Root cause: ssh-keygen -R prints 'Host X not found in F:\CI\State\known_hosts'
to stderr when the IP has no prior entry. In PS5.1 with ErrorActionPreference=Stop,
native stderr is converted to ErrorRecords before 2>$null can discard them,
making the command a terminating error caught by the job's catch block.
This caused all 4 concurrent burn-in jobs to fail after ~15s with:
Error: Host 192.168.79.XXX not found in F:\CI\State\known_hosts
Additionally, 4 concurrent SSH connections writing to the same known_hosts file
with no advisory locking risk file corruption under concurrent load.
Fix: set SshKnownHostsFile default to '' in Invoke-CIJob, Invoke-RemoteBuild,
and Get-BuildArtifacts. When KnownHostsFile='' _Transport.psm1 uses
StrictHostKeyChecking=no + UserKnownHostsFile=NUL (permissive mode), consistent
with Wait-VMReady and Prepare-LinuxBuild2404.ps1. Ephemeral CI VMs on a
local NAT network have no meaningful MITM risk.
Remove the ssh-keygen purge block from Invoke-CIJob.ps1 (no longer needed).
AGENTS.md: document PS5.1 native stderr / 2>$null interaction (error #12).
AGENTS.md (new):
- Environment reference for AI agents: host specs, PS 5.1 constraints,
dir structure, VM templates, transport layer, style rules
- Lessons #9 (snapshot cold state) and #10 (vmrun list vs getGuestIPAddress)
ARCHITECTURE.md:
- Add SSH/SCP transport section (Linux VMs)
- Update system diagram to include _Transport.psm1, SSH transport path
- Network layout: add SSH port 22 for Linux VMs
- Timeline: Linux readiness check phases documented
CI-FLOW.md:
- Prerequisites table: add Template VM (Linux), SSH key row
- Step 6 (readiness): document Windows vs Linux phases
- Step 7 (build) and Step 8 (artifacts): document Linux/SSH paths
- ci-report-ip guestinfo mechanism referenced
HOST-SETUP.md:
- Directory tree: add LinuxBuild2404 template dir and keys/
- Post-setup checklist: add step 5 (SSH key generation + Linux template)
- Fix duplicate step numbering (56, 67)
- Reference Paths table: add Linux template VMX, snapshot, SSH key
LINUX-TEMPLATE-SETUP.md:
- Rewritten as implementation record (no longer a plan)
- Fase A user-data: minimal (user+SSH key only, no packages/runcmd)
- All phases marked complete with actual paths and snapshot names
WINDOWS-TEMPLATE-SETUP.md: minor updates for consistency
TODO.md:
- Summary: update last-updated to 2026-05-11, Sprint 9 description
- Linux Build VM row: all 5 items complete
- Prossimi passi: Test Plan + ยง6.6 Tier-2 as next priorities
Simone