diff --git a/.gitattributes b/.gitattributes
index 3097430..86c799d 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,7 +1,7 @@
 # Without this, a Windows checkout with `core.autocrlf=true` (the Windows
 # default) writes CRLF into the working tree while the committed content is LF.
-# The scripts that parse these files are written against LF, so the pre-push
-# audit fails on files that are perfectly valid, and the push is refused.
+# The scripts that parse these files are written against LF, so the commit
+# hook audit fails on files that are perfectly valid, and the commit is refused.
 # Pinning the checkout to LF keeps the working tree byte-identical to what is
 # committed, on every platform.
 
diff --git a/.github/workflows/hooks.yml b/.github/workflows/hooks.yml
index aac68d7..ff9b9d5 100644
--- a/.github/workflows/hooks.yml
+++ b/.github/workflows/hooks.yml
@@ -1,6 +1,6 @@
 name: Run Git Hooks
 
-# Runs the pre-push hooks from lefthook.yml on the files this PR changes.
+# Runs the pre-commit hooks from lefthook.yml on the files this PR changes.
 # A local hook can be skipped with --no-verify or never installed, so this is
 # the check that cannot be bypassed. Same config as local, nothing to sync.
 
@@ -31,7 +31,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
         with:
-          # lefthook diffs against the base branch, so it needs its commits.
+          # The diff below needs the base branch's commits.
           fetch-depth: 0
 
       - uses: actions/setup-node@v4
@@ -41,20 +41,20 @@ jobs:
 
       - run: npm ci
 
-      - name: Run the pre-push hooks
+      - name: Run the hooks on the files this PR changes
         env:
           BASE_REF: ${{ github.event.pull_request.base.ref }}
         run: |
-          # lefthook reads the base branch from origin/HEAD, which checkout
-          # does not set, then diffs against the LOCAL branch of that name,
-          # which checkout does not create. The PR checkout is the merge of
-          # this PR into the base, so that diff is exactly this PR's changes.
-          git remote set-head origin "$BASE_REF"
-          git branch "$BASE_REF" "origin/$BASE_REF"
-          node_modules/.bin/lefthook run pre-push
+          # Three dots: changes since the merge base, so files that moved on
+          # the base branch are never linted. Deleted files are left out.
+          # -z: lefthook reads stdin as NUL-separated paths, not lines.
+          # pipefail: a failed diff must fail the job, not pass an empty list.
+          set -o pipefail
+          git diff -z --name-only --diff-filter=ACMR "origin/$BASE_REF...HEAD" |
+            node_modules/.bin/lefthook run pre-commit --files-from-stdin
 
       - name: Audit the rules system
-        # lefthook skips every command when a PR only deletes files, and a
+        # The step above sees no file list when a PR only deletes docs, and a
         # deleted rule is what breaks dependencies and the index. This runs the
         # cross-file checks on every PR, with no file list to get wrong.
         run: node scripts/check-rules.mjs --rules
diff --git a/.github/workflows/markdown_lint.yml b/.github/workflows/markdown_lint.yml
index 73df513..1e00731 100644
--- a/.github/workflows/markdown_lint.yml
+++ b/.github/workflows/markdown_lint.yml
@@ -31,7 +31,7 @@ jobs:
         with:
           run-prettier: false
           # Markdown lint runs from lefthook.yml in hooks.yml, with the same
-          # pinned rumdl as the local pre-push hook.
+          # pinned rumdl as the local pre-commit hook.
           run-markdown: false
           run-commits: true
           package-manager: bun
diff --git a/README.md b/README.md
index f306940..a6aee32 100644
--- a/README.md
+++ b/README.md
@@ -12,9 +12,9 @@ improvements.
 ### Local
 
 After cloning, run `npm install` once to install the pinned `rumdl` version and
-enable the markdown lint and rules-audit checks on push (`postinstall` runs
+enable the markdown lint and rules-audit checks on commit (`postinstall` runs
 `lefthook install`). The hooks live in `lefthook.yml`, and CI runs the same
-file.
+file. To skip them once, run `LEFTHOOK=0 git commit`; CI still checks.
 
 ### Stage / Preview
 
diff --git a/docs/rules/DEV-338.md b/docs/rules/DEV-338.md
index 9ff1199..4c1d8e8 100644
--- a/docs/rules/DEV-338.md
+++ b/docs/rules/DEV-338.md
@@ -30,9 +30,9 @@ links `docs/README.md`); this rule covers the landing page's own content.
    [DEV-330](./DEV-330.md). A README that lies about how to run the project is
    worse than one that says nothing.
 1. Where the repository provides an automated README check, run it before
-   pushing and enforce it in the pre-push hook or CI. In this repository that is
-   `npm run check:rules`, run by the pre-push hook; a repo without such a script
-   verifies these requirements by review instead.
+   committing and enforce it in a git hook and CI. In this repository that is
+   `npm run check:rules`, run by the pre-commit hook and CI; a repo without such
+   a script verifies these requirements by review instead.
 
 ### Acceptance Criteria
 
diff --git a/docs/rules/DEV-380.md b/docs/rules/DEV-380.md
index 7e6d645..2b41cb6 100644
--- a/docs/rules/DEV-380.md
+++ b/docs/rules/DEV-380.md
@@ -1,6 +1,6 @@
 ---
 id: DEV-380
-title: "Enforce Markdown Lint on Push With a Pinned rumdl Hook"
+title: "Enforce Markdown Lint on Commit With a Pinned rumdl Hook"
 status: "active"
 enforcement: "automated"
 severity: "error"
@@ -9,31 +9,38 @@ severity: "error"
 ## Problem
 
 If lint runs from whatever `rumdl` a contributor has installed, versions format
-the same file differently and pushes get blocked by unrelated reformatting. If
-it is not enforced at all, malformed markdown lands unchecked.
+the same file differently and contributors get blocked by unrelated
+reformatting. If it is not enforced at all, malformed markdown lands unchecked.
 
 ## Solution
 
 Make lint automatic and version-stable, from the npm-pinned `rumdl` only.
 
 1. Pin `rumdl` as a devDependency, so everyone runs the same version and avoids
-   the version drift that blocks pushes with unrelated reformatting.
+   the version drift that blocks work with unrelated reformatting.
 1. Install the hooks with [lefthook](https://lefthook.dev), pinned as a
    devDependency, and run `lefthook install` in `postinstall`, so the hooks
    install on `npm install`. A hand-written hook script re-implements which
-   files a push changes, and that logic drifts and breaks on new branches.
-1. In `lefthook.yml`, add a `pre-push` command that runs the pinned binary
+   files changed, and that logic drifts and breaks on new branches.
+1. In `lefthook.yml`, add a `pre-commit` command that runs the pinned binary
    (`node_modules/.bin/rumdl check --fix`), never a global one, over
-   `{push_files}`, and set `fail_on_changes: always` so the push is blocked if
-   it reformats anything.
-1. Run the same `lefthook.yml` in CI, so a push that skipped the hook is still
-   checked, and the check lives in one place.
+   `{staged_files}`, with `stage_fixed: true` so the fixes go into the same
+   commit. Check at commit, not at push: the staged files are an exact list,
+   while the files a push changes depend on the local base branch and on which
+   branch is checked out.
+1. Load an `rc` script that finds `node` and the repository's own lefthook, and
+   skips with a one-line note when they are missing, so a checkout without
+   `npm install` is never blocked.
+1. Run the same `lefthook.yml` in CI on the files the pull request changes
+   (`lefthook run pre-commit --files-from-stdin`, with `fail_on_changes: ci`),
+   so a commit that skipped the hook still cannot merge.
 
 ### Acceptance Criteria
 
 - [ ] `rumdl` is pinned in `devDependencies`
 - [ ] `postinstall` runs `lefthook install`
-- [ ] `lefthook.yml` runs `node_modules/.bin/rumdl` on `{push_files}`, not a
-  global binary
-- [ ] CI runs the same `lefthook.yml`
-- [ ] A push containing a lint violation is blocked until it is fixed
+- [ ] `lefthook.yml` runs `node_modules/.bin/rumdl` on `{staged_files}` in
+  `pre-commit`, not a global binary
+- [ ] A commit's own lint fixes land in that commit
+- [ ] CI runs the same `lefthook.yml` and fails a pull request with a lint
+  violation
diff --git a/lefthook.yml b/lefthook.yml
index 808c388..ee98f84 100644
--- a/lefthook.yml
+++ b/lefthook.yml
@@ -1,32 +1,40 @@
 # Git hooks for this repo, managed by lefthook (https://lefthook.dev).
 # `npm install` installs them. This file is the one place to edit hook logic:
-# git runs it on every push, and CI runs the same commands on every PR.
+# git runs it on every commit, and CI runs the same commands on every PR.
+#
+# Checks run at commit time on the staged files: that list is exact, so a
+# commit is never blocked by a file it does not touch. rumdl's fixes go into
+# the same commit. Skip once with `LEFTHOOK=0 git commit`; CI still checks.
 
-pre-push:
-  # rumdl --fix rewrites files in place. Fail the push when it did, so the
-  # fixes get committed instead of pushed around.
-  fail_on_changes: always
-  fail_on_changes_diff: true
+# Finds node and this checkout's lefthook, or skips with a note when the
+# checks cannot run here (no `npm install` yet). CI still checks the PR.
+rc: scripts/hook-env.sh
+
+pre-commit:
+  # Locally rumdl's fixes are staged into the commit. In CI nothing may change.
+  fail_on_changes: ci
   commands:
     markdown:
-      # {push_files} is what this push adds. On a branch with no upstream yet
-      # lefthook diffs against the default branch, not the whole repo.
       glob: "*.md"
       # The npm-pinned rumdl only, never a global one: versions format
-      # differently and would block pushes with unrelated reformatting.
-      run: node_modules/.bin/rumdl check --fix {push_files}
+      # differently and would reformat files inconsistently.
+      run: node_modules/.bin/rumdl check --fix {staged_files}
+      stage_fixed: true
       priority: 1
     rules:
-      # Authoring standard for the rules this push touches, so a push is
+      # Authoring standard for the rules this commit touches, so a commit is
       # blocked by its own rules, never by pre-existing ones.
       glob: "docs/rules/*.md"
-      run: node scripts/check-rules.mjs --rules {push_files}
+      run: node scripts/check-rules.mjs --rules {staged_files}
       priority: 2
     rules-system:
       # Cross-file invariants (dependencies, index, reachability) over the whole
-      # tree, on any push. `--rules` with no names keeps the authoring standard
-      # out of scope. lefthook skips every pre-push command when a push only
-      # deletes files, so hooks.yml also runs this outside lefthook: deleting a
-      # rule is exactly what breaks these invariants.
+      # tree, whenever a doc changes. No file list on purpose: lefthook then
+      # also runs this for a commit that only deletes a doc, which is exactly
+      # what breaks these invariants. `--rules` with no names keeps the
+      # authoring standard out of scope.
+      glob:
+        - "docs/**"
+        - "README.md"
       run: node scripts/check-rules.mjs --rules
       priority: 3
diff --git a/scripts/hook-env.sh b/scripts/hook-env.sh
new file mode 100644
index 0000000..31fbb96
--- /dev/null
+++ b/scripts/hook-env.sh
@@ -0,0 +1,24 @@
+# Sourced by every git hook before lefthook runs (see `rc` in lefthook.yml).
+
+# GUI git clients such as GitHub Desktop start without the shell's PATH, so
+# node from nvm or Homebrew is missing. Add the usual locations.
+if ! command -v node >/dev/null 2>&1; then
+  for dir in /opt/homebrew/bin /usr/local/bin; do
+    [ -x "$dir/node" ] && PATH="$dir:$PATH"
+  done
+fi
+if ! command -v node >/dev/null 2>&1 && [ -d "$HOME/.nvm/versions/node" ]; then
+  PATH="$(ls -d "$HOME/.nvm/versions/node"/*/bin | tail -1):$PATH"
+fi
+export PATH
+
+# Point the hook at this checkout's lefthook. Without this, lefthook's own
+# lookup breaks on paths with spaces and falls through to unrelated tools
+# (such as Mintlify's `mint`). When the checks cannot run here, say so and let
+# the commit through: CI runs the same checks on the PR.
+if ! command -v node >/dev/null 2>&1 || [ ! -x node_modules/.bin/lefthook ]; then
+  echo "git hooks skipped: run \`npm install\` in this checkout (CI still checks)." >&2
+  exit 0
+fi
+LEFTHOOK_BIN=node_modules/.bin/lefthook
+export LEFTHOOK_BIN