Oh My Pi is one of the most capable coding agents for the terminal. But if you’re on macOS and running native grep, there’s a crash waiting to happen — and it can take your entire session with it.
A newly filed issue (#5205) with prio:p1 reveals that Oh My Pi’s native pi_natives grep implementation uses memory-mapped file I/O for files above a threshold. When another process rewrites or truncates the same file while grep is searching it — during a build, a log rotation, or a concurrent write — the mapped page can point past the file’s new end. macOS responds with SIGKILL (Code Signature Invalid), and the entire Oh My Pi process dies.
The macOS crash report reads: Exception Type: EXC_CRASH (SIGKILL), Termination Reason: Namespace CODESIGNING, Code 2 Invalid Page, with the faulting thread inside the Bun Pool at the first byte of a 4 MiB file-backed mapping. The reporter confirmed it with a stress test: a 5 MiB rewrite/search loop crashed on run 4 with Bus error / exit 133.
Are you affected?
You’re affected if you run Oh My Pi 16.4.4 or earlier on macOS and use native grep on files larger than 4 MiB that could be written to concurrently — log files, build artifacts, temp files, anything another process modifies.
# Check your version
omp --version
# Quick stress test (WARNING: will crash your session)
dd if=/dev/urandom of=/tmp/stressfile bs=1048576 count=5
omp exec -- grep -r "test" /tmp/stressfile &
# In another terminal: head -c 5M /dev/urandom > /tmp/stressfileThe fix
A fix is already submitted in PR #5210 — fix(native): read grep files into stable snapshots. The patch replaces both mmap paths with bounded owned reads:
- At most 4 MiB + 1 byte for file classification
- At most 4 MiB for the oversized searchable prefix
- Removes the now-unused
memmap2dependency - Adds a stable-snapshot regression test
Verification on the fixed build: 20/20 clean exits on the concurrent rewrite/search stress test, all 164 native tests passing. Once merged, omp update gets you the fix.
In the meantime, avoid concurrent writes to files you’re searching with native grep, or use the system grep (/usr/bin/grep) as a workaround.
Why it happened
The native grep tool memory-maps regular files above a small-file threshold for performance. The mmap call gives you a live window into the file on disk, not a stable copy. When the underlying file shrinks or gets rewritten, the mapped region can reference pages past the current file boundary. On macOS the kernel flags this as a code-signing violation (invalid page reference). On Linux and other POSIX systems the same pattern triggers SIGBUS.
The root assumption — that a file won’t change during a fast grep — doesn’t hold in an active development environment where builds, watchers, and other agents touch the same files.
FAQ
Q: Does this affect Linux too? A: Yes. The same mmap pattern can raise SIGBUS on Linux when a mapped page is accessed beyond the current end of the backing file, though macOS reports it as a code-signing failure instead.
Q: Is my session recoverable after the crash? A: No. The crash terminates the entire oh-my-pi process with SIGKILL. There’s no recovery path — you lose any unsaved state and must restart the agent.
Q: Will the bounded-read fix hurt performance? A: Negligible impact for typical grep workloads. The 4 MiB cap covers the vast majority of search operations. The trade-off — stable snapshots instead of live mmap windows — eliminates an entire class of crash bugs at essentially zero cost for most users.