Version and stability

Context Graph Protocol has two independent version axes, and it's important not to conflate them:

• The crate version — 0.1.0 today, [workspace.package].version in the workspace root Cargo.toml, inherited by contextgraph-types, contextgraph-host, and contextgraph-conformance alike. This is ordinary Rust/Cargo semver.
• The protocol version — contextgraph/1.0-draft, the PROTOCOL_VERSION constant in contextgraph-types::lib. This is the wire-format identity two Context Graph Protocol implementations negotiate at handshake time, independent of what language or crate version either side is written in.

A crate patch release (bug fix, better error message, an added helper method) does not imply a protocol change. A protocol change, conversely, is what actually breaks interop between a host and a provider built against different crate versions — that's the one that matters most to a third party.

What -draft means right now

Quoting contextgraph-types::PROTOCOL_VERSION's doc comment verbatim, since it's the authoritative statement:

The protocol version string this crate implements. Frozen to contextgraph/1.0 only at the public v1.0 release.

In other words: the wire shape captured in this 0.1.0 release — ContextFrame, ContextQuery, Capabilities, the Envelope vocabulary, the consent/budget/citation contracts documented in protocol-surface.md — is real and implemented today by the reference host (contextgraph-host) and conformance suite (contextgraph-conformance), and is safe to build against. It is not yet a frozen contract: a pre-1.0 revision could still change a field shape or add a required check based on real-world provider implementation feedback, before the public contextgraph/1.0 release drops the -draft suffix.

Why version families interoperate

contextgraph-host::wire::versions_compatible treats two protocol strings as compatible when they share a major family — the substring up to the first .. contextgraph/1.0-draft and contextgraph/1.0 are both family contextgraph/1 and interoperate; contextgraph/2.0 does not interoperate with either. This is deliberate: it means the eventual freeze from contextgraph/1.0-draft to contextgraph/1.0 does not require a flag day where every already-deployed provider breaks the instant the spec freezes — a 1.0-draft provider and a 1.0 host (or vice versa) still handshake successfully within the 1 family. What does break interop is a jump to a new major protocol family (contextgraph/2.0), which is reserved for a genuinely breaking protocol redesign.

The stability guarantee, going forward

• Pre-1.0 (now): crate versions are 0.x, tracking contextgraph/1.0-draft. Cargo semver rules mean any 0.x → 0.y bump may contain breaking changes to either the Rust API or the wire shape — normal pre-1.0 Rust convention. Pin an exact version (contextgraph-types = "=0.1.0") if you need a hard guarantee against churn before the freeze.
• At the freeze: when the protocol is declared contextgraph/1.0 (the -draft suffix drops), contextgraph-types, contextgraph-host, and contextgraph-conformance bump to 1.0.0 in lockstep. That 1.0.0 release is the stability guarantee: from that point on, the crates follow ordinary semver — a 1.x → 1.y minor is additive-only, and a wire-breaking protocol change requires both a new protocol major (contextgraph/2.0) and a new crate major (2.0.0).
• Conformance is the enforcement mechanism. "Context Graph Protocol conformant" is defined as green on contextgraph-conformance's suite for your declared capability set (see running-conformance.md) — that suite, not a hand-audited checklist, is what a third party checks their implementation against, before and after the freeze alike.

Practical guidance for early adopters

• Depend on contextgraph-types with a caret or exact pin, per your risk tolerance — ^0.1 accepts any pre-1.0 patch/minor per Cargo's (unusual) 0.x semver rules, =0.1.0 pins exactly.
• Re-run contextgraph-conformance after every contextgraph-types/contextgraph-host upgrade before the 1.0 freeze — a 0.x bump is exactly the kind of change that can silently add or tighten a conformance check.
• Don't hardcode "contextgraph/1.0-draft" or "contextgraph/1.0" in your own handshake code — read contextgraph_types::PROTOCOL_VERSION and use contextgraph_host::wire::versions_compatible (or the equivalent major-family comparison, if you're implementing a provider outside Rust) so your implementation keeps working across the freeze without a code change.

MSRV and edition

All three crates inherit rust-version = "1.90" and edition = "2024" from the workspace. An MSRV bump is a minor-version-worthy change while pre-1.0 (consistent with the guidance above); after 1.0.0 it will follow the same semver discipline as the rest of the crate's public API.