diff --git a/.forgejo/workflows/check.yml b/.forgejo/workflows/check.yml
new file mode 100644
index 0000000..6e13d91
--- /dev/null
+++ b/.forgejo/workflows/check.yml
@@ -0,0 +1,74 @@
+name: Check
+
+on:
+  push:
+    branches: ['main']
+  pull_request:
+    branches: ['main']
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: '-Dwarnings'
+
+jobs:
+  build:
+    runs-on: docker
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22.x'
+          check-latest: true
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Cache npm dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            reconcile-js/node_modules
+            examples/website/node_modules
+            ~/.npm
+          key: >-
+            ${{ runner.os }}-npm-${{
+            hashFiles(
+              'reconcile-js/package-lock.json',
+              'examples/website/package-lock.json'
+            )
+            }}
+          restore-keys: |
+            ${{ runner.os }}-npm-
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      - name: Install uv
+        run: |
+          curl --proto '=https' --tlsv1.2 -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+
+      - name: Lint
+        run: scripts/lint.sh
+
+      - name: Test
+        run: scripts/test.sh
+
+      - name: Build website
+        run: scripts/build-website.sh
diff --git a/.forgejo/workflows/publish.yml b/.forgejo/workflows/publish.yml
new file mode 100644
index 0000000..bbaf253
--- /dev/null
+++ b/.forgejo/workflows/publish.yml
@@ -0,0 +1,265 @@
+name: Publish
+
+on:
+  push:
+    branches: ['main']
+    tags: ['*']
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: '-Dwarnings'
+
+concurrency:
+  group: 'pages'
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: docker
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22.x'
+          check-latest: true
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Cache npm dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            reconcile-js/node_modules
+            examples/website/node_modules
+            ~/.npm
+          key: >-
+            ${{ runner.os }}-npm-${{
+            hashFiles(
+              'reconcile-js/package-lock.json',
+              'examples/website/package-lock.json'
+            )
+            }}
+          restore-keys: |
+            ${{ runner.os }}-npm-
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      - name: Install uv
+        run: |
+          curl --proto '=https' --tlsv1.2 -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+
+      - name: Lint
+        run: scripts/lint.sh
+
+      - name: Test
+        run: scripts/test.sh
+
+      - name: Build website
+        run: scripts/build-website.sh
+
+      - name: Deploy to pages mount
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          apt-get update && apt-get install -y rsync
+          rsync -a --delete examples/website/dist/ /pages/reconcile
+
+  publish-crate:
+    needs: build
+    runs-on: docker
+    if: startsWith(github.ref, 'refs/tags/')
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      - name: Publish to crates.io
+        run: cargo publish --token ${{ secrets.CRATES_IO_TOKEN }}
+
+  publish-npm:
+    needs: build
+    runs-on: docker
+    if: startsWith(github.ref, 'refs/tags/')
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22.x'
+          check-latest: true
+          registry-url: 'https://registry.npmjs.org'
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Cache npm dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            reconcile-js/node_modules
+            ~/.npm
+          key: >-
+            ${{ runner.os }}-npm-${{
+            hashFiles('reconcile-js/package-lock.json')
+            }}
+          restore-keys: |
+            ${{ runner.os }}-npm-
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      - name: Build website
+        run: scripts/build-website.sh
+
+      - name: Publish reconcile-js to NPM
+        run: |
+          cd reconcile-js
+          cp ../README.md .
+          npm publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
+
+  publish-pypi:
+    needs: build
+    runs-on: docker
+    if: startsWith(github.ref, 'refs/tags/')
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-pypi-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-pypi-
+            ${{ runner.os }}-cargo-
+
+      # clang/lld/llvm provide clang-cl, lld-link and llvm-lib, which cargo-xwin
+      # uses to cross-compile the Windows wheel from this Linux runner.
+      - name: Install cross-compilation system dependencies
+        run: |
+          apt-get update
+          apt-get install -y clang lld llvm
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      # The Linux targets ship in rust-toolchain.toml; add the cross targets.
+      - name: Add cross-compilation Rust targets
+        run: |
+          rustup target add aarch64-unknown-linux-gnu x86_64-pc-windows-msvc
+
+      # zig is the C toolchain maturin's `--zig` uses to produce manylinux2014
+      # wheels with a pinned (old) glibc, independent of the runner's glibc.
+      - name: Install zig
+        run: |
+          ZIG_VERSION=0.13.0
+          curl --proto '=https' --tlsv1.2 -fLsS \
+            "https://ziglang.org/download/${ZIG_VERSION}/zig-linux-x86_64-${ZIG_VERSION}.tar.xz" \
+            | tar -xJ
+          echo "$PWD/zig-linux-x86_64-${ZIG_VERSION}" >> "$GITHUB_PATH"
+
+      - name: Install cargo-xwin
+        run: command -v cargo-xwin || cargo install --locked cargo-xwin
+
+      - name: Install uv
+        run: |
+          curl --proto '=https' --tlsv1.2 -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+
+      - name: Copy README
+        run: cp README.md reconcile-python/
+
+      - name: Build sdist
+        working-directory: reconcile-python
+        run: uv run maturin sdist --out dist
+
+      - name: Build Linux x86_64 wheel
+        working-directory: reconcile-python
+        run: >-
+          uv run maturin build --release --out dist
+          --compatibility manylinux2014
+          --target x86_64-unknown-linux-gnu --zig
+
+      - name: Build Linux aarch64 wheel
+        working-directory: reconcile-python
+        run: >-
+          uv run maturin build --release --out dist
+          --compatibility manylinux2014
+          --target aarch64-unknown-linux-gnu --zig
+
+      - name: Build Windows x86_64 wheel
+        working-directory: reconcile-python
+        run: >-
+          uv run maturin build --release --out dist
+          --target x86_64-pc-windows-msvc
+
+      # Forgejo cannot use PyPI trusted publishing (OIDC), so authenticate with
+      # an API token. --skip-existing makes re-runs of a tag idempotent.
+      - name: Publish to PyPI
+        working-directory: reconcile-python
+        env:
+          MATURIN_PYPI_TOKEN: ${{ secrets.PYPI_TOKEN }}
+        run: uv run maturin upload --skip-existing dist/*
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
deleted file mode 100644
index f5af792..0000000
--- a/.github/dependabot.yml
+++ /dev/null
@@ -1,26 +0,0 @@
-# To get started with Dependabot version updates, you'll need to specify which
-# package ecosystems to update and where the package manifests are located.
-# Please see the documentation for all configuration options:
-# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
-
-version: 2
-updates:
-  - package-ecosystem: 'cargo'
-    directories: ['**']
-    schedule:
-      interval: 'daily'
-
-  - package-ecosystem: 'github-actions'
-    directories: ['**']
-    schedule:
-      interval: 'daily'
-
-  - package-ecosystem: 'npm'
-    directories: ['/reconcile-js', '/examples/website']
-    schedule:
-      interval: 'daily'
-
-  - package-ecosystem: 'pip'
-    directories: ['/reconcile-python']
-    schedule:
-      interval: 'daily'
diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
deleted file mode 100644
index 261031d..0000000
--- a/.github/workflows/check.yml
+++ /dev/null
@@ -1,198 +0,0 @@
-name: Check & publish
-
-on:
-  push:
-    branches: ['main']
-    tags: ['*']
-  pull_request:
-    branches: ['main']
-
-env:
-  CARGO_TERM_COLOR: always
-  RUSTFLAGS: '-Dwarnings'
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - name: Setup Node.js environment
-        uses: actions/setup-node@v6.3.0
-        with:
-          node-version: '22.x'
-          check-latest: true
-
-      - name: Install uv
-        uses: astral-sh/setup-uv@v7
-
-      - name: Cache Rust dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cargo/bin/
-            ~/.cargo/registry/index/
-            ~/.cargo/registry/cache/
-            ~/.cargo/git/db/
-            target/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-
-
-      - name: Lint
-        run: scripts/lint.sh
-
-      - name: Test
-        run: scripts/test.sh
-
-  publish-crate:
-    needs: build
-    runs-on: ubuntu-latest
-    if: startsWith(github.ref, 'refs/tags/')
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - name: Cache Rust dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cargo/bin/
-            ~/.cargo/registry/index/
-            ~/.cargo/registry/cache/
-            ~/.cargo/git/db/
-            target/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-
-
-      - name: Publish to crates.io
-        run: cargo publish --token ${{ secrets.CRATES_IO_TOKEN }}
-
-  publish-npm:
-    needs: build
-    runs-on: ubuntu-latest
-    if: startsWith(github.ref, 'refs/tags/')
-    permissions:
-      contents: read
-      id-token: write
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - name: Setup Node.js environment
-        uses: actions/setup-node@v6.3.0
-        with:
-          node-version: '22.x'
-          check-latest: true
-          registry-url: 'https://registry.npmjs.org'
-
-      - name: Cache Rust dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cargo/bin/
-            ~/.cargo/registry/index/
-            ~/.cargo/registry/cache/
-            ~/.cargo/git/db/
-            target/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-
-
-      - name: Cache npm dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            reconcile-js/node_modules
-            ~/.npm
-          key: ${{ runner.os }}-npm-${{ hashFiles('reconcile-js/package-lock.json') }}
-          restore-keys: |
-            ${{ runner.os }}-npm-
-
-      - name: Build website
-        run: scripts/build-website.sh
-
-      - name: Publish reconcile-js to NPM
-        run: |
-          cd reconcile-js
-          cp ../README.md .
-          npm publish --provenance --access public
-
-  build-python-wheels:
-    needs: build
-    if: startsWith(github.ref, 'refs/tags/')
-    strategy:
-      matrix:
-        include:
-          - os: ubuntu-latest
-            target: x86_64
-          - os: ubuntu-latest
-            target: aarch64
-          - os: macos-latest
-            target: x86_64
-          - os: macos-latest
-            target: aarch64
-          - os: windows-latest
-            target: x86_64
-    runs-on: ${{ matrix.os }}
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - uses: actions/setup-python@v6
-        with:
-          python-version: '3.x'
-
-      - name: Copy README
-        run: cp README.md reconcile-python/
-
-      - uses: PyO3/maturin-action@v1
-        with:
-          target: ${{ matrix.target }}
-          args: --release --out dist --find-interpreter
-          manylinux: auto
-          working-directory: reconcile-python
-
-      - uses: actions/upload-artifact@v7
-        with:
-          name: wheels-${{ matrix.os }}-${{ matrix.target }}
-          path: reconcile-python/dist/*.whl
-
-  build-python-sdist:
-    needs: build
-    if: startsWith(github.ref, 'refs/tags/')
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - name: Copy README
-        run: cp README.md reconcile-python/
-
-      - uses: PyO3/maturin-action@v1
-        with:
-          command: sdist
-          args: --out dist
-          working-directory: reconcile-python
-
-      - uses: actions/upload-artifact@v7
-        with:
-          name: sdist
-          path: reconcile-python/dist/*.tar.gz
-
-  publish-pypi:
-    needs: [build-python-wheels, build-python-sdist]
-    runs-on: ubuntu-latest
-    permissions:
-      id-token: write
-
-    steps:
-      - uses: actions/download-artifact@v8
-        with:
-          pattern: '{wheels-*,sdist}'
-          merge-multiple: true
-          path: dist
-
-      - uses: pypa/gh-action-pypi-publish@release/v1
diff --git a/.github/workflows/gh-pages.yml b/.github/workflows/gh-pages.yml
deleted file mode 100644
index 7ac04ea..0000000
--- a/.github/workflows/gh-pages.yml
+++ /dev/null
@@ -1,72 +0,0 @@
-name: Deploy Website to GitHub Pages
-
-on:
-  push:
-    branches:
-      - main
-  workflow_dispatch:
-
-# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
-permissions:
-  contents: read
-  pages: write
-  id-token: write
-
-# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
-# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
-concurrency:
-  group: 'pages'
-  cancel-in-progress: false
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    permissions:
-      contents: write
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v6
-
-      - name: Cache Rust dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cargo/bin/
-            ~/.cargo/registry/index/
-            ~/.cargo/registry/cache/
-            ~/.cargo/git/db/
-            target/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-
-
-      - name: Cache npm dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            reconcile-js/node_modules
-            ~/.npm
-          key: ${{ runner.os }}-npm-${{ hashFiles('reconcile-js/package-lock.json') }}
-          restore-keys: |
-            ${{ runner.os }}-npm-
-
-      - name: Build wasm
-        run: |
-          which wasm-pack || cargo install wasm-pack
-          scripts/build-website.sh
-
-      - name: Upload artifact
-        uses: actions/upload-pages-artifact@v4
-        with:
-          path: examples/website/dist
-
-  deploy:
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
-    runs-on: ubuntu-latest
-    needs: build
-    steps:
-      - name: Deploy to GitHub Pages
-        id: deployment
-        uses: actions/deploy-pages@v4
diff --git a/.gitignore b/.gitignore
index 0957a69..c58feaf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,5 +10,8 @@ node_modules
 # WebPack build output
 dist
 
+# Generated wasm-bindgen bundler + wasm2js output for the React Native build
+pkg-rn
+
 # Python virtual environment
 .venv
diff --git a/.vscode/settings.json b/.vscode/settings.json
index db11dce..4571f3c 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -8,5 +8,8 @@
     },
     "rust-analyzer.cargo.features": [
         "all"
+    ],
+    "python.analysis.extraPaths": [
+        "./reconcile-python/python"
     ]
 }
\ No newline at end of file
diff --git a/Cargo.lock b/Cargo.lock
index 80b1085..b371452 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -428,7 +428,7 @@ checksum = "f8dcc9c7d52a811697d2151c701e0d08956f92b0e24136cf4cf27b57a6a0d9bf"
 
 [[package]]
 name = "reconcile-text"
-version = "0.9.4"
+version = "0.12.0"
 dependencies = [
  "console_error_panic_hook",
  "diff-match-patch-rs",
diff --git a/Cargo.toml b/Cargo.toml
index b578b91..5e60f78 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "reconcile-text"
 description = "Intelligent 3-way text merging with automated conflict resolution"
-version = "0.9.4"
+version = "0.12.0"
 rust-version = "1.94"
 authors = ["Andras Schmelczer <andras@schmelczer.dev>"]
 edition = "2024"
diff --git a/README.md b/README.md
index c25ef92..b644077 100644
--- a/README.md
+++ b/README.md
@@ -80,6 +80,13 @@ console.log(result.text); // "Hi beautiful world"
 
 See the [example website source](examples/website/src/index.ts) for a more complex example, or the [advanced examples document](docs/advanced-ts.md).
 
+#### React Native (Hermes)
+
+React Native's default engine, Hermes, does not expose a runtime `WebAssembly`
+global, so the WebAssembly build cannot run there. For React Native, the package
+ships a pure-JavaScript build produced by [Binaryen's `wasm2js`](https://github.com/WebAssembly/binaryen)
+via its `react-native` entry point.
+
 ### Python
 
 Install via uv or pip:
diff --git a/docs/advanced-ts.md b/docs/advanced-ts.md
index 7e53bf5..dd1633d 100644
--- a/docs/advanced-ts.md
+++ b/docs/advanced-ts.md
@@ -2,40 +2,65 @@
 
 ## Edit Provenance
 
-Track which changes came from where using `reconcileWithHistory`:
+Track which changes came from where using `reconcileWithHistory`. The result's
+`history` field is typed as `SpanWithHistory[]`, and each span's `history` is a
+`History` string-literal union.
 
-```javascript
-const result = reconcileWithHistory(
-  'Hello world',
-  'Hello beautiful world',
-  'Hi world'
-);
+```typescript
+import { reconcileWithHistory, type History, type SpanWithHistory } from 'reconcile-text';
 
-console.log(result.text);    // "Hi beautiful world"
-console.log(result.history); /*
-[
-  {
-    "text": "Hello",
-    "history": "RemovedFromRight"
-  },
-  {
-    "text": "Hi",
-    "history": "AddedFromRight"
-  },
-  {
-    "text": " beautiful",
-    "history": "AddedFromLeft"
-  },
-  {
-    "text": " ",
-    "history": "Unchanged"
-  },
-  {
-    "text": "world",
-    "history": "Unchanged"
+const result = reconcileWithHistory('Hello world', 'Hello beautiful world', 'Hi world');
+
+console.log(result.text); // "Hi beautiful world"
+
+const history: SpanWithHistory[] = result.history;
+console.log(history);
+// [
+//   { text: "Hello", history: "RemovedFromRight" },
+//   { text: "Hi", history: "AddedFromRight" },
+//   { text: " beautiful", history: "AddedFromLeft" },
+//   { text: " ", history: "Unchanged" },
+//   { text: "world", history: "Unchanged" },
+// ]
+
+const classByHistory = {
+  Unchanged: 'merge-unchanged',
+  AddedFromLeft: 'merge-added-left',
+  AddedFromRight: 'merge-added-right',
+  RemovedFromLeft: 'merge-removed-left',
+  RemovedFromRight: 'merge-removed-right',
+} satisfies Record<History, string>;
+```
+
+Using `satisfies Record<History, string>` keeps the object literal's values
+narrow while forcing every history case to be handled. If a future version adds
+another `History` value, TypeScript will point at this mapping.
+
+For control flow, use the same union as an exhaustiveness check:
+
+```typescript
+import type { History } from 'reconcile-text';
+
+function historyLabel(history: History): string {
+  switch (history) {
+    case 'Unchanged':
+      return 'unchanged';
+    case 'AddedFromLeft':
+      return 'added by left';
+    case 'AddedFromRight':
+      return 'added by right';
+    case 'RemovedFromLeft':
+      return 'removed from left';
+    case 'RemovedFromRight':
+      return 'removed from right';
+    default:
+      return assertNever(history);
   }
-]
-*/
+}
+
+function assertNever(value: never): never {
+  throw new Error(`Unhandled history value: ${value}`);
+}
 ```
 
 ## Tokenisation Strategies
@@ -45,26 +70,162 @@ console.log(result.history); /*
 - **Word tokeniser** (`"Word"`) - Splits on word boundaries (recommended for prose)
 - **Character tokeniser** (`"Character"`) - Individual characters (fine-grained control)
 - **Line tokeniser** (`"Line"`) - Line-by-line (similar to `git merge` or more precisely [`git merge-file`](https://git-scm.com/docs/git-merge-file))
+- **Markdown tokeniser** (`"Markdown"`) - Splits on Markdown structural boundaries (headings, list items, paragraphs)
+
+```typescript
+import { reconcile, type BuiltinTokenizer } from 'reconcile-text';
+
+const tokenizers = [
+  'Word',
+  'Character',
+  'Line',
+  'Markdown',
+] as const satisfies readonly BuiltinTokenizer[];
+
+const result = reconcile('abc', 'axc', 'abyc', 'Character');
+console.log(result.text); // "axyc"
+
+for (const tokenizer of tokenizers) {
+  const merged = reconcile(
+    '# Title\n\n- old item\n',
+    '# Title\n\n- old item\n- left item\n',
+    '# New title\n\n- old item\n',
+    tokenizer
+  );
+
+  console.log(tokenizer, merged.text);
+}
+```
 
 ## Cursor Tracking
 
-`reconcile-text` automatically tracks cursor positions through merges, which is useful for collaborative editors. Selections can be tracked by providing them as a pair of cursors.
+`reconcile-text` automatically tracks cursor positions through merges, which is
+useful for collaborative editors. Selections can be tracked by providing them as
+a pair of cursors.
 
-```javascript
-const result = reconcile(
-  'Hello world',
-  {
-    text: 'Hello beautiful world',
-    cursors: [{ id: 1, position: 6 }], // After "Hello "
-  },
-  {
-    text: 'Hi world',
-    cursors: [{ id: 2, position: 0 }], // At the beginning
-  }
-);
+```typescript
+import { reconcile, type TextWithOptionalCursors } from 'reconcile-text';
+
+const left = {
+  text: 'Hello beautiful world',
+  cursors: [{ id: 1, position: 6 }], // After "Hello "
+} satisfies TextWithOptionalCursors;
+
+const right = {
+  text: 'Hi world',
+  cursors: [{ id: 2, position: 0 }], // At the beginning
+} satisfies TextWithOptionalCursors;
+
+const result = reconcile('Hello world', left, right);
 
 // Result: "Hi beautiful world" with repositioned cursors
-console.log(result.text);    // "Hi beautiful world"
+console.log(result.text); // "Hi beautiful world"
 console.log(result.cursors); // [{ id: 2, position: 0 }, { id: 1, position: 3 }]
 ```
+
 > The `cursors` list is sorted by character position (not IDs).
+
+## Generic Helpers and Inference
+
+The exported merge functions are intentionally small: they merge strings, or
+strings plus cursor metadata. In TypeScript applications, keep domain-specific
+metadata in your own typed wrappers and let inference preserve the surrounding
+shape.
+
+```typescript
+import { reconcile, type BuiltinTokenizer } from 'reconcile-text';
+
+type ReconciledText<T extends { text: string }> = Omit<T, 'text'> & {
+  text: string;
+};
+
+function reconcileDraft<TDraft extends { text: string }>(
+  parent: TDraft,
+  left: TDraft,
+  right: TDraft,
+  tokenizer?: BuiltinTokenizer
+): ReconciledText<TDraft> {
+  return {
+    ...right,
+    text: reconcile(parent.text, left.text, right.text, tokenizer).text,
+  };
+}
+
+interface MarkdownDraft {
+  id: string;
+  text: string;
+  updatedAt: Date;
+}
+
+const parent: MarkdownDraft = {
+  id: 'intro',
+  text: '# Title\n\nOld text\n',
+  updatedAt: new Date('2026-01-01T00:00:00Z'),
+};
+
+const left: MarkdownDraft = {
+  ...parent,
+  text: '# Title\n\nOld text\n\n- left note\n',
+};
+
+const right: MarkdownDraft = {
+  ...parent,
+  text: '# New title\n\nOld text\n',
+};
+
+const merged = reconcileDraft(parent, left, right, 'Markdown');
+// merged is inferred as { id: string; updatedAt: Date; text: string }
+```
+
+Use `satisfies` for configuration objects and cursor payloads when you want
+compile-time checking without widening everything to the library interface.
+
+```typescript
+import type { BuiltinTokenizer, TextWithOptionalCursors } from 'reconcile-text';
+
+const mergeOptions = {
+  tokenizer: 'Markdown',
+  renderDeletedSpans: true,
+} satisfies {
+  tokenizer: BuiltinTokenizer;
+  renderDeletedSpans: boolean;
+};
+
+const documentWithSelection = {
+  text: 'Hello beautiful world',
+  cursors: [
+    { id: 1, position: 6 },
+    { id: 2, position: 15 },
+  ],
+} satisfies TextWithOptionalCursors;
+```
+
+## Compact Diffs
+
+Generate and apply compact diff representations. The TypeScript type is
+`Array<number | string>` for `diff()` and `Array<number | bigint | string>` for
+`undiff()`, because the underlying WebAssembly layer may represent integer
+entries as `bigint`.
+
+```typescript
+import { diff, undiff } from 'reconcile-text';
+
+const original = 'Hello world';
+const changed = 'Hello beautiful world';
+
+// Generate a compact diff
+const changes = diff(original, changed);
+console.log(changes); // [5, " beautiful world"]
+
+// Reconstruct the changed text from the diff
+const reconstructed = undiff(original, changes);
+console.assert(reconstructed === changed);
+```
+
+Diff entries are positive integers (retain N characters), negative integers
+(delete N characters), and strings (insert text).
+
+## Complete Example
+
+For a complete browser example that renders `SpanWithHistory` values and cursor
+selections, see the [example website source](../examples/website/src/index.ts).
diff --git a/examples/website/package-lock.json b/examples/website/package-lock.json
index 39397c3..a9369d7 100644
--- a/examples/website/package-lock.json
+++ b/examples/website/package-lock.json
@@ -28,11 +28,12 @@
     },
     "../../reconcile-js": {
       "name": "reconcile-text",
-      "version": "0.9.4",
+      "version": "0.12.0",
       "dev": true,
       "license": "MIT",
       "devDependencies": {
         "@types/jest": "^30.0.0",
+        "binaryen": "^123.0.0",
         "jest": "^30.3.0",
         "prettier": "^3.8.1",
         "reconcile-text": "file:../pkg",
@@ -1135,6 +1136,7 @@
       "integrity": "sha512-UVJyE9MttOsBQIDKw1skb9nAwQuR5wuGD3+82K6JgJlm/Y+KI92oNsMNGZCYdDsVtRHSak0pcV5Dno5+4jh9sw==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -1175,6 +1177,7 @@
       "integrity": "sha512-PlXPeEWMXMZ7sPYOHqmDyCJzcfNrUr3fGNKtezX14ykXOEIvyK81d+qydx89KY5O71FKMPaQ2vBfBFI5NHR63A==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "fast-deep-equal": "^3.1.3",
         "fast-uri": "^3.0.1",
@@ -1411,6 +1414,7 @@
         }
       ],
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "baseline-browser-mapping": "^2.9.0",
         "caniuse-lite": "^1.0.30001759",
@@ -3976,6 +3980,7 @@
         }
       ],
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "nanoid": "^3.3.11",
         "picocolors": "^1.1.1",
@@ -4484,6 +4489,7 @@
       "integrity": "sha512-+4N/u9dZ4PrgzGgPlKnaaRQx64RO0JBKs9sDhQ2pLgN6JQZ25uPQZKQYaBJU48Kd5BxgXoJ4e09Dq7nMcOUW3A==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "chokidar": "^4.0.0",
         "immutable": "^5.1.5",
@@ -5303,6 +5309,7 @@
       "integrity": "sha512-M7BAV6Rlcy5u+m6oPhAPFgJTzAioX/6B0DxyvDlo9l8+T3nLKbrczg2WLUyzd45L8RqfUMyGPzekbMvX2Ldkwg==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=12"
       },
@@ -5386,7 +5393,8 @@
       "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.8.1.tgz",
       "integrity": "sha512-oJFu94HQb+KVduSUQL7wnpmqnfmLsOA/nAh6b6EH0wCEoK0/mPeXU6c3wKDV83MkOuHPRHtSXKKU99IBazS/2w==",
       "dev": true,
-      "license": "0BSD"
+      "license": "0BSD",
+      "peer": true
     },
     "node_modules/tsyringe": {
       "version": "4.10.0",
@@ -5428,6 +5436,7 @@
       "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
       "dev": true,
       "license": "Apache-2.0",
+      "peer": true,
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
@@ -5568,6 +5577,7 @@
       "integrity": "sha512-jTywjboN9aHxFlToqb0K0Zs9SbBoW4zRUlGzI2tYNxVYcEi/IPpn+Xi4ye5jTLvX2YeLuic/IvxNot+Q1jMoOw==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@types/eslint-scope": "^3.7.7",
         "@types/estree": "^1.0.8",
@@ -5617,6 +5627,7 @@
       "integrity": "sha512-MfwFQ6SfwinsUVi0rNJm7rHZ31GyTcpVE5pgVA3hwFRb7COD4TzjUUwhGWKfO50+xdc2MQPuEBBJoqIMGt3JDw==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@discoveryjs/json-ext": "^0.6.1",
         "@webpack-cli/configtest": "^3.0.1",
diff --git a/reconcile-js/package-lock.json b/reconcile-js/package-lock.json
index 5fe2e42..b1a50b6 100644
--- a/reconcile-js/package-lock.json
+++ b/reconcile-js/package-lock.json
@@ -1,15 +1,16 @@
 {
   "name": "reconcile-text",
-  "version": "0.9.4",
+  "version": "0.12.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "reconcile-text",
-      "version": "0.9.4",
+      "version": "0.12.0",
       "license": "MIT",
       "devDependencies": {
         "@types/jest": "^30.0.0",
+        "binaryen": "^123.0.0",
         "jest": "^30.3.0",
         "prettier": "^3.8.1",
         "reconcile-text": "file:../pkg",
@@ -24,7 +25,7 @@
     },
     "../pkg": {
       "name": "reconcile-text",
-      "version": "0.9.4",
+      "version": "0.12.0",
       "dev": true,
       "license": "MIT"
     },
@@ -65,6 +66,7 @@
       "version": "7.28.0",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@ampproject/remapping": "^2.2.0",
         "@babel/code-frame": "^7.27.1",
@@ -1656,6 +1658,7 @@
       "integrity": "sha512-UVJyE9MttOsBQIDKw1skb9nAwQuR5wuGD3+82K6JgJlm/Y+KI92oNsMNGZCYdDsVtRHSak0pcV5Dno5+4jh9sw==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -1682,6 +1685,7 @@
       "integrity": "sha512-PlXPeEWMXMZ7sPYOHqmDyCJzcfNrUr3fGNKtezX14ykXOEIvyK81d+qydx89KY5O71FKMPaQ2vBfBFI5NHR63A==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "fast-deep-equal": "^3.1.3",
         "fast-uri": "^3.0.1",
@@ -1908,6 +1912,24 @@
         "node": ">=6.0.0"
       }
     },
+    "node_modules/binaryen": {
+      "version": "123.0.0",
+      "resolved": "https://registry.npmjs.org/binaryen/-/binaryen-123.0.0.tgz",
+      "integrity": "sha512-/hls/a309aZCc0itqP6uhoR+5DsKSlJVfB8Opd2BY9Ndghs84IScTunlyidyF4r2Xe3lQttnfBNIDjaNpj6mTw==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "wasm-as": "bin/wasm-as",
+        "wasm-ctor-eval": "bin/wasm-ctor-eval",
+        "wasm-dis": "bin/wasm-dis",
+        "wasm-merge": "bin/wasm-merge",
+        "wasm-metadce": "bin/wasm-metadce",
+        "wasm-opt": "bin/wasm-opt",
+        "wasm-reduce": "bin/wasm-reduce",
+        "wasm-shell": "bin/wasm-shell",
+        "wasm2js": "bin/wasm2js"
+      }
+    },
     "node_modules/brace-expansion": {
       "version": "1.1.12",
       "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.12.tgz",
@@ -1950,6 +1972,7 @@
         }
       ],
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "baseline-browser-mapping": "^2.9.0",
         "caniuse-lite": "^1.0.30001759",
@@ -3053,6 +3076,7 @@
       "integrity": "sha512-AkXIIFcaazymvey2i/+F94XRnM6TsVLZDhBMLsd1Sf/W0wzsvvpjeyUrCZD6HGG4SDYPgDJDBKeiJTBb10WzMg==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@jest/core": "30.3.0",
         "@jest/types": "30.3.0",
@@ -4936,6 +4960,7 @@
       "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
       "dev": true,
       "license": "Apache-2.0",
+      "peer": true,
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
@@ -5072,6 +5097,7 @@
       "integrity": "sha512-jTywjboN9aHxFlToqb0K0Zs9SbBoW4zRUlGzI2tYNxVYcEi/IPpn+Xi4ye5jTLvX2YeLuic/IvxNot+Q1jMoOw==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@types/eslint-scope": "^3.7.7",
         "@types/estree": "^1.0.8",
@@ -5119,6 +5145,7 @@
       "version": "6.0.1",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@discoveryjs/json-ext": "^0.6.1",
         "@webpack-cli/configtest": "^3.0.1",
diff --git a/reconcile-js/package.json b/reconcile-js/package.json
index 3b28195..da3a0ce 100644
--- a/reconcile-js/package.json
+++ b/reconcile-js/package.json
@@ -1,9 +1,10 @@
 {
   "name": "reconcile-text",
-  "version": "0.9.4",
+  "version": "0.12.0",
   "description": "Intelligent 3-way text merging with automated conflict resolution",
   "main": "dist/reconcile.node.js",
   "browser": "dist/reconcile.web.js",
+  "react-native": "dist/reconcile.rn.js",
   "keywords": [
     "text editing",
     "sync",
@@ -18,7 +19,7 @@
   "homepage": "https://schmelczer.dev/reconcile/",
   "repository": {
     "type": "git",
-    "url": "https://github.com/schmelczer/reconcile.git"
+    "url": "git+https://github.com/schmelczer/reconcile.git"
   },
   "bugs": {
     "url": "https://github.com/schmelczer/reconcile/issues",
@@ -31,12 +32,13 @@
     "dist/**/*"
   ],
   "scripts": {
-    "build": "webpack --mode production",
-    "format": "prettier --write \"./**/*.(ts|scss|json|html)\"",
+    "build": "node scripts/build-rn.mjs && webpack --mode production",
+    "format": "prettier --write \"./**/*.(ts|mjs|scss|json|html)\"",
     "test": "NODE_OPTIONS=\"$NODE_OPTIONS --experimental-vm-modules\" jest"
   },
   "devDependencies": {
     "@types/jest": "^30.0.0",
+    "binaryen": "^123.0.0",
     "jest": "^30.3.0",
     "prettier": "^3.8.1",
     "reconcile-text": "file:../pkg",
diff --git a/reconcile-js/scripts/build-rn.mjs b/reconcile-js/scripts/build-rn.mjs
new file mode 100644
index 0000000..dadbc82
--- /dev/null
+++ b/reconcile-js/scripts/build-rn.mjs
@@ -0,0 +1,307 @@
+// Generates `pkg-rn/`: a React Native / Hermes-compatible build of the
+// wasm-bindgen bindings in which the WebAssembly module is replaced by its
+// wasm2js (pure-JS) translation.
+
+import { execFileSync } from 'node:child_process';
+import { existsSync, readdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
+import { dirname, resolve } from 'node:path';
+import { fileURLToPath, pathToFileURL } from 'node:url';
+import { homedir } from 'node:os';
+
+const here = dirname(fileURLToPath(import.meta.url));
+const reconcileJsDir = resolve(here, '..');
+const repoRoot = resolve(reconcileJsDir, '..');
+
+const releaseWasm = resolve(
+  repoRoot,
+  'target/wasm32-unknown-unknown/release/reconcile_text.wasm'
+);
+const outDir = resolve(reconcileJsDir, 'pkg-rn');
+const bgWasm = resolve(outDir, 'reconcile_text_bg.wasm');
+const bgWasmJs = resolve(outDir, 'reconcile_text_bg.wasm.js');
+const loweredWasm = resolve(outDir, '_lowered.wasm');
+const entryJs = resolve(outDir, 'reconcile_text.js');
+
+const wasmOpt = resolve(reconcileJsDir, 'node_modules/.bin/wasm-opt');
+const wasm2js = resolve(reconcileJsDir, 'node_modules/.bin/wasm2js');
+
+function run(cmd, args) {
+  execFileSync(cmd, args, { stdio: 'inherit' });
+}
+
+// Locate the wasm-bindgen CLI. It MUST match the `wasm-bindgen` crate version pinned
+// in Cargo.toml: a mismatched CLI emits bindings the runtime can't use. So we resolve
+// the required version first and verify every candidate against it, failing loudly
+// rather than silently falling back to whatever other version happens to be around.
+function findWasmBindgen() {
+  const cargoToml = readFileSync(resolve(repoRoot, 'Cargo.toml'), 'utf8');
+  const wanted = cargoToml.match(
+    /wasm-bindgen\s*=\s*\{[^}]*version\s*=\s*"([^"]+)"/
+  )?.[1];
+  if (!wanted) {
+    throw new Error(
+      '[build-rn] Could not parse the pinned wasm-bindgen version from Cargo.toml, so ' +
+        'the required CLI version is unknown. Has the dependency declaration changed?'
+    );
+  }
+
+  // 1. On PATH: accept it only if its version matches the pin.
+  let onPath = null;
+  try {
+    onPath = execFileSync('which', ['wasm-bindgen'], { encoding: 'utf8' }).trim();
+  } catch {
+    /* not on PATH; try the wasm-pack cache next */
+  }
+  if (onPath) {
+    const version = execFileSync(onPath, ['--version'], { encoding: 'utf8' }).match(
+      /\d+\.\d+\.\d+/
+    )?.[0];
+    if (version !== wanted) {
+      throw new Error(
+        `[build-rn] wasm-bindgen on PATH (${onPath}) is ${version ?? 'an unknown version'}, ` +
+          `but Cargo.toml pins ${wanted}. Install the matching CLI ` +
+          `(\`cargo install wasm-bindgen-cli --version ${wanted}\`) or remove the mismatched one.`
+      );
+    }
+    return onPath;
+  }
+
+  const cacheRoots = [
+    resolve(homedir(), 'Library/Caches/.wasm-pack'),
+    resolve(homedir(), '.cache/.wasm-pack'),
+  ];
+  for (const root of cacheRoots) {
+    if (!existsSync(root)) {
+      continue;
+    }
+    for (const entry of readdirSync(root)) {
+      const candidate = resolve(root, entry, 'wasm-bindgen');
+      if (!existsSync(candidate)) {
+        continue;
+      }
+      let version;
+      try {
+        version = execFileSync(candidate, ['--version'], { encoding: 'utf8' }).match(
+          /\d+\.\d+\.\d+/
+        )?.[0];
+      } catch {
+        continue; // not an invokable wasm-bindgen; ignore
+      }
+      if (version === wanted) {
+        return candidate;
+      }
+    }
+  }
+
+  throw new Error(
+    `[build-rn] No wasm-bindgen ${wanted} found on PATH or in the wasm-pack cache. ` +
+      'Run `wasm-pack build --target web --features wasm` first (it caches the matching ' +
+      `wasm-bindgen), or \`cargo install wasm-bindgen-cli --version ${wanted}\`.`
+  );
+}
+
+if (!existsSync(releaseWasm)) {
+  throw new Error(
+    `Missing ${releaseWasm}.\nRun \`wasm-pack build --target web --features wasm\` from the repo root first.`
+  );
+}
+
+console.log('[build-rn] generating bundler-target bindings with wasm-bindgen');
+rmSync(outDir, { recursive: true, force: true });
+const wasmBindgen = findWasmBindgen();
+run(wasmBindgen, ['--target', 'bundler', '--out-dir', outDir, releaseWasm]);
+
+// --- Patch wasm-bindgen's cached-memory getters for wasm2js -----------------
+//
+// wasm-bindgen caches typed-array / DataView views over `wasm.memory.buffer` and
+// only re-creates them when it detects the heap grew. It detects a grow by looking
+// for ArrayBuffer *detachment*: a real `WebAssembly.Memory.grow()` detaches the old
+// buffer (its `byteLength` becomes 0 and `.detached` becomes true), and those are the
+// only signals the generated getters check:
+//   - getUint8ArrayMemory0(): refreshes when `byteLength === 0`           (detach only)
+//   - getDataViewMemory0():   refreshes when `.detached === true`, OR when the buffer
+//     identity changed but only `if (.detached === undefined)` — i.e. that identity
+//     fallback runs solely on engines lacking `ArrayBuffer.prototype.detached`.
+//
+// wasm2js grows differently: `__wasm_memory_grow` (in reconcile_text_bg.wasm.js)
+// allocates a NEW ArrayBuffer, copies the old heap into it, and reassigns
+// `memory.buffer` WITHOUT ever detaching the old buffer. So the old buffer keeps
+// `byteLength > 0` and `.detached === false`, and on modern engines that DO expose
+// `ArrayBuffer.prototype.detached` (Node 25+, current Hermes) the identity fallback is
+// gated off. Net effect: after a grow the getters keep returning views over the stale
+// pre-grow buffer, silently corrupting any operation large enough to grow the heap.
+// Small inputs never grow, so this escapes naive testing.
+//
+// WHY WE PATCH INSTEAD OF CONFIGURING.
+// This is not fixed or configurable upstream: wasm-bindgen has no wasm2js / asm.js /
+// React Native / "no-WebAssembly" target (every target assumes real WebAssembly
+// detach-on-grow semantics), there is no flag to force buffer-identity comparison, and
+// the getter-generation logic (crates/cli-support/src/js/mod.rs `memview`) is
+// byte-for-byte identical from the pinned 0.2.114 through the latest release and
+// `main`. The non-detaching-grow case is not even a tracked upstream issue. Rewriting
+// the generated glue is therefore the only available fix: the two replacements below
+// make BOTH getters also refresh on a buffer-identity change
+// (`buffer !== wasm.memory.buffer`), which is the one signal wasm2js does give.
+//
+// Each replacement is asserted independently. If a future wasm-bindgen reshapes one
+// getter but not the other, we MUST fail the build rather than ship a half-patched
+// module whose un-patched getter corrupts large inputs. The post-build self-test at
+// the bottom of this file is the backstop that proves the result survives a real grow.
+const bgJsPath = resolve(outDir, 'reconcile_text_bg.js');
+let bgJs = readFileSync(bgJsPath, 'utf8');
+
+// (1) Uint8Array getter: append an unconditional buffer-identity check to the
+//     `byteLength === 0` detach guard (upstream has no identity check here at all).
+const byteLengthGuard = /(cached\w*Memory0)\.byteLength === 0/g;
+const byteLengthHits = bgJs.match(byteLengthGuard)?.length ?? 0;
+if (byteLengthHits === 0) {
+  throw new Error(
+    `[build-rn] Could not find the Uint8Array \`byteLength === 0\` growth guard in ` +
+      `${bgJsPath} to patch for wasm2js. The wasm-bindgen output shape changed; update ` +
+      'this patch (see crates/cli-support/src/js/mod.rs `memview`) — do NOT ship an ' +
+      'unpatched getter, it will corrupt large inputs under wasm2js.'
+  );
+}
+bgJs = bgJs.replace(
+  byteLengthGuard,
+  '$1.byteLength === 0 || $1.buffer !== wasm.memory.buffer'
+);
+
+// (2) DataView getter: drop the `detached === undefined &&` prefix so the existing
+//     buffer-identity check runs on every runtime, not only legacy ones.
+const gatedGuard =
+  /(cached\w*Memory0)\.buffer\.detached === undefined && \1\.buffer !== wasm\.memory\.buffer/g;
+const gatedHits = bgJs.match(gatedGuard)?.length ?? 0;
+if (gatedHits === 0) {
+  throw new Error(
+    `[build-rn] Could not find the DataView \`detached === undefined\`-gated buffer-identity ` +
+      `check in ${bgJsPath} to un-gate for wasm2js. The wasm-bindgen output shape changed; ` +
+      'update this patch (see crates/cli-support/src/js/mod.rs `memview`) — do NOT ship an ' +
+      'unpatched getter, it will corrupt large inputs under wasm2js.'
+  );
+}
+bgJs = bgJs.replace(gatedGuard, '$1.buffer !== wasm.memory.buffer');
+
+writeFileSync(bgJsPath, bgJs);
+
+// Post-MVP features that wasm2js cannot translate must be lowered to MVP first.
+// reference-types stays enabled: it only covers the funcref table here, which
+// wasm2js handles via call_indirect.
+const featureFlags = [
+  '--enable-bulk-memory',
+  '--enable-sign-ext',
+  '--enable-nontrapping-float-to-int',
+  '--enable-mutable-globals',
+  '--enable-reference-types',
+];
+
+console.log('[build-rn] optimising and lowering to MVP with wasm-opt');
+run(wasmOpt, [
+  ...featureFlags,
+  '-O3',
+  '--signext-lowering',
+  '--llvm-memory-copy-fill-lowering',
+  '--llvm-nontrapping-fptoint-lowering',
+  bgWasm,
+  '-o',
+  loweredWasm,
+]);
+
+console.log('[build-rn] translating wasm -> JS with wasm2js');
+run(wasm2js, ['--enable-reference-types', loweredWasm, '-o', bgWasmJs]);
+
+console.log('[build-rn] wiring the JS translation into reconcile_text.js');
+const entry = readFileSync(entryJs, 'utf8');
+const rewired = entry.replace(
+  /from\s+(['"])\.\/reconcile_text_bg\.wasm\1/,
+  'from $1./reconcile_text_bg.wasm.js$1'
+);
+if (rewired === entry) {
+  throw new Error(
+    `Could not find the \`./reconcile_text_bg.wasm\` import in ${entryJs}; ` +
+      'the wasm-bindgen bundler output layout may have changed.'
+  );
+}
+writeFileSync(entryJs, rewired);
+
+// The binary and the intermediate are no longer referenced; remove them so no
+// bundler attempts to instantiate WebAssembly from this directory.
+rmSync(bgWasm, { force: true });
+rmSync(loweredWasm, { force: true });
+
+// Mark the directory as ESM (matching the web `pkg/`) so Node and Jest treat
+// these `.js` files as modules. `sideEffects` stays true because importing the
+// entry runs `__wbg_set_wasm(...)`, which must not be tree-shaken away.
+writeFileSync(
+  resolve(outDir, 'package.json'),
+  JSON.stringify({ type: 'module', sideEffects: true }, null, 2) + '\n'
+);
+
+// Backstop: import the freshly generated module and prove it survives a heap grow.
+// The patches above are matched by regex against wasm-bindgen output; a silently
+// mis-applied patch (or a wasm-bindgen change we matched too loosely) would leave a
+// getter reading the stale pre-grow buffer and corrupt large inputs only. Rather than
+// trust the regexes, we force a grow here and assert a byte-exact round-trip, so a
+// broken bundle fails the build instead of reaching a React Native consumer.
+async function selfTest() {
+  // Importing the entry runs `__wbg_set_wasm(...)`, initialising the wasm2js module.
+  const api = await import(pathToFileURL(entryJs).href);
+  // Same module instance (Node caches by resolved path), so this `memory` is the heap
+  // the API operates on; its `.buffer` getter reflects the current (post-grow) buffer.
+  const { memory } = await import(pathToFileURL(bgWasmJs).href);
+
+  // ~100 KB of distinct tokens. The diff working set amplifies the input many-fold
+  // (a ~50 KB input already forces dozens of grows), so this reliably grows the heap
+  // well past wasm2js's ~1 MB initial allocation while staying fast. A tiny parent
+  // keeps the edit distance — and therefore the runtime — small.
+  const tokens = [];
+  for (let i = 0; i < 10000; i++) {
+    tokens.push(`token-${i}`);
+  }
+  const target = tokens.join(' ');
+  const parent = 'reconcile self-test';
+
+  const heapBefore = memory.buffer.byteLength;
+
+  // Stale post-grow reads surface either as an out-of-bounds throw or as silently
+  // wrong bytes, so handle both: a throw here is itself the failure signal.
+  let roundTripped;
+  try {
+    const changed = new api.TextWithCursors(target, []);
+    const compact = api
+      .diff(parent, changed, 'Word')
+      // This build's `undiff` rejects BigInt; normalise exactly as src/core.ts does.
+      .map((item) => (typeof item === 'bigint' ? Number(item) : item));
+    changed.free();
+    roundTripped = api.undiff(parent, compact, 'Word');
+  } catch (cause) {
+    throw new Error(
+      '[build-rn] self-test crashed during a large diff/undiff round-trip (after the heap ' +
+        'grew). This is the signature of unpatched wasm2js cached-memory getters reading the ' +
+        'stale pre-grow buffer. The growth patch is not taking effect. Refusing to ship this ' +
+        'React Native bundle.',
+      { cause }
+    );
+  }
+
+  const heapAfter = memory.buffer.byteLength;
+
+  if (heapAfter <= heapBefore) {
+    throw new Error(
+      `[build-rn] self-test did not grow the wasm heap (stayed at ${heapBefore} bytes), ` +
+        'so it cannot validate the memory-growth patch. Enlarge the self-test input.'
+    );
+  }
+  if (roundTripped !== target) {
+    throw new Error(
+      '[build-rn] self-test FAILED: diff/undiff round-trip did not match after a heap grow. ' +
+        'The patched wasm2js cached-memory getters are returning stale/corrupt data — the ' +
+        'growth patch is not taking effect. Refusing to ship this React Native bundle.'
+    );
+  }
+}
+
+console.log('[build-rn] self-testing the patched module (forces a heap grow)');
+await selfTest();
+
+console.log('[build-rn] done -> pkg-rn/');
diff --git a/reconcile-js/src/core.ts b/reconcile-js/src/core.ts
new file mode 100644
index 0000000..cf2d1ec
--- /dev/null
+++ b/reconcile-js/src/core.ts
@@ -0,0 +1,400 @@
+// Shared, platform-agnostic wrapper around the generated wasm-bindgen surface.
+//
+// The actual wasm bindings are injected by a platform-specific entrypoint:
+//   - `index.ts`     (web/node) instantiates the real WebAssembly module lazily
+//                    on first use via `initSync`.
+//   - `index.rn.ts`  (React Native / Hermes) links a wasm2js (pure-JS)
+//                    implementation, since Hermes does not expose a runtime
+//                    `WebAssembly` global. See `scripts/build-rn.mjs`.
+
+type WasmModule = typeof import('reconcile-text');
+
+/**
+ * The generated wasm-bindgen surface this library wraps, plus a hook to make
+ * sure the underlying module is ready. Supplied by a platform entrypoint.
+ */
+export interface WasmBackend {
+  CursorPosition: WasmModule['CursorPosition'];
+  TextWithCursors: WasmModule['TextWithCursors'];
+  reconcile: WasmModule['reconcile'];
+  reconcileWithHistory: WasmModule['reconcileWithHistory'];
+  diff: WasmModule['diff'];
+  undiff: WasmModule['undiff'];
+  /**
+   * Make the wasm module ready for use. Invoked before every operation, so it
+   * must be cheap and idempotent (a no-op once initialised).
+   */
+  ensureReady(): void;
+}
+
+// Define the enum values as a const array to avoid duplication
+const BUILTIN_TOKENIZERS = ['Character', 'Line', 'Markdown', 'Word'] as const;
+
+/**
+ * Tokenisation strategies for text merging.
+ *
+ * These correspond to the built-in tokenizers available in the underlying WASM module.
+ */
+export type BuiltinTokenizer = (typeof BUILTIN_TOKENIZERS)[number];
+
+/**
+ * History classification for text spans in merge results.
+ *
+ * Indicates the origin of each text span in the merged document.
+ */
+export type History =
+  | 'Unchanged'
+  | 'AddedFromLeft'
+  | 'AddedFromRight'
+  | 'RemovedFromLeft'
+  | 'RemovedFromRight';
+
+/**
+ * Represents a text document with associated cursor positions.
+ *
+ * This interface is used both as input to reconcile functions (to specify where
+ * cursors are positioned in the original documents) and as output (with cursors
+ * automatically repositioned after merging).
+ */
+export interface TextWithCursors {
+  /** The document's entire content as a string */
+  text: string;
+
+  /**
+   * Array of cursor positions within the text. Can be empty if there are no cursors to track.
+   * Each cursor has a unique ID and position.
+   */
+  cursors: CursorPosition[];
+}
+
+/**
+ * Like `TextWithCursors`, but cursors may be null or undefined (treated as empty).
+ * Used as input where cursor tracking is optional.
+ */
+export interface TextWithOptionalCursors {
+  /** The document's entire content as a string */
+  text: string;
+
+  /**
+   * Array of cursor positions within the text. Can be null, undefined, or empty
+   * if there are no cursors to track. Each cursor has a unique ID and position.
+   */
+  cursors: null | undefined | CursorPosition[];
+}
+
+/**
+ * Represents a cursor position within a text document.
+ *
+ * Cursors are automatically repositioned during text merging to maintain their
+ * relative positions as text is inserted, deleted, or modified around them.
+ */
+export interface CursorPosition {
+  /** Unique identifier for the cursor (can be any number, must be unique within the document) */
+  id: number;
+
+  /** Character position in the text, 0-based index from the beginning of the document */
+  position: number;
+}
+
+/**
+ * Represents a merged text document with cursor positions and detailed change history.
+ *
+ * This is the return type of `reconcileWithHistory()` and provides complete information
+ * about how the merge was performed, including which parts of the final text came from
+ * which source documents.
+ */
+export interface TextWithCursorsAndHistory {
+  /** The merged document's entire content */
+  text: string;
+
+  /**
+   * Array of cursor positions within the merged text. Can be empty if there are no cursors to track.
+   * All cursors are automatically repositioned from the left and right documents.
+   */
+  cursors: CursorPosition[];
+
+  /**
+   * Detailed provenance information showing the origin of each text span in the result.
+   * Each span indicates whether it was unchanged, added from left, added from right, etc.
+   */
+  history: SpanWithHistory[];
+}
+
+/**
+ * Represents a span of text in the merged result with its change history.
+ *
+ * This shows exactly which source document contributed each piece of text to the
+ * final merged result. Useful for understanding merge decisions and creating
+ * visualisations of how documents were combined.
+ */
+export interface SpanWithHistory {
+  /** The text content of this span */
+  text: string;
+
+  /** The origin of this text span in the merge result */
+  history: History;
+}
+
+/** The public, synchronous API surface, identical across platforms. */
+export interface ReconcileApi {
+  /**
+   * Merges three versions of text using intelligent conflict resolution.
+   *
+   * This is the primary function for 3-way text merging. Unlike traditional merge tools
+   * that produce conflict markers, this function automatically resolves conflicts by
+   * applying both sets of changes where possible.
+   *
+   * @param original - The original/base version of the text that both sides diverged from
+   * @param left - The left version of the text (either string or TextWithCursors with cursor positions)
+   * @param right - The right version of the text (either string or TextWithCursors with cursor positions)
+   * @param tokenizer - The tokenisation strategy: "Word" (default, recommended for prose),
+   *                    "Character" (fine-grained), "Line" (similar to git merge), or
+   *                    "Markdown" (splits on Markdown structure)
+   * @returns The reconciled text with automatically repositioned cursor positions
+   *
+   * @example
+   * ```typescript
+   * const original = "Hello world";
+   * const left = "Hello beautiful world";    // Added "beautiful"
+   * const right = "Hi world";                // Changed "Hello" to "Hi"
+   *
+   * const result = reconcile(original, left, right);
+   * console.log(result.text); // "Hi beautiful world"
+   * ```
+   */
+  reconcile(
+    original: string,
+    left: string | TextWithOptionalCursors,
+    right: string | TextWithOptionalCursors,
+    tokenizer?: BuiltinTokenizer
+  ): TextWithCursors;
+
+  /**
+   * Generates a compact diff representation between an original and changed text.
+   *
+   * These can be parsed and unpacked using the `undiff` function or the Rust crate's EditedText::from_diff.
+   * Cursor positions are omitted from the diff result.
+   *
+   * This function computes the differences between two versions of text and returns
+   * a compact representation of those changes.
+   *
+   * @param original - The original/base version of the text
+   * @param changed - The modified version of the text (either string or TextWithCursors with cursor positions)
+   * @param tokenizer - The tokenisation strategy, which is the same as used in `reconcile`.
+   * @returns An array of inserts (strings), deletes (negative integers), and retained spans (positive integers).
+   */
+  diff(
+    original: string,
+    changed: string | TextWithOptionalCursors,
+    tokenizer?: BuiltinTokenizer
+  ): Array<number | string>;
+
+  /**
+   * Applies a compact diff to an original text to reconstruct the changed version.
+   *
+   * This function takes an original text and a compact diff representation (as produced
+   * by the `diff` function) and reconstructs the modified text.
+   *
+   * @param original - The original/base version of the text
+   * @param diff - The compact diff array (inserts as strings, deletes as negative integers, retained spans as positive integers)
+   * @param tokenizer - The tokenisation strategy, which is the same as used in `reconcile`.
+   * @returns The reconstructed changed text as a string.
+   */
+  undiff(
+    original: string,
+    diff: Array<number | bigint | string>,
+    tokenizer?: BuiltinTokenizer
+  ): string;
+
+  /**
+   * Merges three versions of text and returns detailed provenance information.
+   *
+   * This function behaves like `reconcile()` but also provides
+   * detailed historical information about the origin of each text span in the result.
+   * This is valuable for understanding how the merge was performed and which changes
+   * came from which source.
+   *
+   * Note: Computing the history is computationally more expensive than the basic merge.
+   *
+   * @param original - The original/base version of the text that both sides diverged from
+   * @param left - The left version of the text (either string or TextWithCursors with cursor positions)
+   * @param right - The right version of the text (either string or TextWithCursors with cursor positions)
+   * @param tokenizer - The tokenisation strategy: "Word" (default, recommended for prose),
+   *                    "Character" (fine-grained), "Line" (similar to git merge), or
+   *                    "Markdown" (splits on Markdown structure)
+   * @returns The reconciled text with cursor positions and detailed change history
+   *
+   * @example
+   * ```typescript
+   * const original = "Hello world";
+   * const left = "Hello beautiful world";
+   * const right = "Hi world";
+   *
+   * const result = reconcileWithHistory(original, left, right);
+   * console.log(result.text); // "Hi beautiful world"
+   * console.log(result.history); // Array of SpanWithHistory objects showing change origins
+   * ```
+   */
+  reconcileWithHistory(
+    original: string,
+    left: string | TextWithOptionalCursors,
+    right: string | TextWithOptionalCursors,
+    tokenizer?: BuiltinTokenizer
+  ): TextWithCursorsAndHistory;
+}
+
+const UNSUPPORTED_TOKENIZER_ERROR = `Unsupported tokenizer, only ${BUILTIN_TOKENIZERS.join(
+  ', '
+)} are supported`;
+
+/**
+ * Build the public {@link ReconcileApi} on top of a {@link WasmBackend}.
+ *
+ * Each operation calls `backend.ensureReady()` first, then marshals JS values
+ * into the wasm representation, invokes the binding, and frees the wasm-side
+ * objects. The behaviour is identical regardless of whether the backend is a
+ * real WebAssembly module or its wasm2js translation.
+ */
+export function makeReconcileApi(backend: WasmBackend): ReconcileApi {
+  function assertTokenizer(tokenizer: BuiltinTokenizer): void {
+    if (!BUILTIN_TOKENIZERS.includes(tokenizer)) {
+      throw new Error(UNSUPPORTED_TOKENIZER_ERROR);
+    }
+  }
+
+  function toWasmTextWithCursors(text: string | TextWithOptionalCursors) {
+    const isInputString = typeof text === 'string';
+    const innerText = isInputString ? text : text.text;
+    const innerCursors = isInputString ? [] : (text.cursors ?? []);
+
+    return new backend.TextWithCursors(
+      innerText,
+      innerCursors.map(({ id, position }) => new backend.CursorPosition(id, position))
+    );
+  }
+
+  function toTextWithCursors(textWithCursor: {
+    text(): string;
+    cursors(): Array<{ id(): number; characterIndex(): number; free(): void }>;
+  }): TextWithCursors {
+    const wasmCursors = textWithCursor.cursors();
+    const cursors = wasmCursors.map((cursor) => ({
+      id: cursor.id(),
+      position: cursor.characterIndex(),
+    }));
+    for (const cursor of wasmCursors) {
+      cursor.free();
+    }
+
+    return {
+      text: textWithCursor.text(),
+      cursors,
+    };
+  }
+
+  function toSpanWithHistory(span: {
+    text(): string;
+    history(): History;
+    free(): void;
+  }): SpanWithHistory {
+    const result = {
+      text: span.text(),
+      history: span.history(),
+    };
+    span.free();
+    return result;
+  }
+
+  function reconcile(
+    original: string,
+    left: string | TextWithOptionalCursors,
+    right: string | TextWithOptionalCursors,
+    tokenizer: BuiltinTokenizer = 'Word'
+  ): TextWithCursors {
+    backend.ensureReady();
+    assertTokenizer(tokenizer);
+
+    const leftCursor = toWasmTextWithCursors(left);
+    const rightCursor = toWasmTextWithCursors(right);
+
+    const result = backend.reconcile(original, leftCursor, rightCursor, tokenizer);
+
+    leftCursor.free();
+    rightCursor.free();
+
+    const jsResult = toTextWithCursors(result);
+    result.free();
+
+    return jsResult;
+  }
+
+  function diff(
+    original: string,
+    changed: string | TextWithOptionalCursors,
+    tokenizer: BuiltinTokenizer = 'Word'
+  ): Array<number | string> {
+    backend.ensureReady();
+    assertTokenizer(tokenizer);
+
+    const changedWasm = toWasmTextWithCursors(changed);
+
+    const result = backend.diff(original, changedWasm, tokenizer);
+
+    changedWasm.free();
+
+    return result.map((item) => (typeof item === 'bigint' ? Number(item) : item));
+  }
+
+  function undiff(
+    original: string,
+    diffValue: Array<number | bigint | string>,
+    tokenizer: BuiltinTokenizer = 'Word'
+  ): string {
+    backend.ensureReady();
+    assertTokenizer(tokenizer);
+
+    // The real-WebAssembly backend's `diff` emits BigInt spans, whereas the
+    // wasm2js (React Native) backend rejects BigInt outright. Normalise to
+    // plain numbers - exactly as `diff` does on the way out - so a `diff`
+    // result round-trips through `undiff` identically on every platform.
+    return backend.undiff(
+      original,
+      diffValue.map((item) => (typeof item === 'bigint' ? Number(item) : item)),
+      tokenizer
+    );
+  }
+
+  function reconcileWithHistory(
+    original: string,
+    left: string | TextWithOptionalCursors,
+    right: string | TextWithOptionalCursors,
+    tokenizer: BuiltinTokenizer = 'Word'
+  ): TextWithCursorsAndHistory {
+    backend.ensureReady();
+    assertTokenizer(tokenizer);
+
+    const leftCursor = toWasmTextWithCursors(left);
+    const rightCursor = toWasmTextWithCursors(right);
+
+    const result = backend.reconcileWithHistory(
+      original,
+      leftCursor,
+      rightCursor,
+      tokenizer
+    );
+
+    leftCursor.free();
+    rightCursor.free();
+
+    const jsResult = toTextWithCursors(result);
+    const history = result.history().map(toSpanWithHistory);
+    result.free();
+
+    return {
+      ...jsResult,
+      history,
+    };
+  }
+
+  return { reconcile, diff, undiff, reconcileWithHistory };
+}
diff --git a/reconcile-js/src/index.rn.ts b/reconcile-js/src/index.rn.ts
new file mode 100644
index 0000000..1487a59
--- /dev/null
+++ b/reconcile-js/src/index.rn.ts
@@ -0,0 +1,47 @@
+// React Native entrypoint (resolved via the `react-native` package field).
+//
+// Hermes — the default React Native engine since RN 0.84 / Expo SDK 56 — does
+// not expose a runtime `WebAssembly` global, so the normal `new
+// WebAssembly.Module(...)` path used by `index.ts` throws
+// `ReferenceError: Property 'WebAssembly' doesn't exist`.
+//
+// Instead we link a wasm2js translation of the module: pure JavaScript that
+// needs no `WebAssembly` global and is instantiated synchronously at import
+// time. The public API and its synchronous signatures are unchanged, so
+// callers need no modification. The `pkg-rn` directory is generated by
+// `scripts/build-rn.mjs`.
+
+import {
+  CursorPosition as wasmCursorPosition,
+  TextWithCursors as wasmTextWithCursors,
+  reconcile as wasmReconcile,
+  reconcileWithHistory as wasmReconcileWithHistory,
+  diff as wasmDiff,
+  undiff as wasmUndiff,
+} from '../pkg-rn/reconcile_text.js';
+
+import { makeReconcileApi, type WasmBackend } from './core';
+
+const backend: WasmBackend = {
+  CursorPosition: wasmCursorPosition,
+  TextWithCursors: wasmTextWithCursors,
+  reconcile: wasmReconcile,
+  reconcileWithHistory: wasmReconcileWithHistory,
+  diff: wasmDiff,
+  undiff: wasmUndiff,
+  // The wasm2js module initialises itself at import time, so this is a no-op.
+  ensureReady() {},
+};
+
+export const { reconcile, diff, undiff, reconcileWithHistory } =
+  makeReconcileApi(backend);
+
+export type {
+  BuiltinTokenizer,
+  History,
+  CursorPosition,
+  TextWithCursors,
+  TextWithOptionalCursors,
+  TextWithCursorsAndHistory,
+  SpanWithHistory,
+} from './core';
diff --git a/reconcile-js/src/index.test.ts b/reconcile-js/src/index.test.ts
index 0de924c..66d385b 100644
--- a/reconcile-js/src/index.test.ts
+++ b/reconcile-js/src/index.test.ts
@@ -1,4 +1,5 @@
-import { reconcile, reconcileWithHistory, diff, undiff } from './index';
+import * as webApi from './index';
+import * as rnApi from './index.rn';
 import { installWasmLeakDetector, checkForWasmLeaks } from './wasm-leak-detector';
 import * as fs from 'fs';
 import * as path from 'path';
@@ -17,7 +18,18 @@ afterEach(() => {
   }
 });
 
-describe('reconcile', () => {
+// `./index` is the web/node build (real WebAssembly); `./index.rn` is the React
+// Native build (the wasm2js pure-JS translation). Both are thin backends over the
+// same `src/core.ts` wrapper and expose an identical public API, so the behavioural
+// suite below runs against both to guarantee they stay in lock-step.
+const backends = [
+  { name: 'web/node (WebAssembly)', api: webApi },
+  { name: 'React Native (wasm2js)', api: rnApi },
+];
+
+describe.each(backends)('reconcile [$name]', ({ api }) => {
+  const { reconcile, reconcileWithHistory, diff, undiff } = api;
+
   it('call reconcile without cursors', () => {
     expect(reconcile('Hello', 'Hello world', 'Hi world').text).toEqual('Hi world');
   });
@@ -60,9 +72,26 @@ describe('reconcile', () => {
     expect(result.text).toEqual('Hi world');
     expect(result.history.length).toBeGreaterThan(0);
   });
+
+  it('undiff accepts bigint entries (per the Array<number | bigint | string> type)', () => {
+    const original = 'Hello world';
+    const changed = 'Hello cruel world';
+
+    // `diff` returns plain numbers; emulate a caller that supplies BigInt, which the
+    // public signature permits. The wasm2js build rejects raw BigInt, so the shared
+    // wrapper must normalise it — running this on both backends asserts the contract.
+    const withBigints = diff(original, changed).map((item) =>
+      typeof item === 'number' ? BigInt(item) : item
+    );
+
+    expect(withBigints.some((item) => typeof item === 'bigint')).toBe(true);
+    expect(undiff(original, withBigints)).toEqual(changed);
+  });
 });
 
-describe('test_diff_and_undiff_are_inverse', () => {
+describe.each(backends)('diff and undiff are inverse [$name]', ({ api }) => {
+  const { diff, undiff } = api;
+
   const resourcesPath = path.join(__dirname, '../../tests/resources');
 
   const readFileSlice = (fileName: string, start: number, end: number): string => {
@@ -93,3 +122,31 @@ describe('test_diff_and_undiff_are_inverse', () => {
     });
   });
 });
+
+// React-Native-only: Hermes exposes no `WebAssembly` global, which is the whole reason
+// the RN entry point links a wasm2js build. Only the wasm2js backend can satisfy this.
+describe('React Native (wasm2js) Hermes parity', () => {
+  const { reconcile, reconcileWithHistory, diff, undiff } = rnApi;
+
+  it('runs every operation with no WebAssembly global', () => {
+    const descriptor = Object.getOwnPropertyDescriptor(globalThis, 'WebAssembly');
+    delete (globalThis as { WebAssembly?: unknown }).WebAssembly;
+    try {
+      expect((globalThis as { WebAssembly?: unknown }).WebAssembly).toBeUndefined();
+
+      expect(reconcile('Hello', 'Hello world', 'Hi world').text).toEqual('Hi world');
+
+      const changes = diff('Hello world', 'Hello cruel world');
+      expect(undiff('Hello world', changes)).toEqual('Hello cruel world');
+
+      expect(
+        reconcileWithHistory('Hello', 'Hello world', 'Hi world').history.length
+      ).toBeGreaterThan(0);
+    } finally {
+      // Restore the global so the leak check and later suites are unaffected.
+      if (descriptor) {
+        Object.defineProperty(globalThis, 'WebAssembly', descriptor);
+      }
+    }
+  });
+});
diff --git a/reconcile-js/src/index.ts b/reconcile-js/src/index.ts
index d00051c..7371169 100644
--- a/reconcile-js/src/index.ts
+++ b/reconcile-js/src/index.ts
@@ -1,8 +1,7 @@
 import {
   CursorPosition as wasmCursorPosition,
-  reconcile as wasmReconcile,
   TextWithCursors as wasmTextWithCursors,
-  SpanWithHistory as wasmSpanWithHistory,
+  reconcile as wasmReconcile,
   reconcileWithHistory as wasmReconcileWithHistory,
   diff as wasmDiff,
   undiff as wasmUndiff,
@@ -11,341 +10,40 @@ import {
 
 import wasmBytes from 'reconcile-text/reconcile_text_bg.wasm';
 
-// Define the enum values as const arrays to avoid duplication
-const BUILTIN_TOKENIZERS = ['Character', 'Line', 'Markdown', 'Word'] as const;
-const HISTORY_VALUES = [
-  'Unchanged',
-  'AddedFromLeft',
-  'AddedFromRight',
-  'RemovedFromLeft',
-  'RemovedFromRight',
-] as const;
-
-/**
- * Tokenisation strategies for text merging.
- *
- * These correspond to the built-in tokenizers available in the underlying WASM module.
- */
-export type BuiltinTokenizer = (typeof BUILTIN_TOKENIZERS)[number];
-
-/**
- * History classification for text spans in merge results.
- *
- * Indicates the origin of each text span in the merged document.
- */
-export type History = (typeof HISTORY_VALUES)[number];
-
-/**
- * Represents a text document with associated cursor positions.
- *
- * This interface is used both as input to reconcile functions (to specify where
- * cursors are positioned in the original documents) and as output (with cursors
- * automatically repositioned after merging).
- */
-export interface TextWithCursors {
-  /** The document's entire content as a string */
-  text: string;
-
-  /**
-   * Array of cursor positions within the text. Can be empty if there are no cursors to track.
-   * Each cursor has a unique ID and position.
-   */
-  cursors: CursorPosition[];
-}
-
-/**
- * Like `TextWithCursors`, but cursors may be null or undefined (treated as empty).
- * Used as input where cursor tracking is optional.
- */
-export interface TextWithOptionalCursors {
-  /** The document's entire content as a string */
-  text: string;
-
-  /**
-   * Array of cursor positions within the text. Can be null, undefined, or empty
-   * if there are no cursors to track. Each cursor has a unique ID and position.
-   */
-  cursors: null | undefined | CursorPosition[];
-}
-
-/**
- * Represents a cursor position within a text document.
- *
- * Cursors are automatically repositioned during text merging to maintain their
- * relative positions as text is inserted, deleted, or modified around them.
- */
-export interface CursorPosition {
-  /** Unique identifier for the cursor (can be any number, must be unique within the document) */
-  id: number;
-
-  /** Character position in the text, 0-based index from the beginning of the document */
-  position: number;
-}
-
-/**
- * Represents a merged text document with cursor positions and detailed change history.
- *
- * This is the return type of `reconcileWithHistory()` and provides complete information
- * about how the merge was performed, including which parts of the final text came from
- * which source documents.
- */
-export interface TextWithCursorsAndHistory {
-  /** The merged document's entire content */
-  text: string;
-
-  /**
-   * Array of cursor positions within the merged text. Can be empty if there are no cursors to track.
-   * All cursors are automatically repositioned from the left and right documents.
-   */
-  cursors: CursorPosition[];
-
-  /**
-   * Detailed provenance information showing the origin of each text span in the result.
-   * Each span indicates whether it was unchanged, added from left, added from right, etc.
-   */
-  history: SpanWithHistory[];
-}
-
-/**
- * Represents a span of text in the merged result with its change history.
- *
- * This shows exactly which source document contributed each piece of text to the
- * final merged result. Useful for understanding merge decisions and creating
- * visualisations of how documents were combined.
- */
-export interface SpanWithHistory {
-  /** The text content of this span */
-  text: string;
-
-  /** The origin of this text span in the merge result */
-  history: History;
-}
-
-const UNSUPPORTED_TOKENIZER_ERROR = `Unsupported tokenizer, only ${BUILTIN_TOKENIZERS.join(
-  ', '
-)} are supported`;
+import { makeReconcileApi, type WasmBackend } from './core';
 
 let isInitialised = false;
 
-/**
- * Merges three versions of text using intelligent conflict resolution.
- *
- * This is the primary function for 3-way text merging. Unlike traditional merge tools
- * that produce conflict markers, this function automatically resolves conflicts by
- * applying both sets of changes where possible.
- *
- * @param original - The original/base version of the text that both sides diverged from
- * @param left - The left version of the text (either string or TextWithCursors with cursor positions)
- * @param right - The right version of the text (either string or TextWithCursors with cursor positions)
- * @param tokenizer - The tokenisation strategy: "Word" (default, recommended for prose),
- *                    "Character" (fine-grained), or "Line" (similar to git merge)
- * @returns The reconciled text with automatically repositioned cursor positions
- *
- * @example
- * ```typescript
- * const original = "Hello world";
- * const left = "Hello beautiful world";    // Added "beautiful"
- * const right = "Hi world";                // Changed "Hello" to "Hi"
- *
- * const result = reconcile(original, left, right);
- * console.log(result.text); // "Hi beautiful world"
- * ```
- */
-export function reconcile(
-  original: string,
-  left: string | TextWithOptionalCursors,
-  right: string | TextWithOptionalCursors,
-  tokenizer: BuiltinTokenizer = 'Word'
-): TextWithCursors {
-  init();
+const backend: WasmBackend = {
+  CursorPosition: wasmCursorPosition,
+  TextWithCursors: wasmTextWithCursors,
+  reconcile: wasmReconcile,
+  reconcileWithHistory: wasmReconcileWithHistory,
+  diff: wasmDiff,
+  undiff: wasmUndiff,
+  ensureReady() {
+    if (isInitialised) {
+      return;
+    }
 
-  if (!BUILTIN_TOKENIZERS.includes(tokenizer)) {
-    throw new Error(UNSUPPORTED_TOKENIZER_ERROR);
-  }
+    const wasmBinary = Uint8Array.from(atob(wasmBytes as unknown as string), (c) =>
+      c.charCodeAt(0)
+    );
+    initSync({ module: wasmBinary });
 
-  const leftCursor = toWasmTextWithCursors(left);
-  const rightCursor = toWasmTextWithCursors(right);
+    isInitialised = true;
+  },
+};
 
-  const result = wasmReconcile(original, leftCursor, rightCursor, tokenizer);
+export const { reconcile, diff, undiff, reconcileWithHistory } =
+  makeReconcileApi(backend);
 
-  leftCursor.free();
-  rightCursor.free();
-
-  const jsResult = toTextWithCursors(result);
-  result.free();
-
-  return jsResult;
-}
-
-/**
- * Generates a compact diff representation between an original and changed text.
- *
- * These can be parsed and unpacked using the `undiff` function or the Rust crate's EditedText::from_diff.
- * Cursor positions are omitted from the diff result.
- *
- * This function computes the differences between two versions of text and returns
- * a compact representation of those changes.
- *
- * @param original - The original/base version of the text
- * @param changed - The modified version of the text (either string or TextWithCursors with cursor positions)
- * @param tokenizer - The tokenisation strategy, which is the same as used in `reconcile`.
- * @returns An array of inserts (strings), deletes (negative integers), and retained spans (positive integers).
- */
-export function diff(
-  original: string,
-  changed: string | TextWithOptionalCursors,
-  tokenizer: BuiltinTokenizer = 'Word'
-): Array<number | string> {
-  init();
-
-  if (!BUILTIN_TOKENIZERS.includes(tokenizer)) {
-    throw new Error(UNSUPPORTED_TOKENIZER_ERROR);
-  }
-
-  const changedWasm = toWasmTextWithCursors(changed);
-
-  const result = wasmDiff(original, changedWasm, tokenizer);
-
-  changedWasm.free();
-
-  return result.map((item) => (typeof item === 'bigint' ? Number(item) : item));
-}
-
-/**
- * Applies a compact diff to an original text to reconstruct the changed version.
- *
- * This function takes an original text and a compact diff representation (as produced
- * by the `diff` function) and reconstructs the modified text.
- *
- * @param original - The original/base version of the text
- * @param diff - The compact diff array (inserts as strings, deletes as negative integers, retained spans as positive integers)
- * @param tokenizer - The tokenisation strategy, which is the same as used in `reconcile`.
- * @returns The reconstructed changed text as a string.
- */
-export function undiff(
-  original: string,
-  diff: Array<number | bigint | string>,
-  tokenizer: BuiltinTokenizer = 'Word'
-): string {
-  init();
-
-  if (!BUILTIN_TOKENIZERS.includes(tokenizer)) {
-    throw new Error(UNSUPPORTED_TOKENIZER_ERROR);
-  }
-
-  return wasmUndiff(original, diff, tokenizer);
-}
-
-/**
- * Merges three versions of text and returns detailed provenance information.
- *
- * This function behaves like `reconcile()` but also provides
- * detailed historical information about the origin of each text span in the result.
- * This is valuable for understanding how the merge was performed and which changes
- * came from which source.
- *
- * Note: Computing the history is computationally more expensive than the basic merge.
- *
- * @param original - The original/base version of the text that both sides diverged from
- * @param left - The left version of the text (either string or TextWithCursors with cursor positions)
- * @param right - The right version of the text (either string or TextWithCursors with cursor positions)
- * @param tokenizer - The tokenisation strategy: "Word" (default, recommended for prose),
- *                    "Character" (fine-grained), or "Line" (similar to git merge)
- * @returns The reconciled text with cursor positions and detailed change history
- *
- * @example
- * ```typescript
- * const original = "Hello world";
- * const left = "Hello beautiful world";
- * const right = "Hi world";
- *
- * const result = reconcileWithHistory(original, left, right);
- * console.log(result.text); // "Hi beautiful world"
- * console.log(result.history); // Array of SpanWithHistory objects showing change origins
- * ```
- */
-export function reconcileWithHistory(
-  original: string,
-  left: string | TextWithOptionalCursors,
-  right: string | TextWithOptionalCursors,
-  tokenizer: BuiltinTokenizer = 'Word'
-): TextWithCursorsAndHistory {
-  init();
-
-  if (!BUILTIN_TOKENIZERS.includes(tokenizer)) {
-    throw new Error(UNSUPPORTED_TOKENIZER_ERROR);
-  }
-
-  const leftCursor = toWasmTextWithCursors(left);
-  const rightCursor = toWasmTextWithCursors(right);
-
-  const result = wasmReconcileWithHistory(original, leftCursor, rightCursor, tokenizer);
-
-  leftCursor.free();
-  rightCursor.free();
-
-  const jsResult = toTextWithCursors(result);
-  const history = result.history().map(toSpanWithHistory);
-  result.free();
-
-  return {
-    ...jsResult,
-    history,
-  };
-}
-
-function init() {
-  if (isInitialised) {
-    return;
-  }
-
-  const wasmBinary = Uint8Array.from(atob(wasmBytes as unknown as string), (c) =>
-    c.charCodeAt(0)
-  );
-  initSync({ module: wasmBinary });
-
-  isInitialised = true;
-}
-
-function toWasmTextWithCursors(
-  text: string | TextWithOptionalCursors
-): wasmTextWithCursors {
-  const isInputString = typeof text === 'string';
-  const leftText = isInputString ? text : text.text;
-  const leftCursors = isInputString ? [] : (text.cursors ?? []);
-
-  return new wasmTextWithCursors(leftText, leftCursors.map(toWasmCursorPosition));
-}
-
-function toWasmCursorPosition({ id, position }: CursorPosition): wasmCursorPosition {
-  return new wasmCursorPosition(id, position);
-}
-
-function toTextWithCursors(textWithCursor: wasmTextWithCursors): TextWithCursors {
-  const wasmCursors = textWithCursor.cursors();
-  const cursors = wasmCursors.map(toCursorPosition);
-  for (const cursor of wasmCursors) {
-    cursor.free();
-  }
-
-  return {
-    text: textWithCursor.text(),
-    cursors,
-  };
-}
-
-function toCursorPosition(cursor: wasmCursorPosition): CursorPosition {
-  return {
-    id: cursor.id(),
-    position: cursor.characterIndex(),
-  };
-}
-
-function toSpanWithHistory(span: wasmSpanWithHistory): SpanWithHistory {
-  const result = {
-    text: span.text(),
-    history: span.history(),
-  };
-  span.free();
-  return result;
-}
+export type {
+  BuiltinTokenizer,
+  History,
+  CursorPosition,
+  TextWithCursors,
+  TextWithOptionalCursors,
+  TextWithCursorsAndHistory,
+  SpanWithHistory,
+} from './core';
diff --git a/reconcile-js/webpack.config.js b/reconcile-js/webpack.config.js
index bf126fa..280bc52 100644
--- a/reconcile-js/webpack.config.js
+++ b/reconcile-js/webpack.config.js
@@ -2,7 +2,6 @@ const path = require('path');
 const { merge } = require('webpack-merge');
 
 const common = {
-  entry: './src/index.ts',
   optimization: {
     // the consuming project should take care of minification
     minimize: false,
@@ -38,8 +37,10 @@ const common = {
 };
 
 module.exports = [
+  // Web build: real WebAssembly, instantiated synchronously from inlined base64.
   merge(common, {
     target: 'web',
+    entry: './src/index.ts',
     output: {
       path: path.resolve(__dirname, 'dist'),
       filename: 'reconcile.web.js',
@@ -50,12 +51,31 @@ module.exports = [
       globalObject: 'this',
     },
   }),
+
+  // Node build: real WebAssembly.
   merge(common, {
     target: 'node',
+    entry: './src/index.ts',
     output: {
       path: path.resolve(__dirname, 'dist'),
       filename: 'reconcile.node.js',
       libraryTarget: 'commonjs2',
     },
   }),
+
+  // React Native build: wasm2js (pure JS), for Hermes which has no
+  // `WebAssembly` global. Sources come from `pkg-rn/`
+  merge(common, {
+    target: 'web',
+    entry: './src/index.rn.ts',
+    output: {
+      path: path.resolve(__dirname, 'dist'),
+      filename: 'reconcile.rn.js',
+      library: {
+        name: 'reconcile',
+        type: 'umd',
+      },
+      globalObject: 'this',
+    },
+  }),
 ];
diff --git a/reconcile-python/Cargo.lock b/reconcile-python/Cargo.lock
index 8e9b36c..07e6da6 100644
--- a/reconcile-python/Cargo.lock
+++ b/reconcile-python/Cargo.lock
@@ -104,14 +104,14 @@ dependencies = [
 
 [[package]]
 name = "reconcile-text"
-version = "0.9.4"
+version = "0.12.0"
 dependencies = [
  "thiserror",
 ]
 
 [[package]]
 name = "reconcile-text-python"
-version = "0.9.4"
+version = "0.12.0"
 dependencies = [
  "pyo3",
  "reconcile-text",
diff --git a/reconcile-python/Cargo.toml b/reconcile-python/Cargo.toml
index db78e3a..0ecdbf6 100644
--- a/reconcile-python/Cargo.toml
+++ b/reconcile-python/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "reconcile-text-python"
-version = "0.9.4"
+version = "0.12.0"
 edition = "2024"
 rust-version = "1.94"
 authors = ["Andras Schmelczer <andras@schmelczer.dev>"]
@@ -13,4 +13,4 @@ crate-type = ["cdylib"]
 
 [dependencies]
 reconcile-text = { path = ".." }
-pyo3 = { version = "0.28.2", features = ["extension-module"] }
+pyo3 = { version = "0.28.2", features = ["extension-module", "abi3-py39"] }
diff --git a/reconcile-python/pyproject.toml b/reconcile-python/pyproject.toml
index 75d91cf..ba367f2 100644
--- a/reconcile-python/pyproject.toml
+++ b/reconcile-python/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "maturin"
 
 [project]
 name = "reconcile-text"
-version = "0.9.4"
+version = "0.12.0"
 description = "Intelligent 3-way text merging with automated conflict resolution"
 readme = "README.md"
 license = { text = "MIT" }
diff --git a/reconcile-python/uv.lock b/reconcile-python/uv.lock
index de403a2..8a3d3a4 100644
--- a/reconcile-python/uv.lock
+++ b/reconcile-python/uv.lock
@@ -168,7 +168,7 @@ wheels = [
 
 [[package]]
 name = "reconcile-text"
-version = "0.9.4"
+version = "0.12.0"
 source = { editable = "." }
 
 [package.dev-dependencies]
diff --git a/scripts/lint.sh b/scripts/lint.sh
index c46991d..6ae4f66 100755
--- a/scripts/lint.sh
+++ b/scripts/lint.sh
@@ -5,9 +5,6 @@ set -e
 which cargo-machete || cargo install cargo-machete
 cargo machete
 
-which lychee || cargo install lychee
-lychee --verbose --exclude npmjs.com README.md
-
 cargo clippy --all-targets --all-features --fix --allow-dirty --allow-staged
 cargo fmt --all
 
diff --git a/src/tokenizer/token.rs b/src/tokenizer/token.rs
index 5d82eb5..0f45d41 100644
--- a/src/tokenizer/token.rs
+++ b/src/tokenizer/token.rs
@@ -1,4 +1,7 @@
-use std::fmt::Debug;
+use std::{
+    fmt::Debug,
+    hash::{Hash, Hasher},
+};
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -78,3 +81,14 @@ where
         self.normalized == other.normalized
     }
 }
+
+/// Hashes based on the `normalized` field only, consistent with the
+/// [`PartialEq`] implementation.
+impl<T> Hash for Token<T>
+where
+    T: PartialEq + Clone + Debug + Hash,
+{
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.normalized.hash(state);
+    }
+}
diff --git a/src/utils/myers_diff.rs b/src/utils/myers_diff.rs
index b9a8b25..f04df56 100644
--- a/src/utils/myers_diff.rs
+++ b/src/utils/myers_diff.rs
@@ -11,13 +11,11 @@
 //! The implementation of this algorithm is based on the implementation by
 //! Brandon Williams.
 //!
-//! # Heuristics
+//! # Complexity
 //!
-//! At present this implementation of Myers' does not implement any more
-//! advanced heuristics that would solve some pathological cases.  For instance
-//! passing two large and completely distinct sequences to the algorithm will
-//! make it spin without making reasonable progress.
-//! For potential improvements here see [similar#15](https://github.com/mitsuhiko/similar/issues/15).
+//! The worst case (completely dissimilar inputs) is `O((N+M)²)` time. In
+//! practice the divide-and-conquer strategy with prefix/suffix stripping keeps
+//! subproblems small for typical text.
 
 use std::{
     fmt::Debug,
@@ -41,26 +39,21 @@ pub fn myers_diff<T>(old: &[Token<T>], new: &[Token<T>]) -> Vec<RawOperation<T>>
 where
     T: PartialEq + Clone + Debug,
 {
-    let max_d = (old.len() + new.len()).div_ceil(2) + 1;
-    let mut vb = V::new(max_d);
-    let mut vf = V::new(max_d);
-    let mut result = Vec::new();
+    let max_edit_distance = (old.len() + new.len()).div_ceil(2) + 1;
+    let mut backward_endpoints = FurthestEndpoints::new(max_edit_distance);
+    let mut forward_endpoints = FurthestEndpoints::new(max_edit_distance);
+    let mut result = Vec::with_capacity(old.len() + new.len());
 
     conquer(
         old,
         0..old.len(),
         new,
         0..new.len(),
-        &mut vf,
-        &mut vb,
+        &mut forward_endpoints,
+        &mut backward_endpoints,
         &mut result,
     );
 
-    debug_assert!(
-        result.iter().all(|op| op.tokens().len() == 1),
-        "All operations must be of length 1"
-    );
-
     result
 }
 
@@ -68,50 +61,52 @@ where
 // edges. All D-paths consist of a (D - 1)-path followed by a non-diagonal edge
 // and then a possibly empty sequence of diagonal edges called a snake.
 
-/// `V` contains the endpoints of the furthest reaching `D-paths`. For each
-/// recorded endpoint `(x,y)` in diagonal `k`, we only need to retain `x`
-/// because `y` can be computed from `x - k`. In other words, `V` is an array of
-/// integers where `V[k]` contains the row index of the endpoint of the furthest
-/// reaching path in diagonal `k`.
+/// Contains the endpoints of the furthest reaching `D-paths`. For each
+/// recorded endpoint `(x, y)` on diagonal `k`, we only need to retain `x`
+/// because `y` can be computed from `x - k`. In other words, this is an array
+/// of integers where `endpoints[k]` contains the row index of the endpoint of
+/// the furthest reaching path on diagonal `k`.
 ///
-/// We can't use a traditional Vec to represent `V` since we use `k` as an index
-/// and it can take on negative values. So instead `V` is represented as a
-/// light-weight wrapper around a Vec plus an `offset` which is the maximum
-/// value `k` can take on to map negative `k`'s back to a value >= 0.
+/// We can't use a traditional Vec since we use `k` as an index and it can take
+/// on negative values. So instead this is a light-weight wrapper around a Vec
+/// plus an `offset` which is the maximum value `k` can take on, used to map
+/// negative `k`'s back to a value >= 0.
 #[derive(Debug)]
-struct V {
+struct FurthestEndpoints {
     offset: isize,
-    v: Vec<usize>,
+    endpoints: Vec<usize>,
 }
 
-impl V {
-    fn new(max_d: usize) -> Self {
-        // max_d should fit in isize for the algorithm to work correctly
-        let offset = isize::try_from(max_d).expect("max_d must fit in isize");
+impl FurthestEndpoints {
+    fn new(max_edit_distance: usize) -> Self {
+        let offset =
+            isize::try_from(max_edit_distance).expect("max_edit_distance must fit in isize");
         Self {
             offset,
-            v: vec![0; 2 * max_d + 1],
+            endpoints: vec![0; 2 * max_edit_distance + 1],
         }
     }
 
     fn len(&self) -> usize {
-        self.v.len()
+        self.endpoints.len()
     }
 }
 
-impl Index<isize> for V {
+impl Index<isize> for FurthestEndpoints {
     type Output = usize;
 
-    fn index(&self, index: isize) -> &Self::Output {
-        let idx = usize::try_from(index + self.offset).expect("index + offset must fit in usize");
-        &self.v[idx]
+    fn index(&self, diagonal: isize) -> &Self::Output {
+        let idx =
+            usize::try_from(diagonal + self.offset).expect("diagonal + offset must fit in usize");
+        &self.endpoints[idx]
     }
 }
 
-impl IndexMut<isize> for V {
-    fn index_mut(&mut self, index: isize) -> &mut Self::Output {
-        let idx = usize::try_from(index + self.offset).expect("index + offset must fit in usize");
-        &mut self.v[idx]
+impl IndexMut<isize> for FurthestEndpoints {
+    fn index_mut(&mut self, diagonal: isize) -> &mut Self::Output {
+        let idx =
+            usize::try_from(diagonal + self.offset).expect("diagonal + offset must fit in usize");
+        &mut self.endpoints[idx]
     }
 }
 
@@ -119,6 +114,26 @@ fn split_at(range: Range<usize>, at: usize) -> (Range<usize>, Range<usize>) {
     (range.start..at, at..range.end)
 }
 
+/// Adjust a lower diagonal bound so it has the same parity as `edit_distance`.
+/// Diagonals are visited in steps of 2, so `lower` must share `edit_distance`'s
+/// parity.
+fn align_lower_bound(lower: isize, edit_distance: isize) -> isize {
+    if (lower & 1) == (edit_distance & 1) {
+        lower
+    } else {
+        lower + 1
+    }
+}
+
+/// Adjust an upper diagonal bound so it has the same parity as `edit_distance`.
+fn align_upper_bound(upper: isize, edit_distance: isize) -> isize {
+    if (upper & 1) == (edit_distance & 1) {
+        upper
+    } else {
+        upper - 1
+    }
+}
+
 /// A `Snake` is a sequence of diagonal edges in the edit graph.  Normally
 /// a snake has a start end end point (and it is possible for a snake to have
 /// a length of zero, meaning the start and end points are the same) however
@@ -135,106 +150,143 @@ fn find_middle_snake<T>(
     old_range: Range<usize>,
     new: &[Token<T>],
     new_range: Range<usize>,
-    vf: &mut V,
-    vb: &mut V,
+    forward_endpoints: &mut FurthestEndpoints,
+    backward_endpoints: &mut FurthestEndpoints,
 ) -> Option<(usize, usize)>
 where
     T: PartialEq + Clone + Debug,
 {
-    let n = old_range.len();
-    let m = new_range.len();
+    let old_len = old_range.len();
+    let new_len = new_range.len();
+
+    let old_len_signed = isize::try_from(old_len).expect("old_len must fit in isize");
+    let new_len_signed = isize::try_from(new_len).expect("new_len must fit in isize");
 
     // By Lemma 1 in the paper, the optimal edit script length is odd or even as
     // `delta` is odd or even.
-    let delta = isize::try_from(n).expect("n must fit in isize")
-        - isize::try_from(m).expect("m must fit in isize");
-    let odd = delta & 1 == 1;
+    let delta = old_len_signed - new_len_signed;
+    let delta_is_odd = delta & 1 == 1;
 
     // The initial point at (0, -1)
-    vf[1] = 0;
+    forward_endpoints[1] = 0;
     // The initial point at (N, M+1)
-    vb[1] = 0;
+    backward_endpoints[1] = 0;
 
-    let d_max = (n + m).div_ceil(2) + 1;
-    assert!(vf.len() >= d_max);
-    assert!(vb.len() >= d_max);
+    let max_edit_distance = (old_len + new_len).div_ceil(2) + 1;
+    assert!(forward_endpoints.len() >= max_edit_distance);
+    assert!(backward_endpoints.len() >= max_edit_distance);
+
+    let max_edit_distance_signed =
+        isize::try_from(max_edit_distance).expect("max_edit_distance must fit in isize");
+
+    for edit_distance in 0..max_edit_distance_signed {
+        // Tighter diagonal bounds: on diagonal k = x - y the constraints
+        // 0 <= x <= old_len and 0 <= y <= new_len give k in [-new_len, old_len].
+        // Intersect with the algorithm's [-edit_distance, edit_distance]
+        // range and snap to the correct parity (k advances in steps of 2).
+        let forward_diagonal_lo =
+            align_lower_bound((-edit_distance).max(-new_len_signed), edit_distance);
+        let forward_diagonal_hi =
+            align_upper_bound(edit_distance.min(old_len_signed), edit_distance);
 
-    let d_max_isize = isize::try_from(d_max).expect("d_max must fit in isize");
-    for d in 0..d_max_isize {
         // Forward path
-        for k in (-d..=d).rev().step_by(2) {
-            let mut x = if k == -d || (k != d && vf[k - 1] < vf[k + 1]) {
-                vf[k + 1]
+        for diagonal in (forward_diagonal_lo..=forward_diagonal_hi).rev().step_by(2) {
+            let mut old_idx = if diagonal == -edit_distance
+                || (diagonal != edit_distance
+                    && forward_endpoints[diagonal - 1] < forward_endpoints[diagonal + 1])
+            {
+                forward_endpoints[diagonal + 1]
             } else {
-                vf[k - 1] + 1
+                forward_endpoints[diagonal - 1] + 1
             };
-            let y = usize::try_from(isize::try_from(x).expect("x must fit in isize") - k)
-                .expect("x - k must be non-negative and fit in usize");
+            let new_idx = usize::try_from(
+                isize::try_from(old_idx).expect("old_idx must fit in isize") - diagonal,
+            )
+            .expect("old_idx - diagonal must be non-negative and fit in usize");
 
             // The coordinate of the start of a snake
-            let (x0, y0) = (x, y);
-            //  While these sequences are identical, keep moving through the
-            //  graph with no cost
-            if x < old_range.len() && y < new_range.len() {
+            let (snake_start_old, snake_start_new) = (old_idx, new_idx);
+
+            // While these sequences are identical, keep moving through the
+            // graph with no cost
+            if old_idx < old_range.len() && new_idx < new_range.len() {
                 let advance = common_prefix_len(
                     old,
-                    old_range.start + x..old_range.end,
+                    old_range.start + old_idx..old_range.end,
                     new,
-                    new_range.start + y..new_range.end,
+                    new_range.start + new_idx..new_range.end,
                 );
-                x += advance;
+                old_idx += advance;
             }
 
             // This is the new best x value
-            vf[k] = x;
+            forward_endpoints[diagonal] = old_idx;
 
             // Only check for connections from the forward search when N - M is
             // odd and when there is a reciprocal k line coming from the other
-            // direction.
-            if odd && (k - delta).abs() <= (d - 1) {
-                // TODO optimise this so we don't have to compare against n
-                if vf[k] + vb[-(k - delta)] >= n {
-                    // Return the snake
-                    return Some((x0 + old_range.start, y0 + new_range.start));
-                }
+            // direction. Forward diagonal k maps to backward diagonal
+            // (delta - k). Overlap occurs when the combined forward + backward
+            // reach covers the full width:
+            //   forward_endpoints[k] + backward_endpoints[delta - k] >= old_len.
+            if delta_is_odd
+                && (diagonal - delta).abs() <= (edit_distance - 1)
+                && forward_endpoints[diagonal] + backward_endpoints[-(diagonal - delta)] >= old_len
+            {
+                return Some((
+                    snake_start_old + old_range.start,
+                    snake_start_new + new_range.start,
+                ));
             }
         }
 
-        // Backward path
-        for k in (-d..=d).rev().step_by(2) {
-            let mut x = if k == -d || (k != d && vb[k - 1] < vb[k + 1]) {
-                vb[k + 1]
-            } else {
-                vb[k - 1] + 1
-            };
-            let mut y = usize::try_from(isize::try_from(x).expect("x must fit in isize") - k)
-                .expect("x - k must be non-negative and fit in usize");
+        let backward_diagonal_lo =
+            align_lower_bound((-edit_distance).max(-new_len_signed), edit_distance);
+        let backward_diagonal_hi =
+            align_upper_bound(edit_distance.min(old_len_signed), edit_distance);
 
-            // The coordinate of the start of a snake
-            if x < n && y < m {
+        // Backward path
+        for diagonal in (backward_diagonal_lo..=backward_diagonal_hi)
+            .rev()
+            .step_by(2)
+        {
+            let mut old_idx = if diagonal == -edit_distance
+                || (diagonal != edit_distance
+                    && backward_endpoints[diagonal - 1] < backward_endpoints[diagonal + 1])
+            {
+                backward_endpoints[diagonal + 1]
+            } else {
+                backward_endpoints[diagonal - 1] + 1
+            };
+            let mut new_idx = usize::try_from(
+                isize::try_from(old_idx).expect("old_idx must fit in isize") - diagonal,
+            )
+            .expect("old_idx - diagonal must be non-negative and fit in usize");
+
+            // Extend the snake backward (matching suffix)
+            if old_idx < old_len && new_idx < new_len {
                 let advance = common_suffix_len(
                     old,
-                    old_range.start..old_range.start + n - x,
+                    old_range.start..old_range.start + old_len - old_idx,
                     new,
-                    new_range.start..new_range.start + m - y,
+                    new_range.start..new_range.start + new_len - new_idx,
                 );
-                x += advance;
-                y += advance;
+                old_idx += advance;
+                new_idx += advance;
             }
 
             // This is the new best x value
-            vb[k] = x;
+            backward_endpoints[diagonal] = old_idx;
 
-            if !odd && (k - delta).abs() <= d {
-                // TODO optimise this so we don't have to compare against n
-                if vb[k] + vf[-(k - delta)] >= n {
-                    // Return the snake
-                    return Some((n - x + old_range.start, m - y + new_range.start));
-                }
+            if !delta_is_odd
+                && (diagonal - delta).abs() <= edit_distance
+                && backward_endpoints[diagonal] + forward_endpoints[-(diagonal - delta)] >= old_len
+            {
+                return Some((
+                    old_len - old_idx + old_range.start,
+                    new_len - new_idx + new_range.start,
+                ));
             }
         }
-
-        // TODO: Maybe there's an opportunity to optimise and bail early?
     }
 
     None
@@ -245,54 +297,72 @@ fn conquer<T>(
     mut old_range: Range<usize>,
     new: &[Token<T>],
     mut new_range: Range<usize>,
-    vf: &mut V,
-    vb: &mut V,
+    forward_endpoints: &mut FurthestEndpoints,
+    backward_endpoints: &mut FurthestEndpoints,
     result: &mut Vec<RawOperation<T>>,
 ) where
     T: PartialEq + Clone + Debug,
 {
     // Check for common prefix
-    let common_prefix_len = common_prefix_len(old, old_range.clone(), new, new_range.clone());
-    if common_prefix_len > 0 {
+    let prefix_len = common_prefix_len(old, old_range.clone(), new, new_range.clone());
+    if prefix_len > 0 {
         result.extend(
-            old[old_range.start..old_range.start + common_prefix_len]
+            old[old_range.start..old_range.start + prefix_len]
                 .iter()
                 .map(|token| RawOperation::Equal(vec![token.clone()])),
         );
     }
-    old_range.start += common_prefix_len;
-    new_range.start += common_prefix_len;
+    old_range.start += prefix_len;
+    new_range.start += prefix_len;
 
     // Check for common suffix
-    let common_suffix_len = common_suffix_len(old, old_range.clone(), new, new_range.clone());
-    let common_suffix = (
-        old_range.end - common_suffix_len,
-        new_range.end - common_suffix_len,
-    );
-    old_range.end -= common_suffix_len;
-    new_range.end -= common_suffix_len;
+    let suffix_len = common_suffix_len(old, old_range.clone(), new, new_range.clone());
+    let suffix_start = old_range.end - suffix_len;
+    old_range.end -= suffix_len;
+    new_range.end -= suffix_len;
 
     if old_range.is_empty() && new_range.is_empty() {
         // do nothing
     } else if new_range.is_empty() {
         result.extend(
-            old[old_range.start..old_range.start + old_range.len()]
+            old[old_range.start..old_range.end]
                 .iter()
                 .map(|token| RawOperation::Delete(vec![token.clone()])),
         );
     } else if old_range.is_empty() {
         result.extend(
-            new[new_range.start..new_range.start + new_range.len()]
+            new[new_range.start..new_range.end]
                 .iter()
                 .map(|token| RawOperation::Insert(vec![token.clone()])),
         );
-    } else if let Some((x_start, y_start)) =
-        find_middle_snake(old, old_range.clone(), new, new_range.clone(), vf, vb)
-    {
-        let (old_a, old_b) = split_at(old_range, x_start);
-        let (new_a, new_b) = split_at(new_range, y_start);
-        conquer(old, old_a, new, new_a, vf, vb, result);
-        conquer(old, old_b, new, new_b, vf, vb, result);
+    } else if let Some((split_old, split_new)) = find_middle_snake(
+        old,
+        old_range.clone(),
+        new,
+        new_range.clone(),
+        forward_endpoints,
+        backward_endpoints,
+    ) {
+        let (old_before, old_after) = split_at(old_range, split_old);
+        let (new_before, new_after) = split_at(new_range, split_new);
+        conquer(
+            old,
+            old_before,
+            new,
+            new_before,
+            forward_endpoints,
+            backward_endpoints,
+            result,
+        );
+        conquer(
+            old,
+            old_after,
+            new,
+            new_after,
+            forward_endpoints,
+            backward_endpoints,
+            result,
+        );
     } else {
         result.extend(
             old[old_range.start..old_range.end]
@@ -306,9 +376,9 @@ fn conquer<T>(
         );
     }
 
-    if common_suffix_len > 0 {
+    if suffix_len > 0 {
         result.extend(
-            old[common_suffix.0..common_suffix.0 + common_suffix_len]
+            old[suffix_start..suffix_start + suffix_len]
                 .iter()
                 .map(|token| RawOperation::Equal(vec![token.clone()])),
         );