[BUG] Custom dealer inventories are cleared after save reload

[ifBars]

Summary

Custom dealers added by multiple NPC mods reportedly lose all inventory contents after quitting/reloading a save. The same behavior has been observed with three different custom-NPC mods, which points to a shared S1API persistence path rather than one mod's configuration.

This issue is intentionally limited to inventory persistence:

• Relationship resets and scheduled-deal cancellation across save/load are tracked in [BUG] Custom NPC relationships and scheduled deals reset after save reload #260.
• Relationship restoration had an earlier fix in fix(npc): restore custom NPC relationships from saves #219, but [BUG] Custom NPC relationships and scheduled deals reset after save reload #260 reports the symptom again on S1API 3.1.14 and therefore needs regression triage.
• fix(npc): restore behaviour lifecycle across runtimes #258 fixed custom NPC deal attendance/completion at runtime; it did not address accepted contracts disappearing after save/load.
• Addiction level and NPC unlock state reportedly continue to persist.

A similar inventory-loss bug was previously tracked in #61 and fixed by #69, so this may be a regression or a newer load-order variant.

Environment

• Schedule I version: not yet supplied; report followed the recent large game update
• S1API version at reproduction: not yet confirmed; retest on 3.1.14 is needed
• MelonLoader version: not yet supplied
• Runtime: not yet supplied (Mono vs IL2CPP)
• Affected mods: three separate custom-NPC mods were reported, but names were not supplied

Steps to reproduce

1. Install S1API and a mod that adds a custom dealer NPC.
2. Unlock/recruit the dealer if required.
3. Put items into the dealer's inventory and save the game.
4. Quit to the menu or exit the game.
5. Reload the save.
6. Inspect the custom dealer's inventory.

Expected behavior

The custom dealer's saved inventory contents, quantities, and slot state are restored.

Actual behavior

The custom dealer's inventory is empty after reload. Other persisted state, including addiction level and unlocked status, remains intact.

Impact

Players lose all stock assigned to custom dealers whenever they reload, breaking the core dealer loop across multiple NPC mods.

Investigation notes

The current custom-NPC loader deserializes Inventory directly in NPCLoader_Load_Prefix. The dealer-specific load prefix also stores the same payload in _pendingInventoryLoads, which is consumed from the NPCInventory.Awake postfix. Please verify the actual lifecycle ordering after the current game update, particularly whether Awake has already completed before the dealer load queues the pending item set, whether a later initialization/default pass clears restored slots, and whether the affected inventory is NPCInventory, dealer overflow inventory, or both.

Relevant code:

• S1API/Internal/Patches/NPCPatches.cs: NPCInventory_Awake_Postfix
• S1API/Internal/Patches/NPCPatches.cs: NPCLoader_Load_Prefix
• S1API/Internal/Patches/NPCPatches.cs: Dealer_Load_Prefix

Acceptance criteria

• Custom dealer inventory survives save -> quit/menu -> reload with the same items, quantities, and slots.
• Restored inventory is not overwritten by startup/default inventory initialization.
• Dealer overflow inventory continues to restore correctly.
• Base-game NPC/dealer inventory behavior is unchanged.
• The fix is validated separately on Mono and IL2CPP.
• Regression coverage exercises the relevant NPCInventory.Awake / NPC load / dealer load ordering.

Additional evidence requested

To narrow the regression, please add the exact Schedule I, S1API, MelonLoader, and runtime versions; the affected mod names; and a MelonLoader log from one save/reload cycle.

[ifBars]

@Diffuin Do a quick review of this issue and create a plan to fix it

[diffuin]

Implementation plan

Summary

The issue is actionable and does not need rewriting. Static review identifies a likely load-order regression: custom dealer inventory is both restored directly in NPCLoader_Load_Prefix and queued later for an NPCInventory.Awake postfix that may already have run. Move to one post-native-load restoration point that first ensures slots exist, while retaining the separate dealer overflow path. Runtime confirmation is still required.

Design decisions

1. Use NPCLoader_Load_Prefix as the sole owner of custom NPC inventory hydration after its native s1BaseNpc.Load(...) call, because this point follows dealer-specific load work.
2. Before loading an item set, call the existing wrapper initialization path and then load once into the resulting slots. Remove the dealer-only pending queue rather than retaining two competing restore paths.
3. Leave DealerData.OverflowItems restoration in Dealer_Load_Prefix; it uses dealer-owned overflow slots and is a separate persisted payload.

Implementation

1. Confirm the lifecycle boundary — Verify the exact ordering and payload shape before changing behavior.
   • Trace NPCLoader.Load, NPC.Load, Dealer.Load, and NPCInventory.Awake in current Mono and IL2CPP references; record whether Awake precedes dealer hydration. (S1API/Internal/Patches/NPCPatches.cs)
   • Capture one reporter log and save payload from a custom dealer with stocked primary and overflow inventories.
2. Consolidate primary-inventory restoration — Restore each custom NPC inventory once, after native loading has completed and slots are ready.
   • Replace direct primary-inventory hydration with a private helper that ensures the custom NPC inventory is initialized, deserializes the saved item set, and loads it into the final slot collection. (S1API/Internal/Patches/NPCPatches.cs, S1API/Entities/NPCInventory.cs)
   • Remove _pendingInventoryLoads and its NPCInventory.Awake consumption, or retain neither path if the helper covers every custom dealer load. (S1API/Internal/Patches/NPCPatches.cs)
   • Preserve base-game NPC behavior by invoking the helper only for custom wrappers and retaining the original path for non-custom NPCs. (S1API/Internal/Patches/NPCPatches.cs)
3. Protect dealer-specific persistence — Keep dealer overflow behavior separate and avoid duplicate or late restoration.
   • Audit Dealer_Load_Prefix so it restores recruitment, cash, contracts, customer assignment, and overflow items without reading or queueing the primary Inventory payload. (S1API/Internal/Patches/NPCPatches.cs)
   • Verify overflow-slot initialization and OverflowItems.LoadTo continue to use the Mono array and IL2CPP array paths already present. (S1API/Internal/Patches/NPCPatches.cs)
4. Add regression coverage and validate — Freeze the ordering contract and collect runtime evidence.
   • Add focused policy or helper tests for initialization-before-restore, one primary restoration per custom dealer load, and an already-awake ordering case. (S1API.Tests/Entities/NPCInventoryPersistencePolicyTests.cs, S1API/Internal/Patches/NPCPatches.cs)
   • Run restore, build, and the full contract suite for MonoMelon and Il2CppMelon. (S1API.sln, S1API.Tests/S1API.Tests.csproj)
   • Perform human save-to-menu-to-reload checks on Mono and IL2CPP with stocked slots, quantities, empty slots, and overflow inventory; repeat for a base-game dealer.

Implementation gates

• Does the current runtime invoke NPCInventory.Awake before Dealer.Load_Prefix queues the payload? A single lifecycle log or breakpoint trace will confirm or falsify the leading diagnosis.
• Which Schedule I, S1API, MelonLoader, runtime, and affected custom-NPC mod versions reproduce the issue?
• Does the report affect only NPCInventory.ItemSlots, or DealerData.OverflowItems as well?

Evidence and validation

Evidence inspected

• NPCLoader_Load_Prefix calls s1BaseNpc.Load(...) before directly deserializing Inventory into s1BaseNpc.Inventory.ItemSlots in S1API/Internal/Patches/NPCPatches.cs.
• Dealer_Load_Prefix separately queues that same Inventory payload only after its dealer-load work, while NPCInventory_Awake_Postfix is the sole pending-load consumer. A queue added after Awake cannot be consumed by that postfix.
• NPCInventory.EnsureInitialized() creates and normalizes slots, including removing excess slots. Inventory hydration must occur after this initialization to avoid loading into absent or later-replaced slots.
• The regular and beta stripped sources retain the relevant NPCLoader, NPCInventory, Dealer, and DealerData.OverflowItems seams. They establish named Mono seams only; they do not prove IL2CPP patch behavior or live ordering.

Validation performed

• Read the Schedule One modding, issue-review, NPC-creation, and writing guidance.
• Inspected the clean checkout, current NPC persistence patches, inventory initialization code, and existing test coverage.
• Read issues [BUG] Dealer Inventories get wiped #61 and [BUG] Custom dealer inventories are cleared after save reload #259 plus PRs Various fixed: PlaceableStorageEntity ID NRE, red eyes not applying, dealer inventory wipe #69, fix(npc): restore custom NPC relationships from saves #219, and fix(npc): restore behaviour lifecycle across runtimes #258 through the read-only GitHub broker.
• Inspected regular and beta stripped-source declarations for the relevant persistence and dealer seams.

Runtime validation remaining

• No repository build or test suite was run.
• Human Mono save, quit/menu, reload, and dealer-inventory inspection remains required.
• Human IL2CPP save, quit/menu, reload, and dealer-inventory inspection remains required.
• Human verification of primary inventory slots, quantities, empty-slot layout, dealer overflow, and unchanged base-game dealer behavior remains required.

• Create a pull request to implement this plan and close this issue when merged.

Diffuin run details

• Provider: codex
• Model: gpt-5.6-terra
• Reasoning: medium (bounded request)
• Elapsed: 122s
• Codex thread: 019ff2d0-caf7-7cc3-b194-eb50707f7df3

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AI notice: Generated with AI assistance and not guaranteed accurate. Verify findings and plans against the current source and runtime.

[diffuin]

I opened #261