feat(message): add comprehensive message system with database migrations and health checks

- Add database migrations for message base table with indexes for efficient querying
- Implement rich content support with attachment, embed, and poll tables
- Create social features including reactions, bookmarks, mentions, and read states
- Add thread management with participant tracking and resolution capabilities
- Include article posts with title, cover image, tags, and engagement metrics
- Support scheduled messages, stickers, forwards, and interactive components
- Fix UUID defaults and ensure proper uniqueness constraints for drafts
- Add gRPC health server for imks and health check client for appks connectivity
- Replace non-connectable 0.0.0.0 addresses with localhost in service discovery
- Normalize addresses during RPC configuration to handle bind address issues

main.rs

@@ -58,12 +58,16 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     // Discover appks from etcd (priority > env).
     // etcd-registered addresses are bare "host:port" — prepend http:// for gRPC.
+    // Bind address 0.0.0.0 is not connectable; replace with localhost.
     let appks_addr = etcd
         .discover_service("appks")
         .await
         .ok()
         .and_then(|addrs| addrs.into_iter().next())
-        .map(|addr| format!("http://{}", addr))
+        .map(|addr| {
+            let normalized = addr.replace("0.0.0.0", "127.0.0.1");
+            format!("http://{}", normalized)
+        })
         .unwrap_or_else(|| {
             std::env::var("APPKS_GRPC_ADDR")
                 .unwrap_or_else(|_| "http://localhost:50051".to_string())
@@ -183,52 +187,77 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             let namespaces = namespaces.clone();
             let current_addr = current_addr.clone();
             let mut rpc = rpc_config.clone();
-            // etcd-registered address is bare "host:port" — prepend scheme for gRPC
+            // etcd-registered address is bare "host:port" — prepend scheme for gRPC.
-            rpc.appks_addr = if addr.starts_with("http") {
+            // Bind address 0.0.0.0 is not connectable; replace with localhost.
-                addr
+            let normalized = addr.replace("0.0.0.0", "127.0.0.1");
+            rpc.appks_addr = if normalized.starts_with("http") {
+                normalized
             } else {
-                format!("http://{}", addr)
+                format!("http://{}", normalized)
             };
             async move {
-                match AppksClients::connect(&rpc).await {
+                // Retry with backoff — appks may have registered in etcd
-                    Ok(clients) => {
+                // before its gRPC server finished binding.
-                        match MessageService::new((*repo).clone(), clients, namespaces.clone())
+                let max_retries = 5;
-                            .await
+                let mut delay = std::time::Duration::from_millis(500);
-                        {
-                            Ok(svc) => {
-                                let svc = Arc::new(svc);
-                                let mut guard = service.write().await;
-                                *guard = Some(svc);
 
-                                // Update the active appks address for health checker
+                for attempt in 1..=max_retries {
-                                let mut addr_guard = current_addr.write().await;
+                    match AppksClients::connect(&rpc).await {
-                                *addr_guard = Some(rpc.appks_addr.clone());
+                        Ok(clients) => {
+                            match MessageService::new((*repo).clone(), clients, namespaces.clone())
+                                .await
+                            {
+                                Ok(svc) => {
+                                    let svc = Arc::new(svc);
+                                    let mut guard = service.write().await;
+                                    *guard = Some(svc);
 
-                                tracing::info!(
+                                    // Update the active appks address for health checker
-                                    addr = %rpc.appks_addr,
+                                    let mut addr_guard = current_addr.write().await;
-                                    "Message service initialized"
+                                    *addr_guard = Some(rpc.appks_addr.clone());
-                                );
+
-                                true
+                                    tracing::info!(
+                                        addr = %rpc.appks_addr,
+                                        attempt,
+                                        "Message service initialized"
+                                    );
+                                    return true;
+                                }
+                                Err(e) => {
+                                    tracing::warn!(
+                                        addr = %rpc.appks_addr,
+                                        attempt,
+                                        error = %e,
+                                        "Failed to init message service"
+                                    );
+                                    if attempt < max_retries {
+                                        tokio::time::sleep(delay).await;
+                                        delay *= 2;
+                                    }
+                                }
                             }
-                            Err(e) => {
+                        }
-                                tracing::warn!(
+                        Err(e) => {
-                                    addr = %rpc.appks_addr,
+                            tracing::warn!(
-                                    error = %e,
+                                addr = %rpc.appks_addr,
-                                    "Failed to init message service"
+                                attempt,
-                                );
+                                error = %e,
-                                false
+                                "gRPC connect failed"
+                            );
+                            if attempt < max_retries {
+                                tokio::time::sleep(delay).await;
+                                delay *= 2;
                             }
                         }
                     }
-                    Err(e) => {
-                        tracing::warn!(
-                            addr = %rpc.appks_addr,
-                            error = %e,
-                            "gRPC connect failed"
-                        );
-                        false
-                    }
                 }
+
+                tracing::error!(
+                    addr = %rpc.appks_addr,
+                    max_retries,
+                    "All connection attempts to appks exhausted"
+                );
+                false
             }
         }
     };

migrate/000_message_base.sql

@@ -0,0 +1,46 @@
+-- ============================================================
+-- Migration: 000_message_base.sql
+-- Tables:  message
+-- ============================================================
+-- Core message table managed by imks. All companion tables
+-- (thread, attachment, embed, reaction, ...) reference message(id).
+
+BEGIN;
+
+CREATE TABLE IF NOT EXISTS message (
+    id                  UUID PRIMARY KEY,
+    channel_id          UUID NOT NULL,
+    author_id           UUID NOT NULL,
+    thread_id           UUID NULL,
+    reply_to_message_id UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    message_type        TEXT NOT NULL DEFAULT 'text',
+    body                TEXT NOT NULL,
+    metadata            JSONB NULL,
+    pinned              BOOLEAN NOT NULL DEFAULT FALSE,
+    system              BOOLEAN NOT NULL DEFAULT FALSE,
+    edited_at           TIMESTAMPTZ NULL,
+    deleted_at          TIMESTAMPTZ NULL,
+    created_at          TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at          TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+-- Cursor pagination: WHERE id < $cursor ORDER BY id DESC
+CREATE INDEX IF NOT EXISTS idx_message_channel_created
+    ON message (channel_id, created_at DESC);
+
+CREATE INDEX IF NOT EXISTS idx_message_author
+    ON message (author_id);
+
+CREATE INDEX IF NOT EXISTS idx_message_thread
+    ON message (thread_id)
+    WHERE thread_id IS NOT NULL;
+
+CREATE INDEX IF NOT EXISTS idx_message_reply_to
+    ON message (reply_to_message_id)
+    WHERE reply_to_message_id IS NOT NULL;
+
+CREATE INDEX IF NOT EXISTS idx_message_deleted
+    ON message (deleted_at)
+    WHERE deleted_at IS NOT NULL;
+
+COMMIT;

migrate/001_message_thread_base.sql

@@ -0,0 +1,23 @@
+-- Create message_thread before migrations that reference it.
+-- Safe for existing databases because the table may already exist from 004.
+
+BEGIN;
+
+CREATE TABLE IF NOT EXISTS message_thread (
+    id                     UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    channel_id             UUID NOT NULL,
+    root_message_id        UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    created_by             UUID NOT NULL,
+    replies_count          BIGINT NOT NULL DEFAULT 0,
+    participants_count     BIGINT NOT NULL DEFAULT 0,
+    last_reply_message_id  UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    last_reply_at          TIMESTAMPTZ NULL,
+    resolved               BOOLEAN NOT NULL DEFAULT FALSE,
+    resolved_by            UUID NULL,
+    resolved_at            TIMESTAMPTZ NULL,
+    created_at             TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at             TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_thread_root UNIQUE (root_message_id)
+);
+
+COMMIT;

migrate/002_message_rich_content.sql

@@ -0,0 +1,115 @@
+-- ============================================================
+-- Migration: 001_message_rich_content.sql
+-- Tables:  message_attachment, message_embed, message_embed_field,
+--          message_poll, message_poll_option, message_poll_vote
+-- ============================================================
+-- These tables extend the existing `message` table (from appks 001_init.sql)
+-- with Discord-style rich content: file attachments, link preview embeds,
+-- and interactive polls.
+
+BEGIN;
+
+-- models/message_attachment.rs  →  message_attachment
+CREATE TABLE IF NOT EXISTS message_attachment (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id    UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    filename      TEXT NOT NULL,
+    content_type  TEXT NULL,
+    size          BIGINT NOT NULL,
+    url           TEXT NOT NULL,
+    storage_key   TEXT NULL,
+    width         INTEGER NULL,
+    height        INTEGER NULL,
+    duration_secs DOUBLE PRECISION NULL,
+    blurhash      TEXT NULL,
+    spoiler       BOOLEAN NOT NULL DEFAULT FALSE,
+    created_at    TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS idx_message_attachment_message_id
+    ON message_attachment (message_id);
+
+-- models/message_embed.rs  →  message_embed
+CREATE TABLE IF NOT EXISTS message_embed (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id       UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    embed_type       TEXT NOT NULL,
+    title            TEXT NULL,
+    description      TEXT NULL,
+    url              TEXT NULL,
+    color            INTEGER NULL,
+    image_url        TEXT NULL,
+    image_width      INTEGER NULL,
+    image_height     INTEGER NULL,
+    thumbnail_url    TEXT NULL,
+    thumbnail_width  INTEGER NULL,
+    thumbnail_height INTEGER NULL,
+    video_url        TEXT NULL,
+    video_width      INTEGER NULL,
+    video_height     INTEGER NULL,
+    author_name      TEXT NULL,
+    author_url       TEXT NULL,
+    author_icon_url  TEXT NULL,
+    footer_text      TEXT NULL,
+    footer_icon_url  TEXT NULL,
+    provider_name    TEXT NULL,
+    provider_url     TEXT NULL,
+    created_at       TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS idx_message_embed_message_id
+    ON message_embed (message_id);
+
+-- models/message_embed.rs  →  message_embed_field
+CREATE TABLE IF NOT EXISTS message_embed_field (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    embed_id UUID NOT NULL REFERENCES message_embed(id) ON DELETE CASCADE,
+    name     TEXT NOT NULL,
+    value    TEXT NOT NULL,
+    inline   BOOLEAN NOT NULL DEFAULT FALSE,
+    position INTEGER NOT NULL DEFAULT 0
+);
+CREATE INDEX IF NOT EXISTS idx_message_embed_field_embed_id
+    ON message_embed_field (embed_id);
+
+-- models/message_poll.rs  →  message_poll
+CREATE TABLE IF NOT EXISTS message_poll (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id        UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    question          TEXT NOT NULL,
+    allow_multiselect BOOLEAN NOT NULL DEFAULT FALSE,
+    max_selections    INTEGER NULL,
+    expires_at        TIMESTAMPTZ NULL,
+    total_votes       BIGINT NOT NULL DEFAULT 0,
+    created_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_poll_message UNIQUE (message_id)
+);
+CREATE INDEX IF NOT EXISTS idx_message_poll_message_id
+    ON message_poll (message_id);
+
+-- models/message_poll.rs  →  message_poll_option
+CREATE TABLE IF NOT EXISTS message_poll_option (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    poll_id    UUID NOT NULL REFERENCES message_poll(id) ON DELETE CASCADE,
+    text       TEXT NOT NULL,
+    emoji      TEXT NULL,
+    vote_count BIGINT NOT NULL DEFAULT 0,
+    position   INTEGER NOT NULL DEFAULT 0
+);
+CREATE INDEX IF NOT EXISTS idx_message_poll_option_poll_id
+    ON message_poll_option (poll_id);
+
+-- models/message_poll.rs  →  message_poll_vote
+CREATE TABLE IF NOT EXISTS message_poll_vote (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    poll_id    UUID NOT NULL REFERENCES message_poll(id) ON DELETE CASCADE,
+    option_id  UUID NOT NULL REFERENCES message_poll_option(id) ON DELETE CASCADE,
+    user_id    UUID NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_poll_vote UNIQUE (poll_id, user_id, option_id)
+);
+CREATE INDEX IF NOT EXISTS idx_message_poll_vote_poll_id
+    ON message_poll_vote (poll_id);
+CREATE INDEX IF NOT EXISTS idx_message_poll_vote_user_id
+    ON message_poll_vote (user_id);
+
+COMMIT;

migrate/003_message_social.sql

@@ -0,0 +1,76 @@
+-- ============================================================
+-- Migration: 002_message_social.sql
+-- Tables:  message_pin, message_read_state, message_draft, message_edit
+-- ============================================================
+-- Extends the message subsystem with pinned messages, read receipts,
+-- drafts, and edit history.
+
+BEGIN;
+
+-- models/message_pin.rs  →  message_pin
+CREATE TABLE IF NOT EXISTS message_pin (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    channel_id  UUID NOT NULL,
+    message_id  UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    pinned_by   UUID NOT NULL,
+    position    INTEGER NOT NULL DEFAULT 0,
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_pin_channel_message UNIQUE (channel_id, message_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_pin_channel_id
+    ON message_pin (channel_id);
+
+-- models/message_read_state.rs  →  message_read_state
+CREATE TABLE IF NOT EXISTS message_read_state (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    channel_id            UUID NOT NULL,
+    user_id               UUID NOT NULL,
+    last_read_message_id  UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    last_read_at          TIMESTAMPTZ NULL,
+    unread_count          BIGINT NOT NULL DEFAULT 0,
+    unread_mentions       BIGINT NOT NULL DEFAULT 0,
+    created_at            TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at            TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_read_state_channel_user UNIQUE (channel_id, user_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_read_state_user_id
+    ON message_read_state (user_id);
+CREATE INDEX IF NOT EXISTS idx_message_read_state_channel_id
+    ON message_read_state (channel_id);
+
+-- models/message_draft.rs  →  message_draft
+CREATE TABLE IF NOT EXISTS message_draft (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    channel_id           UUID NOT NULL,
+    user_id              UUID NOT NULL,
+    thread_id            UUID NULL REFERENCES message_thread(id) ON DELETE CASCADE,
+    reply_to_message_id  UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    body                 TEXT NOT NULL DEFAULT '',
+    metadata             JSONB NULL,
+    created_at           TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at           TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_draft_channel_user_thread
+        UNIQUE (channel_id, user_id, thread_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_draft_user_id
+    ON message_draft (user_id);
+
+-- models/message_edit.rs  →  message_edit
+CREATE TABLE IF NOT EXISTS message_edit (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id  UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    edited_by   UUID NOT NULL,
+    old_body    TEXT NOT NULL,
+    new_body    TEXT NOT NULL,
+    edited_at   TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_edit_message_id
+    ON message_edit (message_id);
+CREATE INDEX IF NOT EXISTS idx_message_edit_edited_at
+    ON message_edit (edited_at);
+
+COMMIT;

migrate/004_message_article.sql

@@ -0,0 +1,45 @@
+-- ============================================================
+-- Migration: 003_message_article.sql
+-- Tables:  message_article
+-- ============================================================
+-- Extends the message subsystem with forum-style article posts.
+-- Articles extend regular messages with title, cover image, tags,
+-- and view/like stats. Rendered as waterfall cards in forum channels.
+
+BEGIN;
+
+-- models/message_article.rs  →  message_article
+CREATE TABLE IF NOT EXISTS message_article (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id            UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    title                 TEXT NOT NULL,
+    summary               TEXT NULL,
+    cover_url             TEXT NULL,
+    cover_width           INTEGER NULL,
+    cover_height          INTEGER NULL,
+    cover_color           TEXT NULL,
+    tags                  JSONB NULL,
+    view_count            BIGINT NOT NULL DEFAULT 0,
+    like_count            BIGINT NOT NULL DEFAULT 0,
+    bookmark_count        BIGINT NOT NULL DEFAULT 0,
+    reply_count           BIGINT NOT NULL DEFAULT 0,
+    last_reply_message_id UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    last_reply_at         TIMESTAMPTZ NULL,
+    last_reply_user_id    UUID NULL,
+    is_pinned_to_top      BOOLEAN NOT NULL DEFAULT FALSE,
+    is_answered           BOOLEAN NOT NULL DEFAULT FALSE,
+    answered_by           UUID NULL,
+    answered_at           TIMESTAMPTZ NULL,
+    created_at            TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at            TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_article_message UNIQUE (message_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_article_last_reply_at
+    ON message_article (last_reply_at DESC NULLS LAST);
+CREATE INDEX IF NOT EXISTS idx_message_article_is_pinned_to_top
+    ON message_article (is_pinned_to_top DESC, last_reply_at DESC NULLS LAST);
+CREATE INDEX IF NOT EXISTS idx_message_article_view_count
+    ON message_article (view_count DESC);
+
+COMMIT;

migrate/005_message_social_part2.sql

@@ -0,0 +1,98 @@
+-- ============================================================
+-- Migration: 004_message_social_part2.sql
+-- Tables:  message_reaction, message_bookmark, message_mention,
+--          message_thread, message_thread_participant
+-- ============================================================
+
+BEGIN;
+
+-- models/message_reaction.rs  →  message_reaction
+CREATE TABLE IF NOT EXISTS message_reaction (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id  UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    channel_id  UUID NOT NULL,
+    user_id     UUID NOT NULL,
+    content     TEXT NOT NULL,
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_reaction_user_content UNIQUE (message_id, user_id, content)
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_reaction_message_id
+    ON message_reaction (message_id);
+CREATE INDEX IF NOT EXISTS idx_message_reaction_user_id
+    ON message_reaction (user_id);
+
+-- models/message_bookmark.rs  →  message_bookmark
+CREATE TABLE IF NOT EXISTS message_bookmark (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id  UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    channel_id  UUID NOT NULL,
+    user_id     UUID NOT NULL,
+    note        TEXT NULL,
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_bookmark_user_message UNIQUE (user_id, message_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_bookmark_user_id
+    ON message_bookmark (user_id);
+CREATE INDEX IF NOT EXISTS idx_message_bookmark_message_id
+    ON message_bookmark (message_id);
+
+-- models/message_mention.rs  →  message_mention
+CREATE TABLE IF NOT EXISTS message_mention (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id         UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    channel_id         UUID NOT NULL,
+    mentioned_user_id  UUID NOT NULL,
+    mentioned_by       UUID NOT NULL,
+    read_at            TIMESTAMPTZ NULL,
+    created_at         TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_mention_message_id
+    ON message_mention (message_id);
+CREATE INDEX IF NOT EXISTS idx_message_mention_mentioned_user
+    ON message_mention (mentioned_user_id);
+
+-- models/message_thread.rs  →  message_thread
+CREATE TABLE IF NOT EXISTS message_thread (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    channel_id             UUID NOT NULL,
+    root_message_id        UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    created_by             UUID NOT NULL,
+    replies_count          BIGINT NOT NULL DEFAULT 0,
+    participants_count     BIGINT NOT NULL DEFAULT 0,
+    last_reply_message_id  UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    last_reply_at          TIMESTAMPTZ NULL,
+    resolved               BOOLEAN NOT NULL DEFAULT FALSE,
+    resolved_by            UUID NULL,
+    resolved_at            TIMESTAMPTZ NULL,
+    created_at             TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at             TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_message_thread_root UNIQUE (root_message_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_thread_channel_id
+    ON message_thread (channel_id);
+CREATE INDEX IF NOT EXISTS idx_message_thread_last_reply_at
+    ON message_thread (last_reply_at DESC NULLS LAST);
+
+-- models/message_thread_participant.rs  →  message_thread_participant
+CREATE TABLE IF NOT EXISTS message_thread_participant (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    thread_id             UUID NOT NULL REFERENCES message_thread(id) ON DELETE CASCADE,
+    user_id               UUID NOT NULL,
+    joined_reason         TEXT NULL,
+    last_read_message_id  UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    last_read_at          TIMESTAMPTZ NULL,
+    joined_at             TIMESTAMPTZ NOT NULL DEFAULT now(),
+    CONSTRAINT uq_thread_participant UNIQUE (thread_id, user_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_thread_participant_thread_id
+    ON message_thread_participant (thread_id);
+CREATE INDEX IF NOT EXISTS idx_thread_participant_user_id
+    ON message_thread_participant (user_id);
+
+COMMIT;

migrate/006_message_misc.sql

@@ -0,0 +1,102 @@
+-- ============================================================
+-- Migration: 005_message_misc.sql
+-- Tables:  message_notification, message_scheduled, message_sticker,
+--          message_forward, message_component
+-- ============================================================
+
+BEGIN;
+
+-- models/message_notification.rs  →  message_notification
+CREATE TABLE IF NOT EXISTS message_notification (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id        UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    channel_id        UUID NOT NULL,
+    user_id           UUID NOT NULL,
+    reason            TEXT NOT NULL,
+    status            TEXT NOT NULL DEFAULT 'pending',
+    delivery_channel  TEXT NULL,
+    delivered_at      TIMESTAMPTZ NULL,
+    read_at           TIMESTAMPTZ NULL,
+    created_at        TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_notification_user_id
+    ON message_notification (user_id, created_at DESC);
+CREATE INDEX IF NOT EXISTS idx_message_notification_status
+    ON message_notification (status);
+
+-- models/message_scheduled.rs  →  message_scheduled
+CREATE TABLE IF NOT EXISTS message_scheduled (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    channel_id            UUID NOT NULL,
+    author_id             UUID NOT NULL,
+    thread_id             UUID NULL REFERENCES message_thread(id) ON DELETE SET NULL,
+    reply_to_message_id   UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    body                  TEXT NOT NULL,
+    metadata              JSONB NULL,
+    scheduled_at          TIMESTAMPTZ NOT NULL,
+    status                TEXT NOT NULL DEFAULT 'pending',
+    sent_message_id       UUID NULL REFERENCES message(id) ON DELETE SET NULL,
+    error                 TEXT NULL,
+    created_at            TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at            TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_scheduled_status_at
+    ON message_scheduled (status, scheduled_at);
+
+-- models/message_sticker.rs  →  message_sticker
+CREATE TABLE IF NOT EXISTS message_sticker (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id   UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    sticker_id   UUID NOT NULL,
+    name         TEXT NOT NULL,
+    image_url    TEXT NOT NULL,
+    format_type  TEXT NOT NULL DEFAULT 'png',
+    pack_name    TEXT NULL,
+    tags         TEXT NULL,
+    created_at   TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_sticker_message_id
+    ON message_sticker (message_id);
+
+-- models/message_forward.rs  →  message_forward
+CREATE TABLE IF NOT EXISTS message_forward (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id          UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    source_message_id   UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    source_channel_id   UUID NOT NULL,
+    forwarded_by        UUID NOT NULL,
+    created_at          TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_forward_message_id
+    ON message_forward (message_id);
+CREATE INDEX IF NOT EXISTS idx_message_forward_source_message_id
+    ON message_forward (source_message_id);
+
+-- models/message_component.rs  →  message_component
+CREATE TABLE IF NOT EXISTS message_component (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    message_id      UUID NOT NULL REFERENCES message(id) ON DELETE CASCADE,
+    row             INTEGER NOT NULL DEFAULT 0,
+    position        INTEGER NOT NULL DEFAULT 0,
+    component_type  TEXT NOT NULL,
+    custom_id       TEXT NOT NULL,
+    label           TEXT NULL,
+    emoji           TEXT NULL,
+    style           TEXT NULL,
+    url             TEXT NULL,
+    disabled        BOOLEAN NOT NULL DEFAULT FALSE,
+    placeholder     TEXT NULL,
+    min_values      INTEGER NULL,
+    max_values      INTEGER NULL,
+    options         JSONB NULL,
+    created_at      TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_message_component_message_id
+    ON message_component (message_id);
+
+COMMIT;

migrate/007_fix_uuid_defaults_and_draft_null.sql

@@ -0,0 +1,33 @@
+-- Align imks-managed IDs with application-generated UUID v7 values and
+-- make top-level drafts unique when thread_id is NULL.
+
+BEGIN;
+
+CREATE UNIQUE INDEX IF NOT EXISTS uq_message_draft_channel_user_no_thread
+    ON message_draft (channel_id, user_id)
+    WHERE thread_id IS NULL;
+
+ALTER TABLE message ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_attachment ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_embed ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_embed_field ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_poll ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_poll_option ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_poll_vote ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_pin ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_read_state ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_draft ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_edit ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_article ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_reaction ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_bookmark ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_mention ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_thread ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_thread_participant ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_notification ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_scheduled ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_sticker ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_forward ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_component ALTER COLUMN id DROP DEFAULT;
+
+COMMIT;

rpc/health.rs

@@ -0,0 +1,63 @@
+//! gRPC health module for imks.
+//!
+//! Provides:
+//! - imks's own gRPC health server (for external health checks)
+//! - Health check client for probing appks health (5s interval)
+
+use std::net::SocketAddr;
+use std::time::Duration;
+
+use tonic_health::pb::HealthCheckRequest;
+use tonic_health::pb::health_check_response::ServingStatus;
+use tonic_health::pb::health_client::HealthClient;
+
+use crate::{ImksError, ImksResult};
+
+/// Start imks's own gRPC health server on the given address.
+///
+/// Reports `SERVING` for the overall server status (empty service name).
+pub async fn start_health_server(addr: SocketAddr) -> ImksResult<()> {
+    let (reporter, health_service) = tonic_health::server::health_reporter();
+
+    // Empty service name = overall server health.
+    // reporter is an owned handle — the server will remain SERVING
+    // indefinitely unless a caller updates the status.
+    reporter
+        .set_service_status("", tonic_health::ServingStatus::Serving)
+        .await;
+
+    tracing::info!(%addr, "imks gRPC health server started");
+
+    tonic::transport::Server::builder()
+        .add_service(health_service)
+        .serve(addr)
+        .await
+        .map_err(|e| ImksError::Internal(format!("Health gRPC server: {e:?}")))?;
+
+    Ok(())
+}
+
+/// Check appks health by opening a short-lived gRPC connection and calling `Check`.
+///
+/// Uses a 3-second connect timeout to fail fast when appks is unreachable.
+pub async fn check_appks_health(addr: &str) -> ImksResult<bool> {
+    let endpoint = tonic::transport::Endpoint::from_shared(addr.to_string())
+        .map_err(|e| ImksError::Internal(format!("health endpoint: {e}")))?;
+
+    // Short-lived connection for health probe only
+    let channel = endpoint
+        .connect_timeout(Duration::from_secs(3))
+        .connect()
+        .await
+        .map_err(ImksError::GrpcTransport)?;
+
+    let mut client = HealthClient::new(channel);
+    let resp = client
+        .check(HealthCheckRequest {
+            service: "".to_string(),
+        })
+        .await
+        .map_err(ImksError::GrpcStatus)?;
+
+    Ok(resp.into_inner().status == ServingStatus::Serving as i32)
+}