Deprecations¶

This page lists active deprecations and migration guidance.

Rust MCP runtime sidecar¶

Deprecated controls include RUST_MCP_MODE, EXPERIMENTAL_RUST_MCP_*, and MCP_RUST_* settings that enable or configure the Rust MCP sidecar.

Use the default Python MCP transport path by leaving RUST_MCP_MODE=off and EXPERIMENTAL_RUST_MCP_RUNTIME_ENABLED=false.

Runtime signals:

• Gateway startup logs include a deprecation warning when the Rust MCP runtime path is enabled.
• Rust MCP runtime responses include Deprecation, Sunset, and Link: <...>; rel="deprecation" headers.

Rust A2A runtime sidecar¶

Deprecated controls include RUST_A2A_MODE, EXPERIMENTAL_RUST_A2A_*, and A2A_RUST_* settings that enable or configure the Rust A2A sidecar.

Use the default Python A2A invocation path by leaving RUST_A2A_MODE=off, EXPERIMENTAL_RUST_A2A_RUNTIME_ENABLED=false, and EXPERIMENTAL_RUST_A2A_RUNTIME_DELEGATE_ENABLED=false.

Runtime signals:

• Gateway A2A delegation logs include a deprecation warning when an invocation uses the Rust A2A runtime.
• The Rust A2A binary logs a deprecation warning at startup.

ValidationMiddleware¶

mcpgateway.middleware.validation_middleware.ValidationMiddleware is deprecated.

Use endpoint-level Pydantic models, the existing SecurityValidator helpers, and protocol-specific validation middleware instead. Leave VALIDATION_MIDDLEWARE_ENABLED=false unless you need compatibility with an existing deployment that already depends on this middleware.

Runtime signals:

• Gateway startup logs include a deprecation warning when the middleware is enabled.
• Instantiating the middleware emits a Python DeprecationWarning.