docs(deps): triage report for held bincode/rand/hkdf bumps

docs/README.md

@@ -62,11 +62,12 @@ Every entry below carries one of:
 **Plans**
 
 - [Iroh migration](plans/2026-03-29-iroh-migration.md) — migrates networking layer from libp2p to iroh with `IrohNetwork` and `MemNetwork`. `[landed]`
-- [Relay upgrade bundle](plans/2026-05-28-relay-upgrade-bundle.md) — six sequential PRs realizing the capability-doc, heads-based sync, history-sync EOSE, and pkarr-discovery specs. `[active]`
+- [Relay upgrade bundle](plans/2026-05-28-relay-upgrade-bundle.md) — six sequential PRs realizing the capability-doc, heads-based sync, history-sync EOSE, and pkarr-discovery specs. Landed as #664. `[landed]`
 
 **Reports**
 
 - [Heads-sync owner-serve gate + gossip EOSE emission](reports/2026-05-30-heads-sync-owner-serve-and-eose-emission.md) — two PR4/PR5 E2E regressions root-caused: the serving gate excluded the owner (now honors the owner/admins' implicit `SyncProvider`), and the EOSE marker was worker-only and unobservable by gossip clients (now also emitted by the `SyncRequestV2` responder). `[landed]`
+- [Dependency-bump triage](reports/2026-06-03-dependency-bump-triage.md) — bincode 3 / rand 0.10 / hkdf 0.13 all correctly held: bincode is the canonical signed+hashed event encoding (format break), hkdf 0.13 needs pre-release `sha2` 0.11, rand 0.10 collides with `rand_core` 0.6 pinned by `x25519-dalek` 2 + `chacha20poly1305` 0.10. `[landed]`
 
 ### Identity, Crypto & Trust
 

docs/reports/2026-06-03-dependency-bump-triage.md

@@ -0,0 +1,111 @@
+# Dependency-bump triage — bincode 3, rand 0.10, hkdf 0.13
+
+**Date:** 2026-06-03
+**Status:** landed
+**PRs:** #559 (bincode), #558 (rand), #555 (hkdf), #404 (feedback feature — flagged, not a bump)
+
+## Summary
+
+Three open Dependabot major-version bumps were evaluated for merge against
+current `main`. **All three are correctly held, not merged** — each is blocked
+by a hard constraint, not a fixable lint:
+
+| PR | Bump | Verdict | Blocker |
+|----|------|---------|---------|
+| #559 | bincode 1.3 → 3.0 | **Hold (pin 1.x)** | Canonical signed+hashed event encoding — format break invalidates the DAG |
+| #555 | hkdf 0.12 → 0.13 | **Hold** | Needs `sha2` 0.11, which only exists as `0.11.0-rc.5` (pre-release) |
+| #558 | rand 0.8 → 0.10 | **Hold** | `willow-crypto` is pinned to `rand_core` 0.6 by `x25519-dalek` 2 + `chacha20poly1305` 0.10 |
+
+A fourth red PR, **#404**, is *not* a dependency bump — it is a full feature
+crate (`crates/feedback/`, ~20 files). It is triaged separately at the bottom.
+
+All three Dependabot branches were 200–250 commits behind `main`, so their CI
+red was partly stale. Each bump was re-applied to current `main` and built
+locally to get an accurate verdict; the blockers below reproduce on today's tree.
+
+## #559 — bincode 1.3 → 3.0: format-stability boundary
+
+bincode's byte encoding is **the canonical representation of a signed event**,
+not an interchangeable serializer:
+
+- `crates/state/src/event.rs:600-602` — `bincode::serialize(&signable)` produces
+  the bytes that are SHA-256'd into the `EventHash` *and* Ed25519-signed. The
+  `EventHash` **is** the event's identity (`event.rs:547`).
+- `crates/state/src/event.rs:520-535` — `EventKind::discriminant()` depends on
+  bincode 1.x encoding an enum variant index as a fixed-width little-endian
+  `u32`. A sync test (`discriminant_matches_bincode_variant_index_low_byte`)
+  pins this.
+- `crates/transport/src/lib.rs:159,182` — bincode is the wire framing.
+- bincode is also the on-disk encoding for persisted state (storage crate).
+
+bincode 2/3 changes the default encoding (fixed-int → varint, endianness) **and**
+removes the free `serialize`/`deserialize` functions (now `bincode::serde::*`
+with an explicit config). The encoding change alone re-hashes every event:
+existing `EventHash`es no longer match, old signatures no longer verify, the
+per-author DAG chain (`prev`/`deps` by hash) breaks, persisted state is
+unreadable, and peers on different bincode majors cannot interoperate.
+
+Moving to bincode 2/3 is therefore a deliberate **protocol-version migration**
+(canonical-encoding decision + format-version field + migration path), not a
+Dependabot auto-bump. **Decision: pin bincode 1.x.** Revisit only behind a
+spec'd protocol-version change.
+
+## #555 — hkdf 0.12 → 0.13: blocked on pre-release RustCrypto
+
+`willow-crypto` sits on one coherent RustCrypto generation: `sha2` 0.10 +
+`hkdf` 0.12 + `hmac` 0.12 (all `digest` 0.10), alongside `chacha20poly1305` 0.10
+and `x25519-dalek` 2.
+
+hkdf 0.13 pulls `hmac` 0.13 / `digest` 0.11, so `Hkdf::<Sha256>` then needs a
+`digest` 0.11 hash. The CI errors (`CoreProxy` / `HashMarker` / `FixedOutput`
+not satisfied for `Sha256VarCore`) are exactly that mismatch. The fix would be
+`sha2` 0.11 — but the registry only offers `0.11.0-rc.5`; stable is `0.10.9`.
+Pulling a pre-release hash crate into a security-critical path is not acceptable.
+
+**Decision: hold until the RustCrypto `digest` 0.11 generation ships stable**
+(`sha2`/`hmac`/`hkdf` move together).
+
+## #558 — rand 0.8 → 0.10: blocked on rand_core generation split
+
+The tree already carries `rand` 0.8.5, 0.9.4, and 0.10.1 — `willow-identity`
+and `willow-worker` are on 0.9 cleanly. The bump's problem is `willow-crypto`
+(and the bundled `willow-agent`), which use `rand` 0.8.
+
+`willow-crypto`'s `OsRng` must satisfy `rand_core` 0.6 to feed `x25519-dalek` 2
+(`StaticSecret`/`EphemeralSecret`) and `chacha20poly1305` 0.10. Bumping crypto
+to rand 0.10 moves it to `rand_core` 0.10; rustc then can't find a `RngCore`
+impl those crates accept (the compiler even suggests
+`chacha20poly1305::aead::rand_core::RngCore`). crypto cannot leave `rand_core`
+0.6 until `x25519-dalek` and `chacha20poly1305` publish stable next-gen
+releases on `rand_core` 0.9+.
+
+**Decision: hold.** (A narrower bump of only `willow-agent`'s non-crypto RNG to
+0.9 is possible but is a different change than this PR, which bundles crypto.)
+
+## Tradeoffs / alternatives considered
+
+- **Force the bumps with pinned pre-release crates** (`sha2 0.11.0-rc.5`,
+  `rand_core` shims). Rejected: pre-release crypto in a P2P security app; and a
+  rand_core shim cannot bridge `x25519-dalek` 2's trait bounds.
+- **bincode 2/3 with `bincode::serde` + `legacy()` config** to preserve the 1.x
+  encoding. Plausible *future* path, but still an API migration touching every
+  call site and a risk to the canonical hash; out of scope for an auto-bump.
+- **Leave the PRs open, red.** Rejected: they sit red indefinitely and re-churn
+  on every Dependabot run. Closing with rationale is cleaner — Dependabot
+  re-opens automatically when a compatible version appears.
+
+## #404 — in-app feedback (NOT a dependency bump)
+
+#404 adds a full `crates/feedback/` worker crate plus worker-actor wiring and a
+spec/plan. Its red check is a `mio`-in-wasm build error (`crate::sys::*`
+unresolved on `wasm32`), most likely stale-base noise — but it is a substantial
+unrelated feature from a separate session, not a bump. It needs its own review
+and a current-base CI run before any merge decision. Triaged out of this pass.
+
+## Outcome
+
+Merged this pass (green, low-risk): #664 (relay upgrade bundle), #557 (iroh
+0.98.2), #556 (rmcp 1.6), #666 (taiki-e/install-action 2.80).
+
+Held with rationale (this report + per-PR comment): #559, #558, #555.
+Deferred for separate review: #404.