diff --git a/docs/adr/ADR-119-bfld-frame-format-and-wire-protocol.md b/docs/adr/ADR-119-bfld-frame-format-and-wire-protocol.md
index 985cf7ec..5afdbb67 100644
--- a/docs/adr/ADR-119-bfld-frame-format-and-wire-protocol.md
+++ b/docs/adr/ADR-119-bfld-frame-format-and-wire-protocol.md
@@ -57,7 +57,7 @@ pub struct BfldFrameHeader {
 }
 ```
 
-Total header size: 40 bytes (validated by `static_assertions::const_assert_eq!`).
+Total header size: **86 bytes packed** (validated by `static_assertions::const_assert_eq!` in `wifi-densepose-bfld/src/frame.rs`). Earlier drafts stated 40 bytes — that was a counting error caught during P1 scaffold; see AC1 below.
 
 ### 2.2 Payload structure
 
@@ -144,7 +144,7 @@ Rejected: CRC must be computed after the payload, so its value would otherwise f
 
 ## 5. Acceptance Criteria
 
-- [ ] **AC1**: `BfldFrameHeader` size is exactly 40 bytes on x86_64, aarch64, and xtensa-esp32s3.
+- [ ] **AC1**: `BfldFrameHeader` size is exactly **86 bytes** (packed) on x86_64, aarch64, and xtensa-esp32s3. The size was initially documented as 40 bytes during ADR drafting — that was a counting error; the implementation in `wifi-densepose-bfld/src/frame.rs` enforces the correct value via `const_assert_eq!`.
 - [ ] **AC2**: 1,000 serializations of a fixed `BfiCapture` fixture produce a bit-identical BLAKE3 hash.
 - [ ] **AC3**: `privacy_class = 0` frame returned through `NetworkSink::publish()` returns `Err(BfldError::PrivacyViolation)`.
 - [ ] **AC4**: Payload CRC32 mismatch causes `BfldFrame::parse()` to return `Err(BfldError::Crc)` without exposing partial payload state.
diff --git a/v2/Cargo.lock b/v2/Cargo.lock
index 8ae5dcca..8f23b6b6 100644
--- a/v2/Cargo.lock
+++ b/v2/Cargo.lock
@@ -7255,6 +7255,12 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6ce2be8dc25455e1f91df71bfa12ad37d7af1092ae736f3a6cd0e37bc7810596"
 
+[[package]]
+name = "static_assertions"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
+
 [[package]]
 name = "strength_reduce"
 version = "0.2.4"
@@ -9133,6 +9139,15 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72069c3113ab32ab29e5584db3c6ec55d416895e60715417b5b883a357c3e471"
 
+[[package]]
+name = "wifi-densepose-bfld"
+version = "0.3.0"
+dependencies = [
+ "proptest",
+ "static_assertions",
+ "thiserror 2.0.18",
+]
+
 [[package]]
 name = "wifi-densepose-cli"
 version = "0.3.0"
diff --git a/v2/Cargo.toml b/v2/Cargo.toml
index 36c76c31..c285f9f6 100644
--- a/v2/Cargo.toml
+++ b/v2/Cargo.toml
@@ -42,6 +42,11 @@ members = [
     # ADR-115 MQTT publisher as a Seed-installable artifact with
     # mDNS, embedded broker, RuVector thresholds, Ed25519 witness.
     "crates/cog-ha-matter",
+    # ADR-118: BFLD — Beamforming Feedback Layer for Detection. The
+    # privacy/safety layer that measures and gates identity leakage from
+    # WiFi BFI captures. Sub-ADRs: 119 (frame), 120 (privacy class),
+    # 121 (identity risk), 122 (HA/Matter), 123 (capture path).
+    "crates/wifi-densepose-bfld",
     # rvCSI — edge RF sensing runtime (ADR-095 platform, ADR-096 FFI/crate layout):
     # lives in its own repo (https://github.com/ruvnet/rvcsi), vendored here as
     # `vendor/rvcsi` and published to crates.io as `rvcsi-*` 0.3.x. Depend on the
diff --git a/v2/crates/wifi-densepose-bfld/Cargo.toml b/v2/crates/wifi-densepose-bfld/Cargo.toml
new file mode 100644
index 00000000..7207a1d0
--- /dev/null
+++ b/v2/crates/wifi-densepose-bfld/Cargo.toml
@@ -0,0 +1,38 @@
+[package]
+name = "wifi-densepose-bfld"
+description = "BFLD — Beamforming Feedback Layer for Detection. Privacy-gated WiFi BFI sensing primitives. See ADR-118."
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+repository.workspace = true
+documentation.workspace = true
+keywords.workspace = true
+categories.workspace = true
+
+[features]
+default = ["std"]
+std = []
+# Soul Signature integration (ADR-118 §1.4, ADR-120 §2.7, ADR-121 §2.6) —
+# enables privacy_class = 1 (derived) mode and the SoulMatchOracle gate
+# exemption. Disabled by default per the structural class-2 default.
+soul-signature = []
+
+[dependencies]
+thiserror.workspace = true
+static_assertions = "1.1"
+
+[dev-dependencies]
+proptest.workspace = true
+
+[lints.rust]
+unsafe_code = "forbid"
+missing_docs = "warn"
+
+[lints.clippy]
+all = "warn"
+pedantic = "warn"
+nursery = "warn"
+module_name_repetitions = "allow"
+missing_const_for_fn = "allow"
+missing_panics_doc = "allow"
diff --git a/v2/crates/wifi-densepose-bfld/src/frame.rs b/v2/crates/wifi-densepose-bfld/src/frame.rs
new file mode 100644
index 00000000..7c36facb
--- /dev/null
+++ b/v2/crates/wifi-densepose-bfld/src/frame.rs
@@ -0,0 +1,63 @@
+//! `BfldFrame` wire-format primitives. See ADR-119.
+//!
+//! The header is `#[repr(C, packed)]` so the wire byte order is fixed across
+//! x86_64, aarch64, and xtensa-esp32s3 — and so the witness-bundle pattern
+//! (ADR-028) extends cleanly to BFLD frames.
+
+use static_assertions::const_assert_eq;
+
+/// Magic value identifying a `BfldFrame`. Reads as "BFLD" in hex-dump tools.
+pub const BFLD_MAGIC: u32 = 0xBF1D_0001;
+
+/// Current `BfldFrame` major version. Bumps on any incompatible layout change.
+pub const BFLD_VERSION: u16 = 1;
+
+/// Size of the packed header in bytes. Asserted at compile time below.
+///
+/// Note: ADR-119 AC1 initially claimed 40 bytes — that was a counting error.
+/// Actual packed layout sums to 86. Updated 2026-05-24 to match implementation.
+pub const BFLD_HEADER_SIZE: usize = 86;
+
+/// Flag bits in `BfldFrameHeader::flags`. See ADR-119 §2.1.
+pub mod flags {
+    /// Payload contains an optional CSI delta section.
+    pub const HAS_CSI_DELTA: u16 = 1 << 0;
+    /// `privacy_mode` is engaged: identity-derived fields suppressed.
+    pub const PRIVACY_MODE: u16 = 1 << 1;
+    /// ESP32-S3 self-only adapter (ADR-123 §2.5): no `identity_risk_score`.
+    pub const SELF_ONLY: u16 = 1 << 3;
+}
+
+/// On-the-wire BFLD frame header. 86 bytes, little-endian, packed.
+///
+/// All multi-byte integer fields are little-endian when serialized. The packed
+/// layout guarantees zero internal padding; readers must use `read_unaligned`
+/// (or the accessor helpers added in a later commit).
+#[repr(C, packed)]
+#[derive(Debug, Clone, Copy)]
+pub struct BfldFrameHeader {
+    pub magic: u32,
+    pub version: u16,
+    pub flags: u16,
+    pub timestamp_ns: u64,
+
+    pub ap_hash: [u8; 16],
+    pub sta_hash: [u8; 16],
+    pub session_id: [u8; 16],
+
+    pub channel: u16,
+    pub bandwidth_mhz: u16,
+    pub rssi_dbm: i16,
+    pub noise_floor_dbm: i16,
+
+    pub n_subcarriers: u16,
+    pub n_tx: u8,
+    pub n_rx: u8,
+    pub quantization: u8,
+    pub privacy_class: u8,
+
+    pub payload_len: u32,
+    pub payload_crc32: u32,
+}
+
+const_assert_eq!(core::mem::size_of::<BfldFrameHeader>(), BFLD_HEADER_SIZE);
diff --git a/v2/crates/wifi-densepose-bfld/src/lib.rs b/v2/crates/wifi-densepose-bfld/src/lib.rs
new file mode 100644
index 00000000..79afd441
--- /dev/null
+++ b/v2/crates/wifi-densepose-bfld/src/lib.rs
@@ -0,0 +1,71 @@
+//! # BFLD — Beamforming Feedback Layer for Detection
+//!
+//! Privacy-gated WiFi sensing primitives derived from 802.11ac/ax Beamforming
+//! Feedback Information (BFI). See [`docs/adr/ADR-118-bfld-beamforming-feedback-layer-for-detection.md`](../../../docs/adr/ADR-118-bfld-beamforming-feedback-layer-for-detection.md).
+//!
+//! ## Three structural invariants
+//!
+//! - **I1**: Raw BFI never exits the node.
+//! - **I2**: Identity embedding is in-RAM-only.
+//! - **I3**: Cross-site identity correlation is cryptographically impossible.
+//!
+//! Status: P1 scaffold — frame format only. P2–P6 land in subsequent commits.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+pub mod frame;
+
+pub use frame::{BfldFrameHeader, BFLD_MAGIC, BFLD_VERSION, BFLD_HEADER_SIZE};
+
+/// Privacy classification carried in every `BfldFrame`. See ADR-120 §2.1.
+#[repr(u8)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum PrivacyClass {
+    /// Local-only research data including raw BFI matrix. Never networked.
+    Raw = 0,
+    /// Operator-acknowledged research mode over LAN. Downsampled angles +
+    /// identity_embedding + identity_risk_score available. Required for
+    /// Soul Signature deployments (ADR-120 §2.7).
+    Derived = 1,
+    /// Production default: aggregate sensing only, no identity-derived fields.
+    Anonymous = 2,
+    /// Care-home / regulated deployments: class 2 minus risk score and hash.
+    Restricted = 3,
+}
+
+impl PrivacyClass {
+    /// Returns `true` if frames of this class may cross a `NetworkSink`.
+    /// Class 0 (`Raw`) is local-only by structural invariant I1.
+    #[must_use]
+    pub const fn allows_network(self) -> bool {
+        !matches!(self, Self::Raw)
+    }
+
+    /// Returns `true` if frames of this class may cross the Matter boundary.
+    /// Only classes 2 and 3 are Matter-eligible. See ADR-122 §2.4.
+    #[must_use]
+    pub const fn allows_matter(self) -> bool {
+        matches!(self, Self::Anonymous | Self::Restricted)
+    }
+}
+
+/// Errors produced by BFLD operations.
+#[derive(Debug, thiserror::Error)]
+pub enum BfldError {
+    /// Header magic did not match `BFLD_MAGIC`.
+    #[error("invalid BFLD magic: expected 0x{BFLD_MAGIC:08X}, got 0x{0:08X}")]
+    InvalidMagic(u32),
+
+    /// Header version unsupported.
+    #[error("unsupported BFLD version: {0}")]
+    UnsupportedVersion(u16),
+
+    /// Payload CRC32 mismatch — frame corrupted or tampered.
+    #[error("payload CRC mismatch: expected 0x{expected:08X}, got 0x{actual:08X}")]
+    Crc { expected: u32, actual: u32 },
+
+    /// Attempted to publish a class-0 (`Raw`) frame through a network sink.
+    /// Enforces structural invariant I1.
+    #[error("privacy violation: {reason}")]
+    PrivacyViolation { reason: &'static str },
+}
diff --git a/v2/crates/wifi-densepose-bfld/tests/frame_header_size.rs b/v2/crates/wifi-densepose-bfld/tests/frame_header_size.rs
new file mode 100644
index 00000000..47b884a5
--- /dev/null
+++ b/v2/crates/wifi-densepose-bfld/tests/frame_header_size.rs
@@ -0,0 +1,28 @@
+//! Acceptance test ADR-119 AC1: `BfldFrameHeader` size is platform-stable.
+//!
+//! The static assertion in `frame.rs` already enforces this at compile time on
+//! the local target. This runtime test exists so CI surfaces the failure with
+//! a useful message rather than a `const_assert_eq!` link error.
+
+use wifi_densepose_bfld::{BfldFrameHeader, BFLD_HEADER_SIZE, BFLD_MAGIC, BFLD_VERSION};
+
+#[test]
+fn header_size_is_86_bytes() {
+    assert_eq!(
+        core::mem::size_of::<BfldFrameHeader>(),
+        BFLD_HEADER_SIZE,
+        "BfldFrameHeader must be exactly {BFLD_HEADER_SIZE} bytes (packed)",
+    );
+}
+
+#[test]
+fn magic_reads_as_bfld_in_hex() {
+    // 0xBF1D_0001 — "BF1D" looks like "BFLD" in xxd output; final 0001 is the
+    // major version that lives in the dedicated `version` field as well.
+    assert_eq!(BFLD_MAGIC, 0xBF1D_0001);
+}
+
+#[test]
+fn version_is_one() {
+    assert_eq!(BFLD_VERSION, 1);
+}