xAI added safety_identifier in its September 25, 2026 API release notes, giving multi-user applications a documented field for end-user attribution across Chat Completions, Responses, deferred completions, Batch and gRPC. For SaaS teams and model gateways sharing an API key, the implementation task is to attach a stable, application-controlled pseudonym to each user’s requests.
A shared API key can serve many people; stable user pseudonyms keep their requests distinguishable without sending raw account identifiers. xAI says it can use the value to identify the user in a policy-violation report. That is an attribution capability, not a guarantee against action affecting the API key. Security FAQ.
Derive identity on the server
The FAQ calls for a stable, opaque value assigned by your application, not chosen by the end user. Hash an internal identifier or use another opaque value; do not send an email address, phone number or display name. The provider says it does not validate the format.
Implementation recommendation: resolve the authenticated account in trusted backend code, then derive its pseudonym. If account IDs are unique only within a tenant, include the tenant in that identity. A browser-supplied hash still lets the caller choose whom to impersonate; a fresh request UUID loses continuity between the same user’s requests.
One optional design is HMAC-SHA-256 with a dedicated server-held secret. Unlike a plain hash of predictable account numbers, a keyed construction prevents someone without the key from simply hashing candidate IDs to find matches. This is an application-design choice, not an xAI-mandated algorithm. HMAC specification.
Illustrative Python only; this example has not been executed or tested against xAI. The standard-library hmac interface supplies the keyed digest:
import hashlib
import hmac
import json
def attribution_id(pseudonym_key: bytes, environment: str, tenant_id: str, user_id: str) -> str:
# Identity arguments must come from trusted server-side account records.
identity = json.dumps(
["xai-safety-v1", environment, tenant_id, user_id],
ensure_ascii=True, separators=(",", ":")
).encode("utf-8")
return hmac.new(pseudonym_key, identity, hashlib.sha256).hexdigest()Pass immutable account IDs from server records. Obtain pseudonym_key from your protected key-management system; do not reuse the API credential. The JSON array separates identity components unambiguously. The provider and environment labels scope the pseudonym, so test and production identities need not match.
This construction returns 64 hexadecimal characters; that is not an xAI length requirement. Keep a restricted way to map the pseudonym back to an account for investigations. Changing the key or namespace changes the pseudonyms, so plan that migration separately from routine API-key rotation. A linkable pseudonym is not guaranteed anonymity.
Attach the field to the request, not the prompt
The Responses request schema accepts safety_identifier as a top-level string or null. The following unexecuted body illustrates POST /v1/responses. Replace SERVER_DERIVED_PSEUDONYM with the derived value; keep authentication in your existing server-side integration. The model is illustrative, not a requirement for the field.
{
"model": "grok-4.7",
"input": "Summarize this public product description.",
"safety_identifier": "SERVER_DERIVED_PSEUDONYM"
}Request path | Where attribution belongs | What to keep separate |
|---|---|---|
| Response IDs track individual results, not a person. | |
Top-level field beside | Do not add the identifier to message text. | |
On the initial Chat Completions POST with | The returned | |
Inside each row’s |
| |
In the Responses-shaped |
| |
| Schema support does not establish installed SDK support. |
For example, two batch jobs from one account need different custom_id values but the same safety_identifier. That separation follows from the batch file format: the item ID matches a result to work, while the attribution ID associates work with a user. Do not assume that text-field support covers separate image, video or voice schemas.
Streaming is explicitly covered. As a defensive integration rule, attach identity on every outbound request, retry and WebSocket turn, including after reconnects. Do not depend on an undocumented inheritance rule. Keep cache affinity separate as well; the Grok 4.6 integration analysis explains that distinct concern.
Check the SDK release before changing call sites
As checked on October 8, 2026, PyPI metadata still lists xai-sdk 1.20.0. Its tagged chat source exposes user but no named safety_identifier argument. The SDK changelog places the new argument under Unreleased. Installing the latest published package therefore does not, by itself, establish support for the new keyword.
Use the documented REST route or a client version whose serialization you have verified. If retaining the older SDK, preserve the existing user path during migration: xAI’s release notes say it remains accepted. The older SDK source already describes user-level abuse monitoring, so per-user attribution itself did not begin with this field.
Prefer one documented attribution field per request. The reviewed sources do not settle which value wins if user and safety_identifier conflict. Do not assume that a gateway forwards a parameter merely because its name is compatible with another provider’s API.
Roll out with identity and transport checks
These are proposed acceptance checks, not results from a tested deployment:
Use synthetic accounts to check stability: repeated requests from one account keep the same value; different accounts differ; tenant-local ID reuse stays distinct.
Attempt a client-side override and confirm that trusted backend identity wins. Set attribution after assembling user-controlled request options.
Inspect sanitized outgoing payloads from each deployed adapter. Cover synchronous calls, streams, retries, deferred submissions, batch bodies and WebSocket reconnects.
Confirm that incident responders can resolve a pseudonym through restricted internal records without exposing raw IDs or key material in routine logs.
Keep authentication, authorization, moderation and incident response in place. A successful API response can help verify transport, but it cannot demonstrate how a future policy case will be handled. The reviewed documentation supplies no user-only enforcement guarantee, and it does not specify a maximum identifier length or the identifier’s metadata lifetime under Zero Data Retention. Treat those as separate questions, not properties supplied by hashing. Security and retention documentation.
Methodology: AI-assisted reporting and implementation analysis based on official documentation, package metadata and public source code, rechecked October 8, 2026. No live inference calls, SDK execution, enforcement experiments or performance measurements were performed.