[Bug]: When `-mcp-stdio` is used, control the output

[JerryNixon]

What?

This is set as a bug because any developer using DAB would think this is a bug regardless of the details.

Standard output causes MCP clients to misread even information as a warning.

Note

This is important because we want to seamlessly snap into the AI workflow, not look like we are failing.

Why?

The MCP client should be able to start DAB without looking like we have errored.

How?

When -mcp-stdio, default --LogLevel flag to none but allow it to override if set explicitly.

Important

We must ensure that loglevel:none in the command-line ACTUALLY emits ZERO CHARACTERS!

[anushakolan]

Version 1.7

[anushakolan]

Before MCP:

stdout = human‑readable logs, banners, info messages
This was correct and expected for a CLI tool

With MCP stdio:

stdout = JSON‑RPC protocol channel
Anything else (even “info”) is interpreted as:

a protocol violation
a warning
or a failure by MCP clients

This rule is strictly defined by the MCP stdio transport: stdout must contain only protocol messages, never logs. So that needs to be fixed.

[anushakolan]

The root cause is that DAB’s logging and startup behavior was originally designed for a human‑facing CLI, but MCP stdio requires stdout to be a strictly silent protocol channel; when MCP stdio was added in 1.7, this mismatch caused normal CLI output to be misinterpreted as protocol errors.