClosure
+      2    1.0%        JS: ~benchAsync file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:56:26
+      2  100.0%          Builtin: AsyncFunctionAwaitResolveClosure
+      2    1.0%        JS: ^bench file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:10:15
+      2  100.0%          Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      2  100.0%            Builtin: AsyncModuleEvaluate
+      5    2.5%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      5  100.0%        Builtin: AsyncModuleEvaluate
+    237   13.5%  UNKNOWN
+    196   82.7%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+    196  100.0%      Builtin: AsyncModuleEvaluate
+     14    5.9%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+     14  100.0%      JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+     14  100.0%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     14  100.0%          Builtin: AsyncModuleEvaluate
+     11    4.6%    Builtin: AsyncFunctionAwaitResolveClosure
+      6    2.5%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:821:19
+      6  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      6  100.0%        Builtin: AsyncModuleEvaluate
+      3    1.3%    JS: ^bench file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:10:15
+      3  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      3  100.0%        Builtin: AsyncModuleEvaluate
+     55    3.1%  syscall@@GLIBC_2.2.5
+      5    9.1%    /var/agent-loop/repo/target/release/deno
+      1   20.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      1  100.0%        Builtin: AsyncModuleEvaluate
+      1   20.0%      JS: ~benchAsync file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:56:26
+      1  100.0%        Builtin: AsyncFunctionAwaitResolveClosure
+      1   20.0%      JS: ^Request ext:deno_fetch/23_request.js:321:14
+      1  100.0%        JS: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:43:28
+      1  100.0%          JS: ^bench file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:10:15
+      1  100.0%            Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      1   20.0%      JS: +json ext:deno_fetch/22_body.js:348:27
+      1  100.0%        JS: ^<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:71:44
+      1  100.0%          JS: ^benchAsync file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:56:26
+      1  100.0%            Builtin: AsyncFunctionAwaitResolveClosure
+      1   20.0%      JS: +consumeBody ext:deno_fetch/22_body.js:254:29
+      1  100.0%        JS: +text ext:deno_fetch/22_body.js:358:27
+      1  100.0%          Builtin: AsyncFunctionAwaitResolveClosure
+     50    2.8%  Builtin: LoadIC
+     37   74.0%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     37  100.0%      Builtin: AsyncModuleEvaluate
+      4    8.0%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:821:19
+      4  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      4  100.0%        Builtin: AsyncModuleEvaluate
+      4    8.0%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+      4  100.0%      JS: *<anonymous> ext:deno_webidl/00_webidl.js:821:19
+      4  100.0%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      4  100.0%          Builtin: AsyncModuleEvaluate
+      3    6.0%    JS: *get headerList ext:deno_fetch/23_request.js:120:19
+      3  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      3  100.0%        Builtin: AsyncModuleEvaluate
+      1    2.0%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+      1  100.0%      JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+      1  100.0%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      1  100.0%          Builtin: AsyncModuleEvaluate
+      1    2.0%    Builtin: AsyncFunctionAwaitResolveClosure
+     31    1.8%  Builtin: StringToLowerCaseIntl
+     30   96.8%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     30  100.0%      Builtin: AsyncModuleEvaluate
+      1    3.2%    JS: +next ext:deno_webidl/00_webidl.js:1235:9
+      1  100.0%      JS: +<anonymous> ext:deno_webidl/00_webidl.js:932:19
+      1  100.0%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      1  100.0%          Builtin: AsyncModuleEvaluate
+     29    1.6%  __lll_lock_wake_private@@GLIBC_PRIVATE
+     29  100.0%    /var/agent-loop/repo/target/release/deno
+     29  100.0%      Builtin: TypedArrayPrototypeSlice
+     20   69.0%        Builtin: AsyncFunctionAwaitResolveClosure
+      9   31.0%        JS: +set method ext:deno_fetch/23_request.js:116:15
+      9  100.0%          Builtin: AsyncFunctionAwaitResolveClosure
+     28    1.6%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:821:19
+     28  100.0%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     28  100.0%      Builtin: AsyncModuleEvaluate
+     27    1.5%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+     18   66.7%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     18  100.0%      Builtin: AsyncModuleEvaluate
+      9   33.3%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+      9  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      9  100.0%        Builtin: AsyncModuleEvaluate
+     27    1.5%  Builtin: CreateShallowObjectLiteral
+     22   81.5%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     22  100.0%      Builtin: AsyncModuleEvaluate
+      4   14.8%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:821:19
+      4  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      4  100.0%        Builtin: AsyncModuleEvaluate
+      1    3.7%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+      1  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      1  100.0%        Builtin: AsyncModuleEvaluate
+     23    1.3%  Builtin: StringAdd_CheckNone
+     22   95.7%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     22  100.0%      Builtin: AsyncModuleEvaluate
+      1    4.3%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+      1  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      1  100.0%        Builtin: AsyncModuleEvaluate
+     21    1.2%  Builtin: KeyedStoreIC
+     10   47.6%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:932:19
+     10  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     10  100.0%        Builtin: AsyncModuleEvaluate
+      7   33.3%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      7  100.0%      Builtin: AsyncModuleEvaluate
+      3   14.3%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:821:19
+      3  100.0%      Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      3  100.0%        Builtin: AsyncModuleEvaluate
+      1    4.8%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+      1  100.0%      JS: *<anonymous> ext:deno_webidl/00_webidl.js:821:19
+      1  100.0%        Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+      1  100.0%          Builtin: AsyncModuleEvaluate
+     19    1.1%  Builtin: ObjectPrototypeIsPrototypeOf
+     14   73.7%    Script: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/micro/request_response_micro.js:1:1
+     14  100.0%      Builtin: AsyncModuleEvaluate
+      3   15.8%    Builtin: AsyncFunctionAwaitResolveClosure
+      1    5.3%    JS: +consumeBody ext:deno_fetch/22_body.js:254:29
+      1  100.0%      JS: +json ext:deno_fetch/22_body.js:348:27
+      1  100.0%        Builtin: AsyncFunctionAwaitResolveClosure
diff --git a/tools/perf_research/fetch/profiles/request_response_micro.v8.log.gz b/tools/perf_research/fetch/profiles/request_response_micro.v8.log.gz
new file mode 100644
index 00000000000000..e37c4c0976a992
Binary files /dev/null and b/tools/perf_research/fetch/profiles/request_response_micro.v8.log.gz differ
diff --git a/tools/perf_research/fetch/profiles/request_response_micro_deno.json b/tools/perf_research/fetch/profiles/request_response_micro_deno.json
new file mode 100644
index 00000000000000..4efe73925d6a7a
--- /dev/null
+++ b/tools/perf_research/fetch/profiles/request_response_micro_deno.json
@@ -0,0 +1,7 @@
+{"name":"response_construct_string","ms":"25.30","ns_per_op":"126.5"}
+{"name":"response_construct_u8","ms":"213.78","ns_per_op":"1068.9"}
+{"name":"response_construct_with_headers","ms":"113.71","ns_per_op":"568.6"}
+{"name":"response_construct_reused_headers","ms":"277.05","ns_per_op":"1385.2"}
+{"name":"request_construct","ms":"728.00","ns_per_op":"3640.0"}
+{"name":"response_text_smallish","ms":"81.27","ns_per_op":"1625.5"}
+{"name":"response_json_smallish","ms":"196.90","ns_per_op":"3937.9"}
diff --git a/tools/perf_research/fetch/profiles/server_hello.prof.txt b/tools/perf_research/fetch/profiles/server_hello.prof.txt
new file mode 100644
index 00000000000000..2b9f936dd2ce4f
--- /dev/null
+++ b/tools/perf_research/fetch/profiles/server_hello.prof.txt
@@ -0,0 +1,134 @@
+Testing v8 version different from logging version
+(node:75388) ExperimentalWarning: VM Modules is an experimental feature and might change at any time
+(Use `node --trace-warnings ...` to show where the warning was created)
+Statistical profiling result from /tmp/prof_server/v8.log, (2619 ticks, 284 unaccounted, 0 excluded).
+ [Shared libraries]:
+   ticks  total  nonlib   name
+   1371   52.3%          /var/agent-loop/repo/target/release/deno
+    109    4.2%          /usr/lib/x86_64-linux-gnu/libc.so.6
+ [JavaScript]:
+   ticks  total  nonlib   name
+     98    3.7%    8.6%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+     57    2.2%    5.0%  Builtin: KeyedStoreIC
+     48    1.8%    4.2%  Builtin: LoadIC
+     45    1.7%    4.0%  Builtin: CreateTypedArray
+     41    1.6%    3.6%  Builtin: CreateShallowObjectLiteral
+     37    1.4%    3.2%  Builtin: RunMicrotasks
+     35    1.3%    3.1%  Builtin: GetProperty
+     34    1.3%    3.0%  Builtin: TypedArrayPrototypeSlice
+     33    1.3%    2.9%  Builtin: ObjectPrototypeIsPrototypeOf
+     30    1.1%    2.6%  Builtin: LoadICTrampoline
+     22    0.8%    1.9%  Builtin: JSConstructStubGeneric
+     20    0.8%    1.8%  Builtin: AsyncFunctionAwait
+     18    0.7%    1.6%  Builtin: ObjectPrototypeHasOwnProperty
+     17    0.6%    1.5%  Builtin: ResolvePromise
+     17    0.6%    1.5%  Builtin: PerformPromiseThen
+     17    0.6%    1.5%  Builtin: KeyedLoadIC
+     17    0.6%    1.5%  Builtin: EnqueueMicrotask
+     14    0.5%    1.2%  Builtin: KeyedLoadIC_PolymorphicName
+     14    0.5%    1.2%  Builtin: CallApiCallbackOptimizedNoProfiling
+     12    0.5%    1.1%  Builtin: Construct
+     11    0.4%    1.0%  JS: *get ext:deno_fetch/22_body.js:290:10
+     11    0.4%    1.0%  Builtin: ForInEnumerate
+     10    0.4%    0.9%  Builtin: ObjectHasOwn
+     10    0.4%    0.9%  Builtin: GrowFastSmiOrObjectElements
+      8    0.3%    0.7%  Builtin: FastNewObject
+      8    0.3%    0.7%  Builtin: CallFunction_ReceiverIsAny
+      7    0.3%    0.6%  Builtin: ResumeGeneratorTrampoline
+      7    0.3%    0.6%  Builtin: PromisePrototypeThen
+      7    0.3%    0.6%  Builtin: FulfillPromise
+      6    0.2%    0.5%  Builtin: StringToLowerCaseIntl
+      6    0.2%    0.5%  Builtin: JSRunMicrotasksEntry
+      6    0.2%    0.5%  Builtin: ConstructFunction
+      6    0.2%    0.5%  Builtin: ArrayBufferConstructor
+      5    0.2%    0.4%  Builtin: StringSubstring
+      5    0.2%    0.4%  Builtin: JSEntry
+      4    0.2%    0.4%  Builtin: StringAdd_CheckNone
+      4    0.2%    0.4%  Builtin: KeyedStoreICTrampoline
+      3    0.1%    0.3%  Builtin: StringEqual
+      3    0.1%    0.3%  Builtin: CallFunction_ReceiverIsNullOrUndefined
+      3    0.1%    0.3%  Builtin: AsyncFunctionAwaitResolveClosure
+      3    0.1%    0.3%  Builtin: AdaptorWithBuiltinExitFrame1
+      2    0.1%    0.2%  JS: +get ext:deno_fetch/22_body.js:290:10
+      2    0.1%    0.2%  JS: +<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+      2    0.1%    0.2%  Builtin: Typeof
+      2    0.1%    0.2%  Builtin: TypedArrayPrototypeByteLength
+      2    0.1%    0.2%  Builtin: StringPrototypeSlice
+      2    0.1%    0.2%  Builtin: PromiseFulfillReactionJob
+      2    0.1%    0.2%  Builtin: LoadICGenericBaseline
+      2    0.1%    0.2%  Builtin: JSBuiltinsConstructStub
+      2    0.1%    0.2%  Builtin: ForInFilter
+      2    0.1%    0.2%  Builtin: Call_ReceiverIsNullOrUndefined
+      1    0.0%    0.1%  JS: ~<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/servers/deno_server.js:10:42
+      1    0.0%    0.1%  Builtin: ToBooleanForBaselineJump
+      1    0.0%    0.1%  Builtin: StringPrototypeCharCodeAt
+      1    0.0%    0.1%  Builtin: KeyedLoadICTrampoline
+      1    0.0%    0.1%  Builtin: FunctionPrototypeCall
+      1    0.0%    0.1%  Builtin: ForInPrepare
+      1    0.0%    0.1%  Builtin: Call_ReceiverIsAny
+      1    0.0%    0.1%  Builtin: CallFunction_ReceiverIsNotNullOrUndefined
+      1    0.0%    0.1%  Builtin: AsyncFunctionEnter
+ [C++]:
+   ticks  total  nonlib   name
+     28    1.1%    2.5%  __libc_malloc@@GLIBC_2.2.5
+     15    0.6%    1.3%  __libc_free@@GLIBC_2.2.5
+     11    0.4%    1.0%  syscall@@GLIBC_2.2.5
+      7    0.3%    0.6%  __libc_calloc@@GLIBC_2.2.5
+      3    0.1%    0.3%  clock_nanosleep@GLIBC_2.2.5
+      1    0.0%    0.1%  __read_nocancel@@GLIBC_PRIVATE
+      1    0.0%    0.1%  __mmap@@GLIBC_PRIVATE
+      1    0.0%    0.1%  __madvise@@GLIBC_PRIVATE
+ [Summary]:
+   ticks  total  nonlib   name
+    788   30.1%   69.2%  JavaScript
+     67    2.6%    5.9%  C++
+     43    1.6%    3.8%  GC
+   1480   56.5%          Shared libraries
+    284   10.8%          Unaccounted
+ [C++ entry points]:
+   ticks    cpp   total   name
+     26   49.1%    1.0%  __libc_malloc@@GLIBC_2.2.5
+     15   28.3%    0.6%  __libc_free@@GLIBC_2.2.5
+      7   13.2%    0.3%  __libc_calloc@@GLIBC_2.2.5
+      3    5.7%    0.1%  clock_nanosleep@GLIBC_2.2.5
+      2    3.8%    0.1%  syscall@@GLIBC_2.2.5
+ [Bottom up (heavy) profile]:
+  Note: percentage shows a share of a particular caller in the total
+  amount of its parent calls.
+  Callers occupying less than 1.0% are not shown.
+   ticks parent  name
+   1371   52.3%  /var/agent-loop/repo/target/release/deno
+    370   27.0%    /var/agent-loop/repo/target/release/deno
+    203   54.9%      Builtin: TypedArrayPrototypeSlice
+    161   11.7%    Builtin: AsyncFunctionAwaitResolveClosure
+    284   10.8%  UNKNOWN
+     34   12.0%    Builtin: AsyncFunctionAwaitResolveClosure
+      3    1.1%    JS: ^<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/servers/deno_server.js:10:42
+    109    4.2%  /usr/lib/x86_64-linux-gnu/libc.so.6
+     30   27.5%    /var/agent-loop/repo/target/release/deno
+     29   96.7%      Builtin: TypedArrayPrototypeSlice
+      3    2.8%    Builtin: TypedArrayPrototypeSlice
+      1   33.3%      JS: ^<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/servers/deno_server.js:10:42
+      3    2.8%    Builtin: AsyncFunctionAwaitResolveClosure
+     98    3.7%  JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+     57    2.2%  Builtin: KeyedStoreIC
+     25   43.9%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+      1    1.8%    JS: ^<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/servers/deno_server.js:10:42
+      1    1.8%    JS: +<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+     48    1.8%  Builtin: LoadIC
+     45    1.7%  Builtin: CreateTypedArray
+     45  100.0%    Builtin: TypedArrayPrototypeSlice
+     41    1.6%  Builtin: CreateShallowObjectLiteral
+      4    9.8%    JS: *<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+      1    2.4%    JS: +<anonymous> ext:deno_webidl/00_webidl.js:1101:10
+     37    1.4%  Builtin: RunMicrotasks
+     35    1.3%  Builtin: GetProperty
+     34    1.3%  Builtin: TypedArrayPrototypeSlice
+      1    2.9%    JS: ^<anonymous> file:///var/agent-loop/repo/tools/perf_research/fetch/servers/deno_server.js:10:42
+     33    1.3%  Builtin: ObjectPrototypeIsPrototypeOf
+      1    3.0%    Builtin: AsyncFunctionAwaitResolveClosure
+     30    1.1%  Builtin: LoadICTrampoline
+     28    1.1%  __libc_malloc@@GLIBC_2.2.5
+     10   35.7%    /var/agent-loop/repo/target/release/deno
+     10  100.0%      Builtin: TypedArrayPrototypeSlice
+      1    3.6%    Builtin: AsyncFunctionAwaitResolveClosure
diff --git a/tools/perf_research/fetch/profiles/server_hello.v8.log.gz b/tools/perf_research/fetch/profiles/server_hello.v8.log.gz
new file mode 100644
index 00000000000000..4f00d7e8d5c265
Binary files /dev/null and b/tools/perf_research/fetch/profiles/server_hello.v8.log.gz differ
diff --git a/tools/perf_research/fetch/results.jsonl b/tools/perf_research/fetch/results.jsonl
new file mode 100644
index 00000000000000..cc1e4b4f5c346c
--- /dev/null
+++ b/tools/perf_research/fetch/results.jsonl
@@ -0,0 +1,12 @@
+{"label":"deno_hello","method":"GET","url":"http://127.0.0.1:8080/hello","rps":"39775.16","lat_avg":"1.63ms","lat_p99":"4.33ms","non2xx":"0"}
+{"label":"deno_headers","method":"GET","url":"http://127.0.0.1:8080/headers","rps":"33803.13","lat_avg":"1.91ms","lat_p99":"4.03ms","non2xx":"0"}
+{"label":"deno_echo_small","method":"POST","url":"http://127.0.0.1:8080/echo","rps":"30408.38","lat_avg":"2.10ms","lat_p99":"3.40ms","non2xx":"0"}
+{"label":"deno_bigbody","method":"GET","url":"http://127.0.0.1:8080/bigbody","rps":"1246.27","lat_avg":"51.21ms","lat_p99":"80.21ms","non2xx":"0"}
+{"label":"node_hello","method":"GET","url":"http://127.0.0.1:8081/hello","rps":"32225.68","lat_avg":"2.27ms","lat_p99":"4.67ms","non2xx":"0"}
+{"label":"node_headers","method":"GET","url":"http://127.0.0.1:8081/headers","rps":"37094.63","lat_avg":"1.75ms","lat_p99":"3.23ms","non2xx":"0"}
+{"label":"node_echo_small","method":"POST","url":"http://127.0.0.1:8081/echo","rps":"18456.21","lat_avg":"3.46ms","lat_p99":"5.50ms","non2xx":"0"}
+{"label":"node_bigbody","method":"GET","url":"http://127.0.0.1:8081/bigbody","rps":"2435.40","lat_avg":"32.72ms","lat_p99":"335.22ms","non2xx":"0"}
+{"label":"bun_hello","method":"GET","url":"http://127.0.0.1:8082/hello","rps":"69190.38","lat_avg":"0.94ms","lat_p99":"2.16ms","non2xx":"0"}
+{"label":"bun_headers","method":"GET","url":"http://127.0.0.1:8082/headers","rps":"55933.44","lat_avg":"1.14ms","lat_p99":"2.30ms","non2xx":"0"}
+{"label":"bun_echo_small","method":"POST","url":"http://127.0.0.1:8082/echo","rps":"51143.70","lat_avg":"1.26ms","lat_p99":"2.55ms","non2xx":"0"}
+{"label":"bun_bigbody","method":"GET","url":"http://127.0.0.1:8082/bigbody","rps":"1081.59","lat_avg":"58.86ms","lat_p99":"108.30ms","non2xx":"0"}
diff --git a/tools/perf_research/fetch/run_micro.sh b/tools/perf_research/fetch/run_micro.sh
new file mode 100755
index 00000000000000..35eee90a434888
--- /dev/null
+++ b/tools/perf_research/fetch/run_micro.sh
@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+# Run microbenches in all three runtimes.
+# Usage: bash run_micro.sh
+set -euo pipefail
+cd "$(dirname "$0")"
+
+DENO_BIN="${DENO_BIN:-../../../target/release/deno}"
+NODE_BIN="${NODE_BIN:-node}"
+BUN_BIN="${BUN_BIN:-bun}"
+
+OUT="micro_results.jsonl"
+: > "$OUT"
+
+run_one() {
+  local script=$1
+  echo "===== $script ====="
+  for rt in deno node bun; do
+    case $rt in
+      deno) cmd="$DENO_BIN run -A --no-prompt $script" ;;
+      node) cmd="$NODE_BIN $script" ;;
+      bun)  cmd="$BUN_BIN $script" ;;
+    esac
+    while IFS= read -r line; do
+      printf '%s\n' "$line" | jq --arg rt "$rt" --arg script "$(basename $script)" '. + {runtime: $rt, script: $script}' >> "$OUT" 2>/dev/null || \
+        printf '{"runtime":"%s","script":"%s","raw":%s}\n' "$rt" "$(basename $script)" "$(printf '%s' "$line" | jq -Rs .)" >> "$OUT"
+    done < <($cmd 2>/dev/null)
+  done
+}
+
+run_one "micro/headers_micro.js"
+run_one "micro/request_response_micro.js"
+
+echo
+echo "--- summary ---"
+cat "$OUT"
diff --git a/tools/perf_research/fetch/run_servers.sh b/tools/perf_research/fetch/run_servers.sh
new file mode 100755
index 00000000000000..e4581411ebd3dd
--- /dev/null
+++ b/tools/perf_research/fetch/run_servers.sh
@@ -0,0 +1,103 @@
+#!/usr/bin/env bash
+# Launch all three servers and benchmark them with wrk on each route.
+# Outputs JSON-lines results to results.jsonl in this directory.
+#
+# Usage: bash run_servers.sh [duration_seconds] [connections]
+#
+# Requires: ./target/release/deno, node, bun, wrk on PATH.
+
+set -uo pipefail
+cd "$(dirname "$0")"
+
+DENO_BIN="${DENO_BIN:-../../../target/release/deno}"
+NODE_BIN="${NODE_BIN:-node}"
+BUN_BIN="${BUN_BIN:-bun}"
+
+DURATION="${1:-10}"
+CONNS="${2:-64}"
+THREADS=4
+
+OUT="results.jsonl"
+: > "$OUT"
+
+versions() {
+  echo "deno=$($DENO_BIN --version | head -1)"
+  echo "node=$($NODE_BIN --version)"
+  echo "bun=$($BUN_BIN --version)"
+}
+versions > versions.txt
+cat versions.txt
+
+# pre-cleanup any lingering listeners
+for p in 8080 8081 8082; do
+  pid=$(ss -lntp 2>/dev/null | awk -v port=":$p" '$4 ~ port {sub(/.*pid=/,""); sub(/,.*/,""); print}')
+  if [ -n "$pid" ]; then kill -9 "$pid" 2>/dev/null || true; fi
+done
+sleep 1
+
+wait_port() {
+  local port=$1
+  for i in $(seq 1 50); do
+    if exec 3<>/dev/tcp/127.0.0.1/$port 2>/dev/null; then
+      exec 3<&-; exec 3>&-
+      return 0
+    fi
+    sleep 0.2
+  done
+  echo "port $port never came up"
+  return 1
+}
+
+# Lua script for POST. wrk substitutes %BODY% via shell.
+cat > post.lua <<'EOF'
+wrk.method = "POST"
+wrk.headers["Content-Type"] = "application/json"
+wrk.body = '{"a":1,"b":2,"c":[1,2,3]}'
+EOF
+
+run_wrk() {
+  local label=$1 url=$2 method=${3:-GET}
+  local extra=""
+  if [ "$method" = "POST" ]; then extra="-s post.lua"; fi
+  echo "==> $label  $method $url"
+  out=$(wrk -t$THREADS -c$CONNS -d${DURATION}s --latency $extra "$url" 2>&1 || true)
+  echo "$out"
+  rps=$(echo "$out" | awk '/Requests\/sec/ {print $2}')
+  lat_avg=$(echo "$out" | awk '/^    Latency/ {print $2; exit}')
+  # Latency p99 lives in a Latency Distribution block; grab the FIRST 99% match
+  lat_p99=$(echo "$out" | awk '/Latency Distribution/{f=1; next} f && /99%/ {print $2; exit}')
+  non2xx=$(echo "$out" | awk '/Non-2xx or 3xx/ {print $5; exit}')
+  printf '{"label":"%s","method":"%s","url":"%s","rps":"%s","lat_avg":"%s","lat_p99":"%s","non2xx":"%s"}\n' \
+    "$label" "$method" "$url" "$rps" "$lat_avg" "$lat_p99" "${non2xx:-0}" >> "$OUT"
+}
+
+run_runtime() {
+  local name=$1 port=$2 cmd=$3
+  local logfile="server_${name}.log"
+  echo "===== $name on port $port ====="
+  bash -c "exec $cmd" > "$logfile" 2>&1 &
+  local pid=$!
+  if ! wait_port "$port"; then
+    echo "server failed; log:" && cat "$logfile" | head -20
+    kill -9 "$pid" 2>/dev/null || true
+    return
+  fi
+  sleep 1
+
+  run_wrk "${name}_hello"      "http://127.0.0.1:${port}/hello"
+  run_wrk "${name}_headers"    "http://127.0.0.1:${port}/headers"
+  run_wrk "${name}_echo_small" "http://127.0.0.1:${port}/echo" POST
+  run_wrk "${name}_bigbody"    "http://127.0.0.1:${port}/bigbody"
+
+  kill -9 "$pid" 2>/dev/null || true
+  # Give the kernel time to release the port
+  sleep 2
+}
+
+run_runtime deno 8080 "$DENO_BIN run -A --no-prompt servers/deno_server.js --port=8080"
+run_runtime node 8081 "$NODE_BIN servers/node_server.mjs --port=8081"
+run_runtime bun  8082 "$BUN_BIN  servers/bun_server.js --port=8082"
+
+echo
+echo "--- summary ---"
+cat "$OUT"
diff --git a/tools/perf_research/fetch/run_v8_prof.sh b/tools/perf_research/fetch/run_v8_prof.sh
new file mode 100755
index 00000000000000..f998330b45c7ee
--- /dev/null
+++ b/tools/perf_research/fetch/run_v8_prof.sh
@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# Run a Deno microbench with --v8-flags=--prof, then post-process via
+# `node --prof-process` to produce a readable tick summary committed to
+# profiles/.  This is the attribution mechanism used in the report.
+#
+# Usage:  bash run_v8_prof.sh
+set -euo pipefail
+cd "$(dirname "$0")"
+DENO_BIN="${DENO_BIN:-../../../target/release/deno}"
+NODE_BIN="${NODE_BIN:-node}"
+mkdir -p profiles
+
+run_prof() {
+  local tag=$1 script=$2
+  local workdir
+  workdir=$(mktemp -d)
+  echo "==> $tag: $DENO_BIN run -A --v8-flags=--prof $script (workdir=$workdir)"
+  ( cd "$workdir" && "$DENO_BIN" run -A --no-prompt --v8-flags=--prof,--no-logfile-per-isolate "$OLDPWD/$script" ) > "profiles/${tag}.stdout.txt" 2> "profiles/${tag}.stderr.txt" || true
+  local log
+  log=$(find "$workdir" -maxdepth 1 -name '*-v8.log' -o -name 'v8.log' | head -1)
+  if [ -z "$log" ]; then echo "no v8 log produced for $tag (workdir=$workdir)"; ls "$workdir"; return 1; fi
+  cp "$log" "profiles/${tag}.v8.log"
+  $NODE_BIN --prof-process "profiles/${tag}.v8.log" > "profiles/${tag}.prof.txt" 2>&1 || true
+  echo "--- top entries for $tag ---"
+  awk '/\[Bottom up \(heavy\) profile\]/{f=1} f' "profiles/${tag}.prof.txt" | head -40
+}
+
+run_prof headers_micro micro/headers_micro.js
+run_prof request_response_micro micro/request_response_micro.js
diff --git a/tools/perf_research/fetch/servers/bun_server.js b/tools/perf_research/fetch/servers/bun_server.js
new file mode 100644
index 00000000000000..3caaa008024311
--- /dev/null
+++ b/tools/perf_research/fetch/servers/bun_server.js
@@ -0,0 +1,47 @@
+// HTTP server using Bun.serve.
+// Run: bun servers/bun_server.js --port=8082
+const port = Number(
+  Bun.argv.find((a) => a.startsWith("--port="))?.slice(7),
+) || 8082;
+
+const helloBytes = new TextEncoder().encode(
+  JSON.stringify({ ok: true, msg: "hello" }),
+);
+
+Bun.serve({
+  port,
+  async fetch(req) {
+    const url = new URL(req.url);
+    switch (url.pathname) {
+      case "/hello":
+        return new Response(helloBytes, {
+          headers: { "content-type": "application/json" },
+        });
+      case "/echo": {
+        const body = await req.json();
+        return new Response(JSON.stringify(body), {
+          headers: { "content-type": "application/json" },
+        });
+      }
+      case "/echo-bytes": {
+        const buf = await req.arrayBuffer();
+        return new Response(buf, {
+          headers: { "content-type": "application/octet-stream" },
+        });
+      }
+      case "/headers": {
+        let count = 0;
+        for (const _h of req.headers) count++;
+        return new Response(`${count}`);
+      }
+      case "/bigbody": {
+        const buf = new Uint8Array(1 << 20).fill(0x41);
+        return new Response(buf, {
+          headers: { "content-type": "application/octet-stream" },
+        });
+      }
+      default:
+        return new Response("not found", { status: 404 });
+    }
+  },
+});
diff --git a/tools/perf_research/fetch/servers/deno_server.js b/tools/perf_research/fetch/servers/deno_server.js
new file mode 100644
index 00000000000000..6481932a36d7ba
--- /dev/null
+++ b/tools/perf_research/fetch/servers/deno_server.js
@@ -0,0 +1,47 @@
+// HTTP server using Deno.serve. JSON echo / simple text routes.
+// Run: deno run -A --no-prompt servers/deno_server.js [--port=8080]
+const port = Number(Deno.args.find((a) => a.startsWith("--port="))?.slice(7)) ||
+  8080;
+
+const helloBytes = new TextEncoder().encode(
+  JSON.stringify({ ok: true, msg: "hello" }),
+);
+
+Deno.serve({ port, onListen: () => {} }, async (req) => {
+  const url = new URL(req.url);
+  switch (url.pathname) {
+    case "/hello": {
+      return new Response(helloBytes, {
+        headers: { "content-type": "application/json" },
+      });
+    }
+    case "/echo": {
+      const body = await req.json();
+      return new Response(JSON.stringify(body), {
+        headers: { "content-type": "application/json" },
+      });
+    }
+    case "/echo-bytes": {
+      const buf = await req.arrayBuffer();
+      return new Response(buf, {
+        headers: { "content-type": "application/octet-stream" },
+      });
+    }
+    case "/headers": {
+      // Force consumption of all headers
+      let count = 0;
+      for (const _h of req.headers) count++;
+      return new Response(`${count}`);
+    }
+    case "/bigbody": {
+      // 1 MB ASCII body. Server allocates a fresh buffer each request to
+      // exercise the response body construction path.
+      const buf = new Uint8Array(1 << 20).fill(0x41);
+      return new Response(buf, {
+        headers: { "content-type": "application/octet-stream" },
+      });
+    }
+    default:
+      return new Response("not found", { status: 404 });
+  }
+});
diff --git a/tools/perf_research/fetch/servers/deno_server_stdrouter.js b/tools/perf_research/fetch/servers/deno_server_stdrouter.js
new file mode 100644
index 00000000000000..08b179fb569f3e
--- /dev/null
+++ b/tools/perf_research/fetch/servers/deno_server_stdrouter.js
@@ -0,0 +1,17 @@
+// HTTP server using Deno.serve, with Request/Response semantics (Web Fetch surface).
+// This stresses the Web Fetch Request/Response/Headers JS layer on the server side,
+// in contrast to deno_server.js which uses the same surface but is the same path.
+// Kept for future variants (e.g. router-style).
+const port = Number(Deno.args.find((a) => a.startsWith("--port="))?.slice(7)) ||
+  8083;
+
+Deno.serve({ port, onListen: () => {} }, (req) => {
+  const url = new URL(req.url);
+  const out = new Headers();
+  out.set("x-original-method", req.method);
+  out.set("x-original-path", url.pathname);
+  for (const [k, v] of req.headers) {
+    out.append(`x-echo-${k}`, v);
+  }
+  return new Response("ok", { headers: out });
+});
diff --git a/tools/perf_research/fetch/servers/node_server.mjs b/tools/perf_research/fetch/servers/node_server.mjs
new file mode 100644
index 00000000000000..cf738ba2b0e05d
--- /dev/null
+++ b/tools/perf_research/fetch/servers/node_server.mjs
@@ -0,0 +1,51 @@
+// HTTP server using Node's built-in fetch-compatible primitives via node:http.
+// Uses standard node:http for parity with Deno.serve (both are native HTTP servers
+// without an undici-style Request/Response wrapper). Run with Node 22+.
+import http from "node:http";
+
+const port = Number(
+  process.argv.find((a) => a.startsWith("--port="))?.slice(7),
+) || 8081;
+
+const helloBytes = Buffer.from(JSON.stringify({ ok: true, msg: "hello" }));
+
+const server = http.createServer(async (req, res) => {
+  switch (req.url) {
+    case "/hello": {
+      res.setHeader("content-type", "application/json");
+      res.end(helloBytes);
+      return;
+    }
+    case "/echo": {
+      const chunks = [];
+      for await (const c of req) chunks.push(c);
+      const body = JSON.parse(Buffer.concat(chunks).toString("utf8"));
+      res.setHeader("content-type", "application/json");
+      res.end(JSON.stringify(body));
+      return;
+    }
+    case "/echo-bytes": {
+      const chunks = [];
+      for await (const c of req) chunks.push(c);
+      res.setHeader("content-type", "application/octet-stream");
+      res.end(Buffer.concat(chunks));
+      return;
+    }
+    case "/headers": {
+      let count = 0;
+      for (const _ of Object.entries(req.headers)) count++;
+      res.end(`${count}`);
+      return;
+    }
+    case "/bigbody": {
+      const buf = Buffer.alloc(1 << 20, 0x41);
+      res.setHeader("content-type", "application/octet-stream");
+      res.end(buf);
+      return;
+    }
+    default:
+      res.statusCode = 404;
+      res.end("not found");
+  }
+});
+server.listen(port);
diff --git a/tools/perf_research/fetch/versions.txt b/tools/perf_research/fetch/versions.txt
new file mode 100644
index 00000000000000..61285c83deefd3
--- /dev/null
+++ b/tools/perf_research/fetch/versions.txt
@@ -0,0 +1,3 @@
+deno=deno 2.7.14 (stable, release, x86_64-unknown-linux-gnu)
+node=v22.22.2
+bun=1.3.14