droid 0.190.0: ACP daemon passes unsupported `--mcp-servers` to child process -> "Droid process exited unexpectedly (exit code 1)"

[shuuul]

Droid version: 0.190.0 (both $HOME/.local/bin/droid and npm droid@0.190.0)
OS: macOS (arm64)
Zed version: 1.14.2

What happened

Using Factory Droid as an ACP agent from Zed (external_agents registry entry runs droid exec --output-format acp-daemon) always fails with:

Internal error: { "details": "Droid process exited unexpectedly (exit code 1)" }

Evidence (from $HOME/.factory/logs/droid-log-single.log)

The ACP daemon spawns a child process and passes a --mcp-servers argument:

droid exec --output-format acp --session-id <id> --mcp-servers <base64>

The child exits immediately with:

error: unknown option '--mcp-servers'

(exit code 1), which the wrapper reports as ProcessExitError: Droid process exited unexpectedly (exit code 1).

--mcp-servers is not defined for droid exec in 0.190.0 (confirmed via droid exec --help on both installs).

The base64 payload is a JSON list of the client's MCP servers, so the failure occurs whenever the ACP client has any MCP/context servers enabled (reproduced with stdio-style servers such as exa-search and with http-style servers such as deepwiki). With no servers configured, session creation succeeds and the daemon works.

Steps to reproduce

1. Register droid as an ACP agent in a client that supports ACP (e.g. Zed), with one or more MCP servers configured.
2. Start a new session.
3. The daemon spawns the child with the unsupported --mcp-servers flag; the child exits 1 and the client shows the error above.

Expected behavior

• Either droid exec accepts --mcp-servers, or the ACP daemon stops passing flags that the exec command does not support.
• ACP sessions with MCP servers configured should start normally.

Impact

Factory Droid in Zed is unusable whenever any MCP/context servers are enabled. 0.190.0 is the latest version on npm as of 2026-08-09, so there is no known fixed version to upgrade to.