What's new in 6.20.0

Miller and AI

Miller now treats AI agents as first-class users. Everything an agent needs to drive Miller well — discovering what exists, learning your data's shape, validating expressions before running them, and recovering from errors — is now a built-in, structured feature of the mlr binary, packaged for MCP-speaking agents (Claude Code, Claude Desktop, Cursor, ...) via a one-line setup:

claude mcp add miller -- mlr mcp

See the new Miller and AI docs page for the quick start. The pieces, all usable individually from the command line:

• Machine-readable help catalog, mlr help --as-json: by @johnkerl in #2099, #2106
• JSON capability index and mlr which intent router by @johnkerl in #2107
• Structured verb options, with enum value-sets by @johnkerl in #2111
• Structured error output, --errors-json, with hints and did-you-mean suggestions by @johnkerl in #2113
• DSL validate/dry-run, mlr put --explain / mlr filter --explain by @johnkerl in #2131
• New mlr describe verb: field names, types, cardinality, and value domains of your data in one pass by @johnkerl in #2132
• New mlr mcp MCP server and agent playbook, with a --no-shell sandbox flag by @johnkerl in #2133
• Roadmap doc by @johnkerl in #2103; "Miller and AI" docs page by @johnkerl in #2134

A first-class bytes type in the DSL

• New bytes type with b"..." literals and base64/hex codecs by @johnkerl in #2122

More features

• New tail -n +N and head -n -N options by @farnoy in #2071
• Shell tab-completion for bash and zsh by @johnkerl in #2096
• Long-overdue --md flag by @johnkerl in #2100
• Windows-arm64 releases by @teo-tsirpanis in #2127

Bug fixes

• Fix masked unset-on-array error path (along with govet lint findings) by @johnkerl in #2129

Documentation

• CSV and JSON troubleshooting tips by @dashitongzhi in #2123, with page-refactor by @johnkerl in #2128
• Document time-conversion thread safety by @dashitongzhi in #2115
• PNG graphics in perf docs for issue-2084 perf mods by @johnkerl in #2095

Internals

• golangci-lint CI workflow by @dashitongzhi in #2076
• Lint fixes bringing staticcheck and errcheck to zero by @johnkerl in #2108, #2110, #2112, #2130
• Strip dead code from pkg/ by @johnkerl in #2121
• CI/actions updates by @johnkerl in #2119 and by @dependabot in #2101, #2102, #2104, #2105, #2114, #2116, #2118, #2124, #2125, #2126
• Dependency bumps by @dependabot in #2117, #2120

New Contributors

• @farnoy made their first contribution in #2071
• @dashitongzhi made their first contribution in #2076
• @teo-tsirpanis made their first contribution in #2127

Full Changelog: v6.19.0...v6.20.0