Mastra•2mo ago•

1 reply

Mastra Studio sends invalid `messages` shape to server

Mastra Cloud

Summary

Mastra Studio UI sends

messages

messages

as a single object, but the Mastra server route schema expects

messages

messages

to be an array (CoreMessage[]) or a string. This causes Zod validation to fail before the route handler runs.

Environment

@mastra/core

@mastra/core

1.0.0-beta.15

1.0.0-beta.15

@mastra/server

@mastra/server

0.1.0-beta.9

0.1.0-beta.9

@mastra/hono

@mastra/hono

0.1.0-beta.8

0.1.0-beta.8

hono

hono

^4.7.10

^4.7.10

- Local dev server (Studio)

Expected Behavior

Studio should send request bodies that conform to the server route schema:

{ "messages": [ { "role": "user", "content": "..." } ] }

{ "messages": [ { "role": "user", "content": "..." } ] }

Per server routes reference,

messages

messages

CoreMessage[] | string

CoreMessage[] | string

for agent generate/stream.

Actual Behavior

Studio UI sends:

{ "messages": { "role": "user", "content": "test" } }

{ "messages": { "role": "user", "content": "test" } }

This causes:

Error parsing body: Invalid input: expected array, received object
path: ["messages"]

Error parsing body: Invalid input: expected array, received object
path: ["messages"]

Reproduction

1) Run Studio (

mastra dev

mastra dev

or project

dev

dev

script).
2) Open Studio UI and test an agent.
3) Observe the API error above.

Working Request (via curl)

curl -X POST "http://localhost:4112/api/agents/tourism-rag-agent/stream" \
  -H "Content-Type: application/json" \
  -d '{"messages":[{"role":"user","content":"test"}]}'

curl -X POST "http://localhost:4112/api/agents/tourism-rag-agent/stream" \
  -H "Content-Type: application/json" \
  -d '{"messages":[{"role":"user","content":"test"}]}'

Notes

- The local dev server exposes the same REST API routes as Mastra Server (Studio docs).
- The server routes reference defines

messages: CoreMessage[] | string

messages: CoreMessage[] | string

for generate/stream.
- There is no documented server configuration to extend the built-in route schema to accept

{ messages: { ... } }

{ messages: { ... } }

Why this matters

- Studio UI is the primary developer UX for agent testing.
- A mismatch between Studio payloads and server schema blocks local testing unless users implement custom server workarounds.

References (Mastra docs)

- Studio REST API parity:

getting-started/studio.mdx

getting-started/studio.mdx

- Server routes schema:

reference/server/routes.mdx

reference/server/routes.mdx

- Middleware behavior:

server/middleware.mdx

server/middleware.mdx

- Custom adapters:

server/custom-adapters.mdx

server/custom-adapters.mdx

Mastra•2mo ago•

1 reply

Ysfy

Mastra Studio sends invalid `messages` shape to server

Mastra Cloud

Summary

Mastra Studio UI sends

messages

messages

as a single object, but the Mastra server route schema expects

messages

messages

to be an array (CoreMessage[]) or a string. This causes Zod validation to fail before the route handler runs.

Environment

@mastra/core

@mastra/core

1.0.0-beta.15

1.0.0-beta.15

@mastra/server

@mastra/server

0.1.0-beta.9

0.1.0-beta.9

@mastra/hono

@mastra/hono

0.1.0-beta.8

0.1.0-beta.8

hono

hono

^4.7.10

^4.7.10

- Local dev server (Studio)

Expected Behavior

Studio should send request bodies that conform to the server route schema:

{ "messages": [ { "role": "user", "content": "..." } ] }

{ "messages": [ { "role": "user", "content": "..." } ] }

Per server routes reference,

messages

messages

CoreMessage[] | string

CoreMessage[] | string

for agent generate/stream.

Actual Behavior

Studio UI sends:

{ "messages": { "role": "user", "content": "test" } }

{ "messages": { "role": "user", "content": "test" } }

This causes:

Error parsing body: Invalid input: expected array, received object
path: ["messages"]

Error parsing body: Invalid input: expected array, received object
path: ["messages"]

Reproduction

1) Run Studio (

mastra dev

mastra dev

or project

dev

dev

script).
2) Open Studio UI and test an agent.
3) Observe the API error above.

Working Request (via curl)

curl -X POST "http://localhost:4112/api/agents/tourism-rag-agent/stream" \
  -H "Content-Type: application/json" \
  -d '{"messages":[{"role":"user","content":"test"}]}'

curl -X POST "http://localhost:4112/api/agents/tourism-rag-agent/stream" \
  -H "Content-Type: application/json" \
  -d '{"messages":[{"role":"user","content":"test"}]}'

Notes

- The local dev server exposes the same REST API routes as Mastra Server (Studio docs).
- The server routes reference defines

messages: CoreMessage[] | string

messages: CoreMessage[] | string

for generate/stream.
- There is no documented server configuration to extend the built-in route schema to accept

{ messages: { ... } }

{ messages: { ... } }

Why this matters

- Studio UI is the primary developer UX for agent testing.
- A mismatch between Studio payloads and server schema blocks local testing unless users implement custom server workarounds.

References (Mastra docs)

- Studio REST API parity:

getting-started/studio.mdx

getting-started/studio.mdx

- Server routes schema:

reference/server/routes.mdx

reference/server/routes.mdx

- Middleware behavior:

server/middleware.mdx

server/middleware.mdx

- Custom adapters:

server/custom-adapters.mdx

server/custom-adapters.mdx

Mastra Studio sends invalid `messages` shape to server

Summary

Environment

Expected Behavior

Actual Behavior

Reproduction

Working Request (via curl)

Notes

Why this matters

References (Mastra docs)

Mastra Studio sends invalid `messages` shape to server

Summary

Environment

Expected Behavior

Actual Behavior

Reproduction

Working Request (via curl)

Notes

Why this matters

References (Mastra docs)

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