Creating snip Filters

You are an expert at writing declarative YAML filters for snip, a CLI proxy that reduces LLM token consumption by filtering shell output.

Filter File Location

• Built-in filters: filters/*.yaml (embedded in the binary at build time)
• User filters: ~/.config/snip/filters/*.yaml (override built-in filters by name)
• Per-project filters: configure additional directories via filters.dir array in ~/.config/snip/config.toml (e.g. dir = ["~/.config/snip/filters", "${env.PWD}/.snip"]). Later directories take priority.

Filter Structure

Every filter is a YAML file with this structure:

name: "tool-subcommand"          # Required. Unique identifier, used for registry lookup.
version: 1                       # Schema version (always 1 for now).
description: "What this filter does"  # Human-readable purpose.

match:                           # Required. When to apply this filter.
  command: "tool"                # Required. The CLI tool name (e.g., "git", "go", "npm").
  subcommand: "sub"             # Optional. First non-flag argument (e.g., "test", "log").
  exclude_flags: ["-v", "--json"]  # Optional. Skip filter if user passes any of these.
  require_flags: ["--all"]      # Optional. Only apply if user passes ALL of these.

inject:                          # Optional. Modify command args before execution.
  args: ["--json"]              # Arguments to append to the command.
  defaults:                     # Flag defaults, only added if flag not already present.
    "-n": "10"
  skip_if_present: ["--json"]   # Don't inject anything if any of these flags are present.

streams: ["stdout", "stderr"]    # Optional. Which streams to filter. Default: ["stdout"].
                                 # Use ["stderr"] for tools that output to stderr (e.g., bun test).
                                 # Use ["stdout", "stderr"] to filter both streams merged together.

pipeline:                        # Required. Ordered list of transformation actions.
  - action: "keep_lines"
    pattern: "\\S"
  - action: "head"
    n: 20

on_error: "passthrough"          # What to do if the pipeline fails: "passthrough" or "empty".

Match Rules

• command is matched exactly against the first token of the shell command.
• subcommand is matched against the first non-flag argument.
• Flag matching uses prefix matching: "-v" matches both -v and -verbose.
• Registry lookup is O(1) by key "command" or "command:subcommand".

Inject Behavior

• Injected args are inserted before any -- separator, otherwise appended.
• defaults only apply if their flag key is not already present in the user's args.
• If any flag in skip_if_present is found, the entire inject block is skipped.

The 16 Pipeline Actions

Line Filtering

Line Transformation

Extraction & Grouping

JSON Processing

Formatting

Template Data for format_template

The template receives:

• {{.lines}} - all current lines joined with newlines
• {{.count}} - number of lines
• {{.groups}} - map from group_by action (if used earlier in pipeline)
• {{.stats}} - map from aggregate action (if used earlier in pipeline)

Metadata Flow Between Actions

• group_by sets metadata "groups" (map[string]int)
• aggregate sets metadata "stats" (map[string]int)
• format_template can access both via {{.groups}} and {{.stats}}
• All other actions pass metadata through unchanged

Design Principles

1. Start with keep_lines pattern "\\S" to strip blank lines early.
2. Use inject to request machine-readable output (e.g., --json, --porcelain) then filter that structured data.
3. Respect user intent: use exclude_flags to skip filtering when the user explicitly requests a different format.
4. Always set on_error: "passthrough" so raw output is returned if filtering fails.
5. Chain actions from broad to specific: filter noise first, then extract, then format.
6. Keep output minimal but useful: the goal is 60-90% token reduction while preserving actionable information.

Examples

Simple: remove noise lines

name: "npm-install"
version: 1
description: "Condensed npm install output"
match:
  command: "npm"
  subcommand: "install"
pipeline:
  - action: "remove_lines"
    pattern: "^(npm warn|npm notice)"
  - action: "keep_lines"
    pattern: "\\S"
  - action: "aggregate"
    patterns:
      added: "^added "
      removed: "^removed "
      up_to_date: "up to date"
    format: "{{if gt .up_to_date 0}}up to date{{else}}{{.added}} added, {{.removed}} removed{{end}}"
on_error: "passthrough"

Intermediate: inject flags + extract structured data

name: "go-test"
version: 1
description: "Condensed go test output with pass/fail summary"
match:
  command: "go"
  subcommand: "test"
  exclude_flags: ["-json", "-v", "-bench", "-run"]
inject:
  args: ["-json"]
  skip_if_present: ["-json", "-v", "-bench"]
pipeline:
  - action: "keep_lines"
    pattern: "\\S"
  - action: "keep_lines"
    pattern: "\"Test\":\""
  - action: "keep_lines"
    pattern: "\"Action\":\"(pass|fail)\""
  - action: "aggregate"
    patterns:
      passed: '"Action":"pass"'
      failed: '"Action":"fail"'
    format: "{{if and (eq .passed 0) (eq .failed 0)}}No tests found{{else}}{{.passed}} passed, {{.failed}} failed{{end}}"
on_error: "passthrough"

Advanced: state machine for multi-section output

name: "cargo-test"
version: 1
description: "Condensed cargo test output"
match:
  command: "cargo"
  subcommand: "test"
pipeline:
  - action: "remove_lines"
    pattern: "^\\s*(Compiling|Downloading|Downloaded|Updating|Running|Executable)"
  - action: "keep_lines"
    pattern: "\\S"
  - action: "state_machine"
    states:
      start:
        keep: "^(test |running |test result)"
        until: "^failures"
        next: "failures"
      failures:
        keep: "."
        until: "^$"
        next: "done"
  - action: "aggregate"
    patterns:
      pass: "\\.\\.\\. ok$"
      fail: "\\.\\.\\. FAILED$"
      ignored: "\\.\\.\\. ignored$"
  - action: "format_template"
    template: "{{.lines}}"
on_error: "passthrough"

Workflow to Create a New Filter

1. Identify the command and its typical verbose output.
2. Run the command and capture raw output to understand the structure.
3. Decide what to keep: what information does the LLM actually need?
4. Check if the tool has a machine-readable flag (--json, --porcelain, etc.) that would make filtering easier -- use inject if so.
5. Write the pipeline: strip blanks, filter/extract, aggregate, format.
6. Test the filter by placing it in ~/.config/snip/filters/ and running the command through snip.
7. To contribute: add the YAML to filters/ in the repo and submit a PR.

snip - Reduce LLM Token Usage by 60-90%

CLI proxy that filters shell output before it reaches your AI coding assistant's context window. Works with Claude Code, Cursor, Copilot, Gemini CLI, Windsurf, Cline, Codex, Kilo Code, Antigravity, Aider, and any tool that runs shell commands.

AI coding agents burn tokens on verbose shell output that adds zero signal. A passing go test produces hundreds of lines the LLM will never use. git log dumps full commit metadata when a one-liner per commit suffices.

snip sits between your AI tool and the shell, filtering output through declarative YAML pipelines. Write a YAML file, drop it in a folder, done. The extensible LLM token optimizer: filters are YAML data files, not compiled code.

  snip — Token Savings Report
  ══════════════════════════════

  Commands filtered     128
  Tokens saved          2.3M
  Avg savings           99.8%
  Efficiency            Elite
  Total time            725.9s

  ███████████████████░ 100%

  14-day trend  ▁█▇

  Top commands by tokens saved

  Command                    Runs  Saved   Savings  Impact
  ─────────────────────────  ────  ──────  ───────  ────────────
  go test ./...              8     806.2K  99.8%    ████████████
  go test ./pkg/...          3     482.9K  99.8%    ███████░░░░░
  go test ./... -count=1     3     482.0K  99.8%    ███████░░░░░

Measured on a real Claude Code session — 128 commands, 2.3M tokens saved.

Quick Start

# Quick install (macOS/Linux)
curl -fsSL https://raw.githubusercontent.com/edouard-claude/snip/master/install.sh | sh

# Or via Homebrew
brew install edouard-claude/tap/snip

# Or with Go
go install github.com/edouard-claude/snip/cmd/snip@latest

# Then hook into Claude Code
snip init
# That's it. Every shell command Claude runs now goes through snip.

How It Works

Before — Claude Code sees this (689 tokens):

$ go test ./...
ok  	github.com/edouard-claude/snip/internal/cli	3.728s	coverage: 14.4% of statements
ok  	github.com/edouard-claude/snip/internal/config	2.359s	coverage: 65.0% of statements
ok  	github.com/edouard-claude/snip/internal/display	1.221s	coverage: 72.6% of statements
ok  	github.com/edouard-claude/snip/internal/engine	1.816s	coverage: 47.9% of statements
ok  	github.com/edouard-claude/snip/internal/filter	4.306s	coverage: 72.3% of statements
ok  	github.com/edouard-claude/snip/internal/initcmd	2.981s	coverage: 59.1% of statements
ok  	github.com/edouard-claude/snip/internal/tee	0.614s	coverage: 70.6% of statements
ok  	github.com/edouard-claude/snip/internal/tracking	5.355s	coverage: 75.0% of statements
ok  	github.com/edouard-claude/snip/internal/utils	5.515s	coverage: 100.0% of statements

After — snip returns this (16 tokens):

10 passed, 0 failed

That's 97.7% fewer tokens. The LLM gets the same signal — all tests pass — without the noise.

┌─────────────┐     ┌─────────────────┐     ┌──────────────┐     ┌────────────┐
│ Claude Code │────>│ snip intercept  │────>│ run command  │────>│   filter   │
│  runs git   │     │  match filter   │     │  capture I/O │     │  pipeline  │
└─────────────┘     └─────────────────┘     └──────────────┘     └─────┬──────┘
                                                                       │
                    ┌─────────────────┐     ┌──────────────┐           │
                    │   Claude Code   │<────│ track savings│<──────────┘
                    │  sees filtered  │     │  in SQLite   │
                    └─────────────────┘     └──────────────┘

No filter match? The command passes through unchanged — zero overhead.

Token Savings by Command

Stop wasting tokens on noise. snip gives the LLM the same signal in a fraction of the context window.

Installation

Homebrew (recommended)

brew install edouard-claude/tap/snip

From GitHub Releases

Download the latest binary for your platform from Releases.

# macOS (Apple Silicon)
curl -Lo snip.tar.gz https://github.com/edouard-claude/snip/releases/latest/download/snip_$(curl -s https://api.github.com/repos/edouard-claude/snip/releases/latest | grep tag_name | cut -d'"' -f4 | tr -d v)_darwin_arm64.tar.gz
tar xzf snip.tar.gz && mv snip /usr/local/bin/

From source

go install github.com/edouard-claude/snip/cmd/snip@latest

Or build locally:

git clone https://github.com/edouard-claude/snip.git
cd snip && make install

Requires Go 1.25+.

Supported AI Tools

snip integrates with every major AI coding assistant. One binary, universal compatibility.

Claude Code

snip init

This installs a PreToolUse hook that transparently rewrites supported commands. Claude Code never sees the substitution -- it receives compressed output as if the original command produced it.

Supported commands: 127 filters covering git, go, cargo, npm, yarn, pnpm, docker, kubectl, terraform, aws, gh, and 80+ more tools.

snip init --uninstall   # remove the hook

Cursor

snip init --agent cursor

This patches ~/.cursor/hooks.json with a beforeShellExecution hook. Works the same way as Claude Code.

snip init --agent cursor --uninstall   # remove the hook

Pi (pi.dev)

snip init --agent pi

This patches ~/.pi/agent/settings.json with a PreToolUse entry matching the bash tool. The runtime hook is interpreted by the community extension @hsingjui/pi-hooks, which mirrors Claude Code's hookSpecificOutput format (including command rewriting via updatedInput). Install it once:

pi install npm:@hsingjui/pi-hooks

Then run /reload (or restart Pi). Once active, snip rewrites supported commands transparently.

snip init --agent pi --uninstall   # remove the hook

Copilot / Gemini / Codex / Windsurf / Cline / Kilo Code / Antigravity

snip init --agent copilot      # creates .github/copilot-instructions.md
snip init --agent gemini       # creates GEMINI.md
snip init --agent codex        # creates AGENTS.md
snip init --agent windsurf     # creates .windsurfrules
snip init --agent cline        # creates .clinerules
snip init --agent kilocode     # creates .kilocode/rules/snip-rules.md
snip init --agent antigravity  # creates .agents/rules/snip-rules.md

These agents use prompt injection: a markdown file instructs the LLM to prefix shell commands with snip. Project-scoped (created in the current directory).

OpenCode

Install the opencode-snip plugin by adding it to your OpenCode config (~/.config/opencode/opencode.json):

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-snip@latest"]
}

The plugin uses the tool.execute.before hook to automatically prefix all commands with snip. Commands not supported by snip pass through unchanged.

OpenClaw

openclaw plugins install openclaw-snip

Aider

Use shell aliases to route commands through snip:

# Add to ~/.bashrc or ~/.zshrc
alias git="snip git"
alias go="snip go"
alias cargo="snip cargo"

Or instruct the LLM via system prompt to prefix commands with snip.

Standalone

snip works without any AI tool:

snip git log -10
snip go test ./...
snip gain             # token savings report

Usage

snip <command> [args]       # filter a command
snip gain                   # full dashboard (summary + sparkline + top commands)
snip gain --daily           # daily breakdown
snip gain --weekly          # weekly breakdown
snip gain --monthly         # monthly breakdown
snip gain --top 10          # top N commands by tokens saved
snip gain --history 20      # last 20 commands
snip gain --no-truncate     # disable command truncation
snip gain --json            # machine-readable output
snip gain --csv             # CSV export
snip discover               # find