Crate Sentinel

Rust MCP server for governed dependency upgrades in Rust workspaces.

Quick Install

cargo install crate-sentinel-mcp
codex add mcp crate-sentinel crate-sentinel-mcp

After this, crate-sentinel is registered in Codex as an MCP server.

It is recommended to install additional crates globally in advance to speed up crate-sentinel workflows:

cargo install cargo-semver-checks cargo-public-api cargo-download

What It Does

• Discovers external dependencies (deps.scan)
• Checks latest versions and policy allow/deny (deps.check_updates)
• Simulates upgrades in isolated copies (deps.try_upgrade)
• Detects breaking API changes (deps.api_diff)
• Applies controlled real upgrades (deps.apply_upgrade)
• Supports refactor planning/validation bridge (refactor.plan, refactor.validate)
• Supports CI summaries (ci.report)

Governance Model

• Policy file: upgrade_policy.toml
• Default denies major updates, allows patch/minor
• Optional guards:
  • MSRV guard
  • Performance regression guard
  • CI fail-on-disallowed mode

Session Model

• Start a session with session.start
• One active session per workspace lock
• Session tracks current crate, state, and audit events
• End each active session with session.end to remove persisted session files
• Recover persisted sessions with session.recover

Policy Example

[general]
allow_patch = true
allow_minor = true
allow_major = false
include_dev_dependencies = false

[msrv]
enforce = true
max_allowed = "1.85"

[performance]
enforce = false
command = "cargo bench -p mybenchcrate"
max_slowdown_percent = 5

[ci]
mode = true
fail_on_any_disallowed_update = true

CI Usage

crate-sentinel-mcp --ci --workspace .

Exit codes:

• 0 success
• 1 validation/recoverable failure
• 2 policy violation
• 3 internal/runtime failure

Refactor Bridge Workflow

1. deps.api_diff
2. refactor.plan
3. LLM proposes unified diff patch
4. refactor.validate
5. deps.try_upgrade
6. deps.apply_upgrade

deps.apply_upgrade is blocked unless required gates pass.