Update @github/copilot to 1.0.21

docs/troubleshooting/compatibility.md

@@ -86,7 +86,9 @@ The Copilot SDK communicates with the CLI via JSON-RPC protocol. Features must b
 | **Experimental** | | |
 | Agent management | `session.rpc.agent.*` | List, select, deselect, get current agent |
 | Fleet mode | `session.rpc.fleet.start()` | Parallel sub-agent execution |
-| Manual compaction | `session.rpc.compaction.compact()` | Trigger compaction on demand |
+| Manual compaction | `session.rpc.history.compact()` | Trigger compaction on demand |
+| History truncation | `session.rpc.history.truncate()` | Remove events from a point onward |
+| Session forking | `server.rpc.sessions.fork()` | Fork a session at a point in history |
 
 ### ❌ Not Available in SDK (CLI-Only)
 
@@ -222,7 +224,7 @@ const session = await client.createSession({
 });
 
 // Manual compaction (experimental)
-const result = await session.rpc.compaction.compact();
+const result = await session.rpc.history.compact();
 console.log(`Removed ${result.tokensRemoved} tokens, ${result.messagesRemoved} messages`);
 ```
 

dotnet/test/AgentAndCompactRpcTests.cs

@@ -135,7 +135,7 @@ public async Task Should_Compact_Session_History_After_Messages()
         await session.SendAndWaitAsync(new MessageOptions { Prompt = "What is 2+2?" });
 
         // Compact the session
-        var result = await session.Rpc.Compaction.CompactAsync();
+        var result = await session.Rpc.History.CompactAsync();
         Assert.NotNull(result);
     }
 }

dotnet/test/SessionFsTests.cs

@@ -211,7 +211,7 @@ public async Task Should_Succeed_With_Compaction_While_Using_SessionFs()
             var contentBefore = await ReadAllTextSharedAsync(eventsPath);
             Assert.DoesNotContain("checkpointNumber", contentBefore);
 
-            await session.Rpc.Compaction.CompactAsync();
+            await session.Rpc.History.CompactAsync();
             await WaitForConditionAsync(() => compactionEvent is not null, TimeSpan.FromSeconds(30));
             Assert.True(compactionEvent!.Data.Success);
 

go/internal/e2e/agent_and_compact_rpc_test.go

@@ -281,7 +281,7 @@ func TestSessionCompactionRpc(t *testing.T) {
 		}
 
 		// Compact the session
-		result, err := session.RPC.Compaction.Compact(t.Context())
+		result, err := session.RPC.History.Compact(t.Context())
 		if err != nil {
 			t.Fatalf("Failed to compact session: %v", err)
 		}