Please someone help to make Database adapter like thing

[devshahoriar]

TanStack AI version

"@tanstack/ai": "^0.28.0",

Framework/Library version

"react": "^19.2.7",

Describe the bug and the steps to reproduce it

import {
chat,
ChatMiddleware,
convertMessagesToModelMessages,
toHttpResponse,
toolDefinition,
uiMessageToModelMessages
} from '@tanstack/ai'
import { Hono } from 'hono'
import z from 'zod'
import { gemini25FlashLite, openRouterChat } from '../ai/models'
import needAuth, { WithAuth } from '../middleware/auth'

export const aiChatRouter = new Hono()

aiChatRouter.use('*',needAuth)

const changeThemeDef = toolDefinition({
name: 'changeTheme',
description: 'Change the theme of the application',
inputSchema: z.object({
theme: z.enum(['light', 'dark']),
}),
outputSchema: z.object({
success: z.boolean(),
}),
})

const messageSaveToDB :ChatMiddleware={
name:'saveToDb',
onFinish(ctx, info) {
console.log(ctx.messages)
},

}

aiChatRouter.post('/chat', async (c) => {
const body = await c.req.json()
const messages = Array.isArray(body?.messages) ? body.messages : []
const threadId = body.threadId || thread-${Date.now()}
try {
const stream = chat({
adapter: openRouterChat,
messages,
tools: [changeThemeDef],
middleware: [messageSaveToDB],
threadId,
systemPrompts: [
'You are a helpful assistant that answers in GitHub Flavored Markdown (GFM). When you include math, use proper LaTeX: inline math in $...$ and block math in $$...$$. For matrices and aligned equations, use LaTeX environments . Do not output matrices as plain text. Prefer clear, minimal expressions; do not mix plain text with math inside the same delimiters. If a formula is wide, render it as block math.',
],
})

return toHttpResponse(stream, {
  headers: {
    'Content-Type': 'application/x-ndjson',
    'Cache-Control': 'no-cache',
  },
})

} catch (error) {
console.log(error)
return c.json({ error: 'Failed to get response from AI model' }, 500)
}
})

Look at the code i use onFinish but it do't show last ai replay how to make a database adapter. i use openrouter and reactnative.

Your Minimal, Reproducible Example - (Sandbox Highly Recommended)

code given

Screenshots or Videos (Optional)

Do you intend to try to help solve this bug with your own PR?

No, because I do not know how

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• I understand that if my bug cannot be reliable reproduced in a debuggable environment, it will probably not be fixed and this issue may even be closed.