psxrecomp/docs/MOD_PACKAGES.md

PSXRecomp mod packages and features

A .psxmod is a versioned installation, provenance, and trust boundary. A package may contribute any number of independently configurable features. The launcher presents those features as the primary Mods list; package installation, version selection, and removal are a secondary management view.

Feature identity is always (package_id, feature_id). Enabling one feature never enables, disables, or reconfigures another feature.

The player selects a verified stock BIN/CUE. Resolution produces guarded native operations and sparse disc overlays without rewriting or replacing that stock image.

Where packages live

Two catalog roots sit beside the executable, split by who owns the files:

<exe>/mods/
  bundled/     build output — the framework's mods/builtin/packages (minus any
               the title declines with EXCLUDE_BUILTIN_MODS) plus the title's
               mods/preloaded/packages. Every build WIPES and re-stages this
               tree, so nothing a player owns may live here.
  installed/   launcher-owned — .psxmod archives installed through the Mods
               manager. No build ever touches this tree.
  state.toml   user selection state (enabled features, option values).

Both roots use the same <package-id>/<version>/manifest.toml layout and are scanned into one catalog, bundled first. An installed package with the same id as a bundled one deliberately shadows it and records that it did so, so an override is visible rather than decided by directory-iteration order.

A bundled package is not removable from the Mods page: deleting build output would succeed and then be undone by the next build. Remove it from the title's mods/preloaded/packages instead.

Only bundled/ ships in a release. installed/ and state.toml are the local machine's and are excluded by every packager.

Migration. A pre-split install has one mods/packages/ tree holding both. The first scan moves each package the current build did not also stage into installed/, drops the rest as redundant build output, and removes the old tree — but only once every version directory has been dealt with. Anything that could not be moved is left exactly where it is and reported.

A manifest that fails to parse is never skipped silently: it is reported by scan_errors() and logged, naming the path and the reason.

How bundled/ gets staged (titles: read this)

The framework owns the layout. A title declares a directory, never a path shape. Hand the title's catalog to psxrecomp_add_runtime_target():

set(MYGAME_PRELOADED_MODS "${CMAKE_CURRENT_SOURCE_DIR}/mods/preloaded")

psxrecomp_add_runtime_target(psx-runtime
    ...
    PRELOADED_MODS_DIR "${MYGAME_PRELOADED_MODS}"
)

PRELOADED_MODS_DIR names a directory shaped like <dir>/packages/<package-id>/<version>/manifest.toml, optionally with a README.md beside packages/. On every build of that target the framework:

1. wipes <exe-dir>/mods/bundled (build output only — never installed/ or state.toml),
2. removes exactly the ids it is about to stage from any pre-existing mods/packages, which migrates a build directory made before the split while leaving a player's own legacy packages for migrate_legacy_root(),
3. copies the framework's mods/builtin/packages/<id> then the title's <dir>/packages/<id> into mods/bundled/<id> — in that order, so a title may deliberately OVERRIDE a builtin at the same id and version (Tomba 2's Italian runtime ships localized psx.* manifests exactly this way),
4. copies <dir>/README.md to mods/README.md, and
5. verifies the result with runtime/psx_check_mod_catalog.cmake.

Pass PRELOADED_MODS_DIR NONE to declare that a target intentionally ships no game catalog. A target built with COSIM stages nothing: it has no launcher, and it shares an output directory with the real runtime.

Declining a framework builtin (EXCLUDE_BUILTIN_MODS)

Every package under the framework's mods/builtin/packages targets game_id = "*", so by default every title ships all of them. A title that does not want one — because it ships its own replacement, or because the feature is wrong for it — names it:

psxrecomp_add_game_runtime(psx-runtime
    ...
    PRELOADED_MODS_DIR "${CMAKE_CURRENT_SOURCE_DIR}/mods/preloaded"
    # WipEout 3's own team-mark bezel replaces the generic file-picker one,
    # and host-paced fast loading is not offered for it.
    EXCLUDE_BUILTIN_MODS
        psx.enhancement.fast-loading
        psx.presentation.bezel
)

EXCLUDE_BUILTIN_MODS is accepted by both psxrecomp_add_game_runtime() and psxrecomp_add_runtime_target() (the PGXP clone inherits it). An excluded package is absent, not hidden, the same rule as the developer channel:

• it is never copied into <exe-dir>/mods/bundled, so the launcher cannot list it and every release packager — which all ship the build's staged tree — cannot ship it either;
• the build publishes the exclusions beside the catalog manifest as psx_mod_catalog_<target>.excluded.txt. The build-time guard fails if an excluded id turns up in mods/bundled anyway, and tools/release_stage.py stage-mods both refuses such a catalog and stops counting an excluded builtin as missing when a caller passes the framework's mods/builtin as a --mod-source;
• the framework itself is unchanged: the package, its plugin and its C API stay available to every other title.

Configure fails loudly when an excluded id is not a framework builtin (a typo would otherwise leave the package shipping while the CMakeLists reads as if it did not), and when the title's own catalog provides the same id — that is an override, and excluding and overriding one id at once contradicts itself. The selection lives in runtime/psx_mod_catalog_select.cmake; both it and the guard are exercised by runtime/tests/test_mod_catalog_layout.py.

A player's mods/state.toml written by an earlier build may still name an excluded package. That selection is dormant, not an error: see State and migration.

Do NOT write your own copy_directory into <exe-dir>/mods. Five titles did, and the reason it is now a build error is worth stating: a hand-written copy names the destination as a string, so when framework commit 4cc04be3 renamed the staged catalog from mods/packages to mods/bundled, all five kept staging into a directory nothing reads. Nothing failed to configure, compile or link — the coupling has no compile-time or link-time consumer — and the defect surfaced only when a release packager ran, in a different repository, on a later day. Two guards now close that window:

• configure time — a project with packages under mods/preloaded/packages that does not declare PRELOADED_MODS_DIR is a FATAL_ERROR, naming the packages and the argument to add.
• build time — psx_check_mod_catalog.cmake runs as the last POST_BUILD step (registered through cmake_language(DEFER), so it lands after anything the title registered) and fails the build if a declared package did not reach mods/bundled, or if any package this build stages turned up under mods/packages. It is also registered as the ctest psx_staged_mod_catalog_test.

Both are exercised by runtime/tests/test_mod_catalog_layout.py.

The release packagers assert the same invariant one layer out: Add-ModCatalog in tools/release_overlay_stage.ps1 reads mods/bundled and refuses to package when a package the sources define is missing from it. It asserts that invariant rather than a hard-coded count, because a count describes only one side of a catalog two repositories contribute to and goes stale the moment either side gains a mod.

Feature manifest

Write new manifests at the current format version, which is 7. Older versions stay readable so installed packages survive an update, and each section below notes the version a field first required.

format_version = 7
id = "example.localization"
version = "1.2.0"
name = "Example Localization Pack"
author = "Example Author"
description = "Independent title and script features."
license = "MIT"
resolver = "declarative"

[[target]]
game_id = "SLUS-00000"
# Required for disc overlays. Use the digest of the supported stock image.
disc_sha256 = "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"

[[feature]]
id = "title-screen"
name = "Title Screen"
description = "Selects the title-screen artwork."
group = "Localization"
default_enabled = false

[[feature]]
id = "retranslation"
name = "Retranslation"
description = "Uses the revised English script."
group = "Localization"

[[option]]
feature = "title-screen"
id = "variant"
label = "Title artwork"
type = "choice"
default = "rockman"

[[option.choice]]
value = "mega-man"
label = "Mega Man X6 (USA)"

[[option.choice]]
value = "rockman"
label = "Rockman X6 (Japan)"

[[patch]]
feature = "title-screen"
target = "main_exe"
address = 0x80041234
expected = "2a 00 02 24"
replace = "0e 00 02 24"
when = { variant = "rockman" }

[[overlay]]
feature = "retranslation"
target = "disc_raw"
offset = 123456
file = "assets/retranslated-script.bin"
sha256 = "..."
# Optional additional guard over the same range in the stock image.
expected_sha256 = "..."

Every [[option]], [[patch]], and [[overlay]] in a feature-style manifest must name its owning feature. Ambiguous operations are rejected.

Option types are boolean, choice, and bounded integer. Conditions are feature-local: when = { option = "value", ... } requires every listed option to match. The legacy when_option/when_value pair remains accepted for a single condition.

A feature with hidden = true is left out of the launcher's lists while it is disabled; while enabled it is listed so the player can turn it off. A title that sets [runtime] hide_hidden_mod_features = true in game.toml never shows it: the launcher does not list it (enabled or not), does not name it in the lobby summary, "Enable all" / "Disable all" leave it alone, and a package whose every feature is hidden is not listed under "Installed packages". Either way it runs exactly as default_enabled and mods/state.toml say, so a hidden default-on feature is simply active. (recomp-ui launcher_mod_visibility.h.)

Bounded integer patches

Package format 2 can encode a bounded integer option directly into a guarded write:

format_version = 2

[[feature]]
id = "starting-lives"
name = "Starting Lives"

[[option]]
feature = "starting-lives"
id = "count"
label = "Lives"
type = "integer"
min = 0
max = 99
step = 1
default = 2

[[patch]]
feature = "starting-lives"
target = "main_exe"
address = 0x8001DE64
expected = "02 00 02 24"
replace_from = { option = "count", encoding = "u16le", offset = 0 }

[[patch]]
feature = "starting-lives"
target = "main_exe"
address = 0x8001DE70
expected = "03 00 02 24"
replace_from = { option = "count", encoding = "u16le", offset = 0, addend = 1 }

replace_from and literal replace are mutually exclusive. The referenced option must be a bounded integer owned by the same feature. The initial encodings are u8, u16le, and u32le. offset selects a byte field inside the expected guard and defaults to zero. Generated replacement bytes begin as an exact copy of the expected bytes, then the encoded value replaces only that field. This lets a MIPS immediate, for example, retain a guard and collision claim over its complete instruction. addend is the only supported transform, and the complete declared option range after that addend must fit the unsigned encoding.

There is deliberately no host-endian encoding, signed inference, mask, shift, scale, expression language, or partial-field merge. A package uses multiple guarded [[patch]] entries when the same value has multiple destinations. Generated bytes enter the ordinary pre-boot write plan, collision checks, and fingerprint. A generated value identical to the stock guard is omitted as a no-op, so an enabled stock-valued option does not claim or conflict on bytes it does not change.

Integer values use canonical decimal text. Leading plus signs, redundant leading zeroes, values outside the bounds, and values not aligned to step are rejected.

Ordered values and split MIPS immediates

Package format 3 adds feature-local ordering constraints for related integer fields:

format_version = 3

[[constraint]]
feature = "rank-thresholds"
kind = "ordered_integer"
direction = "nondecreasing"
options = ["rank-c", "rank-b", "rank-a"]

All listed options must be integer options on that feature. Defaults must satisfy the constraint. While a feature is enabled, an edit that would invert the order is rejected with the neighboring option labels. Disabled features may retain an incomplete or invalid draft, but cannot be enabled until it is valid. nonincreasing is also supported.

Format 3 also provides a narrow, typed transform for constants constructed by a linked MIPS LUI/ORI pair:

replace_from = {
  option = "speed",
  encoding = "mips_lui_ori_u32",
  omit_when_default = true
}

The patch must target one aligned, fully guarded eight-byte main_exe instruction pair. The loader verifies the opcodes and register linkage, then places the raw high and low 16-bit halves into the two immediates. It does not apply signed-ADDIU carry adjustment. offset and addend are not accepted for this encoding.

omit_when_default suppresses the entire patch when the selected value equals the option default. This models source tools whose declared default means "make no writes," including cases where multiple guarded sites contain different stock values. For any nondefault selection, every declared site retains its collision claim even if one generated replacement happens to equal its stock guard.

Sparse fields and integer predicates

Package format 4 separates a patch's complete expected-byte guard from the fields it owns and writes. This is for semantic records whose independently configurable fields share one useful guard:

format_version = 4

[[option]]
feature = "saber-timing"
id = "frames"
label = "Frames"
type = "integer"
min = 0
max = 99
default = 2

# Positive values change only byte 0.
[[patch]]
feature = "saber-timing"
target = "main_exe"
address = 0x80077640
expected = "02 42 01 02"
fields = [
  { offset = 0, option = "frames", encoding = "u8" },
]
when_integer = { option = "frames", op = "gt", value = 0 }

# Zero has a narrow, explicitly declared compound representation.
[[patch]]
feature = "saber-timing"
target = "main_exe"
address = 0x80077640
expected = "02 42 01 02"
fields = [
  { offset = 0, replace = "01" },
  { offset = 2, replace = "00" },
]
when_integer = { option = "frames", op = "eq", value = 0 }

fields is mutually exclusive with replace and replace_from. Every field has a nonnegative offset and exactly one payload form:

• replace = "..." supplies non-empty literal bytes; or
• option plus encoding uses a bounded integer option on the same feature, with the optional checked addend.

Fields must fit inside expected and their owned byte ranges may not overlap. The supported dynamic encodings are the existing u8, u16le, u32le, and linked mips_lui_ori_u32 forms. A sparse MIPS field owns only the two immediate halfwords while the complete linked instruction pair remains guarded; as with format 3, that encoding does not accept an addend.

Resolution omits individual fields whose generated payload already equals the guard. If no field changes, the patch is a no-op. Otherwise the plan retains the complete guard and the exact remaining owned ranges. Runtime guard validation checks every byte of expected before applying any writes, while collision detection and writing use only the owned fields. Thus two features can safely own adjacent bytes in one record without either overwriting the other. Overlapping guards must still agree on their expected bytes; conflicting guards make the plan unsatisfiable and are rejected.

when_integer is a patch-level, feature-local predicate over one bounded integer option. op is exactly one of eq, ne, lt, le, gt, or ge, and value is an integer constant inside the option bounds. Equality constants must also be selectable under the option's step. String-valued when conditions and one when_integer predicate may coexist and are ANDed.

Sparse fields and integer predicates are still pre-boot plan construction. They do not provide a general expression evaluator, masks, arithmetic beyond the checked field addend, package code execution, or per-frame dispatch.

Channels

A feature declares how finished it is. Format 6 puts channel on the feature, not the package:

format_version = 6
id = "example.enhancements"

[[feature]]
id = "widescreen"
channel = "experimental"     # ships, badged, default off

[[feature]]
id = "hook-trace"
channel = "developer"        # absent from any release build

Channel	Ships	In the launcher
stable (default)	yes	no tag — the absence is the stable case
experimental	yes	amber EXP tag, and a line saying it is unvalidated
developer	no	secondary-accent DEV tag; only ever visible on a local build

An absent channel means stable. A package may still declare one, which its features inherit unless they state their own — which is how a format-5 manifest carrying a package-level channel keeps working unchanged.

Why the feature and not the package. A package is the installation and trust boundary; how finished one of its features is has nothing to do with that. When the marker sat on the package, a catalog holding one player-ready feature and one developer instrument had to declare itself entirely developer — so neither shipped, and the documented workaround was to split the catalog into two packages. Channels per feature remove that trade.

"Developer does not ship" means absent, not hidden. Two mechanisms, one per catalog root:

• bundled/ is filtered when it is staged. tools/mod_channel_filter.py emits a manifest without the developer features and without the [[option]], [[patch]], [[overlay]], [[plugin]], [[resource]], [[constraint]] and [[requirement]] entries that only served them; a package whose every feature is developer has its directory removed. This is generation, not rewriting: the staged catalog is build output and the author's manifest in the repo is never touched.
• installed/ is refused at load. A third-party archive is never modified, so the runtime declines to surface developer features from one instead.

The runtime gate is the build definition PSX_MOD_DEVELOPER_CHANNEL, which runtime.cmake sets for a local build and clears under $CI. A contributor reaches developer features by cloning the repo and building; a release build carries neither the features nor their operations, so a stale state.toml naming one cannot reach them either.

Packaging defaults the exclusion from $CI — on under any CI provider, off locally. --exclude-dev-mods / --include-dev-mods (or EXCLUDE_DEV_MODS=0|1) override it, and project_studio build export --exclude-dev-mods reproduces what a release would contain.

Trusted static plugins

Package format 5 can activate a game-owned plugin that is already statically linked into the executable:

format_version = 5

[[feature]]
id = "warp-debug-menu"
name = "Warp Debug Menu"

[[plugin]]
feature = "warp-debug-menu"
id = "example.warp-debug"

The plugin id is a stable registry key, not a library path or symbol name. The package archive supplies no native code. Resolution fails before launch when an enabled plugin has no registered implementation or when two features claim the same plugin id. Active plugin identities and owners participate in the canonical plan fingerprint.

An implementation may register an activation callback, a deterministic guest-VBlank callback, function-entry hooks, or any combination under the same id. A function-entry hook (psx_mod_register_function_entry_plugin) runs at the top of a generated function the game config lists in [recompiler] mod_function_entry_funcs, and at every interpreted entry to the same address (segment bits ignored), so the backend running the page does not matter. Like the other kinds it satisfies a manifest [[plugin]] and runs only while the resolved plan activates its id: the active hooks are flattened into an address table at plugin activation, and a plan change drops them until the next activation. Activation runs after the launcher's final mod-plan commit and before renderer/window initialization; it is appropriate for a game-owned mod that selects a fixed display aspect or another pre-boot host feature. VBlank callbacks run from the emulated GPU VBlank event, independent of host presentation, pacing, turbo, or skipped frames. Trusted callbacks receive only the narrow C services exposed by runtime/include/mod_plugins.h. Games should continue to use declarative patches and overlays when those operations are sufficient.

Session starts and mod-owned state

What a plugin sets up should last only for a session whose resolved plan activates it. Function-entry hooks follow that rule by construction: the commit and the netplay clear empty the hook table, and only activation rebuilds it, so a hook never runs in a session that did not activate its id (including a netplay session, which clears the plan). The host state a plugin changes through the psx_mod_* setters is process-wide, so the runtime resets it at every session start instead.

An offline session ends the process when the player closes the game. The one in-process second session is the lobby rematch: a netplay match launched from the lobby returns to the lobby launcher when it ends, and the next launch from there, netplay or offline, re-enters the emulator in the same process. The session before a rematch is therefore always a netplay match, which ran with the plan cleared, so no plugin activated in it.

The reset runs immediately before activation in the first session, and on the rematch path after its commit or netplay clear. What it fixes today is the netplay local viewport's Fit and fixed aspect carrying from a match into an offline rematch. The rest of the table is defensive, for the state listed here.

State	Setter	Reset to	When
Fit / capped adaptive aspect	psx_mod_set_adaptive_display_aspect	off, cap 16:9	every session
World-scene predicate	psx_mod_set_world_scene_predicate	NULL	every session
Retained-scene predicate	psx_mod_set_retained_scene_predicate	NULL	every session
Adaptive backdrop preload	psx_mod_set_adaptive_backdrop_preload	0	every session
Bezel artwork	psx_mod_set_bezel_artwork	none (see below)	every session
Frame-interpolation blend mode	psx_mod_set_frame_interpolation_blend	default	every session
Native VBlank pacing and its rate	psx_mod_set_native_vblank_rate	off, 0	every session
Frame period, if native VBlank pacing was on	psx_mod_set_native_vblank_rate	first-session value	later sessions
Frame interpolation and its rate	psx_mod_set_frame_interpolation	first-session value	later sessions
Vsync forced off	psx_mod_set_frame_interpolation, psx_mod_set_native_vblank_rate	first-session value	later sessions
Automatic FMV skipping	psx_mod_set_auto_skip_fmv	first-session value	later sessions
8 MiB main RAM request	psx_mod_set_main_ram_8mb	retail 2 MiB	later sessions
Texture-bank resolver and batching	psx_mod_set_texture_bank_resolver, psx_mod_set_texture_bank_batching	NULL, off	later sessions

"First-session value" is what settings, environment overrides (such as PSX_VSYNC) and the launcher resolved before the process's first activation. The first call records those values and changes nothing that is not already at its initial value, so the first session, and every run that never soft-returns, behaves exactly as without the reset. The RAM request matters on a rematch because memory_init() latches the requested geometry again at every boot, including the rematch's.

Bezel artwork has two parts. The reset clears the artwork path, so the next session start loads nothing unless its own activation selects artwork again. The OpenGL renderer drops the loaded texture itself when it shuts down, which happens when a session ends by returning to the lobby (and at process exit), so a rematch never draws the previous session's artwork in its new context.

Not reset, and why:

• The fixed display aspect (psx_mod_set_fixed_display_aspect) and the renderer (OpenGL, which psx_mod_set_frame_interpolation and psx_mod_set_bezel_artwork force) are launcher controls. A rematch takes both from the lobby launcher, which is seeded from the live values. For the aspect, the rematch path then re-applies the Settings clamp (4:3, since widescreen is mod-owned) before the netplay local viewport, so a match's 16:9 or 21:9 does not carry into an offline rematch. A renderer forced by a plugin would be carried the same way, but no plugin activates in the session before a rematch.
• Guest memory, GPU-DMA memory, texture-packet arenas and defined texture banks (psx_mod_alloc_guest_memory, psx_mod_alloc_gpu_dma_memory, psx_mod_alloc_texture_packet_memory, psx_mod_define_texture_bank) live for the process. A bank ID is read only from packets in a plugin's own arena, which stock game code does not use.

A rematch is not a full session start. It re-enters below the first session's setup block, so it does not run mod_runtime_activate_plugins() and does not reset controller overrides and policies, load acceleration or disc speed (the first session resets those before activation). An offline rematch with mods enabled therefore applies the plan's main-EXE and disc patches and runs its VBlank callbacks, but no activation callback runs and no function-entry hook runs. A VBlank callback must not assume its plugin's activation ran in the same session. If the rematch path ever activates plugins, the reset must run before that activation.

A plugin should establish what it needs in its activation callback and not rely on state from an earlier session; its own static variables are its responsibility.

psx_mod_set_load_acceleration(multiplier, release_frames) is the narrow pre-boot service for a game-owned fast-loading feature. It changes host wall-clock pacing only: guest VBlanks, CD deadlines, interrupts, callbacks, and game logic still execute. Multipliers 2 through 16 are bounded choices; zero selects uncapped host speed. A zero-frame release stops acceleration as soon as the sustained-load predicate clears, which is appropriate for timing-sensitive or speedrun-oriented packages.

psx_mod_set_disc_speed(divisor, instant_max_per_frame) is the guest-visible alternative. Divisors 2 and 4 shorten emulated CD deadlines; zero selects the bounded instant scheduler. Because this changes interrupt timing, packages should label it experimental and make it mutually exclusive with host-only load acceleration (normally as choices in one default-off feature).

Native operations

main_exe writes use PSX guest virtual addresses. Expected bytes are checked after the BIOS loads the executable, then the complete write plan is applied before its entry point. Changed executable ranges use the existing dirty-RAM interpreter/native-overlay machinery; untouched functions remain on the static native path.

Small disc_raw and disc_user patches are equal-length guarded writes and may not cross a sector boundary:

• disc_raw offsets use lba * 2352 + byte_in_sector.
• disc_user offsets use lba * 2048 + byte_in_sector.

File-backed [[overlay]] operations are intended for large assets and may span any number of sectors. Their paths must remain inside the archive. Payload size and SHA-256 are verified while scanning, but disabled payloads are not retained in memory. Enabled payloads are loaded and reverified during resolution, then indexed by target and LBA before boot. A CD read performs a direct indexed lookup rather than scanning every installed mod.

Feature disc overlays require an exact disc_sha256 on every target entry. expected_sha256 can additionally guard the replaced stock range.

State and migration

mods/state.toml format 2 stores selected package versions separately from per-feature enabled states and values:

format_version = 2

[[package]]
id = "example.localization"
version = "1.2.0"

[[feature]]
package_id = "example.localization"
id = "title-screen"
enabled = true

[feature.values]
variant = "rockman"

[feature.resources]
artwork = "C:/Users/You/Pictures/example-bezel.png"

State format 1 and package-only manifests remain readable as a migration aid. They appear through one synthetic legacy feature. New packages should use explicit features.

Selections for packages the catalog does not hold are dormant. State can outlive the package it names: the player deleted an installed archive, a release build stripped a developer-only package, or the title now declines a framework builtin with EXCLUDE_BUILTIN_MODS. Resolution only visits packages that are present, so such a selection contributes nothing to the plan (and does not change its fingerprint), and it is not a launch error — the Mods page no longer lists the package, so the player would have no way to clear one. save_state() keeps the entry verbatim, so the choice applies again if the package ever returns, and the runtime names each one at startup (mod selection kept but inactive: <id> is not in this build's mod catalog). A selection pinned to a version that is missing while other versions of the package are present remains an error, because the Mods page can fix that one.

The old derived_disc VCDIFF mechanism is legacy conversion scaffolding only. Feature-style manifests reject it. It is not a product mod primitive, fallback, or image-selection workflow; patched discs may be used offline as parity oracles while converting known mods to native operations.

Resolution and diagnostics

Before boot, the manager:

1. verifies the selected stock game and revision;
2. expands only enabled features and their selected options, plus every feature an active [[requirement]] activates (see Implicit requirements);
3. orders active packages deterministically by dependencies;
4. verifies enabled payloads and operation bounds;
5. collision-checks the complete owned byte-range plan and guard compatibility;
6. coalesces only truly identical target/range/expected/replacement writes or identical overlays; and
7. produces a canonical SHA-256 plan fingerprint.

Incompatible overlaps fail before launch. Structured diagnostics identify both (package, feature) owners and the exact contested target range. The launcher marks both feature rows and lets the user decide what to disable. It never silently chooses a winner.

Operation boundaries are not semantic boundaries. Legacy full-record writes compose when both their expected and replacement bytes agree throughout the owned intersection. Format-4 sparse patches collide only on declared owned fields, while their complete guards must remain mutually compatible. Partially overlapping overlays compose when their replacement payload bytes agree. A differing owned byte or incompatible guard produces a diagnostic at that exact location. Exact duplicate operations may be coalesced.

Package-level dependencies and conflicts are reserved for actual implementation relationships. Mutually exclusive choices such as US versus Japanese artwork belong inside one feature as option values. A relationship that holds only for some selections of one feature is a [[requirement]], not a dependency.

Implicit requirements across packages

Package format 7 lets a feature, while a condition on its own options holds, need a feature of another package:

format_version = 7
id = "wipeout3.enhancement.framerate"

[[requirement]]
feature = "framerate"                 # the requiring feature (owner)
package = "psx.enhancement.8mb-ram"   # the package that provides it
requires_feature = "8mb-ram"          # its feature to activate
when = { extras = "enhanced" }        # same condition syntax as [[plugin]]

[[requirement]]
feature = "framerate"
package = "psx.enhancement.8mb-ram"
requires_feature = "8mb-ram"
when = { extras = "full" }

when (or when_option/when_value) is the same feature-local condition plugins and overlays use; every listed option must match, so a requirement that holds for several values is written once per value. Omit it for a requirement that holds whenever the feature is enabled. version optionally restricts the provider with the [[dependency]] range syntax ("*" by default). Unknown fields are rejected, and so is a requirement naming its own package: a feature of the same package is a requires_feature [[constraint]].

The two existing mechanisms could not express this. [[dependency]] is package-level and unconditional, so WipEout 3's "NTSC / PAL Mode" would need 8 MB RAM even with Extras = None; a requires_feature constraint cannot name another package.

Resolution. While the requiring feature is enabled and its condition holds, resolve() activates the required feature for the session:

• even when it is hidden, default-off, or explicitly disabled in mods/state.toml -- the player chose the requiring option, and the requiring option cannot run without it;
• recursively: a derived feature's own [[requirement]]s and in-package requires_feature constraints are derived too, to a fixed point;
• without writing it to state.toml. A derived activation is not a player choice, so save_state() persists only what the player selected, and turning the requiring option back off leaves nothing behind. feature_enabled() keeps reporting the player's choice (the launcher's checkbox, so a hidden required feature stays hidden); feature_implicitly_enabled() reports the derived one.

The plan lists each derived feature in ModResolution::implicit_features with what required it, plans with and without the derivation have different fingerprints, and a committed plan's plugins read option values from ModResolution::selections -- the selection the plan was actually built from. The runtime names every derived feature at launch:

psxrecomp: mod feature psx.enhancement.8mb-ram/8mb-ram activated implicitly (required by wipeout3.enhancement.framerate/framerate)

An unmet requirement fails loudly. When the provider is absent from the catalog (removed, stripped from a release, or declined with EXCLUDE_BUILTIN_MODS), the selected version is missing, the version is out of range, or the provider has no such feature, the plan is rejected before launch:

wipeout3.enhancement.framerate/framerate requires psx.enhancement.8mb-ram/8mb-ram, but package psx.enhancement.8mb-ram is not in this build's mod catalog

It is also a diagnostic on the requiring feature, so the launcher marks that row. The requiring selection never runs without what it requires -- an 8 MB build on 2 MB RAM is exactly the failure this prevents. A package an active requirement uses cannot be removed from the Mods manager.

AOT profiles pin active requirements the way they pin plugins: tools/mod_package_images.py reports each active one as "<package>/<feature>" and a mod_packages entry must list the exact set under requirements.

The launcher needs no change for a hidden required feature: it lists a hidden feature only when the player enabled it, and the player did not. A visible required feature still shows the player's own checkbox state while it is derived; showing "on, required by X" needs a launcher field that does not exist yet.

Trusted adapters and archive safety

Owner-selected resources

Format-5 packages may declare feature-owned resources that the launcher renders with its native file/folder picker:

[[resource]]
feature = "bezel"
id = "artwork"
label = "Bezel image"
description = "Select an image to draw behind the game frame."
format = "file"
file_patterns = "*.png,*.jpg,*.jpeg,*.bmp"
file_description = "Image files"
required = false

Resources are paths selected by the player and persisted in mods/state.toml; they are not copied into the package. Optional resources with no selected path are omitted from the committed plan. Required resources reject launch while the feature is enabled and unset.

resolver = "builtin:<id>" selects a resolver statically registered by the game. Format-5 plugin ids likewise select only statically registered implementations. Packages cannot load arbitrary native code or select arbitrary symbols.

The installer accepts stored or DEFLATE-compressed ZIP entries, validates CRCs, rejects encrypted entries and unsafe or absolute paths, limits archives to 4096 files and 256 MiB expanded size, stages extraction, validates the manifest, and publishes the version atomically.

Presentation bezel packages

The framework registers psx.bezel, a trusted presentation plugin for OpenGL margin artwork. The built-in package declares an optional artwork image resource; when the feature is enabled and the player has selected an image, the runtime draws that image behind the game frame before presenting the normal 4:3 or widescreen content.

The built-in package psx.presentation.bezel targets every game but defaults to off, so the default presentation is unchanged: letterbox and pillarbox margins remain black. Enabling the feature without choosing artwork is also a no-op. The package supplies only the declaration and trusted plugin selection; archives still cannot load native code.

A title's own trusted plugin can call psx_mod_set_bezel_artwork(path) directly to ship its artwork. An absolute path (such as the built-in package's selected resource) is used as-is; a relative path like "bezels/qirex.png" is resolved against the executable's directory when the artwork loads, never the current working directory, so artwork the title stages beside its binary is found however the game was launched.

Retained-scene loading presentation (native-wide opt-in)

A trusted game plugin can register psx_mod_set_retained_scene_predicate(predicate) from mod_plugins.h when the game keeps displaying its previous framebuffer while loading. The cheap, pure emulation-thread callback returns PSX_MOD_SCENE_HOLD while that same scene is retained. It must not call presentation APIs recursively. Passing NULL removes the opt-in. Without registration, existing presentation behavior is unchanged.

In native-wide mode this holds the previous wide/4:3 classification even if a game-state flag or absent GTE activity would normally classify loading as 2D. It does not force menus wide, stretch artwork, change guest rendering or memory, or override the FMV veto. Return PSX_MOD_SCENE_RELEASE when a new scene replaces the retained image, so ordinary classification resumes. For double-buffered games whose draw-ready signal precedes the actual display flip, return PSX_MOD_SCENE_UNTIL_FLIP: the prior hold ends only when the displayed VRAM origin changes. Without a prior HOLD it behaves like RELEASE. Do not use UNTIL_FLIP for in-place image replacement. Crash's experimental adaptive feature uses its pending level transition and draw-skip globals for this; these game-specific addresses do not belong in the framework.

GPU reset and savestate restore discard this host-only history. A save loaded directly into a frozen loading frame cannot recreate wide reveal strips absent from the canonical saved framebuffer. ws_scene_hold_test covers long holds, menu release, delayed buffer flips, retained 4:3 scenes, FMV and timeline reset.