diff --git a/server/src/chat/commands/mod.rs b/server/src/chat/commands/mod.rs
index b3254a78..ab65096b 100644
--- a/server/src/chat/commands/mod.rs
+++ b/server/src/chat/commands/mod.rs
@@ -425,10 +425,15 @@ fn handle_reset_fallback(_ctx: &CommandContext) -> Option<String> {
     None
 }
 
-/// Fallback handler for the `compact` command when it is not intercepted by
-/// the async handler in `on_room_message`.  In practice this is never called —
-/// compact is detected and handled before `try_handle_command` is invoked.
-/// The entry exists in the registry only so `help` lists it.
+/// Fallback handler for the `compact` command.
+///
+/// This IS called on every `compact` dispatch — `try_handle_command` always
+/// invokes the matched handler, so this runs before the async `compact`
+/// check each transport performs afterward (`on_room_message` for Matrix; an
+/// inline check in `handle_incoming_message` for Discord/Slack/WhatsApp). It
+/// deliberately always returns `None` so that check gets a chance to run the
+/// real handler instead of the LLM. The entry exists in the registry so
+/// `help` lists it.
 ///
 /// Returns `None` to prevent the LLM from receiving "compact" as a prompt.
 fn handle_compact_fallback(_ctx: &CommandContext) -> Option<String> {
diff --git a/server/src/chat/compact/mod.rs b/server/src/chat/compact/mod.rs
index 9034bee5..6dd76e2e 100644
--- a/server/src/chat/compact/mod.rs
+++ b/server/src/chat/compact/mod.rs
@@ -12,9 +12,11 @@ pub mod digest;
 /// Resolves a Claude Code session transcript's path on disk from its id.
 pub(crate) mod transcript;
 
+use std::collections::HashMap;
 use std::fs;
 use std::path::{Path, PathBuf};
 
+use crate::chat::transport::matrix::RoomConversation;
 use crate::chat::util::strip_bot_mention;
 
 /// A parsed `compact` command.
@@ -118,6 +120,50 @@ pub fn compact_session(
     })
 }
 
+/// Handle a `compact` command for any transport that keys its conversation
+/// history by a plain string (Discord channel id, Slack channel id, WhatsApp
+/// phone number, …), rather than Matrix's `OwnedRoomId`.
+///
+/// Mirrors [`crate::chat::transport::matrix::compact::handle_compact`]: looks
+/// up the room's session, distills its transcript into a digest, writes the
+/// digest as a seed, clears the session id and entries, sets `pending_seed`,
+/// then calls `save` to persist the updated history. Returns an actionable
+/// message and changes nothing when there is no active session, or when the
+/// session transcript cannot be read.
+pub async fn handle_compact_for_key(
+    room_key: &str,
+    history: &tokio::sync::Mutex<HashMap<String, RoomConversation>>,
+    project_root: &Path,
+    max_bytes: usize,
+    save: impl FnOnce(&Path, &HashMap<String, RoomConversation>),
+) -> String {
+    let mut guard = history.lock().await;
+    let conv = guard.entry(room_key.to_string()).or_default();
+
+    let Some(session_id) = conv.session_id.clone() else {
+        return "No active session to compact. Send a message first to start one.".to_string();
+    };
+
+    let transcript_path = transcript::transcript_path(project_root, &session_id);
+
+    match compact_session(project_root, &transcript_path, room_key, max_bytes) {
+        Ok(outcome) => {
+            conv.session_id = None;
+            conv.entries.clear();
+            conv.pending_seed = Some(outcome.digest);
+            save(project_root, &guard);
+            format!(
+                "Compacted session context: {} → {} bytes. Starting fresh — the distilled \
+                 summary will be included as background in your next message.",
+                outcome.before_bytes, outcome.after_bytes
+            )
+        }
+        Err(CompactError::TranscriptUnreadable(e)) => format!(
+            "Could not compact: session transcript is unreadable ({e}). Nothing was changed."
+        ),
+    }
+}
+
 /// Path to the seed file for a given room, under
 /// `project_root/.huskies/chat_seeds/`.
 fn seed_file_path(project_root: &Path, room_key: &str) -> PathBuf {
diff --git a/server/src/chat/transport/discord/commands.rs b/server/src/chat/transport/discord/commands.rs
index 89c90022..54cc26b4 100644
--- a/server/src/chat/transport/discord/commands.rs
+++ b/server/src/chat/transport/discord/commands.rs
@@ -216,6 +216,27 @@ pub(super) async fn handle_incoming_message(
         return;
     }
 
+    if crate::chat::compact::extract_compact_command(
+        message,
+        &ctx.services.bot_name,
+        &ctx.services.bot_user_id,
+    )
+    .is_some()
+    {
+        slog!("[discord] Handling compact command from {user} in {channel}");
+        let response = crate::chat::compact::handle_compact_for_key(
+            channel,
+            &ctx.history,
+            &ctx.services.project_root,
+            8_000,
+            save_discord_history,
+        )
+        .await;
+        let response = markdown_to_discord(&response);
+        let _ = ctx.transport.send_message(channel, &response, "").await;
+        return;
+    }
+
     if let Some(start_cmd) = crate::chat::transport::matrix::start::extract_start_command(
         message,
         &ctx.services.bot_name,
@@ -630,4 +651,104 @@ mod tests {
             "assembled prompt must contain user message; got: {prompt}"
         );
     }
+
+    /// Regression test for story 1192: `compact` must not be swallowed by the
+    /// registry placeholder. Drives the real entrypoint
+    /// (`handle_incoming_message`, not `handle_compact_for_key` directly) so a
+    /// future regression in the dispatch order is caught, and asserts the
+    /// real handler ran: reply mentions the byte-size confirmation, and the
+    /// history's session_id/entries were cleared with pending_seed set.
+    #[tokio::test]
+    async fn compact_command_runs_through_full_dispatch_and_clears_session() {
+        use crate::chat::transport::matrix::{
+            ConversationEntry, ConversationRole, RoomConversation,
+        };
+        use std::collections::HashSet;
+        use std::sync::Arc;
+
+        let channel = "555444333";
+        let session_id = "sess-discord-compact";
+
+        let tmp = tempfile::tempdir().unwrap();
+        let project_root = tmp.path().join("project");
+        std::fs::create_dir_all(&project_root).unwrap();
+        let home = tempfile::tempdir().unwrap();
+        // SAFETY: this test owns HOME for its duration; no other test in this
+        // process reads HOME concurrently with this call.
+        unsafe {
+            std::env::set_var("HOME", home.path());
+        }
+        let transcript_dir =
+            crate::chat::compact::transcript::transcript_path(&project_root, session_id)
+                .parent()
+                .unwrap()
+                .to_path_buf();
+        std::fs::create_dir_all(&transcript_dir).unwrap();
+        let jsonl = r#"{"type":"user","message":{"role":"user","content":"hello"}}
+{"type":"assistant","message":{"role":"assistant","content":[{"type":"text","text":"hi there"}]}}"#;
+        std::fs::write(transcript_dir.join(format!("{session_id}.jsonl")), jsonl).unwrap();
+
+        let history: DiscordConversationHistory = Arc::new(TokioMutex::new({
+            let mut m = HashMap::new();
+            m.insert(
+                channel.to_string(),
+                RoomConversation {
+                    session_id: Some(session_id.to_string()),
+                    entries: vec![ConversationEntry {
+                        role: ConversationRole::User,
+                        sender: "user123".to_string(),
+                        content: "hi".to_string(),
+                    }],
+                    pending_seed: None,
+                    last_compact_suggested_at_ms: None,
+                },
+            );
+            m
+        }));
+
+        let mut server = mockito::Server::new_async().await;
+        let mock = server
+            .mock("POST", format!("/channels/{channel}/messages").as_str())
+            .match_body(mockito::Matcher::Regex(
+                "Compacted session context".to_string(),
+            ))
+            .with_body(r#"{"id": "1"}"#)
+            .create_async()
+            .await;
+
+        let services =
+            crate::services::Services::new_test(project_root.clone(), "Huskies".to_string());
+        let ctx = DiscordContext {
+            services,
+            bot_token: "test-token".to_string(),
+            transport: Arc::new(DiscordTransport::with_api_base(
+                "test-token".to_string(),
+                server.url(),
+            )),
+            history: history.clone(),
+            history_size: 20,
+            channel_ids: HashSet::new(),
+            allowed_users: HashSet::new(),
+        };
+
+        handle_incoming_message(&ctx, channel, "user123", "compact").await;
+
+        mock.assert_async().await;
+
+        let guard = history.lock().await;
+        let conv = guard.get(channel).unwrap();
+        assert!(
+            conv.session_id.is_none(),
+            "session_id must be cleared after compact"
+        );
+        assert!(
+            conv.entries.is_empty(),
+            "entries must be cleared after compact"
+        );
+        assert_eq!(
+            conv.pending_seed.as_deref(),
+            Some("User: hello\nAssistant: hi there"),
+            "pending_seed must hold the distilled digest"
+        );
+    }
 }
diff --git a/server/src/chat/transport/discord/meta.rs b/server/src/chat/transport/discord/meta.rs
index db5a497d..dda410a2 100644
--- a/server/src/chat/transport/discord/meta.rs
+++ b/server/src/chat/transport/discord/meta.rs
@@ -34,8 +34,10 @@ impl DiscordTransport {
         }
     }
 
+    /// Creates a `DiscordTransport` pointed at a custom API base URL, for
+    /// tests that mock the Discord API instead of hitting discord.com.
     #[cfg(test)]
-    fn with_api_base(bot_token: String, api_base: String) -> Self {
+    pub(crate) fn with_api_base(bot_token: String, api_base: String) -> Self {
         Self {
             bot_token,
             client: reqwest::Client::new(),
diff --git a/server/src/chat/transport/slack/commands/mod.rs b/server/src/chat/transport/slack/commands/mod.rs
index dd7a0e53..e0e9251d 100644
--- a/server/src/chat/transport/slack/commands/mod.rs
+++ b/server/src/chat/transport/slack/commands/mod.rs
@@ -263,6 +263,27 @@ pub(super) async fn handle_incoming_message(
         return;
     }
 
+    if crate::chat::compact::extract_compact_command(
+        message,
+        &ctx.services.bot_name,
+        &ctx.services.bot_user_id,
+    )
+    .is_some()
+    {
+        slog!("[slack] Handling compact command from {user} in {channel}");
+        let response = crate::chat::compact::handle_compact_for_key(
+            channel,
+            &ctx.history,
+            &ctx.services.project_root,
+            8_000,
+            save_slack_history,
+        )
+        .await;
+        let response = markdown_to_slack(&response);
+        let _ = ctx.transport.send_message(channel, &response, "").await;
+        return;
+    }
+
     if let Some(start_cmd) = crate::chat::transport::matrix::start::extract_start_command(
         message,
         &ctx.services.bot_name,
diff --git a/server/src/chat/transport/whatsapp/commands/mod.rs b/server/src/chat/transport/whatsapp/commands/mod.rs
index b5f0d660..9eca793f 100644
--- a/server/src/chat/transport/whatsapp/commands/mod.rs
+++ b/server/src/chat/transport/whatsapp/commands/mod.rs
@@ -174,6 +174,27 @@ pub(super) async fn handle_incoming_message(
         return;
     }
 
+    if crate::chat::compact::extract_compact_command(
+        message,
+        &ctx.services.bot_name,
+        &ctx.services.bot_user_id,
+    )
+    .is_some()
+    {
+        slog!("[whatsapp] Handling compact command from {sender}");
+        let response = crate::chat::compact::handle_compact_for_key(
+            sender,
+            &ctx.history,
+            &ctx.services.project_root,
+            8_000,
+            save_whatsapp_history,
+        )
+        .await;
+        let formatted = markdown_to_whatsapp(&response);
+        let _ = ctx.transport.send_message(sender, &formatted, "").await;
+        return;
+    }
+
     if let Some(start_cmd) = crate::chat::transport::matrix::start::extract_start_command(
         message,
         &ctx.services.bot_name,