How do I install the Working On D2r skill?

Run npx skillmds@latest add joshsymonds/working-on-d2r in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Working On D2r safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Working On D2r?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Working On D2r free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Working On D2r?

joshsymonds (@joshsymonds) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Working On D2r by joshsymonds — Agent Skill

Name: Working On D2r
Author: joshsymonds

Working On D2r

D2R save file parser development for Savecraft. Use when working on files in plugins/d2r/, including d2s binary parsing, item decoding, skill trees, attribute parsing, or shared stash. Triggers on D2R plugin code, d2s format, Huffman decoding, item properties, treasure classes, or Reign of the Warlock.

joshsymonds 5b8361a 3.3 KB Updated Sep 17, 2026

File contents

Working on the D2R Parser

The parser lives in plugins/d2r/d2s/. It's a WASM plugin that reads .d2s binary save files and emits ndjson to stdout. See docs/plugins.md for the plugin contract and working-on-plugins skill for section design guidance.

Verification

cd plugins/d2r && just test      # D2R-specific tests
just test-go                      # Full Go test suite
just lint-go                      # Includes D2R with relaxed lint rules

D2R v105 (Reign of the Warlock) Specifics

This parser targets v105 only (version byte 0x69). Classic LoD saves are not supported.

Expansion detection: v105+ saves do NOT set the LoD status bit (0x20) in the header. You must check header.Realm >= RealmLoD to gate mercenary and golem parsing. This is a common trap — the LoD bit check works for older saves but silently misparses v105.

Warlock class: Class index 7. Skill offset is 373 (not 281 — those are monster skills). Skills.txt extracted via CASC.

Item codes: Huffman-encoded in D2R (not ASCII like LoD). The Huffman tree is in d2s/huffman.go.

ISC (ItemStatCost): RotW ISC is IDENTICAL to vanilla D2R — zero property bit width changes. RotW added properties 365 (sB=6) and 366 (sB=8), plus items not in vanilla tables.

Lint Exceptions

golangci-lint config has exclusions for plugins/d2r/:

govet/shadow (binary parsing has lots of shadowed err)
globals (lookup tables are package-level)
complexity (binary parsing functions are inherently complex)
magic numbers (byte offsets, bit widths)

These exclusions are intentional. Don't try to "fix" them.

Test Data

Primary test save: reference/Diablo II Resurrected/Atmus.d2s — Level 74 Warlock, 45 items + 3 merc items.
Reference implementation: reference/olegbl-d2rmm/.../d2s/d2/items.ts — readItem() function.

CASC Data

Game data tables are extracted from the D2R CASC archive:

Archive: reference/d2r-casc/ (gitignored, must copy locally)
Extracted tables: reference/d2r-rotw-excel/ (gitignored — Blizzard IP, NEVER check in)
Extract tool: plugins/d2r/tools/casc-extract/ (uses CascLib, cloned at build time)
Plugin devenv.nix adds cmake/gcc/zlib for building the extract tool

cd plugins/d2r
just build-casc-extract
just casc-extract "data/global/excel/Skills.txt"

Shared Stash

.d2i files (e.g. ModernSharedStashSoftCoreV2.d2i) — multi-section format with 64-byte headers per tab, same item format as d2s. Not yet implemented.

Architecture

One plugin per game. The plugin detects save version internally. Only v105 for now.

plugins/d2r/
├── d2s/           # Parser source (header, attributes, skills, items, merc, corpse, golem)
├── parser/        # WASM entrypoint (main.go → stdin bytes → ndjson stdout)
├── data/          # Shared lookup tables (items, runewords, treasure classes)
├── tools/         # casc-extract tool
└── plugin.toml    # Plugin metadata

---name: working-on-d2rdescription: D2R save file parser development for Savecraft. Use when working on files in plugins/d2r/, including d2s binary parsing, item decoding, skill trees, attribute parsing, or shared stash. Triggers on D2R plugin code, d2s format, Huffman decoding, item properties, treasure classes, or Reign of the Warlock.---# Working on the D2R ParserThe parser lives in `plugins/d2r/d2s/`. It's a WASM plugin that reads `.d2s` binary save files and emits ndjson to stdout. See `docs/plugins.md` for the plugin contract and `working-on-plugins` skill for section design guidance.## Verification```bashcd plugins/d2r && just test # D2R-specific testsjust test-go # Full Go test suitejust lint-go # Includes D2R with relaxed lint rules```## D2R v105 (Reign of the Warlock) SpecificsThis parser targets **v105 only** (version byte `0x69`). Classic LoD saves are not supported.**Expansion detection:** v105+ saves do NOT set the LoD status bit (0x20) in the header. You must check `header.Realm >= RealmLoD` to gate mercenary and golem parsing. This is a common trap — the LoD bit check works for older saves but silently misparses v105.**Warlock class:** Class index 7. Skill offset is **373** (not 281 — those are monster skills). Skills.txt extracted via CASC.**Item codes:** Huffman-encoded in D2R (not ASCII like LoD). The Huffman tree is in `d2s/huffman.go`.**ISC (ItemStatCost):** RotW ISC is IDENTICAL to vanilla D2R — zero property bit width changes. RotW added properties 365 (sB=6) and 366 (sB=8), plus items not in vanilla tables.## Lint Exceptions`golangci-lint` config has exclusions for `plugins/d2r/`:- govet/shadow (binary parsing has lots of shadowed `err`)- globals (lookup tables are package-level)- complexity (binary parsing functions are inherently complex)- magic numbers (byte offsets, bit widths)These exclusions are intentional. Don't try to "fix" them.## Test Data- **Primary test save:** `reference/Diablo II Resurrected/Atmus.d2s` — Level 74 Warlock, 45 items + 3 merc items.- **Reference implementation:** `reference/olegbl-d2rmm/.../d2s/d2/items.ts` — `readItem()` function.## CASC DataGame data tables are extracted from the D2R CASC archive:- Archive: `reference/d2r-casc/` (gitignored, must copy locally)- Extracted tables: `reference/d2r-rotw-excel/` (gitignored — **Blizzard IP, NEVER check in**)- Extract tool: `plugins/d2r/tools/casc-extract/` (uses CascLib, cloned at build time)- Plugin `devenv.nix` adds cmake/gcc/zlib for building the extract tool```bashcd plugins/d2rjust build-casc-extractjust casc-extract "data/global/excel/Skills.txt"```## Shared Stash`.d2i` files (e.g. `ModernSharedStashSoftCoreV2.d2i`) — multi-section format with 64-byte headers per tab, same item format as d2s. **Not yet implemented.**## ArchitectureOne plugin per game. The plugin detects save version internally. Only v105 for now.```plugins/d2r/├── d2s/ # Parser source (header, attributes, skills, items, merc, corpse, golem)├── parser/ # WASM entrypoint (main.go → stdin bytes → ndjson stdout)├── data/ # Shared lookup tables (items, runewords, treasure classes)├── tools/ # casc-extract tool└── plugin.toml # Plugin metadata```

Frequently asked questions