feat(plex): opt into hardware.gpu: intel-quicksync, and write the runbook for the step GitOps cannot reach

Plex has been transcoding in software on hardware that can do it in the iGPU. This
opts its ServiceDefinition into the `hardware` capability from #27 and re-renders.

catalog/plex.yaml gains four lines of YAML and the comment that explains them:

    hardware:
      gpu: intel-quicksync

which renders exactly two things into apps/wave-0/plex.yaml and nothing else — a
`dri` hostPath volume (/dev/dri, type: DirectoryOrCreate) and a read-write /dev/dri
volumeMount on the app container. Whole-tree render diff: 6 added lines, one file.

The comment records what is not obvious from the four lines: the device exists on
ALL THREE prod nodes with i915 bound (so no nodeSelector is rendered and none is
wanted); why `supplementalGroups` would be INERT rather than a hardening (the
image's cont-init hook adds the plex user to the device's group inside the
container, and s6-setuidgid then REPLACES the process group list from /etc/group,
discarding anything Kubernetes supplied); and why `DirectoryOrCreate` is
load-bearing (apps-wave-0 is wait:true with apps-wave-1 depending on it, so a
failed mount would stall the whole app tier for a feature that is not).

THE FEATURE IS INERT UNTIL A HUMAN CLICKS A BOX, and that is the part this commit
is really about. Mounting the device does not enable hardware transcoding; Plex's
`HardwareAcceleratedCodecs` preference does, and it is ABSENT from Preferences.xml
— the toggle has never been on. It cannot be automated: a bounded grep across the
running image's entire init surface (/etc/cont-init.d, /etc/services.d,
/etc/fix-attrs.d, /plex-common.sh, /usr/local/bin) found ZERO PLEX_PREFERENCE*
support, and the six setPref keys the image does write are all unrelated. So
runbooks/plex-quicksync.md is the procedure, registered in the configMapGenerator
(a runbook in git with no generator entry is reviewed, merged, and still a 404) and
indexed in runbooks/README.md. It covers the GitOps/manual boundary, the toggle and
the real preference keys (including the widely-cited one that does not exist and
the upstream misspelling nobody should "fix"), verification via `Transcode (hw)` on
the Plex dashboard — stated plainly as the ONLY proof, because Plex renders no
ServiceMonitor and an alert could never fire — the device-cgroup failure to expect
first with its Intel-device-plugin fallback, and the floating-`:latest` caveat.

Stacked on #27 (feat/sd-hardware-capability), which is open and unmerged; that
branch's commit is in this range by design and this must merge after it.

NOT VERIFIED, and the handoff says so at length: hardware transcoding has not been
observed working. Whether containerd's device cgroup lets a non-privileged pod
open() a bind-mounted char device is an open question that only deploying settles,
and the Plex-side toggle was still unset at the time of writing. A green gate
proves the manifest renders; it proves nothing about transcoding.

Gate (pinned toolbox, worktree): rc 3 — UNDETERMINED, not green. Passed:
decisions-log, lint, l0, render-golden, l1, approval-policy. Skipped (the known
local ceiling): spec-immutability (no sibling spec repo), gitea-settings (no
SETTINGS_API_TOKEN), conformance (CLUSTER_AVAILABLE unset, so L2/L3 did not run).
No fourth skip, nothing failed.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

apps/wave-0/plex.yaml

@@ -143,6 +143,8 @@ spec:
         - name: media
           mountPath: /media
           readOnly: true
+        - name: dri
+          mountPath: /dev/dri
       volumes:
       - name: config
         persistentVolumeClaim:
@@ -150,6 +152,10 @@ spec:
       - name: media
         persistentVolumeClaim:
           claimName: plex-media
+      - name: dri
+        hostPath:
+          path: /dev/dri
+          type: DirectoryOrCreate
 ---
 # Service
 apiVersion: v1

catalog/plex.yaml

@@ -80,6 +80,58 @@ env:
   # remote access are UNVERIFIED. Advertising a wrong/internal-only URL breaks remote access for ALL
   # clients, so per "prefer safety over completeness" it is left unset. FOLLOW-UP: once remote
   # reachability through the Gateway is confirmed, set ADVERTISE_IP: "https://plex.home.keithjackson.dev:443".
+# HARDWARE TRANSCODING — the host iGPU's render device (schema 1.8.0 `hardware`; R-PLAT-02).
+# INTENT ONLY. This says "this workload needs an Intel Quick Sync render device"; it does NOT name a
+# device path. The renderer currently satisfies it with exactly two things — a `/dev/dri` hostPath
+# volume (`type: DirectoryOrCreate`) and a read-write `/dev/dri` volumeMount on the app container —
+# and nothing else: no nodeSelector, no privileged, no resources (schemas/renderer-contract.md
+# `### hardware`). If that mechanism is later replaced by the Intel GPU device plugin
+# (`gpu.intel.com/i915`), it is a `catalog/render.py` change and THIS BLOCK DOES NOT MOVE. Do not
+# "simplify" it into a raw `/dev/...` path; that is the whole point of the enum.
+#
+# THE DEVICE IS PRESENT ON EVERY PROD NODE, so nothing had to be installed and Plex can land
+# anywhere. Measured on all three nodes 2026-09-30: `/dev/dri/renderD128` present, `root:render`,
+# GID 992, mode 0660, driver `i915` bound (NOT `xe`), UHD Graphics 630 on an i7-9700T, media engines
+# `vcs0`/`vecs0` live, iGPU enabled in BIOS on each. Plex happens to run on k3s-prod-2 today, but
+# that is scheduler history rather than a requirement — this field deliberately renders no
+# nodeSelector, because placement is a separate concern with its own justification.
+#
+# NO `podSecurityContext.supplementalGroups`, AND ADDING ONE WOULD BE INERT — do not "fix" this.
+# The device is `root:render` 0660 and this process is uid/gid 1000, so the obvious move is to push
+# the host `render` GID in as a supplemental group. It cannot work here. MEASURED IN THE RUNNING
+# CONTAINER, 2026-09-30: the image's own
+# `/etc/cont-init.d/45-plex-hw-transcode-and-connected-tuner` stats every char device under
+# `/dev/dri`, `groupadd`s a matching group INSIDE the container when none exists, and
+# `usermod -a -G`s the `plex` user into it — every start, nothing hardcoded, which also makes a host
+# GID renumbering self-healing (no GID is pinned anywhere in this repo). The service then execs via
+# `s6-setuidgid plex`, and `s6-setuidgid` REPLACES the process group list from `/etc/group` rather
+# than appending to it: `Plex Media Server` runs with `Groups: 100 1000`, and root's gid `0` — which
+# PID 1 (`s6-svscan`) does hold — is GONE. Anything Kubernetes supplies therefore reaches s6-svscan
+# and is discarded before Plex ever starts. Mounting the device is sufficient; the group is the
+# image's job and it does it correctly. `render.py --selftest` asserts the ABSENCE of a pod
+# securityContext for this field precisely so nobody adds an inert one back later.
+#
+# `DirectoryOrCreate` IS THE SAFE FAILURE MODE, not laziness. A node that comes back without the
+# device (rebuild, BIOS reset, driver regression, hardware swap) gets an empty directory and Plex
+# degrades to SOFTWARE transcoding. `Directory` would fail the mount instead — and because
+# `apps-wave-0` is `wait: true` with `apps-wave-1` `dependsOn` it, that would stall the WHOLE app
+# tier for a feature that is not load-bearing. The price, stated plainly: a missing device is
+# SILENT. This SD renders no `metricsEndpoint`, so there is no ServiceMonitor, no transcode-mode
+# metric, and no alert that could ever fire. The only proof is an operator reading the Plex
+# dashboard.
+#
+# THE LAST MILE IS A MANUAL OPERATOR STEP AND CANNOT LIVE IN THIS REPO. Mounting the device does
+# not enable hardware transcoding — Plex's own `HardwareAcceleratedCodecs` preference does, and it
+# is ABSENT from `Preferences.xml` today (the toggle has never been on). NO environment variable can
+# set it: a grep of the running image's entire init surface (`/etc/cont-init.d`, `/etc/services.d`,
+# `/etc/fix-attrs.d`, `/plex-common.sh`, `/usr/local/bin`) found ZERO `PLEX_PREFERENCE*` support,
+# and the six prefs the image does write (`MachineIdentifier`, `ProcessedMachineIdentifier`,
+# `PlexOnlineToken`, `customConnections`, `allowedNetworks`, `TranscoderTempDirectory`) are all
+# unrelated. So there is no GitOps path to the toggle; an operator clicks it once in the web UI.
+# `runbooks/plex-quicksync.md` is that procedure, plus how to verify it took and the
+# device-cgroup failure mode to expect first.
+hardware:
+  gpu: intel-quicksync
 exposure: public              # edge port-forward + public DNS; clients + Seerr reach it (docs/09; R-DNS/R-NET)
 egress: internet              # normal WAN egress (docs/03; R-NET-05)
 storage:

decisions/2026-09-30-plex-quicksync.md

@@ -0,0 +1,149 @@
+---
+date: 2026-09-30
+branch: feat/plex-quicksync
+title: Plex opts into `hardware.gpu: intel-quicksync` — the device mount is GitOps, the Plex-side toggle is a documented manual step, and hardware transcoding has NOT been observed working
+---
+
+## What changed
+
+Three things, and the third is the point of the branch.
+
+1. **`catalog/plex.yaml`** — added the four lines the whole feature reduces to:
+
+   ```yaml
+   hardware:
+     gpu: intel-quicksync
+   ```
+
+   placed between `env` and `exposure` to match the schema's own property order, with ~48 lines of
+   comment in the file's established style. The comment records: the field is **intent, not
+   mechanism** (a later move to the Intel device plugin is a `render.py` change and this block does
+   not move); that `/dev/dri/renderD128` is present on **all three** prod nodes with `i915` bound;
+   **why a `supplementalGroups` entry would be inert** (the image's cont-init hook does the group
+   work inside the container and `s6-setuidgid` replaces the process group list from `/etc/group`);
+   why `DirectoryOrCreate` is the load-bearing safe failure mode (`apps-wave-0` is `wait: true` with
+   `apps-wave-1` depending on it, so a failed mount would stall the whole app tier for a feature
+   that is not load-bearing); and that the Plex-side toggle is a **separate manual operator step**,
+   pointing at the new runbook.
+
+2. **`apps/wave-0/plex.yaml`** — re-rendered. Six added lines, nothing else, in the whole `apps/`
+   tree:
+
+   ```
+           - name: dri
+             mountPath: /dev/dri
+         - name: dri
+           hostPath:
+             path: /dev/dri
+             type: DirectoryOrCreate
+   ```
+
+3. **`runbooks/plex-quicksync.md`** (new), registered in `runbooks/kustomization.yaml`'s
+   `configMapGenerator` as `- plex-quicksync=plex-quicksync.md` and indexed in `runbooks/README.md`
+   under "Operator procedures". **The file alone would have been a 404** — the pod serves a
+   ConfigMap, not the git tree, and `conformance/tests/l0-static/alert-runbooks-resolvable` exists
+   precisely because "the file is in git" and "the URL resolves" are different claims. The page
+   covers: the GitOps/manual boundary as a table; the toggle (Settings → Transcoder → "Use hardware
+   acceleration when available", preference key `HardwareAcceleratedCodecs`); the real neighbouring
+   keys and the widely-cited one that **does not exist**; that the only proof is `Transcode (hw)` on
+   the Plex dashboard **and why no alert is possible**; the device-cgroup failure to expect first
+   with a concrete open() diagnostic and the Intel-device-plugin fallback; and the floating-`:latest`
+   caveat with a digest check.
+
+**Stacked on PR #27 (`feat/sd-hardware-capability`), which is open and unmerged.** This branch was
+cut from it rather than from `main`, so its one commit (`d9baa2a`, the schema + renderer + contract)
+is in this PR's range. That is deliberate: merging #27 is not an agent's action (CLAUDE.md §1), and
+duplicating its changes here would have been worse than showing them. **This must merge after #27.**
+
+Not done, deliberately: no `--emit-waves` (it writes into `clusters/base/`, a sensitive path that
+would force a human reviewer, and it is a no-op unless the *set* of files under `apps/` changes — it
+does not here). No `podSecurityContext`. No `nodeSelector`. No alert rule. No `kubectl apply`.
+
+### Two follow-ups left unclaimed, with the reasoning
+
+- **Transcode scratch is on the wrong medium, and it is invisible.** The image sets
+  `TranscoderTempDirectory=/transcode`, which is **not a volume** — it is the container's writable
+  overlay, i.e. the node's `/data`. That is NVMe on prod-2 but **SATA on prod-1 and prod-3**, so
+  transcode scratch performance changes silently on reschedule, with nothing reporting it. Both
+  candidate fixes need a **schema** change and so neither belongs in this PR: pin Plex to prod-2
+  (needs a `nodeSelector` field the schema does not have), or give `/transcode` a `medium: Memory`
+  emptyDir and transcode in RAM (~31 GiB per node; needs an emptyDir field the schema does not
+  have). **The RAM option is the better one** — it removes the node asymmetry outright instead of
+  working around it — which is exactly why it deserves its own PR and its own review rather than
+  being smuggled in behind a four-line catalog change. Documented in the runbook's "Known gaps".
+- **GuC/HuC firmware is not loaded** (`i915.enable_guc=0`). The cost is low-power H.264 **encode**
+  quality only; decode and this feature are unaffected. Changing it needs a kernel parameter plus a
+  **serialized rolling reboot** — an operator action under CLAUDE.md §5, on a cluster with a
+  documented history of that going badly (a prod node hung on a warm reboot on 2026-09-03). Kept
+  well clear of this PR.
+
+## What I verified
+
+- **The render is exactly the intended change, and nothing else moved.** After
+  `python3 catalog/render.py --all catalog -o apps --wave-layout --no-image-automation` (exit 0,
+  silent): `git diff --stat apps/` = `apps/wave-0/plex.yaml | 6 ++++++`, and
+  `git status --porcelain apps/` = a single ` M apps/wave-0/plex.yaml`. Read line by line, the diff
+  is the `dri` volumeMount and the `dri` hostPath volume, and nothing more. **Specifically checked:**
+  the same invocation also rewrites `apps/wave-1/keycloak.yaml` and `apps/wave-0/vm-demo.yaml`, which
+  are git-tracked but excluded from the golden comparison by `RENDER_GOLDEN_NOT_ONBOARDED` in
+  `ci/render-golden.sh` — a spurious diff there would have landed **ungated**. Neither file shows a
+  diff; whole-repo `git status --porcelain` lists only `apps/wave-0/plex.yaml` and `catalog/plex.yaml`
+  plus my new files.
+- **The rendered output matches what the contract promises** — `schemas/renderer-contract.md`
+  `### hardware` says exactly two things (a `/dev/dri` hostPath with `type: DirectoryOrCreate` and a
+  read-write mount on the app container) and exactly two things appeared. No `securityContext`, no
+  `nodeSelector`, no resources in the diff.
+- **The runbook is projected into the server, not merely committed.** `runbooks/kustomization.yaml`
+  carries `- plex-quicksync=plex-quicksync.md`, whose shape matches the generator-entry regex the
+  L0 check parses; the extensionless key is what makes `/runbooks/plex-quicksync` a plain static
+  lookup. Also indexed in `runbooks/README.md`.
+- **The runbook clears the L0 quality floor** that `alert-runbooks-resolvable` applies to
+  alert-linked pages, even though nothing links to this one (it is advisory for an unreferenced
+  page): all four required sections (`## What this means here`, `## First commands`,
+  `## Likely causes, most likely first`, `## When to escalate or stop`), well over the 1500-byte
+  floor, `dev.sh` used throughout, and `--context k3s-prod` on every command.
+- **The gate.** See the run recorded in the PR description for the per-stage table and the real rc.
+- **No secret was printed.** Every `Preferences.xml` read in the runbook greps one named key, and the
+  page states explicitly why: the file holds `PlexOnlineToken`. Nothing was `sops -d`'d.
+
+## What I did NOT verify
+
+**Hardware transcoding has NOT been observed working.** Nothing in this branch is evidence that it
+does. A green gate here proves the manifest renders and the golden matches — it proves nothing about
+runtime behaviour, and `vars.CLUSTER_AVAILABLE` is unset so L2/L3 conformance did not run at all.
+
+- **The device-cgroup question is OPEN, and it is the largest remaining technical risk.** Whether
+  containerd on this k3s build permits a **non-privileged** pod to `open()` a bind-mounted character
+  device is **UNVERIFIED**. It can only be settled by deploying and trying. The container inits as
+  uid 0, which settles *file* permissions, but uid 0 does **not** bypass the cgroup device gate — and
+  the two failures look identical from the outside. If it is refused, the fallback is the Intel
+  Device Plugin (`gpu.intel.com/i915`), which is a `catalog/render.py` change plus a re-render with
+  **no ServiceDefinition edit**; `privileged: true` is not available (Kyverno
+  `restrict-host-namespaces` is Enforce). The runbook has the diagnostic sequence.
+- **The Plex-side toggle was still unset at the time of writing.** `HardwareAcceleratedCodecs` was
+  **absent** from `Preferences.xml` — the toggle has never been enabled on this server. Until an
+  operator ticks it in the UI, this branch changes the pod spec and **nothing about transcoding**.
+  That is the whole reason the runbook exists.
+- **No metric, so no alert, so no automated detection — permanently.** `catalog/plex.yaml` declares
+  no `metricsEndpoint`, so Plex renders no ServiceMonitor; there is no transcode-mode signal for a
+  rule to evaluate. A silent degradation to software transcoding (a node losing its iGPU, the
+  `DirectoryOrCreate` path) will **not** be reported by anything. I deliberately did not add an
+  alert: with no metric behind it, it could never fire, and this repo has been burned at scale by
+  exactly that. Closing the gap honestly means an exporter first.
+- **I did not re-derive this session's node or in-container measurements.** The three-node
+  `renderD128`/`i915`/GID-992 facts, the cont-init hook behaviour, the `s6-setuidgid` group
+  replacement, the `PLEX_PREFERENCE*` absence, the six `setPref` keys and the
+  `HardwareAcceleratedCodecs` string were established earlier in this session and are cited, not
+  re-measured, by me. Per CLAUDE.md §2b, treat this file as a record of belief and re-measure against
+  the cluster before relying on any of it.
+- **The image is a floating tag.** Everything known about the hook came from digest
+  `sha256:e0ab27395614…` (`plexmediaserver 1.43.4.10903`), while the Deployment runs
+  `plexinc/pms-docker:latest` with `imagePullPolicy: Always`. A silent pull can invalidate the
+  "no `supplementalGroups` needed" conclusion **with no commit in this repo**. Not guarded against —
+  the runbook tells the reader to re-check the hook after an image bump, which is documentation, not
+  enforcement.
+- **I did not verify the live Gitea gate state** (branch protection, required contexts, runner
+  online) for this PR. Per §2b that must be queried, not read out of `CLAUDE.md`'s table; I did not
+  query it.
+- **`/runbooks/plex-quicksync` was not fetched.** The L0 check asserts every static precondition for
+  an HTTP 200; it does not make the request, and I did not either.

runbooks/README.md

@@ -115,6 +115,14 @@ Each affected runbook says so on its own page and gives the by-hand equivalent.
   plex.tv/claim — so it is a timed sequence, scripted as `infra/plex/claim-ship.sh`:
   token → `sops` → PR → gate → merge → **forced** `flux reconcile` → pod roll (~2m45s measured).
   Includes why a changed Secret does not restart anything, and why an expired token is harmless.
+- **`plex-quicksync`** — hardware transcoding on the host iGPU. GitOps puts `/dev/dri` in the pod
+  (`hardware.gpu: intel-quicksync`); **a human still has to tick Settings → Transcoder → "Use hardware
+  acceleration when available"**, and no environment variable can do it (the image supports no
+  `PLEX_PREFERENCE*`, verified). The page names the real preference key (`HardwareAcceleratedCodecs`,
+  read out of the binary), says which widely-cited key **does not exist**, and is explicit that the
+  **only** proof is `Transcode (hw)` on the Plex dashboard — Plex renders no ServiceMonitor, so no
+  alert could ever fire. Also: the device-cgroup failure to expect first and its device-plugin
+  fallback, and why a `:latest` pull can silently break it.
 - **`crafty-admin-credential`** — you signed into Keycloak and Crafty *still* asks for a password.
   Expected: Crafty 4 has no OIDC, so its own local login sits behind the oauth2-proxy gate as a second
   factor. The page tells the two layers apart from the sidecar log, and explains that the bootstrap

runbooks/kustomization.yaml

@@ -90,6 +90,12 @@ configMapGenerator:
       # because the plex.tv claim window is short and is not a thing to go looking
       # for in git: /runbooks/plex-claim has to resolve the moment it is needed.
       - plex-claim=plex-claim.md
+      # Operator procedure, not an alert page, and NO alert is possible for it: plex renders no
+      # metricsEndpoint, so there is no ServiceMonitor, no transcode-mode metric and nothing a rule
+      # could evaluate. Served because the feature it completes is INERT until a human ticks a box in
+      # the Plex UI — the one step GitOps cannot reach — and a page nobody can find is how a shipped
+      # feature stays switched off for months.
+      - plex-quicksync=plex-quicksync.md
       - pvc-capacity=pvc-capacity.md
       - targets-down=targets-down.md
       - update-rollback=update-rollback.md

runbooks/plex-quicksync.md

@@ -0,0 +1,283 @@
+# plex-quicksync — making Plex actually use Intel Quick Sync, and proving it did
+
+**Alert:** none, and none is possible — see "How to verify" below. This is an **operator procedure**,
+not an incident page. It is indexed here because the feature it completes is **inert until a human
+clicks one button**, and a switched-off feature that looks shipped is exactly what this page exists
+to prevent.
+**Files:** `catalog/plex.yaml` (`hardware.gpu: intel-quicksync`), `apps/wave-0/plex.yaml` (the
+rendered golden — the `dri` hostPath volume and the `/dev/dri` mount), `catalog/render.py` (the
+mechanism), `schemas/renderer-contract.md` `### hardware` (the contract).
+**Related:** `runbooks/plex-claim.md` — the other Plex procedure with a manual last mile.
+
+## What this means here
+
+Plex transcodes in **software** by default. On the UHD Graphics 630 iGPU of an i7-9700T, Quick Sync
+moves that work off the CPU — which matters on a three-node cluster where the CPU is also running
+everything else. Two independent things have to be true before that happens, and **only one of them
+is in git**:
+
+| Half | Who does it | State |
+|---|---|---|
+| The render device is inside the container at `/dev/dri` | **GitOps.** `hardware.gpu: intel-quicksync` in `catalog/plex.yaml` renders a `dri` hostPath volume (`/dev/dri`, `type: DirectoryOrCreate`) and a read-write `/dev/dri` volumeMount on the app container. Flux applies it. | Done by merging that change. |
+| Plex is *told* to use it | **The operator, by hand, in the Plex web UI.** | **NOT done.** `HardwareAcceleratedCodecs` was **absent** from `Preferences.xml` when this page was written — the toggle has never been on. |
+
+**There is no GitOps path to the second half, and that is verified rather than assumed.** A bounded
+grep across the running image's entire init surface — `/etc/cont-init.d`, `/etc/services.d`,
+`/etc/fix-attrs.d`, `/plex-common.sh`, `/usr/local/bin` — found **zero** `PLEX_PREFERENCE*` support.
+Every `setPref` the image performs is one of six hardcoded keys (`MachineIdentifier`,
+`ProcessedMachineIdentifier`, `PlexOnlineToken`, `customConnections`, `allowedNetworks`,
+`TranscoderTempDirectory`), none of them the transcode toggle. No environment variable, no ConfigMap
+and no `postBuild` substitution can set it. So do not go looking for the clever way to automate this;
+there isn't one, and the search has already been done.
+
+What the device mount does **not** do, so nobody reads more into a green gate than is there: it does
+not enable hardware transcoding, it does not prove the device can be *opened* from inside a
+non-privileged pod (see "Likely causes" #2), and it renders no `nodeSelector` — Plex can land on any
+of the three nodes and all three carry the device.
+
+## Running the commands in this runbook
+
+`kubectl` does not work on the operator workstation; the toolchain lives only in the pinned dev
+container. Every command below runs as:
+
+    infra/devcontainer/dev.sh run bash -c 'kubectl --context k3s-prod get nodes'
+
+Always pass `--context k3s-prod` explicitly. `dev.sh` merges both clusters into one kubeconfig and
+picks a current-context **per invocation**, and that default has already changed once. Do not run two
+`dev.sh` invocations at once.
+
+**Never `cat` `Preferences.xml`.** It contains `PlexOnlineToken`, a plex.tv account credential. Every
+read of that file below greps a single named key — do not widen one.
+
+## First commands
+
+**1. Is the device mounted into the pod at all?** (Proves Flux applied the change, not that it works.)
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n plex get pod -l app.kubernetes.io/name=plex \
+     -o jsonpath="{.items[0].spec.containers[0].volumeMounts[*].mountPath}"; echo'
+```
+
+`/dev/dri` in that list ⇒ the GitOps half landed. Absent ⇒ the running pod predates the merge; compare
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n flux-system get kustomization apps-wave-0 \
+     -o jsonpath="{.status.lastAppliedRevision}"; echo'
+```
+
+against the merge commit before blaming anything else.
+
+**2. Is the device actually visible inside the container?**
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n plex exec deploy/plex -- ls -l /dev/dri'
+```
+
+Expect `renderD128` (usually `card0` too), mode `crw-rw----`, group `render`. An **empty directory**
+here is the `DirectoryOrCreate` degradation: the kubelet created an empty `/dev/dri` because the node
+had none. That is the designed-safe outcome — the app tier still reconciles — but it means software
+transcoding, silently. Find which node the pod is on and ask why that node lost its iGPU:
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n plex get pod -l app.kubernetes.io/name=plex -o wide'
+```
+
+**3. Can Plex *open* it?** This is the question the manifest cannot answer — see "Likely causes" #2.
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n plex exec deploy/plex -- \
+     bash -c "exec 3<>/dev/dri/renderD128 && echo RW-OPEN-OK || echo RW-OPEN-DENIED"'
+```
+
+`RW-OPEN-DENIED` (or `Operation not permitted` / `Permission denied`) with the device plainly visible
+in step 2 is the **device-cgroup** failure, not a file-permission failure. The two look identical from
+the outside and are not the same problem.
+
+**4. Is the toggle on?** Named key only — never the whole file:
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n plex exec deploy/plex -- \
+     grep -o "HardwareAcceleratedCodecs=\"[01]\"" \
+     "/config/Library/Application Support/Plex Media Server/Preferences.xml" || echo ABSENT'
+```
+
+`ABSENT` ⇒ never enabled (the state this page was written in). `="0"` ⇒ explicitly off. `="1"` ⇒ on,
+and the remaining question is whether it *works* — go to "How to verify".
+
+## The one manual step
+
+Plex web UI → **Settings → Transcoder → "Use hardware acceleration when available"** → tick → Save.
+(It sits under *Show Advanced*.) A transcode already in flight is unaffected; the next one picks it up.
+
+The underlying preference key is **`HardwareAcceleratedCodecs`**. That name was confirmed by
+extracting strings from the 23 MB `Plex Media Server` binary in the running container — **not** from
+recall and not from a forum post. Real neighbouring keys from the same binary, so you can recognise
+them and not invent them:
+
+| Key | What it is |
+|---|---|
+| `HardwareAcceleratedCodecs` | the toggle this page is about |
+| `HardwareAcceleratedEncoders` | hardware **encode**, as distinct from decode |
+| `HardwareDevicePath` | how Plex is pointed at a *specific* render node — relevant only if a host ever exposes more than one |
+| `TranscoderToneMapping`, `TranscoderToneMappingAgorithm` | HDR→SDR tone mapping. **That misspelling of "Algorithm" is upstream's, in the binary. It is not a typo in this page — do not "fix" it** here or anywhere else; the corrected spelling is not a key Plex reads. |
+| `TranscoderHEVCEncoding` | HEVC output |
+
+**`HardwareAcceleratedCodecsEnableHEVC` does not exist.** It is widely cited and it is not in the
+binary. Recorded explicitly so nobody spends an evening hunting for it or, worse, writes it into
+`Preferences.xml` and concludes hardware transcoding is broken.
+
+Editing `Preferences.xml` by hand is **not** the procedure. It is app state on the replicated Longhorn
+tier, it is in no git commit, and the UI writes the key correctly. Use the UI.
+
+## How to verify — and why there is no alert
+
+Start a playback that **forces a transcode** (a client that cannot direct-play the source, or pick a
+lower quality explicitly), then read Plex's own **Dashboard → Activity**:
+
+- **`Transcode (hw)`** on the session ⇒ hardware transcoding. **This is the proof.**
+- plain **`Transcode`** ⇒ software. The feature is not working, whatever the manifest says.
+
+**That dashboard is the *only* proof available, and nothing else will ever tell you.**
+`catalog/plex.yaml` declares no `metricsEndpoint`, so Plex renders **no ServiceMonitor at all** —
+there is no scrape, no transcode-mode metric, and therefore no alert that could fire. Do not open work
+to "alert on software-transcode fallback": with no metric behind it such a rule would be permanently
+inert, and this repo has already been burned at scale by rules that evaluated against nothing while
+looking like coverage (`runbooks/README.md`, "Alerts you should not trust the silence of"). If that
+gap is ever worth closing, the honest order is a real exporter first and a rule second.
+
+Corroborating, not a substitute — the server log on the config PVC:
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n plex exec deploy/plex -- \
+     sh -c "grep -i -m20 -e hardware -e vaapi -e hwdevice \
+     \"/config/Library/Application Support/Plex Media Server/Logs/Plex Media Server.log\""'
+```
+
+Treat those strings as advisory: they are Plex's, not this repo's, and they move between versions.
+Absence of a match is **not** evidence of software transcoding; a VA-API device open is good evidence
+of hardware. The dashboard remains the verdict.
+
+## Likely causes, most likely first
+
+When the dashboard still says plain `Transcode`:
+
+1. **The toggle is off.** Overwhelmingly the most likely answer, and the reason this page exists.
+   First-command #4 returns `ABSENT` or `="0"`. Remedy: the manual step above. Check this **before**
+   investigating anything technical.
+
+2. **containerd's device cgroup is refusing the `open()` — UNVERIFIED, and the largest remaining
+   technical risk in this feature.** Whether a non-privileged pod may `open()` a bind-mounted
+   character device on this k3s/containerd build **has not been established**; it can only be settled
+   by deploying and trying. The container inits as uid 0, which settles *file* permissions, but
+   **uid 0 does not bypass the cgroup device gate.** Symptom: step 2 shows `renderD128` present and
+   correctly owned, step 3 returns `RW-OPEN-DENIED`.
+   **The documented fallback is the Intel Device Plugin for Kubernetes** (`gpu.intel.com/i915` as a
+   resource request, no hostPath). Because the ServiceDefinition field expresses *intent* rather than
+   a device path, that migration is a **`catalog/render.py` change plus a re-render — with no
+   ServiceDefinition edit anywhere**; `catalog/plex.yaml` keeps saying exactly what it says today.
+   **`privileged: true` is not an available escape hatch:** Kyverno `restrict-host-namespaces` is in
+   **Enforce** mode and rejects it in app namespaces. Do not reach for it.
+
+3. **The pod landed on a node without the device.** Step 2 shows an empty `/dev/dri`. All three prod
+   nodes carried `renderD128` with `i915` bound when this was measured (2026-09-30), so this means a
+   node changed — a rebuild, a BIOS reset, or a driver regression. `DirectoryOrCreate` is why the app
+   tier still came up; the cost is that the loss is silent. **Fix the node, do not tighten the mount:**
+   `Directory` would stall `apps-wave-0` (`wait: true`, with `apps-wave-1` depending on it) for a
+   feature that is not load-bearing.
+
+4. **The image changed under you.** See "The floating-image caveat". A `:latest` pull can remove the
+   mechanism this feature leans on with no commit in this repo.
+
+5. **The session was never transcoding.** Direct Play / Direct Stream never touches the transcoder, so
+   `Transcode (hw)` cannot appear. Confirm the session actually says `Transcode` before treating it as
+   a hardware failure.
+
+6. **The source needs a codec Quick Sync on this generation cannot handle** — e.g. AV1 decode, which
+   Coffee Lake's UHD 630 has no engine for. Plex falls back to software *per stream*. Symptom: some
+   sessions show `(hw)` and others do not. Not a fault.
+
+## The floating-image caveat
+
+Everything this page states about the image's behaviour — the `cont-init.d` hook that adds the app
+user to the device's group, the absence of `PLEX_PREFERENCE*`, the six `setPref` keys, the
+`HardwareAcceleratedCodecs` string — was read from digest **`sha256:e0ab27395614…`**
+(`plexmediaserver 1.43.4.10903`).
+
+The deployment runs **`plexinc/pms-docker:latest` with `imagePullPolicy: Always`**. A silent pull can
+therefore change the behaviour this feature depends on **with no commit in this repo**, while the
+manifest still looks identical. Symptom to watch for: hardware transcoding that worked and quietly
+stopped, with no git change to point at.
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n plex get pod -l app.kubernetes.io/name=plex \
+     -o jsonpath="{.items[0].status.containerStatuses[0].imageID}"; echo'
+```
+
+If that digest is not the one above, **re-verify the hook before trusting this page**:
+
+```
+infra/devcontainer/dev.sh run bash -c \
+  'kubectl --context k3s-prod -n plex exec deploy/plex -- ls /etc/cont-init.d/'
+```
+
+`45-plex-hw-transcode-and-connected-tuner` still present ⇒ the group mechanism is still the one
+described here. Gone or renamed ⇒ stop and re-measure. In particular the "no `supplementalGroups`
+needed" conclusion in `catalog/plex.yaml` and `schemas/renderer-contract.md` is only true while that
+hook exists.
+
+## When to escalate or stop
+
+- **Do not add `supplementalGroups` or a `podSecurityContext` to `catalog/plex.yaml`.** It would be
+  **inert**, and it would mislead the next person. Measured in-container 2026-09-30: the image's
+  `cont-init.d` hook stats each `/dev/dri` char device and `usermod -a -G`s the `plex` user into its
+  group *inside* the container, and the service then execs via `s6-setuidgid plex`, which **replaces**
+  the process group list from `/etc/group` rather than appending — `Plex Media Server` runs with
+  `Groups: 100 1000`, root's gid `0` (which PID 1 does hold) gone. Anything Kubernetes supplies is
+  discarded before Plex starts. `render.py --selftest` asserts that absence deliberately.
+- **Do not reach for `privileged: true`.** Kyverno `restrict-host-namespaces` is Enforce and will
+  reject it. If the cgroup gate is the blocker, the answer is the Intel device plugin (cause #2).
+- **Do not `kubectl edit`/`patch` the Deployment to add or change the device mount.** Flux reconciles
+  `main`; a hand-applied change is drift that the next reconcile reverts or, worse, adopts. Mutating
+  `kubectl` and `flux reconcile` are **operator** actions, and the durable change is a git change
+  through a branch, a PR and a green gate.
+- **Do not edit `Preferences.xml` on the PVC**, never `cat` it, and never `sops -d` anything into a
+  terminal. It holds `PlexOnlineToken`.
+- **Do not delete the `plex-config` PVC to "start clean".** It is the library database, metadata and
+  watch state (`policy: daily-offcluster`). The transcode toggle is one preference, not a reason to
+  lose the DB.
+- **Stop and get the operator** if the device cannot be opened from the pod (cause #2 confirmed). The
+  next step is a platform change — the Intel device plugin — with its own PR, not more poking at this
+  workload.
+
+## Known gaps, deliberately not fixed here
+
+Recorded so they are findable, and so nobody assumes they were overlooked:
+
+- **Transcode scratch is on the wrong medium, and it is invisible.** The image sets
+  `TranscoderTempDirectory=/transcode`, which is **not a volume** — it is the container's writable
+  overlay, i.e. the node's `/data`. That is NVMe on prod-2 but **SATA on prod-1 and prod-3**, so
+  transcode scratch performance changes silently whenever the pod is rescheduled. Both candidate fixes
+  need a **schema** change and are therefore out of scope here: pin Plex to prod-2 (needs a
+  `nodeSelector` field the schema does not have), or give `/transcode` a `medium: Memory` emptyDir and
+  transcode in RAM (~31 GiB per node; needs an emptyDir field the schema does not have). The RAM option
+  is the better one, because it removes the node asymmetry outright instead of working around it.
+- **GuC/HuC firmware is not loaded** (`i915.enable_guc=0`). The cost is low-power H.264 **encode**
+  quality only — decode, and the feature on this page, are unaffected. Changing it needs a kernel
+  parameter and a **serialized rolling reboot**, which is an operator action (CLAUDE.md §5), and this
+  cluster has a documented history of that going badly (a prod node hung on a warm reboot on
+  2026-09-03). Not worth coupling to this change.
+
+---
+Source of truth: `runbooks/plex-quicksync.md`. Index: `/runbooks/`
+The node measurements (all three prod nodes) and the in-container image measurements cited here were
+taken **2026-09-30** against `plexinc/pms-docker` digest `sha256:e0ab27395614…`
+(`plexmediaserver 1.43.4.10903`). Hardware transcoding had **not** been observed working at the time
+of writing, and the Plex-side toggle was still unset.