mono-memory-reader

name	mono-memory-reader
description	Use when working on Scry2.Collection's walker path — the Rust NIF crate under native/scry2_collection_reader that navigates MTGA's in-process Mono runtime. Covers the pointer chain, Mono struct offsets, PE/prologue decoding, and the canonical sources for cross-verification.

MTGA Mono Memory Reader

Technical reference for the walker path of Scry2.Collection's reader (the Rust NIF crate at native/scry2_collection_reader/). The walker resolves MTGA's live collection, wildcards, gold, gems, and vault progress by walking named pointers through the process's Mono runtime.

For the fallback structural-scan path, see the POC at mtga-duress/experiments/mtga-reader-poc/.

MTGA runtime identity

Property	Value
Engine	Unity 2022.3.62f2 (Proton/Wine on Linux)
Scripting backend	Mono (not IL2CPP)
Mono runtime DLL	mono-2.0-bdwgc.dll (MonoBleedingEdge)
Mono DLL on-disk	$STEAM/common/MTGA/MonoBleedingEdge/EmbedRuntime/mono-2.0-bdwgc.dll
Managed assemblies	Core.dll, Assembly-CSharp.dll, SharedClientCore.dll
PE layout	PE32+, ImageBase = 0x180000000

MTGA's mono-2.0-bdwgc.dll on-disk and mapped bytes are byte-identical across its read-only code sections. The disassembly below is derived from the on-disk file; verification against live memory is a straight read_bytes at the RVA.

The pointer chain

From the Unity 2022.3.62f2 build, the walker navigates:

mono_get_root_domain()                  -> MonoDomain *
  (walk assemblies to Core.dll or Assembly-CSharp.dll)
  class PAPA
    <Instance>k__BackingField           (STATIC field — read via VTable)
      <InventoryManager>k__BackingField (instance)
        _inventoryServiceWrapper        (instance)
          <Cards>k__BackingField        -> Dictionary<int,int>   (collection)
          m_inventory                   -> ClientPlayerInventory
                                            { wcCommon, wcUncommon,
                                              wcRare,  wcMythic,
                                              gold, gems, vaultProgress,
                                              boosters: List<ClientBoosterInfo> }

ClientPlayerInventory instance fields (16 total; verified 2026-05-02 via inventory-field-spike — mtga-duress/experiments/spikes/spike18_booster_inventory/FINDING.md):

Offset	Field	Type	Notes
0x0010	boosters	List<ClientBoosterInfo>	booster inventory; element layout below
0x0018	vouchers	reference	(shape unverified — likely a list/dict)
0x0020	prizeWallsUnlocked	reference	(cosmetic)
0x0028	basicLandSet	reference	(cosmetic)
0x0030	latestBasicLandSet	reference	(cosmetic)
0x0038	starterDecks	reference
0x0040	tickets	reference	(event entry tokens)
0x0048	CustomTokens	reference
0x0050	wcCommon	i32	walker phase 6
0x0054	wcUncommon	i32	walker phase 6
0x0058	wcRare	i32	walker phase 6
0x005c	wcMythic	i32	walker phase 6
0x0060	gold	i32	walker phase 6
0x0064	gems	i32	walker phase 6
0x0068	wcTrackPosition	i32	wildcard track progress
0x0070	vaultProgress	f64	walker phase 6 (System.Double)

ClientBoosterInfo element fields (verified 2026-05-02; same spike):

Offset	Field	Type
0x0010	collationId	i32 (matches MTGA's log Changes[*].Boosters[].collationId)
0x0014	count	i32

Field resolution rule (from spike 5):

1. Exact name match first.
2. Fall back to <UpperCamel>k__BackingField (C# auto-property backing field) — with a single leading underscore stripped and first letter uppercased on the requested name.
3. Static vs instance: dispatch on MONO_FIELD_ATTR_STATIC = 0x10 in MonoClassField.type->attrs. Static reads from vtable->data[field->offset]; instance reads from obj_ptr + field->offset.

Match-state pointer chains (verified 2026-04-30)

Beyond the inventory chain, the walker has two more chains for in-match data. Both were validated end-to-end against MTGA build timestamp Fri Apr 11 17:22:20 2025 on 2026-04-30 — see mtga-duress/experiments/spikes/spike16_match_manager/FINDING.md for the full evidence.

Two-source coverage for these chains:

1. Untapped's decompiled TypeScript sources in mtga-duress/experiments/untapped-analysis/source-maps/ (clean-room rule per DOSSIER.md — idea, not code).
2. Live disassembly + offset dump via match-manager-spike (sibling binary in the production crate, src/bin/match_manager_spike.rs).

Chain 1 — match info (rank, commander) — VERIFIED

Anchored at the same PAPA._instance static the inventory walker uses. Provides what the log can never deliver — opponent rank and real screen name.

PAPA instance fields (47 total; only the relevant ones listed):

Offset	Field	Notes
0x0000	_instance	STATIC, attrs 0x0011 — singleton anchor
0x0138	<MatchManager>k__BackingField	instance, attrs 0x0001
0x00e8	<InventoryManager>k__BackingField	(existing inventory walker uses this)

MatchManager instance fields (43 total; relevant to rank/commander extraction):

Offset	Field	Type
0x0048	<MatchID>k__BackingField	string ref
0x0058	<LocalPlayerInfo>k__BackingField	PlayerInfo *
0x0060	<OpponentInfo>k__BackingField	PlayerInfo *
0x0068	Players	collection (List/Dict) of all PlayerInfo
0x0098	<Event>k__BackingField	EventContext *, null when not in event
0x0108	<LocalPlayerSeatId>k__BackingField	i32
0x010c	<WinCondition>k__BackingField	i32 enum
0x0110	<CurrentGameNumber>k__BackingField	i32
0x0114	<MatchState>k__BackingField	i32 enum
0x0118	<Format>k__BackingField	i32 enum
0x011c	<Variant>k__BackingField	i32 enum
0x0120	<SessionType>k__BackingField	i32 enum
0x0125	<IsPracticeGame>k__BackingField	bool (1 byte)
0x0126	<IsPrivateGame>k__BackingField	bool

PlayerInfo class (used for both LocalPlayerInfo and OpponentInfo — same class, 19 fields):

Offset	Field	Type	Notes
0x0000	PrivateMatchOpponentNotJoinedYet	STATIC	skip in instance reads
0x0010	_screenName	MonoString *	real opponent username (closes log gap)
0x0018	WizardsAccountIdForPrivateGaming	string ref
0x0040	_deckCards	List<???>*	private readonly. Empty for OpponentInfo — client never has opponent's submitted deck
0x0048	_sideboardCards	List<???>*	same as above
0x0050	_cardStyles	List<???>*
0x0058	<CommanderGrpIds>k__BackingField	List<i32>*	populated for Brawl/Commander
0x0060	<EmoteSelection>k__BackingField	ref
0x0068	SeatId	i32
0x006c	TeamId	i32
0x0070	IsWotc	bool
0x0074	RankingClass	i32 enum	[None, Bronze, Silver, Gold, Platinum, Diamond, Mythic] (index 0..6)
0x0078	RankingTier	i32	1..4 within each class
0x007c	MythicPercentile	i32 (probable)	0 for sub-Mythic; live verification with a Mythic player needed to disambiguate i32 vs f32
0x0080	MythicPlacement	i32	leaderboard placement for top players

Tear-down behaviour (critical): after a match completes, MTGA resets both LocalPlayerInfo and OpponentInfo to placeholder defaults — _screenName reverts to "Local Player" / "Opponent", all rank ints zero, _deckCards._size = 0, Event becomes null. The underlying objects persist; only the values are wiped. A one-shot read at MatchCompleted log-event time is too late. Read at MatchCreated instead — the opponent's PlayerInfo is populated from the moment ConnectResp arrives.

PAPA._instance                                       (existing anchor)
  .MatchManager                                      (instance)
    .Event.PlayerEvent.Format.UseRebalancedCards   : bool  (nullable chain)
    .LocalPlayerInfo
      .RankingClass                                : enum [None, Bronze,
                                                          Silver, Gold,
                                                          Platinum,
                                                          Diamond, Mythic]
      .RankingTier                                 : i32
      .MythicPercentile                            : f32 / f64 (TBD)
      .MythicPlacement                             : i32
      .CommanderGrpIds                             : List<i32>
    .OpponentInfo
      .RankingClass, .RankingTier,
      .MythicPercentile, .MythicPlacement,
      .CommanderGrpIds                             : (same shape as above)

OpponentInfo is the gap-filler — MTGA does not include opponent rank in match-room log events. CommanderGrpIds is the Brawl/ Commander commander identity.

Source: ScryIpcHandler-x0rjOwCx/src/scry/readers/mtga/ScryMtgaMatchInfo.ts.

Chain 2 — board state (every card, every zone, both players) — VERIFIED

Anchored at the MatchSceneManager class's static Instance field — distinct from the PAPA anchor used by Chain 1.

MatchSceneManager class (looked up by name in the loaded images; addr varies per build):

Offset	Field	Notes
0x0000	Instance	STATIC, attrs 0x0016 — becomes NULL after match scene tears down
0x0078	_gameManager	instance, attrs 0x0001 — GameManager *

GameManager instance fields (50 total; relevant fields):

Offset	Field	Notes
0x0050	<CardHolderManager>k__BackingField	instance
0x00c0	<MatchManager>k__BackingField	instance — alternative path to MatchManager (PAPA path is simpler)
0x0118	_gameStateManager	instance, attrs 0x0021 — additional state worth probing

CardHolderManager class (5 fields):

Offset	Field
0x0010	<DefaultBrowser>k__BackingField
0x0018	<Examine>k__BackingField
0x0020	_provider (private, attrs 0x0021) — MutableCardHolderProvider *
0x0028	_builder
0x0030	_zoneCardHolderCreated

MutableCardHolderProvider class (4 fields, all Dictionary\2`):

Offset	Field
0x0010	ZoneIdToCardHolder
0x0018	SubCardHolderMap
0x0020	PlayerTypeMap ← Dict<GREPlayerNum, Dict<CardHolderType, ICardHolder>>
0x0028	AllCardHolders

GREPlayerNum   = { Invalid=0, LocalPlayer=1, Opponent=2, Teammate=3 }
CardHolderType = { Invalid=0, Library=1, OffCameraLibrary=2, Hand=3,
                   Battlefield=4, Graveyard=5, Exile=6, Stack=9,
                   Command=10, CardBrowserDefault=12,
                   CardBrowserViewDismiss=13, Examine=16,
                   Deckbuilder=17, CardViewer=18, Store=19,
                   RolloverZoom=20, Reveal=21, None=-1 }

Tear-down behaviour: the MatchSceneManager.Instance static is nulled out as soon as MTGA exits the match scene — verified post- match via match-manager-spike. The class definition stays loaded; only the singleton pointer goes to zero. Reads must complete during the match.

For non-battlefield zones, each holder is a BaseCardHolder:

BaseCardHolder._previousLayoutData : List<CardLayoutData>

CardLayoutData
  .IsVisibleInLayout : bool
  .Card : BaseCDC
    ._model : CardDataAdapter
      ._printing : CardPrintingData       (Scryfall-shape — large)
      ._instance
        .BaseGrpId             : i32      ← arena_id
        .OverlayGrpId.value    : i32      (alt-art arena_id; nullable)
        .IsTapped              : bool
        .FaceDownState._reasonFaceDown : enum

Battlefield is the special case — it's split into regions instead of a flat list:

BattlefieldCardHolder.Layout
  ._localCreatureRegion       : BattlefieldRegion
  ._localLandRegion           : BattlefieldRegion
  ._localArtifactRegion       : BattlefieldRegion
  ._localPlaneswalkerRegion   : BattlefieldRegion
  ._opponentCreatureRegion    : BattlefieldRegion
  ._opponentLandRegion        : BattlefieldRegion
  ._opponentArtifactRegion    : BattlefieldRegion
  ._opponentPlaneswalkerRegion: BattlefieldRegion

BattlefieldRegion
  ._stacksByShape  : Dict<i32, List<BattlefieldStack>>
  .CardBounds      : { m_Height, m_Width, m_XMin, m_YMin } (f32)

BattlefieldStack
  .AllCards         : List<BaseCDC>     ← cards in this stack
  .AttachmentCount  : i32
  .CardCount        : i32
  .ExileCount       : i32
  .IsAttackStack    : bool
  .IsBlockStack     : bool

For "what cards has the opponent revealed" the minimum traversal is:

1. Battlefield → opponent regions → stacks → AllCards
2. (Opponent, Graveyard) → _previousLayoutData
3. (Opponent, Exile) → _previousLayoutData
4. (Opponent, Stack) → _previousLayoutData
5. (Opponent, Command) → _previousLayoutData
6. (Opponent, Hand) → _previousLayoutData filtered to entries with IsVisibleInLayout = true and no FaceDownState — i.e. revealed- in-hand cards (Thoughtseize, Duress, etc.).

Library is opaque — the client never has unrevealed identities; its holder will have entries with face-down state set and no BaseGrpId.

Sources:

• ScryIpcHandler-x0rjOwCx/src/scry/readers/mtga/ScryMtgaMatchReader.ts
• ScryIpcHandler-x0rjOwCx/src/scry/utils/types/mtga/MatchSceneManager.ts
• ScryIpcHandler-x0rjOwCx/src/scry/utils/mtga/ScryBattlefieldStacks.ts
• ScryIpcHandler-x0rjOwCx/src/scry/utils/mtga/ScryMatchZone.ts

Chain 3 — active events (entry, wins/losses, in-flight state) — VERIFIED 2026-05-06

Anchored at the same PAPA._instance static the other chains use. Provides the player's full list of available + in-progress event entries — the data behind the dashboard's "Active events" / "4-1 in Premier Draft" surface.

Verified live against MTGA build timestamp Fri Apr 11 17:22:20 2025. 52 EventContexts observed; entry [12] (DualColorPrecons) read 22W-17L matching MTGA's UI exactly. See spike21_active_events/FINDING.md for full evidence.

Tear-down behaviour: EventManager and the EventContexts list persist across match boundaries — unlike MatchSceneManager.Instance (Chain 2) and MatchManager.LocalPlayerInfo/OpponentInfo (Chain 1 post-match), this chain is safe to read at any time after MTGA finishes loading. Pre-login, PAPA._instance.EventManager is null.

PAPA → EventManager (same anchor as Chain 1):

Offset	Field	Notes
0x0110	<EventManager>k__BackingField	instance, attrs 0x0001 — verified by spike20 PAPA manifest and spike21

EventManager class (9 instance fields):

Offset	Field	Notes
0x0010	_eventsServiceWrapper	AwsEventServiceWrapper (network)
0x0018	_accountClient	WizardsAccountsClient
0x0028	_cardDatabase	CardDatabase (shared with other chains)
0x0030	<EventContexts>k__BackingField	List<EventContext> — primary collection
0x0038	<DynamicFilterTags>k__BackingField	List<ClientDynamicFilterTag> (Play-screen filter chips)
0x0040	<EventsByInternalName>k__BackingField	Dictionary — empty in steady state
0x0048	_lastEventContextRefresh	timestamp

EventContext (3 instance fields):

Offset	Field	Notes
0x0010	PlayerEvent	polymorphic — BasicPlayerEvent or LimitedPlayerEvent
0x0018	PostMatchContext	null unless event just completed (transient)
0x0020	DeckSelectContext	null unless in deck-select state (transient)

BasicPlayerEvent (parent class — 9 instance fields, 1 static skipped):

Offset	Field	Notes
0x0010	<EventInfo>k__BackingField	BasicEventInfo
0x0018	<EventUXInfo>k__BackingField
0x0020	<Format>k__BackingField	DeckFormat (NULL on LimitedPlayerEvent — format derived from draft pool)
0x0028	<CourseData>k__BackingField	public-API mirror with CurrentEventState/CurrentModule ints
0x0038	_courseInfo	private — AwsCourseInfo wrapper around the wire-format course mirror
0x0040	_eventsServiceWrapper	(private)

LimitedPlayerEvent : BasicPlayerEvent adds one field:

Offset	Field	Notes
0x0058	<DraftPod>k__BackingField	DraftPod — populated only while a draft is in progress

CourseData (9 instance fields — public state, used to discriminate entries):

Offset	Field	Notes
0x0040	Id	course id (string)
0x0050	CurrentEventState	i32 — see "State enum values" below
0x0054	CurrentModule	i32 — round/stage pointer
0x0030	DraftId	string id (limited only)
0x0038	MadeChoice	bool? (deck choice flag)

AwsCourseInfo (1 instance field):

Offset	Field	Notes
0x0010	_clientPlayerCourse	ClientPlayerCourseV3 — the wire-format mirror

ClientPlayerCourseV3 (15 instance fields — primary state holder, where wins/losses live):

Offset	Field	Type	Notes
0x0010	InternalEventName	MonoString	duplicates EventInfoV3.InternalEventName
0x0018	ModulePayload	MonoString	empty in observed entries
0x0020	CourseDeckSummary	DTO_DeckSummaryV3 *	name, mana cost summary, deck-art
0x0028	CourseDeck	Deck *	submitted deck (MainDeck, Sideboard, CommandZone, Companions)
0x0030	CardPool	List<???>	drafted cards (limited)
0x0050	DraftId	MonoString
0x0058	TournamentId	MonoString
0x0060	MadeChoice	MonoString	course-instance UUID set when player picks event deck (despite the name, NOT a bool)
0x0068	CourseId	MonoString
0x0078	CurrentModule	i32	round/module pointer (mirrors CourseData.CurrentModule)
0x007c	CurrentWins	i32	win count for this entry
0x0080	CurrentLosses	i32	loss count for this entry

BasicEventInfo (2 instance fields):

Offset	Field	Notes
0x0010	<EntryFees>k__BackingField	List<???> — entry tokens / gems
0x0018	_eventInfoV3	EventInfoV3 — canonical wire-format event-template metadata

EventInfoV3 (14 instance fields — event-template metadata, not per-player progress):

Offset	Field	Notes
0x0010	InternalEventName	MonoString — e.g. Premier_Draft_DFT
0x0018	Flags	bitfield
0x0020	PastEntries	List<???> — empty in observed entries (server-pushed history?)
0x0028	EntryFees	duplicate of BasicEventInfo.EntryFees
0x0030	EventTags	List<???>
0x0050	EventState	i32 — 0 = open, 1 = closed/expired, 2 = special
0x0054	FormatType	i32 — 1 = Limited, 2 = Sealed, 3 = Constructed
0x0058	StartTime	DateTime
0x0070	WinCondition	i32

State enum values (CurrentEventState / CurrentModule) — captured live across 52 entries:

CurrentEventState	CurrentModule	Meaning	Examples
0	0	Available — never entered, root entry-point	ColorChallenge
0	1	Available — never entered (default)	ColorChallenge_Node5_*, TradDraft_SOS_…, Sealed_SOS_…
1	7	Entered / in progress	Jump_In_2024, QuickDraft_SOS_…, DualColorPrecons
3	11	Standing / always-on (no entry fee)	Play, Constructed_BestOf3, Traditional_Ladder, Ladder

Walker rule: an entry is "actively engaged" when CurrentEventState != 0. Wins/losses can still be 0 in an Entered entry (entered but no matches played yet) — the state enum is the truth, not the counters.

PAPA._instance                                       (existing anchor)
  .EventManager
    .EventContexts                              : List<EventContext>
      [i].PlayerEvent
            .EventInfo._eventInfoV3
              .InternalEventName              : string  ("Premier_Draft_DFT")
              .EventState / .FormatType       : i32 enums
              .EntryFees                      : List<entry-fee>
            .CourseData
              .CurrentEventState              : i32 enum (0/1/3 → see table)
              .CurrentModule                  : i32 (1/7/11)
            .Format._formatName               : string ("Standard", null on Limited)
            ._courseInfo._clientPlayerCourse
              .CurrentWins                    : i32
              .CurrentLosses                  : i32
              .CourseDeck                     : Deck
      [i].PostMatchContext  ── transient post-match
      [i].DeckSelectContext ── transient deck-select

Resolution discipline: every field above must be looked up by name (field::find_field_by_name / _in_chain). The literal offsets are reproduced here for documentation and unit-test fixtures only. Game-class field offsets are not pinned as constants — only MonoOffsets (Mono runtime offsets) are.

Source: this skill block + mtga-duress/experiments/spikes/spike21_active_events/FINDING.md.

Generic types the walker doesn't yet handle

Both chains use Mono List<T> (T[] _items + i32 _size + i32 _version) and Dictionary<K, V> with non-int generic parameters. The current walker's dict.rs is hardcoded to Dictionary<int, int> (the inventory cards collection). Reuse it for the new chains will require parameterising the value-size and pointer-vs-inline read.

List<T> has no walker module yet. It's straightforward — header fields then dereference _items as a Mono MonoArray<T> (obj + bounds + max_length + flex vector[] per the existing MonoArray offsets) — but it's a new module nonetheless.

Research note

Full feasibility analysis, capture-model trade-offs (one-shot at MatchCompleted vs Scry2.LiveState polling), and recommended implementation contour: decisions/research/2026-04-30-001-opponent-game-state-memory-read.md.

Canonical sources

Walker offsets must be confirmed against at least two independent sources before any #[repr(C)] or offset constant is pinned in the Rust crate. The ranked sources are:

1. Unity-Technologies/mono @ unity-2022.3-mbe (MIT). Authoritative struct definitions. Pull the raw file via gh api -H 'Accept: application/vnd.github.raw' 'repos/Unity-Technologies/mono/contents/mono/metadata/<file>?ref=unity-2022.3-mbe'. Key files:
   • mono/metadata/class-private-definition.h — struct _MonoClass (the real definition; class-internals.h only forward-declares it)
   • mono/metadata/class-internals.h — struct _MonoClassField, struct MonoVTable, union _MonoClassSizes, enum MonoTypeKind
   • mono/metadata/class-getters.h — the full m_class_offsetof_* macro list; authoritative field-name manifest
   • mono/metadata/domain-internals.h — struct _MonoDomain
   • mono/metadata/metadata-internals.h — struct _MonoAssembly, _MonoAssemblyName, _MonoImage
   • mono/metadata/object-internals.h — _MonoArray, _MonoString
2. Live disassembly of MTGA's mono-2.0-bdwgc.dll (see "Disassembly evidence" below). Authoritative for this specific build; deviates from source only if the build pinned a patch.
3. Unispect / Unispect-DMA — AGPL-3.0. Technique and cross-check only; do not copy source. Useful as a third independent voice when the first two disagree.

Conditional-compilation gates that change layout between builds: DISABLE_REMOTING, DISABLE_COM, MONO_SMALL_CONFIG, ENABLE_CHECKED_BUILD_PRIVATE_TYPES. The Unity MonoBleedingEdge build has none of these defined — every #ifndef DISABLE_* branch is taken. Verify this assumption against any new build before trusting derived offsets.

Verified findings (2026-04-25 reading of MTGA build timestamp

Fri Apr 11 17:22:20 2025, file size 7,897,520 bytes)

Export RVAs in mono-2.0-bdwgc.dll

Export	Ordinal	RVA	File offset
mono_get_root_domain	489	0x000a71b0	0x000a65b0
mono_assembly_loaded	69	0x000b6be0	0x000b5fe0
mono_domain_assembly_open	301	0x000a7e50	0x000a7250
mono_class_vtable	183	0x001ca860	0x001c9c60
mono_class_get_field_from_name	135	0x000bd140	0x000bc540
mono_image_loaded	526	0x0014cdb0	0x0014c1b0

These are derived from the PE export directory at RVA 0x73be00. To re-derive on a newer build, parse the export directory (or use native/scry2_collection_reader/src/walker/pe.rs::find_export_rva).

mono_get_root_domain prologue — validated

First 8 bytes at RVA 0xa71b0:

48 8b 05 69 9e 6a 00  c3
mov  rax, [rip+0x6a9e69]
ret

Canonical mov rax, [rip+disp32]; ret pattern expected by walker/prologue.rs. Derived static pointer address:

• RIP after mov = 0xa71b0 + 7 = 0xa71b7
• disp32 = 0x006a9e69
• mono_root_domain static pointer RVA = 0xa71b7 + 0x6a9e69 = 0x746020

At runtime, read_u64(mono_base + 0x746020) yields the live MonoDomain *.

Disassembly evidence for struct offsets (first-pass, needs confirmation)

Leading bytes of mono_class_vtable(MonoDomain *domain, MonoClass *class):

1801ca880  mov  rdi, rdx               ; rdi = class
1801ca888  mov  r14, rcx               ; r14 = domain
   ...safepoint / telemetry prologue...
1801ca954  test dword [rdi+0x28], 0x100000
1801ca95d  mov  rax, qword [rdi+0xe0]

• [rdi+0x28] read as a 32-bit flags word with 0x100000 likely being MONO_CLASS_IS_ARRAY-adjacent — suggests the bitfield byte cluster in _MonoClass around the inited/valuetype/enumtype/... group lives at offset 0x28. First-pass candidate, not confirmed.
• [rdi+0xe0] looks like MonoClass.runtime_info (used to find a per-domain VTable). First-pass candidate, not confirmed.

Leading bytes of mono_class_get_field_from_name(MonoClass *klass, const char *name):

1800bd14a  ...
1800bd164  mov  rdi, rcx               ; rdi = klass
1800bd20e  test dword [rdi+0x28], 0x100000
1800bd226  mov  rbx, qword [rdi+0x98]

• [rdi+0x98] is likely MonoClass.fields — the MonoClassField array the function iterates. First-pass candidate, not confirmed.

Verified offset table (2026-04-25 reading)

Cross-checked by two independent sources: the offsets_probe/dump.c program (compiled with gcc -mms-bitfields against Unity's headers) and live disassembly of the MTGA DLL. Values marked ✓ agree between both sources.

MonoClass:

Offset	Field	Evidence
0x00	element_class	dumper
0x08	cast_class	dumper
0x10	supertypes	dumper
0x18	idepth (u16)	dumper
0x1a	rank (u8)	dumper
0x1b	class_kind (u8)	dumper
0x1c	instance_size (i32)	dumper
0x20	bitfield group 1 (inited…is_byreflike)	dumper
0x24	min_align (u8)	dumper
0x28	bitfield group 2 (packing_size…has_dim_conflicts, 23 bits; has_failure at bit 20)	✓ dumper + test [rdi+0x28], 0x100000 in mono_class_vtable
0x30	parent	dumper
0x38	nested_in	dumper
0x40	image	dumper
0x48	name	dumper
0x50	name_space	dumper
0x58	type_token (u32)	dumper
0x5c	vtable_size (i32)	dumper
0x60	interface_count (u16)	dumper
0x64	interface_id (u32)	dumper
0x68	max_interface_id (u32)	dumper
0x6c	interface_offsets_count (u16)	dumper
0x70	interfaces_packed	dumper
0x78	interface_offsets_packed	dumper
0x80	interface_bitmap	dumper
0x88	interfaces	dumper
0x90	sizes (union, 4 bytes)	dumper
0x98	fields	✓ dumper + mov rbx,[rdi+0x98] in mono_class_get_field_from_name
0xa0	methods	dumper
0xa8	this_arg (MonoType, 16 bytes)	dumper
0xb8	_byval_arg (MonoType, 16 bytes)	dumper
0xc8	gc_descr (pointer-sized)	dumper
0xd0	runtime_info	✓ dumper + mov rsi,[rdi+0xd0] in mono_class_vtable post-has_failure-branch
0xd8	vtable	dumper
0xe0	infrequent_data (MonoPropertyBag, 8 bytes)	✓ dumper + mov rax,[rdi+0xe0] in mono_class_vtable on-has_failure branch
0xe8	unity_user_data	dumper

Total sizeof(MonoClass) = 240 (= 0xf0).

MonoClassField (each entry 32 bytes):

Offset	Field
0x00	type (MonoType *)
0x08	name (const char *)
0x10	parent (MonoClass *)
0x18	offset (i32)

MonoVTable (base size 80, plus flex trailing vtable[]):

Offset	Field
0x00	klass
0x08	gc_descr
0x10	domain
0x18	type
0x20	interface_bitmap
0x28	max_interface_id (u32)
0x2c	rank (u8)
0x2d	initialized (u8)
0x2e	flags (u8)
0x34	imt_collisions_bitmap (u32)
0x38	runtime_generic_context
0x40	interp_vtable
0x48	vtable[0] — start of static storage / method trampolines

vtable->data[offset] reads (for STATIC-flagged fields) land at vtable_base + 0x48 + offset. This is the address the walker uses to read PAPA.<Instance>k__BackingField.

MonoObject (16 bytes):

Offset	Field
0x00	vtable
0x08	synchronisation

MonoArray (32 bytes fixed + flex trailing vector[]):

Offset	Field
0x00	obj (MonoObject)
0x10	bounds
0x18	max_length (uintptr_t)
0x20	vector[0] — start of element storage

MonoDomain:

Offset	Field	Evidence
0x90	state (u32)	cmp DWORD PTR [rcx+0x90], 0x3 in mono_domain_assembly_open_internal (rcx = domain)
0x94	domain_id (i32)	movsxd rcx,[r14+0x94] in mono_class_vtable fast path (r14 = domain param)
0x98	shadow_serial (i32)	source order — gint32 immediately after domain_id per domain-internals.h
0xa0	domain_assemblies (GSList *)	✓ source order (8-byte aligned after shadow_serial) + mov r14,[r13+0xa0]; mov rsi,[r14]; mov r14,[r14+0x8] GSList loop in mono_domain_assembly_open_internal (loop at 1800a8219..1800a828d)

Class-VTable hash and other MonoDomain fields are still TBD — those land when the walker stops needing the assembly walk and switches to class_vtable_hash for class lookup.

GSList (mono/eglib singly linked list, 16 bytes):

Offset	Field
0x00	data (gpointer)
0x08	next (GSList *)

✓ dumper + live disassembly: mov rsi,[r14] (data) and mov r14,[r14+0x8] (next) form the GSList loop in mono_domain_assembly_open_internal.

MonoAssemblyName (80 bytes, ENABLE_NETCORE off in MBE so major/ minor/build/revision/arch are u16):

Offset	Field
0x00	name (const char *)
0x08	culture (const char *)
0x10	hash_value (const char *)
0x18	public_key (const mono_byte *)
0x20	public_key_token[17]
0x34	hash_alg (u32)
0x38	hash_len (u32)
0x3c	flags (u32)
0x40	major/minor/build/revision/arch (5 × u16)

MonoAssembly (truncated to image — fields beyond not consumed):

Offset	Field	Evidence
0x00	ref_count (i32)	dumper
0x08	basedir (char *)	dumper
0x10	aname (MonoAssemblyName, embedded) — first field is aname.name so [asm+0x10] IS the name pointer	✓ dumper + mov rax,[rbx+0x10] reading the assembly name in mono_domain_assembly_open_internal (rbx = assembly)
0x60	image (MonoImage *)	✓ dumper + mov rsi,[rsi+0x60] reading the image pointer right after dereferencing the GSList data slot

MonoImage (truncated to class_cache):

Offset	Field
0x00	ref_count (int)
0x08	storage (MonoImageStorage *)
0x10	raw_data (char *)
0x18	raw_data_len (u32)
0x20	name (char *)
0x28	filename (char *)
0x30	assembly_name (const char *)
0x38	module_name (const char *)
0x4c0	assembly (MonoAssembly *)
0x4c8	method_cache (GHashTable *)
0x4d0	class_cache (MonoInternalHashTable, embedded by value)

✓ dumper for the full prefix; live disassembly confirms class_cache via lea rcx, [r13+0x4d0]; call mono_internal_hash_table_lookup at 1800c83b3..1800c83bc.

The intermediate offsets between module_name and assembly are controlled by the embedded MonoStreamHeader heap_* (6 × 16 bytes), the MonoTableInfo tables[MONO_TABLE_NUM] array (56 × 16 bytes), and several pointer fields. Re-derive from the dumper if you need them.

MonoInternalHashTable (40 bytes, embedded in MonoImage.class_cache):

Offset	Field	Evidence
0x00	hash_func (GHashFunc — function pointer)	✓ dumper + call QWORD PTR [rdi] in mono_internal_hash_table_lookup
0x08	key_extract (function pointer)	✓ dumper + call QWORD PTR [rdi+0x8]
0x10	next_value (function pointer)	✓ dumper + call QWORD PTR [rdi+0x10]
0x18	size (i32 — bucket count)	✓ dumper + div DWORD PTR [rdi+0x18]
0x1c	num_entries (i32)	dumper (source order between size and table; both gint with no padding)
0x20	table (gpointer * — heap-allocated array of size chain heads)	✓ dumper + mov rbx, [rdi+0x20]

For class_cache iteration the walker bypasses the function-pointer callbacks (we can't invoke remote function pointers) and walks MonoClassDef.next_class_cache = 0x108 directly. Each chain entry is a MonoClassDef * whose embedded MonoClass lives at offset 0; its name (offset 0x48) and class_kind (offset 0x1b) are already in MonoOffsets.

MonoClassDef.next_class_cache (chain pointer for class_cache buckets): offset 0x108 per dumper. Stored as MonoClass * in the header but always points to the next MonoClassDef * in the bucket.

MonoClassRuntimeInfo (inferred from mono_class_vtable fast path):

Offset	Field
0x00	max_domain (u16)
0x08	domain_vtables[N] (array of pointers, indexed by domain_id)

The disagreement that is now resolved

Earlier sessions flagged a 0xd0 vs 0xe0 disagreement on runtime_info. Root cause: the disassembly I initially eyeballed as the runtime_info load was actually on the has_failure branch, where [rdi+0xe0] reads infrequent_data (the property bag used to fetch the failure's exception data). The real runtime_info load is at [rdi+0xd0] on the non-failure branch. Both the dumper and the live disassembly now agree: runtime_info = 0xd0. The earlier interpretation error was mine, not a build-layout anomaly.

Walker code in sync

native/scry2_collection_reader/src/walker/mono.rs's MonoOffsets::mtga_default() pins class_fields=0x98, class_runtime_info=0xd0, class_flags_cluster=0x28 — all verified. The module's unit tests (43 across the crate) exercise every accessor against synthetic byte buffers. No live-memory reads yet; those land when field.rs / dict.rs / inventory.rs are wired up.

Struct offsets — open work

The walker's mono.rs module pins offsets verified by both the offsets_probe/ dumper and live disassembly. All offsets required by class_lookup, image_lookup, and the existing inventory walk are now in. The next walker module (domain.rs) needs no new struct offsets — it composes existing pieces (pe, prologue, mono_get_root_domain).

Method for each offset

For each field:

1. Locate the field in the Unity header (class-private-definition.h or equivalent).
2. Count bytes from the top of the struct, respecting:
   • Pointer alignment (8 bytes on x86-64)
   • Bitfield packing (Windows MSVC ABI differs from Itanium/SysV — the MonoBleedingEdge Windows DLL uses MSVC bitfield rules)
   • #ifdef branches taken (see "Conditional-compilation gates" above)
3. Pick a Mono function that reads or computes with the field.
4. Disassemble it against MTGA's live bytes (see "Disassembly evidence" pattern above) to confirm the literal offset matches.
5. If the two agree, pin in mono.rs. If they diverge, widen the investigation — do not ship a guess.

Disassembly recipe

DLL=/home/shawn/.local/share/Steam/steamapps/common/MTGA/MonoBleedingEdge/EmbedRuntime/mono-2.0-bdwgc.dll
# find the export:
objdump -p "$DLL" | grep -E '^\s+\[.*<symbol_name>'
# parse the export table yourself, or use walker/pe.rs::find_export_rva.
# then disassemble (VA = 0x180000000 + RVA):
objdump -d --disassembler-options=intel --start-address=<VA> --stop-address=<VA+N> "$DLL"

Read budget — operational knob

Every NIF wraps its process_vm_readv closure in read_budget::bounded to cap one walk at WALK_READ_BUDGET reads. The cap exists to stop runaway walks (PID reuse against an unrelated process; self- referential pointer loops on partially-zeroed memory) from pegging a dirty-IO scheduler thread.

The cap is load-bearing. Past the limit every read returns None and the walker silently bails as if the chain were broken — typically surfacing as WalkError::ClassNotFound("PAPA") because PAPA discovery is the first big read-burner.

Measured against MTGA build Fri Apr 11 17:22:20 2025 (222 loaded Mono images), a single walk costs:

Walker	reads_used
walk_match_info (Chain-1)	~69,000
walk_match_board (Chain-2)	~64,000

Both chains scale with the image count, since find_class_in_images iterates every image looking for the target class. Class lookup within an image walks the class hash buckets (cost ~ O(classes per image)).

Current cap: 200,000 reads (set v0.30.3, ~3× headroom over measured cost). When MTGA grows further:

1. Use walker_debug_walk_match_info_with_stats(pid) / walker_debug_walk_match_board_with_stats(pid) (NIFs in Scry2.MtgaMemory.Nif) to read live reads_used against the running process. Both return (result, %{reads_used, budget}).
2. The Settings → Memory reading "Run diagnostic capture now" button surfaces these inline.
3. If reads_used creeps above 70% of budget, raise the cap (and document the new measurement in this section).

The structural fix is to cache discovery results (PAPA, MatchSceneManager, runtime class addresses) per (pid, mono_base), dropping the steady-state cost from "scan 222 images" to "follow 5 pointers" (a few hundred reads). v0.31.0 adds that cache; until then, the budget is the load-bearing defense.

Full diagnostic procedure and evidence: spike19_read_budget_regression/FINDING.md.

Sibling module: the POC

mtga-duress/experiments/mtga-reader-poc/ — working structural-scan implementation. 4,091 cards recovered on the research machine in ~1.4s. Does not use any Mono offsets. Value: its address-discovery and process_vm_readv-based read primitives are a reference for how the production crate handles memory access, even though the walker uses a completely different locator strategy.

Related scry_2 artifacts

• native/scry2_collection_reader/src/walker/prologue.rs — parses mov rax, [rip+disp32]; ret (validated against mono_get_root_domain above).
• native/scry2_collection_reader/src/walker/pe.rs — finds a named export in a mapped PE32+ image (used before prologue.rs runs).
• decisions/architecture/2026-04-22-034-memory-read-collection.md — ADR for the overall reader, including the walker-in-Rust decision (Revision 2026-04-25). Decision document, not a protocol reference — details live here.
• plans.md — "Currently in progress — Walker phase 6 (Rust)" tracks module status.
• mtga-duress/experiments/spikes/spike{5,6,7,10}/FINDING.md — prior research.