diff --git a/.changeset/release-dispatch-rerun.md b/.changeset/release-dispatch-rerun.md
new file mode 100644
index 00000000..a3dbcbf8
--- /dev/null
+++ b/.changeset/release-dispatch-rerun.md
@@ -0,0 +1,16 @@
+---
+"nostream": patch
+"nostream-website": patch
+---
+
+ci(release): allow the image build to be dispatched for an existing tag
+
+A published release is immutable, so when the image build fails while publishing
+it, the release cannot be re-published to retry: GitHub refuses the round trip
+with `immutable cannot be changed when release is immutable`. That left #964's
+release with no image and no way to build one.
+
+`release.yml` now accepts `workflow_dispatch` with a `tag` input, and refuses a
+tag that is not a relay release, since the event carries no tag of its own. With
+no release flags present the prerelease is read from the version, so a dispatch
+of `nostream@3.8.0-rc.1` still leaves `latest` where it is.
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 27e307be..8d43b158 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -3,6 +3,17 @@ name: Release
 on:
   release:
     types: [published]
+  # A published release is immutable, so a build that fails while publishing it
+  # cannot be retried by re-publishing the event that triggered it — GitHub
+  # refuses the draft/publish round trip with `immutable cannot be changed when
+  # release is immutable`. This is the only path to (re)build an image for a tag
+  # whose release already exists (#964).
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Relay release tag to build, e.g. nostream@3.7.0'
+        required: true
+        type: string
 
 jobs:
   build-and-push-image:
@@ -10,7 +21,7 @@ jobs:
     # nostream@X.Y.Z, website releases tag nostream-website@X.Y.Z. Only a relay
     # tag should build the relay container image. The v* branch is kept for the
     # releases cut before the repo moved to changesets tagging.
-    if: startsWith(github.event.release.tag_name, 'nostream@') || startsWith(github.event.release.tag_name, 'v')
+    if: github.event_name == 'workflow_dispatch' || startsWith(github.event.release.tag_name, 'nostream@') || startsWith(github.event.release.tag_name, 'v')
     name: Build and push container image
     runs-on: ubuntu-latest
     env:
@@ -22,6 +33,12 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3
+        # Build the code the tag names, not the branch the dispatch was started
+        # from. A release event already carries the tag as GITHUB_REF, so the
+        # input only overrides it; checking out `main` while pushing the image as
+        # `3.7.0` would publish the wrong source under a release version.
+        with:
+          ref: ${{ inputs.tag && format('refs/tags/{0}', inputs.tag) || github.ref }}
       - name: Log in to the Container registry
         uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
         with:
@@ -46,11 +63,18 @@ jobs:
         id: tags
         shell: bash
         env:
-          RELEASE_TAG: ${{ github.event.release.tag_name }}
+          RELEASE_TAG: ${{ github.event.release.tag_name || inputs.tag }}
           PRERELEASE: ${{ github.event.release.prerelease }}
         run: |
           set -euo pipefail
           image="$REGISTRY/$IMAGE_NAME"
+          # A dispatch has no release flags, so a tag that is not a relay release
+          # is refused here rather than built: `github.event.release.tag_name` is
+          # empty, and only this check stands between a typo and a pushed image.
+          case "$RELEASE_TAG" in
+            nostream@*|v*) ;;
+            *) echo "::error::not a relay release tag: '$RELEASE_TAG'"; exit 1 ;;
+          esac
           # `nostream@3.7.0` -> `3.7.0`; the pre-changesets form `v3.4.1` -> `3.4.1`.
           version="${RELEASE_TAG##*@}"
           version="${version#v}"
@@ -61,8 +85,16 @@ jobs:
             v*) tags="$tags,$image:$RELEASE_TAG" ;;
           esac
           # `latest` is the tag both deploy stacks pull, so a prerelease must not
-          # move it onto a test build.
-          if [ "$PRERELEASE" != "true" ]; then
+          # move it onto a test build. A release event states this directly; a
+          # dispatch does not, so a pre-release version is read from the tag.
+          prerelease="${PRERELEASE:-}"
+          if [ -z "$prerelease" ]; then
+            case "$version" in
+              *-*) prerelease=true ;;
+              *) prerelease=false ;;
+            esac
+          fi
+          if [ "$prerelease" != "true" ]; then
             tags="$tags,$image:latest"
           fi
           for tag in ${tags//,/ }; do
diff --git a/test/unit/ci/publish-container-image.spec.ts b/test/unit/ci/publish-container-image.spec.ts
index 3b1a9095..71289c6b 100644
--- a/test/unit/ci/publish-container-image.spec.ts
+++ b/test/unit/ci/publish-container-image.spec.ts
@@ -25,26 +25,30 @@ type Workflow = {
 // and a relay image built from the wrong commit, so it is exercised rather than
 // string-matched: a typo that still contains the right substring would pass a
 // `to.include` and skip every relay release.
-const evaluateReleaseGate = (tagName: string): boolean => {
+const evaluateReleaseGate = (tagName: string, isDispatch = false): boolean => {
   const expression =
     (load(
       readFileSync(join(process.cwd(), '.github', 'workflows', 'release.yml'), 'utf-8'),
     ) as Workflow).jobs['build-and-push-image'].if ?? ''
-  // Only the `startsWith(github.event.release.tag_name, '…')` clauses are used
-  // in this expression; anything else is a workflow change that needs review.
+  // Only two clause forms are allowed in this expression; anything else is a
+  // workflow change that needs review rather than a silent pass.
   const clauses = String(expression)
     .split('||')
     .map((clause) => clause.trim())
   const startsWith = (value: string, prefix: string) => value.startsWith(prefix)
-  // Translate the two GitHub expression forms into JavaScript.
-  const js = clauses
-    .map((clause) =>
-      clause.replace(/^startsWith\(github\.event\.release\.tag_name, '([^']*)'\)$/,
-        (_, prefix: string) => `startsWith(tagName, ${JSON.stringify(prefix)})`),
-    )
-    .join(' || ')
+  const toJs = (clause: string): string => {
+    const prefix = clause.match(/^startsWith\(github\.event\.release\.tag_name, '([^']*)'\)$/)
+    if (prefix) return `startsWith(tagName, ${JSON.stringify(prefix[1])})`
+    const event = clause.match(/^github\.event_name == '([^']*)'$/)
+    if (event) return `isDispatch === ${event[1] === 'workflow_dispatch'}`
+    throw new Error(`unsupported clause in the release gate: ${clause}`)
+  }
   // eslint-disable-next-line no-new-func
-  return new Function('tagName', 'startsWith', `return ${js}`)(tagName, startsWith) as boolean
+  return new Function('tagName', 'startsWith', 'isDispatch', `return ${clauses.map(toJs).join(' || ')}`)(
+    tagName,
+    startsWith,
+    isDispatch,
+  ) as boolean
 }
 
 // The tags are computed by a `run:` block, not by metadata-action's rules,
@@ -59,9 +63,10 @@ const tagStep = (workflow: Workflow): string => {
   return run
 }
 
-// Executes the step's own `run:` block with the two inputs it maps from the
-// release event, and returns the tags it wrote to the job output.
-const imageTags = (workflow: Workflow, releaseTag: string, prerelease: boolean): string[] => {
+// Executes the step's own `run:` block with the inputs it maps from the release
+// event, and returns the tags it wrote to the job output. `undefined` means a
+// `workflow_dispatch`, where the event carries no flags at all.
+const imageTags = (workflow: Workflow, releaseTag: string, prerelease?: boolean): string[] => {
   const dir = mkdtempSync(join(tmpdir(), 'release-tags-'))
   try {
     const out = join(dir, 'github-output')
@@ -73,7 +78,7 @@ const imageTags = (workflow: Workflow, releaseTag: string, prerelease: boolean):
         REGISTRY: 'ghcr.io',
         IMAGE_NAME: 'cameri/nostream',
         RELEASE_TAG: releaseTag,
-        PRERELEASE: String(prerelease),
+        ...(prerelease === undefined ? {} : { PRERELEASE: String(prerelease) }),
         GITHUB_OUTPUT: out,
       },
     })
@@ -127,6 +132,14 @@ describe('container image publishing workflow', () => {
     expect(evaluateReleaseGate('nostream-website@1.3.1')).to.equal(false)
   })
 
+  // A published release is immutable, so the build that publishes its image
+  // cannot be retried through the same event. The dispatch path is what makes a
+  // failed build recoverable; the step's own range check keeps it from building
+  // a non-relay tag, since a dispatch carries no release tag at all.
+  it('accepts a dispatched run so a failed build can be retried', () => {
+    expect(evaluateReleaseGate('', true)).to.equal(true)
+  })
+
   // The deploy path pulls `:latest`, so the release must actually push it.
   it('tags a stable release with its version and latest', () => {
     expect(imageTags(releaseWorkflow, 'nostream@3.7.0', false)).to.deep.equal(['3.7.0', 'latest'])
@@ -151,6 +164,36 @@ describe('container image publishing workflow', () => {
     expect(() => imageTags(releaseWorkflow, 'nostream@3.7.0+build', false)).to.throw(/not a legal Docker tag/)
   })
 
+  // A published release is immutable, so a failed build has to be re-runnable
+  // by hand — that is what workflow_dispatch exists for, and it carries no
+  // release flags for the step to read.
+  it('builds a dispatched tag with the same tags as the release event', () => {
+    expect(imageTags(releaseWorkflow, 'nostream@3.7.0')).to.deep.equal(['3.7.0', 'latest'])
+  })
+
+  // Without the event's flag the prerelease has to be read from the tag, or a
+  // dispatch of an rc silently moves `latest` onto a test build.
+  it('reads a prerelease out of a dispatched tag', () => {
+    expect(imageTags(releaseWorkflow, 'nostream@3.8.0-rc.1')).to.deep.equal(['3.8.0-rc.1'])
+  })
+
+  // `github.event.release.tag_name` is empty on a dispatch, so a mistyped input
+  // is the only thing that would otherwise reach the build.
+  it('refuses a dispatched tag that is not a relay release', () => {
+    expect(() => imageTags(releaseWorkflow, 'nostream-website@1.3.2')).to.throw(/not a relay release tag/)
+  })
+
+  // The image must be built from the code its tag names. A dispatch starts on a
+  // branch, so without this the default ref is checked out and that branch's
+  // HEAD is published as a release version. The expression itself only runs on
+  // GitHub, so this asserts its shape: the tag form for a dispatch, and the
+  // event's own ref when no input is present.
+  it('checks out the release tag rather than the dispatching branch', () => {
+    const step = (releaseWorkflow.jobs['build-and-push-image'].steps ?? []).find((entry) => entry.with?.ref)
+    const expression = (step?.with?.ref ?? '').replace(/^\$\{\{\s*/, '').replace(/\s*\}\}$/, '')
+    expect(expression, 'a dispatch must build the tag it was given').to.include("format('refs/tags/{0}', inputs.tag)")
+    expect(expression, 'a release event already carries its tag in github.ref').to.include('|| github.ref')
+  })
   it('builds with the tags the step computed', () => {
     const build = (releaseWorkflow.jobs['build-and-push-image'].steps ?? []).find((step) => step.with?.tags)
     expect(build?.with?.tags, 'the build must consume the computed tags').to.equal('${{ steps.tags.outputs.tags }}')