Rtk

RTK

CLI proxy reduces LLM token consumption 60-90% on dev commands. Intercepts command output (git, test runners, linters, build tools), returns only essential info to agent context window.

• Single Rust binary, zero runtime deps
• <10ms overhead per command
• Fail-safe: falls back to raw output if filter breaks
• Preserves exit codes for CI/CD compatibility

Installation

brew install rtk          # macOS (Homebrew)
cargo install rtk-ai      # From crates.io

Verify correct binary (name collision with another rtk package):

rtk --version    # Should show "rtk 0.31.0" or newer
rtk gain         # Should show token savings (NOT "command not found")

Global Setup

Use rtk init -g for hook-based integration. Recommended approach -- transparently rewrites commands with zero manual effort:

rtk init -g

Installs:

• ~/.claude/hooks/rtk-rewrite.sh — PreToolUse hook rewrites Bash commands through rtk hook
• ~/.claude/RTK.md — slim reference (10 lines, minimal token cost)
• Hook entry in ~/.claude/settings.json

After setup, all agent Bash commands auto-rewritten. Example: git status becomes rtk git status transparently.

Other Agents

rtk init --agent cursor     # Cursor
rtk init --codex            # Codex CLI (base + variants)

Windsurf and Cline use rules files (.windsurfrules, .clinerules) generated by rtk init.

Uninstall

rtk init -g --uninstall

How It Works

Hook intercepts PreToolUse Bash events, rewrites commands via rtk rewrite, returns compressed output. Strategies: filtering (ANSI, boilerplate), grouping (errors by rule), truncation, deduplication.

Supported Commands

• Git: status ~80%, log ~75-92%, diff ~70%, commit ~90%
• Tests: pytest/cargo test ~90%, vitest ~99%
• Linters: ruff/eslint ~80-84%, tsc/mypy ~80-83%
• Builds: cargo build ~80%, next build ~87%
• File ops: ls/tree ~80%, grep/rg ~75%, find/fd ~70%

Meta Commands

Run directly -- never through proxy:

rtk gain              # Token savings dashboard
rtk gain --history    # Per-command history with savings %
rtk gain --graph      # Visual savings graph
rtk gain --project    # Scoped to current project
rtk discover          # Scan agent history for missed optimizations
rtk learn             # Detect project patterns, suggest optimizations
rtk session           # Adoption overview
rtk proxy <cmd>       # Run raw command (no filtering), still tracked
rtk rewrite "<cmd>"   # Preview what a command would be rewritten to
rtk config            # Show current configuration
rtk verify            # Integrity check
rtk hook-audit        # Audit hook installations

Configuration

User Config

~/.config/rtk/config.toml:

[tracking]
history_days = 90

[display]
colors = true
max_width = 120

[filters]
ignore_dirs = [".git", "node_modules", "target", "__pycache__", ".venv"]

[hooks]
exclude = []          # commands to skip rewriting

Use [hooks] exclude to bypass rewriting where raw output needed.

Custom Filters (TOML)

Declarative filter pipelines for commands RTK doesn't cover natively.

Project-local: .rtk/filters.toml (requires rtk trust for security)

User-global: ~/.config/rtk/filters.toml

Example -- compress Terraform plan output:

[filters.terraform-plan]
command = "terraform"
subcommand = "plan"
strip_ansi = true
strip_lines_matching = ["Refreshing state...", "Reading...", "data\\."]
truncate_lines_at = 200
max_lines = 100 changes detected"

[[filters.terraform-plan.replace]]
pattern = "Plan: (\\d+) to add"
replacement = "+$1"

[[tests.terraform-plan]]
input = "Refreshing state...\nPlan: 3 to add"
expected = "+3"

Pipeline stages (applied sequentially):

1. strip_ansi — remove escape codes
2. replace — regex substitutions (chainable)
3. match_output — short-circuit if pattern matches (with unless)
4. strip_lines_matching / keep_lines_matching — filter lines by regex
5. truncate_lines_at — limit line length
6. head_lines / tail_lines — retain first/last N lines
7. max_lines — absolute line cap
8. on_empty — fallback message if result empty

Trust Gating

Project-local .rtk/filters.toml requires explicit trust:

rtk trust             # Trust current project's filters
rtk untrust           # Revoke trust

Debugging

RTK_TOML_DEBUG=1 rtk <cmd>    # Log matched filters to stderr
RTK_DISABLED=1 <cmd>          # Bypass RTK entirely
RTK_NO_TOML=1 rtk <cmd>      # Bypass TOML filters only
rtk proxy <cmd>               # Run raw, still track usage

File Reading Modes

rtk read filter levels: NoFilter (unchanged), MinimalFilter (strips comments/blanks), AggressiveFilter (imports + signatures only). Data formats (JSON, YAML, TOML) bypass aggressive filtering.

Best Practices

• Use rtk init -g for global hook -- most transparent
• Let hook rewrite automatically, don't manually prefix
• Run rtk gain regularly, rtk discover for missed opportunities
• Use rtk proxy <cmd> for full unfiltered output
• Start with defaults; add TOML filters only for project-specific tools
• Include [[tests]] in custom filters
• Tee saves raw output on failures to ~/.local/share/rtk/tee/