Rename MaxPromptTokens to MaxInputTokens and clarify ProviderConfig docs

Renames the SDK-facing ProviderConfig field across all four languages while preserving the wire JSON key as maxPromptTokens:

- .NET: MaxPromptTokens -> MaxInputTokens (JsonPropertyName unchanged)

- Go: MaxPromptTokens -> MaxInputTokens (json tag unchanged)

- Python: max_prompt_tokens -> max_input_tokens (wire conversion in _convert_provider_to_wire_format unchanged)

- Node: maxPromptTokens -> maxInputTokens; adds a small toWireProviderConfig helper in client.ts that remaps the field before sending session.create / session.resume.

Also rewrites the doc comments for modelId, wireModel, maxInputTokens, and maxOutputTokens to make the priority order clear: WireModel falls back to ModelId falls back to SessionConfig.Model, and ModelId drives both runtime configuration lookup and the wire model when WireModel is unset.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: MackinnonBuck

dotnet/src/Types.cs

@@ -1530,38 +1530,35 @@ public class ProviderConfig
     public IDictionary<string, string>? Headers { get; set; }
 
     /// <summary>
-    /// Well-known model ID used to look up agent configuration (tools, prompts,
-    /// reasoning behavior) and default token limits from the capability catalog.
-    /// Useful for fine-tuned models that should inherit the configuration of a
-    /// known base model.
-    /// Defaults to the session's configured model (see <see cref="SessionConfig.Model"/>)
-    /// when not explicitly set.
+    /// Well-known model name used by the runtime to look up agent configuration
+    /// (tools, prompts, reasoning behavior) and default token limits. Also used
+    /// as the wire model when <see cref="WireModel"/> is not set.
+    /// Falls back to <see cref="SessionConfig.Model"/>.
     /// </summary>
     [JsonPropertyName("modelId")]
     public string? ModelId { get; set; }
 
     /// <summary>
-    /// Model identifier sent to the provider API for inference.
-    /// Use this when the name your provider knows (e.g. an Azure deployment name
-    /// or a custom fine-tune name) differs from the well-known model ID used for
-    /// configuration lookup.
-    /// Defaults to the session's configured model (see <see cref="SessionConfig.Model"/>)
-    /// when not explicitly set.
+    /// Model name sent to the provider API for inference. Use this when the
+    /// provider's model name (e.g. an Azure deployment name or a custom
+    /// fine-tune name) differs from <see cref="ModelId"/>.
+    /// Falls back to <see cref="ModelId"/>, then <see cref="SessionConfig.Model"/>.
     /// </summary>
     [JsonPropertyName("wireModel")]
     public string? WireModel { get; set; }
 
     /// <summary>
-    /// Maximum number of tokens allowed in the prompt for a single LLM API request.
-    /// Used by the runtime to trigger conversation compaction before sending a request
-    /// when the prompt (system message, history, tool definitions, user message) exceeds this limit.
+    /// Overrides the resolved model's default max prompt tokens. The runtime
+    /// triggers conversation compaction before sending a request when the
+    /// prompt (system message, history, tool definitions, user message) would
+    /// exceed this limit.
     /// </summary>
     [JsonPropertyName("maxPromptTokens")]
-    public int? MaxPromptTokens { get; set; }
+    public int? MaxInputTokens { get; set; }
 
     /// <summary>
-    /// Maximum number of tokens the model can generate in a single response.
-    /// When hit, the model stops generating and returns a truncated response.
+    /// Overrides the resolved model's default max output tokens. When hit, the
+    /// model stops generating and returns a truncated response.
     /// </summary>
     [JsonPropertyName("maxOutputTokens")]
     public int? MaxOutputTokens { get; set; }

dotnet/test/Unit/SerializationTests.cs

@@ -23,7 +23,7 @@ public void ProviderConfig_CanSerializeHeaders_WithSdkOptions()
             Headers = new Dictionary<string, string> { ["Authorization"] = "Bearer provider-token" },
             ModelId = "gpt-4o",
             WireModel = "my-finetune-v3",
-            MaxPromptTokens = 100_000,
+            MaxInputTokens = 100_000,
             MaxOutputTokens = 4096
         };
 
@@ -43,7 +43,7 @@ public void ProviderConfig_CanSerializeHeaders_WithSdkOptions()
         Assert.Equal("Bearer provider-token", deserialized.Headers!["Authorization"]);
         Assert.Equal("gpt-4o", deserialized.ModelId);
         Assert.Equal("my-finetune-v3", deserialized.WireModel);
-        Assert.Equal(100_000, deserialized.MaxPromptTokens);
+        Assert.Equal(100_000, deserialized.MaxInputTokens);
         Assert.Equal(4096, deserialized.MaxOutputTokens);
     }
 

go/types.go

@@ -859,28 +859,24 @@ type ProviderConfig struct {
 	Azure *AzureProviderOptions `json:"azure,omitempty"`
 	// Headers are custom HTTP headers included in outbound provider requests.
 	Headers map[string]string `json:"headers,omitempty"`
-	// ModelID is the well-known model ID used to look up agent configuration
-	// (tools, prompts, reasoning behavior) and default token limits from the
-	// capability catalog. Useful for fine-tuned models that should inherit the
-	// configuration of a known base model.
-	// Defaults to the session's configured model (SessionConfig.Model) when
-	// not explicitly set.
+	// ModelID is the well-known model name used by the runtime to look up
+	// agent configuration (tools, prompts, reasoning behavior) and default
+	// token limits. Also used as the wire model when WireModel is not set.
+	// Falls back to SessionConfig.Model.
 	ModelID string `json:"modelId,omitempty"`
-	// WireModel is the model identifier sent to the provider API for inference.
-	// Use this when the name your provider knows (e.g. an Azure deployment name
-	// or a custom fine-tune name) differs from the well-known model ID used for
-	// configuration lookup.
-	// Defaults to the session's configured model (SessionConfig.Model) when
-	// not explicitly set.
+	// WireModel is the model name sent to the provider API for inference. Use
+	// this when the provider's model name (e.g. an Azure deployment name or a
+	// custom fine-tune name) differs from ModelID.
+	// Falls back to ModelID, then SessionConfig.Model.
 	WireModel string `json:"wireModel,omitempty"`
-	// MaxPromptTokens is the maximum number of tokens allowed in the prompt for
-	// a single LLM API request. Used by the runtime to trigger conversation
-	// compaction before sending a request when the prompt (system message,
-	// history, tool definitions, user message) exceeds this limit.
-	MaxPromptTokens int `json:"maxPromptTokens,omitempty"`
-	// MaxOutputTokens is the maximum number of tokens the model can generate in
-	// a single response. When hit, the model stops generating and returns a
-	// truncated response.
+	// MaxInputTokens overrides the resolved model's default max prompt tokens.
+	// The runtime triggers conversation compaction before sending a request
+	// when the prompt (system message, history, tool definitions, user
+	// message) would exceed this limit.
+	MaxInputTokens int `json:"maxPromptTokens,omitempty"`
+	// MaxOutputTokens overrides the resolved model's default max output
+	// tokens. When hit, the model stops generating and returns a truncated
+	// response.
 	MaxOutputTokens int `json:"maxOutputTokens,omitempty"`
 }
 

go/types_test.go

@@ -159,7 +159,7 @@ func TestProviderConfig_JSONIncludesAllFields(t *testing.T) {
 		Headers:         map[string]string{"Authorization": "Bearer provider-token"},
 		ModelID:         "gpt-4o",
 		WireModel:       "my-finetune-v3",
-		MaxPromptTokens: 100000,
+		MaxInputTokens:  100000,
 		MaxOutputTokens: 4096,
 	}
 

nodejs/src/client.ts

@@ -42,6 +42,7 @@ import type {
     GetAuthStatusResponse,
     GetStatusResponse,
     ModelInfo,
+    ProviderConfig,
     ResumeSessionConfig,
     SectionTransformFn,
     SessionConfig,
@@ -64,6 +65,17 @@ import type {
 } from "./types.js";
 import { defaultJoinSessionPermissionHandler } from "./types.js";
 
+/**
+ * Convert a {@link ProviderConfig} to its JSON-RPC wire shape, remapping
+ * camelCase SDK property names to the wire keys expected by the runtime
+ * (e.g. `maxInputTokens` → `maxPromptTokens`).
+ */
+function toWireProviderConfig(provider: ProviderConfig): Record<string, unknown> {
+    const { maxInputTokens, ...rest } = provider;
+    if (maxInputTokens === undefined) return rest;
+    return { ...rest, maxPromptTokens: maxInputTokens };
+}
+
 /**
  * Minimum protocol version this SDK can communicate with.
  * Servers reporting a version below this are rejected.
@@ -788,7 +800,7 @@ export class CopilotClient {
                 systemMessage: wireSystemMessage,
                 availableTools: config.availableTools,
                 excludedTools: config.excludedTools,
-                provider: config.provider,
+                provider: config.provider ? toWireProviderConfig(config.provider) : undefined,
                 modelCapabilities: config.modelCapabilities,
                 requestPermission: true,
                 requestUserInput: !!config.onUserInputRequest,
@@ -931,7 +943,7 @@ export class CopilotClient {
                     name: cmd.name,
                     description: cmd.description,
                 })),
-                provider: config.provider,
+                provider: config.provider ? toWireProviderConfig(config.provider) : undefined,
                 modelCapabilities: config.modelCapabilities,
                 requestPermission:
                     config.onPermissionRequest !== defaultJoinSessionPermissionHandler,

nodejs/src/types.ts

@@ -1505,35 +1505,32 @@ export interface ProviderConfig {
     headers?: Record<string, string>;
 
     /**
-     * Well-known model ID used to look up agent configuration (tools, prompts,
-     * reasoning behavior) and default token limits from the capability catalog.
-     * Useful for fine-tuned models that should inherit the configuration of a
-     * known base model.
-     * Defaults to the session's configured model (see {@link SessionConfig.model})
-     * when not explicitly set.
+     * Well-known model name used by the runtime to look up agent configuration
+     * (tools, prompts, reasoning behavior) and default token limits. Also used
+     * as the wire model when {@link wireModel} is not set.
+     * Falls back to {@link SessionConfig.model}.
      */
     modelId?: string;
 
     /**
-     * Model identifier sent to the provider API for inference.
-     * Use this when the name your provider knows (e.g. an Azure deployment name
-     * or a custom fine-tune name) differs from the well-known model ID used
-     * for configuration lookup.
-     * Defaults to the session's configured model (see {@link SessionConfig.model})
-     * when not explicitly set.
+     * Model name sent to the provider API for inference. Use this when the
+     * provider's model name (e.g. an Azure deployment name or a custom
+     * fine-tune name) differs from {@link modelId}.
+     * Falls back to {@link modelId}, then {@link SessionConfig.model}.
      */
     wireModel?: string;
 
     /**
-     * Maximum number of tokens allowed in the prompt for a single LLM API request.
-     * Used by the runtime to trigger conversation compaction before sending a request
-     * when the prompt (system message, history, tool definitions, user message) exceeds this limit.
+     * Overrides the resolved model's default max prompt tokens. The runtime
+     * triggers conversation compaction before sending a request when the
+     * prompt (system message, history, tool definitions, user message) would
+     * exceed this limit.
      */
-    maxPromptTokens?: number;
+    maxInputTokens?: number;
 
     /**
-     * Maximum number of tokens the model can generate in a single response.
-     * When hit, the model stops generating and returns a truncated response.
+     * Overrides the resolved model's default max output tokens. When hit, the
+     * model stops generating and returns a truncated response.
      */
     maxOutputTokens?: number;
 }

nodejs/test/client.test.ts

@@ -226,7 +226,7 @@ describe("CopilotClient", () => {
                 headers: { Authorization: "Bearer provider-token" },
                 modelId: "gpt-4o",
                 wireModel: "my-finetune-v3",
-                maxPromptTokens: 100_000,
+                maxInputTokens: 100_000,
                 maxOutputTokens: 4096,
             },
         });
@@ -265,7 +265,7 @@ describe("CopilotClient", () => {
                 headers: { Authorization: "Bearer resume-token" },
                 modelId: "gpt-4o",
                 wireModel: "my-finetune-v3",
-                maxPromptTokens: 100_000,
+                maxInputTokens: 100_000,
                 maxOutputTokens: 4096,
             },
         });

python/copilot/client.py

@@ -2279,8 +2279,8 @@ def _convert_provider_to_wire_format(
             wire_provider["modelId"] = provider["model_id"]
         if "wire_model" in provider:
             wire_provider["wireModel"] = provider["wire_model"]
-        if "max_prompt_tokens" in provider:
-            wire_provider["maxPromptTokens"] = provider["max_prompt_tokens"]
+        if "max_input_tokens" in provider:
+            wire_provider["maxPromptTokens"] = provider["max_input_tokens"]
         if "max_output_tokens" in provider:
             wire_provider["maxOutputTokens"] = provider["max_output_tokens"]
         if "azure" in provider:

python/copilot/session.py

@@ -832,27 +832,23 @@ class ProviderConfig(TypedDict, total=False):
     bearer_token: str
     azure: AzureProviderOptions  # Azure-specific options
     headers: dict[str, str]
-    # Well-known model ID used to look up agent configuration (tools, prompts,
-    # reasoning behavior) and default token limits from the capability catalog.
-    # Useful for fine-tuned models that should inherit the configuration of a
-    # known base model.
-    # Defaults to the session's configured model (SessionConfig.model) when
-    # not explicitly set.
+    # Well-known model name used by the runtime to look up agent configuration
+    # (tools, prompts, reasoning behavior) and default token limits. Also used
+    # as the wire model when wire_model is not set.
+    # Falls back to SessionConfig.model.
     model_id: str
-    # Model identifier sent to the provider API for inference. Use this when the
-    # name your provider knows (e.g. an Azure deployment name or a custom
-    # fine-tune name) differs from the well-known model ID used for
-    # configuration lookup.
-    # Defaults to the session's configured model (SessionConfig.model) when
-    # not explicitly set.
+    # Model name sent to the provider API for inference. Use this when the
+    # provider's model name (e.g. an Azure deployment name or a custom
+    # fine-tune name) differs from model_id.
+    # Falls back to model_id, then SessionConfig.model.
     wire_model: str
-    # Maximum number of tokens allowed in the prompt for a single LLM API
-    # request. Used by the runtime to trigger conversation compaction before
-    # sending a request when the prompt (system message, history, tool
-    # definitions, user message) exceeds this limit.
-    max_prompt_tokens: int
-    # Maximum number of tokens the model can generate in a single response.
-    # When hit, the model stops generating and returns a truncated response.
+    # Overrides the resolved model's default max prompt tokens. The runtime
+    # triggers conversation compaction before sending a request when the prompt
+    # (system message, history, tool definitions, user message) would exceed
+    # this limit.
+    max_input_tokens: int
+    # Overrides the resolved model's default max output tokens. When hit, the
+    # model stops generating and returns a truncated response.
     max_output_tokens: int
 
 

python/test_client.py

@@ -566,7 +566,7 @@ async def mock_request(method, params):
                     "headers": {"Authorization": "Bearer provider-token"},
                     "model_id": "gpt-4o",
                     "wire_model": "my-finetune-v3",
-                    "max_prompt_tokens": 100_000,
+                    "max_input_tokens": 100_000,
                     "max_output_tokens": 4096,
                 },
             )
@@ -609,7 +609,7 @@ async def mock_request(method, params):
                     "headers": {"Authorization": "Bearer resume-token"},
                     "model_id": "gpt-4o",
                     "wire_model": "my-finetune-v3",
-                    "max_prompt_tokens": 100_000,
+                    "max_input_tokens": 100_000,
                     "max_output_tokens": 4096,
                 },
             )