diff --git a/docs/methodology.md b/docs/methodology.md
index 6f08461..cbd7923 100644
--- a/docs/methodology.md
+++ b/docs/methodology.md
@@ -26,10 +26,11 @@ LLM。設計原則見 `research-plan.md`；本檔記載可重現的
 ### 步驟 2-1 進池
 
 兩次標註執行的全部關鍵字取聯集、逐字串精確去重、字典序
-排列。失敗與拒答的記錄跳過（其歌曲不貢獻關鍵字）；解析
-時偵測重複鍵，違規即失敗。同時寫出處記錄（關鍵字 →
-（執行別，歌曲 ID）清單），供收斂軌跡分析；出處記錄不
-進任何下游輸入。
+排列，寫成純文字檔（一行一個關鍵字）。失敗與拒答的記錄
+跳過（其歌曲不貢獻關鍵字）；解析時偵測重複鍵，違規即
+失敗。同時寫出處 CSV（欄位 Keyword、Run、Song，一列一筆
+出現，依三欄排序），供收斂軌跡分析；出處記錄不進任何
+下游輸入。
 
 ### 步驟 2-2 分群
 
@@ -103,9 +104,9 @@ LLM。設計原則見 `research-plan.md`；本檔記載可重現的
 - **步驟 1 → 2-1**：`pool-keywords` 讀兩份執行歸檔的
   `output.jsonl`（一律以換行字元 `\n` 切行——歌詞含
   U+0085 等控制字元時，`str.splitlines()` 類的通用切行
-  會截斷 JSON 字串，實測踩中），輸出關鍵字 JSON 陣列
-  與出處記錄。
-- **步驟 2-1 → 2-2**：`cluster-keywords` 讀關鍵字陣列，
+  會截斷 JSON 字串，實測踩中），輸出關鍵字純文字檔與
+  出處 CSV。
+- **步驟 2-1 → 2-2**：`cluster-keywords` 讀關鍵字純文字檔，
   輸出具名分組（組名 → 成員詞，組名與成員皆字典序）
   與記錄嵌入模型、revision、演算法參數、輸入 SHA-256 的
   meta。
@@ -123,10 +124,12 @@ LLM。設計原則見 `research-plan.md`；本檔記載可重現的
   保留的標籤，寫入逐首紀錄檔（歌依 ID 升序、標籤按
   字典序，各標籤附其定案時的引述與來源層——共識或
   仲裁）。
-- **序列化通則**：所有中間檔為 UTF-8 JSON，鍵序與元素
-  序皆依上列規則明定，無時間戳、無隨機成分；解析一律
-  偵測重複鍵，違規即失敗。給定相同的 LLM 執行輸出，
-  全部交接產物逐位元組可再生。
+- **序列化通則**：所有中間檔為 UTF-8，欄序、鍵序與元素
+  序皆依上列規則明定，無時間戳、無隨機成分；JSON 解析
+  一律偵測重複鍵，違規即失敗。人讀為主的產物採純文字或
+  CSV（CSV 依 RFC 4180，標題列字首大寫），機器交接檔採
+  JSON。給定相同的 LLM 執行輸出，全部交接產物逐位元組
+  可再生。
 
 ## 執行與稽核
 
diff --git a/tools/README.rst b/tools/README.rst
index c7d1ae1..bbc0e80 100644
--- a/tools/README.rst
+++ b/tools/README.rst
@@ -61,6 +61,12 @@ run-llm
 A general command that runs specific LLM instructions with the Anthropic API.  The API key must be present in the ``.env`` file in the working directory.  Check ``pop-fem-audit-tools run-llm -h`` for complete instructions on its usage.
 
 
+pool-keywords
+-------------
+
+Deterministically pool the keywords of the two tagging runs into the clustering step's input, per the project's handoff contract.  Check ``pop-fem-audit-tools pool-keywords -h`` for complete instructions on its usage.
+
+
 Copyright
 =========
 
diff --git a/tools/docs/source/pop_fem_audit_tools.commands.rst b/tools/docs/source/pop_fem_audit_tools.commands.rst
index d6f7471..0a13fcf 100644
--- a/tools/docs/source/pop_fem_audit_tools.commands.rst
+++ b/tools/docs/source/pop_fem_audit_tools.commands.rst
@@ -36,6 +36,14 @@ pop\_fem\_audit\_tools.commands.fetch\_lyrics module
    :show-inheritance:
    :undoc-members:
 
+pop\_fem\_audit\_tools.commands.pool\_keywords module
+-----------------------------------------------------
+
+.. automodule:: pop_fem_audit_tools.commands.pool_keywords
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
 pop\_fem\_audit\_tools.commands.run\_llm module
 -----------------------------------------------
 
diff --git a/tools/src/pop_fem_audit_tools/__main__.py b/tools/src/pop_fem_audit_tools/__main__.py
index 5c1ae36..828c788 100644
--- a/tools/src/pop_fem_audit_tools/__main__.py
+++ b/tools/src/pop_fem_audit_tools/__main__.py
@@ -20,6 +20,7 @@ from .commands import (
     export_llm_input_command,
     fetch_artists_command,
     fetch_lyrics_command,
+    pool_keywords_command,
     run_llm_command,
 )
 
@@ -31,6 +32,7 @@ SUBCOMMANDS: dict[str, Callable[[list[str] | None], int]] = {
     "export-llm-input": export_llm_input_command,
     "fetch-artists": fetch_artists_command,
     "fetch-lyrics": fetch_lyrics_command,
+    "pool-keywords": pool_keywords_command,
     "run-llm": run_llm_command,
 }
 """The dispatch table from the subcommand name to the tool main."""
diff --git a/tools/src/pop_fem_audit_tools/commands/__init__.py b/tools/src/pop_fem_audit_tools/commands/__init__.py
index 5a3065d..4f39df8 100644
--- a/tools/src/pop_fem_audit_tools/commands/__init__.py
+++ b/tools/src/pop_fem_audit_tools/commands/__init__.py
@@ -7,4 +7,5 @@ from .build_db import main as build_db_command
 from .export_llm_input import main as export_llm_input_command
 from .fetch_artists import main as fetch_artists_command
 from .fetch_lyrics import main as fetch_lyrics_command
+from .pool_keywords import main as pool_keywords_command
 from .run_llm import main as run_llm_command
diff --git a/tools/src/pop_fem_audit_tools/commands/pool_keywords.py b/tools/src/pop_fem_audit_tools/commands/pool_keywords.py
new file mode 100644
index 0000000..5cc8d33
--- /dev/null
+++ b/tools/src/pop_fem_audit_tools/commands/pool_keywords.py
@@ -0,0 +1,233 @@
+# Tools for A Feminist Audit of Pop Music.
+# Copyright 2026 imacat.  All rights reserved.
+# Authors:
+#   imacat@mail.imacat.idv.tw (imacat), 2026/8/5
+"""The deterministic pooler of the tagging runs' keywords.
+
+Pools the keywords produced by the two runs of the tagging step
+into the clustering step's input, given as the third positional
+command-line argument, per the project's handoff contract: the
+pool is the plain union of every keyword key observed across both
+runs' valid records, exact-string deduplicated and sorted, written
+as a plain text file with one keyword per line.  The provenance
+mapping, given as the fourth positional argument, records where
+every keyword came from for audit purposes as a CSV file; it never
+enters any LLM input.
+"""
+import argparse
+import csv
+import json
+import sys
+from pathlib import Path
+from typing import Any
+
+type Records = list[tuple[int, dict[str, Any]]]
+"""The valid records of one run: (song ID, keyword mapping) pairs."""
+
+type Provenance = dict[str, list[tuple[str, int]]]
+"""The occurrences of every keyword, keyed by the keyword."""
+
+
+def parse_args(argv: list[str] | None) -> argparse.Namespace:
+    """Parse the command-line arguments.
+
+    :param argv: The command-line arguments, or None for
+        ``sys.argv``.
+    :return: The parsed arguments.
+    """
+    parser: argparse.ArgumentParser = argparse.ArgumentParser(
+        description="Pool the keywords of the two tagging runs"
+                    " into the clustering step's input.")
+    parser.add_argument(
+        "run_dir_1", type=Path,
+        help="the first tagging run's archive directory")
+    parser.add_argument(
+        "run_dir_2", type=Path,
+        help="the second tagging run's archive directory")
+    parser.add_argument(
+        "pool_txt", type=Path,
+        help="the pooled keyword text output file, one keyword"
+             " per line")
+    parser.add_argument(
+        "provenance_csv", type=Path,
+        help="the keyword provenance CSV output file")
+    return parser.parse_args(argv)
+
+
+def reject_duplicate_keys(
+        pairs: list[tuple[str, Any]]) -> dict[str, Any]:
+    """Build a mapping from key-value pairs, rejecting duplicates.
+
+    :param pairs: The key-value pairs, in document order.
+    :return: The mapping built from the pairs.
+    :raises ValueError: When a key appears more than once.
+    """
+    result: dict[str, Any] = {}
+    key: str
+    value: Any
+    for key, value in pairs:
+        if key in result:
+            raise ValueError(f"duplicate key \"{key}\"")
+        result[key] = value
+    return result
+
+
+def parse_song_id(item_id: str, path: Path) -> int:
+    """Parse the integer song ID out of an item ID.
+
+    :param item_id: The item ID, expected as ``song-<ID>``.
+    :param path: The output file the ID came from, for the error
+        message.
+    :return: The parsed song ID.
+    :raises ValueError: When the item ID is not ``song-<ID>``.
+    """
+    prefix: str = "song-"
+    if not item_id.startswith(prefix) \
+            or not item_id[len(prefix):].isdigit():
+        raise ValueError(
+            f"{path}: id \"{item_id}\": not in \"song-<ID>\" form")
+    return int(item_id[len(prefix):])
+
+
+def load_run(run_dir: Path) -> tuple[str, Records]:
+    """Load and validate the keyword records of one tagging run.
+
+    Records carrying an "error" field are skipped.  A "text"
+    field that fails to parse as JSON is a refusal and is
+    skipped; a "text" field that parses to anything other than a
+    JSON object, or whose keys are not unique, fails the run.
+
+    :param run_dir: The run's archive directory, containing
+        ``output.jsonl``.
+    :return: The run label (the directory's basename) and its
+        valid records, each the song ID and the parsed keyword
+        mapping, in file order.
+    :raises OSError: When ``output.jsonl`` cannot be read.
+    :raises ValueError: When a line is not a well-formed output
+        record, or a "text" field is invalid per the rules above.
+    """
+    path: Path = run_dir / "output.jsonl"
+    text: str = path.read_text(encoding="utf-8")
+    records: Records = []
+    line: str
+    for line in text.split("\n"):
+        if line.strip() == "":
+            continue
+        record: Any = json.loads(line)
+        if not isinstance(record, dict) or "id" not in record:
+            raise ValueError(
+                f"{path}: record without \"id\": {line}")
+        if "error" in record:
+            continue
+        if "text" not in record:
+            raise ValueError(
+                f"{path}: id {record['id']}: record without"
+                " \"text\" or \"error\"")
+        song_id: int = parse_song_id(record["id"], path)
+        try:
+            keywords: Any = json.loads(
+                record["text"],
+                object_pairs_hook=reject_duplicate_keys)
+        except json.JSONDecodeError:
+            continue
+        if not isinstance(keywords, dict):
+            raise ValueError(
+                f"{path}: id {record['id']}: \"text\" does not"
+                " parse to a JSON object")
+        records.append((song_id, keywords))
+    return run_dir.name, records
+
+
+def pool_keywords(runs: list[tuple[str, Records]],
+                  ) -> tuple[list[str], Provenance]:
+    """Pool the keywords of the given tagging runs.
+
+    :param runs: The runs, each the run label and its valid
+        records (song ID, keyword mapping).
+    :return: The sorted, exact-string-deduplicated keyword list
+        and the provenance mapping from each keyword to its
+        occurrences, sorted by (run label, song ID).
+    """
+    provenance: Provenance = {}
+    label: str
+    records: Records
+    for label, records in runs:
+        song_id: int
+        keywords: dict[str, Any]
+        for song_id, keywords in records:
+            keyword: str
+            for keyword in keywords:
+                provenance.setdefault(keyword, []).append(
+                    (label, song_id))
+    for occurrences in provenance.values():
+        occurrences.sort()
+    return sorted(provenance.keys()), provenance
+
+
+def write_pool(path: Path, keywords: list[str]) -> None:
+    """Write the pooled keyword list as the clustering input.
+
+    Writes a plain text file, one keyword per line, in the given
+    order, UTF-8, LF line endings, with a trailing newline.
+
+    :param path: The path of the pool text file to write.
+    :param keywords: The sorted, deduplicated keyword list.
+    :return: None.
+    """
+    path.write_text(
+        "".join(f"{keyword}\n" for keyword in keywords),
+        encoding="utf-8")
+
+
+def write_provenance(path: Path, provenance: Provenance) -> None:
+    """Write the keyword provenance mapping.
+
+    Writes a CSV file with the header row
+    ``Keyword,Run,Song``, one row per occurrence, long format.
+    Rows are sorted by keyword lexicographically, then by run
+    label, then by song ID.
+
+    :param path: The path of the provenance CSV file to write.
+    :param provenance: The provenance mapping from each keyword
+        to its occurrences (run label, song ID).
+    :return: None.
+    :raises OSError: When the file cannot be written.
+    """
+    keyword: str
+    with open(path, "w", encoding="utf-8", newline="") as file:
+        writer: Any = csv.writer(file)
+        writer.writerow(["Keyword", "Run", "Song"])
+        for keyword in sorted(provenance.keys()):
+            label: str
+            song_id: int
+            for label, song_id in provenance[keyword]:
+                writer.writerow([keyword, label, song_id])
+
+
+def main(argv: list[str] | None = None) -> int:
+    """Pool the two tagging runs' keywords for clustering.
+
+    :param argv: The command-line arguments, or None for
+        ``sys.argv``.
+    :return: The exit status: 0 on success, non-zero on failure.
+    """
+    args: argparse.Namespace = parse_args(argv)
+    run1: tuple[str, Records]
+    run2: tuple[str, Records]
+    try:
+        run1 = load_run(args.run_dir_1)
+        run2 = load_run(args.run_dir_2)
+    except (OSError, ValueError) as error:
+        print(f"error: {error}", file=sys.stderr)
+        return 1
+    keywords: list[str]
+    provenance: Provenance
+    keywords, provenance = pool_keywords([run1, run2])
+    args.pool_txt.parent.mkdir(parents=True, exist_ok=True)
+    args.provenance_csv.parent.mkdir(parents=True, exist_ok=True)
+    write_pool(args.pool_txt, keywords)
+    write_provenance(args.provenance_csv, provenance)
+    print(
+        f"done: {len(keywords)} keywords pooled from"
+        f" {len(run1[1])}+{len(run2[1])} records", file=sys.stderr)
+    return 0
diff --git a/tools/tests/test_pool_keywords.py b/tools/tests/test_pool_keywords.py
new file mode 100644
index 0000000..43cf2a7
--- /dev/null
+++ b/tools/tests/test_pool_keywords.py
@@ -0,0 +1,217 @@
+# Tools for A Feminist Audit of Pop Music.
+# Copyright 2026 imacat.  All rights reserved.
+# Authors:
+#   imacat@mail.imacat.idv.tw (imacat), 2026/8/5
+"""Unit tests for the keyword pooler module."""
+import csv
+import io
+import json
+import tempfile
+import unittest
+from contextlib import redirect_stderr
+from pathlib import Path
+from typing import Any
+
+from pop_fem_audit_tools.commands import pool_keywords
+
+
+class TestPoolKeywords(unittest.TestCase):
+    """Test cases for the keyword pooler."""
+
+    def setUp(self) -> None:
+        """Create a temporary directory with two run directories."""
+        tmp: tempfile.TemporaryDirectory[str] \
+            = tempfile.TemporaryDirectory()
+        self.addCleanup(tmp.cleanup)
+        self.__dir: Path = Path(tmp.name)
+        self.__run1: Path = self.__dir / "run1"
+        self.__run2: Path = self.__dir / "run2"
+        self.__run1.mkdir()
+        self.__run2.mkdir()
+        self.__pool: Path = self.__dir / "pool.txt"
+        self.__provenance: Path = self.__dir / "provenance.csv"
+
+    @staticmethod
+    def __write_output(
+            run_dir: Path, records: list[dict[str, Any]]) -> None:
+        """Write the ``output.jsonl`` file of one run.
+
+        :param run_dir: The run's archive directory.
+        :param records: The envelope records, in file order.
+        :return: None.
+        """
+        lines: list[str] = [
+            json.dumps(x, ensure_ascii=False) for x in records]
+        (run_dir / "output.jsonl").write_text(
+            "\n".join(lines) + "\n", encoding="utf-8")
+
+    def __run_pool(self) -> tuple[int, str]:
+        """Run the pooler with the standard error captured.
+
+        :return: A tuple of the exit status and the standard
+            error.
+        """
+        stderr: io.StringIO = io.StringIO()
+        with redirect_stderr(stderr):
+            status: int = pool_keywords.main([
+                str(self.__run1), str(self.__run2),
+                str(self.__pool), str(self.__provenance)])
+        return status, stderr.getvalue()
+
+    def __read_pool(self) -> list[str]:
+        """Read the pool text file.
+
+        :return: The keyword list, one keyword per line, with the
+            trailing empty line from the final newline removed.
+        """
+        lines: list[str] = self.__pool.read_text(
+            encoding="utf-8").split("\n")
+        self.assertEqual(lines[-1], "")
+        return lines[:-1]
+
+    def __read_provenance(self) -> list[list[str]]:
+        """Read the provenance CSV file.
+
+        :return: All rows, including the header row, in file
+            order.
+        """
+        with open(self.__provenance, encoding="utf-8",
+                  newline="") as file:
+            return list(csv.reader(file))
+
+    def test_pools_union_dedup_sorted(self) -> None:
+        """Test the union, dedup, and lexicographic ordering, and
+        the plain one-keyword-per-line pool file shape."""
+        self.__write_output(self.__run1, [
+            {"id": "song-1",
+             "text": json.dumps({"strength": 1, "shared": 1})},
+        ])
+        self.__write_output(self.__run2, [
+            {"id": "song-3",
+             "text": json.dumps({"warrior": 1, "shared": 1})},
+        ])
+        status: int
+        stderr: str
+        status, stderr = self.__run_pool()
+        self.assertEqual(status, 0)
+        self.assertEqual(
+            self.__read_pool(), ["shared", "strength", "warrior"])
+        self.assertIn(
+            "done: 3 keywords pooled from 1+1 records", stderr)
+
+    def test_skips_error_records(self) -> None:
+        """Test that records carrying an "error" field are
+        excluded from the pool and the record count."""
+        self.__write_output(self.__run1, [
+            {"id": "song-1",
+             "text": json.dumps({"strength": 1})},
+            {"id": "song-2", "error": "invalid_request_error"},
+        ])
+        self.__write_output(self.__run2, [
+            {"id": "song-3", "text": json.dumps({"warrior": 1})},
+        ])
+        status: int
+        stderr: str
+        status, stderr = self.__run_pool()
+        self.assertEqual(status, 0)
+        self.assertEqual(
+            self.__read_pool(), ["strength", "warrior"])
+        self.assertIn(
+            "done: 2 keywords pooled from 1+1 records", stderr)
+
+    def test_skips_non_json_text_records(self) -> None:
+        """Test that a refusal, whose "text" does not parse as
+        JSON, is skipped rather than failing the run."""
+        self.__write_output(self.__run1, [
+            {"id": "song-1",
+             "text": json.dumps({"strength": 1})},
+            {"id": "song-2", "text": "I cannot help with that."},
+        ])
+        self.__write_output(self.__run2, [
+            {"id": "song-3", "text": json.dumps({"warrior": 1})},
+        ])
+        status: int
+        stderr: str
+        status, stderr = self.__run_pool()
+        self.assertEqual(status, 0)
+        self.assertEqual(
+            self.__read_pool(), ["strength", "warrior"])
+        self.assertIn(
+            "done: 2 keywords pooled from 1+1 records", stderr)
+
+    def test_duplicate_key_in_text_rejected(self) -> None:
+        """Test that a "text" JSON object with a duplicate key
+        fails the run without writing any output file."""
+        self.__write_output(self.__run1, [
+            {"id": "song-1",
+             "text": '{"strength": 1, "strength": 2}'},
+        ])
+        self.__write_output(self.__run2, [
+            {"id": "song-3", "text": json.dumps({"warrior": 1})},
+        ])
+        status: int
+        stderr: str
+        status, stderr = self.__run_pool()
+        self.assertEqual(status, 1)
+        self.assertIn("duplicate key", stderr)
+        self.assertFalse(self.__pool.exists())
+        self.assertFalse(self.__provenance.exists())
+
+    def test_non_object_text_rejected(self) -> None:
+        """Test that a "text" JSON value that is not an object
+        fails the run without writing any output file."""
+        self.__write_output(self.__run1, [
+            {"id": "song-1", "text": json.dumps(["strength"])},
+        ])
+        self.__write_output(self.__run2, [
+            {"id": "song-3", "text": json.dumps({"warrior": 1})},
+        ])
+        status: int
+        stderr: str
+        status, stderr = self.__run_pool()
+        self.assertEqual(status, 1)
+        self.assertIn("song-1", stderr)
+        self.assertFalse(self.__pool.exists())
+        self.assertFalse(self.__provenance.exists())
+
+    def test_provenance_content_and_ordering(self) -> None:
+        """Test the provenance content and its ordering: rows
+        sorted by keyword lexicographically, then by run label,
+        then by song ID."""
+        self.__write_output(self.__run1, [
+            {"id": "song-2", "text": json.dumps({"shared": 1})},
+            {"id": "song-1", "text": json.dumps({"shared": 1})},
+        ])
+        self.__write_output(self.__run2, [
+            {"id": "song-5",
+             "text": json.dumps({"shared": 1, "warrior": 1})},
+        ])
+        status: int
+        status, _ = self.__run_pool()
+        self.assertEqual(status, 0)
+        rows: list[list[str]] = self.__read_provenance()
+        self.assertEqual(rows[1:], [
+            ["shared", "run1", "1"],
+            ["shared", "run1", "2"],
+            ["shared", "run2", "5"],
+            ["warrior", "run2", "5"],
+        ])
+
+    def test_provenance_file_header_and_row_count(self) -> None:
+        """Test that the provenance CSV file starts with the
+        ``Keyword,Run,Song`` header row and has exactly one row
+        per keyword occurrence."""
+        self.__write_output(self.__run1, [
+            {"id": "song-2", "text": json.dumps({"shared": 1})},
+            {"id": "song-1", "text": json.dumps({"shared": 1})},
+        ])
+        self.__write_output(self.__run2, [
+            {"id": "song-5",
+             "text": json.dumps({"shared": 1, "warrior": 1})},
+        ])
+        status: int
+        status, _ = self.__run_pool()
+        self.assertEqual(status, 0)
+        rows: list[list[str]] = self.__read_provenance()
+        self.assertEqual(rows[0], ["Keyword", "Run", "Song"])
+        self.assertEqual(len(rows), 1 + 4)