Add history.clearContext and Tool.isTerminal across all SDKs

Regenerates the RPC clients for the new `session.history.clearContext` method
and the `session.context_cleared` event, and adds a hand-authored `isTerminal`
tool flag to every language surface.

`isTerminal` lets a tool declare that a successful call ends the agent turn:
the runtime's tool phase halts instead of feeding the result back to the model
for another round. A failed call leaves the loop running so the model can read
the error and retry. Without it a turn-ending tool can only approximate the
behavior by returning a rejected result, which halts the loop but is
semantically wrong.

Per language:
- Node.js: `Tool.isTerminal`, `defineTool` config, both session-config
  serialization sites.
- Go: `Tool.IsTerminal` with `json:"isTerminal,omitempty"`.
- Python: `Tool.is_terminal`, `define_tool` overloads, both client
  serialization sites.
- Rust: `Tool::is_terminal`, skipped when false.
- Java: `ToolDefinition.isTerminal` as a record component, plus a
  seven-argument convenience constructor so existing call sites keep compiling.
- .NET: `CopilotToolOptions.IsTerminal`, the `is_terminal` additional-property
  key, and the wire `ToolDefinition`.

Adds serialization tests in Go, Rust and Java covering both the camelCase wire
name and omission when unset; the Java test also pins the seven-argument
constructor so the record change stays source-compatible.

Author: examon

dotnet/src/Client.cs

@@ -2485,17 +2485,20 @@ internal record ToolDefinition(
         JsonElement Parameters, /* JSON schema */
         bool? OverridesBuiltInTool = null,
         bool? SkipPermission = null,
-        CopilotToolDefer? Defer = null)
+        CopilotToolDefer? Defer = null,
+        bool? IsTerminal = null)
     {
         public static ToolDefinition FromAIFunction(AIFunctionDeclaration function)
         {
             var overrides = function.AdditionalProperties.TryGetValue(CopilotTool.OverridesBuiltInToolKey, out var val) && val is true;
             var skipPerm = function.AdditionalProperties.TryGetValue(CopilotTool.SkipPermissionKey, out var skipVal) && skipVal is true;
             var defer = function.AdditionalProperties.TryGetValue(CopilotTool.DeferKey, out var deferVal) && deferVal is CopilotToolDefer d ? d : (CopilotToolDefer?)null;
+            var isTerminal = function.AdditionalProperties.TryGetValue(CopilotTool.IsTerminalKey, out var terminalVal) && terminalVal is true;
             return new ToolDefinition(function.Name, function.Description, function.JsonSchema,
                 overrides ? true : null,
                 skipPerm ? true : null,
-                defer);
+                defer,
+                isTerminal ? true : null);
         }
     }
 

dotnet/src/CopilotTool.cs

@@ -17,6 +17,9 @@ public static class CopilotTool
     /// <summary>The key used in <see cref="AITool.AdditionalProperties"/> to indicate that a tool can execute without a permission prompt.</summary>
     internal const string SkipPermissionKey = "skip_permission";
 
+    /// <summary>The key used in <see cref="AITool.AdditionalProperties"/> to indicate that a successful call to the tool ends the agent turn.</summary>
+    internal const string IsTerminalKey = "is_terminal";
+
     /// <summary>The key used in <see cref="AITool.AdditionalProperties"/> to carry the tool's <see cref="CopilotToolDefer"/> deferral mode.</summary>
     internal const string DeferKey = "defer";
 
@@ -87,7 +90,7 @@ static void ApplyToolInvocationBinding(AIFunctionFactoryOptions factoryOptions)
 
         static void ApplyToolOptions(AIFunctionFactoryOptions factoryOptions, CopilotToolOptions? toolOptions)
         {
-            if (toolOptions is not null && (toolOptions.OverridesBuiltInTool || toolOptions.SkipPermission || toolOptions.Defer is not null))
+            if (toolOptions is not null && (toolOptions.OverridesBuiltInTool || toolOptions.SkipPermission || toolOptions.IsTerminal || toolOptions.Defer is not null))
             {
                 Dictionary<string, object?> additionalProperties = new(StringComparer.Ordinal);
                 if (factoryOptions.AdditionalProperties is not null)
@@ -108,6 +111,11 @@ static void ApplyToolOptions(AIFunctionFactoryOptions factoryOptions, CopilotToo
                     additionalProperties[SkipPermissionKey] = true;
                 }
 
+                if (toolOptions.IsTerminal)
+                {
+                    additionalProperties[IsTerminalKey] = true;
+                }
+
                 if (toolOptions.Defer is { } defer)
                 {
                     additionalProperties[DeferKey] = defer;
@@ -143,6 +151,16 @@ public sealed class CopilotToolOptions
     /// </remarks>
     public bool SkipPermission { get; set; }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether a successful call to this tool ends the agent turn.
+    /// </summary>
+    /// <remarks>
+    /// When true, the runtime's tool phase halts after a successful call instead of feeding the result back to the
+    /// model for another round. A failed call leaves the loop running so the model can read the error and retry.
+    /// The resulting <see cref="AIFunction"/> includes "is_terminal": true in its <see cref="AITool.AdditionalProperties"/>.
+    /// </remarks>
+    public bool IsTerminal { get; set; }
+
     /// <summary>
     /// Gets or sets a value controlling whether this tool may be deferred (loaded lazily via tool search) rather than always pre-loaded.
     /// </summary>

dotnet/src/Generated/Rpc.cs

@@ -2302,3 +2302,40 @@ func TestResumeSessionRequest_ExpAssignments(t *testing.T) {
 		}
 	})
 }
+
+func TestIsTerminal(t *testing.T) {
+	t.Run("IsTerminal is serialized in tool definition", func(t *testing.T) {
+		tool := Tool{
+			Name:        "clear_context",
+			Description: "Clear the conversation",
+			IsTerminal:  true,
+			Handler:     func(_ ToolInvocation) (ToolResult, error) { return ToolResult{}, nil },
+		}
+		data, err := json.Marshal(tool)
+		if err != nil {
+			t.Fatalf("Failed to marshal: %v", err)
+		}
+		var m map[string]any
+		if err := json.Unmarshal(data, &m); err != nil {
+			t.Fatalf("Failed to unmarshal: %v", err)
+		}
+		if m["isTerminal"] != true {
+			t.Errorf("Expected isTerminal to be true, got %v", m["isTerminal"])
+		}
+	})
+
+	t.Run("IsTerminal is omitted when false", func(t *testing.T) {
+		tool := Tool{Name: "plain", Description: "A plain tool"}
+		data, err := json.Marshal(tool)
+		if err != nil {
+			t.Fatalf("Failed to marshal: %v", err)
+		}
+		var m map[string]any
+		if err := json.Unmarshal(data, &m); err != nil {
+			t.Fatalf("Failed to unmarshal: %v", err)
+		}
+		if _, ok := m["isTerminal"]; ok {
+			t.Error("Expected isTerminal to be omitted when false")
+		}
+	})
+}

dotnet/src/Generated/SessionEvents.cs

@@ -1178,6 +1178,11 @@ type Tool struct {
 	Parameters           map[string]any `json:"parameters,omitzero"`
 	OverridesBuiltInTool bool           `json:"overridesBuiltInTool,omitempty"`
 	SkipPermission       bool           `json:"skipPermission,omitempty"`
+	// IsTerminal reports that a successful call to this tool ends the agent
+	// turn: the runtime halts instead of feeding the result back to the model
+	// for another round. A failed call leaves the loop running so the model can
+	// read the error and retry.
+	IsTerminal bool `json:"isTerminal,omitempty"`
 	// Defer controls whether the tool may be deferred (loaded lazily via tool
 	// search) rather than always pre-loaded. When empty, the runtime decides.
 	Defer ToolDefer `json:"defer,omitempty"`