Add headless JSON-RPC API for programmatic PoB access

[ianderse]

Changes/Additions to the headless/API layer to provide support for a WIP Path of Building MCP. Open to comments or suggestions!

Description of the problem being solved:

Changes

1. Fix: save_build ascendancy class sync and gem persistence

• Sync spec.curAscendClassName from live class data before saving, so the output XML always reflects the current ascendancy rather than a stale name from a previously-loaded file.
• Re-process all socket groups before saving so gems added or modified via add_gem / set_gem_level / set_gem_quality are fully resolved and written correctly to the output XML.
• Fix get_build_info to read className/ascendClassName from the correct fields (build.spec.curClassName / curAscendClassName) instead of non-existent build.buildClassName / build.buildAscendName.

2. Fix: Extend set_config to support enemy resistance and condition toggles

• Added enemy stat overrides: enemyFireResist, enemyColdResist, enemyLightningResist, enemyChaosResist, enemyArmour, enemyEvasion
• Added charge toggles: usePowerCharges, useFrenzyCharges, useEnduranceCharges
• Added condition flags: conditionFortify, conditionLeeching, conditionShockedGround
• Added buff/enemy modifiers: buffOnslaught, enemyIsBoss

Steps taken to verify a working solution:

1. Installed the MCP server backed by this API and connected it to Claude Code. Confirmed PoB starts in headless mode via the lua_start command triggered by the MCP in Claude Code
2. Created a build from scratch via the API (new_build → set_tree → set_config → get_stats) and confirmed stats were calculated correctly.
3. Loaded and modified an existing build (load_build_xml → set_gem_level / set_config → save_build) and verified the output XML reflected the changes.
4. Directed Claude Code to create a new build and update an existing build through natural language — both completed successfully with correct PoB output.

Link to a build that showcases this PR:

https://github.com/ianderse/pob-mcp

Screenshots:

Only affects the headless layer, no changes to the main application necessary

[tinycrops]

I'm doing this too at github.com/tinycrops/assistant-poe but I'm not build an mcp. i've never used mcp. i don't see the need for mcp. it was just a good idea some developer at anthropic had before the models were as smart as they are now.

I would love to be shown why I'm wrong though.

[tinycrops]

do you want to create an official poe app together? i need to get a client api key from them to get access to their api and do analytics. I'm doing a data analytics hackathon as well on devpost called ZerveHack

[ianderse]

@tinycrops You're right about not needing an MCP for the architecture of your app. Mine is interactive rather than a pipeline — the model is driving PoB in real time, which is where the tool discovery and schema layer actually pays off. Yours seems to be reading static files and outputting information to Discord (which is very cool and I like a lot of what you've got going on there). I think my vision is to build something more bi-directional where the model can create and modify builds in real time. Either way, cool to see you doing something similar!

[tinycrops]

I will check your work out in the coming days. Are you playing Mirage league? Thank you for looking at my work.
do you have discord? let's talk. I am coconutchoir

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Mission

Make Path of Exile's depth accessible to every player by giving them an AI that actually understands the game.

What we're building

An AI assistant for Path of Exile that speaks the game's language. It helps players plan builds, evaluate gear, make crafting decisions, and navigate the game's complexity with confidence. Not a trade macro. Not a calculator. A companion that thinks.

Where we're headed

A world where no exile quits because the game was too confusing. Where new players get the same quality advice that took veterans thousands of hours to learn. Where the community's collective knowledge isn't locked in forum threads and YouTube videos, but alive in a tool that meets you where you are in your journey. Path of Exile is the deepest ARPG ever made. It deserves an AI that matches that depth.