Crate mcp_trace_validator 

Deterministic offline validation of recorded MCP protocol traces.

The validator replays a trace (JSON Lines of mcp_conformance_core::trace::TraceEvent) against a requirement registry and produces a report::Report with one outcome per requirement and a precise report::Finding for every violation: requirement ID, offending event seq, and an actionable detail string.

Three properties are load-bearing and tested, not aspirational:

1. Determinism — same trace bytes, same registry: byte-identical report. The engine touches no clock, no randomness, no environment.
2. No I/O in the engine — engine::validate is a pure function over parsed events; reading files and rendering output happen at the CLI edge.
3. Honest accounting — requirements the registry excludes are reported as excluded (never as passed), and registry entries referencing checks this build does not implement are reported as unsupported (never silently skipped).

Example

use mcp_conformance_core::requirement::Registry;
use mcp_trace_validator::{engine, reader};

let trace = r#"{"seq":0,"direction":"client-to-server","transport":"stdio","kind":"message","payload":{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"x","version":"0"}}}}
{"seq":1,"direction":"server-to-client","transport":"stdio","kind":"message","payload":{"jsonrpc":"2.0","id":1,"result":{"protocolVersion":"2025-11-25","capabilities":{},"serverInfo":{"name":"y","version":"0"}}}}
{"seq":2,"direction":"client-to-server","transport":"stdio","kind":"message","payload":{"jsonrpc":"2.0","method":"notifications/initialized"}}
"#;

let registry = Registry::builtin_2025_11_25().expect("embedded registry is valid");
let events = reader::parse_trace(trace, &reader::Limits::default()).expect("valid trace");
let report = engine::validate(&registry, &events);
assert!(!report.has_errors(), "{report:#?}");

Modules

checks

Checks: what one is, and what every one of them promises.

context

Precomputed per-trace context shared by all checks.

declared

What protocol revision a session says it is, read from the session itself.

engine

The validation engine: registry × trace → report.

junit

JUnit XML rendering of validation reports, for CI systems that ingest test result files.

multi

Multi-revision judgment: one trace against several protocol revisions in a single pass, with per-clause applicability differences made visible.

reader

Trace parsing with hard resource limits.

report

Validation reports: per-requirement outcomes with actionable findings.