Goal and scope

Back-fill Architecture Decision Records for decisions that already shape Phlo but had no record. Each ADR is written from the repository itself: code, configuration, CI and release tooling, the CHANGELOG, and the closed issues and pull requests that introduced the behaviour. Each has the status Accepted (back-filled 2026-10-30), the approximate original date and the evidence. Where the original rationale is not recoverable, the Context section says so instead of supplying one.

Non-goals: no runtime, configuration or policy change. No existing ADR is edited.

ADR	Title	Primary evidence
0054	Workspace monorepo released as one release set	#300, commit `8f8247e2`, #732, #895, #914, #1102; `relx.toml`
0055	Provider-neutral core and declared package edges	#639/#709, #994/#1036; boundary AST tests
0056	Core layering and acyclic imports enforced by import-linter	#1019/#1096; `[tool.importlinter]` contracts
0057	Cyclomatic complexity gate with a shrinking baseline	#1001/#1033, #996/#1106
0058	Support manifest as the authority for support scope, maturity and gates	#579, #895; `registry/support/v1.json` and its validator
0059	Python 3.12 and generated Docker Compose as the runtime baseline	#52, #579, #962 (3.11 to 3.12), #1104
0060	Regulated mode and signed service-to-service identity	#466, #583, #600, #611; later changes in ADR 0047 and #813
0061	Run-evidence store on SQLite in development and PostgreSQL in production	#577, #726/#737
0062	Cap dependencies that break contracts, and qualify before lifting	#1097, #1021/#1110; `registry/support/dependency-qualification.md`
0063	Fail-closed vulnerability policy with time-boxed, human-reviewed exceptions	#655, #1063, #1068, #1168; `security/dependency-policy.md`
0064	Separate CI contracts with one required result and no silent skips	#999, #1068, #998/#1111; `docs/contributing/ci.md`
0065	Deprecations name a removal release, a replacement and a usage measure	#860/#899, #997/#1082
0066	Observatory keeps its Node runtime as an authenticated API-adapter tier	#1051, #1013, #998/#1111
0067	Explicit freshness, grain, reconciliation and data-interval contracts	#1197, #1198, #1199; research assessment

Candidates considered and not recorded

Lockstep versioning of all packages: not what the code does. Packages keep independent versions (0.1.0 to 0.18.0) released as one ReleaseX release set. ADR 0054 records the actual decision.
Observatory as a Python-served frontend: ADR 0032 already records that target, and the shipped Observatory runs its own Node server. ADR 0066 records the decision that replaced the target.
Plugin discovery through entry points: already covered by ADRs 0030, 0033 and 0041. Only the missing boundary rule is recorded, in ADR 0055.
Nessie/Iceberg/Trino/MinIO/PostgreSQL/Dagster as the blessed stack: folded into ADR 0058 as the blessed_core profile. ADR 0047 already names the production stack.
Single-maintainer ownership and material-change review policy (#1015): docs/contributing/change-policy-proposal.md and CONTRIBUTING.md state that this is not accepted policy.
Package-owned typed process settings (#1012): covered by ADR 0045.
Separate support-decision governance (#837): closed as deferred; the support manifest carries those decisions (ADR 0058).

Change map and risk

Documentation only: 14 new files under docs/architecture/decisions/, plus appended rows in index.md and meta.json. No behaviour changes.

A concurrent PR adds ADR 0053 and also appends to index.md and meta.json. Whichever merges second needs a trivial rebase to keep both entries in numerical order.

Observed while writing (not changed here): CONTRIBUTING.md still refers to an Observatory eslint-suppressions.json, which was deleted with the legacy UI in #1051.

Verification

At df426c12 on top of origin/main 7feced4d:

python3 scripts/check_new_suppressions.py --base 7feced4d... --head HEAD: "New suppression inventory checked." (ADR 0057 now writes the marker as noqa: C901 without the hash.)
python3 scripts/check_adr_index.py: "ADR index records and statuses match."
python3 scripts/check_markdown_links.py: "All tracked Markdown links resolve."
make docs-build: build complete at 65750c58, with all 14 pages rendered. The rebuild after the two-character prose fix was killed for running out of memory locally; CI's docs lane covers it.
codespell on the new files and git diff --check: clean.
Facts were checked against the source: import-linter contracts, relx.toml, provider phlo>=0.18.0,<0.19 ranges, three remaining noqa: C901 markers, support-manifest profiles, run-evidence store selection, dependency caps in each manifest, sorted phlo.__all__, and the Observatory service manifest.
Not applicable: this change is documentation only and has no regression to test.

Recovery and maintainer decisions

Revert the commit to remove the records; nothing else depends on them. Please check that each ADR states the decision as you understand it, particularly 0054 (the reason for the release_set switch is not recoverable), 0059 (#962 does not state why the minimum became Python 3.12) and 0066 (it records a departure from ADR 0032's target).