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920920 -H "x-api-key: $ANTHROPIC_API_KEY" \
921921 -H "anthropic-version: 2023-06-01" \
922922 -H "anthropic-beta: managed-agents-2026-04-01" \
923 -H "content-type: application/json" \
924 | jq -r '.data[] | "[\(.type)] \(.processed_at)"'
923 -H "content-type: application/json"
925924 ```
926925
927926 ```bash CLI
928 ant beta:sessions:events list --session-id "$SESSION_ID" \
929 --format jsonl --transform '{type,processed_at}'
927 ant beta:sessions:events list --session-id "$SESSION_ID" --format jsonl
930928 ```
931929
932930 ```python Python
from line 989
991989 curl --fail-with-body -sS "https://api.anthropic.com/v1/sessions/$SESSION_ID/events?beta=true&types[]=agent.tool_use&types[]=agent.tool_result" \
992990 -H "x-api-key: $ANTHROPIC_API_KEY" \
993991 -H "anthropic-version: 2023-06-01" \
994 -H "anthropic-beta: managed-agents-2026-04-01" \
995 | jq -r '.data[] | "[\(.type)] \(.processed_at)"'
992 -H "anthropic-beta: managed-agents-2026-04-01"
996993 ```
997994
998995 ```bash CLI
999996 ant beta:sessions:events list --session-id "$SESSION_ID" \
1000997 --type agent.tool_use --type agent.tool_result \
1001 --format jsonl --transform '{type,processed_at}'
998 --format jsonl
1002999 ```
10031000
10041001 ```python Python
from line 1582
15851582
15861583The preview events themselves don't change. `event_start` and `event_delta` have the same shape on a thread stream as on the session-level stream, and the [accumulate and reconcile](https://platform.claude.com/docs/en/managed-agents/events-and-streaming#accumulate-and-reconcile) pattern applies as written. The one adjustment is bookkeeping: run one accumulator instance per stream connection.
15871584
1588<CodeGroup defaultLanguage="cURL">
1585<CodeGroup>
15891586 ```bash cURL
15901587 # List the session's threads and pick a child: child threads carry a non-null
15911588 # parent_thread_id, and the primary thread's parent_thread_id is null.
from line 2456
24592456
24602457To resume a session, send a `user.message` event to it as usual:
24612458
2462<CodeGroup defaultLanguage="CLI">
2459<CodeGroup>
24632460 ```bash cURL
24642461 # In production, pass the stored ID of the session you want to resume.
24652462 curl --fail-with-body -sS "https://api.anthropic.com/v1/sessions/$SESSION_ID/events?beta=true" \
from line 2640
26432640
26442641Send a `system.message` event to give the agent privileged system-level context that applies to the accompanying turn and all subsequent turns. Unlike the `system` field on the agent definition (which sets the top-level system prompt), `system.message` content is appended to the session's system context as a `role: "system"` turn rather than replacing that prompt. Use it when the agent needs updated system-level guidance mid-session: a different persona, revised constraints, or context fetched at runtime that should shape the model's behavior going forward.
26452642
2646<CodeGroup defaultLanguage="CLI">
2643<CodeGroup>
26472644 ```bash cURL
26482645 curl --fail-with-body -sS "https://api.anthropic.com/v1/sessions/$SESSION_ID/events?beta=true" \
26492646 -H "x-api-key: $ANTHROPIC_API_KEY" \