Clarify custom agent effort omission

Document that omitted per-agent reasoning effort sends no override and lets the backend choose its default rather than inheriting the parent session effort.

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

Copilot-Session: 32727fc4-2ac8-41eb-a68a-e74674ecf155

Author: roji

docs/features/custom-agents.md

@@ -254,12 +254,12 @@ try (var client = new CopilotClient()) {
 | `infer` | `boolean` | | Whether the runtime can auto-select this agent (default: `true`) |
 | `skills` | `string[]` | | Skill names to preload into the agent's context at startup |
 | `model` | `string` | | Model identifier to use while this agent runs |
-| `reasoningEffort` | `string` | | Reasoning effort to use while this agent runs. Inherits an explicit parent session effort when omitted |
+| `reasoningEffort` | `string` | | Reasoning effort to use while this agent runs. When omitted, no override is sent and the backend chooses its default |
 
 > [!TIP]
 > A good `description` helps the runtime match user intent to the right agent. Be specific about the agent's expertise and capabilities.
 
-Set `model` and `reasoningEffort` to override the parent session's model settings while a custom agent runs. When `reasoningEffort` is omitted, the runtime currently inherits an explicitly configured parent session effort. If the parent session effort is also omitted, no effort is sent and the backend chooses. The SDK does not add a per-agent default. Python uses `reasoning_effort`, .NET uses `ReasoningEffort`, Go uses `ReasoningEffort`, Java uses `setReasoningEffort`, and Rust uses `with_reasoning_effort`.
+Set `model` and `reasoningEffort` to override the parent session's model settings while a custom agent runs. When `reasoningEffort` is omitted, the SDK sends no per-agent override and the backend chooses its default. The parent session effort is not inherited, and the SDK does not add a per-agent default. Python uses `reasoning_effort`, .NET uses `ReasoningEffort`, Go uses `ReasoningEffort`, Java uses `setReasoningEffort`, and Rust uses `with_reasoning_effort`.
 
 In addition to per-agent configuration above, you can set `agent` on the **session config** itself to pre-select which custom agent is active when the session starts. See [Selecting an Agent at Session Creation](#selecting-an-agent-at-session-creation) below.
 

dotnet/src/Types.cs

@@ -2660,8 +2660,8 @@ public sealed class CustomAgentConfig
 
     /// <summary>
     /// Reasoning effort level for this agent's model.
-    /// When omitted, the runtime inherits an explicit parent session effort.
-    /// If the parent effort is also omitted, the backend chooses the effort.
+    /// When omitted, no per-agent override is sent and the backend chooses its
+    /// default. The parent session effort is not inherited.
     /// </summary>
     [JsonPropertyName("reasoningEffort")]
     public string? ReasoningEffort { get; set; }

go/types.go

@@ -950,8 +950,8 @@ type CustomAgentConfig struct {
 	// falling back to the parent session model if unavailable.
 	Model string `json:"model,omitempty"`
 	// ReasoningEffort is the reasoning effort level for this agent's model.
-	// When empty, the runtime inherits an explicit parent session effort.
-	// If the parent effort is also empty, the backend chooses the effort.
+	// When empty, no per-agent override is sent and the backend chooses its
+	// default. The parent session effort is not inherited.
 	ReasoningEffort string `json:"reasoningEffort,omitempty"`
 }
 

java/src/main/java/com/github/copilot/rpc/CustomAgentConfig.java

@@ -298,8 +298,8 @@ public String getReasoningEffort() {
     /**
      * Sets the reasoning effort level for this agent's model.
      * <p>
-     * When omitted, the runtime inherits an explicit parent session effort. If the
-     * parent effort is also omitted, the backend chooses the effort.
+     * When omitted, no per-agent override is sent and the backend chooses its
+     * default. The parent session effort is not inherited.
      *
      * @param reasoningEffort
      *            the reasoning effort level

nodejs/src/types.ts

@@ -1634,8 +1634,8 @@ export interface CustomAgentConfig {
     model?: string;
     /**
      * Reasoning effort level for this agent's model.
-     * When omitted, the runtime inherits an explicit parent session effort.
-     * If the parent effort is also omitted, the backend chooses the effort.
+     * When omitted, no per-agent override is sent and the backend chooses its
+     * default. The parent session effort is not inherited.
      */
     reasoningEffort?: ReasoningEffort;
 }

python/copilot/session.py

@@ -1080,8 +1080,8 @@ class CustomAgentConfig(TypedDict, total=False):
     skills: NotRequired[list[str]]
     # Model identifier (e.g. "claude-haiku-4.5"); runtime falls back to parent model if unavailable
     model: NotRequired[str]
-    # Reasoning effort for this agent's model. When omitted, inherits an explicit
-    # parent session effort; if that is also omitted, the backend chooses.
+    # Reasoning effort for this agent's model. When omitted, no per-agent override
+    # is sent and the backend chooses its default; the parent effort is not inherited.
     reasoning_effort: NotRequired[ReasoningEffort]
 
 

rust/src/types.rs

@@ -630,8 +630,8 @@ pub struct CustomAgentConfig {
     pub model: Option<String>,
     /// Reasoning effort level for this agent's model.
     ///
-    /// When unset, the runtime inherits an explicit parent session effort. If
-    /// the parent effort is also unset, the backend chooses the effort.
+    /// When unset, no per-agent override is sent and the backend chooses its
+    /// default. The parent session effort is not inherited.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub reasoning_effort: Option<String>,
 }