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+# 0052: Reviewed license supplements cover redistributed dependencies whose packages omit required material
+
+- Status: Proposed
+- Date: 2026-10-07
+- Extends: [0049](0049-module-package-v1.md), in one respect only. ADR 0049 left exactly how licence
+  and notice material is collected to the packager's implementation. That implementation, and the
+  module development guide, then took material only from a redistributed package's own files, or
+  from a predefined standard licence text that needs no project-specific lines. This ADR adds one
+  further source: a reviewed supplement. Everything else in ADR 0049 is unchanged, as is
+  `packageFormat`.
+- Related: [ADR 0048](0048-generic-image-and-installed-module-storage.md),
+  [ADR 0051](0051-module-package-license-material.md)
+
+## Context
+
+ADR 0049 requires every Module Package v1 to carry `THIRD_PARTY_NOTICES`: the licence and notice
+material that redistributing its third-party code requires. It also states that no package is a
+distributable release until licence and notice collection is proven. The canonical packager collects
+material from two places:
+
+- the licence, copying, copyright, and notice files a redistributed package ships at its root;
+- the standard text of the package's declared licence, but only when that text is complete without
+  project-specific lines (Apache-2.0 today).
+
+A package that has neither stops packaging. That is fail-closed by design: an MIT or BSD package
+without its file is refused, because its copyright line exists only in that file.
+
+The first native-target module package needs a dependency that this rule cannot handle.
+`@img/sharp-libvips-linux-x64@1.3.3` is the prebuilt libvips that `sharp` loads on Linux x64 with
+glibc. It declares `LGPL-3.0-or-later`. The package itself, like its latest release 1.3.4, contains
+only these files:
+- `README.md`
+- `versions.json`
+- `lib/index.js`
+- one glib header
+- one shared library
+
+That shared library includes about 29 libraries. Its README names each one and the licence it is
+used under, mostly with a link:
+- LGPL components, such as libvips, glib, and pango;
+- cairo, under MPL-2.0;
+- many BSD-, MIT-, zlib-, IJG-, and FreeType-licensed libraries.
+
+The package ships no licence text and no copyright notice for any of them. No standard text can stand
+in for that material: it includes per-project copyright notices and several different licences.
+
+Options that were ruled out before this decision:
+- **Downloading material while packaging.** Packaging must stay offline and deterministic (ADR 0049,
+  ADR 0051).
+- **Inventing material.** A packager that guesses notices produces artifacts that look compliant and
+  may not be.
+
+Ekklesia needs a way to carry material that a dependency's own package omits. It has to be reviewed
+by people, tied to exactly the bytes it was reviewed for, and fail closed whenever that tie breaks.
+
+Some of these licences may also impose obligations beyond carrying text: the LGPL and the MPL can
+require recipients to be able to obtain corresponding source. Whether and how such an obligation is
+met for a particular redistributed binary is a legal and compliance determination. This decision
+does not make that determination.
+
+## Decision
+
+### Package-provided material stays the preferred source
+
+The licence, copying, copyright, and notice material that a redistributed package ships remains the
+primary source, collected exactly as it is today. Nothing in this ADR removes, replaces, or rewrites
+package-provided material. A supplement only adds to it.
+
+### A reviewed supplement fills what a package omits
+
+When a redistributed dependency omits material that redistribution requires, the canonical Ekklesia
+packager may use a **license supplement**: a checked-in, reviewed record of that material for one
+exact dependency.
+
+- **Where supplements live.** In the Ekklesia repository, as part of the canonical packager's own
+  versioned inputs. A supplement enters only through Ekklesia's normal reviewed change process, and
+  the change that adds it is its review. A given packager version therefore always carries the same
+  supplements.
+- **What a supplement may contain:**
+  - licence texts;
+  - copyright and attribution notices;
+  - provenance: where each piece of material was obtained, and which upstream component versions it
+    covers;
+  - corresponding-source information, such as where upstream source for the exact build is
+    published;
+  - other material that accompanies the dependency's redistribution.
+- **Generic by construction.** Supplements are data. The mechanism contains no package-specific code
+  and treats every supplement identically, whether it is for libvips or for any other dependency.
+
+### A supplement matches one exact package, or it fails closed
+
+A supplement names exactly one redistributed package:
+
+- its package name;
+- its exact version;
+- an integrity value for the package's contents. The implementation defines this value as a digest
+  that the packager computes from the package files it reads and redistributes. The algorithm is
+  documented and does not depend on any package manager.
+
+The packager uses a supplement only when all three match the package it is about to redistribute.
+
+- **A mismatch on any of the three fails packaging.** This covers, for example, a supplement whose
+  name and version match but whose integrity differs. It never falls back to a nearby version, and
+  it never silently skips the supplement.
+- **Every match is used.** A supplement that matches is always merged into the notices, including
+  when the package also ships some material of its own.
+- **Gaps still fail.** If a dependency lacks required material and no exact supplement matches, the
+  packager stops, exactly as it does today.
+
+### Supplements are immutable build inputs
+
+- **Immutable.** A supplement is never edited in place to cover a different build. A changed
+  package, a new version, or different contents need a new supplement, reviewed again.
+- **No network.** Packaging reads supplements from the packager's own inputs and never downloads
+  anything. Assembling a supplement's content is a separate, offline-reviewed curation step done
+  when the supplement is authored, never during packaging.
+
+### Merging is deterministic and labelled
+
+The notice generator merges package-provided material and supplement material deterministically. The
+same packager version and the same inputs still produce a byte-identical `THIRD_PARTY_NOTICES`
+(ADR 0049).
+
+- **Order.** Within a dependency's entry, package-provided material comes first, then supplement
+  material.
+- **Labelling.** Supplement material is marked as supplied by Ekklesia's reviewed supplement, never
+  presented as if it came from the package.
+- **No other change.** Dependencies are still sorted, line endings normalized, and each dependency
+  keeps its own entry, exactly as before.
+
+### A supplement never changes a dependency's declared licence
+
+`THIRD_PARTY_NOTICES` keeps reporting the licence the dependency itself declares.
+
+- **No override.** A supplement can add material about the components a dependency contains, but it
+  cannot replace, override, or rewrite the dependency's declared licence.
+- **Consistency check.** A supplement records the declared licence it was reviewed against. If that
+  disagrees with the package's actual declaration, packaging fails.
+
+### Legal and compliance determinations are not made here
+
+A supplement can record corresponding-source information, but this ADR does not decide what
+satisfies any licence's source obligation, and neither does the mechanism:
+- the mechanism never asserts that a written offer, a source URL, a mirror, or any other arrangement
+  satisfies a licence;
+- carrying a supplement shows that the reviewed material is present in the package. It does not
+  certify that the package is compliant;
+- for every redistributed binary under the LGPL, the MPL, or any other licence with source or
+  similar obligations, the determination of whether and how those obligations are met is deferred.
+  It must be made, and verified, separately.
+
+ADR 0049's release gate still applies. A package that redistributes such a binary does not become a
+distributable release just because its supplement was merged. It becomes one only once that
+binary's compliance determination has been made and verified.
+
+### Scope
+
+- **Third-party code only.** Supplements apply only to redistributed third-party dependencies,
+  whether bundled or copied into the package. They never apply to the module's own licence or
+  `LICENSE` (ADR 0051), or to incorporated Ekklesia packages.
+- **No package format change.** `packageFormat` stays **1**. A supplement changes only the content of
+  `THIRD_PARTY_NOTICES`, which is already a listed, digested payload file. No metadata field, archive
+  rule, or verifier contract changes.
+
+### The motivating case
+
+`@img/sharp-libvips-linux-x64@1.3.3` is the first dependency expected to need a supplement. This ADR
+does not curate it. Its supplement will be assembled, reviewed, and merged separately, together with
+the native-target packaging work that redistributes it. The source-obligation determination for its
+LGPL and MPL components remains open, as above.
+
+## Consequences
+
+- A dependency whose package omits required material can be redistributed after review, offline and
+  deterministically, instead of making native packaging impossible.
+- Each supplement is tied to exact package bytes, so a changed or unexpected dependency fails
+  packaging rather than inheriting material reviewed for something else.
+- Ekklesia takes on reviewing and maintaining supplements. Every version bump of a supplemented
+  dependency needs a new reviewed supplement before packaging works again.
+- `THIRD_PARTY_NOTICES` can now contain material that did not come from the dependency's package. It
+  is always labelled.
+- Carrying material and meeting obligations stay separate. Source-availability questions remain open
+  until they are determined per binary.
+
+## Alternatives
+
+- **Download licence material while packaging.** Rejected: packaging must stay offline,
+  deterministic, and independent of a mutable remote source (ADR 0049, ADR 0051).
+- **Extend the standard-text list.** Rejected: standard texts only work when the licence needs no
+  project-specific line. Bundled native libraries need per-project copyright notices, and several
+  different licences.
+- **Match supplements by name and version alone.** Rejected: identical versions can differ in content
+  across registries or rebuilds, and the material was reviewed for specific bytes.
+- **Fall back to the nearest supplemented version.** Rejected: material reviewed for one build says
+  nothing reliable about another.
+- **Let a supplement restate a dependency's licence.** Rejected: the declaration belongs to the
+  dependency's publisher. A supplement that could override it could misrepresent what is being
+  redistributed.
+- **Per-package special cases in the packager** (for example, code that knows about libvips).
+  Rejected: every supplemented dependency would need new code, and review would be split between
+  code and data.
+- **Treat a recorded source URL or written offer as satisfying copyleft obligations.** Rejected for
+  this ADR: that is a legal determination that has to be verified per binary, not assumed by a build
+  mechanism.
+- **Supplements provided by module authors.** Not adopted now: the canonical packager uses only
+  supplements reviewed into Ekklesia. Whether module repositories may contribute their own reviewed
+  supplements is deferred.
+
+## Deferred
+
+- Implementing the mechanism in the canonical packager: the supplement format and storage location,
+  the integrity algorithm, the matching, the merge, and the tests.
+- Curating and reviewing the supplement for `@img/sharp-libvips-linux-x64@1.3.3`.
+- The legal and compliance determination of source obligations for each redistributed binary, and
+  how a determination is recorded.
+- Whether the packager should refuse, or flag, packages whose supplements note an open determination.
+- Supplements provided by module repositories.
+- Recording which supplements were used in `ekklesia.package.json`, should that ever be needed.
diff --git a/docs/architecture/decisions/README.md b/docs/architecture/decisions/README.md
index ca22414..9c3dcad 100644
--- a/docs/architecture/decisions/README.md
+++ b/docs/architecture/decisions/README.md
@@ -60,3 +60,4 @@ ADRs capture durable choices that affect more than one package or phase.
 - [0049: A module release is one immutable, self-contained package: Ekklesia Module Package v1](0049-module-package-v1.md) — Accepted
 - [0050: Module Database ABI v1: modules and Core exchange SQL, never ORM objects](0050-module-database-abi-v1.md) — Accepted
 - [0051: Module packages declare their own license and carry its text](0051-module-package-license-material.md) — Accepted
+- [0052: Reviewed license supplements cover redistributed dependencies whose packages omit required material](0052-reviewed-license-supplements.md) — Proposed