Record headset results for sideloading and devkit pairing

Tested on a Frame (BUILD_ID 20260922.6101926):

- Devkit pairing: the service runs and answers properties.json, but /register
  refuses with "please put the Steam client in pairing mode" unless Steam is on
  Settings > Developer > Pair new host. Both setup paths now say so and keep
  asking for 2 minutes before falling back to the password.
- Sideloading: registering, launching, quoted start paths and Remove work; a
  Windows exe runs under Proton 11 through FEX. An aarch64 build starts but
  outside the runtime container, and an x86-64 Linux build doesn't start
  because the x86-64 Steam Linux Runtime 4.0 isn't installed. The inspect note
  for x86-64 Linux builds now says so.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

README.md

@@ -149,10 +149,11 @@ computer.
    password once in a terminal window. If it can't find the Frame, type the
    IP address from the Frame's Quick Settings.
 
-   Before asking for the password it tries Valve's SteamOS devkit pairing: if
-   the headset shows a pairing request, approve it and no password is needed.
-   (**Inferred from Valve's source** ([steamos-devkit-service](https://gitlab.steamos.cloud/devkit/steamos-devkit-service)),
-   not yet verified on a Frame; see [SSH](docs/ssh.md#password-free-pairing-steamos-devkit-service).)
+   Before asking for the password it tries Valve's SteamOS devkit pairing: in
+   the headset, open Steam Settings → Developer → **Pair new host** and approve
+   the request, and no password is needed. (The service and the pairing-mode
+   step are verified on a Frame; the approval itself isn't yet. See
+   [SSH](docs/ssh.md#password-free-pairing-steamos-devkit-service).)
 3. That's it. The app now reaches the headset whenever it's awake and on the
    same network. For anywhere else, see [Tailscale](docs/tailscale.md).
 

docs/sideloading.md

@@ -48,8 +48,8 @@ The program's header decides, not its file name:
 |---|---|---|---|
 | Windows `.exe`, x86-64 (PE machine `0x8664`) | `proton-experimental` | 1 | Inferred: ARM64 Proton runs x86-64 code through FEX |
 | Windows `.exe`, 32-bit x86 (`0x14c`) or ARM64 (`0xaa64`) | `proton-experimental` | 1 | Inferred |
-| Linux ELF, aarch64 (`e_machine` `0xB7`) | `SteamLinuxRuntime_4-arm64` | 0 | Inferred: native |
-| Linux ELF, x86-64 (`0x3E`) | `SteamLinuxRuntime_4` | 0 | Inferred: runs through FEX; the least certain row |
+| Linux ELF, aarch64 (`e_machine` `0xB7`) | `SteamLinuxRuntime_4-arm64` | 0 | Verified: starts, but natively (see below) |
+| Linux ELF, x86-64 (`0x3E`) | `SteamLinuxRuntime_4` | 0 | Verified not to start: the runtime isn't installed (see below) |
 | Shell script | the runtime of the Linux binary beside it, else `SteamLinuxRuntime_4-arm64` | 0 | Guess |
 | Anything else (32-bit Linux, other CPUs, DLLs, data) | refused with a message | | |
 
@@ -142,12 +142,30 @@ splits that string is **not checked**.
   server, which only accepts requests from its own page (see
   [frame-control.md](frame-control.md#how-it-works)).
 
-## To check on a headset
+## Checked on a headset
 
-- [ ] `create-shortcut` registers a title and it shows in the library under its id.
-- [ ] An aarch64 build launches in `SteamLinuxRuntime_4-arm64`.
-- [ ] An x86-64 Windows `.exe` launches under Proton Experimental through FEX.
-- [ ] An x86-64 Linux build launches in `SteamLinuxRuntime_4` through FEX.
-- [ ] `steam-devkit-rpc run-game` starts it, and `steamos-delete` removes the shortcut.
-- [ ] How Steam splits a start command with a quoted path.
+Tested 2026-09-26 on a Frame (BUILD_ID 20260922.6101926) with small static test
+programs and PuTTY's official 64-bit `putty.exe`, through both the command line
+and the app (inspect, install job, ▶, Remove, and install links):
+
+- [x] `create-shortcut` registers a title; it shows in the Steam library and in
+  **Sideloaded titles**, and Steam maps it to the chosen compat tool.
+- [x] `steam-devkit-rpc run-game` starts it (Steam logs `devkit run-game: started
+  devkit game "<id>"`), and Remove (`steamos-delete`) deletes the files, the
+  shortcut and the Proton prefix.
+- [x] A quoted path in the start command is fine: Steam runs
+  `proton waitforexitandrun "/home/steamos/devkit-game/<id>/<exe>"`.
+- [x] An x86-64 Windows `.exe` runs under **Proton 11 (stable)** through FEX
+  (ARM64EC) inside the Steam Linux Runtime 4.0 ARM64 container; PuTTY stayed up.
+  Proton Experimental wasn't installed at the time (it was downloading), so it's
+  untested. A Go-built x86-64 test program crashed in `libarm64ecfex.dll`
+  (a FEX limitation with that program, not the sideloading).
+- [ ] **An aarch64 build runs natively, not in `SteamLinuxRuntime_4-arm64`**:
+  Steam records the mapping (`CompatToolMapping`, `compat_log.txt`) but launches
+  the devkit title without the runtime's `_v2-entry-point` prefix. Fine for a
+  self-contained build; a build that needs the runtime's libraries may not start.
+- [ ] **An x86-64 Linux build doesn't start**: Steam logs `Tool 4183110 "Steam
+  Linux Runtime 4.0" is found for appID …, but is not installed`, and the Frame
+  doesn't install that x86-64 runtime for a devkit title (a `steam://install/4183110`
+  request did nothing).
 - [ ] Whether these titles open as flat panels or need anything VR-specific.

docs/ssh.md

@@ -65,15 +65,23 @@ The script only asks for the password if the pairing below doesn't work.
 
 ## Password-free pairing (SteamOS devkit service)
 
-**Inferred from Valve's source ([steamos-devkit-service](https://gitlab.steamos.cloud/devkit/steamos-devkit-service),
-[steamos-devkit](https://gitlab.steamos.cloud/devkit/steamos-devkit) client); not yet
-verified on a Frame.** SteamOS's devkit service is what Valve's Devkit Client
-uses to pair. `scripts/connect.sh` and `ui/frame_connect.py` try it first:
+From Valve's source ([steamos-devkit-service](https://gitlab.steamos.cloud/devkit/steamos-devkit-service),
+[steamos-devkit](https://gitlab.steamos.cloud/devkit/steamos-devkit) client). **Verified on a
+Frame 2026-09-26** (BUILD_ID 20260922.6101926): the service runs with Developer Mode
+on, `properties.json` answers with `"login": "steamos"`, the headset advertises
+`_steamos-devkit._tcp` as `frame`, and `/register` needs pairing mode (below). The
+approve prompt and key install are not verified yet. SteamOS's devkit service is
+what Valve's Devkit Client uses to pair. `scripts/connect.sh` and
+`ui/frame_connect.py` try it first:
 
 - The headset serves HTTP on port **32000** and advertises mDNS
   `_steamos-devkit._tcp`. `GET /properties.json` gives the `login` user; the
   script uses it as `User` (unless you set `FRAME_USER`, or it says `root`),
   for the password fallback too, and keeps it on re-runs.
+- **Open Steam Settings → Developer → Pair new host in the headset first.**
+  Otherwise `/register` answers at once with `403` `"please put the Steam client
+  in pairing mode: Settings -> Developer -> Pair new host"` (verified). The
+  scripts say so and keep asking for 2 minutes while you open it.
 - `POST /register` with `ssh-rsa <key> <comment> 900b919520e4cf601998a71eec318fec`
   (a fixed token from Valve's client) shows an approve prompt inside the
   headset naming the comment (`frame-control@<your computer>`). It waits 30 s,
@@ -89,8 +97,7 @@ uses to pair. `scripts/connect.sh` and `ui/frame_connect.py` try it first:
   to copying the ed25519 key with the Developer Mode password, as before.
 
 Anyone on your network can send the request, so only approve a prompt you
-started. Whether the Frame runs this service with Developer Mode on is the
-unverified part: `curl http://frame.local:32000/properties.json` answers the question.
+started. `curl http://<frame-ip>:32000/properties.json` shows whether the service is up.
 
 `~/.ssh/authorized_keys` lives under `/home`, which SteamOS keeps across OS
 updates (inferred from Deck; the Frame uses the same A/B image scheme).

scripts/connect.sh

@@ -182,17 +182,23 @@ pair_with_devkit() {
   comment="frame-control@$(hostname -s | tr -cs 'A-Za-z0-9._-' '-' | sed 's/^[-.]*//; s/[-.]*$//')"
   [[ "$comment" == "frame-control@" ]] && comment="frame-control@computer"
   body="ssh-rsa $(awk '{print $2}' "$DEVKIT_KEY.pub") $comment $MAGIC_PHRASE"
-  print "    Approve the pairing request in the headset (it waits about 30 seconds)"
-  if ! resp=$(print -r -- "$body" | curl -sS --noproxy '*' -m 60 -H 'Content-Type: text/plain' \
-      --data-binary @- -w '\n%{http_code}' "$(devkit_url /register)" 2>&1); then
-    devkit_why="devkit pairing failed: no answer (${${resp##*curl: }%%$'\n'*})"; return 1
-  fi
-  code=${resp##*$'\n'}
-  text=${resp%$'\n'*}
-  if [[ "$code" != 2* ]]; then
+  print "    In the headset: Steam Settings > Developer > Pair new host, then approve the request"
+  # The headset refuses at once unless Steam is on its "Pair new host" screen
+  # (verified on a Frame, 2026-09-26), so keep asking for 2 minutes while it's opened.
+  local deadline=$(( SECONDS + 120 ))
+  while true; do
+    if ! resp=$(print -r -- "$body" | curl -sS --noproxy '*' -m 60 -H 'Content-Type: text/plain' \
+        --data-binary @- -w '\n%{http_code}' "$(devkit_url /register)" 2>&1); then
+      devkit_why="devkit pairing failed: no answer (${${resp##*curl: }%%$'\n'*})"; return 1
+    fi
+    code=${resp##*$'\n'}
+    text=${resp%$'\n'*}
+    [[ "$code" == 2* ]] && break
     err=$(print -r -- "$text" | sed -n 's/.*"error"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/p' | head -n 1)
-    devkit_why="devkit pairing failed: ${err:-${text:-HTTP $code}}"; return 1
-  fi
+    devkit_why="devkit pairing failed: ${err:-${text:-HTTP $code}}"
+    [[ "$devkit_why" == *"pairing mode"* ]] && (( SECONDS < deadline )) || return 1
+    sleep 3
+  done
   # The approval is what turns sshd on, so it may take a moment to answer.
   local i
   for i in {1..10}; do

tests/test_connect.py

@@ -22,6 +22,7 @@ PUB = "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQC+/x= frame-control@old\n"
 class StubDevkit(BaseHTTPRequestHandler):
     """Answers like steamos-devkit-service; `reply` picks the /register outcome."""
     reply = (200, b"Registered\n")
+    replies = []  # if set, each /register takes the next one instead of `reply`
     properties = {"txtvers": 1, "login": "steamos", "settings": "{}", "devkit1": ["devkit-1"]}
     bodies = []
 
@@ -41,7 +42,7 @@ class StubDevkit(BaseHTTPRequestHandler):
     def do_POST(self):
         body = self.rfile.read(int(self.headers["Content-Length"]))
         StubDevkit.bodies.append((self.path, self.headers["Content-Type"], body))
-        code, text = self.reply
+        code, text = StubDevkit.replies.pop(0) if StubDevkit.replies else self.reply
         self.send_response(code)
         self.send_header("Content-type", "text/plain")
         self.end_headers()
@@ -63,6 +64,7 @@ class DevkitPairing(unittest.TestCase):
     def setUp(self):
         StubDevkit.reply = (200, b"Registered\n")
         StubDevkit.bodies = []
+        StubDevkit.replies = []
         self.said = []
         self._say, fc.say = fc.say, self.said.append
 
@@ -104,7 +106,31 @@ class DevkitPairing(unittest.TestCase):
         path, ctype, body = StubDevkit.bodies[0]
         self.assertEqual((path, ctype), ("/register", "text/plain"))
         self.assertEqual(body.decode(), fc.register_body(PUB, "frame-control@test"))
-        self.assertTrue(any("Approve the pairing request" in s for s in self.said))
+        self.assertTrue(any("Pair new host" in s for s in self.said))
+
+    NOT_PAIRING = (403, b'{"error": "devkit approve-ssh-key: please put the Steam client in pairing mode: '
+                        b'Settings -> Developer -> Pair new host"}')
+
+    def test_pair_waits_for_pairing_mode(self):
+        # The headset refuses until Steam is on "Pair new host", then prompts.
+        StubDevkit.replies = [self.NOT_PAIRING, self.NOT_PAIRING, (200, b"Registered\n")]
+        sleep, fc.time.sleep = fc.time.sleep, lambda s: None
+        try:
+            reason = fc.devkit_pair("127.0.0.1", PUB, "c", self.port)
+        finally:
+            fc.time.sleep = sleep
+        self.assertIsNone(reason)
+        self.assertEqual(len(StubDevkit.bodies), 3)
+
+    def test_pair_gives_up_without_pairing_mode(self):
+        StubDevkit.reply = self.NOT_PAIRING
+        wait, fc.PAIRING_MODE_WAIT = fc.PAIRING_MODE_WAIT, 0
+        try:
+            reason = fc.devkit_pair("127.0.0.1", PUB, "c", self.port)
+        finally:
+            fc.PAIRING_MODE_WAIT = wait
+        self.assertIn("pairing mode", reason)
+        self.assertEqual(len(StubDevkit.bodies), 1)
 
     def test_pair_refused_falls_back(self):
         StubDevkit.reply = (403, b'{"error": "timeout - Steam did not respond to the pairing request"}')

tests/test_frame_titles.py

@@ -109,10 +109,10 @@ class Targets(unittest.TestCase):
         self.assertEqual((p['target'], p['runtime']), ('game.arm64', 'SteamLinuxRuntime_4-arm64'))
         self.assertEqual(p['runtimes'], ['SteamLinuxRuntime_4-arm64'])
 
-    def test_x86_64_linux_build_is_marked_inferred(self):
+    def test_x86_64_linux_build_warns_it_may_not_start(self):
         p = self.plan({'game.x86_64': elf(0x3E)}, 'game')
         self.assertEqual(p['runtime'], 'SteamLinuxRuntime_4')
-        self.assertIn('inferred', p['note'])
+        self.assertIn("won't start", p['note'])
 
     def test_native_arm64_beats_x86_64(self):
         p = self.plan({'game.x86_64': elf(0x3E, pad=900), 'game.arm64': elf(0xB7)}, 'game')

ui/frame_connect.py

@@ -58,11 +58,14 @@ def say(msg):
 # port 32000: GET /properties.json names the user to log in as; POST /register with
 # "ssh-rsa <key> <comment> <magic>" shows an approve prompt in the headset (the
 # comment is what it displays, 30 s to answer), then installs the key and turns sshd on.
+# The prompt only appears while Steam is on Settings > Developer > Pair new host;
+# otherwise /register answers 403 "please put the Steam client in pairing mode".
 
 DEVKIT_PORT = 32000
 DEVKIT_SERVICE = "_steamos-devkit._tcp"
 MAGIC_PHRASE = "900b919520e4cf601998a71eec318fec"  # fixed token Valve's client appends
 REGISTER_TIMEOUT = 60
+PAIRING_MODE_WAIT = 120  # seconds to keep asking while the user opens "Pair new host"
 # A LAN host: never go through an HTTP(S)_PROXY from the environment.
 _opener = urllib.request.build_opener(urllib.request.ProxyHandler({}))
 
@@ -141,8 +144,15 @@ def devkit_pair(host, pub, comment, port=DEVKIT_PORT, on_login=None):
         return f"devkit service not reachable on port {port}: {why(e)}"
     if login and on_login:
         on_login(login)
-    say("    Approve the pairing request in the headset (it waits about 30 seconds)")
-    ok, msg = register(host, register_body(pub, comment), port)
+    say("    In the headset: Steam Settings > Developer > Pair new host, then approve the request")
+    body = register_body(pub, comment)
+    ok, msg = register(host, body, port)
+    # The headset refuses at once unless Steam is on its "Pair new host" screen
+    # (verified on a Frame, 2026-09-26), so keep asking while the user opens it.
+    deadline = time.monotonic() + PAIRING_MODE_WAIT
+    while not ok and "pairing mode" in msg and time.monotonic() < deadline:
+        time.sleep(3)
+        ok, msg = register(host, body, port)
     return None if ok else f"devkit pairing failed: {msg}"
 
 

ui/frame_titles.py

@@ -399,7 +399,9 @@ def runtime_for(target, found=()):
     if fmt == 'elf' and arch == 'arm64':
         return 'SteamLinuxRuntime_4-arm64', 'Native ARM64 Linux build.'
     if fmt == 'elf' and arch == 'x86_64':
-        return 'SteamLinuxRuntime_4', 'x86-64 Linux build: runs through FEX (inferred, not yet checked).'
+        return 'SteamLinuxRuntime_4', ("x86-64 Linux build: probably won't start. It needs the x86-64 Steam "
+                                       "Linux Runtime 4.0, which the Frame didn't install for a sideloaded title "
+                                       "(2026-09-26). Use an ARM64 or Windows build if there is one.")
     raise FrameError(f"{target['path']} is a {arch} Linux program; the Frame runs ARM64 and x86-64 (through FEX) only")