feat(sdk): implement context compaction for long sessions

package.json

@@ -36,6 +36,7 @@
     "@office-agents/bridge": "workspace:*",
     "@types/node": "^25.1.0",
     "happy-dom": "^20.8.4",
+    "office-addin-dev-certs": "^2.0.6",
     "svelte-check": "^4.3.3",
     "typescript": "^5.4.2",
     "vitest": "^4.0.18",

packages/sdk/src/index.ts

@@ -15,7 +15,9 @@ export {
   type ChatMessage,
   deriveStats,
   extractPartsFromAssistantMessage,
+  filterMessagesForLLM,
   generateId,
+  isContextOverflow,
   type MessagePart,
   type SessionStats,
   stripEnrichment,

packages/sdk/src/message-utils.ts

@@ -9,6 +9,87 @@ import type {
 
 export type ToolCallStatus = "pending" | "running" | "complete" | "error";
 
+/**
+ * Filters agent messages for LLM context.
+ * Finds the last compactionSummary message and returns it + everything after it.
+ * The compactionSummary is converted to a UserMessage with the summary wrapped in tags.
+ * This is used to prevent context overflow when messages become too long.
+ */
+export function filterMessagesForLLM(
+  messages: AgentMessage[],
+): AgentMessage[] {
+  // Find the last compactionSummary message
+  let lastCompactionIdx = -1;
+  for (let i = messages.length - 1; i >= 0; i--) {
+    const msg = messages[i] as unknown as { role: string; summary?: string; timestamp?: number };
+    if (msg.role === "compactionSummary") {
+      lastCompactionIdx = i;
+      break;
+    }
+  }
+
+  // If no compactionSummary, return all
+  if (lastCompactionIdx === -1) {
+    return messages;
+  }
+
+  // Get the compactionSummary and extract summary text
+  const compactionMsg = messages[lastCompactionIdx] as unknown as { summary?: string; timestamp?: number };
+  const summaryText = compactionMsg.summary || "Previous conversation summary";
+
+  // Create a user message with the summary wrapped in tags
+  const summaryUserMsg = {
+    role: "user",
+    content: [
+      {
+        type: "text",
+        text: `<compaction_summary>\n${summaryText}\n</compaction_summary>`,
+      },
+    ],
+    timestamp: (compactionMsg.timestamp as number) || Date.now(),
+  } as unknown as AgentMessage;
+
+  // Return: summary as user message + everything after it
+  return [summaryUserMsg, ...messages.slice(lastCompactionIdx + 1)] as AgentMessage[];
+}
+
+/**
+ * Detects if an assistant message indicates a context overflow error.
+ */
+export function isContextOverflow(
+  message: AssistantMessage,
+  contextWindow: number,
+  reserveTokens: number = 4000,
+): boolean {
+  // Check if it's an error with overflow indicators
+  if (message.stopReason === "error" && message.errorMessage) {
+    const errorLower = message.errorMessage.toLowerCase();
+    if (
+      errorLower.includes("context") ||
+      errorLower.includes("limit") ||
+      errorLower.includes("max") ||
+      errorLower.includes("token") ||
+      errorLower.includes("overflow") ||
+      errorLower.includes("context_length")
+    ) {
+      return true;
+    }
+  }
+
+  // Check if usage exceeds context window (with reserve)
+  if (message.usage && contextWindow > 0) {
+    const totalTokens =
+      message.usage.input +
+      message.usage.cacheRead +
+      message.usage.cacheWrite;
+    if (totalTokens > contextWindow - reserveTokens) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 export type MessagePart =
   | { type: "text"; text: string }
   | { type: "thinking"; thinking: string }
@@ -56,11 +137,11 @@ export function stripEnrichment(
   if (metadataTag) {
     const escaped = metadataTag.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
     text = text.replace(
-      new RegExp(`^<${escaped}>\\n[\\s\\S]*?\\n</${escaped}>\\n\\n`),
+      new RegExp(`^<${escaped}>\n[\\s\\S]*?</${escaped}>\n\n`),
       "",
     );
   } else {
-    text = text.replace(/^<\w+_context>\n[\s\S]*?\n<\/\w+_context>\n\n/, "");
+    text = text.replace(/^<\w+_context>\n[\\s\\S]*?<\/\w+_context>\n\n/, "");
   }
   return text;
 }
@@ -73,9 +154,11 @@ export function extractPartsFromAssistantMessage(
   message: AgentMessage,
   existingParts: MessagePart[] = [],
 ): MessagePart[] {
-  if (message.role !== "assistant") return existingParts;
+  // Skip non-assistant messages
+  const role = message.role;
+  if (role !== "assistant") return existingParts;
 
-  const assistantMsg = message as AssistantMessage;
+  const assistantMsg = message as unknown as AssistantMessage;
   const existingToolCalls = new Map<string, MessagePart>();
   for (const part of existingParts) {
     if (part.type === "toolCall") {
@@ -108,24 +191,31 @@ export function agentMessagesToChatMessages(
 ): ChatMessage[] {
   const result: ChatMessage[] = [];
   for (const msg of agentMessages) {
-    if (msg.role === "user") {
-      const text = stripEnrichment((msg as UserMessage).content, metadataTag);
+    // Skip compactionSummary messages - they're for LLM context only
+    const rawMsg = msg as unknown as { role: string };
+    if (rawMsg.role === "compactionSummary") {
+      continue;
+    }
+
+    if (rawMsg.role === "user") {
+      const userMsg = msg as unknown as UserMessage;
+      const text = stripEnrichment(userMsg.content, metadataTag);
       result.push({
         id: generateId(),
         role: "user",
         parts: [{ type: "text", text }],
-        timestamp: msg.timestamp,
+        timestamp: userMsg.timestamp,
       });
     } else if (msg.role === "assistant") {
       const parts = extractPartsFromAssistantMessage(msg);
       result.push({
         id: generateId(),
         role: "assistant",
         parts,
-        timestamp: msg.timestamp,
+        timestamp: (msg as unknown as AssistantMessage).timestamp,
       });
     } else if (msg.role === "toolResult") {
-      const toolResult = msg as ToolResultMessage;
+      const toolResult = msg as unknown as ToolResultMessage;
       for (let i = result.length - 1; i >= 0; i--) {
         const chatMsg = result[i];
         if (chatMsg.role !== "assistant") continue;
@@ -167,16 +257,17 @@ export function deriveStats(
   let totalCost = 0;
   let lastInputTokens = 0;
   for (const msg of agentMessages) {
-    if (msg.role === "assistant") {
-      const u = (msg as AssistantMessage).usage;
-      if (u) {
-        inputTokens += u.input;
-        outputTokens += u.output;
-        cacheRead += u.cacheRead;
-        cacheWrite += u.cacheWrite;
-        totalCost += u.cost.total;
-        lastInputTokens = u.input + u.cacheRead + u.cacheWrite;
-      }
+    // Skip non-assistant messages
+    if (msg.role !== "assistant") continue;
+
+    const u = (msg as unknown as AssistantMessage).usage;
+    if (u) {
+      inputTokens += u.input;
+      outputTokens += u.output;
+      cacheRead += u.cacheRead;
+      cacheWrite += u.cacheWrite;
+      totalCost += u.cost.total;
+      lastInputTokens = u.input + u.cacheRead + u.cacheWrite;
     }
   }
   return {
@@ -187,4 +278,4 @@ export function deriveStats(
     totalCost,
     lastInputTokens,
   };
-}
+}