diff --git a/.gitignore b/.gitignore
index 060aac8..2a4faed 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,9 +11,13 @@ coverage
 !.env.*.example
 
 # Local data / caches (matches at any depth — covers
-# deploy/simulation/data/, indexer/data/, etc.)
+# deploy/simulation/data/, indexer/data/, wallet-monitor/data/, etc.)
 data/
 *.log
+
+# wallet-monitor: the real wallet list holds production mainnet addresses —
+# keep it out of git; only wallets.example.json is committed.
+wallet-monitor/wallets.json
 .vitest-cache
 .DS_Store
 
diff --git a/deploy/mainnet/docker-compose.wallet-monitor.yml b/deploy/mainnet/docker-compose.wallet-monitor.yml
new file mode 100644
index 0000000..5417107
--- /dev/null
+++ b/deploy/mainnet/docker-compose.wallet-monitor.yml
@@ -0,0 +1,40 @@
+# deploy/mainnet/docker-compose.wallet-monitor.yml — Wallet-balance Slack alerter — MAINNET
+#
+# A ONE-SHOT, not a long-running server: it checks every wallet listed in
+# wallet-monitor/wallets.json, posts a Slack alert for any below threshold,
+# then exits. There is no port, healthcheck, or restart policy.
+#
+# Invoked hourly by cron (see /etc/cron.d/wallet-monitor):
+#   cd /root/agents-marketplace && \
+#   docker compose -f deploy/mainnet/docker-compose.wallet-monitor.yml run --rm wallet-monitor
+#
+# One-time setup on the box:
+#   1) populate wallet-monitor/wallets.json (the 7 addresses — see the package README)
+#   2) create wallet-monitor/.env with SLACK_WEBHOOK_URL=...
+#   3) docker compose -f deploy/mainnet/docker-compose.wallet-monitor.yml build
+#   4) smoke test: docker compose -f ... run --rm -e TEST=1 wallet-monitor
+
+name: marketplace-mainnet-wallet-monitor
+
+services:
+  wallet-monitor:
+    build:
+      context: ../..
+      dockerfile: wallet-monitor/Dockerfile
+    env_file:
+      - path: ../../wallet-monitor/.env
+        required: false
+    environment:
+      # Mainnet-only service; pin the public Ogmios endpoint explicitly.
+      # (config.ts also defaults to this, but this compose is mainnet-specific.)
+      OGMIOS_URL: https://ogmios.vector.mainnet.apexfusion.org
+    volumes:
+      # The wallet list is read-only. The dedup state dir is writable and
+      # persists across runs (data/ is gitignored).
+      - ../../wallet-monitor/wallets.json:/repo/wallet-monitor/wallets.json:ro
+      - ../../wallet-monitor/data:/repo/wallet-monitor/data
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "3"
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 9f42f63..1432f74 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -290,6 +290,16 @@ importers:
         specifier: ^5.7.2
         version: 5.9.3
 
+  wallet-monitor:
+    dependencies:
+      '@marketplace/shared':
+        specifier: workspace:*
+        version: link:../packages/shared
+    devDependencies:
+      typescript:
+        specifier: ^5.7.2
+        version: 5.9.3
+
 packages:
 
   '@adobe/css-tools@4.4.4':
diff --git a/pnpm-workspace.yaml b/pnpm-workspace.yaml
index c88c1e3..a1ea6a7 100644
--- a/pnpm-workspace.yaml
+++ b/pnpm-workspace.yaml
@@ -4,3 +4,4 @@ packages:
   - "supplier"
   - "indexer"
   - "indexer-ui"
+  - "wallet-monitor"
diff --git a/wallet-monitor/.env.example b/wallet-monitor/.env.example
new file mode 100644
index 0000000..c80710f
--- /dev/null
+++ b/wallet-monitor/.env.example
@@ -0,0 +1,19 @@
+# wallet-monitor/.env — copy to wallet-monitor/.env and fill in.
+# (.env is gitignored; only this .env.example template is committed.)
+
+# REQUIRED — Slack Incoming Webhook URL alerts are POSTed to.
+# Create one at https://api.slack.com/messaging/webhooks
+SLACK_WEBHOOK_URL=https://hooks.slack.com/services/XXXX/YYYY/ZZZZ
+
+# OPTIONAL — Ogmios HTTP endpoint used to read balances.
+# Defaults to the mainnet public endpoint (also pinned in the compose file).
+# OGMIOS_URL=https://ogmios.vector.mainnet.apexfusion.org
+
+# OPTIONAL — override the wallets.json default threshold / reminder cadence
+# without editing the mounted wallets file.
+# DEFAULT_MIN_AP3X=10
+# REMINDER_HOURS=6
+
+# OPTIONAL — paths inside the container (defaults shown; bind-mounted by compose).
+# WALLETS_PATH=/repo/wallet-monitor/wallets.json
+# STATE_PATH=/repo/wallet-monitor/data/state.json
diff --git a/wallet-monitor/Dockerfile b/wallet-monitor/Dockerfile
new file mode 100644
index 0000000..708cfc0
--- /dev/null
+++ b/wallet-monitor/Dockerfile
@@ -0,0 +1,70 @@
+# syntax=docker/dockerfile:1.7
+#
+# wallet-monitor/Dockerfile — image for the one-shot wallet-balance alerter.
+#
+# Same multi-stage tsx strategy as supplier/Dockerfile: install workspace deps
+# in a builder stage, ship source + node_modules to a slim runtime stage, run
+# the entry point with tsx (we do NOT compile ahead-of-time because
+# @marketplace/shared exports .ts via package.json#exports — see supplier/Dockerfile).
+#
+# This is NOT a long-running server: there is no HEALTHCHECK / EXPOSE. It's
+# invoked one-shot by cron: `docker compose -f deploy/mainnet/docker-compose.wallet-monitor.yml run --rm wallet-monitor`.
+#
+# Build context MUST be the repo root so pnpm can resolve workspace deps:
+#   docker build -f wallet-monitor/Dockerfile -t marketplace-wallet-monitor .
+
+ARG NODE_VERSION=20.19.0
+
+# ─── builder ──────────────────────────────────────────────────────────────
+FROM node:${NODE_VERSION}-alpine AS builder
+WORKDIR /repo
+
+# pnpm via corepack — lockfile pins pnpm@10.33.2.
+RUN corepack enable && corepack prepare pnpm@10.33.2 --activate
+
+# Workspace manifests first to maximise layer cache reuse. pnpm-lock.yaml indexes
+# the whole workspace, so every package's manifest must be present even though
+# --filter only installs what wallet-monitor needs.
+COPY pnpm-workspace.yaml pnpm-lock.yaml package.json tsconfig.base.json .npmrc ./
+COPY packages/shared/package.json ./packages/shared/package.json
+COPY wallet-monitor/package.json ./wallet-monitor/package.json
+COPY buyer/package.json ./buyer/package.json
+COPY supplier/package.json ./supplier/package.json
+COPY indexer/package.json ./indexer/package.json
+
+# Install only what wallet-monitor needs (+ its transitive workspace deps, i.e.
+# @marketplace/shared and the chain stack).
+RUN pnpm install --frozen-lockfile --filter '@marketplace/wallet-monitor...'
+
+# libsodium-wrappers-sumo patch — @marketplace/shared/chain re-exports
+# LiveOgmiosProvider, which pulls @lucid-evolution/lucid → CML → the broken
+# relative `import "./libsodium-sumo.mjs"`. Copy the file into the wrapper's
+# expected path. Identical to supplier/Dockerfile. ARCHITECTURE.md §9 #16.
+RUN set -e \
+ && SRC=$(find node_modules/.pnpm -name "libsodium-sumo.mjs" -path "*/libsodium-sumo/dist/*" 2>/dev/null | head -1) \
+ && DST=$(find node_modules/.pnpm -type d -path "*libsodium-wrappers-sumo@*/node_modules/libsodium-wrappers-sumo/dist/modules-sumo-esm" 2>/dev/null | head -1) \
+ && [ -n "$SRC" ] && [ -n "$DST" ] || (echo "FATAL: libsodium-sumo paths not resolved" && exit 1) \
+ && cp "$SRC" "$DST/" \
+ && echo "patched libsodium wrapper: $DST/libsodium-sumo.mjs"
+
+# Copy the actual source — shared + wallet-monitor.
+COPY packages/shared ./packages/shared
+COPY wallet-monitor ./wallet-monitor
+
+# ─── runtime ──────────────────────────────────────────────────────────────
+FROM node:${NODE_VERSION}-alpine AS runtime
+WORKDIR /repo
+
+# tini for signal-forwarding (graceful SIGTERM → process.exit).
+RUN apk add --no-cache tini
+
+COPY --from=builder /repo /repo
+
+# Run as root (the default for this image): the one-shot writes its dedup state
+# to a bind-mounted host dir (/repo/wallet-monitor/data), which is typically
+# root-owned on the box. No ports, no privileges to drop for a server.
+ENV NODE_ENV=production
+
+# tsx is hoisted to /repo/node_modules/.bin by pnpm — invoke via the workspace bin.
+ENTRYPOINT ["/sbin/tini", "--"]
+CMD ["node_modules/.bin/tsx", "wallet-monitor/src/index.ts"]
diff --git a/wallet-monitor/README.md b/wallet-monitor/README.md
new file mode 100644
index 0000000..8dce549
--- /dev/null
+++ b/wallet-monitor/README.md
@@ -0,0 +1,49 @@
+# wallet-monitor
+
+One-shot wallet-balance Slack alerter for the `vector-marketplace` mainnet box.
+
+Checks every wallet in `wallets.json` against a threshold (default **10 APEX**),
+posts a combined Slack message when any wallet is below it, re-reminds every
+`reminder_hours` while a wallet stays low, and posts a recovery message when it
+climbs back above. Balances are read from Ogmios via
+`ReadOnlyOgmiosProvider` (`@marketplace/shared/chain`) — the same client behind
+the buyer's `/v1/wallet/balance` and `buyer/scripts/monitor-wallets.ts`.
+
+It is **not** a long-running server: it runs once and exits, invoked hourly by
+cron through `docker compose run --rm`. Dedup state lives in
+`wallet-monitor/data/state.json` (bind-mounted, gitignored).
+
+## Files
+
+| File | Purpose |
+| --- | --- |
+| `src/index.ts` | one-shot check + classify + Slack post + state |
+| `src/config.ts` | env loading + `wallets.json` parsing/validation |
+| `src/slack.ts` | `postSlack()` Incoming-Webhook helper |
+| `wallets.json` | the wallet list + thresholds (gitignored; see `wallets.example.json`) |
+| `.env` | `SLACK_WEBHOOK_URL` (gitignored; see `.env.example`) |
+
+## Deploy on the box (one-time)
+
+1. **Generate `wallets.json`.** From a laptop with SSH access, run
+   `pnpm tsx buyer/scripts/monitor-wallets.ts --json` and copy the `address` of
+   each of the 7 `*@vector-marketplace` rows into `wallet-monitor/wallets.json`
+   (start from `wallets.example.json`). Per-wallet `min_ap3x` is optional.
+2. **Set the webhook.** `cp wallet-monitor/.env.example wallet-monitor/.env` and
+   fill in `SLACK_WEBHOOK_URL`.
+3. **Build.** `docker compose -f deploy/mainnet/docker-compose.wallet-monitor.yml build`
+4. **Smoke-test the webhook.**
+   `docker compose -f deploy/mainnet/docker-compose.wallet-monitor.yml run --rm -e TEST=1 wallet-monitor`
+   → expect a "✅ wallet-monitor configured" message in Slack.
+5. **Schedule it.** Add `/etc/cron.d/wallet-monitor`:
+   ```cron
+   0 * * * * root cd /root/agents-marketplace && docker compose -f deploy/mainnet/docker-compose.wallet-monitor.yml run --rm wallet-monitor >> /var/log/wallet-monitor.log 2>&1
+   ```
+
+## Behaviour notes
+
+- **Failures don't alert.** If Ogmios is unreachable or a wallet query errors,
+  the run logs to stderr and exits non-zero — no Slack noise — and that wallet's
+  state is left untouched (an Ogmios blip is never mistaken for a recovery).
+- **State only advances on a successful post.** A failed Slack POST leaves the
+  state file unchanged so the alert retries on the next run.
diff --git a/wallet-monitor/package.json b/wallet-monitor/package.json
new file mode 100644
index 0000000..b1f2aaa
--- /dev/null
+++ b/wallet-monitor/package.json
@@ -0,0 +1,16 @@
+{
+  "name": "@marketplace/wallet-monitor",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "typecheck": "tsc --noEmit",
+    "check": "tsx src/index.ts"
+  },
+  "dependencies": {
+    "@marketplace/shared": "workspace:*"
+  },
+  "devDependencies": {
+    "typescript": "^5.7.2"
+  }
+}
diff --git a/wallet-monitor/src/config.ts b/wallet-monitor/src/config.ts
new file mode 100644
index 0000000..489084c
--- /dev/null
+++ b/wallet-monitor/src/config.ts
@@ -0,0 +1,156 @@
+/**
+ * wallet-monitor/src/config.ts — env + wallets-file loading.
+ *
+ * Env vars:
+ *   SLACK_WEBHOOK_URL  — (required) Slack Incoming Webhook URL to post alerts to.
+ *   OGMIOS_URL         — Ogmios HTTP endpoint. Default mainnet public endpoint.
+ *   WALLETS_PATH       — path to wallets.json. Default /repo/wallet-monitor/wallets.json.
+ *   STATE_PATH         — path to the dedup state file (read/written each run).
+ *                        Default /repo/wallet-monitor/data/state.json.
+ *   DEFAULT_MIN_AP3X   — (optional) overrides wallets.json default_min_ap3x.
+ *   REMINDER_HOURS     — (optional) overrides wallets.json reminder_hours.
+ *   TEST               — "1" posts a one-line "configured" message to Slack and exits.
+ *
+ * wallets.json owns the wallet list + the default threshold / reminder cadence;
+ * the env overrides exist only so an operator can retune without editing the
+ * mounted wallets file.
+ */
+
+const DEFAULT_OGMIOS_URL = "https://ogmios.vector.mainnet.apexfusion.org";
+const DEFAULT_WALLETS_PATH = "/repo/wallet-monitor/wallets.json";
+const DEFAULT_STATE_PATH = "/repo/wallet-monitor/data/state.json";
+
+const FALLBACK_DEFAULT_MIN_AP3X = 10;
+const FALLBACK_REMINDER_HOURS = 6;
+
+export interface EnvConfig {
+  slackWebhookUrl: string;
+  ogmiosUrl: string;
+  walletsPath: string;
+  statePath: string;
+  /** When set, overrides the wallets-file default_min_ap3x. */
+  defaultMinAp3xOverride: number | null;
+  /** When set, overrides the wallets-file reminder_hours. */
+  reminderHoursOverride: number | null;
+  testMode: boolean;
+}
+
+export interface WalletEntry {
+  name: string;
+  address: string;
+  /** Per-wallet threshold override (APEX). Falls back to the file default. */
+  minAp3x?: number;
+}
+
+export interface WalletsFile {
+  defaultMinAp3x: number;
+  reminderHours: number;
+  wallets: WalletEntry[];
+}
+
+function requireField(env: Record<string, string | undefined>, name: string): string {
+  const v = env[name];
+  if (v === undefined || v === null || v === "") {
+    throw new Error(`loadConfig: missing required env var ${name}`);
+  }
+  return v;
+}
+
+function nonEmpty(env: Record<string, string | undefined>, name: string, fallback: string): string {
+  const v = env[name];
+  return v !== undefined && v !== "" ? v : fallback;
+}
+
+function parseOptionalPositiveNumber(
+  raw: string | undefined,
+  name: string,
+): number | null {
+  if (raw === undefined || raw === "") return null;
+  const n = Number(raw);
+  if (!Number.isFinite(n) || n <= 0) {
+    throw new Error(`loadConfig: ${name} must be a positive number, got "${raw}"`);
+  }
+  return n;
+}
+
+export function loadConfig(env: Record<string, string | undefined>): EnvConfig {
+  const slackWebhookUrl = requireField(env, "SLACK_WEBHOOK_URL");
+  return {
+    slackWebhookUrl,
+    ogmiosUrl: nonEmpty(env, "OGMIOS_URL", DEFAULT_OGMIOS_URL),
+    walletsPath: nonEmpty(env, "WALLETS_PATH", DEFAULT_WALLETS_PATH),
+    statePath: nonEmpty(env, "STATE_PATH", DEFAULT_STATE_PATH),
+    defaultMinAp3xOverride: parseOptionalPositiveNumber(env.DEFAULT_MIN_AP3X, "DEFAULT_MIN_AP3X"),
+    reminderHoursOverride: parseOptionalPositiveNumber(env.REMINDER_HOURS, "REMINDER_HOURS"),
+    testMode: env.TEST === "1",
+  };
+}
+
+// ── wallets.json parsing ─────────────────────────────────────────────────
+
+function isObject(v: unknown): v is Record<string, unknown> {
+  return typeof v === "object" && v !== null && !Array.isArray(v);
+}
+
+function parsePositiveNumberField(raw: unknown, label: string, fallback: number): number {
+  if (raw === undefined) return fallback;
+  if (typeof raw !== "number" || !Number.isFinite(raw) || raw <= 0) {
+    throw new Error(`wallets.json: ${label} must be a positive number`);
+  }
+  return raw;
+}
+
+/**
+ * Validate + normalise the parsed wallets.json. Pure (takes already-parsed
+ * JSON) so it's easy to unit-test. Snake_case JSON keys → camelCase fields.
+ */
+export function parseWalletsFile(raw: unknown): WalletsFile {
+  if (!isObject(raw)) {
+    throw new Error("wallets.json: top-level value must be an object");
+  }
+  const defaultMinAp3x = parsePositiveNumberField(
+    raw.default_min_ap3x,
+    "default_min_ap3x",
+    FALLBACK_DEFAULT_MIN_AP3X,
+  );
+  const reminderHours = parsePositiveNumberField(
+    raw.reminder_hours,
+    "reminder_hours",
+    FALLBACK_REMINDER_HOURS,
+  );
+
+  const walletsRaw = raw.wallets;
+  if (!Array.isArray(walletsRaw) || walletsRaw.length === 0) {
+    throw new Error("wallets.json: 'wallets' must be a non-empty array");
+  }
+
+  const seen = new Set<string>();
+  const wallets: WalletEntry[] = walletsRaw.map((w, i) => {
+    if (!isObject(w)) {
+      throw new Error(`wallets.json: wallets[${i}] must be an object`);
+    }
+    const name = w.name;
+    const address = w.address;
+    if (typeof name !== "string" || name === "") {
+      throw new Error(`wallets.json: wallets[${i}].name must be a non-empty string`);
+    }
+    if (typeof address !== "string" || !address.startsWith("addr")) {
+      throw new Error(`wallets.json: wallets[${i}].address must be a bech32 address (addr…)`);
+    }
+    if (seen.has(name)) {
+      throw new Error(`wallets.json: duplicate wallet name "${name}"`);
+    }
+    seen.add(name);
+
+    const entry: WalletEntry = { name, address };
+    if (w.min_ap3x !== undefined) {
+      if (typeof w.min_ap3x !== "number" || !Number.isFinite(w.min_ap3x) || w.min_ap3x <= 0) {
+        throw new Error(`wallets.json: wallets[${i}].min_ap3x must be a positive number`);
+      }
+      entry.minAp3x = w.min_ap3x;
+    }
+    return entry;
+  });
+
+  return { defaultMinAp3x, reminderHours, wallets };
+}
diff --git a/wallet-monitor/src/index.ts b/wallet-monitor/src/index.ts
new file mode 100644
index 0000000..80721d6
--- /dev/null
+++ b/wallet-monitor/src/index.ts
@@ -0,0 +1,188 @@
+/**
+ * wallet-monitor/src/index.ts — one-shot wallet-balance Slack alerter.
+ *
+ * Runs once and exits (invoked hourly by cron via `docker compose run --rm`).
+ * For each wallet in wallets.json: query its on-chain balance via Ogmios, and
+ * if it's below threshold post a combined Slack alert. A persisted state file
+ * dedups so a still-low wallet only re-alerts every `reminder_hours`, and a
+ * recovery message fires when a wallet climbs back above its threshold.
+ *
+ * Reuses ReadOnlyOgmiosProvider from @marketplace/shared/chain — the same
+ * client behind the buyer's /v1/wallet/balance and buyer/scripts/monitor-wallets.ts.
+ */
+/* eslint-disable no-console */
+
+import { readFileSync, writeFileSync, mkdirSync, renameSync } from "fs";
+import { dirname } from "path";
+import { ReadOnlyOgmiosProvider } from "@marketplace/shared/chain";
+import { loadConfig, parseWalletsFile, type WalletEntry } from "./config.js";
+import { postSlack } from "./slack.js";
+
+const LOVELACE_PER_AP3X = 1_000_000;
+const MS_PER_HOUR = 3_600_000;
+
+type Status = "ok" | "low";
+
+interface WalletState {
+  status: Status;
+  /** Epoch ms of the last alert we successfully posted for this wallet. */
+  lastAlertMs: number;
+}
+
+type StateFile = Record<string, WalletState>;
+
+interface CheckedWallet {
+  name: string;
+  address: string;
+  minLovelace: bigint;
+  /** null when the balance query failed. */
+  lovelace: bigint | null;
+  error: string | null;
+}
+
+// ── helpers ───────────────────────────────────────────────────────────────
+
+function ap3xToLovelace(ap3x: number): bigint {
+  return BigInt(Math.round(ap3x * LOVELACE_PER_AP3X));
+}
+
+function fmtAp3x(lovelace: bigint): string {
+  return (Number(lovelace) / LOVELACE_PER_AP3X).toFixed(2);
+}
+
+function shortAddr(a: string): string {
+  return a.length <= 18 ? a : `${a.slice(0, 10)}…${a.slice(-6)}`;
+}
+
+function loadState(path: string): StateFile {
+  try {
+    const obj: unknown = JSON.parse(readFileSync(path, "utf-8"));
+    if (obj && typeof obj === "object" && !Array.isArray(obj)) {
+      return obj as StateFile;
+    }
+    return {};
+  } catch {
+    // Missing / unreadable / malformed state → start clean.
+    return {};
+  }
+}
+
+function saveState(path: string, state: StateFile): void {
+  mkdirSync(dirname(path), { recursive: true });
+  const tmp = `${path}.tmp`;
+  writeFileSync(tmp, `${JSON.stringify(state, null, 2)}\n`);
+  renameSync(tmp, path); // atomic replace
+}
+
+// ── main ────────────────────────────────────────────────────────────────
+
+async function main(): Promise<void> {
+  const cfg = loadConfig(process.env);
+
+  // TEST mode: confirm the webhook works, then exit.
+  if (cfg.testMode) {
+    const r = await postSlack(
+      cfg.slackWebhookUrl,
+      "✅ *wallet-monitor configured* — test message from the vector-marketplace box.",
+    );
+    if (!r.ok) {
+      console.error(`[wallet-monitor] test Slack post failed: ${r.error}`);
+      process.exitCode = 1;
+      return;
+    }
+    console.log("[wallet-monitor] test Slack post ok");
+    return;
+  }
+
+  const walletsFile = parseWalletsFile(
+    JSON.parse(readFileSync(cfg.walletsPath, "utf-8")) as unknown,
+  );
+  const defaultMinAp3x = cfg.defaultMinAp3xOverride ?? walletsFile.defaultMinAp3x;
+  const reminderMs = (cfg.reminderHoursOverride ?? walletsFile.reminderHours) * MS_PER_HOUR;
+
+  const provider = new ReadOnlyOgmiosProvider({ ogmiosUrl: cfg.ogmiosUrl });
+
+  const checked: CheckedWallet[] = await Promise.all(
+    walletsFile.wallets.map(async (w: WalletEntry): Promise<CheckedWallet> => {
+      const minLovelace = ap3xToLovelace(w.minAp3x ?? defaultMinAp3x);
+      try {
+        const utxos = await provider.queryUtxosByAddress(w.address);
+        const lovelace = utxos.reduce((a, u) => a + BigInt(u.lovelace), 0n);
+        return { name: w.name, address: w.address, minLovelace, lovelace, error: null };
+      } catch (e) {
+        const error = e instanceof Error ? e.message : String(e);
+        console.error(`[wallet-monitor] query failed for ${w.name} (${w.address}): ${error}`);
+        return { name: w.name, address: w.address, minLovelace, lovelace: null, error };
+      }
+    }),
+  );
+
+  const anyQueryFailed = checked.some((c) => c.error !== null);
+
+  const prevState = loadState(cfg.statePath);
+  const now = Date.now();
+  const nextState: StateFile = { ...prevState };
+
+  const lowLines: string[] = [];
+  const recoveredLines: string[] = [];
+
+  for (const c of checked) {
+    // Skip wallets we couldn't query — leave their state untouched so we don't
+    // mistake an Ogmios blip for a recovery.
+    if (c.error !== null || c.lovelace === null) continue;
+
+    const prev = prevState[c.name];
+    const isLow = c.lovelace < c.minLovelace;
+
+    if (isLow) {
+      const wasLow = prev?.status === "low";
+      const due = !wasLow || now - (prev?.lastAlertMs ?? 0) >= reminderMs;
+      if (due) {
+        lowLines.push(
+          `🔴 ${c.name}  ${fmtAp3x(c.lovelace)} / ${fmtAp3x(c.minLovelace)} APEX  ${shortAddr(c.address)}`,
+        );
+        nextState[c.name] = { status: "low", lastAlertMs: now };
+      } else {
+        // Still low but the reminder window hasn't elapsed — keep prev as-is.
+        nextState[c.name] = prev ?? { status: "low", lastAlertMs: now };
+      }
+    } else {
+      if (prev?.status === "low") {
+        recoveredLines.push(`✅ ${c.name}  ${fmtAp3x(c.lovelace)} APEX (recovered)`);
+      }
+      nextState[c.name] = { status: "ok", lastAlertMs: prev?.lastAlertMs ?? 0 };
+    }
+  }
+
+  const needPost = lowLines.length > 0 || recoveredLines.length > 0;
+
+  if (needPost) {
+    const title =
+      lowLines.length > 0
+        ? "⚠️ *Wallet balance alert* — vector-marketplace"
+        : "✅ *Wallet balance recovered* — vector-marketplace";
+    const text = [title, ...lowLines, ...recoveredLines].join("\n");
+
+    const r = await postSlack(cfg.slackWebhookUrl, text);
+    if (!r.ok) {
+      // Leave state untouched so the alert retries next run.
+      console.error(`[wallet-monitor] Slack post failed (state unchanged): ${r.error}`);
+      process.exitCode = 1;
+      return;
+    }
+    console.log(`[wallet-monitor] posted: ${lowLines.length} low, ${recoveredLines.length} recovered`);
+  } else {
+    console.log("[wallet-monitor] all wallets healthy — no Slack post");
+  }
+
+  // Persist the new state (records ok/low statuses + advanced reminder stamps).
+  // Only reached when there was nothing to post or the post succeeded.
+  saveState(cfg.statePath, nextState);
+
+  if (anyQueryFailed) process.exitCode = 1;
+}
+
+main().catch((e) => {
+  console.error("[wallet-monitor] fatal:", e instanceof Error ? e.stack ?? e.message : e);
+  process.exit(1);
+});
diff --git a/wallet-monitor/src/slack.ts b/wallet-monitor/src/slack.ts
new file mode 100644
index 0000000..d08a08b
--- /dev/null
+++ b/wallet-monitor/src/slack.ts
@@ -0,0 +1,42 @@
+/**
+ * wallet-monitor/src/slack.ts — post a message to a Slack Incoming Webhook.
+ *
+ * Never throws: returns { ok, error } so the caller can decide whether to
+ * advance the dedup state. A failed post leaves state untouched so the alert
+ * retries on the next run.
+ */
+
+export interface SlackResult {
+  ok: boolean;
+  error?: string;
+}
+
+const TIMEOUT_MS = 15_000;
+
+export async function postSlack(
+  webhookUrl: string,
+  text: string,
+  fetchImpl: typeof globalThis.fetch = globalThis.fetch,
+): Promise<SlackResult> {
+  try {
+    const init: RequestInit = {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ text }),
+    };
+    if (typeof AbortSignal !== "undefined" && typeof AbortSignal.timeout === "function") {
+      init.signal = AbortSignal.timeout(TIMEOUT_MS);
+    }
+    const res = await fetchImpl(webhookUrl, init);
+    if (!res.ok) {
+      const body = await res.text().catch(() => "");
+      return {
+        ok: false,
+        error: `Slack HTTP ${res.status} ${res.statusText}${body ? ` — ${body.slice(0, 200)}` : ""}`,
+      };
+    }
+    return { ok: true };
+  } catch (e) {
+    return { ok: false, error: e instanceof Error ? e.message : String(e) };
+  }
+}
diff --git a/wallet-monitor/tsconfig.json b/wallet-monitor/tsconfig.json
new file mode 100644
index 0000000..56d0e64
--- /dev/null
+++ b/wallet-monitor/tsconfig.json
@@ -0,0 +1,8 @@
+{
+  "extends": "../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "./src",
+    "outDir": "./dist"
+  },
+  "include": ["src/**/*.ts"]
+}
diff --git a/wallet-monitor/wallets.example.json b/wallet-monitor/wallets.example.json
new file mode 100644
index 0000000..0c4496b
--- /dev/null
+++ b/wallet-monitor/wallets.example.json
@@ -0,0 +1,13 @@
+{
+  "default_min_ap3x": 10,
+  "reminder_hours": 6,
+  "wallets": [
+    { "name": "buyer",             "address": "addr1_REPLACE_ME" },
+    { "name": "supplier-ollama",   "address": "addr1_REPLACE_ME" },
+    { "name": "supplier-gpt",      "address": "addr1_REPLACE_ME" },
+    { "name": "supplier-deepseek", "address": "addr1_REPLACE_ME" },
+    { "name": "supplier-kimi",     "address": "addr1_REPLACE_ME" },
+    { "name": "supplier-kimi-chat","address": "addr1_REPLACE_ME" },
+    { "name": "supplier-tts",      "address": "addr1_REPLACE_ME", "min_ap3x": 8 }
+  ]
+}