diff --git a/ffi/zig/src/catalogue.zig b/ffi/zig/src/catalogue.zig
index 99c268cb..16caf52d 100644
--- a/ffi/zig/src/catalogue.zig
+++ b/ffi/zig/src/catalogue.zig
@@ -12,15 +12,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 
 // ═══════════════════════════════════════════════════════════════════════
 // Types (must match src/abi/Catalogue.idr encodings)
diff --git a/ffi/zig/src/community.zig b/ffi/zig/src/community.zig
index 70904be9..bb5e9271 100644
--- a/ffi/zig/src/community.zig
+++ b/ffi/zig/src/community.zig
@@ -15,15 +15,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 
 // ═══════════════════════════════════════════════════════════════════════
 // Constants
diff --git a/ffi/zig/src/coprocessor.zig b/ffi/zig/src/coprocessor.zig
index 38ab9156..6f4919ba 100644
--- a/ffi/zig/src/coprocessor.zig
+++ b/ffi/zig/src/coprocessor.zig
@@ -20,15 +20,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 
 extern fn getenv(name: [*:0]const u8) ?[*:0]const u8;
 
diff --git a/ffi/zig/src/federation.zig b/ffi/zig/src/federation.zig
index 01b607cf..c65b3532 100644
--- a/ffi/zig/src/federation.zig
+++ b/ffi/zig/src/federation.zig
@@ -20,15 +20,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 
 // ═══════════════════════════════════════════════════════════════════════
 // Proven-hardened: Circuit breaker, retry, and rate limiter state
diff --git a/ffi/zig/src/guardian.zig b/ffi/zig/src/guardian.zig
index 8370c029..0624cc1a 100644
--- a/ffi/zig/src/guardian.zig
+++ b/ffi/zig/src/guardian.zig
@@ -22,15 +22,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 
 // ═══════════════════════════════════════════════════════════════════════
 // Constants
diff --git a/ffi/zig/src/loader.zig b/ffi/zig/src/loader.zig
index 40bd6d58..41bd1528 100644
--- a/ffi/zig/src/loader.zig
+++ b/ffi/zig/src/loader.zig
@@ -13,15 +13,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 const crypto = std.crypto;
 const fs = std.fs;
 
diff --git a/ffi/zig/src/sdp.zig b/ffi/zig/src/sdp.zig
index f3fe51a0..fbcde370 100644
--- a/ffi/zig/src/sdp.zig
+++ b/ffi/zig/src/sdp.zig
@@ -16,15 +16,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 
 // ═══════════════════════════════════════════════════════════════════════
 // Constants
diff --git a/ffi/zig/src/sla.zig b/ffi/zig/src/sla.zig
index 50fe5342..a91d66dd 100644
--- a/ffi/zig/src/sla.zig
+++ b/ffi/zig/src/sla.zig
@@ -15,15 +15,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 
 // ═══════════════════════════════════════════════════════════════════════
 // Constants
diff --git a/ffi/zig/src/verisimdb.zig b/ffi/zig/src/verisimdb.zig
index 8f857665..53935135 100644
--- a/ffi/zig/src/verisimdb.zig
+++ b/ffi/zig/src/verisimdb.zig
@@ -16,15 +16,12 @@
 
 const std = @import("std");
 
-const Mutex = struct {
-    state: std.atomic.Mutex = .unlocked,
-    pub fn lock(m: *Mutex) void {
-        while (!m.state.tryLock()) std.atomic.spinLoopHint();
-    }
-    pub fn unlock(m: *Mutex) void {
-        m.state.unlock();
-    }
-};
+// `std.atomic.Mutex` was removed from the standard library; its replacement is
+// `std.Thread.Mutex`, whose lock/unlock surface is identical to the hand-rolled
+// wrapper this replaces. The wrapper also busy-waited via `spinLoopHint`, burning
+// a core under contention; `std.Thread.Mutex` parks the thread instead. 81 other
+// files in this repo already use this form.
+const Mutex = std.Thread.Mutex;
 const Allocator = std.mem.Allocator;
 
 // ═══════════════════════════════════════════════════════════════════════