API stability

Toise has three public contracts. This page states what is stable, how changes are made, and what is explicitly not covered — so an integration knows what it can build on.

Pre-1.0

Before 1.0, a minor release may make a breaking change to a stable surface, but only with a deprecation notice in the preceding release and an entry in the changelog. After 1.0 the surfaces below follow semantic versioning.

Stable surfaces

Surface	What is covered	Pinned by
Producer wire contract (OTLP entity events)	entity.state / entity.delete records, the entity.* attributes, embedded entity.relationships, identity rules	byte-exact conformance fixture (pkg/emit/conformance, fixture_v1.bin)
MCP surface	the set of tools (name + input/output fields), resources and resource templates (name, URI, MIME), and prompts (name, arguments)	a golden contract test (internal/mcp, tool_contract.golden) — any change fails the build until the golden is deliberately regenerated
GraphQL schema	types, fields and arguments in schema.graphql	the schema is the hand-maintained source of truth; changes are reviewed in the PR diff

Change rules for stable surfaces:

• Additive only within a release series: new tools, new optional fields, new entity/relation types are fine and do not break clients.
• Deprecate before removing: a field/tool to be removed is first marked deprecated (GraphQL @deprecated, a note in the tool/field description) for at least one release.
• No silent retyping or renaming of an existing field — that is a breaking change and follows the deprecation path.

Not covered (may change anytime)

• The debug UI (/), the GraphQL playground and introspection — development aids, off under --production.
• Internal Go packages (internal/...) — not an importable API. The producer SDK pkg/emit is the supported Go surface.
• Prometheus metric names and labels — best-effort stability; dashboards should tolerate additions.
• Log line wording and the on-disk store format (a format change is gated by the store's format_version marker, not by this policy).
• The operator-annotations sidecar on-disk format. Annotations (annotate_entity / the annotateEntity mutation) are an overlay a human or assistant attaches to an entity — never producer truth, never part of the event log, and not replayed. The tool and mutation shapes are covered above; the sidecar storage is not.

The open vocabulary

Producers may emit entity and relation types beyond the built-in registry when the server runs with --accept-unknown-types. Those types are part of your contract with your own consumers, not Toise's — Toise stores and serves them faithfully but makes no stability promise about types it does not define.