0008. A fresh core instance for each step

• Status: accepted (2026-10-04)
• Decided by: during implementation

Context

Reproducing aube #1645 takes four steps (aube install, rm -rf node_modules, aube install --frozen-lockfile, aube list), and the files must carry over from one step to the next.

Decision

Run each command in a new core instance. The working directory and the home directory are copied out on the JavaScript side after a step and placed into the next instance (since the switch to paludarium, fromCoreSnapshot and toCoreEntries; with blink, snapshotFs and populateFs); runSession in runtime/guest-io.ts drives the steps, and rm -rf runs on the JavaScript side. The package’s Session follows the same model with a fresh Worker for each run.

Consequences

• Simple to implement, and the state of each step is cleanly separated.
• Each command pays a fixed start-up cost (0.3 to 0.5 seconds with the blink core), which a JIT does not reduce.
• WebKit reserves the wasm memory maximum for each instance and keeps it until the page is done, which is why guest memory is capped at 1 GB.

Alternatives rejected

• One instance running a shell across commands: it needs a guest shell and process creation (fork and exec), and process fork was disabled in the fork of blink that was the core at the time.