Message Metadata
| ID | message_metadata |
| Category | Core |
| Features | None |
| Dependencies | None |
Annotates user and agent messages with metadata, currently each message’s timestamp (UTC), when building the LLM request. The model sees each message prefixed with an annotation like:
[time 2026-06-11T09:15:42Z] What changed since yesterday?For user messages the timestamp is when the message was received; for agent messages, when the reply was generated.
This lets agents reason about timing: how long ago something was said, gaps between messages, and whether earlier statements are stale.
Enabled by default on the Generic (default) harness.
Annotations are applied only to the prompt-facing view of the conversation. Stored messages are never modified, and timestamps are stable across turns so prompt caching is unaffected. A short system prompt addition explains the annotation format to the model and instructs it not to emit annotations in its replies.
None.
Configuration
Section titled “Configuration”| Field | Type | Default | Description |
|---|---|---|---|
fields | array | ["timestamp"] | Metadata fields to render, in order. Supported: timestamp. An empty array disables annotations. More fields (e.g. the LLM model) will be added over time. |
User and agent messages are always annotated; system and tool-result messages never are.
See Also
Section titled “See Also”- Current Time, tool to get the current wall-clock time
- Capabilities Overview