The simulation

portlight-sim has no UI. portlight-cli runs a script and prints the snapshot JSON. portlight-chart is the dimetric math and does not link Godot. portlight-godot is the view.

A script plus a seed reproduces the same game. The random source is CPython’s MT19937. Prices use Python 3 rounding. Do not swap in Rust’s round.

Check it

cargo test --locked --workspace --exclude portlight-godot
cargo run -p portlight-cli -- --help

scripts/verify.ps1 and scripts/verify.sh run the formatter, those tests, a CLI build, and --help. They do not run the Godot frame compare. That job is Linux CI, because it needs a display.

The live Python oracle in CI checks out mcp-tool-shop-org/portlight at 9b02494. Goldens under parity/golden/ are the recorded witness when the oracle is not in the job. Five captain types have Rust-tuned pricing and burn from a small overlay file applied over the unmodified Python extract (content.json); the python-base build feature turns the overlay off (its pins are in parity/rust_tuned_pins.json, separate from the original expected differences), and CI checks that build against the oracle with only the original expected differences. Saves store computed prices; Load recalculates them with the current (tuned) captain template, so a save made before this change shows the new prices for the five tuned types after loading.

Numbers that stay

Python and the goldens agree. A later screen calls the simulation. It does not correct these.

• Sail-picker days use raw ship speed. Crew, morale, season, and the captain stay off that estimate.
• The picker lists lanes that depart may then block. A rank gap of 1 is a warning. A gap of 2 or more is blocked.
• The victory path id commercial_empire is not the milestone family commercial_finance.
• Advancing the day passes day 0 into the market tick on that path. Seasonal stock drains stay off. Python does the same.
• Route, boarding, and bounty duels apply their standing_delta to standing.underworld.
• The ship-officer crew_roles entries (navigator storm resistance and quartermaster sell bonus) exist in the catalog and are never called; named companion role bonuses on the Crew desk are separate and active.

Errors

A failed action is a sentence, the same sentence the Python game uses where the ports match. The CLI does not wrap that sentence in a code and a hint. Doing so would change the golden text.

Exit codes for the binary: 0 when the run worked, 1 when the simulation or a file failed, 2 when the command was not understood. There is no --debug flag and no log level. The program does not print a credential, because it never reads one.

Where a change belongs

A screen change stays in portlight-godot and godot/. A rules change belongs in portlight-sim, with a parity script and a golden, and it does not reformat the shared files it only had to touch. See CONTRIBUTING.md.