JSON output and exit codes

Each command accepts --json. A script, a tool, and an AI agent can read the same output.

• With --json, stdout holds one JSON value and nothing else.
• Progress lines and warnings go to stderr, also without --json.
• Each path is absolute. Each date is an ISO 8601 string.

Exit codes

Code	Meaning
0	Success.
1	A failure. stdout is empty, and stderr holds the message with the fix.
2	A usage error, for example an unknown option or a missing argument.

These commands print their JSON and also exit with 1:

Command	When
devhub sync --json	A project failed. The JSON shows which one.
devhub devices --json	Each device tool failed. The JSON has the warnings.
devhub match --json	No stored build matches.
devhub whoami --json	eas-cli has no login, or does not run.
devhub doctor --json	A check has the status fail.

The output of each command

Command	Prints
devhub sync --json	SyncReport: dryRun, and for each project its status, its profiles, its builds with the result of each build, and its warnings.
devhub list --json	BuildList: store, builds, incomplete, and unreadable.
devhub where <id> --json	{ "id": string, "path": string }
devhub devices --json	DeviceReport: devices and warnings.
devhub install <id> --json	InstalledBuild: id, path, and the device.
devhub match --json	MatchReport: project, fingerprintVersion, and for each platform its hash and its matches.
devhub ui --json	{ "url": string, "port": number }. The server then runs until Ctrl+C.
devhub whoami --json	WhoamiReport: state, cli, and user or message.
devhub doctor --json	DoctorReport: checks, and for each check its id, label, status, detail, and fix.

The full TypeScript types of each output are in llms.txt.

A build in the list

Each build in devhub list --json and in the matches of devhub match --json has these fields:

Field	Value
id	The full build ID.
source	"eas" for a build that devhub sync downloaded, or "local" for a build that npx expo run:* made.
path	The absolute path of the build file.
size	The size of the file, in bytes.
sha256	The SHA-256 hash of the file.
storedAt	The date on which DevHub stored the build.
installProblem	Why devhub install refuses the build on this system, with the fix. The text says "this build" and names no ID, because the record has id. Absent when it can install the build.
eas	An EAS build: the record of eas build:list --json with no change.
local	A local build: the platform, the fingerprint, the variant, the project folder, and the app values.

eas-cli drops each field with a null value, so an absent field in eas means "no value". The eas record can have more fields than the types name.

A device

{
  "platform": "android",
  "kind": "physical",
  "id": "R5CT21ABCDE",
  "name": "R5CT21ABCDE",
  "state": "unauthorized",
  "ready": false,
  "problem": "Unlock the device, and accept the USB debugging prompt on it."
}

Field	Value
platform	"android" or "ios".
kind	"emulator", "physical", or "simulator".
id	The adb serial, or the simulator UDID.
state	The state as the device tool prints it.
ready	true when DevHub can install a build on the device now.
problem	Why DevHub cannot install on the device now, and the fix.
osVersion	The iOS version of a simulator.

Example: install the newest Android build of a project

id=$(devhub list --json | jq -r '[.builds[] | select(.source == "eas" and .eas.platform == "ANDROID" and .eas.app.slug == "trail-app" and (has("installProblem") | not))][0].id')
devhub install "$id" --json

devhub list sorts the builds of each project newest first, so the first build that fits is the newest one.