Bun crashes (segfault/SIGTRAP) when several opencode instances launch concurrently (macOS arm64)

opencode: 1.18.4 · Bun (bundled): 1.3.14 · macOS: 26.4, Apple Silicon (arm64)

Launching ~6–8 opencode TUI instances near-simultaneously — each in its own pty, same project directory — reliably crashes several of them at startup:

panic(main thread): Segmentation fault at address 0x56ACCBFFC
oh no: Bun has crashed. This indicates a bug in Bun, not your code.

macOS DiagnosticReports for the same batch show EXC_BREAKPOINT (SIGTRAP) with unsymbolicated opencode.exe frames; happy to attach the .ips files.

One crash-report link (transcribed from the terminal — apologies if a character slipped):
https://bun.report/1.3.14/Ma10d9b296mwGugogC________urh5kDunr21Cusw11C+/y34C+qy34C+5sy6Cu657H__urh5kD27p5tC+xt2yCA2K4//y5qD

Repro / mitigation signal: spawning the instances within the same ~100 ms window triggers it; staggering launches by ~400 ms avoids it entirely — which smells like a startup race on shared state (opencode.db WAL? cache dir?). RSS at crash ~0.8–1.05 GB per instance.

Context: filed from Atelier, a multi-pane terminal app where users open many opencode panes at once; we've mitigated on our side with launch staggering, but sequential-only startup shouldn't be a requirement. More traces available on request.