ADR-018: RI implementation stack

Status: Accepted. Source: this ADR is the canonical record of this decision. For implementation and validation context, see RI/docs/AS-BUILT.md and, when applicable, the relevant contract in RI/docs/interfaces/.

Context

RI implementation stack (closes G2).

Decision

Python 3.12+, uv, Pydantic v2, declarative YAML with JSON Schema, official mcp SDK.

Alternatives Considered

Node/TypeScript (the MCP SDK is also official there); Go.

Consequences

Defines the entire repository structure (8.5).

Confirmed Versions (EP-16-T04)

Dependency-free spike, runnable at any time (EP-16-T04): confirm, immediately before pinning in pyproject.toml/ docker-compose.yml, the exact stable version numbers of each piece of the stack — no version cited in code/config without real confirmation (pip index versions/direct download/actual install), never from memory. Consolidated record, with the date each group was verified (see RI/README.md, "Versões fixadas", for the same list maintained alongside pyproject.toml):

Confirmed on 2026-09-11:

mcp 2.2.0 (Python SDK v2 — the API changed significantly from v1; see comments in src/emcp_bus/gateway/server.py)
pydantic 2.13.x, opentelemetry-sdk 1.44.x, uvicorn 0.52.x, pyjwt[crypto] 2.14.x, ruff 0.16.x, mypy 2.3.x, pytest 9.1.x
OPA 1.20.2 (static binary, Rego v1 syntax as default)
pytest-forked 1.7.x

Confirmed on 2026-09-14 (M3/M4, via actual install/docker pull):

langgraph 0.6.x + langgraph-checkpoint-sqlite 2.x (EP-11)
hypothesis 6.1xx.x (dev, EP-10-T02)
openai 1.109.x (EP-13-T01)
python-dotenv 1.2.x (dev)
types-jsonschema 4.26.x (dev, stubs for mypy --strict; jsonschema itself was already a transitive dependency of mcp[cli], EP-15-T01)
Langfuse self-hosted 4.35.0 (docker.langfuse.com/langfuse/langfuse:4, official image, EP-13-T02)
Keycloak 26.7.3 (quay.io/keycloak/keycloak:26.7.3, Quarkus; Standard Token Exchange GA since 26.2 — EP-01-T01/EP-07)
opentelemetry-collector-contrib 0.114.0 and jaeger (all-in-one) 1.62.0 (observability profile of docker-compose.yml, EP-08-T04)

None of the versions above have changed since the original confirmation — this record is the single source of truth that RI/README.md links back to.

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