fix(devices): resolve the Android SDK per spawn, not once at startup

[thelonewander3r]

What Changed

LocalDeviceHost.make resolved androidSdk once at construction and captured the result in run and in the environment handed to the device hub and the agent-device daemon. That resolution now happens per spawn, in a new module-level hostSpawn.

No behaviour changes when the SDK is present before the server starts.

Why

platformReason re-resolves the SDK on every availability check, while run held a copy from startup. The two drift apart as soon as the SDK is installed, moved, or repaired after the server started, and then disagree permanently:

if ((yield* host.platformAvailability("android")).available) { // fresh -> true
  const avds = yield* ready.run("emulator", ["-list-avds"]);   // captured -> bare "emulator"

With sdk.root still null, run spawns a bare emulator that is not on the server's PATH. ProcessRunner maps the spawn failure to exit 127, and fetchDevices turns any non-zero exit into a hard error — so the whole device list fails, iOS simulators included, and stays that way until the app restarts.

Observed on a machine with a complete, working SDK at ~/Library/Android/sdk:

"platforms":[{"platform":"ios","available":true},{"platform":"android","available":true}],
"hostStatuses":{"local":{"status":"failed","detail":"Device list failed: The device command failed (exit code 127)."}}

Android reports available and the same call reports failed. The underlying cause was ProcessSpawnError: Failed to spawn process 'emulator' — note the bare name, which run only passes when sdk.root is falsy.

The same stale value reaches the hub and the daemon, which were spawned with no ANDROID_HOME and without the SDK on their PATH, so they cannot see emulators either.

Resolving per spawn is what keeps spawns and availability reading the same SDK. The cost is one extra SDK probe per spawn, which is the same work platformAvailability already does two to three times per refresh.

Tests

Three cases in LocalDeviceHost.test.ts covering the absolute emulator path, passthrough for other commands, and an SDK that appears after an earlier spawn resolved nothing. Reintroducing the cache makes the third fail.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Android emulator launches now detect the current Android SDK location each time a device starts.
  • Device commands and environment settings are refreshed at launch, improving recovery when the SDK becomes available after an earlier lookup failure.
  • Non-emulator commands continue to run without modification.

[macroscopeapp]

Approvability

Verdict: Approved at bc154c2

Macroscope's review found this PR approvable — This is a narrowly scoped device-host bug fix that resolves the Android SDK per command, preventing stale startup state from breaking emulator discovery after SDK changes. Existing startup behavior remains intact, and targeted tests cover absolute-path execution and dynamic SDK discovery.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: b3b6711e-7c1a-4fa0-bb95-85a8526744fb

📥 Commits

Reviewing files that changed from the base of the PR and between 77bca8b and bc154c2.

📒 Files selected for processing (2)

• apps/server/src/device/LocalDeviceHost.test.ts
• apps/server/src/device/LocalDeviceHost.ts

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📝 Walkthrough

Walkthrough

LocalDeviceHost now resolves the Android SDK, executable command, and environment for each spawn. Emulator commands use the current SDK when available. Host, hub, daemon, and run paths consume the per-spawn results. Tests cover command mapping, environment setup, and SDK rediscovery.

Changes

LocalDeviceHost spawn resolution

Layer / File(s)	Summary
Per-spawn command resolution apps/server/src/device/LocalDeviceHost.ts, apps/server/src/device/LocalDeviceHost.test.ts	hostSpawn resolves the current SDK and environment for each call. Emulator commands map to the SDK emulator path when available. Tests cover emulator mapping, unchanged commands, environment setup, and SDK rediscovery.
Resolved environment propagation apps/server/src/device/LocalDeviceHost.ts	Host, hub, and agent-device daemon paths now consume the per-spawn environment effect.
Command execution integration apps/server/src/device/LocalDeviceHost.ts	run uses the resolved command and environment while preserving timeout, input, result, and exit-code handling.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant LocalDeviceHost
  participant androidSdk
  participant FileSystem
  participant ChildProcess
  LocalDeviceHost->>androidSdk: Resolve SDK for spawn
  androidSdk->>FileSystem: Check current SDK availability
  LocalDeviceHost->>LocalDeviceHost: Build command and environment
  LocalDeviceHost->>ChildProcess: Spawn resolved command with environment

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Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to bc154

The per-launch SDK resolution is propagated to the affected process paths, including SDK rediscovery, with no concrete merge-blocking issue identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: resolving the Android SDK for each process spawn instead of once at startup.
Description check	✅ Passed	The description clearly explains what changed, why the change is needed, the failure mode, and the tests added. The UI Changes and Checklist sections are omitted, but no UI changes are described and t…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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