Problem types

Code	HTTP	Meaning
`invalid-request`	400	Body or parameters fail the schema.
`unsupported-version`	400	Major version not supported.
`unauthenticated`	401	Credentials missing or invalid.
`insufficient-clearance`	403	Clearance or scope too low.
`capability-not-allowed`	403	This kind of caller may not make this request: the capability's or operation's `callers` excludes it, the request needs a `human` (such as deciding, raising the autonomy ceiling `max` or adopting a Playbook), or the approver is the Action's initiator.
`presence-required`	403	Approving, or a person's destructive or physical action, needs proof of presence for this Action's digest (6.3).
`presence-invalid`	403	The proof of presence did not verify (6.3).
`token-not-bound`	401	Over a network, the token must be bound to the caller's key (8.2).
`signature-required`	403	A Connected or Full system must sign the Card it joins with (10.1).
`signature-invalid`	403	The Card's signature does not verify (10.1), a brain lease or signal is not signed with the pinned Command Center key or is for another system (7.4), or an update's manifest or payload does not verify (13.2 rule 4).
`identity-changed`	409	The system joined before with a different identity key (10.1).
`valve-blocked`	403	The Valve refused to release the data.
`autonomy-stopped`	409	Refused because autonomous action is stopped.
`guard-failed`	409	A guard or interlock refused the command (Section 14.4).
`caller-not-allowed`	403	A Proposal names a target whose `callers` excludes `ai` (Core Standard 7.3). It is used only for Proposals: a caller's own request gets `capability-not-allowed`.
`not-found`	404	No such resource, or the caller may not know it exists, such as a property above the caller's clearance, for reading and for writing.
`conflict`	409	Invalid state, such as deciding a finished action, an `actionId` that was already used (6.3), or writing a read-only property.
`idempotency-conflict`	422	Key reused with a different body.
`out-of-range`	422	A value is outside the allowed range or envelope (13.2).
`cannot-undo`	422	A Trial was refused because its change cannot be undone, or the current value is unknown (13.2).
`budget-exceeded`	429	AI cost limit reached.
`rate-limited`	429	Too many requests.
`internal-error`	500	Unexpected failure.
`native-failed`	502	The device or native protocol returned an error.
`native-timeout`	504	The device did not answer in time.
`not-implemented`	501	Above this system's level.
`model-unavailable`	503	No permitted model can answer.
`system-unreachable`	503	A HEART Gateway could not reach the hosted system.

These are errors from the HEART API. A problem on a device has a fault code instead, such as HEART storage.full (H-04002): see every fault code, by H-number.