diff --git a/docs/feature-decisions.md b/docs/feature-decisions.md
index 4aa5e34..fb10b58 100644
--- a/docs/feature-decisions.md
+++ b/docs/feature-decisions.md
@@ -6,7 +6,32 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 ## Declined Features
 
-### 1. Admin Commands (/stats)
+### 1. Fan-Out Decoupling (Two-Phase Queue)
+
+**Idea**: Webhook handler enqueues a single "dispatch" message; queue consumer lists subscribers and re-enqueues individual "deliver" messages. Converts O(N) webhook handler to O(1).
+
+**Decision**: Skip. Current subscriber count is small. The webhook handler completing in one pass is simpler to reason about and debug. Adding a two-phase queue introduces message type routing, a new queue message schema, and makes the data flow harder to follow — all for a scaling problem that doesn't exist yet.
+
+**Why this rank**: Clear trigger: webhook response times or CPU usage climbing in CF dashboard. Straightforward to implement when needed.
+
+### 2. Queue Message Idempotency Keys
+
+**Idea**: Include `{ incidentId, chatId }` hash as dedup key. Check short-TTL KV key before sending to prevent duplicate delivery on queue retries.
+
+**Decision**: Skip. Duplicate notifications are a minor UX annoyance, not a correctness issue. Adding a KV read+write per message doubles KV operations in the queue consumer for a rare edge case (crash between successful Telegram send and `msg.ack()`). CF Queues retry is already bounded to 3 attempts.
+
+**Why this rank**: Only worth it if users report duplicate notifications as a real problem.
+
+### 3. /ping Command
+
+**Idea**: Bot replies with worker region + timestamp for liveness check.
+
+**Decision**: Skip. `/status` already proves the bot is alive (it fetches from external API and replies). A dedicated `/ping` adds another command for marginal value. The web health check endpoint (`GET /`) serves the same purpose for monitoring.
+
+**Why this rank**: Trivial to add but not useful enough to justify another command.
+
+### 4. Admin Commands (/stats)
+
 
 **Idea**: `/stats` to show subscriber count, recent webhook events (useful for bot operator).
 
@@ -14,7 +39,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why highest**: Low effort, no architectural changes. Just a new command + `kv.list()` count. First thing to add if the bot grows.
 
-### 2. Webhook HMAC Signature Verification
+### 5. Webhook HMAC Signature Verification
 
 **Idea**: Verify Statuspage webhook payloads using HMAC signatures as a second auth layer beyond URL secret.
 
@@ -22,7 +47,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Not blocked by effort — blocked by platform. Would be implemented immediately if Atlassian ships HMAC support.
 
-### 3. Proactive Rate Limit Tracking
+### 6. Proactive Rate Limit Tracking
 
 **Idea**: Track per-chat message counts to stay within Telegram's rate limits proactively.
 
@@ -30,7 +55,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Becomes necessary at scale. Clear trigger: frequent 429 errors in logs.
 
-### 4. Status Change Deduplication
+### 7. Status Change Deduplication
 
 **Idea**: If a component flaps (operational → degraded → operational in 2 minutes), debounce into one message.
 
@@ -38,7 +63,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Useful if flapping becomes noisy. Moderate effort with clear user-facing benefit.
 
-### 5. Inline Keyboard for /subscribe
+### 8. Inline Keyboard for /subscribe
 
 **Idea**: Replace text commands with clickable buttons using grammY's inline keyboard support.
 
@@ -46,7 +71,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Nice UX polish but not functional gap. grammY supports it well — moderate effort.
 
-### 6. Scheduled Status Digest
+### 9. Scheduled Status Digest
 
 **Idea**: CF Workers `scheduled` cron trigger sends a daily "all clear" or summary to subscribers.
 
@@ -54,7 +79,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Low user value. Only useful if users explicitly request daily summaries.
 
-### 7. Mute Command (/mute \<duration>)
+### 10. Mute Command (/mute \<duration>)
 
 **Idea**: Temporarily pause notifications without unsubscribing (e.g., `/mute 2h`).
 
@@ -62,7 +87,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Contradicts real-time purpose. `/stop` + `/start` is sufficient.
 
-### 8. Multi-Language Support
+### 11. Multi-Language Support
 
 **Idea**: At minimum English/Vietnamese support.
 
@@ -70,7 +95,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Source data is English-only. Translating bot chrome while incidents stay English creates a mixed-language experience.
 
-### 9. Web Dashboard
+### 12. Web Dashboard
 
 **Idea**: Replace the `/` health check with a status page showing subscriber count and recent webhook events.
 
@@ -78,7 +103,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Out of scope. The bot is the product — adding a web frontend changes the project's nature.
 
-### 10. Dead Letter Queue for Failed Messages
+### 13. Dead Letter Queue for Failed Messages
 
 **Idea**: After CF Queues exhausts 3 retries, persist failed messages to KV or a dedicated DLQ for debugging.
 
@@ -86,7 +111,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Logging is sufficient for current scale. Revisit only if log retention (3-day free tier) is too short for debugging patterns.
 
-### 11. KV List Scalability (Subscriber Sharding)
+### 14. KV List Scalability (Subscriber Sharding)
 
 **Idea**: Shard subscriber keys by event type (e.g., `sub:incident:{chatId}`, `sub:component:{chatId}`) to avoid listing all subscribers on every webhook.
 
@@ -94,7 +119,7 @@ Ordered by likelihood of future implementation (top = most likely to revisit).
 
 **Why this rank**: Clear trigger: slow webhook response times at high subscriber counts. Migration path is straightforward when needed.
 
-### 12. Digest / Quiet Mode
+### 15. Digest / Quiet Mode
 
 **Idea**: Batch notifications into a daily summary instead of instant alerts.
 
diff --git a/src/bot-commands.js b/src/bot-commands.js
index fad2a79..1f8693c 100644
--- a/src/bot-commands.js
+++ b/src/bot-commands.js
@@ -1,3 +1,5 @@
+/** @import { ChatTarget } from "./types.js" */
+
 import { Bot, webhookCallback } from "grammy";
 import {
   addSubscriber,
@@ -17,6 +19,7 @@ let kv = null;
 
 /**
  * Extract chatId and threadId from grammY context
+ * @returns {ChatTarget}
  */
 function getChatTarget(ctx) {
   return {
diff --git a/src/bot-info-commands.js b/src/bot-info-commands.js
index 7b81f3b..6d3d79e 100644
--- a/src/bot-info-commands.js
+++ b/src/bot-info-commands.js
@@ -69,7 +69,7 @@ export function registerInfoCommands(bot) {
         );
       }
     } catch (err) {
-      console.error("status command error:", err);
+      console.error(JSON.stringify({ event: "command_error", command: "status", error: err.message }));
       await ctx.reply("Unable to fetch status. Please try again later.");
     }
   });
@@ -91,7 +91,7 @@ export function registerInfoCommands(bot) {
         { parse_mode: "HTML", disable_web_page_preview: true }
       );
     } catch (err) {
-      console.error("history command error:", err);
+      console.error(JSON.stringify({ event: "command_error", command: "history", error: err.message }));
       await ctx.reply("Unable to fetch incident history. Please try again later.");
     }
   });
@@ -116,7 +116,7 @@ export function registerInfoCommands(bot) {
         { parse_mode: "HTML", disable_web_page_preview: true }
       );
     } catch (err) {
-      console.error("uptime command error:", err);
+      console.error(JSON.stringify({ event: "command_error", command: "uptime", error: err.message }));
       await ctx.reply("Unable to fetch uptime data. Please try again later.");
     }
   });
diff --git a/src/kv-store.js b/src/kv-store.js
index 3cd8415..389a045 100644
--- a/src/kv-store.js
+++ b/src/kv-store.js
@@ -1,3 +1,5 @@
+/** @import { Subscriber, ChatTarget } from "./types.js" */
+
 const KEY_PREFIX = "sub:";
 
 /**
@@ -54,6 +56,10 @@ async function listAllSubscriberKeys(kv) {
 
 /**
  * Add or re-subscribe a user. Preserves existing types and components if already subscribed.
+ * @param {KVNamespace} kv
+ * @param {number} chatId
+ * @param {?number} threadId
+ * @param {string[]} types
  */
 export async function addSubscriber(kv, chatId, threadId, types = ["incident", "component"]) {
   const key = buildKvKey(chatId, threadId);
@@ -105,6 +111,10 @@ export async function updateSubscriberComponents(kv, chatId, threadId, component
 
 /**
  * Get a single subscriber's data, or null if not subscribed
+ * @param {KVNamespace} kv
+ * @param {number} chatId
+ * @param {?number} threadId
+ * @returns {Promise<?Subscriber>}
  */
 export async function getSubscriber(kv, chatId, threadId) {
   const key = buildKvKey(chatId, threadId);
@@ -114,6 +124,10 @@ export async function getSubscriber(kv, chatId, threadId) {
 /**
  * Get subscribers filtered by event type and optional component name.
  * Uses KV metadata from list() — O(1) list call, no individual get() needed.
+ * @param {KVNamespace} kv
+ * @param {string} eventType
+ * @param {?string} componentName
+ * @returns {Promise<ChatTarget[]>}
  */
 export async function getSubscribersByType(kv, eventType, componentName = null) {
   const keys = await listAllSubscriberKeys(kv);
diff --git a/src/queue-consumer.js b/src/queue-consumer.js
index 0f564c5..da119f3 100644
--- a/src/queue-consumer.js
+++ b/src/queue-consumer.js
@@ -1,8 +1,12 @@
+/** @import { QueueMessage } from "./types.js" */
+
 import { removeSubscriber } from "./kv-store.js";
 import { telegramUrl } from "./telegram-api.js";
 /**
  * Process a batch of queued messages, sending each to Telegram.
  * Handles rate limits (429 → retry), blocked bots (403/400 → remove subscriber).
+ * @param {{ messages: Array<{ body: QueueMessage, ack: () => void, retry: () => void }> }} batch
+ * @param {object} env
  */
 export async function handleQueue(batch, env) {
   let sent = 0, failed = 0, retried = 0, removed = 0;
@@ -12,7 +16,7 @@ export async function handleQueue(batch, env) {
 
     // Defensive check for malformed messages
     if (!chatId || !html) {
-      console.error("Queue: malformed message, skipping", msg.body);
+      console.error(JSON.stringify({ event: "queue_skip", reason: "malformed", body: msg.body }));
       msg.ack();
       continue;
     }
@@ -37,32 +41,32 @@ export async function handleQueue(batch, env) {
         sent++;
         msg.ack();
       } else if (res.status === 403 || res.status === 400) {
-        console.log(`Queue: removing subscriber ${chatId}:${threadId} (HTTP ${res.status})`);
+        console.log(JSON.stringify({ event: "queue_remove", chatId, threadId, status: res.status }));
         await removeSubscriber(env.claude_status, chatId, threadId);
         removed++;
         msg.ack();
       } else if (res.status === 429) {
         const retryAfter = res.headers.get("Retry-After");
-        console.log(`Queue: rate limited for ${chatId}, Retry-After: ${retryAfter ?? "unknown"}`);
+        console.log(JSON.stringify({ event: "queue_ratelimit", chatId, retryAfter }));
         retried++;
         msg.retry();
       } else if (res.status >= 500) {
-        console.error(`Queue: Telegram 5xx (${res.status}) for ${chatId}, retrying`);
+        console.error(JSON.stringify({ event: "queue_retry", chatId, status: res.status }));
         retried++;
         msg.retry();
       } else {
-        console.error(`Queue: unexpected HTTP ${res.status} for ${chatId}`);
+        console.error(JSON.stringify({ event: "queue_error", chatId, status: res.status }));
         failed++;
         msg.ack();
       }
     } catch (err) {
-      console.error("Queue: network error, retrying", err);
+      console.error(JSON.stringify({ event: "queue_network_error", chatId, error: err.message }));
       retried++;
       msg.retry();
     }
   }
 
   if (sent || failed || retried || removed) {
-    console.log(`Queue batch: sent=${sent} failed=${failed} retried=${retried} removed=${removed}`);
+    console.log(JSON.stringify({ event: "queue_batch", sent, failed, retried, removed }));
   }
 }
diff --git a/src/statuspage-webhook.js b/src/statuspage-webhook.js
index 44add6f..d7a8cb8 100644
--- a/src/statuspage-webhook.js
+++ b/src/statuspage-webhook.js
@@ -40,9 +40,15 @@ function formatComponentMessage(component, update) {
 export async function handleStatuspageWebhook(c) {
   try {
     // Validate URL secret (timing-safe)
+    // Guard against misconfigured deploy (undefined env var)
+    if (!c.env.WEBHOOK_SECRET) {
+      console.error(JSON.stringify({ event: "webhook_error", reason: "WEBHOOK_SECRET not configured" }));
+      return c.text("OK", 200);
+    }
+
     const secret = c.req.param("secret");
     if (!await timingSafeEqual(secret, c.env.WEBHOOK_SECRET)) {
-      console.error("Statuspage webhook: invalid secret");
+      console.error(JSON.stringify({ event: "webhook_error", reason: "invalid_secret" }));
       return c.text("OK", 200);
     }
 
@@ -51,37 +57,37 @@ export async function handleStatuspageWebhook(c) {
     try {
       body = await c.req.json();
     } catch {
-      console.error("Statuspage webhook: invalid JSON body");
+      console.error(JSON.stringify({ event: "webhook_error", reason: "invalid_json" }));
       return c.text("OK", 200);
     }
 
     const eventType = body?.meta?.event_type;
     if (!eventType) {
-      console.error("Statuspage webhook: missing event_type");
+      console.error(JSON.stringify({ event: "webhook_error", reason: "missing_event_type" }));
       return c.text("OK", 200);
     }
 
-    console.log(`Statuspage webhook: ${eventType}`);
+    console.log(JSON.stringify({ event: "webhook_received", eventType }));
 
     // Determine category and format message
     let category, html, componentName;
     if (eventType.startsWith("incident.")) {
       if (!body.incident) {
-        console.error("Statuspage webhook: incident event missing incident data");
+        console.error(JSON.stringify({ event: "webhook_error", reason: "missing_incident_data", eventType }));
         return c.text("OK", 200);
       }
       category = "incident";
       html = formatIncidentMessage(body.incident);
     } else if (eventType.startsWith("component.")) {
       if (!body.component) {
-        console.error("Statuspage webhook: component event missing component data");
+        console.error(JSON.stringify({ event: "webhook_error", reason: "missing_component_data", eventType }));
         return c.text("OK", 200);
       }
       category = "component";
       componentName = body.component.name || null;
       html = formatComponentMessage(body.component, body.component_update);
     } else {
-      console.error(`Statuspage webhook: unknown event type ${eventType}`);
+      console.error(JSON.stringify({ event: "webhook_error", reason: "unknown_event_type", eventType }));
       return c.text("OK", 200);
     }
 
@@ -96,11 +102,11 @@ export async function handleStatuspageWebhook(c) {
       await c.env["claude-status"].sendBatch(messages.slice(i, i + 100));
     }
 
-    console.log(`Enqueued ${messages.length} messages for ${category}${componentName ? `:${componentName}` : ""}`);
+    console.log(JSON.stringify({ event: "webhook_enqueued", category, componentName, count: messages.length }));
     return c.text("OK", 200);
   } catch (err) {
     // Catch-all: log error but still return 200 to prevent Statuspage from removing us
-    console.error("Statuspage webhook: unexpected error", err);
+    console.error(JSON.stringify({ event: "webhook_error", reason: "unexpected", error: err.message }));
     return c.text("OK", 200);
   }
 }
diff --git a/src/types.js b/src/types.js
new file mode 100644
index 0000000..e1c8df0
--- /dev/null
+++ b/src/types.js
@@ -0,0 +1,21 @@
+/**
+ * Shared JSDoc type definitions for the project.
+ * Import via: @import { Subscriber, QueueMessage, ChatTarget } from "./types.js"
+ */
+
+/**
+ * Subscriber preferences stored in KV value and metadata
+ * @typedef {{ types: string[], components: string[] }} Subscriber
+ */
+
+/**
+ * Message body enqueued to CF Queue for fan-out delivery
+ * @typedef {{ chatId: number, threadId: ?number, html: string }} QueueMessage
+ */
+
+/**
+ * Chat target extracted from Telegram update
+ * @typedef {{ chatId: number, threadId: ?number }} ChatTarget
+ */
+
+export {};