Add runtime_instructions system message section to all SDKs

docs/getting-started.md

@@ -1909,7 +1909,7 @@ const session = await client.createSession({
 });
 ```
 
-Available section IDs: `identity`, `tone`, `tool_efficiency`, `environment_context`, `code_change_rules`, `guidelines`, `safety`, `tool_instructions`, `custom_instructions`, `last_instructions`.
+Available section IDs: `identity`, `tone`, `tool_efficiency`, `environment_context`, `code_change_rules`, `guidelines`, `safety`, `tool_instructions`, `custom_instructions`, `runtime_instructions`, `last_instructions`.
 
 Each override supports four actions: `replace`, `remove`, `append`, and `prepend`. Unknown section IDs are handled gracefully—content is appended to additional instructions and a warning is emitted; `remove` on unknown sections is silently ignored.
 

dotnet/README.md

@@ -1,4 +1,4 @@
-# Copilot SDK
+# Copilot SDK
 
 SDK for programmatic control of GitHub Copilot CLI.
 
@@ -627,18 +627,18 @@ var session = await client.CreateSessionAsync(new SessionConfig
     SystemMessage = new SystemMessageConfig
     {
         Mode = SystemMessageMode.Customize,
-        Sections = new Dictionary<string, SectionOverride>
+        Sections = new Dictionary<SystemMessageSection, SectionOverride>
         {
-            [SystemPromptSections.Tone] = new() { Action = SectionOverrideAction.Replace, Content = "Respond in a warm, professional tone. Be thorough in explanations." },
-            [SystemPromptSections.CodeChangeRules] = new() { Action = SectionOverrideAction.Remove },
-            [SystemPromptSections.Guidelines] = new() { Action = SectionOverrideAction.Append, Content = "\n* Always cite data sources" },
+            [SystemMessageSection.Tone] = new() { Action = SectionOverrideAction.Replace, Content = "Respond in a warm, professional tone. Be thorough in explanations." },
+            [SystemMessageSection.CodeChangeRules] = new() { Action = SectionOverrideAction.Remove },
+            [SystemMessageSection.Guidelines] = new() { Action = SectionOverrideAction.Append, Content = "\n* Always cite data sources" },
         },
         Content = "Focus on financial analysis and reporting."
     }
 });
 ```
 
-Available section IDs are defined as constants on `SystemPromptSections`: `Identity`, `Tone`, `ToolEfficiency`, `EnvironmentContext`, `CodeChangeRules`, `Guidelines`, `Safety`, `ToolInstructions`, `CustomInstructions`, `LastInstructions`.
+Available section IDs are defined as static properties on the `SystemMessageSection` struct: `Identity`, `Tone`, `ToolEfficiency`, `EnvironmentContext`, `CodeChangeRules`, `Guidelines`, `Safety`, `ToolInstructions`, `CustomInstructions`, `RuntimeInstructions`, `LastInstructions`.
 
 Each section override supports four actions: `Replace`, `Remove`, `Append`, and `Prepend`. Unknown section IDs are handled gracefully: content is appended to additional instructions, and `Remove` overrides are silently ignored.
 

dotnet/src/Client.cs

@@ -1,4 +1,4 @@
-/*---------------------------------------------------------------------------------------------
+/*---------------------------------------------------------------------------------------------
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *--------------------------------------------------------------------------------------------*/
 
@@ -464,13 +464,13 @@ private static (SystemMessageConfig? wireConfig, Dictionary<string, Func<string,
         }
 
         var callbacks = new Dictionary<string, Func<string, Task<string>>>();
-        var wireSections = new Dictionary<string, SectionOverride>();
+        var wireSections = new Dictionary<SystemMessageSection, SectionOverride>();
 
         foreach (var (sectionId, sectionOverride) in systemMessage.Sections)
         {
             if (sectionOverride.Transform != null)
             {
-                callbacks[sectionId] = sectionOverride.Transform;
+                callbacks[sectionId.Value] = sectionOverride.Transform;
                 wireSections[sectionId] = new SectionOverride { Action = SectionOverrideAction.Transform };
             }
             else

dotnet/src/Types.cs

@@ -1748,7 +1748,7 @@ public enum SystemMessageMode
 }
 
 /// <summary>
-/// Specifies the operation to perform on a system prompt section.
+/// Specifies the operation to perform on a system message section.
 /// </summary>
 [JsonConverter(typeof(JsonStringEnumConverter<SectionOverrideAction>))]
 public enum SectionOverrideAction
@@ -1771,7 +1771,7 @@ public enum SectionOverrideAction
 }
 
 /// <summary>
-/// Override operation for a single system prompt section.
+/// Override operation for a single system message section.
 /// </summary>
 public sealed class SectionOverride
 {
@@ -1797,30 +1797,95 @@ public sealed class SectionOverride
 }
 
 /// <summary>
-/// Known system prompt section identifiers for the "customize" mode.
+/// Identifies a system message section for the "customize" mode.
 /// </summary>
-public static class SystemPromptSections
+[JsonConverter(typeof(SystemMessageSection.Converter))]
+public readonly struct SystemMessageSection : IEquatable<SystemMessageSection>
 {
     /// <summary>Agent identity preamble and mode statement.</summary>
-    public const string Identity = "identity";
+    public static SystemMessageSection Identity { get; } = new("identity");
     /// <summary>Response style, conciseness rules, output formatting preferences.</summary>
-    public const string Tone = "tone";
+    public static SystemMessageSection Tone { get; } = new("tone");
     /// <summary>Tool usage patterns, parallel calling, batching guidelines.</summary>
-    public const string ToolEfficiency = "tool_efficiency";
+    public static SystemMessageSection ToolEfficiency { get; } = new("tool_efficiency");
     /// <summary>CWD, OS, git root, directory listing, available tools.</summary>
-    public const string EnvironmentContext = "environment_context";
+    public static SystemMessageSection EnvironmentContext { get; } = new("environment_context");
     /// <summary>Coding rules, linting/testing, ecosystem tools, style.</summary>
-    public const string CodeChangeRules = "code_change_rules";
+    public static SystemMessageSection CodeChangeRules { get; } = new("code_change_rules");
     /// <summary>Tips, behavioral best practices, behavioral guidelines.</summary>
-    public const string Guidelines = "guidelines";
+    public static SystemMessageSection Guidelines { get; } = new("guidelines");
     /// <summary>Environment limitations, prohibited actions, security policies.</summary>
-    public const string Safety = "safety";
+    public static SystemMessageSection Safety { get; } = new("safety");
     /// <summary>Per-tool usage instructions.</summary>
-    public const string ToolInstructions = "tool_instructions";
+    public static SystemMessageSection ToolInstructions { get; } = new("tool_instructions");
     /// <summary>Repository and organization custom instructions.</summary>
-    public const string CustomInstructions = "custom_instructions";
+    public static SystemMessageSection CustomInstructions { get; } = new("custom_instructions");
+    /// <summary>Runtime-provided context and instructions (e.g. system notifications, memories, workspace context, mode-specific instructions, content-exclusion policy).</summary>
+    public static SystemMessageSection RuntimeInstructions { get; } = new("runtime_instructions");
     /// <summary>End-of-prompt instructions: parallel tool calling, persistence, task completion.</summary>
-    public const string LastInstructions = "last_instructions";
+    public static SystemMessageSection LastInstructions { get; } = new("last_instructions");
+
+    /// <summary>Gets the underlying string value of this <see cref="SystemMessageSection"/>.</summary>
+    public string Value => _value ?? string.Empty;
+
+    private readonly string? _value;
+
+    /// <summary>Initializes a new instance of the <see cref="SystemMessageSection"/> struct.</summary>
+    /// <param name="value">The string value for this section identifier.</param>
+    [JsonConstructor]
+    public SystemMessageSection(string value) => _value = value;
+
+    /// <inheritdoc/>
+    public static bool operator ==(SystemMessageSection left, SystemMessageSection right) => left.Equals(right);
+
+    /// <inheritdoc/>
+    public static bool operator !=(SystemMessageSection left, SystemMessageSection right) => !left.Equals(right);
+
+    /// <inheritdoc/>
+    public override bool Equals([NotNullWhen(true)] object? obj) => obj is SystemMessageSection other && Equals(other);
+
+    /// <inheritdoc/>
+    public bool Equals(SystemMessageSection other) => string.Equals(Value, other.Value, StringComparison.OrdinalIgnoreCase);
+
+    /// <inheritdoc/>
+    public override int GetHashCode() => StringComparer.OrdinalIgnoreCase.GetHashCode(Value);
+
+    /// <inheritdoc/>
+    public override string ToString() => Value;
+
+    /// <summary>Provides a <see cref="JsonConverter{SystemMessageSection}"/> for serializing <see cref="SystemMessageSection"/> instances.</summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public sealed class Converter : JsonConverter<SystemMessageSection>
+    {
+        /// <inheritdoc/>
+        public override SystemMessageSection Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            if (reader.TokenType != JsonTokenType.String)
+            {
+                throw new JsonException("Expected string for SystemMessageSection.");
+            }
+
+            var value = reader.GetString();
+            if (value is null)
+            {
+                throw new JsonException("SystemMessageSection value cannot be null.");
+            }
+
+            return new SystemMessageSection(value);
+        }
+
+        /// <inheritdoc/>
+        public override void Write(Utf8JsonWriter writer, SystemMessageSection value, JsonSerializerOptions options) =>
+            writer.WriteStringValue(value.Value);
+
+        /// <inheritdoc/>
+        public override SystemMessageSection ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) =>
+            new(reader.GetString()!);
+
+        /// <inheritdoc/>
+        public override void WriteAsPropertyName(Utf8JsonWriter writer, SystemMessageSection value, JsonSerializerOptions options) =>
+            writer.WritePropertyName(value.Value);
+    }
 }
 
 /// <summary>
@@ -1841,9 +1906,9 @@ public sealed class SystemMessageConfig
 
     /// <summary>
     /// Section-level overrides for customize mode.
-    /// Keys are section identifiers (see <see cref="SystemPromptSections"/>).
+    /// Keys are section identifiers (see <see cref="SystemMessageSection"/>).
     /// </summary>
-    public IDictionary<string, SectionOverride>? Sections { get; set; }
+    public IDictionary<SystemMessageSection, SectionOverride>? Sections { get; set; }
 }
 
 /// <summary>
@@ -3001,7 +3066,7 @@ public sealed class SetForegroundSessionResponse
 }
 
 /// <summary>
-/// Content data for a single system prompt section in a transform RPC call.
+/// Content data for a single system message section in a transform RPC call.
 /// </summary>
 public sealed class SystemMessageTransformSection
 {

dotnet/test/E2E/SessionE2ETests.cs

@@ -1,4 +1,4 @@
-/*---------------------------------------------------------------------------------------------
+/*---------------------------------------------------------------------------------------------
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *--------------------------------------------------------------------------------------------*/
 
@@ -101,10 +101,10 @@ public async Task Should_Create_A_Session_With_Customized_SystemMessage_Config()
             SystemMessage = new SystemMessageConfig
             {
                 Mode = SystemMessageMode.Customize,
-                Sections = new Dictionary<string, SectionOverride>
+                Sections = new Dictionary<SystemMessageSection, SectionOverride>
                 {
-                    [SystemPromptSections.Tone] = new() { Action = SectionOverrideAction.Replace, Content = customTone },
-                    [SystemPromptSections.CodeChangeRules] = new() { Action = SectionOverrideAction.Remove },
+                    [SystemMessageSection.Tone] = new() { Action = SectionOverrideAction.Replace, Content = customTone },
+                    [SystemMessageSection.CodeChangeRules] = new() { Action = SectionOverrideAction.Remove },
                 },
                 Content = appendedContent
             }

dotnet/test/E2E/SystemMessageTransformE2ETests.cs

@@ -22,9 +22,9 @@ public async Task Should_Invoke_Transform_Callbacks_With_Section_Content()
             SystemMessage = new SystemMessageConfig
             {
                 Mode = SystemMessageMode.Customize,
-                Sections = new Dictionary<string, SectionOverride>
+                Sections = new Dictionary<SystemMessageSection, SectionOverride>
                 {
-                    ["identity"] = new SectionOverride
+                    [SystemMessageSection.Identity] = new SectionOverride
                     {
                         Transform = async (content) =>
                         {
@@ -33,7 +33,7 @@ public async Task Should_Invoke_Transform_Callbacks_With_Section_Content()
                             return content;
                         }
                     },
-                    ["tone"] = new SectionOverride
+                    [SystemMessageSection.Tone] = new SectionOverride
                     {
                         Transform = async (content) =>
                         {
@@ -68,9 +68,9 @@ public async Task Should_Apply_Transform_Modifications_To_Section_Content()
             SystemMessage = new SystemMessageConfig
             {
                 Mode = SystemMessageMode.Customize,
-                Sections = new Dictionary<string, SectionOverride>
+                Sections = new Dictionary<SystemMessageSection, SectionOverride>
                 {
-                    ["identity"] = new SectionOverride
+                    [SystemMessageSection.Identity] = new SectionOverride
                     {
                         Transform = async (content) =>
                         {
@@ -108,13 +108,13 @@ public async Task Should_Work_With_Static_Overrides_And_Transforms_Together()
             SystemMessage = new SystemMessageConfig
             {
                 Mode = SystemMessageMode.Customize,
-                Sections = new Dictionary<string, SectionOverride>
+                Sections = new Dictionary<SystemMessageSection, SectionOverride>
                 {
-                    ["safety"] = new SectionOverride
+                    [SystemMessageSection.Safety] = new SectionOverride
                     {
                         Action = SectionOverrideAction.Remove
                     },
-                    ["identity"] = new SectionOverride
+                    [SystemMessageSection.Identity] = new SectionOverride
                     {
                         Transform = async (content) =>
                         {

dotnet/test/Unit/PublicDtoTests.cs

@@ -174,15 +174,17 @@ private static bool TryCreateGenericCollection(Type type, HashSet<Type> visited,
             .FirstOrDefault(candidate =>
                 candidate.IsGenericType &&
                 (candidate.GetGenericTypeDefinition() == typeof(IDictionary<,>) ||
-                 candidate.GetGenericTypeDefinition() == typeof(IReadOnlyDictionary<,>)) &&
-                candidate.GetGenericArguments()[0] == typeof(string));
+                 candidate.GetGenericTypeDefinition() == typeof(IReadOnlyDictionary<,>)));
 
         if (dictionaryInterface is not null)
         {
+            var keyType = dictionaryInterface.GetGenericArguments()[0];
             var valueType = dictionaryInterface.GetGenericArguments()[1];
+            TryCreateSampleValue(keyType, visited, out var sampleKey);
             TryCreateSampleValue(valueType, visited, out var sampleValue);
-            var dictionary = (IDictionary)Activator.CreateInstance(typeof(Dictionary<,>).MakeGenericType(typeof(string), valueType))!;
-            dictionary["key"] = sampleValue;
+            var dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+            var dictionary = (IDictionary)Activator.CreateInstance(dictionaryType)!;
+            dictionary[sampleKey!] = sampleValue;
             value = dictionary;
             return true;
         }

go/README.md

@@ -160,7 +160,7 @@ Event types: `SessionLifecycleCreated`, `SessionLifecycleDeleted`, `SessionLifec
 - `SystemMessage` (\*SystemMessageConfig): System message configuration. Supports three modes:
   - **append** (default): Appends `Content` after the SDK-managed prompt
   - **replace**: Replaces the entire prompt with `Content`
-  - **customize**: Selectively override individual sections via `Sections` map (keys: `SectionIdentity`, `SectionTone`, `SectionToolEfficiency`, `SectionEnvironmentContext`, `SectionCodeChangeRules`, `SectionGuidelines`, `SectionSafety`, `SectionToolInstructions`, `SectionCustomInstructions`, `SectionLastInstructions`; values: `SectionOverride` with `Action` and optional `Content`)
+  - **customize**: Selectively override individual sections via `Sections` map (keys: `SectionIdentity`, `SectionTone`, `SectionToolEfficiency`, `SectionEnvironmentContext`, `SectionCodeChangeRules`, `SectionGuidelines`, `SectionSafety`, `SectionToolInstructions`, `SectionCustomInstructions`, `SectionRuntimeInstructions`, `SectionLastInstructions`; values: `SectionOverride` with `Action` and optional `Content`)
 - `Provider` (\*ProviderConfig): Custom API provider configuration (BYOK). See [Custom Providers](#custom-providers) section.
 - `Streaming` (*bool): Enable streaming delta events (nil = runtime default)
 - `InfiniteSessions` (\*InfiniteSessionConfig): Automatic context compaction configuration
@@ -233,7 +233,7 @@ session, err := client.CreateSession(ctx, &copilot.SessionConfig{
 })
 ```
 
-Available section constants: `SectionIdentity`, `SectionTone`, `SectionToolEfficiency`, `SectionEnvironmentContext`, `SectionCodeChangeRules`, `SectionGuidelines`, `SectionSafety`, `SectionToolInstructions`, `SectionCustomInstructions`, `SectionLastInstructions`.
+Available section constants: `SectionIdentity`, `SectionTone`, `SectionToolEfficiency`, `SectionEnvironmentContext`, `SectionCodeChangeRules`, `SectionGuidelines`, `SectionSafety`, `SectionToolInstructions`, `SectionCustomInstructions`, `SectionRuntimeInstructions`, `SectionLastInstructions`.
 
 Each section override supports four actions: