diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bfc4805..bd11ceb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,17 +25,14 @@ jobs:
       - name: install libdbus on linux
         if: matrix.os == 'ubuntu-latest'
         run: sudo apt-get update && sudo apt-get install -y --no-install-recommends libdbus-1-dev pkg-config
-      - uses: jdx/mise-action@5083fe46898c414b2475087cc79da59e7da859e8 # v2.1.11
+      # No mise here: the test matrix only needs rust + cargo-nextest. Letting
+      # rustup own the toolchain avoids the mise/host-rustup divergence we hit
+      # on macOS (mise's cargo and rustup component add ended up on different
+      # toolchains and clippy wouldn't resolve).
+      - uses: dtolnay/rust-toolchain@b3b07ba8b418998c39fb20f53e8b695cdcc8de1b # stable
         with:
-          install: true
-          cache: true
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      - name: ensure rustfmt + clippy components
-        # `mise.toml` requests rust profile=default, but mise's rust backend
-        # may install a cached minimal toolchain. Add the components
-        # explicitly so `cargo fmt` and `cargo clippy` always resolve.
-        run: rustup component add rustfmt clippy
+          toolchain: "1.89"
+          components: rustfmt, clippy
       - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.7.4
       - uses: taiki-e/install-action@v2
         with:
@@ -79,6 +76,26 @@ jobs:
       - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.7.4
       - run: cargo check --all-features
 
+  pre-commit:
+    name: pre-commit
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - name: install libdbus
+        run: sudo apt-get update && sudo apt-get install -y --no-install-recommends libdbus-1-dev pkg-config
+      - uses: jdx/mise-action@5083fe46898c414b2475087cc79da59e7da859e8 # v2.1.11
+        with:
+          install: true
+          cache: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      - name: ensure rustfmt + clippy components
+        # Route through mise so components land in the same toolchain the
+        # pre-commit cargo hooks (`mise exec -- cargo ...`) will use.
+        run: mise exec -- rustup component add rustfmt clippy
+      - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.7.4
+      - uses: pre-commit/action@2c7b3805fd2a0fd8c1884dcaebf91fc102a13ecd # v3.0.1
+
   linux-headless:
     name: linux headless (no D-Bus)
     runs-on: ubuntu-latest
diff --git a/.markdownlint-cli2.yaml b/.markdownlint-cli2.yaml
new file mode 100644
index 0000000..e1a2a75
--- /dev/null
+++ b/.markdownlint-cli2.yaml
@@ -0,0 +1,21 @@
+# markdownlint-cli2 config for slack-cli.
+# Mainly relaxes rules that fight against Japanese line widths and
+# legitimate inline HTML / bare URLs in README content.
+
+config:
+  line-length: false
+  no-inline-html: false
+  no-bare-urls: false
+  first-line-h1: false
+  no-duplicate-heading: false
+  no-emphasis-as-heading: false
+  # Tables with mixed-width (CJK + ASCII) characters cannot be aligned by
+  # column at the byte/code-point level. Keep tables readable by content,
+  # not by pipe alignment.
+  table-column-style: false
+
+ignores:
+  - 'CHANGELOG.md'
+  - 'target/**'
+  # Internal brainstorming spec + implementation plan, kept as-is.
+  - 'docs/superpowers/**'
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..f35ff96
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,65 @@
+# pre-commit hooks for slack-cli.
+#
+# Install (one-time, per clone):
+#   pip install --user pre-commit   # or: brew install pre-commit, pipx install pre-commit
+#   pre-commit install
+#   pre-commit install --hook-type commit-msg
+#
+# Run manually on every tracked file:
+#   pre-commit run --all-files
+
+repos:
+  # ----- File hygiene -----
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v6.0.0
+    hooks:
+      - id: trailing-whitespace
+        exclude: '\.snap$'
+      - id: end-of-file-fixer
+        exclude: '\.snap$'
+      - id: check-yaml
+      - id: check-toml
+      - id: check-json
+      - id: check-merge-conflict
+      - id: check-added-large-files
+        args: [--maxkb=1024]
+      - id: mixed-line-ending
+        args: [--fix=lf]
+      - id: detect-private-key
+
+  # ----- Secret detection -----
+  - repo: https://github.com/gitleaks/gitleaks
+    rev: v8.30.0
+    hooks:
+      - id: gitleaks
+
+  # ----- Markdown lint -----
+  - repo: https://github.com/DavidAnson/markdownlint-cli2
+    rev: v0.22.1
+    hooks:
+      - id: markdownlint-cli2
+        args: ['--config', '.markdownlint-cli2.yaml']
+
+  # ----- Conventional Commits (commit-msg only) -----
+  - repo: https://github.com/compilerla/conventional-pre-commit
+    rev: v4.4.0
+    hooks:
+      - id: conventional-pre-commit
+        stages: [commit-msg]
+        args: [feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert]
+
+  # ----- Rust (local hooks via mise so the toolchain is always pinned) -----
+  - repo: local
+    hooks:
+      - id: cargo-fmt
+        name: cargo fmt --check
+        entry: mise exec -- cargo fmt --all -- --check
+        language: system
+        types: [rust]
+        pass_filenames: false
+      - id: cargo-clippy
+        name: cargo clippy --all-targets -- -D warnings
+        entry: mise exec -- cargo clippy --all-targets -- -D warnings
+        language: system
+        types: [rust]
+        pass_filenames: false
diff --git a/README.ja.md b/README.ja.md
index ecffaed..3bb43c4 100644
--- a/README.ja.md
+++ b/README.ja.md
@@ -149,6 +149,27 @@ mise run snap        # 未確定の insta スナップショットをレビュ
 mise run run -- channel list
 ```
 
+### pre-commit hooks
+
+クローン直後に一度だけ設定（`pre-commit` を PATH に入れて `.git/hooks` に登録します）:
+
+```sh
+pip install --user pre-commit   # または brew install pre-commit / pipx install pre-commit
+pre-commit install
+pre-commit install --hook-type commit-msg
+```
+
+全 tracked file に対して手動実行:
+
+```sh
+pre-commit run --all-files
+```
+
+`.pre-commit-config.yaml` で次を設定: ファイル衛生チェック、gitleaks
+（secret scan）、markdownlint、Conventional Commits validator（commit-msg）、
+ローカル hook として `cargo fmt --check` と `cargo clippy --all-targets -- -D warnings`。
+CI でも同じ hook 群を各 PR で実行します。
+
 ## ライセンス
 
 MIT OR Apache-2.0 のデュアルライセンス。
diff --git a/README.md b/README.md
index 5617c1e..8774d8b 100644
--- a/README.md
+++ b/README.md
@@ -153,6 +153,28 @@ mise run snap        # Review pending insta snapshots
 mise run run -- channel list
 ```
 
+### pre-commit hooks
+
+One-time setup per clone (installs `pre-commit` to your PATH and wires up
+`.git/hooks`):
+
+```sh
+pip install --user pre-commit   # or: brew install pre-commit / pipx install pre-commit
+pre-commit install
+pre-commit install --hook-type commit-msg
+```
+
+Run all hooks against every tracked file:
+
+```sh
+pre-commit run --all-files
+```
+
+Configured in `.pre-commit-config.yaml`: file hygiene, gitleaks (secret
+scan), markdownlint, Conventional Commits validator (commit-msg), plus
+`cargo fmt --check` and `cargo clippy --all-targets -- -D warnings` as
+local hooks. The CI workflow runs the same set on every PR.
+
 ## License
 
 Dual-licensed under MIT OR Apache-2.0.