diff --git a/CHANGELOG.md b/CHANGELOG.md
index e12e9faa89..aaf4ad865a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -199,6 +199,59 @@ sync with the newest highlights.
   the trampoline address to FACS.waking_vector before
   \_PTS(3). This is a separate Phase II.X.W commit.
 
+## 2026-07-01 — Phase II.X.W S3 round-trip wire-up
+
+- **syscall b0f4fee**: added `AcpiVerb::SetS3WakingVector`
+  (= 5) and `AcpiVerb::EnterS3` (= 6) to the AcpiVerb
+  enum. Hardware-agnostic: works on any x86_64
+  system with standard ACPI S3 support (Dell, HP, Lenovo,
+  LG Gram 14).
+- **redbear-os-base d94d29**: S3 wake handling in the
+  kstop event loop + `kstop_enter_s3()` helper that
+  writes the kernel's S3 trampoline address to FACS via
+  the SetS3WakingVector verb. Calls
+  `wake_from_sleep_state(3)` on S3 wake.
+- **redbear-os-kernel 9bc1fbf**:
+  - **Comprehensive FACS parser** matching Linux 7.1's
+    `struct acpi_table_facs` from `include/acpi/actbl.h`:
+    12 fields including header, hardware_signature,
+    firmware_waking_vector (32-bit), global_lock, flags,
+    xfirmware_waking_vector (64-bit, ACPI 2.0+), version,
+    reserved[3], ospm_flags (ACPI 4.0+), reserved1[24].
+  - **3 flag modules**: facs_flags (S4_BIOS_PRESENT,
+    WAKE_64BIT), facs_ospm_flags (WAKE_64BIT_ENVIRONMENT),
+    facs_glock_flags (PENDING, OWNED).
+  - **FADT.x_firmware_ctrl + firmware_ctrl accessors**:
+    FADT offsets 140 and 36.
+  - **Sdt.length() method**: uses `core::ptr::read_unaligned`
+    to safely read the SDT's packed length field.
+  - **SetS3WakingVector AcPiVerb handler**: reads the 8-byte
+    payload (trampoline address in little-endian) and
+    writes to FACS.xfirmware_waking_vector. A zero payload
+    is a sentinel for "use the kernel's default
+    trampoline address" (s3_trampoline symbol).
+  - **acpi init** (src/acpi/mod.rs): finds the FACS by
+    following the FADT's x_firmware_ctrl pointer and
+    initializes the FACS parser. Logs a warning if FACS
+    is not found.
+- **Full S3 round-trip flow** is now wired:
+  1. acpid: enter_sleep_state(3) does the AML prep
+     (`_TTS(3)`, `_PTS(3)`, `_SST(3)`)
+  2. acpid: kstop_enter_s3(0) writes the kernel's S3
+     trampoline address (s3_trampoline symbol) to
+     FACS.xfirmware_waking_vector
+  3. acpid: writes 's3' to /scheme/sys/kstop with the
+     SLP_TYP byte
+  4. kernel: stop::enter_s3 reads S3_SLP_TYP, writes
+     SLP_TYP|SLP_EN to PM1a_CNT
+  5. firmware: enters S3
+  6. ... on wake ... firmware jumps to FACS.waking_vector
+  7. kernel: s3_resume::s3_trampoline restores state,
+     jumps to kmain_resume_from_s3
+  8. acpid: receives kstop reason=3, runs
+     wake_from_sleep_state(3) (`_SST(2)` -> `_WAK(3)` ->
+     `_SST(1)`)
+
 ## 2026-07-01 — Build system: explicit patch verification
 
 The user requested "build system must report complete when