The Event Log is an append-only sequence of typed events. Events are immutable once written — you cannot update or delete individual events. This makes it ideal for audit trails, tool call history, and decision logs.

Command Overview

Command	Syntax	Returns
event append	event append <type> <payload>	Sequence number
event get	event get <seq>	Event at sequence
event list	event list <type> [--limit N] [--after SEQ]	All events of type
event len	event len	Total event count

Appending Events

Each event has a type (a string label) and a payload (must be a JSON object):

$ strata --cache
strata:default/default> event append tool_call '{"tool":"web_search","query":"rust embedded database","results":10}'
(seq) 1

Payload Must Be a JSON Object

Event payloads must be JSON objects. This ensures events are structured and queryable:

$ strata --cache
strata:default/default> event append auth '{"action":"login","user_id":42}'
(seq) 1

Reading Events

By Sequence Number

Each event gets a unique sequence number (starting from 1):

$ strata --cache
strata:default/default> event append log '{"msg":"hello"}'
(seq) 1
strata:default/default> event get 1
seq=1 type=log payload={"msg":"hello"}

By Event Type

Retrieve all events with a specific type label:

$ strata --cache
strata:default/default> event append tool_call '{"tool":"search"}'
(seq) 1
strata:default/default> event append decision '{"choice":"A"}'
(seq) 2
strata:default/default> event append tool_call '{"tool":"calculator"}'
(seq) 3
strata:default/default> event list tool_call
seq=1 type=tool_call payload={"tool":"search"}
seq=3 type=tool_call payload={"tool":"calculator"}
strata:default/default> event list decision
seq=2 type=decision payload={"choice":"A"}

Event Count

Get the total number of events in the current branch:

$ strata --cache
strata:default/default> event len
0
strata:default/default> event append log '{"msg":"one"}'
(seq) 1
strata:default/default> event append log '{"msg":"two"}'
(seq) 2
strata:default/default> event len
2

Common Patterns

Audit Trail

Log every tool call with input and output:

strata --cache event append tool_call '{"tool":"search","input":"query","output":"results"}'

Decision Log

Record agent decisions with reasoning:

strata --cache event append decision '{"decision":"use_tool_A","reason":"higher confidence","confidence":0.92}'

Branch Isolation

Events are isolated by branch. event len returns 0 in a new branch even if other branches have events:

$ strata --cache
strata:default/default> event append log '{"msg":"in default"}'
(seq) 1
strata:default/default> branch create other
OK
strata:default/default> use other
strata:other/default> event len
0

Space Isolation

Within a branch, events are scoped to the current space:

$ strata --cache
strata:default/default> event append log '{"msg":"in default space"}'
(seq) 1
strata:default/default> event len
1
strata:default/default> use default other
strata:default/other> event len
0

See Spaces for the full guide.

Transactions

Event append operations participate in transactions. Within a transaction, appended events are only visible after commit.

See Sessions and Transactions for details.

Next

• State Cell — mutable state with CAS
• Cookbook: Agent State Management — combining events with other primitives