diff --git a/.github/workflows/pypi-publish.yml b/.github/workflows/pypi-publish.yml
index f811e46..2f44920 100644
--- a/.github/workflows/pypi-publish.yml
+++ b/.github/workflows/pypi-publish.yml
@@ -1,25 +1,33 @@
 name: Publish
 
+# Real publishes happen only on a v* tag push. workflow_dispatch is a dry run:
+# it builds and checks the package but never publishes, so who can release is
+# exactly who can push a v* tag (enforced by a tag ruleset), not who can click
+# "Run workflow".
+
 on:
+  push:
+    tags: ["v*"]
   workflow_dispatch:
-    inputs:
-      dry_run:
-        description: Run checks and package build without publishing
-        type: boolean
-        default: true
 
 permissions:
   contents: read
-  id-token: write
 
 concurrency:
   group: pypi-publish-${{ github.ref }}
   cancel-in-progress: false
 
 jobs:
-  publish:
+  # Always runs. On workflow_dispatch this is the whole thing (a dry run). On a
+  # v* tag push it also gates the publish job: the tag has to match the packaged
+  # version, and the build + checks have to pass, before anything is published.
+  # The artifact it uploads is exactly what gets published, so the bytes that
+  # reach PyPI are the bytes that were tested and twine-checked here.
+  build:
+    name: Build and check
     runs-on: tenki-standard-small-2c-4g
-    environment: pypi-publish
+    outputs:
+      published: ${{ steps.version.outputs.published }}
     steps:
       - name: Checkout
         uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
@@ -44,6 +52,18 @@ jobs:
       - name: Check package
         run: twine check dist/*
 
+      - name: Verify tag matches version
+        if: github.event_name == 'push'
+        run: |
+          set -euo pipefail
+          tag="${GITHUB_REF_NAME#v}"
+          version=$(python -c 'import tomllib; print(tomllib.load(open("pyproject.toml", "rb"))["project"]["version"])')
+          echo "tag=${tag} pyproject-version=${version}"
+          if [ "${tag}" != "${version}" ]; then
+            echo "::error::tag v${tag} does not match pyproject.toml version ${version}"
+            exit 1
+          fi
+
       - name: Check if version is already published
         id: version
         run: |
@@ -59,6 +79,32 @@ jobs:
             echo "published=false" >> "$GITHUB_OUTPUT"
           fi
 
+      - name: Upload distribution
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: dist
+          path: dist/
+          retention-days: 1
+          if-no-files-found: error
+
+  # Real publish. Only a v* tag push reaches this job, and it is the only one
+  # bound to the pypi-publish environment / OIDC trusted publisher. It runs no
+  # arbitrary code before the publish: it downloads the exact dist/ the build
+  # job tested and twine-checked, and publishes that.
+  publish:
+    name: Publish to PyPI
+    needs: build
+    if: ${{ github.event_name == 'push' && needs.build.outputs.published == 'false' }}
+    runs-on: tenki-standard-small-2c-4g
+    environment: pypi-publish
+    permissions:
+      id-token: write
+    steps:
+      - name: Download distribution
+        uses: actions/download-artifact@9000827ccba6bdab643e8b6fd33ac0654aef8333 # v8.0.2
+        with:
+          name: dist
+          path: dist/
+
       - name: Publish to PyPI
-        if: ${{ steps.version.outputs.published == 'false' && (github.event_name == 'push' || inputs.dry_run == false) }}
         uses: pypa/gh-action-pypi-publish@dc37677b2e1c63e2034f94d8a5b11f265b73ba33 # v1.14.2
diff --git a/docs/release-process.md b/docs/release-process.md
new file mode 100644
index 0000000..db2bbd8
--- /dev/null
+++ b/docs/release-process.md
@@ -0,0 +1,78 @@
+# Release Process
+
+How a version of the `tenki` SDK is published to PyPI. A release is an
+immutable artifact: a git tag `vX.Y.Z` and the matching
+[`tenki` X.Y.Z](https://pypi.org/project/tenki/) on PyPI. Pushing the tag is the
+only thing that publishes.
+
+## How a version number is chosen
+
+You do not hand-pick a version in this repository. The version in
+`pyproject.toml` is owned upstream and lands here through a
+`sync from tenki.app@<sha>` commit on `main` (for example `1.4.0 → 1.4.1`). A
+release tag always matches whatever `pyproject.toml` says on the commit being
+tagged — the publish workflow fails the release if they disagree.
+
+## How to cut a release
+
+Once the version you want to ship is on `main` (its `sync` commit has merged):
+
+```bash
+git checkout main && git pull --ff-only
+git tag v1.4.1          # must equal the pyproject.toml version on this commit
+git push origin v1.4.1
+```
+
+Pushing the `v*` tag triggers the **Publish** workflow. It runs the tests, builds
+the package, checks it, verifies the tag matches the packaged version, and then
+publishes to PyPI. If that version is already on PyPI the publish is skipped, so
+re-pushing a tag is safe.
+
+That is the whole job: push the tag.
+
+## Who can release
+
+Publishing is gated on **who can push a `v*` tag**, not on who can run a
+workflow:
+
+- A **tag ruleset** (`v*`, _Restrict creations_) limits tag creation to the
+  release managers on its bypass list. That list is the publish allowlist.
+- The **`pypi-publish` environment** is restricted to `v*` tags and is the only
+  thing bound to PyPI's OIDC trusted publisher.
+- Publishing uses **PyPI Trusted Publishing** (OIDC) — there is no long-lived API
+  token to leak, and the publish job mints a short-lived token scoped to this
+  workflow and environment. The upload is signed with PEP 740 attestations.
+
+## Dry run
+
+Running the **Publish** workflow manually (`workflow_dispatch`, from the Actions
+tab) builds, tests, and `twine check`s the package but **never publishes**. Use
+it to validate a build before tagging. Only a `v*` tag push can publish.
+
+## The flow end to end
+
+```mermaid
+graph TD
+    SYNC[sync from tenki.app: version bump] -->|merge| MAIN[main]
+    MAIN -->|git push origin vX.Y.Z| TAG[tag vX.Y.Z]
+    TAG -->|triggers Publish| BUILD[build: test, build, twine check, tag == version]
+    BUILD --> PUB[publish: download artifact, OIDC publish to PyPI]
+    PUB --> PYPI[tenki X.Y.Z on PyPI]
+```
+
+## The workflows
+
+| Workflow | File | Trigger | What it does |
+|----------|------|---------|--------------|
+| Test | `.github/workflows/test.yml` | every PR; push to test paths; manual dispatch | runs the protobuf-compatibility matrix; a `Test` gate reports on every PR |
+| Publish | `.github/workflows/pypi-publish.yml` | `v*` tag push (publishes); `workflow_dispatch` (dry run) | builds and checks the package, then publishes the tested artifact to PyPI |
+
+## How the published bytes are the tested bytes
+
+The **Publish** workflow is split in two jobs. The `build` job tests, builds, and
+`twine check`s the package, then uploads `dist/` as an artifact. The `publish`
+job — the only one holding `id-token: write` and bound to the `pypi-publish`
+environment — downloads that exact artifact and publishes it. It runs no
+checkout, `pip install`, or build, so no freshly resolved code executes in the
+job that can mint a trusted-publisher token, and what reaches PyPI is byte-for-byte
+what was tested.