go.pennock.tech/aifr

CLI/MCP/Co-process tool for read-only filesystem DESCRIPTION git access

• Current public git hosting (GitHub)
• Go package documentation
• 

aifr — AI File Reader

A read-only filesystem and git-tree access tool, with both a standalone CLI and a JSON-RPC co-process mode which happens to fit the MCP schema for AI agents.

AI agents (Claude Code, Cursor, etc.) resort to shell pipelines (sed -n, find | grep, head/tail) that trigger security checks and produce brittle, unstructured output. aifr replaces all of those with a single binary that is always safe (never writes) and always scoped (enforces allow/deny lists with a built-in sensitive-file blocklist).

The aifr tool can read files, read git state, read “getent” system files, some basic system information, and more. Everything read-only (except the MCP self reload task). No network access, but some network state querying.

A number of filters traditionally done with the Unix pipe handling are moved left into aifr, to limit the output without needing a pipeline. This avoids triggering security checks for a shell invocation, even when using aifr purely as a CLI tool, let alone when you start it as a co-process server so that it can quickly answer many questions. The queries often support options to filter which data rows are returned, which columns, to sort, and more.

Outside of AI, scripts which do a lot of git operations often end up repeatedly shelling out to git. With this agent running as a co-process, they can query configuration and contents and some history with a read-only tool: safe, because it will not touch anything or break the repo; at worst, it will fail to parse something, not break your setup.

Install

Binary releases are available; currently hosted at: https://github.com/PennockTech/aifr/releases

Or you can build from source.

# From source
go install go.pennock.tech/aifr/cmd/aifr@latest

# Or build from the repo
task build

MCP Server for Claude Code

claude mcp add --scope user aifr -- aifr mcp

This registers aifr as an MCP server using stdio transport. Claude Code will then have access to aifr_read, aifr_cat, aifr_stat, aifr_list, aifr_search, aifr_find, aifr_refs, aifr_log, and aifr_diff tools.

Skill File

The MCP server’s built-in instructions are intentionally brief. For richer agent guidance (tool routing, advanced patterns, error handling), install the skill file:

# Symlink into user-level skills (recommended — stays in sync with repo)
mkdir -p ~/.claude/skills
ln -s "$(pwd)/skills/aifr" ~/.claude/skills/aifr

# Or copy if you prefer a snapshot
cp -r skills/aifr ~/.claude/skills/aifr

You can also generate the embedded (shorter) skill file at any time:

aifr skill > /tmp/aifr-skill.md

HTTP Transport

For HTTP transport (multi-client setups):

aifr mcp --transport http --addr :8080

Quick Start

# Read a file
aifr read src/main.go

# Read first 50 lines
aifr read --lines 1:50 src/main.go

# Read a file from git history
aifr read HEAD~3:src/main.go

# Concatenate all Go files, skipping vendor
aifr cat --name '*.go' --exclude-path '**/vendor/**' .

# Head: first 10 lines of each Go file with dividers
aifr cat --name '*.go' --lines 10 --divider plain --format text .

# Search for a pattern
aifr search 'func.*Handler' ./src/

# Find files by name
aifr find --name '*.yaml' --max-depth 2 .

# List directory
aifr list --depth -1 --type f .

# Git refs and log
aifr refs --branches --tags
aifr log --max-count 5

# Compare files across refs
aifr diff HEAD~1:README.md README.md

All commands output JSON by default. Use --format text for human-readable output.

Configuration

Create .aifr.toml in the working directory or ~/.config/aifr/config.toml:

allow = ["~/projects/**"]
deny = ["~/projects/secrets/**"]

[git.repos]
myapp = "~/projects/myapp"

If no config is found, aifr operates in “current directory only” mode — it allows the cwd and everything beneath it.

See configs/aifr.example.toml for the full config reference.

Access Control

Every path request is evaluated in order:

1. Resolve symlinks to canonical path
2. Sensitive list (built-in, 120+ patterns) → blocked, always
3. Deny list (from config) → blocked
4. Allow list (from config, or cwd fallback) → permitted
5. Default → blocked

Sensitive files (SSH keys, cloud credentials, .env, shell history, etc.) return a distinct ACCESS_DENIED_SENSITIVE error. The agent is expected to tell the user to read the file themselves if needed, and must not retry.

Run aifr sensitive to see the full pattern list.

Commands

Git Path Syntax

Git objects are addressed as [repo:]<ref>:<path>:

All git reads go directly through the object store — no checkout, no side effects on the working tree.

Building

task build              # build with version ldflags
task test               # run tests with race detector
task check              # fmt + lint + test
task release:snapshot   # goreleaser snapshot build

Build targets: Linux (amd64), macOS (arm64), FreeBSD (amd64).

License

FIXME: but for now, private and confidential.