Tool Streaming Inside Mastra Doesn't Work

M

mechXsteam(dataloom.app)OP•10/24/25, 3:21 PM

cc @spo0nman

M

Mastra Triager•10/25/25, 12:04 PM

Created GitHub issue: https://github.com/mastra-ai/mastra/issues/9270

GitHub

[DISCORD:1431301548331372716] Tool Streaming Inside Mastra Doesn't ...

This issue was created from Discord post: https://discord.com/channels/1309558646228779139/1431301548331372716 I am trying to create a tool that in turn calls a different agent to do some work and ...

M

mechXsteam(dataloom.app)OP•10/27/25, 11:06 AM

Update on this issue, the mastra instance in the tool execute args is always undefined that's why the rest of things is undefined

export const artifactTool = createTool({
  id: 'create_rca_artifact',
  description: 'Generate a root cause analysis summary from incident findings',
  inputSchema: artifactInputSchema,
  execute: async ({ context, writer, mastra }) => {
    const logger = toolLogger;
    try {
       const agents = mastra?.getAgents();
       logger.info("[CREATE ARTIFACT TOOL] RCA Summarizing Agent retrieved successfully", {
        "foo": "bar",
        "agents": agents, <--- ALWAYS UNDEFINED
       });
      return {
        "status": "success",
      }
    } catch (error) {
      throw error;
    }
  },
});

export const artifactTool = createTool({
  id: 'create_rca_artifact',
  description: 'Generate a root cause analysis summary from incident findings',
  inputSchema: artifactInputSchema,
  execute: async ({ context, writer, mastra }) => {
    const logger = toolLogger;
    try {
       const agents = mastra?.getAgents();
       logger.info("[CREATE ARTIFACT TOOL] RCA Summarizing Agent retrieved successfully", {
        "foo": "bar",
        "agents": agents, <--- ALWAYS UNDEFINED
       });
      return {
        "status": "success",
      }
    } catch (error) {
      throw error;
    }
  },
});

export const artifactTool = createTool({
  id: 'create_rca_artifact',
  description: 'Generate a root cause analysis summary from incident findings',
  inputSchema: artifactInputSchema,
  execute: async ({ context, writer, mastra }) => {
    const logger = toolLogger;
    try {
       const agents = mastra?.getAgents();
       logger.info("[CREATE ARTIFACT TOOL] RCA Summarizing Agent retrieved successfully", {
        "foo": "bar",
        "agents": agents, <--- ALWAYS UNDEFINED
       });
      return {
        "status": "success",
      }
    } catch (error) {
      throw error;
    }
  },
});

export const artifactTool = createTool({
  id: 'create_rca_artifact',
  description: 'Generate a root cause analysis summary from incident findings',
  inputSchema: artifactInputSchema,
  execute: async ({ context, writer, mastra }) => {
    const logger = toolLogger;
    try {
       const agents = mastra?.getAgents();
       logger.info("[CREATE ARTIFACT TOOL] RCA Summarizing Agent retrieved successfully", {
        "foo": "bar",
        "agents": agents, <--- ALWAYS UNDEFINED
       });
      return {
        "status": "success",
      }
    } catch (error) {
      throw error;
    }
  },
});

W

Ward•10/27/25, 12:29 PM

That is very strange, can you give us a full reproduction? We cannot reproduce this on latest.

M

mechXsteam(dataloom.app)OP•10/28/25, 9:28 AM

Here's the full video of the bug

_

_roamin_•10/31/25, 9:11 PM

Hi @mechXsteam(dataloom.app) ! Could you share a minimal reproducible example with us? Thanks

M

mechXsteam(dataloom.app)OP•11/1/25, 7:57 AM

Yeah, for sure, I'll share this exact same repo in some time.

M

mechXsteam(dataloom.app)OP•11/2/25, 1:32 PM

@roamin , here is the repo which can help to reproduce the error

https://github.com/Ve2s4/mastra-bug

GitHub

GitHub - Ve2s4/mastra-bug

Contribute to Ve2s4/mastra-bug development by creating an account on GitHub.

S

spo0nman•11/4/25, 12:54 PM

@Romain is there an update on this bug?

S

spo0nman•11/4/25, 12:54 PM

https://github.com/mastra-ai/mastra/issues/9270

GitHub

[DISCORD:1431301548331372716] Tool Streaming Inside Mastra Doesn't ...

This issue was created from Discord post: https://discord.com/channels/1309558646228779139/1431301548331372716 I am trying to create a tool that in turn calls a different agent to do some work and ...

W

Ward•11/4/25, 3:27 PM

works fine for me on latest mastra

export const weatherTool = createTool({
  id: "get-weather",
  description: "Get current weather for a location",
  inputSchema: z.object({
    location: z.string().describe("City name"),
  }),
  outputSchema: z.object({
    temperature: z.number(),
    feelsLike: z.number(),
    humidity: z.number(),
    windSpeed: z.number(),
    windGust: z.number(),
    conditions: z.string(),
    location: z.string(),
  }),
  execute: async ({ context, mastra, writer }) => {
    const agent = mastra?.getAgent("testAgent");

    if (agent) {
      const stream = await agent?.stream("What does the weather do with me?");
      await stream.textStream.pipeTo(writer!);
    }
    return await getWeather(context.location);
  },
});

export const weatherTool = createTool({
  id: "get-weather",
  description: "Get current weather for a location",
  inputSchema: z.object({
    location: z.string().describe("City name"),
  }),
  outputSchema: z.object({
    temperature: z.number(),
    feelsLike: z.number(),
    humidity: z.number(),
    windSpeed: z.number(),
    windGust: z.number(),
    conditions: z.string(),
    location: z.string(),
  }),
  execute: async ({ context, mastra, writer }) => {
    const agent = mastra?.getAgent("testAgent");

    if (agent) {
      const stream = await agent?.stream("What does the weather do with me?");
      await stream.textStream.pipeTo(writer!);
    }
    return await getWeather(context.location);
  },
});

export const weatherTool = createTool({
  id: "get-weather",
  description: "Get current weather for a location",
  inputSchema: z.object({
    location: z.string().describe("City name"),
  }),
  outputSchema: z.object({
    temperature: z.number(),
    feelsLike: z.number(),
    humidity: z.number(),
    windSpeed: z.number(),
    windGust: z.number(),
    conditions: z.string(),
    location: z.string(),
  }),
  execute: async ({ context, mastra, writer }) => {
    const agent = mastra?.getAgent("testAgent");

    if (agent) {
      const stream = await agent?.stream("What does the weather do with me?");
      await stream.textStream.pipeTo(writer!);
    }
    return await getWeather(context.location);
  },
});

export const weatherTool = createTool({
  id: "get-weather",
  description: "Get current weather for a location",
  inputSchema: z.object({
    location: z.string().describe("City name"),
  }),
  outputSchema: z.object({
    temperature: z.number(),
    feelsLike: z.number(),
    humidity: z.number(),
    windSpeed: z.number(),
    windGust: z.number(),
    conditions: z.string(),
    location: z.string(),
  }),
  execute: async ({ context, mastra, writer }) => {
    const agent = mastra?.getAgent("testAgent");

    if (agent) {
      const stream = await agent?.stream("What does the weather do with me?");
      await stream.textStream.pipeTo(writer!);
    }
    return await getWeather(context.location);
  },
});

_

_roamin_•11/4/25, 6:23 PM

Hey, @spo0nman & @mechXsteam(dataloom.app) ! can you guys try updating to the latest mastra packages?

WWard works fine for me on latest mastra ``` export const weatherTool = createTool({ ...

S

spo0nman•11/5/25, 8:07 AM

I used 0.23.3 and can confirm streaming works now

N

nemar•11/5/25, 8:19 AM

I’m not try streaming the agent’s output, just a status update, but I’m encountering a similar issue.

Using newest snapshot 0.0.0-fix-9244-clickhouse-metadata-20251105010900 (probably v1) and @mastra/ai-sdk. route:

chatRoute({
  path: '/chat',
  agent: 'agent',
})

chatRoute({
  path: '/chat',
  agent: 'agent',
})

chatRoute({
  path: '/chat',
  agent: 'agent',
})

chatRoute({
  path: '/chat',
  agent: 'agent',
})

doesn’t work custom writer like this:

await writer?.custom({
  type: "data-tool-progress",
  status: "pending"
});

await writer?.custom({
  type: "data-tool-progress",
  status: "pending"
});

await writer?.custom({
  type: "data-tool-progress",
  status: "pending"
});

await writer?.custom({
  type: "data-tool-progress",
  status: "pending"
});

No errors, but the stream gets stuck.
Without writer.custom() tool works fine.

N

nemar•11/5/25, 8:50 AM

When using an agent network with a networkRoute that calls a sub-agent containing a tool using writer?.custom, the route compiles the final output, but the data inside writer?.custom is not streamed, and no event is triggered.

@Romain Does the network agent support writer.custom() functionality in sub-agents tools?

D

dero•11/5/25, 2:17 PM

Hi @nemar , custom data from

writer?.custom

writer?.custom

writer?.custom

writer?.custom in a subagent tool will now come through when using the

networkRoute

networkRoute

networkRoute

networkRoute after this PR https://github.com/mastra-ai/mastra/pull/9717

GitHub

Improve ai-sdk transformers, handle custom data writes in agent net...

Handle custom data writes in agent network execution events in ai sdk transformers
changeset

Description

Related Issue(s)
Fixes #9270

Type of Change

Bug fix (non-breaking change that fixes an ...

N

nemar•11/5/25, 7:53 PM

Hi @dero, thanks! Now writer?.custom works fine in both chatRoute and networkRoute. I tested it with snapshot 0.0.0-main-test-20251105183450.

Tool Streaming Inside Mastra Doesn't Work

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