[Bug]: ACP provider health probe creates a persistent empty OpenCode session on every refresh#25382

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/server

Steps to reproduce

1. Configure T3 Code with the ACP Registry opencode-v2 provider enabled.
2. Keep a T3 client connected so background provider-status work is allowed. Defaults: providerHealthRefreshInterval = 5 min; a successful probe is cached for 15 min (PROBE_SUCCESS_TTL_MS).
3. Let T3 run for 15-30 minutes (or overnight).
4. Inspect the OpenCode session list (opencode TUI, GET /api/session, or the SQLite DB).

Expected behavior

A provider health probe should be invisible to the user's OpenCode session history. If the probe must create a test session to validate the agent, it should delete that session before finishing — e.g. a best-effort runtime.deleteSession(sessionId) (or reuse of deleteAcpRegistrySession) guarded by sessionCapabilities.delete, with cleanup failures ignored. Sending session/close alone would not delete on 2.1.4; it only becomes useful once anomalyco/opencode#56088 ships.

Actual behavior

Every probe leaves a durable empty session in OpenCode:

• title empty/NULL
• agent empty, model empty
• 0 message rows
• version = "2.1.4" (T3's managed opencode-v2 binary)
• cwd = the T3 server's cwd

At least 33 untitled, 0-message rows accumulated. They appear every ~15 minutes while T3 is in use (~4/hour) and persist until manually deleted. This is continuous, not occasional: every T3 session produces more rows, and real sessions get buried in the list.

The probe path is AcpRegistryDriver.checkProviderStatus → AcpRegistryProbe.probeConfiguration. packages/provider-acp-registry/src/server/probe.ts calls runtime.start() (ACP session/new in AcpSessionRuntime) with clientInfo.name = "t3-code-provider-test". When the probe's effect scope closes, AcpSessionRuntime terminates the ACP child process; the probe never sends session/close or session/delete. OpenCode persists the session eagerly on session/new (anomalyco/opencode#55293, anomalyco/opencode#38064), so the row survives. deleteAcpRegistrySession already exists in the same file (~line 646 on main), but it is wired only to user-initiated session management (driver.ts → AcpSessionManagementSection), not the probe path.

Impact

Major degradation or frequent failure

Version or commit

0.1.3-nightly.20261025.3692

Environment

Linux, T3 Code nightly desktop 0.1.3-nightly.20261025.3692, managed opencode-v2 2.1.4 (ACP), default "balanced" background activity profile; ACP Registry provider with agentId opencode-v2, distribution auto.

Logs or stack traces

Screenshots, recordings, or supporting files

No response

Workaround

Settings → Background Activity → Provider health interval = 0 seconds stops the periodic probes (T3 still probes once at startup).