Address review feedback on the Auto tier surface

Gate the experimental Auto tier options consistently. The .NET
SetModelOptions.AutoTier and .ResetAutoTier properties, the Java Auto tier
accessors, and the Python set_model auto_tier parameter now carry the same
experimental marker their dedicated setAutoTier counterparts already had.

Correct two documentation errors. The reset-state paragraph claimed four SDKs
cannot express reset in a single value; Rust can, through
AutoTierPreference::Reset, so only Go, .NET, and Java need a separate flag.
The live-switching section now states that it needs Copilot CLI 1.0.83-4,
which is newer than the 1.0.82-1 required to select a tier at create or resume.

Fix the Java class Javadoc, which said every option is optional when setModel
rejects a null model, and rewrite the Rust E2E doc comment to describe what it
covers instead of pointing at the Node.js test.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 2aad36e9-e078-4b9c-afa1-0c7cd2c71f74

Author: andyfeller

docs/features/session-persistence.md

@@ -271,7 +271,7 @@ The `session.start` and `session.resume` events expose the selected tier in thei
 
 ### Changing the Auto tier during a session
 
-Call `setAutoTier` to change the routing preference on a live session without changing the selected model. Pass `null` (Python `None`, Go `nil`) to return to the provider's default Auto routing.
+Call `setAutoTier` to change the routing preference on a live session without changing the selected model. Pass `null` (Python `None`, Go `nil`) to return to the provider's default Auto routing. This requires Copilot CLI `1.0.83-4` or later, which is newer than the `1.0.82-1` needed to select a tier when creating or resuming a session.
 
 ```typescript
 const result = await session.setAutoTier("intelligence");
@@ -309,7 +309,7 @@ To select the `auto` model and its routing preference in a single call, stage th
 | Rust | `SetModelOptions::default().with_auto_tier(AutoTier::Balance)` | `SetModelOptions::default().with_reset_auto_tier()` |
 | Java | `new SetModelOptions().setModel("auto").setAutoTier(AutoTier.BALANCE)` | `new SetModelOptions().setModel("auto").setResetAutoTier(true)` |
 
-Node.js and Python express all three states natively, because `null`/`None` is distinguishable from an omitted argument. The other four SDKs cannot make that distinction in a single value, so they carry a separate reset option. Omitting both always means "leave the current preference alone."
+Node.js, Python, and Rust express all three states in a single value: Node.js and Python because `null`/`None` is distinguishable from an omitted argument, and Rust because `AutoTierPreference::Reset` is a distinct variant of the same option. Go, .NET, and Java have no way to distinguish "reset" from "unset" in one value, so they carry a separate reset flag. Omitting both always means "leave the current preference alone."
 
 ### Example: changing model on resume
 

dotnet/src/Types.cs

@@ -3030,12 +3030,14 @@ public struct SetModelOptions
     /// <c>auto</c>; use <see cref="CopilotSession.SetAutoTierAsync"/> to change the
     /// preference without changing the selected model.
     /// </remarks>
+    [Experimental(Diagnostics.Experimental)]
     public AutoTier? AutoTier { get; set; }
 
     /// <summary>
     /// Returns to the provider's default Auto routing as part of this switch.
     /// Mutually exclusive with <see cref="AutoTier"/>.
     /// </summary>
+    [Experimental(Diagnostics.Experimental)]
     public bool ResetAutoTier { get; set; }
 }
 

java/sdk/src/main/java/com/github/copilot/rpc/SetModelOptions.java

@@ -4,11 +4,14 @@
 
 package com.github.copilot.rpc;
 
+import com.github.copilot.CopilotExperimental;
+
 /**
  * Optional settings for a model switch.
  * <p>
- * All setter methods return {@code this} for method chaining. Every option is
- * optional; an unset option leaves the corresponding session state unchanged.
+ * All setter methods return {@code this} for method chaining. {@code model} is
+ * required. Every other option is optional; an unset option leaves the
+ * corresponding session state unchanged.
  *
  * <pre>{@code
  * session.setModel(new SetModelOptions().setModel("auto").setAutoTier(AutoTier.INTELLIGENCE)).get();
@@ -122,6 +125,7 @@ public SetModelOptions setModelCapabilities(ModelCapabilitiesOverride modelCapab
      *
      * @return the requested tier, or {@code null} when no tier was requested
      */
+    @CopilotExperimental
     public AutoTier getAutoTier() {
         return autoTier;
     }
@@ -139,6 +143,7 @@ public AutoTier getAutoTier() {
      *            current preference unchanged
      * @return this options object for method chaining
      */
+    @CopilotExperimental
     public SetModelOptions setAutoTier(AutoTier autoTier) {
         this.autoTier = autoTier;
         return this;
@@ -149,6 +154,7 @@ public SetModelOptions setAutoTier(AutoTier autoTier) {
      *
      * @return {@code true} when the request clears the Auto routing preference
      */
+    @CopilotExperimental
     public boolean isResetAutoTier() {
         return resetAutoTier;
     }
@@ -163,6 +169,7 @@ public boolean isResetAutoTier() {
      *            {@code true} to return to provider-default Auto routing
      * @return this options object for method chaining
      */
+    @CopilotExperimental
     public SetModelOptions setResetAutoTier(boolean resetAutoTier) {
         this.resetAutoTier = resetAutoTier;
         return this;

python/copilot/session.py

@@ -3101,7 +3101,9 @@ async def set_model(
             context_tier: Optional context window tier for supported models.
                 Omit to use normal model behavior with no explicit tier.
             model_capabilities: Override individual model capabilities resolved by the runtime.
-            auto_tier: Routing preference to apply when ``model`` is ``"auto"``.
+            auto_tier: **Experimental.** Part of an experimental Auto routing
+                surface and may change or be removed in a future release.
+                Routing preference to apply when ``model`` is ``"auto"``.
                 Pass ``None`` to return to the provider's default Auto routing.
                 Omit the argument to leave the current preference alone. The
                 runtime rejects this option when ``model`` is anything other than

rust/tests/e2e/auto_tier.rs

@@ -7,7 +7,8 @@ use super::support::with_dedicated_e2e_context;
 
 const MODEL_ID: &str = "auto";
 
-/// Mirrors nodejs/test/e2e/auto_tier.e2e.test.ts (snapshot category "auto_tier").
+/// End-to-end coverage for staging and resetting an Auto routing preference
+/// (snapshot category "auto_tier").
 ///
 /// The runtime stages an Auto routing preference instead of applying it immediately: a
 /// request stays unclaimed until a later turn using the `auto` model mints a usable model