diff --git a/hooks/claude-code/handler.js b/hooks/claude-code/handler.js
index 10ce6ee..413ef13 100755
--- a/hooks/claude-code/handler.js
+++ b/hooks/claude-code/handler.js
@@ -1,48 +1,13 @@
 #!/usr/bin/env node
-import { randomUUID } from "node:crypto";
+
+// handler.ts
+import { randomUUID as randomUUID2 } from "node:crypto";
 import { hostname, homedir } from "node:os";
 import { readFileSync, writeFileSync, mkdirSync, unlinkSync } from "node:fs";
 import { join } from "node:path";
-const INGEST_URL = process.env.AGENTMON_INGEST_URL || "http://localhost:8080";
-const FRAMEWORK = process.env.AGENTMON_FRAMEWORK || "claude-code";
-const HOST = process.env.AGENTMON_HOST || hostname();
-const BATCH_SIZE = 10;
-const FLUSH_MS = 2e3;
-const FETCH_TIMEOUT_MS = 500;
-const STATE_DIR = join(homedir(), ".agentmon-state");
-function ensureStateDir() {
-  try {
-    mkdirSync(STATE_DIR, { recursive: true });
-  } catch {
-  }
-}
-function loadState(sessionKey) {
-  try {
-    const raw = readFileSync(join(STATE_DIR, sessionKey + ".json"), "utf8");
-    return JSON.parse(raw);
-  } catch {
-    return { spans: {} };
-  }
-}
-function saveState(sessionKey, state) {
-  ensureStateDir();
-  try {
-    writeFileSync(join(STATE_DIR, sessionKey + ".json"), JSON.stringify(state), "utf8");
-  } catch {
-  }
-}
-function clearState(sessionKey) {
-  try {
-    unlinkSync(join(STATE_DIR, sessionKey + ".json"));
-  } catch {
-  }
-}
-let buffer = [];
-let flushTimer = null;
-let isFlushing = false;
-const activeRuns = /* @__PURE__ */ new Map();
-const activeSpans = /* @__PURE__ */ new Map();
-const activeSubagents = /* @__PURE__ */ new Map();
+
+// ../shared/lib.ts
+import { randomUUID } from "node:crypto";
 function isRecord(value) {
   return value !== null && typeof value === "object" && !Array.isArray(value);
 }
@@ -82,6 +47,163 @@ function safeJSONStringify(value) {
     return String(value);
   }
 }
+function buildEnvelope(framework, host, type, sessionKey, opts = {}) {
+  const correlation = {};
+  if (sessionKey) {
+    correlation.session_id = sessionKey;
+  }
+  if (opts.runId) {
+    correlation.run_id = opts.runId;
+  }
+  if (opts.spanId) {
+    correlation.span_id = opts.spanId;
+  }
+  if (opts.parentSpanId) {
+    correlation.parent_span_id = opts.parentSpanId;
+  }
+  const envelope = {
+    schema: { name: "agentmon.event", version: 1 },
+    event: {
+      id: randomUUID(),
+      type,
+      ts: (/* @__PURE__ */ new Date()).toISOString(),
+      source: {
+        framework,
+        client_id: host,
+        host
+      }
+    }
+  };
+  if (Object.keys(correlation).length > 0) {
+    envelope.correlation = correlation;
+  }
+  if (opts.attributes && Object.keys(opts.attributes).length > 0) {
+    envelope.attributes = opts.attributes;
+  }
+  if (opts.payload && Object.keys(opts.payload).length > 0) {
+    envelope.payload = opts.payload;
+  }
+  return envelope;
+}
+function createTransport(ingestUrl, opts) {
+  const batchSize = opts?.batchSize ?? 10;
+  const flushMs = opts?.flushMs ?? 2e3;
+  const fetchTimeoutMs = opts?.fetchTimeoutMs ?? 500;
+  let buffer = [];
+  let flushTimer = null;
+  let isFlushing = false;
+  async function postBatch(batch) {
+    const controller = new AbortController();
+    const timeout = setTimeout(() => controller.abort(), fetchTimeoutMs);
+    try {
+      await fetch(`${ingestUrl}/v1/events`, {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(batch),
+        signal: controller.signal
+      });
+    } finally {
+      clearTimeout(timeout);
+    }
+  }
+  function scheduleFlush() {
+    if (!flushTimer) {
+      flushTimer = setTimeout(() => {
+        void flush2();
+      }, flushMs);
+    }
+  }
+  async function flush2() {
+    if (flushTimer) {
+      clearTimeout(flushTimer);
+      flushTimer = null;
+    }
+    if (isFlushing || buffer.length === 0) {
+      return;
+    }
+    isFlushing = true;
+    const batch = buffer.splice(0, batchSize);
+    try {
+      await postBatch(batch);
+    } catch {
+      console.debug(`[agentmon] failed to flush ${batch.length} events`);
+    } finally {
+      isFlushing = false;
+      if (buffer.length > 0) {
+        if (buffer.length >= batchSize) {
+          void flush2();
+        } else {
+          scheduleFlush();
+        }
+      }
+    }
+  }
+  function enqueue2(event) {
+    buffer.push(event);
+    if (buffer.length >= batchSize) {
+      void flush2();
+    } else {
+      scheduleFlush();
+    }
+  }
+  return { enqueue: enqueue2, flush: flush2 };
+}
+async function readStdin() {
+  return new Promise((resolve) => {
+    let data = "";
+    let done = false;
+    const timer = setTimeout(() => finish(data), 100);
+    const finish = (value) => {
+      if (done)
+        return;
+      done = true;
+      clearTimeout(timer);
+      resolve(value);
+    };
+    process.stdin.on("data", (chunk) => {
+      data += chunk;
+    });
+    process.stdin.on("end", () => finish(data));
+    process.stdin.on("error", () => finish(""));
+  });
+}
+
+// handler.ts
+var INGEST_URL = process.env.AGENTMON_INGEST_URL || "http://localhost:8080";
+var FRAMEWORK = process.env.AGENTMON_FRAMEWORK || "claude-code";
+var HOST = process.env.AGENTMON_HOST || hostname();
+var { enqueue, flush } = createTransport(INGEST_URL);
+var STATE_DIR = join(homedir(), ".agentmon-state");
+function ensureStateDir() {
+  try {
+    mkdirSync(STATE_DIR, { recursive: true });
+  } catch {
+  }
+}
+function loadState(sessionKey) {
+  try {
+    const raw = readFileSync(join(STATE_DIR, sessionKey + ".json"), "utf8");
+    return JSON.parse(raw);
+  } catch {
+    return { spans: {} };
+  }
+}
+function saveState(sessionKey, state) {
+  ensureStateDir();
+  try {
+    writeFileSync(join(STATE_DIR, sessionKey + ".json"), JSON.stringify(state), "utf8");
+  } catch {
+  }
+}
+function clearState(sessionKey) {
+  try {
+    unlinkSync(join(STATE_DIR, sessionKey + ".json"));
+  } catch {
+  }
+}
+var activeRuns = /* @__PURE__ */ new Map();
+var activeSpans = /* @__PURE__ */ new Map();
+var activeSubagents = /* @__PURE__ */ new Map();
 function getSessionKey(input) {
   return pickString(
     input.sessionId,
@@ -128,98 +250,6 @@ function getContextWindow(input) {
     result.tokens_remaining = stats.tokens_remaining;
   return Object.keys(result).length > 0 ? result : void 0;
 }
-function buildEnvelope(type, sessionKey, opts = {}) {
-  const correlation = {};
-  if (sessionKey) {
-    correlation.session_id = sessionKey;
-  }
-  if (opts.runId) {
-    correlation.run_id = opts.runId;
-  }
-  if (opts.spanId) {
-    correlation.span_id = opts.spanId;
-  }
-  if (opts.parentSpanId) {
-    correlation.parent_span_id = opts.parentSpanId;
-  }
-  const envelope = {
-    schema: { name: "agentmon.event", version: 1 },
-    event: {
-      id: randomUUID(),
-      type,
-      ts: (/* @__PURE__ */ new Date()).toISOString(),
-      source: {
-        framework: FRAMEWORK,
-        client_id: HOST,
-        host: HOST
-      }
-    }
-  };
-  if (Object.keys(correlation).length > 0) {
-    envelope.correlation = correlation;
-  }
-  if (opts.attributes && Object.keys(opts.attributes).length > 0) {
-    envelope.attributes = opts.attributes;
-  }
-  if (opts.payload && Object.keys(opts.payload).length > 0) {
-    envelope.payload = opts.payload;
-  }
-  return envelope;
-}
-function scheduleFlush() {
-  if (!flushTimer) {
-    flushTimer = setTimeout(() => {
-      void flush();
-    }, FLUSH_MS);
-  }
-}
-function enqueue(event) {
-  buffer.push(event);
-  if (buffer.length >= BATCH_SIZE) {
-    void flush();
-  } else {
-    scheduleFlush();
-  }
-}
-async function postBatch(batch) {
-  const controller = new AbortController();
-  const timeout = setTimeout(() => controller.abort(), FETCH_TIMEOUT_MS);
-  try {
-    await fetch(`${INGEST_URL}/v1/events`, {
-      method: "POST",
-      headers: { "Content-Type": "application/json" },
-      body: JSON.stringify(batch),
-      signal: controller.signal
-    });
-  } finally {
-    clearTimeout(timeout);
-  }
-}
-async function flush() {
-  if (flushTimer) {
-    clearTimeout(flushTimer);
-    flushTimer = null;
-  }
-  if (isFlushing || buffer.length === 0) {
-    return;
-  }
-  isFlushing = true;
-  const batch = buffer.splice(0, BATCH_SIZE);
-  try {
-    await postBatch(batch);
-  } catch {
-    console.debug(`[agentmon] failed to flush ${batch.length} events`);
-  } finally {
-    isFlushing = false;
-    if (buffer.length > 0) {
-      if (buffer.length >= BATCH_SIZE) {
-        void flush();
-      } else {
-        scheduleFlush();
-      }
-    }
-  }
-}
 function emitError(sessionKey, runId, spanId, errorValue) {
   if (errorValue === void 0 || errorValue === null || errorValue === false) {
     return;
@@ -227,7 +257,7 @@ function emitError(sessionKey, runId, spanId, errorValue) {
   const errorRecord = isRecord(errorValue) ? errorValue : {};
   const message = pickString(errorRecord.message, errorRecord.error, errorValue) || "unknown";
   const errType = pickString(errorRecord.type, errorRecord.code) || FRAMEWORK;
-  enqueue(buildEnvelope("error", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "error", sessionKey, {
     runId,
     spanId,
     payload: {
@@ -239,15 +269,24 @@ function emitError(sessionKey, runId, spanId, errorValue) {
   }));
 }
 async function handleSessionStart(input) {
-  const sessionKey = getSessionKey(input) || randomUUID();
-  const runId = randomUUID();
+  const sessionKey = getSessionKey(input);
+  if (!sessionKey) {
+    console.error("[agentmon] ignoring claude-code session.start without session_id");
+    return;
+  }
+  const hookEventName = pickString(input.hook_event_name);
+  if (hookEventName && hookEventName !== "SessionStart") {
+    console.error(`[agentmon] ignoring claude-code session.start with hook_event_name=${hookEventName}`);
+    return;
+  }
+  const runId = randomUUID2();
   activeRuns.set(sessionKey, runId);
   saveState(sessionKey, { runId, spans: {} });
   const contextWindow = getContextWindow(input);
-  enqueue(buildEnvelope("session.start", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "session.start", sessionKey, {
     attributes: contextWindow ? { context_window: contextWindow } : void 0
   }));
-  enqueue(buildEnvelope("run.start", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "run.start", sessionKey, {
     runId,
     attributes: {
       trigger: pickString(input.trigger_type, input.trigger)
@@ -266,7 +305,7 @@ async function handleSessionEnd(input) {
   const contextWindow = getContextWindow(input);
   const duration = pickNumber(input.duration_ms, input.elapsed_ms);
   if (runId) {
-    enqueue(buildEnvelope("run.end", sessionKey, {
+    enqueue(buildEnvelope(FRAMEWORK, HOST, "run.end", sessionKey, {
       runId,
       payload: {
         status: "success",
@@ -277,7 +316,7 @@ async function handleSessionEnd(input) {
       }
     }));
   }
-  enqueue(buildEnvelope("session.end", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "session.end", sessionKey, {
     payload: {
       ...usage && { usage },
       ...contextWindow && { context_window: contextWindow }
@@ -296,7 +335,7 @@ async function handlePromptSubmit(input) {
   const runId = sessionKey ? activeRuns.get(sessionKey) || state.runId : void 0;
   const prompt = pickString(input.prompt, input.text, input.message);
   if (runId && prompt) {
-    enqueue(buildEnvelope("run.end", sessionKey, {
+    enqueue(buildEnvelope(FRAMEWORK, HOST, "run.end", sessionKey, {
       runId,
       payload: {
         status: "success",
@@ -304,12 +343,12 @@ async function handlePromptSubmit(input) {
       }
     }));
   }
-  const newRunId = randomUUID();
+  const newRunId = randomUUID2();
   if (sessionKey) {
     activeRuns.set(sessionKey, newRunId);
     saveState(sessionKey, { runId: newRunId, spans: {} });
   }
-  enqueue(buildEnvelope("run.start", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "run.start", sessionKey, {
     runId: newRunId,
     attributes: {
       type: "user_prompt"
@@ -326,7 +365,7 @@ async function handleToolStart(input) {
   const runId = sessionKey ? activeRuns.get(sessionKey) || state.runId : void 0;
   const toolName = pickString(input.tool, input.tool_name, input.name) || "unknown";
   const toolInput = isRecord(input.input) ? input.input : {};
-  const spanId = randomUUID();
+  const spanId = randomUUID2();
   const spanKey = sessionKey ? sessionKey + ":" + toolName : void 0;
   if (spanKey) {
     activeSpans.set(spanKey, spanId);
@@ -338,7 +377,7 @@ async function handleToolStart(input) {
     if (sessionKey)
       saveState(sessionKey, state);
   }
-  enqueue(buildEnvelope("span.start", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "span.start", sessionKey, {
     runId,
     spanId,
     attributes: {
@@ -367,7 +406,7 @@ async function handleToolEnd(input) {
     if (sessionKey)
       saveState(sessionKey, state);
   }
-  enqueue(buildEnvelope("span.end", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "span.end", sessionKey, {
     runId,
     spanId,
     attributes: {
@@ -391,7 +430,7 @@ async function handleSubagentStart(input) {
   const state = sessionKey ? loadState(sessionKey) : { spans: {} };
   const runId = sessionKey ? activeRuns.get(sessionKey) || state.runId : void 0;
   const agentName = pickString(input.agent, input.agent_name, input.name) || "unknown";
-  const spanId = randomUUID();
+  const spanId = randomUUID2();
   if (sessionKey) {
     activeSubagents.set(sessionKey, { name: agentName, spanId });
     state.subagent = { name: agentName, spanId };
@@ -401,7 +440,7 @@ async function handleSubagentStart(input) {
       state.runId = runId;
     saveState(sessionKey, state);
   }
-  enqueue(buildEnvelope("span.start", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "span.start", sessionKey, {
     runId,
     spanId,
     attributes: {
@@ -430,7 +469,7 @@ async function handleSubagentStop(input) {
     if (sessionKey)
       saveState(sessionKey, state);
   }
-  enqueue(buildEnvelope("span.end", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "span.end", sessionKey, {
     runId,
     spanId,
     attributes: {
@@ -451,7 +490,7 @@ async function handleCompactStart(input) {
   const sessionKey = getSessionKey(input);
   const state = sessionKey ? loadState(sessionKey) : { spans: {} };
   const runId = sessionKey ? activeRuns.get(sessionKey) || state.runId : void 0;
-  const spanId = randomUUID();
+  const spanId = randomUUID2();
   if (sessionKey) {
     activeSpans.set(sessionKey + ":compact", spanId);
     state.compactSpanId = spanId;
@@ -461,7 +500,7 @@ async function handleCompactStart(input) {
       state.runId = runId;
     saveState(sessionKey, state);
   }
-  enqueue(buildEnvelope("span.start", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "span.start", sessionKey, {
     runId,
     spanId,
     attributes: {
@@ -485,7 +524,7 @@ async function handleCompactEnd(input) {
     if (sessionKey)
       saveState(sessionKey, state);
   }
-  enqueue(buildEnvelope("span.end", sessionKey, {
+  enqueue(buildEnvelope(FRAMEWORK, HOST, "span.end", sessionKey, {
     runId,
     spanId,
     attributes: {
@@ -511,7 +550,7 @@ async function handleNotification(input) {
     const state = sessionKey ? loadState(sessionKey) : { spans: {} };
     const runId = sessionKey ? activeRuns.get(sessionKey) || state.runId : void 0;
     if (runId) {
-      enqueue(buildEnvelope("run.end", sessionKey, {
+      enqueue(buildEnvelope(FRAMEWORK, HOST, "run.end", sessionKey, {
         runId,
         payload: {
           status: "success",
@@ -525,7 +564,7 @@ async function handleNotification(input) {
   }
   await flush();
 }
-const handler = async () => {
+var handler = async () => {
   const args = process.argv.slice(2);
   const hookType = args[0] || "unknown";
   let input = {};
@@ -576,13 +615,4 @@ const handler = async () => {
     console.debug("[agentmon] handler error:", err);
   }
 };
-async function readStdin() {
-  return new Promise((resolve) => {
-    let data = "";
-    process.stdin.on("data", (chunk) => data += chunk);
-    process.stdin.on("end", () => resolve(data));
-    process.stdin.on("error", () => resolve(""));
-    setTimeout(() => resolve(data), 100);
-  });
-}
 handler();
diff --git a/hooks/claude-code/handler.ts b/hooks/claude-code/handler.ts
index 4a4af0b..e0aa25e 100644
--- a/hooks/claude-code/handler.ts
+++ b/hooks/claude-code/handler.ts
@@ -124,7 +124,18 @@ function emitError(sessionKey: string | undefined, runId: string | undefined, sp
 }
 
 async function handleSessionStart(input: Dict) {
-  const sessionKey = getSessionKey(input) || randomUUID();
+  const sessionKey = getSessionKey(input);
+  if (!sessionKey) {
+    console.error('[agentmon] ignoring claude-code session.start without session_id');
+    return;
+  }
+
+  const hookEventName = pickString(input.hook_event_name);
+  if (hookEventName && hookEventName !== 'SessionStart') {
+    console.error(`[agentmon] ignoring claude-code session.start with hook_event_name=${hookEventName}`);
+    return;
+  }
+
   const runId = randomUUID();
   activeRuns.set(sessionKey, runId);
   saveState(sessionKey, { runId, spans: {} });
diff --git a/hooks/claude-code/package.json b/hooks/claude-code/package.json
index 9cda803..d989d83 100644
--- a/hooks/claude-code/package.json
+++ b/hooks/claude-code/package.json
@@ -8,7 +8,7 @@
     "agentmon-handler": "./handler.js"
   },
   "scripts": {
-    "build": "npx esbuild handler.ts --platform=node --format=esm --outfile=handler.js"
+    "build": "npx esbuild handler.ts --bundle --platform=node --format=esm --outfile=handler.js"
   },
   "dependencies": {},
   "devDependencies": {