feat: add Answer agent for automatic post answer generation

agent/answer-agent.ts

@@ -0,0 +1,119 @@
+import { stepCountIs, streamText, tool } from "ai"
+import { eq } from "drizzle-orm"
+import { updateTag } from "next/cache"
+import { z } from "zod"
+import { db } from "@/lib/db/client"
+import { posts } from "@/lib/db/schema"
+import { getSiteOrigin } from "@/lib/utils"
+import type { NoAnswerReason, PostAnswer } from "./types"
+
+export async function runAnswerAgent({
+  postId,
+  owner,
+  repo,
+  postNumber,
+  currentAnswer,
+}: {
+  postId: string
+  owner: string
+  repo: string
+  postNumber: number
+  currentAnswer?: PostAnswer | null
+}) {
+  const result: { answer?: PostAnswer } = {}
+
+  const llmsTxtUrl = `${getSiteOrigin()}/${owner}/${repo}/${postNumber}/llms.txt`
+
+  let transcript: string
+  try {
+    const res = await fetch(llmsTxtUrl)
+    if (!res.ok) {
+      console.error("Failed to fetch llms.txt:", res.status)
+      return
+    }
+    transcript = await res.text()
+  } catch (err) {
+    console.error("Failed to fetch llms.txt:", err)
+    return
+  }
+
+  const currentAnswerContext = currentAnswer
+    ? currentAnswer.type === "answer"
+      ? `\n\nYour previous answer was:\n${currentAnswer.text}\n\nReview if this is still accurate given any new comments.`
+      : `\n\nYou previously determined this was not a question (reason: ${currentAnswer.reason}).`
+    : ""
+
+  const systemPrompt = `You are a forum answer assistant. Your job is to analyze a forum post transcript and determine the best answer to the original question (the first comment in the post).
+
+Rules:
+- Focus on answering the ORIGINAL question (first comment) - the post may have evolved but we want to answer what was initially asked
+- If the post contains a clear answer to the original question (from any participant), use SetAnswer with a concise summary
+- If the post is NOT a question (it's an announcement, discussion, or purely informational), use SetNoAnswer with reason "not-a-question"
+- If the question is unclear or cannot be answered from the available context, use SetNoAnswer with reason "unclear" or "needs-more-context"
+- Be extremely concise in your answer - summarize the key points without unnecessary verbosity
+- Only call ONE tool: either SetAnswer OR SetNoAnswer${currentAnswerContext}`
+
+  const tools: Parameters<typeof streamText>[0]["tools"] = {
+    SetAnswer: tool({
+      description:
+        "Set the answer to the original question. Use when a clear answer exists in the transcript.",
+      inputSchema: z.object({
+        text: z
+          .string()
+          .describe(
+            "Concise answer to the original question, summarizing the key points"
+          ),
+      }),
+      // biome-ignore lint/suspicious/useAwait: .
+      execute: async (params) => {
+        result.answer = {
+          type: "answer",
+          text: params.text,
+          updatedAt: Date.now(),
+        }
+        return { ok: true }
+      },
+    }),
+    SetNoAnswer: tool({
+      description:
+        "Indicate that no answer can be provided. Use when the post is not a question or lacks enough context.",
+      inputSchema: z.object({
+        reason: z
+          .enum(["not-a-question", "unclear", "needs-more-context"])
+          .describe("Why no answer can be provided"),
+      }),
+      // biome-ignore lint/suspicious/useAwait: .
+      execute: async (params) => {
+        result.answer = {
+          type: "no-answer",
+          reason: params.reason as NoAnswerReason,
+          updatedAt: Date.now(),
+        }
+        return { ok: true }
+      },
+    }),
+  }
+
+  const stream = streamText({
+    model: "anthropic/claude-haiku-4.5",
+    system: systemPrompt,
+    prompt: `Here's the full post transcript:\n\n${transcript}`,
+    tools,
+    stopWhen: stepCountIs(3),
+  })
+
+  await stream.finishReason
+
+  if (!result.answer) {
+    console.log("Answer agent did not produce an answer")
+    return
+  }
+
+  await db
+    .update(posts)
+    .set({ answer: result.answer, updatedAt: Date.now() })
+    .where(eq(posts.id, postId))
+
+  updateTag(`repo:${owner}:${repo}`)
+  updateTag(`post:${postId}`)
+}

agent/types.ts

@@ -9,3 +9,9 @@ export type GitContextData = {
   message: string
   date: string
 }
+
+export type NoAnswerReason = "not-a-question" | "unclear" | "needs-more-context"
+
+export type PostAnswer =
+  | { type: "answer"; text: string; updatedAt: number }
+  | { type: "no-answer"; reason: NoAnswerReason; updatedAt: number }

app/[owner]/[repo]/[postNumber]/comment-thread-client.tsx

@@ -2,6 +2,7 @@
 
 import type { InferSelectModel } from "drizzle-orm"
 import { useEffect, useMemo, useState } from "react"
+import type { PostAnswer } from "@/agent/types"
 import { authClient } from "@/lib/auth-client"
 import type {
   comments as commentsSchema,
@@ -39,6 +40,7 @@ export function CommentThreadClient({
   rootCommentId,
   commentNumbers,
   askingOptions,
+  answer,
 }: {
   owner: string
   repo: string
@@ -49,6 +51,7 @@ export function CommentThreadClient({
   rootCommentId: string | null
   commentNumbers: Map<string, string>
   askingOptions: AskingOption[]
+  answer?: PostAnswer | null
 }) {
   const [replyingToId, setReplyingToId] = useState<string | null>(null)
   const isSignedIn = !!authClient.useSession().data?.session
@@ -85,6 +88,7 @@ export function CommentThreadClient({
 
   return (
     <CommentThread
+      answer={answer}
       askingOptions={askingOptions}
       authorsById={authorsById}
       commentNumbers={commentNumbers}

app/[owner]/[repo]/[postNumber]/comment-thread.tsx

@@ -2,7 +2,7 @@ import type { InferSelectModel } from "drizzle-orm"
 import Link from "next/link"
 import { useParams } from "next/navigation"
 import { Suspense } from "react"
-import type { AgentUIMessage } from "@/agent/types"
+import type { AgentUIMessage, PostAnswer } from "@/agent/types"
 import type { ComposerProps } from "@/components/composer"
 import { CopyLinkButton } from "@/components/copy-link-button"
 import { CopyMarkdownButton } from "@/components/copy-markdown-button"
@@ -18,6 +18,7 @@ import type {
 import { cn } from "@/lib/utils"
 import { CommentContent } from "./comment-content"
 import { MentionBanner } from "./mention-banner"
+import { PostAnswerBox } from "./post-answer"
 import { PostComposer } from "./post-composer"
 import {
   StreamingBadge,
@@ -119,9 +120,7 @@ function CommentItem({
             isRootComment={isRootComment}
           />
           {comment.streamStatus !== "streaming" && (
-            <CopyMarkdownButton
-              content={comment.content as AgentUIMessage[]}
-            />
+            <CopyMarkdownButton content={comment.content as AgentUIMessage[]} />
           )}
           <CopyLinkButton
             commentNumber={commentNumber}
@@ -219,6 +218,7 @@ export function CommentThread({
   onReply,
   onCancelReply,
   askingOptions,
+  answer,
 }: {
   owner: string
   repo: string
@@ -232,6 +232,7 @@ export function CommentThread({
   onReply?: (commentId: string) => void
   onCancelReply?: () => void
   askingOptions: ComposerProps["options"]["asking"]
+  answer?: PostAnswer | null
 }) {
   const reactionsByComment: Record<string, Reaction[]> = {}
   for (const reaction of reactions) {
@@ -283,51 +284,59 @@ export function CommentThread({
         const replies = repliesByThread.get(comment.id) ?? []
         const hasReplies = replies.length > 0
 
+        const showAnswer = isRootComment && answer?.type === "answer"
+
         return (
-          <CommentItem
-            askingOptions={askingOptions}
-            author={author}
-            comment={comment}
-            commentId={comment.id}
-            commentNumber={commentNumber}
-            depth={0}
-            hasReplies={hasReplies}
-            isReplying={replyingToId === comment.id}
-            isRootComment={isRootComment}
-            key={comment.id}
-            onCancelReply={onCancelReply}
-            onReply={onReply}
-            owner={owner}
-            reactions={reactionsByComment[comment.id] ?? []}
-            repo={repo}
-          >
-            {hasReplies && (
-              <div className="space-y-4">
-                {replies.map((reply) => {
-                  const replyAuthor = authorsById[reply.authorId]
-                  if (!replyAuthor) {
-                    return null
-                  }
-                  const replyNumber = commentNumbers.get(reply.id) ?? "?"
-                  return (
-                    <CommentItem
-                      askingOptions={askingOptions}
-                      author={replyAuthor}
-                      comment={reply}
-                      commentId={reply.id}
-                      commentNumber={replyNumber}
-                      depth={1}
-                      isRootComment={false}
-                      key={reply.id}
-                      owner={owner}
-                      reactions={reactionsByComment[reply.id] ?? []}
-                      repo={repo}
-                    />
-                  )
-                })}
+          <div key={comment.id}>
+            <CommentItem
+              askingOptions={askingOptions}
+              author={author}
+              comment={comment}
+              commentId={comment.id}
+              commentNumber={commentNumber}
+              depth={0}
+              hasReplies={hasReplies}
+              isReplying={replyingToId === comment.id}
+              isRootComment={isRootComment}
+              onCancelReply={onCancelReply}
+              onReply={onReply}
+              owner={owner}
+              reactions={reactionsByComment[comment.id] ?? []}
+              repo={repo}
+            >
+              {hasReplies && (
+                <div className="space-y-4">
+                  {replies.map((reply) => {
+                    const replyAuthor = authorsById[reply.authorId]
+                    if (!replyAuthor) {
+                      return null
+                    }
+                    const replyNumber = commentNumbers.get(reply.id) ?? "?"
+                    return (
+                      <CommentItem
+                        askingOptions={askingOptions}
+                        author={replyAuthor}
+                        comment={reply}
+                        commentId={reply.id}
+                        commentNumber={replyNumber}
+                        depth={1}
+                        isRootComment={false}
+                        key={reply.id}
+                        owner={owner}
+                        reactions={reactionsByComment[reply.id] ?? []}
+                        repo={repo}
+                      />
+                    )
+                  })}
+                </div>
+              )}
+            </CommentItem>
+            {showAnswer && (
+              <div className="mt-8">
+                <PostAnswerBox answer={answer} />
               </div>
             )}
-          </CommentItem>
+          </div>
         )
       })}
     </div>

app/[owner]/[repo]/[postNumber]/page.tsx

@@ -157,6 +157,7 @@ export default async function PostPage({
         createdAt: posts.createdAt,
         updatedAt: posts.updatedAt,
         gitContexts: posts.gitContexts,
+        answer: posts.answer,
         category: {
           id: categories.id,
           title: categories.title,
@@ -343,6 +344,7 @@ export default async function PostPage({
 
           <div className="mt-8 space-y-4">
             <CommentThreadClient
+              answer={post.answer}
               askingOptions={askingOptions}
               authorsById={authorsById}
               commentNumbers={commentNumbers}

app/[owner]/[repo]/[postNumber]/post-answer.tsx

@@ -0,0 +1,26 @@
+import type { PostAnswer } from "@/agent/types"
+import { cn } from "@/lib/utils"
+
+export function PostAnswerBox({ answer }: { answer: PostAnswer }) {
+  if (answer.type !== "answer") {
+    return null
+  }
+
+  return (
+    <div
+      className={cn(
+        "relative border-2 border-green-600/40 bg-green-950/20 p-4",
+        "before:absolute before:top-0 before:left-0 before:h-full before:w-1 before:bg-green-500"
+      )}
+    >
+      <div className="mb-2 flex items-center gap-2">
+        <span className="font-semibold text-green-400 text-sm uppercase tracking-wide">
+          Answer
+        </span>
+      </div>
+      <div className="prose prose-sm prose-invert max-w-none text-foreground">
+        {answer.text}
+      </div>
+    </div>
+  )
+}

components/copy-markdown-button.tsx

@@ -28,11 +28,7 @@ function convertMessagesToMarkdown(messages: AgentUIMessage[]): string {
     .join("\n\n")
 }
 
-export function CopyMarkdownButton({
-  content,
-}: {
-  content: AgentUIMessage[]
-}) {
+export function CopyMarkdownButton({ content }: { content: AgentUIMessage[] }) {
   const [isCopied, setIsCopied] = useState(false)
 
   const Icon = isCopied ? CheckIcon : FileTextIcon