diff --git a/.github/ci/minio/Dockerfile b/.github/ci/minio/Dockerfile
new file mode 100644
index 00000000000..79fe0e8e350
--- /dev/null
+++ b/.github/ci/minio/Dockerfile
@@ -0,0 +1,16 @@
+# CI-only AMD64 image. Versions match the development Compose services.
+# Upstream registries deny pulls; official release binaries remain available.
+FROM alpine:3.22.6@sha256:5291449c3df73caf6ed85e649dec1b9e818b39a5d8c871e97afc13e9cd5e8fa8
+
+LABEL org.opencontainers.image.source="https://github.com/block/buzz" \
+      org.opencontainers.image.title="Buzz CI MinIO" \
+      org.opencontainers.image.licenses="AGPL-3.0-only"
+
+RUN apk add --no-cache ca-certificates curl
+
+ADD --checksum=sha256:7c5bd8512c6e966455b1d198209358b2d191c77a83ab377c4073281065fb855f --chmod=755 \
+    https://github.com/minio/minio/releases/download/RELEASE.2025-09-07T16-13-09Z/minio.linux-amd64.RELEASE.2025-09-07T16-13-09Z /usr/local/bin/minio
+ADD --checksum=sha256:01f866e9c5f9b87c2b09116fa5d7c06695b106242d829a8bb32990c00312e891 --chmod=755 \
+    https://github.com/minio/mc/releases/download/RELEASE.2025-08-13T08-35-41Z/mc.linux-amd64.RELEASE.2025-08-13T08-35-41Z /usr/local/bin/mc
+
+ENTRYPOINT ["minio"]
diff --git a/.github/ci/minio/README.md b/.github/ci/minio/README.md
new file mode 100644
index 00000000000..51bf7c70a25
--- /dev/null
+++ b/.github/ci/minio/README.md
@@ -0,0 +1,51 @@
+# Buzz CI MinIO
+
+`ghcr.io/block/buzz-minio:latest` contains MinIO and `mc` for the disposable
+Linux AMD64 CI runners. `docker-compose.ci.yml` selects it for both services;
+development and deployment defaults stay in `docker-compose.yml`.
+
+The **MinIO image** workflow builds only when its inputs change, or on a manual
+dispatch. Pull requests build and smoke-test without publishing. On `main`, a
+successful smoke test publishes the same image as
+`sha-<full commit>-run-<run id>-<attempt>` and `latest`. The run-specific tag
+preserves each build, including package refreshes from the same source commit.
+Once consumers adopt the override, ordinary CI only pulls it; there is no build
+fallback or dependency on the publisher. `latest` deliberately floats, and
+Compose always pulls it. Docker's pull output records the resolved digest.
+
+The Dockerfile uses the same upstream releases as the development services,
+with checksummed official GitHub release binaries and a digest-pinned Alpine
+base. MinIO and `mc` are AGPL-3.0; their corresponding source is available at
+the [MinIO release](https://github.com/minio/minio/tree/RELEASE.2025-09-07T16-13-09Z)
+and [mc release](https://github.com/minio/mc/tree/RELEASE.2025-08-13T08-35-41Z).
+
+## First publication
+
+The image must exist and be publicly pullable before the CI switch can pass.
+Use two separate PRs: Buzz only permits squash merges, so two commits in one
+PR cannot stage this rollout.
+
+1. Merge the publisher-only PR containing `.github/ci/minio/`,
+   `.github/workflows/minio-image.yml`, and the opt-in `docker-compose.ci.yml`.
+   Ordinary CI does not select the override yet, so it does not need this image
+   to validate the publisher PR. The merge triggers the first publication.
+2. After publication succeeds, an org/package admin must make **buzz-minio**
+   public in its GitHub package settings (new GHCR packages default to private,
+   even for public repositories). Verify an anonymous pull of
+   `ghcr.io/block/buzz-minio:latest`.
+3. Rebase the separate consumer PR onto `main`, run its integration checks, and
+   merge it. That PR selects the override in relay and mesh lifecycle CI.
+
+Subsequent publications preserve package visibility.
+
+## Updating or rebuilding
+
+Update the release URLs/checksums or base digest in the Dockerfile and open a
+PR. Merging triggers publication. To rebuild the existing recipe (for example,
+to pick up Alpine package updates), dispatch **MinIO image** from `main`.
+Manual dispatch disables Docker's layer cache so the package installation
+runs again. Other refs can build and test but cannot publish `latest`.
+
+To reproduce a CI run with a recorded version, set `MINIO_CI_IMAGE` to
+the published run-specific tag or digest while using
+`COMPOSE_FILE=docker-compose.yml:docker-compose.ci.yml`.
diff --git a/.github/ci/minio/smoke-test.sh b/.github/ci/minio/smoke-test.sh
new file mode 100644
index 00000000000..c04f1c0cf1f
--- /dev/null
+++ b/.github/ci/minio/smoke-test.sh
@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# Run on a disposable Docker host with the CI Compose files and a built image.
+set -euo pipefail
+: "${MINIO_CI_IMAGE:?Set MINIO_CI_IMAGE to the locally built image}"
+: "${COMPOSE_FILE:?Select docker-compose.yml and docker-compose.ci.yml}"
+
+# Exercise the real healthcheck and initializer without pulling over the image
+# under test. No application services or tests need a MinIO build step.
+docker compose up -d --wait --wait-timeout 90 --pull never minio
+docker compose run --rm --no-deps --pull never minio-init
+docker compose exec -T minio sh -eu -c '
+  minio --version
+  mc --version
+  mc alias set local http://localhost:9000 buzz_dev buzz_dev_secret
+  printf "buzz-minio-smoke\n" > /tmp/expected
+  mc cp /tmp/expected local/buzz-media/smoke-test
+  mc cat local/buzz-media/smoke-test > /tmp/actual
+  cmp /tmp/expected /tmp/actual
+  status=$(curl --silent --show-error --output /dev/null --write-out "%{http_code}" \
+    http://localhost:9000/buzz-media/smoke-test)
+  test "$status" = 403
+  mc rm local/buzz-media/smoke-test
+  if mc stat local/buzz-media/smoke-test; then
+    echo "Deleted object is still present" >&2
+    exit 1
+  fi
+'
diff --git a/.github/workflows/_ci-relay.yml b/.github/workflows/_ci-relay.yml
index 5fa7eb53c25..dadbcd5881f 100644
--- a/.github/workflows/_ci-relay.yml
+++ b/.github/workflows/_ci-relay.yml
@@ -207,6 +207,8 @@ jobs:
             --archive-file target/ci/postgres-tests.tar.zst
 
   desktop-e2e-integration-shard:
+    env:
+      COMPOSE_FILE: docker-compose.yml:docker-compose.ci.yml
     name: Desktop E2E Integration (${{ matrix.shard }}/2)
     runs-on: ubuntu-latest
     timeout-minutes: 20
@@ -400,6 +402,8 @@ jobs:
           echo "Desktop E2E Integration shards passed"
 
   backend-integration:
+    env:
+      COMPOSE_FILE: docker-compose.yml:docker-compose.ci.yml
     name: Backend Integration (relay e2e)
     runs-on: ubuntu-latest
     timeout-minutes: 20
@@ -541,6 +545,8 @@ jobs:
           if-no-files-found: ignore
 
   relay-e2e:
+    env:
+      COMPOSE_FILE: docker-compose.yml:docker-compose.ci.yml
     name: Relay E2E
     runs-on: ubuntu-latest
     timeout-minutes: 20
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a663ef957c5..eb870baed26 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -55,6 +55,8 @@ jobs:
               - 'deny.toml'
               - '.github/workflows/ci.yml'
               - '.github/workflows/_ci-*.yml'
+              - 'docker-compose.yml'
+              - 'docker-compose.ci.yml'
               - 'scripts/run-tests.sh'
               - 'scripts/model-capabilities.json'
               - 'scripts/normative-corpus.json'
diff --git a/.github/workflows/mesh-lifecycle.yml b/.github/workflows/mesh-lifecycle.yml
index c699439980b..1b311574b64 100644
--- a/.github/workflows/mesh-lifecycle.yml
+++ b/.github/workflows/mesh-lifecycle.yml
@@ -22,6 +22,8 @@ on:
       - 'scripts/ci-mesh-lifecycle-smoke.sh'
       - 'scripts/start-relay-for-tests.sh'
       - '.github/workflows/mesh-lifecycle.yml'
+      - 'docker-compose.yml'
+      - 'docker-compose.ci.yml'
   pull_request:
     paths:
       - 'crates/buzz-relay/examples/mesh_*.rs'
@@ -34,6 +36,8 @@ on:
       - 'scripts/ci-mesh-lifecycle-smoke.sh'
       - 'scripts/start-relay-for-tests.sh'
       - '.github/workflows/mesh-lifecycle.yml'
+      - 'docker-compose.yml'
+      - 'docker-compose.ci.yml'
   workflow_dispatch:
 
 concurrency:
@@ -45,6 +49,8 @@ env:
 
 jobs:
   lifecycle-smoke:
+    env:
+      COMPOSE_FILE: docker-compose.yml:docker-compose.ci.yml
     name: Relay-Driven Mesh Lifecycle Smoke
     runs-on: ubuntu-24.04
     timeout-minutes: 45
diff --git a/.github/workflows/minio-image.yml b/.github/workflows/minio-image.yml
new file mode 100644
index 00000000000..5a9e970dc64
--- /dev/null
+++ b/.github/workflows/minio-image.yml
@@ -0,0 +1,80 @@
+name: MinIO image
+
+# A separate publisher, never a dependency of ordinary CI. Image changes get
+# a build/smoke test on PRs; only reviewed main commits can move :latest.
+on:
+  push:
+    branches: [main]
+    paths:
+      - '.github/ci/minio/**'
+      - '.github/workflows/minio-image.yml'
+      - 'docker-compose.yml'
+      - 'docker-compose.ci.yml'
+  pull_request:
+    paths:
+      - '.github/ci/minio/**'
+      - '.github/workflows/minio-image.yml'
+      - 'docker-compose.yml'
+      - 'docker-compose.ci.yml'
+  workflow_dispatch:
+
+concurrency:
+  group: minio-image-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+permissions:
+  contents: read
+
+env:
+  IMAGE_NAME: ghcr.io/block/buzz-minio
+  COMPOSE_FILE: docker-compose.yml:docker-compose.ci.yml
+  MINIO_CI_IMAGE: ghcr.io/block/buzz-minio:sha-${{ github.sha }}-run-${{ github.run_id }}-${{ github.run_attempt }}
+
+jobs:
+  image:
+    name: Build and smoke-test MinIO
+    runs-on: ubuntu-24.04
+    timeout-minutes: 15
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+        with:
+          persist-credentials: false
+      - uses: docker/setup-buildx-action@d7f5e7f509e45cec5c76c4d5afdd7de93d0b3df5 # v4.1.0
+      - name: Build image
+        uses: docker/build-push-action@f9f3042f7e2789586610d6e8b85c8f03e5195baf # v7.2.0
+        with:
+          context: .github/ci/minio
+          platforms: linux/amd64
+          load: true
+          tags: ${{ env.MINIO_CI_IMAGE }}
+          labels: org.opencontainers.image.revision=${{ github.sha }}
+          # A maintenance dispatch must refresh apk packages even with a warm
+          # layer cache. Normal image changes can still reuse cached layers.
+          no-cache: ${{ github.event_name == 'workflow_dispatch' }}
+          cache-from: type=gha,scope=minio
+          cache-to: type=gha,scope=minio,mode=max
+      - name: Smoke-test CI services
+        run: bash .github/ci/minio/smoke-test.sh
+      - name: Clean up smoke test
+        if: always()
+        run: docker compose down --volumes
+      - name: Log in to GHCR
+        if: github.repository == 'block/buzz' && github.ref == 'refs/heads/main' && github.event_name != 'pull_request'
+        uses: docker/login-action@650006c6eb7dba73a995cc03b0b2d7f5ca915bee # v4.2.0
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Publish tested image
+        if: github.repository == 'block/buzz' && github.ref == 'refs/heads/main' && github.event_name != 'pull_request'
+        run: |
+          docker push "$MINIO_CI_IMAGE"
+          docker tag "$MINIO_CI_IMAGE" "$IMAGE_NAME:latest"
+          docker push "$IMAGE_NAME:latest"
+          {
+            echo "Published $MINIO_CI_IMAGE and $IMAGE_NAME:latest"
+            echo 'First publication: make the buzz-minio package public before enabling CI consumers.'
+          } >> "$GITHUB_STEP_SUMMARY"
diff --git a/deploy/charts/buzz/ci/quickstart-values.yaml b/deploy/charts/buzz/ci/quickstart-values.yaml
index 4dcf6bcd21b..1a7f4d58389 100644
--- a/deploy/charts/buzz/ci/quickstart-values.yaml
+++ b/deploy/charts/buzz/ci/quickstart-values.yaml
@@ -9,6 +9,8 @@ redis:
   enabled: true
 minio:
   enabled: true
+  image: ghcr.io/block/buzz-minio:latest
+  mcImage: ghcr.io/block/buzz-minio:latest
 relayUrl: wss://buzz.test.local
 ownerPubkey: "0000000000000000000000000000000000000000000000000000000000000001"
 relay:
diff --git a/docker-compose.ci.yml b/docker-compose.ci.yml
new file mode 100644
index 00000000000..9fe6e7a9a8e
--- /dev/null
+++ b/docker-compose.ci.yml
@@ -0,0 +1,12 @@
+# CI pulls the published image; only minio-image.yml builds it.
+# MINIO_CI_IMAGE lets the publisher smoke-test an unpublished image or an
+# operator reproduce a run with its recorded run-specific tag/digest.
+services:
+  minio:
+    image: ${MINIO_CI_IMAGE:-ghcr.io/block/buzz-minio:latest}
+    platform: linux/amd64
+    pull_policy: always
+  minio-init:
+    image: ${MINIO_CI_IMAGE:-ghcr.io/block/buzz-minio:latest}
+    platform: linux/amd64
+    pull_policy: always