[Feature]: Device panel and device_open can't open a Simlock device from a baseline (a saved, signed-in simulator or emulator)

[maxlapides]

Summary

Neither the Device panel nor device_open can open a Simlock device from a baseline. A baseline is a saved simulator or emulator, for example one with a dev client installed and a test account signed in. Every Simlock device T3 Code opens is a factory device, so each thread installs the app and signs in again, which takes minutes. A baseline copy leased some other way can't be used either: T3 Code shows only devices it opened itself.

What happens today

On main (71c2d3a3), apps/server/src/device/SimlockDeviceHost.ts opens a catalog device with:

["open", "--platform", target.platform, "--device", target.model]

There is no way to name a baseline. device_open takes only hostId and id, and the Device panel's picker lists models only.

Real example from 2026-11-07, on a Simlock 0.6.0 host with agent-device 0.21.36:

1. An admin saved five baselines (simlock baseline save): three iOS simulators and two Android emulators. Each has our development client installed and a staging test account signed in.
2. simlock lease --platform ios --baseline <name> (or the Simlock MCP lease_simulator with baseline) gives a fresh copy of the newest version, already signed in.
3. That copy appears on no T3 host: device_list doesn't list it, and device_open with its UDID on local fails with "No device".
4. Agents can only drive the copy with agent-device outside T3, so they lose the Device panel, its stream, and the user's ability to watch or take over.

Request

Let a Simlock open name a baseline:

• An optional baseline on device_open, passed through to the Simlock lease.
• In the Device panel, a way to choose one of the host's baselines (simlock baseline list, or the gateway's equivalent) next to the model picker. The platform, model and OS come from the baseline.
• Clear errors when Simlock refuses the baseline: unknown, stale (BASELINE_STALE), or not matching the platform.

The plumbing is mostly in place:

• Simlock: the agent-device front leases from a named baseline since feat(agent-device): the front leases from a named baseline callstackincubator/simlock#1319 (merged 2026-11-05, for agent-device: allocate a device from a named baseline callstackincubator/simlock#1308). The grant reports the baseline name and version.

• agent-device: feat(lease): name a backend baseline in a proxy lease device spec callstack/agent-device#4236 (open) adds --device-baseline <name> (the deviceBaseline spec key) to proxy leases. Once it ships, the open above can become:

  agent-device open --platform ios --device-baseline <name>
  

Why it matters

For mobile teams, the slow part of every device task is getting to a signed-in app: installing the right dev client, then a sign-in flow that often goes through a web view. Baselines remove both steps. Today that saving costs the Device panel, which is the main reason to run device work inside T3 Code.

Related: #28567 (choosing the iOS model and version) and #30336 (choosing the Android API level and image). Both are closed, but main still passes only --platform and --device on open.