diff --git a/.buildkite/pipeline-default.yml b/.buildkite/pipeline-default.yml
index 4457b0aef..244e970ab 100644
--- a/.buildkite/pipeline-default.yml
+++ b/.buildkite/pipeline-default.yml
@@ -35,36 +35,7 @@ agents:
   queue: buildkite-gcp
 
 steps:
-  - name: ":go: 1.21 test - %n"
-    parallelism: 2
-    plugins:
-      - kubernetes:
-          <<: *kubernetes
-          podSpec:
-            <<: *podSpec
-            containers:
-              - <<: *commandContainer
-                command:
-                - |-
-                  make test
-      - docker-compose#v3.13.0:
-          run: yarpc-go-1.21
-
-  - name: ":go: 1.21 examples"
-    plugins:
-      - kubernetes:
-          <<: *kubernetes
-          podSpec:
-            <<: *podSpec
-            containers:
-              - <<: *commandContainer
-                command:
-                - |-
-                  make examples
-      - docker-compose#v3.13.0:
-          run: yarpc-go-1.21
-
-  - name: ":go: 1.22 test - %n"
+  - name: ":go: 1.23 test - %n"
     parallelism: 6
     plugins:
       - kubernetes:
@@ -77,9 +48,9 @@ steps:
                 - |-
                   make codecov
       - docker-compose#v3.13.0:
-          run: yarpc-go-1.22
+          run: yarpc-go-1.23
 
-  - name: ":go: 1.22 crossdock"
+  - name: ":go: 1.23 crossdock"
     plugins:
       - kubernetes:
           <<: *kubernetes
@@ -91,9 +62,9 @@ steps:
                 - |-
                   make crossdock-codecov
       - docker-compose#v3.13.0:
-          run: yarpc-go-1.22
+          run: yarpc-go-1.23
 
-  - name: ":go: 1.22 lint"
+  - name: ":go: 1.23 lint"
     plugins:
       - kubernetes:
           <<: *kubernetes
@@ -105,9 +76,9 @@ steps:
                 - |-
                   make lint
       - docker-compose#v3.13.0:
-          run: yarpc-go-1.22
+          run: yarpc-go-1.23
 
-  - name: ":go: 1.22 examples"
+  - name: ":go: 1.23 examples"
     plugins:
       - kubernetes:
           <<: *kubernetes
@@ -119,4 +90,4 @@ steps:
                 - |-
                   make examples
       - docker-compose#v3.13.0:
-          run: yarpc-go-1.22
+          run: yarpc-go-1.23
diff --git a/Dockerfile.1.23 b/Dockerfile.1.23
new file mode 100644
index 000000000..bfd1cac68
--- /dev/null
+++ b/Dockerfile.1.23
@@ -0,0 +1,24 @@
+FROM golang:1.23
+
+ENV SUPPRESS_DOCKER 1
+WORKDIR /yarpc
+RUN apt-get update -yq && apt-get install -yq jq unzip netcat-openbsd
+ADD dockerdeps.mk /yarpc/
+ADD etc/make/base.mk etc/make/deps.mk /yarpc/etc/make/
+RUN make -f dockerdeps.mk predeps
+ADD etc/bin/vendor-build.sh /yarpc/etc/bin/
+
+# Download and cache dependencies in the image so that we're not constantly
+# re-downloading them locally.
+
+ADD tools_test.go go.mod go.sum /yarpc/
+RUN go mod download
+
+ADD internal/examples/go.mod /yarpc/internal/examples/
+RUN cd /yarpc/internal/examples && go mod download
+
+ADD internal/crossdock/go.mod /yarpc/internal/crossdock/
+RUN cd /yarpc/internal/crossdock && go mod download
+
+RUN make -f dockerdeps.mk deps
+ADD . /yarpc/
diff --git a/api/encoding/call.go b/api/encoding/call.go
index 363e538f7..5a399a73c 100644
--- a/api/encoding/call.go
+++ b/api/encoding/call.go
@@ -22,6 +22,7 @@ package encoding
 
 import (
 	"context"
+	"iter"
 	"sort"
 
 	"go.uber.org/yarpc/api/transport"
@@ -140,6 +141,22 @@ func (c *Call) OriginalHeaders() map[string]string {
 	return h
 }
 
+// OriginalHeadersAll returns an iterator over the original (non-canonicalized)
+// header key-value pairs provided with the request.
+// The header keys are not canonicalized and suitable for case-sensitive transport like TChannel.
+func (c *Call) OriginalHeadersAll() iter.Seq2[string, string] {
+	return func(yield func(string, string) bool) {
+		if c == nil {
+			return
+		}
+		for k, v := range c.md.Headers().OriginalItemsAll() {
+			if !yield(k, v) {
+				return
+			}
+		}
+	}
+}
+
 // HeaderNames returns a sorted list of the names of user defined headers
 // provided with this request.
 func (c *Call) HeaderNames() []string {
@@ -156,6 +173,30 @@ func (c *Call) HeaderNames() []string {
 	return names
 }
 
+// HeaderNamesAll returns an iterator over the names of user defined headers
+// provided with this request.
+func (c *Call) HeaderNamesAll() iter.Seq[string] {
+	return func(yield func(string) bool) {
+		if c == nil {
+			return
+		}
+		for k := range c.md.Headers().All() {
+			if !yield(k) {
+				return
+			}
+		}
+	}
+}
+
+// HeadersLen returns the number of user defined headers provided with this request.
+// Useful for pre-allocating slices.
+func (c *Call) HeadersLen() int {
+	if c == nil {
+		return 0
+	}
+	return c.md.Headers().Len()
+}
+
 // ShardKey returns the shard key for this request.
 func (c *Call) ShardKey() string {
 	if c == nil {
diff --git a/api/encoding/call_test.go b/api/encoding/call_test.go
index 23dcc1955..01c2b938d 100644
--- a/api/encoding/call_test.go
+++ b/api/encoding/call_test.go
@@ -22,6 +22,8 @@ package encoding
 
 import (
 	"context"
+	"slices"
+	"strconv"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -46,6 +48,8 @@ func TestNilCall(t *testing.T) {
 	assert.Equal(t, "", call.OriginalHeader("foo"))
 	assert.Empty(t, call.HeaderNames())
 	assert.Nil(t, call.OriginalHeaders())
+	assert.Equal(t, 0, call.HeadersLen())
+	assert.Len(t, slices.Collect(call.HeaderNamesAll()), 0, "nil call should yield no headers")
 
 	assert.Error(t, call.WriteResponseHeader("foo", "bar"))
 }
@@ -82,6 +86,20 @@ func TestReadFromRequest(t *testing.T) {
 	assert.Equal(t, map[string]string{"Foo": "Bar", "foo": "bar"}, call.OriginalHeaders())
 	assert.Equal(t, "cp", call.CallerProcedure())
 	assert.Len(t, call.HeaderNames(), 1)
+	assert.Equal(t, 1, call.HeadersLen())
+
+	headerNames := call.HeaderNames()
+	headerNamesFromIterator := slices.Collect(call.HeaderNamesAll())
+	slices.Sort(headerNames)
+	slices.Sort(headerNamesFromIterator)
+	assert.Equal(t, headerNames, headerNamesFromIterator)
+
+	originalHeaders := call.OriginalHeaders()
+	headersFromIterator := make(map[string]string)
+	for k, v := range call.OriginalHeadersAll() {
+		headersFromIterator[k] = v
+	}
+	assert.Equal(t, originalHeaders, headersFromIterator)
 
 	assert.NoError(t, call.WriteResponseHeader("foo2", "bar2"))
 	assert.Equal(t, icall.resHeaders[0].k, "foo2")
@@ -158,3 +176,77 @@ func TestDisabledResponseHeaders(t *testing.T) {
 	assert.Error(t, call.WriteResponseHeader("foo", "bar"))
 	assert.Nil(t, icall.resHeaders)
 }
+
+func BenchmarkCallHeaderNames(b *testing.B) {
+	benchmarkSizes := []int{1, 2, 3, 4, 5, 6, 8, 10, 25, 50, 100}
+
+	testCalls := make(map[int]*Call)
+	for _, size := range benchmarkSizes {
+		headers := transport.NewHeadersWithCapacity(size)
+		for i := 0; i < size; i++ {
+			headers = headers.With("header-"+strconv.Itoa(i), "value-"+strconv.Itoa(i))
+		}
+		ctx, icall := NewInboundCall(context.Background())
+		icall.ReadFromRequest(&transport.Request{Headers: headers})
+		testCalls[size] = CallFromContext(ctx)
+	}
+
+	// Benchmark HeaderNames (with sorting).
+	b.Run("HeaderNames", func(b *testing.B) {
+		for _, size := range benchmarkSizes {
+			call := testCalls[size]
+			b.Run("size="+strconv.Itoa(size), func(b *testing.B) {
+				b.ResetTimer()
+				for i := 0; i < b.N; i++ {
+					call.HeaderNames()
+				}
+			})
+		}
+	})
+
+	// Benchmark HeaderNamesAll (no sorting).
+	b.Run("HeaderNamesAll", func(b *testing.B) {
+		for _, size := range benchmarkSizes {
+			call := testCalls[size]
+			b.Run("size="+strconv.Itoa(size), func(b *testing.B) {
+				b.ResetTimer()
+				for i := 0; i < b.N; i++ {
+					// Consume the iterator.
+					for name := range call.HeaderNamesAll() {
+						_ = name
+					}
+				}
+			})
+		}
+	})
+
+	// Benchmark OriginalHeaders (creates map copy).
+	b.Run("OriginalHeaders", func(b *testing.B) {
+		for _, size := range benchmarkSizes {
+			call := testCalls[size]
+			b.Run("size="+strconv.Itoa(size), func(b *testing.B) {
+				b.ResetTimer()
+				for i := 0; i < b.N; i++ {
+					call.OriginalHeaders()
+				}
+			})
+		}
+	})
+
+	// Benchmark OriginalHeadersAll (no copy).
+	b.Run("OriginalHeadersAll", func(b *testing.B) {
+		for _, size := range benchmarkSizes {
+			call := testCalls[size]
+			b.Run("size="+strconv.Itoa(size), func(b *testing.B) {
+				b.ResetTimer()
+				for i := 0; i < b.N; i++ {
+					// Consume the iterator.
+					for k, v := range call.OriginalHeadersAll() {
+						_ = k
+						_ = v
+					}
+				}
+			})
+		}
+	})
+}
diff --git a/api/transport/header.go b/api/transport/header.go
index 8215a0807..6b7d6b56d 100644
--- a/api/transport/header.go
+++ b/api/transport/header.go
@@ -20,7 +20,10 @@
 
 package transport
 
-import "strings"
+import (
+	"iter"
+	"strings"
+)
 
 // CanonicalizeHeaderKey canonicalizes the given header key for storage into
 // Headers.
@@ -103,6 +106,18 @@ func (h Headers) Items() map[string]string {
 	return h.items
 }
 
+// All returns an iterator over the header key-value pairs.
+// Keys are normalized using CanonicalizeHeaderKey.
+func (h Headers) All() iter.Seq2[string, string] {
+	return func(yield func(string, string) bool) {
+		for k, v := range h.items {
+			if !yield(k, v) {
+				return
+			}
+		}
+	}
+}
+
 // OriginalItems returns the non-canonicalized version of the underlying map
 // for this Headers object. The returned map MUST NOT be changed.
 // Doing so will result in undefined behavior.
@@ -110,6 +125,18 @@ func (h Headers) OriginalItems() map[string]string {
 	return h.originalItems
 }
 
+// OriginalItemsAll returns an iterator over the original (non-canonicalized)
+// header key-value pairs.
+func (h Headers) OriginalItemsAll() iter.Seq2[string, string] {
+	return func(yield func(string, string) bool) {
+		for k, v := range h.originalItems {
+			if !yield(k, v) {
+				return
+			}
+		}
+	}
+}
+
 // HeadersFromMap builds a new Headers object from the given map of header
 // key-value pairs.
 func HeadersFromMap(m map[string]string) Headers {
diff --git a/docker-compose.yml b/docker-compose.yml
index 2cbe4a967..f588824e8 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -48,3 +48,24 @@ services:
       - BUILDKITE_PROJECT_SLUG
       - BUILDKITE_REPO
       - GO111MODULE=on
+
+  yarpc-go-1.23:
+    build:
+      context: .
+      dockerfile: Dockerfile.1.23
+    environment:
+      - TEST_TIME_SCALE=5
+      - THIS_CHUNK=${BUILDKITE_PARALLEL_JOB}
+      - TOTAL_CHUNKS=${BUILDKITE_PARALLEL_JOB_COUNT}
+      - CODECOV_TOKEN
+      - CI=true
+      - BUILDKITE
+      - BUILDKITE_AGENT_ID
+      - BUILDKITE_BRANCH
+      - BUILDKITE_BUILD_NUMBER
+      - BUILDKITE_BUILD_URL
+      - BUILDKITE_COMMIT
+      - BUILDKITE_JOB_ID
+      - BUILDKITE_PROJECT_SLUG
+      - BUILDKITE_REPO
+      - GO111MODULE=on
diff --git a/etc/make/docker.mk b/etc/make/docker.mk
index b13c7987f..abd14a24e 100644
--- a/etc/make/docker.mk
+++ b/etc/make/docker.mk
@@ -1,4 +1,4 @@
-DOCKER_GO_VERSION ?= 1.22
+DOCKER_GO_VERSION ?= 1.23
 DOCKERFILE := Dockerfile.$(DOCKER_GO_VERSION)
 DOCKER_IMAGE := uber/yarpc-go-$(DOCKER_GO_VERSION)
 
diff --git a/go.mod b/go.mod
index ee7d62749..c15fabf34 100644
--- a/go.mod
+++ b/go.mod
@@ -1,8 +1,8 @@
 module go.uber.org/yarpc
 
-go 1.21
+go 1.23
 
-toolchain go1.22.2
+toolchain go1.23.0
 
 require (
 	github.com/dgryski/go-farm v0.0.0-20200201041132-a6ae2369ad13
diff --git a/internal/crossdock/go.mod b/internal/crossdock/go.mod
index 39727bed6..c03e02503 100644
--- a/internal/crossdock/go.mod
+++ b/internal/crossdock/go.mod
@@ -1,8 +1,8 @@
 module go.uber.org/yarpc/internal/crossdock
 
-go 1.21
+go 1.23
 
-toolchain go1.22.2
+toolchain go1.23.0
 
 require (
 	github.com/apache/thrift v0.13.0
diff --git a/internal/examples/go.mod b/internal/examples/go.mod
index 6fea7e07c..c06732b70 100644
--- a/internal/examples/go.mod
+++ b/internal/examples/go.mod
@@ -1,8 +1,8 @@
 module go.uber.org/yarpc/internal/examples
 
-go 1.21
+go 1.23
 
-toolchain go1.22.2
+toolchain go1.23.0
 
 require (
 	github.com/gogo/protobuf v1.3.2
diff --git a/yarpcconfig/spec_test.go b/yarpcconfig/spec_test.go
index bd2bddf11..c25d19180 100644
--- a/yarpcconfig/spec_test.go
+++ b/yarpcconfig/spec_test.go
@@ -116,7 +116,7 @@ func TestCompileTransportSpec(t *testing.T) {
 				BuildTransport:     func(**struct{}, *Kit) (transport.Transport, error) { panic("kthxbye") },
 				BuildUnaryOutbound: func(debt, transport.Transport, *Kit) (transport.UnaryOutbound, error) { panic("kthxbye") },
 			},
-			transportInput:     reflect.PtrTo(reflect.TypeOf(&struct{}{})),
+			transportInput:     reflect.PointerTo(reflect.TypeOf(&struct{}{})),
 			supportsUnary:      true,
 			unaryOutboundInput: reflect.TypeOf(debt{}),
 		},
@@ -461,7 +461,7 @@ func TestCompileTransportConfig(t *testing.T) {
 		{
 			desc:          "valid: *struct{}",
 			build:         func(*struct{}, *Kit) (transport.Transport, error) { panic("kthxbye") },
-			wantInputType: reflect.PtrTo(_typeOfEmptyStruct),
+			wantInputType: reflect.PointerTo(_typeOfEmptyStruct),
 		},
 	}
 
@@ -1180,10 +1180,10 @@ func TestIsDecodable(t *testing.T) {
 		want bool
 	}{
 		{give: _typeOfError, want: false},
-		{give: reflect.PtrTo(_typeOfError), want: false},
+		{give: reflect.PointerTo(_typeOfError), want: false},
 		{give: _typeOfEmptyStruct, want: true},
-		{give: reflect.PtrTo(_typeOfEmptyStruct), want: true},
-		{give: reflect.PtrTo(reflect.PtrTo(_typeOfEmptyStruct)), want: true},
+		{give: reflect.PointerTo(_typeOfEmptyStruct), want: true},
+		{give: reflect.PointerTo(reflect.PointerTo(_typeOfEmptyStruct)), want: true},
 	}
 
 	for _, tt := range tests {