GordonYuanyc · Oct 2, 2026 · Oct 2, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -66,6 +66,10 @@ signals a backwards-compatible change.
   worker's seed and the aggregator's from one seed. The unseeded constructors
   draw from the thread generator. The seed is not serialized, and the ASAPv1
   payload is unchanged.
+- **ASAPv1 golden fixtures for Hydra's five counter variants** (`0x07 0x00`
+  KLL, `0x07 0x01` Count-Min, `0x07 0x02` Count Sketch, `0x07 0x03` HLL,
+  `0x07 0x04` UnivMon), each a small grid whose cell states are set directly,
+  checked by `tests/asapv1_golden.rs`.
 
 ### Changed
 
@@ -88,6 +92,21 @@ signals a backwards-compatible change.
   as an empty window like any other, and that window takes a place in
   `max_windows`.
 
+### Removed
+
+- **Hydra's proto and portable formats.** `Hydra` serializes as ASAPv1 only
+  (`serialize_to_bytes` / `deserialize_from_bytes`, kinds `0x07 0x00`-`0x07
+  0x04`). Removed: the portable `HydraKllSketch` and `HydraKllSketchWire`
+  (module `message_pack_format::portable::hydra_kll`, and the crate-root
+  `HydraKllSketch` re-export), with `HydraKllSketch`'s `MessagePackCodec` impl,
+  `with_seed`, `merge_refs` and `aggregate_hydrakll`; the proto file
+  `hydra/hydra.proto` with `HydraState`, `HydraCell` and `HydraCounterType`
+  (and their generated `proto::sketchlib` types); and `SketchEnvelope`'s
+  `hydra` field (16, now reserved). The nearest replacement is `Hydra` with a
+  one-column schema and `HydraCounter::KLL`, but it routes `label:value`
+  subkeys through the matrix hash at `HYDRA_SEED`, not `xxh32(key, row) %
+  cols`, so `HydraKllSketch` cells do not map onto the new grid.
+
 ### Fixed
 
 - `KLLDynamic` panicked on every quantile query once a NaN had entered the

diff --git a/asapv1_golden b/asapv1_golden
diff --git a/docs/asapv1_wire_format.md b/docs/asapv1_wire_format.md
@@ -707,8 +707,6 @@ A Hydra is a `rows x cols` grid of counters over a fixed set of named key column
 
 **Counters are inlined, not nested.** A cell's raw state goes straight into Hydra's positional array in the shape that counter's own section fixes; no cell carries an envelope, a magic or a metadata map of its own.
 
-**Not this: `portable/hydra_kll.rs`.** `HydraKllSketch` is a legacy Go-interop type, not `0x07 0x00`, and it is the counter-example this rule exists to rule out: every cell of its matrix carries a **full ASAPv1 KLL envelope** — magic, version, kind_id, both length prefixes and a complete metadata map — plus `k` repeated once per cell beside it, in a msgpack shape of its own with no ASAPv1 envelope around the whole. That is exactly what Q-NEST forbids, and `0x07 0x00` does none of it: one envelope for the grid, `counter_k` / `counter_m` / `counter_item_type` carried once in its metadata, and each cell just the `[levels, items, coin]` array §3.3 fixes.
-
 **`0x07 0x01` Count-Min counter, `0x07 0x02` Count Sketch counter** — the fixed-size matrix counters tile one array:
 
 | Pos | Field | Type | Notes |
@@ -1341,14 +1339,14 @@ Good direction (more compact, higher fidelity, less Rust-internal duplication),
 2. **Golden byte-vector fixtures** in one shared repo, [`sketchlib-golden-bytes`](https://github.com/ProjectASAP/sketchlib-golden-bytes), which each implementation mounts at `asapv1_golden/`; both languages decode and re-encode them byte-identically. These replace the `portable`-as-oracle round-trip test.
 3. **This registry**, mirrored, never independently allocated.
 
-Fixtures exist for six `kind_id`s — HLL's three estimators, Count-Min, Count Sketch and compact KLL — and `sketchlib-go` mirrors those. Every other kind here has a payload and **no fixture**, so this document is its only contract; `asapv1_golden/README.md` lists the gap. `portable` carries its own Go goldens.
+`asapv1_golden/README.md`'s Coverage section lists which `kind_id`s have fixtures. Every other kind here has a payload and **no fixture**, so this document is its only contract. `portable` carries its own Go goldens.
 
 **Hash profile on the Go side.**
 Rust derives the hash spec from a generic `HashProfile` bound on the hasher type; Go has no generic hasher type, so there is nothing to derive from.
 On the Go side the profile is simply **written into** the metadata on encode and **read from** it on decode.
 Go MUST validate the profile it reads (same fail-closed intent as Rust): a sketch is only mergeable/queryable if its `hash_profile_id` + seeds match the profile Go is prepared to reproduce.
 
-Sequencing: (2) covers six `kind_id`s, and the one `native bytes == portable bytes` test is HLL-only, since no other `portable` type emits ASAPv1 bytes.
+Sequencing: (2) covers the `kind_id`s that README lists, and the one `native bytes == portable bytes` test is HLL-only, since no other `portable` type emits ASAPv1 bytes.
 Retire `portable` once the fixtures cover the rest.
 
 ---

diff --git a/docs/features.md b/docs/features.md
@@ -112,7 +112,7 @@ MessagePack (`rmp-serde`) support. **serde support** means the type derives `Ser
 | EHSketchList | Yes | Yes |
 | ExponentialHistogram | No | Yes |
 
-Protobuf (prost): `.proto` definitions exist for CountMin, Count, HLL, DDSketch, KLL, Elastic, Coco, Hydra, and UnivMon. Rust conversion code is in progress.
+Protobuf (prost): `.proto` definitions exist for CountMin, Count, HLL, DDSketch, KLL, Elastic, Coco, and UnivMon. Rust conversion code is in progress.
 
 ### API Stability
 

diff --git a/docs/message_pack_format.md b/docs/message_pack_format.md
@@ -169,10 +169,10 @@ decode → re-encode them byte-identically. The `kind_id` registry is mirrored
 verbatim with Go's `wire/asapmsgpack/magic_ids.go`, never independently
 allocated.
 
-That proof covers the six `kind_id`s a fixture exists for — HLL's three
-estimators, Count-Min, Count Sketch and compact KLL. Every other implemented
-kind has **no ASAPv1 golden and therefore no ASAPv1 drift guard**;
-[its README](https://github.com/ProjectASAP/sketchlib-golden-bytes#coverage) lists what is covered.
+`asapv1_golden/README.md`'s
+[Coverage section](https://github.com/ProjectASAP/sketchlib-golden-bytes#coverage)
+lists which `kind_id`s have fixtures. Every other implemented kind has **no
+ASAPv1 golden and therefore no ASAPv1 drift guard**.
 The older `portable` path is guarded separately, by the `sketchlib-go` goldens
 of its own listed above.
+59 −12		README.md
+1 −0		cmsheap_i32_fast_2x3_i64keys.hex
+1 −0		cmsheap_i64_regular_2x3_strkeys.hex
+1 −0		csheap_i64_regular_2x4_strkeys.hex
+1 −0		ddsketch_positive_a001.hex
+1 −0		ddsketch_signed_a001.hex
+1 −0		hydra_cm_2x2_counter_2x2.hex
+1 −0		hydra_cs_2x2_counter_2x2.hex
+1 −0		hydra_hll_1x2_p14.hex
+1 −0		hydra_kll_2x2_k200.hex
+1 −0		hydra_univmon_1x2.hex
+1 −0		kll_dynamic_f64_k200.hex
+1 −0		kll_dynamic_i64_k200.hex