BossMakerAPI

A server-authoritative boss framework for How to Fish, by SkyLiN3.

This is a library, not a boss pack. Install a compatible content mod to add bosses, or use the included documentation and source starter to make your own. Neither Devourer of Light nor Voltfin is installed by this package. Both are separate content mods; Voltfin also serves as the introductory creator tutorial.

Features

• Build bosses from verified vanilla creature templates while retaining their network components, movement, physics, hitboxes and compatible native AI.
• Configure stats, phases, phase gates, telegraphs, bounded charges, ability damage, forces, minions, rewards and catch-based encounters.
• Use the game's original boss bar and lifecycle for supported encounters.
• Validate host-controlled settings and synchronize them without overwriting client configuration files. Live edits affect future catches and new bosses; active encounters keep their captured balance.
• Opt into supported corpse identity/scale and living-encounter save checkpoints.
• Reject incompatible content or unsafe catch replacement while preserving the original fish when the replacement transaction fails.

Version 0.10.3 confirms supported custom-boss hit/kill feedback against the server's accepted hit and actual death. Feedback does not apply damage again. It retains encounter-local maximum HP and the native health bar; no artificial bar fill or healing is used. The vanilla-creature feedback path is unchanged.

Installation

Use a Thunderstore-compatible mod manager to install BossMakerAPI and its dependency, BepInExPack 5.4.2305, then add a compatible boss content mod.

For a manual installation:

1. Close the game and back up the mod profile and any worlds you intend to use.
2. Install BepInExPack in the game directory containing the game executable.
3. Copy this package's BepInEx folder into that same directory.
4. Install your chosen content mod and its dependencies, then launch the game.

Keep only one copy of each plugin. When upgrading, close the game before replacing DLLs and update every multiplayer peer together. This public package includes no game assemblies, loader binaries, personal CFGs or third-party ModMenu DLLs.

Installing only the API does not create a boss or enable a summon shortcut. Content mods decide where encounters occur, their appearance chance and rewards. Startup/developer options live in BepInEx/config/com.skylin3.howtofish.bossmakerapi.advanced.cfg and require a restart.

Compatibility and multiplayer

• Primary audited target: How to Fish 1.0.12, Steam build 25127368.
• Secondary reference target: 1.0.11, Steam build 25065888.
• The general guard recognizes 1.0.10 / 24975015, but newer rod-return, pickup-scale and native relocation adapters are audited only on the exact 1.0.11/1.0.12 builds. General recognition is not full feature support.
• Runtime baseline: FishNet 4.6.12, Unity Mono 6000.4.4f1.

Compatibility checks use exact game assembly identities, not display versions alone. Unknown builds disable custom prefab construction. An advanced override does not make an unverified build supported or unlock narrowly guarded hooks.

The host and every client need matching API/content DLLs and required assets. This is not a server-only mod and it does not download missing mods. Declared numeric settings use the host's values during the session; local CFG files stay local. Client menu edits are preferences for future hosting, not changes to the connected host. Settings that a content author has not declared for host configuration still require matching definitions.

Custom spawning waits for compatibility approval. The gate checks protocol, game build, content structure, assets, reward providers and network prefab assignments. Inspect the first reported difference when a peer is rejected; do not disable the checks to force a connection.

This release uses wire protocol 12, manifest protocol 4 and content schema 10. Update older peers together. The stable assembly-binding version 0.2.0.0 is not the release version or a promise of older network compatibility.

For content authors

The English author SDK is included under BepInEx/plugins/BossMakerAPI/ in the installed profile or extracted ZIP.

Start here, relative to that folder:

These are files inside the download, not web links to a separate hosted wiki. Reference BossMakerAPI.Contracts.dll, declare a hard BepInEx dependency on com.skylin3.howtofish.bossmakerapi, wait for BossRegistry.RegistryReady, resolve a verified template and register your definition. Registration alone does not summon a boss: provide an encounter trigger or a server-side spawn request. Use SkyLiN3-BossMakerAPI-0.10.3 in your content package's Thunderstore dependencies.

The independent Voltfin 1.3.1 mod and source starter demonstrate an ordinary Eel with configurable health, an eligible-catch chance, a telegraphed line attack and a faster phase below 50% health. Install Voltfin separately to play it. To create your own boss, copy the starter to a separate folder, change its public identity, supply your own original/licensed icon and follow its build instructions using your installed loader/game references. No compiled starter boss or game assemblies are bundled.

docs/examples/Starter/TEST_SHORTCUT.md explains Voltfin's own opt-in host-only F8 test shortcut, disabled by default. The API has no generic F8 listener. The helper uses bounded camera/terrain positioning, not the body-aware fishing transaction; test actual fishing separately. docs/examples/ReefTyrant/ provides a second source-only example, not another installed boss.

Limits worth knowing

BossMakerAPI builds on supported templates; it does not provide arbitrary new AI, a general pathfinder, automatic live-boss hooking or unrestricted custom projectiles/hitboxes. Definitions are validated and copied defensively, and invalid or unverifiable data is rejected.

BossManager-backed encounters share the game's single active-boss slot. Safe surface entry and aquatic recovery help supported encounters but cannot guarantee a valid location at every coastline. A committed catch replacement is not undone if the later owner-side rod-return delivery fails.

Persistence is opt-in and content-specific. Native item eligibility and world caps still apply; private plugin state and arbitrary mid-cast gameplay are not restored. Missing or changed definition fingerprints can leave historical boss records unresolved rather than guessing how to migrate them. Back up worlds before upgrading or removing content, and read docs/PERSISTENCE.md.

Optional ModMenu integration uses standard BepInEx settings discovery in compatible content mods. ModMenu is neither required nor bundled here. Its controls show local preferences, not necessarily the connected host's values; see docs/MODMENU.md for supported controls and verification limits.

Troubleshooting and validation

Start with BepInEx/LogOutput.log: check the loaded versions, game-build guard, template catalog, registration errors and first manifest mismatch. If no boss appears, confirm that a content mod is installed and that its trigger conditions, chance, free native boss slot and placement checks are satisfied.

Version 0.10.3 passes 444/444 managed checks on each audited 1.0.12 and 1.0.11 reference set, with zero build warnings/errors. Voltfin 1.3.1 also compiles independently. On 2026-09-21, the user reported successful combat, multiplayer and save/load testing with 0.10.3. This is user-reported acceptance, not exhaustive certification: particular late-join/reconnect cases, Steam Cloud, menu interaction and broader performance/coastline coverage remain separate.

This is a 0.x beta; author contracts may evolve before 1.0. For limitations, reporting guidance and detailed evidence, read docs/COMPATIBILITY.md, docs/SUPPORT.md, docs/TROUBLESHOOTING.md and docs/RELEASE_CANDIDATE.md. When reporting a problem, include game/build, host/client role, mod versions and sanitized relevant logs. Do not post credentials, personal paths or entire saves.

Development was assisted by OpenAI Codex. Project direction, integration, testing and release ownership remain with SkyLiN3.