diff --git a/.github/workflows/README.md b/.github/workflows/README.md
index ad8a9d8..e5a291a 100644
--- a/.github/workflows/README.md
+++ b/.github/workflows/README.md
@@ -4,7 +4,7 @@ Shared [reusable workflows](https://docs.github.com/en/actions/sharing-automatio
 
 The `OTFABRIC_READ_TOKEN` secret gives access to private `github.com/otfabric/*` modules. In `go-ci.yml` it is needed when a module has private dependencies, and by the policy job when `.otfabric/policy.yaml` exists. The token must be able to read `otfabric/engineering`.
 
-**Permissions.** The organisation's default `GITHUB_TOKEN` is read-only, and a caller must grant at least what a called workflow requests, or the run fails at startup with no job started. Grant `contents: read` and `id-token: write` for `go-ci.yml` (Codecov OIDC), and `contents: write` for the release workflows.
+**Permissions.** The organisation's default `GITHUB_TOKEN` is read-only, and a caller must grant at least what a called workflow requests, or the run fails at startup with no job started. Grant `contents: read` and `id-token: write` for `go-ci.yml` (Codecov OIDC), `contents: read` for `docs-check.yml`, and `contents: write` for the release workflows.
 
 **Versions.** `v3` turns on govulncheck, tests `cmd/`, uses atomic coverage and starts the matrix at the go directive. `v2` and `v2.1.0` were moved to the same commit by the maintainer on 2026-10-30, so they have these defaults too.
 
@@ -19,6 +19,7 @@ Reusable workflows share whole pipelines (the caller's job is `uses:` one of the
 | [`go-ci.yml`](go-ci.yml) | Lint, static analysis, coverage, and multi-version test matrix |
 | [`go-package-release.yml`](go-package-release.yml) | Semver-tagged release for Go libraries / packages |
 | [`go-binary-release.yml`](go-binary-release.yml) | Cross-compiled binary release with SHA-256 checksums |
+| [`docs-check.yml`](docs-check.yml) | [docsync](https://github.com/otfabric/docsync) and otfabric-policy, on every push, Markdown-only ones included |
 
 ## Which workflows to use
 
@@ -148,6 +149,56 @@ Both release workflows support an optional `RELEASE.md` file in the repo root. W
 
 Sections are delimited by `---`. Only the section matching the tag being released is extracted.
 
+## Markdown-only changes
+
+A push or pull request that changes only Markdown needs no build, tests or
+interop run. The heavy workflows of a repository skip it:
+
+```yaml
+on:
+  push:
+    branches: [main]
+    paths-ignore: ['**/*.md']
+  pull_request:
+    paths-ignore: ['**/*.md']
+```
+
+A workflow that checks a generated Markdown file (for example `OBJECTS.md`)
+lists it instead: `paths: ['**', '!**/*.md', 'OBJECTS.md']`. Tag pushes and
+`workflow_dispatch` are never filtered.
+
+The documents are still checked: `docs-check.yml` runs on every push and pull
+request, with no path filter, so the Docs and Policy checks always report. A
+branch protection rule must require those, never a job of a workflow that a
+path filter can skip: a skipped required workflow leaves the check pending.
+
+```yaml
+# .github/workflows/docs.yml
+name: Docs
+on:
+  push:
+    branches: [main]
+  pull_request:
+permissions:
+  contents: read
+jobs:
+  docs:
+    uses: otfabric/.github/.github/workflows/docs-check.yml@v3
+    secrets: inherit
+```
+
+| Input | Default | Description |
+|-------|---------|-------------|
+| `module-dir` | `.` | Directory of the Go module docsync checks |
+| `docsync-version` | `v0.1.0` | Tag of `otfabric/docsync` to run |
+| `mode` | `enforce` | `warn` turns findings into warnings; a docsync error fails in both modes |
+| `run-policy` | `true` | Run `otfabric-policy`, as in `go-ci.yml` |
+| `policy-version` | `v1.3.0` | Tag of `otfabric/engineering` whose `otfabric-policy` to run |
+| `timeout-minutes` | `15` | Job timeout |
+
+With the Policy job here, a repository that calls both can set
+`run-policy: false` in `go-ci.yml`.
+
 ## Inputs reference
 
 Each workflow's inputs are fully documented with descriptions inside the YAML files themselves. Key inputs worth highlighting:
diff --git a/.github/workflows/docs-check.yml b/.github/workflows/docs-check.yml
new file mode 100644
index 0000000..270a823
--- /dev/null
+++ b/.github/workflows/docs-check.yml
@@ -0,0 +1,237 @@
+# yaml-language-server: $schema=https://json.schemastore.org/github-workflow.json
+#
+# Docs Check — Reusable Workflow
+#
+# Checks that a Go module's documents say what its code does, with
+# otfabric/docsync, and runs otfabric-policy. It is cheap, so it runs on every
+# push and pull request, including those that change Markdown only, which the
+# heavy workflows skip with paths-ignore. That makes its jobs the ones a
+# branch protection rule can require.
+#
+# Jobs:
+#   docsync  — docsync check in module-dir, annotations and a summary.
+#   policy   — Optional (run-policy), otfabric-policy on repositories with
+#              .otfabric/policy.yaml, as in go-ci.yml.
+#
+# Caller example (.github/workflows/docs.yml):
+#
+#   name: Docs
+#   on:
+#     push:
+#       branches: [main]
+#     pull_request:
+#   permissions:
+#     contents: read
+#   jobs:
+#     docs:
+#       uses: otfabric/.github/.github/workflows/docs-check.yml@v3
+#       secrets: inherit
+
+name: Docs Check
+
+on:
+  workflow_call:
+    inputs:
+      module-dir:
+        description: "Directory of the Go module to check."
+        required: false
+        type: string
+        default: "."
+      docsync-version:
+        description: "Tag of otfabric/docsync to run."
+        required: false
+        type: string
+        default: "v0.1.0"
+      mode:
+        description: >-
+          enforce: findings fail the job. warn: findings are annotations and
+          the job passes. A docsync error (exit code 2 or more) fails the job
+          in both modes.
+        required: false
+        type: string
+        default: "enforce"
+      timeout-minutes:
+        description: "Job timeout in minutes."
+        required: false
+        type: number
+        default: 15
+      run-policy:
+        description: >-
+          Run otfabric-policy on the repository root, in its own job, when
+          .otfabric/policy.yaml exists. Needs OTFABRIC_READ_TOKEN.
+        required: false
+        type: boolean
+        default: true
+      policy-version:
+        description: "Tag of otfabric/engineering whose otfabric-policy to run."
+        required: false
+        type: string
+        default: "v1.3.0"
+    secrets:
+      OTFABRIC_READ_TOKEN:
+        description: >-
+          PAT with read access to private github.com/otfabric/* modules.
+          docsync type-checks the documents' Go blocks against the module, so
+          it loads the module's dependencies; the policy job fetches
+          otfabric-policy. Forks and Dependabot never have it.
+        required: false
+
+permissions:
+  contents: read
+
+env:
+  GOPRIVATE: github.com/otfabric/*
+
+concurrency:
+  group: docs-check-${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}-${{ inputs.module-dir }}
+  cancel-in-progress: true
+
+jobs:
+  docsync:
+    name: Docs
+    runs-on: ubuntu-latest
+    timeout-minutes: ${{ inputs.timeout-minutes }}
+    permissions:
+      contents: read
+    defaults:
+      run:
+        working-directory: ${{ inputs.module-dir }}
+
+    steps:
+      # The tags and history: DS-SEC compares SECURITY.md with the latest
+      # tag, DS-REL compares RELEASE.md with the commit dates.
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+
+      # docsync needs Go 1.26; the module's go directive only sets a floor,
+      # and the type check of the documents runs on the toolchain it is given.
+      - name: Set up Go
+        uses: actions/setup-go@v7
+        with:
+          go-version: stable
+          cache: true
+          cache-dependency-path: |
+            ${{ inputs.module-dir }}/go.sum
+
+      - name: Configure private module access
+        shell: bash
+        env:
+          TOKEN: ${{ secrets.OTFABRIC_READ_TOKEN }}
+        run: |
+          if [ -n "${TOKEN}" ]; then
+            git config --global url."https://x-access-token:${TOKEN}@github.com/otfabric/".insteadOf "https://github.com/otfabric/"
+          fi
+
+      # Installed, not run with go run, which turns every exit code into 1.
+      - name: Install docsync
+        shell: bash
+        env:
+          GOWORK: "off"
+          VERSION: ${{ inputs.docsync-version }}
+        run: GOBIN="$RUNNER_TEMP/bin" go install "github.com/otfabric/docsync@${VERSION}"
+
+      # One run gives the annotations and the summary, so the module is loaded
+      # once. Exit code 1 means findings, 2 and above an error of docsync or
+      # of the configuration.
+      - name: docsync
+        shell: bash
+        env:
+          GOWORK: "off"
+          VERSION: ${{ inputs.docsync-version }}
+          MODE: ${{ inputs.mode }}
+        run: |
+          set +e -uo pipefail
+          case "$MODE" in enforce|warn) ;; *) echo "::error::mode must be enforce or warn, not '$MODE'"; exit 2 ;; esac
+          "$RUNNER_TEMP/bin/docsync" check --format github . > "$RUNNER_TEMP/docsync.txt"
+          code=$?
+          if [ "$MODE" = warn ]; then
+            sed 's/^::error /::warning /' "$RUNNER_TEMP/docsync.txt"
+          else
+            cat "$RUNNER_TEMP/docsync.txt"
+          fi
+          count=$(grep -c '^::error ' "$RUNNER_TEMP/docsync.txt" || true)
+          {
+            echo "### docsync ${VERSION}"
+            echo
+            if [ "$code" -eq 0 ]; then
+              echo "The documents agree with the code."
+            elif [ "$code" -eq 1 ]; then
+              echo "$count findings (mode: $MODE). Run \`go run github.com/otfabric/docsync@${VERSION} check .\` locally for the list."
+            else
+              echo "docsync failed with exit code $code; see the log."
+            fi
+          } >> "$GITHUB_STEP_SUMMARY"
+          if [ "$code" -eq 1 ] && [ "$MODE" = warn ]; then
+            exit 0
+          fi
+          exit "$code"
+
+  # As in go-ci.yml: the check is about the repository, so it runs at the
+  # root. A secret cannot be read in a job-level if, so a step decides.
+  policy:
+    name: Policy
+    if: inputs.run-policy
+    runs-on: ubuntu-latest
+    timeout-minutes: ${{ inputs.timeout-minutes }}
+    permissions:
+      contents: read
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - name: Decide whether the policy check runs
+        id: gate
+        shell: bash
+        env:
+          TOKEN: ${{ secrets.OTFABRIC_READ_TOKEN }}
+          EVENT: ${{ github.event_name }}
+          HEAD_REPO: ${{ github.event.pull_request.head.repo.full_name }}
+          REPO: ${{ github.repository }}
+          ACTOR: ${{ github.actor }}
+        run: |
+          set -euo pipefail
+          run=false
+          if [ ! -f .otfabric/policy.yaml ]; then
+            echo "::notice::otfabric-policy skipped: no .otfabric/policy.yaml"
+          elif [ "$EVENT" = pull_request ] && [ "$HEAD_REPO" != "$REPO" ]; then
+            echo "::notice::otfabric-policy skipped: pull request from a fork has no secrets"
+          elif [ -n "$TOKEN" ]; then
+            run=true
+          elif [ "$ACTOR" = 'dependabot[bot]' ]; then
+            echo "::notice::otfabric-policy skipped: Dependabot runs have no Actions secrets"
+          else
+            echo "::error::OTFABRIC_READ_TOKEN is empty, so otfabric-policy cannot be fetched. Pass it with 'secrets: inherit', or set run-policy: false."
+            exit 1
+          fi
+          echo "run=$run" >> "$GITHUB_OUTPUT"
+
+      - name: Set up Go
+        if: steps.gate.outputs.run == 'true'
+        uses: actions/setup-go@v7
+        with:
+          go-version: stable
+          cache: false
+
+      - name: Configure private module access
+        if: steps.gate.outputs.run == 'true'
+        shell: bash
+        env:
+          TOKEN: ${{ secrets.OTFABRIC_READ_TOKEN }}
+        run: git config --global url."https://x-access-token:${TOKEN}@github.com/otfabric/engineering".insteadOf "https://github.com/otfabric/engineering"
+
+      - name: otfabric-policy
+        if: steps.gate.outputs.run == 'true'
+        shell: bash
+        env:
+          GOWORK: "off"
+          GOPRIVATE: github.com/otfabric/engineering
+          VERSION: ${{ inputs.policy-version }}
+        run: |
+          set -euo pipefail
+          go run "github.com/otfabric/engineering/cmd/otfabric-policy@${VERSION}" check -format markdown . | tee -a "$GITHUB_STEP_SUMMARY"
diff --git a/.github/workflows/selftest.yml b/.github/workflows/selftest.yml
index 5e3f120..1dbe327 100644
--- a/.github/workflows/selftest.yml
+++ b/.github/workflows/selftest.yml
@@ -62,6 +62,25 @@ jobs:
       run-govulncheck: false
       run-policy: false
 
+  # docs-check.yml: a module whose documents agree with its code, enforced,
+  # with the policy job on.
+  docs-check-pass:
+    uses: ./.github/workflows/docs-check.yml
+    with:
+      module-dir: testdata/docs-check/pass
+      mode: enforce
+      policy-version: v1.2.0
+    secrets:
+      OTFABRIC_READ_TOKEN: ${{ secrets.OTFABRIC_READ_TOKEN }}
+
+  # A module with a finding passes in warn mode.
+  docs-check-warn:
+    uses: ./.github/workflows/docs-check.yml
+    with:
+      module-dir: testdata/docs-check/fail
+      mode: warn
+      run-policy: false
+
   matrix-floor:
     name: Matrix floor cases
     runs-on: ubuntu-latest
@@ -112,6 +131,18 @@ jobs:
       - uses: actions/checkout@v7
       - run: scripts/selftest/policy.sh
 
+  docs-check-modes:
+    name: Docs check cases
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v7
+      - uses: actions/setup-go@v7
+        with:
+          go-version: stable
+          cache: false
+      - run: scripts/selftest/docs-check.sh
+
   release-notes:
     name: Release notes extraction
     runs-on: ubuntu-latest
diff --git a/AGENTS.md b/AGENTS.md
index bfb5e59..43d21b6 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -2,7 +2,7 @@
 
 ## What this is
 
-The organisation's shared GitHub configuration: the reusable workflows `go-ci.yml`, `go-package-release.yml` and `go-binary-release.yml`, the composite actions for the `*-interop` repositories, the organisation profile page, and the selftest of the workflows. There is no product and no Go module of its own; the Go code under `testdata/` is fixtures. Every OT Fabric repository depends on this one, so a mistake here reaches all of them. Profile: **infrastructure**.
+The organisation's shared GitHub configuration: the reusable workflows `go-ci.yml`, `docs-check.yml`, `go-package-release.yml` and `go-binary-release.yml`, the composite actions for the `*-interop` repositories, the organisation profile page, and the selftest of the workflows. There is no product and no Go module of its own; the Go code under `testdata/` is fixtures. Every OT Fabric repository depends on this one, so a mistake here reaches all of them. Profile: **infrastructure**.
 
 ## Organisation standards
 
@@ -34,6 +34,7 @@ This repository follows **otfabric/engineering policy 1.2**, profile **infrastru
 | anything | `go run ./cmd/otfabric-policy check <this repository>` from otfabric/engineering |
 | `go-ci.yml` policy steps | `scripts/selftest/policy.sh` |
 | release notes extraction | `scripts/selftest/release-notes.sh` |
+| `docs-check.yml` docsync step | `scripts/selftest/docs-check.sh` |
 | a workflow | the Selftest workflow, on the pull request |
 
 There is no Makefile.
diff --git a/scripts/selftest/docs-check.sh b/scripts/selftest/docs-check.sh
new file mode 100755
index 0000000..1544c39
--- /dev/null
+++ b/scripts/selftest/docs-check.sh
@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+# Cases of the docsync step of docs-check.yml, run on the fixtures with the
+# exact step script. The reusable workflow cannot be called with
+# continue-on-error, so the failing case runs here.
+set -euo pipefail
+
+root=$(cd "$(dirname "$0")/../.." && pwd)
+work=$(mktemp -d)
+trap 'rm -rf "$work"' EXIT
+
+python3 "$root/scripts/selftest/extract-step.py" "$root/.github/workflows/docs-check.yml" docsync > "$work/step.sh"
+version=$(sed -nE '/docsync-version:/,/default:/s/^ *default: "(v[^"]+)"$/\1/p' "$root/.github/workflows/docs-check.yml")
+mkdir -p "$work/bin"
+GOBIN="$work/bin" GOWORK=off go install "github.com/otfabric/docsync@${version}"
+
+fail=0
+check() { # fixture mode want
+  local got=0
+  (cd "$root/testdata/docs-check/$1" && RUNNER_TEMP="$work" GITHUB_STEP_SUMMARY="$work/summary" VERSION="$version" MODE="$2" GOWORK=off bash -e "$work/step.sh") > "$work/out" 2>&1 || got=$?
+  if [ "$got" = "$3" ]; then
+    echo "ok   $1 $2: exit $got"
+  else
+    echo "FAIL $1 $2: exit $got, want $3"; cat "$work/out"; fail=1
+  fi
+}
+
+check pass enforce 0
+check fail enforce 1
+check fail warn 0
+check pass bogus 2
+grep -q '^::warning ' "$work/out" && { echo "FAIL a bad mode printed findings"; fail=1; }
+exit "$fail"
diff --git a/testdata/docs-check/fail/API.md b/testdata/docs-check/fail/API.md
new file mode 100644
index 0000000..9eb5531
--- /dev/null
+++ b/testdata/docs-check/fail/API.md
@@ -0,0 +1,3 @@
+# API
+
+`Hello(name string) string` returns a greeting; `greet.Goodbye` does not exist.
diff --git a/testdata/docs-check/fail/go.mod b/testdata/docs-check/fail/go.mod
new file mode 100644
index 0000000..3925dc6
--- /dev/null
+++ b/testdata/docs-check/fail/go.mod
@@ -0,0 +1,3 @@
+module example.com/fail
+
+go 1.23
diff --git a/testdata/docs-check/fail/greet.go b/testdata/docs-check/fail/greet.go
new file mode 100644
index 0000000..d92b9a1
--- /dev/null
+++ b/testdata/docs-check/fail/greet.go
@@ -0,0 +1,6 @@
+// Package greet is the fixture of the docs-check selftest: its documents
+// name a function it does not have, so docsync reports a finding.
+package greet
+
+// Hello returns a greeting for name.
+func Hello(name string) string { return "hello, " + name }
diff --git a/testdata/docs-check/pass/API.md b/testdata/docs-check/pass/API.md
new file mode 100644
index 0000000..fd1fd17
--- /dev/null
+++ b/testdata/docs-check/pass/API.md
@@ -0,0 +1,10 @@
+# API
+
+| Function | Returns |
+|---|---|
+| `Hello(name string) string` | A greeting for name |
+
+```go
+msg := greet.Hello("world")
+_ = msg
+```
diff --git a/testdata/docs-check/pass/go.mod b/testdata/docs-check/pass/go.mod
new file mode 100644
index 0000000..06587dc
--- /dev/null
+++ b/testdata/docs-check/pass/go.mod
@@ -0,0 +1,3 @@
+module example.com/pass
+
+go 1.23
diff --git a/testdata/docs-check/pass/greet.go b/testdata/docs-check/pass/greet.go
new file mode 100644
index 0000000..9abec48
--- /dev/null
+++ b/testdata/docs-check/pass/greet.go
@@ -0,0 +1,6 @@
+// Package greet is the fixture of the docs-check selftest: its documents
+// agree with its code.
+package greet
+
+// Hello returns a greeting for name.
+func Hello(name string) string { return "hello, " + name }