Federated relay tier: peer flooding, per-member isolation, registry admission and relay discovery

AGENTS.md

@@ -3,7 +3,7 @@
 ## Repo shape
 - `rfc.txt` (FRX — Federated Retrieval Exchange, Draft 0.5) is the normative spec; `src/` is the Phase 1 `frxd` implementation (single crate, two binaries).
 - `frxd` is the member node (init/add/index/serve/relay/query/status); `frx` is the thin client (search/query/status). Relay and node roles are separate subcommands.
-- Commands: `cargo build`, `cargo test` (80 tests: unit in `src/`; e2e `tests/phase1.rs`; conformance `tests/conformance.rs`; aggregates + member directory `tests/aggregates.rs`; registry `tests/registry.rs`; concurrency/restart `tests/concurrency.rs`; real subprocess CLI `tests/cli.rs`; 1000-doc `tests/scale.rs`; purge-log absence `tests/purges.rs`; shared fixtures `tests/common/mod.rs`). No CI/lint config.
+- Commands: `cargo build`, `cargo test` (85 tests: unit in `src/`; e2e `tests/phase1.rs`; conformance `tests/conformance.rs`; aggregates + member directory `tests/aggregates.rs`; registry `tests/registry.rs`; federation/isolation/admission `tests/federation.rs`; concurrency/restart `tests/concurrency.rs`; real subprocess CLI `tests/cli.rs`; 1000-doc `tests/scale.rs`; purge-log absence `tests/purges.rs`; shared fixtures `tests/common/mod.rs`). No CI/lint config.
 - E2E pattern: relay + nodes in-process on ephemeral ports with tempdir corpora; use `tests/common/mod.rs` helpers (`spawn_relay*`, `query_envelope`, `poll_messages`, `register`) for new coverage. Raw relay polls return envelopes (payload under `body`), not response bodies.
 
 ## Editing the spec
@@ -21,7 +21,7 @@
 - Relay addresses transport mailboxes by `key` (unicast `to` = recipient pubkey; queues keyed by pubkey); the identifier is protocol identity only. Registry binding checks `map[key].id == from`.
 - Built: envelope/query/response, Tantivy index, aggregates, member directory. Not built: dashboard UI, directory watching, TLS, lineage/delegation. Responses travel relay-mediated unicast; transport is HTTP long-poll, not SSE.
 - Economics is out of protocol scope (I4: aggregates advise, contracts govern): no receipt, citation, pricing, or settlement fields or message types exist or may be added.
-- Relay verifies signatures and ±300s timestamp skew, carries only `query` broadcasts, holds no history (queue drained on poll), and returns 429 + Retry-After under backpressure — never silent drops. Mailbox polls require proof of key possession: `GET /v1/challenge` then a signed single-use nonce, so knowing a pubkey is not enough to drain its queue.
+- Relay verifies signatures and ±300s timestamp skew, carries only `query` broadcasts, holds no history (queues drained on poll), and requires challenge–response proof of key possession for mailbox polls. Per-member queues are isolated: a lagging member gets 429 + Retry-After with a `missed` count; publishers and other members are never stalled. Relays MAY flood to configured peers (`/v1/federation`, `--peer`+`--url`, hop-bounded, seen-set dedup without suppressing identical direct publishes) and MAY gate senders against a registry (`--registry`+`--ma-key`).
 - Responder searches only collections marked shared (I9), stays silent when nothing matches, and emits results with honest `truncated`/`more_available` and no scores (I6). BM25 order is a local implementation detail, not protocol surface.
 - Index layout: Tantivy at `<data_dir>/index`, collections manifest at `<data_dir>/collections.toml`; `exposure` (metadata|full) gates whether `content` is returned.
 - Egress checks live in the responder path (`src/node.rs` `respond`), not the relay — keep private collections unreachable there.
@@ -30,11 +30,11 @@
 - Relay backpressure is global: any member's full queue 429s every publisher until drained (visible per §3, but one lagging member can stall the firehose — revisit before scale).
 - Member authority (Draft 0.5 §6): the MA-signed registry snapshot is authoritative when configured (`[node] registry` = file path or URL, `ma_key` pinned; monotonic version — rollback and forgery close the node; file path is mtime-reloaded, URL is fetched at start + every 60s and cached to `<data_dir>/registry-cache.json`, so outage fails static). Keys carry optional validity windows (`not_before`/`not_after`); rotation = `registry add-key` then `revoke-key`.
 - `<data_dir>/members.toml` (name, pubkey, class, `previous` keys, mtime-reloaded) is a dev/local fallback used only when no registry is configured; empty directory without a registry is open bootstrap only when `dev_bootstrap = true` (RFC §6: explicit dev flag). Receivers drop content-bearing responses from enrichment-class senders (metadata-only, §6).
-- MA tooling: `frxd registry init|add|add-key|revoke-key|remove|list|show|serve` (signed `registry.json` + `ma-key.hex` in `--dir`); `frxd init --id/--registry/--ma-key`; `frxd key show|rotate`; `member add --previous <old>` for the fallback path.
+- MA tooling: `frxd registry init|add|add-key|revoke-key|remove|list|set-relays|show|serve` (signed `registry.json` + `ma-key.hex` in `--dir`); `frxd init --id/--registry/--ma-key`; `frxd key show|rotate`; `member add --previous <old>` for the fallback path. A node with no `[node] relays` discovers them from the registry snapshot (`doc.relays`).
 - Aggregate semantics are our implementation choices from a terse spec: requests are `aggregate` envelopes carrying only `period`; replies carry `sent` (broadcasts that month) / `passed` (responses consumed from that member); granularity floor is enforced as YYYY or YYYY-MM only (finer rejected), yearly rolls up months. Revisit with §10 sufficiency review.
 
 ## Known gaps (Phase 2/3, intentional — don't fake them)
-- No dashboard UI, no directory watching (new files need `reindex`), no TLS, no user-supplied URL ingestion, no node-side (bilateral) rate limiting.
+- No dashboard UI, no directory watching (new files need `reindex`), no TLS, no user-supplied URL ingestion, no node-side (bilateral) rate limiting, no SSE streaming (long-poll only), no unicast confidentiality (HPKE).
 - Receipts/settlement are out of protocol scope, not unimplemented (I4; Appendix B row 2). Lineage and delegation remain §10 open issues — unspecified without a supply stream, so not buildable as written; don't invent them silently.
 - Node query dedup is by `qid` only; replay inside the ±300s skew window remains possible (no nonce cache at nodes), relays have no directory/admission, and there is no end-to-end encryption — relays see everything in clear.