test: assert the 2x-budget ceiling the watchdog now guarantees, not 4s

The Windows job went green, but CTest prints test output only on failure, so a
pass says nothing about WHAT cancelled the request. Under the old 4000ms bound
a pass is ambiguous: the watchdog firing at ~1400ms and WinHTTP's own erratic
cancellation (measured at 1490-4506ms for this same 700ms budget) both fit
under it.

So assert the guarantee the code actually makes now -- a hard ceiling of twice
the caller's budget -- at 2500ms, which is 1400ms plus slack for a loaded
runner. If the watchdog stops doing the work, roughly half the attempts land
above this and print their elapsed time and error string, instead of quietly
passing.

Linux is unaffected: curl honours the 700ms budget exactly, 5/5 at ~701ms.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AzGnvQ6wfD7bw7PZN35ft9

.gitea/scripts/publish-release.sh

@@ -1,9 +1,15 @@
 #!/usr/bin/env bash
-# Creates a (draft) Gitea Release for the tag that triggered
+# Creates a published Gitea Release for the tag that triggered
 # .gitea/workflows/release.yml, and uploads every archive in $DIST_DIR as a
-# release asset. Draft because nobody has run this plugin in the OBS GUI on
-# any platform yet -- a human still opens it and clicks Publish once that's
-# no longer true (or once they're satisfied regardless).
+# release asset.
+#
+# This used to create a DRAFT, on the grounds that nobody had run the plugin
+# in the OBS GUI on any platform. That stopped being true on 2026-09-09, when
+# the v0.1.0 Windows artifact loaded into OBS 32.2.2 on Windows 11 -- so the
+# release publishes directly and the per-platform table below carries the
+# remaining caveats instead. Assets upload AFTER the release row is created
+# either way, so a release is briefly visible with no files attached; that is
+# the tradeoff for not needing a human click.
 #
 # Required env: GITEA_TOKEN, SERVER, OWNER, REPO, TAG, SHA, DIST_DIR
 # Optional env: MACOS_BUNDLE_FOUND ("true"/"false", default "false")
@@ -30,26 +36,44 @@ cat > "${NOTES_FILE}" <<EOF
 
 Built from commit \`${SHA}\`.
 
-**Nobody has yet run this plugin in the OBS GUI, on any platform.** See "What
-is verified, and how" in \`README.md\` for exactly what has and has not been
-checked, including which claims are backed by automated tests versus a human
-watching OBS. This is why the release is a draft -- open it and click Publish
-once you're satisfied.
+**Read the per-platform notes below before relying on this.** The module has
+been loaded in the OBS GUI exactly once -- Windows, OBS 32.2.2 on Windows 11,
+2026-09-09 -- and only "it loads and registers its source type" is confirmed
+there. Whether video renders correctly, A/V sync, end-to-end latency and
+mid-show publisher restart are all still unverified on every platform. See
+"What is verified, and how" in \`README.md\` for exactly what is backed by
+automated tests versus a human watching OBS.
 
 | Platform | Archive | Notes |
 |---|---|---|
 | Linux (x64) | \`streamer-tools-camera-${TAG}-linux-x64.zip\` | Functionally complete and verified end to end against a real LiveKit server and a real libobs (see README); OBS GUI itself still unverified |
-| Windows (x64) | \`streamer-tools-camera-${TAG}-windows-x64.zip\` | Built and tested by this workflow's Windows job; the WinHTTP backend has never been exercised against a real streamer-tools server, only a loopback test server -- see README's Windows CI section |
+| Windows (x64) | \`streamer-tools-camera-${TAG}-windows-x64.zip\` | Built and tested by this workflow's Windows job. Confirmed to load in the OBS GUI (32.2.2 / Windows 11, 2026-09-09); nothing past module load is verified. The WinHTTP backend has never been exercised against a real streamer-tools server, only a loopback test server -- see README's Windows CI section |
 | macOS | \`streamer-tools-camera-${TAG}-macos.zip\` | Built and tested by this workflow's macOS job. ${MACOS_NOTE} |
 
 ## Installing
 
-Extract the archive into your OBS plugins folder for your platform (the
-default locations are easy to find online -- typically
-\`~/.config/obs-studio/plugins/\` on Linux, \`%APPDATA%\\obs-studio\\plugins\\\`
-on Windows, \`~/Library/Application Support/obs-studio/plugins/\` on macOS).
-Each archive's top-level folder already matches the shape OBS expects there,
-so extracting is the whole install step. Then in OBS: Sources -> \`+\` ->
+Extract the archive into your OBS plugins folder. **The directory is not the
+same shape on every platform, and picking the wrong one fails silently -- OBS
+logs nothing at all for a plugin it never finds:**
+
+| Platform | Extract into |
+|---|---|
+| Windows | \`C:\\ProgramData\\obs-studio\\plugins\\\` -- **not** \`%APPDATA%\\obs-studio\\\`, which is where OBS keeps its config and is never scanned for plugins |
+| macOS | \`~/Library/Application Support/obs-studio/plugins/\` |
+| Linux | \`~/.config/obs-studio/plugins/\` |
+
+Each archive's top-level folder already matches the shape OBS expects, so
+extracting is the whole install step -- but check the result is exactly one
+folder deep. Windows Explorer's "Extract All..." adds a folder named after the
+zip unless you clear it from the destination box, which nests it one level too
+far and is equally silent. On Windows the finished path must be:
+
+\`\`\`
+C:\\ProgramData\\obs-studio\\plugins\\streamer-tools-camera\\bin\\64bit\\streamer-tools-camera.dll
+\`\`\`
+
+To confirm it loaded, restart OBS and check Help -> Log Files -> View Current
+Log for \`streamer-tools-camera\` under "Loaded Modules". Then in OBS: Sources -> \`+\` ->
 "streamer-tools Camera" -> fill in the server URL, room slug and read key
 from the room's settings page -> "Refresh camera list" -> pick a camera.
 
@@ -73,7 +97,7 @@ print(json.dumps({
     "tag_name": tag,
     "name": tag,
     "body": notes,
-    "draft": True,
+    "draft": False,
     "prerelease": False,
 }))
 PYEOF
@@ -87,7 +111,7 @@ RESP="$(curl -sS -f -X POST \
   "${SERVER}/api/v1/repos/${OWNER}/${REPO}/releases")"
 
 RELEASE_ID="$(python3 -c 'import json,sys; print(json.load(sys.stdin)["id"])' <<<"${RESP}")"
-echo "Created release id ${RELEASE_ID} (draft)."
+echo "Created release id ${RELEASE_ID} (published; assets upload next)."
 
 shopt -s nullglob
 ASSETS=("${DIST_DIR}"/*)
@@ -106,4 +130,4 @@ for f in "${ASSETS[@]}"; do
     > /dev/null
 done
 
-echo "Done. Draft release: ${SERVER}/${OWNER}/${REPO}/releases/${RELEASE_ID}"
+echo "Done. Release: ${SERVER}/${OWNER}/${REPO}/releases/${RELEASE_ID}"

.gitea/workflows/build.yml

@@ -31,7 +31,29 @@ on:
     # job is ordinary commits.
     branches:
       - "**"
+    # Documentation-only changes cannot break a build, and this workflow is a
+    # full three-platform build (Windows included) behind a runner with
+    # capacity:1. Six of these fired for one afternoon of README/release-notes
+    # edits on 2026-09-09. Anything that feeds a build or a test is absent
+    # from this list on purpose -- release.yml and publish-release.sh only run
+    # on a `v*` tag, via release.yml's own trigger.
+    #
+    # Tradeoff: a docs-only push now shows NO status at all on the branch,
+    # rather than a green one. If a required-status check is ever added, these
+    # paths have to be reconsidered.
+    paths-ignore:
+      - "**.md"
+      - "LICENSE"
+      - "NOTICE"
+      - ".gitea/workflows/release.yml"
+      - ".gitea/scripts/publish-release.sh"
   pull_request:
+    paths-ignore:
+      - "**.md"
+      - "LICENSE"
+      - "NOTICE"
+      - ".gitea/workflows/release.yml"
+      - ".gitea/scripts/publish-release.sh"
 
 jobs:
   linux:

.gitea/workflows/release.yml

@@ -1,14 +1,16 @@
 name: Release
 
 # Packages a build of each platform into a downloadable archive and creates
-# a (draft) Gitea Release for it, so the project owner and other directors
+# a published Gitea Release for it, so the project owner and other directors
 # can grab a ready-to-use build instead of compiling from source.
 #
 # Runs only on a pushed version tag (see `on.push.tags` below) -- never on an
-# ordinary push or PR, unlike build.yml. The release it creates is a DRAFT:
-# it stays invisible to anyone without write access until a human explicitly
-# opens it and clicks Publish, since nobody has run this plugin in the OBS
-# GUI on any platform yet.
+# ordinary push or PR, unlike build.yml. The release it creates is PUBLISHED
+# immediately. It used to be a draft, gated on a human clicking Publish
+# because nobody had run the plugin in the OBS GUI on any platform; the first
+# confirmed GUI load (Windows, 2026-09-09) retired that. The caveats that
+# remain live in the generated release notes, not in the draft flag -- see
+# .gitea/scripts/publish-release.sh.
 #
 # The actual per-platform build commands live in .gitea/scripts/ and are the
 # same scripts .gitea/workflows/build.yml uses, so this workflow can't drift
@@ -183,7 +185,7 @@ jobs:
           path: dist
 
   release:
-    name: Create Gitea Release (draft)
+    name: Create Gitea Release
     needs: [linux, macos, windows]
     runs-on: ubuntu-24.04
     permissions:
@@ -214,7 +216,7 @@ jobs:
           name: release-archive-windows-x64
           path: dist
 
-      - name: Create draft release and upload assets
+      - name: Create release and upload assets
         run: .gitea/scripts/publish-release.sh
         env:
           GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}

README.md

@@ -14,18 +14,32 @@ match the vendored LiveKit binaries, which are also Apache-2.0 — see
 
 `.gitea/workflows/build.yml` builds, tests, and uploads CI-internal build
 artifacts on every push. `.gitea/workflows/release.yml` packages a tagged
-build (`v*`) into a **draft** Gitea Release — draft because nobody has run
-this in the OBS GUI yet (see below), not because of anything else; a human
-still needs to open it and click Publish.
+build (`v*`) into a **published** Gitea Release. It created drafts until
+2026-09-09, gated on a human clicking Publish because nobody had run the
+plugin in the OBS GUI; the first confirmed GUI load retired that gate, and the
+remaining caveats live in the generated release notes instead.
 
 The plugin is **functionally complete on Linux and verified end to end there**
 (module loads into real libobs, connects to a real LiveKit server through the
 real streamer-tools API shape, and pushes decoded frames into
 `obs_source_output_video`/`_audio`).
 
-It has **not been run in the OBS GUI on any platform.** macOS builds the real
-module in CI but its artifact is not yet loadable (see the macOS packaging gap
-under CI).
+**First confirmed OBS GUI load: Windows, 2026-09-09** — the v0.1.0 release
+artifact loaded into OBS 32.2.2 on Windows 11 (build 26200) on a director's
+machine, from
+`C:\ProgramData\obs-studio\plugins\streamer-tools-camera\bin\64bit\`.
+That retires "the module will not even load in a real OBS" for Windows. It
+does **not** yet cover whether video renders correctly, colours, A/V sync or
+latency — see "Not verified anywhere" below for what is still open. Linux and
+macOS have still never been opened in the GUI; macOS builds the real module in
+CI but its artifact is not yet loadable (see the macOS packaging gap under CI).
+
+⚠️ **The install directory is not the same on every platform, and getting it
+wrong fails silently.** On Windows it is
+`C:\ProgramData\obs-studio\plugins\` (`GetProgramDataPath` →
+`CSIDL_COMMON_APPDATA`), **not** `%APPDATA%\obs-studio\` — see the packaging
+section. That mistake cost the director above an evening: OBS logs nothing at
+all for a plugin it never finds.
 
 **Windows CI is now green.** The run at `f27b1c0` is the first completed
 green Windows job on this repository: the from-source libobs bootstrap
@@ -35,8 +49,8 @@ suites pass, and `build\package\bin\64bit\streamer-tools-camera.dll`
 out of the job's own log body, not inferred from the job status. That also
 retires three previously-unproven items in one go: the `-A x64` argument fix,
 the PowerShell rewrite of the Windows steps, and the `add_subdirectory`
-patch for `OBS::w32-pthreads`. Windows is still **unverified in the OBS GUI**,
-exactly like the other two platforms. See "Where the Windows bootstrap got
+patch for `OBS::w32-pthreads`. Windows has since been **loaded in the real OBS
+GUI** (see above); Linux and macOS have not. See "Where the Windows bootstrap got
 to" under CI below for the whole trace, and check current CI status rather
 than trusting this paragraph's age.
 
@@ -66,7 +80,7 @@ scripts/livekit-dev-room.py - mints tokens for the integration test
 third_party/livekit/     - redistribution notices for the LiveKit binaries
 .gitea/scripts/          - the actual per-platform build commands, shared by build.yml and release.yml
 .gitea/workflows/build.yml    - 3-platform CI matrix (every push/PR; never publishes)
-.gitea/workflows/release.yml  - packages + creates a draft Gitea Release (only on a `v*` tag push; see Status above)
+.gitea/workflows/release.yml  - packages + publishes a Gitea Release (only on a `v*` tag push; see Status above)
 ```
 
 ## How it works
@@ -142,17 +156,28 @@ build/package/licenses/...
 ```
 
 That is exactly the layout OBS searches on Linux and Windows —
-`<config>/obs-studio/plugins/<name>/bin/64bit` plus a sibling `data/`, per
-`AddExtraModulePaths()` in obs-studio's `UI/window-basic-main.cpp` — so
-`build/package/` is a straight drop-in. The module resolves the LiveKit
-libraries from `$ORIGIN` (verified: `ldd` on the staged copy resolves both
+`<base>/obs-studio/plugins/<name>/bin/64bit` plus a sibling `data/`, per
+`AddExtraModulePaths()` in obs-studio (`UI/window-basic-main.cpp` in 30.x,
+`frontend/widgets/OBSBasic.cpp` in 32.x) — so `build/package/` is a straight
+drop-in. **`<base>` is NOT the same directory on every platform**, and getting
+this wrong is silent: OBS logs nothing at all for a plugin it never finds.
+Linux uses the user config dir (`GetAppConfigPath` → `~/.config`), but Windows
+uses `GetProgramDataPath` (`CSIDL_COMMON_APPDATA`) — i.e.
+`C:\ProgramData\obs-studio\plugins\`, **not** `%APPDATA%\obs-studio\`
+(`CSIDL_APPDATA`), which on Windows holds OBS's config and is never scanned for
+plugins. This bit a director on 2026-09-09: a correctly-shaped install under
+`AppData\Roaming` produced a log with zero mention of the module.
+
+The module resolves the LiveKit libraries from `$ORIGIN` (verified: `ldd` on the staged copy resolves both
 to `bin/64bit/`), not from the build tree. macOS is not this shape; see the
 macOS packaging gap under CI.
 
 ## Testing this by hand
 
-**Nobody has yet run this in the OBS GUI. That test is still outstanding on
-all three platforms.** To do it on Linux:
+**The module has been loaded in the OBS GUI on Windows once (2026-09-09, OBS
+32.2.2 / Windows 11 26200) — nothing beyond "it loads and registers its source"
+is confirmed there, and Linux and macOS have never been opened in the GUI at
+all.** To do it on Linux:
 
 ```
 mkdir -p ~/.config/obs-studio/plugins/streamer-tools-camera
@@ -208,7 +233,11 @@ livekit-server 1.13.6 in dev mode):
 | Two sources in one OBS process | same harness with a second source added: both connect with distinct nonce identities, both receive frames, both tear down cleanly |
 
 **Not verified anywhere:**
-- The OBS GUI, on any platform. No human has looked at this in OBS.
+- Anything past module load in the OBS GUI. Windows 2026-09-09 confirms the
+  module loads and its source type appears; whether video actually renders
+  (right way up, right colours), what the A/V sync and latency look like, and
+  whether a publisher restarting mid-show recovers on screen are all still
+  unanswered. Linux and macOS have not been opened in the GUI at all.
 - macOS beyond "CI builds and links the real module and the core tests pass".
   Its artifact is a bare `.so` with a relative libobs install name and will
   not load in OBS.app — see the macOS packaging gap under CI.

core/src/http_winhttp.cpp

@@ -19,8 +19,13 @@ You may obtain a copy of the License at
 #include <windows.h>
 #include <winhttp.h>
 
+#include <atomic>
+#include <chrono>
+#include <condition_variable>
 #include <cstddef>
+#include <mutex>
 #include <string>
+#include <thread>
 #include <vector>
 
 namespace stplugin {
@@ -72,6 +77,79 @@ private:
     HINTERNET h_ = nullptr;
 };
 
+/// Hard deadline for one WinHTTP exchange, enforced by cancelling it.
+///
+/// Neither receive timeout is a guaranteed deadline: Microsoft documents both
+/// as "checked only when data is received from the socket", so an expired
+/// timeout is not surfaced until the peer finally sends something. Measured on
+/// the Windows CI runner against a server that accepts and then stalls 5s: a
+/// 700ms budget returned after 1490, 1529, 2485, 3493 and 4506ms across five
+/// attempts -- always cancelled, never on time.
+///
+/// That overshoot matters because `fetchSlots` is called synchronously on the
+/// OBS UI thread behind the properties dialog's "Refresh camera list" button
+/// (obs-adapter/src/plugin-main.cpp), with a 5s budget. At the ratio above
+/// that is a frozen dialog for half a minute.
+///
+/// The documented way to force cancellation is to close the handle from
+/// another thread; the pending call then fails with
+/// ERROR_WINHTTP_OPERATION_CANCELLED. This owns the request handle so that
+/// exactly one of the two threads ever closes it: `handle_.exchange(nullptr)`
+/// hands the close to whichever gets there first.
+///
+/// Known, accepted race: the caller may load the handle and have the watchdog
+/// close it before the WinHttp* call reads it, in which case the call fails
+/// with ERROR_INVALID_HANDLE instead. Both outcomes are "the deadline
+/// expired", which is what the caller is told either way.
+class RequestDeadline {
+public:
+    RequestDeadline(HINTERNET request, DWORD after_ms) : handle_(request)
+    {
+        watchdog_ = std::thread([this, after_ms] {
+            std::unique_lock<std::mutex> lock(mutex_);
+            if (cv_.wait_for(lock, std::chrono::milliseconds(after_ms), [this] { return finished_; }))
+                return; // exchange finished inside the deadline
+            if (closeOnce())
+                expired_.store(true);
+        });
+    }
+
+    ~RequestDeadline()
+    {
+        {
+            std::lock_guard<std::mutex> lock(mutex_);
+            finished_ = true;
+        }
+        cv_.notify_all();
+        if (watchdog_.joinable())
+            watchdog_.join();
+        closeOnce(); // no-op if the watchdog got there first
+    }
+
+    RequestDeadline(const RequestDeadline &) = delete;
+    RequestDeadline &operator=(const RequestDeadline &) = delete;
+
+    HINTERNET get() const { return handle_.load(); }
+    bool expired() const { return expired_.load(); }
+
+private:
+    bool closeOnce()
+    {
+        HINTERNET h = handle_.exchange(nullptr);
+        if (!h)
+            return false;
+        WinHttpCloseHandle(h);
+        return true;
+    }
+
+    std::atomic<HINTERNET> handle_;
+    std::atomic<bool> expired_{false};
+    std::mutex mutex_;
+    std::condition_variable cv_;
+    bool finished_ = false;
+    std::thread watchdog_;
+};
+
 class WinHttpClient : public HttpClient {
 public:
     HttpResponse send(const HttpRequest &request) override
@@ -116,6 +194,39 @@ public:
         WinHttpSetTimeouts(session.get(), static_cast<int>(timeout), static_cast<int>(timeout),
                            static_cast<int>(timeout), static_cast<int>(timeout));
 
+        // WinHttpSetTimeouts' receive parameter maps to
+        // WINHTTP_OPTION_RECEIVE_TIMEOUT, which Microsoft documents as a
+        // PER-PACKET Winsock-layer read timeout ("applies to fetching each
+        // packet of data off the socket"), not a deadline on the response.
+        // The wait for the response HEADERS is a *separate* option,
+        // WINHTTP_OPTION_RECEIVE_RESPONSE_TIMEOUT ("to wait to receive all
+        // response headers to a request"), which WinHttpSetTimeouts does not
+        // touch and which defaults to 90 SECONDS. Without this call a server
+        // that accepts, reads the request and then stalls can hold this
+        // thread for a minute and a half regardless of request.timeout_ms --
+        // exactly the "blocking an OBS thread indefinitely" failure
+        // testPlatformBackendTimeout exists to prevent, and the likely
+        // mechanism behind that test's intermittent Windows failures.
+        //
+        // Caveat, also documented: this timeout "is checked only when data is
+        // received from the socket", so it bounds the wait but does not
+        // guarantee a hard deadline. A guaranteed deadline needs a watchdog
+        // thread calling WinHttpCloseHandle; not done here.
+        //
+        // Guarded because the constant postdates some Windows SDK headers; a
+        // toolchain without it keeps the previous (90s default) behaviour
+        // rather than failing to build.
+#ifdef WINHTTP_OPTION_RECEIVE_RESPONSE_TIMEOUT
+        DWORD response_timeout = timeout;
+        // Return value deliberately unchecked: a rejected option leaves the
+        // documented default in place, which is degraded but still correct
+        // behaviour, and there is no logging sink in this layer to report it
+        // to. The timeout probe in test_api_client.cpp is what would catch a
+        // regression here.
+        WinHttpSetOption(session.get(), WINHTTP_OPTION_RECEIVE_RESPONSE_TIMEOUT, &response_timeout,
+                         sizeof(response_timeout));
+#endif
+
         Handle connect(WinHttpConnect(session.get(), host, parts.nPort, 0));
         if (!connect) {
             response.network_error = lastErrorMessage("WinHttpConnect");
@@ -126,13 +237,36 @@ public:
         target += extra;
 
         const DWORD flags = (parts.nScheme == INTERNET_SCHEME_HTTPS) ? WINHTTP_FLAG_SECURE : 0u;
-        Handle req(WinHttpOpenRequest(connect.get(), widen(request.method).c_str(), target.c_str(), nullptr,
-                                      WINHTTP_NO_REFERER, WINHTTP_DEFAULT_ACCEPT_TYPES, flags));
-        if (!req) {
+        HINTERNET raw_req = WinHttpOpenRequest(connect.get(), widen(request.method).c_str(), target.c_str(),
+                                               nullptr, WINHTTP_NO_REFERER, WINHTTP_DEFAULT_ACCEPT_TYPES,
+                                               flags);
+        if (!raw_req) {
             response.network_error = lastErrorMessage("WinHttpOpenRequest");
             return response;
         }
 
+        // Ceiling at twice the caller's budget: each of the four
+        // WinHttpSetTimeouts phases (resolve, connect, send, receive) is
+        // allowed `timeout` on its own, so a slow-but-progressing exchange can
+        // legitimately exceed one budget, and this must not cancel those. The
+        // floor keeps a very small timeout_ms from producing a deadline the
+        // exchange cannot meet on a cold connection.
+        const DWORD deadline_ms = (timeout > 500u) ? (timeout * 2u) : 1000u;
+        RequestDeadline req(raw_req, deadline_ms);
+
+        // From here on, `req.get()` can be closed underneath us by the
+        // watchdog; every WinHttp* failure below is therefore checked against
+        // req.expired() before its GetLastError text is reported, so an
+        // expired deadline reads as a timeout rather than as
+        // "WinHttpReceiveResponse failed (GetLastError=12017)".
+        const auto fail = [&](const char *what) -> HttpResponse {
+            if (req.expired())
+                response.network_error = "timed out after " + std::to_string(deadline_ms) + " ms";
+            else
+                response.network_error = lastErrorMessage(what);
+            return response;
+        };
+
         std::wstring headers;
         if (!request.content_type.empty())
             headers = L"Content-Type: " + widen(request.content_type) + L"\r\n";
@@ -144,31 +278,23 @@ public:
                                               : const_cast<char *>(request.body.data());
         const DWORD body_len = static_cast<DWORD>(request.body.size());
 
-        if (!WinHttpSendRequest(req.get(), header_ptr, header_len, body_ptr, body_len, body_len, 0)) {
-            response.network_error = lastErrorMessage("WinHttpSendRequest");
-            return response;
-        }
-        if (!WinHttpReceiveResponse(req.get(), nullptr)) {
-            response.network_error = lastErrorMessage("WinHttpReceiveResponse");
-            return response;
-        }
+        if (!WinHttpSendRequest(req.get(), header_ptr, header_len, body_ptr, body_len, body_len, 0))
+            return fail("WinHttpSendRequest");
+        if (!WinHttpReceiveResponse(req.get(), nullptr))
+            return fail("WinHttpReceiveResponse");
 
         DWORD status = 0;
         DWORD status_size = sizeof(status);
         if (!WinHttpQueryHeaders(req.get(), WINHTTP_QUERY_STATUS_CODE | WINHTTP_QUERY_FLAG_NUMBER,
-                                 WINHTTP_HEADER_NAME_BY_INDEX, &status, &status_size, WINHTTP_NO_HEADER_INDEX)) {
-            response.network_error = lastErrorMessage("WinHttpQueryHeaders");
-            return response;
-        }
+                                 WINHTTP_HEADER_NAME_BY_INDEX, &status, &status_size, WINHTTP_NO_HEADER_INDEX))
+            return fail("WinHttpQueryHeaders");
         response.status = static_cast<long>(status);
 
         std::string body;
         for (;;) {
             DWORD available = 0;
-            if (!WinHttpQueryDataAvailable(req.get(), &available)) {
-                response.network_error = lastErrorMessage("WinHttpQueryDataAvailable");
-                return response;
-            }
+            if (!WinHttpQueryDataAvailable(req.get(), &available))
+                return fail("WinHttpQueryDataAvailable");
             if (available == 0)
                 break;
             if (body.size() + available > kMaxResponseBytes) {
@@ -177,10 +303,8 @@ public:
             }
             std::vector<char> chunk(available);
             DWORD read = 0;
-            if (!WinHttpReadData(req.get(), chunk.data(), available, &read)) {
-                response.network_error = lastErrorMessage("WinHttpReadData");
-                return response;
-            }
+            if (!WinHttpReadData(req.get(), chunk.data(), available, &read))
+                return fail("WinHttpReadData");
             if (read == 0)
                 break;
             body.append(chunk.data(), read);

core/tests/test_api_client.cpp

@@ -16,6 +16,7 @@ You may obtain a copy of the License at
 //      three runners rather than assumed to work.
 
 #include <chrono>
+#include <cstdio>
 #include <memory>
 #include <string>
 #include <thread>
@@ -422,22 +423,77 @@ void testPlatformBackendTimeout()
 {
     // A server that accepts and then stalls. The plugin must give up on its
     // own timeout rather than blocking an OBS thread indefinitely.
-    sttest::LoopbackServer server([](const std::string &) {
-        std::this_thread::sleep_for(std::chrono::seconds(5));
-        return sttest::httpResponse(200, "OK", R"({"slots":[]})");
-    });
-    ST_ASSERT(server.valid());
+    //
+    // INSTRUMENTED (2026-09-09) while chasing an intermittent Windows-only
+    // failure: on roughly 2 of 6 CI runs both assertions below fail together,
+    // meaning the request waited out the full 5s stall and returned 200 --
+    // the timeout did not fire at all. Same failure seen on 2026-09-07
+    // (job 5834) and 2026-09-09 (job 5911), on identical code that passed on
+    // other runs, so it is not a code change that caused it.
+    //
+    // The probe runs kProbes times and prints one line per attempt so a
+    // single CI run yields a failure RATE and the WinHTTP error code, rather
+    // than one bit. `ST_ASSERT` records and continues, so every attempt is
+    // reported even when one fails. Remove the loop and this comment once the
+    // mechanism is understood and fixed.
+    constexpr int kProbes = 5;
+    constexpr long long kStallMs = 5000;
+    constexpr long kTimeoutMs = 700;
 
-    std::shared_ptr<HttpClient> http(createPlatformHttpClient());
-    HttpRequest request;
-    request.url = server.baseUrl() + "/api/obs/main-room/slots?key=k";
-    request.timeout_ms = 700;
+    int timed_out = 0;
+    for (int i = 0; i < kProbes; ++i) {
+        // A FRESH server per attempt, deliberately. `LoopbackServer` accepts
+        // and handles one connection at a time on a single thread, so reusing
+        // one server across attempts would leave attempts 2..n sitting in the
+        // accept backlog -- a different scenario (never accepted) from the one
+        // that fails on Windows (accepted, request read, then stalled).
+        sttest::LoopbackServer server([kStallMs](const std::string &) {
+            std::this_thread::sleep_for(std::chrono::milliseconds(kStallMs));
+            return sttest::httpResponse(200, "OK", R"({"slots":[]})");
+        });
+        ST_ASSERT(server.valid());
 
-    const auto start = std::chrono::steady_clock::now();
-    const HttpResponse response = http->send(request);
-    const auto elapsed = std::chrono::steady_clock::now() - start;
-    ST_ASSERT(!response.ok());
-    ST_ASSERT(std::chrono::duration_cast<std::chrono::milliseconds>(elapsed).count() < 4000);
+        std::shared_ptr<HttpClient> http(createPlatformHttpClient());
+        HttpRequest request;
+        request.url = server.baseUrl() + "/api/obs/main-room/slots?key=k";
+        request.timeout_ms = kTimeoutMs;
+
+        const auto start = std::chrono::steady_clock::now();
+        const HttpResponse response = http->send(request);
+        const auto elapsed = std::chrono::steady_clock::now() - start;
+        const long long ms = std::chrono::duration_cast<std::chrono::milliseconds>(elapsed).count();
+
+        // 4000 was the old bound, chosen when nothing bounded the wait. The
+        // code now promises a hard ceiling of 2x the caller's budget
+        // (RequestDeadline in http_winhttp.cpp), so assert THAT -- 1400ms
+        // here, plus slack for a loaded runner. This is also the only signal
+        // that survives a green run: CTest prints nothing on success, so if
+        // WinHTTP's own erratic cancellation (measured at 1490-4506ms for
+        // this same 700ms budget) were doing the work instead of the
+        // watchdog, roughly half the attempts would land above this bound and
+        // say so, instead of quietly passing under a 4s ceiling.
+        constexpr long long kCeilingMs = 2500;
+        const bool gave_up = !response.ok() && ms < kCeilingMs;
+        if (gave_up)
+            ++timed_out;
+
+        // Always printed, pass or fail: elapsed time and the backend's own
+        // error string (which carries GetLastError on Windows) are the
+        // evidence. requests_seen separates "the client never reached the
+        // server" (0) from "the server read the request and the client then
+        // waited it out" (1).
+        std::fprintf(stderr,
+                     "  [timeout-probe %d/%d] elapsed=%lldms ok=%d status=%ld "
+                     "requests_seen=%d network_error='%s' -> %s\n",
+                     i + 1, kProbes, ms, response.ok() ? 1 : 0, response.status,
+                     server.requestCount(), response.network_error.c_str(),
+                     gave_up ? "gave up (expected)" : "WAITED OUT THE STALL");
+
+        ST_ASSERT(!response.ok());
+        ST_ASSERT(ms < kCeilingMs);
+    }
+    std::fprintf(stderr, "  [timeout-probe] %d/%d attempts honoured the %ldms timeout\n",
+                 timed_out, kProbes, kTimeoutMs);
 }
 
 } // namespace