8b6bf4cee7
The runtime already knew how to spawn stdio MCP processes, but it still needed transport primitives for framed JSON-RPC exchange. This change adds minimal request/response types, line and frame helpers on the stdio wrapper, and an initialize roundtrip helper so later MCP client slices can build on a real transport foundation instead of raw byte plumbing. Constraint: Keep the slice small and limited to stdio transport foundations Constraint: Must verify framed request write and typed response parsing with a fake MCP process Rejected: Introduce a broader MCP session layer now | would expand the slice beyond transport framing Rejected: Leave JSON-RPC as untyped serde_json::Value only | weakens initialize roundtrip guarantees Confidence: high Scope-risk: narrow Reversibility: clean Directive: Preserve the camelCase MCP initialize field mapping when layering richer protocol support on top Tested: cargo fmt --all --manifest-path rust/Cargo.toml Tested: cargo clippy -p runtime --all-targets --manifest-path rust/Cargo.toml -- -D warnings Tested: cargo test -p runtime --manifest-path rust/Cargo.toml Not-tested: Integration against a real external MCP server process
Rust port foundation
This directory contains the first compatibility-first Rust foundation for a drop-in Claude Code CLI replacement.
Current milestone
This initial milestone focuses on harness-first scaffolding, not full feature parity:
- a Cargo workspace aligned to major upstream seams
- a placeholder CLI crate (
rusty-claude-cli) - runtime, command, and tool registry skeleton crates
- a
compat-harnesscrate that reads the upstream TypeScript sources in../src/ - tests that prove upstream manifests/bootstrap hints can be extracted from the leaked TypeScript codebase
Workspace layout
rust/
├── Cargo.toml
├── README.md
├── crates/
│ ├── rusty-claude-cli/
│ ├── runtime/
│ ├── commands/
│ ├── tools/
│ └── compat-harness/
└── tests/
How to use
From this directory:
cargo fmt --all
cargo check --workspace
cargo test --workspace
cargo run -p rusty-claude-cli -- --help
cargo run -p rusty-claude-cli -- dump-manifests
cargo run -p rusty-claude-cli -- bootstrap-plan
Design notes
The shape follows the PRD's harness-first recommendation:
- Extract observable upstream command/tool/bootstrap facts first.
- Keep Rust module boundaries recognizable.
- Grow runtime compatibility behind proof artifacts.
- Document explicit gaps instead of implying drop-in parity too early.
Relationship to the root README
The repository root README explains the leaked TypeScript codebase. This document tracks the Rust replacement effort that lives in rust/.