After Start() is called and creates a new stopChan on line 41, the old goroutine from a previous runLoop (if it exists) continues running with the old channel and won't be stopped. This creates a goroutine leak. The check on line 33 should verify if a goroutine is actually running, not just if stopChan exists. Consider tracking the running state separately (similar to how cron service uses the 'running' boolean), or ensure Stop() is always called before Start().

The shallow copy of Messages on line 166 doesn't properly deep-copy nested structures. Each Message contains a ToolCalls slice, and within ToolCalls there are pointer fields (Function *FunctionCall) and map fields (Arguments map[string]interface{}). These are shared with the original, not copied. If the original session's messages are modified after this copy (which shouldn't happen but could in concurrent scenarios), the snapshot could be affected. Consider implementing a proper deep copy that also copies the ToolCalls slice and its nested structures.

The saveStore call on line 149 ignores its error return value. If the save fails, the job state updates (LastRunAtMS, LastStatus, etc.) are lost on the next restart, even though the job executed. This could lead to inconsistent state where jobs appear to have never run or have outdated status information. Consider logging or handling the error from saveStore to ensure persistence failures are visible.

The atomic write implementation uses CreateTemp with a pattern that includes the key, which could be problematic if the key contains characters invalid in filenames (e.g., path separators like '/' or '\'). The agent code uses keys like "channel:chat_id" which are safe, but if keys from other sources contain problematic characters, CreateTemp could fail. Consider sanitizing the key or using a fixed prefix like ".tmp" to make the pattern more robust.

The new edge case handling for keepLast <= 0 on lines 127-131 clears all messages, which is a reasonable interpretation. However, this behavior is undocumented and may be unexpected. When keepLast is 0, users might expect either an error or no-op behavior rather than clearing the history. Consider documenting this behavior or validating that keepLast is positive before proceeding.

The shallow copy of CronJob on line 160 shares pointer references in the State field. State contains *int64 pointers for NextRunAtMS and LastRunAtMS, which are shared between the original and the copy. While the current code doesn't modify the pointed-to values (it only reassigns the pointers themselves), this creates a subtle coupling. If future code modifies values through these pointers, it could affect both the original and the callback copy unexpectedly. Consider creating new int64 values and copying the dereferenced values for complete isolation.

The TruncateHistory method doesn't update the session's Updated timestamp when keepLast is greater than the current message count (line 133-135). While the method does nothing in this case, it might be expected to update the timestamp to reflect that the truncation operation was attempted. For consistency with other branches that do update the timestamp, consider whether an update is needed here as well.

There's a potential issue where a job could be deleted (by removeJobUnsafe on line 203 or externally via RemoveJob) between finding the job on line 158-164 and re-finding it on line 179-188. When this happens, the second lookup returns nil (line 186-188), but no error state is recorded. The job executed successfully, but its state update is silently lost. Consider tracking the deletion separately or logging when a job disappears between execution and state update.

Similar to the CreateTemp pattern issue, the sessionPath construction on line 177 is vulnerable to path traversal if the key contains ".." or path separators. A malicious or misconfigured key could write outside the storage directory. Consider sanitizing the key by replacing path separators or validating that the resolved path is still within the storage directory using filepath.Clean and checking the prefix.