What's new in 6.20.2

• Miller now treats AI agents as first-class users
• There is shell tab-completion for bash and zsh
• There is a new bytes datatype, along with base64 encode/decode support

(Note: versions 6.20.0 and 6.20.1 were in error and are not released.)

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. Your choice of

# Claude
mlr skill install ~/.claude/skills/miller
# Codex and Gemini
mlr skill install ~/.agents/skills/miller

or

# Claude
claude mcp add miller --  mlr mcp
# Codex
codex mcp add miller --  mlr mcp
# Gemini
gemini mcp add miller mlr mcp

See the new Miller and AI docs page for the quick start.

Reference pages:

• https://miller.readthedocs.io/en/latest/ai
• https://miller.readthedocs.io/en/latest/agent-skill
• https://miller.readthedocs.io/en/latest/mcp-server
• https://miller.readthedocs.io/en/latest/ai-support

PRs:

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

Shell tab-completion for bash and zsh

Documentation:

https://miller.readthedocs.io/en/latest/shell-completion/

PR:

• Shell tab-completion for bash and zsh by @johnkerl in https://github.com/johnkerl/miller/pull/2096

A first-class bytes type in the DSL

Docs:

• https://miller.readthedocs.io/en/latest/reference-main-data-types/
• https://miller.readthedocs.io/en/latest/reference-dsl-builtin-functions/#base64_encode
• https://miller.readthedocs.io/en/latest/reference-dsl-builtin-functions/#base64_decode

PR:

• New bytes type with b"..." literals and base64/hex codecs by @johnkerl in https://github.com/johnkerl/miller/pull/2122

More features

• New tail -n +N and head -n -N options by @farnoy in https://github.com/johnkerl/miller/pull/2071
• Long-overdue --md flag by @johnkerl in https://github.com/johnkerl/miller/pull/2100
• Windows-arm64 releases by @teo-tsirpanis in https://github.com/johnkerl/miller/pull/2127

Bug fixes

• Fix masked unset-on-array error path (along with govet lint findings) by @johnkerl in https://github.com/johnkerl/miller/pull/2129

Documentation

• CSV and JSON troubleshooting tips by @dashitongzhi in https://github.com/johnkerl/miller/pull/2123, with page-refactor by @johnkerl in https://github.com/johnkerl/miller/pull/2128
• Document time-conversion thread safety by @dashitongzhi in https://github.com/johnkerl/miller/pull/2115
• PNG graphics in perf docs for issue-2084 perf mods by @johnkerl in https://github.com/johnkerl/miller/pull/2095

Internals

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

New Contributors

• @farnoy made their first contribution in https://github.com/johnkerl/miller/pull/2071
• @dashitongzhi made their first contribution in https://github.com/johnkerl/miller/pull/2076
• @teo-tsirpanis made their first contribution in https://github.com/johnkerl/miller/pull/2127

Full Changelog: https://github.com/johnkerl/miller/compare/v6.19.0...v6.20.0