diff --git a/Packages/ClientRuntime/Sources/Networking/Http/UnknownHttpServiceError.swift b/Packages/ClientRuntime/Sources/Networking/Http/UnknownHttpServiceError.swift
index b4f21d81c..69b436105 100644
--- a/Packages/ClientRuntime/Sources/Networking/Http/UnknownHttpServiceError.swift
+++ b/Packages/ClientRuntime/Sources/Networking/Http/UnknownHttpServiceError.swift
@@ -4,7 +4,7 @@
  */
 
 /// General Service Error structure used when exact error could not be deduced from the `HttpResponse`
-public struct UnknownHttpServiceError: HttpServiceError {
+public struct UnknownHttpServiceError: HttpServiceError, Swift.Equatable {
     public var _isThrottling: Bool = false
     
     public var _statusCode: HttpStatusCode?
diff --git a/Packages/ClientRuntime/Sources/Serialization/SerializationUtils/HeaderUtils.swift b/Packages/ClientRuntime/Sources/Serialization/SerializationUtils/HeaderUtils.swift
index 967704692..1408f2da9 100644
--- a/Packages/ClientRuntime/Sources/Serialization/SerializationUtils/HeaderUtils.swift
+++ b/Packages/ClientRuntime/Sources/Serialization/SerializationUtils/HeaderUtils.swift
@@ -5,49 +5,153 @@
 
 import Foundation
 
+fileprivate extension String {
+    func readNextQuoted(startIdx: String.Index, delim: Character = ",") throws -> (String.Index, String) {
+        // startIdx is start of the quoted value, there must be at least an ending quotation mark
+        if !(self.index(after: startIdx) < self.endIndex) {
+            throw HeaderDeserializationError.invalidStringHeaderList(value: self)
+        }
+        
+        // find first non-escaped quote or end of string
+        var endIdx = self.index(after: startIdx)
+        while endIdx < self.endIndex {
+            let char = self[endIdx]
+            if char == "\\" {
+                // skip escaped chars
+                endIdx = self.index(after: endIdx)
+            } else if char == "\"" {
+                break
+            }
+            endIdx = self.index(after: endIdx)
+        }
+        
+        let next = self[self.index(after: startIdx)..<endIdx]
+        
+        // consume trailing quote
+        if endIdx >= self.endIndex || self[endIdx] != "\"" {
+            throw HeaderDeserializationError.invalidStringHeaderList(value: self)
+        }
+        assert(endIdx < self.endIndex)
+        assert(self[endIdx] == "\"")
+        
+        endIdx = self.index(after: endIdx)
+        
+        // consume delim
+        while endIdx < self.endIndex {
+            let char = self[endIdx]
+            if char == " " || char == "\t" {
+                endIdx = self.index(after: endIdx)
+            } else if char == delim {
+                endIdx = self.index(after: endIdx)
+                break
+            } else {
+                throw HeaderDeserializationError.invalidStringHeaderList(value: self)
+            }
+        }
+        
+        let unescaped = next.replacingOccurrences(of: "\\\"", with: "\"")
+            .replacingOccurrences(of: "\\\\", with: "\\")
+        
+        return (endIdx, unescaped)
+    }
+    
+    func readNextUnquoted(startIdx: String.Index, delim: Character = ",") -> (String.Index, String) {
+        assert(startIdx < self.endIndex)
+        
+        var endIdx = startIdx
+        
+        while endIdx < self.endIndex && self[endIdx] != delim {
+            endIdx = self.index(after: endIdx)
+        }
+        
+        let next = self[startIdx..<endIdx]
+        if endIdx < self.endIndex && self[endIdx] == delim {
+            endIdx = self.index(after: endIdx)
+        }
+        
+        return (endIdx, next.trim())
+    }
+}
+
+// chars in an HTTP header value that require quotations
+private let QUOTABLE_HEADER_VALUE_CHARS = "\",()"
+
+public func quoteHeaderValue(_ value: String) -> String {
+    if value.trim().count != value.count || value.contains(where: { char1 in
+        QUOTABLE_HEADER_VALUE_CHARS.contains { char2 in
+            char1 == char2
+        }
+    }) {
+        let formatted = value.replacingOccurrences(of: "\\", with: "\\\\")
+            .replacingOccurrences(of: "\"", with: "\\\"")
+        return "\"\(formatted)\""
+    } else {
+        return value
+    }
+}
+
 /// Expands the compact Header Representation of List of any type except Dates
-public func splitHeaderListValues(_ value: String?) -> [String]? {
-    guard let value = value else { return nil}
-    return value.components(separatedBy: ",").map { $0.trim() }
+public func splitHeaderListValues(_ value: String?) throws -> [String]? {
+    guard let value = value else {
+        return nil
+    }
+    var results: [String] = []
+    var currIdx = value.startIndex
+    
+    while currIdx < value.endIndex {
+        let next: (idx: String.Index, str: String)
+        
+        switch value[currIdx] {
+        case " ", "\t":
+            currIdx = value.index(after: currIdx)
+            continue
+        case "\"":
+            next = try value.readNextQuoted(startIdx: currIdx)
+        default:
+            next = value.readNextUnquoted(startIdx: currIdx)
+        }
+        
+        currIdx = next.idx
+        results.append(next.str)
+    }
+    
+    return results
+    
 }
 
 /// Expands the compact HTTP Header Representation of List of Dates
 public func splitHttpDateHeaderListValues(_ value: String?) throws -> [String]? {
     guard let value = value else { return nil}
     
-    let separator = ","
-    let totalSeparators = value.components(separatedBy: separator).count - 1
-    if totalSeparators <= 1 {
+    let n = value.filter({$0 == ","}).count
+    
+    if n <= 1 {
         return [value]
-    } else if totalSeparators % 2 == 0 {
-        return splitHeaderListValues(value)
+    } else if n % 2 == 0 {
+        throw HeaderDeserializationError.invalidTimestampHeaderList(value: value)
     }
     
     var cnt = 0
     var splits: [String] = []
-    var start = 0
-    var startIdx = value.index(value.startIndex, offsetBy: start)
-
-    for i in 1...value.count {
-        let currIdx = value.index(value.startIndex, offsetBy: i-1)
-        if value[currIdx] == "," {
+    var startIdx = value.startIndex
+    
+    for i in value.indices[value.startIndex..<value.endIndex] {
+        if value[i] == "," {
             cnt += 1
         }
-
+        
         // split on every other ','
         if cnt > 1 {
-            startIdx = value.index(value.startIndex, offsetBy: start)
-            splits.append(String(value[startIdx..<currIdx]).trim())
-            start = i + 1
+            splits.append(value[startIdx..<i].trim())
+            startIdx = value.index(after: i)
             cnt = 0
         }
     }
-
-    if start < value.count {
-        startIdx = value.index(value.startIndex, offsetBy: start)
-        splits.append(String(value[startIdx..<value.endIndex]).trim())
+    
+    if startIdx < value.endIndex {
+        splits.append(value[startIdx...].trim())
     }
-
+    
     return splits
 }
 
@@ -64,19 +168,19 @@ extension HeaderDeserializationError: LocalizedError {
         switch self {
         case .invalidTimestampHeaderList(let value):
             return NSLocalizedString("Invalid HTTP Header List with Timestamps: \(value)",
-                comment: "Client Deserialization Error")
+                                     comment: "Client Deserialization Error")
         case .invalidTimestampHeader(let value):
             return NSLocalizedString("Invalid HTTP Header with Timestamp: \(value)",
-            comment: "Client Deserialization Error")
+                                     comment: "Client Deserialization Error")
         case .invalidBooleanHeaderList(let value):
             return NSLocalizedString("Invalid HTTP Header List with Booleans: \(value)",
-                comment: "Client Deserialization Error")
+                                     comment: "Client Deserialization Error")
         case .invalidNumbersHeaderList(let value):
             return NSLocalizedString("Invalid HTTP Header List with Booleans: \(value)",
-                comment: "Client Deserialization Error")
+                                     comment: "Client Deserialization Error")
         case .invalidStringHeaderList(let value):
             return NSLocalizedString("Invalid HTTP Header List with Strings: \(value)",
-                comment: "Client Deserialization Error")
+                                     comment: "Client Deserialization Error")
         }
     }
 }
diff --git a/Packages/ClientRuntime/Tests/SerializationTests/SerializationUtilsTests/HeaderUtilsTests.swift b/Packages/ClientRuntime/Tests/SerializationTests/SerializationUtilsTests/HeaderUtilsTests.swift
index 341501c64..7fbf4e139 100644
--- a/Packages/ClientRuntime/Tests/SerializationTests/SerializationUtilsTests/HeaderUtilsTests.swift
+++ b/Packages/ClientRuntime/Tests/SerializationTests/SerializationUtilsTests/HeaderUtilsTests.swift
@@ -9,15 +9,15 @@ import ClientRuntime
 class HeaderUtilsTests: XCTestCase {
     
     func testSplitHeaderListValues() {
-        guard let headerCollectionValues = splitHeaderListValues("1") else {
+        guard let headerCollectionValues = try! splitHeaderListValues("1") else {
             XCTFail("splitting header list values unexpectedly returned nil")
             return
         }
         XCTAssertEqual([1], headerCollectionValues.map { Int($0) })
-        XCTAssertEqual([1, 2, 3], splitHeaderListValues("1,2,3")?.map { Int($0) })
+        XCTAssertEqual([1, 2, 3], try! splitHeaderListValues("1,2,3")?.map { Int($0) })
         // Trim whitespaces in beginning and end of string components
-        XCTAssertEqual([1, 2, 3], splitHeaderListValues(" 1, 2, 3 ")?.map { Int($0) })
-        XCTAssertEqual([nil, 1], splitHeaderListValues(",1")?.map { Int($0) })
+        XCTAssertEqual([1, 2, 3], try! splitHeaderListValues(" 1, 2, 3 ")?.map { Int($0) })
+        XCTAssertEqual([nil, 1], try! splitHeaderListValues(",1")?.map { Int($0) })
     }
     
     func testSplitHttpDateHeaderListValues() {
@@ -31,7 +31,67 @@ class HeaderUtilsTests: XCTestCase {
         ]
         
         for (headerListString, headerList) in dateHeaderTransformations {
-            XCTAssertEqual(headerList, try? splitHttpDateHeaderListValues(headerListString))
+            XCTAssertEqual(headerList, try! splitHttpDateHeaderListValues(headerListString))
+        }
+        
+        XCTAssertThrowsError(try splitHttpDateHeaderListValues("Mon, 16 Dec 2019 23:48:18 GMT, , Tue, 17 Dec 2019 23:48:18 GMT")) { error in
+            XCTAssertEqual("Invalid HTTP Header List with Timestamps: Mon, 16 Dec 2019 23:48:18 GMT, , Tue, 17 Dec 2019 23:48:18 GMT", error.localizedDescription)
+        }
+    }
+    
+    func testSplitBoolList() {
+        XCTAssertEqual(["true", "false", "true", "true"], try! splitHeaderListValues("true,\"false\",true,\"true\""))
+    }
+    
+    func testSplitIntList() {
+        XCTAssertEqual(["1"], try! splitHeaderListValues("1"))
+        XCTAssertEqual(["1", "2", "3"], try! splitHeaderListValues("1,2,3"))
+        XCTAssertEqual(["1", "2", "3"], try! splitHeaderListValues("1,  2,  3"))
+        
+        // quoted
+        XCTAssertEqual(["1", "2", "3", "-4", "5"], try! splitHeaderListValues("1,\"2\",3,\"-4\",5"))
+    }
+    
+    func testSplitStringList() {
+        XCTAssertEqual(["foo"], try! splitHeaderListValues("foo"))
+        
+        // trailing space
+        XCTAssertEqual(["fooTrailing"], try! splitHeaderListValues("fooTrailing   "))
+        
+        // leading and trailing space
+        XCTAssertEqual(["  foo  "], try! splitHeaderListValues("\"  foo  \""))
+        
+        // ignore spaces between values
+        XCTAssertEqual(["foo", "bar"], try! splitHeaderListValues("foo  ,  bar"))
+        XCTAssertEqual(["foo", "bar"], try! splitHeaderListValues("\"foo\"  ,  \"bar\""))
+        
+        // comma in quotes
+        XCTAssertEqual(["foo,bar", "baz"], try! splitHeaderListValues("\"foo,bar\",baz"))
+        
+        // comm in quotes w/trailing space
+        XCTAssertEqual(["foo,bar", "baz"], try! splitHeaderListValues("\"foo,bar\",baz  "))
+        
+        // quote in quotes
+        XCTAssertEqual(["foo\",bar", "\"asdf\"", "baz"], try! splitHeaderListValues("\"foo\\\",bar\",\"\\\"asdf\\\"\",baz"))
+        
+        // quote in quote w/spaces
+        XCTAssertEqual(["foo\",bar", "\"asdf  \"", "baz"], try! splitHeaderListValues("\"foo\\\",bar\", \"\\\"asdf  \\\"\", baz"))
+        
+        // empty quotes
+        XCTAssertEqual(["", "baz"], try! splitHeaderListValues("\"\",baz"))
+        
+        // escaped slashes
+        XCTAssertEqual(["foo", "(foo\\bar)"], try! splitHeaderListValues("foo, \"(foo\\\\bar)\""))
+        
+        // empty
+        XCTAssertEqual(["", "1"], try! splitHeaderListValues(",1"))
+        
+        XCTAssertThrowsError(try splitHeaderListValues("foo, bar, \"baz")) { error in
+            XCTAssertEqual("Invalid HTTP Header List with Strings: foo, bar, \"baz", error.localizedDescription)
+        }
+        
+        XCTAssertThrowsError(try splitHeaderListValues("foo  ,  \"bar\"  \tf,baz")) { error in
+            XCTAssertEqual("Invalid HTTP Header List with Strings: foo  ,  \"bar\"  \tf,baz", error.localizedDescription)
         }
     }
 }
diff --git a/Packages/SmithyTestUtil/Sources/RequestTestUtil/HttpRequestTestBase.swift b/Packages/SmithyTestUtil/Sources/RequestTestUtil/HttpRequestTestBase.swift
index db5ea813f..4b836eb76 100644
--- a/Packages/SmithyTestUtil/Sources/RequestTestUtil/HttpRequestTestBase.swift
+++ b/Packages/SmithyTestUtil/Sources/RequestTestUtil/HttpRequestTestBase.swift
@@ -57,13 +57,7 @@ open class HttpRequestTestBase: XCTestCase {
         if let headers = headers {
             for (headerName, headerValue) in headers {
                 let value = sanitizeStringForNonConformingValues(headerValue)
-                do {
-                    if let values = try splitHttpDateHeaderListValues(value) {
-                        builder.withHeader(name: headerName, values: values)
-                    }
-                } catch let err {
-                    XCTFail(err.localizedDescription)
-                }
+                builder.withHeader(name: headerName, value: value)
             }
         }
         
@@ -288,20 +282,20 @@ open class HttpRequestTestBase: XCTestCase {
             XCTFail("There are expected headers and no actual headers.")
             return
         }
-
-        for expectedHeader in expected.headers {
-            XCTAssertTrue(actual.exists(name: expectedHeader.name),
-                          "expected header \(expectedHeader.name) has no actual values")
-            guard let values = actual.values(for: expectedHeader.name) else {
-                XCTFail("actual values expected to not be null")
+        
+        expected.headers.forEach { header in
+            XCTAssertTrue(actual.exists(name: header.name))
+            
+            guard actual.values(for: header.name) != header.value else {
+                XCTAssertEqual(actual.values(for: header.name), header.value)
                 return
             }
             
-            XCTAssert(expectedHeader.value.containsSameElements(as: values),
-                      """
-                      expected header name value pair not equal: \(expectedHeader.name):
-                      \(expectedHeader.value); found: \(expectedHeader.name):\(values)
-                      """)
+            let actualValue = actual.values(for: header.name)?.joined(separator: ", ")
+            XCTAssertNotNil(actualValue)
+            
+            let expectedValue = header.value.joined(separator: ", ")
+            XCTAssertEqual(actualValue, expectedValue)
         }
     }
     
diff --git a/gradle.properties b/gradle.properties
index 2474cdeaf..885b4e618 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -3,8 +3,8 @@ kotlin.code.style=official
 # config
 
 # codegen
-smithyVersion=1.13.1
-smithyGradleVersion=0.5.3
+smithyVersion=1.22.0
+smithyGradleVersion=0.6.0
 
 # kotlin
 kotlinVersion=1.5.31
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/CodegenVisitor.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/CodegenVisitor.kt
index f919cc13b..c841665d8 100644
--- a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/CodegenVisitor.kt
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/CodegenVisitor.kt
@@ -155,9 +155,9 @@ class CodegenVisitor(context: PluginContext) : ShapeVisitor.Default<Void>() {
 
     override fun structureShape(shape: StructureShape): Void? {
         writers.useShapeWriter(shape) { writer: SwiftWriter -> StructureGenerator(model, symbolProvider, writer, shape, settings, protocolGenerator?.serviceErrorProtocolSymbol).render() }
-        if (shape.hasTrait<SensitiveTrait>() || shape.members().any { it.hasTrait<SensitiveTrait>() }) {
+        if (shape.hasTrait<SensitiveTrait>() || shape.members().any { it.hasTrait<SensitiveTrait>() || model.expectShape(it.target).hasTrait<SensitiveTrait>() }) {
             writers.useShapeExtensionWriter(shape, "CustomDebugStringConvertible") { writer: SwiftWriter ->
-                CustomDebugStringConvertibleGenerator(symbolProvider, writer, shape).render()
+                CustomDebugStringConvertibleGenerator(symbolProvider, writer, shape, model).render()
             }
         }
         return null
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/CustomDebugStringConvertibleGenerator.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/CustomDebugStringConvertibleGenerator.kt
index 1b301a977..90ab94009 100644
--- a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/CustomDebugStringConvertibleGenerator.kt
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/CustomDebugStringConvertibleGenerator.kt
@@ -7,6 +7,7 @@ package software.amazon.smithy.swift.codegen.integration
 
 import software.amazon.smithy.codegen.core.Symbol
 import software.amazon.smithy.codegen.core.SymbolProvider
+import software.amazon.smithy.model.Model
 import software.amazon.smithy.model.shapes.MemberShape
 import software.amazon.smithy.model.shapes.StructureShape
 import software.amazon.smithy.model.traits.SensitiveTrait
@@ -18,7 +19,8 @@ import software.amazon.smithy.swift.codegen.model.toMemberNames
 class CustomDebugStringConvertibleGenerator(
     private val symbolProvider: SymbolProvider,
     private val writer: SwiftWriter,
-    private val shape: StructureShape
+    private val shape: StructureShape,
+    private val model: Model
 ) {
     companion object {
         const val REDACT_STRING = "CONTENT_REDACTED"
@@ -46,11 +48,11 @@ class CustomDebugStringConvertibleGenerator(
         val symbolName = structSymbol.name
         writer.writeInline("\"$symbolName(")
         val membersWithoutSensitiveTrait = membersSortedByName
-            .filterNot { it.hasTrait(SensitiveTrait::class.java) }
+            .filterNot { it.hasTrait<SensitiveTrait>() || model.expectShape(it.target).hasTrait<SensitiveTrait>() }
             .sortedBy { it.memberName }
             .toList()
         val membersWithSensitiveTrait = membersSortedByName
-            .filter { it.hasTrait(SensitiveTrait::class.java) }
+            .filter { it.hasTrait<SensitiveTrait>() || model.expectShape(it.target).hasTrait<SensitiveTrait>() }
             .sortedBy { it.memberName }
             .toList()
         for (member in membersWithoutSensitiveTrait) {
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/HttpProtocolUnitTestResponseGenerator.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/HttpProtocolUnitTestResponseGenerator.kt
index 3b3837b22..9d0b3ff08 100644
--- a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/HttpProtocolUnitTestResponseGenerator.kt
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/HttpProtocolUnitTestResponseGenerator.kt
@@ -58,25 +58,36 @@ open class HttpProtocolUnitTestResponseGenerator protected constructor(builder:
     }
 
     private fun renderBuildHttpResponseParams(test: HttpResponseTestCase) {
-        val params = mutableListOf<String>()
-        params.add("code: ${test.code}")
-        if (test.headers.isNotEmpty()) {
-            params.add(renderBuildHttpResponseHeaderParams(test))
-        }
-        test.body.ifPresent { body ->
-            if (body.isNotBlank() && body.isNotEmpty()) {
-                params.add("content: HttpBody.stream(ByteStream.from(data: \"\"\"\n${body.replace(".000", "")}\n\"\"\".data(using: .utf8)!))")
+        writer.write("code: \$L,", test.code)
+        renderExpectedHeaders(test)
+        test.body.ifPresentOrElse(
+            {
+                body ->
+                if (body.isNotBlank() && body.isNotEmpty()) {
+                    writer.write("content: HttpBody.stream(ByteStream.from(data: \"\"\"\n${body.replace(".000", "")}\n\"\"\".data(using: .utf8)!))")
+                } else {
+                    writer.write("content: HttpBody.empty")
+                }
+            },
+            {
+                writer.write("content: HttpBody.empty")
             }
-        }
-        writer.write(params.joinToString(",\n"))
+        )
     }
 
-    private fun renderBuildHttpResponseHeaderParams(test: HttpResponseTestCase): String {
-        var headers = mutableListOf<String>()
-        for (hdr in test.headers.entries) {
-            headers.add("    \"${hdr.key}\": \"${hdr.value}\"")
+    private fun renderExpectedHeaders(test: HttpResponseTestCase) {
+        if (test.headers.isNotEmpty()) {
+            writer.openBlock("headers: [")
+                .call {
+                    for ((idx, hdr) in test.headers.entries.withIndex()) {
+                        val suffix = if (idx < test.headers.size - 1) "," else ""
+                        writer.write("\$S: \$S$suffix", hdr.key, hdr.value)
+                    }
+                }
+                .closeBlock("],")
+        } else {
+            writer.write("headers: nil,")
         }
-        return "headers: [\n${headers.joinToString(",\n")}\n]"
     }
 
     protected fun needsResponseDecoder(test: HttpResponseTestCase): Boolean {
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/codingKeys/DefaultCodingKeysCustomizable.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/codingKeys/DefaultCodingKeysCustomizable.kt
new file mode 100644
index 000000000..55c16f864
--- /dev/null
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/codingKeys/DefaultCodingKeysCustomizable.kt
@@ -0,0 +1,14 @@
+package software.amazon.smithy.swift.codegen.integration.codingKeys
+
+import software.amazon.smithy.model.shapes.MemberShape
+import software.amazon.smithy.swift.codegen.SwiftWriter
+import software.amazon.smithy.swift.codegen.integration.ProtocolGenerator
+
+class DefaultCodingKeysCustomizable : CodingKeysCustomizable {
+    override fun shouldHandleMember(member: MemberShape): Boolean {
+        return false
+    }
+
+    override fun handleMember(ctx: ProtocolGenerator.GenerationContext, writer: SwiftWriter, member: MemberShape) {
+    }
+}
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/httpResponse/HttpResponseHeaders.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/httpResponse/HttpResponseHeaders.kt
index cca5adf4b..3f3c24e90 100644
--- a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/httpResponse/HttpResponseHeaders.kt
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/httpResponse/HttpResponseHeaders.kt
@@ -141,7 +141,7 @@ class HttpResponseHeaders(
                     if (memberTarget.isSetShape) {
                         memberValue = "${SwiftTypes.Set}(${memberName}HeaderValues)"
                     }
-                    writer.write("if let ${memberName}HeaderValues = $splitFnPrefix$splitFn(${memberName}HeaderValue) {")
+                    writer.write("if let ${memberName}HeaderValues = try $splitFnPrefix$splitFn(${memberName}HeaderValue) {")
                     writer.indent()
                     // render map function
                     val collectionMemberTargetShape = ctx.model.expectShape(memberTarget.member.target)
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/middlewares/providers/HttpHeaderProvider.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/middlewares/providers/HttpHeaderProvider.kt
index 279fa581f..0fec462d2 100644
--- a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/middlewares/providers/HttpHeaderProvider.kt
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/middlewares/providers/HttpHeaderProvider.kt
@@ -11,6 +11,7 @@ import software.amazon.smithy.model.knowledge.HttpBindingIndex
 import software.amazon.smithy.model.shapes.CollectionShape
 import software.amazon.smithy.model.shapes.MemberShape
 import software.amazon.smithy.model.shapes.OperationShape
+import software.amazon.smithy.model.shapes.TimestampShape
 import software.amazon.smithy.model.traits.TimestampFormatTrait
 import software.amazon.smithy.swift.codegen.ClientRuntimeTypes
 import software.amazon.smithy.swift.codegen.SwiftDependency
@@ -114,6 +115,8 @@ class HttpHeaderProvider(
                 writer.openBlock("if $memberName != ${member.defaultValue(ctx.symbolProvider)} {", "}") {
                     writer.write("items.add(Header(name: \"$paramName\", value: \$N($memberNameWithExtension)))", SwiftTypes.String)
                 }
+            } else if (inCollection && ctx.model.expectShape(member.target) !is TimestampShape) {
+                writer.write("items.add(Header(name: \"$paramName\", value: quoteHeaderValue(\$N($memberNameWithExtension))))", SwiftTypes.String)
             } else {
                 writer.write("items.add(Header(name: \"$paramName\", value: \$N($memberNameWithExtension)))", SwiftTypes.String)
             }
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/MemberShapeDecodeGenerator.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/MemberShapeDecodeGenerator.kt
index 13e79da03..2cbf7e380 100644
--- a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/MemberShapeDecodeGenerator.kt
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/MemberShapeDecodeGenerator.kt
@@ -123,9 +123,9 @@ abstract class MemberShapeDecodeGenerator(
         memberName: String,
         containerName: String,
         topLevelMember: MemberShape,
+        parentMember: Shape,
         level: Int = 0
     ) {
-        val isSparse = ctx.model.expectShape(topLevelMember.target).hasTrait<SparseTrait>()
         val symbolName = determineSymbolForShape(shape, true)
         val originalSymbol = ctx.symbolProvider.toSymbol(shape)
         val decodedMemberName = "${memberName.removeSurroundingBackticks()}Decoded$level"
@@ -153,15 +153,15 @@ abstract class MemberShapeDecodeGenerator(
             writer.write("var \$L:\$T = nil", decodedMemberName, originalSymbol)
             writer.openBlock("if let \$L = \$L {", "}", listContainerName, listContainerName) {
                 writer.write("\$L = \$N()", decodedMemberName, originalSymbol)
-                renderDecodeListTarget(nestedTarget, decodedMemberName, listContainerName, insertMethod, topLevelMember, shape.isSetShape, level)
+                renderDecodeListTarget(nestedTarget, decodedMemberName, listContainerName, insertMethod, topLevelMember, shape, level)
             }
             renderAssigningDecodedMember(topLevelMember, decodedMemberName)
         } else {
             writer.openBlock("if let \$L = \$L {", "}", memberName, memberName) {
                 val previousDecodedMemberName = "${memberName.removeSurroundingBackticks()}Decoded${level - 1}"
-                val symbolName = determineSymbolForShape(shape, isSparse)
+                val symbolName = determineSymbolForShape(shape, false)
                 writer.write("\$L = \$L()", previousDecodedMemberName, symbolName)
-                renderDecodeListTarget(nestedTarget, containerName, memberName, insertMethod, topLevelMember, shape.isSetShape, level)
+                renderDecodeListTarget(nestedTarget, containerName, memberName, insertMethod, topLevelMember, shape, level)
             }
         }
     }
@@ -175,9 +175,8 @@ abstract class MemberShapeDecodeGenerator(
         writer.write("\$L = \$L", topLevelMemberName, decodedMemberName)
     }
 
-    private fun renderDecodeListTarget(shape: Shape, decodedMemberName: String, collectionName: String, insertMethod: String, topLevelMember: MemberShape, isSetShape: Boolean, level: Int = 0) {
-        val topLevelShape = ctx.model.expectShape(topLevelMember.target)
-        val isSparse = topLevelShape.hasTrait<SparseTrait>()
+    private fun renderDecodeListTarget(shape: Shape, decodedMemberName: String, collectionName: String, insertMethod: String, topLevelMember: MemberShape, parentMember: Shape, level: Int = 0) {
+        val isSparse = parentMember.hasTrait<SparseTrait>()
         val iteratorName = "${shape.type.name.lowercase()}$level"
         val symbolName = determineSymbolForShape(shape, false)
         val terminator = "?"
@@ -190,7 +189,7 @@ abstract class MemberShapeDecodeGenerator(
                         .orElse(defaultTimestampFormat)
 
                     if (tsFormat == TimestampFormatTrait.Format.EPOCH_SECONDS) { // if decoding a double decode as normal from [[Date]].self
-                        if (!isSparse && !isSetShape) {
+                        if (!isSparse) {
                             writer.openBlock("if let $iteratorName = $iteratorName {", "}") {
                                 writer.write("${decodedMemberName}$terminator.$insertMethod($iteratorName)")
                             }
@@ -210,7 +209,7 @@ abstract class MemberShapeDecodeGenerator(
                 is CollectionShape -> {
                     val nestedDecodedMemberName = "${iteratorName}Decoded$level"
                     writer.write("var \$L: \$L? = nil", nestedDecodedMemberName, symbolName)
-                    renderDecodeListMember(shape, iteratorName, nestedDecodedMemberName, topLevelMember, level + 1)
+                    renderDecodeListMember(shape, iteratorName, nestedDecodedMemberName, topLevelMember, parentMember, level + 1)
                     writer.openBlock("if let $nestedDecodedMemberName = $nestedDecodedMemberName {", "}") {
                         writer.write("$decodedMemberName$terminator.$insertMethod($nestedDecodedMemberName)")
                     }
@@ -224,7 +223,7 @@ abstract class MemberShapeDecodeGenerator(
                     }
                 }
                 else -> {
-                    if (!isSparse && !isSetShape) {
+                    if (!isSparse) {
                         writer.openBlock("if let $iteratorName = $iteratorName {", "}") {
                             writer.write("${decodedMemberName}$terminator.$insertMethod($iteratorName)")
                         }
@@ -289,7 +288,7 @@ abstract class MemberShapeDecodeGenerator(
                 is CollectionShape -> {
                     val nestedDecodedMemberName = "${valueIterator}Decoded$level"
                     writer.write("var \$L: \$L? = nil", nestedDecodedMemberName, symbolName)
-                    renderDecodeListMember(valueTargetShape, valueIterator, nestedDecodedMemberName, topLevelMember, level + 1)
+                    renderDecodeListMember(valueTargetShape, valueIterator, nestedDecodedMemberName, topLevelMember, valueTargetShape.member, level + 1)
                     writer.write("$decodedMemberName?[key$level] = $nestedDecodedMemberName")
                 }
                 is MapShape -> {
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/StructDecodeGenerator.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/StructDecodeGenerator.kt
index 75119efed..b5cc06a22 100644
--- a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/StructDecodeGenerator.kt
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/StructDecodeGenerator.kt
@@ -57,7 +57,7 @@ class StructDecodeGenerator(
                     val target = ctx.model.expectShape(member.target)
                     val memberNames = ctx.symbolProvider.toMemberNames(member)
                     when (target) {
-                        is CollectionShape -> renderDecodeListMember(target, memberNames.second, containerName, member)
+                        is CollectionShape -> renderDecodeListMember(target, memberNames.second, containerName, member, parentMember = member)
                         is MapShape -> renderDecodeMapMember(target, memberNames.second, containerName, member)
                         is TimestampShape -> renderDecodeForTimestamp(ctx, target, member, containerName)
                         else -> writeDecodeForPrimitive(target, member, containerName)
diff --git a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/UnionDecodeGenerator.kt b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/UnionDecodeGenerator.kt
index 07be84ce6..7216840a0 100644
--- a/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/UnionDecodeGenerator.kt
+++ b/smithy-swift-codegen/src/main/kotlin/software/amazon/smithy/swift/codegen/integration/serde/json/UnionDecodeGenerator.kt
@@ -27,7 +27,7 @@ class UnionDecodeGenerator(
                 val target = ctx.model.expectShape(member.target)
                 val memberName = ctx.symbolProvider.toMemberName(member)
                 when (target) {
-                    is CollectionShape -> renderDecodeListMember(target, memberName, containerName, member)
+                    is CollectionShape -> renderDecodeListMember(target, memberName, containerName, member, member)
                     is MapShape -> renderDecodeMapMember(target, memberName, containerName, member)
                     is TimestampShape -> renderDecodeForTimestamp(ctx, target, member, containerName)
                     else -> writeDecodeForPrimitive(target, member, containerName)
diff --git a/smithy-swift-codegen/src/test/kotlin/HttpProtocolUnitTestResponseGeneratorTests.kt b/smithy-swift-codegen/src/test/kotlin/HttpProtocolUnitTestResponseGeneratorTests.kt
index 3e5fa2fd4..212932c39 100644
--- a/smithy-swift-codegen/src/test/kotlin/HttpProtocolUnitTestResponseGeneratorTests.kt
+++ b/smithy-swift-codegen/src/test/kotlin/HttpProtocolUnitTestResponseGeneratorTests.kt
@@ -95,7 +95,8 @@ open class HttpProtocolUnitTestResponseGeneratorTests {
                 "X-Foo": "Foo",
                 "X-Foo-abc": "ABC",
                 "X-Foo-xyz": "XYZ"
-            ]
+            ],
+            content: HttpBody.empty
         ) else {
             XCTFail("Something is wrong with the created http response")
             return
@@ -130,7 +131,8 @@ open class HttpProtocolUnitTestResponseGeneratorTests {
             code: 200,
             headers: [
                 "X-Foo": "Foo"
-            ]
+            ],
+            content: HttpBody.empty
         ) else {
             XCTFail("Something is wrong with the created http response")
             return
diff --git a/smithy-swift-codegen/src/test/kotlin/IsolatedHttpProtocolUnitTestRequestGeneratorTests.kt b/smithy-swift-codegen/src/test/kotlin/IsolatedHttpProtocolUnitTestRequestGeneratorTests.kt
index a6a868d8d..5bd06edb5 100644
--- a/smithy-swift-codegen/src/test/kotlin/IsolatedHttpProtocolUnitTestRequestGeneratorTests.kt
+++ b/smithy-swift-codegen/src/test/kotlin/IsolatedHttpProtocolUnitTestRequestGeneratorTests.kt
@@ -114,7 +114,8 @@ class InputAndOutputWithHeadersResponseTest: HttpResponseTestBase {
             headers: [
                 "X-Double": "NaN",
                 "X-Float": "NaN"
-            ]
+            ],
+            content: HttpBody.empty
         ) else {
             XCTFail("Something is wrong with the created http response")
             return
diff --git a/smithy-swift-codegen/src/test/resources/sensitive-trait-test.smithy b/smithy-swift-codegen/src/test/resources/sensitive-trait-test.smithy
index 7b2d81b16..54a98384e 100644
--- a/smithy-swift-codegen/src/test/resources/sensitive-trait-test.smithy
+++ b/smithy-swift-codegen/src/test/resources/sensitive-trait-test.smithy
@@ -29,8 +29,7 @@ operation SensitiveTraitTestRequest {
 }
 
 structure SensitiveTraitInRequestInput {
-    @sensitive
-    baz: String,
+    baz: SensitiveString,
     foo: String
 }
 
@@ -46,10 +45,10 @@ structure SensitiveTraitTestRequestInput {
 }
 
 structure SensitiveTraitTestRequestOutput {
-   @sensitive
-   foo: String,
-   @sensitive
-   bar: String,
-   @sensitive
-   baz: String
-}
\ No newline at end of file
+   foo: SensitiveString,
+   bar: SensitiveString,
+   baz: SensitiveString
+}
+
+@sensitive
+string SensitiveString
\ No newline at end of file