ObsidianDragon/docs/daemon-startup-hardening.md

# Daemon Startup Hardening — Implementation Plan

Eight verified edge-case defects in how ObsidianDragon brings up (and watches) the
`dragonxd` daemon at launch. Each entry is a buildable fix: the defect (with exact
line references), the chosen approach, the call sites, a representative change, and how
to verify it.

- **Scope:** full-node startup path (`--lite` excludes the embedded daemon entirely).
- **Source:** line references are exact against branch `dev` @ `45b652f`.
- **Provenance:** findings verified by direct source read; each fix designed by an
  independent agent grounded in the cited files, with a sequencing pass for ordering,
  shared helpers, and merge conflicts.

**Severity:** 2 High, 6 Medium · **Effort:** ≈ 25–35 engineering-hours · **7 landing steps.**

Status legend: ☐ not started · ◐ in progress · ☑ landed & verified

---

## Recommended rollout sequence

A real dependency order, not a checklist. The daemon-lifecycle cluster lands first
because it makes the `State::Error` / `crash_count_` contract trustworthy — which the
connect-stall panel and the lock gate both build on. The filesystem cluster lands
around a single shared helper. The connectivity-breaking security flip lands last.

| Step | Finding(s) | Site | Why here | Status |
|------|-----------|------|----------|--------|
| 1 | **F1** | `embedded_daemon.cpp` · `isRunning()` | Smallest/highest-severity; establishes the reliable Error/crash-count transition steps 3 & 6 depend on. | ☑ |
| 2 | **F2** | `embedded_daemon.cpp` · `startProcess()` | Same file family, different function; test the F1+F2 pair together with `kill -SEGV` / bad-binary repros. | ☑ |
| 3 | **F4** | `embedded_daemon.cpp` · `start()` | After F1/F2 so crash-count semantics are settled; its bail deliberately stays out of the crash path. | ☑ |
| 4 | **F7** | `util/platform` · `connection.cpp` | Structural owner of the fs-error idiom + `ConnectionConfig` that F5/F6/F8 reuse. | ☑ |
| 5 | **F6 + F5** | `app.cpp` · `verifySaplingParams()` | Same `startEmbeddedDaemon` / `verifySaplingParams` block; land together. | ☑ |
| 6 | **F3** | `app.cpp` · `renderLoadingOverlay()` | After F1 — panel is guarded off during `State::Error` (owned by the crash-count hint). | ☐ |
| 7 | **F8** | `connection.cpp` · `tryConnect()` | Largest; only connectivity-breaking default flip — land last, with release notes. | ☐ |

---

## F1 — Double-`waitpid` race can swallow a daemon crash

**Severity:** High · **Effort:** S (~1–2h) · **Status:** ☑ landed & verified

### The defect
`EmbeddedDaemon::isRunning()` (`embedded_daemon.cpp:1136`, POSIX branch) calls
`waitpid(WNOHANG)` — from the **UI thread, nearly every frame** — racing
`monitorProcess()`'s own reap at `:1244`. `waitpid` is one-shot: if the UI thread wins,
the monitor never decodes the exit, so `crash_count_` never increments, `State::Error`
never fires, and the 3-strike auto-restart cap (`app_network.cpp:479`) is defeated. The
sibling `XmrigManager::isRunning()` (`xmrig_manager.cpp:512`) already fixed exactly this
with an atomic read.

### The fix
Make `isRunning()` read the existing `std::atomic<State> state_` (member at
`embedded_daemon.h:253`) instead of calling `waitpid`, leaving `monitorProcess()` as the
sole reaper. Predicate is `Running || Stopping` — `Stopping` must stay "alive" because
`stop()`'s graceful/SIGTERM wait loops poll `isRunning()` before the process has exited.

### Files touched
- `src/daemon/embedded_daemon.cpp` — `isRunning()`, POSIX branch (~1136)

### Core change
```cpp
bool EmbeddedDaemon::isRunning() const   // POSIX branch
{
    // Read the atomic state_ instead of waitpid() — monitorProcess() is the
    // sole reaper. Previously both threads reaped; if the UI thread won, the
    // monitor never saw the exit (crash_count_ / exit code / Error all lost).
    if (process_pid_ <= 0) return false;

    State s = state_.load(std::memory_order_relaxed);
    // Stopping stays "alive": stop()'s wait loops poll isRunning() while
    // state_ == Stopping, before the process has actually terminated.
    return (s == State::Running || s == State::Stopping);
}
```

### Verification
- Manual: `kill -SEGV` the daemon 10–20×; the monitor must report the exit and increment `crash_count_` every time (previously intermittent).
- Regression: a normal Settings-driven stop still escalates SIGTERM→SIGKILL (the `Stopping` predicate).
- Not unit-testable (real fork/exec/waitpid) — consistent with the no-process-spawn harness.

### Dependencies
Mirrors `XmrigManager::isRunning()`. Flags a separate latent hazard (out of scope):
`stop()`'s final blocking `waitpid` (`:1220`) can still race a mid-sleep monitor
iteration — file as its own ticket.

---

## F2 — exec-after-fork silent failure: "Running" for a daemon that never started

**Severity:** High · **Effort:** S (~2–3h) · **Status:** ☑ landed & verified

### The defect
In `startProcess()` (`embedded_daemon.cpp:957–1061`, POSIX) the parent runs
`process_pid_ = pid; return true;` **unconditionally** after `fork()` — with no
exec-status handshake. On a non-executable / wrong-arch / corrupt binary the child's
`execv` fails and it `_exit(127)`s, but `start()` has already set `State::Running`
(`:565`). The real cause never reaches `last_error_`; it surfaces later, generically,
as "exited unexpectedly (exit code 127)".

### The fix
Add a **close-on-exec self-pipe** handshake — `pipe() + fcntl(FD_CLOEXEC)`, deliberately
**not** `pipe2()` (macOS lacks it; the POSIX branch is shared). The child writes `errno`
only on `execv` failure; a successful exec closes the write end for free. Parent reads:
EOF ⇒ success; 4 bytes ⇒ reap the zombie, set a precise `last_error_` ("not executable
or wrong architecture"), and return `false` so `start()` never reports Running. EINTR-safe
on both ends. Also comments the unchecked parent-side `setpgid` at `:1053`.

### Files touched
- `src/daemon/embedded_daemon.cpp` — `startProcess()` parent read path
- `src/daemon/embedded_daemon.cpp` — child `execv`-failure write (~1043)
- `src/daemon/embedded_daemon.cpp` — `setpgid` best-effort comment (~1053)

### Core change
```cpp
// Self-pipe exec handshake (pipe()+FD_CLOEXEC; NOT pipe2 — macOS lacks it).
int execpipe[2]; pipe(execpipe);
fcntl(execpipe[0], F_SETFD, FD_CLOEXEC);
fcntl(execpipe[1], F_SETFD, FD_CLOEXEC);

pid_t pid = fork();
if (pid == 0) {                        // child
    close(execpipe[0]);
    /* setpgid / chdir / dup2 / argv … */
    execv(binary_path.c_str(), argv.data());
    int e = errno;                     // execv failed
    while (write(execpipe[1], &e, sizeof e) < 0 && errno == EINTR) {}
    _exit(127);
}

close(execpipe[1]);                    // parent: must close or read() never EOFs
int child_errno = 0, total = 0;
for (;;) {                             // EOF ⇒ exec ok; 4 bytes ⇒ exec failed
    ssize_t n = read(execpipe[0], (char*)&child_errno + total, sizeof(int) - total);
    if (n == 0) break;
    if (n < 0) { if (errno == EINTR) continue; break; }
    if ((total += n) >= (int)sizeof(int)) break;
}
close(execpipe[0]);
if (total >= (int)sizeof(int)) {       // exec never happened
    waitpid(pid, nullptr, 0);          // reap the zombie
    last_error_ = "dragonxd could not be executed: " +
                  std::string(strerror(child_errno)) +
                  " — not executable or wrong architecture";
    return false;                      // start() no longer reports Running
}
```

### Verification
- Point at a `chmod -x` / wrong-arch file → `start()` returns false immediately, precise message, no leftover zombie.
- Success path: real binary still starts with no perceptible added latency.
- Optional pure `formatExecFailureError(errno)` helper for a `test_phase4.cpp` unit test.

### Dependencies
F1 (same function family; sequence F1→F2). **Highest-risk mistake:** forgetting
`FD_CLOEXEC` makes every successful start hang the parent read forever.

---

## F4 — Stale datadir-lock start → restart storm that wedges the UI

**Severity:** Medium · **Effort:** S (~3–5h) · **Status:** ☑ landed & verified

### The defect
`start()` (`embedded_daemon.cpp:466`) gates only on the RPC port (`:482`), never on
`isDaemonProcessRunning()` (`:1292`). A graceful shutdown frees the port but keeps the
datadir `.lock` for up to ~90s. A rapid stop→start spawns a daemon that dies "Cannot
obtain a lock on data directory" — routed to the generic crash path. With a ~4s retry
cadence, **three lock races in ~12s exhaust the 3-strike budget** and wedge the UI long
before the lock actually clears.

### The fix
Fail-fast with a **short bounded local wait (~300ms), not a 90s block**. After the port
bail, consult `isDaemonProcessRunning()` — gated by `!skip_port_check_` and exempt when
`override_datadir_` is set, so the isolated migrate-to-seed daemon still works. A pure
`evaluateDatadirLockGate()` returns a **distinct non-crash Error** that never increments
`crash_count_`. The connect loop's own retry then absorbs the transient.

### Files touched
- `src/daemon/embedded_daemon.h` — decision struct, helper decl, poll constants
- `src/daemon/embedded_daemon.cpp` — `start()` gate + `evaluateDatadirLockGate()`

### Core change
```cpp
static StartLockGateDecision evaluateDatadirLockGate(
        bool skipPortCheck, bool isolatedOverride, bool stillRunningAfterWait) {
    if (skipPortCheck || isolatedOverride) return {true,  ""};   // migrate-to-seed exempt
    if (!stillRunningAfterWait)            return {true,  ""};
    return {false, "A previous dragonxd is still shutting down and holding the "
                   "data directory lock. Retrying shortly…"};
}

// start() — after the isPortInUse() bail, before setState(Starting):
if (!skip_port_check_ && override_datadir_.empty()) {
    bool stillLocked = false;                       // ~300ms bounded wait, NOT ~90s
    for (int i = 0; i < kDatadirLockWaitMaxPolls; ++i) {
        if (!isDaemonProcessRunning()) { stillLocked = false; break; }
        stillLocked = true;
        std::this_thread::sleep_for(std::chrono::milliseconds(kDatadirLockWaitPollMs));
    }
    auto gate = evaluateDatadirLockGate(false, false, stillLocked);
    if (!gate.proceed) { setState(State::Error, gate.errorMessage); return false; }
}
```

### Verification
- Unit: `evaluateDatadirLockGate()` across the skip / isolated / still-running matrix.
- Manual: rapid restart into a lingering lock → distinct message, no crash-cap wedge.
- Migrate-to-seed second daemon still starts (isolated exemption).

### Dependencies
F1/F2 (must not touch `crash_count_`; wording must not collide with the monitor's
"exited unexpectedly"). Same TU, different function.

---

## F5 — Extraction / copy write-failures never surfaced up front

**Severity:** Medium · **Effort:** S (~2–3h) · **Status:** ☑ landed & verified

### The defect
`startEmbeddedDaemon()` discards `extractEmbeddedResources()`'s `bool` return
(`app.cpp:4152`) and the second copy-fallback loop drops `copy_file`'s `error_code`
entirely (`:4236`). Only Sapling params **existence** is re-checked — never the daemon
binary/CLI/tx/asmap. A disk-full or truncated `dragonxd` write falls straight through to
spawn and fails opaquely. The innermost write already returns `false`
(`embedded_resources.cpp:307`) — the signal is simply thrown away.

### The fix
Minimal, surgical wiring — no new abstraction. Capture the extraction return and, on
failure, set `daemon_status_ = TR("sb_daemon_extract_failed")` and `return false` before
spawning. In the second copy loop, check `ec` after each `copy_file`, track `copyFailed`,
and abort with a dir-parameterized `sb_daemon_files_failed`. An **absent source** stays
fine (optional files); only an actual `error_code` counts. Written so F6/F7 slot in later
without re-touching this control flow.

### Files touched
- `src/app.cpp` — `startEmbeddedDaemon()` extraction check (~4152)
- `src/app.cpp` — second copy-fallback loop (~4210–4242)
- `src/util/i18n.cpp` + `res/lang/*.json` — 2 additive keys

### Core change
```cpp
// stop discarding the extraction result (~4152)
if (!resources::extractEmbeddedResources()) {
    daemon_status_ = TR("sb_daemon_extract_failed");   // disk full / permission denied
    return false;                                      // abort before spawning
}

// second copy-fallback loop — was dropping ec entirely (~4236)
bool copyFailed = false;
for (const char* name : { "asmap.dat", "dragonxd", "dragonx-cli", "dragonx-tx" }) {
    fs::path dst = fs::path(daemon_dir) / name;
    if (fs::exists(dst)) continue;                      // already present — skip
    for (const auto& dir : searchDirs) {
        fs::path src = fs::path(dir) / name;
        if (!fs::exists(src)) continue;                 // absent source is OK, not a failure
        fs::copy_file(src, dst, ec);
        if (ec) { copyFailed = true; ec.clear(); }
        break;
    }
}
if (copyFailed) {
    char buf[512];
    snprintf(buf, sizeof buf, TR("sb_daemon_files_failed"), daemon_dir.c_str());
    daemon_status_ = buf;
    return false;                                       // don't fall through to spawn
}
```

### Verification
- Unit: `extractEmbeddedResources()` returns false without embedded resources.
- Extract the copy loop into a testable helper; force one dst write to fail (dst is an existing directory).
- Manual: near-full tmpfs / read-only dir → clear status, daemon controller never constructed.

### Dependencies
Shares the `daemon_status_` surfacing convention with F6; its early-return pattern is the
template F7 matches. Open item: remove truncated dst files so a retry re-copies.

---

## F6 — Sapling params validated by existence/size only, never hashed

**Severity:** Medium · **Effort:** S (~3–5h) · **Status:** ☑ landed & verified

> **As-built note.** `verifySaplingParams()` now delegates to a public, injectable
> `verifySaplingParamsIn(dir, digests)` so the integrity + marker-cache logic is unit-testable
> with synthetic small files (the real 48 MB params aren't in the repo). i18n keys for F5 were
> added to `i18n.cpp` (English source of truth); the `res/lang/*.json` back-fill via
> `scripts/add_missing_translations.py` is deferred to a single run at the end of the batch,
> per the cross-cutting note. Non-English locales fall back to English until then.

### The defect
`verifySaplingParams()` (`connection.cpp:123`) only calls `fs::exists()`;
`resourceNeedsUpdate()` (`embedded_resources.cpp:250`) is size-only. On Linux (no
embedded resources) a **truncated-but-present** param passes and is handed to the daemon,
which then fails to build shielded proofs mid-operation — far from the real cause.

### The fix
Add a pinned `{ filename → size, sha256 }` table (one source of truth, cross-referenced
to `scripts/build-lite-backend-artifact.sh`) and hash-check each param after the
existence check, reusing the existing `util::sha256Hex` (no second implementation). Since
these are ~48 MB, **cache the result** via a `.sapling_verified` marker keyed on
`size:mtime` — re-hash only when the stat line changes, so startup isn't slowed.

### Files touched
- `src/rpc/connection.h` — `verifySaplingParams` decl
- `src/rpc/connection.cpp` — digest table, marker helpers, rewrite

### Core change
```cpp
// connection.cpp — pinned known-good digests
// (source of truth: scripts/build-lite-backend-artifact.sh ensure_sapling_params)
constexpr SaplingParamDigest kSaplingParamDigests[] = {
  { "sapling-spend.params",  47958396, "8e48ffd2…efc13" },
  { "sapling-output.params",  3592860, "2f0ebbcb…fb0e4" },
};

bool Connection::verifySaplingParams() {
    // existence check (unchanged) …
    // cache: skip re-hashing a ~48 MB file unless size:mtime changed
    if (readMarkerMatches(marker, statLines)) return true;
    for (auto& d : kSaplingParamDigests)
        if (util::sha256Hex(bytes) != d.sha256) return false;   // reuse existing helper
    writeMarker(marker, statLines);
    return true;
}
```

### Verification
- Unit: good params pass; truncated / wrong-bytes rejected; marker cache short-circuits re-hash unless size/mtime changed. Real temp-file fixtures (matches existing `sha256Hex` tests).

### Dependencies
F7 (reuse fs-error idiom; shares the `startEmbeddedDaemon`/`verifySaplingParams` block).
Third caller of the existing `util::sha256Hex`.

---

## F7 — Directory-create errors universally ignored on the daemon-env path

**Severity:** Medium · **Effort:** S (~3–4h) · **Status:** ☑ landed & verified

> **As-built notes.** Two deviations from the original design, both confirmed against the code:
> (1) `embedded_resources.cpp:270` already checks its `error_code` and returns `false` on failure — it was **not** a bug, so it is left untouched.
> (2) Of the four `autoDetectConfig` callers, only the primary connect path (`app_network.cpp:243`) was wired to check `dir_error`; the other three degrade gracefully on their own — `app.cpp:4306` and `app_wizard.cpp:912` are stop paths that already gate on empty creds, and `settings_page.cpp:434` is read-only display. `dir_error` is set by `autoDetectConfig`, so they can be wired later if desired.

### The defect
Five startup directory-create sites either drop the `error_code` or use the throwing
overload with no `catch`: `main.cpp:730`, `connection.cpp:216` (can throw **uncaught**
through its callers), `embedded_resources.cpp:270`, `app.cpp:4172`/`4218`. A read-only
home or permission-denied yields a confusing "conf missing" / "binary not found"
downstream — or an uncaught `filesystem_error` — instead of a clear cause.

### The fix
One shared, non-throwing `Platform::ensureDirectory(dir, outError)` in
`util/platform.{h,cpp}` that produces a single consistent message. Replace all five
sites; `autoDetectConfig()` moves off the throwing overload and sets a new
`ConnectionConfig::dir_error` that its four callers check and bail on. This is the
**structural owner** of the fs-error idiom that F5 and F6 reuse.

### Files touched
- `src/util/platform.h` / `.cpp` — `ensureDirectory()`
- `src/rpc/connection.h` / `.cpp` — `dir_error` + `autoDetectConfig`
- `main.cpp`, `app.cpp`, `app_network.cpp`, `app_wizard.cpp`, `settings_page.cpp`, `embedded_resources.cpp` — 5 sites + 4 callers
- `tests/test_phase4.cpp` — `TestPlatformEnsureDirectory`

### Core change
```cpp
// util/platform.cpp — one shared, non-throwing helper
bool Platform::ensureDirectory(const std::string& dir, std::string* outError) {
    std::error_code ec;
    if (std::filesystem::is_directory(dir, ec)) return true;
    ec.clear();
    std::filesystem::create_directories(dir, ec);
    if (ec) {
        if (outError)
            *outError = "Cannot create " + dir + ": " + ec.message() +
                        ". Check permissions / free space.";
        return false;
    }
    return true;
}
// Replaces 5 ad-hoc sites; autoDetectConfig() now sets ConnectionConfig::dir_error,
// and its 4 callers bail on it.
```

### Verification
- Unit `TestPlatformEnsureDirectory`: existing dir → true; fresh nested → created; POSIX unwritable → false + message.
- All four `autoDetectConfig` callers tolerate `dir_error`. Pre-App-init site (main.cpp) reports via stderr / MessageBox.

### Dependencies
**Owns** `Platform::ensureDirectory` (used by F5, F6) and the `ConnectionConfig`
extension (coordinated with F8). Land before F5/F6/F8.

---

## F8 — Plaintext-remote RPC credential transmission is warn-only

**Severity:** Medium · **Effort:** M (~6–9h) · **Status:** ☐

### The defect
A remote `rpchost` without `rpctls=1` sends Basic-auth `rpcuser:rpcpassword` over
cleartext HTTP. `tryConnect()` (`app_network.cpp:314`) only shows a **dismissible
warning** then proceeds — a local-network MITM sees the credentials. Compounding it,
`isLocalHost()`'s naive `rfind("127.",0)==0` misclassifies `127.evil.com` as local,
suppressing even the warning.

### The fix
Change the policy to **refuse-by-default with an explicit, persisted opt-in** — a
`rpcallowplaintext=1` conf key (for hand-editors) and a Settings toggle. Block the
connect and show a **blocking modal** explaining the risk and how to enable TLS or opt
in; localhost is unaffected. Tighten `isLocalHost()` to exact `127.x.y.z` / `::1` /
`localhost` via `isExactIPv4Loopback()`. **Back-compat:** default off ⇒ existing remote
users hit a hard stop until they opt in — **ship with prominent release notes.**

### Files touched
- `src/rpc/connection.h` / `.cpp` — `isLocalHost`, `allow_plaintext_remote`, `parseConfFile`
- `src/config/settings.h` / `.cpp` — persisted opt-in
- `src/app_network.cpp`, `src/app.h` — refuse + modal dispatch
- `src/ui/windows/plaintext_remote_rpc_dialog.h` — new blocking modal
- `src/ui/pages/settings_page.cpp` — toggle UI

### Core change
```cpp
// Tightened loopback test — "127.evil.com" is NOT local
bool Connection::isLocalHost(const std::string& host) {
    std::string h = stripBrackets(lowercase(host));
    return h == "localhost" || h == "::1" || isExactIPv4Loopback(h);  // exact 127.x.y.z
}

// Refuse-by-default with an explicit, persisted opt-in
const bool plaintextRemote  = rpc::Connection::usesPlaintextRemote(config);
const bool plaintextAllowed = config.allow_plaintext_remote          // rpcallowplaintext=1
                           || settings_.getAllowPlaintextRemoteRpc(); // Settings toggle
if (plaintextRemote && !plaintextAllowed) {
    connection_status_ = TR("sb_plaintext_remote_blocked");
    showPlaintextRemoteRpcDialog(config.host + ":" + config.port);    // blocking modal
    return;                                                           // no creds sent
}
```

### Verification
- Unit: `isLocalHost` — `127.evil.com` false, `127.0.0.1`/`::1`/`localhost` true; `allowsPlaintextRemote` honors conf key + settings flag.
- Manual: remote plaintext blocked; modal fires; opt-in persists across restart.

### Dependencies
F7 (second extender of `ConnectionConfig`/`parseConfFile`; land after so the struct grows
once). Wire `renderPlaintextRemoteRpcDialog` into the app modal-dispatch list.

---

## Shared helpers & coordination points

| Helper | Purpose | Used by |
|--------|---------|---------|
| `Platform::ensureDirectory()` | Single non-throwing directory-create with one consistent message; replaces five ad-hoc sites. Owned by F7. | F7, F5, F6 |
| `ConnectionConfig` extension | Coordination point, not a function: F7 adds `dir_error`, F8 adds `allow_plaintext_remote`. Land F7→F8 so it grows once per step. | F7, F8 |
| `util::sha256Hex` *(existing)* | Already-compiled, curl-free SHA-256. F6 becomes its third caller — no second hash routine. | F6 |
| `connectHasStalled()` *(new, pure)* | Stall predicate split out of the ImGui/App code for unit testing, per the `*_updater_core.cpp` precedent. | F3 |
| `evaluateDatadirLockGate()` *(new, pure)* | Lock-gate decision as `{proceed, message}` from three booleans — unit-testable without real process/fs I/O. | F4 |

## F3 — Unbounded connect spinner (deferred to step 6)

**Severity:** Medium · **Effort:** S (~3–5h) · **Status:** ☐

The connect loop retries forever while `!state_.connected` (`app.cpp:1239`);
`loading_timer_` only animates the spinner. Stamp `connect_stall_since_` when
"reachable but not ready" is first seen; a pure `connectHasStalled()` helper (new
`util/connect_stall.h`, default 45s from `ui.toml`) flips `state_.connect_stalled` at
threshold, and `renderLoadingOverlay()` shows a "Taking longer than expected" panel with
Retry / Restart daemon / Open console (full-node gated). The background retry keeps
firing — recovery clears the panel automatically. Guarded off while the daemon is in
`State::Error` (owned by F1's crash-count hint). Full detail lives in the sequencing/
design record; see the shared-helper table above.

---

## Cross-cutting notes

- **One TU, three functions.** `embedded_daemon.cpp` is edited by F1 (`isRunning`),
  F2 (`startProcess`) and F4 (`start`) — no literal hunk overlap, but land in order to
  keep "monitorProcess is the sole reaper" coherent.
- **Connection struct grows twice.** `connection.h/.cpp` is touched by F6, F7 and F8;
  F7 and F8 both extend `ConnectionConfig` and `parseConfFile` — highest collision risk.
  Sequence F7→F6→F8.
- **Testability split.** The three new pure predicates all get `tests/test_phase4.cpp`
  coverage. F1/F2's fork/exec/waitpid changes are **not** unit-testable — they rely on
  manual `kill` / non-executable-binary repros, consistent with the no-process-spawn harness.
- **i18n is additive-only.** Add each finding's English keys to `strings_`, then run
  `scripts/add_missing_translations.py` **once at the very end**
  (`json.dump indent=4, sort_keys=True, ensure_ascii=False`) — never bulk-regenerate a
  `res/lang/*.json`.
- **F8 is a breaking default flip.** Refuse-plaintext-by-default stops existing
  remote-RPC users cold until they opt in. Lands last, gated behind a persisted opt-in,
  with release notes calling out the new `rpcallowplaintext` key and the Settings toggle.
- **Latent hazard, out of scope.** F1 surfaces (but doesn't fix) a second
  double-`waitpid` window between `stop()`'s final blocking reap (`:1220`) and a
  mid-sleep monitor iteration — file it as its own ticket.

---

## Progress log

- **F1** — ☑ landed: `isRunning()` (POSIX) now reads the atomic `state_` (predicate `Running || Stopping`) instead of calling `waitpid`, leaving `monitorProcess()` the sole reaper. Clean build (all targets link); `ctest` 1/1 passing. Not unit-testable — needs the manual `kill -SEGV` repro before release.
- **F2** — ☑ landed: `startProcess()` (POSIX) now creates a `FD_CLOEXEC` self-pipe before `fork()`; the child writes `errno` to it on `execv` failure, the parent reads EOF-vs-errno and, on failure, reaps the zombie + sets a precise `last_error_` ("not executable or wrong architecture") + returns `false` (so `start()` no longer reports `Running` for a daemon that never started). Parent-side `setpgid` is now best-effort with a `DEBUG_LOGF` on failure. Clean build; `ctest` 1/1 passing. Not unit-testable — needs the manual non-executable / wrong-arch-binary repro before release.
- **F6** — ☑ landed: `verifySaplingParams()` now hash-verifies each Sapling param against its pinned canonical SHA-256 (from `build-lite-backend-artifact.sh`), replacing the existence-only check, so a truncated/corrupt-but-present param is rejected instead of failing later on a shielded op. A `<params_dir>/.sapling_verified` marker keyed on `size:mtime` skips re-hashing ~48 MB on every startup. Logic extracted to the injectable `verifySaplingParamsIn(dir, digests)`; new `testVerifySaplingParams` unit test (valid / marker fast-path / wrong-hash / truncated / missing). Clean build; `ctest` 1/1 passing.
- **F5** — ☑ landed: `startEmbeddedDaemon()` now checks `extractEmbeddedResources()`'s return (abort with `sb_daemon_extract_failed` on failure) and the previously-dropped `copy_file` `error_code` in the daemon-binary fallback loop (abort with `sb_daemon_files_failed` incl. the dir), so a disk-full / truncated `dragonxd` write is surfaced up front instead of failing opaquely at spawn. An absent source file stays non-fatal. Two i18n keys added to `i18n.cpp`. Clean build; `ctest` 1/1 passing.
- **F7** — ☑ landed: new non-throwing `Platform::ensureDirectory(dir, outError)` in `util/platform.{h,cpp}` with one consistent message. Replaces the unchecked/throwing directory-create sites at `main.cpp:730` (pre-init: now logs + `MessageBoxA` on Windows + `return 1`), `connection.cpp:216` (autoDetectConfig now uses the ec overload — **no more uncaught `filesystem_error`** — and sets the new `ConnectionConfig::dir_error`), and both `app.cpp` daemon-dir sites (surface via `daemon_status_` + `return false`). Primary connect path (`app_network.cpp:243`) checks `dir_error` and bails to the status line instead of mislabelling it "waiting for config". `embedded_resources.cpp:270` left as-is (already correct). New `testPlatformEnsureDirectory` unit test (existing-dir / fresh-nested / empty / parent-is-file). Clean build; `ctest` 1/1 passing.
- **F4** — ☑ landed: `start()` now gates on a lingering datadir lock after the port bail. When `!skip_port_check_ && override_datadir_.empty()`, it polls `isDaemonProcessRunning()` with a bounded ~300 ms wait (3 × 100 ms, breaks early), then a pure header-inline `evaluateDatadirLockGate()` decides: if a sibling `dragonxd` is still alive it bails with a distinct **non-crash** `State::Error` ("…holding the data directory lock. Retrying shortly…") that never touches `crash_count_`, so the 3-strike cap can't trip; the connect loop's retry resumes once the lock clears. Isolated migrate-to-seed starts are exempt. New `testDatadirLockGate` unit test (5 assertions, proceed/bail/2× exempt) added to `test_phase4.cpp`. Clean build; `ctest` 1/1 passing.