Description
When running 2 concurrent Claude Code CLI sessions on macOS, attempting to launch a 3rd instance results in immediate SIGKILL — the process is killed before any output is displayed. The macOS crash report confirms the cause is code signature validation failure by taskgated, not an OOM condition.
Environment
- macOS 26.3 (Build 25D125) — Apple Silicon
- Mac model: Mac16,10
- Claude Code: 2.1.59
- RAM: 24 GB (free ~86% at time of crash)
- Shell: zsh
Steps to Reproduce
- Open Terminal 1, run
claude → starts normally
- Open Terminal 2, run
claude → starts normally
- Open Terminal 3, run
claude → immediately killed
Output in Terminal 3:
Even claude --version is killed when 2 sessions are already running:
$ claude --version
$ echo $?
137
Crash Report Evidence
macOS generates crash reports at ~/Library/Logs/DiagnosticReports/2.1.59-*.ips (26 reports accumulated in one day).
Key fields from the crash report:
{
"exception": {
"type": "EXC_CRASH",
"signal": "SIGKILL (Code Signature Invalid)"
},
"termination": {
"flags": 66,
"code": 1,
"namespace": "CODESIGNING",
"indicator": "Taskgated Invalid Signature"
}
}Analysis
- Not a memory issue:
memory_pressure reports 86% free, node -e "Buffer.alloc(500*1024*1024)" succeeds, and no Jetsam logs are found
- Code signature appears valid:
codesign -vv returns "valid on disk" and "satisfies its Designated Requirement", signed by "Developer ID Application: Anthropic PBC (Q6L2SF6YDW)"
- Gatekeeper rejects it:
spctl --assess --type execute returns "rejected (the code is valid but does not seem to be an app)"
- Binary has
com.apple.provenance xattr that cannot be removed
CLAUDE_DEBUG=1 claude --version succeeds (exit 0), while without the env var it fails (exit 137) — suggesting a timing or initialization path difference affects the signature validation
Codesign Details
Identifier=com.anthropic.claude-code
Format=Mach-O thin (arm64)
CodeDirectory v=20500 size=1450661 flags=0x10000(runtime) hashes=45322+7
Authority=Developer ID Application: Anthropic PBC (Q6L2SF6YDW)
Authority=Developer ID Certification Authority
Authority=Apple Root CA
Timestamp=Feb 26, 2026 at 8:52:45
TeamIdentifier=Q6L2SF6YDW
Runtime Version=14.5.0
Impact
This limits concurrent Claude Code sessions to 2 on macOS, making parallel workflows (e.g., 2 PR reviews + 1 development session) impossible.
Potentially Related Issues
Description
When running 2 concurrent Claude Code CLI sessions on macOS, attempting to launch a 3rd instance results in immediate
SIGKILL— the process is killed before any output is displayed. The macOS crash report confirms the cause is code signature validation failure bytaskgated, not an OOM condition.Environment
Steps to Reproduce
claude→ starts normallyclaude→ starts normallyclaude→ immediately killedOutput in Terminal 3:
Even
claude --versionis killed when 2 sessions are already running:Crash Report Evidence
macOS generates crash reports at
~/Library/Logs/DiagnosticReports/2.1.59-*.ips(26 reports accumulated in one day).Key fields from the crash report:
{ "exception": { "type": "EXC_CRASH", "signal": "SIGKILL (Code Signature Invalid)" }, "termination": { "flags": 66, "code": 1, "namespace": "CODESIGNING", "indicator": "Taskgated Invalid Signature" } }Analysis
memory_pressurereports 86% free,node -e "Buffer.alloc(500*1024*1024)"succeeds, and no Jetsam logs are foundcodesign -vvreturns "valid on disk" and "satisfies its Designated Requirement", signed by "Developer ID Application: Anthropic PBC (Q6L2SF6YDW)"spctl --assess --type executereturns "rejected (the code is valid but does not seem to be an app)"com.apple.provenancexattr that cannot be removedCLAUDE_DEBUG=1 claude --versionsucceeds (exit 0), while without the env var it fails (exit 137) — suggesting a timing or initialization path difference affects the signature validationCodesign Details
Impact
This limits concurrent Claude Code sessions to 2 on macOS, making parallel workflows (e.g., 2 PR reviews + 1 development session) impossible.
Potentially Related Issues