Sippion

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Sippion is a local, read-only MCP server that helps AI coding agents find the right parts of a repository before they start opening source files broadly. Its primary job is to organize and bound repository context before it is passed to an AI model, so clients avoid spending model-input tokens on irrelevant source while preserving the evidence needed to solve the task.

Sippion exposes one MCP tool, repo_context, which combines bounded lexical search, structural context, and source-only semantic ranking to return a small, relevant set of code excerpts.

Quick start

Install Sippion with one command. The bootstrap verifies its downloaded installer checksum and GitHub artifact attestation before executing the installer. The installer then verifies the selected binary checksum and its GitHub artifact attestation before installing it and running transactional sippion setup.

The default path fails closed unless the GitHub CLI (gh) is installed, has gh attestation support, and can authenticate to GitHub. This deliberately keeps release provenance verification enabled on the primary install path.

macOS / Linux

curl -fsSL --proto '=https' --proto-redir '=https' --tlsv1.2 https://raw.githubusercontent.com/Sitten-Tokyo/Sippion/a28b611f169a2731ca89dd59db89ccf00940185f/scripts/bootstrap.sh | sh

Windows PowerShell

irm https://raw.githubusercontent.com/Sitten-Tokyo/Sippion/a28b611f169a2731ca89dd59db89ccf00940185f/scripts/bootstrap.ps1 | iex

After installation:

verify installer checksum + GitHub artifact attestation
    ↓
verify binary checksum + GitHub artifact attestation
    ↓
Sippion installed
    ↓
Codex + Claude Code + Antigravity pre-registered
    ↓
Restart those AI clients

Both attestation checks are bound to the Sippion repository, the expected release signer workflow, and the exact commit SHA resolved from the selected release tag.

Sippion pre-registers all three clients, even if one is not installed yet. Each client launches Sippion with --root-auto. Sippion selects the nearest recognized Git/project boundary and refuses automatic selection of the user's home directory or filesystem root. On Unix, shared group/other-writable ancestor directories are not trusted as automatic boundaries. On Windows, --root-auto is deliberately limited to projects under the canonical current user profile because Sippion cannot safely verify arbitrary shared-directory ACLs through stable safe Rust APIs; trusted projects elsewhere can use an explicit --root. You do not need to register Sippion separately for every repository under the normal automatic scope.

A checksum-only direct installer mode remains available as an explicit opt-out for controlled environments where provenance was verified by another trusted mechanism. See Security and trust boundary.

Official MCP Registry

Sippion is published in the Official MCP Registry as io.github.Sitten-Tokyo/sippion. The canonical Registry record can be inspected through the stable API at the latest Sippion Registry entry.

Each release intended for Registry distribution contains four checksummed, provenance-attested MCPB bundles alongside the native binaries:

sippion-linux-x86_64.mcpb
sippion-windows-x86_64.mcpb
sippion-macos-aarch64.mcpb
sippion-macos-x86_64.mcpb

The MCPB manifest asks the host for an explicit project root and launches the same local stdio server. The bootstrap + sippion setup path above remains the recommended route when you want Sippion to configure Codex, Claude Code, and Antigravity automatically; Registry/MCPB distribution is an additional standards-based installation and discovery channel.

What Sippion does

A client can ask Sippion for focused repository context such as:

repo_context {"q":"authentication token validation"}

Sippion returns bounded excerpts and structural evidence instead of dumping a large part of the repository into the model context.

Typical flow:

AI coding agent
    ↓ asks what part of the repo matters
Sippion repo_context
    ↓ returns focused evidence
AI opens the relevant source files normally

This is useful for large repositories, unfamiliar codebases, and multi-agent workflows where broad source exploration would otherwise consume time and context.

Optional session_id and agent_id values can coordinate cooperating agents in process memory. They are not persisted.

Safety model

Sippion itself is:

• local stdio MCP
• project-scoped
• read-only
• no-network while serving repository context
• RAM-only for retrieval state; it does not create a persistent index

It does not run repository code, proxy model traffic, store provider credentials, start a daemon, or modify the repository.

Repository reads are bounded, reject symlinks and unsafe hard links, revalidate source identity around reads, and redact high-confidence secrets before output. Repository text is treated as untrusted data, not as instructions to the AI.

For the full trust boundary and installation trust model, see Security and trust boundary.

Supported clients

sippion setup configures the current user for:

• Codex
• Claude Code
• Antigravity

Restart an already-running client after installation so it reloads its MCP configuration.

Useful commands:

sippion setup
sippion doctor
sippion uninstall

setup is idempotent and transactional across the managed client files. It refuses to rewrite a Sippion-managed text block if its management markers are missing, duplicated, or out of order, rather than risking unrelated user settings. Managed files and their managed parent directories are refused when they are symlinks. On Unix, MCP client configuration files are created or repaired as owner-only 0600; rollback also restores the previous permission bits. Persistent .sippion-backup copies are not created, and legacy copies from older releases are removed transactionally. If any client update fails, files touched by that setup attempt are restored.

doctor checks registration health and exits non-zero when any expected registration is unhealthy. uninstall is transactional too: it snapshots the managed configuration/rule files before removal and restores the pre-attempt state if any removal fails. It removes Sippion-managed client configuration and rules but does not remove unrelated settings or the binary.

See Client setup for manual configuration and diagnostics.

Run Sippion manually

To infer a safe project root from the current directory:

sippion mcp --root-auto

Automatic discovery uses the nearest recognized Git/project marker. It does not continue past a nearer project manifest merely to find a farther .git marker; on Unix it also stops before trusting a group/other-writable shared directory. Resolving the current user's home directory is part of the safety check, so failure to resolve it stops automatic discovery instead of silently disabling the home/ancestor guard.

On Windows, --root-auto is limited to projects under the canonical current user profile. To use a trusted project elsewhere, bind it explicitly:

sippion mcp --root /ABSOLUTE/PATH/TO/PROJECT

Home-directory, filesystem-root, and home-ancestor scans are rejected by default. An intentional broad manual scan requires the explicit --allow-broad-root opt-in. Setup never enables that override.

To lower the adaptive scan ceiling:

sippion mcp --root /ABSOLUTE/PATH/TO/PROJECT --scan-budget-mib 128

How it works

Retrieval starts with a RAM-only lexical index, expands scan work only while the previous round is still yielding useful evidence, parses ranked candidates, and can add a bounded set of deterministic import/semantic neighbors. Verified excerpts and structural facts are then selected by utility per estimated token, with redundant same-file context discounted. The estimated-token target is a soft packing goal; an independent byte cap is the hard model-visible output guard. Structural parsing currently covers Rust, Python, JavaScript/TypeScript, Go, Java, C#, C, and C++. Search-term matching is Unicode-aware while filesystem safety policy remains deliberately separate and conservative.

Sippion is a repository-context tool, not a compiler or language server. It does not claim compiler-authoritative type resolution or LSP-grade references.

See Architecture and Integration boundaries for details.

Development

The project pins Rust 1.85.0 and commits Cargo.lock.

cargo fmt --check
cargo build --release --locked
cargo test --locked
cargo clippy --all-targets --all-features --locked -- -D warnings

CI also audits Cargo.lock against the RustSec advisory database.

The native binary is target/release/sippion or target/release/sippion.exe on Windows.

For maintainers: releases

Supported release binaries:

sippion-linux-x86_64
sippion-windows-x86_64.exe
sippion-macos-aarch64
sippion-macos-x86_64

Release workflows build all four targets, generate portable SHA-256 files, and produce GitHub artifact attestations. Third-party GitHub Actions are pinned to full commit SHAs. Pull-request supply-chain smoke builds and assembles the release payload without minting distributable attestations, then separately verifies a published installer and binary with the same strict repository, signer-workflow, and source-SHA policy used by the installers.