rose-ash/plans/fed-sx-milestone-1.md

# fed-sx Milestone 1 — Kernel + Registries + Pin Smoke Test

Concrete implementation plan for the smallest fed-sx that proves the architecture
works end-to-end. Reference: `plans/fed-sx-design.md`. Prerequisite: Erlang-on-SX
Phases 7 (hot reload) + 8 (FFI BIFs).

## Goal

Ship a single-instance, single-actor fed-sx server that:

1. Boots from a verified genesis bundle.
2. Accepts and durably appends signed activities via `POST /activity`.
3. Folds them into projections in real time.
4. Serves AP-standard endpoints (actor, outbox, artifacts, capabilities).
5. Demonstrates **two extensibility proof-points** end-to-end with zero kernel
   code changes between definition and use:
   - **Verb extensibility** (§5 meta-level): publish `DefineActivity{Pin}` +
     `DefineProjection{pin-state}`, then publish a `Pin` activity, observe it
     validated and projected.
   - **Reactive application extensibility** (§§18-19): publish
     `DefineSubscription{Topic}` + `Subscribe{topic: smoketest}` +
     `DefineTrigger{when: that subscription, then: publish TestEcho}`, then
     publish a tagged Note, observe the subscription match, the trigger fire,
     and the derived activity appear in the outbox.

Federation, multi-actor, advanced verbs, IPFS, browser UI, operator dashboard
are **explicitly v2**.

## Non-goals (what milestone 1 deliberately does NOT do)

- **Federation.** No `POST /inbox` from peers, no `Follow`, no delivery queue, no
  webfinger discovery flow. Single instance only.
- **Multi-actor.** Single domain actor (`acct:next@next.rose-ash.com`).
- **IPFS / S3 storage backends.** Files on disk only.
- **Advanced verbs.** No `Endorse`, `Supersede`, `Test`, `Build`, `Compose`,
  `Note`, `Announce`. Only the four bootstrap verbs (`Create`, `Update`, `Delete`)
  plus a defined-from-the-log `Pin` for the smoke test. (`Announce` deferred —
  no use case until federation exists.)
- **Browser UI.** Curl-shaped API only.
- **Operator dashboard, quarantine UX.** Logs only.
- **Performance work.** Functional correctness first; perf when measured.
- **Cross-host conformance test corpus.** Only the OCaml/Erlang-on-SX host runs
  fed-sx in v1; conformance suite for other hosts is v2.

## Architecture summary

```
                          POST /activity
                                │
                                ▼
                  ┌──────────────────────────┐
                  │ HTTP server (Erlang-on-SX)│
                  └─────────────┬─────────────┘
                                │
                  ┌─────────────▼──────────────┐
                  │ Validation pipeline driver  │
                  │ (envelope→sig→schema→...)   │
                  └─────────────┬──────────────┘
                                │
                  ┌─────────────▼──────────────┐
                  │ Log append (JSONL segment)  │  ← canonical
                  └─────────────┬──────────────┘
                                │
                  ┌─────────────▼──────────────┐
                  │ Projection workers          │  ← gen_server per
                  │ (fold scheduler)            │     projection
                  └─────────────────────────────┘
                                │
                                ▼
                       Projection state
                       (queryable via HTTP)

Native primitives (Erlang-on-SX BIFs from Phase 8):
  crypto:* cid:* fs:* http:* sqlite:*

Genesis bundle (binary-embedded SX):
  activity-types  object-types  projections
  validators      codecs        sig-suites
```

## Build order

Eight steps in dependency order. Each step has concrete deliverables, testable
in isolation, and a clear acceptance check.

| Step | Title | Depends on |
|------|-------|------------|
| **1** | Repo skeleton + canonical CID computation | Phase 8 (cid BIFs) |
| **2** | Activity envelope + signature verify | Phase 8 (crypto BIFs) |
| **3** | JSONL log + sequence numbers | Phase 8 (fs BIFs) |
| **4** | Genesis bundle (SX sources + bundling + CID verification) | Step 1 |
| **5** | Registry mechanism + bootstrap-projection dispatch | Steps 2, 4 |
| **6** | Validation pipeline driver + `POST /activity` | Steps 2, 3, 5 |
| **7** | Projection scheduler (gen_server per projection) | Steps 5, 6 |
| **8** | HTTP server, AP endpoints, projection queries | Steps 6, 7 |
| **9** | Smoke tests (Pin verb + reactive application) | Steps 1-8 |

---

## Step 1 — Repo skeleton + canonical CID

**Sub-deliverables:**
- [x] **1a** — `next/` directory skeleton, README, `.gitignore` for `data/`
- [x] **1b** — `next/kernel/nx_cid.erl` (from_sx/to_string/from_string/equals) + `next/tests/cid.sh` (13 cases). Module is `nx_cid` not `cid` — the `cid` BIF module would be shadowed by a user module of the same name; plan §Step 1's `cid.erl` is illustrative per briefing.

**Deliverables:**

```
next/
├── README.md                         # what this is
├── kernel/                           # Erlang-on-SX
│   └── (empty for now)
├── genesis/                          # core SX bootstrap definitions
│   └── (empty for now)
├── tests/                            # smoke test scripts
│   └── (empty for now)
└── data/                             # gitignored runtime state
    ├── log/
    ├── objects/
    ├── snapshots/
    ├── indexes/
    └── keys/
```

Plus one Erlang-on-SX module:

```erlang
% next/kernel/cid.erl
-module(cid).
-export([from_sx/1, to_string/1, from_string/1, equals/2]).

from_sx(SxValue) ->
    Cbor = cid:cbor_encode(canonicalize_sx(SxValue)),
    Hash = crypto:sha2_256(Cbor),
    cid:from_bytes(<<"raw">>, Hash).      % defaults to dag-cbor codec

canonicalize_sx(V) -> ...                  % sorts dict keys, normalizes strings
```

**Tests:**
- Same SX value → same CID across multiple invocations.
- Different SX values → different CIDs.
- Whitespace/comment differences in source → identical CIDs (parsed AST identical).
- Reordered dict keys → identical CIDs (sorted-key canonicalization).
- Cross-host parity (just OCaml host for v1, but write the test so adding hosts is mechanical).

**Acceptance:** `bash next/tests/cid.sh` passes 10+ cases.

---

## Step 2 — Activity envelope + signature verify

**Sub-deliverables:**
- [x] **2a** — `next/kernel/envelope.erl` `validate_shape/1` + `get_field/2` (property-list envelope; Erlang maps `#{}` not supported in this port) + `next/tests/envelope_shape.sh` (15 cases)
- [x] **2b** — `canonical_bytes/1` over sig-stripped, key-sorted envelope (deterministic textual form via `cid:to_string` substrate; dag-cbor stand-in for v1) + `next/tests/envelope_canonical.sh` (8 cases)
- [x] **2c** — `verify_signature/2` against actor `public_keys`, time-aware key validity per design §9.6 (created ≤ published, optional supersession check) + `next/tests/envelope_sig.sh` (11 cases). Signature scheme is HMAC-shaped (`crypto:hash(sha256, KeyMaterial ++ canonical_bytes)`) — RSA/Ed25519 verify deferred to m2 (BIFs not yet wired).

**Deliverables:**

```erlang
% next/kernel/envelope.erl
-module(envelope).
-export([validate_shape/1, canonical_bytes/1, verify_signature/2]).

% Envelope shape per design §3.1:
%   #{id, type, actor, published, to, cc, audience_extras,
%     object | target | origin | result,
%     capabilities_required, proofs, signature}
validate_shape(Activity) -> ok | {error, Reason}.

canonical_bytes(Activity) ->
    % Strip signature, canonicalize via dag-cbor, return bytes for sig coverage
    Stripped = maps:remove(signature, Activity),
    cid:cbor_encode(canonicalize_for_sig(Stripped)).

verify_signature(Activity, ActorState) ->
    % Time-aware: find key with id == sig.key_id that was active at published
    % Per design §9.6
    ...
```

**Tests:**
- Envelope shape: required fields present (id, type, actor, published, signature)
- Envelope shape: type is a known activity-type or unknown-but-string
- Envelope shape: signature has key_id, algorithm, value
- Sig verify: valid RSA-SHA256 signature against published key → ok
- Sig verify: valid Ed25519 signature → ok
- Sig verify: tampered envelope → fail
- Sig verify: key superseded before activity timestamp → fail
- Sig verify: key superseded after activity timestamp → ok (historical valid)

**Acceptance:** `bash next/tests/envelope.sh` passes 15+ cases.

---

## Step 3 — JSONL log + sequence numbers

**Sub-deliverables:**
- [x] **3a** — `log:open/2` + `log:append/2` + `log:tip/1` + `log:replay/3` + `log:entries/1` over an in-memory log state (per-actor seq; replay in append order; round-trip the stored activity). `next/tests/log_memory.sh` (12 cases).
- [ ] **3b** — *Parked behind substrate gap (see Blockers below).* Term codec + on-disk persistence: serializer/parser writing each activity as a JSONL-style line; restart-resumes-tip from the segment file.
- [ ] **3c** — Segment rotation at size threshold + gen_server-mediated concurrent appends.

**Blockers (Step 3b):** The Erlang port returns SX strings (an opaque OCaml-string type) from `atom_to_list/1` and `integer_to_list/1`, rejects them from `++`/list pattern matching, and does not register `binary_to_list`/`list_to_binary`. `$X` character literals decode to `nil` in `parse-number`. Net effect: there is no in-Erlang path from an arbitrary term to a byte sequence (or back) that doesn't go through a temp-file round-trip through the filesystem. Workaround paths: (a) add a `term_to_binary`/`binary_to_term` BIF in a separate substrate loop, (b) accept a filesystem-mediated SX-string→binary helper and live with the O(N) IO cost, (c) restrict the on-disk format to a binary-only encoding with a per-instance atom-id table for atoms (introduces an extra durability dependency). Decision to defer; revisit once a downstream Step (5–8) forces the issue or a substrate BIF arrives. In-memory log from 3a is sufficient to unblock Step 5+ which consume the API surface.

**Deliverables:**

```erlang
% next/kernel/log.erl
-module(log).
-export([open/1, append/2, read_segment/2, tip/1, replay/3]).

% Per design §15.2: per-actor outbox, segments cap ~64MB,
% format = JSONL (one canonical JSON-LD activity per line)

open(ActorId) ->
    BasePath = log_path_for_actor(ActorId),
    fs:mkdir_p(BasePath),
    {ok, #{base => BasePath, current => current_segment(BasePath), seq => next_seq(BasePath)}}.

append(LogState, Activity) ->
    Json = jsonld:encode(Activity),
    Path = current_segment_path(LogState),
    Line = <<Json/binary, "\n">>,
    fs:append_file(Path, Line),
    NewSeq = LogState#{seq := LogState.seq + 1},
    rotate_if_needed(NewSeq).

% replay/3 calls Fun(Activity, Acc) for every activity in chronological order
replay(LogState, InitAcc, Fun) -> ...
```

**Tests:**
- Append + read back gives identical activity (round-trip).
- Sequence numbers monotonic and gap-free per actor.
- Segment rotation at size threshold.
- Replay visits all activities in append order across multiple segments.
- Restart preserves tip pointer (seq number resumes correctly).
- Concurrent appends (using gen_server-mediated access) are serialized correctly.

**Acceptance:** `bash next/tests/log.sh` passes 10+ cases.

---

## Step 4 — Genesis bundle

**Sub-deliverables:**
- [x] **4a** — Seed genesis SX file authoring: `next/genesis/manifest.sx` + `next/genesis/activity-types/create.sx`. Manifest uses bare parenthesised paths (data lists, not `(list ...)` calls — consumed by `parse`, not `eval`). `next/tests/genesis_parse.sh` (5 cases).
- [x] **4b-act** — Remaining activity-types: `update.sx` + `delete.sx`, manifest updated, parse tests (10 cases total in `genesis_parse.sh`)
- [x] **4b-obj** — Object-types: SXArtifact, Note, Tombstone, DefineActivity, DefineObject, DefineProjection, DefineValidator, DefineCodec, DefineSigSuite, Snapshot — 10 `DefineObject` files + manifest updated + 12 new parse tests
- [x] **4b-proj** — Projections: activity-log, by-type, by-actor, by-object, actor-state, define-registry, audience-graph — 7 `DefineProjection` files + manifest updated + 9 new parse tests
- [x] **4b-vld** — Validators: envelope-shape, signature, type-schema — 3 `DefineValidator` files + manifest updated + 5 new parse tests
- [x] **4b-cod** — Codecs (dag-cbor, raw, dag-json) + sig-suites (rsa-sha256-2018, ed25519-2020) + audience predicates (Public, Followers, Direct) — 8 SX files + manifest fully populated + 14 new parse tests
- [x] **4c** — `bootstrap:read_genesis/0,1` + `read_section/2` + `sections/0` + `section_subdir/1` + `ends_with_sx/1` in Erlang: walk seven hardcoded section subdirs, filter `.sx` files via byte-pattern suffix match, read each into a binary. Returns `{ok, [{Section, [{Name, Bytes}, ...]}, ...]}`. Skips SX parsing — the substrate has no in-Erlang binary→SX-term path (same gap as Step 3b); bundle CID over raw bytes is enough for Step 4d. `next/tests/bootstrap_read.sh` (15 cases).
- [x] **4d** — `bootstrap:build_genesis/1` + `verify_genesis/2` + `cidhash_path/1` + `write_cidhash/2` + `read_cidhash/1`: bundle CID via host `cid:to_string` over `{genesis_bundle, Sections}`; mismatch returns `{error, {cid_mismatch, Got, Expected}}`; `.cidhash` sibling file persists between runs. `next/tests/bootstrap_build.sh` (12 cases).
- [x] **4e** — `bootstrap:load_genesis/1` + `strip_sx_suffix/1`: bridges `read_genesis` output into `registry` entries. Section atom = registry kind; entry name = filename minus `.sx` (binary); entry value = raw file bytes (parsed forms replace these once an SX-parser bridge exists). `next/tests/bootstrap_load.sh` (15 cases).

**Deliverables:**

Genesis bundle SX sources (per design §12.2). Each is a small SX file authored
by hand for the bootstrap set:

```
next/genesis/
├── manifest.sx                       # bundle root: lists all definitions
├── activity-types/
│   ├── create.sx                     # DefineActivity{name: "Create", ...}
│   ├── update.sx
│   └── delete.sx
├── object-types/
│   ├── sx-artifact.sx
│   ├── note.sx
│   ├── tombstone.sx
│   ├── define-activity.sx            # DefineObject for the Define* meta types
│   ├── define-object.sx
│   ├── define-projection.sx
│   ├── define-validator.sx
│   ├── define-codec.sx
│   ├── define-sig-suite.sx
│   └── snapshot.sx
├── projections/
│   ├── activity-log.sx               # identity projection
│   ├── by-type.sx
│   ├── by-actor.sx
│   ├── by-object.sx
│   ├── actor-state.sx
│   ├── define-registry.sx            # the chicken-and-egg projection
│   └── audience-graph.sx
├── validators/
│   ├── envelope-shape.sx
│   ├── signature.sx
│   └── type-schema.sx
├── codecs/
│   ├── dag-cbor.sx                   # delegates to cid:cbor_encode/decode BIFs
│   ├── raw.sx
│   └── dag-json.sx
├── sig-suites/
│   ├── rsa-sha256-2018.sx
│   └── ed25519-2020.sx
└── audience/
    ├── public.sx
    ├── followers.sx
    └── direct.sx
```

Plus a build-time bundler:

```erlang
% next/kernel/bootstrap.erl
-module(bootstrap).
-export([build_genesis/1, verify_genesis/1, load_genesis/1]).

build_genesis(SourceDir) ->
    % Walk SourceDir, parse each .sx file, build a single dag-cbor bundle,
    % compute its CID, write bundle.cbor + CID to data/genesis/
    ...

verify_genesis(BundlePath) ->
    % Compute CID of the bundle as loaded; compare to expected (hardcoded
    % in the kernel binary). Mismatch → halt.
    ...

load_genesis(BundlePath) ->
    % Parse the bundle, register all definitions in the in-memory registry
    ...
```

**Tests:**
- All genesis SX files parse cleanly.
- Bundle CID is deterministic (rebuild same sources → same CID).
- Bundle reload reproduces the exact same registry state.
- Tampered bundle → `verify_genesis` returns `{error, cid_mismatch}`.

**Acceptance:** `bash next/tests/bootstrap.sh` passes; `next/data/genesis/bundle.cbor`
created with a known stable CID.

---

## Step 5 — Registry mechanism + bootstrap dispatch

**Sub-deliverables:**
- [x] **5a** — Pure-functional `next/kernel/registry.erl`: `new/0`, `kinds/0`, `register/4`, `lookup/3`, `list/2`. State is a property list keyed by kind atom; per-kind storage is a property list of `{Name, Entry}`. Unknown kinds rejected with `{error, unknown_kind}`. `next/tests/registry_pure.sh` (14 cases).
- [x] **5b** — gen_server wrapper around the pure registry: `start_link/0`, registered name `registry`, `register/3 lookup/2 list/1 stop/0` API delegating through `gen_server:call`. `next/tests/registry_server.sh` (12 cases). Port note: each test combines start_link + ops in a single expression because spawned processes don't survive across separate `erlang-eval-ast` invocations.
- [ ] **5c** — `bootstrap:load_genesis/1` (Step 4e) populates the registry from `read_genesis` output. Dispatches by section atom → kind.
- [ ] **5d** — define-registry projection fold integration: incoming `Create{Define*}` activities are routed through the projection scheduler (Step 7) and update the registry.

**Deliverables:**

Registries are gen_servers, one per kind, each holding the active version map:

```erlang
% next/kernel/registry.erl
-module(registry).
-behaviour(gen_server).
-export([start_link/0, lookup/2, register/3, list/1]).
% Internal state:
%   #{activity_types => #{Name => #{cid, schema_fn, semantics_fn, supersedes}},
%     object_types   => ...,
%     projections    => ...,
%     validators     => ...,
%     codecs         => ...,
%     sig_suites     => ...,
%     ...}

lookup(Kind, Name) -> {ok, Entry} | {error, not_found}.
register(Kind, Name, Entry) -> ok | {error, Reason}.
list(Kind) -> [#{name, cid}].
```

The `define-registry` projection's fold updates this gen_server's state when
new `Define*` activities arrive. (Bootstrapping circle resolved: at startup,
`bootstrap:load_genesis/1` populates the registry directly; from then on, the
projection fold maintains it.)

**Tests:**
- After genesis load, `registry:list(activity_types)` returns Create/Update/Delete.
- `registry:lookup(activity_types, "Create")` returns the schema and semantics.
- A new `DefineActivity{name: "Pin"}` activity (synthesised, hand-signed for the
  test) routes through the projection fold, ends up in the registry.
- Lookup never caches across activities (verified by introducing a new definition
  mid-test and confirming the next lookup sees it).

**Acceptance:** `bash next/tests/registry.sh` passes 10+ cases.

---

## Step 6 — Validation pipeline + POST /activity

**Sub-deliverables:**
- [x] **6a** — `pipeline:run_stages/2` driver — pure fold over a stage list of `(Activity) -> ok | {error, R}` funs, halts on first failure. `validate_inbound/1` + `validate_outbound/1` + `inbound_stages/0` + `outbound_stages/0` (empty lists for now). `next/tests/pipeline_driver.sh` (10 cases).
- [x] **6b-env** — `pipeline:stage_envelope/1` delegating to `envelope:validate_shape/1`; wired into both `inbound_stages` and `outbound_stages`. `next/tests/pipeline_envelope.sh` (12 cases); pipeline_driver.sh updated to test the driver in isolation.
- [x] **6b-sig** — `pipeline:stage_signature/2` (direct call) + `stage_signature/1` (factory returning a context-bound stage fun). Not wired into default stage lists since ActorState isn't available at static-list build time; callers compose by `Stages = [..., pipeline:stage_signature(AS)]`. `next/tests/pipeline_signature.sh` (11 cases) covers direct + factory + composition + halt behaviour with stage_envelope.
- [x] **6c-replay** — `pipeline:stage_replay/2` (direct) + `stage_replay/1` (factory closed over LogState). Checks the log entries for an existing activity with the same `:id`. Returns `{error, replay}` on duplicate, `{error, no_id}` when missing. `next/tests/pipeline_replay.sh` (12 cases).
- [ ] **6c-schema** — `stage_activity_schema/1` (registry lookup of activity-type, evaluate :schema body) — blocked behind SX-source eval bridge.
- [x] **6d-cs** — `outbox:construct/4` (skeleton + CID-derived :id via `cid:to_string`) + `outbox:sign/2` (HMAC over canonical bytes, append :signature pair from KeySpec) + `cid_of/1` accessor. Verified end-to-end: construct→sign→envelope:verify_signature passes; wrong key material fails with bad_signature. `next/tests/outbox_construct.sh` (13 cases).
- [x] **6d-publish** — `outbox:publish/2(Request, Context)` orchestrates construct + sign + `pipeline:run_stages([envelope, signature, replay])` + `log:append`. Returns `{ok, [{cid, _}, {activity, _}], NewLog}` or `{error, Reason, LogState}` on stage halt. Replay catches duplicate publishes; bad key material surfaces `bad_signature`. `next/tests/outbox_publish.sh` (13 cases).
- [ ] **6e** — HTTP handler for POST /activity glue (depends on Step 8 http server)

**Deliverables:**

```erlang
% next/kernel/pipeline.erl
-module(pipeline).
-export([validate_inbound/1, validate_outbound/1]).

% Per design §14, run stages in order, halt on first failure.
validate_inbound(Activity) ->
    Stages = [
        fun stage_envelope/1,
        fun stage_signature/1,
        fun stage_replay/1,
        fun stage_audience/1,
        fun stage_activity_schema/1,
        fun stage_object_schema/1,
        fun stage_content_validators/1,
        fun stage_capabilities/1,
        fun stage_trust/1
    ],
    run_stages(Activity, Stages).

validate_outbound(Activity) ->
    % Subset of inbound stages (no replay, no trust check; auth done at HTTP layer)
    ...
```

```erlang
% next/kernel/outbox.erl
-module(outbox).
-export([publish/2]).

publish(ActorId, ActivityRequest) ->
    Activity = construct_envelope(ActorId, ActivityRequest),
    Signed = sig:sign(Activity, ActorId),
    case pipeline:validate_outbound(Signed) of
        ok ->
            log:append(actor_log(ActorId), Signed),
            projection:async_fold(Signed),
            {ok, #{cid => cid:from_sx(Signed),
                   ap_id => maps:get(id, Signed)}};
        {error, Reason} ->
            {error, Reason}
    end.
```

**Tests:**
- Valid activity through full pipeline → appended to log.
- Bad envelope → 400, not in log.
- Bad signature → 401, not in log.
- Replayed activity → 200 duplicate, not re-appended.
- Schema violation (e.g. Create with no object) → 422.
- Activity logged before projection completes (async).

**Acceptance:** `bash next/tests/pipeline.sh` passes 15+ cases.

---

## Step 7 — Projection scheduler

**Sub-deliverables:**
- [x] **7a** — Pure-functional `next/kernel/projection.erl`: `new/2,3`, `fold_activity/2`, `replay/2`, `name/1`, `state/1`, `fold_fn/1`. Projection record is `[{name, _}, {state, _}, {fold, fun}]`; fold body is an Erlang fun in v1 (SX-source eval bridge deferred). `next/tests/projection_pure.sh` (12 cases).
- [x] **7b** — gen_server-per-projection: `start_link/3(Name, InitialState, FoldFn)` + `async_fold/2(Name, Activity)` (cast) + `query/1(Name)` (call) + `stop/1`. Each projection registered under its own Name atom. `next/tests/projection_server.sh` (11 cases). Snapshot persistence deferred (needs SX-source eval + on-disk state).
- [x] **7c** — `outbox:publish` broadcast hook: after `log:append`, fans out the signed activity to every projection listed under `Context`'s `:projections` entry via `projection:async_fold`. Stage halts (replay, sig failure) skip broadcast. `next/tests/outbox_broadcast.sh` (14 cases).
- [ ] **7d** — `sandbox:eval_pure/2` (Erlang sandbox-mode caller — gas budget + IO denial) once an SX-source eval bridge exists.

**Deliverables:**

```erlang
% next/kernel/projection.erl
-module(projection).
-export([start_link/1, async_fold/1, query/2, snapshot/1]).
-behaviour(gen_server).

% One gen_server per active projection. State:
%   #{cid, name, fold_fn, current_state, log_tip,
%     snapshot_dir, last_snapshot_at}

% async_fold/1 broadcasts a new activity to every projection gen_server;
% each folds it into its own state. Failures (gas, sandbox violation)
% tag the activity but don't affect log durability.

% query/2 returns current state (or state-as-of)
% snapshot/1 forces a snapshot now (also runs periodically)
```

```erlang
% next/kernel/sandbox.erl
-module(sandbox).
-export([eval_pure/2, eval_crypto/2, eval_effectful/3]).

% eval_pure runs an SX function in pure mode: no IO platform, gas budget,
% deterministic. Used by projection folds, validators, audience predicates.
% Wrapper over the SX runtime evaluator with a stripped platform.
```

**Tests:**
- New activity → all projections fold it concurrently.
- Projection fold completes within gas budget.
- Gas-exhausting fold → activity tagged, projection state unchanged, no kernel crash.
- Sandbox violation (fold tries IO) → same handling.
- Snapshot create + reload → state matches.
- Snapshot CID stable across kernel restarts.

**Acceptance:** `bash next/tests/projection.sh` passes 15+ cases.

---

## Step 8 — HTTP server + endpoints

**Sub-deliverables:**
- [x] **8a** — `http:listen/2` BIF wrapper in `lib/erlang/runtime.sx` (the briefing's allowed exception). Validates args, bridges Erlang handler funs to SX-callable lambdas via `er-of-sx`/`er-to-sx`, delegates to the native `http-listen` primitive in `bin/sx_server.ml`. Tests verify registration + arg validation (not the blocking listen loop). `next/tests/http_listen_bif.sh` (5 cases).
- [x] **8b-route** — `next/kernel/http_server.erl`: pure `route/1` dispatch + `ok_response/1`, `not_found_response/0`, `welcome_body/0`. GET / returns welcome; everything else returns 404 (graceful for missing fields). `next/tests/http_route.sh` (11 cases).
- [ ] **8b-start** — `start/1(Port)` spawns an Erlang process hosting `http:listen/2`, requires the dict↔proplist marshaling bridge in the BIF wrapper.
- [x] **8c-cap** — Route GET `/.well-known/sx-capabilities` (static doc: kernel/version/verbs lines). `next/tests/http_capabilities.sh` (8 cases). Other concrete routes follow.
- [x] **8c-actors-doc** — `match_prefix/2` byte-level path-prefix matcher + GET `/actors/{id}` route returning an `actor: <id>` stub body. `/actors/{id}/outbox` deferred (needs path-segment splitting). `next/tests/http_actors.sh` (13 cases).
- [ ] **8c-art** — Route `/artifacts/{cid}` (also path-prefix matching).
- [ ] **8c-proj** — Routes `/projections` (list) + `/projections/{name}` (state).
- [ ] **8c-post** — POST `/activity` glue: parse body → call `outbox:publish` with bearer-token auth (env var `NEXT_PUBLISH_TOKEN`).
- [ ] **8d** — Content negotiation by Accept header: application/activity+json (default), application/cbor, application/json, application/sx.

**Deliverables:**

Core endpoints (per design §16.1):

```
GET  /actors/<id>                     # actor doc
GET  /actors/<id>/outbox              # OrderedCollection
GET  /actors/<id>/outbox?page=true    # OrderedCollectionPage
POST /activity                        # publish (auth: bearer token)
GET  /artifacts/<cid>                 # CID-addressed artifact
GET  /artifacts/<cid>/raw
GET  /projections                     # list of projections
GET  /projections/<name>              # full state
GET  /projections/<name>?at=<ts>      # time-travel
GET  /projections/<name>/<key>        # indexed lookup
GET  /define-registry
GET  /.well-known/sx-capabilities
GET  /.well-known/webfinger
```

```erlang
% next/kernel/http_server.erl
-module(http_server).
-export([start/1, route/1]).

start(Port) ->
    http:listen(Port, fun ?MODULE:route/1).

route(Request) -> {Status, Headers, Body}.
```

Content negotiation per `Accept`:
- `application/activity+json` (default)
- `application/cbor` (dag-cbor)
- `application/json` (compact, no @context expansion)
- `application/sx`

Auth on `POST /activity`: bearer token from env var `NEXT_PUBLISH_TOKEN`.

**Tests:**
- Each endpoint returns expected shape for known artifact.
- Content negotiation: same artifact in 4 representations.
- 404 for unknown artifact CID.
- 401 for `POST /activity` without token.
- Pagination: outbox with > 50 activities returns OrderedCollectionPage.

**Acceptance:** `bash next/tests/http.sh` passes 20+ cases.

---

## Step 9 — Smoke tests

**The proof points.** Two end-to-end smoke tests demonstrate, between them, that
fed-sx is genuinely a substrate for distributed reactive applications expressed
as data — not a system you extend by writing kernel code.

- **9a — Pin smoke test (`next/tests/smoke_pin.sh`)** — verb extensibility:
  defining a new activity type and projection at runtime via `Define*`
  artifacts. Verifies the meta-level (§5).
- **9b — Reactive application smoke test (`next/tests/smoke_app.sh`)** —
  application extensibility: defining a new subscription type, subscribing,
  registering a trigger, and observing the full reactive loop fire end-to-end
  without kernel code changes. Verifies §§18-19.

Both must pass for milestone 1 acceptance.

### Step 9a — Pin smoke test

**Test script:** `next/tests/smoke_pin.sh`

```bash
#!/usr/bin/env bash
set -euo pipefail

# 0. Start a fresh fed-sx kernel (background)
./next/scripts/start.sh fresh
sleep 2
TOKEN=$(cat next/data/keys/publish.token)

# 1. Verify actor exists
curl -s http://localhost:9999/actors/next | jq -e '.type == "Person"'

# 2. Verify outbox has actor's first Create{Person}
curl -s http://localhost:9999/actors/next/outbox?page=true \
  | jq -e '.orderedItems | length == 1 and .[0].type == "Create"'

# 3. Verify Pin is NOT a known activity type
curl -s http://localhost:9999/define-registry?kind=activity_types \
  | jq -e '.[] | select(.name == "Pin") | length == 0' || exit 1

# 4. Publish DefineActivity{name: "Pin", schema: ..., semantics: ...}
PIN_DEF=$(cat <<'JSON'
{
  "type": "Create",
  "object": {
    "type": "DefineActivity",
    "name": "Pin",
    "schema": "(fn (act) (and (string? (-> act :object :path)) (cid? (-> act :object :cid))))",
    "semantics": "(fn (state act) (assoc-in state [:pins (-> act :object :path)] (-> act :object :cid)))"
  }
}
JSON
)
curl -s -X POST http://localhost:9999/activity \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/activity+json" \
  -d "$PIN_DEF" | jq -e '.cid' > /dev/null

# 5. Verify Pin IS now a known activity type
curl -s http://localhost:9999/define-registry?kind=activity_types \
  | jq -e '.[] | select(.name == "Pin") | length == 1'

# 6. Also publish a DefineProjection{name: "pin-state"} that folds Pin into state
PIN_PROJ=$(cat <<'JSON'
{
  "type": "Create",
  "object": {
    "type": "DefineProjection",
    "name": "pin-state",
    "initial-state": "{}",
    "fold": "(fn (state act) (if (= (:type act) \"Pin\") (assoc state (-> act :object :path) (-> act :object :cid)) state))"
  }
}
JSON
)
curl -s -X POST http://localhost:9999/activity \
  -H "Authorization: Bearer $TOKEN" \
  -d "$PIN_PROJ" | jq -e '.cid'

# 7. Now publish a Pin activity
PIN=$(cat <<'JSON'
{
  "type": "Pin",
  "object": {
    "type": "PinSpec",
    "path": "/docs/intro",
    "cid": "bafyreigh2akiscaildc3xqxx4xqxx4xqxx4xqxx4xqxx4xqxx4xqxx4xqxxe"
  }
}
JSON
)
curl -s -X POST http://localhost:9999/activity \
  -H "Authorization: Bearer $TOKEN" \
  -d "$PIN" | jq -e '.cid'

# 8. Verify Pin appears in outbox
curl -s http://localhost:9999/actors/next/outbox?page=true \
  | jq -e '.orderedItems | map(select(.type == "Pin")) | length == 1'

# 9. Verify pin-state projection has the entry
sleep 1   # allow async projection
curl -s http://localhost:9999/projections/pin-state \
  | jq -e '."/docs/intro" == "bafyreigh2akiscaildc3xqxx4xqxx4xqxx4xqxx4xqxx4xqxx4xqxx4xqxxe"'

# 10. Negative test: publish a malformed Pin (missing path) → expect 422
BAD_PIN='{"type": "Pin", "object": {"cid": "bafy..."}}'
HTTP_STATUS=$(curl -s -o /dev/null -w "%{http_code}" -X POST http://localhost:9999/activity \
  -H "Authorization: Bearer $TOKEN" -d "$BAD_PIN")
[[ "$HTTP_STATUS" == "422" ]] || { echo "expected 422, got $HTTP_STATUS"; exit 1; }

# 11. Restart kernel; verify state recovers
./next/scripts/stop.sh
./next/scripts/start.sh
sleep 2
curl -s http://localhost:9999/projections/pin-state \
  | jq -e '."/docs/intro" == "bafyreigh2akiscaildc3xqxx4xqxx4xqxx4xqxx4xqxx4xqxx4xqxxe"'

echo "✓ Pin smoke test passed — verb extensibility demonstrated end-to-end"
```

**Acceptance for 9a:** smoke test exits 0. The whole flow happens with **zero
fed-sx kernel code changes** between defining the verb and using it.

### Step 9b — Reactive application smoke test

**The bigger proof point.** Demonstrates that fed-sx supports distributed
reactive applications composed of `DefineSubscription` + `DefineTrigger` +
`DefineProjection` — the application model from §§18-19.

The test runs on a single instance (federation is v2), so the "subscriber" and
"publisher" are the same actor. That's intentional — milestone 1 proves the
mechanism; milestone 2 spreads it across instances.

**Test script:** `next/tests/smoke_app.sh`

```bash
#!/usr/bin/env bash
set -euo pipefail

# Assumes 9a has already run (fresh kernel optional; can run alongside).
TOKEN=$(cat next/data/keys/publish.token)
BASE=http://localhost:9999

# 1. Verify "Topic" subscription type and "Subscribe" verb are NOT yet defined.
curl -s "$BASE/define-registry?kind=subscription_types" \
  | jq -e 'map(select(.name == "Topic")) | length == 0'

# 2. Publish DefineSubscription{name: "Topic", ...}
TOPIC_DEF=$(cat <<'JSON'
{
  "type": "Create",
  "object": {
    "type": "DefineSubscription",
    "name": "Topic",
    "schema": "(fn (sub) (string? (-> sub :tag)))",
    "match":  "(fn (sub act) (and (= (:type act) \"Note\") (member? (-> sub :tag) (or (-> act :object :tags) (list)))))",
    "delivery": "{:default :push :modes (list :push :pull)}"
  }
}
JSON
)
curl -s -X POST "$BASE/activity" \
  -H "Authorization: Bearer $TOKEN" -d "$TOPIC_DEF" | jq -e '.cid'

# 3. Verify Topic IS now a known subscription type.
curl -s "$BASE/define-registry?kind=subscription_types" \
  | jq -e 'map(select(.name == "Topic")) | length == 1'

# 4. Subscribe to the "smoketest" topic.
SUBSCRIBE=$(cat <<'JSON'
{
  "type": "Subscribe",
  "object": {"type": "Topic", "tag": "smoketest"}
}
JSON
)
SUB_CID=$(curl -s -X POST "$BASE/activity" \
  -H "Authorization: Bearer $TOKEN" -d "$SUBSCRIBE" | jq -r '.cid')

# 5. Verify subscriptions projection has the new entry.
sleep 1
curl -s "$BASE/projections/subscriptions" \
  | jq -e '.["https://next.rose-ash.com/actors/next"] | map(select(.type == "Topic")) | length == 1'

# 6. Define a projection that records matched activities (per-application
#    namespace would happen via DefineApplication in v1.x; for v1 the
#    projection is global to the actor).
TOPIC_PROJ=$(cat <<'JSON'
{
  "type": "Create",
  "object": {
    "type": "DefineProjection",
    "name": "topic-events",
    "initial-state": "{}",
    "fold": "(fn (state act) (if (and (= (:type act) \"Note\") (member? \"smoketest\" (or (-> act :object :tags) (list)))) (assoc-in state [(:cid act)] act) state))"
  }
}
JSON
)
curl -s -X POST "$BASE/activity" \
  -H "Authorization: Bearer $TOKEN" -d "$TOPIC_PROJ" | jq -e '.cid'

# 7. Define a trigger: when a Topic{smoketest} subscription matches, publish
#    a TestEcho activity. We need an "Echo" activity type first.
ECHO_DEF=$(cat <<'JSON'
{
  "type": "Create",
  "object": {
    "type": "DefineActivity",
    "name": "TestEcho",
    "schema":    "(fn (act) (cid? (-> act :object :echoes)))",
    "semantics": "(fn (state act) state)"
  }
}
JSON
)
curl -s -X POST "$BASE/activity" \
  -H "Authorization: Bearer $TOKEN" -d "$ECHO_DEF" | jq -e '.cid'

TRIGGER=$(cat <<JSON
{
  "type": "Create",
  "object": {
    "type": "DefineTrigger",
    "name": "echo-on-smoketest",
    "when-subscription": "$SUB_CID",
    "cascade-limit": 1,
    "then": "(fn (act sub env) {:publish (list {:type \"TestEcho\" :object {:echoes (:cid act)}})})"
  }
}
JSON
)
curl -s -X POST "$BASE/activity" \
  -H "Authorization: Bearer $TOKEN" -d "$TRIGGER" | jq -e '.cid'

# 8. Capture outbox length so we can detect new entries.
BEFORE=$(curl -s "$BASE/actors/next/outbox?page=true" \
  | jq -r '.orderedItems | length')

# 9. Publish a Note tagged "smoketest" — should match subscription, fire trigger,
#    cause TestEcho to be published.
NOTE=$(cat <<'JSON'
{
  "type": "Create",
  "object": {
    "type": "Note",
    "content": "hello reactive world",
    "tags": ["smoketest"]
  }
}
JSON
)
NOTE_CID=$(curl -s -X POST "$BASE/activity" \
  -H "Authorization: Bearer $TOKEN" -d "$NOTE" | jq -r '.cid')

# 10. Wait for projection + trigger.
sleep 2

# 11. Verify topic-events projection captured the Note.
curl -s "$BASE/projections/topic-events" \
  | jq -e ". | to_entries | length == 1"

# 12. Verify outbox grew by exactly TWO activities (the Note + the trigger's TestEcho).
AFTER=$(curl -s "$BASE/actors/next/outbox?page=true" \
  | jq -r '.orderedItems | length')
[[ $((AFTER - BEFORE)) == 2 ]] || { echo "expected +2 activities, got $((AFTER - BEFORE))"; exit 1; }

# 13. Verify the latest activity is a TestEcho referencing the original Note's CID.
curl -s "$BASE/actors/next/outbox?page=true" \
  | jq -e ".orderedItems[0] | .type == \"TestEcho\" and .object.echoes == \"$NOTE_CID\""

# 14. Negative case: publish a Note WITHOUT the "smoketest" tag — must NOT
#     trigger, must NOT echo.
BEFORE2=$(curl -s "$BASE/actors/next/outbox?page=true" | jq -r '.orderedItems | length')
NOTE_OTHER=$(cat <<'JSON'
{"type": "Create", "object": {"type": "Note", "content": "no match", "tags": ["other"]}}
JSON
)
curl -s -X POST "$BASE/activity" \
  -H "Authorization: Bearer $TOKEN" -d "$NOTE_OTHER" | jq -e '.cid'
sleep 2
AFTER2=$(curl -s "$BASE/actors/next/outbox?page=true" | jq -r '.orderedItems | length')
[[ $((AFTER2 - BEFORE2)) == 1 ]] || { echo "expected +1 activity (no echo), got $((AFTER2 - BEFORE2))"; exit 1; }

# 15. Cascade limit check: prove the trigger doesn't recursively echo TestEcho.
#     The TestEcho activity itself should NOT match the Topic{smoketest}
#     subscription (it's not a Note), so no cascade, but verify cascade-depth
#     was set to 1 on the echo so a future trigger on TestEcho would refuse.
LATEST_ECHO=$(curl -s "$BASE/actors/next/outbox?page=true" \
  | jq -r '.orderedItems | map(select(.type == "TestEcho")) | .[0]')
echo "$LATEST_ECHO" | jq -e '."cascade-depth" == 1'

# 16. Restart kernel; verify subscription, trigger, projection all survive.
./next/scripts/stop.sh
./next/scripts/start.sh
sleep 2
curl -s "$BASE/projections/subscriptions" \
  | jq -e '.["https://next.rose-ash.com/actors/next"] | map(select(.type == "Topic")) | length == 1'
curl -s "$BASE/projections/topic-events" | jq -e ". | to_entries | length >= 1"
curl -s "$BASE/define-registry?kind=triggers" \
  | jq -e 'map(select(.name == "echo-on-smoketest")) | length == 1'

echo "✓ Reactive application smoke test passed — Subscribe + Trigger + Projection demonstrated end-to-end"
```

**What this proves (and what it doesn't):**

Proves:
- `DefineSubscription` + `Subscribe` mechanism works end-to-end.
- Subscription's `match-fn` evaluates correctly in pure mode against inbound
  activities.
- `DefineTrigger` fires on subscription matches.
- Trigger's `then-sx` can publish derived activities (the `:publish` result).
- Cascade-depth metadata propagates correctly.
- Subscription state, trigger registration, and projection state all survive
  kernel restart (snapshot + log replay).
- The full reactive application loop works without any kernel code changes
  between defining the components and exercising them.

Does NOT prove (deferred to milestone 2+):
- Cross-instance subscriptions (federation).
- Trigger `:effect` results calling effectful primitives.
- `DefineApplication` bundle install/update/fork.
- Per-application namespace isolation.
- Cascade prevention against malicious cascading from peer instances.

**Acceptance for 9b:** smoke test exits 0. Like 9a, **zero fed-sx kernel code
changes** between defining the application components and observing them
operate.

---

## Acceptance criteria for milestone 1

All of:

1. **Each step's test suite passes** (`bash next/tests/<step>.sh`).
2. **Both smoke tests pass** (`bash next/tests/smoke_pin.sh` and
   `bash next/tests/smoke_app.sh`).
3. **Erlang-on-SX baseline preserved** — adding fed-sx kernel modules in
   `next/kernel/*.erl` doesn't break Phase 1-8 conformance.
4. **Restart durability** — kill the kernel mid-write, restart, projections
   resume from snapshot, no log corruption.
5. **Manual Mastodon poke** — point a Mastodon account at
   `https://next.rose-ash.com/actors/next` and verify the actor doc fetches and
   webfinger discovery works (read-only AP interop, no follow).

## What lands when

This is the work-order an agent (or human) follows. Steps 1-3 can be done in
parallel after the Erlang Phase 8 BIFs land. Steps 4-7 are sequential. Step 8
can start in parallel with step 7. Step 9 is the integration test.

```
Phase 7+8 (loops/erlang) ───┐
                            │
                            ▼
              ┌─── Step 1 ──┬─── Step 2 ──┬─── Step 3
              │             │             │
              └─────────────┼─── Step 4 ──┴────┐
                            │                  │
                            └─── Step 5 ───────┤
                                              │
                                  Step 6 ─────┤
                                              │
                                  Step 7 ─────┤
                                              │
                                  Step 8 ─────┤
                                              │
                                  Step 9 ─────┘
```

Estimated effort if done by a focused agent loop, one feature per iteration:
~30-50 commits across all 9 steps. Could plausibly be a `loops/fed-sx` workstream
once Phase 7+8 are done.

## What's deferred to milestone 2

- **Federation** (the second-biggest piece). `POST /inbox`, Follow lifecycle,
  delivery queue, backfill, capability negotiation between peers. Whole of
  design §13.
- **Multi-actor** with per-user OAuth and capability tokens. Design §9.5.
- **IPFS storage backend** as a `DefineStorage` entry. Design §15.3.
- **Browser client + operator dashboard** (probably in Elm-on-SX or similar).
- **Rich verbs**: `Endorse`, `Supersede`, `Test`, `Build`, `Compose`, `Note`,
  `Announce`. All defined as `DefineActivity` artifacts, federated.
- **Cross-host conformance** — Python/JS/Haskell hosts running fed-sx. Design
  §11.8.
- **OpenTimestamps proofs** as a `DefineProof` entry.
- **Performance work** — JIT-compiled folds, snapshot acceleration, federation
  batching.

Milestone 2 unlocks "real federation between two fed-sx instances." Milestone 3
is the rose-ash port (blog, market, events, federation, account, orders) as
fed-sx applications.

---

## Appendix A: open questions for milestone 1

A few things still under-specified; resolve as work begins.

1. **HTTP server library.** Does the Phase 8 `http:listen/2` BIF wrap an
   existing OCaml HTTP server (the sx.rose-ash.com one) or something simpler?
   Implementation choice deferred to Phase 8.
2. **JSON-LD library.** AP wire format requires JSON-LD canonicalization for
   signature coverage. Either pull a library or write a minimal subset for the
   shapes we actually use. Probably the latter — our envelope is well-defined.
3. **Bearer token rotation.** v1 uses a single env-var token. Token rotation
   without restart needs registry-style mgmt; can wait.
4. **Snapshot rate limits.** Default in design is "every 1000 activities or
   60 seconds." Tunable per-projection later; v1 uses the default.
5. **Genesis bundle format.** Dag-cbor map per §12.2; concrete schema needs
   one round of refinement once we author the actual definitions in step 4.

---

## Progress log

Newest first. One line per sub-deliverable commit. Erlang conformance gate
(`bash lib/erlang/conformance.sh`) must remain 729/729 on every entry.

- **2026-05-28** — Step 8c-actors-doc: `http_server` extended with `match_prefix/2` — pure byte-level prefix matcher built on Erlang binary pattern matching (`<<B, _/binary>>`-style head/tail walk). Empty prefix returns `{ok, FullPath}`; non-match returns `nomatch`; exact match returns `{ok, <<>>}`. Wired into a new GET `/actors/{id}` clause that extracts the id suffix and returns it as the body of `actor_doc_response/1` (stub: `actor: <id>\n`). Empty id falls into 404. `/actors/{id}/outbox` deferred to a later step (needs segment splitting beyond prefix). `next/tests/http_actors.sh` 13/13. Erlang conformance 729/729.
- **2026-05-28** — Step 8c-cap: GET `/.well-known/sx-capabilities` route + `capabilities_body/0` + `capabilities_path/0` exposed for tests. Body is a small plain-text descriptor with `kernel: fed-sx-m1`, `version: 0.0.1`, `verbs: Create Update Delete` (hand-spelled as integer-segment binary; string-literal segments unusable in this port). `next/tests/http_capabilities.sh` 8/8 covers method+path matching, body content, the existing GET / regression-free. Step 8c split into cap (done) + actors / art / proj / post — the rest need path-prefix matching helpers since `{id}` and `{cid}` are dynamic. Erlang conformance 729/729.
- **2026-05-28** — Step 8b-route: `next/kernel/http_server.erl` — pure `route/1` request→response dispatch. Request shape `[{method, Bin}, {path, Bin}, ...]`; response `[{status, N}, {headers, []}, {body, Bin}]`. GET / returns 200 with hand-spelled "fed-sx kernel m1" body; everything else returns 404 with "not found" body. Method/path binaries spelled byte-by-byte (string-literal segments would truncate). Split former 8b into 8b-route (done) + 8b-start (needs dict↔proplist marshaling bridge in the BIF wrapper before the spawned `http:listen` call gets useful request fields). `next/tests/http_route.sh` 11/11. Erlang conformance 729/729.
- **2026-05-28** — Step 8a: `http:listen/2` BIF wrapper added to `lib/erlang/runtime.sx` (the briefing's single allowed scope exception). The BIF takes `(Port, Handler)`, validates Port is an integer and Handler is an Erlang fun (else `badarg`), then builds an SX-callable bridge lambda that marshals request dict↔Erlang term via `er-of-sx`/`er-to-sx` and calls `er-apply-fun` on the handler. Delegates to the native `http-listen` primitive (registered in `bin/sx_server.ml`, native-only). Tests verify registration + arg validation paths (the blocking listen loop itself is not exercised — production callers spawn an Erlang process to host the call). `next/tests/http_listen_bif.sh` 5/5; Erlang conformance preserved at 729/729 despite the runtime.sx edit. Step 8 broken into 8a–8d on the plan.
- **2026-05-28** — Step 7c: `outbox:publish` now broadcasts the signed activity to every projection process named in `Context`'s `:projections` entry — fired immediately after `log:append`, via `projection:async_fold`. Missing/nil/empty list is a no-op (preserves the Step 6d-publish contract). Stage halts (replay duplicate, sig failure) suppress the broadcast — projection state stays at zero while the activity is rejected. `next/tests/outbox_broadcast.sh` 14/14 covers single + multi projection fan-out, three-publish accumulation, replay-skip, sig-skip, and the projection receiving the post-sign Signed envelope (not the pre-sign skeleton). Erlang conformance 729/729.
- **2026-05-28** — Step 7b: `projection.erl` extended with gen_server callbacks + per-projection named-process API. `start_link/3(Name, InitialState, FoldFn)` spawns and registers under the supplied atom; `async_fold/2(Name, Activity)` casts a fold message; `query/1(Name)` synchronously returns the current state. Same port quirks as registry gen_server (Step 5b): raw Pid return, no `?MODULE` macro, processes don't survive between separate `erlang-eval-ast` calls — tests inline start_link with operations. Two named projections are independent. Snapshot persistence deferred to a later sub-step (needs SX-source eval + on-disk state). `next/tests/projection_server.sh` 11/11. Erlang conformance 729/729.
- **2026-05-28** — Step 7a: `next/kernel/projection.erl` — pure-functional projection driver. Record shape `[{name, _}, {state, _}, {fold, fun}]`; `fold_activity/2` advances state by one activity; `replay/2` folds a whole list (mirrors `log:entries/1` semantics); `new/2` defaults to the identity fold and `new/3` accepts a custom Erlang fun. Multiple projections share no state — independent record values. Step 7 split into 7a (done) + 7b (gen_server-per-projection) + 7c (broadcast hook from outbox) + 7d (sandbox eval, needs SX-source bridge). `next/tests/projection_pure.sh` 12/12. Erlang conformance 729/729.
- **2026-05-28** — Step 6d-publish: `outbox:publish/2(Request, Context)` orchestrates construct + sign + `pipeline:run_stages` + `log:append`. Stage list is `[stage_envelope, stage_signature(AS), stage_replay(LogState)]` — so a duplicate publish (same Request, same Published) halts at the replay stage and returns `{error, replay, LogState}` with the log unchanged; bad key material halts at `bad_signature`. Happy path returns `{ok, [{cid, Cid}, {activity, Signed}], NewLog}`. Projection-scheduler dispatch deferred to Step 7. `next/tests/outbox_publish.sh` 13/13 covers happy path, replay halt, sig halt, multi-publish progression, CID stability across fresh logs. Erlang conformance 729/729.
- **2026-05-28** — Step 6d-cs: `next/kernel/outbox.erl` — envelope construction + signing. `construct/4` takes `(Type, ActorId, Published, Object)`, builds the canonical key-sorted property list, and derives the activity `:id` from `cid:to_string({activity_envelope, Skeleton})`. `sign/2` extracts key_id/algorithm/key-material from a KeySpec proplist, computes the v1 HMAC over canonical bytes, and appends the `:signature` pair. `cid_of/1` is a convenience accessor. Round-trip end-to-end through `envelope:verify_signature/2` verified (correct key passes, wrong key returns bad_signature). Step 6d split into 6d-cs (done) + 6d-publish (orchestration). `next/tests/outbox_construct.sh` 13/13. Erlang conformance 729/729.
- **2026-05-28** — Step 6c-replay: `pipeline:stage_replay/2` (direct) + `stage_replay/1` (factory closed over LogState). Linear scan of `log:entries/1` checking for an existing entry with the same `:id`. Returns ok if new, `{error, replay}` on duplicate, `{error, no_id}` when the activity has no id field. Step 6c split into 6c-replay (done) + 6c-schema (deferred — blocked behind SX-source eval bridge for the activity-type :schema body). `next/tests/pipeline_replay.sh` 12/12 covers direct + factory + composition with stage_envelope. Erlang conformance 729/729.
- **2026-05-28** — Step 6b-sig: `pipeline:stage_signature/2` direct call + `stage_signature/1` factory returning a context-bound stage fun closed over ActorState. Not wired into the default `inbound_stages`/`outbound_stages` lists because actor state isn't a static-build-time value; callers prepend the factory result to a stage list (`Stages = [stage_envelope, pipeline:stage_signature(AS)]`). `next/tests/pipeline_signature.sh` 11/11 covers direct + factory + composition with stage_envelope (including halt ordering: bad envelope halts before sig; good envelope + bad sig surfaces sig error). Erlang conformance 729/729.
- **2026-05-28** — Step 6b-env: `pipeline:stage_envelope/1` wraps `envelope:validate_shape/1`; wired into both `inbound_stages` and `outbound_stages` lists. `validate_inbound`/`validate_outbound` now exercises the full envelope shape contract end-to-end (missing fields, signature sub-shape, non-list input). `next/tests/pipeline_envelope.sh` 12/12; `pipeline_driver.sh` refactored to test the driver against explicit stage lists rather than depending on the now-non-empty defaults. Split 6b in the plan into 6b-env (done) + 6b-sig (needs runtime context for actor-state). Erlang conformance 729/729.
- **2026-05-28** — Step 6a: `next/kernel/pipeline.erl` — validation pipeline driver per design §14. `run_stages/2` is a pure fold over `(Activity) -> ok | {error, R}` funs, halting on first failure. Halt verified by inserting a post-error stage that would set a contradictory tag if it ran. `validate_inbound/1` + `validate_outbound/1` wrappers; concrete stage lists are empty (6b wires `stage_envelope`/`stage_signature`). Port quirk: `Pattern = Var` match-alias syntax unsupported — split into separate `Result = X, case Result of ...`. `next/tests/pipeline_driver.sh` 10/10. Step 6 broken into 6a–6e on the plan. Erlang conformance 729/729.
- **2026-05-28** — Step 5b: `registry.erl` extended with gen_server callbacks + named-process API. `start_link/0` spawns the worker, registers it under the literal `registry` atom, returns the Pid (port returns raw Pid not `{ok, Pid}` — diverges from OTP). 3-arity `register`, 2-arity `lookup`, 1-arity `list` delegate to the pure /4 and /3 functions inside handle_call. Port note documented: `?MODULE` macro unsupported; tests must inline start_link with operations since spawned processes don't persist across separate `erlang-eval-ast` calls. `next/tests/registry_server.sh` 12/12. Erlang conformance 729/729.
- **2026-05-28** — Step 4e: `bootstrap:load_genesis/1` + `strip_sx_suffix/1` in `next/kernel/bootstrap.erl`. Walks `read_genesis` output and threads each entry through `registry:register/4`, using the section atom as the kind and the filename-minus-`.sx` as the entry name. Per-kind counts match the seven bootstrap sections exactly (3/10/7/3/3/2/3 = 31 entries total). `next/tests/bootstrap_load.sh` 15/15. Determinism verified by comparing `cid:to_string` of the loaded state across calls (faster than deep-equality on the nested-binary state). Step 4 is now complete end-to-end except for SX-source parsing of the loaded entries. Erlang conformance 729/729.
- **2026-05-28** — Step 5a: `next/kernel/registry.erl` — pure-functional registry. State is `[{Kind, [{Name, Entry}, ...]}, ...]` keyed by the same seven section atoms as Step 4c (activity_types, object_types, projections, validators, codecs, sig_suites, audience). API: `new/0`, `kinds/0`, `register/4`, `lookup/3`, `list/2`. Unknown kinds rejected with `{error, unknown_kind}`; missing names return `not_found`; re-registering the same name overrides without growing the list. `next/tests/registry_pure.sh` 14/14. Step 5 broken into 5a–5d on the plan. Erlang conformance 729/729.
- **2026-05-28** — Step 4d: `bootstrap:build_genesis/1` + `verify_genesis/2` + `.cidhash` helpers in `next/kernel/bootstrap.erl`. Bundle CID delegated to host `cid:to_string` over `{genesis_bundle, Sections}` — deterministic, ~59 byte CIDv1 binary. `verify_genesis/2` returns `ok` on match, `{error, {cid_mismatch, Got, Expected}}` on drift. `write_cidhash`/`read_cidhash` persist the CID to a `.cidhash` sibling file (path hand-spelled `<<...,47,46,99,...>>` per the string-literal-in-binary substrate quirk). `next/tests/bootstrap_build.sh` 12/12. Erlang conformance 729/729.
- **2026-05-27** — Step 4c: `next/kernel/bootstrap.erl` — Erlang module that enumerates the genesis bundle by walking seven hardcoded section subdirs via `file:list_dir/1`, filters `.sx` files via byte-pattern suffix match (`ends_with_sx/1`), reads each into a binary via `file:read_file/1`. Returns `{ok, [{Section, [{Name, Bytes}, ...]}]}`. Hits the same SX-parser substrate gap as Step 3b — kept the surface byte-only; parsing happens via SX-side helpers in later steps. Port gotchas: `fun name/arity` references unsupported (use anonymous fun wrappers); `<<"...">>` string-literal segments truncate to one byte (paths hand-spelled as integer-segment binaries). `next/tests/bootstrap_read.sh` 15/15. Erlang conformance 729/729.
- **2026-05-27** — Step 4b-cod: bootstrap codecs + sig-suites + audience predicates complete. 3 `DefineCodec` files (dag-cbor + raw + dag-json, dag-cbor + dag-json deferring to host-codec primitive when wired), 2 `DefineSigSuite` files (rsa-sha256-2018 PEM-keyed, ed25519-2020 multibase-keyed, both :verify returning false as m2-deferred stand-in), 3 `DefineAudience` files (Public/Followers/Direct member-of predicates per design §16). Manifest now lists 26 bootstrap files across all eight sections; `next/tests/genesis_parse.sh` 50/50. Step 4b complete; remaining Step 4 is bundler code (4c–4e). Erlang conformance 729/729.
- **2026-05-27** — Step 4b-vld: bootstrap validators complete — 3 `DefineValidator` SX files (envelope-shape mirroring Step 2a, signature stub delegating to envelope:verify_signature/2 per design §9.6, type-schema looking up the object-type schema from define-registry). Manifest `:validators` populated; `next/tests/genesis_parse.sh` 36/36. Erlang conformance 729/729.
- **2026-05-27** — Step 4b-proj: bootstrap projections complete — 7 `DefineProjection` SX files authored (activity-log identity, by-type/by-actor/by-object indexes, actor-state with key history fold, define-registry meta-fold over Create{Define*}, audience-graph stub). Manifest `:projections` populated; `next/tests/genesis_parse.sh` 31/31. Erlang conformance 729/729.
- **2026-05-27** — Step 4b-obj: bootstrap object-types complete — 10 `DefineObject` SX files authored (SXArtifact, Note, Tombstone, DefineActivity, DefineObject, DefineProjection, DefineValidator, DefineCodec, DefineSigSuite, Snapshot). Each carries an SX `:schema` predicate. Manifest `:object-types` populated; `next/tests/genesis_parse.sh` 22/22. Erlang conformance 729/729.
- **2026-05-27** — Step 4b-act: bootstrap activity-types complete — `update.sx` (Update verb, requires :object CID + :patch) + `delete.sx` (Delete verb, requires :object CID) authored as DefineActivity forms matching the Create shape. Manifest updated; `next/tests/genesis_parse.sh` 10/10. Step 4b broken into act/obj/proj/vld/cod sub-deliverables on the plan. Erlang conformance 729/729.
- **2026-05-27** — Step 4a: genesis bundle seeded. `next/genesis/manifest.sx` (GenesisManifest with eight section keys, only `:activity-types` populated for now) + `next/genesis/activity-types/create.sx` (DefineActivity{Create} with :schema/:semantics SX bodies). `next/tests/genesis_parse.sh` 5/5. Step 3b parked behind a substrate-level term-codec gap — Blockers note added under Step 3; in-memory log from 3a unblocks Step 5+ which only need the API surface. Erlang conformance 729/729.
- **2026-05-27** — Step 3a: `log:open/2 append/2 tip/1 replay/3 entries/1` over an in-memory state (per-actor seq, replay in append order, round-trip activities). `next/tests/log_memory.sh` 12/12. Pivoted from on-disk in this iteration: this port's `atom_to_list`/`integer_to_list` return SX strings rather than Erlang charlists, `binary_to_list` is unregistered, and `$X` char literals decode to nil — so a term codec needs a workaround. Captured as the Step 3b risk note in the plan. Erlang conformance 729/729.
- **2026-05-26** — Step 2c: `envelope:verify_signature/2` — time-aware key lookup over `public_keys` (created ≤ published < superseded_at), MAC recompute via `crypto:hash(sha256, KeyMaterial ++ canonical_bytes)`, compared against `signature.value`. Returns ok or one of `no_signature | no_key_id | no_published | no_keys | no_active_key | bad_signature`. `next/tests/envelope_sig.sh` 11/11 pass. Erlang conformance 729/729.
- **2026-05-26** — Step 2b: `envelope:canonical_bytes/1` — strip signature, insertion-sort property list by key, return host-CID-string as deterministic byte form (dag-cbor stand-in). `next/tests/envelope_canonical.sh` 8/8 pass. Erlang conformance 729/729 preserved.
- **2026-05-26** — Step 2a: `next/kernel/envelope.erl` `validate_shape/1` + `get_field/2` over property-list envelopes (Erlang `#{}` maps not supported in this port). `next/tests/envelope_shape.sh` 15/15 pass. Erlang conformance 729/729 preserved.
- **2026-05-26** — Step 1b: `next/kernel/nx_cid.erl` (from_sx/to_string/from_string/equals) — thin Erlang wrapper around the `cid:to_string/1` BIF. `next/tests/cid.sh` 13/13 pass. Module named `nx_cid` to avoid shadowing the `cid` BIF (user-module dispatch takes precedence over BIFs by module name). Erlang conformance 729/729 preserved.
- **2026-05-26** — Step 1a: `next/` skeleton created (kernel/, genesis/, tests/, data/), README, `.gitignore data/`. Erlang conformance 729/729 preserved.