fix(hook): harden detour install, unload, and delta reconnection

Initialize every detour before enabling any, so a hook body that calls
another detour's trampoline can never hit an uninitialized detour and abort
the process. Pin the module on load so unloading can no longer leave
kernel32/ntdll patched to jump into freed memory. On a failed FILETIME
conversion, fall through to the real time instead of returning an
uninitialized SYSTEMTIME. Reconnect the shared delta mapping lazily so
setting a delta after injection takes effect instead of being disabled
forever. Add host-agnostic tick-conversion tests.

crates/time-mocker-core/Cargo.toml

@@ -19,5 +19,3 @@ windows-sys = { workspace = true, features = [
     "Win32_System_Time",
     "Win32_Security",
 ] }
-
-[target.'cfg(windows)'.dependencies]

crates/time-mocker-core/src/lib.rs

@@ -15,12 +15,19 @@
 //! then `Local\`, so a controller's elevation state determines the namespace
 //! used and the hook just probes both.
 
-#![cfg(windows)]
-
+// `mmf` wraps Win32-only APIs (named file mappings), so it is gated on
+// `windows` at the module level. `ticks` and `types` hold pure arithmetic —
+// no Win32 dependency at all beyond the FILETIME/SYSTEMTIME conversions
+// inside `ticks`, which are individually `#[cfg(windows)]` — so both stay
+// buildable and testable on any host (e.g. `cargo test -p time-mocker-core`
+// on Linux CI/dev boxes actually exercises the tick-arithmetic tests instead
+// of compiling an empty crate).
+#[cfg(windows)]
 pub mod mmf;
 pub mod ticks;
 pub mod types;
 
+#[cfg(windows)]
 pub use mmf::{CreateOutcome, SharedDeltaReader, SharedDeltaWriter};
 pub use types::MockTimeInfo;
 

crates/time-mocker-core/src/mmf.rs

@@ -24,7 +24,10 @@ use windows_sys::Win32::System::Memory::{
 use crate::types::MockTimeInfo;
 
 fn wide(s: &str) -> Vec<u16> {
-    OsStr::new(s).encode_wide().chain(std::iter::once(0)).collect()
+    OsStr::new(s)
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect()
 }
 
 /// Shared bookkeeping for an open mapping. Owns the handle + view and frees
@@ -96,6 +99,12 @@ impl SharedDeltaWriter {
         let handle = unsafe {
             CreateFileMappingW(
                 INVALID_HANDLE_VALUE,
+                // NOTE: NULL security descriptor -> default DACL (creator +
+                // SYSTEM/Administrators). Fine for same-user debug targets;
+                // a target running as a different user/service identity than
+                // the controller will fail to open this mapping and silently
+                // get no hooks installed. Accepted for now: this is a local
+                // debugging tool, not a service-hardening one.
                 ptr::null(),
                 PAGE_READWRITE,
                 0,
@@ -104,7 +113,9 @@ impl SharedDeltaWriter {
             )
         };
         if handle.is_null() {
-            return Err(io::Error::from_raw_os_error(unsafe { GetLastError() } as i32));
+            return Err(io::Error::from_raw_os_error(
+                unsafe { GetLastError() } as i32
+            ));
         }
         // Capture ERROR_ALREADY_EXISTS *before* any other syscall that may overwrite it.
         let outcome = if unsafe { GetLastError() } == ERROR_ALREADY_EXISTS {
@@ -130,7 +141,9 @@ impl SharedDeltaReader {
         let wname = wide(name);
         let handle = unsafe { OpenFileMappingW(FILE_MAP_READ, 0, wname.as_ptr()) };
         if handle.is_null() {
-            return Err(io::Error::from_raw_os_error(unsafe { GetLastError() } as i32));
+            return Err(io::Error::from_raw_os_error(
+                unsafe { GetLastError() } as i32
+            ));
         }
         let view = unsafe { map_view(handle, FILE_MAP_READ)? };
         Ok(Self(MappingHandle { handle, view }))

crates/time-mocker-core/src/ticks.rs

@@ -2,15 +2,50 @@
 //!
 //! FILETIME = 100-ns units since 1601-01-01 00:00:00 UTC. This crate uses
 //! FILETIME ticks throughout to avoid extra arithmetic on the hot path.
+//!
+//! `apply_delta` and the `*_VALID_TICKS` bounds are plain `i64` arithmetic
+//! with no Win32 dependency, so they build and run on any host. The
+//! FILETIME/SYSTEMTIME conversions below them call into `windows_sys` and are
+//! `#[cfg(windows)]`.
 
+#[cfg(windows)]
 use windows_sys::Win32::Foundation::{FILETIME, SYSTEMTIME};
+#[cfg(windows)]
 use windows_sys::Win32::System::Time::{FileTimeToSystemTime, SystemTimeToFileTime};
 
+/// Lowest FILETIME tick value `FileTimeToSystemTime` accepts. FILETIME is
+/// defined as an unsigned 64-bit tick count from the 1601-01-01 epoch, so a
+/// negative `i64` (sign bit set) is never a valid FILETIME.
+pub const MIN_VALID_TICKS: i64 = 0;
+
+/// Highest FILETIME tick value `FileTimeToSystemTime` accepts: 30827-12-31
+/// 23:59:59.9999999 UTC, the last instant representable in a `SYSTEMTIME`
+/// (`wYear` is a `u16`, and Win32 defines this as the ceiling). Any FILETIME
+/// beyond this fails conversion.
+pub const MAX_VALID_TICKS: i64 = 0x7FFF_35F4_F06C_58F0;
+
+/// Add `delta` to `real_ticks` and clamp to the range `FileTimeToSystemTime`
+/// can convert. A saturating add alone stops at `i64::MIN`/`i64::MAX`, but
+/// those are far outside the valid FILETIME range: the delta comes from
+/// shared memory written by a separate, possibly stale controller process,
+/// so it must not be trusted to keep the result in range. Clamping here means
+/// every caller downstream gets a value that round-trips through
+/// `ticks_to_systemtime` instead of failing conversion with an untouched
+/// output buffer.
+#[inline]
+pub fn apply_delta(real_ticks: i64, delta: i64) -> i64 {
+    real_ticks
+        .saturating_add(delta)
+        .clamp(MIN_VALID_TICKS, MAX_VALID_TICKS)
+}
+
+#[cfg(windows)]
 #[inline]
 pub fn filetime_to_i64(ft: FILETIME) -> i64 {
     ((ft.dwHighDateTime as i64) << 32) | (ft.dwLowDateTime as i64 & 0xFFFF_FFFF)
 }
 
+#[cfg(windows)]
 #[inline]
 pub fn i64_to_filetime(ticks: i64) -> FILETIME {
     FILETIME {
@@ -20,6 +55,7 @@ pub fn i64_to_filetime(ticks: i64) -> FILETIME {
 }
 
 /// Convert FILETIME ticks to SYSTEMTIME (UTC). Returns None on Win32 failure.
+#[cfg(windows)]
 pub fn ticks_to_systemtime(ticks: i64) -> Option<SYSTEMTIME> {
     let ft = i64_to_filetime(ticks);
     let mut st: SYSTEMTIME = unsafe { std::mem::zeroed() };
@@ -32,6 +68,7 @@ pub fn ticks_to_systemtime(ticks: i64) -> Option<SYSTEMTIME> {
 }
 
 /// Convert SYSTEMTIME (UTC) to FILETIME ticks. Returns None on Win32 failure.
+#[cfg(windows)]
 pub fn systemtime_to_ticks(st: &SYSTEMTIME) -> Option<i64> {
     let mut ft: FILETIME = unsafe { std::mem::zeroed() };
     let ok = unsafe { SystemTimeToFileTime(st, &mut ft) };
@@ -46,10 +83,63 @@ pub fn systemtime_to_ticks(st: &SYSTEMTIME) -> Option<i64> {
 mod tests {
     use super::*;
 
+    #[test]
+    fn apply_delta_zero_is_identity() {
+        assert_eq!(apply_delta(1_000, 0), 1_000);
+    }
+
+    #[test]
+    fn apply_delta_positive_offset() {
+        assert_eq!(apply_delta(1_000, 500), 1_500);
+    }
+
+    #[test]
+    fn apply_delta_negative_offset() {
+        assert_eq!(apply_delta(1_000, -500), 500);
+    }
+
+    #[test]
+    fn apply_delta_saturates_instead_of_overflowing() {
+        // i64::MAX + a positive delta would overflow a plain `+`; saturating_add
+        // (and then the clamp below) must not panic or wrap.
+        assert_eq!(apply_delta(i64::MAX, i64::MAX), MAX_VALID_TICKS);
+        assert_eq!(apply_delta(i64::MIN, i64::MIN), MIN_VALID_TICKS);
+    }
+
+    #[test]
+    fn apply_delta_clamps_below_epoch_to_min_valid() {
+        // A large negative delta applied to an early real time would produce a
+        // negative tick count — not representable as FILETIME (unsigned).
+        assert_eq!(apply_delta(100, -1_000), MIN_VALID_TICKS);
+    }
+
+    #[test]
+    fn apply_delta_clamps_above_ceiling_to_max_valid() {
+        assert_eq!(apply_delta(MAX_VALID_TICKS, 1), MAX_VALID_TICKS);
+        assert_eq!(
+            apply_delta(MAX_VALID_TICKS - 10, 1_000_000),
+            MAX_VALID_TICKS
+        );
+    }
+
+    #[test]
+    fn apply_delta_respects_exact_clamp_boundaries() {
+        // One tick inside either boundary must pass through unchanged.
+        assert_eq!(apply_delta(MIN_VALID_TICKS + 1, 0), MIN_VALID_TICKS + 1);
+        assert_eq!(apply_delta(MAX_VALID_TICKS - 1, 0), MAX_VALID_TICKS - 1);
+        assert_eq!(apply_delta(MIN_VALID_TICKS, 0), MIN_VALID_TICKS);
+        assert_eq!(apply_delta(MAX_VALID_TICKS, 0), MAX_VALID_TICKS);
+    }
+
+    #[cfg(windows)]
     #[test]
     fn filetime_i64_roundtrip() {
-        // Covers: zero, small, Unix epoch (1970 in FILETIME ticks), a recent time,
-        // and the i64 boundary (used as a saturating-add sentinel by the hooks).
+        // Covers: zero, small, Unix epoch (1970 in FILETIME ticks), a recent
+        // time, and the i64 boundary. `filetime_to_i64`/`i64_to_filetime` are
+        // plain bit-packing and round-trip the full i64 range (including
+        // negative/out-of-FILETIME-range values) even though those values are
+        // never handed to Win32 conversion APIs — `apply_delta` above is what
+        // keeps callers in the valid range before that happens.
         let cases = [
             0_i64,
             1,
@@ -66,6 +156,7 @@ mod tests {
         }
     }
 
+    #[cfg(windows)]
     #[test]
     fn systemtime_roundtrip_utc() {
         // 2020-06-15 12:34:56 UTC
@@ -88,4 +179,11 @@ mod tests {
         assert_eq!(back.wMinute, st.wMinute);
         assert_eq!(back.wSecond, st.wSecond);
     }
+
+    #[cfg(windows)]
+    #[test]
+    fn ticks_to_systemtime_rejects_out_of_range_values() {
+        assert!(ticks_to_systemtime(MAX_VALID_TICKS + 1).is_none());
+        assert!(ticks_to_systemtime(MIN_VALID_TICKS - 1).is_none());
+    }
 }

crates/time-mocker-hook/Cargo.toml

@@ -15,6 +15,7 @@ path = "src/lib.rs"
 
 [dependencies]
 time-mocker-core = { path = "../time-mocker-core" }
+# Pre-release range: no stable retour release ships static-detour inline x64 hooking yet.
 retour = { version = "0.4.0-alpha.4", features = ["static-detour"] }
 once_cell = "1.20"
 windows-sys = { workspace = true, features = [

crates/time-mocker-hook/src/entrypoint.rs

@@ -9,15 +9,27 @@
 //!
 //! We also call `DisableThreadLibraryCalls(hinst)` to suppress all future
 //! `DLL_THREAD_ATTACH`/`DETACH` notifications for this DLL — we don't need them.
+//!
+//! Load-once, never-unload invariant: `DllMain` pins this module (see
+//! `pin_module`) and there is no `DLL_PROCESS_DETACH` handler. Once the
+//! detours are enabled, kernel32/ntdll contain jumps into this DLL's
+//! trampoline pages; unhooking them would require draining every thread that
+//! might currently be inside a trampoline, which cannot be done safely from
+//! `DLL_PROCESS_DETACH` under the loader lock. Pinning means the loader can
+//! never unmap us out from under those jumps, even if something (a future
+//! `eject` path, or a stray `FreeLibrary`) tries.
 
 use std::ffi::{c_void, OsStr};
 use std::os::windows::ffi::OsStrExt;
 use std::ptr;
 
-use time_mocker_core::{local_mmf_name_for_pid, mmf_name_for_pid, SharedDeltaReader};
+use time_mocker_core::{local_mmf_name_for_pid, mmf_name_for_pid};
 use windows_sys::Win32::Foundation::{CloseHandle, BOOL, HMODULE, TRUE};
 use windows_sys::Win32::System::Diagnostics::Debug::OutputDebugStringW;
-use windows_sys::Win32::System::LibraryLoader::DisableThreadLibraryCalls;
+use windows_sys::Win32::System::LibraryLoader::{
+    DisableThreadLibraryCalls, GetModuleHandleExW, GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
+    GET_MODULE_HANDLE_EX_FLAG_PIN,
+};
 use windows_sys::Win32::System::SystemServices::DLL_PROCESS_ATTACH;
 use windows_sys::Win32::System::Threading::{CreateThread, GetCurrentProcessId};
 
@@ -25,13 +37,10 @@ use crate::hooks::{self, InstallReport};
 
 #[no_mangle]
 #[allow(non_snake_case, clippy::missing_safety_doc)]
-pub unsafe extern "system" fn DllMain(
-    hinst: HMODULE,
-    reason: u32,
-    _reserved: *mut c_void,
-) -> BOOL {
+pub unsafe extern "system" fn DllMain(hinst: HMODULE, reason: u32, _reserved: *mut c_void) -> BOOL {
     if reason == DLL_PROCESS_ATTACH {
         DisableThreadLibraryCalls(hinst);
+        pin_module();
         let thread_handle = CreateThread(
             ptr::null(),
             0,
@@ -50,6 +59,22 @@ pub unsafe extern "system" fn DllMain(
     TRUE
 }
 
+/// Bump this module's loader reference count so it can never be unmapped
+/// (see the module-doc invariant above). `GET_MODULE_HANDLE_EX_FLAG_PIN`
+/// combined with `..._FROM_ADDRESS` resolves the target module from an
+/// address inside it — `DllMain`'s own address — so this needs no file path
+/// or module name. Best-effort: if it ever fails, we still proceed with
+/// install rather than abort the injection, since a pin failure here is far
+/// less likely than the process simply never unloading us in practice.
+unsafe fn pin_module() {
+    let mut pinned: HMODULE = ptr::null_mut();
+    GetModuleHandleExW(
+        GET_MODULE_HANDLE_EX_FLAG_PIN | GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
+        DllMain as *const () as usize as *const u16,
+        &mut pinned,
+    );
+}
+
 unsafe extern "system" fn bootstrap_thread(_param: *mut c_void) -> u32 {
     bootstrap();
     0
@@ -60,25 +85,15 @@ fn bootstrap() {
     let global = mmf_name_for_pid(pid);
     let local = local_mmf_name_for_pid(pid);
 
-    // Probe Global\ first (matches the elevated controller's preferred namespace);
-    // fall back to Local\ for the unelevated dev/debug controller path. Either
-    // name owns an identical 8-byte payload — whichever exists wins.
-    let shared = match SharedDeltaReader::open(&global) {
-        Ok(s) => s,
-        Err(e_global) => match SharedDeltaReader::open(&local) {
-            Ok(s) => s,
-            Err(e_local) => {
-                dbg_log(&format!(
-                    "time-mocker: open MMF '{global}' ({e_global}) and '{local}' ({e_local}) both failed"
-                ));
-                return;
-            }
-        },
-    };
-
-    // Best-effort install. Detours stay armed for the lifetime of the host
-    // process; the bootstrap thread exits immediately after.
-    let report = hooks::install(shared);
+    // Install the hooks unconditionally — do not gate installation on the
+    // delta MMF already existing. The normal workflow order is "inject, then
+    // open the delta channel", so at this point in a fresh injection neither
+    // name may exist yet; `hooks::install` connects to whichever one shows up
+    // lazily (with retry) on first use inside the hot path. Gating install on
+    // a successful open here would leave the hooks permanently uninstalled
+    // for the rest of the process's life whenever the controller sets the
+    // delta after injection completes.
+    let report = hooks::install(global, local);
     log_install_report(&report);
 }
 

crates/time-mocker-hook/src/hooks.rs

@@ -10,13 +10,33 @@
 
 use once_cell::sync::OnceCell;
 use retour::static_detour;
-use time_mocker_core::ticks::{filetime_to_i64, i64_to_filetime};
+use std::sync::atomic::{AtomicU32, Ordering};
+use std::sync::RwLock;
+use time_mocker_core::ticks::{apply_delta, filetime_to_i64, i64_to_filetime};
 use time_mocker_core::SharedDeltaReader;
 use windows_sys::Win32::Foundation::{FILETIME, SYSTEMTIME};
 use windows_sys::Win32::System::LibraryLoader::{GetModuleHandleA, GetProcAddress};
 use windows_sys::Win32::System::Time::{FileTimeToSystemTime, SystemTimeToTzSpecificLocalTime};
 
-static SHARED: OnceCell<SharedDeltaReader> = OnceCell::new();
+/// Re-attempt opening the delta MMF once every this many `delta()` calls while
+/// disconnected. The normal workflow order is inject-then-open-channel, so the
+/// first `bootstrap()` probe commonly runs before the controller has created
+/// the mapping; without a retry the process would carry no-op hooks for its
+/// entire lifetime. A call-count backoff (instead of a wall-clock timer and
+/// its own thread) keeps the hot path — the already-connected case — down to
+/// one relaxed atomic read, and costs nothing extra to implement.
+const RETRY_EVERY_N_CALLS: u32 = 4096;
+
+/// Names to probe plus the lazily-connected reader. `misses_since_retry`
+/// drives the backoff in `try_reconnect`.
+struct DeltaSource {
+    global_name: String,
+    local_name: String,
+    reader: RwLock<Option<SharedDeltaReader>>,
+    misses_since_retry: AtomicU32,
+}
+
+static SOURCE: OnceCell<DeltaSource> = OnceCell::new();
 
 static_detour! {
     static GetSystemTimeDetour: unsafe extern "system" fn(*mut SYSTEMTIME);
@@ -37,52 +57,170 @@ pub struct InstallReport {
     pub failed: Vec<(&'static str, String)>,
 }
 
-/// Resolve+initialize+enable a single detour. Pushes to `installed` on success,
-/// to `failed` (with reason) on any failure — never aborts the wider install.
-macro_rules! install_hook {
+/// Resolve+initialize a single detour (phase 1 of `install`). Pushes to
+/// `failed` (with reason) and yields `false` on any failure instead of
+/// aborting the wider install; yields `true` when the detour is ready to be
+/// enabled in phase 2.
+macro_rules! init_hook {
     ($report:ident, $detour:ident, $module:literal, $proc:literal, $fn_ty:ty, $callback:ident) => {{
         // Safety: `resolve` is unsafe because it dereferences whatever
         // GetProcAddress returns as `$fn_ty`; correctness rests on the
         // module+proc literal pair matching `$fn_ty`'s extern signature.
         match unsafe { resolve::<$fn_ty>($module, $proc) } {
-            None => $report
-                .failed
-                .push(($proc, "GetProcAddress: not found".into())),
+            None => {
+                $report
+                    .failed
+                    .push(($proc, "GetProcAddress: not found".into()));
+                false
+            }
             Some(target) => match unsafe { $detour.initialize(target, $callback) } {
-                Err(e) => $report.failed.push(($proc, format!("initialize: {e}"))),
-                Ok(d) => match unsafe { d.enable() } {
-                    Err(e) => $report.failed.push(($proc, format!("enable: {e}"))),
-                    Ok(()) => $report.installed.push($proc),
-                },
+                Err(e) => {
+                    $report.failed.push(($proc, format!("initialize: {e}")));
+                    false
+                }
+                Ok(_) => true,
             },
         }
     }};
 }
 
-pub fn install(shared: SharedDeltaReader) -> InstallReport {
-    let _ = SHARED.set(shared);
+/// Enable a detour that was successfully initialized in phase 1 (phase 2 of
+/// `install`). `unmet_dependency`, when `Some`, means a *different* detour
+/// this hook body calls through (e.g. `hook_get_system_time` calls
+/// `GetSystemTimeAsFileTimeDetour`) failed to initialize — enabling this hook
+/// anyway would arm a hook body that panics the first time it runs, so it is
+/// recorded as failed instead.
+fn try_enable<T: retour::Function>(
+    report: &mut InstallReport,
+    detour: &'static retour::StaticDetour<T>,
+    name: &'static str,
+    initialized: bool,
+    unmet_dependency: Option<&'static str>,
+) {
+    if !initialized {
+        return; // already recorded as failed by init_hook!
+    }
+    if let Some(dep) = unmet_dependency {
+        report
+            .failed
+            .push((name, format!("dependency {dep} did not initialize")));
+        return;
+    }
+    match unsafe { detour.enable() } {
+        Err(e) => report.failed.push((name, format!("enable: {e}"))),
+        Ok(()) => report.installed.push(name),
+    }
+}
+
+/// Resolve, initialize, and enable every hook, then wire up the (lazily
+/// connected) delta source. `global_name`/`local_name` are the two MMF names
+/// the bootstrap thread probes — connecting happens on first use inside
+/// `delta()`, not here, so hooking still activates even if the controller
+/// creates the mapping after injection has already completed.
+pub fn install(global_name: String, local_name: String) -> InstallReport {
+    let _ = SOURCE.set(DeltaSource {
+        global_name,
+        local_name,
+        reader: RwLock::new(None),
+        misses_since_retry: AtomicU32::new(0),
+    });
 
     let mut report = InstallReport::default();
-    install_hook!(
-        report, GetSystemTimeDetour, "kernel32.dll", "GetSystemTime",
-        FnSystemTime, hook_get_system_time
+
+    // Phase 1: resolve + initialize every detour before enabling any of them.
+    // `hook_get_system_time` and `hook_get_local_time` call through
+    // `GetSystemTimeAsFileTimeDetour`'s trampoline, and the trampoline only
+    // exists once that detour has been initialized — `static_detour!`'s
+    // generated `call()` panics with `NotInitialized` otherwise, and with
+    // `panic = "abort"` in the release profile that panic kills the target
+    // process. Initializing every detour before enabling any of them removes
+    // the racy window (GetSystemTime enabled while another thread is still
+    // initializing the FileTime detour); phase 2 below additionally refuses
+    // to enable a hook whose dependency never initialized at all, which
+    // removes the permanent version of the same failure.
+    let system_time_ok = init_hook!(
+        report,
+        GetSystemTimeDetour,
+        "kernel32.dll",
+        "GetSystemTime",
+        FnSystemTime,
+        hook_get_system_time
     );
-    install_hook!(
-        report, GetLocalTimeDetour, "kernel32.dll", "GetLocalTime",
-        FnSystemTime, hook_get_local_time
+    let local_time_ok = init_hook!(
+        report,
+        GetLocalTimeDetour,
+        "kernel32.dll",
+        "GetLocalTime",
+        FnSystemTime,
+        hook_get_local_time
     );
-    install_hook!(
-        report, GetSystemTimeAsFileTimeDetour, "kernel32.dll", "GetSystemTimeAsFileTime",
-        FnFileTime, hook_get_system_time_as_filetime
+    let filetime_ok = init_hook!(
+        report,
+        GetSystemTimeAsFileTimeDetour,
+        "kernel32.dll",
+        "GetSystemTimeAsFileTime",
+        FnFileTime,
+        hook_get_system_time_as_filetime
     );
-    install_hook!(
-        report, GetSystemTimePreciseAsFileTimeDetour, "kernel32.dll", "GetSystemTimePreciseAsFileTime",
-        FnFileTime, hook_get_system_time_precise_as_filetime
+    let precise_filetime_ok = init_hook!(
+        report,
+        GetSystemTimePreciseAsFileTimeDetour,
+        "kernel32.dll",
+        "GetSystemTimePreciseAsFileTime",
+        FnFileTime,
+        hook_get_system_time_precise_as_filetime
     );
-    install_hook!(
-        report, NtQuerySystemTimeDetour, "ntdll.dll", "NtQuerySystemTime",
-        FnNtQuerySystemTime, hook_nt_query_system_time
+    let nt_query_ok = init_hook!(
+        report,
+        NtQuerySystemTimeDetour,
+        "ntdll.dll",
+        "NtQuerySystemTime",
+        FnNtQuerySystemTime,
+        hook_nt_query_system_time
     );
+
+    // Phase 2: enable. Retour patches the live prologue with no thread
+    // suspension or i-cache flush of its own (verified in the vendored
+    // source); a thread executing that exact prologue mid-`enable()` is a
+    // known, accepted race inherent to this hooking approach, not something
+    // this crate mitigates.
+    let unmet_filetime = (!filetime_ok).then_some("GetSystemTimeAsFileTime");
+    try_enable(
+        &mut report,
+        &GetSystemTimeDetour,
+        "GetSystemTime",
+        system_time_ok,
+        unmet_filetime,
+    );
+    try_enable(
+        &mut report,
+        &GetLocalTimeDetour,
+        "GetLocalTime",
+        local_time_ok,
+        unmet_filetime,
+    );
+    try_enable(
+        &mut report,
+        &GetSystemTimeAsFileTimeDetour,
+        "GetSystemTimeAsFileTime",
+        filetime_ok,
+        None,
+    );
+    try_enable(
+        &mut report,
+        &GetSystemTimePreciseAsFileTimeDetour,
+        "GetSystemTimePreciseAsFileTime",
+        precise_filetime_ok,
+        None,
+    );
+    try_enable(
+        &mut report,
+        &NtQuerySystemTimeDetour,
+        "NtQuerySystemTime",
+        nt_query_ok,
+        None,
+    );
+
     report
 }
 
@@ -99,16 +237,49 @@ unsafe fn resolve<F: Copy>(module: &str, proc: &str) -> Option<F> {
 
 #[inline]
 fn delta() -> i64 {
-    SHARED.get().map(|s| s.read_delta()).unwrap_or(0)
+    let Some(source) = SOURCE.get() else {
+        return 0;
+    };
+    if let Ok(guard) = source.reader.read() {
+        if let Some(reader) = guard.as_ref() {
+            return reader.read_delta();
+        }
+    }
+    try_reconnect(source)
+}
+
+/// Not yet connected to the delta channel. Re-probe both MMF names once every
+/// `RETRY_EVERY_N_CALLS` misses (see its doc comment) instead of on every
+/// call. A race between threads landing on the same retry slot is harmless —
+/// `SharedDeltaReader::open` is idempotent and cheap to call twice.
+fn try_reconnect(source: &DeltaSource) -> i64 {
+    let misses = source.misses_since_retry.fetch_add(1, Ordering::Relaxed);
+    if !misses.is_multiple_of(RETRY_EVERY_N_CALLS) {
+        return 0;
+    }
+    let opened = SharedDeltaReader::open(&source.global_name)
+        .or_else(|_| SharedDeltaReader::open(&source.local_name));
+    match opened {
+        Ok(reader) => {
+            let value = reader.read_delta();
+            if let Ok(mut guard) = source.reader.write() {
+                *guard = Some(reader);
+            }
+            value
+        }
+        Err(_) => 0,
+    }
 }
 
 /// Invoke the supplied trampoline to get the real FILETIME, then add the
-/// shared delta. Saturating arithmetic — no panic-abort even at i64 bounds.
+/// shared delta, clamped to the range `FileTimeToSystemTime` can convert (see
+/// `time_mocker_core::ticks::apply_delta`) so callers never see a conversion
+/// failure caused by an out-of-range delta from shared memory.
 #[inline]
 fn fake_filetime(call_real: impl FnOnce(*mut FILETIME)) -> FILETIME {
     let mut ft: FILETIME = unsafe { std::mem::zeroed() };
     call_real(&mut ft);
-    let ticks = filetime_to_i64(ft).saturating_add(delta());
+    let ticks = apply_delta(filetime_to_i64(ft), delta());
     i64_to_filetime(ticks)
 }
 
@@ -117,7 +288,15 @@ fn hook_get_system_time(out: *mut SYSTEMTIME) {
         return;
     }
     let ft = fake_filetime(|p| unsafe { GetSystemTimeAsFileTimeDetour.call(p) });
-    unsafe { FileTimeToSystemTime(&ft, out) };
+    if unsafe { FileTimeToSystemTime(&ft, out) } == 0 {
+        // `apply_delta` keeps `ft` in the valid FILETIME range, so this should
+        // not happen — but the delta is attacker/bug-controlled input from a
+        // separate process, so never leave `out` uninitialized on the
+        // off-chance it does. `GetSystemTimeDetour` is exactly the detour
+        // currently executing this hook body, so its trampoline is guaranteed
+        // initialized here.
+        unsafe { GetSystemTimeDetour.call(out) };
+    }
 }
 
 fn hook_get_local_time(out: *mut SYSTEMTIME) {
@@ -132,6 +311,10 @@ fn hook_get_local_time(out: *mut SYSTEMTIME) {
     let ft_utc = fake_filetime(|p| unsafe { GetSystemTimeAsFileTimeDetour.call(p) });
     let mut st_utc: SYSTEMTIME = unsafe { std::mem::zeroed() };
     if unsafe { FileTimeToSystemTime(&ft_utc, &mut st_utc) } == 0 {
+        // See `hook_get_system_time` — fall back to the real local time rather
+        // than return with `out` uninitialized. `GetLocalTimeDetour` is this
+        // hook's own detour, so its trampoline is guaranteed initialized here.
+        unsafe { GetLocalTimeDetour.call(out) };
         return;
     }
     if unsafe { SystemTimeToTzSpecificLocalTime(std::ptr::null(), &st_utc, out) } == 0 {
@@ -171,6 +354,6 @@ fn hook_nt_query_system_time(out: *mut i64) -> i32 {
         // delta+0 with a bogus STATUS_SUCCESS if the real API ever failed.
         return status;
     }
-    unsafe { *out = real.saturating_add(delta()) };
+    unsafe { *out = apply_delta(real, delta()) };
     0
 }