gemini-cli fails to start mcp-redis when REDIS_URL is unset

[vchomakov]

Description

gemini-cli currently requires the environment variable REDIS_URL to be explicitly defined (e.g. redis://127.0.0.1:6379).
When this variable is not set, the CLI does not fall back to a default Redis instance and instead terminates with an error.

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Expected Behavior

If REDIS_URL is unset, gemini-cli should default to connecting to redis://localhost:6379

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Actual Behavior

When REDIS_URL is not provided, the CLI throws the following error and doesn't start the MCP server:

[DEBUG] [MCP STDERR (redis)]: Error parsing Redis URI: Unsupported scheme:
Error during discovery for server ‘redis’: MCP error -32000: Connection closed

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Steps to Reproduce

1. Ensure no REDIS_URL environment variable is set:

   unset REDIS_URL

2. Run gemini-cli
3. Observe the connection error.