docs: cmake/platform.cmake belongs to PKG/QA, not PORT (ADR 0020 amendment)

As written, ADR 0020 gave PORT ownership of cmake/platform*.cmake while also making PORT wait for Phase 0 — but Phase 0's seams are exactly what needs velox_platform_sources() to select platform/linux/*.cpp. PORT cannot start until Phase 0 lands, and Phase 0 cannot land without the file PORT owns. PKG/QA caught the circularity before writing anything, which was the right call. Central OS detection is root build infrastructure, so it stays with PKG/QA and lands during Phase 0. PORT keeps the per-OS backend directories and the macOS and Windows packaging, and owns no part of cmake/. Also drops a hardcoded test count from the PORT definition of done; the suite number moves every round and the gate is that it stays green. Co-Authored-By: Claude Opus 5 <[email protected]>
merge: lane/daemon — velox-nmhost, systemd units, velox(1) man page
2026-09-15 17:46:48 +04:00 · 2026-09-15 17:38:46 +04:00 · 2026-09-15 17:36:27 +04:00 · 2026-09-12 22:46:52 +04:00 · 2026-09-12 22:05:06 +04:00 · 2026-09-12 22:04:09 +04:00
43 changed files with 2214 additions and 139 deletions
@@ -18,8 +18,9 @@ policy so it can be re-applied or audited.
  | `bootstrap-script-2604` | now — real `--with-clang` install in a 26.04 container; the release the project ships on |
  | `build (gcc)` / `build (clang)` | now — core, daemon and gui have merged |
  | `sanitizers (dev)` / `sanitizers (tsan)` | now — core, daemon and gui have merged |
-  | `conformance` | **now — `tests/conformance/` has landed; this is the M0 exit gate** |
+  | `conformance` | **now — `tests/conformance/` has landed; this is the M0 exit gate.** Includes the live-`veloxd` runner (step 3b of `run.sh`), unconditional in the script — see `docs/adr/0019-live-veloxd-conformance-is-required.md`. |
  | `extension-lint` | now — `extension/` has merged (MV3 manifest + esbuild build) |
+  | `gui-dod` | now — `gui/tests/dod/` has landed (GUI M1 DoD gates R3: `scroll-60fps`, `unhappy-path`); see `tests/integration/README.md#gui-m1-definition-of-done-gates-r3`. `gui-dod-nightly` (`rss-flat`) is schedule-only and cannot be a required PR check. |

  `clang-tidy` is intentionally **not** required through M1 (`continue-on-error: true`,
  `.clang-tidy` has `WarningsAsErrors: ''`). Make it required at M2.
@@ -248,3 +248,56 @@ jobs:
        run: cmake --build --preset dev --target veloxd
      - name: Nightly integration run
        run: python3 tests/integration/nightly_run.py --veloxd build/dev/bin/veloxd --tasks 50 --timeout 180
+
+  gui-dod:
+    # Per-PR GUI M1 DoD gates (gui/docs/pkg-qa-requests-m1.md R3): scroll-60fps and
+    # unhappy-path. The 10-minute rss-flat gate is gui-dod-nightly, not here. GUI's
+    # harness defaults QT_QPA_PLATFORM=offscreen itself, so no Xvfb/compositor needed.
+    # See tests/integration/README.md#gui-m1-definition-of-done-gates-r3 for what each
+    # gate catches and the forced-failure transcript proving it isn't vacuous.
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Bootstrap toolchain
+        run: sudo ./tools/bootstrap.sh
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'          # tools/mockd
+      - name: Configure + build
+        run: |
+          cmake --preset dev
+          cmake --build --preset dev --target gui-dod-harness
+      - name: Install mockd
+        run: cd tools/mockd && npm ci
+      - name: Gates
+        run: |
+          gui/tests/dod/run.sh scroll-60fps  --json scroll.json
+          gui/tests/dod/run.sh unhappy-path  --json unhappy.json
+      - uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: gui-dod-${{ github.run_id }}
+          path: "*.json"
+
+  gui-dod-nightly:
+    if: github.event_name == 'schedule' || github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Bootstrap toolchain
+        run: sudo ./tools/bootstrap.sh
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+      - name: Configure + build
+        run: |
+          cmake --preset dev
+          cmake --build --preset dev --target gui-dod-harness
+      - run: cd tools/mockd && npm ci
+      - name: RSS soak (10 min)
+        run: gui/tests/dod/run.sh rss-flat --json rss.json
+      - uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: gui-dod-rss-${{ github.run_id }}
+          path: rss.json
@@ -12,6 +12,7 @@ Read this before touching anything. Then read your lane brief in [docs/agents/](
 | GUI | `gui/` | everything else |
 | EXT | `extension/` | everything else |
 | PKG/QA | `packaging/`, `.github/`, `tools/testserver/`, `tests/integration/`, `tests/e2e/`, root build files | any lane's feature code |
+| PORT | `**/platform/<os>/**`, `packaging/macos/`, `packaging/windows/` | all logic, and `cmake/` — see [ADR 0020](docs/adr/0020-cross-platform-strategy.md) |

 If your task seems to require editing another lane's files, that is a signal the interface
 is wrong. **File the request; don't reach across.**
@@ -0,0 +1,129 @@
+.TH VELOX 1 "2026-09-12" "Velox" "User Commands"
+.SH NAME
+velox \- command-line client for veloxd, the Velox download manager daemon
+.SH SYNOPSIS
+.B velox
+.I command
+.RI [ options ]
+.SH DESCRIPTION
+.B velox
+talks to
+\fBveloxd\fR
+over its Unix-domain socket and gives a scriptable, terminal-first view of the same
+downloads the GUI and the Firefox extension see. It does no downloading itself \(em every
+command is a thin JSON-RPC call; the daemon owns all state.
+.PP
+.B veloxd
+must already be running (see
+.B ENVIRONMENT
+below for how
+.B velox
+finds it, and
+.BR systemctl (1)
+.RI ( "systemctl --user status velox" )
+for whether it's up). If nothing is listening on the socket,
+.B velox
+exits with status 3 rather than hanging.
+.SH COMMANDS
+.TP
+.BI "add " url " [\-\-dir " dir "] [\-\-out " name "] [\-\-segments " n ]
+Add a new download. Prints the new task's id and initial state.
+.RS
+.TP
+.BI "\-\-dir " dir
+Destination directory. Must resolve inside one of the daemon's configured
+.B saveTo.allowedRoots
+or the call fails; omit to use the configured default download directory.
+.TP
+.BI "\-\-out " name
+Filename to save as. Omit to derive one from the URL (or, once the daemon has probed it,
+from the server's own
+.BR Content-Disposition ).
+.TP
+.BI "\-\-segments " n
+Requested connection count for this download, 1\(en32. The daemon may use fewer \(em a
+per-host cap or a source that turns out not to support resuming both lower it. The
+.B ls
+table (and
+.RI "\-\-json's " segments
+field) show what was actually granted, not what was asked for.
+.RE
+.TP
+.B ls
+List every download the daemon knows about: id, state, progress, and filename. With
+.BR \-\-json ", the raw " download.list " result instead of the table."
+.TP
+.BI "pause " id " [" id " ...]"
+Pause one or more downloads by id. A download already paused, or already finished, is
+left alone \(em not an error.
+.TP
+.BI "resume " id " [" id " ...]"
+Resume one or more paused downloads.
+.TP
+.BI "rm " id " [" id " ...] " "[\-\-delete\-file]"
+Remove one or more downloads from the list. Without
+.BR \-\-delete\-file ,
+any partial data on disk
+.RI ( .veloxpart / .veloxpart.meta )
+is discarded but a
+.B completed
+file is left in place. With
+.BR \-\-delete\-file ,
+the finished file is deleted too \(em there is deliberately no default for this flag; you
+must say which you mean every time.
+.SH OPTIONS
+.TP
+.B \-\-json
+Print the raw JSON-RPC result instead of a formatted table. Works with every command;
+combine with
+.BR jq (1)
+for scripting. On error, the JSON form is an
+.B {"error": {...}}
+object on stdout rather than a message on stderr.
+.TP
+.B \-h ", " \-\-help
+Print usage and exit 0.
+.SH EXIT STATUS
+.TP
+.B 0
+Success.
+.TP
+.B 1
+The daemon reached the call but returned a JSON-RPC error (bad task id, path outside the
+allowed roots, and so on). The message is on stderr, or in the JSON error object with
+.BR \-\-json .
+.TP
+.B 2
+Usage error \(em missing argument, unknown option, or unknown command.
+.TP
+.B 3
+Could not reach
+.B veloxd
+at all: not running, or its socket is missing or unreachable.
+.SH ENVIRONMENT
+.TP
+.B XDG_RUNTIME_DIR
+.B velox
+connects to
+.IR "$XDG_RUNTIME_DIR/velox/velox.sock" .
+If unset, it falls back to
+.IR /run/user/ <uid> ,
+matching
+\fBveloxd\fR's
+own resolution \(em the two must agree for the client to find the daemon, so this is
+normally left to the desktop session's default rather than set by hand.
+.SH FILES
+.TP
+.I $XDG_RUNTIME_DIR/velox/velox.sock
+The daemon's Unix-domain socket, mode 0600, same-UID only (\fBSO_PEERCRED\fR checked on
+every connection \(em this is the transport's authorization, not an extra login).
+.SH SEE ALSO
+.BR systemctl (1),
+.BR jq (1)
+.PP
+.I docs/01-architecture.md
+and
+.I docs/agents/AGENT-DAEMON.md
+in the Velox source tree for the daemon's own build order and the wire protocol
+.B velox
+speaks.
@@ -506,7 +506,12 @@ def emit_field_parse(f: Field, indent: str) -> list[str]:
         f'{i}    const auto it = j.find("{f.name}");']
    if f.optional:
        # Absent and null mean the same thing: the field is not set. A client that omits
-        # a nullable field and one that sends null are treated identically on purpose.
+        # a nullable field and one that sends null are treated identically on purpose --
+        # correct for create-style params, where there is no existing value to distinguish
+        # "never set" from "explicitly cleared". Patch-style fields need the distinction
+        # (download.update's patch: "an explicit null clears a nullable field") and get an
+        # opt-in exception via x-clearable per ADR 0018 (not implemented yet: this is the
+        # decision record, not the generator change).
        o.append(f"{i}    if (it != j.end() && !it->is_null()) {{")
        o += emit_value_parse(f.type, "(*it)", "val", "fp", i + "        ")
        o.append(f"{i}        out.{m} = std::move(val);")
@@ -21,7 +21,7 @@ fixtures/

 ```jsonc
 {
-  "name": "download.add — start an ISO now, into the Programs category",
+  "name": "download.add — add an ISO for later, into the Programs category",
  "description": "Why this case is worth pinning.",
  "transport": "uds",          // optional: replay only on this transport
  "requires": "...",           // optional: a condition a plain server cannot produce
@@ -81,3 +81,27 @@ cases in `tests/integration/`.
 correct response is *no response*: past 750 ms the extension must abandon the offer and let
 Firefox download normally. A download manager that eats downloads when its daemon is down
 is worse than no download manager.
+
+## No fixture may pair a real external URL with `startMode: "now"`
+
+This suite replays every fixture against a real, live `veloxd` (`tests/conformance/run.sh`),
+not just `mockd`. `mockd` never actually fetches anything, so it hid this for a while: a
+fixture with `startMode: "now"` (or `"queue"` into a running queue — anything that gets
+admitted to the scheduler right away) and a real, resolvable URL makes a **real** daemon
+actually start downloading it, for real, onto whatever machine runs the suite. This
+happened — twice, with `download.add.json` pointed at a ~6 GB Ubuntu ISO, straight into the
+developer's real `~/Downloads`.
+
+The fix in each case is one of:
+- `startMode: "later"` — exercises the add path (validation, category assignment, the
+  event) without ever handing the task to the engine;
+- a URL under `example.org`/`example.com` (IANA-reserved for exactly this, RFC 2606) —
+  resolvable enough to validate as a URL, never a real download source;
+- `requires`, if the fixture's entire point needs a real transfer to fail in a specific way
+  (see `errors/download.add.disk-full.json`) — skipped by default, so it only ever runs
+  where the condition has actually been arranged.
+
+A real `saveDir` gets the same treatment for the same reason: an absolute path like
+`/home/sami/Downloads/...` only means anything on the machine that fixture was written on.
+Omit `saveDir` and let `saveTo.defaultDir` apply, or use a relative-feeling path under a
+root the runner controls.
@@ -1,22 +1,23 @@
 {
  "name": "capture.offer — attachment on a monitored type is taken",
-  "description": "Golden fixture. tests/conformance replays this against the real daemon AND the TS client. If either side drifts, this goes red before the lanes ever integrate.",
+  "description": "Golden fixture. tests/conformance replays this against the real daemon AND the TS client. If either side drifts, this goes red before the lanes ever integrate. url is example.org (RFC 2606), not a real download source: 'take' against a real veloxd (tests/conformance/run.sh) admits a real task and hands it to the engine for real, and no fixture may do that against a real external URL. contentLength is a plausible-but-small 5 MiB rather than a real ISO's size: the 'Programs' category's saveDir is a migration-seeded builtin (~/Downloads/Programs, daemon/src/store/migrations/0001_initial.sql), not something an isolated test run's settings can redirect, so 'take' always sparse-preallocates into that real path on whatever machine runs this suite -- keeping the declared size small keeps that footprint trivial instead of a real ISO's worth of disk. transport is uds only: a real 'take' persists an active task, so replaying this same fixture again on a second live transport against the same daemon would correctly dedupe against it (capture.offer dedupes by exact URL) and get 'ignore' instead -- an artifact of replaying one fixture against one shared daemon over two transports, not a behaviour to golden.",
+  "transport": "uds",
  "request": {
    "jsonrpc": "2.0",
    "id": 42,
    "method": "capture.offer",
    "params": {
-      "url": "https://releases.ubuntu.com/26.04/ubuntu-26.04-desktop-amd64.iso",
+      "url": "https://example.org/dl/ubuntu-26.04-desktop-amd64.iso",
      "method": "GET",
-      "tabUrl": "https://releases.ubuntu.com/26.04/",
+      "tabUrl": "https://example.org/26.04/",
      "headers": {
        "User-Agent": "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:154.0) Gecko/20100101 Firefox/154.0",
-        "Referer": "https://releases.ubuntu.com/26.04/",
+        "Referer": "https://example.org/26.04/",
        "Accept": "*/*"
      },
      "cookies": [],
      "contentType": "application/octet-stream",
-      "contentLength": 6228541440,
+      "contentLength": 5242880,
      "contentDisposition": "attachment; filename=\"ubuntu-26.04-desktop-amd64.iso\"",
      "filename": "ubuntu-26.04-desktop-amd64.iso",
      "origin": "moz-extension://11111111-2222-3333-4444-555555555555"
@@ -1,6 +1,6 @@
 {
-  "name": "download.add \u2014 start an ISO now, into the Programs category",
-  "description": "The ordinary add path. saveDir is canonicalized and checked against the allowed roots before anything is written.",
+  "name": "download.add — add an ISO for later, into the Programs category",
+  "description": "The ordinary add path. saveDir is canonicalized and checked against the allowed roots before anything is written. startMode is 'later' deliberately: this suite replays against a real veloxd (tests/conformance/run.sh), and a real daemon given startMode 'now' would actually start fetching url for real. No fixture may pair a real external URL with startMode 'now' -- see contracts/fixtures/README.md.",
  "request": {
    "jsonrpc": "2.0",
    "id": 11,
@@ -8,10 +8,9 @@
    "params": {
      "url": "https://releases.ubuntu.com/26.04/ubuntu-26.04-desktop-amd64.iso",
      "filename": "ubuntu-26.04-desktop-amd64.iso",
-      "saveDir": "/home/sami/Downloads/Programs",
      "categoryId": "programs",
      "segments": 8,
-      "startMode": "now"
+      "startMode": "later"
    }
  },
  "response": {
@@ -19,13 +18,13 @@
    "id": 11,
    "result": {
      "taskId": "$uuid",
-      "state": "connecting",
+      "state": "paused",
      "duplicate": null
    }
  },
  "assertions": [
-    "the .veloxpart file is created sparse and preallocated at the final size",
-    "saveDir resolves inside saveTo.allowedRoots, or the call fails -32011 having written nothing",
+    "saveDir is omitted here on purpose: it resolves to saveTo.defaultDir, which is itself checked against saveTo.allowedRoots the same way an explicit saveDir would be -- see errors/download.add.invalid-path.json for the -32011 case",
+    "startMode 'later' lands the task in 'paused' and never hands it to the engine, so nothing is fetched and no .veloxpart is created yet -- that only happens once the task is actually started (download.start.json, or startMode 'now'/'queue' against a source this suite controls)",
    "event.task.added is emitted to every subscriber before this reply is sent"
  ]
 }
@@ -1,6 +1,6 @@
 {
  "name": "limiter.get \u2014 the limiter is off",
-  "description": "globalBps still carries the last configured value so the GUI can restore it when the user re-enables the limit.",
+  "description": "globalBps still carries the last configured value so the GUI can restore it when the user re-enables the limit. applyToRunning is a write-only instruction on limiter.set (\"retune already-running transfers now\", not a persisted setting), so it never comes back from get.",
  "request": {
    "jsonrpc": "2.0",
    "id": 52,
@@ -12,11 +12,11 @@
    "id": 52,
    "result": {
      "enabled": false,
-      "globalBps": 2097152,
-      "applyToRunning": false
+      "globalBps": 2097152
    }
  },
  "assertions": [
-    "enabled false means no throttling regardless of globalBps"
+    "enabled false means no throttling regardless of globalBps",
+    "applyToRunning is absent, not false: it's meaningless outside a limiter.set call"
  ]
 }
@@ -64,6 +64,19 @@ std::string lower(std::string s) {
    return s;
 }

+// scheme://host[:port] of `url`, with no path/query/fragment -- what docs/04 §7's "403
+// after redirect: retry once with the original referrer" retries with as the Referer
+// header. Empty on an unparseable URL (the caller just won't get a referrer retry).
+std::string origin_of(std::string_view url) {
+    auto s = net::split_url(url);
+    if (!s.valid)
+        return {};
+    std::string out = s.scheme + "://" + s.host;
+    if (s.port)
+        out += ":" + std::to_string(*s.port);
+    return out;
+}
+
 }  // namespace

 // What to do once every worker has drained (see DownloadTaskState::begin_drain_locked).
@@ -88,6 +101,7 @@ struct SegWorker {
    bool needs_auth = false;
    bool wrong_status = false;
    bool range_bad = false;
+    bool forbidden = false;  // 403 -- docs/04 §7's "retry once with the original referrer"
    bool auth_handshake = false;  // saw a 401/407 and let libcurl resend with credentials
    std::string resp_etag, resp_last_modified;  // captured on a wrong_status 200, for demote
    std::optional<ErrorInfo> flush_error;
@@ -135,6 +149,16 @@ struct DownloadTaskState : std::enable_shared_from_this<DownloadTaskState> {
    std::optional<std::uint64_t> total_size;
    std::string origin_host;

+    // docs/04 §7's "403 after redirect: retry once with the original referrer" -- many
+    // CDNs 403 a bare/foreign Referer. Starts as spec.referrer (the browser's, verbatim);
+    // start_worker_locked() sends this, not spec.referrer directly, so a 403 retry can
+    // override it (to the download URL's own origin) without touching what the caller
+    // actually asked for. referrer_retried bounds it to exactly once per task -- a second
+    // 403 with a same-origin Referer already set is a real, honest failure
+    // (Error::forbidden), not something a referrer swap can fix.
+    std::string effective_referrer;
+    bool referrer_retried = false;
+
    std::unique_ptr<segment::Segmenter> seg;
    std::unique_ptr<io::SparseFile> file;
    std::unordered_map<std::uint32_t, std::unique_ptr<SegWorker>> workers;
@@ -164,7 +188,7 @@ struct DownloadTaskState : std::enable_shared_from_this<DownloadTaskState> {
    std::vector<std::function<void()>> deferred;

    DownloadTaskState(TaskHost &h, TaskId i, DownloadSpec s, DownloadCallbacks c)
-        : host(h), id(i), spec(std::move(s)), cbs(std::move(c)) {}
+        : host(h), id(i), spec(std::move(s)), cbs(std::move(c)), effective_referrer(spec.referrer) {}

    // --- deferred callbacks -------------------------------------------------------------
    void defer(std::function<void()> fn) {
@@ -286,7 +310,7 @@ void DownloadTaskState::restart_probe(bool with_auth) {
    pr.url = spec.url;
    pr.headers = spec.headers;
    pr.cookies = spec.cookies;
-    pr.referrer = spec.referrer;
+    pr.referrer = effective_referrer;
    pr.user_agent = spec.user_agent;
    pr.proxy = spec.proxy;
    if (with_auth)
@@ -299,12 +323,37 @@ void DownloadTaskState::restart_probe(bool with_auth) {
 }

 void DownloadTaskState::on_probe_result(Result<net::ProbeResult> r) {
+    bool retry_probe_with_referrer = false;
    {
        std::unique_lock lk(mu);
        if (retired.load() || is_terminal(state))
            return;
        if (!r.has_value()) {
-            fail_locked(std::move(r).error());
+            ErrorInfo e = std::move(r).error();
+            // docs/04 §7's referrer retry applies here too: a probe (HEAD, or the
+            // ranged-GET fallback when HEAD is refused -- probe.cpp) can be the request
+            // that actually gets 403'd, before any segment worker exists to retry it
+            // (net::Prober builds its own request from ProbeRequest::referrer, not
+            // through start_worker_locked() -- see restart_probe()'s use of
+            // effective_referrer below). Same one-shot bound via referrer_retried as the
+            // worker-level retry (seg_finished's w->forbidden branch) shares.
+            if (e.code == Error::forbidden && !referrer_retried) {
+                referrer_retried = true;
+                effective_referrer = origin_of(spec.url);
+                retry_probe_with_referrer = true;
+            } else if (e.code == Error::forbidden) {
+                // Already retried with the origin referrer and still 403 -- not something
+                // another blind retry fixes (an expired signed URL, a private resource).
+                // Ask rather than fail outright, the same "ask, don't just fail" shape as
+                // wrong_status/range_bad/the worker-level 403 branch: refresh_url() is a
+                // no-op once the task is terminal, and tools/testserver's expiring-signed-
+                // url mode (also a bare 403, indistinguishable from any other without
+                // parsing the body -- CLAUDE.md §3, core never does) is meant to be
+                // recovered exactly that way.
+                auto_pause_locked(std::move(e), false, true);
+            } else {
+                fail_locked(std::move(e));
+            }
        } else {
            probe = std::move(r).value();
            have_probe = true;
@@ -319,6 +368,8 @@ void DownloadTaskState::on_probe_result(Result<net::ProbeResult> r) {
        }
    }
    flush_deferred();
+    if (retry_probe_with_referrer)
+        restart_probe(false);
 }

 void DownloadTaskState::finish_probe_locked() {
@@ -472,7 +523,7 @@ void DownloadTaskState::start_worker_locked(std::uint32_t seg_idx) {
    req.url = current_url();
    req.headers = spec.headers;
    req.cookies = spec.cookies;
-    req.referrer = spec.referrer;
+    req.referrer = effective_referrer;
    req.user_agent = spec.user_agent;
    req.proxy = spec.proxy;
    req.auth = spec.auth;
@@ -552,6 +603,10 @@ net::DataAction DownloadTaskState::seg_head(std::uint32_t seg_idx, const net::Re
        w->range_bad = true;
        return net::DataAction::abort;
    }
+    if (h.status == 403) {
+        w->forbidden = true;
+        return net::DataAction::abort;
+    }
    if (h.status >= 400)
        return net::DataAction::abort;
    seg->set_segment_state(seg_idx, segment::SegState::downloading);
@@ -637,7 +692,7 @@ void DownloadTaskState::seg_finished(std::uint32_t seg_idx, Result<net::Transfer
    // (content-length-mismatch's honest-length lie, flaky-reset's tail, a proxy RST after
    // the last byte). If the segment is fully covered, that's a success.
    if (seg && !cancel_requested && !pause_requested && !w->needs_auth && !w->wrong_status &&
-        !w->flush_error && !w->range_bad) {
+        !w->flush_error && !w->range_bad && !w->forbidden) {
        const std::uint64_t len = seg->segment_end(seg_idx) - seg->segment_start(seg_idx) + 1;
        if (len != 0 && seg->segment_completed(seg_idx) >= len) {
            r = Result<net::TransferStats>(net::TransferStats{});
@@ -756,6 +811,35 @@ void DownloadTaskState::seg_finished(std::uint32_t seg_idx, Result<net::Transfer
        auto_pause_locked(ErrorInfo(Error::range_not_satisfiable, "416"), false, true);
        return done();
    }
+    if (w->forbidden) {
+        // docs/04 §7: "403 after redirect: retry once with the original referrer -- many
+        // CDNs require it." Bare/foreign Referer is the common cause; origin_of() rebuilds
+        // it from the (possibly redirected) URL the response actually came from. Exactly
+        // once per task, not a backoff series -- a second 403 with a same-origin Referer
+        // already set isn't something another blind retry can fix (a private/expired
+        // resource, an expiring signed URL past its window, ...). That's not necessarily
+        // terminal, though: ask (same "ask, don't just fail outright" shape as
+        // wrong_status/range_bad above) rather than fail_locked() outright, specifically
+        // so DownloadHandle::refresh_url() -- do_refresh_url() is a no-op once the task is
+        // terminal -- stays usable for the case tools/testserver's README pairs it with:
+        // a caller that gets a fresh signed URL and hands it back.
+        release_slot();
+        if (!referrer_retried) {
+            referrer_retried = true;
+            effective_referrer = origin_of(current_url());
+            seg->set_segment_state(seg_idx, segment::SegState::stalled);
+            auto wp = weak_from_this();
+            host.schedule(std::chrono::steady_clock::now(), [wp, seg_idx] {
+                if (auto s = wp.lock())
+                    s->retry_worker(seg_idx);
+            });
+            if (workers.empty())
+                transition(EngineState::retry_wait, std::nullopt);
+        } else {
+            auto_pause_locked(ErrorInfo(Error::forbidden, "403", w->http_status), false, true);
+        }
+        return done();
+    }

    if (!r.has_value()) {
        ErrorInfo e = std::move(r).error();
@@ -1215,6 +1299,7 @@ void DownloadTaskState::do_refresh_url(std::string url, std::vector<net::HeaderF
    net::ProbeRequest pr;
    pr.url = spec.url;
    pr.headers = spec.headers;
+    pr.referrer = effective_referrer;
    pr.auth = spec.auth;
    pr.proxy = spec.proxy;
    host.probe(std::move(pr), [wp](Result<net::ProbeResult> r) {
@@ -1224,10 +1309,43 @@ void DownloadTaskState::do_refresh_url(std::string url, std::vector<net::HeaderF
        std::unique_lock lk(s->mu);
        if (s->retired.load() || is_terminal(s->state))
            return;
-        if (r.has_value()) {
-            s->probe.effective_url = r.value().effective_url;
-            s->probe.etag = r.value().etag;
-            s->probe.last_modified = r.value().last_modified;
+        if (!r.has_value()) {
+            lk.unlock();
+            s->flush_deferred();
+            return;  // still paused; the caller can retry refresh_url() or decide()
+        }
+        if (!s->have_probe) {
+            // The task's *first* probe never succeeded (e.g. this session's own
+            // expiring-signed-url path: 403, one referrer retry, still 403 -> ask rather
+            // than fail outright -- see on_probe_result() -- specifically so this branch
+            // exists to recover it). finish_probe_locked() is what actually registers the
+            // task with the budget and builds its Segmenter; nothing downstream of a
+            // partial field copy would ever start a worker without it.
+            s->probe = std::move(r).value();
+            s->have_probe = true;
+            s->awaiting_auth = false;
+            s->awaiting_decision = false;
+            s->finish_probe_locked();
+            lk.unlock();
+            s->flush_deferred();
+            return;
+        }
+        s->probe.effective_url = r.value().effective_url;
+        s->probe.etag = r.value().etag;
+        s->probe.last_modified = r.value().last_modified;
+        // refresh_url()'s own contract is "on a live OR PAUSED task, without losing
+        // progress" -- distinct from do_decide(restart), which discards progress. A task
+        // can be paused here for any of three reasons (a plain user pause, awaiting_auth,
+        // or awaiting_decision -- e.g. this session's own 403-after-referrer-retry path,
+        // or the pre-existing wrong_status/range_bad ones); apply_slot_target()'s guard
+        // blocks on awaiting_auth/awaiting_decision specifically, so leaving either set
+        // would have set_want() below recompute a target that nothing ever acts on --
+        // the caller's new URL re-probed successfully and then the task just sat there.
+        // Clear both and leave `paused` the same way do_decide(restart) does.
+        if (s->state == EngineState::paused) {
+            s->awaiting_auth = false;
+            s->awaiting_decision = false;
+            s->transition(EngineState::connecting, std::nullopt);
        }
        if (s->registered)
            s->host.budget().set_want(s->id, s->want_slots());
@@ -28,7 +28,14 @@ namespace vdm::testing {

 class TestServer {
  public:
-    TestServer() {
+    TestServer() : TestServer(1.0) {}
+
+    // loris_seconds overrides the dribble duration slow-loris mode uses (default matches the
+    // no-arg ctor's long-standing 1s). A test that needs curl's stall detector
+    // (CURLOPT_LOW_SPEED_TIME, hardcoded to 30s in download_task.cpp) to actually fire needs a
+    // dribble that outlasts that threshold, not the short one every other test relies on to
+    // keep runtime down.
+    explicit TestServer(double loris_seconds) {
        const char *script = VDM_TESTSERVER_PY;
        if (!script || !*script || ::access(script, R_OK) != 0)
            return;
@@ -50,8 +57,9 @@ class TestServer {
            int devnull = ::open("/dev/null", O_WRONLY);
            if (devnull >= 0)
                ::dup2(devnull, STDERR_FILENO);
+            std::string loris_str = std::to_string(loris_seconds);
            ::execlp("python3", "python3", script, "--port", "0", "--seed", "9", "--loris-seconds",
-                     "1", "--throttle-bps", "131072", static_cast<char *>(nullptr));
+                     loris_str.c_str(), "--throttle-bps", "131072", static_cast<char *>(nullptr));
            ::_exit(127);
        }
        ::close(pipefd[1]);
@@ -124,6 +124,31 @@ std::string server_sha(TestServer &srv, const std::string &mode, const std::stri
    return out.substr(open + 1, close - open - 1);
 }

+// Small, deliberately identical extraction to server_sha's: GET /<mode>/sign/<size>?ttl=N
+// and pull the "url" field's value out of the {"url":..., "exp":...} JSON body.
+std::string sign_url(TestServer &srv, const std::string &mode, const std::string &size,
+                     int ttl_seconds) {
+    std::string url =
+        srv.url("/" + mode + "/sign/" + size + "?ttl=" + std::to_string(ttl_seconds));
+    std::string cmd = "curl -s '" + url + "'";
+    std::string out;
+    if (FILE *f = ::popen(cmd.c_str(), "r")) {
+        char buf[1024];
+        while (std::fgets(buf, sizeof buf, f))
+            out += buf;
+        ::pclose(f);
+    }
+    auto q = out.find("\"url\"");
+    if (q == std::string::npos)
+        return {};
+    auto colon = out.find(':', q);
+    auto open = out.find('"', colon);
+    auto close = out.find('"', open + 1);
+    if (open == std::string::npos || close == std::string::npos)
+        return {};
+    return out.substr(open + 1, close - open - 1);
+}
+
 DownloadSpec spec_for(TestServer &srv, const std::string &urlpath, const std::string &save) {
    DownloadSpec s;
    s.url = srv.url(urlpath);
@@ -328,6 +353,30 @@ VT_TEST(engine_401_then_provide_auth_completes) {
    VT_CHECK_EQ(file_size(td.file("au.bin")), 1u * 1024 * 1024);
 }

+VT_TEST(engine_401_digest_then_provide_auth_completes) {
+    // Same shape as engine_401_then_provide_auth_completes, but the challenge is HTTP
+    // Digest (qop=auth) rather than Basic. provide_auth() doesn't know or care which --
+    // http_client.cpp always asks libcurl for CURLAUTH_ANY (net::AuthScheme::any) and lets
+    // curl negotiate against whatever WWW-Authenticate the server actually sent -- so this
+    // exists purely to prove that's true end-to-end, not just at the unit level.
+    TestServer srv;
+    VT_REQUIRE(srv.available());
+    TmpDir td;
+    Recorder rec;
+    Engine eng;
+    DownloadHandle h;
+    auto cbs = rec.cbs(&h, "test", "test");
+    h = eng.start(spec_for(srv, "/401-digest/file/1M", td.file("dg.bin")), std::move(cbs));
+    rec.arm(h);
+
+    auto r = rec.wait();
+    VT_REQUIRE(r.has_value());
+    VT_CHECK(rec.auth_calls.load() >= 1);
+    VT_CHECK_EQ(file_size(td.file("dg.bin")), 1u * 1024 * 1024);
+    auto got = hash_file(td.file("dg.bin"), Checksum::Algo::sha256);
+    VT_CHECK_EQ(got.value(), server_sha(srv, "401-digest", "1M"));
+}
+
 // --- hostile-mode matrix: the four where a bug is silent corruption, not a visible
 // failure (docs/04 §5 "ask, never silently corrupt" / §7's failure-policy table). ---

@@ -458,6 +507,142 @@ VT_TEST(engine_content_length_mismatch_fails_honestly) {
    VT_CHECK_EQ(::access(td.file("clm.bin").c_str(), F_OK), -1);  // never renamed into place
 }

+// --- remaining hostile-mode matrix (tools/testserver/README.md's mode table). ---
+
+VT_TEST(engine_expiring_signed_url_recovers_via_refresh_url) {
+    // A signed URL past its ttl 403s (tools/testserver's own JSON body distinguishes
+    // "expired" from "bad signature", but core never parses response bodies -- CLAUDE.md
+    // §3 -- so both just read as a 403). The one automatic referrer retry (see
+    // engine_403_without_referer_retries_with_origin, below) can't fix an expired
+    // signature, so the second 403 asks -- via the same auto_pause_locked(..., false,
+    // true) "ask, don't just fail" path as wrong_status/range_bad -- rather than
+    // terminally failing outright, specifically so DownloadHandle::refresh_url() (its own
+    // contract: works "on a live or paused task", never on a terminal one) stays usable:
+    // the README pairs this mode with exactly that recovery.
+    TestServer srv;
+    VT_REQUIRE(srv.available());
+    TmpDir td;
+    Recorder rec;
+    Engine eng;
+
+    std::string expired = sign_url(srv, "expiring-signed-url", "64K", /*ttl=*/1);
+    VT_REQUIRE(!expired.empty());
+    std::this_thread::sleep_for(1500ms);  // let the ttl actually pass before the first request
+
+    DownloadSpec s;
+    s.url = expired;
+    s.save_path = td.file("exp.bin");
+    auto h = eng.start(std::move(s), rec.cbs());
+
+    for (int i = 0; i < 300 && rec.decision_calls.load() == 0; ++i)
+        std::this_thread::sleep_for(20ms);
+    VT_REQUIRE(rec.decision_calls.load() >= 1);
+    VT_CHECK_EQ(h.state(), EngineState::paused);
+
+    std::string fresh = sign_url(srv, "expiring-signed-url", "64K", /*ttl=*/60);
+    VT_REQUIRE(!fresh.empty());
+    h.refresh_url(fresh);
+
+    auto r = rec.wait(60s);
+    VT_REQUIRE(r.has_value());
+    VT_CHECK_EQ(file_size(td.file("exp.bin")), 64u * 1024);
+    auto got = hash_file(td.file("exp.bin"), Checksum::Algo::sha256);
+    VT_CHECK_EQ(got.value(), server_sha(srv, "expiring-signed-url", "64K"));
+}
+
+VT_TEST(engine_403_without_referer_retries_with_origin) {
+    // docs/04 §7: "403 after redirect: retry once with the original referrer -- many CDNs
+    // require it." No spec.referrer is set here (the common case for anything not
+    // initiated from a browser page, e.g. `velox add <url>`), so the first attempt 403s;
+    // the engine's own retry supplies the download URL's own origin as Referer, which
+    // this mode accepts, and the download completes with no decision ever asked.
+    TestServer srv;
+    VT_REQUIRE(srv.available());
+    TmpDir td;
+    Recorder rec;
+    Engine eng;
+    auto h = eng.start(spec_for(srv, "/403-without-referer/file/128K", td.file("ref.bin")),
+                       rec.cbs());
+    auto r = rec.wait(30s);
+    VT_REQUIRE(r.has_value());
+    VT_CHECK_EQ(rec.decision_calls.load(), 0);  // recovered automatically, not asked
+    VT_CHECK_EQ(file_size(td.file("ref.bin")), 128u * 1024);
+    auto got = hash_file(td.file("ref.bin"), Checksum::Algo::sha256);
+    VT_CHECK_EQ(got.value(), server_sha(srv, "403-without-referer", "128K"));
+}
+
+VT_TEST(engine_redirect_chain_follows_to_completion) {
+    // 5 hops (tools/testserver's own --redirect-depth default) of a plain 302, query
+    // string preserved across each. No CORE-side logic needed for this one -- libcurl's
+    // own CURLOPT_FOLLOWLOCATION (RequestOptions::follow_redirects, already on) and
+    // CURLOPT_MAXREDIRS (default 20, well over 5) do the whole thing -- this is here as
+    // the end-to-end check that they're actually wired through both the probe and every
+    // segment worker's own request, not just one of the two.
+    TestServer srv;
+    VT_REQUIRE(srv.available());
+    TmpDir td;
+    Recorder rec;
+    Engine eng;
+    auto h = eng.start(spec_for(srv, "/redirect-chain/file/1M", td.file("rc.bin")), rec.cbs());
+    auto r = rec.wait(30s);
+    VT_REQUIRE(r.has_value());
+    VT_CHECK_EQ(file_size(td.file("rc.bin")), 1u * 1024 * 1024);
+    auto got = hash_file(td.file("rc.bin"), Checksum::Algo::sha256);
+    VT_CHECK_EQ(got.value(), server_sha(srv, "redirect-chain", "1M"));
+}
+
+VT_TEST(engine_slow_loris_stall_timeout_fires) {
+    // Status line, headers, and body dribbled out one byte at a time for --loris-seconds,
+    // then (if the dribble hasn't already been cut off) normal streaming -- a connection
+    // that's technically alive (bytes ARE arriving, just far too slowly) but must not be
+    // allowed to hang the task forever. http_client.cpp sets CURLOPT_LOW_SPEED_LIMIT/_TIME
+    // (RequestOptions::low_speed_bytes_per_sec/low_speed_secs, hardcoded in
+    // download_task.cpp to 1024 B/s for 30s) for exactly this.
+    //
+    // Every other test in this file uses TestServer's default 1s loris dribble to keep
+    // runtime down, but 1s is far shorter than curl's 30s low_speed_time: a 1s trickle
+    // followed by full-speed streaming never accumulates 30 CONSECUTIVE seconds under the
+    // floor, so curl would never actually abort it -- the download would just complete
+    // slightly late, which would make this test pass for the wrong reason (or not exercise
+    // the stall timeout at all). Explicitly ask for a dribble that outlasts the 30s
+    // threshold so the stall timeout is the thing actually observed firing, not assumed.
+    TestServer srv(40.0);
+    VT_REQUIRE(srv.available());
+    TmpDir td;
+    Recorder rec;
+    Engine eng;
+    auto s = spec_for(srv, "/slow-loris/file/64K", td.file("sl.bin"));
+    s.segments = 1;
+    s.max_retries = 1;
+    auto h = eng.start(std::move(s), rec.cbs());
+    auto r = rec.wait(60s);  // stall timeout fires ~30s in; must resolve, not hang to 60s
+    VT_REQUIRE(!r.has_value());
+    VT_CHECK(is_retryable(r.error().code) || r.error().code == Error::max_retries_exhausted);
+}
+
+VT_TEST(engine_chunked_no_length_completes_single_segment) {
+    // No Content-Length anywhere (HEAD gets none either, since it's the same handler path)
+    // -- the probe can't know total_size or prove resumability, so this should take the
+    // exact same "unknown size, one plain-GET segment" path as engine_non_resumable_single_
+    // segment, just arriving there via a chunked body instead of a server that plainly
+    // refuses Range. No core-side work needed if that demotion is already size-agnostic;
+    // this is here to prove it, since every other test's server tells the probe the size
+    // up front.
+    TestServer srv;
+    VT_REQUIRE(srv.available());
+    TmpDir td;
+    Recorder rec;
+    Engine eng;
+    auto h = eng.start(spec_for(srv, "/chunked-no-length/file/2M", td.file("ch.bin")),
+                       rec.cbs());
+    auto r = rec.wait();
+    VT_REQUIRE(r.has_value());
+    VT_CHECK_EQ(rec.decision_calls.load(), 0);
+    VT_CHECK_EQ(file_size(td.file("ch.bin")), 2u * 1024 * 1024);
+    auto got = hash_file(td.file("ch.bin"), Checksum::Algo::sha256);
+    VT_CHECK_EQ(got.value(), server_sha(srv, "chunked-no-length", "2M"));
+}
+
 // --- DAEMON-reported bug: Progress.speed_bps reads 0 for the whole life of a live
 // download while downloaded bytes visibly advance. DAEMON reads progress by polling
 // DownloadHandle::progress() (engine_port_core.hpp), not the on_progress push callback --
@@ -75,6 +75,7 @@ target_link_libraries(veloxd_sched PUBLIC velox::proto velox::core veloxd_store
 add_library(veloxd_rpc STATIC
    src/rpc/runtime_dir.cpp
    src/rpc/single_instance.cpp
+    src/rpc/systemd_activation.cpp
    src/rpc/event_loop.cpp
    src/rpc/event_hub.cpp
    src/rpc/uds_server.cpp
@@ -7,7 +7,7 @@ close. Kept here (not buried in commit messages) so the next pass can see them a
 |---|---|---|---|---|
 | ~~D7~~ | **Closed — `capture.offer` is real.** Applies `capture.enabled`/`excludedHosts`/`monitoredExtensions`/`monitoredMimeTypes`/`minSizeBytes` from settings, then the rules table (`store::Rules` + CORE's `vdm::rules::match_rules`/`glob_match` — DAEMON only converts its own stored `proto::Rule` JSON into CORE's plain `vdm::rules::Rule` vocabulary, per that header's own layering note), resolves the category folder (a rule's explicit `categoryId`/`saveDir`, else `store::Categories::guess_by_extension` — the same extension-guess `download.probe`'s `suggestedCategoryId` already used, now shared instead of duplicated), dedupes against active (non-terminal) tasks by exact URL, and on `take` calls `add_one()` — the same path `download.add` itself uses — so a captured download is a real, admitted, persisted task, not a special case. The 750 ms deadline (CLAUDE.md §4 / AGENT-DAEMON.md build step 6) is checked cooperatively between every step via a new `rpc::CaptureDataSource` seam (real impl wraps `store::*`; a test fake can jump its own clock forward to simulate "the store was slow just now" with zero real sleep) — catches the realistic failure mode (several slow steps adding up) though it can't preempt one pathologically stuck single call. Verified against real `veloxd` + `tools/testserver`: a monitored-type offer answers in ~5ms and actually creates + downloads the task; an unmonitored type, an excluded host, a rule-vetoed host, and a second offer for a still-active URL all answer `ignore` with the right `reason`; a bad category save dir surfaces its real `-32011` rather than being swallowed. New `capture_offer_test` covers all of the above plus the deadline itself (two cases, one per "slow" checkpoint), asserting real wall-clock time barely moves even though the fake clock jumped 2 simulated seconds — proof the check reads the injected clock, not a disguised sleep. | `rpc/capture_data_source.hpp`, `rpc/dispatcher.{hpp,cpp}`, `store/rules.{hpp,cpp}`, `store/categories.{hpp,cpp}`, `store/tasks.{hpp,cpp}` | — | done |
 | ~~D8~~ | **Closed alongside D7** — `capture.getRules` returns the same settings-backed `enabled`/`monitoredExtensions`/`monitoredMimeTypes`/`minSizeBytes`/`excludedHosts`/`bypassModifier` capture.offer itself reads, so the two can never drift. `rulesVersion` is a constant `1` — there is no persisted revision counter yet (nothing writes `rules.*` outside this process's own lifetime to need one across a restart), and the extension already re-fetches on `event.settings.changed` regardless of what this number does; noted in case a real counter becomes worth adding later. | `rpc/dispatcher.cpp` | `rulesVersion` is a placeholder constant | — |
-| D1 | Pairing prompt is `EnvAutoApprover` (needs `VELOX_PAIR_AUTO=1`) | `rpc/pairing.hpp`, `main.cpp` | A GUI dialog / `org.freedesktop.Notifications` approver is integration work | Build step 7 (systemd + notifications) |
+| D1 | Pairing prompt is `EnvAutoApprover` (needs `VELOX_PAIR_AUTO=1`) | `rpc/pairing.hpp`, `main.cpp` | A GUI dialog / `org.freedesktop.Notifications` approver is integration work | the `org.freedesktop.Notifications` half of build step 7 — the systemd half closed as D11 below |
 | — | **D1, checked this pass, not attempted:** `libdbus-1-dev` (or `libsystemd-dev` for `sd-bus`) has no headers installed in this build environment — only the runtime `.so`s (`dpkg -l`/`apt-cache policy` confirm `libdbus-1-3` present, `libdbus-1-dev` not, "Candidate" available but not installed). A real notification-backed approver needs one of those linked into `veloxd`, which is a new build dependency for `daemon/CMakeLists.txt` (`find_package`/`pkg_check_modules`) and — since packaging manifests need to know about it too — arguably a decision to surface rather than something to reach for silently mid-session. `PairingApprover::approve()` is also still synchronous by shape (its own doc comment already says so: "the real notification-backed approver will run async and is not this shape") — swapping it for the async pattern this session built for `download.probe` (`rpc::TaskActionPort` + the server-layer deferred-reply special-case) is the right shape once there's a real implementation to justify the churn; reshaping the interface with nothing behind it yet would just be churn. Left `EnvAutoApprover` in place rather than build a fragile hand-rolled D-Bus wire client to avoid the missing headers — a broken pairing approver is worse than an honest stub. | `rpc/pairing.hpp` | missing dev headers + an undiscussed new dependency | once `libdbus-1-dev`/`libsystemd-dev` is available and the dependency is approved |
 | ~~D2~~ | **Closed** — `download.probe` is real on both transports. It's genuinely async (the engine's probe pool, up to the schema's 30s `x-deadlineMs`) and so cannot fit `VeloxDispatcher::on_download_probe`'s synchronous `HandlerResult<T>` return — `uds_server.cpp`/`ws_server.cpp` special-case `"download.probe"` before the generic `dispatch()`, exactly the way they already special-case `session.hello`/`session.subscribe`, and queue the reply whenever the callback fires. `rpc::TaskActionPort::probe_now` (kept in proto/std terms, no `vdm::net::*`, so `veloxd_rpc` never needs `core/include`'s vdm headers) is what both transports call; `sched::Scheduler::probe_now` is the implementation — builds a `vdm::net::ProbeRequest`, runs it on the engine's probe pool, maps a failure to `-32013 ProbeFailed` (with `data.httpStatus` when there was one), and fills `suggestedCategoryId`/`suggestedSaveDir` with a plain extension match against the categories table (not the real rules engine — that's still D3). Verified live: a real probe answers in ~5ms; a bad host maps to `-32013`; a connection issuing a 10s `slow-loris` probe does not block a second connection's `download.list` (answered in ~1ms) — confirms the async design actually keeps the loop free, not just compiles. | `rpc/task_action_port.hpp`, `rpc/{uds_server,ws_server}.{hpp,cpp}`, `sched/scheduler.{cpp,hpp}` | — | done |
 | D3 | Stub handlers for the rest: `grabber.*`, `media.*` | `rpc/dispatcher.cpp` | HLS/DASH grabber and media-variant support don't exist anywhere in this build yet — a bigger feature than a store-wiring pass | M4 territory, per AGENT-DAEMON.md |
@@ -26,4 +26,5 @@ close. Kept here (not buried in commit messages) so the next pass can see them a
 | ~~D4b~~ | **Closed** — `download.pause`/`resume`/`start`/`cancel` and `queue.start`/`stop` all drive the scheduler now, and apply *immediately* (not deferred to the next tick — pausing/resuming/cancelling a live transfer can't wait up to 1s, and per ADR 0013 §3 the governor never touches a user-owned pause on its own). New `rpc::TaskActionPort` interface (owned by `rpc/`, implemented by `sched::Scheduler`) is the seam dispatcher.hpp depends on instead of `sched/scheduler.hpp` directly — avoids a real `veloxd_rpc` <-> `veloxd_sched` circular library dependency (`veloxd_sched` already links `veloxd_rpc` for `EventHub`). `Scheduler::user_pause/resume/start/cancel` + `pause_queue` engine-call-then-eager-transition, matching `tick()`'s existing `to_pause` pattern. Fixed a real bug hit while building this: `transition()` always overwrote `pause_reason` to NULL when the engine's own delayed pause-ack callback arrived with no explicit reason, clobbering whatever the actual initiator (user or governor) had just written — now it preserves the stored reason when none is supplied. Verified against real `veloxd` + `tools/testserver`: pausing a live single-segment throttled transfer freezes `downloadedBytes`, resume continues it from that point, cancel stops it; `queue.stop(pauseRunning:true)` pauses the queue's running task immediately. NOTE: `download.start`'s contract "a task in 'queued' jumps its queue" (priority bump) is not implemented — admission is still plain FIFO by `created_at`. | `sched/scheduler.{cpp,hpp}`, `rpc/task_action_port.hpp`, `rpc/dispatcher.{hpp,cpp}`, `store/queues.{cpp,hpp}` | — | done, except the queue-jump priority bump noted above |
 | ~~D5~~ | **Mostly closed** — `rpc/event_hub` fans out per-subscription; `session.subscribe` on both transports registers/updates/tears down a real subscription; `Scheduler::transition()` publishes `event.task.state` (with `previousState`) on every state change, scheduler-driven or engine-reported; `dispatcher::on_download_add` publishes `event.task.added`; a 250 ms timer batches `Scheduler::progress_snapshot()` into one `event.task.progress` array per AGENT-DAEMON.md item 5 / the schema's `x-maxRateHz: 4`. Verified live end to end. | — | `event.task.removed` has no source yet (`download.remove` is D3); `event.speed.global`, `event.notify`, `event.auth.required`, `event.settings.changed`, `event.grabber.progress` are unpublished — each lands with its owning handler | as each owning D3 handler lands |
 | ~~D6~~ | **Closed** — engine numbers now reach the store: `Scheduler::tick()` probes (`EnginePort::probe`) before every `start()`, persisting `sizeBytes`/`resumable`/validators via `Tasks::set_probe_result` before a byte moves; `Scheduler::persist_progress()` (called from `progress_snapshot()` *and* once more from `on_engine_state` right before `release()`/unmap on every terminal transition) writes `downloadedBytes`/`speedBps`/`segments`/`segmentDetail` from the engine's `Progress`, so a task that finishes between two 250 ms ticks (the common case for anything small or fast) still leaves real numbers instead of the pre-persistence defaults. `TaskSummary.segments` is sourced from `segments.size()` when the task has any (matching what actually lands in `segmentDetail`, per the schema's "exactly `segments` entries"), falling back to the engine's `effective_segments` (budget slots *held*, not necessarily physical range count — see `core/include/vdm/task/download.hpp`'s `Progress` comment) only pre-segmentation. `Tasks::set_final_bytes` tops up `on_finished`'s byte count as a last-resort backstop. Migration `0002` adds `speed_bps` to both `tasks` and `segments`, and fixes `segments.state`'s CHECK to include `'pending'` (0001 omitted it, so a pre-connect snapshot could never be written). Verified against real `veloxd` + `tools/testserver` (not just unit tests): `download.list`/`download.get` correct immediately after completion and after a daemon restart. | `sched/scheduler.{cpp,hpp}`, `store/{tasks,segments}.{cpp,hpp}`, `store/migrations/0002_*.sql` | — | done |
+| ~~D11~~ | **Closed — build order items 7 (the systemd half) and 9: `velox-nmhost`, socket activation, the systemd user units, and `velox(1)`.** `nmhost/src/main.cpp` (185 lines): a `poll()`-driven byte pump between Firefox's native-messaging framing on stdio (4-byte native-byte-order length prefix) and `veloxd`'s own NDJSON framing on the Unix socket — reframes each direction, no JSON parsing, no retry/backoff, exits the moment either side closes. Deliberately dependency-free (no `veloxd_*` library, no `nlohmann_json`) since it runs unconfined outside Firefox's sandbox whatever the packaging format. Two real bugs found and fixed while getting the integration test to actually pass rather than hang: (1) never set the pumped fds non-blocking, so the "drain what's available" read loop blocked on its own second `read()` instead of returning to `poll()`; (2) stdin and stdout are two different descriptors (0 and 1), not one — an early draft polled `POLLOUT` on fd 0, which is opened read-only, so EOF/writability were never both observable through the same `pollfd` entry. Both are exactly the class of bug a "trivial pump" invites and unit tests over the real binary (not just its helper functions) exist specifically to catch. `packaging/nativehost/com.velox.host.json` + its own `README.md` supersede `AGENT-DAEMON.md`'s stale "four locations" (spike S1 / ADR 0003 found only three are real — the fourth, `~/snap/firefox/common/.mozilla/...`, is not read by snap Firefox at all) and spell out the per-user-manifest / postinst implication for PKG/QA. `EnginePort`-style: `rpc/systemd_activation.cpp` is a from-scratch `sd_listen_fds()` (env vars only, no `libsystemd` link — `LISTEN_PID`/`LISTEN_FDS`, fd 3) that `UdsServer::start()` checks first, skipping its own create/bind/chmod/listen when systemd already bound the socket; `packaging/systemd/velox.socket` + `velox.service` are the unit pair, verified both by `systemd-analyze verify` and by an actual fork/dup2/execve simulation of the activation handshake (a real `session.hello` round-tripped over the handed-off fd with no `bind()` ever called inside the daemon for that run). `velox.service` deliberately skips `ProtectSystem=`/`ProtectHome=`/`ReadWritePaths=` — `saveTo.allowedRoots` is user-configurable to anywhere on the filesystem, and a sandbox here would turn a legitimately-configured save location into an opaque `EROFS`/`EACCES` instead of the daemon's own clear `-32011`. `cli/man/velox.1` documents the CLI as it actually exists today (`add`/`ls`/`pause`/`resume`/`rm`, `--json`, the three-tier `queue`/`settings` subcommands `AGENT-DAEMON.md` build step 8 originally sketched are not implemented in `cli/src/main.cpp` yet, so the page doesn't claim they are) — checked warning-free with `groff -mandoc -ww -z`. | `nmhost/{CMakeLists.txt,src/main.cpp,tests/}`, `daemon/src/rpc/{systemd_activation.{hpp,cpp},uds_server.cpp}`, `packaging/{nativehost,systemd}/`, `cli/man/velox.1` | — | done |
 | — | ~~Observed, not fixed (CORE, not this lane)~~ — **routed to CORE by the user.** `vdm::task::Progress.speed_bps` reads back as `0` for the whole lifetime of a live, real (non-fake) throttled download, despite `downloadedBytes` visibly advancing between polls — `core/src/task/download_task.cpp`'s per-worker EWMA never seems to produce a nonzero aggregate in this build. DAEMON passes `EnginePort::progress()`'s `speed_bps` straight through (`Scheduler::persist_progress`); nothing in this lane drops it. Still reproduces in the D4b live checks above (0 throughout a paused/resumed/cancelled transfer whose `downloadedBytes` visibly moved) — not re-filed, since it's already CORE's. |
@@ -0,0 +1,37 @@
+#include "rpc/systemd_activation.hpp"
+
+#include <unistd.h>
+
+#include <cstdlib>
+#include <string>
+
+namespace velox::daemon::rpc {
+
+namespace {
+constexpr int kListenFdsStart = 3;  // SD_LISTEN_FDS_START
+}  // namespace
+
+int systemd_activated_fd() {
+    const char* pid_env = std::getenv("LISTEN_PID");
+    const char* fds_env = std::getenv("LISTEN_FDS");
+    int fd = -1;
+
+    if (pid_env != nullptr && fds_env != nullptr) {
+        try {
+            if (std::stol(pid_env) == static_cast<long>(::getpid()) && std::stol(fds_env) == 1) {
+                fd = kListenFdsStart;
+            }
+        } catch (...) {
+            // Malformed env from something other than systemd; treat as not activated.
+        }
+    }
+
+    // Contract: consumed once, then cleared, so a value meant for veloxd is never
+    // mistaken for one meant for a process it might itself exec later.
+    ::unsetenv("LISTEN_PID");
+    ::unsetenv("LISTEN_FDS");
+    ::unsetenv("LISTEN_FDNAMES");
+    return fd;
+}
+
+}  // namespace velox::daemon::rpc
@@ -0,0 +1,20 @@
+#pragma once
+
+// Minimal sd_listen_fds(3) reimplementation — one function, no libsystemd dependency, for
+// the one fd velox.socket ever hands us. See velox.socket / velox.service in
+// packaging/nativehost's systemd unit pair: the socket unit binds
+// $XDG_RUNTIME_DIR/velox/velox.sock itself (before veloxd ever runs, so the very first
+// connection attempt after boot is queued by the kernel rather than refused) and execs
+// veloxd with that listening fd already open at fd 3, LISTEN_FDS=1, LISTEN_PID=<our pid>.
+
+namespace velox::daemon::rpc {
+
+// The systemd-activated listening socket fd, or -1 if this process was not socket-
+// activated (LISTEN_PID doesn't match our pid, or LISTEN_FDS is unset/not exactly 1 — more
+// than one would mean a unit file mismatch, since veloxd only ever asks for one socket).
+// Clears LISTEN_PID/LISTEN_FDS from the environment on the way out either way, per
+// sd_listen_fds's own contract, so a value meant for us is never mistaken for one meant for
+// a process veloxd might itself exec later.
+int systemd_activated_fd();
+
+}  // namespace velox::daemon::rpc
@@ -12,7 +12,10 @@

 #include <nlohmann/json.hpp>

+#include <fcntl.h>
+
 #include "rpc/event_loop.hpp"
+#include "rpc/systemd_activation.hpp"
 #include "version.hpp"

 namespace velox::daemon::rpc {
@@ -74,6 +77,20 @@ UdsServer::~UdsServer() {
 }

 std::error_code UdsServer::start() {
+    // velox.socket (systemd user unit, socket activation): the unit binds this path itself
+    // before veloxd ever runs and hands the already-listening fd over at fd 3 — the first
+    // connection after boot is queued by the kernel rather than refused, and there is no
+    // window where a client sees ECONNREFUSED while the daemon is still starting. Skips
+    // create/bind/chmod/listen entirely; the socket file's lifecycle (including removal on
+    // stop) belongs to the unit, not to us, so bound_ stays false.
+    if (const int activated = systemd_activated_fd(); activated >= 0) {
+        ::fcntl(activated, F_SETFL, O_NONBLOCK);
+        ::fcntl(activated, F_SETFD, FD_CLOEXEC);
+        listen_fd_ = activated;
+        loop_.add_fd(listen_fd_, kRead, [this](int, unsigned) { on_listener_readable(); });
+        return {};
+    }
+
    if (path_.size() + 1 > sizeof(sockaddr_un::sun_path)) return errc(ENAMETOOLONG);

    const int fd = ::socket(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
@@ -24,6 +24,7 @@ veloxd_test(sched_scheduler  LIBS veloxd_sched veloxd_rpc)
 veloxd_test(event_hub               LIBS veloxd_rpc)
 veloxd_test(store_categories_queues LIBS veloxd_store)
 veloxd_test(single_instance          LIBS veloxd_rpc)
+veloxd_test(systemd_activation        LIBS veloxd_rpc)
 veloxd_test(dispatcher_settings      LIBS veloxd_rpc veloxd_store)
 veloxd_test(capture_offer            LIBS veloxd_rpc veloxd_store)
 veloxd_test(dispatcher_misc          LIBS veloxd_rpc veloxd_store)
@@ -0,0 +1,53 @@
+// systemd_activated_fd(): the LISTEN_PID/LISTEN_FDS contract, without a real systemd.
+
+#include <unistd.h>
+
+#include <cstdlib>
+#include <string>
+
+#include "check.hpp"
+#include "rpc/systemd_activation.hpp"
+
+using namespace velox::daemon::rpc;
+
+namespace {
+void set_env(const char* k, const std::string& v) { ::setenv(k, v.c_str(), 1); }
+}  // namespace
+
+void run() {
+    // Not activated: neither var set.
+    ::unsetenv("LISTEN_PID");
+    ::unsetenv("LISTEN_FDS");
+    CHECK_EQ(systemd_activated_fd(), -1);
+
+    // LISTEN_PID for a different process: not us, so not activated.
+    set_env("LISTEN_PID", std::to_string(::getpid() + 1));
+    set_env("LISTEN_FDS", "1");
+    CHECK_EQ(systemd_activated_fd(), -1);
+    // Consumed regardless of the outcome — a stale value from some other process's
+    // exec chain must not leak into what veloxd checks next time.
+    CHECK(::getenv("LISTEN_PID") == nullptr);
+    CHECK(::getenv("LISTEN_FDS") == nullptr);
+
+    // Our own pid, LISTEN_FDS=1: activated, fd 3 (SD_LISTEN_FDS_START).
+    set_env("LISTEN_PID", std::to_string(::getpid()));
+    set_env("LISTEN_FDS", "1");
+    CHECK_EQ(systemd_activated_fd(), 3);
+    CHECK(::getenv("LISTEN_PID") == nullptr);
+
+    // Our own pid but LISTEN_FDS=2: a unit file mismatch (veloxd only ever asks for one
+    // socket) — refuse rather than guess which of two fds is the right one.
+    set_env("LISTEN_PID", std::to_string(::getpid()));
+    set_env("LISTEN_FDS", "2");
+    CHECK_EQ(systemd_activated_fd(), -1);
+
+    // Garbage LISTEN_FDS: not activated, not a crash.
+    set_env("LISTEN_PID", std::to_string(::getpid()));
+    set_env("LISTEN_FDS", "not-a-number");
+    CHECK_EQ(systemd_activated_fd(), -1);
+
+    ::unsetenv("LISTEN_PID");
+    ::unsetenv("LISTEN_FDS");
+}
+
+TEST_MAIN()
@@ -0,0 +1,85 @@
+# 08 — Porting guide (macOS first, Windows later)
+
+Read `docs/adr/0020-cross-platform-strategy.md` first; this file is the concrete inventory
+it refers to. **Rule: Linux behaviour never changes. `#ifdef` never appears in logic.**
+
+## Directory layout
+
+Platform backends live beside the code they serve, one directory per OS:
+
+```
+core/src/io/platform/linux/file_ops.cpp        core/src/io/platform/macos/file_ops.cpp
+core/src/io/platform/file_ops.hpp              # the seam — no #ifdef, no OS types
+daemon/src/rpc/platform/linux/{wakeup,peercred,instance_lock,runtime_dir}.cpp
+daemon/src/rpc/platform/macos/{...}.cpp
+daemon/src/rpc/platform/*.hpp                  # the seams
+cmake/platform.cmake                           # VELOX_OS_* + source selection
+```
+
+`cmake/platform.cmake` sets exactly one of `VELOX_OS_LINUX`, `VELOX_OS_MACOS`,
+`VELOX_OS_WINDOWS`, and exposes `velox_platform_sources(<target> <dir>)` which adds
+`<dir>/platform/<os>/*.cpp`. Selection happens there and nowhere else.
+
+## The seams
+
+Five interfaces cover the whole port. Signatures are indicative, not binding — the owning
+lane settles them in Phase 0.
+
+| Seam | Interface | Why |
+|---|---|---|
+| File preallocation | `Result<void> preallocate(int fd, uint64_t bytes)` | `posix_fallocate` is Linux/glibc |
+| Cache advice | `void advise_dontneed(int fd, uint64_t off, uint64_t len)` | `posix_fadvise` has no macOS equivalent |
+| Durable flush | `Result<void> flush_durable(int fd)` | `fdatasync` vs `F_FULLFSYNC` |
+| Loop wakeup | `class Wakeup { int pollfd(); void signal(); void drain(); }` | `eventfd` is Linux-only |
+| Peer identity | `Result<PeerId> peer_of(int fd)` | `SO_PEERCRED` vs `LOCAL_PEERCRED` |
+| Single instance | `Result<Lock> acquire(string_view runtime_dir)` | abstract sockets are Linux-only |
+| Runtime dir | `string runtime_dir()`, `string data_dir()` | XDG vs `~/Library` |
+
+## API mapping
+
+| Linux (today) | macOS | Windows (later) | Note |
+|---|---|---|---|
+| `posix_fallocate(fd,0,n)` | `fcntl(F_PREALLOCATE)` then `ftruncate(n)` | `SetFileValidData` / `SetEndOfFile` | macOS needs the `ftruncate`; `F_PREALLOCATE` alone does not set size. Fall back to `ftruncate` on failure, exactly as the Linux path already does for `EOPNOTSUPP` |
+| `posix_fadvise(DONTNEED)` | no equivalent — **no-op** | `FILE_FLAG_NO_BUFFERING` | Do **not** substitute `F_NOCACHE`: it changes caching for the whole descriptor, not a written range. A no-op is honest; record it |
+| `fdatasync(fd)` | `fcntl(fd, F_FULLFSYNC)`, fall back to `fsync` | `FlushFileBuffers` | `fsync` on macOS does **not** guarantee the drive flushed. `.veloxpart` resume integrity depends on this — use `F_FULLFSYNC` |
+| `pwrite` | same | `WriteFile` + `OVERLAPPED` | POSIX, no work |
+| `O_NOFOLLOW` | same | `FILE_FLAG_OPEN_REPARSE_POINT` | POSIX, no work |
+| `eventfd` | self-pipe (`pipe2`/`O_NONBLOCK|O_CLOEXEC`) | event object | `poll(2)` already used, so a pipe read-end drops straight in |
+| `timerfd` | `poll()` timeout computed from the next deadline | waitable timer | Simplest port: the loop already has a deadline set |
+| `SO_PEERCRED` + `struct ucred` | `getpeereid(fd,&uid,&gid)` | named-pipe token | Same-UID check is the security property; keep it |
+| abstract socket `\0velox-daemon-<hash>` | socket file in the runtime dir + `flock(LOCK_EX|LOCK_NB)` | named mutex | macOS has no abstract namespace. Must unlink stale sockets on start — the abstract version got that free |
+| `$XDG_RUNTIME_DIR` | `$TMPDIR` (per-user, already private) | `%LOCALAPPDATA%` | macOS has no XDG runtime dir |
+| `$XDG_DATA_HOME` | `~/Library/Application Support/Velox` | `%APPDATA%` | |
+| `libsecret` / Secret Service | Keychain (`Security.framework`) | DPAPI / Credential Manager | Behind the credential-store seam. CLAUDE.md §4 still applies: never SQLite, never logs |
+| `systemd` user units | `launchd` plist (`~/Library/LaunchAgents`) | Service/Task Scheduler | Phase 3 |
+
+## Build dependencies
+
+| Ubuntu | macOS (Homebrew) |
+|---|---|
+| `qt6-base-dev`, `qt6-svg-dev`, `qt6-tools-dev` | `qt@6` |
+| `libcurl4-openssl-dev` | system libcurl, or `curl` |
+| `libsqlite3-dev` | system sqlite, or `sqlite` |
+| `libssl-dev` | `openssl@3` (set `OPENSSL_ROOT_DIR`) |
+| `libsecret-1-dev` | **none** — Keychain is in the SDK |
+| `nlohmann-json3-dev` | `nlohmann-json` |
+| `nodejs`, `npm` | `node` |
+
+The root `CMakeLists.txt` currently does `pkg_check_modules(LIBSECRET REQUIRED ...)`
+unconditionally. That must become Linux-only, or macOS cannot configure at all. It is the
+single hard blocker for a first macOS build.
+
+## What does not change
+
+`contracts/` and both generated clients, `tools/mockd`, `tests/conformance`,
+`tools/testserver`, the whole extension, and every hostile-mode expectation. If a port
+tempts you to change a fixture or a schema, stop — that is a contract change and it goes
+through PROTO.
+
+## Verification gates
+
+- **Phase 0 done:** Ubuntu suite still 57/57, and `git diff` shows only moves behind seams.
+- **Phase 1 done:** `veloxd`, `velox`, `libveloxcore` build on macOS; core unit tests pass.
+- **Phase 2 done:** conformance (mockd **and** live veloxd) and the engine hostile-mode
+  matrix pass on macOS; one real download completes with a matching SHA-256.
+- **Phase 3 done:** `.dmg` or Homebrew formula installs and runs on a clean machine.
@@ -0,0 +1,107 @@
+# ADR 0018 — Nullable optional fields: absent vs. explicit null
+
+**Status:** accepted · **Date:** 2026-09-13 · **Lane:** PROTO
+**Prompted by:** a DAEMON report against `download.update`: the generated C++ parser gives
+`VeloxDispatcher` no way to tell "the caller left this field alone" from "the caller wants
+it cleared," so `download.update` and (the moment a nullable `SettingKey` exists)
+`settings.set` can set a nullable field but never clear it back to `null`.
+
+## Context
+
+`download.update`'s `patch` object documents the convention plainly: "Only the present
+fields change. An explicit null clears a nullable field." That is a deliberate, already-
+committed wire contract — not something up for redesign here. The gap is one layer down:
+`contracts/codegen/gen_cpp.py`'s `emit_field_parse` collapses "key absent" and "key present
+with value `null`" to the same `std::nullopt`, on purpose, and the comment says so:
+
+> Absent and null mean the same thing: the field is not set. A client that omits a
+> nullable field and one that sends null are treated identically on purpose.
+
+That collapse is *correct* for the common case — most nullable-optional fields are on
+create-style params (`DownloadSpec.saveDir`, `.categoryId`, …) where there is no existing
+value to distinguish "never set" from "explicitly cleared" in the first place; either way
+the daemon just uses a default. It is wrong specifically for **patch-style** params, where
+a field can already hold a value and the caller needs to say which of two different things
+they mean: "leave it" or "clear it."
+
+The schema IR (`schema_ir.py`) already tracks `required` and `nullable` as two independent
+booleans per `Field`, so the information needed to make this distinction exists all the way
+through parsing — `emit_field_parse` just doesn't act on it. Only `download.update`'s
+`patch` object is affected today (`filename`, `saveDir`, `categoryId`, `queueId`,
+`description`, `segments`, `bufferBytes`, `checksum` — all eight of its fields are
+nullable-and-optional with exactly this "leave vs. clear" meaning). No `SettingKey` is
+nullable yet, so `settings.set` has no live instance of the bug, but the same shape
+(`values` patches an existing bag) means the first nullable settings key will hit the exact
+same gap.
+
+## Decision
+
+**A JSON-null-aware optional, opt in per field via a new `x-clearable: true` annotation —
+not a blanket rule and not a companion "clear list" field.**
+
+- New per-field schema annotation, `x-clearable: true`, valid only on a field whose type
+  already includes `null` (schema error otherwise — clearable implies nullable). Marks
+  "this field distinguishes absent from explicit null"; every other nullable-optional field
+  keeps today's collapse.
+- The generated C++ type for a `x-clearable` field becomes `std::optional<std::optional<T>>`:
+  outer `nullopt` = absent (leave unchanged), outer engaged with an inner `nullopt` =
+  explicit `null` (clear it), outer engaged with an inner value = set it. One field, three
+  states, no parallel bitset to keep in sync and no second field to forget to check.
+- `emit_field_parse` for such a field stops folding `is_null()` into "absent": absent skips
+  the assignment (outer stays `nullopt`); present-and-null assigns an engaged-but-empty
+  inner optional; present-and-valued parses normally into the inner optional. Every other
+  field's codegen (the `required`/`nullable`-but-not-`clearable` majority) is unchanged.
+- TypeScript needs no generator change: `field?: T | null` already round-trips this exactly
+  the way JSON does — an omitted key serializes as absent, `null` serializes as `null`, and
+  `"field" in obj` / `obj.field === null` already distinguish the three states natively.
+  This gap is a C++-generator-only problem.
+- Applies now to `download.update`'s eight `patch` fields. `Settings` gets no annotation
+  today (nothing nullable to mark); the day a nullable `SettingKey` is added, it gets
+  `x-clearable: true` in the same PR, not left to rediscover this ADR.
+
+## Versioning
+
+Per ADR 0015: this retypes a generated C++ field (`optional<T>` -> `optional<optional<T>>`)
+with the wire byte-for-byte unchanged — a client sending the same JSON parses correctly
+either way. **Minor bump, with a migration note** for anyone reading `patch.filename` et al.
+directly (unwrap twice: check the outer, then the inner). Not major; `session.hello`'s
+major-only check must not refuse a wire-compatible peer over a binding-only change.
+
+## Consequences
+
+- `on_download_update` (DAEMON, not this lane) can finally implement "explicit null
+  clears": read the outer optional for presence, the inner for clear-vs-value, exactly the
+  three states the schema already promised.
+- The collapse comment in `emit_field_parse` stays as the default behavior and gets a
+  pointer to this ADR for the opt-in exception, instead of being read as an oversight.
+- Implementation (schema annotation support in `schema_ir.py`, the `gen_cpp.py` emission
+  change above, regenerating `core/generated/`, the `x-clearable: true` annotations on
+  `download.update`'s eight fields, the VERSION bump and migration note) is **not** done in
+  this change — recorded here so DAEMON isn't blocked on relitigating the design, tracked as
+  its own PROTO PR per the normal contracts process (schema + regenerated code + fixtures +
+  VERSION bump together, CLAUDE.md §2).
+
+## Alternatives rejected
+
+**An explicit clear list** (e.g. `patch.clearFields: ["categoryId", …]`, plain non-nullable
+`optional<T>` fields otherwise). Rejected: the wire contract "an explicit null clears a
+nullable field" is already written into `download.update`'s schema description and is what
+DAEMON built against — this would be a real, disruptive wire redesign to route around a
+generator gap, not a fix for it. It also doesn't compose: every patch-shaped object gains a
+second array to keep in sync with the first, by hand, forever.
+
+**A parallel "which fields were present" bitset** (struct of `optional<T>` fields plus a
+sibling presence-flags struct or bitset). Rejected: two things to check per field instead
+of one, and nothing stops a caller from reading the optional and forgetting the presence
+bit — exactly the class of bug this ADR exists to close.
+
+**Apply the tri-state to every `nullable && !required` field automatically**, using the IR
+flags already present, no annotation needed. Rejected: `emit_field_parse` only backs
+`parse<T>()`, used for *params* types the daemon receives — but the conformance C++ runner
+also instantiates `parse<T>()` for **result** types (round-tripping golden fixtures), and
+plenty of those are nullable-optional with no patch semantics at all (`TaskSummary.effectiveUrl`,
+"null until the first probe succeeds" — a plain nullable value, not a leave-or-clear
+choice). Blanket application would retype those too, forcing every read site across the
+daemon that already does `if (summary.effectiveUrl)` into an unwanted double-unwrap for a
+distinction that field doesn't have. Opt-in keeps the blast radius at exactly the fields
+that need it.
@@ -0,0 +1,45 @@
+# ADR 0019 — The live-`veloxd` conformance runner is a required check, as-is
+
+**Status:** accepted · **Date:** 2026-09-12 · **Lane:** PKG/QA
+
+## Context
+
+`tests/conformance/run.sh` step 3b (ADR 0014's `conformance` ctest, already required
+per `.github/BRANCH_PROTECTION.md`) replays every fixture against a real, isolated
+`veloxd` it builds and starts — not just mockd, which only proves the TS client and the
+fixtures agree with each other. This is the runner that can catch `veloxd` disagreeing
+with its own contract, and it is unconditional in `run.sh` (`set -euo pipefail`, no
+skip flag): it already runs, and already blocks, inside the `conformance` job.
+
+What was open was whether to treat that as a settled, defended gate or as something
+still provisional while `daemon/docs/deferrals.md`'s D1-D4b stub handlers were excused
+via `veloxd-xfail.json`. PROTO's update: 57/57 fixtures pass on `main`, and the xfail
+allowlist is down to 18 entries from 34 as DAEMON lands the deferred handlers behind
+them.
+
+## Decision
+
+The live-`veloxd` conformance runner stays required — no change to CI is needed, since
+it already runs inside the already-required `conformance` job (ADR 0014). What this ADR
+records is the standing: PKG/QA is not carving out an exception, a `continue-on-error`,
+or a separate advisory job for it while the xfail list shrinks. A regression here fails
+the same required check a schema mismatch would.
+
+Verified, not assumed: `tests/conformance/veloxd-xfail.json` has 18 entries as of this
+ADR (`python3 -c "import json; print(len(json.load(open('tests/conformance/veloxd-xfail.json'))))"`).
+Each remaining entry excuses one still-stubbed handler on `deferrals.md`'s D-list, not a
+real disagreement between `veloxd` and its contract — `tests/conformance/README.md`
+already draws that line (an entry for anything else is a `run.sh`-detected "xfail entry
+unexpectedly passed" or a straight failure, not a quiet pass).
+
+## Consequences
+
+- No `ci.yml` or `BRANCH_PROTECTION.md` change: `conformance` was already listed
+  required, and this runner was already inside it.
+- The xfail list is a visible, shrinking number, not a static allowance — as DAEMON
+  clears more of `deferrals.md`'s D-list, entries come out of
+  `tests/conformance/veloxd-xfail.json`, and `replay.ts` fails loudly (per
+  `applyXfail`'s "unexpectedly passed" check) if one is left in after its handler ships.
+- Nothing here changes who owns what: `veloxd-xfail.json` and `run.sh` stay PROTO's;
+  PKG/QA's role is the branch-protection policy this ADR confirms, not the runner
+  itself.
@@ -0,0 +1,72 @@
+# ADR 0020 — Porting to macOS (and later Windows) without forking the tree
+
+Status: **accepted** · Supersedes nothing · Applies to every lane
+
+## Context
+
+The project was built Ubuntu-first and says so in its own project description. A survey of
+`main` (2026-09-15, 57/57 green) found the Linux-specific surface is far smaller than the
+Ubuntu-first framing suggests — roughly ten files, all of them already isolated at the
+bottom of the stack:
+
+| Area | Linux-only thing | Files |
+|---|---|---|
+| `core/io` | `posix_fallocate`, `posix_fadvise`, `fdatasync` | `sparse_file.cpp` |
+| `core/meta` | `fdatasync` | `veloxpart.cpp` |
+| `daemon/rpc` | `eventfd` | `event_loop.{hpp,cpp}`, `main.cpp` |
+| `daemon/rpc` | `timerfd` | `main.cpp`, `sched/scheduler.hpp` |
+| `daemon/rpc` | `SO_PEERCRED` / `struct ucred` | `uds_server.{hpp,cpp}` |
+| `daemon/rpc` | abstract-namespace socket lock | `single_instance.{hpp,cpp}` |
+| `daemon/rpc` | `$XDG_RUNTIME_DIR` layout | `runtime_dir.{hpp,cpp}` |
+| build | `libsecret-1` is `REQUIRED` at the root | `CMakeLists.txt` |
+
+Everything else is already portable: the event loop is `poll(2)` (POSIX, not `epoll`), the
+transfer engine is libcurl, the GUI is Qt 6, `tools/mockd` and `tests/conformance` are
+Node, `tools/testserver` is stdlib Python, and the extension is a WebExtension.
+
+## Decision
+
+**One tree, one logic, per-OS backends behind seams.**
+
+1. **No `#ifdef` in logic.** Platform differences live behind a narrow interface, with one
+   implementation file per OS. A reader of `sparse_file.cpp` must not need to know which OS
+   they are on. `#ifdef` is allowed only inside a `platform/<os>/` file.
+2. **Linux is the reference implementation.** A port may never change Linux behaviour. The
+   gate is mechanical: the full suite stays green on Ubuntu, and the Linux backend keeps
+   the same syscalls it uses today. If a port needs a semantic change, that is an ADR of
+   its own, not a port commit.
+3. **Seams are introduced by the owning lane, on Linux, before any port work.** CORE
+   introduces `core`'s seams; DAEMON introduces `daemon`'s. This is a pure refactor: move
+   the existing Linux code behind the interface unchanged, prove the suite is still green.
+4. **A new lane, PORT, owns only the per-OS backends** — `**/platform/<os>/**`. It never
+   writes logic, and it does not own `cmake/`: the central OS detection module is root
+   build infrastructure and stays with PKG/QA, who must land it during Phase 0 because
+   Phase 0's own seams consume it. PORT owning it would deadlock — PORT cannot start until
+   Phase 0 lands, and Phase 0 cannot select platform sources without it. That keeps CLAUDE.md §1 intact: CORE
+   still owns `core/`'s logic, DAEMON still owns `daemon/`'s, and macOS work can proceed in
+   parallel without cross-lane writes.
+5. **`VELOX_OS_*` is set once, centrally**, in `cmake/platform.cmake` (owned by PKG/QA),
+   and platform sources are selected there — not by globbing, not per-target ad hoc.
+6. **Optional dependencies are gated, never removed.** `libsecret` stays `REQUIRED` on
+   Linux and is replaced by Keychain on macOS behind the same credential-store seam.
+
+## Phases
+
+- **Phase 0 — on Ubuntu, by CORE + DAEMON.** Introduce the seams and move today's Linux
+  code behind them. Zero behaviour change; 57/57 stays green. No macOS code exists yet.
+- **Phase 1 — on macOS, by PORT.** Implement the macOS backends until `veloxd`, `velox`
+  and `libveloxcore` build and their unit tests pass.
+- **Phase 2 — parity.** `tools/testserver`, conformance and the engine's hostile-mode
+  matrix pass on macOS. The GUI builds against Qt 6 for macOS.
+- **Phase 3 — packaging.** `.dmg`/Homebrew, `launchd` instead of `systemd`, and the macOS
+  native-messaging manifest locations. Deliberately last.
+
+## Consequences
+
+- Windows later is the same shape: a third backend directory, no new strategy. The seams
+  chosen here are POSIX-flavoured but interface-level, so a Win32 backend is additive.
+- CI must build both, or macOS rots silently. Until a macOS runner exists, Phase 1 is
+  verified by hand on the porting machine and the Linux gate stays authoritative.
+- The cost is one indirection at the bottom of the I/O and RPC stacks. Measured against
+  the alternative — `#ifdef` drift, or a forked repo that diverges in a month — it is
+  cheap.
@@ -43,7 +43,11 @@ Read `contracts/`, `core/include/`, `docs/`. Never write in `core/`, `gui/`, or
   output. Build this early: it is how you test the daemon before the GUI exists.
 9. **`velox-nmhost`** — 4-byte-length-prefixed stdio ⇄ Unix socket pump. **Under 300 lines,
   zero business logic**, and it must exit cleanly when Firefox closes the pipe. Install
-   manifests to all four locations listed in `docs/05` §4.
+   manifests to the three real locations in `docs/05` §4 / `docs/adr/0003` — not four:
+   spike S1 found `~/snap/firefox/common/.mozilla/native-messaging-hosts/` (the intuitive
+   "inside the snap" path) is not actually read by snap Firefox, and corrected `docs/05` §4
+   down from its original four-location list. `packaging/nativehost/README.md` has the
+   current table.

 ## Definition of done (M1)
 - Passes the full conformance suite as a server, over **both** transports.
@@ -0,0 +1,51 @@
+# Agent brief — PORT (per-OS backends)
+
+**Starts after Phase 0: CORE and DAEMON have landed the seams on Ubuntu.**
+
+## You own
+```
+core/src/**/platform/<os>/**        daemon/src/**/platform/<os>/**
+packaging/macos/**                  packaging/windows/**
+```
+You may read everything. **You never write logic** — not in `core/src/io/*.cpp`, not in
+`daemon/src/rpc/*.cpp`, not in `gui/`, never in `contracts/`.
+
+## Read first
+`docs/adr/0020-cross-platform-strategy.md`, then `docs/08-porting.md` — it has the seam
+list, the API mapping and the dependency table. Then `CLAUDE.md`.
+
+## The one rule that matters
+**Linux behaviour never changes.** If your port needs a seam that doesn't exist, or a seam
+whose shape is wrong, you do not widen it yourself — you file a request with the owning
+lane (CORE for `core/`, DAEMON for `daemon/`) exactly as every other lane does. A port that
+quietly edits shared logic is how one tree becomes two.
+
+## Build order (macOS)
+1. **Configure at all.** The root `CMakeLists.txt` requires `libsecret-1` unconditionally;
+   that must be Linux-gated before anything else compiles. PKG/QA owns that, and also owns
+   `cmake/platform.cmake` (the `VELOX_OS_*` detection and `velox_platform_sources()`); both
+   land in Phase 0, before you start. File anything else you need with them.
+2. `core/` — `preallocate`, `advise_dontneed`, `flush_durable`. Use `F_FULLFSYNC`, not
+   `fsync`: `.veloxpart` resume correctness depends on a real flush.
+3. `daemon/` — `Wakeup` (self-pipe), `peer_of` (`getpeereid`), `instance_lock` (socket file
+   + `flock`, with stale-socket cleanup), `runtime_dir` (`$TMPDIR`, `~/Library/Application
+   Support/Velox`).
+4. Unit tests green for both lanes.
+5. `tools/testserver` (stdlib Python) and conformance (Node) — expected to run unchanged.
+   If they don't, that's a bug worth reporting, not patching around.
+6. GUI against Qt 6 for macOS.
+7. Packaging — `.dmg`/Homebrew, `launchd`, native-messaging manifest locations. Last.
+
+## Definition of done (Phase 1–2)
+- macOS builds `libveloxcore`, `veloxd` and `velox` with `-Wall -Wextra -Werror`.
+- Core and daemon unit tests pass on macOS.
+- One real download completes on macOS against `tools/testserver` with a SHA-256 that
+  matches the server's reference — the same gate the Linux vertical slice passed.
+- `kill -9` mid-download, restart, resume completes and the checksum still matches.
+- The Ubuntu suite is **still** green from the same commit.
+
+## Do not
+- Do not add `#ifdef` outside a `platform/<os>/` file.
+- Do not change a fixture, a schema or a hostile-mode expectation to make macOS pass.
+- Do not substitute `F_NOCACHE` for `posix_fadvise(DONTNEED)` — see `docs/08` for why.
+- Do not start with packaging.
@@ -19,7 +19,12 @@ import {
 } from './context-menus.js';
 import { MediaBridge, notifyTab } from './media-bridge.js';
 import { createTransport, transportStorage, type TransportStatus, type VeloxTransport } from './transport/index.js';
-import type { CaptureOfferParams, CaptureRules, DownloadSpec } from '../shared/protocol/index.js';
+import {
+  SESSION_SUBSCRIBE_PARAMS_EVENTS_ITEM_VALUES,
+  type CaptureOfferParams,
+  type CaptureRules,
+  type DownloadSpec,
+} from '../shared/protocol/index.js';

 let transport: VeloxTransport | undefined;
 let rules: CaptureRules = DEFAULT_CAPTURE_RULES;
@@ -75,10 +80,31 @@ async function refreshRules(): Promise<void> {
  }
 }

+/**
+ * "Nothing is delivered until this is called" (session.subscribe's own description) —
+ * without it, event.task.progress et al. never reach this connection at all, no matter
+ * how many listeners bridge.ts registers locally. Requests the whole set every time
+ * because any popup/options document could open at any moment and none of them narrow
+ * per-tab; a fresh connection (first connect, or after a drop) starts with nothing
+ * subscribed until this runs again.
+ */
+async function subscribeToEvents(): Promise<void> {
+  try {
+    await mustTransport().call('session.subscribe', {
+      events: [...SESSION_SUBSCRIBE_PARAMS_EVENTS_ITEM_VALUES],
+    });
+  } catch {
+    // Best-effort; a reconnect (or the next event.settings.changed-driven refresh) retries.
+  }
+}
+
 function onTransportState(status: TransportStatus): void {
  const detail = status.fatal ?? (status.needsPairing ? 'needs pairing' : '');
  console.debug(`[velox] transport ${status.state}${detail ? ` — ${detail}` : ''}`);
-  if (status.state === 'connected') void refreshRules();
+  if (status.state === 'connected') {
+    void refreshRules();
+    void subscribeToEvents();
+  }
 }

 async function setOverride(override: 'auto' | 'ws' | 'uds'): Promise<void> {
@@ -0,0 +1,389 @@
+// Runs the transport, the capture hook, and the popup event path against a REAL veloxd
+// — not FakeDaemon. Everything else in this suite is faithful to the documented wire
+// protocol, but "faithful" isn't "real"; this is what actually proves it.
+//
+// Requires VELOXD_BIN (path to a built veloxd) in the environment. Skips itself with a
+// clear message otherwise, so `npm test` and CI (no daemon binary lying around) are
+// unaffected. Run it like:
+//
+//   VELOXD_BIN=/path/to/build/dev/bin/veloxd npx vitest run tests/live
+//
+// Each veloxd instance gets its own scratch XDG_RUNTIME_DIR/XDG_DATA_HOME/
+// XDG_CONFIG_HOME/HOME (main.cpp's single-instance lock is keyed to the runtime dir, so
+// this can run alongside another developer's or CI's own veloxd on the same machine).
+// VELOX_PAIR_AUTO=1 stands in for the GUI's Allow-prompt approver during dev/test
+// (rpc/pairing.hpp's EnvAutoApprover) — pairing itself is exercised for real, only the
+// human click is stubbed.
+import { spawn, type ChildProcessWithoutNullStreams } from 'node:child_process';
+import { mkdtempSync, mkdirSync, rmSync } from 'node:fs';
+import { readFile } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { dirname, join, resolve } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { WebSocket as WsClient } from 'ws';
+
+import { RpcError, TransportClosedError } from '../../src/background/transport/types.js';
+import { WebSocketTransport, type WebSocketCtor, type WebSocketTransportDeps } from '../../src/background/transport/websocket.js';
+import { CaptureHook } from '../../src/background/capture/index.js';
+import type { OnHeadersReceivedDetails } from '../../src/background/capture/index.js';
+import type { CaptureRules, DownloadSpec, TaskProgressEvent, TaskStateEvent } from '../../src/shared/protocol/index.js';
+
+const VELOXD_BIN = process.env.VELOXD_BIN;
+const REPO_ROOT = resolve(dirname(fileURLToPath(import.meta.url)), '../../..');
+const TESTSERVER_PY = join(REPO_ROOT, 'tools/testserver/testserver.py');
+
+// A fixed moz-extension origin, used both as session.pair's extensionId and as the WS
+// upgrade's Origin header — real Firefox sets the latter itself; ws's client needs it
+// spelled out (docs/05 §4: the daemon refuses the upgrade without a moz-extension:// Origin).
+const EXTENSION_ID = '11111111-2222-3333-4444-555555555555';
+const ORIGIN = `moz-extension://${EXTENSION_ID}`;
+
+class OriginWebSocket extends WsClient {
+  constructor(url: string) {
+    super(url, { origin: ORIGIN });
+  }
+}
+const CTOR = OriginWebSocket as unknown as WebSocketCtor;
+
+function sleep(ms: number): Promise<void> {
+  return new Promise((r) => setTimeout(r, ms));
+}
+
+async function waitFor(cond: () => Promise<boolean> | boolean, timeoutMs: number, what: string): Promise<void> {
+  const deadline = Date.now() + timeoutMs;
+  for (;;) {
+    if (await cond()) return;
+    if (Date.now() > deadline) throw new Error(`timed out waiting for ${what}`);
+    await sleep(50);
+  }
+}
+
+interface VeloxdInstance {
+  proc: ChildProcessWithoutNullStreams;
+  scratch: string;
+  wsPort: number;
+  /** True once the process has actually exited, by signal or otherwise. Node only sets
+   *  `proc.exitCode` for a normal exit — a signal-killed process reports its death via
+   *  `signalCode` and an `exit` event instead, never a non-null `exitCode`. */
+  hasExited(): boolean;
+  kill(signal?: NodeJS.Signals): void;
+}
+
+async function startVeloxd(bin: string): Promise<VeloxdInstance> {
+  const scratch = mkdtempSync(join(tmpdir(), 'velox-live-'));
+  const runtime = join(scratch, 'rt');
+  const data = join(scratch, 'data');
+  const config = join(scratch, 'cfg');
+  const home = join(scratch, 'home');
+  mkdirSync(runtime, { mode: 0o700 });
+  mkdirSync(data, { recursive: true });
+  mkdirSync(config, { recursive: true });
+  mkdirSync(join(home, 'Downloads'), { recursive: true });
+
+  const proc = spawn(bin, [], {
+    env: {
+      ...process.env,
+      VELOX_PAIR_AUTO: '1',
+      XDG_RUNTIME_DIR: runtime,
+      XDG_DATA_HOME: data,
+      XDG_CONFIG_HOME: config,
+      HOME: home,
+    },
+  });
+  let exited = false;
+  proc.on('exit', () => {
+    exited = true;
+  });
+  let stderr = '';
+  proc.stderr.on('data', (d) => {
+    stderr += String(d);
+  });
+
+  const portFile = join(runtime, 'velox', 'ws.port');
+  try {
+    await waitFor(async () => {
+      if (exited) throw new Error(`veloxd exited early (code ${proc.exitCode}, signal ${proc.signalCode}): ${stderr}`);
+      try {
+        await readFile(portFile);
+        return true;
+      } catch {
+        return false;
+      }
+    }, 10_000, 'veloxd to write ws.port');
+  } catch (e) {
+    proc.kill('SIGKILL');
+    rmSync(scratch, { recursive: true, force: true });
+    throw e;
+  }
+  const wsPort = Number((await readFile(portFile, 'utf8')).trim());
+
+  return {
+    proc,
+    scratch,
+    wsPort,
+    hasExited: () => exited,
+    kill(signal: NodeJS.Signals = 'SIGTERM') {
+      proc.kill(signal);
+    },
+  };
+}
+
+interface TestServerInstance {
+  proc: ChildProcessWithoutNullStreams;
+  baseUrl: string;
+}
+
+async function startTestServer(): Promise<TestServerInstance> {
+  const proc = spawn('python3', [TESTSERVER_PY, '--port', '0'], {});
+  let stdout = '';
+  let port: number | null = null;
+  proc.stdout.on('data', (d) => {
+    stdout += String(d);
+    const m = /^(\d+)\s*$/m.exec(stdout);
+    if (m) port = Number(m[1]);
+  });
+  await waitFor(() => port !== null, 5_000, 'testserver to print its port');
+  const baseUrl = `http://127.0.0.1:${port}`;
+  await waitFor(async () => {
+    try {
+      const res = await fetch(`${baseUrl}/__health`);
+      return res.ok;
+    } catch {
+      return false;
+    }
+  }, 5_000, 'testserver /__health');
+  return { proc, baseUrl };
+}
+
+function memDeps(init: { token?: string | null } = {}): { deps: WebSocketTransportDeps; store: { token: string | null } } {
+  const store = { token: init.token ?? null };
+  return {
+    store,
+    deps: {
+      getToken: async () => store.token,
+      setToken: async (t) => {
+        store.token = t;
+      },
+      getCachedPort: async () => null,
+      setCachedPort: async () => undefined,
+      extensionId: EXTENSION_ID,
+    },
+  };
+}
+
+function makeTransport(port: number, deps: WebSocketTransportDeps, extra: Partial<WebSocketTransportDeps> = {}): WebSocketTransport {
+  return new WebSocketTransport({
+    ...deps,
+    ...extra,
+    webSocketCtor: CTOR,
+    portRange: { start: port, end: port },
+    openTimeoutMs: 2000,
+  });
+}
+
+const maybeDescribe = VELOXD_BIN ? describe : describe.skip;
+
+if (!VELOXD_BIN) {
+  console.warn('tests/live/real-veloxd.test.ts: VELOXD_BIN not set — skipping (see file header).');
+}
+
+maybeDescribe('WebSocketTransport against a real veloxd', () => {
+  let daemon: VeloxdInstance;
+  let testserver: TestServerInstance;
+  // The mid-test fail-open case kills `daemon` and a later test starts a replacement —
+  // every scratch dir that ever existed gets cleaned up here, not just the last one.
+  const allScratchDirs: string[] = [];
+
+  async function freshVeloxd(): Promise<VeloxdInstance> {
+    const d = await startVeloxd(VELOXD_BIN!);
+    allScratchDirs.push(d.scratch);
+    return d;
+  }
+
+  beforeAll(async () => {
+    daemon = await freshVeloxd();
+    testserver = await startTestServer();
+  }, 20_000);
+
+  afterAll(() => {
+    daemon?.kill('SIGKILL');
+    testserver?.proc.kill('SIGKILL');
+    for (const dir of allScratchDirs) rmSync(dir, { recursive: true, force: true });
+  });
+
+  it('session.hello without a token surfaces NotPaired / needsPairing', async () => {
+    const { deps } = memDeps();
+    const t = makeTransport(daemon.wsPort, deps, { autoPair: false });
+    await expect(t.connect()).rejects.toBeInstanceOf(RpcError);
+    expect(t.status.needsPairing).toBe(true);
+    t.disconnect();
+  });
+
+  let pairedToken: string;
+
+  it('pairs (VELOX_PAIR_AUTO=1 stands in for the human Allow click) and hellos with the issued token', async () => {
+    const { deps, store } = memDeps();
+    const t = makeTransport(daemon.wsPort, deps); // autoPair: true (default)
+    await t.connect();
+    expect(t.state).toBe('connected');
+    expect(t.status.daemonVersion).toBeTruthy();
+    expect(store.token).toBeTruthy();
+    pairedToken = store.token!;
+    t.disconnect();
+  });
+
+  it('the pairing token survives a reconnect: a fresh transport reuses it with no fresh pairing', async () => {
+    const { deps } = memDeps({ token: pairedToken });
+    // autoPair: false — if this succeeds at all, it can only be because the stored
+    // token from the previous test was accepted outright, not because this transport
+    // silently re-paired.
+    const t = makeTransport(daemon.wsPort, deps, { autoPair: false });
+    await t.connect();
+    expect(t.state).toBe('connected');
+    t.disconnect();
+  });
+
+  it('a wrong token is rejected, and repeating it rate-limits the next pairing attempt', async () => {
+    // Five failed session.hello attempts from this origin (ws_server.cpp records a
+    // rate-limiter failure on every not-paired hello, not only on a failed session.pair)
+    // exhausts the window; the sixth thing this origin tries — a pairing attempt — gets
+    // RateLimited rather than a fresh token.
+    for (let i = 0; i < 5; i += 1) {
+      const { deps } = memDeps({ token: 'not-the-real-token' });
+      const t = makeTransport(daemon.wsPort, deps, { autoPair: false });
+      await expect(t.connect()).rejects.toBeInstanceOf(RpcError);
+      t.disconnect();
+    }
+
+    const { deps } = memDeps(); // no token -> autoPair kicks in -> session.pair
+    const t = makeTransport(daemon.wsPort, deps);
+    await expect(t.connect()).rejects.toBeInstanceOf(RpcError);
+    expect(t.status.needsPairing).toBe(true);
+    expect(t.status.retryAfterSec).toBeGreaterThan(0);
+    t.disconnect();
+  });
+
+  it('download.add creates a real task the engine picks up', async () => {
+    const { deps } = memDeps({ token: pairedToken });
+    const t = makeTransport(daemon.wsPort, deps, { autoPair: false });
+    await t.connect();
+    try {
+      const spec: DownloadSpec = { url: `${testserver.baseUrl}/plain/file/64K`, filename: 'plain-download.bin' };
+      const added = await t.call('download.add', spec);
+      expect(added.taskId).toBeTruthy();
+
+      await waitFor(async () => {
+        const detail = await t.call('download.get', { taskId: added.taskId });
+        const state = detail.summary.state;
+        return state === 'complete' || state === 'downloading' || state === 'verifying';
+      }, 10_000, 'the task to leave the queued state');
+    } finally {
+      t.disconnect();
+    }
+  }, 15_000);
+
+  it('capture.offer end to end: the real capture path takes a monitored download, ignores its own duplicate, and fails open when the daemon dies mid-offer', async () => {
+    const { deps } = memDeps({ token: pairedToken });
+    const t = makeTransport(daemon.wsPort, deps, { autoPair: false });
+    await t.connect();
+
+    const rules: CaptureRules = await t.call('capture.getRules', {});
+    expect(rules.monitoredExtensions).toContain('zip'); // seeded default (0001_initial.sql)
+
+    const hook = new CaptureHook({
+      offer: (params, opts) => t.call('capture.offer', params, opts),
+      stash: { take: () => undefined, peek: () => undefined },
+      getCookies: async () => [],
+      getRules: () => rules,
+      origin: ORIGIN,
+    });
+
+    // A throttled URL so the task the first offer creates is still active (not yet
+    // complete) when the dedupe offer for the same URL follows immediately after.
+    const url = `${testserver.baseUrl}/throttled/file/512K`;
+    const details: OnHeadersReceivedDetails = {
+      requestId: 'live-1',
+      url,
+      method: 'GET',
+      type: 'other',
+      statusCode: 200,
+      tabId: 1,
+      responseHeaders: [{ name: 'content-disposition', value: 'attachment; filename="live-capture.zip"' }],
+    };
+
+    const first = await hook.handle(details);
+    expect(first).toEqual({ cancel: true }); // the daemon took it — Firefox never starts its own download
+
+    const list = await t.call('download.list', { filter: { query: 'live-capture' } });
+    expect(list.items.length).toBeGreaterThan(0);
+    const task = list.items[0]!;
+    expect(task.categoryId).toBe('programs'); // "zip" routes to the built-in Programs category
+    expect(task.saveDir).toContain('Downloads/Programs');
+
+    // Same URL again, task still active: the daemon's own dedupe (has_active_duplicate)
+    // says Ignore, so the hook proceeds instead of cancelling a second time.
+    const dup = await hook.handle({ ...details, requestId: 'live-2' });
+    expect(dup).toEqual({});
+
+    // Now kill the daemon mid-offer and prove fail-open holds against the REAL binary,
+    // not just FakeDaemon: the hook must still resolve to {} (Firefox downloads
+    // normally) well inside its own 750 ms budget.
+    daemon.kill('SIGKILL');
+    await waitFor(() => daemon.hasExited(), 5_000, 'veloxd to actually die');
+
+    const started = Date.now();
+    const afterDeath = await hook.handle({ ...details, requestId: 'live-3', url: `${url}?after-death=1` });
+    const elapsedMs = Date.now() - started;
+    expect(afterDeath).toEqual({}); // fail open — never {cancel: true} with a dead daemon
+    expect(elapsedMs).toBeLessThan(900); // budget is 750ms; the hook's own timer bounds this
+
+    t.disconnect();
+  }, 20_000);
+
+  it('event.task.progress reaches a subscribed client (the popup\'s own path)', async () => {
+    if (daemon.hasExited()) {
+      // The previous test kills the daemon on purpose to prove fail-open; start a fresh
+      // one so this test still exercises the real event path end to end.
+      daemon = await freshVeloxd();
+    }
+    const { deps } = memDeps();
+    const t = makeTransport(daemon.wsPort, deps); // fresh daemon instance -> fresh pairing
+    await t.connect();
+    try {
+      await t.call('session.subscribe', {
+        events: ['event.task.added', 'event.task.state', 'event.task.progress'],
+      });
+
+      const progressEvents: TaskProgressEvent[] = [];
+      const stateEvents: TaskStateEvent[] = [];
+      t.on('event.task.progress', (p) => progressEvents.push(p as TaskProgressEvent));
+      t.on('event.task.state', (p) => stateEvents.push(p as TaskStateEvent));
+
+      const spec: DownloadSpec = { url: `${testserver.baseUrl}/throttled/file/1M`, filename: 'progress-check.bin' };
+      const added = await t.call('download.add', spec);
+
+      // /throttled defaults to 1 MiB/s, so a 1 MiB file takes ~1s — long enough that at
+      // least one 4 Hz progress tick (event.task.progress's documented cap) lands before
+      // it completes, exactly the path popup/store.ts consumes in the real extension.
+      await waitFor(
+        () => progressEvents.some((e) => e.tasks.some((row) => row.taskId === added.taskId)),
+        8_000,
+        'a live event.task.progress tick for our task',
+      );
+      expect(stateEvents.some((e) => e.taskId === added.taskId)).toBe(true);
+    } finally {
+      t.disconnect();
+    }
+  }, 15_000);
+
+  it('fail-open also holds through the transport itself: a call against a dead socket rejects, never hangs past its deadline', async () => {
+    const { deps } = memDeps();
+    const t = makeTransport(daemon.wsPort, deps);
+    await t.connect();
+    t.disconnect(); // closes the socket without telling the daemon anything is wrong
+    await expect(t.call('capture.offer', { url: 'https://example.com/x.zip', method: 'GET', tabUrl: '' }, { timeoutMs: 200 })).rejects.toBeInstanceOf(
+      TransportClosedError,
+    );
+  });
+});
@@ -0,0 +1,14 @@
+# nmhost/ — velox-nmhost, the Firefox native-messaging host. Owned by lane DAEMON.
+#
+# Deliberately dependency-free: no veloxd_* library, no nlohmann_json, no SQLite. It is a
+# byte-level pump between two framings (see src/main.cpp's own header comment) and runs
+# unconfined outside Firefox's sandbox (ADR 0003) — the less it links, the less there is to
+# go wrong running from wherever a snap/deb/flatpak install puts it.
+
+add_executable(velox-nmhost src/main.cpp)
+target_compile_features(velox-nmhost PRIVATE cxx_std_23)
+target_compile_options(velox-nmhost PRIVATE -Wall -Wextra -Wpedantic -Werror)
+
+if(VELOX_BUILD_TESTS AND EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/tests/CMakeLists.txt)
+    add_subdirectory(tests)
+endif()
@@ -0,0 +1,203 @@
+// velox-nmhost — Firefox native-messaging host. A dumb pump between two framings, nothing
+// else: stdin/stdout speak Firefox's own protocol (a 4-byte native-byte-order length
+// prefix, then that many bytes of UTF-8 JSON); $XDG_RUNTIME_DIR/velox/velox.sock speaks
+// veloxd's own NDJSON (one '\n'-terminated JSON value per line, daemon/src/rpc/ndjson.hpp).
+// Reframing between the two is the entire job.
+//
+// Runs unconfined outside Firefox's snap sandbox with the real $HOME and
+// $XDG_RUNTIME_DIR (ADR 0003 §Q2) — see packaging/nativehost/ for the manifest this is
+// installed as, and which native-messaging-hosts directory actually gets read by which
+// Firefox flavour.
+//
+// No business logic: no JSON parsing (frames are pure byte spans; only the length prefix
+// and the line boundary matter here), no retry/backoff (the extension re-launches a fresh
+// host on its own reconnect), no protocol version check (veloxd and the extension settle
+// that between themselves once the pump hands their bytes through). Exits the moment
+// either side closes.
+
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include <cerrno>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <poll.h>
+#include <string>
+
+namespace {
+
+// Firefox's own cap (host -> browser) is 1 MiB; this is just a sanity backstop against a
+// runaway peer so a malformed stream can't grow a buffer without bound.
+constexpr std::size_t kMaxFrameBytes = 8 * 1024 * 1024;
+
+std::string socket_path() {
+    const char* xdg = std::getenv("XDG_RUNTIME_DIR");
+    std::string base = (xdg != nullptr && xdg[0] != '\0') ? xdg
+                                                          : ("/run/user/" + std::to_string(::getuid()));
+    if (!base.empty() && base.back() == '/') base.pop_back();
+    return base + "/velox/velox.sock";
+}
+
+int connect_socket(const std::string& path) {
+    const int fd = ::socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+    if (fd < 0) return -1;
+    sockaddr_un addr{};
+    addr.sun_family = AF_UNIX;
+    if (path.size() + 1 > sizeof(addr.sun_path)) {
+        ::close(fd);
+        return -1;
+    }
+    std::memcpy(addr.sun_path, path.c_str(), path.size());
+    if (::connect(fd, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) != 0) {
+        ::close(fd);
+        return -1;
+    }
+    return fd;
+}
+
+// Reads everything currently available into `buf`. true on EOF, false otherwise (short
+// reads / EAGAIN just return with whatever was appended).
+bool read_available(int fd, std::string& buf) {
+    char chunk[65536];
+    for (;;) {
+        const ssize_t n = ::read(fd, chunk, sizeof(chunk));
+        if (n > 0) {
+            buf.append(chunk, static_cast<std::size_t>(n));
+            continue;
+        }
+        if (n == 0) return true;  // EOF
+        if (errno == EAGAIN || errno == EWOULDBLOCK) return false;
+        if (errno == EINTR) continue;
+        return true;  // treat any other error as if the peer hung up
+    }
+}
+
+// Writes as much of `buf` as the fd accepts right now, trimming what was sent. Returns
+// false on a hard error (peer gone); EAGAIN is not an error, just "try again later".
+bool flush_some(int fd, std::string& buf) {
+    while (!buf.empty()) {
+        const ssize_t n = ::write(fd, buf.data(), buf.size());
+        if (n > 0) {
+            buf.erase(0, static_cast<std::size_t>(n));
+            continue;
+        }
+        if (n < 0 && (errno == EAGAIN || errno == EWOULDBLOCK)) return true;
+        if (n < 0 && errno == EINTR) continue;
+        return false;
+    }
+    return true;
+}
+
+// stdin frames (4-byte length + payload) -> NDJSON lines appended to `to_socket`.
+// Malformed (oversized) length is a hard stop.
+bool drain_stdin_frames(std::string& in, std::string& to_socket) {
+    for (;;) {
+        if (in.size() < 4) return true;
+        std::uint32_t len;
+        std::memcpy(&len, in.data(), 4);
+        if (len > kMaxFrameBytes) return false;
+        if (in.size() < 4 + len) return true;
+        to_socket.append(in, 4, len);
+        to_socket.push_back('\n');
+        in.erase(0, 4 + len);
+    }
+}
+
+// NDJSON lines from the socket -> stdout frames (4-byte length + payload) appended to
+// `to_stdout`.
+bool drain_socket_lines(std::string& in, std::string& to_stdout) {
+    for (;;) {
+        const auto nl = in.find('\n');
+        if (nl == std::string::npos) {
+            if (in.size() > kMaxFrameBytes) return false;
+            return true;
+        }
+        std::string_view line(in.data(), nl);
+        if (!line.empty() && line.back() == '\r') line.remove_suffix(1);
+        if (line.size() > kMaxFrameBytes) return false;
+        const auto len = static_cast<std::uint32_t>(line.size());
+        to_stdout.append(reinterpret_cast<const char*>(&len), 4);
+        to_stdout.append(line);
+        in.erase(0, nl + 1);
+    }
+}
+
+}  // namespace
+
+int main() {
+    const int sock = connect_socket(socket_path());
+    if (sock < 0) return 1;  // daemon not running / socket missing: nothing to pump
+
+    // Every fd this pumps must be non-blocking: read_available()'s own drain loop keeps
+    // calling read() until it actually sees EAGAIN, and a blocking fd never returns that —
+    // it just blocks inside the "drain what's available" loop instead of going back to
+    // poll(), which stalls the whole pump the moment one side has more to send than fits
+    // in a single read().
+    ::fcntl(0, F_SETFL, ::fcntl(0, F_GETFL) | O_NONBLOCK);
+    ::fcntl(1, F_SETFL, ::fcntl(1, F_GETFL) | O_NONBLOCK);
+    ::fcntl(sock, F_SETFL, ::fcntl(sock, F_GETFL) | O_NONBLOCK);
+
+    std::string stdin_buf, stdout_buf, socket_in_buf, socket_out_buf;
+    bool stdin_eof = false;
+
+    // Three distinct descriptors, not two: stdin (0) and stdout (1) are separate pipes
+    // (read-only and write-only respectively — never the same fd, even though they sit
+    // next to each other in a shell's mental model of "the process's stdio"), plus the
+    // bidirectional socket.
+    enum { kStdin, kStdout, kSock };
+    for (;;) {
+        pollfd fds[3] = {
+            {0, 0, 0},
+            {1, 0, 0},
+            {sock, 0, 0},
+        };
+        if (!stdin_eof) fds[kStdin].events |= POLLIN;
+        if (!stdout_buf.empty()) fds[kStdout].events |= POLLOUT;
+        fds[kSock].events |= POLLIN;
+        if (!socket_out_buf.empty()) fds[kSock].events |= POLLOUT;
+
+        // Nothing left to wait for: both directions exhausted.
+        if (fds[kStdin].events == 0 && fds[kStdout].events == 0 && fds[kSock].events == 0) break;
+
+        const int n = ::poll(fds, 3, -1);
+        if (n < 0) {
+            if (errno == EINTR) continue;
+            break;
+        }
+
+        if (fds[kStdout].revents & POLLOUT) {
+            if (!flush_some(1, stdout_buf)) break;  // Firefox closed our stdout
+        }
+        if (fds[kSock].revents & POLLOUT) {
+            if (!flush_some(sock, socket_out_buf)) break;
+        }
+        if (fds[kStdin].revents & (POLLIN | POLLHUP)) {
+            if (read_available(0, stdin_buf)) stdin_eof = true;
+            if (!drain_stdin_frames(stdin_buf, socket_out_buf)) break;
+        }
+        if (fds[kSock].revents & (POLLIN | POLLHUP)) {
+            const bool socket_eof = read_available(sock, socket_in_buf);
+            if (!drain_socket_lines(socket_in_buf, stdout_buf)) break;
+            if (socket_eof) {
+                // The daemon is gone. Flush whatever we already turned into stdout
+                // frames, then stop — there is nothing left to relay either direction.
+                (void)flush_some(1, stdout_buf);
+                break;
+            }
+        }
+        if ((fds[kStdin].revents | fds[kStdout].revents | fds[kSock].revents) &
+            (POLLERR | POLLNVAL))
+            break;
+
+        // Firefox closed the pipe: nothing more will ever arrive on stdin, and once our
+        // own outbound backlog drains there is nothing left to send it either. Stop
+        // rather than idle forever relaying replies nobody reads.
+        if (stdin_eof && socket_out_buf.empty()) break;
+    }
+
+    ::close(sock);
+    return 0;
+}
@@ -0,0 +1,13 @@
+# Integration test only — velox-nmhost has no internal functions worth unit-testing in
+# isolation (it's ~15 lines of byte-shuffling helpers around one poll() loop); what matters
+# is the real binary's observable behaviour over real pipes and a real socket.
+
+add_executable(velox_nmhost_pump_test pump_test.cpp)
+target_compile_features(velox_nmhost_pump_test PRIVATE cxx_std_23)
+target_compile_options(velox_nmhost_pump_test PRIVATE -Wall -Wextra -Wpedantic -Werror)
+target_compile_definitions(velox_nmhost_pump_test PRIVATE
+    VELOX_NMHOST_BIN="$<TARGET_FILE:velox-nmhost>")
+add_dependencies(velox_nmhost_pump_test velox-nmhost)
+
+add_test(NAME nmhost.pump COMMAND velox_nmhost_pump_test)
+set_tests_properties(nmhost.pump PROPERTIES TIMEOUT 30)
@@ -0,0 +1,54 @@
+#pragma once
+
+// Minimal test harness: CHECK accumulates failures, TEST_MAIN reports and sets the exit
+// code. Copied from daemon/tests/check.hpp rather than shared across a build-dependency —
+// nmhost is deliberately dependency-free, tests included.
+
+#include <cstdio>
+#include <string>
+#include <vector>
+
+namespace veloxd_test {
+
+inline std::vector<std::string>& failures() {
+    static std::vector<std::string> f;
+    return f;
+}
+inline int& checks() {
+    static int n = 0;
+    return n;
+}
+
+}  // namespace veloxd_test
+
+#define CHECK(cond)                                                                     \
+    do {                                                                               \
+        ++::veloxd_test::checks();                                                     \
+        if (!(cond)) {                                                                 \
+            ::veloxd_test::failures().push_back(std::string(__FILE__) + ":" +          \
+                                               std::to_string(__LINE__) + ": " + #cond); \
+        }                                                                              \
+    } while (0)
+
+#define CHECK_EQ(a, b)                                                                  \
+    do {                                                                               \
+        ++::veloxd_test::checks();                                                     \
+        auto _va = (a);                                                                \
+        auto _vb = (b);                                                                \
+        if (!(_va == _vb)) {                                                           \
+            ::veloxd_test::failures().push_back(std::string(__FILE__) + ":" +          \
+                                               std::to_string(__LINE__) + ": " + #a +  \
+                                               " == " + #b);                           \
+        }                                                                              \
+    } while (0)
+
+#define TEST_MAIN()                                                                     \
+    int main() {                                                                        \
+        run();                                                                          \
+        for (const auto& f : ::veloxd_test::failures()) std::printf("FAIL %s\n", f.c_str()); \
+        std::printf("%d/%d checks passed\n",                                            \
+                    ::veloxd_test::checks() -                                           \
+                        static_cast<int>(::veloxd_test::failures().size()),             \
+                    ::veloxd_test::checks());                                           \
+        return ::veloxd_test::failures().empty() ? 0 : 1;                               \
+    }
@@ -0,0 +1,148 @@
+// Integration test for velox-nmhost: spawns the real binary, feeds it a framed stdin
+// message, answers over a fake Unix socket standing in for veloxd, and checks what comes
+// back out on stdout — plus that it exits promptly once stdin closes.
+
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <string>
+
+#include "check.hpp"
+
+namespace {
+
+std::string make_temp_dir() {
+    char tmpl[] = "/tmp/velox-nmhost-test-XXXXXX";
+    const char* dir = ::mkdtemp(tmpl);
+    return dir ? dir : "/tmp";
+}
+
+// Firefox's own framing: 4-byte native-byte-order length, then that many bytes.
+std::string frame(const std::string& payload) {
+    std::uint32_t len = static_cast<std::uint32_t>(payload.size());
+    std::string out(reinterpret_cast<char*>(&len), 4);
+    out += payload;
+    return out;
+}
+
+// Reads exactly one framed message off `fd`, blocking. Empty on EOF/short read.
+std::string read_frame(int fd) {
+    std::uint32_t len = 0;
+    std::size_t got = 0;
+    while (got < 4) {
+        const ssize_t n = ::read(fd, reinterpret_cast<char*>(&len) + got, 4 - got);
+        if (n <= 0) return {};
+        got += static_cast<std::size_t>(n);
+    }
+    std::string payload(len, '\0');
+    got = 0;
+    while (got < len) {
+        const ssize_t n = ::read(fd, payload.data() + got, len - got);
+        if (n <= 0) return {};
+        got += static_cast<std::size_t>(n);
+    }
+    return payload;
+}
+
+bool write_all(int fd, const std::string& s) {
+    std::size_t off = 0;
+    while (off < s.size()) {
+        const ssize_t n = ::write(fd, s.data() + off, s.size() - off);
+        if (n <= 0) return false;
+        off += static_cast<std::size_t>(n);
+    }
+    return true;
+}
+
+}  // namespace
+
+void run() {
+    const std::string dir = make_temp_dir();
+    const std::string velox_dir = dir + "/velox";
+    CHECK(::mkdir(velox_dir.c_str(), 0700) == 0);
+    const std::string sock_path = velox_dir + "/velox.sock";
+
+    // A bare listening socket standing in for veloxd.
+    const int listen_fd = ::socket(AF_UNIX, SOCK_STREAM, 0);
+    CHECK(listen_fd >= 0);
+    sockaddr_un addr{};
+    addr.sun_family = AF_UNIX;
+    std::memcpy(addr.sun_path, sock_path.c_str(), sock_path.size());
+    CHECK(::bind(listen_fd, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) == 0);
+    CHECK(::listen(listen_fd, 1) == 0);
+
+    int child_stdin[2];   // [0] read (child), [1] write (parent)
+    int child_stdout[2];  // [0] read (parent), [1] write (child)
+    CHECK(::pipe(child_stdin) == 0);
+    CHECK(::pipe(child_stdout) == 0);
+
+    ::setenv("XDG_RUNTIME_DIR", dir.c_str(), 1);
+
+    const pid_t pid = ::fork();
+    CHECK(pid >= 0);
+    if (pid == 0) {
+        ::dup2(child_stdin[0], 0);
+        ::dup2(child_stdout[1], 1);
+        ::close(child_stdin[0]);
+        ::close(child_stdin[1]);
+        ::close(child_stdout[0]);
+        ::close(child_stdout[1]);
+        ::close(listen_fd);
+        ::execl(VELOX_NMHOST_BIN, "velox-nmhost", nullptr);
+        ::_exit(127);
+    }
+    ::close(child_stdin[0]);
+    ::close(child_stdout[1]);
+
+    // Accept nmhost's connection.
+    const int conn = ::accept(listen_fd, nullptr, nullptr);
+    CHECK(conn >= 0);
+
+    // stdin (framed) -> socket (NDJSON line).
+    CHECK(write_all(child_stdin[1], frame(R"({"hello":1})")));
+    char line[256] = {};
+    ssize_t n = ::read(conn, line, sizeof(line) - 1);
+    CHECK(n > 0);
+    CHECK_EQ(std::string(line, static_cast<std::size_t>(n)), std::string("{\"hello\":1}\n"));
+
+    // socket (NDJSON line) -> stdout (framed).
+    CHECK(write_all(conn, "{\"world\":2}\n"));
+    const std::string got = read_frame(child_stdout[0]);
+    CHECK_EQ(got, std::string(R"({"world":2})"));
+
+    // A second round trip on the same connection, to prove buffering across calls works
+    // (not just "the first message happens to line up with one read()").
+    CHECK(write_all(child_stdin[1], frame(R"({"again":3})")));
+    n = ::read(conn, line, sizeof(line) - 1);
+    CHECK(n > 0);
+    CHECK_EQ(std::string(line, static_cast<std::size_t>(n)), std::string("{\"again\":3}\n"));
+
+    // Firefox closes the pipe: nmhost must exit promptly rather than hang.
+    ::close(child_stdin[1]);
+    int status = 0;
+    pid_t waited = -1;
+    for (int i = 0; i < 50 && waited != pid; ++i) {
+        waited = ::waitpid(pid, &status, WNOHANG);
+        if (waited == pid) break;
+        struct timespec ts{0, 20'000'000};  // 20ms
+        ::nanosleep(&ts, nullptr);
+    }
+    CHECK_EQ(waited, pid);
+    if (waited == pid) CHECK(WIFEXITED(status));
+
+    ::close(conn);
+    ::close(child_stdout[0]);
+    ::close(listen_fd);
+    ::unlink(sock_path.c_str());
+    ::rmdir(velox_dir.c_str());
+    ::rmdir(dir.c_str());
+}
+
+TEST_MAIN()
@@ -0,0 +1,97 @@
+# packaging/nativehost — the Firefox native-messaging manifest
+
+Owner: lane DAEMON (`packaging/nativehost/**` is explicitly DAEMON's per `CLAUDE.md`'s
+lane table, unlike the rest of `packaging/`, which is PKG/QA's). This directory holds the
+manifest `velox-nmhost` (built from `nmhost/`) is registered under, and this file is the
+one place that says exactly which on-disk locations need it and why — the
+"install manifests to all four locations" line in `docs/agents/AGENT-DAEMON.md`'s build
+order predates `docs/adr/0003-native-messaging-under-snap.md`, which cut that down to
+three *real* ones. Read the ADR before touching this list; it is the empirical spike, not
+a guess.
+
+## The manifest
+
+`com.velox.host.json` in this directory is the template:
+
+```json
+{
+  "name": "com.velox.host",
+  "description": "Velox download manager — native messaging bridge to veloxd",
+  "path": "/usr/libexec/velox/velox-nmhost",
+  "type": "stdio",
+  "allowed_extensions": ["velox@velox.download"]
+}
+```
+
+- `name` is what the extension calls `browser.runtime.connectNative("com.velox.host")`
+  with (`extension/src/background/transport/native.ts`'s `HOST_NAME`) — do not rename one
+  without the other.
+- `allowed_extensions` must match `extension/manifest.json`'s
+  `browser_specific_settings.gecko.id` exactly (`[email protected]`). A mismatch here is
+  a silent failure: Firefox reports "no such native application" as if the manifest didn't
+  exist at all, which reads exactly like a missing-file bug and is easy to chase in the
+  wrong place.
+- `path` is `/usr/libexec/velox/velox-nmhost` — the `.deb`'s install layout
+  (`docs/07-packaging.md`). **Every other packaging format needs a different `path`** —
+  the binary doesn't live at that absolute path inside a Flatpak sandbox or an AppImage
+  mount, so whatever installs the manifest for those formats must rewrite this field to
+  wherever it actually put the binary, not ship this file verbatim. That substitution is
+  the packaging step's job, not this template's.
+
+## Where it has to be written, and why
+
+Per ADR 0003 (spike S1, run against the real snap Firefox on the target machine — not a
+guess about how confinement "should" work):
+
+| Location | Covers | Why |
+|---|---|---|
+| `~/.mozilla/native-messaging-hosts/com.velox.host.json` | **deb/tarball Firefox, and snap Firefox** | The one location snap Firefox 154 actually reads. Firefox's snap launches native-messaging hosts *outside* the sandbox with the user's real `$HOME` — so this is not "the deb location that happens to also work"; it is *the* snap location, full stop. `~/snap/firefox/common/.mozilla/native-messaging-hosts/` (the intuitive "inside the snap" path) is **not** read by Firefox 154 snap — confirmed empirically, not inferred. |
+| `/usr/lib/mozilla/native-messaging-hosts/com.velox.host.json` | **deb/tarball Firefox only** | System-wide, so it covers every user on the box for a real (non-snap) Firefox install — but confirmed **not** read by snap Firefox. Do not treat this path as "covers snap too"; that was the wrong assumption `docs/05` §4 corrected in the same commit as the ADR. |
+| `~/.var/app/org.mozilla.firefox/.mozilla/native-messaging-hosts/com.velox.host.json` | **Flatpak Firefox** | Flatpak's own sandboxed home. Untested on this machine (Firefox here is the snap, not flatpak) — carried over from `docs/05` §4's original four-location list, which this table otherwise supersedes. Verify before relying on it in a release checklist. |
+
+That is three real locations, not four — the fourth
+(`~/snap/firefox/common/.mozilla/native-messaging-hosts/`) was the pre-ADR guess the spike
+disproved. If `docs/agents/AGENT-DAEMON.md`'s build order still says "four locations" when
+you read this, it is stale; this table is the current source of truth alongside the ADR
+itself.
+
+## What this means for `postinst` (PKG/QA's file, not this one)
+
+This directory ships the manifest template and documents the target paths; it does not
+install anything itself (`packaging/**` outside this one directory is PKG/QA's — see
+`CLAUDE.md`'s lane table — and `postinst` specifically is a `.deb`-packaging concern this
+lane doesn't own the file for). For whoever writes it:
+
+- **The two `~/`-relative locations are per-user.** `postinst` runs as root, once, at
+  install time — it does not run once per user session. It needs either a real-user
+  enumeration at install time (every UID with a home directory and no login shell of
+  `/usr/sbin/nologin`-style exclusions, roughly what `deluser --remove-home` scripts already
+  have to reason about) or a first-run hook that runs as the logged-in user (a systemd user
+  unit's `ExecStartPre`, or the GUI's own first-run wizard) and writes its own manifest the
+  first time it starts. `docs/adr/0003`'s own follow-up section flagged this as open; it
+  still is.
+- **`/usr/lib/mozilla/native-messaging-hosts/` is the only one of the three that's a plain
+  root-owned, install-time write** — no per-user enumeration needed for that one.
+- **Detect snap Firefox and say so.** `docs/07-packaging.md` already commits to this
+  ("detects whether Firefox is a snap... prints... a one-line note that the extension will
+  pair over loopback") — the detection matters here specifically because if Firefox turns
+  out to be neither deb/tarball nor a snap this spike covers (a genuinely unknown or future
+  packaging of Firefox), silently trusting `NativeTransport` to work is exactly the failure
+  mode ADR 0003 exists to prevent. `WebSocketTransport` is the guaranteed fallback either
+  way (ADR 0003's own decision) — nothing breaks if the manifest doesn't land correctly, it
+  just means the extension pairs over loopback instead of the (opportunistic, not
+  required) native path.
+- **`docs/07-packaging.md`'s own install layout line currently lists only the
+  system-wide `/usr/lib/mozilla/...` path.** That line is correct as far as it goes (it *is*
+  one of the three locations, and the only pure root-owned one) but reads as if it were the
+  whole story for native messaging; it predates this file and the ADR. Worth a line
+  pointing here so the two documents don't quietly disagree — PKG/QA's call, not edited
+  here since `docs/07` is PKG/QA's own file.
+
+## The binary
+
+`nmhost/` builds `velox-nmhost` — see that directory's own `src/main.cpp` for what it does
+(a byte-level pump, no protocol logic) and `docs/05-extension-spec.md` §4 for the two
+transports it sits behind. It is deliberately dependency-free (not linked against any
+`veloxd_*` library) so wherever a packaging format's sandbox puts it, it has nothing else
+to go looking for at runtime.
@@ -0,0 +1,7 @@
+{
+  "name": "com.velox.host",
+  "description": "Velox download manager — native messaging bridge to veloxd",
+  "path": "/usr/libexec/velox/velox-nmhost",
+  "type": "stdio",
+  "allowed_extensions": ["[email protected]"]
+}
@@ -0,0 +1,65 @@
+# packaging/systemd — the user unit pair for veloxd
+
+Provided by lane DAEMON (`daemon/docs/AGENT-DAEMON.md` build step 7: "systemd user units
+— `velox.service` + `velox.socket` for socket activation"), for PKG/QA to install per
+`docs/07-packaging.md`'s layout:
+
+```
+/usr/lib/systemd/user/velox.service
+/usr/lib/systemd/user/velox.socket
+```
+
+`packaging/` outside `nativehost/` is PKG/QA's per `CLAUDE.md`'s lane table; these two
+files are here because they are inputs to that packaging step, not a claim on the rest of
+the directory — same relationship `packaging/nativehost/` already has.
+
+## Why both files, and what `RuntimeDirectory=` is doing
+
+`velox.socket` binds `$XDG_RUNTIME_DIR/velox/velox.sock` **before `veloxd` ever runs** and
+hands the daemon the already-listening fd at startup (`daemon/src/rpc/systemd_activation.cpp`
+implements the receiving half — `LISTEN_PID`/`LISTEN_FDS`, fd 3 — without a `libsystemd`
+link). Two things this buys over the daemon binding its own socket on every start:
+
+- **No window where a client gets `ECONNREFUSED`.** The socket exists and queues
+  connections from the moment `velox.socket` is active, not from whenever `veloxd`
+  finishes starting up — this is the actual point of socket activation, not just "start
+  on demand."
+- **Cold-boot ordering is free.** Nothing has to wait for `veloxd` to be ready before the
+  GUI, the CLI, or a native-messaging host can attempt a connection; the kernel queues it.
+
+`RuntimeDirectory=velox` on the socket unit creates `%t/velox` (mode 0700) before the
+`ListenStream=` bind — without it, binding fails outright the first time (nothing has
+created the parent directory yet). `veloxd` itself creates that same directory
+(`ensure_private_dir` in `runtime_dir.cpp`) for the case where it's started directly,
+outside systemd (`./veloxd` in a terminal, still supported and how most of this daemon's
+own testing runs) — the two paths converge on the same directory with the same mode
+either way.
+
+`UdsServer::start()` (`daemon/src/rpc/uds_server.cpp`) checks for the activated fd first
+and, if present, skips create/bind/chmod/listen entirely — the socket file's lifecycle then
+belongs to the unit (including `RemoveOnStop=yes` on stop), not to the daemon. Falls back
+to binding its own socket exactly as before when not socket-activated (a manual run, or a
+distro that ships the daemon without the unit files).
+
+## What was deliberately left out
+
+`velox.service` does **not** set `ProtectSystem=`, `ProtectHome=`, or `ReadWritePaths=`.
+`saveTo.allowedRoots` is user-configurable to anywhere on the filesystem — an external
+drive, a second mount, anywhere `fs/safepath.hpp`'s own canonicalize-and-check accepts —
+not a fixed set of directories a unit file could enumerate ahead of time. A filesystem-level
+sandbox here would turn a legitimately-configured save location into an opaque
+`EROFS`/`EACCES` the daemon can't explain, in place of its own clear `-32011` — worse than
+no sandbox, specifically for a download manager. `NoNewPrivileges=yes` is kept: it has no
+such trade-off.
+
+## Verifying socket activation without a real install
+
+`systemd-analyze verify --user velox.service velox.socket` checks unit-file syntax (it
+will complain that `/usr/bin/veloxd` and the `velox(1)` man page don't exist on a dev
+box that hasn't installed the package — expected, not a unit bug). To exercise the actual
+activation handshake without installing anything: bind a Unix socket, `dup2` it onto fd 3,
+fork, set `LISTEN_PID=<child pid>` and `LISTEN_FDS=1` in the child's environment, clear
+`FD_CLOEXEC` on fd 3, and `execve` `veloxd` — a real `session.hello` round-trips over that
+fd with no `bind()`/`listen()` call ever happening inside the daemon for that run. This is
+exactly what `velox.socket`'s `Requires=`/`ExecStart` sequence does in production; systemd
+supplies the fd, `veloxd` doesn't know the difference.
@@ -0,0 +1,38 @@
+[Unit]
+Description=Velox download manager daemon
+Documentation=man:velox(1)
+# Socket activation (velox.socket) means this unit does not need to be enabled or started
+# directly for the RPC transport to come up on demand — the first connection attempt after
+# boot starts veloxd with the listening socket already bound (see velox.socket's own
+# comment). Requires=/After= still matter for a manual `systemctl --user start velox`.
+Requires=velox.socket
+After=velox.socket
+
+# Never more than one real instance for this user regardless of how it was started — the
+# abstract-socket single-instance lock (main.cpp, keyed off the resolved runtime dir) is
+# the actual enforcement; this just keeps systemd itself from racing two starts.
+StartLimitIntervalSec=60
+StartLimitBurst=5
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/veloxd
+# main.cpp's SIGTERM handler stops the event loop and falls through to a clean shutdown
+# (flushes buffers, closes the store, releases the single-instance lock) — the default
+# KillSignal=SIGTERM and TimeoutStopSec are already the right shape for that; no
+# ExecStop/KillMode override needed.
+Restart=on-failure
+RestartSec=2
+
+# Hardening deliberately stops here, not at ProtectSystem=/ProtectHome=/ReadWritePaths=:
+# saveTo.allowedRoots is user-configurable to anywhere (an external drive, a second
+# mount — fs/safepath.hpp is the daemon's own validation boundary, not a fixed set of
+# directories a unit file could enumerate up front). A filesystem-level sandbox here would
+# silently turn a legitimately-configured save location into an opaque EROFS/EACCES the
+# daemon can't explain, instead of its own clear -32011 — worse than no sandbox, for a
+# download manager specifically. NoNewPrivileges is free of that trade-off.
+NoNewPrivileges=yes
+
+[Install]
+WantedBy=default.target
+Also=velox.socket
@@ -0,0 +1,28 @@
+[Unit]
+Description=Velox download manager — RPC socket
+
+[Socket]
+# %t is $XDG_RUNTIME_DIR for a user unit — the exact path veloxd itself resolves
+# (daemon/src/rpc/runtime_dir.cpp's resolve_runtime_dir), and the exact path velox(1)
+# resolves too (default_socket_path() in cli/src/client.cpp). All three must agree; this
+# is the one line that has to.
+ListenStream=%t/velox/velox.sock
+
+# RuntimeDirectory creates %t/velox (mode 0700, this user's own) before binding, so the
+# ListenStream= path above always has somewhere to land — veloxd itself does the same
+# thing (ensure_private_dir) when it creates the directory unassisted (the non-activated
+# path, e.g. a manual `veloxd` run outside systemd).
+RuntimeDirectory=velox
+RuntimeDirectoryMode=0700
+
+# Same-UID-only, matching the socket's own authorization once a connection is accepted
+# (SO_PEERCRED, checked again in uds_server.cpp regardless of this mode bit — belt and
+# braces, not a substitute for it).
+SocketMode=0600
+
+# The socket file belongs to systemd's socket-activation state, not to whatever's on disk
+# from a previous boot; remove it on stop so a stale entry never shadows the next start.
+RemoveOnStop=yes
+
+[Install]
+WantedBy=sockets.target
@@ -160,11 +160,18 @@ if [ -z "$EXTERNAL_UDS" ] && [ -z "$EXTERNAL_WS" ]; then
    for _ in $(seq 1 50); do [ -S "$VUDS" ] && break; sleep 0.2; done
    [ -S "$VUDS" ] || { echo "veloxd did not start:"; cat "$WORK/veloxd.log"; exit 1; }

-    # saveTo.allowedRoots defaults to ["~/Downloads"]; download.add.json (fixture) asks
-    # for a saveDir under $HOME/Downloads, so both that and download.add's own isolated
-    # downloads dir need to be allowed roots, or every download.add fixture fails -32011
-    # before the point of this runner is even reached. settings.set is itself a D3 stub,
-    # so this is written straight into the isolated velox.db rather than over the wire.
+    # saveTo.allowedRoots defaults to ["~/Downloads"]; download.add's own isolated
+    # downloads dir needs to be an allowed root too, or every download.add fixture fails
+    # -32011 before the point of this runner is even reached. $HOME/Downloads stays in
+    # the list alongside it: a few fixtures still set an explicit saveDir there
+    # (category.upsert.json, download.update.json) rather than take the default.
+    # capture.minSizeBytes defaults to 0 (nothing is ever "too small"), which makes
+    # errors/capture.offer.ignore.json's below-minimum-size case impossible to reach
+    # against a fresh daemon; raised here so that fixture's scenario is actually
+    # reachable. Written straight into the isolated velox.db, before veloxd has any RPC
+    # session to write it through: settings.set is real now (D9), but this has to be in
+    # place before the very first fixture runs, and setup happens before any connection
+    # exists.
    python3 - "$VXDG/data/velox/velox.db" "$VXDG/downloads" "$HOME/Downloads" <<'PY'
 import json, sqlite3, sys
 db_path, isolated_downloads, home_downloads = sys.argv[1:4]
@@ -174,6 +181,11 @@ db.execute(
    "ON CONFLICT(key) DO UPDATE SET value = excluded.value",
    ("saveTo.allowedRoots", json.dumps([isolated_downloads, home_downloads])),
 )
+db.execute(
+    "INSERT INTO settings(key, value) VALUES(?, ?) "
+    "ON CONFLICT(key) DO UPDATE SET value = excluded.value",
+    ("capture.minSizeBytes", json.dumps(1000000)),
+)
 db.execute(
    "INSERT INTO settings(key, value) VALUES(?, ?) "
    "ON CONFLICT(key) DO UPDATE SET value = excluded.value",
@@ -1,40 +1,26 @@
 [
-  { "fixture": "contracts/fixtures/download.refreshUrl.json", "reason": "D3: stub handler, -32603" },
-  { "fixture": "contracts/fixtures/download.update.json", "reason": "D3: stub handler, -32603" },
+  { "fixture": "contracts/fixtures/grabber.harvest.json", "reason": "D3: stub handler, -32603 (M4 territory per deferrals.md)" },
+  { "fixture": "contracts/fixtures/grabber.start.json", "reason": "D3: stub handler, -32603 (M4 territory per deferrals.md)" },
+  { "fixture": "contracts/fixtures/grabber.status.json", "reason": "D3: stub handler, -32603 (M4 territory per deferrals.md)" },

-  { "fixture": "contracts/fixtures/rules.list.json", "reason": "D3: stub handler, -32603" },
-  { "fixture": "contracts/fixtures/rules.upsert.json", "reason": "D3: stub handler, -32603" },
-
-  { "fixture": "contracts/fixtures/settings.get.json", "reason": "D3: stub handler, -32603" },
-  { "fixture": "contracts/fixtures/settings.set.json", "reason": "D3: stub handler, -32603" },
-
-  { "fixture": "contracts/fixtures/limiter.get.json", "reason": "D3: stub handler, -32603" },
-  { "fixture": "contracts/fixtures/limiter.set.json", "reason": "D3: stub handler, -32603" },
-
-  { "fixture": "contracts/fixtures/schedule.get.json", "reason": "D3: stub handler, -32603" },
-  { "fixture": "contracts/fixtures/schedule.set.json", "reason": "D3: stub handler, -32603" },
-
-  { "fixture": "contracts/fixtures/queue.reorder.json", "reason": "D3: stub handler, -32603" },
-
-  { "fixture": "contracts/fixtures/grabber.harvest.json", "reason": "D3: stub handler, -32603" },
-  { "fixture": "contracts/fixtures/grabber.start.json", "reason": "D3: stub handler, -32603" },
-  { "fixture": "contracts/fixtures/grabber.status.json", "reason": "D3: stub handler, -32603" },
-
-  { "fixture": "contracts/fixtures/media.addVariant.json", "reason": "D3: stub handler, -32603" },
-  { "fixture": "contracts/fixtures/media.listVariants.json", "reason": "D3: stub handler, -32603" },
-
-  { "fixture": "contracts/fixtures/capture.getRules.json", "reason": "D3: stub handler, -32603 -- DAEMON is filing capture.offer next" },
-  { "fixture": "contracts/fixtures/capture.offer.take.json", "reason": "D3: stub handler, -32603 -- DAEMON is filing capture.offer next" },
-  { "fixture": "contracts/fixtures/errors/capture.offer.ignore.json", "reason": "D3: stub handler, -32603 -- DAEMON is filing capture.offer next" },
+  { "fixture": "contracts/fixtures/media.addVariant.json", "reason": "D3: stub handler, -32603 (M4 territory per deferrals.md)" },
+  { "fixture": "contracts/fixtures/media.listVariants.json", "reason": "D3: stub handler, -32603 (M4 territory per deferrals.md)" },

  { "fixture": "contracts/fixtures/errors/download.provideAuth.not-found.json", "reason": "real bug: on_download_provideAuth (dispatcher.cpp) never checks the task exists -- TaskActionPort::provide_auth returns false for an unknown id, which the handler folds into a normal {ok:false} result instead of -32010" },

  { "fixture": "contracts/fixtures/category.list.json", "reason": "documented gap (deferrals.md D3a note): categories table has no mimeTypes/sortOrder columns, so category.upsert accepts them but category.list never echoes mimeTypes back" },

+  { "fixture": "contracts/fixtures/capture.getRules.json", "reason": "not a bug: capture.monitoredMimeTypes defaults to [] (store/settings.cpp's kDefaults) on a fresh daemon; the golden's non-empty example illustrates a configured one" },
+
  { "fixture": "contracts/fixtures/download.probe.json", "reason": "not a bug: requiresAuth is optional-and-omitted-when-false (schema doesn't require it); the golden shows it because that fixture's probe hit a 401, this run's doesn't" },
  { "fixture": "contracts/fixtures/download.get.json", "reason": "not a bug: effectiveUrl is 'null until the first probe succeeds' (schema) and omitted rather than sent as null; our bound $taskId is a fresh, never-started task, so it's never been probed -- the golden depicts an in-progress download instead" },
  { "fixture": "contracts/fixtures/download.list.json", "reason": "same as download.get.json: effectiveUrl omitted for our never-started bound tasks, golden depicts an in-progress download" },
-  { "fixture": "contracts/fixtures/session.hello.json", "reason": "not a bug: capabilities is genuinely empty because media/grabber/Secret Service aren't implemented yet; the golden's ['media','grabber','secretservice'] illustrates a future daemon, not this one" },
+  { "fixture": "contracts/fixtures/download.update.json", "reason": "not a bug: etaSeconds is only known for a task the engine has probed/is running; our bound $taskId is a fresh, never-started task, so it's absent -- same class as download.get.json's effectiveUrl" },
+  { "fixture": "contracts/fixtures/session.hello.json", "reason": "not a bug: capabilities is genuinely empty because media/grabber aren't implemented yet (capture/Secret Service's parts of it now are); the golden's example list illustrates a future daemon, not this one" },
+
  { "fixture": "contracts/fixtures/queue.start.json", "reason": "not a bug: startedTaskIds is empty because nothing is a member of queue 'main' in this isolated run; the golden depicts a queue with real membership" },
+  { "fixture": "contracts/fixtures/queue.reorder.json", "reason": "not a bug: the fixture's taskIds are two literal ids that only ever existed in a seeded mock; queue 'main' has no members at all in this isolated run, so any non-empty list is correctly rejected as not a permutation of (empty) membership" },
+  { "fixture": "contracts/fixtures/rules.list.json", "reason": "not a bug: no rule is ever seeded in a fresh daemon; the golden depicts a configured rule set" },
+  { "fixture": "contracts/fixtures/schedule.set.json", "reason": "documented gap (deferrals.md D3f note): nextRunAt is deliberately left unset -- computing it needs DST-aware next-transition logic sched/schedule_window.hpp doesn't have yet" },
  { "fixture": "contracts/fixtures/category.remove.json", "reason": "not a bug: reassignedTaskIds is empty because nothing was ever filed under the 'firmware' category this run creates; the golden depicts a category with real membership" }
 ]
@@ -88,88 +88,62 @@ manual testing.
 nowhere to run. GUI owns the harness; PKG/QA owns the CI job. This is the wiring contract
 so the two halves meet without another round trip.

-### What PKG/QA needs from GUI
+### What GUI built, and the invocation contract

-A driver invoked as `gui/tests/dod/run.sh <gate> [--json <path>]` (exact path TBD by GUI),
-headless-capable (Xvfb or offscreen `QT_QPA_PLATFORM`), with:
+`gui/tests/dod/run.sh <gate> [--json <path>]` (`gate` one of `scroll-60fps` / `rss-flat`
+/ `unhappy-path`), backed by `gui/tests/dod/dod_harness.cpp` (target `gui-dod-harness`).
+Headless by default — `run.sh` sets `QT_QPA_PLATFORM=offscreen` itself, so the CI jobs
+below need no Xvfb.

 | `<gate>` | Pass / fail condition | Budget |
 |---|---|---|
-| `scroll-60fps` | `mockd --tasks 10000`, scripted fling scroll; **fail** if p99 frame > 16.6 ms | per-PR |
-| `rss-flat` | `mockd --tasks 10000` + progress events, 10 min; **fail** if RSS growth > a fixed slack (GUI picks the number, states it) | nightly |
-| `unhappy-path` | `mockd --slow` / `--flaky <f>` / `--drop-connection <s>`; **fail** on crash, on watchdog-detected hang, or if connection state never returns to `Connected` | per-PR |
+| `scroll-60fps` | `mockd --tasks 10000`, scripted fling scroll; **fail** if p99 frame > 16.6 ms (×4 under an ASan/UBSan build — `VELOX_DOD_FRAME_BUDGET_MS` overrides outright) | per-PR |
+| `rss-flat` | `mockd --tasks 10000` + progress events, 10 min; **fail** if RSS growth past warm-up exceeds a 20 MiB slack (`VELOX_DOD_RSS_SLACK_KIB` overrides) | nightly |
+| `unhappy-path` | Three phases (`--slow` / `--flaky <f>` / `--drop-connection <s>`), one `mockd` restart each; **fail** on crash, on the harness's own watchdog firing (75 s), or if connection state never (re)reaches `Connected` | per-PR |

-Contract:
+Contract, as built: exit `0` pass, non-zero fail; a hang is the harness's own watchdog
+converting itself into a non-zero exit (`3`), never something CI needs `timeout(1)`
+around; `--json` writes one result object per gate (`unhappy-path` merges its three
+phases into one file); no network, no writes outside a tempdir, no leaked child process
+on any exit path (`run.sh`'s `trap cleanup EXIT INT TERM`).

-* exit `0` pass, non-zero fail; a hang is the harness's own watchdog to catch and turn
-  into a non-zero exit, not something CI should have to `timeout(1)` around.
-* `--json` writes one machine-readable result file (measured p99, RSS series, recovery
-  time) so the job can upload it as an artifact and a regression is a diff, not a re-run.
-* no network, no writes outside a tempdir, no leaked child processes on failure.
+### CI jobs — wired

-### CI job — pre-drafted, add once the harness path is fixed
+`gui-dod` (per-PR: `scroll-60fps` + `unhappy-path`) and `gui-dod-nightly` (`rss-flat`,
+`schedule`/`workflow_dispatch` only) are live in `ci.yml`. Both bootstrap, build
+`gui-dod-harness`, `npm ci` in `tools/mockd`, run `gui/tests/dod/run.sh`, and upload the
+`--json` output as an artifact — no Xvfb step, since `run.sh` already runs offscreen.

-```yaml
-  gui-dod:
-    # Per-PR GUI gates. The 10-minute rss-flat gate is in gui-dod-nightly, not here.
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - name: Bootstrap toolchain
-        run: sudo ./tools/bootstrap.sh
-      - uses: actions/setup-node@v4
-        with:
-          node-version: '22'          # tools/mockd
-      - name: Configure + build
-        run: |
-          cmake --preset dev
-          cmake --build --preset dev --target velox-gui
-      - name: Install mockd
-        run: cd tools/mockd && npm ci
-      - name: Xvfb + gates
-        run: |
-          sudo apt-get install -y --no-install-recommends xvfb
-          xvfb-run -a gui/tests/dod/run.sh scroll-60fps   --json scroll.json    # TODO(GUI): path
-          xvfb-run -a gui/tests/dod/run.sh unhappy-path    --json unhappy.json
-      - uses: actions/upload-artifact@v4
-        if: always()
-        with:
-          name: gui-dod-${{ github.run_id }}
-          path: "*.json"
+### Forced red, once per gate, before wiring it required

-  gui-dod-nightly:
-    if: github.event_name == 'schedule'
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - name: Bootstrap toolchain
-        run: sudo ./tools/bootstrap.sh
-      - uses: actions/setup-node@v4
-        with:
-          node-version: '22'
-      - name: Configure + build
-        run: |
-          cmake --preset dev
-          cmake --build --preset dev --target velox-gui
-      - run: cd tools/mockd && npm ci
-      - name: RSS soak (10 min)
-        run: |
-          sudo apt-get install -y --no-install-recommends xvfb
-          xvfb-run -a gui/tests/dod/run.sh rss-flat --json rss.json
-      - uses: actions/upload-artifact@v4
-        if: always()
-        with:
-          name: gui-dod-rss-${{ github.run_id }}
-          path: rss.json
-```
+| Gate | Forced via | Observed |
+|---|---|---|
+| `scroll-60fps` | `VELOX_DOD_FRAME_BUDGET_MS=0.01` | `FAIL: p99=50.73 ms mean=31.34 ms max=52.88 ms budget=0.01 ms over 240 steps, 10000 rows`, exit 1 |
+| `rss-flat` | `VELOX_DOD_RSS_SLACK_KIB=-999999999` (guarantees `growthKiB > slack` regardless of actual RSS behavior that run) | `FAIL: growth=13644 KiB slack=-999999999 KiB over 15s (warmup 1s), 10000 rows`, exit 1 |
+| `unhappy-path` | ran `gui-dod-harness` directly (bypassing `run.sh`, which always starts a working `mockd`) against a `--sock` path with nothing listening | 75 s of `Connecting`/`Reconnecting`, then `FAIL: dod_harness watchdog fired — hung past 75s`, exit 3 |

-`gui-dod-nightly` needs `if: github.event_name == 'schedule'` (the `nightly-integration`
-job below already added that trigger to `ci.yml` — `cron: '17 3 * * *'` — so this no
-longer needs its own).
+The real (non-forced) runs all pass live: `scroll-60fps` p99 51.28 ms against a 66.4 ms
+budget (ASan/UBSan build), `rss-flat` growth 13504 KiB against the 20480 KiB slack over a
+15 s smoke duration, `unhappy-path` all three phases `PASS` with `finalConnected=true`.
+
+### Known gap: `unhappy-path`'s drop-connection phase doesn't drop anything
+
+Filed by GUI in `gui/docs/proto-requests-m1.md`: `mockd --drop-connection` only works
+over WebSocket — `startUds()` never wires the periodic-drop timer `startWs()` has, so the
+UDS transport (GUI/CLI/nmhost's only one) never sees a connection actually die. GUI's own
+live verification: 45 s observing a `--drop-connection 5` mockd over UDS, `stateChanged`
+never fires. The phase still runs and its JSON honestly records `sawDisruption: false`
+rather than silently passing as if it proved something — that's what the real run above
+shows, `pass: true` alongside `sawDisruption: false`, so a reviewer reading the JSON sees
+exactly how much this phase currently covers.
+
+This is PROTO's fix, not PKG/QA's or GUI's to route around locally — coordinating on it
+rather than patching mockd from this lane. Once PROTO lands `dropEverySec` on `startUds`,
+`unhappy-path`'s drop-connection phase starts exercising a real drop and this note comes
+out; until then `gui-dod` stays required as specified (crash/hang/never-reconnects still
+catch real regressions), just not yet catching a swallowed real disconnect.

 ### Status

-Blocked on GUI's harness. Not urgent (GUI M1 DoD, not M0). When GUI files the follow-up
-with the real `run.sh` path and the `rss-flat` slack number, PKG/QA drops the `TODO(GUI)`
-markers and marks `gui-dod` required. The `schedule:` trigger `gui-dod-nightly` needs is
-already in `ci.yml`.
+Wired and required: `gui-dod` runs per-PR, `gui-dod-nightly` on schedule. Revisit once
+PROTO's UDS `--drop-connection` fix lands (see above).
@@ -288,7 +288,10 @@ export class Dispatcher {
      }

      case 'limiter.get':
-        return state.limiter;
+        // applyToRunning is a write-only instruction on limiter.set ("retune already-
+        // running transfers now"), not a persisted setting, so get never echoes it back
+        // (contracts/fixtures/limiter.get.json).
+        return { enabled: state.limiter.enabled, globalBps: state.limiter.globalBps };

      case 'limiter.set': {
        state.limiter = {