uefn-session-regression

Source: Claude/docs/mcp/session-regression.md (incl. T-015 C2 update), recipes.json (only tool-ok or proven; proven = the same call form already worked in real work), SKILLS-PROPOSAL.md B6.

Read first

1. Read uefn-mcp-lab-guard and uefn-verse-build.
2. Ping with a cheap read before the first write and before every session action.
3. If the MCP does not answer: stop and report. Never close or kill a running editor (after a crash: uefn_session.py recover, opt-in), never loop on a hung MCP.

Rules

• Paths in arguments: GUID form /09e4e8d3-83f9-4ee0-9777-072ed3984380/root_ai_lab/....
• The guard is not bypassed; a refusal is reported verbatim.
• If a recipe fails: exact error text, then STOP.
• Always StopGame then StopSession in try/finally and verify GetSessionStatus = Disconnected. Never leave a session open.
• Do not start a session while a disallowed actor is in the level (see TargetPoint trap).
• One process for session actions; a second process may poll with read tools only (replies can cross).

Verified recipes (toolset ValkyrieToolset.SessionToolset)

Tool	Args	Measured / note
GetSessionStatus	{}	Disconnected, Connected, UpdatingContent; 0.01 s
GetGameState	{}	Unconnected, CanStart, Running; CanStart does NOT mean StartGame works
StartSession	{}	~88 s (67-87 s measured: 11 s upload, ~13 s beacon + client launch, ~65 s cook). The reply text may be an unrelated stale error: confirm with GetSessionStatus = Connected
StartGame	{}	0.28 s after Connected (0.27-0.4 s), GetGameState Running at once, Verse begins ~0.8 s later. Only after StartSession returned AND status Connected after UpdatingContent; otherwise The Start Game command is not currently available.
PushChanges	{bVerseOnly:true}	7.9 s; needs a real Verse change, else The Refresh command is not currently available.
StopGame	{}	1.3-1.5 s
StopSession	{}	null, status Disconnected; FortniteClient processes stay alive afterwards
LogsToolset/GetLogEntries #why_startsession_failed	{category:"", maxEntries:0, pattern:"UEFNValidation"}	reason of Failed: Validation failed
Verse runtime output	LogsToolset/GetLogEntries {category:"", maxEntries:0, pattern:"<marker>"}	forwarded as LogVerse: : <text> ~0.8-4 s after StartGame

Full smoke (R1): ping, StartSession (ignore reply text), poll GetSessionStatus until Connected, StartGame, check Running, finally StopGame + StopSession, status Disconnected.

Cycle (R3, ~10 s without StartSession): WriteFile/Replace -> BuildAll ([] = PASS, else FAIL with code+span; this is the gate) -> only if PASS and Connected: PushChanges {bVerseOnly:true} -> read new log lines -> verdict with timings.

Traps

• TargetPoint: an actor of class /Script/Engine.TargetPoint makes StartSession answer Failed: Validation failed (UEFNValidation: Error: Disallowed reference to /Script/Engine.TargetPoint), and the editor MCP then stops answering for minutes. Do not place such classes; diagnose with the UEFNValidation log recipe above.
• StartGame too early (16 s in the old loop) fails because status is still Connected-early/UpdatingContent: poll GetSessionStatus, not GetGameState.
• With a broken source, PushChanges only answers "Refresh command is not currently available" (session stays healthy): the BuildAll result is the verdict, not the push.
• Closing or killing a running editor is refused by design; relaunch after a crash only with uefn_session.py recover --wait 150 (opt-in, max 2 in 30 min; the project reopens by itself about 47 s later with Load on Startup = Most Recent Project).

To try (not verified)

• GetClientLogEntries {pattern, maxResults, startLine}: status unverified. Always No client log was found; start a play-in-client session first. in every state (10+ attempts, live client running); Pattern must not be empty. for an empty pattern. Use the LogsToolset recipe instead. Cause not found, owner decision pending.
• Runtime "missing event" test and placing a lab-built Verse device in a session: not possible, the guard refuses the placing route (level-devices area).