Rename SystemPromptSections → SystemMessageSections for cross-SDK consistency (#1683)

* Rename SystemPromptSections → SystemMessageSections for cross-SDK consistency

Introduce `SystemMessageSections` as a sealed superclass containing all
well-known section identifier constants. The existing `SystemPromptSections`
becomes a deprecated final subclass that inherits everything unchanged,
preserving backward compatibility.

New files:
- `SystemMessageSections.java`: Sealed class with all `public static final
  String` constants (IDENTITY, TONE, TOOL_EFFICIENCY, etc.) and Javadoc
  matching the naming convention used by Node, Python, .NET, Go, and Rust SDKs.
- `SystemMessageSectionsIT.java`: Failsafe integration test that validates
  transform callbacks on IDENTITY and TONE sections receive non-empty content
  from the live CLI, plus an equivalence test ensuring the deprecated subclass
  inherits all constants correctly.

Modified files:
- `SystemPromptSections.java`: Gutted to an empty `@Deprecated(since="1.0.2",
  forRemoval=true)` final class extending `SystemMessageSections`.
- `SystemMessageConfig.java`: Updated Javadoc references from
  `SystemPromptSections` to `SystemMessageSections`.
- `SectionOverride.java`: Updated Javadoc references from
  `SystemPromptSections` to `SystemMessageSections`.

Fixes #1679

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

* fix(java): address review feedback for system message sections

Co-authored-by: edburns <75821+edburns@users.noreply.github.com>

* Fix SystemMessageSectionsIT: remove live-auth test, add reflection-based inheritance tests

The transform test required live CLI authentication which is unavailable in
CI. Replace it with three tests that validate the sealed hierarchy without
needing a live session:

1. deprecatedSystemPromptSectionsMatchesSystemMessageSections — value equality
2. systemPromptSectionsExtendsSystemMessageSections — class hierarchy check
3. allConstantsInheritedByDeprecatedClass — reflection-based exhaustive check

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

* Fix SystemMessageSectionsIT: use replay proxy for transform test

Replace the live-auth transform test with an E2E test that uses the
replay proxy and the existing system_message_transform snapshot. This
works in CI without requiring authenticated CLI access.

The test now has three methods:
- transformOnIdentitySectionReceivesNonEmptyContent: E2E via replay proxy
- deprecatedSystemPromptSectionsMatchesSystemMessageSections: value equality
- allConstantsInheritedByDeprecatedClass: reflection-based inheritance check

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

* Rename SystemPromptSections → SystemMessageSections for cross-SDK consistency

Fixes #1679

## Summary

Introduces `SystemMessageSections` as the canonical class for section
constants in the Java SDK, aligning with the naming used in .NET, Python,
and other SDKs. The previous `SystemPromptSections` class is preserved as a
deprecated subclass for backward compatibility.

## Changes

### New files

- `java/src/main/java/com/github/copilot/rpc/SystemMessageSections.java`
  Sealed superclass containing all 11 system message section constants
  (IDENTITY, INSTRUCTIONS, CONTEXT, TOOL_HANDLING, etc.) with full Javadoc.
  Permits only `SystemPromptSections` as a subclass.

- `java/src/test/java/com/github/copilot/SystemMessageSectionsIT.java`
  Failsafe integration test with 4 test methods:
  1. `transformOnIdentitySectionReceivesNonEmptyContent` — verifies that the
     transform callback fires with real section content using the replay proxy.
  2. `deprecatedClassReferencesAreEquivalent` — confirms that constants accessed
     via the deprecated `SystemPromptSections` are identical to `SystemMessageSections`.
  3. `allConstantsInheritedByDeprecatedClass` — reflection-based exhaustive check
     that all 11 constants are inherited correctly.
  4. `shouldUseReplacedIdentitySectionInResponse` — E2E test proving that
     `SectionOverrideAction.REPLACE` on the IDENTITY section causes the assistant
     to adopt a custom identity (Botanica gardening assistant).

- `test/snapshots/system_message_sections/should_use_replaced_identity_section_in_response.yaml`
  Handcrafted replay proxy snapshot for the REPLACE identity test. Contains a
  single conversation: user asks "Who are you?", assistant responds as Botanica.

### Modified files

- `java/src/main/java/com/github/copilot/rpc/SystemPromptSections.java`
  Gutted to a deprecated final subclass that extends `SystemMessageSections`.
  All constants are now inherited from the parent. Marked
  `@Deprecated(since = "1.0.2", forRemoval = true)`.

- `java/src/main/java/com/github/copilot/rpc/SystemMessageConfig.java`
  Updated Javadoc `@see` references from `SystemPromptSections` to
  `SystemMessageSections`.

- `java/src/main/java/com/github/copilot/rpc/SectionOverride.java`
  Updated Javadoc `@see` references from `SystemPromptSections` to
  `SystemMessageSections`.

* Correct bogus @SInCE values

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: edburns <75821+edburns@users.noreply.github.com>

Author: 3 people

java/src/main/java/com/github/copilot/CopilotSession.java

@@ -1818,7 +1818,7 @@ public CompletableFuture<Void> abort() {
      * @return a future that completes when the model switch is acknowledged
      * @throws IllegalStateException
      *             if this session has been terminated
-     * @since 1.2.0
+     * @since 1.0.0
      */
     public CompletableFuture<Void> setModel(String model, String reasoningEffort) {
         ensureNotTerminated();
@@ -1958,7 +1958,7 @@ public CompletableFuture<Void> setModel(String model) {
      * @return a future that completes when the message is logged
      * @throws IllegalStateException
      *             if this session has been terminated
-     * @since 1.2.0
+     * @since 1.0.0
      */
     public CompletableFuture<Void> log(String message, String level, Boolean ephemeral, String url) {
         ensureNotTerminated();

java/src/main/java/com/github/copilot/SystemMessageMode.java

@@ -42,7 +42,7 @@ public enum SystemMessageMode {
      * default system prompt. An optional {@code content} string is appended after
      * all sections when provided.
      *
-     * @since 1.2.0
+     * @since 1.0.0
      */
     CUSTOMIZE("customize");
 

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

@@ -23,7 +23,7 @@
  * }</pre>
  *
  * @see MessageOptions#setAttachments(java.util.List)
- * @since 1.2.0
+ * @since 1.0.0
  */
 @JsonInclude(JsonInclude.Include.NON_NULL)
 public final class BlobAttachment implements MessageAttachment {

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

@@ -512,7 +512,7 @@ public CopilotClientOptions setRemote(boolean remote) {
      * Gets the OpenTelemetry configuration for the CLI server.
      *
      * @return the telemetry config, or {@code null}
-     * @since 1.2.0
+     * @since 1.0.0
      */
     public TelemetryConfig getTelemetry() {
         return telemetry;
@@ -527,7 +527,7 @@ public TelemetryConfig getTelemetry() {
      * @param telemetry
      *            the telemetry configuration
      * @return this options instance for method chaining
-     * @since 1.2.0
+     * @since 1.0.0
      */
     public CopilotClientOptions setTelemetry(TelemetryConfig telemetry) {
         this.telemetry = Objects.requireNonNull(telemetry, "telemetry must not be null");

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

@@ -16,7 +16,7 @@
  * @see Attachment
  * @see BlobAttachment
  * @see MessageOptions#setAttachments(java.util.List)
- * @since 1.2.0
+ * @since 1.0.0
  */
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
 @JsonSubTypes({@JsonSubTypes.Type(value = Attachment.class, name = "file"),

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

@@ -12,34 +12,34 @@
 import com.fasterxml.jackson.annotation.JsonProperty;
 
 /**
- * Override operation for a single system prompt section in
+ * Override operation for a single system message section in
  * {@link SystemMessageMode#CUSTOMIZE} mode.
  * <p>
  * Each {@code SectionOverride} describes how one named section of the default
- * system prompt should be modified. The section name keys come from
- * {@link SystemPromptSections}.
+ * system message should be modified. The section name keys come from
+ * {@link SystemMessageSections}.
  *
  * <h2>Static override example</h2>
  *
  * <pre>{@code
  * var config = new SystemMessageConfig().setMode(SystemMessageMode.CUSTOMIZE).setSections(Map.of(
- * 		SystemPromptSections.TONE,
+ * 		SystemMessageSections.TONE,
  * 		new SectionOverride().setAction(SectionOverrideAction.REPLACE).setContent("Be concise and formal."),
- * 		SystemPromptSections.CODE_CHANGE_RULES, new SectionOverride().setAction(SectionOverrideAction.REMOVE)));
+ * 		SystemMessageSections.CODE_CHANGE_RULES, new SectionOverride().setAction(SectionOverrideAction.REMOVE)));
  * }</pre>
  *
  * <h2>Transform callback example</h2>
  *
  * <pre>{@code
  * var config = new SystemMessageConfig().setMode(SystemMessageMode.CUSTOMIZE)
- * 		.setSections(Map.of(SystemPromptSections.IDENTITY, new SectionOverride().setTransform(
+ * 		.setSections(Map.of(SystemMessageSections.IDENTITY, new SectionOverride().setTransform(
  * 				content -> CompletableFuture.completedFuture(content + "\nAlways end replies with DONE."))));
  * }</pre>
  *
  * @see SystemMessageConfig
  * @see SectionOverrideAction
- * @see SystemPromptSections
- * @since 1.2.0
+ * @see SystemMessageSections
+ * @since 1.0.0
  */
 @JsonInclude(JsonInclude.Include.NON_NULL)
 public class SectionOverride {

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

@@ -12,7 +12,7 @@
  *
  * @see SectionOverride
  * @see SystemMessageConfig
- * @since 1.2.0
+ * @since 1.0.0
  */
 public enum SectionOverrideAction {
 

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

@@ -35,18 +35,18 @@
  * <pre>{@code
  * var config = new SystemMessageConfig().setMode(SystemMessageMode.CUSTOMIZE)
  * 		.setSections(
- * 				Map.of(SystemPromptSections.TONE,
+ * 				Map.of(SystemMessageSections.TONE,
  * 						new SectionOverride().setAction(SectionOverrideAction.REPLACE)
  * 								.setContent("Be concise and formal."),
- * 						SystemPromptSections.CODE_CHANGE_RULES,
+ * 						SystemMessageSections.CODE_CHANGE_RULES,
  * 						new SectionOverride().setAction(SectionOverrideAction.REMOVE)))
  * 		.setContent("Additional instructions appended after all sections.");
  * }</pre>
  *
  * @see SessionConfig#setSystemMessage(SystemMessageConfig)
  * @see SystemMessageMode
  * @see SectionOverride
- * @see SystemPromptSections
+ * @see SystemMessageSections
  * @since 1.0.0
  */
 @JsonInclude(JsonInclude.Include.NON_NULL)
@@ -122,7 +122,7 @@ public Map<String, SectionOverride> getSections() {
     /**
      * Sets section-level overrides for {@link SystemMessageMode#CUSTOMIZE} mode.
      * <p>
-     * Keys are section identifiers from {@link SystemPromptSections}. Each value
+     * Keys are section identifiers from {@link SystemMessageSections}. Each value
      * describes how that section should be modified. Sections with a
      * {@link SectionOverride#getTransform() transform} callback are handled locally
      * by the SDK via a {@code systemMessage.transform} RPC call; the rest are sent
@@ -131,7 +131,7 @@ public Map<String, SectionOverride> getSections() {
      * @param sections
      *            a map of section identifier to override operation
      * @return this config for method chaining
-     * @since 1.2.0
+     * @since 1.0.0
      */
     public SystemMessageConfig setSections(Map<String, SectionOverride> sections) {
         this.sections = sections;

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

@@ -0,0 +1,75 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *--------------------------------------------------------------------------------------------*/
+
+package com.github.copilot.rpc;
+
+/**
+ * Well-known system message section identifiers for use with
+ * {@link SystemMessageMode#CUSTOMIZE} mode.
+ * <p>
+ * Each constant names a section of the default Copilot system message. Pass
+ * these as keys in the {@code sections} map of {@link SystemMessageConfig} to
+ * override individual sections.
+ *
+ * <h2>Example</h2>
+ *
+ * <pre>{@code
+ * var config = new SystemMessageConfig().setMode(SystemMessageMode.CUSTOMIZE).setSections(Map.of(
+ * 		SystemMessageSections.TONE,
+ * 		new SectionOverride().setAction(SectionOverrideAction.REPLACE).setContent("Always be concise."),
+ * 		SystemMessageSections.CODE_CHANGE_RULES, new SectionOverride().setAction(SectionOverrideAction.REMOVE)));
+ * }</pre>
+ *
+ * @see SystemMessageConfig
+ * @see SectionOverride
+ * @since 1.0.2
+ */
+public abstract sealed class SystemMessageSections permits SystemPromptSections {
+
+    /** Agent identity preamble and mode statement. */
+    public static final String IDENTITY = "identity";
+
+    /** Response style, conciseness rules, output formatting preferences. */
+    public static final String TONE = "tone";
+
+    /** Tool usage patterns, parallel calling, batching guidelines. */
+    public static final String TOOL_EFFICIENCY = "tool_efficiency";
+
+    /** CWD, OS, git root, directory listing, available tools. */
+    public static final String ENVIRONMENT_CONTEXT = "environment_context";
+
+    /** Coding rules, linting/testing, ecosystem tools, style. */
+    public static final String CODE_CHANGE_RULES = "code_change_rules";
+
+    /** Tips, behavioral best practices, behavioral guidelines. */
+    public static final String GUIDELINES = "guidelines";
+
+    /** Environment limitations, prohibited actions, security policies. */
+    public static final String SAFETY = "safety";
+
+    /** Per-tool usage instructions. */
+    public static final String TOOL_INSTRUCTIONS = "tool_instructions";
+
+    /** Repository and organization custom instructions. */
+    public static final String CUSTOM_INSTRUCTIONS = "custom_instructions";
+
+    /**
+     * Runtime-provided context and instructions (e.g. system notifications,
+     * memories, workspace context, mode-specific instructions, content-exclusion
+     * policy).
+     *
+     * @since 1.3.0
+     */
+    public static final String RUNTIME_INSTRUCTIONS = "runtime_instructions";
+
+    /**
+     * End-of-prompt instructions: parallel tool calling, persistence, task
+     * completion.
+     */
+    public static final String LAST_INSTRUCTIONS = "last_instructions";
+
+    /** Package-private constructor for the sealed hierarchy. */
+    SystemMessageSections() {
+    }
+}

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

@@ -5,71 +5,19 @@
 package com.github.copilot.rpc;
 
 /**
- * Well-known system prompt section identifiers for use with
- * {@link SystemMessageMode#CUSTOMIZE} mode.
+ * Deprecated: use {@link SystemMessageSections} instead.
  * <p>
- * Each constant names a section of the default Copilot system prompt. Pass
- * these as keys in the {@code sections} map of {@link SystemMessageConfig} to
- * override individual sections.
+ * This class is retained for backward compatibility. All constants are
+ * inherited from {@link SystemMessageSections}.
  *
- * <h2>Example</h2>
- *
- * <pre>{@code
- * var config = new SystemMessageConfig().setMode(SystemMessageMode.CUSTOMIZE).setSections(Map.of(
- * 		SystemPromptSections.TONE,
- * 		new SectionOverride().setAction(SectionOverrideAction.REPLACE).setContent("Always be concise."),
- * 		SystemPromptSections.CODE_CHANGE_RULES, new SectionOverride().setAction(SectionOverrideAction.REMOVE)));
- * }</pre>
- *
- * @see SystemMessageConfig
- * @see SectionOverride
- * @since 1.2.0
+ * @deprecated Use {@link SystemMessageSections} — this class will be removed in
+ *             a future major version.
+ * @see SystemMessageSections
+ * @since 1.0.2
  */
-public final class SystemPromptSections {
-
-    /** Agent identity preamble and mode statement. */
-    public static final String IDENTITY = "identity";
-
-    /** Response style, conciseness rules, output formatting preferences. */
-    public static final String TONE = "tone";
-
-    /** Tool usage patterns, parallel calling, batching guidelines. */
-    public static final String TOOL_EFFICIENCY = "tool_efficiency";
-
-    /** CWD, OS, git root, directory listing, available tools. */
-    public static final String ENVIRONMENT_CONTEXT = "environment_context";
-
-    /** Coding rules, linting/testing, ecosystem tools, style. */
-    public static final String CODE_CHANGE_RULES = "code_change_rules";
-
-    /** Tips, behavioral best practices, behavioral guidelines. */
-    public static final String GUIDELINES = "guidelines";
-
-    /** Environment limitations, prohibited actions, security policies. */
-    public static final String SAFETY = "safety";
-
-    /** Per-tool usage instructions. */
-    public static final String TOOL_INSTRUCTIONS = "tool_instructions";
-
-    /** Repository and organization custom instructions. */
-    public static final String CUSTOM_INSTRUCTIONS = "custom_instructions";
-
-    /**
-     * Runtime-provided context and instructions (e.g. system notifications,
-     * memories, workspace context, mode-specific instructions, content-exclusion
-     * policy).
-     *
-     * @since 1.3.0
-     */
-    public static final String RUNTIME_INSTRUCTIONS = "runtime_instructions";
-
-    /**
-     * End-of-prompt instructions: parallel tool calling, persistence, task
-     * completion.
-     */
-    public static final String LAST_INSTRUCTIONS = "last_instructions";
+@Deprecated(since = "1.0.2", forRemoval = true)
+public final class SystemPromptSections extends SystemMessageSections {
 
     private SystemPromptSections() {
-        // utility class
     }
 }