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+# Session handoff — 2026-06-02 (56)
+
+Fifty-sixth handover, same day as #54/#55. **Clears the pre-existing
+YAML security debt flagged in handoff-55 §3:** migrated off the
+unsound + unmaintained `serde_yml` / `libyml` to the maintained
+**`serde_norway`**. Clean dependency swap — no API friction, no
+behaviour change, full suite unchanged.
+
+## §1. State at handoff
+
+**Branch:** `main`. Builds on handoff-55's two commits (`d0c8f9d` #11,
+`c9a92c9` handoff-55). This session adds the migration commit + this
+handoff on top. **Tests: 2151 passing / 0 failing / 1 ignored**
+(identical to post-#11 — the migration changed no behaviour). **Clippy
+clean** (nursery, all targets, `-D warnings`). Push is the user's step.
+
+GitHub **#11 is closed** (done this session, after the #55 work).
+Per the user: this repo's GitHub issues are dev-phase bug tracking
+only (the repo will move elsewhere), so follow-on tasks like this
+migration are tracked **in handoffs, not issues**.
+
+## §2. The migration — `serde_yml` → `serde_norway`
+
+**Why.** Handoff-55 §3 flagged two RustSec advisories, both dated
+2025-09-11, both `informational = "unsound"` (not exploitable-CVE
+class — hence cargo audit's exit-0 "allowed warnings"):
+
+- **RUSTSEC-2025-0068** — `serde_yml` 0.0.12: `Serializer.emitter` can
+  segfault; project archived; **no patched version**.
+- **RUSTSEC-2025-0067** — its `libyml` 0.0.5 backend:
+  `yaml_string_extend` has UB; project archived; **no patched
+  version**.
+
+`serde_yml` was a fork of the deprecated `serde_yaml` that then got
+flagged + archived itself. The only remedy RustSec offers is switching
+crates. `serde_norway` (0.9.42, MIT OR Apache-2.0, MSRV 1.71.1) is the
+maintained `serde_yaml` fork (repo `cafkafk/serde-yaml`), backed by the
+maintained `unsafe-libyaml-norway`.
+
+**Threat that motivated it.** Input is normally the project's own
+`project.yaml` / undo index / embedded catalog, but **`import <zip>`
+and shared/exported projects** carry externally-authored YAML — a
+crafted `project.yaml` could trigger the segfault (crash/DoS) or UB.
+
+**What changed (mechanical — `serde_norway` is API-compatible with
+`serde_yaml`/`serde_yml` for everything we use):**
+- `Cargo.toml` — `serde_yml = "0.0.12"` → `serde_norway = "0.9.42"`
+  (with a comment recording the two RUSTSEC IDs).
+- `src/persistence/yaml.rs` — `from_str` (project + raw-project read);
+  doc comments updated to name the new crate.
+- `src/persistence/migrations.rs` — `from_str` (version probe).
+- `src/undo.rs` — `from_str` / `to_string` (snapshot index round-trip).
+- `src/friendly/format.rs` — `Value` / `Value::{Mapping,String,Null}`
+  (embedded `en-US.yaml` catalog parse).
+
+No function signatures, call shapes, or `Value` pattern matches needed
+adjustment — a straight identifier swap (`serde_yml::` →
+`serde_norway::`).
+
+**Verification:**
+- `cargo build --all-targets` — clean (drop-in confirmed).
+- Full `cargo test` — **2151 / 0 / 1**, unchanged from post-#11; the
+  existing `project.yaml` round-trip + persistence + undo-index +
+  catalog-format suites are the safety net and all stayed green.
+- `clippy` nursery `-D warnings` — clean.
+- **Advisories cleared, three scanners agree:** `cargo audit` (294
+  crates) → no advisories; `osv-scanner` → No issues found; `grype` →
+  no findings. `cargo tree -i serde_yml` / `-i libyml` → both **gone**
+  from the tree; `serde_norway` present. `serde_norway` introduces no
+  advisory of its own.
+
+## §3. What's open
+
+- The two arboard decisions from handoff-55 §3 remain
+  open-for-correction (no-Wayland-feature; verbatim-copy-with-tags).
+- Other tracks unchanged from handoff-55 §5 (Track 2 Iter 6 leftovers;
+  C3a/C4; H1 friendly errors; tutorial system; V4 session-log/Markdown
+  export; I1/I1b/I3/I4 input UX). **The serde_yml security debt is now
+  resolved** — strike it from the list.
+
+## §4. How to take over
+
+1. Read handoff-55 first (the #11 / clipboard / ADR-0041 work), then
+   this note, then `CLAUDE.md` / `requirements.md` / `docs/adr/README.md`.
+2. The codebase is on `main`; this migration commit + handoff sit on
+   top of the handoff-55 commits, all unpushed (the user's step).
+3. No ADR was written for the migration — it's a like-for-like
+   dependency swap with no design decision, tracked here per the
+   handoff-not-issue convention. If the project later wants a written
+   record of the dependency rationale, this handoff §2 is it.