feat: render summarization/compact user message (#736)

src/cli/helpers/accumulator.ts

@@ -5,8 +5,12 @@
 // - Exposes `onChunk` to feed SDK events and `toLines` to render.
 
 import type { LettaStreamingResponse } from "@letta-ai/letta-client/resources/agents/messages";
-import { INTERRUPTED_BY_USER } from "../../constants";
+import {
+  COMPACTION_SUMMARY_HEADER,
+  INTERRUPTED_BY_USER,
+} from "../../constants";
 import { runPostToolUseHooks, runPreToolUseHooks } from "../../hooks";
+import { extractCompactionSummary } from "./backfill";
 import { findLastSafeSplitPoint } from "./markdownSplit";
 import { isShellTool } from "./toolNameMapping";
 
@@ -505,6 +509,33 @@ export function onChunk(b: Buffers, chunk: LettaStreamingResponse) {
       break;
     }
 
+    case "user_message": {
+      // Use otid if available, fall back to id (server sends otid: null for summary messages)
+      const chunkWithId = chunk as LettaStreamingResponse & { id?: string };
+      const id = chunk.otid || chunkWithId.id;
+      if (!id) break;
+
+      // Handle otid transition (mark previous line as finished)
+      handleOtidTransition(b, id);
+
+      // Extract text content from the user message
+      const rawText = extractTextPart(chunk.content);
+      if (!rawText) break;
+
+      // Check if this is a compaction summary message
+      const compactionSummary = extractCompactionSummary(rawText);
+      if (compactionSummary) {
+        // Render as a user message with context header and summary
+        ensure(b, id, () => ({
+          kind: "user",
+          id,
+          text: `${COMPACTION_SUMMARY_HEADER}\n\n${compactionSummary}`,
+        }));
+      }
+      // If not a summary, ignore it (user messages aren't rendered during streaming)
+      break;
+    }
+
     case "tool_call_message":
     case "approval_request_message": {
       /* POST-FIX VERSION (what this should look like after backend fix):

src/cli/helpers/backfill.ts

@@ -5,7 +5,11 @@ import type {
   Message,
   TextContent,
 } from "@letta-ai/letta-client/resources/agents/messages";
-import { SYSTEM_REMINDER_CLOSE, SYSTEM_REMINDER_OPEN } from "../../constants";
+import {
+  COMPACTION_SUMMARY_HEADER,
+  SYSTEM_REMINDER_CLOSE,
+  SYSTEM_REMINDER_OPEN,
+} from "../../constants";
 import type { Buffers } from "./accumulator";
 
 /**
@@ -81,7 +85,7 @@ function truncateSystemReminder(text: string, maxLength: number): string {
  * Check if a user message is a compaction summary (system_alert with summary content).
  * Returns the summary text if found, null otherwise.
  */
-function extractCompactionSummary(text: string): string | null {
+export function extractCompactionSummary(text: string): string | null {
   try {
     const parsed = JSON.parse(text);
     if (
@@ -182,17 +186,12 @@ export function backfillBuffers(buffers: Buffers, history: Message[]): void {
         // Check if this is a compaction summary message (system_alert with summary)
         const compactionSummary = extractCompactionSummary(rawText);
         if (compactionSummary) {
-          // Render as a synthetic tool call showing the compaction
+          // Render as a user message with context header and summary
           const exists = buffers.byId.has(lineId);
           buffers.byId.set(lineId, {
-            kind: "tool_call",
+            kind: "user",
             id: lineId,
-            toolCallId: `compaction-${lineId}`,
-            name: "Compact",
-            argsText: "messages[...]",
-            resultText: compactionSummary,
-            resultOk: true,
-            phase: "finished",
+            text: `${COMPACTION_SUMMARY_HEADER}\n\n${compactionSummary}`,
           });
           if (!exists) buffers.order.push(lineId);
           break;

src/constants.ts

@@ -24,6 +24,12 @@ export const SYSTEM_REMINDER_TAG = "system-reminder";
 export const SYSTEM_REMINDER_OPEN = `<${SYSTEM_REMINDER_TAG}>`;
 export const SYSTEM_REMINDER_CLOSE = `</${SYSTEM_REMINDER_TAG}>`;
 
+/**
+ * Header displayed before compaction summary when conversation context is truncated
+ */
+export const COMPACTION_SUMMARY_HEADER =
+  "This session is being continued from a previous conversation that ran out of context. The summary below covers the earlier portion of the conversation.";
+
 /**
  * Status bar thresholds - only show indicators when values exceed these
  */