diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index fc4bbf7eb4..4bab1fcd81 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -17,6 +17,14 @@ on:
   pull_request:
     # The branches below must be a subset of the branches above
     branches: ["master"]
+    # Skip kotoba-only PRs; those run .github/workflows/kotoba-v1.yml.
+    paths:
+      - 'java/**'
+      - 'javascript/**'
+      - 'cpp/**'
+      - 'resources/**'
+      - 'tools/**'
+      - 'pom.xml'
   schedule:
     - cron: "0 0 * * 1"
 
diff --git a/.github/workflows/cpp-unit-test.yml b/.github/workflows/cpp-unit-test.yml
index f8f4e78823..c6b8c9ce2c 100644
--- a/.github/workflows/cpp-unit-test.yml
+++ b/.github/workflows/cpp-unit-test.yml
@@ -1,7 +1,13 @@
 # This workflow builds and unit tests both main C++ API and also build/data tools for metadata generation.
 
 name: Testing C++ API
-on: pull_request
+on:
+  pull_request:
+    # Skip kotoba-only PRs; those run .github/workflows/kotoba-v1.yml.
+    paths:
+      - 'cpp/**'
+      - 'tools/cpp/**'
+      - 'resources/**'
 permissions:
   contents: read
 
diff --git a/.github/workflows/dependency-review.yml b/.github/workflows/dependency-review.yml
index 437275ac0b..967edf7887 100644
--- a/.github/workflows/dependency-review.yml
+++ b/.github/workflows/dependency-review.yml
@@ -7,7 +7,17 @@
 #
 # Source repository: https://github.com/actions/dependency-review-action
 name: 'Dependency Review'
-on: [pull_request]
+on:
+  pull_request:
+    # Skip kotoba-only PRs; those run .github/workflows/kotoba-v1.yml.
+    paths-ignore:
+      - 'kotoba/**'
+      - '.github/workflows/kotoba-v1.yml'
+      - '.github/workflows/java-unit-test.yml'
+      - '.github/workflows/cpp-unit-test.yml'
+      - '.github/workflows/codeql.yml'
+      - '.github/workflows/osv-scanner-unified.yml'
+      - '.github/workflows/dependency-review.yml'
 
 permissions:
   contents: read
diff --git a/.github/workflows/java-unit-test.yml b/.github/workflows/java-unit-test.yml
index 2e2672970f..655ed40354 100644
--- a/.github/workflows/java-unit-test.yml
+++ b/.github/workflows/java-unit-test.yml
@@ -1,7 +1,15 @@
 # This workflow builds and unit tests both main Java API and also build/data tools for metadata generation.
 
 name: Testing Java API
-on: pull_request
+on:
+  pull_request:
+    # Skip kotoba-only PRs; those run .github/workflows/kotoba-v1.yml.
+    paths:
+      - 'java/**'
+      - 'javascript/**'
+      - 'resources/**'
+      - 'tools/java/**'
+      - 'pom.xml'
 permissions:
   contents: read
 
diff --git a/.github/workflows/kotoba-v1.yml b/.github/workflows/kotoba-v1.yml
new file mode 100644
index 0000000000..b97ec28f8d
--- /dev/null
+++ b/.github/workflows/kotoba-v1.yml
@@ -0,0 +1,42 @@
+name: Kotoba v1
+
+on:
+  push:
+    branches: [master]
+    paths:
+      - 'kotoba/**'
+      - '.github/workflows/kotoba-v1.yml'
+  pull_request:
+    paths:
+      - 'kotoba/**'
+      - '.github/workflows/kotoba-v1.yml'
+
+permissions:
+  contents: read
+
+jobs:
+  kotoba:
+    name: kotoba compile + fixture
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install kotoba v0.7.2
+        shell: bash
+        run: |
+          set -euo pipefail
+          release_dir="$RUNNER_TEMP/kotoba-v0.7.2"
+          cli_dir="$RUNNER_TEMP/kotoba-cli"
+          mkdir -p "$release_dir" "$cli_dir"
+          curl -L --fail --silent --show-error \
+            -o "$release_dir/kotoba-linux-amd64.tar.gz" \
+            https://github.com/kotoba-lang/kotoba/releases/download/v0.7.2/kotoba-linux-amd64.tar.gz
+          curl -L --fail --silent --show-error \
+            -o "$release_dir/kotoba-linux-amd64.tar.gz.sha256" \
+            https://github.com/kotoba-lang/kotoba/releases/download/v0.7.2/kotoba-linux-amd64.tar.gz.sha256
+          (cd "$release_dir" && sha256sum -c kotoba-linux-amd64.tar.gz.sha256)
+          tar -xzf "$release_dir/kotoba-linux-amd64.tar.gz" -C "$cli_dir"
+          echo "$cli_dir" >> "$GITHUB_PATH"
+
+      - name: Compile wasm and run fixture
+        run: kotoba/checks.sh
diff --git a/.github/workflows/osv-scanner-unified.yml b/.github/workflows/osv-scanner-unified.yml
index 1c6ba2c2c2..f18d3cb0b6 100644
--- a/.github/workflows/osv-scanner-unified.yml
+++ b/.github/workflows/osv-scanner-unified.yml
@@ -18,6 +18,15 @@ name: OSV-Scanner
 on:
   pull_request:
     branches: ["master"]
+    # Skip kotoba-only PRs; those run .github/workflows/kotoba-v1.yml.
+    paths-ignore:
+      - 'kotoba/**'
+      - '.github/workflows/kotoba-v1.yml'
+      - '.github/workflows/java-unit-test.yml'
+      - '.github/workflows/cpp-unit-test.yml'
+      - '.github/workflows/codeql.yml'
+      - '.github/workflows/dependency-review.yml'
+      - '.github/workflows/osv-scanner-unified.yml'
   schedule:
   - cron: "12 12 * * 1"
   push:
diff --git a/kotoba/README.md b/kotoba/README.md
new file mode 100644
index 0000000000..67316af8ea
--- /dev/null
+++ b/kotoba/README.md
@@ -0,0 +1,84 @@
+# Kotoba v1 for libphonenumber
+
+First-class sibling tree to `cpp/`, `java/`, and `javascript/`. This directory
+is a Kotoba check surface for the fork, not a language binding over the Java,
+C++, or JavaScript libraries.
+
+Public operator: awai.network. Sales: Ryo Awai.
+
+License: Apache-2.0 (same as this repository).
+
+## Honest scope
+
+v1 checks whether a short hardcoded fixture is a **well-formed E.164-looking**
+string: a plus prefix plus a digit length.
+
+- First byte must be `+` (ASCII 43).
+- Every following byte must be an ASCII digit `0`–`9`.
+- Digit count must be in `2..15`.
+  - `15` is the ITU E.164 maximum for the complete international number.
+  - `2` is this repository's `PhoneNumberUtil.MIN_LENGTH_FOR_NSN`, applied
+    here to the complete digit string, not to a region national number.
+
+Two accept fixtures and two reject fixtures are taken from this repository's
+own testdata (`US_NUMBER` / `GB_NUMBER` in
+`java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberUtilTest.java`):
+
+| fixture | bytes | expected |
+|---|---|---|
+| `fixtures/us-e164.txt` | `+16502530000` | accept (E.164 of US_NUMBER) |
+| `fixtures/gb-e164.txt` | `+442070313000` | accept (E.164 of GB_NUMBER) |
+| `fixtures/us-international.txt` | `+1 650 253 0000` | reject (INTERNATIONAL spaces) |
+| `fixtures/us-nsn.txt` | `6502530000` | reject (national number, no plus) |
+
+This is **not**:
+
+- a drop-in replacement for the Java, C++, or JavaScript libraries
+- full region metadata / carrier / geocoding / timezone lookup
+- `isValidNumber`, `isPossibleNumber` against country ranges
+- parse, format, AsYouType, matcher, or short-number support
+- a copy of `resources/phonenumber.proto` or the metadata proto set
+- an FFI or JNI/C++ driver
+
+A full libphonenumber port will not fit on wasm32 i64-v1. That dialect has no
+IEEE floats, no admitted byte-builder, and no host imports in the
+host-independent profile. Shrinking to a plus-prefix digit-length check of a
+few project fixtures is the smallest codec/header/fixture that still proves a
+real accept and a real reject. The shrink is documented here, not stubbed.
+
+## Module
+
+`phonenumber.kotoba` is one compilation unit (`phonenumber.v1`).
+
+| export | meaning |
+|---|---|
+| `e164-looking` | `1` if fixture `id` is E.164-looking, else `0` |
+| `accept-us` / `accept-gb` | `1` if the matching accept fixture is admitted |
+| `reject-spaces` / `reject-nsn` | `1` if the matching reject fixture is refused |
+| `main` | `1` if both accepts and both rejects hold |
+
+## Build (kotoba CLI v0.7.2)
+
+Language authority: [kotoba-lang/kotoba-lang](https://github.com/kotoba-lang/kotoba-lang).
+CLI: [kotoba-lang/kotoba](https://github.com/kotoba-lang/kotoba) tag **v0.7.2**.
+
+```sh
+kotoba compile kotoba/phonenumber.kotoba --target wasm --output phonenumber.wasm --json
+```
+
+Accept `kotoba.cli/ok?` true, `kotoba.cli/code` `emitted`,
+`value-profile` `i64-v1`. The artifact is host-independent wasm32
+(`wasm32-kotoba-v1`, `value-abi` `direct-v1`): no `kotoba:typed` imports, no
+libphonenumber native code.
+
+`kotoba compile --target wasm --run` is not used. The i64-v1 guest does not
+match the kototama/chicory runner on v0.7.2. Fixture execution is
+`--target web --run` (`js-kotoba-v1`), which still reports `value-profile`
+`i64-v1`.
+
+```sh
+kotoba/checks.sh
+```
+
+Install the CLI from the v0.7.2 release tarball or
+`brew tap kotoba-lang/kotoba && brew trust kotoba-lang/kotoba && brew install kotoba`.
diff --git a/kotoba/checks.sh b/kotoba/checks.sh
new file mode 100755
index 0000000000..87d4b5fa48
--- /dev/null
+++ b/kotoba/checks.sh
@@ -0,0 +1,123 @@
+#!/usr/bin/env bash
+# Compile phonenumber.kotoba with kotoba 0.7.2 and assert accept/reject fixtures.
+set -euo pipefail
+
+root=$(CDPATH= cd -- "$(dirname "$0")/.." && pwd)
+cd "$root"
+
+if ! command -v kotoba >/dev/null 2>&1; then
+  echo "kotoba CLI is required (kotoba-lang/kotoba v0.7.2)" >&2
+  exit 1
+fi
+
+if ! command -v python3 >/dev/null 2>&1; then
+  echo "python3 is required to parse kotoba --json and check wasm/fixtures" >&2
+  exit 1
+fi
+
+work=$(mktemp -d)
+trap 'rm -rf "$work"' EXIT
+
+python3 - "$root" <<'PY'
+import pathlib, sys
+root = pathlib.Path(sys.argv[1])
+fixtures = {
+    "kotoba/fixtures/us-e164.txt": "+16502530000",
+    "kotoba/fixtures/gb-e164.txt": "+442070313000",
+    "kotoba/fixtures/us-international.txt": "+1 650 253 0000",
+    "kotoba/fixtures/us-nsn.txt": "6502530000",
+}
+
+
+def e164_looking(s: str) -> bool:
+    if not (3 <= len(s) <= 16):
+        return False
+    if s[0] != "+":
+        return False
+    return all("0" <= ch <= "9" for ch in s[1:])
+
+
+for rel, expected in fixtures.items():
+    got = (root / rel).read_text().rstrip("\n")
+    if got != expected:
+        raise SystemExit("%s is %r, expected %r" % (rel, got, expected))
+
+accept_us = e164_looking(fixtures["kotoba/fixtures/us-e164.txt"])
+accept_gb = e164_looking(fixtures["kotoba/fixtures/gb-e164.txt"])
+reject_spaces = not e164_looking(fixtures["kotoba/fixtures/us-international.txt"])
+reject_nsn = not e164_looking(fixtures["kotoba/fixtures/us-nsn.txt"])
+print("fixture independent")
+print("  accept +16502530000", accept_us)
+print("  accept +442070313000", accept_gb)
+print("  reject +1 650 253 0000", reject_spaces)
+print("  reject 6502530000", reject_nsn)
+if not (accept_us and accept_gb and reject_spaces and reject_nsn):
+    raise SystemExit("independent E.164-looking predicate disagreed with fixture table")
+PY
+
+compile_json=$(kotoba compile kotoba/phonenumber.kotoba --target wasm --output "$work/phonenumber.wasm" --json)
+COMPILE_JSON="$compile_json" WASM_PATH="$work/phonenumber.wasm" python3 <<'PY'
+import json, os
+wasm_path = os.environ["WASM_PATH"]
+d = json.loads(os.environ["COMPILE_JSON"])
+ok = d.get("kotoba.cli/ok?")
+code = d.get("kotoba.cli/code")
+data = d.get("kotoba.cli/data") or {}
+profile = data.get("value-profile")
+compat = data.get("compatibility") or {}
+print("wasm", ok, code, "profile", profile, "abi", compat.get("value-abi"), "target", compat.get("target"))
+if not ok or code != "emitted":
+    raise SystemExit(d.get("kotoba.cli/message") or "wasm compile failed")
+if profile != "i64-v1":
+    raise SystemExit("expected value-profile i64-v1, got %r" % (profile,))
+if compat.get("value-abi") != "direct-v1":
+    raise SystemExit("expected value-abi direct-v1")
+if compat.get("target") != "wasm32-kotoba-v1":
+    raise SystemExit("expected target wasm32-kotoba-v1")
+blob = open(wasm_path, "rb").read()
+if blob[:4] != b"\x00asm":
+    raise SystemExit("not wasm magic")
+
+def read_u32(buf, i):
+    n = 0
+    shift = 0
+    while True:
+        b = buf[i]
+        i += 1
+        n |= (b & 0x7F) << shift
+        if b < 0x80:
+            return n, i
+        shift += 7
+
+i = 8
+imports = False
+while i < len(blob):
+    sid = blob[i]
+    i += 1
+    size, i = read_u32(blob, i)
+    if sid == 2:
+        imports = True
+    i += size
+if imports:
+    raise SystemExit("wasm has an import section; host-independent i64-v1 must not")
+print("wasm host-independent", len(blob), "bytes")
+PY
+
+run_json=$(kotoba compile kotoba/phonenumber.kotoba --target web --output "$work/phonenumber.mjs" --run --json)
+RUN_JSON="$run_json" python3 <<'PY'
+import json, os
+d = json.loads(os.environ["RUN_JSON"])
+ok = d.get("kotoba.cli/ok?")
+code = d.get("kotoba.cli/code")
+data = d.get("kotoba.cli/data") or {}
+result = data.get("result")
+profile = data.get("value-profile")
+print("web", ok, code, "result", result, "profile", profile)
+if not ok or code != "ran":
+    raise SystemExit(d.get("kotoba.cli/message") or "web fixture run failed")
+if profile != "i64-v1":
+    raise SystemExit("expected value-profile i64-v1 on web run")
+if result != 1:
+    raise SystemExit("main returned %r, expected 1 (accept US/GB and reject spaces/NSN)" % (result,))
+print("accept/reject fixture match ok")
+PY
diff --git a/kotoba/fixtures/gb-e164.txt b/kotoba/fixtures/gb-e164.txt
new file mode 100644
index 0000000000..8e5f1ae0c8
--- /dev/null
+++ b/kotoba/fixtures/gb-e164.txt
@@ -0,0 +1 @@
++442070313000
diff --git a/kotoba/fixtures/us-e164.txt b/kotoba/fixtures/us-e164.txt
new file mode 100644
index 0000000000..e89a39afa4
--- /dev/null
+++ b/kotoba/fixtures/us-e164.txt
@@ -0,0 +1 @@
++16502530000
diff --git a/kotoba/fixtures/us-international.txt b/kotoba/fixtures/us-international.txt
new file mode 100644
index 0000000000..4b8a9ead16
--- /dev/null
+++ b/kotoba/fixtures/us-international.txt
@@ -0,0 +1 @@
++1 650 253 0000
diff --git a/kotoba/fixtures/us-nsn.txt b/kotoba/fixtures/us-nsn.txt
new file mode 100644
index 0000000000..ce4448f074
--- /dev/null
+++ b/kotoba/fixtures/us-nsn.txt
@@ -0,0 +1 @@
+6502530000
diff --git a/kotoba/phonenumber.kotoba b/kotoba/phonenumber.kotoba
new file mode 100644
index 0000000000..d6cd41d929
--- /dev/null
+++ b/kotoba/phonenumber.kotoba
@@ -0,0 +1,142 @@
+;; Kotoba v1 libphonenumber surface (awai.network).
+;;
+;; Honest scope: well-formed E.164-looking check (plus prefix + digit length).
+;; Two accept fixtures and two reject fixtures are taken from this repository's
+;; own testdata (US_NUMBER / GB_NUMBER in java/.../PhoneNumberUtilTest.java).
+;;
+;; Not implemented: region metadata, carrier, geocoding, timezones,
+;; AsYouTypeFormatter, parse/format beyond the E.164-looking predicate,
+;; short numbers, or the PhoneNumber proto. Those need the metadata database
+;; this tree does not copy.
+;;
+;; i64-v1 only: integers and explicit byte values. No IEEE floats, no strings,
+;; no vectors (nth would leave i64-v1 and import kotoba:typed).
+
+(ns phonenumber.v1
+  (:export [main e164-looking accept-us accept-gb reject-spaces reject-nsn]))
+
+;; Fixture ids:
+;; 0 accept  +16502530000        US_NUMBER E.164 (CC 1 + NSN 6502530000)
+;; 1 accept  +442070313000       GB_NUMBER E.164 (CC 44 + NSN 2070313000)
+;; 2 reject  +1 650 253 0000     US_NUMBER INTERNATIONAL (spaces)
+;; 3 reject  6502530000          US_NUMBER national significant number (no plus)
+
+(defn fixture-len [id :i64] :i64
+  (cond
+    (= id 0) 12
+    (= id 1) 13
+    (= id 2) 15
+    :else 10))
+
+(defn fixture-byte [id :i64 i :i64] :i64
+  (cond
+    (= id 0)
+    (cond
+      (= i 0) 43
+      (= i 1) 49
+      (= i 2) 54
+      (= i 3) 53
+      (= i 4) 48
+      (= i 5) 50
+      (= i 6) 53
+      (= i 7) 51
+      (= i 8) 48
+      (= i 9) 48
+      (= i 10) 48
+      :else 48)
+    (= id 1)
+    (cond
+      (= i 0) 43
+      (= i 1) 52
+      (= i 2) 52
+      (= i 3) 50
+      (= i 4) 48
+      (= i 5) 55
+      (= i 6) 48
+      (= i 7) 51
+      (= i 8) 49
+      (= i 9) 51
+      (= i 10) 48
+      (= i 11) 48
+      :else 48)
+    (= id 2)
+    (cond
+      (= i 0) 43
+      (= i 1) 49
+      (= i 2) 32
+      (= i 3) 54
+      (= i 4) 53
+      (= i 5) 48
+      (= i 6) 32
+      (= i 7) 50
+      (= i 8) 53
+      (= i 9) 51
+      (= i 10) 32
+      (= i 11) 48
+      (= i 12) 48
+      (= i 13) 48
+      :else 48)
+    :else
+    (cond
+      (= i 0) 54
+      (= i 1) 53
+      (= i 2) 48
+      (= i 3) 50
+      (= i 4) 53
+      (= i 5) 51
+      (= i 6) 48
+      (= i 7) 48
+      (= i 8) 48
+      :else 48)))
+
+(defn- ascii-digit? [b :i64] :i64
+  (if (< b 48)
+    0
+    (if (< 57 b)
+      0
+      1)))
+
+;; Plus prefix, then 2..15 ASCII digits. Digit max is ITU E.164 (15).
+;; Digit min is this repo's PhoneNumberUtil.MIN_LENGTH_FOR_NSN (2), applied
+;; to the complete international digit string, not to a region NSN.
+(defn e164-looking [id :i64] :i64
+  (let [n (fixture-len id)]
+    (if (< n 3)
+      0
+      (if (< 16 n)
+        0
+        (if (= (fixture-byte id 0) 43)
+          (loop [i 1]
+            (if (>= i n)
+              1
+              (if (= (ascii-digit? (fixture-byte id i)) 1)
+                (recur (+ i 1))
+                0)))
+          0)))))
+
+(defn accept-us [] :i64
+  (e164-looking 0))
+
+(defn accept-gb [] :i64
+  (e164-looking 1))
+
+(defn reject-spaces [] :i64
+  (if (= (e164-looking 2) 0)
+    1
+    0))
+
+(defn reject-nsn [] :i64
+  (if (= (e164-looking 3) 0)
+    1
+    0))
+
+(defn main [] :i64
+  (if (= (accept-us) 1)
+    (if (= (accept-gb) 1)
+      (if (= (reject-spaces) 1)
+        (if (= (reject-nsn) 1)
+          1
+          0)
+        0)
+      0)
+    0))