diff --git a/.github/workflows/quality.yml b/.github/workflows/quality.yml
index 834dca413b..0fed21369e 100644
--- a/.github/workflows/quality.yml
+++ b/.github/workflows/quality.yml
@@ -303,7 +303,12 @@ jobs:
             # #8522: file-size is base-relative on PR events (compare against
             # max(frozen, base)) so inherited drift doesn't red an innocent PR;
             # workflow_dispatch (no PR base) falls back to absolute comparison.
-            if [ "$g" = "file-size" ] && [ -n "${PR_BASE_SHA:-}" ]; then
+            # New-code mode (Clean-as-You-Code, 2026-08-30): complexity-ratchets and
+            # dead-code compare the PR's files against the merge-base and block only on
+            # what the PR added; the global totals are advisory on PRs and re-frozen at
+            # release. See scripts/check/newCodeMode.mjs.
+            case "$g" in file-size|complexity-ratchets|dead-code) NEW_CODE=1 ;; *) NEW_CODE= ;; esac
+            if [ -n "$NEW_CODE" ] && [ -n "${PR_BASE_SHA:-}" ]; then
               npm run "check:$g" -- --base-ref "$PR_BASE_SHA" || failed+=("$g")
             else
               npm run "check:$g" || failed+=("$g")
diff --git a/docs/architecture/QUALITY_GATES.md b/docs/architecture/QUALITY_GATES.md
index 490b87cc96..46e53b5f86 100644
--- a/docs/architecture/QUALITY_GATES.md
+++ b/docs/architecture/QUALITY_GATES.md
@@ -262,6 +262,23 @@ docs/env contract, i18n parity, unit tests) are unchanged — a red test is stil
   is the early warning: a budget that fills in days means the relaxation is being consumed by
   a few PRs, not by the whole team — look at the offending gate's `_rebaseline_*` notes.
 
+**New-code mode (Clean-as-You-Code) — since 2026-08-30, PR fast-path only**
+
+On `pull_request` events `quality.yml` passes `--base-ref <PR base SHA>` to `check:file-size`,
+`check:complexity-ratchets` and `check:dead-code`. In that mode the gate compares HEAD with the
+merge-base **restricted to the files the PR touched** (`scripts/check/newCodeMode.mjs`: the
+merge-base is materialized in a throwaway `git worktree`, ESLint/knip run there and on HEAD, the
+per-file counts are diffed):
+
+- **blocking** — the PR added cyclomatic/cognitive violations or dead exports in files it changed
+  (`complexityNewCode=`, `cognitiveComplexityNewCode=`, `deadExportsNewCode=` in the log);
+- **advisory** — the global total vs. the frozen baseline. Inherited drift never reds an
+  innocent PR; the drift is re-frozen at release reconciliation and watched by the headroom job.
+
+`workflow_dispatch` runs, the release-green sweep and the nightly headroom job have no PR base
+and keep the absolute (global) comparison. Coverage, duplication and type-coverage stay global
+for now (their tools do not produce a per-file diff cheaply) — candidates for the same treatment.
+
 **Closing the phase at v4.0 (LTS = tighter than before, not "back to normal")**
 
 1. On the pure `release/v4.0.0` tip: `npm run quality:headroom --json` for the record, then
diff --git a/scripts/check/check-complexity-ratchets.mjs b/scripts/check/check-complexity-ratchets.mjs
index 22bcc02fef..59ae575a93 100644
--- a/scripts/check/check-complexity-ratchets.mjs
+++ b/scripts/check/check-complexity-ratchets.mjs
@@ -19,6 +19,78 @@ import {
   countComplexityViolations,
   getComplexityEslintReport,
 } from "./complexityEslintReport.mjs";
+import {
+  baseRefArg,
+  diffNewCode,
+  listChangedFiles,
+  perFileRuleCounts,
+  resolveMergeBase,
+  withBaseWorktree,
+} from "./newCodeMode.mjs";
+import { runComplexityEslintOn } from "./complexityEslintReport.mjs";
+
+const BASE_REF = baseRefArg();
+const NEW_CODE_SCOPE = {
+  dirs: ["src", "open-sse", "electron", "bin"],
+  exts: [".ts", ".tsx", ".js", ".mjs"],
+};
+const CYCLOMATIC_RULES = new Set(["complexity", "max-lines-per-function"]);
+const COGNITIVE_RULES = new Set(["sonarjs/cognitive-complexity"]);
+
+/**
+ * New-code mode (PR events, `--base-ref <sha>`): blocking only on violations the PR added in
+ * the files it touched; the global totals are NOT measured here (the release reconciliation
+ * and the nightly headroom job run the full walk). See newCodeMode.mjs.
+ */
+function mainNewCode() {
+  const mergeBase = resolveMergeBase(BASE_REF);
+  const changed = listChangedFiles(mergeBase, NEW_CODE_SCOPE);
+  console.log(
+    `[complexity-ratchets] new-code mode: merge-base ${mergeBase.slice(0, 12)}, ${changed.length} changed file(s) in scope`
+  );
+  if (changed.length === 0) {
+    console.log("[complexity-ratchets] OK — no source files changed; nothing to compare.");
+    return;
+  }
+  const headReport = runComplexityEslintOn(changed, ROOT);
+  const headCounts = {
+    complexity: perFileRuleCounts(headReport, CYCLOMATIC_RULES, ROOT),
+    cognitive: perFileRuleCounts(headReport, COGNITIVE_RULES, ROOT),
+  };
+  // Base paths are absolute inside the throwaway worktree → relativize while it exists.
+  const baseCounts = withBaseWorktree(mergeBase, (dir) => {
+    const report = runComplexityEslintOn(changed, dir);
+    return {
+      complexity: perFileRuleCounts(report, CYCLOMATIC_RULES, dir),
+      cognitive: perFileRuleCounts(report, COGNITIVE_RULES, dir),
+    };
+  });
+  let failed = false;
+  for (const [label, key, metric] of [
+    ["complexity", "complexity", "complexityNewCode"],
+    ["cognitive-complexity", "cognitive", "cognitiveComplexityNewCode"],
+  ]) {
+    const { regressions, head, base, delta } = diffNewCode(
+      headCounts[key],
+      baseCounts[key],
+      changed
+    );
+    console.log(`${metric}=${delta}`);
+    if (regressions.length) {
+      console.error(
+        `[${label}] REGRESSÃO (código novo) — ${head} violações nos arquivos tocados vs ${base} na base (+${delta}):\n` +
+          regressions.map((r) => `  ✗ ${r.file}: ${r.base} → ${r.head}`).join("\n") +
+          "\n  → quebre a função em helpers menores; o total global do repo NÃO conta aqui, só o que esta PR adicionou."
+      );
+      failed = true;
+    } else {
+      console.log(
+        `[${label}] OK (código novo) — ${head} violações nos arquivos tocados (base ${base})`
+      );
+    }
+  }
+  if (failed) process.exit(1);
+}
 
 const ROOT = process.cwd();
 const UPDATE = process.argv.includes("--update");
@@ -31,6 +103,7 @@ const COMPLEXITY_BASELINE = path.resolve(
 const QUALITY_BASELINE = path.join(ROOT, "config/quality/quality-baseline.json");
 
 function main() {
+  if (BASE_REF) return mainNewCode();
   if (!fs.existsSync(COMPLEXITY_BASELINE)) {
     console.error(`[complexity-ratchets] FAIL — complexity-baseline.json ausente.`);
     process.exit(2);
diff --git a/scripts/check/check-dead-code.mjs b/scripts/check/check-dead-code.mjs
index 1c7f5c5e34..ca5eddcd8c 100644
--- a/scripts/check/check-dead-code.mjs
+++ b/scripts/check/check-dead-code.mjs
@@ -18,10 +18,18 @@ import { execFileSync } from "node:child_process";
 import fs from "node:fs";
 import path from "node:path";
 import { pathToFileURL } from "node:url";
+import {
+  baseRefArg,
+  listChangedFiles,
+  newDeadSymbols,
+  resolveMergeBase,
+  withBaseWorktree,
+} from "./newCodeMode.mjs";
 
 const ROOT = process.cwd();
 const KNIP_BIN = path.join(ROOT, "node_modules", ".bin", "knip");
 const QUIET = process.argv.includes("--quiet");
+const BASE_REF = baseRefArg();
 const PRINT_JSON = process.argv.includes("--json");
 const UPDATE = process.argv.includes("--update");
 
@@ -103,7 +111,7 @@ export function evaluateDeadCode(current, baseline) {
   };
 }
 
-function runKnip() {
+function runKnip(cwd = ROOT) {
   const args = [
     "--reporter",
     "json",
@@ -118,7 +126,7 @@ function runKnip() {
   let stdout;
   try {
     stdout = execFileSync(KNIP_BIN, args, {
-      cwd: ROOT,
+      cwd,
       encoding: "utf8",
       maxBuffer: 128 * 1024 * 1024,
       timeout: 300_000, // 5 min (knip pode ser lento em monorepos grandes)
@@ -144,6 +152,44 @@ function runKnip() {
   return knipJson;
 }
 
+/**
+ * New-code mode (PR events, `--base-ref <sha>`): knip on HEAD and on the merge-base; blocking
+ * only on dead symbols the PR introduced in files it touched. The global count is printed as
+ * an advisory (the release reconciliation re-freezes it). See newCodeMode.mjs.
+ */
+function mainNewCode(baselineValue) {
+  const mergeBase = resolveMergeBase(BASE_REF);
+  const changed = listChangedFiles(mergeBase, {
+    dirs: ["src", "open-sse", "electron", "bin", "scripts"],
+    exts: [".ts", ".tsx", ".js", ".mjs"],
+  });
+  const headKnip = runKnip();
+  const { deadTotal } = parseKnipMetrics(headKnip);
+  console.log(`DEAD_TOTAL=${deadTotal}`);
+  const over = deadTotal > baselineValue ? " — OVER, re-freeze at release" : "";
+  console.log(
+    `[dead-code] new-code mode: merge-base ${mergeBase.slice(0, 12)}, ${changed.length} changed file(s); global ${deadTotal} vs baseline ${baselineValue} (advisory${over})`
+  );
+  if (changed.length === 0) {
+    console.log("[dead-code] OK — no source files changed; nothing to compare.");
+    return;
+  }
+  const baseKnip = withBaseWorktree(mergeBase, (dir) => runKnip(dir));
+  const added = newDeadSymbols(headKnip, baseKnip, changed);
+  console.log(`deadExportsNewCode=${added.length}`);
+  if (added.length) {
+    process.stderr.write(
+      `[dead-code] REGRESSÃO (código novo) — ${added.length} símbolo(s) morto(s) introduzido(s) nos arquivos tocados:\n` +
+        added.map((k) => `  ✗ ${k}`).join("\n") +
+        "\n  → remova o export (ou use-o). O total global do repo não conta aqui.\n"
+    );
+    process.exit(1);
+  }
+  console.log(
+    `[dead-code] OK (código novo) — nenhum símbolo morto novo nos ${changed.length} arquivo(s) tocado(s)`
+  );
+}
+
 function main() {
   if (!fs.existsSync(BASELINE_PATH)) {
     process.stderr.write(`[dead-code] FAIL — ${path.basename(BASELINE_PATH)} ausente.\n`);
@@ -159,6 +205,7 @@ function main() {
     process.exit(2);
   }
   const baselineValue = baselineMetric.value;
+  if (BASE_REF && !PRINT_JSON && !UPDATE) return mainNewCode(baselineValue);
 
   const knipJson = runKnip();
 
diff --git a/scripts/check/complexityEslintReport.mjs b/scripts/check/complexityEslintReport.mjs
index 4c65efa3a3..e77863a61a 100644
--- a/scripts/check/complexityEslintReport.mjs
+++ b/scripts/check/complexityEslintReport.mjs
@@ -102,3 +102,38 @@ export function getComplexityEslintReport() {
 }
 
 getComplexityEslintReport._cache = null;
+
+/**
+ * New-code mode (#newCodeMode): lint ONLY `files` (relative to `cwd`) with the same config,
+ * in `cwd` (ROOT for HEAD, a throwaway base worktree for the merge-base). No cache: the
+ * cache key would otherwise leak between the two trees. Returns [] for an empty file list.
+ * @param {string[]} files
+ * @param {string} cwd
+ * @returns {Array<object>}
+ */
+export function runComplexityEslintOn(files, cwd = ROOT) {
+  const existing = files.filter((f) => fs.existsSync(path.join(cwd, f)));
+  if (existing.length === 0) return [];
+  const args = [
+    "--no-config-lookup",
+    "--config",
+    path.join(cwd, "eslint.complexity-ratchets.config.mjs"),
+    "--format",
+    "json",
+    "--no-error-on-unmatched-pattern",
+    ...existing,
+  ];
+  let stdout;
+  try {
+    stdout = execFileSync(ESLINT_BIN, args, {
+      cwd,
+      encoding: "utf8",
+      maxBuffer: 64 * 1024 * 1024,
+      shell: process.platform === "win32",
+    });
+  } catch (err) {
+    stdout = err.stdout ? String(err.stdout) : "";
+    if (!stdout.trim()) throw err;
+  }
+  return JSON.parse(stdout);
+}
diff --git a/scripts/check/newCodeMode.mjs b/scripts/check/newCodeMode.mjs
new file mode 100644
index 0000000000..3dad8c96be
--- /dev/null
+++ b/scripts/check/newCodeMode.mjs
@@ -0,0 +1,163 @@
+// scripts/check/newCodeMode.mjs
+// "New code" mode for the ratchet gates (Sonar "Clean as You Code", applied 2026-08-30).
+//
+// A global ratchet ("total violations ≤ baseline") makes an innocent PR red whenever the
+// base drifted — and it lets a PR that adds 10 violations pass as long as someone else
+// removed 11. In new-code mode (`--base-ref <sha>`, PR events only) a gate compares the
+// PR's HEAD against the merge-base **restricted to the files the PR touched**:
+//
+//   blocking  → the PR added violations / dead symbols in files it changed
+//   advisory  → the global total vs. the frozen baseline (printed, never exit 1);
+//               the release reconciliation re-measures and re-freezes it
+//
+// Shared by check-complexity-ratchets.mjs and check-dead-code.mjs. Everything git-related
+// is here; the pure comparison helpers are unit-tested (tests/unit/build/new-code-mode.test.ts).
+
+import { execFileSync } from "node:child_process";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+export const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..", "..");
+
+/** CLI arg helper shared by the gates: `--base-ref <sha>` → sha | null. */
+export function baseRefArg(argv = process.argv) {
+  const i = argv.indexOf("--base-ref");
+  return i >= 0 && argv[i + 1] ? argv[i + 1] : null;
+}
+
+function git(args, opts = {}) {
+  return execFileSync("git", args, {
+    cwd: ROOT,
+    encoding: "utf8",
+    stdio: ["ignore", "pipe", "pipe"],
+    maxBuffer: 64 * 1024 * 1024,
+    ...opts,
+  }).trim();
+}
+
+/** Merge-base between the PR base ref and HEAD (falls back to the ref itself). */
+export function resolveMergeBase(baseRef) {
+  try {
+    return git(["merge-base", baseRef, "HEAD"]);
+  } catch {
+    return git(["rev-parse", baseRef]);
+  }
+}
+
+/**
+ * Files added/copied/modified/renamed between `mergeBase` and HEAD, filtered to the gate's
+ * scope. Deleted files are irrelevant (nothing to measure on HEAD).
+ */
+export function listChangedFiles(mergeBase, { dirs, exts }) {
+  const out = git(["diff", "--name-only", "--diff-filter=ACMR", `${mergeBase}...HEAD`]);
+  return filterScope(out.split("\n"), { dirs, exts });
+}
+
+/** Pure: keep paths under one of `dirs` with one of `exts`. */
+export function filterScope(paths, { dirs, exts }) {
+  return paths
+    .map((p) => p.trim())
+    .filter(Boolean)
+    .filter((p) => dirs.some((d) => p === d || p.startsWith(`${d}/`)))
+    .filter((p) => exts.some((e) => p.endsWith(e)))
+    .sort();
+}
+
+/**
+ * Materialize `sha` in a throwaway worktree with node_modules linked from ROOT, run `fn(dir)`,
+ * always tear it down. Never touches the caller's tree or index (no stash, no checkout).
+ */
+export function withBaseWorktree(sha, fn) {
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-newcode-base-"));
+  fs.rmdirSync(dir); // git worktree add wants a non-existent path
+  git(["worktree", "add", "--detach", "--quiet", dir, sha]);
+  try {
+    const nm = path.join(ROOT, "node_modules");
+    if (fs.existsSync(nm)) fs.symlinkSync(nm, path.join(dir, "node_modules"), "dir");
+    return fn(dir);
+  } finally {
+    try {
+      git(["worktree", "remove", "--force", dir]);
+    } catch {
+      fs.rmSync(dir, { recursive: true, force: true, maxRetries: 5, retryDelay: 100 });
+      try {
+        git(["worktree", "prune"]);
+      } catch {
+        /* best effort */
+      }
+    }
+  }
+}
+
+/**
+ * Pure: per-file count of ESLint messages whose ruleId is in `rules`.
+ * `filePath` is made relative to `cwd` so HEAD and base reports share keys.
+ */
+export function perFileRuleCounts(report, rules, cwd) {
+  const counts = new Map();
+  for (const entry of report || []) {
+    const rel = path.isAbsolute(entry.filePath)
+      ? path.relative(cwd, entry.filePath).split(path.sep).join("/")
+      : entry.filePath;
+    let n = 0;
+    for (const m of entry.messages || []) if (rules.has(m.ruleId)) n++;
+    counts.set(rel, (counts.get(rel) || 0) + n);
+  }
+  return counts;
+}
+
+/**
+ * Pure: which changed files gained violations. A file absent from the base map is new
+ * (base = 0). Returns the per-file regressions and the net delta over the changed set.
+ */
+export function diffNewCode(headCounts, baseCounts, changedFiles) {
+  const regressions = [];
+  let head = 0;
+  let base = 0;
+  for (const file of changedFiles) {
+    const h = headCounts.get(file) || 0;
+    const b = baseCounts.get(file) || 0;
+    head += h;
+    base += b;
+    if (h > b) regressions.push({ file, base: b, head: h });
+  }
+  return { regressions, head, base, delta: head - base };
+}
+
+/** Pure: `file:symbol` keys of every dead export/type in a knip JSON report. */
+export function deadSymbolKeys(knipJson) {
+  const keys = new Set();
+  for (const entry of knipJson?.issues || []) {
+    for (const field of ["exports", "types", "nsExports", "nsTypes"]) {
+      for (const sym of entry[field] || []) keys.add(`${entry.file}:${sym.name}`);
+    }
+  }
+  for (const entry of knipJson?.issues || []) {
+    for (const f of entry.files || []) keys.add(`${f}:<file>`);
+  }
+  return keys;
+}
+
+/**
+ * Pure: dead symbols present on HEAD but not on the base, in files the PR touched — the
+ * only ones the PR is answerable for. A symbol that went dead in an UNTOUCHED file because
+ * the PR deleted its last consumer is also flagged when `includeUntouched` is set.
+ */
+export function newDeadSymbols(
+  headKnip,
+  baseKnip,
+  changedFiles,
+  { includeUntouched = false } = {}
+) {
+  const changed = new Set(changedFiles);
+  const base = deadSymbolKeys(baseKnip);
+  const out = [];
+  for (const key of deadSymbolKeys(headKnip)) {
+    if (base.has(key)) continue;
+    const file = key.slice(0, key.lastIndexOf(":"));
+    if (changed.has(file) || includeUntouched) out.push(key);
+  }
+  return out.sort();
+}
diff --git a/tests/unit/build/new-code-mode.test.ts b/tests/unit/build/new-code-mode.test.ts
new file mode 100644
index 0000000000..e9cfdafa91
--- /dev/null
+++ b/tests/unit/build/new-code-mode.test.ts
@@ -0,0 +1,112 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  baseRefArg,
+  deadSymbolKeys,
+  diffNewCode,
+  filterScope,
+  newDeadSymbols,
+  perFileRuleCounts,
+} from "../../../scripts/check/newCodeMode.mjs";
+
+test("baseRefArg reads --base-ref <sha> and ignores a dangling flag", () => {
+  assert.equal(baseRefArg(["node", "x", "--base-ref", "abc123"]), "abc123");
+  assert.equal(baseRefArg(["node", "x", "--base-ref"]), null);
+  assert.equal(baseRefArg(["node", "x"]), null);
+});
+
+test("filterScope keeps only in-scope dirs/extensions, sorted and trimmed", () => {
+  const files = filterScope(
+    [
+      " src/a.ts",
+      "open-sse/b.tsx",
+      "tests/unit/c.test.ts",
+      "src/d.md",
+      "srcx/e.ts",
+      "",
+      "bin/f.mjs",
+    ],
+    { dirs: ["src", "open-sse", "bin"], exts: [".ts", ".tsx", ".mjs"] }
+  );
+  assert.deepEqual(files, ["bin/f.mjs", "open-sse/b.tsx", "src/a.ts"]);
+});
+
+test("perFileRuleCounts counts only the requested rules and relativizes absolute paths", () => {
+  const report = [
+    {
+      filePath: "/repo/src/a.ts",
+      messages: [
+        { ruleId: "complexity" },
+        { ruleId: "max-lines-per-function" },
+        { ruleId: "no-unused-vars" },
+      ],
+    },
+    { filePath: "/repo/src/b.ts", messages: [{ ruleId: "sonarjs/cognitive-complexity" }] },
+    { filePath: "src/c.ts", messages: [] },
+  ];
+  const cyc = perFileRuleCounts(report, new Set(["complexity", "max-lines-per-function"]), "/repo");
+  assert.equal(cyc.get("src/a.ts"), 2);
+  assert.equal(cyc.get("src/b.ts"), 0);
+  assert.equal(cyc.get("src/c.ts"), 0);
+  const cog = perFileRuleCounts(report, new Set(["sonarjs/cognitive-complexity"]), "/repo");
+  assert.equal(cog.get("src/b.ts"), 1);
+});
+
+test("diffNewCode flags only changed files that grew; new files count from zero", () => {
+  const head = new Map([
+    ["src/a.ts", 3],
+    ["src/new.ts", 1],
+    ["src/untouched.ts", 9],
+  ]);
+  const base = new Map([
+    ["src/a.ts", 3],
+    ["src/untouched.ts", 2],
+  ]);
+  const r = diffNewCode(head, base, ["src/a.ts", "src/new.ts"]);
+  assert.deepEqual(r.regressions, [{ file: "src/new.ts", base: 0, head: 1 }]);
+  assert.equal(r.head, 4);
+  assert.equal(r.base, 3);
+  assert.equal(r.delta, 1);
+  // a file that got better is not a regression
+  const better = diffNewCode(new Map([["src/a.ts", 1]]), new Map([["src/a.ts", 3]]), ["src/a.ts"]);
+  assert.deepEqual(better.regressions, []);
+  assert.equal(better.delta, -2);
+});
+
+test("deadSymbolKeys covers exports, types, namespace members and unused files", () => {
+  const keys = deadSymbolKeys({
+    issues: [
+      {
+        file: "src/a.ts",
+        exports: [{ name: "foo" }],
+        types: [{ name: "Bar" }],
+        nsExports: [{ name: "ns" }],
+      },
+      { file: "src/dead.ts", files: ["src/dead.ts"] },
+    ],
+  });
+  assert.deepEqual([...keys].sort(), [
+    "src/a.ts:Bar",
+    "src/a.ts:foo",
+    "src/a.ts:ns",
+    "src/dead.ts:<file>",
+  ]);
+  assert.equal(deadSymbolKeys(null).size, 0);
+});
+
+test("newDeadSymbols reports only symbols that are new on HEAD, in touched files by default", () => {
+  const base = { issues: [{ file: "src/a.ts", exports: [{ name: "old" }] }] };
+  const head = {
+    issues: [
+      { file: "src/a.ts", exports: [{ name: "old" }, { name: "fresh" }] },
+      { file: "src/other.ts", exports: [{ name: "orphaned" }] },
+    ],
+  };
+  assert.deepEqual(newDeadSymbols(head, base, ["src/a.ts"]), ["src/a.ts:fresh"]);
+  assert.deepEqual(newDeadSymbols(head, base, ["src/a.ts"], { includeUntouched: true }), [
+    "src/a.ts:fresh",
+    "src/other.ts:orphaned",
+  ]);
+  assert.deepEqual(newDeadSymbols(base, head, ["src/a.ts"]), []);
+});