diff --git a/demo/circuit-breaker-snapshot.json b/demo/circuit-breaker-snapshot.json
new file mode 100644
index 0000000000..10fab2c815
--- /dev/null
+++ b/demo/circuit-breaker-snapshot.json
@@ -0,0 +1,53 @@
+{
+  "generatedAt": "2026-05-14T13:16:13.824Z",
+  "source": "tools/bus/export-cb-snapshot.ts",
+  "busDir": "/tmp/zeta-bus",
+  "envelopeCount": 73,
+  "entries": [
+    {
+      "model": "Otto",
+      "harness": "Claude Code",
+      "state": "CLOSED",
+      "consecutiveFailures": 0,
+      "threshold": 5,
+      "lastCheck": "2026-05-14T13:14:21.460Z",
+      "note": "Active work detected — normal operation"
+    },
+    {
+      "model": "Alexa",
+      "harness": "Kiro / Qwen",
+      "state": "CLOSED",
+      "consecutiveFailures": 0,
+      "threshold": 5,
+      "lastCheck": "2026-05-14T13:16:13.824Z",
+      "note": "No recent bus activity — assuming healthy"
+    },
+    {
+      "model": "Lior",
+      "harness": "Gemini",
+      "state": "CLOSED",
+      "consecutiveFailures": 0,
+      "threshold": 5,
+      "lastCheck": "2026-05-14T13:16:13.824Z",
+      "note": "No recent bus activity — assuming healthy"
+    },
+    {
+      "model": "Vera",
+      "harness": "Codex / GPT",
+      "state": "CLOSED",
+      "consecutiveFailures": 0,
+      "threshold": 5,
+      "lastCheck": "2026-05-13T22:38:20.254Z",
+      "note": "Active work detected — normal operation"
+    },
+    {
+      "model": "Riven",
+      "harness": "Grok",
+      "state": "CLOSED",
+      "consecutiveFailures": 0,
+      "threshold": 5,
+      "lastCheck": "2026-05-14T13:16:13.824Z",
+      "note": "No recent bus activity — assuming healthy"
+    }
+  ]
+}
diff --git a/demo/index.html b/demo/index.html
index eed5ae7a15..b292f7d8f9 100644
--- a/demo/index.html
+++ b/demo/index.html
@@ -1603,8 +1603,22 @@ <h2>How Circuit Breakers Work Here</h2>
             return li;
         }
 
-        function renderCircuitBreakerTab() {
-            const entries = buildCbMockData();
+        async function renderCircuitBreakerTab() {
+            // Try live snapshot first; fall back to mock data when absent or on error.
+            // Snapshot generated by: bun tools/bus/export-cb-snapshot.ts
+            let entries;
+            try {
+                const resp = await fetch('./circuit-breaker-snapshot.json', { cache: 'no-cache' });
+                if (resp.ok) {
+                    const snap = await resp.json();
+                    if (Array.isArray(snap.entries) && snap.entries.length > 0) {
+                        entries = snap.entries;
+                    }
+                }
+            } catch {
+                // network or parse error — fall through to mock
+            }
+            if (!entries) entries = buildCbMockData();
 
             const closed = entries.filter(e => e.state === 'CLOSED').length;
             const open = entries.filter(e => e.state === 'OPEN').length;
diff --git a/docs/backlog/P1/B-0494-circuit-breaker-live-bus-snapshot-2026-05-14.md b/docs/backlog/P1/B-0494-circuit-breaker-live-bus-snapshot-2026-05-14.md
new file mode 100644
index 0000000000..ef3c73fc8e
--- /dev/null
+++ b/docs/backlog/P1/B-0494-circuit-breaker-live-bus-snapshot-2026-05-14.md
@@ -0,0 +1,93 @@
+---
+id: B-0494
+priority: P1
+status: open
+title: "Circuit breaker viz — slice-2: wire renderCircuitBreakerTab() to live bus snapshot"
+type: feature
+origin: B-0435 slice-2 (noted in PR #3133 body)
+created: 2026-05-14
+last_updated: 2026-05-14
+depends_on: [B-0435]
+composes_with:
+  - B-0401
+  - B-0435
+  - docs/backlog/P1/B-0213-broadcast-bus-production-hardening-2026-05-13.md
+tags: [demo, circuit-breaker, alignment-ui, github-pages, html, js, bus]
+---
+
+# B-0494 — Circuit breaker viz: slice-2 live bus snapshot
+
+## What
+
+B-0435 slice-1 (PR #3133, merged 2026-05-14) ships the circuit breaker panel with
+**static mock data**. Slice-2 wires `renderCircuitBreakerTab()` to read a committed
+JSON snapshot generated from the live `/tmp/zeta-bus/` envelopes, so the panel
+reflects actual agent activity rather than hardcoded values.
+
+## Approach
+
+Two-part change:
+
+### Part A — `tools/bus/export-cb-snapshot.ts`
+
+A TypeScript script (run via `bun tools/bus/export-cb-snapshot.ts`) that:
+
+1. Reads all non-expired envelopes from `/tmp/zeta-bus/`
+2. Groups by agent identity (`from` field, normalising surface-tagged variants
+   back to identity level, e.g. `otto-cli` → `otto`)
+3. Derives circuit-breaker state per agent:
+   - `CLOSED` — no idle heartbeats, or recent claim/work-assignment activity
+   - `HALF_OPEN` — some idle heartbeats (1–4) in the window
+   - `OPEN` — ≥5 consecutive idle heartbeats (matches `threshold: 5` in the UI)
+4. Writes output to `demo/circuit-breaker-snapshot.json`
+
+### Part B — `demo/index.html` update
+
+Change `renderCircuitBreakerTab()` from synchronous (calls `buildCbMockData()`)
+to async: first tries `fetch('./circuit-breaker-snapshot.json', {cache:'no-cache'})`,
+falls back to `buildCbMockData()` if the file is absent or the fetch fails.
+`buildCbMockData()` remains as the authoritative fallback.
+
+### Part C — committed initial snapshot
+
+Run `bun tools/bus/export-cb-snapshot.ts` once and commit the output as
+`demo/circuit-breaker-snapshot.json` so GitHub Pages visitors see real data
+from the build moment rather than the mock.
+
+## Acceptance criteria
+
+- [ ] `tools/bus/export-cb-snapshot.ts` exists and runs without errors via `bun`
+- [ ] `demo/circuit-breaker-snapshot.json` is committed (generated by the script)
+- [ ] `renderCircuitBreakerTab()` in `demo/index.html` tries the snapshot first,
+      falls back to `buildCbMockData()` — no visible change when snapshot absent
+- [ ] Panel renders correctly in both paths (snapshot present and absent)
+- [ ] `dotnet build -c Release` → 0 warnings, 0 errors
+- [ ] `bun tsc --noEmit tools/bus/export-cb-snapshot.ts` passes (TypeScript clean)
+
+## Not in scope
+
+- A live relay / HTTP server to serve fresh bus data to GitHub Pages visitors
+  (requires CORS / deployment plumbing — future slice)
+- Automated refresh of the snapshot in CI (future slice; for now, snapshot is
+  committed from a local run)
+- Adding new bus topics for richer circuit-breaker signals (B-0213 territory)
+
+## Pre-start checklist (backlog-item-start-gate)
+
+**Prior-art search (2026-05-14):**
+
+- Surfaces searched: `tools/bus/` (bus.ts, types.ts, claim.ts), `demo/index.html`
+  (renderCircuitBreakerTab, buildCbMockData), backlog for circuit-breaker +
+  live-bus + snapshot keywords
+- Queries run: grep for "circuit-breaker-snapshot", "export-cb", "live.*bus.*demo"
+- Results: No prior snapshot script or fetch path exists; `buildCbMockData()` is
+  the only current data source; `types.ts` defines the envelope schema
+- Prior-art gap confirmed: output is net-new on both script and HTML sides
+
+**Dependency check:**
+
+- `depends_on: [B-0435]` — slice-1 merged (PR #3133, 2026-05-14) ✓
+- `composes_with: B-0213` — bus hardening is a sibling, not a blocker
+- No blockers; all scaffolding in place from slice-1
+
+**Claim acquired:** otto-cli, 2026-05-14, branch `feat/b-0494-circuit-breaker-live-bus-snapshot`
diff --git a/tools/bus/export-cb-snapshot.ts b/tools/bus/export-cb-snapshot.ts
new file mode 100644
index 0000000000..4b028ae773
--- /dev/null
+++ b/tools/bus/export-cb-snapshot.ts
@@ -0,0 +1,203 @@
+#!/usr/bin/env bun
+/**
+ * export-cb-snapshot.ts — derive circuit-breaker state from live bus envelopes
+ *
+ * Reads non-expired envelopes from /tmp/zeta-bus/, groups by agent identity,
+ * derives CLOSED/HALF_OPEN/OPEN state, and writes demo/circuit-breaker-snapshot.json.
+ *
+ * Usage:
+ *   bun tools/bus/export-cb-snapshot.ts [--bus-dir <path>] [--out <path>]
+ *
+ * Defaults:
+ *   --bus-dir  /tmp/zeta-bus
+ *   --out      demo/circuit-breaker-snapshot.json  (relative to repo root)
+ *
+ * Run from any directory; paths resolve relative to this file's location.
+ *
+ * B-0494 slice-2.
+ */
+
+import { readdir, readFile, writeFile } from "fs/promises";
+import { join, resolve, dirname } from "path";
+import type { MessageEnvelope, SenderAgentId } from "./types.ts";
+
+// ── constants ─────────────────────────────────────────────────────────────────
+
+const REPO_ROOT = resolve(dirname(import.meta.path), "../..");
+const DEFAULT_BUS_DIR = "/tmp/zeta-bus";
+const DEFAULT_OUT = join(REPO_ROOT, "demo/circuit-breaker-snapshot.json");
+
+/** Circuit-breaker trips at this many consecutive idle heartbeats. */
+const THRESHOLD = 5;
+
+/** Canonical identity → display metadata. Order determines output order. */
+const AGENT_META: Record<string, { model: string; harness: string }> = {
+  otto: { model: "Otto", harness: "Claude Code" },
+  alexa: { model: "Alexa", harness: "Kiro / Qwen" },
+  lior: { model: "Lior", harness: "Gemini" },
+  vera: { model: "Vera", harness: "Codex / GPT" },
+  riven: { model: "Riven", harness: "Grok" },
+};
+
+/** Known identity prefixes in longest-match order. */
+const IDENTITIES = Object.keys(AGENT_META);
+
+// ── helpers ───────────────────────────────────────────────────────────────────
+
+/** Normalise a surface-tagged sender ID back to identity level.
+ *  e.g. "otto-cli" → "otto", "lior-gemini" → "lior", "otto" → "otto"
+ */
+function toIdentity(from: SenderAgentId): string | null {
+  for (const id of IDENTITIES) {
+    if (from === id || from.startsWith(id + "-")) return id;
+  }
+  return null;
+}
+
+async function readEnvelopes(busDir: string): Promise<MessageEnvelope[]> {
+  const now = Date.now();
+  // Let readdir throw — silent suppression would turn a missing or unreadable bus
+  // directory into a "healthy/no recent activity" snapshot, hiding misconfiguration.
+  const files = await readdir(busDir);
+  const envelopes: MessageEnvelope[] = [];
+  for (const file of files) {
+    if (!file.endsWith(".json")) continue;
+    try {
+      const raw = JSON.parse(await readFile(join(busDir, file), "utf8")) as MessageEnvelope;
+      if (new Date(raw.expiresAt).getTime() > now) {
+        envelopes.push(raw);
+      }
+    } catch {
+      // corrupted or partial file — skip
+    }
+  }
+  return envelopes;
+}
+
+// ── circuit-breaker derivation ────────────────────────────────────────────────
+
+type CbState = "CLOSED" | "HALF_OPEN" | "OPEN";
+
+interface CbEntry {
+  model: string;
+  harness: string;
+  state: CbState;
+  consecutiveFailures: number;
+  threshold: number;
+  lastCheck: string;
+  note: string;
+}
+
+function deriveEntry(
+  identity: string,
+  meta: { model: string; harness: string },
+  envelopes: MessageEnvelope[]
+): CbEntry {
+  // Collect envelopes from this identity (any surface variant)
+  const own = envelopes
+    .filter(e => toIdentity(e.from) === identity)
+    .sort((a, b) => new Date(b.timestamp).getTime() - new Date(a.timestamp).getTime());
+
+  const lastCheck = own[0]?.timestamp ?? new Date().toISOString();
+
+  if (own.length === 0) {
+    return {
+      model: meta.model,
+      harness: meta.harness,
+      state: "CLOSED",
+      consecutiveFailures: 0,
+      threshold: THRESHOLD,
+      lastCheck,
+      note: "No recent bus activity — assuming healthy",
+    };
+  }
+
+  // Walk newest-first and count the trailing run of idle heartbeats.
+  // Stop at the first envelope that is not an idle heartbeat so that a working
+  // signal resets the streak (e.g. idle→working→idle→idle counts 2, not 3).
+  let consecutiveIdle = 0;
+  for (const e of own) {
+    if (e.topic === "heartbeat" && e.payload.status === "idle") {
+      consecutiveIdle++;
+    } else {
+      break;
+    }
+  }
+
+  // Any positive signal: active claim-acquire, work-assignment, or working heartbeat.
+  // Claim-release does NOT count — an agent relinquishing work should not be treated
+  // as a health signal (it may be about to go idle).
+  const hasWorkSignal = own.some(
+    e =>
+      (e.topic === "claim" && e.payload.action === "claim") ||
+      e.topic === "work-assignment" ||
+      (e.topic === "heartbeat" && e.payload.status === "working")
+  );
+
+  let state: CbState;
+  let note: string;
+
+  if (consecutiveIdle >= THRESHOLD) {
+    state = "OPEN";
+    note = `Tripped — ${consecutiveIdle} consecutive idle heartbeats exceeded threshold (${THRESHOLD})`;
+  } else if (consecutiveIdle > 0) {
+    state = "HALF_OPEN";
+    note = `${consecutiveIdle} consecutive idle heartbeat(s) — watching; threshold ${THRESHOLD}`;
+  } else if (hasWorkSignal) {
+    state = "CLOSED";
+    note = "Active work detected — normal operation";
+  } else {
+    state = "CLOSED";
+    note = "Bus activity present; no idle pattern detected";
+  }
+
+  return {
+    model: meta.model,
+    harness: meta.harness,
+    state,
+    consecutiveFailures: consecutiveIdle,
+    threshold: THRESHOLD,
+    lastCheck,
+    note,
+  };
+}
+
+// ── main ──────────────────────────────────────────────────────────────────────
+
+async function main() {
+  const args = process.argv.slice(2);
+  const busDir = args.includes("--bus-dir")
+    ? (args[args.indexOf("--bus-dir") + 1] ?? DEFAULT_BUS_DIR)
+    : DEFAULT_BUS_DIR;
+  const outPath = args.includes("--out")
+    ? (args[args.indexOf("--out") + 1] ?? DEFAULT_OUT)
+    : DEFAULT_OUT;
+
+  let envelopes: MessageEnvelope[];
+  try {
+    envelopes = await readEnvelopes(busDir);
+  } catch (err) {
+    const msg = err instanceof Error ? err.message : String(err);
+    console.error(`Cannot read bus directory ${busDir}: ${msg}`);
+    process.exit(1);
+  }
+
+  const entries: CbEntry[] = Object.entries(AGENT_META).map(([id, meta]) =>
+    deriveEntry(id, meta, envelopes)
+  );
+
+  const snapshot = {
+    generatedAt: new Date().toISOString(),
+    source: "tools/bus/export-cb-snapshot.ts",
+    busDir,
+    envelopeCount: envelopes.length,
+    entries,
+  };
+
+  await writeFile(outPath, JSON.stringify(snapshot, null, 2) + "\n");
+  console.log(`Wrote ${entries.length} entries (${envelopes.length} envelopes) → ${outPath}`);
+}
+
+if (import.meta.main) {
+  main();
+}