feat: ephemeral channels with TTL-based auto-archiving

Add ephemeral channels that auto-archive after a configurable period of
inactivity. Full vertical slice: schema → DB → relay → REST API → desktop UI.

Schema:
- Add ttl_seconds (INT) and ttl_deadline (TIMESTAMPTZ) to channels table
- Add partial index for efficient reaper queries

Database (sprout-db):
- Extend ChannelRecord with ttl_seconds and ttl_deadline fields
- Add bump_ttl_deadline() to reset deadline on channel activity
- Add reap_expired_ephemeral_channels() to archive expired channels
- Thread ttl_seconds through create_channel and create_channel_with_id

Relay (sprout-relay):
- Parse 'ttl' tag from NIP-29 create-group events
- Bump TTL deadline on every channel-scoped event (skip kind:9007 create)
- Add background reaper task (configurable interval, default 60s)
- Support SPROUT_EPHEMERAL_TTL_OVERRIDE env var for testing
- Emit system messages and discovery events on auto-archive

Desktop:
- Add ephemeral checkbox to channel/forum creation forms
- Thread ttl_seconds through Tauri commands and event builders
- Expose ttl_seconds and ttl_deadline in TypeScript types and API layer
- Bump check-file-sizes override for types.ts

Author: wesbillman

.env.example

@@ -81,6 +81,17 @@ OKTA_AUDIENCE=sprout-desktop
 # OKTA_AUDIENCE=sprout-api
 # OKTA_PUBKEY_CLAIM=nostr_pubkey
 
+# -----------------------------------------------------------------------------
+# Ephemeral Channels (TTL testing)
+# -----------------------------------------------------------------------------
+# Override the TTL for all ephemeral channels (in seconds). When set, any
+# channel created with a TTL tag will use this value instead of the
+# client-provided one. Unset to use the client-provided TTL.
+# SPROUT_EPHEMERAL_TTL_OVERRIDE=60
+
+# How often the reaper checks for expired ephemeral channels (default: 60s).
+# SPROUT_REAPER_INTERVAL_SECS=5
+
 # -----------------------------------------------------------------------------
 # Logging / Tracing
 # -----------------------------------------------------------------------------

crates/sprout-db/src/channel.rs

@@ -58,6 +58,10 @@ pub struct ChannelRecord {
     pub purpose_set_by: Option<Vec<u8>>,
     /// When the purpose was last set.
     pub purpose_set_at: Option<DateTime<Utc>>,
+    /// TTL in seconds for ephemeral channels. `None` means permanent.
+    pub ttl_seconds: Option<i32>,
+    /// Deadline by which a new message must arrive or the channel is auto-archived.
+    pub ttl_deadline: Option<DateTime<Utc>>,
 }
 
 /// A channel membership row as returned from the database.
@@ -85,6 +89,7 @@ pub async fn create_channel(
     visibility: ChannelVisibility,
     description: Option<&str>,
     created_by: &[u8],
+    ttl_seconds: Option<i32>,
 ) -> Result<ChannelRecord> {
     if created_by.len() != 32 {
         return Err(DbError::InvalidData(format!(
@@ -99,8 +104,9 @@ pub async fn create_channel(
 
     sqlx::query(
         r#"
-        INSERT INTO channels (id, name, channel_type, visibility, description, created_by)
-        VALUES ($1, $2, $3::channel_type, $4::channel_visibility, $5, $6)
+        INSERT INTO channels (id, name, channel_type, visibility, description, created_by, ttl_seconds, ttl_deadline)
+        VALUES ($1, $2, $3::channel_type, $4::channel_visibility, $5, $6, $7,
+                CASE WHEN $7 IS NOT NULL THEN NOW() + ($7 || ' seconds')::interval ELSE NULL END)
         "#,
     )
     .bind(id)
@@ -109,6 +115,7 @@ pub async fn create_channel(
     .bind(visibility.as_str())
     .bind(description)
     .bind(created_by)
+    .bind(ttl_seconds)
     .execute(&mut *tx)
     .await?;
 
@@ -135,7 +142,8 @@ pub async fn create_channel(
                created_by, created_at, updated_at, archived_at, deleted_at,
                nip29_group_id, topic_required, max_members,
                topic, topic_set_by, topic_set_at,
-               purpose, purpose_set_by, purpose_set_at
+               purpose, purpose_set_by, purpose_set_at,
+               ttl_seconds, ttl_deadline
         FROM channels WHERE id = $1
         "#,
     )
@@ -152,6 +160,7 @@ pub async fn create_channel(
 ///
 /// Returns `(record, true)` if the channel was newly created, or `(record, false)` if a
 /// channel with `channel_id` already exists (duplicate — caller should reject the event).
+#[allow(clippy::too_many_arguments)]
 pub async fn create_channel_with_id(
     pool: &PgPool,
     channel_id: Uuid,
@@ -160,6 +169,7 @@ pub async fn create_channel_with_id(
     visibility: ChannelVisibility,
     description: Option<&str>,
     created_by: &[u8],
+    ttl_seconds: Option<i32>,
 ) -> Result<(ChannelRecord, bool)> {
     if created_by.len() != 32 {
         return Err(DbError::InvalidData(format!(
@@ -172,8 +182,9 @@ pub async fn create_channel_with_id(
 
     let rows_affected = sqlx::query(
         r#"
-        INSERT INTO channels (id, name, channel_type, visibility, description, created_by)
-        VALUES ($1, $2, $3::channel_type, $4::channel_visibility, $5, $6)
+        INSERT INTO channels (id, name, channel_type, visibility, description, created_by, ttl_seconds, ttl_deadline)
+        VALUES ($1, $2, $3::channel_type, $4::channel_visibility, $5, $6, $7,
+                CASE WHEN $7 IS NOT NULL THEN NOW() + ($7 || ' seconds')::interval ELSE NULL END)
         ON CONFLICT (id) DO NOTHING
         "#,
     )
@@ -183,6 +194,7 @@ pub async fn create_channel_with_id(
     .bind(visibility.as_str())
     .bind(description)
     .bind(created_by)
+    .bind(ttl_seconds)
     .execute(&mut *tx)
     .await?
     .rows_affected();
@@ -215,7 +227,8 @@ pub async fn create_channel_with_id(
                created_by, created_at, updated_at, archived_at, deleted_at,
                nip29_group_id, topic_required, max_members,
                topic, topic_set_by, topic_set_at,
-               purpose, purpose_set_by, purpose_set_at
+               purpose, purpose_set_by, purpose_set_at,
+               ttl_seconds, ttl_deadline
         FROM channels WHERE id = $1
         "#,
     )
@@ -237,7 +250,8 @@ pub async fn get_channel(pool: &PgPool, channel_id: Uuid) -> Result<ChannelRecor
                created_by, created_at, updated_at, archived_at, deleted_at,
                nip29_group_id, topic_required, max_members,
                topic, topic_set_by, topic_set_at,
-               purpose, purpose_set_by, purpose_set_at
+               purpose, purpose_set_by, purpose_set_at,
+               ttl_seconds, ttl_deadline
         FROM channels WHERE id = $1 AND deleted_at IS NULL
         "#,
     )
@@ -535,7 +549,8 @@ pub async fn list_channels(pool: &PgPool, visibility: Option<&str>) -> Result<Ve
                    created_by, created_at, updated_at, archived_at, deleted_at,
                    nip29_group_id, topic_required, max_members,
                    topic, topic_set_by, topic_set_at,
-                   purpose, purpose_set_by, purpose_set_at
+                   purpose, purpose_set_by, purpose_set_at,
+                   ttl_seconds, ttl_deadline
             FROM channels
             WHERE deleted_at IS NULL AND visibility::text = $1
             ORDER BY created_at DESC
@@ -553,7 +568,8 @@ pub async fn list_channels(pool: &PgPool, visibility: Option<&str>) -> Result<Ve
                    created_by, created_at, updated_at, archived_at, deleted_at,
                    nip29_group_id, topic_required, max_members,
                    topic, topic_set_by, topic_set_at,
-                   purpose, purpose_set_by, purpose_set_at
+                   purpose, purpose_set_by, purpose_set_at,
+                   ttl_seconds, ttl_deadline
             FROM channels
             WHERE deleted_at IS NULL
             ORDER BY created_at DESC
@@ -596,7 +612,8 @@ async fn get_channel_tx(
                created_by, created_at, updated_at, archived_at, deleted_at,
                nip29_group_id, topic_required, max_members,
                topic, topic_set_by, topic_set_at,
-               purpose, purpose_set_by, purpose_set_at
+               purpose, purpose_set_by, purpose_set_at,
+               ttl_seconds, ttl_deadline
         FROM channels WHERE id = $1 AND deleted_at IS NULL
         "#,
     )
@@ -685,6 +702,7 @@ pub async fn get_accessible_channels(
                c.nip29_group_id, c.topic_required, c.max_members,
                c.topic, c.topic_set_by, c.topic_set_at,
                c.purpose, c.purpose_set_by, c.purpose_set_at,
+               c.ttl_seconds, c.ttl_deadline,
                (cm.channel_id IS NOT NULL) AS is_member
         FROM channels c
         LEFT JOIN channel_members cm
@@ -807,6 +825,8 @@ fn row_to_channel_record(row: sqlx::postgres::PgRow) -> Result<ChannelRecord> {
     let purpose: Option<String> = row.try_get("purpose").unwrap_or(None);
     let purpose_set_by: Option<Vec<u8>> = row.try_get("purpose_set_by").unwrap_or(None);
     let purpose_set_at: Option<DateTime<Utc>> = row.try_get("purpose_set_at").unwrap_or(None);
+    let ttl_seconds: Option<i32> = row.try_get("ttl_seconds").unwrap_or(None);
+    let ttl_deadline: Option<DateTime<Utc>> = row.try_get("ttl_deadline").unwrap_or(None);
 
     Ok(ChannelRecord {
         id,
@@ -829,6 +849,8 @@ fn row_to_channel_record(row: sqlx::postgres::PgRow) -> Result<ChannelRecord> {
         purpose,
         purpose_set_by,
         purpose_set_at,
+        ttl_seconds,
+        ttl_deadline,
     })
 }
 
@@ -1086,3 +1108,42 @@ pub async fn get_member_role(
     .await?;
     Ok(row.map(|r| r.try_get("role")).transpose()?)
 }
+
+/// Bump the TTL deadline for an ephemeral channel after a new message.
+///
+/// No-op for permanent channels or channels that are already archived/deleted.
+pub async fn bump_ttl_deadline(pool: &PgPool, channel_id: Uuid) -> Result<()> {
+    sqlx::query(
+        "UPDATE channels SET ttl_deadline = NOW() + (ttl_seconds || ' seconds')::interval \
+         WHERE id = $1 AND ttl_seconds IS NOT NULL AND archived_at IS NULL AND deleted_at IS NULL",
+    )
+    .bind(channel_id)
+    .execute(pool)
+    .await?;
+    Ok(())
+}
+
+/// Archive ephemeral channels whose TTL deadline has passed.
+///
+/// Returns the list of channel IDs that were archived. Idempotent — the
+/// `archived_at IS NULL` guard prevents double-archiving even if called
+/// concurrently from multiple relay pods.
+pub async fn reap_expired_ephemeral_channels(pool: &PgPool) -> Result<Vec<Uuid>> {
+    let rows = sqlx::query(
+        "UPDATE channels SET archived_at = NOW() \
+         WHERE ttl_seconds IS NOT NULL \
+           AND ttl_deadline < NOW() \
+           AND archived_at IS NULL \
+           AND deleted_at IS NULL \
+         RETURNING id",
+    )
+    .fetch_all(pool)
+    .await?;
+
+    rows.into_iter()
+        .map(|row| {
+            let id: Uuid = row.try_get("id")?;
+            Ok(id)
+        })
+        .collect()
+}

crates/sprout-db/src/dm.rs

@@ -439,6 +439,8 @@ fn row_to_channel_record(row: sqlx::postgres::PgRow) -> Result<ChannelRecord> {
         purpose: row.try_get("purpose").unwrap_or(None),
         purpose_set_by: row.try_get("purpose_set_by").unwrap_or(None),
         purpose_set_at: row.try_get("purpose_set_at").unwrap_or(None),
+        ttl_seconds: row.try_get("ttl_seconds").unwrap_or(None),
+        ttl_deadline: row.try_get("ttl_deadline").unwrap_or(None),
     })
 }
 

crates/sprout-db/src/lib.rs

@@ -298,6 +298,7 @@ impl Db {
         visibility: channel::ChannelVisibility,
         description: Option<&str>,
         created_by: &[u8],
+        ttl_seconds: Option<i32>,
     ) -> Result<channel::ChannelRecord> {
         channel::create_channel(
             &self.pool,
@@ -306,13 +307,15 @@ impl Db {
             visibility,
             description,
             created_by,
+            ttl_seconds,
         )
         .await
     }
 
     /// Creates a channel with a client-supplied UUID.
     ///
     /// Returns `(record, true)` if newly created, `(record, false)` if already exists.
+    #[allow(clippy::too_many_arguments)]
     pub async fn create_channel_with_id(
         &self,
         channel_id: Uuid,
@@ -321,6 +324,7 @@ impl Db {
         visibility: channel::ChannelVisibility,
         description: Option<&str>,
         created_by: &[u8],
+        ttl_seconds: Option<i32>,
     ) -> Result<(channel::ChannelRecord, bool)> {
         channel::create_channel_with_id(
             &self.pool,
@@ -330,6 +334,7 @@ impl Db {
             visibility,
             description,
             created_by,
+            ttl_seconds,
         )
         .await
     }
@@ -465,6 +470,16 @@ impl Db {
         channel::get_member_role(&self.pool, channel_id, pubkey).await
     }
 
+    /// Bump the TTL deadline for an ephemeral channel after a new message.
+    pub async fn bump_ttl_deadline(&self, channel_id: Uuid) -> Result<()> {
+        channel::bump_ttl_deadline(&self.pool, channel_id).await
+    }
+
+    /// Archive ephemeral channels whose TTL deadline has passed.
+    pub async fn reap_expired_ephemeral_channels(&self) -> Result<Vec<Uuid>> {
+        channel::reap_expired_ephemeral_channels(&self.pool).await
+    }
+
     // ── Users ────────────────────────────────────────────────────────────────
 
     /// Ensure a user record exists (upsert).

crates/sprout-relay/src/api/channels.rs

@@ -112,6 +112,8 @@ fn channel_record_to_json(
         "participants": participants,
         "participant_pubkeys": participant_pubkeys,
         "is_member": is_member,
+        "ttl_seconds": channel.ttl_seconds,
+        "ttl_deadline": channel.ttl_deadline.map(|t| t.to_rfc3339()),
     })
 }
 

crates/sprout-relay/src/api/channels_metadata.rs

@@ -50,6 +50,8 @@ fn channel_detail_to_json(record: &ChannelRecord, member_count: i64) -> serde_js
         "topic_required": record.topic_required,
         "max_members": record.max_members,
         "nip29_group_id": record.nip29_group_id,
+        "ttl_seconds": record.ttl_seconds,
+        "ttl_deadline": record.ttl_deadline.map(|t| t.to_rfc3339()),
     })
 }
 

crates/sprout-relay/src/config.rs

@@ -61,6 +61,13 @@ pub struct Config {
     pub pubkey_allowlist_enabled: bool,
     /// Media storage configuration (S3/MinIO).
     pub media: sprout_media::MediaConfig,
+
+    /// Optional override for ephemeral channel TTL (in seconds).
+    /// When set, any channel created with a TTL tag will use this value instead
+    /// of the client-provided one. Useful for testing ephemeral expiry quickly.
+    /// Example: `SPROUT_EPHEMERAL_TTL_OVERRIDE=60` → all ephemeral channels expire
+    /// 60 seconds after the last message.
+    pub ephemeral_ttl_override: Option<i32>,
 }
 
 impl Config {
@@ -194,6 +201,18 @@ impl Config {
                 }),
         };
 
+        let ephemeral_ttl_override = std::env::var("SPROUT_EPHEMERAL_TTL_OVERRIDE")
+            .ok()
+            .and_then(|v| v.parse::<i32>().ok())
+            .filter(|&v| v > 0);
+
+        if let Some(ttl) = ephemeral_ttl_override {
+            warn!(
+                "SPROUT_EPHEMERAL_TTL_OVERRIDE={ttl}s — all ephemeral channels will use \
+                 this TTL instead of the client-provided value."
+            );
+        }
+
         Ok(Self {
             bind_addr,
             database_url,
@@ -213,6 +232,7 @@ impl Config {
             metrics_port,
             pubkey_allowlist_enabled,
             media,
+            ephemeral_ttl_override,
         })
     }
 }

crates/sprout-relay/src/handlers/ingest.rs

@@ -1029,6 +1029,8 @@ pub async fn ingest_event(
                 }
             });
 
+            let ttl_seconds = super::resolve_ttl(&event, state.config.ephemeral_ttl_override);
+
             let actor_bytes = event.pubkey.serialize().to_vec();
             let (_, was_created) = state
                 .db
@@ -1039,6 +1041,7 @@ pub async fn ingest_event(
                     visibility,
                     description.as_deref(),
                     &actor_bytes,
+                    ttl_seconds,
                 )
                 .await
                 .map_err(|e| IngestError::Internal(format!("error: {e}")))?;
@@ -1304,6 +1307,17 @@ pub async fn ingest_event(
         });
     }
 
+    // ── 20b. Bump ephemeral channel TTL deadline ──────────────────────
+    // Any successfully stored channel-scoped event keeps the channel alive.
+    // Skip kind:9007 (create) — the deadline was just set during creation.
+    if let Some(ch_id) = channel_id {
+        if kind_u32 != KIND_NIP29_CREATE_GROUP {
+            if let Err(e) = state.db.bump_ttl_deadline(ch_id).await {
+                warn!(channel = %ch_id, "TTL deadline bump failed: {e}");
+            }
+        }
+    }
+
     // ── 21. Side effects ─────────────────────────────────────────────────
     if crate::handlers::side_effects::is_side_effect_kind(kind_u32) {
         if let Err(e) =