diff --git a/.story_kit/bot.toml.example b/.story_kit/bot.toml.example
index 3219ba2..7e104a2 100644
--- a/.story_kit/bot.toml.example
+++ b/.story_kit/bot.toml.example
@@ -46,3 +46,16 @@ enabled = false
 #
 # Once approved, set the name below (default: "pipeline_notification"):
 # whatsapp_notification_template = "pipeline_notification"
+
+# ── Slack Bot API ─────────────────────────────────────────────────────
+# Set transport = "slack" to use Slack instead of Matrix.
+# The webhook endpoint will be available at /webhook/slack.
+# Configure this URL in the Slack App → Event Subscriptions → Request URL.
+#
+# Required Slack App scopes: chat:write, chat:update
+# Subscribe to bot events: message.channels, message.groups, message.im
+#
+# transport = "slack"
+# slack_bot_token = "xoxb-..."
+# slack_signing_secret = "your-signing-secret"
+# slack_channel_ids = ["C01ABCDEF"]
diff --git a/server/src/http/mod.rs b/server/src/http/mod.rs
index 19c3c15..b8d9fb6 100644
--- a/server/src/http/mod.rs
+++ b/server/src/http/mod.rs
@@ -29,6 +29,7 @@ use settings::SettingsApi;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
+use crate::slack::SlackWebhookContext;
 use crate::whatsapp::WhatsAppWebhookContext;
 
 const DEFAULT_PORT: u16 = 3001;
@@ -56,6 +57,7 @@ pub fn remove_port_file(path: &Path) {
 pub fn build_routes(
     ctx: AppContext,
     whatsapp_ctx: Option<Arc<WhatsAppWebhookContext>>,
+    slack_ctx: Option<Arc<SlackWebhookContext>>,
 ) -> impl poem::Endpoint {
     let ctx_arc = std::sync::Arc::new(ctx);
 
@@ -87,6 +89,13 @@ pub fn build_routes(
         );
     }
 
+    if let Some(sl_ctx) = slack_ctx {
+        route = route.at(
+            "/webhook/slack",
+            post(crate::slack::webhook_receive).data(sl_ctx),
+        );
+    }
+
     route.data(ctx_arc)
 }
 
@@ -196,6 +205,6 @@ mod tests {
     fn build_routes_constructs_without_panic() {
         let tmp = tempfile::tempdir().unwrap();
         let ctx = context::AppContext::new_test(tmp.path().to_path_buf());
-        let _endpoint = build_routes(ctx, None);
+        let _endpoint = build_routes(ctx, None, None);
     }
 }
diff --git a/server/src/main.rs b/server/src/main.rs
index 7427750..6fbcbdb 100644
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -14,6 +14,7 @@ mod state;
 mod store;
 pub mod transport;
 mod workflow;
+pub mod slack;
 pub mod whatsapp;
 mod worktree;
 
@@ -228,7 +229,38 @@ async fn main() -> Result<(), std::io::Error> {
             })
         });
 
-    let app = build_routes(ctx, whatsapp_ctx);
+    // Build Slack webhook context if bot.toml configures transport = "slack".
+    let slack_ctx: Option<Arc<slack::SlackWebhookContext>> = startup_root
+        .as_ref()
+        .and_then(|root| matrix::BotConfig::load(root))
+        .filter(|cfg| cfg.transport == "slack")
+        .map(|cfg| {
+            let transport = Arc::new(slack::SlackTransport::new(
+                cfg.slack_bot_token.clone().unwrap_or_default(),
+            ));
+            let bot_name = cfg
+                .display_name
+                .clone()
+                .unwrap_or_else(|| "Assistant".to_string());
+            let root = startup_root.clone().unwrap();
+            let history = slack::load_slack_history(&root);
+            let channel_ids: std::collections::HashSet<String> =
+                cfg.slack_channel_ids.iter().cloned().collect();
+            Arc::new(slack::SlackWebhookContext {
+                signing_secret: cfg.slack_signing_secret.clone().unwrap_or_default(),
+                transport,
+                project_root: root,
+                agents: Arc::clone(&startup_agents),
+                bot_name,
+                bot_user_id: "slack-bot".to_string(),
+                ambient_rooms: Arc::new(std::sync::Mutex::new(std::collections::HashSet::new())),
+                history: std::sync::Arc::new(tokio::sync::Mutex::new(history)),
+                history_size: cfg.history_size,
+                channel_ids,
+            })
+        });
+
+    let app = build_routes(ctx, whatsapp_ctx, slack_ctx);
 
 
     // Optional Matrix bot: connect to the homeserver and start listening for
diff --git a/server/src/matrix/config.rs b/server/src/matrix/config.rs
index 9c5e585..35861d8 100644
--- a/server/src/matrix/config.rs
+++ b/server/src/matrix/config.rs
@@ -87,6 +87,19 @@ pub struct BotConfig {
     /// use.  Defaults to `"pipeline_notification"`.
     #[serde(default)]
     pub whatsapp_notification_template: Option<String>,
+
+    // ── Slack Bot API fields ─────────────────────────────────────────
+    // These are only required when `transport = "slack"`.
+
+    /// Slack Bot User OAuth Token (starts with `xoxb-`).
+    #[serde(default)]
+    pub slack_bot_token: Option<String>,
+    /// Slack Signing Secret used to verify incoming webhook requests.
+    #[serde(default)]
+    pub slack_signing_secret: Option<String>,
+    /// Slack channel IDs the bot should listen in.
+    #[serde(default)]
+    pub slack_channel_ids: Vec<String>,
 }
 
 fn default_transport() -> String {
@@ -142,6 +155,29 @@ impl BotConfig {
                 );
                 return None;
             }
+        } else if config.transport == "slack" {
+            // Validate Slack-specific fields.
+            if config.slack_bot_token.as_ref().is_none_or(|s| s.is_empty()) {
+                eprintln!(
+                    "[bot] bot.toml: transport=\"slack\" requires \
+                     slack_bot_token"
+                );
+                return None;
+            }
+            if config.slack_signing_secret.as_ref().is_none_or(|s| s.is_empty()) {
+                eprintln!(
+                    "[bot] bot.toml: transport=\"slack\" requires \
+                     slack_signing_secret"
+                );
+                return None;
+            }
+            if config.slack_channel_ids.is_empty() {
+                eprintln!(
+                    "[bot] bot.toml: transport=\"slack\" requires \
+                     at least one slack_channel_ids entry"
+                );
+                return None;
+            }
         } else if config.room_ids.is_empty() {
             eprintln!(
                 "[matrix-bot] bot.toml has no room_ids configured — \
@@ -680,6 +716,97 @@ enabled = true
 transport = "whatsapp"
 whatsapp_phone_number_id = "123456"
 whatsapp_access_token = "EAAtoken"
+"#,
+        )
+        .unwrap();
+        assert!(BotConfig::load(tmp.path()).is_none());
+    }
+
+    // ── Slack config tests ─────────────────────────────────────────────
+
+    #[test]
+    fn load_slack_transport_reads_config() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sk = tmp.path().join(".story_kit");
+        fs::create_dir_all(&sk).unwrap();
+        fs::write(
+            sk.join("bot.toml"),
+            r#"
+homeserver = "https://matrix.example.com"
+username = "@bot:example.com"
+password = "secret"
+enabled = true
+transport = "slack"
+slack_bot_token = "xoxb-123"
+slack_signing_secret = "secret123"
+slack_channel_ids = ["C01ABCDEF"]
+"#,
+        )
+        .unwrap();
+        let config = BotConfig::load(tmp.path()).unwrap();
+        assert_eq!(config.transport, "slack");
+        assert_eq!(config.slack_bot_token.as_deref(), Some("xoxb-123"));
+        assert_eq!(config.slack_signing_secret.as_deref(), Some("secret123"));
+        assert_eq!(config.slack_channel_ids, vec!["C01ABCDEF"]);
+    }
+
+    #[test]
+    fn load_slack_returns_none_when_missing_bot_token() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sk = tmp.path().join(".story_kit");
+        fs::create_dir_all(&sk).unwrap();
+        fs::write(
+            sk.join("bot.toml"),
+            r#"
+homeserver = "https://matrix.example.com"
+username = "@bot:example.com"
+password = "secret"
+enabled = true
+transport = "slack"
+slack_signing_secret = "secret123"
+slack_channel_ids = ["C01ABCDEF"]
+"#,
+        )
+        .unwrap();
+        assert!(BotConfig::load(tmp.path()).is_none());
+    }
+
+    #[test]
+    fn load_slack_returns_none_when_missing_signing_secret() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sk = tmp.path().join(".story_kit");
+        fs::create_dir_all(&sk).unwrap();
+        fs::write(
+            sk.join("bot.toml"),
+            r#"
+homeserver = "https://matrix.example.com"
+username = "@bot:example.com"
+password = "secret"
+enabled = true
+transport = "slack"
+slack_bot_token = "xoxb-123"
+slack_channel_ids = ["C01ABCDEF"]
+"#,
+        )
+        .unwrap();
+        assert!(BotConfig::load(tmp.path()).is_none());
+    }
+
+    #[test]
+    fn load_slack_returns_none_when_missing_channel_ids() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sk = tmp.path().join(".story_kit");
+        fs::create_dir_all(&sk).unwrap();
+        fs::write(
+            sk.join("bot.toml"),
+            r#"
+homeserver = "https://matrix.example.com"
+username = "@bot:example.com"
+password = "secret"
+enabled = true
+transport = "slack"
+slack_bot_token = "xoxb-123"
+slack_signing_secret = "secret123"
 "#,
         )
         .unwrap();
diff --git a/server/src/matrix/mod.rs b/server/src/matrix/mod.rs
index c6537fe..7231ce7 100644
--- a/server/src/matrix/mod.rs
+++ b/server/src/matrix/mod.rs
@@ -62,9 +62,12 @@ pub fn spawn_bot(
         }
     };
 
-    // WhatsApp transport is handled via HTTP webhooks, not the Matrix sync loop.
-    if config.transport == "whatsapp" {
-        crate::slog!("[bot] transport=whatsapp — skipping Matrix bot; webhooks handle WhatsApp");
+    // WhatsApp and Slack transports are handled via HTTP webhooks, not the Matrix sync loop.
+    if config.transport == "whatsapp" || config.transport == "slack" {
+        crate::slog!(
+            "[bot] transport={} — skipping Matrix bot; webhooks handle this transport",
+            config.transport
+        );
         return;
     }
 
diff --git a/server/src/slack.rs b/server/src/slack.rs
new file mode 100644
index 0000000..b6c011d
--- /dev/null
+++ b/server/src/slack.rs
@@ -0,0 +1,1180 @@
+//! Slack Bot API integration.
+//!
+//! Provides:
+//! - [`SlackTransport`] — a [`ChatTransport`] that sends messages via the
+//!   Slack Web API (`api.slack.com/api/chat.postMessage` / `chat.update`).
+//! - [`webhook_receive`] — Poem handler for the Slack Events API webhook
+//!   (POST incoming events including URL verification challenge).
+
+use async_trait::async_trait;
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::fmt::Write as FmtWrite;
+use std::sync::Arc;
+use tokio::sync::Mutex as TokioMutex;
+
+use crate::agents::AgentPool;
+use crate::matrix::{ConversationEntry, ConversationRole, RoomConversation};
+use crate::slog;
+use crate::transport::{ChatTransport, MessageId};
+
+// ── Slack API base URL (overridable for tests) ──────────────────────────
+
+const SLACK_API_BASE: &str = "https://slack.com/api";
+
+// ── SlackTransport ──────────────────────────────────────────────────────
+
+/// Slack Bot API transport.
+///
+/// Sends messages via `POST {SLACK_API_BASE}/chat.postMessage` and edits
+/// via `POST {SLACK_API_BASE}/chat.update`.
+pub struct SlackTransport {
+    bot_token: String,
+    client: reqwest::Client,
+    /// Optional base URL override for tests.
+    api_base: String,
+}
+
+impl SlackTransport {
+    pub fn new(bot_token: String) -> Self {
+        Self {
+            bot_token,
+            client: reqwest::Client::new(),
+            api_base: SLACK_API_BASE.to_string(),
+        }
+    }
+
+    #[cfg(test)]
+    fn with_api_base(bot_token: String, api_base: String) -> Self {
+        Self {
+            bot_token,
+            client: reqwest::Client::new(),
+            api_base,
+        }
+    }
+}
+
+// ── Slack API response types ────────────────────────────────────────────
+
+#[derive(Deserialize, Debug)]
+struct SlackApiResponse {
+    ok: bool,
+    #[serde(default)]
+    error: Option<String>,
+    /// Message timestamp (acts as message ID in Slack).
+    #[serde(default)]
+    ts: Option<String>,
+}
+
+// ── Slack API request types ─────────────────────────────────────────────
+
+#[derive(Serialize)]
+struct PostMessageRequest<'a> {
+    channel: &'a str,
+    text: &'a str,
+}
+
+#[derive(Serialize)]
+struct UpdateMessageRequest<'a> {
+    channel: &'a str,
+    ts: &'a str,
+    text: &'a str,
+}
+
+#[async_trait]
+impl ChatTransport for SlackTransport {
+    async fn send_message(
+        &self,
+        channel: &str,
+        plain: &str,
+        _html: &str,
+    ) -> Result<MessageId, String> {
+        slog!("[slack] send_message to {channel}: {plain:.80}");
+        let url = format!("{}/chat.postMessage", self.api_base);
+
+        let payload = PostMessageRequest {
+            channel,
+            text: plain,
+        };
+
+        let resp = self
+            .client
+            .post(&url)
+            .bearer_auth(&self.bot_token)
+            .json(&payload)
+            .send()
+            .await
+            .map_err(|e| format!("Slack API request failed: {e}"))?;
+
+        let status = resp.status();
+        let resp_text = resp
+            .text()
+            .await
+            .unwrap_or_else(|_| "<no body>".to_string());
+
+        if !status.is_success() {
+            return Err(format!("Slack API returned {status}: {resp_text}"));
+        }
+
+        let parsed: SlackApiResponse = serde_json::from_str(&resp_text).map_err(|e| {
+            format!("Failed to parse Slack API response: {e} — body: {resp_text}")
+        })?;
+
+        if !parsed.ok {
+            return Err(format!(
+                "Slack API error: {}",
+                parsed.error.unwrap_or_else(|| "unknown".to_string())
+            ));
+        }
+
+        Ok(parsed.ts.unwrap_or_default())
+    }
+
+    async fn edit_message(
+        &self,
+        channel: &str,
+        original_message_id: &str,
+        plain: &str,
+        _html: &str,
+    ) -> Result<(), String> {
+        slog!("[slack] edit_message in {channel}: ts={original_message_id}");
+        let url = format!("{}/chat.update", self.api_base);
+
+        let payload = UpdateMessageRequest {
+            channel,
+            ts: original_message_id,
+            text: plain,
+        };
+
+        let resp = self
+            .client
+            .post(&url)
+            .bearer_auth(&self.bot_token)
+            .json(&payload)
+            .send()
+            .await
+            .map_err(|e| format!("Slack chat.update request failed: {e}"))?;
+
+        let status = resp.status();
+        let resp_text = resp
+            .text()
+            .await
+            .unwrap_or_else(|_| "<no body>".to_string());
+
+        if !status.is_success() {
+            return Err(format!("Slack chat.update returned {status}: {resp_text}"));
+        }
+
+        let parsed: SlackApiResponse = serde_json::from_str(&resp_text).map_err(|e| {
+            format!("Failed to parse Slack chat.update response: {e} — body: {resp_text}")
+        })?;
+
+        if !parsed.ok {
+            return Err(format!(
+                "Slack chat.update error: {}",
+                parsed.error.unwrap_or_else(|| "unknown".to_string())
+            ));
+        }
+
+        Ok(())
+    }
+
+    async fn send_typing(&self, _channel: &str, _typing: bool) -> Result<(), String> {
+        // Slack Bot API does not expose typing indicators for bots.
+        Ok(())
+    }
+}
+
+// ── Slack Events API types ──────────────────────────────────────────────
+
+/// Outer envelope for Slack Events API callbacks.
+///
+/// Slack sends three types of payloads:
+/// - `url_verification`: challenge-response handshake during app setup
+/// - `event_callback`: actual events (messages, reactions, etc.)
+#[derive(Deserialize, Debug)]
+pub struct SlackEventEnvelope {
+    pub r#type: String,
+    /// Present only for `url_verification` events.
+    pub challenge: Option<String>,
+    /// Present only for `event_callback` events.
+    pub event: Option<SlackEvent>,
+}
+
+#[derive(Deserialize, Debug)]
+pub struct SlackEvent {
+    pub r#type: Option<String>,
+    /// Channel or DM where the message was sent.
+    pub channel: Option<String>,
+    /// User who sent the message.
+    pub user: Option<String>,
+    /// Message text.
+    pub text: Option<String>,
+    /// Bot ID — present if the message was sent by a bot.
+    pub bot_id: Option<String>,
+    /// Subtype (e.g. "bot_message", "message_changed") — absent for plain user messages.
+    pub subtype: Option<String>,
+}
+
+// ── Request signature verification ──────────────────────────────────────
+
+/// Verify the Slack request signature using HMAC-SHA256.
+///
+/// Slack sends `X-Slack-Signature` and `X-Slack-Request-Timestamp` headers.
+/// We compute `HMAC-SHA256(signing_secret, "v0:{timestamp}:{body}")` and
+/// compare it to the provided signature.
+///
+/// This uses a constant-time comparison to prevent timing attacks.
+fn verify_slack_signature(
+    signing_secret: &str,
+    timestamp: &str,
+    body: &[u8],
+    signature: &str,
+) -> bool {
+    // Compute HMAC-SHA256 manually using the signing secret.
+    // Slack signature format: v0={hex(HMAC-SHA256(secret, "v0:{ts}:{body}"))}
+    let base_string = format!("v0:{timestamp}:");
+
+    // Simple HMAC-SHA256 implementation using ring-style approach.
+    // We use the hmac crate pattern with SHA-256.
+    // Since we don't want to add a dependency, we'll use a manual approach:
+    // HMAC(K, m) = H((K' ^ opad) || H((K' ^ ipad) || m))
+    // where K' is the key padded/hashed to block size.
+
+    let key = signing_secret.as_bytes();
+    let block_size = 64; // SHA-256 block size
+
+    // If key is longer than block size, hash it first.
+    let key_block = if key.len() > block_size {
+        let digest = sha256(key);
+        let mut k = vec![0u8; block_size];
+        k[..32].copy_from_slice(&digest);
+        k
+    } else {
+        let mut k = vec![0u8; block_size];
+        k[..key.len()].copy_from_slice(key);
+        k
+    };
+
+    // Inner and outer padded keys.
+    let mut ipad = vec![0x36u8; block_size];
+    let mut opad = vec![0x5cu8; block_size];
+    for i in 0..block_size {
+        ipad[i] ^= key_block[i];
+        opad[i] ^= key_block[i];
+    }
+
+    // Inner hash: H(ipad || message)
+    let mut inner_data = ipad;
+    inner_data.extend_from_slice(base_string.as_bytes());
+    inner_data.extend_from_slice(body);
+    let inner_hash = sha256(&inner_data);
+
+    // Outer hash: H(opad || inner_hash)
+    let mut outer_data = opad;
+    outer_data.extend_from_slice(&inner_hash);
+    let hmac_result = sha256(&outer_data);
+
+    // Format as "v0={hex}"
+    let mut expected = String::from("v0=");
+    for byte in &hmac_result {
+        write!(expected, "{byte:02x}").unwrap();
+    }
+
+    // Constant-time comparison.
+    constant_time_eq(expected.as_bytes(), signature.as_bytes())
+}
+
+/// Minimal SHA-256 implementation (no external dependency).
+///
+/// This follows FIPS 180-4.  Only used for HMAC signature verification,
+/// not for any security-critical path beyond webhook authentication.
+fn sha256(data: &[u8]) -> [u8; 32] {
+    let mut h: [u32; 8] = [
+        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab,
+        0x5be0cd19,
+    ];
+
+    let k: [u32; 64] = [
+        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4,
+        0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe,
+        0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f,
+        0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
+        0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc,
+        0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
+        0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116,
+        0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+        0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7,
+        0xc67178f2,
+    ];
+
+    // Pre-processing: padding
+    let bit_len = (data.len() as u64) * 8;
+    let mut padded = data.to_vec();
+    padded.push(0x80);
+    while (padded.len() % 64) != 56 {
+        padded.push(0);
+    }
+    padded.extend_from_slice(&bit_len.to_be_bytes());
+
+    // Process each 512-bit block
+    for chunk in padded.chunks_exact(64) {
+        let mut w = [0u32; 64];
+        for i in 0..16 {
+            w[i] = u32::from_be_bytes([
+                chunk[4 * i],
+                chunk[4 * i + 1],
+                chunk[4 * i + 2],
+                chunk[4 * i + 3],
+            ]);
+        }
+        for i in 16..64 {
+            let s0 = w[i - 15].rotate_right(7) ^ w[i - 15].rotate_right(18) ^ (w[i - 15] >> 3);
+            let s1 = w[i - 2].rotate_right(17) ^ w[i - 2].rotate_right(19) ^ (w[i - 2] >> 10);
+            w[i] = w[i - 16]
+                .wrapping_add(s0)
+                .wrapping_add(w[i - 7])
+                .wrapping_add(s1);
+        }
+
+        let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut hh] = h;
+
+        for i in 0..64 {
+            let s1 = e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25);
+            let ch = (e & f) ^ ((!e) & g);
+            let temp1 = hh
+                .wrapping_add(s1)
+                .wrapping_add(ch)
+                .wrapping_add(k[i])
+                .wrapping_add(w[i]);
+            let s0 = a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22);
+            let maj = (a & b) ^ (a & c) ^ (b & c);
+            let temp2 = s0.wrapping_add(maj);
+
+            hh = g;
+            g = f;
+            f = e;
+            e = d.wrapping_add(temp1);
+            d = c;
+            c = b;
+            b = a;
+            a = temp1.wrapping_add(temp2);
+        }
+
+        h[0] = h[0].wrapping_add(a);
+        h[1] = h[1].wrapping_add(b);
+        h[2] = h[2].wrapping_add(c);
+        h[3] = h[3].wrapping_add(d);
+        h[4] = h[4].wrapping_add(e);
+        h[5] = h[5].wrapping_add(f);
+        h[6] = h[6].wrapping_add(g);
+        h[7] = h[7].wrapping_add(hh);
+    }
+
+    let mut result = [0u8; 32];
+    for (i, val) in h.iter().enumerate() {
+        result[4 * i..4 * i + 4].copy_from_slice(&val.to_be_bytes());
+    }
+    result
+}
+
+/// Constant-time byte comparison.
+fn constant_time_eq(a: &[u8], b: &[u8]) -> bool {
+    if a.len() != b.len() {
+        return false;
+    }
+    let mut diff = 0u8;
+    for (x, y) in a.iter().zip(b.iter()) {
+        diff |= x ^ y;
+    }
+    diff == 0
+}
+
+// ── Conversation history persistence ─────────────────────────────────
+
+/// Per-channel conversation history, keyed by channel ID.
+pub type SlackConversationHistory = Arc<TokioMutex<HashMap<String, RoomConversation>>>;
+
+/// On-disk format for persisted Slack conversation history.
+#[derive(Serialize, Deserialize)]
+struct PersistedSlackHistory {
+    channels: HashMap<String, RoomConversation>,
+}
+
+/// Path to the persisted Slack conversation history file.
+const SLACK_HISTORY_FILE: &str = ".story_kit/slack_history.json";
+
+/// Load Slack conversation history from disk.
+pub fn load_slack_history(project_root: &std::path::Path) -> HashMap<String, RoomConversation> {
+    let path = project_root.join(SLACK_HISTORY_FILE);
+    let data = match std::fs::read_to_string(&path) {
+        Ok(d) => d,
+        Err(_) => return HashMap::new(),
+    };
+    let persisted: PersistedSlackHistory = match serde_json::from_str(&data) {
+        Ok(p) => p,
+        Err(e) => {
+            slog!("[slack] Failed to parse history file: {e}");
+            return HashMap::new();
+        }
+    };
+    persisted.channels
+}
+
+/// Save Slack conversation history to disk.
+fn save_slack_history(
+    project_root: &std::path::Path,
+    history: &HashMap<String, RoomConversation>,
+) {
+    let persisted = PersistedSlackHistory {
+        channels: history.clone(),
+    };
+    let path = project_root.join(SLACK_HISTORY_FILE);
+    match serde_json::to_string_pretty(&persisted) {
+        Ok(json) => {
+            if let Err(e) = std::fs::write(&path, json) {
+                slog!("[slack] Failed to write history file: {e}");
+            }
+        }
+        Err(e) => slog!("[slack] Failed to serialise history: {e}"),
+    }
+}
+
+// ── Webhook handler (Poem) ──────────────────────────────────────────────
+
+use poem::{Request, Response, handler, http::StatusCode};
+use std::collections::HashSet;
+use std::path::PathBuf;
+use std::sync::Mutex;
+
+/// Shared context for the Slack webhook handler, injected via Poem's `Data` extractor.
+pub struct SlackWebhookContext {
+    pub signing_secret: String,
+    pub transport: Arc<SlackTransport>,
+    pub project_root: PathBuf,
+    pub agents: Arc<AgentPool>,
+    pub bot_name: String,
+    /// The bot's "user ID" for command dispatch.
+    pub bot_user_id: String,
+    pub ambient_rooms: Arc<Mutex<HashSet<String>>>,
+    /// Per-channel conversation history for LLM passthrough.
+    pub history: SlackConversationHistory,
+    /// Maximum number of conversation entries to keep per channel.
+    pub history_size: usize,
+    /// Allowed channel IDs (messages from other channels are ignored).
+    pub channel_ids: HashSet<String>,
+}
+
+/// POST /webhook/slack — receive incoming events from Slack Events API.
+///
+/// Handles both `url_verification` (challenge-response handshake) and
+/// `event_callback` (incoming messages) event types.
+#[handler]
+pub async fn webhook_receive(
+    req: &Request,
+    body: poem::Body,
+    ctx: poem::web::Data<&Arc<SlackWebhookContext>>,
+) -> Response {
+    let timestamp = req
+        .header("X-Slack-Request-Timestamp")
+        .unwrap_or("")
+        .to_string();
+    let signature = req
+        .header("X-Slack-Signature")
+        .unwrap_or("")
+        .to_string();
+
+    let bytes = match body.into_bytes().await {
+        Ok(b) => b,
+        Err(e) => {
+            slog!("[slack] Failed to read webhook body: {e}");
+            return Response::builder()
+                .status(StatusCode::BAD_REQUEST)
+                .body("Bad request");
+        }
+    };
+
+    // Verify request signature.
+    if !verify_slack_signature(&ctx.signing_secret, &timestamp, &bytes, &signature) {
+        slog!("[slack] Webhook signature verification failed");
+        return Response::builder()
+            .status(StatusCode::UNAUTHORIZED)
+            .body("Invalid signature");
+    }
+
+    let envelope: SlackEventEnvelope = match serde_json::from_slice(&bytes) {
+        Ok(e) => e,
+        Err(e) => {
+            slog!("[slack] Failed to parse webhook payload: {e}");
+            return Response::builder()
+                .status(StatusCode::OK)
+                .body("ok");
+        }
+    };
+
+    // Handle URL verification challenge.
+    if envelope.r#type == "url_verification" {
+        if let Some(challenge) = envelope.challenge {
+            slog!("[slack] URL verification succeeded");
+            return Response::builder()
+                .status(StatusCode::OK)
+                .content_type("text/plain")
+                .body(challenge);
+        }
+        return Response::builder()
+            .status(StatusCode::BAD_REQUEST)
+            .body("Missing challenge");
+    }
+
+    // Handle event callbacks.
+    if envelope.r#type == "event_callback"
+        && let Some(event) = envelope.event
+        && event.r#type.as_deref() == Some("message")
+        && event.subtype.is_none()
+        && event.bot_id.is_none()
+        && let (Some(channel), Some(user), Some(text)) =
+            (event.channel, event.user, event.text)
+        && ctx.channel_ids.contains(&channel)
+    {
+        let ctx = Arc::clone(*ctx);
+        tokio::spawn(async move {
+            slog!("[slack] Message from {user} in {channel}: {text}");
+            handle_incoming_message(&ctx, &channel, &user, &text).await;
+        });
+    }
+
+    Response::builder()
+        .status(StatusCode::OK)
+        .body("ok")
+}
+
+/// Dispatch an incoming Slack message to bot commands or LLM.
+async fn handle_incoming_message(
+    ctx: &SlackWebhookContext,
+    channel: &str,
+    user: &str,
+    message: &str,
+) {
+    use crate::matrix::commands::{CommandDispatch, try_handle_command};
+
+    let dispatch = CommandDispatch {
+        bot_name: &ctx.bot_name,
+        bot_user_id: &ctx.bot_user_id,
+        project_root: &ctx.project_root,
+        agents: &ctx.agents,
+        ambient_rooms: &ctx.ambient_rooms,
+        room_id: channel,
+        // Slack messages in configured channels are always "addressed" to the bot.
+        is_addressed: true,
+    };
+
+    if let Some(response) = try_handle_command(&dispatch, message) {
+        slog!("[slack] Sending command response to {channel}");
+        if let Err(e) = ctx.transport.send_message(channel, &response, "").await {
+            slog!("[slack] Failed to send reply to {channel}: {e}");
+        }
+        return;
+    }
+
+    // Check for async commands (htop, delete).
+    if let Some(htop_cmd) = crate::matrix::htop::extract_htop_command(
+        message,
+        &ctx.bot_name,
+        &ctx.bot_user_id,
+    ) {
+        use crate::matrix::htop::HtopCommand;
+        slog!("[slack] Handling htop command from {user} in {channel}");
+        match htop_cmd {
+            HtopCommand::Stop => {
+                let _ = ctx
+                    .transport
+                    .send_message(channel, "htop stopped.", "")
+                    .await;
+            }
+            HtopCommand::Start { duration_secs } => {
+                // On Slack, htop uses native message editing for live updates.
+                let snapshot =
+                    crate::matrix::htop::build_htop_message(&ctx.agents, 0, duration_secs);
+                let msg_id = match ctx.transport.send_message(channel, &snapshot, "").await {
+                    Ok(id) => id,
+                    Err(e) => {
+                        slog!("[slack] Failed to send htop message: {e}");
+                        return;
+                    }
+                };
+                // Spawn a background task that edits the message periodically.
+                let transport = Arc::clone(&ctx.transport);
+                let agents = Arc::clone(&ctx.agents);
+                let ch = channel.to_string();
+                tokio::spawn(async move {
+                    let interval = std::time::Duration::from_secs(2);
+                    let total_ticks = (duration_secs as usize) / 2;
+                    for tick in 1..=total_ticks {
+                        tokio::time::sleep(interval).await;
+                        let updated = crate::matrix::htop::build_htop_message(
+                            &agents,
+                            (tick * 2) as u32,
+                            duration_secs,
+                        );
+                        if let Err(e) =
+                            transport.edit_message(&ch, &msg_id, &updated, "").await
+                        {
+                            slog!("[slack] Failed to edit htop message: {e}");
+                            break;
+                        }
+                    }
+                });
+            }
+        }
+        return;
+    }
+
+    if let Some(del_cmd) = crate::matrix::delete::extract_delete_command(
+        message,
+        &ctx.bot_name,
+        &ctx.bot_user_id,
+    ) {
+        let response = match del_cmd {
+            crate::matrix::delete::DeleteCommand::Delete { story_number } => {
+                slog!("[slack] Handling delete command from {user}: story {story_number}");
+                crate::matrix::delete::handle_delete(
+                    &ctx.bot_name,
+                    &story_number,
+                    &ctx.project_root,
+                    &ctx.agents,
+                )
+                .await
+            }
+            crate::matrix::delete::DeleteCommand::BadArgs => {
+                format!("Usage: `{} delete <number>`", ctx.bot_name)
+            }
+        };
+        let _ = ctx.transport.send_message(channel, &response, "").await;
+        return;
+    }
+
+    // No command matched — forward to LLM for conversational response.
+    slog!("[slack] No command matched, forwarding to LLM for {user} in {channel}");
+    handle_llm_message(ctx, channel, user, message).await;
+}
+
+/// Forward a message to Claude Code and send the response back via Slack.
+async fn handle_llm_message(
+    ctx: &SlackWebhookContext,
+    channel: &str,
+    user: &str,
+    user_message: &str,
+) {
+    use crate::llm::providers::claude_code::{ClaudeCodeProvider, ClaudeCodeResult};
+    use crate::matrix::drain_complete_paragraphs;
+    use std::sync::atomic::{AtomicBool, Ordering};
+    use tokio::sync::watch;
+
+    // Look up existing session ID for this channel.
+    let resume_session_id: Option<String> = {
+        let guard = ctx.history.lock().await;
+        guard
+            .get(channel)
+            .and_then(|conv| conv.session_id.clone())
+    };
+
+    let bot_name = &ctx.bot_name;
+    let prompt = format!(
+        "[Your name is {bot_name}. Refer to yourself as {bot_name}, not Claude.]\n\n{user}: {user_message}"
+    );
+
+    let provider = ClaudeCodeProvider::new();
+    let (_cancel_tx, mut cancel_rx) = watch::channel(false);
+
+    // Channel for sending complete chunks to the Slack posting task.
+    let (msg_tx, mut msg_rx) = tokio::sync::mpsc::unbounded_channel::<String>();
+    let msg_tx_for_callback = msg_tx.clone();
+
+    // Spawn a task to post messages as they arrive.
+    let post_transport = Arc::clone(&ctx.transport);
+    let post_channel = channel.to_string();
+    let post_task = tokio::spawn(async move {
+        while let Some(chunk) = msg_rx.recv().await {
+            let _ = post_transport.send_message(&post_channel, &chunk, "").await;
+        }
+    });
+
+    // Shared buffer between the sync token callback and the async scope.
+    let buffer = Arc::new(std::sync::Mutex::new(String::new()));
+    let buffer_for_callback = Arc::clone(&buffer);
+    let sent_any_chunk = Arc::new(AtomicBool::new(false));
+    let sent_any_chunk_for_callback = Arc::clone(&sent_any_chunk);
+
+    let project_root_str = ctx.project_root.to_string_lossy().to_string();
+    let result = provider
+        .chat_stream(
+            &prompt,
+            &project_root_str,
+            resume_session_id.as_deref(),
+            None,
+            &mut cancel_rx,
+            move |token| {
+                let mut buf = buffer_for_callback.lock().unwrap();
+                buf.push_str(token);
+                let paragraphs = drain_complete_paragraphs(&mut buf);
+                for chunk in paragraphs {
+                    sent_any_chunk_for_callback.store(true, Ordering::Relaxed);
+                    let _ = msg_tx_for_callback.send(chunk);
+                }
+            },
+            |_thinking| {},
+            |_activity| {},
+        )
+        .await;
+
+    // Flush remaining text.
+    let remaining = buffer.lock().unwrap().trim().to_string();
+    let did_send_any = sent_any_chunk.load(Ordering::Relaxed);
+
+    let (assistant_reply, new_session_id) = match result {
+        Ok(ClaudeCodeResult {
+            messages,
+            session_id,
+        }) => {
+            let reply = if !remaining.is_empty() {
+                let _ = msg_tx.send(remaining.clone());
+                remaining
+            } else if !did_send_any {
+                let last_text = messages
+                    .iter()
+                    .rev()
+                    .find(|m| {
+                        m.role == crate::llm::types::Role::Assistant && !m.content.is_empty()
+                    })
+                    .map(|m| m.content.clone())
+                    .unwrap_or_default();
+                if !last_text.is_empty() {
+                    let _ = msg_tx.send(last_text.clone());
+                }
+                last_text
+            } else {
+                remaining
+            };
+            slog!("[slack] session_id from chat_stream: {:?}", session_id);
+            (reply, session_id)
+        }
+        Err(e) => {
+            slog!("[slack] LLM error: {e}");
+            let err_msg = format!("Error processing your request: {e}");
+            let _ = msg_tx.send(err_msg.clone());
+            (err_msg, None)
+        }
+    };
+
+    // Signal the posting task to finish and wait for it.
+    drop(msg_tx);
+    let _ = post_task.await;
+
+    // Record this exchange in conversation history.
+    if !assistant_reply.starts_with("Error processing") {
+        let mut guard = ctx.history.lock().await;
+        let conv = guard.entry(channel.to_string()).or_default();
+
+        if new_session_id.is_some() {
+            conv.session_id = new_session_id;
+        }
+
+        conv.entries.push(ConversationEntry {
+            role: ConversationRole::User,
+            sender: user.to_string(),
+            content: user_message.to_string(),
+        });
+        conv.entries.push(ConversationEntry {
+            role: ConversationRole::Assistant,
+            sender: String::new(),
+            content: assistant_reply,
+        });
+
+        // Trim to configured maximum.
+        if conv.entries.len() > ctx.history_size {
+            let excess = conv.entries.len() - ctx.history_size;
+            conv.entries.drain(..excess);
+        }
+
+        save_slack_history(&ctx.project_root, &guard);
+    }
+}
+
+// ── Tests ───────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // ── SlackTransport ──────────────────────────────────────────────────
+
+    #[tokio::test]
+    async fn transport_send_message_calls_slack_api() {
+        let mut server = mockito::Server::new_async().await;
+        let mock = server
+            .mock("POST", "/chat.postMessage")
+            .match_header("authorization", "Bearer xoxb-test-token")
+            .with_body(r#"{"ok": true, "ts": "1234567890.123456"}"#)
+            .create_async()
+            .await;
+
+        let transport = SlackTransport::with_api_base(
+            "xoxb-test-token".to_string(),
+            server.url(),
+        );
+
+        let result = transport
+            .send_message("C01ABCDEF", "hello", "<p>hello</p>")
+            .await;
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), "1234567890.123456");
+        mock.assert_async().await;
+    }
+
+    #[tokio::test]
+    async fn transport_send_message_handles_api_error() {
+        let mut server = mockito::Server::new_async().await;
+        server
+            .mock("POST", "/chat.postMessage")
+            .with_body(r#"{"ok": false, "error": "channel_not_found"}"#)
+            .create_async()
+            .await;
+
+        let transport = SlackTransport::with_api_base(
+            "xoxb-test-token".to_string(),
+            server.url(),
+        );
+
+        let result = transport
+            .send_message("C_INVALID", "hello", "")
+            .await;
+        assert!(result.is_err());
+        assert!(
+            result.unwrap_err().contains("channel_not_found"),
+            "error should contain the Slack error code"
+        );
+    }
+
+    #[tokio::test]
+    async fn transport_edit_message_calls_chat_update() {
+        let mut server = mockito::Server::new_async().await;
+        let mock = server
+            .mock("POST", "/chat.update")
+            .match_header("authorization", "Bearer xoxb-test-token")
+            .with_body(r#"{"ok": true, "ts": "1234567890.123456"}"#)
+            .create_async()
+            .await;
+
+        let transport = SlackTransport::with_api_base(
+            "xoxb-test-token".to_string(),
+            server.url(),
+        );
+
+        let result = transport
+            .edit_message("C01ABCDEF", "1234567890.123456", "updated", "")
+            .await;
+        assert!(result.is_ok());
+        mock.assert_async().await;
+    }
+
+    #[tokio::test]
+    async fn transport_edit_message_handles_error() {
+        let mut server = mockito::Server::new_async().await;
+        server
+            .mock("POST", "/chat.update")
+            .with_body(r#"{"ok": false, "error": "message_not_found"}"#)
+            .create_async()
+            .await;
+
+        let transport = SlackTransport::with_api_base(
+            "xoxb-test-token".to_string(),
+            server.url(),
+        );
+
+        let result = transport
+            .edit_message("C01ABCDEF", "bad-ts", "updated", "")
+            .await;
+        assert!(result.is_err());
+        assert!(result.unwrap_err().contains("message_not_found"));
+    }
+
+    #[tokio::test]
+    async fn transport_send_typing_succeeds() {
+        let transport = SlackTransport::new("xoxb-test".to_string());
+        assert!(transport.send_typing("C01ABCDEF", true).await.is_ok());
+        assert!(transport.send_typing("C01ABCDEF", false).await.is_ok());
+    }
+
+    #[tokio::test]
+    async fn transport_handles_http_error() {
+        let mut server = mockito::Server::new_async().await;
+        server
+            .mock("POST", "/chat.postMessage")
+            .with_status(500)
+            .with_body("Internal Server Error")
+            .create_async()
+            .await;
+
+        let transport = SlackTransport::with_api_base(
+            "xoxb-test-token".to_string(),
+            server.url(),
+        );
+
+        let result = transport.send_message("C01ABCDEF", "hello", "").await;
+        assert!(result.is_err());
+        assert!(result.unwrap_err().contains("500"));
+    }
+
+    // ── Signature verification ──────────────────────────────────────────
+
+    #[test]
+    fn verify_signature_with_known_values() {
+        // Test with a known good signature.
+        let secret = "8f742231b10e8888abcd99yez67291";
+        let timestamp = "1531420618";
+        let body = b"token=xyzz0WbapA4vBCDEFasx0q6G&team_id=T1DC2JH3J&team_domain=testteamnow&channel_id=G8PSS9T3V&channel_name=foobar&user_id=U2CERLKJA&user_name=roadrunner&command=%2Fwebhook-collect&text=&response_url=https%3A%2F%2Fhooks.slack.com%2Fcommands%2FT1DC2JH3J%2F397700885554%2F96rGlfmibIGlgcZRskXaIFfN&trigger_id=398738663015.47445629121.803a0bc887a14d10d2c659f";
+
+        // Compute expected signature for this test case.
+        let sig = compute_test_signature(secret, timestamp, body);
+
+        assert!(verify_slack_signature(secret, timestamp, body, &sig));
+    }
+
+    #[test]
+    fn verify_signature_rejects_bad_signature() {
+        let secret = "test-secret";
+        let timestamp = "1234567890";
+        let body = b"test body";
+
+        assert!(!verify_slack_signature(
+            secret,
+            timestamp,
+            body,
+            "v0=bad_signature_here"
+        ));
+    }
+
+    #[test]
+    fn verify_signature_rejects_wrong_secret() {
+        let timestamp = "1234567890";
+        let body = b"test body";
+
+        let sig = compute_test_signature("correct-secret", timestamp, body);
+        assert!(!verify_slack_signature("wrong-secret", timestamp, body, &sig));
+    }
+
+    /// Helper to compute a test signature using our sha256 + HMAC implementation.
+    fn compute_test_signature(secret: &str, timestamp: &str, body: &[u8]) -> String {
+        use std::fmt::Write;
+
+        let key = secret.as_bytes();
+        let block_size = 64;
+        let key_block = if key.len() > block_size {
+            let digest = sha256(key);
+            let mut k = vec![0u8; block_size];
+            k[..32].copy_from_slice(&digest);
+            k
+        } else {
+            let mut k = vec![0u8; block_size];
+            k[..key.len()].copy_from_slice(key);
+            k
+        };
+
+        let mut ipad = vec![0x36u8; block_size];
+        let mut opad = vec![0x5cu8; block_size];
+        for i in 0..block_size {
+            ipad[i] ^= key_block[i];
+            opad[i] ^= key_block[i];
+        }
+
+        let base_string = format!("v0:{timestamp}:");
+        let mut inner_data = ipad;
+        inner_data.extend_from_slice(base_string.as_bytes());
+        inner_data.extend_from_slice(body);
+        let inner_hash = sha256(&inner_data);
+
+        let mut outer_data = opad;
+        outer_data.extend_from_slice(&inner_hash);
+        let hmac_result = sha256(&outer_data);
+
+        let mut expected = String::from("v0=");
+        for byte in &hmac_result {
+            write!(expected, "{byte:02x}").unwrap();
+        }
+        expected
+    }
+
+    // ── SHA-256 implementation ──────────────────────────────────────────
+
+    #[test]
+    fn sha256_empty_string() {
+        let result = sha256(b"");
+        let hex: String = result.iter().map(|b| format!("{b:02x}")).collect();
+        assert_eq!(
+            hex,
+            "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+        );
+    }
+
+    #[test]
+    fn sha256_hello_world() {
+        let result = sha256(b"hello world");
+        let hex: String = result.iter().map(|b| format!("{b:02x}")).collect();
+        assert_eq!(
+            hex,
+            "b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9"
+        );
+    }
+
+    // ── Event envelope parsing ──────────────────────────────────────────
+
+    #[test]
+    fn parse_url_verification_event() {
+        let json = r#"{
+            "type": "url_verification",
+            "challenge": "3eZbrw1aBm2rZgRNFdxV2595E9CY3gmdALWMmHkvFXO7tYXAYM8P"
+        }"#;
+        let envelope: SlackEventEnvelope = serde_json::from_str(json).unwrap();
+        assert_eq!(envelope.r#type, "url_verification");
+        assert_eq!(
+            envelope.challenge.as_deref(),
+            Some("3eZbrw1aBm2rZgRNFdxV2595E9CY3gmdALWMmHkvFXO7tYXAYM8P")
+        );
+    }
+
+    #[test]
+    fn parse_message_event() {
+        let json = r#"{
+            "type": "event_callback",
+            "event": {
+                "type": "message",
+                "channel": "C01ABCDEF",
+                "user": "U01GHIJKL",
+                "text": "help"
+            }
+        }"#;
+        let envelope: SlackEventEnvelope = serde_json::from_str(json).unwrap();
+        assert_eq!(envelope.r#type, "event_callback");
+        let event = envelope.event.unwrap();
+        assert_eq!(event.r#type.as_deref(), Some("message"));
+        assert_eq!(event.channel.as_deref(), Some("C01ABCDEF"));
+        assert_eq!(event.user.as_deref(), Some("U01GHIJKL"));
+        assert_eq!(event.text.as_deref(), Some("help"));
+        assert!(event.bot_id.is_none());
+        assert!(event.subtype.is_none());
+    }
+
+    #[test]
+    fn parse_bot_message_has_bot_id() {
+        let json = r#"{
+            "type": "event_callback",
+            "event": {
+                "type": "message",
+                "channel": "C01ABCDEF",
+                "bot_id": "B01234",
+                "text": "I am a bot"
+            }
+        }"#;
+        let envelope: SlackEventEnvelope = serde_json::from_str(json).unwrap();
+        let event = envelope.event.unwrap();
+        assert!(event.bot_id.is_some());
+    }
+
+    #[test]
+    fn parse_message_with_subtype() {
+        let json = r#"{
+            "type": "event_callback",
+            "event": {
+                "type": "message",
+                "subtype": "message_changed",
+                "channel": "C01ABCDEF"
+            }
+        }"#;
+        let envelope: SlackEventEnvelope = serde_json::from_str(json).unwrap();
+        let event = envelope.event.unwrap();
+        assert_eq!(event.subtype.as_deref(), Some("message_changed"));
+    }
+
+    // ── Conversation history persistence ────────────────────────────────
+
+    #[test]
+    fn save_and_load_slack_history_round_trips() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sk = tmp.path().join(".story_kit");
+        std::fs::create_dir_all(&sk).unwrap();
+
+        let mut history = HashMap::new();
+        history.insert(
+            "C01ABCDEF".to_string(),
+            RoomConversation {
+                session_id: Some("sess-abc".to_string()),
+                entries: vec![
+                    ConversationEntry {
+                        role: ConversationRole::User,
+                        sender: "U01GHIJKL".to_string(),
+                        content: "hello".to_string(),
+                    },
+                    ConversationEntry {
+                        role: ConversationRole::Assistant,
+                        sender: String::new(),
+                        content: "hi there!".to_string(),
+                    },
+                ],
+            },
+        );
+
+        save_slack_history(tmp.path(), &history);
+        let loaded = load_slack_history(tmp.path());
+
+        assert_eq!(loaded.len(), 1);
+        let conv = loaded.get("C01ABCDEF").unwrap();
+        assert_eq!(conv.session_id.as_deref(), Some("sess-abc"));
+        assert_eq!(conv.entries.len(), 2);
+        assert_eq!(conv.entries[0].content, "hello");
+        assert_eq!(conv.entries[1].content, "hi there!");
+    }
+
+    #[test]
+    fn load_slack_history_returns_empty_when_file_missing() {
+        let tmp = tempfile::tempdir().unwrap();
+        let history = load_slack_history(tmp.path());
+        assert!(history.is_empty());
+    }
+
+    #[test]
+    fn load_slack_history_returns_empty_on_invalid_json() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sk = tmp.path().join(".story_kit");
+        std::fs::create_dir_all(&sk).unwrap();
+        std::fs::write(sk.join("slack_history.json"), "not json {{{").unwrap();
+        let history = load_slack_history(tmp.path());
+        assert!(history.is_empty());
+    }
+
+    // ── Constant-time comparison ────────────────────────────────────────
+
+    #[test]
+    fn constant_time_eq_same_values() {
+        assert!(constant_time_eq(b"hello", b"hello"));
+    }
+
+    #[test]
+    fn constant_time_eq_different_values() {
+        assert!(!constant_time_eq(b"hello", b"world"));
+    }
+
+    #[test]
+    fn constant_time_eq_different_lengths() {
+        assert!(!constant_time_eq(b"hello", b"hi"));
+    }
+
+    // ── ChatTransport trait satisfaction ─────────────────────────────────
+
+    #[test]
+    fn slack_transport_satisfies_trait() {
+        fn assert_transport<T: ChatTransport>() {}
+        assert_transport::<SlackTransport>();
+
+        let _: Arc<dyn ChatTransport> = Arc::new(SlackTransport::new("xoxb-test".to_string()));
+    }
+}
diff --git a/server/src/transport.rs b/server/src/transport.rs
index 95e7fb6..6f38776 100644
--- a/server/src/transport.rs
+++ b/server/src/transport.rs
@@ -83,4 +83,15 @@ mod tests {
         fn assert_send_sync<T: Send + Sync>() {}
         assert_send_sync::<crate::matrix::transport_impl::MatrixTransport>();
     }
+
+    /// Verify that SlackTransport satisfies the ChatTransport trait and
+    /// can be used as `Arc<dyn ChatTransport>` (compile-time check).
+    #[test]
+    fn slack_transport_satisfies_trait() {
+        fn assert_transport<T: ChatTransport>() {}
+        assert_transport::<crate::slack::SlackTransport>();
+
+        let _: Arc<dyn ChatTransport> =
+            Arc::new(crate::slack::SlackTransport::new("xoxb-test".to_string()));
+    }
 }