diff --git a/CHANGELOG.md b/CHANGELOG.md
index 243213ea7..dc7650805 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,14 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
+- Annotated 11 `lading_payload` functions that intentionally panic on
+  invariant violations with `#[expect(clippy::expect_used, reason = "...")]`.
+  Covered: `block::Cache::read_at` (documented `usize`/`u64` overflow
+  panic), `RandomStringPool::using_handle` and
+  `StringListPool::using_handle` (handle-type contract), and the
+  `Display::fmt` impls for `Event`, `ServiceCheck`, `Count`, `Gauge`,
+  `Timer`, `Dist`, `Set`, `Histogram` (tag-pool handle lookups). No
+  runtime behavior change; the `.expect()` calls remain in place.
 - Replaced 6 in-function-invariant `.expect()` sites in `lading_payload`
   with `.unwrap_or_else(|_| unreachable!("..."))` /
   `.unwrap_or_else(|| unreachable!("..."))`. Covered: `usize → u32`
diff --git a/lading_payload/src/block.rs b/lading_payload/src/block.rs
index 62e2b0327..1684b1068 100644
--- a/lading_payload/src/block.rs
+++ b/lading_payload/src/block.rs
@@ -506,6 +506,10 @@ impl Cache {
     /// # Panics
     ///
     /// Function will panic if reads are larger than machine word bytes wide.
+    #[expect(
+        clippy::expect_used,
+        reason = "u64-to-usize panic on overflow is the documented contract of this function"
+    )]
     pub fn read_at(&self, offset: u64, size: usize) -> Bytes {
         let mut data = BytesMut::with_capacity(size);
 
diff --git a/lading_payload/src/common/strings/random_string_pool.rs b/lading_payload/src/common/strings/random_string_pool.rs
index b07bb7f2a..211df2de8 100644
--- a/lading_payload/src/common/strings/random_string_pool.rs
+++ b/lading_payload/src/common/strings/random_string_pool.rs
@@ -131,6 +131,10 @@ impl Pool for RandomStringPool {
     }
 
     #[inline]
+    #[expect(
+        clippy::expect_used,
+        reason = "handle was issued by this pool earlier in the call chain; a non-PosAndLength handle indicates a cross-pool programming error"
+    )]
     fn using_handle(&self, handle: Handle) -> Option<&str> {
         let (offset, length) = handle
             .as_pos_and_length()
diff --git a/lading_payload/src/common/strings/string_list_pool.rs b/lading_payload/src/common/strings/string_list_pool.rs
index 967eb2135..c3470db7d 100644
--- a/lading_payload/src/common/strings/string_list_pool.rs
+++ b/lading_payload/src/common/strings/string_list_pool.rs
@@ -417,6 +417,10 @@ impl Pool for StringListPool {
         Some((&self.metric_names[idx], Handle::Index(idx)))
     }
 
+    #[expect(
+        clippy::expect_used,
+        reason = "handle was issued by this pool earlier in the call chain; a non-Index handle indicates a cross-pool programming error"
+    )]
     fn using_handle(&self, handle: Handle) -> Option<&str> {
         let idx = handle
             .as_index()
diff --git a/lading_payload/src/dogstatsd/event.rs b/lading_payload/src/dogstatsd/event.rs
index e68304f35..6f46a4410 100644
--- a/lading_payload/src/dogstatsd/event.rs
+++ b/lading_payload/src/dogstatsd/event.rs
@@ -102,6 +102,10 @@ pub struct Event<'a> {
 }
 
 impl fmt::Display for Event<'_> {
+    #[expect(
+        clippy::expect_used,
+        reason = "tag handles were issued by self.pools at event construction; mismatched lookup indicates an internal invariant violation"
+    )]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // _e{<TITLE_UTF8_LENGTH>,<TEXT_UTF8_LENGTH>}:<TITLE>|<TEXT>|d:<TIMESTAMP>|h:<HOSTNAME>|p:<PRIORITY>|t:<ALERT_TYPE>|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>
         write!(
diff --git a/lading_payload/src/dogstatsd/metric.rs b/lading_payload/src/dogstatsd/metric.rs
index 71d604460..e78470fe3 100644
--- a/lading_payload/src/dogstatsd/metric.rs
+++ b/lading_payload/src/dogstatsd/metric.rs
@@ -339,6 +339,10 @@ pub struct Count<'a> {
 }
 
 impl fmt::Display for Count<'_> {
+    #[expect(
+        clippy::expect_used,
+        reason = "tag handles were issued by self.pools at metric construction; mismatched lookup indicates an internal invariant violation"
+    )]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // <METRIC_NAME>:<VALUE>|d|#<TAG_KEY_1>:<TAGVALUE_1>,<TAG_2>|c:<CONTAINER_ID>
         // <METRIC_NAME>:<VALUE1>:<VALUE2>:<VALUE3>|d|@<SAMPLE_RATE>|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>
@@ -411,6 +415,10 @@ pub struct Gauge<'a> {
 }
 
 impl fmt::Display for Gauge<'_> {
+    #[expect(
+        clippy::expect_used,
+        reason = "tag handles were issued by self.pools at metric construction; mismatched lookup indicates an internal invariant violation"
+    )]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // <METRIC_NAME>:<VALUE>|d|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>|c:<CONTAINER_ID>
         // <METRIC_NAME>:<VALUE1>:<VALUE2>:<VALUE3>|d|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>
@@ -479,6 +487,10 @@ pub struct Timer<'a> {
 }
 
 impl fmt::Display for Timer<'_> {
+    #[expect(
+        clippy::expect_used,
+        reason = "tag handles were issued by self.pools at metric construction; mismatched lookup indicates an internal invariant violation"
+    )]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // <METRIC_NAME>:<VALUE>|d|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>|c:<CONTAINER_ID>
         // <METRIC_NAME>:<VALUE1>:<VALUE2>:<VALUE3>|d|@<SAMPLE_RATE>|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>
@@ -547,6 +559,10 @@ pub struct Dist<'a> {
 }
 
 impl fmt::Display for Dist<'_> {
+    #[expect(
+        clippy::expect_used,
+        reason = "tag handles were issued by self.pools at metric construction; mismatched lookup indicates an internal invariant violation"
+    )]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // <METRIC_NAME>:<VALUE>|d|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>|c:<CONTAINER_ID>
         // <METRIC_NAME>:<VALUE1>:<VALUE2>:<VALUE3>|d|@<SAMPLE_RATE>|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>
@@ -613,6 +629,10 @@ pub struct Set<'a> {
 }
 
 impl fmt::Display for Set<'_> {
+    #[expect(
+        clippy::expect_used,
+        reason = "tag handles were issued by self.pools at metric construction; mismatched lookup indicates an internal invariant violation"
+    )]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // <METRIC_NAME>:<VALUE>|s|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>|c:<CONTAINER_ID>
         let name = &self.name;
@@ -674,6 +694,10 @@ pub struct Histogram<'a> {
 }
 
 impl fmt::Display for Histogram<'_> {
+    #[expect(
+        clippy::expect_used,
+        reason = "tag handles were issued by self.pools at metric construction; mismatched lookup indicates an internal invariant violation"
+    )]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // <METRIC_NAME>:<VALUE>|h|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>|c:<CONTAINER_ID>
         // <METRIC_NAME>:<VALUE1>:<VALUE2>:<VALUE3>|h|@<SAMPLE_RATE>|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>
diff --git a/lading_payload/src/dogstatsd/service_check.rs b/lading_payload/src/dogstatsd/service_check.rs
index 1cae4a3de..7df116bdd 100644
--- a/lading_payload/src/dogstatsd/service_check.rs
+++ b/lading_payload/src/dogstatsd/service_check.rs
@@ -71,6 +71,10 @@ pub struct ServiceCheck<'a> {
 }
 
 impl fmt::Display for ServiceCheck<'_> {
+    #[expect(
+        clippy::expect_used,
+        reason = "tag handles were issued by self.pools at service-check construction; mismatched lookup indicates an internal invariant violation"
+    )]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // _sc|<NAME>|<STATUS>|d:<TIMESTAMP>|h:<HOSTNAME>|#<TAG_KEY_1>:<TAG_VALUE_1>,<TAG_2>|m:<SERVICE_CHECK_MESSAGE>
         write!(