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>

Author: edburns

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

@@ -12,33 +12,33 @@
 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
+ * @see SystemMessageSections
  * @since 1.2.0
  */
 @JsonInclude(JsonInclude.Include.NON_NULL)

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

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 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
+ * @deprecated Use {@link SystemMessageSections} — this class will be removed in
+ *             a future major version.
+ * @see SystemMessageSections
  * @since 1.2.0
  */
-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
     }
 }

java/src/test/java/com/github/copilot/SystemMessageSectionsIT.java

@@ -0,0 +1,124 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *--------------------------------------------------------------------------------------------*/
+
+package com.github.copilot;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import com.github.copilot.rpc.CopilotClientOptions;
+import com.github.copilot.rpc.MessageOptions;
+import com.github.copilot.rpc.PermissionHandler;
+import com.github.copilot.rpc.SectionOverride;
+import com.github.copilot.rpc.SessionConfig;
+import com.github.copilot.rpc.SystemMessageConfig;
+import com.github.copilot.rpc.SystemMessageSections;
+import com.github.copilot.rpc.SystemPromptSections;
+
+/**
+ * Failsafe integration test that validates {@link SystemMessageSections}
+ * constants are recognized by the live Copilot CLI runtime.
+ * <p>
+ * Uses a transform callback on the {@code identity} section to assert the
+ * runtime invokes the callback with non-empty content — proving the constant is
+ * a valid section identifier understood by the runtime.
+ * <p>
+ * Requires the CLI to be installed and the user to be signed in. Uses
+ * {@link TestUtil#findCliPath()} so the test harness binary is found in CI.
+ */
+@SuppressWarnings("deprecation")
+class SystemMessageSectionsIT {
+
+    private static CopilotClient client;
+
+    @BeforeAll
+    static void setup() throws Exception {
+        String cliPath = TestUtil.findCliPath();
+        CopilotClientOptions options = new CopilotClientOptions().setCliPath(cliPath).setUseLoggedInUser(true);
+        client = new CopilotClient(options);
+        client.start().get(30, TimeUnit.SECONDS);
+    }
+
+    @AfterAll
+    static void teardown() throws Exception {
+        if (client != null) {
+            client.close();
+        }
+    }
+
+    /**
+     * Verifies that a transform callback on {@link SystemMessageSections#IDENTITY}
+     * is invoked by the runtime with non-empty section content.
+     * <p>
+     * This proves the constant {@code "identity"} is a real section ID that the
+     * runtime recognizes and populates.
+     */
+    @Test
+    void transformOnIdentitySectionReceivesNonEmptyContent() throws Exception {
+        // Thread-safe container to capture what the runtime passes to our transform
+        ConcurrentHashMap<String, String> capturedContent = new ConcurrentHashMap<>();
+
+        var systemMessage = new SystemMessageConfig().setMode(SystemMessageMode.CUSTOMIZE)
+                .setSections(Map.of(SystemMessageSections.IDENTITY, new SectionOverride().setTransform(content -> {
+                    capturedContent.put("identity", content);
+                    return CompletableFuture.completedFuture(content);
+                }), SystemMessageSections.TONE, new SectionOverride().setTransform(content -> {
+                    capturedContent.put("tone", content);
+                    return CompletableFuture.completedFuture(content);
+                })));
+
+        CopilotSession session = client.createSession(new SessionConfig().setSystemMessage(systemMessage)
+                .setOnPermissionRequest(PermissionHandler.APPROVE_ALL)).get(30, TimeUnit.SECONDS);
+
+        try {
+            // Send a message to trigger the runtime to build the system message
+            // (transforms fire during session creation or first message)
+            session.sendAndWait(new MessageOptions().setPrompt("Say hello"), 60_000).get(90, TimeUnit.SECONDS);
+
+            // Assert: identity transform was invoked with non-empty content
+            String identityContent = capturedContent.get("identity");
+            assertNotNull(identityContent, "Expected identity transform callback to be invoked by the runtime");
+            assertTrue(!identityContent.isBlank(), "Expected identity section content to be non-empty but was blank");
+
+            // Assert: tone transform was also invoked
+            String toneContent = capturedContent.get("tone");
+            assertNotNull(toneContent, "Expected tone transform callback to be invoked by the runtime");
+            assertTrue(!toneContent.isBlank(), "Expected tone section content to be non-empty but was blank");
+        } finally {
+            session.close();
+        }
+    }
+
+    /**
+     * Verifies that the deprecated {@link SystemPromptSections} constants resolve
+     * to the same values as {@link SystemMessageSections} — ensuring backward
+     * compatibility.
+     */
+    @Test
+    void deprecatedSystemPromptSectionsMatchesSystemMessageSections() {
+        // These are compile-time constants so this test guards against accidental
+        // divergence if someone edits one class but not the other.
+        assertEquals(SystemMessageSections.IDENTITY, SystemPromptSections.IDENTITY);
+        assertEquals(SystemMessageSections.TONE, SystemPromptSections.TONE);
+        assertEquals(SystemMessageSections.TOOL_EFFICIENCY, SystemPromptSections.TOOL_EFFICIENCY);
+        assertEquals(SystemMessageSections.ENVIRONMENT_CONTEXT, SystemPromptSections.ENVIRONMENT_CONTEXT);
+        assertEquals(SystemMessageSections.CODE_CHANGE_RULES, SystemPromptSections.CODE_CHANGE_RULES);
+        assertEquals(SystemMessageSections.GUIDELINES, SystemPromptSections.GUIDELINES);
+        assertEquals(SystemMessageSections.SAFETY, SystemPromptSections.SAFETY);
+        assertEquals(SystemMessageSections.TOOL_INSTRUCTIONS, SystemPromptSections.TOOL_INSTRUCTIONS);
+        assertEquals(SystemMessageSections.CUSTOM_INSTRUCTIONS, SystemPromptSections.CUSTOM_INSTRUCTIONS);
+        assertEquals(SystemMessageSections.RUNTIME_INSTRUCTIONS, SystemPromptSections.RUNTIME_INSTRUCTIONS);
+        assertEquals(SystemMessageSections.LAST_INSTRUCTIONS, SystemPromptSections.LAST_INSTRUCTIONS);
+    }
+}