neqsim: Instructions file for GitHub Copilot

Answering a NeqSim calculation request

Prefer the MCP tool for a one-off calculation

A single property, flash, phase-envelope, sizing, PVT, or standards lookup is served by a curated mcp_neqsim_* tool when the NeqSim MCP server is available. Use it first: it needs no local Python, no terminal, and no Java, and it returns a schema-checked result with provenance. Write Python or Java only when the task needs loops, plotting, a notebook, a report, or state inspected between steps.

Calculate methane density at 20 C and 20 bara
-> mcp_neqsim_runFlash {"components":"{\"methane\": 1.0}", "eos":"SRK",
                        "flashType":"TP", "temperature":20, "temperatureUnit":"C",
                        "pressure":20, "pressureUnit":"bara"}

Java is often installed but hidden — find it, do not give up

JVMNotFoundException, "No JVM shared library file (jvm.dll) found", or a JPype failure on import neqsim usually means the JVM is not discoverable, not that Java is missing. On managed corporate machines Java is regularly installed with no java on PATH and no JAVA_HOME.

Do not hand-scan C:\Program Files and do not tell the user to install a JDK before checking. Run the locator, which searches vendor installs, the user profile, the Windows registry, and the JRE bundled with the VS Code Java extension:

uv run --project devtools --locked devtools/java_locator.py        # source checkout: lists every usable Java
neqsim doctor                          # pip install of the CLI: names the found Java

If neqsim is not on PATH, run python -m neqsim_cli doctor with the same arguments. With only the agent plugin installed (no checkout, no CLI) neither command exists — but the plugin's session hook resolves a JDK 21+ for the MCP server on its own, so the mcp_neqsim_* tools still work and remain the route to prefer.

In Python, make a hidden JVM usable for the current process before touching JPype or NeqSim:

import neqsim_dev_setup, sys, pathlib
sys.path.insert(0, str(pathlib.Path(neqsim_dev_setup.__file__).parent))
from java_locator import ensure_java_home
ensure_java_home()          # sets JAVA_HOME + PATH for this process only
import neqsim