improve meta core user management

.gitattributes

@@ -0,0 +1,6 @@
+# FIX CRLF always when developer has not set
+# Linux/Mac: git config --global core.autocrlf input
+# Windows: git config --global core.autocrlf true
+# Auto detect text files and perform LF normalization
+* text=auto
+* eol=lf

README.md

@@ -138,7 +138,7 @@ Environment variables consumed by `internal/config/config.go`:
 | `BASE_URL` | _empty_ | Overrides the constructed `baseUrl` if set (used for HTTPS perimeter). |
 | `REDIS_PORT` | `6379` | Local Redis port. |
 | `META_CORE_HTTP_PORT` | `9000` | Go HTTP+SSE+WebDAV port. |
-| `META_CORE_HTTP_HOST` | `127.0.0.1` | HTTP bind. |
+| `META_CORE_HTTP_HOST` | `0.0.0.0` | HTTP bind. |
 | `HEALTH_CHECK_INTERVAL_MS` | `5000` | Internal health-loop cadence. |
 | `HEARTBEAT_INTERVAL_MS` | `30000` | Service registry heartbeat. |
 | `STALE_THRESHOLD_MS` | `60000` | Age past which a registry entry is marked stale. |

docs/api-mediated-access.md

@@ -18,7 +18,7 @@ out to be load-bearing).
 
 meta-core was designed as the sidecar that mediates every metadata read and
 write — a single point that owns the Redis schema, enforces invariants
-(reverse index, canonical_cid reconciliation, schema-version sentinel),
+(reverse index, `cids/` key-set integrity, schema-version sentinel),
 and presents a stable HTTP contract. Other services were meant to talk to
 meta-core, not to Redis.
 
@@ -392,7 +392,7 @@ specifically with the Kubernetes flavour where streams are mediated too.
   coordinating releases across every other service. The UUID-root
   migration is the cautionary tale of what happens without this.
 - **Validation choke point.** Every write passes through one code path
-  that can enforce invariants (reverse index, canonical_cid, type
+  that can enforce invariants (reverse index, `cids/` key-set, type
   constraints, schema version).
 - **Observability.** Audit logs, request metrics, slow-query detection
   all live at one layer.
@@ -697,11 +697,11 @@ contract violation."
 **The fix.** Three layers in `internal/storage/cid_resolution.go`:
 
 1. **`ResolveRoot(hash)`** — at the entry of every `/meta/{hash}`
-   read/write handler, look up `cid:midhash256:<hash>` in the reverse
+   read/write handler, look up `cid:<hash>` in the reverse index (bare
-   index. If found, use the UUID as the storage root. Falls through to
+   CID — no algorithm prefix). If found, use the UUID as the storage root.
-   the bare hash for direct-UUID writes / legacy entries.
+   Falls through to the bare hash for direct-UUID writes / legacy entries.
 2. **Self-pointing alias guard in `addAliasLocked`** — refuse to
-   register `cid:<algo>:<v>` → `<v>`. The dual-root bug's chicken-and-
+   register `cid:<v>` → `<v>`. The dual-root bug's chicken-and-
    egg is: meta-sort writes first, registers self-pointing alias,
    watcher then can't recover. Refusing the self-write keeps the
    watcher's legitimate alias intact.

docs/meta-core-architecture.md

@@ -221,12 +221,13 @@ operators wipe with `pnpm run clean:all` and restart.
 │  Root: opaque UUIDv7 (Crockford Base32; ULID layout, 26 chars)     │
 │  Storage: flat string keys                                         │
 │           file:<uuid>/<property>           → string value          │
-│           file:<uuid>/cids                 → SET of CID tokens     │
+│           file:<uuid>/cids/<bareCid>       → "true" (key-set)      │
-│           file:<uuid>/canonical_cid        → preferred CID         │
 │           file:<uuid>/duplicates           → SET of paths          │
 │                                                                    │
+│  No stored canonical_cid — derived by rank on read.                │
+│                                                                    │
 │  Aliases (reverse index, one Redis STRING each):                   │
-│           cid:<algorithm>:<value>          → <uuid>                │
+│           cid:<bareCid>                    → <uuid>                │
 │                                                                    │
 │  Index:   file:__index__                   → SET of all UUIDs      │
 │                                                                    │
@@ -515,7 +516,7 @@ via `/health`; metadata I/O and SSE event streams stop.
 | `BASE_URL` | _empty_ | Overrides constructed `baseUrl` (HTTPS perimeter). |
 | `REDIS_PORT` | `6379` | Local Redis port. |
 | `META_CORE_HTTP_PORT` | `9000` | Go HTTP+SSE+WebDAV port. |
-| `META_CORE_HTTP_HOST` | `127.0.0.1` | HTTP bind address. |
+| `META_CORE_HTTP_HOST` | `0.0.0.0` | HTTP bind address. |
 | `HEALTH_CHECK_INTERVAL_MS` | `5000` | Internal health-loop cadence. |
 | `HEARTBEAT_INTERVAL_MS` | `30000` | Service registry heartbeat. |
 | `STALE_THRESHOLD_MS` | `60000` | Age past which a registry entry is stale. |

docs/metadata-storage-structure.md

@@ -19,10 +19,13 @@ For the external-access contract (HTTP-only, SSE for events), see
   `01JKR8XW5T4QMV7AHNJ2DEFGHK`.
 - **Properties are flat Redis STRING keys**, one per leaf:
   `file:<uuid>/<property/path>` → string value. *Not* Redis Hashes.
-- **CIDs are reverse-index aliases**: `cid:<algorithm>:<value>` → `<uuid>`
+- **CIDs are reverse-index aliases**: `cid:<bareCid>` → `<uuid>`
-  (a Redis STRING per known CID).
+  (a Redis STRING per known CID; no algorithm prefix — the multicodec
-- **Per-root sets**: `file:<uuid>/cids` (every CID), `file:<uuid>/duplicates`
+  already carries it).
+- **Per-root sets**: `file:<uuid>/cids/<bareCid>` (a *key-set*: one STRING
+  `"true"` per known CID, midhash included), `file:<uuid>/duplicates`
   (alternate paths with the same content), plus `file:__index__` (every UUID).
+  There is **no stored `canonical_cid`** — it is derived by rank on read.
 - **A schema-version sentinel** (`meta-core:schema-version`) refuses to
   boot against legacy data.
 
@@ -59,37 +62,54 @@ file:01JKR8XW5T4QMV7AHNJ2DEFGHK/tmdb/poster                       = "bafkreih...
 
 ### Reverse-index aliases (CIDs)
 
-Every CID known for a file is registered as its own Redis STRING:
+Every CID known for a file is registered as its own Redis STRING, keyed by
+the **bare CID** — no algorithm prefix. A CIDv1 already encodes its hash
+function in the multicodec, so naming it again in the key would be
+redundant (and would let the same digest be indexed under two spellings):
 
 ```
-cid:<algorithm>:<value>   →   <uuid>
+cid:<bareCid>   →   <uuid>
 ```
 
 Examples:
 
 ```
-cid:midhash256:bafkreih5kapbjzq...   →   01JKR8XW5T4QMV7AHNJ2DEFGHK
+cid:bafkreih5kapbjzq...   →   01JKR8XW5T4QMV7AHNJ2DEFGHK
-cid:sha256:abc...                    →   01JKR8XW5T4QMV7AHNJ2DEFGHK
+cid:bagacbabaec7v3...     →   01JKR8XW5T4QMV7AHNJ2DEFGHK
-cid:ipfs:bafy...                     →   01JKR8XW5T4QMV7AHNJ2DEFGHK
 ```
 
 The reverse index makes `GET /api/meta/<cid>` an O(1) lookup for any
-registered CID, independent of which hash algorithm "primary" — there is
+registered CID, independent of which hash algorithm — there is no primary.
-no primary. The auto-alias hooks in `SetProperty` and `SetMetadataFlat`
+The auto-alias hook (`maybeAddAliasFromFieldLocked` in
-(see `internal/storage/cid_resolution.go`) catch any write of a `cid_*`
+`internal/storage/cid_resolution.go`, called from `SetProperty`,
-or `midhash256` field and register the alias automatically, so plugins
+`SetMetadataFlat` and `MergeMetadataFlat`) registers the alias for any
-don't need to know about the reverse index.
+field whose name starts with `cids/`, so writers emit key-set members
+without knowing the reverse index exists.
+
+> ⚠ The hook matches **only** the `cids/` prefix. A legacy `cid_*` or
+> `midhash256` *named* field written to a root is stored verbatim and is
+> **never indexed** — the record becomes unresolvable by that CID. Writers
+> must collapse such fields to `cids/<cid>` members before the write. See
+> `METADATA_KEYS.md` §14.13.
 
 ### Per-root sets
 
 ```
-file:<uuid>/cids              →   Redis SET of "<algorithm>:<value>" tokens
+file:<uuid>/cids/<bareCid>    →   STRING "true" — one key per known CID (a key-set, not a Redis SET)
-file:<uuid>/canonical_cid     →   STRING — the highest-ranked CID for advertising externally
 file:<uuid>/duplicates        →   Redis SET of alternate paths with same content
 ```
 
-`canonical_cid` is reconciled by `reconcileCanonicalCIDLocked` whenever
+`cids` is a **key-set**: one flat `file:<uuid>/cids/<cid>` STRING per member,
-the `cids` set changes; ranking is done by `internal/cid/rank.go`.
+which keeps it conflict-free to merge across peers (a SET would not be).
+The record's own address (the midhash) is just the `0x1000` member — it has
+no separate field.
+
+There is **no stored `canonical_cid`**. The canonical CID is *derived on
+read*: `GetMetadataDocument` (`internal/storage/cid_resolution.go`) ranks the
+key-set's members through `internal/cid/rank.go` (`cid.Better`) and returns
+the winner as the `canonical_cid` field of the JSON response only. Nothing
+reconciles or persists it — an earlier `reconcileCanonicalCIDLocked` did, and
+was removed with the flat `cid_*` keys.
 
 ### Global index
 
@@ -141,14 +161,15 @@ The Go API in `internal/storage/client.go`:
 | Method | Behaviour |
 |---|---|
 | `GetMetadataFlat(uuid)` | `SCAN` for `file:<uuid>/*`, `MGET` the values, return `map[string]string`. |
-| `SetMetadataFlat(uuid, m)` | Pipeline `SET` per field; `SADD file:__index__`; auto-register any `cid_*` aliases. |
+| `SetMetadataFlat(uuid, m)` | Pipeline `SET` per field; `SADD file:__index__`; auto-register an alias for every `cids/<cid>` member. |
 | `MergeMetadataFlat(uuid, m)` | Like `SetMetadataFlat` but doesn't pre-clear; used by `PATCH /meta/{hash}`. |
 | `GetProperty(uuid, field)` | `GET file:<uuid>/<field>`. |
 | `SetProperty(uuid, field, value)` | `SET file:<uuid>/<field>`; auto-register alias if the field is a CID. |
 | `DeleteRoot(uuid)` | `SCAN` + `DEL` for `file:<uuid>/*`, unmap every reverse-index entry. |
 | `Mint(filePath, size, mtimeNano)` | `NewUUID()` + write `filePath/sizeByte/mtimeNano` + add to index. |
-| `AddAlias(uuid, "<algo>:<value>")` | Set `cid:<algo>:<value>` → `<uuid>`, add to `file:<uuid>/cids`, reconcile `canonical_cid`. |
+| `AddAlias(uuid, "<bareCid>")` | Set `cid:<bareCid>` → `<uuid>` and the key-set member `file:<uuid>/cids/<bareCid>` = `"true"`. Nothing to reconcile — canonical is derived on read. |
-| `ResolveCID("<algo>:<value>")` | `GET cid:<algo>:<value>` → uuid. |
+| `ResolveRoot("<bareCid>")` | `GET cid:<bareCid>` → uuid (returns the input unchanged if it is already a UUID root). |
+| `GetMetadataDocument(uuid)` | Flat fields + `cids` hoisted to an array + `canonical_cid` **derived** by `cid.Better` rank + `duplicates`. Backs `GET /api/meta/{cid}`. |
 
 ## Reconstruction (flat → nested)
 
@@ -237,10 +258,14 @@ docker exec metacore-app redis-cli GET 'file:01JKR8XW5T4QMV7AHNJ2DEFGHK/fileinfo
 docker exec metacore-app redis-cli TYPE 'file:01JKR8XW5T4QMV7AHNJ2DEFGHK/filePath'
 # string
 
-# Reverse-index lookups
+# Reverse-index lookup (bare CID — no algorithm prefix)
-docker exec metacore-app redis-cli GET 'cid:midhash256:bafkreih...'      # → uuid
+docker exec metacore-app redis-cli GET 'cid:bafkreih...'      # → uuid
-docker exec metacore-app redis-cli SMEMBERS 'file:01JKR8XW5T4QMV7AHNJ2DEFGHK/cids'
+
-docker exec metacore-app redis-cli GET 'file:01JKR8XW5T4QMV7AHNJ2DEFGHK/canonical_cid'
+# The cids key-set (one STRING per member, NOT a Redis SET — SMEMBERS won't work)
+docker exec metacore-app redis-cli --scan --pattern 'file:01JKR8XW5T4QMV7AHNJ2DEFGHK/cids/*'
+
+# canonical_cid is NOT stored. Derive it via the API instead:
+curl -k https://metacore-dev.localhost:8083/api/meta/<cid> | jq '.canonical_cid, .cids'
 
 # Schema-version sentinel
 docker exec metacore-app redis-cli GET 'meta-core:schema-version'

docs/uuid-rooted-metadata.md

@@ -4,6 +4,25 @@
 
 **Status:** Implemented (2026 alpha clean-wipe gate landed). Kept for design rationale.
 
+> ⚠ **Two parts of this proposal were superseded before shipping.** This doc
+> is the design record; it is *not* the schema reference. For what is actually
+> stored, see `METADATA_KEYS.md` §2/§14.13 and
+> [metadata-storage-structure.md](./metadata-storage-structure.md).
+>
+> 1. **`canonical_cid` is not a stored key.** The proposed reconciler
+>    (`reconcileCanonicalCIDLocked`) was never kept — a stored scalar isn't
+>    conflict-free to merge across peers. The canonical CID is **derived on
+>    read** by ranking the `cids` members (`internal/cid/rank.go` →
+>    `cid.Better`), and appears only in the `GET /api/meta/{cid}` response.
+> 2. **`cids` is a key-set, not a Redis SET, and holds bare CIDs, not
+>    `<algo>:<value>` tokens.** One flat STRING per member:
+>    `file:<uuid>/cids/<bareCid>` = `"true"`. The reverse index is likewise
+>    `cid:<bareCid>` → uuid. A CIDv1's multicodec already names its hash
+>    function, so the `<algo>:` prefix was redundant.
+>
+> Text below that references either shape describes the *proposal*, not the
+> code. The rank ordering and everything else did ship as written.
+
 ## Motivation
 
 Today, every metadata entry in Redis is keyed by a content hash, specifically
@@ -79,19 +98,21 @@ today — anything that wrote `file:<midhash>/fileinfo/duration` now writes
 file:01JKR8XW5T4QMV7AHNJ2DEFGHK/filePath          = /watch/Inception.mkv
 file:01JKR8XW5T4QMV7AHNJ2DEFGHK/size              = 4500000000
 file:01JKR8XW5T4QMV7AHNJ2DEFGHK/mtime             = 1729872000000000000
-file:01JKR8XW5T4QMV7AHNJ2DEFGHK/cids              = SET{midhash256:abc, sha256:def, ipfs:bafy...}
+file:01JKR8XW5T4QMV7AHNJ2DEFGHK/cids/bagacbabaec…  = "true"    ← midhash (record address)
+file:01JKR8XW5T4QMV7AHNJ2DEFGHK/cids/bafybeigd…    = "true"    ← sha2-256
 file:01JKR8XW5T4QMV7AHNJ2DEFGHK/duplicates        = SET{/watch/dup1.mkv, /watch/dup2.mkv}
-file:01JKR8XW5T4QMV7AHNJ2DEFGHK/canonical_cid     = ipfs:bafy...
 file:01JKR8XW5T4QMV7AHNJ2DEFGHK/title             = "Inception"
 file:01JKR8XW5T4QMV7AHNJ2DEFGHK/fileinfo/duration = 7200.5
 file:01JKR8XW5T4QMV7AHNJ2DEFGHK/tmdb/poster       = bafy...
 file:01JKR8XW5T4QMV7AHNJ2DEFGHK/subtitle/eng      = ...
 
-cid:midhash256:abc  → 01JKR8XW5T4QMV7AHNJ2DEFGHK
+cid:bagacbabaec…  → 01JKR8XW5T4QMV7AHNJ2DEFGHK
-cid:sha256:def      → 01JKR8XW5T4QMV7AHNJ2DEFGHK
+cid:bafybeigd…    → 01JKR8XW5T4QMV7AHNJ2DEFGHK
-cid:ipfs:bafy...    → 01JKR8XW5T4QMV7AHNJ2DEFGHK
 ```
 
+*(As shipped — the proposal originally wrote `cids` as a Redis SET of
+`<algo>:<value>` tokens plus a `canonical_cid` scalar. See the Status note.)*
+
 ### UUID format: UUIDv7
 
 UUIDv7 chosen over UUIDv4 or 64-bit random:
@@ -111,26 +132,33 @@ The metadata schema is open — any writer can put any key under
 `file:<uuid>/`. This proposal does not change that. It adds three keys whose
 sole writer is meta-core itself:
 
-| Key | Type | Purpose |
+| Key | Type (as shipped) | Purpose |
 |-----|------|---------|
-| `cids` | Redis SET | All CIDs known for this file. Mirror of the `cid:*` reverse index. Source of truth for delete-time GC. |
+| `cids/<bareCid>` | STRING `"true"` — a *key-set*, one key per member | All CIDs known for this file, midhash included. Mirror of the `cid:*` reverse index. Source of truth for delete-time GC. **Proposed as a Redis SET of `<algo>:<value>` tokens; shipped as a key-set of bare CIDs** — a key-set merges conflict-free across peers and the multicodec already names the algorithm. |
 | `duplicates` | Redis SET | Additional file paths whose content matches this entry. One UUID = one set of metadata; multiple physical files may share that content. Consumed by meta-dup. |
-| `canonical_cid` | STRING | The CID this entry should be presented as externally (meta-share announce, UI display). Selected by the rank function (below). |
+| ~~`canonical_cid`~~ | *(not stored)* | **Dropped.** Was to hold the externally-presented CID. Now derived on read by ranking the `cids` members; surfaced only on `GET /api/meta/{cid}`. |
 
 Existing meta-core-owned fields (`filePath`, `size`, `mtime`, `midhash256`)
 keep their names and writers. Plugin-written fields (`tmdb/*`, `fileinfo/*`,
 `subtitle/<lang>`, …) are unaffected.
 
-Redis SET is a departure from the all-strings convention in the current
+~~Redis SET is a departure from the all-strings convention in the current
 storage doc, but `file:__index__` is already a SET — so the precedent exists
-for using sets where they're the right structure.
+for using sets where they're the right structure.~~ **Reversed for `cids`.**
+The all-strings convention won: `cids` ships as flat `cids/<cid>` STRING keys
+so that two peers merging the same record can never disagree about set
+membership. `duplicates` remained a Redis SET (it is leader-local and never
+merged across peers).
 
 ### Canonical CID selection
 
-`canonical_cid` is a label, not a key. Updating it costs one write — no
+The canonical CID is a label, not a key — so nothing external breaks when it
-rename, no race, no broken external references.
+changes. **As shipped it is not written at all**: it is computed on every read
+from the `cids` members, which makes the "update" cost zero and removes the
+reconciler entirely.
 
-Selection rule, highest-wins:
+Selection rule, highest-wins (this part shipped as designed —
+`internal/cid/rank.go`):
 
 1. IPFS CID (any variant)
 2. SHA-256 / SHA-3 family
@@ -142,8 +170,10 @@ midhash256 and sha256 are both 256-bit, but only sha256/IPFS CIDs are
 externally meaningful for content addressing. btih ranks above midhash because
 it enables swarm interop even if it's weaker as a digest.
 
-Reconciler runs on the leader, recomputes `canonical_cid` whenever
+~~Reconciler runs on the leader, recomputes `canonical_cid` whenever
-`AddAlias` registers a new CID for an entry.
+`AddAlias` registers a new CID for an entry.~~ **Not shipped** — there is no
+reconciler. `GetMetadataDocument` folds the members through `cid.Better` on
+each read.
 
 ## Internal operations
 
@@ -157,8 +187,8 @@ CID-based API.
 Mint(filePath string, size int64, mtime int64) (uuid string, err error)
 
 // AddAlias registers a CID as resolving to this UUID. Updates both the
-// cid:<cid> reverse index and the file:<uuid>/cids set atomically.
+// cid:<cid> reverse index and the file:<uuid>/cids/<cid> key-set member.
-// Triggers canonical_cid reconciliation.
+// (As shipped: no reconciliation step — canonical is derived on read.)
 AddAlias(uuid string, cid string) error
 
 // GetByCID resolves any known CID to its UUID. Returns ("", nil) if unknown.
@@ -199,7 +229,8 @@ DeleteRoot(uuid string) error
    - Plugin reports back: "for CID midhash256:abc..., sha256 is sha256:def...".
    - meta-core resolves midhash256:abc → uuid_Y via GetByCID.
    - meta-core calls AddAlias(uuid_Y, "sha256:def...").
-   - Reconciler updates canonical_cid if sha256 outranks midhash256.
+   - Nothing else to do: the next read of this entry derives a canonical CID
+     of sha2-256, because it outranks the midhash.
 ```
 
 ### Lifecycle: file deletion
@@ -250,13 +281,20 @@ so the impact is contained but real.
   client.
 - **meta-dup**: gains a cleaner data source — duplicates are now explicit in
   the `duplicates` set, not implicit in colliding writes.
-- **meta-share**: announces `canonical_cid` rather than midhash. Federated
+- **meta-search / meta-share**: announce the *derived* canonical CID rather
-  search responses include all CIDs from the `cids` set so any peer querying
+  than the midhash — each mirrors the Go rank in `ingest::canonical_cid_from_metadata`
-  by any digest gets a hit.
+  rather than reading a stored field. Federated search responses include all
+  CIDs from the `cids` key-set so any peer querying by any digest gets a hit.
+  (Written before the 2026-06 discovery/transport split; discovery is now
+  meta-search's job.)
 - **Plugins**: no change. They speak CIDs only.
 
 ## Migration
 
+> **Historical — this sweep was never run.** The alpha shipped behind a
+> clean-wipe gate (Redis was flushed and the library re-ingested), so no
+> in-place migration code exists. Kept for the record.
+
 One-time sweep, idempotent, runs on first boot after upgrade:
 
 ```
@@ -285,7 +323,8 @@ roots and resumes by detecting which step completed (presence of
 | UUID visible externally? | No | Pure meta-core internal. Clients address by CID only. |
 | Merge semantics | One UUID per content; additional paths into `duplicates` | One file (logical) = one metadata set. Multiple physical paths supported via `duplicates`. |
 | Canonical CID rank | IPFS > sha-family > btih > midhash | Utility-weighted, not strength-weighted. |
-| `cids` and `duplicates` field type | Redis SET | Departure from "all-strings" convention but consistent with the existing `file:__index__` precedent. |
+| ~~`cids` and `duplicates` field type~~ | ~~Redis SET~~ → **`cids` is a key-set of bare CIDs; `duplicates` stayed a SET** | Reversed before shipping. Flat `cids/<cid>` STRING keys merge conflict-free across peers; a SET does not. See §14.13 of `METADATA_KEYS.md`. |
+| ~~Stored `canonical_cid`~~ | **Dropped — derived on read** | A stored scalar is not conflict-free to merge. `GetMetadataDocument` ranks the `cids` members per request. |
 | Reverse-index format | Flat `cid:<cid>` STRING keys | Simple, scan-friendly, no hot-key contention. |
 
 ## Open questions
@@ -297,9 +336,10 @@ roots and resumes by detecting which step completed (presence of
   hashing reveals the collision. Worth doing eventually; not required for
   this iteration.
 
-- **meta-share announce strategy.** Announce only `canonical_cid`, or every
+- ~~**meta-share announce strategy.**~~ **Settled.** The record carries *every*
-  entry in `cids`? Maximum discoverability vs. DHT footprint. Decide as part
+  member of `cids` on the wire (`Record.cids`) and addresses itself by the
-  of the meta-share work, not here.
+  single derived canonical (`Record.cid`), so a peer querying by any digest
+  gets a hit without the DHT footprint of announcing each one separately.
 
 - **IPFS gateway endpoint.** Should meta-core expose `/ipfs/<cid>` as a
   content-streaming endpoint for external IPFS clients? Adjacent to this

go.mod

@@ -3,6 +3,7 @@ module github.com/metazla/meta-core
 go 1.21
 
 require (
+	github.com/alicebob/miniredis/v2 v2.31.1
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.1
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/mux v1.8.1
@@ -13,6 +14,8 @@ require (
 )
 
 require (
+	github.com/alicebob/gopher-json v0.0.0-20200520072559-a9ecdc9d1d3a // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
+	github.com/yuin/gopher-lua v1.1.0 // indirect
 )

go.sum

@@ -1,15 +1,24 @@
+github.com/DmitriyVTitov/size v1.5.0/go.mod h1:le6rNI4CoLQV1b9gzp1+3d7hMAD/uu2QcJ+aYbNgiU0=
+github.com/alicebob/gopher-json v0.0.0-20200520072559-a9ecdc9d1d3a h1:HbKu58rmZpUGpz5+4FfNmIU+FmZg2P3Xaj2v2bfNWmk=
+github.com/alicebob/gopher-json v0.0.0-20200520072559-a9ecdc9d1d3a/go.mod h1:SGnFV6hVsYE877CKEZ6tDNTjaSXYUk6QqoIK6PrAtcc=
+github.com/alicebob/miniredis/v2 v2.31.1 h1:7XAt0uUg3DtwEKW5ZAGa+K7FZV2DdKQo5K/6TTnfX8Y=
+github.com/alicebob/miniredis/v2 v2.31.1/go.mod h1:UB/T2Uztp7MlFSDakaX1sTXUv5CASoprx0wulRT6HBg=
 github.com/bsm/ginkgo/v2 v2.12.0 h1:Ny8MWAHyOepLGlLKYmXG4IEkioBysk6GpaRTLC8zwWs=
 github.com/bsm/ginkgo/v2 v2.12.0/go.mod h1:SwYbGRRDovPVboqFv0tPTcG1sN61LM1Z4ARdbAV9g4c=
 github.com/bsm/gomega v1.27.10 h1:yeMWxP2pV2fG3FgAODIY8EiRE3dy0aeFYt4l7wh6yKA=
 github.com/bsm/gomega v1.27.10/go.mod h1:JyEr/xRbxbtgWNi8tIEVPUYZ5Dzef52k01W3YH0H+O0=
 github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
 github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
 github.com/decred/dcrd/crypto/blake256 v1.1.0 h1:zPMNGQCm0g4QTY27fOCorQW7EryeQ/U0x++OzVrdms8=
 github.com/decred/dcrd/crypto/blake256 v1.1.0/go.mod h1:2OfgNZ5wDpcsFmHmCK5gZTPcCXqlm2ArzUIkw9czNJo=
 github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.1 h1:5RVFMOWjMyRy8cARdy79nAmgYw3hK/4HUq48LQ6Wwqo=
 github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.1/go.mod h1:ZXNYxsqcloTdSy/rNShjYzMhyjf0LaoftYK0p+A3h40=
 github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
 github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
+github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/gorilla/mux v1.8.1 h1:TuBL49tXwgrFYWhqrNgrUNEY92u81SPhu7sTdzQEiWY=
@@ -18,7 +27,10 @@ github.com/mr-tron/base58 v1.3.0 h1:K6Y13R2h+dku0wOqKtecgRnBUBPrZzLZy5aIj8lCcJI=
 github.com/mr-tron/base58 v1.3.0/go.mod h1:2BuubE67DCSWwVfx37JWNG8emOC0sHEU4/HpcYgCLX8=
 github.com/redis/go-redis/v9 v9.4.0 h1:Yzoz33UZw9I/mFhx4MNrB6Fk+XHO1VukNcCa1+lwyKk=
 github.com/redis/go-redis/v9 v9.4.0/go.mod h1:hdY0cQFCN4fnSYT6TkisLufl/4W5UIXyv0b/CLO2V2M=
+github.com/yuin/gopher-lua v1.1.0 h1:BojcDhfyDWgU2f2TOzYK/g5p2gxMrku8oupLDqlnSqE=
+github.com/yuin/gopher-lua v1.1.0/go.mod h1:GBR0iDaNXjAgGg9zfCvksxSRnQx76gclCIb7kdAd1Pw=
 golang.org/x/crypto v0.31.0 h1:ihbySMvVjLAeSH1IbfcRTkD/iNscyz8rGzjF/E5hV6U=
 golang.org/x/crypto v0.31.0/go.mod h1:kDsLvtWBEx7MV9tJOj9bnXsPbxwJQ6csT/x4KIN4Ssk=
 golang.org/x/net v0.21.0 h1:AQyQV4dYCvJ7vGmJyKki9+PBdyvhkSd8EIx/qb0AYv4=
 golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=
+golang.org/x/sys v0.0.0-20190204203706-41f3e6584952/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

internal/api/deprecated_field_test.go

@@ -0,0 +1,86 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+// The per-algorithm CID fields (`cid_sha2-256`, `cid_midhash256`, …) and the
+// stored `canonical_cid` scalar were removed (METADATA_KEYS.md §14.13). They
+// must be rejected at the write boundary rather than stored.
+//
+// Why a hard 400 and not a silent rewrite: the reverse-index hook
+// (maybeAddAliasFromFieldLocked) only registers an alias for a field named
+// `cids/<cid>`. A `cid_*` field was therefore written verbatim and never
+// indexed — the record silently became unresolvable by that CID. A loud
+// failure is strictly better than a record that looks correct and cannot be
+// found.
+func TestRejectDeprecatedField(t *testing.T) {
+	rejected := []string{
+		"cid_midhash256",
+		"cid_sha2-256",
+		"cid_btih_v2",
+		"cid_crc32",
+		"midhash256",
+		"canonical_cid",
+	}
+	for _, f := range rejected {
+		if !rejectDeprecatedField(f) {
+			t.Errorf("rejectDeprecatedField(%q) = false, want true (deprecated shape)", f)
+		}
+	}
+
+	accepted := []string{
+		"cids/bagacbabaec7v3fu2ygzh3e2sybg3fbzmisry2hbtpmck6vx3yftea6vzq35r4",
+		"filePath",
+		"title",
+		"fileinfo/duration",
+		"tmdb/poster",
+		// Near-misses that must NOT be caught: the prefix is `cid_`, with an
+		// underscore. A field merely starting with "cid" is fine.
+		"cids",
+		"cidrank",
+	}
+	for _, f := range accepted {
+		if rejectDeprecatedField(f) {
+			t.Errorf("rejectDeprecatedField(%q) = true, want false (legitimate field)", f)
+		}
+	}
+}
+
+func TestValidateFields_Rejects400WithSlug(t *testing.T) {
+	rr := httptest.NewRecorder()
+	blocked := validateFields(rr, map[string]string{
+		"title":          "Inception",
+		"cid_midhash256": "bagacbabaec7v3fu2ygzh3e2sybg3fbzmisry2hbtpmck6vx3yftea6vzq35r4",
+	})
+
+	if !blocked {
+		t.Fatal("validateFields returned false for a payload carrying cid_midhash256; the write would have been stored unindexed")
+	}
+	if rr.Code != http.StatusBadRequest {
+		t.Errorf("status = %d, want %d", rr.Code, http.StatusBadRequest)
+	}
+
+	var body map[string]interface{}
+	if err := json.Unmarshal(rr.Body.Bytes(), &body); err != nil {
+		t.Fatalf("response is not JSON: %v", err)
+	}
+	if got := body["error"]; got != ErrDeprecatedField {
+		t.Errorf("error slug = %v, want %q", got, ErrDeprecatedField)
+	}
+}
+
+func TestValidateFields_AllowsCidsKeyset(t *testing.T) {
+	rr := httptest.NewRecorder()
+	blocked := validateFields(rr, map[string]string{
+		"filePath": "/watch/Inception.mkv",
+		"cids/bagacbabaec7v3fu2ygzh3e2sybg3fbzmisry2hbtpmck6vx3yftea6vzq35r4": "true",
+		"cids/baejbeibku6ua2l6r5olnggx4pto2sii2s5jeeawgh4cbkhlbmp52gudbua":     "true",
+	})
+	if blocked {
+		t.Fatalf("validateFields rejected a legitimate cids/ key-set write: %s", rr.Body.String())
+	}
+}

internal/api/handlers.go

@@ -4,6 +4,7 @@ import (
 	"crypto/sha256"
 	"encoding/base32"
 	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 	"os"
@@ -84,8 +85,45 @@ const (
 	ErrSchemaViolation   = "schema_violation"
 	ErrStorageUnavailable = "storage_unavailable"
 	ErrInternal          = "internal"
+	ErrDeprecatedField   = "deprecated_field"
 )
 
+// rejectDeprecatedField reports whether a field name is one of the removed
+// per-algorithm CID shapes (`cid_sha2-256`, `cid_midhash256`, `midhash256`, …).
+//
+// This is a tripwire, not a compatibility shim. Such a field used to be
+// accepted and written verbatim — but the reverse-index hook
+// (`maybeAddAliasFromFieldLocked`) only registers aliases for fields named
+// `cids/<cid>`, so a `cid_*` field was stored and then NEVER INDEXED: the
+// record silently became unresolvable by that CID. Failing the write loudly is
+// strictly better than a record that looks fine and cannot be found.
+//
+// Writers must emit the bare-CID key-set instead: `cids/<bareCid>` = "true".
+// See METADATA_KEYS.md §2/§14.13.
+func rejectDeprecatedField(field string) bool {
+	return strings.HasPrefix(field, "cid_") ||
+		field == "midhash256" ||
+		field == "canonical_cid"
+}
+
+// validateFields rejects a write carrying any deprecated CID field. Returns
+// true if the request was rejected (the handler must return immediately).
+func validateFields(w http.ResponseWriter, metadata map[string]string) bool {
+	for field := range metadata {
+		if rejectDeprecatedField(field) {
+			writeErrorSlug(w, http.StatusBadRequest, ErrDeprecatedField,
+				fmt.Sprintf("field %q is a removed per-algorithm CID shape; "+
+					"write the bare-CID key-set instead: \"cids/<bareCid>\": \"true\" "+
+					"(a cid_* field would be stored but never indexed, leaving the "+
+					"record unresolvable by that CID). See METADATA_KEYS.md §2/§14.13.",
+					field),
+				false)
+			return true
+		}
+	}
+	return false
+}
+
 // defaultSlugFor maps an HTTP status code to the most likely error slug.
 // Handlers that want to override (e.g. /api/meta/{cid} → "unknown_cid"
 // instead of "unknown_root" on 404) call writeErrorSlug directly.
@@ -255,6 +293,10 @@ func (s *Server) handlePutMeta(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if validateFields(w, metadata) {
+		return
+	}
+
 	if err := s.storage.SetMetadataFlat(hashID, metadata); err != nil {
 		writeError(w, http.StatusInternalServerError, err.Error())
 		return
@@ -620,6 +662,10 @@ func (s *Server) handlePatchMeta(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if validateFields(w, metadata) {
+		return
+	}
+
 	updated, err := s.storage.MergeMetadataFlat(hashID, metadata)
 	if err != nil {
 		writeError(w, http.StatusInternalServerError, err.Error())
@@ -697,6 +743,10 @@ func (s *Server) handlePutProperty(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if validateFields(w, map[string]string{key: ""}) {
+		return
+	}
+
 	if !s.storage.IsConnected() {
 		writeError(w, http.StatusServiceUnavailable, "storage not connected")
 		return
@@ -790,6 +840,10 @@ func (s *Server) handleAddToSet(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if validateFields(w, map[string]string{key: ""}) {
+		return
+	}
+
 	if !s.storage.IsConnected() {
 		writeError(w, http.StatusServiceUnavailable, "storage not connected")
 		return

internal/api/metadata.go

@@ -193,6 +193,9 @@ func (s *Server) handleGetMetadataByHashId(w http.ResponseWriter, r *http.Reques
 		return
 	}
 
+	// Same resolution as the PUT below: callers hold a CID, not the root.
+	hashID = s.storage.ResolveRoot(hashID)
+
 	metadata, err := s.storage.GetMetadataFlat(hashID)
 	if err != nil {
 		writeError(w, http.StatusInternalServerError, err.Error())
@@ -227,6 +230,17 @@ func (s *Server) handleUpdateMetadataByHashId(w http.ResponseWriter, r *http.Req
 		return
 	}
 
+	// The {hashId} in the URL is whatever CID the caller knows the file by —
+	// the gateway's auto-store keys this PUT by the hash it just computed
+	// (dispatch.rs → store_metadata_only), which for a usenet→IPFS fetch is
+	// the dag-pb root, not the nzb-release cid the record was minted under.
+	// Without resolving, the write lands on file:<thatCid>/* and forks a
+	// second root for a file that already has one: a full duplicate record,
+	// cross-linked and separately indexed, which every downstream ingest then
+	// sees as two files. Unknown CIDs pass through unchanged, so a genuinely
+	// new gateway record still mints its root at the hash.
+	hashID = s.storage.ResolveRoot(hashID)
+
 	var metadata map[string]string
 	if err := json.NewDecoder(r.Body).Decode(&metadata); err != nil {
 		writeError(w, http.StatusBadRequest, "invalid JSON body")
@@ -263,6 +277,12 @@ func (s *Server) handleDeleteMetadataByHashId(w http.ResponseWriter, r *http.Req
 		return
 	}
 
+	// meta-gateway retracts a dropped hit by whichever CID it holds
+	// (meta_core.rs `delete`, which documents this resolution as a
+	// precondition). Without it, deleting by a non-root CID is a silent
+	// no-op and the retracted record lingers.
+	hashID = s.storage.ResolveRoot(hashID)
+
 	deletedCount, err := s.storage.DeleteMetadata(hashID)
 	if err != nil {
 		writeError(w, http.StatusInternalServerError, err.Error())

internal/api/server.go

@@ -201,6 +201,15 @@ func (s *Server) setupRoutes() {
 	s.router.HandleFunc("/api/kv/value", s.handleKVValueDelete).Methods("DELETE")
 	s.router.HandleFunc("/api/kv/key/{key:.*}", s.handleKVGetKey).Methods("GET")
 
+	// User Data Layer (UDL) routes — per-user signed records (My List,
+	// Continue Watching, ratings, profile). See internal/api/udl.go.
+	s.router.HandleFunc("/api/udl/record", s.handleUDLRecordGet).Methods("GET")
+	s.router.HandleFunc("/api/udl/record", s.handleUDLRecordPut).Methods("PUT")
+	s.router.HandleFunc("/api/udl/user/{uid}/key/{key}", s.handleUDLUserKey).Methods("GET")
+	s.router.HandleFunc("/api/udl/user/{uid}/cid/{cid}", s.handleUDLUserCid).Methods("GET")
+	s.router.HandleFunc("/api/udl/cid/{cid}/users", s.handleUDLCidUsers).Methods("GET")
+	s.router.HandleFunc("/api/udl/cid/{cid}/aggregate", s.handleUDLAggregate).Methods("GET")
+
 	// Metadata operations - base endpoints
 	s.router.HandleFunc("/meta/{hash}", s.handleGetMeta).Methods("GET")
 	s.router.HandleFunc("/meta/{hash}", s.handlePutMeta).Methods("PUT")

internal/api/udl.go

@@ -0,0 +1,239 @@
+package api
+
+// User Data Layer (UDL) HTTP surface.
+//
+// Backs meta-watch's per-user store (My List, Continue Watching, ratings,
+// profile) now that the authoritative store lives in meta-core instead of
+// meta-watch's local op-log. Records arrive already signed (and, for
+// private-tier keys, already encrypted) as opaque base64 CBOR blobs; meta-core
+// version-gates and indexes them but never inspects the crypto. See
+// internal/storage/udl.go for the Redis model.
+
+import (
+	"encoding/json"
+	"math"
+	"net/http"
+	"strings"
+
+	"github.com/gorilla/mux"
+)
+
+// UDLPutRequest is the body of PUT /api/udl/record.
+type UDLPutRequest struct {
+	Uid     string           `json:"uid"`
+	Cid     string           `json:"cid"`
+	Key     string           `json:"key"`
+	Version int64            `json:"version"`
+	Ts      int64            `json:"ts"`
+	Record  string           `json:"record"` // base64 CBOR, opaque + signed
+	Value   *json.RawMessage `json:"value,omitempty"`
+}
+
+// UDLPutResponse is the response of PUT /api/udl/record.
+type UDLPutResponse struct {
+	Accepted bool `json:"accepted"`
+}
+
+// UDLRecordResponse is the response of GET /api/udl/record.
+type UDLRecordResponse struct {
+	Record  string `json:"record"`
+	Version int64  `json:"version"`
+	Ts      int64  `json:"ts"`
+	Exists  bool   `json:"exists"`
+}
+
+// UDLAggregate mirrors meta-watch's Aggregate wire shape exactly (snake_case
+// field names; `avg` is null for boolean keys like `like`), so the meta-watch
+// client deserializes it into the same struct it serializes to the UI.
+type UDLAggregate struct {
+	Key        string   `json:"key"`
+	Count      int      `json:"count"`
+	Avg        *float64 `json:"avg"`
+	Trues      int      `json:"trues"`
+	SampleSize int      `json:"sample_size"`
+}
+
+// handleUDLRecordGet handles GET /api/udl/record?uid&cid&key
+func (s *Server) handleUDLRecordGet(w http.ResponseWriter, r *http.Request) {
+	if !s.storage.IsConnected() {
+		writeError(w, http.StatusServiceUnavailable, "storage not connected")
+		return
+	}
+	q := r.URL.Query()
+	uid, cid, key := q.Get("uid"), q.Get("cid"), q.Get("key")
+	if uid == "" || cid == "" || key == "" {
+		writeError(w, http.StatusBadRequest, "uid, cid and key are required")
+		return
+	}
+
+	cell, exists, err := s.storage.UDLGetCell(uid, cid, key)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, UDLRecordResponse{
+		Record:  cell.Record,
+		Version: cell.Version,
+		Ts:      cell.Ts,
+		Exists:  exists,
+	})
+}
+
+// handleUDLRecordPut handles PUT /api/udl/record. Version-gated: a stale write
+// (version <= stored) returns 409 stale_version so the client can re-read and
+// retry with a higher version.
+func (s *Server) handleUDLRecordPut(w http.ResponseWriter, r *http.Request) {
+	if !s.storage.IsConnected() {
+		writeError(w, http.StatusServiceUnavailable, "storage not connected")
+		return
+	}
+	var req UDLPutRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+	if req.Uid == "" || req.Cid == "" || req.Key == "" || req.Record == "" {
+		writeError(w, http.StatusBadRequest, "uid, cid, key and record are required")
+		return
+	}
+
+	publicValue := ""
+	hasValue := false
+	if req.Value != nil {
+		publicValue = string(*req.Value)
+		hasValue = true
+	}
+
+	accepted, err := s.storage.UDLUpsertIfNewer(req.Uid, req.Cid, req.Key, req.Version, req.Ts, req.Record, publicValue, hasValue)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	if !accepted {
+		writeErrorSlug(w, http.StatusConflict, "stale_version", "a record with an equal or newer version already exists", true)
+		return
+	}
+	writeJSON(w, http.StatusOK, UDLPutResponse{Accepted: true})
+}
+
+// handleUDLUserKey handles GET /api/udl/user/{uid}/key/{key}
+// (active_for_user_key — My List, Continue Watching).
+func (s *Server) handleUDLUserKey(w http.ResponseWriter, r *http.Request) {
+	if !s.storage.IsConnected() {
+		writeError(w, http.StatusServiceUnavailable, "storage not connected")
+		return
+	}
+	vars := mux.Vars(r)
+	uid, key := vars["uid"], vars["key"]
+	if uid == "" || key == "" {
+		writeError(w, http.StatusBadRequest, "uid and key are required")
+		return
+	}
+	entries, err := s.storage.UDLListUserKey(uid, key)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]interface{}{"entries": entries})
+}
+
+// handleUDLUserCid handles GET /api/udl/user/{uid}/cid/{cid}
+// (list_for_user_cid).
+func (s *Server) handleUDLUserCid(w http.ResponseWriter, r *http.Request) {
+	if !s.storage.IsConnected() {
+		writeError(w, http.StatusServiceUnavailable, "storage not connected")
+		return
+	}
+	vars := mux.Vars(r)
+	uid, cid := vars["uid"], vars["cid"]
+	if uid == "" || cid == "" {
+		writeError(w, http.StatusBadRequest, "uid and cid are required")
+		return
+	}
+	entries, err := s.storage.UDLListUserCid(uid, cid)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]interface{}{"entries": entries})
+}
+
+// handleUDLCidUsers handles GET /api/udl/cid/{cid}/users (uids_for_cid).
+func (s *Server) handleUDLCidUsers(w http.ResponseWriter, r *http.Request) {
+	if !s.storage.IsConnected() {
+		writeError(w, http.StatusServiceUnavailable, "storage not connected")
+		return
+	}
+	cid := mux.Vars(r)["cid"]
+	if cid == "" {
+		writeError(w, http.StatusBadRequest, "cid is required")
+		return
+	}
+	users, err := s.storage.UDLCidUsers(cid)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]interface{}{"users": users})
+}
+
+// handleUDLAggregate handles GET /api/udl/cid/{cid}/aggregate?keys=like,rating.
+// Computes per-key population stats from the stored public value fields
+// (absorbs meta-watch's aggregate.rs). Reflects only records this core holds.
+func (s *Server) handleUDLAggregate(w http