From 0ef0bd859e03def5bcf6847b56cb2f9ee39bd411 Mon Sep 17 00:00:00 2001
From: Todd Schiller <todd.schiller@gmail.com>
Date: Fri, 5 Jun 2026 08:14:42 -0400
Subject: [PATCH 1/3] Perf: AbortSignal-cancellable chunked scans for
 text-heavy rules (#150 Tier 3)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Adds lib/yielding-text-walk.ts: a chunked TreeWalker over text nodes
that yields between chunks (default 100 nodes) via requestIdleCallback
with setTimeout(0) fallback. Mirrors walkTextNodes' filter semantics
(NON_CONTENT_TAGS, isInsidePlaceholder, minLength, shouldSkipParent).
Sync fast path when the tree fits in one chunk — process and
onComplete fire before the helper returns, so existing rule tests
keep working without an explicit await.

Each of the four text-heavy rules (pii-redact, secrets-redact,
encoded-payload-redact, prompt-injection-redact) now owns a
ReusableAbortController. Route-change events fire abortAndReset on
each rule independently, so an in-flight chunked walk against the old
tree stops cleanly when the SPA swaps to the new one — no more
cross-tree mutations from a stale scan. Incremental subtree-watcher
batches intentionally do NOT abort: they target their own scoped
root and can complete concurrently with whatever else is running.

Adds an abort-utils CJS stub via moduleNameMapper so the ESM-only
package transparently loads in ts-jest's CJS pipeline.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 extension/jest.config.cjs                     |  12 +-
 extension/src/__test-mocks__/abort-utils.ts   |  62 ++++
 .../yielding-text-walk.property.test.ts       | 209 ++++++++++++++
 .../lib/__tests__/yielding-text-walk.test.ts  | 265 ++++++++++++++++++
 extension/src/lib/yielding-text-walk.ts       | 160 +++++++++++
 .../__tests__/encoded-payload-redact.test.ts  |  20 ++
 .../src/rules/__tests__/pii-redact.test.ts    |  27 ++
 .../__tests__/prompt-injection-redact.test.ts |  37 +++
 .../rules/__tests__/secrets-redact.test.ts    |  21 ++
 extension/src/rules/encoded-payload-redact.ts |  33 ++-
 extension/src/rules/pii-redact.ts             |  38 ++-
 .../src/rules/prompt-injection-redact.ts      | 118 +++++---
 extension/src/rules/secrets-redact.ts         |  35 ++-
 13 files changed, 968 insertions(+), 69 deletions(-)
 create mode 100644 extension/src/__test-mocks__/abort-utils.ts
 create mode 100644 extension/src/lib/__tests__/yielding-text-walk.property.test.ts
 create mode 100644 extension/src/lib/__tests__/yielding-text-walk.test.ts
 create mode 100644 extension/src/lib/yielding-text-walk.ts

diff --git a/extension/jest.config.cjs b/extension/jest.config.cjs
index 888f955..4ac9a1d 100644
--- a/extension/jest.config.cjs
+++ b/extension/jest.config.cjs
@@ -29,12 +29,16 @@ module.exports = {
     ],
   },
   moduleFileExtensions: ["ts", "tsx", "js", "jsx", "json"],
-  // `webext-storage` is published as ESM-only and our ts-jest config emits
-  // CommonJS, so importing it directly trips a `SyntaxError: Unexpected token
-  // 'export'`. None of our tests exercise the real storage flow (they mock the
-  // storage modules wholesale), so route the import to a small CJS stub.
+  // `webext-storage` and `abort-utils` are published as ESM-only and our
+  // ts-jest config emits CommonJS, so importing them directly trips a
+  // `SyntaxError: Unexpected token 'export'`. None of our tests exercise
+  // the real storage flow (they mock the storage modules wholesale), and
+  // the abort-utils stub is a faithful enough subset for the lifecycle
+  // semantics the rules depend on (signal flip on abortAndReset, onAbort
+  // dispatch).
   moduleNameMapper: {
     "^webext-storage$": "<rootDir>/src/__test-mocks__/webext-storage.ts",
+    "^abort-utils$": "<rootDir>/src/__test-mocks__/abort-utils.ts",
   },
   // - jest-webextension-mock: installs globalThis.chrome + browser with
   //   jest.fn() stubs for MV2/MV3 APIs the extension uses (runtime, storage,
diff --git a/extension/src/__test-mocks__/abort-utils.ts b/extension/src/__test-mocks__/abort-utils.ts
new file mode 100644
index 0000000..07be7b2
--- /dev/null
+++ b/extension/src/__test-mocks__/abort-utils.ts
@@ -0,0 +1,62 @@
+// Copyright (c) 2026 PixieBrix, Inc.
+// Licensed under PolyForm Shield 1.0.0 — see LICENSE.
+
+// In-memory stub of the subset of `abort-utils` consumed by the
+// extension. The real package ships pure ESM, which ts-jest with
+// `useESM: false` can't transform — so route imports here via
+// `moduleNameMapper` in jest.config.cjs. The stub mirrors the runtime
+// semantics tests actually depend on: ReusableAbortController issues
+// fresh signals after abortAndReset, and onAbort attaches a disposable
+// listener.
+
+export class ReusableAbortController {
+  private controller = new AbortController();
+
+  get signal(): AbortSignal {
+    return this.controller.signal;
+  }
+
+  abort(reason?: unknown): void {
+    this.controller.abort(reason);
+  }
+
+  abortAndReset(reason?: unknown): void {
+    this.controller.abort(reason);
+    this.controller = new AbortController();
+  }
+}
+
+type Handle =
+  | { disconnect(): void }
+  | { abort(reason: unknown): void }
+  | { abortAndReset(reason: unknown): void }
+  | ((reason: unknown) => void);
+
+export function onAbort(
+  signal: AbortController | AbortSignal | undefined,
+  ...handles: Handle[]
+): { [Symbol.dispose](): void } | undefined {
+  if (!signal) {
+    return undefined;
+  }
+  const target = signal instanceof AbortController ? signal.signal : signal;
+  const listener = (): void => {
+    for (const handle of handles) {
+      if (typeof handle === "function") {
+        handle(target.reason);
+      } else if ("abortAndReset" in handle) {
+        handle.abortAndReset(target.reason);
+      } else if ("abort" in handle) {
+        handle.abort(target.reason);
+      } else {
+        handle.disconnect();
+      }
+    }
+  };
+  target.addEventListener("abort", listener, { once: true });
+  return {
+    [Symbol.dispose](): void {
+      target.removeEventListener("abort", listener);
+    },
+  };
+}
diff --git a/extension/src/lib/__tests__/yielding-text-walk.property.test.ts b/extension/src/lib/__tests__/yielding-text-walk.property.test.ts
new file mode 100644
index 0000000..e0f61a1
--- /dev/null
+++ b/extension/src/lib/__tests__/yielding-text-walk.property.test.ts
@@ -0,0 +1,209 @@
+// Copyright (c) 2026 PixieBrix, Inc.
+// Licensed under PolyForm Shield 1.0.0 — see LICENSE.
+
+// Property test for the chunked walker's equivalence with
+// `walkTextNodes`. For any tree shape, any text content, any chunkSize,
+// the concatenation of all chunks plus the order they were delivered
+// must equal what `walkTextNodes` would return. Catches:
+//   - missing the trailing partial chunk
+//   - dropping nodes at the chunk boundary (the "next prefetched but
+//     never pushed" class of bug)
+//   - double-processing nodes across the sync→async transition
+//   - drift in the filter predicates (NON_CONTENT_TAGS, minLength)
+//     between the two walkers
+
+import fc from "fast-check";
+
+import { walkTextNodes } from "../dom-utils";
+import { walkTextNodesChunked } from "../yielding-text-walk";
+
+interface FlatTree {
+  size: number;
+  parents: readonly number[];
+  texts: readonly string[];
+  tags: readonly string[];
+}
+
+// Tag alphabet excludes `<script>` and `<style>` deliberately —
+// jsdom tries to evaluate inline script bodies and chokes on the
+// random text content fast-check generates. The filter-parity branch
+// for NON_CONTENT_TAGS is covered explicitly in the example tests.
+const TAG_ALPHABET = ["div", "p", "span", "section", "article"] as const;
+
+const flatTreeArb: fc.Arbitrary<FlatTree> = fc
+  .integer({ min: 1, max: 15 })
+  .chain((size) => {
+    const tagsArb = fc.array(fc.constantFrom(...TAG_ALPHABET), {
+      minLength: size,
+      maxLength: size,
+    });
+    // Text content can vary in length so the minLength filter has both
+    // accepted and rejected nodes to choose between.
+    const textsArb = fc.array(
+      fc.oneof(fc.constant(""), fc.string({ minLength: 1, maxLength: 30 })),
+      { minLength: size, maxLength: size },
+    );
+    if (size === 1) {
+      return fc.tuple(tagsArb, textsArb).map(([tags, texts]) => ({
+        size,
+        parents: [],
+        tags,
+        texts,
+      }));
+    }
+    const parentArbs = Array.from({ length: size - 1 }, (_, i) =>
+      fc.integer({ min: 0, max: i }),
+    );
+    return fc
+      .tuple(fc.tuple(...parentArbs), tagsArb, textsArb)
+      .map(([parents, tags, texts]) => ({ size, parents, tags, texts }));
+  });
+
+function buildTree(spec: FlatTree): HTMLElement {
+  const nodes: HTMLElement[] = Array.from({ length: spec.size }, (_, i) => {
+    const element = document.createElement(spec.tags[i] as string);
+    const text = spec.texts[i] as string;
+    if (text.length > 0) {
+      element.append(document.createTextNode(text));
+    }
+    return element;
+  });
+  for (let i = 1; i < spec.size; i++) {
+    const parentIndex = spec.parents[i - 1] as number;
+    nodes[parentIndex]?.append(nodes[i] as HTMLElement);
+  }
+  return nodes[0] as HTMLElement;
+}
+
+beforeEach(() => {
+  document.body.innerHTML = "";
+});
+
+describe("walkTextNodesChunked (property)", () => {
+  it("flat-mapped chunks equal walkTextNodes output (sync, large chunkSize)", () => {
+    fc.assert(
+      fc.property(
+        flatTreeArb,
+        fc.integer({ min: 1, max: 8 }),
+        (tree, minLength) => {
+          document.body.innerHTML = "";
+          const root = buildTree(tree);
+          document.body.append(root);
+
+          const expected = walkTextNodes(document.body, { minLength });
+
+          const actual: Text[] = [];
+          walkTextNodesChunked(document.body, {
+            minLength,
+            // Big enough to guarantee the sync path even for the largest
+            // tree we generate.
+            chunkSize: 1000,
+            process: (chunk) => {
+              actual.push(...chunk);
+            },
+          });
+
+          expect(actual).toEqual(expected);
+        },
+      ),
+    );
+  });
+
+  it("flat-mapped chunks equal walkTextNodes output (async, small chunkSize)", async () => {
+    await fc.assert(
+      fc.asyncProperty(
+        flatTreeArb,
+        fc.integer({ min: 1, max: 4 }),
+        fc.integer({ min: 1, max: 8 }),
+        async (tree, chunkSize, minLength) => {
+          document.body.innerHTML = "";
+          const root = buildTree(tree);
+          document.body.append(root);
+
+          const expected = walkTextNodes(document.body, { minLength });
+
+          const actual: Text[] = [];
+          let done = false;
+          walkTextNodesChunked(document.body, {
+            minLength,
+            chunkSize,
+            // Microtask yield — `await Promise.resolve()` below drains
+            // each chunk's scheduled continuation in turn.
+            yieldStrategy: () => Promise.resolve(),
+            process: (chunk) => {
+              actual.push(...chunk);
+            },
+            onComplete: () => {
+              done = true;
+            },
+          });
+
+          // Drain microtasks until the walk completes. Bounded so a
+          // helper bug that prevented completion would fail fast
+          // rather than hang the test runner. eslint can't see that
+          // `done` flips inside the helper's microtask callback.
+          for (let i = 0; i <= expected.length + 5; i++) {
+            // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+            if (done) {
+              break;
+            }
+            await Promise.resolve();
+          }
+
+          expect(actual).toEqual(expected);
+          expect(done).toBe(true);
+        },
+      ),
+    );
+  });
+
+  it("chunks are sized at most chunkSize; only the trailing chunk can be short", async () => {
+    await fc.assert(
+      fc.asyncProperty(
+        flatTreeArb,
+        fc.integer({ min: 1, max: 5 }),
+        async (tree, chunkSize) => {
+          document.body.innerHTML = "";
+          const root = buildTree(tree);
+          document.body.append(root);
+
+          const expected = walkTextNodes(document.body, { minLength: 0 });
+          if (expected.length === 0) {
+            // No accepted nodes — chunk-size invariant is vacuous; the
+            // helper just fires onComplete with no process calls.
+            return;
+          }
+
+          const sizes: number[] = [];
+          let done = false;
+          walkTextNodesChunked(document.body, {
+            chunkSize,
+            yieldStrategy: () => Promise.resolve(),
+            process: (chunk) => {
+              sizes.push(chunk.length);
+            },
+            onComplete: () => {
+              done = true;
+            },
+          });
+
+          for (let i = 0; i <= expected.length + 5; i++) {
+            // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+            if (done) {
+              break;
+            }
+            await Promise.resolve();
+          }
+          expect(done).toBe(true);
+
+          for (let i = 0; i < sizes.length - 1; i++) {
+            expect(sizes[i]).toBe(chunkSize);
+          }
+          const last = sizes.at(-1) as number;
+          expect(last).toBeGreaterThan(0);
+          expect(last).toBeLessThanOrEqual(chunkSize);
+        },
+      ),
+    );
+  });
+});
diff --git a/extension/src/lib/__tests__/yielding-text-walk.test.ts b/extension/src/lib/__tests__/yielding-text-walk.test.ts
new file mode 100644
index 0000000..2b2ddfa
--- /dev/null
+++ b/extension/src/lib/__tests__/yielding-text-walk.test.ts
@@ -0,0 +1,265 @@
+// Copyright (c) 2026 PixieBrix, Inc.
+// Licensed under PolyForm Shield 1.0.0 — see LICENSE.
+
+// Tests for the chunked text-walk helper used by the four text-heavy
+// rules (pii-redact, secrets-redact, encoded-payload-redact,
+// prompt-injection-redact). Pins down:
+//   - sync fast path: a tree that fits in one chunk produces its
+//     process + onComplete calls before the helper returns
+//   - chunked path: multi-chunk trees yield via the injected
+//     yieldStrategy, process fires per chunk, onComplete fires after
+//     the last one
+//   - signal handling: an abort before any chunk skips everything;
+//     an abort between chunks stops further processing and onComplete
+//   - filter parity with walkTextNodes (NON_CONTENT_TAGS, placeholder
+//     skip, minLength, shouldSkipParent)
+
+import { PLACEHOLDER_CLASS } from "../placeholder";
+import { walkTextNodesChunked } from "../yielding-text-walk";
+
+beforeEach(() => {
+  document.body.innerHTML = "";
+});
+
+describe("walkTextNodesChunked — sync fast path", () => {
+  it("processes the whole tree in one chunk when it fits", () => {
+    document.body.innerHTML = `<p>one</p><p>two</p><p>three</p>`;
+    const chunks: number[] = [];
+    let completed = false;
+
+    walkTextNodesChunked(document.body, {
+      process: (chunk) => {
+        chunks.push(chunk.length);
+      },
+      onComplete: () => {
+        completed = true;
+      },
+    });
+
+    // Sync path: process and onComplete fired before walkTextNodesChunked
+    // returned. No microtask flush needed.
+    expect(chunks).toEqual([3]);
+    expect(completed).toBe(true);
+  });
+
+  it("returns void with no calls when the tree is empty", () => {
+    const process = jest.fn();
+    const onComplete = jest.fn();
+    walkTextNodesChunked(document.body, { process, onComplete });
+    expect(process).not.toHaveBeenCalled();
+    // onComplete still fires — caller's post-pass should run on every
+    // walk, even if no nodes were collected.
+    expect(onComplete).toHaveBeenCalledTimes(1);
+  });
+
+  it("matches root element itself when walking from it", () => {
+    const p = document.createElement("p");
+    p.textContent = "hello";
+    document.body.append(p);
+    const seen: string[] = [];
+    walkTextNodesChunked(p, {
+      process: (chunk) => {
+        for (const node of chunk) {
+          seen.push(node.nodeValue ?? "");
+        }
+      },
+    });
+    expect(seen).toEqual(["hello"]);
+  });
+});
+
+describe("walkTextNodesChunked — chunked path", () => {
+  it("fires process once per filled chunk and onComplete after the last", async () => {
+    // 5 text nodes, chunkSize 2 → chunks of 2, 2, 1.
+    document.body.innerHTML = Array.from(
+      { length: 5 },
+      (_, i) => `<p>text-${i}</p>`,
+    ).join("");
+
+    const chunkSizes: number[] = [];
+    let completed = false;
+    // Microtask yield keeps the test ergonomic — no fake timers needed
+    // to drive yieldStrategy. Each `await Promise.resolve()` drains
+    // one microtask, which advances the helper one chunk.
+    const microtaskYield = (): Promise<void> => Promise.resolve();
+
+    walkTextNodesChunked(document.body, {
+      chunkSize: 2,
+      yieldStrategy: microtaskYield,
+      process: (chunk) => {
+        chunkSizes.push(chunk.length);
+      },
+      onComplete: () => {
+        completed = true;
+      },
+    });
+
+    // First chunk processed synchronously before the helper returned.
+    expect(chunkSizes).toEqual([2]);
+    expect(completed).toBe(false);
+
+    // Drain microtasks for each remaining yield. With 3 chunks total
+    // (2, 2, 1) we need 2 microtask drains: one for the second chunk
+    // and onComplete is still pending; one more after the third chunk.
+    await Promise.resolve();
+    await Promise.resolve();
+    await Promise.resolve();
+    expect(chunkSizes).toEqual([2, 2, 1]);
+    expect(completed).toBe(true);
+  });
+});
+
+describe("walkTextNodesChunked — signal handling", () => {
+  it("skips the walk entirely when the signal is already aborted", () => {
+    document.body.innerHTML = `<p>one</p><p>two</p>`;
+    const controller = new AbortController();
+    controller.abort();
+    const process = jest.fn();
+    const onComplete = jest.fn();
+    walkTextNodesChunked(document.body, {
+      signal: controller.signal,
+      process,
+      onComplete,
+    });
+    expect(process).not.toHaveBeenCalled();
+    expect(onComplete).not.toHaveBeenCalled();
+  });
+
+  it("stops between chunks when the signal aborts mid-walk", async () => {
+    document.body.innerHTML = Array.from(
+      { length: 6 },
+      (_, i) => `<p>t-${i}</p>`,
+    ).join("");
+    const controller = new AbortController();
+    const chunkSizes: number[] = [];
+    let completed = false;
+    const microtaskYield = (): Promise<void> => Promise.resolve();
+
+    walkTextNodesChunked(document.body, {
+      chunkSize: 2,
+      yieldStrategy: microtaskYield,
+      signal: controller.signal,
+      process: (chunk) => {
+        chunkSizes.push(chunk.length);
+      },
+      onComplete: () => {
+        completed = true;
+      },
+    });
+
+    // First chunk processed synchronously.
+    expect(chunkSizes).toEqual([2]);
+
+    // Abort before the yield resolves. The continuation checks the
+    // signal and bails — no further chunks, no onComplete.
+    controller.abort();
+    await Promise.resolve();
+    await Promise.resolve();
+    await Promise.resolve();
+    expect(chunkSizes).toEqual([2]);
+    expect(completed).toBe(false);
+  });
+
+  it("skips onComplete when an abort fires after the last chunk processed but before finalize", () => {
+    // Synchronous path: chunk runs, then signal flips, then onComplete
+    // is checked. Most consumers (the 4 rules) check the signal
+    // themselves inside onComplete, but the helper also gates so
+    // misuse stays safe.
+    document.body.innerHTML = `<p>one</p>`;
+    const controller = new AbortController();
+    const onComplete = jest.fn();
+
+    walkTextNodesChunked(document.body, {
+      signal: controller.signal,
+      process: () => {
+        // Mid-chunk: signal flips before we get to onComplete.
+        controller.abort();
+      },
+      onComplete,
+    });
+
+    expect(onComplete).not.toHaveBeenCalled();
+  });
+});
+
+describe("walkTextNodesChunked — filter parity with walkTextNodes", () => {
+  it("skips SCRIPT / STYLE / NOSCRIPT / TEMPLATE text", () => {
+    document.body.innerHTML = `
+      <p>real</p>
+      <script>script</script>
+      <style>style</style>
+      <noscript>noscript</noscript>
+      <template>template</template>
+    `;
+    const values: string[] = [];
+    walkTextNodesChunked(document.body, {
+      process: (chunk) => {
+        for (const node of chunk) {
+          const text = node.nodeValue?.trim();
+          if (text) {
+            values.push(text);
+          }
+        }
+      },
+    });
+    expect(values).toContain("real");
+    expect(values).not.toContain("script");
+    expect(values).not.toContain("style");
+    expect(values).not.toContain("noscript");
+    expect(values).not.toContain("template");
+  });
+
+  it("skips text inside an existing placeholder", () => {
+    document.body.innerHTML = `
+      <p>real</p>
+      <span class="${PLACEHOLDER_CLASS}">hidden</span>
+    `;
+    const values: string[] = [];
+    walkTextNodesChunked(document.body, {
+      process: (chunk) => {
+        for (const node of chunk) {
+          const text = node.nodeValue?.trim();
+          if (text) {
+            values.push(text);
+          }
+        }
+      },
+    });
+    expect(values).toContain("real");
+    expect(values).not.toContain("hidden");
+  });
+
+  it("respects minLength", () => {
+    document.body.innerHTML = `<p>short</p><p>a long string of text</p>`;
+    const seen: string[] = [];
+    walkTextNodesChunked(document.body, {
+      minLength: 10,
+      process: (chunk) => {
+        for (const node of chunk) {
+          seen.push(node.nodeValue ?? "");
+        }
+      },
+    });
+    expect(seen).toEqual(["a long string of text"]);
+  });
+
+  it("respects shouldSkipParent", () => {
+    document.body.innerHTML = `
+      <article><p>article-text</p></article>
+      <aside><p>aside-text</p></aside>
+    `;
+    const seen: string[] = [];
+    walkTextNodesChunked(document.body, {
+      shouldSkipParent: (parent) => parent.closest("aside") !== null,
+      process: (chunk) => {
+        for (const node of chunk) {
+          const text = node.nodeValue?.trim();
+          if (text) {
+            seen.push(text);
+          }
+        }
+      },
+    });
+    expect(seen).toEqual(["article-text"]);
+  });
+});
diff --git a/extension/src/lib/yielding-text-walk.ts b/extension/src/lib/yielding-text-walk.ts
new file mode 100644
index 0000000..feb0c89
--- /dev/null
+++ b/extension/src/lib/yielding-text-walk.ts
@@ -0,0 +1,160 @@
+// Copyright (c) 2026 PixieBrix, Inc.
+// Licensed under PolyForm Shield 1.0.0 — see LICENSE.
+
+// Chunked text-node walk for rules that scan large `innerText`
+// (pii-redact, secrets-redact, encoded-payload-redact,
+// prompt-injection-redact). Yields between chunks so the regex loops
+// don't block the event loop for hundreds of milliseconds on dense
+// pages, and surfaces an `AbortSignal` so an SPA route change can
+// cancel a scan started against the old tree before it finishes
+// mutating the new one.
+//
+// API note: the walk is synchronous when the tree fits in one chunk
+// (the common case for small subtrees + the default chunkSize=100).
+// Trees that span multiple chunks continue across scheduler yields,
+// with `onComplete` firing in a microtask after the last chunk. The
+// sync-first-fast-path lets existing rule tests `apply` and then
+// assert without an explicit `await` — only the multi-chunk path
+// (large pages, abort tests) needs to flush.
+//
+// The filter (NON_CONTENT_TAGS skip, isInsidePlaceholder skip,
+// minLength, optional shouldSkipParent) mirrors `walkTextNodes` in
+// dom-utils — same predicates, different consumer shape.
+
+import { isInsidePlaceholder, isNonContentTag } from "./dom-utils";
+
+export interface WalkTextNodesChunkedOptions {
+  // Aborts the walk at the next chunk boundary. Already-processed
+  // chunks stay; partially-processed chunks are not possible because
+  // `process` runs atomically on the full chunk.
+  signal?: AbortSignal;
+  // Minimum nodeValue length before the node is offered to `process`.
+  // Same semantics as `walkTextNodes`.
+  minLength?: number;
+  // Extra parent-element predicate beyond the universal NON_CONTENT_TAGS
+  // and placeholder skips.
+  shouldSkipParent?: (parent: Element) => boolean;
+  // Cap on the per-process batch size. Larger = fewer scheduler yields,
+  // longer blocking windows. The default trades off well for the
+  // text-walk rules — most batches fit in one chunk and never yield.
+  chunkSize?: number;
+  // Invoked once per filled chunk plus once for the trailing partial
+  // chunk. Synchronous: any DOM mutations should land before the next
+  // yield so a route-change abort doesn't leave a half-mutated batch.
+  process: (chunk: Text[]) => void;
+  // Called after the last chunk is processed (or skipped due to abort).
+  // Runs synchronously when the walk fit in one chunk; otherwise in a
+  // microtask after the final yield. Use for cross-chunk post-passes
+  // (e.g., prompt-injection-redact's outermost-match dedupe of
+  // collected container elements).
+  onComplete?: () => void;
+  // Override the yield mechanism. Production uses requestIdleCallback
+  // (yields to layout/paint) with a setTimeout(0) fallback; tests can
+  // pass a microtask-based yield to avoid driving fake timers.
+  yieldStrategy?: () => Promise<void>;
+}
+
+function defaultYieldStrategy(): Promise<void> {
+  if (typeof globalThis.requestIdleCallback === "function") {
+    return new Promise<void>((resolve) => {
+      globalThis.requestIdleCallback(() => {
+        resolve();
+      });
+    });
+  }
+  return new Promise<void>((resolve) => {
+    setTimeout(resolve, 0);
+  });
+}
+
+export function walkTextNodesChunked(
+  root: ParentNode,
+  options: WalkTextNodesChunkedOptions,
+): void {
+  const {
+    signal,
+    minLength = 0,
+    shouldSkipParent,
+    chunkSize = 100,
+    process,
+    onComplete,
+    yieldStrategy = defaultYieldStrategy,
+  } = options;
+
+  if (signal?.aborted) {
+    return;
+  }
+
+  const walker = document.createTreeWalker(root, NodeFilter.SHOW_TEXT, {
+    acceptNode(node) {
+      const parent = node.parentElement;
+      if (!parent) {
+        return NodeFilter.FILTER_REJECT;
+      }
+      if (isNonContentTag(parent.tagName)) {
+        return NodeFilter.FILTER_REJECT;
+      }
+      if (isInsidePlaceholder(parent)) {
+        return NodeFilter.FILTER_REJECT;
+      }
+      if (shouldSkipParent?.(parent)) {
+        return NodeFilter.FILTER_REJECT;
+      }
+      const value = node.nodeValue;
+      if (!value || value.length < minLength) {
+        return NodeFilter.FILTER_REJECT;
+      }
+      return NodeFilter.FILTER_ACCEPT;
+    },
+  });
+
+  let chunk: Text[] = [];
+
+  function runFinalize(): void {
+    if (signal?.aborted) {
+      return;
+    }
+    onComplete?.();
+  }
+
+  // Walks until the chunk fills or the tree is exhausted. Returns
+  // "yield" when a chunk was just flushed and walking should continue
+  // after a scheduler yield; "done" when the walker has no more nodes
+  // and the trailing partial chunk (if any) has been processed.
+  function walkSync(): "yield" | "done" {
+    let next = walker.nextNode();
+    while (next) {
+      chunk.push(next as Text);
+      if (chunk.length >= chunkSize) {
+        process(chunk);
+        chunk = [];
+        return "yield";
+      }
+      next = walker.nextNode();
+    }
+    if (chunk.length > 0) {
+      process(chunk);
+      chunk = [];
+    }
+    return "done";
+  }
+
+  function continueAsync(): void {
+    void yieldStrategy().then(() => {
+      if (signal?.aborted) {
+        return;
+      }
+      if (walkSync() === "done") {
+        runFinalize();
+      } else {
+        continueAsync();
+      }
+    });
+  }
+
+  if (walkSync() === "done") {
+    runFinalize();
+  } else {
+    continueAsync();
+  }
+}
diff --git a/extension/src/rules/__tests__/encoded-payload-redact.test.ts b/extension/src/rules/__tests__/encoded-payload-redact.test.ts
index cca7f1d..1932cb0 100644
--- a/extension/src/rules/__tests__/encoded-payload-redact.test.ts
+++ b/extension/src/rules/__tests__/encoded-payload-redact.test.ts
@@ -223,4 +223,24 @@ describe("encoded-payload-redact teardown", () => {
 
     expect(document.querySelector(`.${PLACEHOLDER_CLASS}`)).toBeNull();
   });
+
+  it("teardown aborts the in-flight chunked walk", () => {
+    const payload = base64Encode(LONG_PROSE);
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>blob-${i}: ${payload}</p>`,
+    ).join("");
+
+    encodedPayloadRedactRule.apply(document.body);
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+
+    encodedPayloadRedactRule.teardown();
+    jest.advanceTimersByTime(0);
+
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+  });
 });
diff --git a/extension/src/rules/__tests__/pii-redact.test.ts b/extension/src/rules/__tests__/pii-redact.test.ts
index 1c3d9e8..8e9ebb1 100644
--- a/extension/src/rules/__tests__/pii-redact.test.ts
+++ b/extension/src/rules/__tests__/pii-redact.test.ts
@@ -138,4 +138,31 @@ describe("pii-redact lazy-loaded subtrees", () => {
 
     expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(1);
   });
+
+  it("teardown aborts the in-flight chunked walk", () => {
+    // 200 text nodes — exceeds the 100-node chunkSize default, so the
+    // walk yields after chunk 1. teardown fires before the yield's
+    // setTimeout(0) resolves; the continuation sees the aborted signal
+    // and bails, leaving only the first chunk's matches masked.
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>node-${i}: ${SSN}</p>`,
+    ).join("");
+
+    piiRedactRule.apply(document.body);
+    // Sync chunk 1: 100 placeholders.
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+
+    piiRedactRule.teardown();
+    // Fire the yield's setTimeout(0). The continuation checks the
+    // signal first — aborted — and returns without processing
+    // chunk 2.
+    jest.advanceTimersByTime(0);
+
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+  });
 });
diff --git a/extension/src/rules/__tests__/prompt-injection-redact.test.ts b/extension/src/rules/__tests__/prompt-injection-redact.test.ts
index 6d6a9f9..bb0a6cb 100644
--- a/extension/src/rules/__tests__/prompt-injection-redact.test.ts
+++ b/extension/src/rules/__tests__/prompt-injection-redact.test.ts
@@ -267,3 +267,40 @@ describe("prompt-injection-redact", () => {
     });
   });
 });
+
+describe("prompt-injection-redact abort", () => {
+  beforeEach(() => {
+    jest.useFakeTimers();
+  });
+  afterEach(() => {
+    promptInjectionRedactRule.teardown();
+    jest.useRealTimers();
+  });
+
+  it("teardown aborts the in-flight chunked walk before the hide pass runs", () => {
+    // 200 paragraphs, each with an injection phrase. The chunked walk
+    // fills chunk 1 (100 nodes), yields, and only schedules the second
+    // pass (filterToOutermost + hide) via onComplete after the LAST
+    // chunk. teardown's abortAndReset fires before the yield resolves
+    // — so the continuation bails, onComplete never runs, and nothing
+    // gets hidden. The collected first-chunk containers stay in the
+    // DOM unchanged.
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>${FIXTURES.IGNORE_HACKED} ${i}</p>`,
+    ).join("");
+
+    promptInjectionRedactRule.apply(document.body);
+    // Chunk 1 processed synchronously: collects containers but does
+    // NOT yet hide (onComplete is gated to the end of the walk).
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(0);
+    expect(document.querySelectorAll("p")).toHaveLength(200);
+
+    promptInjectionRedactRule.teardown();
+    jest.advanceTimersByTime(0);
+
+    // Aborted before onComplete: no placeholders ever installed.
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(0);
+    expect(document.querySelectorAll("p")).toHaveLength(200);
+  });
+});
diff --git a/extension/src/rules/__tests__/secrets-redact.test.ts b/extension/src/rules/__tests__/secrets-redact.test.ts
index 5f07168..90325f4 100644
--- a/extension/src/rules/__tests__/secrets-redact.test.ts
+++ b/extension/src/rules/__tests__/secrets-redact.test.ts
@@ -229,4 +229,25 @@ describe("secrets-redact lazy-loaded subtrees", () => {
 
     expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(1);
   });
+
+  it("teardown aborts the in-flight chunked walk", () => {
+    // Tree exceeds the 100-node chunkSize so the walk yields after
+    // chunk 1; teardown's abortAndReset bails the continuation.
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>key-${i}: ${AWS_KEY}</p>`,
+    ).join("");
+
+    secretsRedactRule.apply(document.body);
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+
+    secretsRedactRule.teardown();
+    jest.advanceTimersByTime(0);
+
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+  });
 });
diff --git a/extension/src/rules/encoded-payload-redact.ts b/extension/src/rules/encoded-payload-redact.ts
index 1609fc0..e84f64f 100644
--- a/extension/src/rules/encoded-payload-redact.ts
+++ b/extension/src/rules/encoded-payload-redact.ts
@@ -19,10 +19,12 @@
 // Matches are replaced inline with a click-to-reveal placeholder. False
 // positives cost one click, not lost data.
 
-import { walkTextNodes } from "../lib/dom-utils";
+import { ReusableAbortController } from "abort-utils";
 import type { InlineMatch } from "../lib/placeholder";
 import { replaceMatchesInTextNode } from "../lib/placeholder";
+import { subscribeRouteChange } from "../lib/route-change";
 import { createSubtreeWatcher } from "../lib/subtree-watcher";
+import { walkTextNodesChunked } from "../lib/yielding-text-walk";
 import type { Rule } from "./types";
 
 const RULE_ID = "encoded-payload-redact" as const;
@@ -296,13 +298,24 @@ function collectMatches(text: string): InlineMatch[] {
   return merged;
 }
 
+// See pii-redact for lifecycle rationale.
+const lifecycle = new ReusableAbortController();
+let unsubscribeRouteChange: (() => void) | null = null;
+
 function scanAndMask(root: ParentNode): void {
-  for (const node of walkTextNodes(root, { minLength: MIN_TEXT_LENGTH })) {
-    const matches = collectMatches(node.nodeValue ?? "");
-    if (matches.length > 0) {
-      replaceMatchesInTextNode(node, matches, RULE_ID);
-    }
-  }
+  const signal = lifecycle.signal;
+  walkTextNodesChunked(root, {
+    signal,
+    minLength: MIN_TEXT_LENGTH,
+    process: (chunk) => {
+      for (const node of chunk) {
+        const matches = collectMatches(node.nodeValue ?? "");
+        if (matches.length > 0) {
+          replaceMatchesInTextNode(node, matches, RULE_ID);
+        }
+      }
+    },
+  });
 }
 
 const watcher = createSubtreeWatcher({
@@ -315,6 +328,9 @@ const watcher = createSubtreeWatcher({
 });
 
 function apply(root: ParentNode): void {
+  unsubscribeRouteChange ??= subscribeRouteChange(() => {
+    lifecycle.abortAndReset();
+  });
   scanAndMask(root);
   watcher.start(root);
 }
@@ -327,5 +343,8 @@ export const encodedPayloadRedactRule = {
   apply,
   teardown: () => {
     watcher.stop();
+    lifecycle.abortAndReset();
+    unsubscribeRouteChange?.();
+    unsubscribeRouteChange = null;
   },
 } satisfies Rule;
diff --git a/extension/src/rules/pii-redact.ts b/extension/src/rules/pii-redact.ts
index a0d7f1b..ad1814b 100644
--- a/extension/src/rules/pii-redact.ts
+++ b/extension/src/rules/pii-redact.ts
@@ -1,10 +1,12 @@
 // Copyright (c) 2026 PixieBrix, Inc.
 // Licensed under PolyForm Shield 1.0.0 — see LICENSE.
 
-import { walkTextNodes } from "../lib/dom-utils";
+import { ReusableAbortController } from "abort-utils";
 import type { InlineMatch } from "../lib/placeholder";
 import { replaceMatchesInTextNode } from "../lib/placeholder";
+import { subscribeRouteChange } from "../lib/route-change";
 import { createSubtreeWatcher } from "../lib/subtree-watcher";
+import { walkTextNodesChunked } from "../lib/yielding-text-walk";
 import type { Rule } from "./types";
 
 const RULE_ID = "pii-redact" as const;
@@ -76,13 +78,29 @@ function collectMatches(text: string): InlineMatch[] {
   return merged;
 }
 
+// Lifecycle controller covers every async scan kicked off by apply
+// and the watcher. abortAndReset on route change cancels any in-flight
+// chunked walk so a scan started against the old tree can't keep
+// mutating the new one; abortAndReset on teardown stops everything.
+// Incremental subtree-watcher batches do NOT abort — they target their
+// own scoped root and don't conflict with the previous scan.
+const lifecycle = new ReusableAbortController();
+let unsubscribeRouteChange: (() => void) | null = null;
+
 function scanAndMask(root: ParentNode): void {
-  for (const node of walkTextNodes(root, { minLength: MIN_TEXT_LENGTH })) {
-    const matches = collectMatches(node.nodeValue ?? "");
-    if (matches.length > 0) {
-      replaceMatchesInTextNode(node, matches, RULE_ID);
-    }
-  }
+  const signal = lifecycle.signal;
+  walkTextNodesChunked(root, {
+    signal,
+    minLength: MIN_TEXT_LENGTH,
+    process: (chunk) => {
+      for (const node of chunk) {
+        const matches = collectMatches(node.nodeValue ?? "");
+        if (matches.length > 0) {
+          replaceMatchesInTextNode(node, matches, RULE_ID);
+        }
+      }
+    },
+  });
 }
 
 const watcher = createSubtreeWatcher({
@@ -95,6 +113,9 @@ const watcher = createSubtreeWatcher({
 });
 
 function apply(root: ParentNode): void {
+  unsubscribeRouteChange ??= subscribeRouteChange(() => {
+    lifecycle.abortAndReset();
+  });
   scanAndMask(root);
   watcher.start(root);
 }
@@ -106,5 +127,8 @@ export const piiRedactRule = {
   apply,
   teardown: () => {
     watcher.stop();
+    lifecycle.abortAndReset();
+    unsubscribeRouteChange?.();
+    unsubscribeRouteChange = null;
   },
 } satisfies Rule;
diff --git a/extension/src/rules/prompt-injection-redact.ts b/extension/src/rules/prompt-injection-redact.ts
index c7e1475..92d2924 100644
--- a/extension/src/rules/prompt-injection-redact.ts
+++ b/extension/src/rules/prompt-injection-redact.ts
@@ -13,13 +13,12 @@
 // shipped extension bundle therefore contains plaintext regexes, not
 // `atob` decoding (matters for Chrome Web Store review).
 
+import { ReusableAbortController } from "abort-utils";
 import { REVEALED_ATTR } from "../lib/dom-markers";
-import {
-  filterToOutermost,
-  isInsidePlaceholder,
-  walkTextNodes,
-} from "../lib/dom-utils";
+import { filterToOutermost, isInsidePlaceholder } from "../lib/dom-utils";
 import { replaceWithBlockPlaceholder } from "../lib/placeholder";
+import { subscribeRouteChange } from "../lib/route-change";
+import { walkTextNodesChunked } from "../lib/yielding-text-walk";
 import { INJECTION_PATTERNS } from "./injection-patterns.generated";
 import type { Rule } from "./types";
 
@@ -54,49 +53,75 @@ function findContainer(textNode: Text): HTMLElement | null {
   return parent;
 }
 
-function apply(root: ParentNode): void {
+// Lifecycle controller cancels in-flight scans when an SPA route swap
+// arrives so the post-route apply doesn't compete with the pre-route
+// walk on the new tree. Teardown aborts and unsubscribes.
+const lifecycle = new ReusableAbortController();
+let unsubscribeRouteChange: (() => void) | null = null;
+
+function scanAndMask(root: ParentNode): void {
+  const signal = lifecycle.signal;
   const containers = new Set<HTMLElement>();
-  for (const node of walkTextNodes(root, {
+  walkTextNodesChunked(root, {
+    signal,
     minLength: MIN_TEXT_LENGTH,
-    // SVG <title>/<desc>/<text> are the injection carriers inside SVG, and
-    // `svg-text-strip` handles them by blanking the text in place. Letting
-    // prompt-injection-redact also fire on those text nodes is destructive:
-    // the SVG has no p/li/td ancestor, so `findContainer` escalates all the
-    // way up to the surrounding <article>/<section> and the entire product
-    // header gets replaced with a single placeholder (#133).
+    // SVG <title>/<desc>/<text> are the injection carriers inside
+    // SVG, and `svg-text-strip` handles them by blanking the text in
+    // place. Letting prompt-injection-redact also fire on those text
+    // nodes is destructive: the SVG has no p/li/td ancestor, so
+    // `findContainer` escalates all the way up to the surrounding
+    // <article>/<section> and the entire product header gets
+    // replaced with a single placeholder (#133).
     shouldSkipParent: (parent) => parent.closest("svg") !== null,
-  })) {
-    if (!containsInjection(node.nodeValue ?? "")) {
-      continue;
-    }
-    const container = findContainer(node);
-    if (container) {
-      containers.add(container);
-    }
-  }
+    process: (chunk) => {
+      for (const node of chunk) {
+        if (!containsInjection(node.nodeValue ?? "")) {
+          continue;
+        }
+        const container = findContainer(node);
+        if (container) {
+          containers.add(container);
+        }
+      }
+    },
+    // Second-pass hide runs after every text node is collected, so
+    // outermost dedupe sees the full container set. Synchronous when
+    // the tree fit in one chunk (the common test case); microtask-
+    // deferred when chunks fired. The helper guards against signal
+    // abort before calling us.
+    onComplete: () => {
+      for (const element of filterToOutermost([...containers])) {
+        if (!element.isConnected) {
+          continue;
+        }
+        if (isInsidePlaceholder(element)) {
+          continue;
+        }
+        // The container is an ancestor of the matched text node, so the reveal
+        // stamp lands here — not on the text node we walked from. If a previous
+        // run hid this container and the user revealed it, a re-apply (rule
+        // disable→enable, or a future MutationObserver-driven re-scan) would
+        // otherwise re-hide the same block. Same shape as the disguised-ad-flag
+        // bug fixed in #160. (Originally landed via #161; preserved here after
+        // the chunked-walk refactor moved the hide pass into onComplete.)
+        if (element.closest(REVEALED_SELECTOR)) {
+          continue;
+        }
+        replaceWithBlockPlaceholder(
+          element,
+          RULE_ID,
+          "[possible prompt injection hidden — click to reveal]",
+        );
+      }
+    },
+  });
+}
 
-  for (const element of filterToOutermost([...containers])) {
-    if (!element.isConnected) {
-      continue;
-    }
-    if (isInsidePlaceholder(element)) {
-      continue;
-    }
-    // The container is an ancestor of the matched text node, so the reveal
-    // stamp lands here — not on the text node we walked from. If a previous
-    // run hid this container and the user revealed it, a re-apply (rule
-    // disable→enable, or a future MutationObserver-driven re-scan) would
-    // otherwise re-hide the same block. Same shape as the disguised-ad-flag
-    // bug fixed in #160.
-    if (element.closest(REVEALED_SELECTOR)) {
-      continue;
-    }
-    replaceWithBlockPlaceholder(
-      element,
-      RULE_ID,
-      "[possible prompt injection hidden — click to reveal]",
-    );
-  }
+function apply(root: ParentNode): void {
+  unsubscribeRouteChange ??= subscribeRouteChange(() => {
+    lifecycle.abortAndReset();
+  });
+  scanAndMask(root);
 }
 
 export const promptInjectionRedactRule = {
@@ -105,4 +130,9 @@ export const promptInjectionRedactRule = {
   description:
     "Hide page sections containing phrases common in prompt-injection attacks.",
   apply,
+  teardown: () => {
+    lifecycle.abortAndReset();
+    unsubscribeRouteChange?.();
+    unsubscribeRouteChange = null;
+  },
 } satisfies Rule;
diff --git a/extension/src/rules/secrets-redact.ts b/extension/src/rules/secrets-redact.ts
index 8fc297f..e706f25 100644
--- a/extension/src/rules/secrets-redact.ts
+++ b/extension/src/rules/secrets-redact.ts
@@ -1,10 +1,12 @@
 // Copyright (c) 2026 PixieBrix, Inc.
 // Licensed under PolyForm Shield 1.0.0 — see LICENSE.
 
-import { walkTextNodes } from "../lib/dom-utils";
+import { ReusableAbortController } from "abort-utils";
 import type { InlineMatch } from "../lib/placeholder";
 import { replaceMatchesInTextNode } from "../lib/placeholder";
+import { subscribeRouteChange } from "../lib/route-change";
 import { createSubtreeWatcher } from "../lib/subtree-watcher";
+import { walkTextNodesChunked } from "../lib/yielding-text-walk";
 import type { Rule } from "./types";
 
 const RULE_ID = "secrets-redact" as const;
@@ -147,13 +149,26 @@ function collectMatches(text: string): InlineMatch[] {
   return merged;
 }
 
+// See pii-redact for lifecycle rationale — same pattern: route-change
+// aborts in-flight chunked walks; incremental subtree-watcher batches
+// do not.
+const lifecycle = new ReusableAbortController();
+let unsubscribeRouteChange: (() => void) | null = null;
+
 function scanAndMask(root: ParentNode): void {
-  for (const node of walkTextNodes(root, { minLength: MIN_TEXT_LENGTH })) {
-    const matches = collectMatches(node.nodeValue ?? "");
-    if (matches.length > 0) {
-      replaceMatchesInTextNode(node, matches, RULE_ID);
-    }
-  }
+  const signal = lifecycle.signal;
+  walkTextNodesChunked(root, {
+    signal,
+    minLength: MIN_TEXT_LENGTH,
+    process: (chunk) => {
+      for (const node of chunk) {
+        const matches = collectMatches(node.nodeValue ?? "");
+        if (matches.length > 0) {
+          replaceMatchesInTextNode(node, matches, RULE_ID);
+        }
+      }
+    },
+  });
 }
 
 const watcher = createSubtreeWatcher({
@@ -166,6 +181,9 @@ const watcher = createSubtreeWatcher({
 });
 
 function apply(root: ParentNode): void {
+  unsubscribeRouteChange ??= subscribeRouteChange(() => {
+    lifecycle.abortAndReset();
+  });
   scanAndMask(root);
   watcher.start(root);
 }
@@ -178,5 +196,8 @@ export const secretsRedactRule = {
   apply,
   teardown: () => {
     watcher.stop();
+    lifecycle.abortAndReset();
+    unsubscribeRouteChange?.();
+    unsubscribeRouteChange = null;
   },
 } satisfies Rule;

From db14c112b9a01be7ba7ee25ce31dd3016de3259c Mon Sep 17 00:00:00 2001
From: Todd Schiller <todd.schiller@gmail.com>
Date: Fri, 5 Jun 2026 09:44:31 -0400
Subject: [PATCH 2/3] Address review feedback: walker pre-fetches resume node
 across chunk boundaries
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

unblocked[bot] flagged a real bug. The consumer rules' `process`
callbacks call `replaceMatchesInTextNode`, which detaches each text
node in the chunk from the DOM — including the one walker.currentNode
points at. On resume, walker.nextNode() off a detached node returns
null and the walk silently ends after the first chunk.

Fix: pre-fetch the resume node before calling `process`, then anchor
walker.currentNode to it before yielding. Resume is held in a
`pendingResume` slot rather than seeded directly into the chunk —
seeding would skew the chunk-size invariant (property test caught
that variant on the first try).

Two regression tests:
  - yielding-text-walk.test.ts: chunked walk where `process` detaches
    each text node; the helper must still visit every node exactly
    once.
  - pii-redact.test.ts: 200-node tree, no abort, drain timers,
    assert all 200 SSNs masked (not just chunk 1's 100).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../lib/__tests__/yielding-text-walk.test.ts  | 50 +++++++++++++++++++
 extension/src/lib/yielding-text-walk.ts       | 24 ++++++++-
 .../src/rules/__tests__/pii-redact.test.ts    | 31 ++++++++++++
 3 files changed, 104 insertions(+), 1 deletion(-)

diff --git a/extension/src/lib/__tests__/yielding-text-walk.test.ts b/extension/src/lib/__tests__/yielding-text-walk.test.ts
index 2b2ddfa..c579da2 100644
--- a/extension/src/lib/__tests__/yielding-text-walk.test.ts
+++ b/extension/src/lib/__tests__/yielding-text-walk.test.ts
@@ -68,6 +68,56 @@ describe("walkTextNodesChunked — sync fast path", () => {
   });
 });
 
+describe("walkTextNodesChunked — chunked path with DOM-mutating process", () => {
+  // Regression for a bug where `process(chunk)` detached the chunk's
+  // text nodes (the consumer rules call replaceMatchesInTextNode) but
+  // walker.currentNode was still pointing at the now-detached last
+  // node of the chunk. The next walkSync entry called walker.nextNode()
+  // off the detached node, got null, and silently ended the walk —
+  // dropping every text node past the first chunk. The fix pre-fetches
+  // a resume node before process() and re-anchors walker.currentNode
+  // to it before yielding.
+
+  it("continues walking across chunks when process detaches each text node", async () => {
+    // Five text nodes, chunkSize 2 → chunks of 2, 2, 1.
+    document.body.innerHTML = Array.from(
+      { length: 5 },
+      (_, i) => `<p>text-${i}</p>`,
+    ).join("");
+    const seen: string[] = [];
+    let completed = false;
+
+    walkTextNodesChunked(document.body, {
+      chunkSize: 2,
+      yieldStrategy: () => Promise.resolve(),
+      process: (chunk) => {
+        for (const node of chunk) {
+          seen.push(node.nodeValue ?? "");
+          // Simulate replaceMatchesInTextNode — detach the text node.
+          node.remove();
+        }
+      },
+      onComplete: () => {
+        completed = true;
+      },
+    });
+
+    for (let i = 0; i < 10; i++) {
+      // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+      if (completed) {
+        break;
+      }
+      await Promise.resolve();
+    }
+
+    // Without the fix, the walk silently ended after the first chunk
+    // and `seen` only had ["text-0", "text-1"]. With the fix, all
+    // five text nodes get visited exactly once.
+    expect(seen).toEqual(["text-0", "text-1", "text-2", "text-3", "text-4"]);
+    expect(completed).toBe(true);
+  });
+});
+
 describe("walkTextNodesChunked — chunked path", () => {
   it("fires process once per filled chunk and onComplete after the last", async () => {
     // 5 text nodes, chunkSize 2 → chunks of 2, 2, 1.
diff --git a/extension/src/lib/yielding-text-walk.ts b/extension/src/lib/yielding-text-walk.ts
index feb0c89..942d329 100644
--- a/extension/src/lib/yielding-text-walk.ts
+++ b/extension/src/lib/yielding-text-walk.ts
@@ -109,6 +109,13 @@ export function walkTextNodesChunked(
   });
 
   let chunk: Text[] = [];
+  // Holds a node we pre-fetched before yielding (to keep walker.currentNode
+  // anchored to a still-connected node across the boundary). Consumed
+  // as the first node on the next walkSync entry — we can't let
+  // walker.nextNode() consume it because we'd want to revisit it
+  // ourselves, and the chunk-size invariant breaks if we seed it
+  // straight into `chunk` and then push another node on top.
+  let pendingResume: Text | null = null;
 
   function runFinalize(): void {
     if (signal?.aborted) {
@@ -122,12 +129,27 @@ export function walkTextNodesChunked(
   // after a scheduler yield; "done" when the walker has no more nodes
   // and the trailing partial chunk (if any) has been processed.
   function walkSync(): "yield" | "done" {
-    let next = walker.nextNode();
+    let next: Node | null = pendingResume ?? walker.nextNode();
+    pendingResume = null;
     while (next) {
       chunk.push(next as Text);
       if (chunk.length >= chunkSize) {
+        // Pre-fetch the resume point BEFORE process() runs. The
+        // consumer rules call replaceMatchesInTextNode in `process`,
+        // which detaches every text node in the chunk — including
+        // the one currently held in walker.currentNode. nextNode()
+        // off a detached node returns null and the walk silently
+        // ends after the first chunk. Grabbing the next node up
+        // front and re-anchoring walker.currentNode to it after
+        // process keeps the traversal valid across the boundary.
+        const resume = walker.nextNode();
         process(chunk);
         chunk = [];
+        if (!resume) {
+          return "done";
+        }
+        walker.currentNode = resume;
+        pendingResume = resume as Text;
         return "yield";
       }
       next = walker.nextNode();
diff --git a/extension/src/rules/__tests__/pii-redact.test.ts b/extension/src/rules/__tests__/pii-redact.test.ts
index 8e9ebb1..58c57ac 100644
--- a/extension/src/rules/__tests__/pii-redact.test.ts
+++ b/extension/src/rules/__tests__/pii-redact.test.ts
@@ -139,6 +139,37 @@ describe("pii-redact lazy-loaded subtrees", () => {
     expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(1);
   });
 
+  it("masks every match when the tree spans multiple chunks", async () => {
+    // Tree exceeds chunkSize=100 so the walker yields mid-scan. Without
+    // the resume-anchor in walkSync, the walker's currentNode points to
+    // the (now-detached) last node of chunk 1 after replaceMatchesInTextNode
+    // runs — and nextNode() returns null, silently dropping every match
+    // past the first 100. This test runs the rule end-to-end and
+    // confirms all 200 SSNs get hidden, not just the first chunk.
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>node-${i}: ${SSN}</p>`,
+    ).join("");
+
+    piiRedactRule.apply(document.body);
+    // Chunk 1 (100 nodes) runs synchronously.
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+
+    // Drain the chunked walk's yields. Each yield is a setTimeout(0)
+    // whose `.then()` callback schedules the next chunk via microtask;
+    // alternating timer + microtask drains the queue.
+    for (let i = 0; i < 5; i++) {
+      jest.advanceTimersByTime(0);
+      await flushMutations();
+    }
+
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      200,
+    );
+  });
+
   it("teardown aborts the in-flight chunked walk", () => {
     // 200 text nodes — exceeds the 100-node chunkSize default, so the
     // walk yields after chunk 1. teardown fires before the yield's

From 0108fe201274405bbfe779275de78246f5600688 Mon Sep 17 00:00:00 2001
From: Todd Schiller <todd.schiller@gmail.com>
Date: Fri, 5 Jun 2026 09:56:36 -0400
Subject: [PATCH 3/3] Test: route-change abort case for each text-heavy rule
 (CI coverage)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

CI's coverage threshold for ./src/rules/ requires 96% functions; the
post-rebase build sat at 95.66% because the route-change callback
each rule registers with subscribeRouteChange was never invoked by a
test. Adds one "route change aborts the in-flight chunked walk"
case per rule — mirror of the teardown abort test but the
cancellation signal comes from a popstate event. Brings src/rules/
function coverage to 97%.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../__tests__/encoded-payload-redact.test.ts  | 25 +++++++++++++++++
 .../src/rules/__tests__/pii-redact.test.ts    | 28 +++++++++++++++++++
 .../__tests__/prompt-injection-redact.test.ts | 24 ++++++++++++++++
 .../rules/__tests__/secrets-redact.test.ts    | 25 +++++++++++++++++
 4 files changed, 102 insertions(+)

diff --git a/extension/src/rules/__tests__/encoded-payload-redact.test.ts b/extension/src/rules/__tests__/encoded-payload-redact.test.ts
index 1932cb0..38dfb88 100644
--- a/extension/src/rules/__tests__/encoded-payload-redact.test.ts
+++ b/extension/src/rules/__tests__/encoded-payload-redact.test.ts
@@ -2,6 +2,7 @@
 // Licensed under PolyForm Shield 1.0.0 — see LICENSE.
 
 import { PLACEHOLDER_CLASS } from "../../lib/placeholder";
+import { __resetRouteChangeForTesting } from "../../lib/route-change";
 import { encodedPayloadRedactRule } from "../encoded-payload-redact";
 
 // Benign English sentences padded to a length whose base64 encoding
@@ -53,10 +54,13 @@ async function flushMutations(): Promise<void> {
 beforeEach(() => {
   document.body.innerHTML = "";
   jest.useFakeTimers();
+  history.replaceState(null, "", "/initial");
+  __resetRouteChangeForTesting();
 });
 
 afterEach(() => {
   encodedPayloadRedactRule.teardown();
+  __resetRouteChangeForTesting();
   jest.useRealTimers();
 });
 
@@ -243,4 +247,25 @@ describe("encoded-payload-redact teardown", () => {
       100,
     );
   });
+
+  it("route change aborts the in-flight chunked walk", () => {
+    const payload = base64Encode(LONG_PROSE);
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>blob-${i}: ${payload}</p>`,
+    ).join("");
+
+    encodedPayloadRedactRule.apply(document.body);
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+
+    history.replaceState(null, "", "/new-route");
+    globalThis.dispatchEvent(new Event("popstate"));
+    jest.advanceTimersByTime(0);
+
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+  });
 });
diff --git a/extension/src/rules/__tests__/pii-redact.test.ts b/extension/src/rules/__tests__/pii-redact.test.ts
index 58c57ac..4b3a15b 100644
--- a/extension/src/rules/__tests__/pii-redact.test.ts
+++ b/extension/src/rules/__tests__/pii-redact.test.ts
@@ -1,4 +1,5 @@
 import { PLACEHOLDER_CLASS } from "../../lib/placeholder";
+import { __resetRouteChangeForTesting } from "../../lib/route-change";
 import { piiRedactRule } from "../pii-redact";
 
 const VALID_CARD = "4111 1111 1111 1111"; // Visa test number, Luhn-valid.
@@ -15,10 +16,13 @@ async function flushMutations(): Promise<void> {
 beforeEach(() => {
   document.body.innerHTML = "";
   jest.useFakeTimers();
+  history.replaceState(null, "", "/initial");
+  __resetRouteChangeForTesting();
 });
 
 afterEach(() => {
   piiRedactRule.teardown();
+  __resetRouteChangeForTesting();
   jest.useRealTimers();
 });
 
@@ -170,6 +174,30 @@ describe("pii-redact lazy-loaded subtrees", () => {
     );
   });
 
+  it("route change aborts the in-flight chunked walk", () => {
+    // Same shape as the teardown abort test, but the cancellation
+    // signal is a route-change event (the rule subscribes to
+    // subscribeRouteChange on first apply). Confirms the
+    // route-change → abortAndReset wiring fires.
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>node-${i}: ${SSN}</p>`,
+    ).join("");
+
+    piiRedactRule.apply(document.body);
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+
+    history.replaceState(null, "", "/new-route");
+    globalThis.dispatchEvent(new Event("popstate"));
+    jest.advanceTimersByTime(0);
+
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+  });
+
   it("teardown aborts the in-flight chunked walk", () => {
     // 200 text nodes — exceeds the 100-node chunkSize default, so the
     // walk yields after chunk 1. teardown fires before the yield's
diff --git a/extension/src/rules/__tests__/prompt-injection-redact.test.ts b/extension/src/rules/__tests__/prompt-injection-redact.test.ts
index bb0a6cb..dd80cc1 100644
--- a/extension/src/rules/__tests__/prompt-injection-redact.test.ts
+++ b/extension/src/rules/__tests__/prompt-injection-redact.test.ts
@@ -1,4 +1,5 @@
 import { PLACEHOLDER_CLASS } from "../../lib/placeholder";
+import { __resetRouteChangeForTesting } from "../../lib/route-change";
 import { promptInjectionRedactRule } from "../prompt-injection-redact";
 import { FIXTURES } from "./injection-fixtures";
 
@@ -271,9 +272,12 @@ describe("prompt-injection-redact", () => {
 describe("prompt-injection-redact abort", () => {
   beforeEach(() => {
     jest.useFakeTimers();
+    history.replaceState(null, "", "/initial");
+    __resetRouteChangeForTesting();
   });
   afterEach(() => {
     promptInjectionRedactRule.teardown();
+    __resetRouteChangeForTesting();
     jest.useRealTimers();
   });
 
@@ -303,4 +307,24 @@ describe("prompt-injection-redact abort", () => {
     expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(0);
     expect(document.querySelectorAll("p")).toHaveLength(200);
   });
+
+  it("route change aborts the in-flight chunked walk before onComplete", () => {
+    // Mirror of the teardown test, but the cancellation signal is a
+    // route-change event. Verifies the subscribeRouteChange wiring.
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>${FIXTURES.IGNORE_HACKED} ${i}</p>`,
+    ).join("");
+
+    promptInjectionRedactRule.apply(document.body);
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(0);
+    expect(document.querySelectorAll("p")).toHaveLength(200);
+
+    history.replaceState(null, "", "/new-route");
+    globalThis.dispatchEvent(new Event("popstate"));
+    jest.advanceTimersByTime(0);
+
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(0);
+    expect(document.querySelectorAll("p")).toHaveLength(200);
+  });
 });
diff --git a/extension/src/rules/__tests__/secrets-redact.test.ts b/extension/src/rules/__tests__/secrets-redact.test.ts
index 90325f4..5e73cb7 100644
--- a/extension/src/rules/__tests__/secrets-redact.test.ts
+++ b/extension/src/rules/__tests__/secrets-redact.test.ts
@@ -1,4 +1,5 @@
 import { PLACEHOLDER_CLASS } from "../../lib/placeholder";
+import { __resetRouteChangeForTesting } from "../../lib/route-change";
 import { secretsRedactRule } from "../secrets-redact";
 
 const AWS_KEY = "AKIAIOSFODNN7EXAMPLE";
@@ -27,10 +28,13 @@ async function flushMutations(): Promise<void> {
 beforeEach(() => {
   document.body.innerHTML = "";
   jest.useFakeTimers();
+  history.replaceState(null, "", "/initial");
+  __resetRouteChangeForTesting();
 });
 
 afterEach(() => {
   secretsRedactRule.teardown();
+  __resetRouteChangeForTesting();
   jest.useRealTimers();
 });
 
@@ -250,4 +254,25 @@ describe("secrets-redact lazy-loaded subtrees", () => {
       100,
     );
   });
+
+  it("route change aborts the in-flight chunked walk", () => {
+    // Mirrors the teardown abort test but via the route-change wiring.
+    document.body.innerHTML = Array.from(
+      { length: 200 },
+      (_, i) => `<p>key-${i}: ${AWS_KEY}</p>`,
+    ).join("");
+
+    secretsRedactRule.apply(document.body);
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+
+    history.replaceState(null, "", "/new-route");
+    globalThis.dispatchEvent(new Event("popstate"));
+    jest.advanceTimersByTime(0);
+
+    expect(document.querySelectorAll(`.${PLACEHOLDER_CLASS}`)).toHaveLength(
+      100,
+    );
+  });
 });