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Fallow reads a small set of environment variables to override default behavior. These are useful for CI pipelines, editor integrations, and the MCP server.
VariableDescriptionValues
FALLOW_FORMATDefault output formathuman, json, sarif, compact
FALLOW_QUIETSuppress progress output1 or true
FALLOW_BINPath to the fallow binaryAny valid path

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FALLOW_FORMAT

Set the default output format so you don’t need to pass --format every time. 
export FALLOW_FORMAT=json
fallow check   # Outputs JSON without --format flag
The --format CLI flag takes precedence over FALLOW_FORMAT when both are set.

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FALLOW_QUIET

Suppress progress bars and status messages. Useful in CI environments or when piping output. 
export FALLOW_QUIET=1
fallow check   # No progress output, only results
Equivalent to passing --quiet on every command.

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FALLOW_BIN

Path to the fallow binary. Used by the MCP server (fallow-mcp) and the LSP server to locate the fallow CLI. 
export FALLOW_BIN=/usr/local/bin/fallow
fallow-mcp   # MCP server uses the specified binary
Defaults to fallow on PATH when not set.
Set FALLOW_FORMAT=json and FALLOW_QUIET=1 in CI pipelines for clean machine-readable output.

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See also

MCP server

AI agent integration using the Model Context Protocol.

fallow check

Full CLI reference including all output format options.