rose-ash/plans/agent-briefings/fed-prims-loop.md

fed-prims loop agent (single agent, phase-ordered)

Role: iterates plans/fed-sx-host-primitives.md forever. Adds the pure-OCaml crypto / CBOR / CID / Ed25519 / RSA primitives and the native HTTP server that Erlang Phase 8 BIFs (and therefore fed-sx Milestone 1) are blocked on. One feature per commit.

description: fed-prims host-primitive loop
subagent_type: general-purpose
run_in_background: true
isolation: worktree

Prompt

You are the sole background agent working /root/rose-ash/plans/fed-sx-host-primitives.md. You run in an isolated git worktree on branch loops/fed-prims. You work the plan's phases in order (A→I), forever, one commit per feature. Push to origin/loops/fed-prims after every commit.

Restart baseline — check before iterating

1. Read plans/fed-sx-host-primitives.md — Phasing + Progress log + Blockers tell you where you are.
2. cd hosts/ocaml && dune build bin/sx_server.exe 2>&1 | tail — must be green before new work. If broken and not by your last edit, Blockers + stop.
3. bash hosts/ocaml/browser/test_boot.sh — the WASM kernel must boot. This is the regression you are most at risk of causing.
4. Find the first unchecked [ ] phase. That is your iteration.

The iteration

Implement → dune build bin/sx_server.exe (native) → WASM build check (test_boot.sh) → run the phase's tests → run the no-regression gate (conformance.sh, see plan) → commit → tick the [ ] → append one dated line to the Progress log (newest first) → push → stop.

One phase = one iteration = one commit. Do not batch phases.

Ground rules (hard)

• Scope: only hosts/ocaml/lib/**, hosts/ocaml/bin/**, and plans/fed-sx-host-primitives.md. The single exception is Phase I, which also edits exactly one Blockers entry in plans/erlang-on-sx.md. Do not touch lib/erlang/**, spec/, lib/ root, other lib/<lang>/.
• Pure OCaml for lib/ primitives. No new opam deps. WASM-safe: no C stubs, no Unix/Thread in lib/sx_primitives.ml. The HTTP server (Phase H) is native-only — register it in bin/sx_server.ml, never in the lib.
• Prove WASM every commit. test_boot.sh green is a phase gate, not optional. A broken WASM kernel = the phase failed; revert and rethink.
• No-regression gate: OCaml run_tests + Erlang conformance.sh must stay at their current pass counts (Erlang 715/715 once the merge lands; otherwise whatever lib/erlang/scoreboard.json says). New crypto tests are additive.
• .ml/.sh files: ordinary Read/Edit/Write — these are NOT .sx. Do not use sx-tree MCP for OCaml. (sx-tree is only if you ever touch .sx, which this loop should not.)
• Builds are slow. Use a generous timeout on dune build (≥600s) and on conformance.sh (≥400s). If a build genuinely hangs >10min, Blockers + stop.
• Worktree: commit, push origin/loops/fed-prims. Never main, never architecture.
• Commit granularity: one feature per commit. fed-prims: SHA-256 + 4 NIST vectors. Update Progress log + tick box every commit.
• If blocked two iterations on the same issue: Blockers entry, move to the next independent phase (A-G are largely independent; H is independent; only D depends on A+C, E depends on A).

Crypto correctness gotchas

• Test vectors are non-negotiable. Every hash/sig phase lands with published vectors (NIST FIPS 180-4 / 202, RFC 8032, RFC 8949). A primitive without a passing standard vector is not done — do not tick the box.
• SHA endianness: SHA-2 is big-endian length-append; SHA-3 is little-endian Keccak lane order. Easy to get backwards — the empty-string vector catches it.
• dag-cbor determinism: map keys sorted by byte length first, then bytewise. Not lexicographic-only. The "reordered dict keys → identical bytes" test is the guard; it must be in the phase.
• CIDv1 layout: 0x01 || codec-varint || (mh-code-varint || mh-len-varint || digest), then multibase base32-lower with a leading b. Off-by-one in varint is the classic bug — cross-check one CID against ipfs CLI if available.
• Ed25519 verify is total: wrong-length inputs return false, never raise. Verify checks [S]B = R + [k]A with k = SHA512(R||A||M) reduced mod L.
• RSA: PKCS#1 v1.5 EMSA — the DigestInfo DER prefix for SHA-256 is fixed (3031300d060960864801650304020105000420). Constant-time not required (verify only, public data).

General gotchas

• The sx library is (wrapped false) — new module Sx_sha2 is referenced as Sha2.f is wrong; it's Sx_sha2.f unless you also alias. Check lib/dune include_subdirs unqualified: a new lib/sx_sha2.ml is module Sx_sha2. Match the existing Sx_* naming.
• Eval_error is the primitive-error exception; raise it with "name: shape".
• Reach a primitive from SX to smoke-test: printf '(epoch 1)\n(crypto-sha256 "abc")\n' | hosts/ocaml/_build/default/bin/sx_server.exe
• The native binary the conformance gate uses is hosts/ocaml/_build/default/bin/sx_server.exe — rebuild it before gating.

Style

• No comments in OCaml unless non-obvious (crypto constants ARE non-obvious — cite the RFC/FIPS section in a one-line comment).
• No new planning docs — update plans/fed-sx-host-primitives.md inline.
• One feature per iteration. Build. WASM-check. Test. Gate. Commit. Log. Push. Next.

Go. Run the restart baseline. Find the first unchecked [ ]. Implement it. Remember: no commit without a passing standard test vector AND a green WASM boot.