acdream/CLAUDE.md

# acdream — project instructions for Claude

## Goal

Build **acdream**, a modern open-source C# .NET 10 Asheron's Call client.
A faithful port of the retail AC client's behavior to modern C# + Silk.NET,
with a plugin API the original never had.

**The code is modern. The behavior is retail.**

Every AC-specific algorithm is ported from the decompiled retail client
(`docs/research/decompiled/`, 22,225 functions, 688K lines of C). The code
around those algorithms is modern C# with clean architecture. The plugin API
exposes game state through well-defined interfaces.

**Architecture:** `docs/architecture/acdream-architecture.md` is the
single source of truth for how the client is structured. All work must
align with this document. When the architecture doc and reality diverge,
update one or the other — never leave them out of sync.

**Execution phases:** R1→R8 in the architecture doc. Each phase has clear
goals, test criteria, and builds on the previous. Don't skip phases.

The codebase is organized by layer (see architecture doc). Current phase
state lives in memory (`memory/project_*.md`), plans in `docs/plans/`,
research in `docs/research/`.

## How to operate

**You are the lead engineer AND architect on this project at all times.**
You own the architecture (`docs/architecture/acdream-architecture.md`),
the execution plan (phases R1–R8), the development workflow, and all
technical decisions. Stop as little as possible. Drive work autonomously and continuously through full phases and
across commit boundaries. Do not stop mid-phase for routine progress check-ins,
permission asks on low-stakes design calls, or "should I continue?" confirmations.
The user has repeatedly authorized direct-to-main commits, multi-commit sessions,
and cross-phase jumps when the work is sequenced in the roadmap.

The only thing that genuinely requires stopping is **visual confirmation** — the
user needs to look at the running client and tell you whether it matches
retail. Everything else is your call.

**Only stop and wait for the user when:**

- Visual verification is the acceptance test ("does the drudge look right now?")
- The roadmap and the observed bug disagree and you need to brainstorm a
  new phase or sub-step (use `superpowers:brainstorming`, not a freeform chat)
- A genuinely destructive or hard-to-reverse action is on the table outside
  the normal commit workflow (force push, history rewrite, deleting memory
  files, reverting multiple commits)
- Memory or committed history shows a clear user preference you're about to
  diverge from

**Things you should just do without asking:**

- Continue to the next planned sub-step of a phase after the previous one
  lands clean — including immediately starting work on the next phase if the
  current one is done
- Pick between two roughly equivalent implementations; justify the choice in
  the commit message
- Refactor small amounts of surrounding code when genuinely needed to land a
  change cleanly (but not "while I'm here" scope creep)
- Run the test suite, build the project, commit to main with co-author
  attribution
- Add diagnostic logging when you need evidence, then strip it when the
  evidence is in hand
- Spawn subagents for bounded implementation chunks (see Subagent policy)

Before claiming a phase or sub-step is done: run `dotnet build` and
`dotnet test` green, commit with a message that explains the "why", update
memory if there's a durable lesson, update the roadmap's "shipped" table if
a phase just landed, and move to the next todo item.

**If you catch yourself about to ask "should I continue?", the answer is
always yes — keep going.** The single exception is visual verification;
otherwise, act.

## Development workflow: decompile → verify → port

**This is the mandatory workflow for implementing ANY AC-specific behavior.**
The triangle-boundary Z bug cost 5 failed fix attempts from guessing.
The animation frame-swap bug cost 4 failed attempts. Every time we
checked the decompiled code first, we got it right on the first try.

### For each new feature or bug fix:

1. **DECOMPILE FIRST.** Before writing any AC-specific code, find the
   matching function in the decompiled client (`docs/research/decompiled/`)
   or decompile a new region using `tools/decompile_acclient.py`. Use
   the function map at `docs/research/acclient_function_map.md` to find
   known functions. If the function isn't mapped yet, search by
   characteristic constants (motion commands, magic numbers, string
   literals).

2. **CROSS-REFERENCE.** Check the decompiled code against ACE's C# port
   (`references/ACE/Source/ACE.Server/Physics/`) and ACME's
   `ClientReference.cs`. The decompiled code is ground truth; ACE and
   ACME are interpretation aids. If they disagree, the decompiled code
   wins.

3. **WRITE PSEUDOCODE.** Translate the decompiled C into readable
   pseudocode before porting to C#. Save it in
   `docs/research/*_pseudocode.md` for future reference. This step
   catches misinterpretations before they become bugs.

4. **PORT FAITHFULLY.** Translate the pseudocode to C# line-by-line.
   Use the same variable names, the same control flow, the same boundary
   conditions. Do not "improve" or "simplify" the algorithm — the retail
   client's code works; our job is to match it.

5. **CONFORMANCE TEST.** Write tests that verify our port matches the
   decompiled behavior. Use golden values from the decompiled code or
   from ACME's conformance tests. If the function touches terrain, port
   the 4M-cell sweep from `TerrainConformanceTests.cs`.

6. **INTEGRATE SURGICALLY.** When wiring ported code into the renderer
   or game loop, change the MINIMUM necessary. Keep existing working
   transform pipelines, only replace the specific computation. The
   animation sequencer integration proved this: replacing the slerp
   source was safe; replacing the entire transform composition broke
   everything.

### What NOT to do:

- **Do not guess** at AC-specific algorithms, formulas, constants, wire
  formats, or coordinate conventions. Ever.
- **Do not "fix" the decompiled code.** If the retail client does
  something that looks wrong, it's probably right. Verify before
  changing.
- **Do not skip the pseudocode step.** The frame-swap bug was caused by
  misreading the decompiled C directly into C# without an intermediate
  translation.
- **Do not integrate via subagent** unless the subagent has the full
  context of the existing code it's modifying. The first animation
  sequencer integration was done by a subagent that didn't understand
  the transform pipeline — it broke everything.

### Phase completion checklist:

Before marking any phase as done:

- [ ] Every AC-specific algorithm has a decompiled reference cited in
      comments (function address + chunk file)
- [ ] Conformance tests exist for the critical paths
- [ ] The code was cross-referenced against at least 2 reference repos
- [ ] `dotnet build` green, `dotnet test` green
- [ ] Visual verification by the user (if applicable)
- [ ] Roadmap updated
- [ ] Memory updated if there's a durable lesson

## Subagent policy

Subagents are the primary tool for saving parent-context and keeping one
session productive across many phases. Use them liberally for:

- Bounded implementation chunks with a clear spec (one file, one test suite,
  a targeted refactor)
- Parallel independent tasks with no shared state
- Research that would otherwise fill the parent context with file reads

**Model selection:**

- **Default: Sonnet.** Use Sonnet for all execution work — implementers,
  research agents, spec-following work, test writing, refactors, repeated
  patterns. Sonnet is the right cost/context/capability tradeoff for this
  codebase and has been validated on every phase since Phase 2a. Do not
  reach for Opus unless you have a specific reason.
- **Opus only for load-bearing quality review** — code review of a phase
  boundary, a design that must be right the first time, a gnarly
  cross-system refactor. "This feels hard" is not enough; specify why it
  needs Opus in the task description.
- Never use Haiku for acdream work unless the task is literally checking
  whether another process is alive.

**Prompt discipline:** when dispatching a subagent, include the relevant
spec path, the files it should read, the acceptance criteria (build + test
green), and the commit message style. Subagents inherit CLAUDE.md so they
follow the same rules.

## Roadmap discipline

acdream's plan lives in two files committed to the repo:

- **`docs/plans/2026-04-11-roadmap.md`** — the strategic roadmap. Single
  source of truth for what's shipped, what's next, and the agreed order.
  When you're about to pick up new work, read this first. When you ship a
  phase or sub-step, move it from "ahead" to "shipped" in the same commit
  that lands the work (or the very next commit).

- **`docs/superpowers/specs/*.md`** — per-phase detailed implementation
  specs. Each active phase has one. When you're about to write code for a
  named phase, read its spec, follow its component boundaries, and match its
  acceptance criteria. Do not drift from the spec without explicit user
  approval.

**Rules:**

1. Before starting a new phase or sub-piece, re-read the roadmap and the
   relevant spec. State which phase you're on in the first action you take.

2. When reality and the plan diverge — the user observes a bug that doesn't
   fit any existing phase, a technical discovery makes a phase description
   wrong, a sub-piece turns out to be larger than expected — **pause and
   brainstorm** with the `superpowers:brainstorming` skill before writing
   code. Update the roadmap in the same session.

3. When shipping a phase, update the roadmap's "shipped" table and commit
   the update in the same commit as (or immediately after) the
   implementation commit.

4. Do not invent new phase numbers / letters on the fly. If you need a new
   phase, add it to the roadmap first with the user, then reference it by
   its assigned identifier. "Phase 11" and "Phase 9.3" conjured
   mid-sentence are process smells — they mean the plan got out of sync
   with the work.

5. If a single session ends up shipping work that spans multiple roadmap
   phases, that's fine, but each commit message should name the phase it
   belongs to (e.g. `feat(core): Phase A.1 — streaming region`).

The roadmap is not sacred — it changes. It IS the source of truth at any
given moment. When it's wrong, fix it. When it's right, follow it.

## Reference repos: check ALL FOUR, not just one

When researching a protocol detail, dat format, rendering algorithm, or
any "how does AC do X" question, **check all four of the vendored
references in `references/`** before committing to an approach. Do not
settle on the first hit and move on — cross-reference at least two of
these, ideally all four:

- **`references/ACE/`** — ACEmulator server. Authority on the wire
  protocol (packet framing, ISAAC, game message opcodes, serialization
  order). The things a server has to know to parse and produce bytes.
- **`references/ACViewer/`** — MonoGame-based dat viewer that actually
  renders characters + world. Authority on the client-side visual
  pipeline: ObjDesc application, palette overlays, texture decoding
  for the palette-indexed formats. See
  `ACViewer/Render/TextureCache.cs::IndexToColor` for the canonical
  subpalette overlay algorithm.
- **`references/WorldBuilder/`** — C# + Silk.NET dat editor. Exact-stack
  match to acdream for rendering approaches: terrain blending, texture
  atlases, shader patterns. Most useful for "how do I do this GL thing
  with Silk.NET on net10 idiomatically?" Less useful for protocol or
  character appearance (dat editor, not game client).
- **`references/Chorizite.ACProtocol/`** — clean-room C# protocol
  library generated from a protocol XML description. Useful sanity check
  on field order, packed-dword conventions, type-prefix handling. The
  generated Types/*.cs files have accurate field comments (e.g. "If
  it is 0, it defaults to 256*8") that ACE's server-side code doesn't.
- **`references/holtburger/`** — **Almost-complete Rust TUI AC client.**
  Not just a crate or a handshake reference: it's a full client that
  logs in, plays the game, sends/receives chat, handles combat, and
  renders state in a terminal. **This is acdream's most authoritative
  reference for client-side behavior** — anything about how a client
  is *supposed* to talk to the server lives here. Specifically:
    - Handshake / login flow including all the post-EnterWorld
      messages retail clients send (LoginComplete, ack pump,
      DDDInterrogation responses, etc).
    - The proper ACK_SEQUENCE pattern (every received packet with
      sequence > 0 gets an ack queued back; not periodic).
    - Outbound game-action message construction with sequence
      numbering.
    - Message routing and session lifecycle.
  Look here FIRST when implementing anything in `WorldSession` or
  the message-builder layer. ACE shows what the server expects;
  holtburger shows what a real client actually sends.

- **`references/AC2D/`** — **C++ AC client emulator.** Oldest reference,
  fixed-function OpenGL, but has the **real AC terrain split formula**
  (`FSplitNESW` with constants `0x0CCAC033`, `0x421BE3BD`, `0x6C1AC587`,
  `0x519B8F25`) which differs from WorldBuilder's physics-path formula.
  Also has the complete `0xF61C` movement packet format with flag bits
  and the `stMoveInfo` sequence counters. Key lesson from AC2D: it does
  NOT do client-side terrain Z — it sends movement keys to the server
  and uses the server's authoritative Z. See
  `docs/research/2026-04-12-movement-deep-dive.md` for the full analysis.

Pattern: when you encounter an unknown behavior, grep all four for the
relevant term, read each hit, and compose a multi-source understanding
BEFORE writing acdream code. A single reference can be misleading; the
intersection of all four is almost always the truth. The user has
repeatedly had to remind me about this when I narrowly searched one ref
and missed obvious answers in another.

### Reference hierarchy by domain

**NEVER GUESS an algorithm, formula, constant, wire format, or coordinate
convention.** Every AC-specific behavior has a reference implementation in
one of the repos below. If you find yourself writing AC-specific code
without having read the matching reference first, STOP and read it. The
triangle-boundary Z bug cost 5 failed fix attempts because we guessed
instead of checking ACME's `ClientReference.cs` — which had the exact
decompiled client code and would have fixed it in minutes.

**The rule: read the reference FIRST, write code SECOND. Always.**

| Domain | Primary Oracle | Secondary | Notes |
|--------|---------------|-----------|-------|
| **Terrain** (split direction, height sampling, palCode, vertex position, normals) | **ACME `ClientReference.cs`** — decompiled retail client with exact offsets | ACME `TerrainGeometryGenerator.cs` (matches the mesh index buffer) | WorldBuilder original is SUPERSEDED for terrain algorithms. AC2D confirms the same formula. |
| **Terrain blending** (texture atlas, alpha masks, road overlays) | **ACME `LandSurfaceManager.cs`** | WorldBuilder original `LandSurfaceManager.cs` (same code, less tested) | Both use the same TexMerge pipeline. ACME has conformance tests. |
| **GfxObj / Setup rendering** (mesh extraction, multi-part assembly, ObjDesc) | **ACME `StaticObjectManager.cs`** — includes CreaturePalette, GfxObjRemapping, HiddenParts | ACViewer `Render/` namespace | ACME has the complete creature appearance pipeline in one file. |
| **Texture decoding** (INDEX16, P8, DXT, BGRA, alpha) | **ACME `TextureHelpers.cs`** | ACViewer `Render/TextureCache.cs` (palette overlay = `IndexToColor`) | For subpalette overlay specifically, ACViewer's `IndexToColor` is the canonical algorithm. |
| **EnvCell / dungeon rendering** (cell geometry, portal visibility, collision mesh) | **ACME `EnvCellManager.cs`** — portal traversal, mixed landblock detection, collision cache | ACViewer `Physics/Common/EnvCell.cs` | ACME is significantly more complete than original WorldBuilder for dungeons. |
| **Network protocol** (wire format, packet framing, fragment assembly, ISAAC) | **holtburger** `crates/holtburger-session/` | AC2D `cNetwork.cpp` (simpler, good for cross-check) | ACE shows the server side; holtburger + AC2D show the client side. |
| **Client behavior** (what to send when, login flow, ack pattern, keepalive) | **holtburger** `crates/holtburger-core/src/client/` | AC2D `cNetwork.cpp` + `cInterface.cpp` | holtburger is the most complete; AC2D is simpler but confirmed working. |
| **Movement** (MoveToState format, AutonomousPosition, sequence counters, speed) | **holtburger** `client/movement/` | AC2D `cNetwork.cpp:2592-2664` (0xF61C format) | See `docs/research/2026-04-12-movement-deep-dive.md` for the full cross-reference. |
| **Server expectations** (what ACE accepts/rejects, validation thresholds) | **ACE** `Source/ACE.Server/Network/` | — | Only ACE knows what the server actually validates. |
| **Silk.NET / .NET 10 idioms** (GL calls, shader setup, VAO patterns) | **WorldBuilder original** | ACME (same stack) | Both use the same backend; original has cleaner isolated examples. |
| **Protocol field order** (packed dwords, type prefixes, flag enums) | **Chorizite.ACProtocol** `Types/*.cs` | holtburger (cross-check) | Generated from protocol XML; has accurate field comments. |

### ACME key files quick reference

These are the files you should open FIRST when working on any rendering
or dat-interpretation task:

- **`WorldBuilder.Tests/ClientReference.cs`** — decompiled retail AC
  client C# port. `IsSWtoNECut`, `GetPalCode`, `GetVertexHeight`,
  `GetVertexPosition`. **The ground truth.** If your code disagrees
  with this file, your code is wrong.
- **`WorldBuilder.Tests/TerrainConformanceTests.cs`** — 4M+ cell sweep
  proving ACME matches retail. Port these into acdream's test suite for
  any algorithm you touch.
- **`StaticObjectManager.cs`** — GfxObj+Setup+CreaturePalette pipeline.
- **`EnvCellManager.cs`** — dungeon cells + portal visibility.
- **`TerrainGeometryGenerator.cs`** — `GetHeight()`, `GetNormal()`,
  `CalculateSplitDirection()` matching the mesh index buffer.
- **`TextureHelpers.cs`** — INDEX16, BGRA, DXT decode helpers.

### holtburger key files quick reference

These are the files you should open FIRST when working on any networking
or client-behavior task:

- **`client/movement/system.rs`** — the movement state machine (when to
  send MoveToState vs AutonomousPosition, deduplication logic).
- **`client/movement/actions.rs`** — MoveToState, AutonomousPosition,
  Jump wire format builders.
- **`client/movement/types.rs`** — RawMotionState packed format with
  all flag bits documented.
- **`session/send.rs`** — packet construction, checksum, ISAAC, ACK
  piggybacking.
- **`client/messages.rs`** — post-login message handlers (PlayerCreate
  → LoginComplete, DddInterrogation → response, PlayerTeleport).
- **`spatial/physics.rs`** — dead-reckoning solver (how the client
  advances position between server updates).