No supported way to delete a conversation's stored data (needed for retention and GDPR erasure)

[kstulgys]

Version: @flue/runtime 2.1.0, checked against 2.1.1. Node target, built-in sqlite() adapter.

Describe the Bug

Flue has no supported way to delete one conversation's stored data. The dist/ of @flue/runtime@2.1.1 has three DELETE FROM statements. All three replace a fold checkpoint or a submission's chunks, and none of them removes a conversation. The PersistenceStores interfaces in @flue/runtime/adapter have no delete method either.

This blocks a common requirement. Our app is a chat about legal questions. A user can delete a conversation or all their data, and conversations expire 30 days after the last message. Privacy law (GDPR in our case) requires this deletion to actually happen, so a missing delete is a compliance problem, not only a storage problem.

Our workaround is raw SQL against the private tables of the 2.1 sqlite() adapter, keyed the way that version keys them:

• flue_conversation_streams, flue_conversation_stream_batches, flue_conversation_stream_batch_chunks, flue_conversation_fold_checkpoints, flue_conversation_fold_checkpoint_chunks by path = 'agents/<agent>/<id>'
• flue_attachments, flue_attachment_chunks by stream_path, same value
• flue_agent_submissions by a prefix match on session_key (agent-session:["<agent>","<id>",...)
• flue_submission_chunks by the submission_id of those submissions

We run it only when every submission of the conversation is settled, so a running turn never loses rows under it. This works, but it has problems:

• Any change to the table layout or key format in a Flue release can break deletion without an error. We pin Flue exactly and gate every upgrade on a test that seeds each table through the adapter and checks that the purge empties it.
• It is only for SQLite. Moving to @flue/postgres or to the Cloudflare target means writing it again against other internals. On Cloudflare the rows live in each agent's Durable Object storage, so the app would have to run the deletes from inside it.
• "Is a turn in flight?" is also read from flue_agent_submissions, because there is no public API for it.

Related: #658 (stream batches are never compacted or deleted). That issue is about storage growth inside a conversation that stays. This one is about removing a conversation completely.

Expected Behavior

A supported API that deletes everything Flue stores for one agent instance: stream, batches, fold checkpoints, attachments, submissions and their chunks. Adapters implement it, so it works the same on SQLite, Postgres and Cloudflare. For example:

// HTTP, or on the router / runtime
await deleteAgentInstance("Teisora", conversationId);

The API should define what happens while a submission is queued or running. It could refuse with a typed error, or abort the submission first and then delete. Either works for us if it is documented.

A read-only "has unsettled submissions" check would also help, so the app can show a conversation as busy without reading the submission ledger itself.

Steps to Reproduce

1. Start from any Node-target example with db.ts exporting sqlite(...).
2. Send a message to an agent instance and let the submission settle.
3. Try to delete that instance's data through a public API. There is none: the rows stay in the tables listed above until the database file is removed.