diff --git a/.github/workflows/dotnetcore.yml b/.github/workflows/dotnetcore.yml
index 7685e5f1..91c52508 100644
--- a/.github/workflows/dotnetcore.yml
+++ b/.github/workflows/dotnetcore.yml
@@ -5,8 +5,6 @@ on:
     branches:
       - master
   pull_request:
-    branches:
-      - master
 
 jobs:
   build:
diff --git a/global.json b/global.json
index badcd443..b24aad66 100644
--- a/global.json
+++ b/global.json
@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "10.0.103",
-    "rollForward": "minor"
+    "version": "10.0.100",
+    "rollForward": "latestPatch"
   }
 }
diff --git a/src/SwaggerProvider.Runtime/RuntimeHelpers.fs b/src/SwaggerProvider.Runtime/RuntimeHelpers.fs
index 05c23962..9ee42e10 100644
--- a/src/SwaggerProvider.Runtime/RuntimeHelpers.fs
+++ b/src/SwaggerProvider.Runtime/RuntimeHelpers.fs
@@ -85,38 +85,42 @@ module RuntimeHelpers =
         | _ -> obj.ToString()
 
     let toQueryParams (name: string) (obj: obj) (client: Swagger.ProvidedApiClientBase) =
-        match obj with
-        | :? array<byte> as xs -> [ name, (client.Serialize xs).Trim('\"') ] // TODO: Need to verify how servers parse byte[] from query string
-        | :? array<bool> as xs -> xs |> toStrArray name
-        | :? array<int32> as xs -> xs |> toStrArray name
-        | :? array<int64> as xs -> xs |> toStrArray name
-        | :? array<float32> as xs -> xs |> toStrArray name
-        | :? array<double> as xs -> xs |> toStrArray name
-        | :? array<string> as xs -> xs |> toStrArray name
-        | :? array<DateTime> as xs -> xs |> toStrArrayDateTime name
-        | :? array<DateTimeOffset> as xs -> xs |> toStrArrayDateTimeOffset name
-        | :? array<Guid> as xs -> xs |> toStrArray name
-        | :? array<Option<bool>> as xs -> xs |> toStrArrayOpt name
-        | :? array<Option<int32>> as xs -> xs |> toStrArrayOpt name
-        | :? array<Option<int64>> as xs -> xs |> toStrArrayOpt name
-        | :? array<Option<float32>> as xs -> xs |> toStrArrayOpt name
-        | :? array<Option<double>> as xs -> xs |> toStrArrayOpt name
-        | :? array<Option<string>> as xs -> xs |> toStrArrayOpt name
-        | :? array<Option<DateTime>> as xs -> xs |> toStrArrayDateTimeOpt name
-        | :? array<Option<DateTimeOffset>> as xs -> xs |> toStrArrayDateTimeOffsetOpt name
-        | :? array<Option<Guid>> as xs -> xs |> toStrArray name
-        | :? Option<bool> as x -> x |> toStrOpt name
-        | :? Option<int32> as x -> x |> toStrOpt name
-        | :? Option<int64> as x -> x |> toStrOpt name
-        | :? Option<float32> as x -> x |> toStrOpt name
-        | :? Option<double> as x -> x |> toStrOpt name
-        | :? Option<string> as x -> x |> toStrOpt name
-        | :? Option<DateTime> as x -> x |> toStrDateTimeOpt name
-        | :? Option<DateTimeOffset> as x -> x |> toStrDateTimeOffsetOpt name
-        | :? DateTime as x -> [ name, x.ToString("O") ]
-        | :? DateTimeOffset as x -> [ name, x.ToString("O") ]
-        | :? Option<Guid> as x -> x |> toStrOpt name
-        | _ -> [ name, (if isNull obj then null else obj.ToString()) ]
+        if isNull obj then
+            []
+        else
+
+            match obj with
+            | :? array<byte> as xs -> [ name, (client.Serialize xs).Trim('\"') ] // TODO: Need to verify how servers parse byte[] from query string
+            | :? array<bool> as xs -> xs |> toStrArray name
+            | :? array<int32> as xs -> xs |> toStrArray name
+            | :? array<int64> as xs -> xs |> toStrArray name
+            | :? array<float32> as xs -> xs |> toStrArray name
+            | :? array<double> as xs -> xs |> toStrArray name
+            | :? array<string> as xs -> xs |> toStrArray name
+            | :? array<DateTime> as xs -> xs |> toStrArrayDateTime name
+            | :? array<DateTimeOffset> as xs -> xs |> toStrArrayDateTimeOffset name
+            | :? array<Guid> as xs -> xs |> toStrArray name
+            | :? array<Option<bool>> as xs -> xs |> toStrArrayOpt name
+            | :? array<Option<int32>> as xs -> xs |> toStrArrayOpt name
+            | :? array<Option<int64>> as xs -> xs |> toStrArrayOpt name
+            | :? array<Option<float32>> as xs -> xs |> toStrArrayOpt name
+            | :? array<Option<double>> as xs -> xs |> toStrArrayOpt name
+            | :? array<Option<string>> as xs -> xs |> toStrArrayOpt name
+            | :? array<Option<DateTime>> as xs -> xs |> toStrArrayDateTimeOpt name
+            | :? array<Option<DateTimeOffset>> as xs -> xs |> toStrArrayDateTimeOffsetOpt name
+            | :? array<Option<Guid>> as xs -> xs |> toStrArray name
+            | :? Option<bool> as x -> x |> toStrOpt name
+            | :? Option<int32> as x -> x |> toStrOpt name
+            | :? Option<int64> as x -> x |> toStrOpt name
+            | :? Option<float32> as x -> x |> toStrOpt name
+            | :? Option<double> as x -> x |> toStrOpt name
+            | :? Option<string> as x -> x |> toStrOpt name
+            | :? Option<DateTime> as x -> x |> toStrDateTimeOpt name
+            | :? Option<DateTimeOffset> as x -> x |> toStrDateTimeOffsetOpt name
+            | :? DateTime as x -> [ name, x.ToString("O") ]
+            | :? DateTimeOffset as x -> [ name, x.ToString("O") ]
+            | :? Option<Guid> as x -> x |> toStrOpt name
+            | _ -> [ name, obj.ToString() ]
 
     let getPropertyNameAttribute name =
         { new Reflection.CustomAttributeData() with
@@ -145,6 +149,22 @@ module RuntimeHelpers =
             content
         | _ -> failwith $"Unexpected parameter type {boxedStream.GetType().Name} instead of IO.Stream"
 
+    // Unwraps F# option values: returns the inner value for Some, null for None.
+    // This prevents `Some(value)` from being sent as-is in form data.
+    let private unwrapFSharpOption(value: obj) : obj =
+        if isNull value then
+            null
+        else
+            let ty = value.GetType()
+
+            if
+                ty.IsGenericType
+                && ty.GetGenericTypeDefinition() = typedefof<option<_>>
+            then
+                ty.GetProperty("Value").GetValue(value)
+            else
+                value
+
     let getPropertyValues(object: obj) =
         if isNull object then
             Seq.empty
@@ -162,6 +182,7 @@ module RuntimeHelpers =
                     | _ -> prop.Name
 
                 prop.GetValue(object)
+                |> unwrapFSharpOption
                 |> Option.ofObj
                 |> Option.map(fun value -> (name, value)))
 
diff --git a/tests/SwaggerProvider.Tests/RuntimeHelpersTests.fs b/tests/SwaggerProvider.Tests/RuntimeHelpersTests.fs
new file mode 100644
index 00000000..f6a9a3b6
--- /dev/null
+++ b/tests/SwaggerProvider.Tests/RuntimeHelpersTests.fs
@@ -0,0 +1,338 @@
+namespace SwaggerProvider.Tests.RuntimeHelpersTests
+
+open System
+open System.IO
+open System.Net.Http
+open System.Text.Json
+open Xunit
+open FsUnitTyped
+open Swagger.Internal.RuntimeHelpers
+
+/// Unit tests for RuntimeHelpers — the runtime parameter serialization and HTTP utilities.
+/// These functions are used by every generated API client but previously had no dedicated tests.
+module ToParamTests =
+
+    [<Fact>]
+    let ``toParam formats DateTime as ISO 8601 round-trip``() =
+        let dt = DateTime(2024, 6, 15, 10, 30, 0, DateTimeKind.Utc)
+        let result = toParam(box dt)
+        result |> shouldEqual(dt.ToString("O"))
+
+    [<Fact>]
+    let ``toParam formats DateTimeOffset as ISO 8601 round-trip``() =
+        let dto = DateTimeOffset(2024, 6, 15, 10, 30, 0, TimeSpan.FromHours(2.0))
+        let result = toParam(box dto)
+        result |> shouldEqual(dto.ToString("O"))
+
+    [<Fact>]
+    let ``toParam returns null for null input``() =
+        let result = toParam null
+        result |> shouldEqual null
+
+    [<Fact>]
+    let ``toParam uses ToString for integers``() =
+        let result = toParam(box 42)
+        result |> shouldEqual "42"
+
+    [<Fact>]
+    let ``toParam uses ToString for strings``() =
+        let result = toParam(box "hello world")
+        result |> shouldEqual "hello world"
+
+    [<Fact>]
+    let ``toParam uses ToString for Guid``() =
+        let g = Guid("d3b07384-d9a2-4e3f-9a4b-1234567890ab")
+        let result = toParam(box g)
+        result |> shouldEqual(g.ToString())
+
+
+module ToQueryParamsTests =
+
+    let private stubClient =
+        { new Swagger.ProvidedApiClientBase(null, JsonSerializerOptions()) with
+            override _.Serialize(v) =
+                JsonSerializer.Serialize v
+
+            override _.Deserialize(s, t) =
+                JsonSerializer.Deserialize(s, t) }
+
+    [<Fact>]
+    let ``toQueryParams handles string array``() =
+        let result = toQueryParams "tag" (box [| "alpha"; "beta"; "gamma" |]) stubClient
+
+        result
+        |> shouldEqual [ ("tag", "alpha"); ("tag", "beta"); ("tag", "gamma") ]
+
+    [<Fact>]
+    let ``toQueryParams handles int32 array``() =
+        let result = toQueryParams "id" (box [| 1; 2; 3 |]) stubClient
+        result |> shouldEqual [ ("id", "1"); ("id", "2"); ("id", "3") ]
+
+    [<Fact>]
+    let ``toQueryParams handles int64 array``() =
+        let result = toQueryParams "id" (box [| 1L; 2L; 3L |]) stubClient
+        result |> shouldEqual [ ("id", "1"); ("id", "2"); ("id", "3") ]
+
+    [<Fact>]
+    let ``toQueryParams handles bool array``() =
+        let result = toQueryParams "flag" (box [| true; false |]) stubClient
+        result |> shouldEqual [ ("flag", "True"); ("flag", "False") ]
+
+    [<Fact>]
+    let ``toQueryParams formats DateTime array as ISO 8601``() =
+        let dt = DateTime(2024, 1, 15, 12, 0, 0, DateTimeKind.Utc)
+        let result = toQueryParams "d" (box [| dt |]) stubClient
+        result |> shouldHaveLength 1
+        fst result[0] |> shouldEqual "d"
+        snd result[0] |> shouldEqual(dt.ToString("O"))
+
+    [<Fact>]
+    let ``toQueryParams formats DateTimeOffset array as ISO 8601``() =
+        let dto = DateTimeOffset(2024, 1, 15, 12, 0, 0, TimeSpan.Zero)
+        let result = toQueryParams "d" (box [| dto |]) stubClient
+        result |> shouldHaveLength 1
+        snd result[0] |> shouldEqual(dto.ToString("O"))
+
+    [<Fact>]
+    let ``toQueryParams handles Option<string> Some``() =
+        let result = toQueryParams "q" (box(Some "hello")) stubClient
+        result |> shouldEqual [ ("q", "hello") ]
+
+    [<Fact>]
+    let ``toQueryParams handles Option<string> None``() =
+        let result = toQueryParams "q" (box(Option<string>.None)) stubClient
+        result |> shouldEqual []
+
+    [<Fact>]
+    let ``toQueryParams handles Option<int32> Some``() =
+        let result = toQueryParams "n" (box(Some 99)) stubClient
+        result |> shouldEqual [ ("n", "99") ]
+
+    [<Fact>]
+    let ``toQueryParams handles Option<int32> None``() =
+        let result = toQueryParams "n" (box(Option<int>.None)) stubClient
+        result |> shouldEqual []
+
+    [<Fact>]
+    let ``toQueryParams handles Option<DateTime> Some as ISO 8601``() =
+        let dt = DateTime(2024, 3, 1, 0, 0, 0, DateTimeKind.Utc)
+        let result = toQueryParams "d" (box(Some dt)) stubClient
+        result |> shouldHaveLength 1
+        snd result[0] |> shouldEqual(dt.ToString("O"))
+
+    [<Fact>]
+    let ``toQueryParams handles Option<DateTime> None``() =
+        let result = toQueryParams "d" (box(Option<DateTime>.None)) stubClient
+        result |> shouldEqual []
+
+    [<Fact>]
+    let ``toQueryParams handles Option<Guid> Some``() =
+        let g = Guid.NewGuid()
+        let result = toQueryParams "id" (box(Some g)) stubClient
+        result |> shouldEqual [ ("id", g.ToString()) ]
+
+    [<Fact>]
+    let ``toQueryParams handles plain DateTime as ISO 8601``() =
+        let dt = DateTime(2024, 6, 1, 8, 0, 0, DateTimeKind.Utc)
+        let result = toQueryParams "dt" (box dt) stubClient
+        result |> shouldHaveLength 1
+        snd result[0] |> shouldEqual(dt.ToString("O"))
+
+    [<Fact>]
+    let ``toQueryParams handles plain DateTimeOffset as ISO 8601``() =
+        let dto = DateTimeOffset(2024, 6, 1, 8, 0, 0, TimeSpan.FromHours(-5.0))
+        let result = toQueryParams "dto" (box dto) stubClient
+        result |> shouldHaveLength 1
+        snd result[0] |> shouldEqual(dto.ToString("O"))
+
+    [<Fact>]
+    let ``toQueryParams handles plain string``() =
+        let result = toQueryParams "q" (box "search term") stubClient
+        result |> shouldEqual [ ("q", "search term") ]
+
+    [<Fact>]
+    let ``toQueryParams returns empty list for null input (treated as Option None)``() =
+        // In F#, None for any option type is compiled as null at the .NET level,
+        // so a null obj is treated as Option None and returns an empty list.
+        let result = toQueryParams "q" null stubClient
+        result |> shouldEqual []
+
+    [<Fact>]
+    let ``toQueryParams skips None items in Option array``() =
+        let values: Option<int>[] = [| Some 1; None; Some 3 |]
+        let result = toQueryParams "n" (box values) stubClient
+        result |> shouldEqual [ ("n", "1"); ("n", "3") ]
+
+    [<Fact>]
+    let ``toQueryParams handles Guid array``() =
+        let g1 = Guid("aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa")
+        let g2 = Guid("bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb")
+        let result = toQueryParams "id" (box [| g1; g2 |]) stubClient
+        result |> shouldEqual [ ("id", g1.ToString()); ("id", g2.ToString()) ]
+
+    [<Fact>]
+    let ``toQueryParams handles float32 array``() =
+        let result = toQueryParams "v" (box [| 1.5f; 2.5f |]) stubClient
+        result |> shouldEqual [ ("v", "1.5"); ("v", "2.5") ]
+
+    [<Fact>]
+    let ``toQueryParams handles double array``() =
+        let result = toQueryParams "v" (box [| 1.5; 2.5 |]) stubClient
+        result |> shouldEqual [ ("v", "1.5"); ("v", "2.5") ]
+
+    [<Fact>]
+    let ``toQueryParams handles byte array as base64``() =
+        // byte[] is serialized via client.Serialize (JSON base64) with surrounding quotes trimmed
+        let bytes = [| 72uy; 101uy; 108uy; 108uy; 111uy |] // "Hello" in ASCII
+        let expected = (JsonSerializer.Serialize bytes).Trim('"')
+        let result = toQueryParams "data" (box bytes) stubClient
+        result |> shouldEqual [ ("data", expected) ]
+
+    [<Fact>]
+    let ``toQueryParams skips None items in Option<string> array``() =
+        let values: Option<string>[] = [| Some "a"; None; Some "c" |]
+        let result = toQueryParams "q" (box values) stubClient
+        result |> shouldEqual [ ("q", "a"); ("q", "c") ]
+
+    [<Fact>]
+    let ``toQueryParams skips None items in Option<float32> array``() =
+        let values: Option<float32>[] = [| Some 1.5f; None; Some 3.5f |]
+        let result = toQueryParams "v" (box values) stubClient
+        result |> shouldEqual [ ("v", "1.5"); ("v", "3.5") ]
+
+    [<Fact>]
+    let ``toQueryParams skips None items in Option<double> array``() =
+        let values: Option<double>[] = [| Some 1.5; None; Some 3.5 |]
+        let result = toQueryParams "v" (box values) stubClient
+        result |> shouldEqual [ ("v", "1.5"); ("v", "3.5") ]
+
+
+module CombineUrlTests =
+
+    [<Fact>]
+    let ``combineUrl joins paths without extra slashes``() =
+        combineUrl "http://example.com/api" "v1/users"
+        |> shouldEqual "http://example.com/api/v1/users"
+
+    [<Fact>]
+    let ``combineUrl trims trailing slash from left``() =
+        combineUrl "http://example.com/api/" "v1/users"
+        |> shouldEqual "http://example.com/api/v1/users"
+
+    [<Fact>]
+    let ``combineUrl trims leading slash from right``() =
+        combineUrl "http://example.com/api" "/v1/users"
+        |> shouldEqual "http://example.com/api/v1/users"
+
+    [<Fact>]
+    let ``combineUrl trims both slashes``() =
+        combineUrl "http://example.com/api/" "/v1/users"
+        |> shouldEqual "http://example.com/api/v1/users"
+
+    [<Fact>]
+    let ``combineUrl works with empty path segment``() =
+        combineUrl "http://example.com" ""
+        |> shouldEqual "http://example.com/"
+
+
+module CreateHttpRequestTests =
+
+    [<Fact>]
+    let ``createHttpRequest creates GET request``() =
+        use req = createHttpRequest "GET" "v1/users" []
+        req.Method |> shouldEqual HttpMethod.Get
+
+    [<Fact>]
+    let ``createHttpRequest creates POST request``() =
+        use req = createHttpRequest "POST" "v1/users" []
+        req.Method |> shouldEqual HttpMethod.Post
+
+    [<Fact>]
+    let ``createHttpRequest creates DELETE request``() =
+        use req = createHttpRequest "DELETE" "v1/users/42" []
+        req.Method |> shouldEqual HttpMethod.Delete
+
+    [<Fact>]
+    let ``createHttpRequest is case-insensitive for method``() =
+        use req = createHttpRequest "get" "v1/users" []
+        req.Method |> shouldEqual HttpMethod.Get
+
+    [<Fact>]
+    let ``createHttpRequest appends query parameters``() =
+        use req = createHttpRequest "GET" "v1/users" [ ("page", "2"); ("size", "10") ]
+        let uri = req.RequestUri.ToString()
+        uri |> shouldContainText "page=2"
+        uri |> shouldContainText "size=10"
+
+    [<Fact>]
+    let ``createHttpRequest skips null query parameter values``() =
+        use req = createHttpRequest "GET" "v1/users" [ ("q", null) ]
+        let uri = req.RequestUri.ToString()
+        uri |> shouldNotContainText "q="
+
+    [<Fact>]
+    let ``createHttpRequest includes path in request URI``() =
+        use req = createHttpRequest "GET" "v1/pets/42" []
+        req.RequestUri.ToString() |> shouldContainText "v1/pets/42"
+
+
+module FillHeadersTests =
+
+    [<Fact>]
+    let ``fillHeaders adds standard headers``() =
+        use req = new HttpRequestMessage(HttpMethod.Get, "http://example.com/")
+        fillHeaders req [ ("Accept", "application/json"); ("X-Api-Key", "secret") ]
+        req.Headers.Contains("Accept") |> shouldEqual true
+        req.Headers.Contains("X-Api-Key") |> shouldEqual true
+
+    [<Fact>]
+    let ``fillHeaders skips null-value headers``() =
+        use req = new HttpRequestMessage(HttpMethod.Get, "http://example.com/")
+        fillHeaders req [ ("X-Missing", null) ]
+        req.Headers.Contains("X-Missing") |> shouldEqual false
+
+    [<Fact>]
+    let ``fillHeaders silently ignores Content-Type header``() =
+        // Content-Type must be set on HttpContent, not on the request; this should not throw
+        use req = new HttpRequestMessage(HttpMethod.Get, "http://example.com/")
+        // Should not raise an exception even though Content-Type cannot be added to request headers
+        fillHeaders req [ ("Content-Type", "application/json") ]
+
+
+module ToContentTests =
+
+    [<Fact>]
+    let ``toStringContent returns JSON content type``() =
+        use c = toStringContent "{\"key\":\"value\"}"
+        c.Headers.ContentType.MediaType |> shouldEqual "application/json"
+
+    [<Fact>]
+    let ``toStringContent preserves the body``() =
+        let body = "{\"name\":\"Alice\"}"
+        use c = toStringContent body
+        let text = c.ReadAsStringAsync() |> Async.AwaitTask |> Async.RunSynchronously
+        text |> shouldEqual body
+
+    [<Fact>]
+    let ``toTextContent returns text/plain content type``() =
+        use c = toTextContent "hello"
+        c.Headers.ContentType.MediaType |> shouldEqual "text/plain"
+
+    [<Fact>]
+    let ``toStreamContent sets provided content type``() =
+        use stream = new MemoryStream([| 1uy; 2uy; 3uy |])
+        use c = toStreamContent(box stream, "application/octet-stream")
+
+        c.Headers.ContentType.MediaType
+        |> shouldEqual "application/octet-stream"
+
+    [<Fact>]
+    let ``toStreamContent omits content type when empty``() =
+        use stream = new MemoryStream([| 1uy; 2uy |])
+        use c = toStreamContent(box stream, "")
+        c.Headers.ContentType |> shouldEqual null
+
+    [<Fact>]
+    let ``toStreamContent throws for non-stream input``() =
+        Assert.Throws<Exception>(fun () -> toStreamContent(box "not a stream", "application/json") |> ignore)
+        |> ignore
diff --git a/tests/SwaggerProvider.Tests/SwaggerProvider.Tests.fsproj b/tests/SwaggerProvider.Tests/SwaggerProvider.Tests.fsproj
index d2c7357e..c69a40be 100644
--- a/tests/SwaggerProvider.Tests/SwaggerProvider.Tests.fsproj
+++ b/tests/SwaggerProvider.Tests/SwaggerProvider.Tests.fsproj
@@ -18,6 +18,7 @@
     <Compile Include="Schema.Parser.Tests.fs" />
     <Compile Include="PathResolutionTests.fs" />
     <Compile Include="SsrfSecurityTests.fs" />
+    <Compile Include="RuntimeHelpersTests.fs" />
     <None Include="paket.references" />
     <ProjectReference Include="..\..\src\SwaggerProvider.DesignTime\SwaggerProvider.DesignTime.fsproj" />
   </ItemGroup>