Optimize summarization (#487)

src/__tests__/formatMessagesForSummary.test.ts

+import { formatMessagesForSummary } from "../ipc/handlers/chat_stream_handlers";
+
+describe("formatMessagesForSummary", () => {
+  it("should return all messages when there are 8 or fewer messages", () => {
+    const messages = [
+      { role: "user", content: "Hello" },
+      { role: "assistant", content: "Hi there!" },
+      { role: "user", content: "How are you?" },
+      { role: "assistant", content: "I'm doing well, thanks!" },
+    ];
+
+    const result = formatMessagesForSummary(messages);
+    const expected = [
+      '<message role="user">Hello</message>',
+      '<message role="assistant">Hi there!</message>',
+      '<message role="user">How are you?</message>',
+      '<message role="assistant">I\'m doing well, thanks!</message>',
+    ].join("\n");
+
+    expect(result).toBe(expected);
+  });
+
+  it("should return all messages when there are exactly 8 messages", () => {
+    const messages = Array.from({ length: 8 }, (_, i) => ({
+      role: i % 2 === 0 ? "user" : "assistant",
+      content: `Message ${i + 1}`,
+    }));
+
+    const result = formatMessagesForSummary(messages);
+    const expected = messages
+      .map((m) => `<message role="${m.role}">${m.content}</message>`)
+      .join("\n");
+
+    expect(result).toBe(expected);
+  });
+
+  it("should truncate messages when there are more than 8 messages", () => {
+    const messages = Array.from({ length: 12 }, (_, i) => ({
+      role: i % 2 === 0 ? "user" : "assistant",
+      content: `Message ${i + 1}`,
+    }));
+
+    const result = formatMessagesForSummary(messages);
+
+    // Should contain first 2 messages
+    expect(result).toContain('<message role="user">Message 1</message>');
+    expect(result).toContain('<message role="assistant">Message 2</message>');
+
+    // Should contain omission indicator
+    expect(result).toContain(
+      '<message role="system">[... 4 messages omitted ...]</message>',
+    );
+
+    // Should contain last 6 messages
+    expect(result).toContain('<message role="user">Message 7</message>');
+    expect(result).toContain('<message role="assistant">Message 8</message>');
+    expect(result).toContain('<message role="user">Message 9</message>');
+    expect(result).toContain('<message role="assistant">Message 10</message>');
+    expect(result).toContain('<message role="user">Message 11</message>');
+    expect(result).toContain('<message role="assistant">Message 12</message>');
+
+    // Should not contain middle messages
+    expect(result).not.toContain('<message role="user">Message 3</message>');
+    expect(result).not.toContain(
+      '<message role="assistant">Message 4</message>',
+    );
+    expect(result).not.toContain('<message role="user">Message 5</message>');
+    expect(result).not.toContain(
+      '<message role="assistant">Message 6</message>',
+    );
+  });
+
+  it("should handle messages with undefined content", () => {
+    const messages = [
+      { role: "user", content: "Hello" },
+      { role: "assistant", content: undefined },
+      { role: "user", content: "Are you there?" },
+    ];
+
+    const result = formatMessagesForSummary(messages);
+    const expected = [
+      '<message role="user">Hello</message>',
+      '<message role="assistant">undefined</message>',
+      '<message role="user">Are you there?</message>',
+    ].join("\n");
+
+    expect(result).toBe(expected);
+  });
+
+  it("should handle empty messages array", () => {
+    const messages: { role: string; content: string | undefined }[] = [];
+    const result = formatMessagesForSummary(messages);
+    expect(result).toBe("");
+  });
+
+  it("should handle single message", () => {
+    const messages = [{ role: "user", content: "Hello world" }];
+    const result = formatMessagesForSummary(messages);
+    expect(result).toBe('<message role="user">Hello world</message>');
+  });
+
+  it("should correctly calculate omitted messages count", () => {
+    const messages = Array.from({ length: 20 }, (_, i) => ({
+      role: i % 2 === 0 ? "user" : "assistant",
+      content: `Message ${i + 1}`,
+    }));
+
+    const result = formatMessagesForSummary(messages);
+
+    // Should indicate 12 messages omitted (20 total - 2 first - 6 last = 12)
+    expect(result).toContain(
+      '<message role="system">[... 12 messages omitted ...]</message>',
+    );
+  });
+
+  it("should handle messages with special characters in content", () => {
+    const messages = [
+      { role: "user", content: 'Hello <world> & "friends"' },
+      { role: "assistant", content: "Hi there! <tag>content</tag>" },
+    ];
+
+    const result = formatMessagesForSummary(messages);
+
+    // Should preserve special characters as-is (no HTML escaping)
+    expect(result).toContain(
+      '<message role="user">Hello <world> & "friends"</message>',
+    );
+    expect(result).toContain(
+      '<message role="assistant">Hi there! <tag>content</tag></message>',
+    );
+  });
+
+  it("should maintain message order in truncated output", () => {
+    const messages = Array.from({ length: 15 }, (_, i) => ({
+      role: i % 2 === 0 ? "user" : "assistant",
+      content: `Message ${i + 1}`,
+    }));
+
+    const result = formatMessagesForSummary(messages);
+    const lines = result.split("\n");
+
+    // Should have exactly 9 lines (2 first + 1 omission + 6 last)
+    expect(lines).toHaveLength(9);
+
+    // Check order: first 2, then omission, then last 6
+    expect(lines[0]).toBe('<message role="user">Message 1</message>');
+    expect(lines[1]).toBe('<message role="assistant">Message 2</message>');
+    expect(lines[2]).toBe(
+      '<message role="system">[... 7 messages omitted ...]</message>',
+    );
+
+    // Last 6 messages are messages 10-15 (indices 9-14)
+    // Message 10 (index 9): 9 % 2 === 1, so "assistant"
+    // Message 11 (index 10): 10 % 2 === 0, so "user"
+    // Message 12 (index 11): 11 % 2 === 1, so "assistant"
+    // Message 13 (index 12): 12 % 2 === 0, so "user"
+    // Message 14 (index 13): 13 % 2 === 1, so "assistant"
+    // Message 15 (index 14): 14 % 2 === 0, so "user"
+    expect(lines[3]).toBe('<message role="assistant">Message 10</message>');
+    expect(lines[4]).toBe('<message role="user">Message 11</message>');
+    expect(lines[5]).toBe('<message role="assistant">Message 12</message>');
+    expect(lines[6]).toBe('<message role="user">Message 13</message>');
+    expect(lines[7]).toBe('<message role="assistant">Message 14</message>');
+    expect(lines[8]).toBe('<message role="user">Message 15</message>');
+  });
+});

src/ipc/handlers/chat_stream_handlers.ts

@@ -446,7 +446,7 @@ This conversation includes one or more image attachments. When the user uploads
               role: "user",
               content:
                 "Summarize the following chat: " +
-                formatMessages(previousChat?.messages ?? []),
+                formatMessagesForSummary(previousChat?.messages ?? []),
             } satisfies CoreMessage,
           ];
         }
@@ -775,10 +775,31 @@ This conversation includes one or more image attachments. When the user uploads
   });
 }
 
-export function formatMessages(
+export function formatMessagesForSummary(
   messages: { role: string; content: string | undefined }[],
 ) {
-  return messages
+  if (messages.length <= 8) {
+    // If we have 8 or fewer messages, include all of them
+    return messages
+      .map((m) => `<message role="${m.role}">${m.content}</message>`)
+      .join("\n");
+  }
+
+  // Take first 2 messages and last 6 messages
+  const firstMessages = messages.slice(0, 2);
+  const lastMessages = messages.slice(-6);
+
+  // Combine them with an indicator of skipped messages
+  const combinedMessages = [
+    ...firstMessages,
+    {
+      role: "system",
+      content: `[... ${messages.length - 8} messages omitted ...]`,
+    },
+    ...lastMessages,
+  ];
+
+  return combinedMessages
     .map((m) => `<message role="${m.role}">${m.content}</message>`)
     .join("\n");
 }