[doc] Support TTL on ShortTermMemory in User Documentation

docs/content/docs/development/memory/overview.md

@@ -57,6 +57,7 @@ For more details, see [Sensory & Short-term Memory]({{< ref "docs/development/me
 * **Characteristics**: 
   * The lifecycle of the stored data can across multiple runs. 
   * Complete original data retrieval.
+  * Supports optional automatic expiration and cleanup.
 
 For more details, see [Sensory & Short-Term Memory]({{< ref "docs/development/memory/sensory_and_short_term_memory" >}}).
 

docs/content/docs/development/memory/sensory_and_short_term_memory.md

@@ -252,8 +252,11 @@ public static void secondAction(Event event, RunnerContext ctx) throws Exception
 {{< /tab >}}
 
 {{< /tabs >}}
+
 ## Auto-Cleanup Behavior
 
+### Sensory Memory
+
 Sensory Memory is automatically cleared by the framework after each agent run completes. This cleanup happens:
 
 - **When**: After the agent run finishes processing all events trigger by one input event.
@@ -263,4 +266,56 @@ Sensory Memory is automatically cleared by the framework after each agent run co
 
 {{< hint info >}}
 During execution, sensory memory data is checkpointed by Flink for fault tolerance. However, once the run completes, all sensory memory is cleared and will not be available in subsequent runs.
-{{< /hint >}}
+{{< /hint >}}
+
+### Short-Term Memory
+
+Short-term memory can be configured with a time-to-live (TTL) so that older state expires automatically. This is useful for agents that may run for a long time: if the agent only needs recent memories, expiring historical data directly keeps the stored state focused on the latest context and avoids retaining stale information.
+
+Set `short-term-memory.state-ttl.ms` to a value greater than 0 in milliseconds to enable TTL. You can also configure how the TTL is refreshed and whether expired state can be returned before Flink cleans it up:
+
+- `short-term-memory.state-ttl.update-type`: controls whether TTL is refreshed on create/write or on read/write.
+- `short-term-memory.state-ttl.visibility`: controls whether expired memory is never returned or may be returned if it has not been cleaned up yet.
+
+{{< tabs "Short-Term Memory TTL Configuration" >}}
+
+{{< tab "Python" >}}
+```python
+from flink_agents.api.core_options import (
+    AgentExecutionOptions,
+    ShortTermMemoryTtlUpdate,
+    ShortTermMemoryTtlVisibility,
+)
+from flink_agents.api.execution_environment import AgentsExecutionEnvironment
+
+agents_env = AgentsExecutionEnvironment.get_execution_environment(env=env)
+agents_config = agents_env.get_config()
+
+agents_config.set(AgentExecutionOptions.SHORT_TERM_MEMORY_STATE_TTL_MS, 60_000)
+agents_config.set(
+    AgentExecutionOptions.SHORT_TERM_MEMORY_STATE_TTL_UPDATE_TYPE,
+    ShortTermMemoryTtlUpdate.ON_READ_AND_WRITE,
+)
+agents_config.set(
+    AgentExecutionOptions.SHORT_TERM_MEMORY_STATE_TTL_VISIBILITY,
+    ShortTermMemoryTtlVisibility.NEVER_RETURN_EXPIRED,
+)
+```
+{{< /tab >}}
+
+{{< tab "Java" >}}
+```java
+AgentsExecutionEnvironment agentsEnv = AgentsExecutionEnvironment.getExecutionEnvironment(env);
+AgentConfiguration agentsConfig = (AgentConfiguration) agentsEnv.getConfig();
+
+agentsConfig.set(AgentExecutionOptions.SHORT_TERM_MEMORY_STATE_TTL_MS, 60_000L);
+agentsConfig.set(
+        AgentExecutionOptions.SHORT_TERM_MEMORY_STATE_TTL_UPDATE_TYPE,
+        ShortTermMemoryTtlUpdate.ON_READ_AND_WRITE);
+agentsConfig.set(
+        AgentExecutionOptions.SHORT_TERM_MEMORY_STATE_TTL_VISIBILITY,
+        ShortTermMemoryTtlVisibility.NEVER_RETURN_EXPIRED);
+```
+{{< /tab >}}
+
+{{< /tabs >}}

docs/content/docs/operations/configuration.md

@@ -146,7 +146,9 @@ Here is the list of all built-in core configuration options.
 | `event-log.standard.max-string-length` | 2000              | int                   | At `STANDARD` level, strings in the event payload longer than this are truncated. Has no effect at `VERBOSE`.                                                                                                                                                  |
 | `event-log.standard.max-array-elements` | 20               | int                   | At `STANDARD` level, arrays in the event payload with more than this many elements are truncated. Has no effect at `VERBOSE`.                                                                                                                                  |
 | `event-log.standard.max-depth` | 5                     | int                   | At `STANDARD` level, objects nested deeper than this are summarized. Has no effect at `VERBOSE`.                                                                                                                                                               |
-
+| `short-term-memory.state-ttl.ms` | 0                    | long                  | Time-to-live for short-term memory state in milliseconds. Set to a value greater than 0 to enable TTL; 0 disables it.                                                                                                                                           |
+| `short-term-memory.state-ttl.update-type` | `ON_READ_AND_WRITE` | ShortTermMemoryTtlUpdate | Update policy for short-term memory TTL. Only applies when `short-term-memory.state-ttl.ms` is greater than 0. Valid values: `ON_CREATE_AND_WRITE`, `ON_READ_AND_WRITE`.                                                                                       |
+| `short-term-memory.state-ttl.visibility` | `NEVER_RETURN_EXPIRED` | ShortTermMemoryTtlVisibility | Visibility policy for expired short-term memory state. Only applies when `short-term-memory.state-ttl.ms` is greater than 0. Valid values: `NEVER_RETURN_EXPIRED`, `RETURN_EXPIRED_IF_NOT_CLEANED_UP`.                                                        |
 
 ### Action State Store