release: 0.6.3

docs/release-notes/0.6.3.md

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+**Correctness fixes for seat lifecycle, and the first release whose changes were exercised on real
+hardware rather than only in tests.**
+
+## A process is now identified by more than its PID
+
+Windows recycles process IDs. MultiSeat recorded a seat's Apollo by PID alone and then acted on
+that number later — checking whether it was alive, and terminating it on teardown. Once the
+original process exits, that PID can belong to something else entirely, and nothing checked.
+
+A seat's Apollo is now identified by its PID **and** the start time the operating system reports
+for it. Termination happens only while both still match, and the check and the kill share a single
+open handle, because Windows will not recycle a PID while a handle to that process is open. If the
+identity does not match, nothing is killed and the mismatch is logged.
+
+Where no identity could be recorded — the start time was unreadable at launch — the process name is
+checked before terminating. That is weaker, and it is the last resort rather than the default.
+
+**A restart used to break this**, and that is fixed here too. Restarting a seat's Apollo advanced
+the PID while leaving the recorded identity pointing at the process that had just exited. The
+record then contradicted itself: liveness checks reported a perfectly healthy Apollo as dead, and
+teardown killed the old PID and left the running one behind. Both are corrected.
+
+## Teardown holds the lock before it changes anything
+
+Tearing a seat down removed it from the registry and *then* waited for that seat's lifecycle lock.
+Acquiring the lock can time out when another operation holds it, and a timeout at that point left
+the seat unregistered while its session, its Apollo and its ports were all still running — with no
+way back, because everything that tears a seat down starts by looking it up.
+
+The lock is now acquired first. A timeout leaves the seat registered and untouched, so the request
+can simply be retried.
+
+## Operations check the seat is still there
+
+Any operation that waits for a seat's lifecycle lock can be admitted after a teardown has already
+removed that seat. Changing resolution was the worst case: it creates a **new** Windows session and
+a new Apollo, both belonging to a seat that no longer exists and which nothing would ever clean up.
+
+Every such operation now re-checks the seat after acquiring the lock and stops if it is gone.
+Resetting the display, the audio routing or the controller, and launching an app into a seat, take
+the lock at all now — previously they did not.
+
+## The API answers with the right status codes
+
+Every failure used to answer `400 Bad Request`, including "the host is full", which tells a client
+its request was malformed when the request was fine.
+
+| condition | was | now |
+|---|---|---|
+| Seat limit reached, or no free port block | 400 | **503** Service Unavailable |
+| Account already has a seat, or already exists | 400 | **409** Conflict |
+| Seat not found | 400 | **404** Not Found |
+| A genuinely malformed request | 400 | **400** |
+
+503 and 409 are deliberately different: one is worth retrying later, the other cannot succeed until
+something changes.
+
+## What was actually tested
+
+Unlike previous releases, these changes were run on real hardware before shipping, not only in CI:
+
+- a seat provisioned, streamed to a Moonlight client, and was torn down cleanly
+- the client received the seat's own desktop, and input worked
+- `hevc_nvenc` opened inside the seat's session without trouble
+- a seat's Apollo was restarted mid-life, and the recorded identity followed the new process
+- teardown after that restart terminated the running Apollo rather than leaking it
+- a standalone Apollo streamed simultaneously throughout and was never touched
+
+## Install
+
+Download `multiseat-windows-x64.zip`, extract it anywhere, and run both scripts from inside the
+extracted folder:
+
+```powershell
+.\prerequisites\install-prerequisites.ps1     # drivers - needed either way
+.\scripts\install-service.ps1 -FromZip .
+```
+
+Self-contained as before: no clone, no .NET SDK, no .NET runtime, no Node.
+
+## If your seats stopped working recently
+
+A Windows update can replace `termsrv.dll` with a build RDP Wrapper has no offsets for. RDP Wrapper
+then silently stops patching, and because every seat is an RDP session, every seat dies with it.
+That happened on our own machine while preparing this release, and it had been broken for two days
+without anything reporting it.
+
+```powershell
+.\scripts\check-rdpwrap-offsets.ps1            # is this build covered?
+.\scripts\check-rdpwrap-offsets.ps1 -Apply     # compute and apply offsets locally
+```
+
+0.6.2 added the check that makes this visible at install time; this release does not change it.
+
+## Known limitations
+
+- **Seats capture the RDP surface, not a dedicated virtual display.** A seat's display reports a
+  1000 Hz refresh rate, which is the sign of this. It is a Windows constraint on where a virtual
+  display can be attached, not a regression, and it is unchanged here.
+- **A streaming seat still reports its status as `Ready`.** The stream works; the status simply
+  does not reflect it.
+- Seat auto-discovery in MoonlightVibe does not find seats from another machine. Add the seat by
+  address and port instead — a seat's port block starts at 48100 by default.

version.txt

@@ -1 +1 @@
-0.6.2
+0.6.3