mesh: POST /api/respond + MCP respond tool — reply to a message by packet id

src/mesh/fake-bridge.ts

@@ -148,6 +148,34 @@ export function telemetryPacketFrame(
   );
 }
 
+/** Inbound text message: TEXT_MESSAGE_APP packet with UTF-8 in Data.payload (fixed packet id 1). */
+export function textPacketFrame(
+  from: number,
+  to: number,
+  text: string,
+  channel = 0,
+): Uint8Array {
+  const data = create(P.Mesh.DataSchema, {
+    portnum: P.Portnums.PortNum.TEXT_MESSAGE_APP,
+    payload: new TextEncoder().encode(text),
+  });
+  const pkt = create(P.Mesh.MeshPacketSchema, {
+    from,
+    to,
+    id: 1,
+    channel,
+    payloadVariant: { case: 'decoded', value: data },
+  });
+  return frame(
+    toBinary(
+      P.Mesh.FromRadioSchema,
+      create(P.Mesh.FromRadioSchema, {
+        payloadVariant: { case: 'packet', value: pkt },
+      }),
+    ),
+  );
+}
+
 export const KAMIL_NUM = 123456789;
 
 export function kamilNodeInfo(): NodeInfoFields {

src/mesh/mcp.controller.spec.ts

@@ -11,6 +11,7 @@ import {
   nodeInfoFrame,
   startBridge,
   telemetryPacketFrame,
+  textPacketFrame,
   waitFor,
 } from './fake-bridge.js';
 import { createMeshMcpServer } from './mcp.controller.js';
@@ -67,7 +68,7 @@ async function connectMcp(svc: MeshService): Promise<{
 }
 
 describe('MCP server tools', () => {
-  it('lists all nine tools with descriptions and input schemas', async () => {
+  it('lists all ten tools with descriptions and input schemas', async () => {
     const env = await connectedService();
     try {
       const mcp = await connectMcp(env.svc);
@@ -82,6 +83,7 @@ describe('MCP server tools', () => {
           'list_channels',
           'list_nodes',
           'mesh_status',
+          'respond',
           'send_message',
         ]);
         for (const t of tools) expect(t.description?.length).toBeGreaterThan(0);
@@ -100,6 +102,13 @@ describe('MCP server tools', () => {
           'text',
           'from',
         ]);
+
+        const respond = tools.find((t) => t.name === 'respond')!;
+        expect(respond.inputSchema.required).toEqual(['messageId', 'content']);
+        expect(Object.keys(respond.inputSchema.properties ?? {})).toEqual([
+          'messageId',
+          'content',
+        ]);
       } finally {
         await mcp.close();
       }
@@ -196,6 +205,57 @@ describe('MCP server tools', () => {
     }
   });
 
+  it('respond routes the reply automatically and surfaces failures as tool errors', async () => {
+    const env = await connectedService();
+    try {
+      // rx DM from KAMIL on channel 3 (packet id 1)
+      env.sockets[0].write(textPacketFrame(KAMIL_NUM, 42, 'ping', 3));
+      await waitFor(() => env.svc.messages().length === 1);
+
+      const mcp = await connectMcp(env.svc);
+      try {
+        const r1 = await mcp.client.callTool({
+          name: 'respond',
+          arguments: { messageId: 1, content: 'pong' },
+        });
+        expect(r1.isError).not.toBe(true);
+        const reply = JSON.parse(toolText(r1)) as { id: number };
+        expect(reply.id).toBeGreaterThan(0);
+        // DM back to the original sender on the original channel
+        expect(env.svc.messages()[0]).toMatchObject({
+          dir: 'tx',
+          to: KAMIL_NUM,
+          text: 'pong',
+          channel: 3,
+        });
+
+        const r2 = await mcp.client.callTool({
+          name: 'respond',
+          arguments: { messageId: 999, content: 'x' },
+        });
+        expect(r2.isError).toBe(true);
+        expect(toolText(r2)).toContain('no message with id 999');
+
+        const r3 = await mcp.client.callTool({
+          name: 'respond',
+          arguments: { messageId: 0, content: 'x' },
+        });
+        expect(r3.isError).toBe(true); // out-of-range rejected before the service sees it
+
+        const r4 = await mcp.client.callTool({
+          name: 'respond',
+          arguments: { messageId: 1, content: '' },
+        });
+        expect(r4.isError).toBe(true);
+        expect(toolText(r4)).toContain('content must be a non-empty string');
+      } finally {
+        await mcp.close();
+      }
+    } finally {
+      env.close();
+    }
+  });
+
   it('inject_message records an rx entry without sending over RF', async () => {
     const env = await connectedService();
     try {

src/mesh/mcp.controller.ts

@@ -46,6 +46,19 @@ export function createMeshMcpServer(mesh: MeshService): McpServer {
       }),
   );
 
+  server.registerTool(
+    'respond',
+    {
+      description: `Reply to an earlier message by its packet id (from get_messages); returns { id } — the Meshtastic packet id of the reply. Routing is automatic: rx records are answered as a DM back to the original sender, tx records go to their destination; broadcast originals and injected messages without a sender get a broadcast. The reply always rides the record's channel and carries replyId = messageId (threaded quote in the recipient app). Invalid messageId/content or an unknown id are tool errors.`,
+      inputSchema: {
+        messageId: z.number().int().min(1).max(0xffffffff),
+        content: z.string(),
+      },
+    },
+    async ({ messageId, content }) =>
+      jsonResult(await mesh.respond(messageId, content)),
+  );
+
   server.registerTool(
     'list_channels',
     {

src/mesh/mesh.controller.ts

@@ -29,6 +29,17 @@ export class InjectMessageDto {
   from?: number;
 }
 
+export class RespondDto {
+  @ApiProperty({
+    description:
+      'Packet id of the earlier message (from GET /api/messages) that this one replies to. Integer in 1..0xffffffff.',
+    example: 456789,
+  })
+  messageId!: number;
+  @ApiProperty({ description: 'Reply text', example: 'on my way' })
+  content!: string;
+}
+
 export class SendTextDto {
   @ApiProperty({ description: 'Message text', example: 'hello' })
   text!: string;
@@ -111,6 +122,24 @@ export class MeshController {
     return { id: await this.mesh.sendText(to, body.text, replyId) };
   }
 
+  @Post('respond')
+  @ApiOperation({
+    summary: 'Reply to an earlier message by packet id',
+    description:
+      "Routing is automatic — the caller never thinks about where it goes: rx records are answered as a DM back to the original sender, tx records go to their destination; broadcast originals (and injected messages without a sender) get a broadcast. The reply always rides the record's channel and carries replyId = messageId, so the recipient app renders it as a threaded quote of that packet. Returns { id } with the new packet id.",
+  })
+  @ApiResponse({
+    status: 200,
+    description: 'Packet queued',
+    example: { id: 123456789 },
+  })
+  @ApiResponse({ status: 400, description: 'Invalid messageId or content' })
+  @ApiResponse({ status: 404, description: 'No message with the given id' })
+  @ApiResponse({ status: 503, description: 'Bridge not connected' })
+  async respond(@Body() body: RespondDto) {
+    return this.mesh.respond(body?.messageId, body?.content);
+  }
+
   @Get('channels')
   @ApiOperation({
     summary: "The device's Meshtastic channels (keys redacted)",

src/mesh/mesh.service.spec.ts

@@ -1,5 +1,6 @@
 import { create, fromBinary, toBinary } from '@bufbuild/protobuf';
 import * as P from '@meshtastic/protobufs';
+import { BadRequestException, NotFoundException } from '@nestjs/common';
 import { DatabaseSync } from 'node:sqlite';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import { BROADCAST_ADDR, extractFrames, frame } from './codec.js';
@@ -12,6 +13,7 @@ import {
   nodeInfoFrame,
   startBridge,
   telemetryPacketFrame,
+  textPacketFrame,
   waitFor,
 } from './fake-bridge.js';
 import { OpencodeService } from '../opencode/opencode.service.js';
@@ -74,34 +76,6 @@ function nodeInfoPacketFrame(
   );
 }
 
-// inbound text message: TEXT_MESSAGE_APP packet with UTF-8 in Data.payload
-function textPacketFrame(
-  from: number,
-  to: number,
-  text: string,
-  channel = 0,
-): Uint8Array {
-  const data = create(P.Mesh.DataSchema, {
-    portnum: P.Portnums.PortNum.TEXT_MESSAGE_APP,
-    payload: new TextEncoder().encode(text),
-  });
-  const pkt = create(P.Mesh.MeshPacketSchema, {
-    from,
-    to,
-    id: 1,
-    channel,
-    payloadVariant: { case: 'decoded', value: data },
-  });
-  return frame(
-    toBinary(
-      P.Mesh.FromRadioSchema,
-      create(P.Mesh.FromRadioSchema, {
-        payloadVariant: { case: 'packet', value: pkt },
-      }),
-    ),
-  );
-}
-
 // ACK/NACK for our sends: ROUTING_APP packet with Data.requestId = original id and a serialized Routing in the payload
 function routingFrame(
   requestId: number,
@@ -693,6 +667,228 @@ describe('MeshService message history', () => {
   });
 });
 
+// outbound text packets written to the bridge, in order (want_config frames skipped)
+function outboundPackets(out: Uint8Array[]): P.Mesh.MeshPacket[] {
+  const merged = new Uint8Array(out.reduce((n, c) => n + c.length, 0));
+  let off = 0;
+  for (const c of out) {
+    merged.set(c, off);
+    off += c.length;
+  }
+  return extractFrames(merged).packets.flatMap((p) => {
+    const tr = fromBinary(P.Mesh.ToRadioSchema, p);
+    if (tr.payloadVariant?.case === 'packet') return [tr.payloadVariant.value];
+    return [];
+  });
+}
+
+describe('MeshService respond', () => {
+  it('replies to an rx DM as a directed send back to the sender on the original channel with replyId = messageId', async () => {
+    const bridge = await startBridge();
+    process.env.MESH_HOST = '127.0.0.1';
+    process.env.MESH_PORT = String(bridge.port);
+    const svc = new MeshService();
+    try {
+      svc.onModuleInit();
+      await waitFor(
+        () => bridge.sockets.length === 1 && svc.status().connected,
+      );
+
+      // rx DM from KAMIL to our node on channel 2 (packet id 1)
+      bridge.sockets[0].write(textPacketFrame(KAMIL_NUM, 42, 'ping', 2));
+      await waitFor(() => svc.messages().length === 1);
+
+      const out: Uint8Array[] = [];
+      bridge.sockets[0].on('data', (c) => out.push(c));
+      const { id } = await svc.respond(1, 'pong');
+
+      expect(id).toBeGreaterThan(0);
+      // DM back to the original sender on the original channel
+      expect(svc.messages()[0]).toMatchObject({
+        id,
+        dir: 'tx',
+        to: KAMIL_NUM,
+        text: 'pong',
+        channel: 2,
+        status: 'pending',
+      });
+
+      await waitFor(() => outboundPackets(out).length === 1);
+      const pkt = outboundPackets(out)[0]!;
+      expect(pkt.to).toBe(KAMIL_NUM);
+      expect(pkt.channel).toBe(2);
+      const data =
+        pkt.payloadVariant?.case === 'decoded'
+          ? pkt.payloadVariant.value
+          : undefined;
+      expect(data?.replyId).toBe(1); // threaded quote of the original packet
+    } finally {
+      svc.onModuleDestroy();
+      bridge.close();
+    }
+  });
+
+  it('replies to a broadcast original as a broadcast on the original channel with replyId = messageId', async () => {
+    const bridge = await startBridge();
+    process.env.MESH_HOST = '127.0.0.1';
+    process.env.MESH_PORT = String(bridge.port);
+    const svc = new MeshService();
+    try {
+      svc.onModuleInit();
+      await waitFor(
+        () => bridge.sockets.length === 1 && svc.status().connected,
+      );
+
+      // rx broadcast from KAMIL on channel 2 (packet id 1)
+      bridge.sockets[0].write(
+        textPacketFrame(KAMIL_NUM, BROADCAST_ADDR, 'hello all', 2),
+      );
+      await waitFor(() => svc.messages().length === 1);
+
+      const out: Uint8Array[] = [];
+      bridge.sockets[0].on('data', (c) => out.push(c));
+      const { id } = await svc.respond(1, 'pong');
+
+      expect(id).toBeGreaterThan(0);
+      expect(svc.messages()[0]).toMatchObject({
+        dir: 'tx',
+        to: BROADCAST_ADDR, // broadcast original → broadcast reply
+        text: 'pong',
+        channel: 2,
+      });
+
+      await waitFor(() => outboundPackets(out).length === 1);
+      const pkt = outboundPackets(out)[0]!;
+      expect(pkt.to).toBe(BROADCAST_ADDR);
+      expect(pkt.channel).toBe(2);
+      const data =
+        pkt.payloadVariant?.case === 'decoded'
+          ? pkt.payloadVariant.value
+          : undefined;
+      expect(data?.replyId).toBe(1);
+    } finally {
+      svc.onModuleDestroy();
+      bridge.close();
+    }
+  });
+
+  it('replies to a tx record targeting its destination on its channel with replyId = messageId', async () => {
+    const bridge = await startBridge();
+    process.env.MESH_HOST = '127.0.0.1';
+    process.env.MESH_PORT = String(bridge.port);
+    const svc = new MeshService();
+    try {
+      svc.onModuleInit();
+      await waitFor(
+        () => bridge.sockets.length === 1 && svc.status().connected,
+      );
+
+      const origId = await svc.sendText(42, 'orig'); // tx record: to=42, default channel 3
+      const out: Uint8Array[] = [];
+      bridge.sockets[0].on('data', (c) => out.push(c));
+      const { id } = await svc.respond(origId, 'reply');
+
+      expect(id).toBeGreaterThan(0);
+      expect(svc.messages()[0]).toMatchObject({
+        dir: 'tx',
+        to: 42, // the tx record's own destination
+        text: 'reply',
+        channel: 3,
+      });
+
+      // the orig send may share a chunk with the reply — take the newest packet
+      await waitFor(() => outboundPackets(out).length >= 1);
+      const pkts = outboundPackets(out);
+      const pkt = pkts[pkts.length - 1]!;
+      expect(pkt.to).toBe(42);
+      const data =
+        pkt.payloadVariant?.case === 'decoded'
+          ? pkt.payloadVariant.value
+          : undefined;
+      expect(data?.replyId).toBe(origId);
+    } finally {
+      svc.onModuleDestroy();
+      bridge.close();
+    }
+  });
+
+  it('throws NotFoundException when no message has the given id (memory or SQLite)', async () => {
+    const svc = new MeshService();
+    await expect(svc.respond(999, 'hi')).rejects.toBeInstanceOf(
+      NotFoundException,
+    );
+    await expect(svc.respond(999, 'hi')).rejects.toThrow(
+      'no message with id 999',
+    );
+
+    const db = new DatabaseSync(':memory:'); // empty table — the DB lookup path also misses
+    initMessagesTable(db);
+    const svc2 = new MeshService(db);
+    await expect(svc2.respond(999, 'hi')).rejects.toBeInstanceOf(
+      NotFoundException,
+    );
+  });
+
+  it('falls back to SQLite when the record is not in the in-memory buffer', async () => {
+    const db = new DatabaseSync(':memory:');
+    initMessagesTable(db);
+    // 150 rows — onModuleInit seeds only the newest 100 into the buffer (ids 2050..2149)
+    const ins = db.prepare(
+      'INSERT INTO messages(id, dir, to_node, from_node, text, channel, at, status, ack_error) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)',
+    );
+    for (let i = 0; i < 150; i++)
+      ins.run(
+        2000 + i,
+        'rx',
+        42,
+        KAMIL_NUM,
+        `old-${i}`,
+        2,
+        1_700_000_000_000 + i * 1000,
+        null,
+        null,
+      );
+
+    const bridge = await startBridge();
+    process.env.MESH_HOST = '127.0.0.1';
+    process.env.MESH_PORT = String(bridge.port);
+    const svc = new MeshService(db);
+    try {
+      svc.onModuleInit();
+      await waitFor(
+        () => bridge.sockets.length === 1 && svc.status().connected,
+      );
+
+      // id 2000 is in SQLite but outside the seeded buffer
+      const { id } = await svc.respond(2000, 'pong');
+      expect(id).toBeGreaterThan(0);
+      expect(svc.messages()[0]).toMatchObject({
+        dir: 'tx',
+        to: KAMIL_NUM, // DM back to the sender of the old rx record
+        text: 'pong',
+        channel: 2, // the record's channel
+      });
+    } finally {
+      svc.onModuleDestroy();
+      bridge.close();
+    }
+  });
+
+  it('rejects invalid messageId and empty content with BadRequestException', async () => {
+    const svc = new MeshService();
+    for (const bad of [0, BROADCAST_ADDR + 1, 42.5, 'x' as unknown as number])
+      await expect(svc.respond(bad, 'hi')).rejects.toBeInstanceOf(
+        BadRequestException,
+      );
+    await expect(svc.respond(1, '')).rejects.toThrow(
+      'content must be a non-empty string',
+    );
+    await expect(svc.respond(1, undefined)).rejects.toBeInstanceOf(
+      BadRequestException,
+    );
+  });
+});
+
 describe('MeshService opencode notifier', () => {
   // our own node number for the self-echo filter specs (distinct from KAMIL_NUM, an external user)
   const MY_NODE = 987654321;

src/mesh/mesh.service.ts

@@ -1,6 +1,8 @@
 import {
+  BadRequestException,
   Injectable,
   Logger,
+  NotFoundException,
   OnModuleDestroy,
   OnModuleInit,
   ServiceUnavailableException,
@@ -84,6 +86,22 @@ export function initMessagesTable(db: DatabaseSync): void {
   db.exec(MESSAGES_DDL);
 }
 
+/** Map a messages-table row to a MessageRecord (NULLs → omitted optionals). */
+function recordFromRow(row: Record<string, unknown>): MessageRecord {
+  const rec: MessageRecord = {
+    id: Number(row.id),
+    dir: row.dir === 'tx' ? 'tx' : 'rx',
+    text: String(row.text),
+    channel: Number(row.channel),
+    at: Number(row.at),
+  };
+  if (row.to_node != null) rec.to = Number(row.to_node);
+  if (row.from_node != null) rec.from = Number(row.from_node);
+  if (row.status != null) rec.status = row.status as MessageRecord['status'];
+  if (row.ack_error != null) rec.ackError = String(row.ack_error);
+  return rec;
+}
+
 /** What we know about a node so far: full NodeInfo after sync, possibly just {num}+position for live-only nodes. */
 type NodeEntry = Pick<Proto.Mesh.NodeInfo, 'num'> &
   Partial<Omit<Proto.Mesh.NodeInfo, 'num'>>;
@@ -393,21 +411,55 @@ export class MeshService implements OnModuleInit, OnModuleDestroy {
       'SELECT id, dir, to_node, from_node, text, channel, at, status, ack_error FROM messages ORDER BY at DESC LIMIT ?',
     ).all(HISTORY_LIMIT) as Array<Record<string, unknown>>;
     // rows come back newest first — the buffer is oldest-first
-    for (const row of [...rows].reverse()) {
-      const rec: MessageRecord = {
-        id: Number(row.id),
-        dir: row.dir === 'tx' ? 'tx' : 'rx',
-        text: String(row.text),
-        channel: Number(row.channel),
-        at: Number(row.at),
-      };
-      if (row.to_node != null) rec.to = Number(row.to_node);
-      if (row.from_node != null) rec.from = Number(row.from_node);
-      if (row.status != null)
-        rec.status = row.status as MessageRecord['status'];
-      if (row.ack_error != null) rec.ackError = String(row.ack_error);
-      this.history.push(rec);
-    }
+    for (const row of [...rows].reverse())
+      this.history.push(recordFromRow(row));
+  }
+
+  /** Look up a history record by packet id: in-memory buffer first, then SQLite (newest 1000). */
+  private findRecord(id: number): MessageRecord | undefined {
+    const hit = this.history.find((r) => r.id === id);
+    if (hit) return hit;
+    const db = this.db;
+    if (!db) return undefined;
+    const row = db
+      .prepare(
+        'SELECT id, dir, to_node, from_node, text, channel, at, status, ack_error FROM messages WHERE id = ?',
+      )
+      .get(id) as Record<string, unknown> | undefined;
+    return row ? recordFromRow(row) : undefined;
+  }
+
+  /**
+   * Reply to an earlier message by packet id — the caller never thinks about where it goes:
+   * rx records are answered as a DM back to the original sender, tx records go to their destination;
+   * broadcast originals (and injected messages without a sender) get a broadcast. The reply always
+   * rides the record's channel and carries replyId = messageId, so the recipient app renders it as a
+   * threaded quote of that packet. Returns { id } with the new packet id. Throws BadRequest on invalid
+   * arguments, NotFound when no message has the given id (in memory or in SQLite), 503 when the bridge is down.
+   */
+  async respond(messageId: number, content: string): Promise<{ id: number }> {
+    if (
+      !Number.isInteger(messageId) ||
+      messageId < 1 ||
+      messageId > BROADCAST_ADDR
+    )
+      throw new BadRequestException(
+        'messageId must be an integer in 1..0xffffffff',
+      );
+    if (typeof content !== 'string' || content.length === 0)
+      throw new BadRequestException('content must be a non-empty string');
+    const rec = this.findRecord(messageId);
+    if (!rec) throw new NotFoundException(`no message with id ${messageId}`);
+    // rx → DM back to the sender unless the original was a broadcast (then reply as a broadcast — that's what the stored destination is for);
+    // tx → its own destination; injected records without a sender → broadcast
+    const target =
+      rec.dir === 'rx'
+        ? rec.to === BROADCAST_ADDR
+          ? BROADCAST_ADDR
+          : rec.from
+        : rec.to;
+    const to = target ?? BROADCAST_ADDR;
+    return { id: await this.sendText(to, content, messageId, rec.channel) };
   }
 
   /**