diff --git a/docs/ops.md b/docs/ops.md
index 2948e41b..1effa385 100644
--- a/docs/ops.md
+++ b/docs/ops.md
@@ -1027,9 +1027,19 @@ wrangler flagship flags update 8371bfe7-9767-4b4d-b75a-37b94d2724f7 \
   attachment-index-shadow --default on
 ```
 
-**Reading it:** one Workers Logs line per real sync while the flag is on
+**Reading it:** the quickest way is the report script, which prints match
+rate, how many syncs had real attachments, and the most common mismatched
+keys over a window:
+
+```bash
+CLOUDFLARE_API_TOKEN=… node scripts/attachment-index-shadow-report.mjs --hours 24
+```
+
+Under the hood: one Workers Logs line per real sync while the flag is on
 (link adoption's pre-write baseline gather opts out), `component:
-"attachment-index"`, `event: "shadow"`. `match: true` means the index and the
+"attachment-index"`, `event: "shadow"`. The line has no `message` field, so
+the Workers Logs UI shows an empty message and a message-text search finds
+nothing; filter on the parsed `component` field instead. `match: true` means the index and the
 post-detach fan-out agree. `missing` lists keys the fan-out rendered that the
 index lacks: a write path the index misses, or an object that predates #938
 and needs the backfill. `extra` lists index rows the fan-out did not render,
diff --git a/scripts/attachment-index-shadow-report.mjs b/scripts/attachment-index-shadow-report.mjs
new file mode 100644
index 00000000..220a26dd
--- /dev/null
+++ b/scripts/attachment-index-shadow-report.mjs
@@ -0,0 +1,145 @@
+#!/usr/bin/env node
+/**
+ * Summarizes the attachment-index shadow lines (#934 phase 2) from Workers
+ * Logs: match rate, how many syncs had real attachments, and the most
+ * common `missing` / `extra` keys, over the last N hours.
+ *
+ *   CLOUDFLARE_API_TOKEN=… node scripts/attachment-index-shadow-report.mjs [--hours 24] [--json]
+ *
+ * The token needs Workers Observability read on the account. Account id
+ * defaults to the production account; override with CLOUDFLARE_ACCOUNT_ID.
+ *
+ * Shadow lines carry no `message` field, so they are matched on the parsed
+ * `component` / `event` fields — a message-text search finds nothing.
+ */
+
+const args = process.argv.slice(2);
+const flag = (name, fallback) => {
+  const i = args.indexOf(name);
+  return i === -1 ? fallback : args[i + 1];
+};
+const hours = Number(flag("--hours", "24"));
+const asJson = args.includes("--json");
+const token = process.env.CLOUDFLARE_API_TOKEN;
+const account = process.env.CLOUDFLARE_ACCOUNT_ID ?? "b082600d280d44fd5da3501bc1bffe2f";
+if (!token) throw new Error("missing CLOUDFLARE_API_TOKEN");
+if (!Number.isFinite(hours) || hours <= 0) throw new Error("--hours must be a positive number");
+
+const LIMIT = 1000;
+const now = Date.now();
+const timeframe = { from: now - hours * 3_600_000, to: now };
+const service = { key: "$metadata.service", operation: "eq", value: "uploads-api", type: "string" };
+
+async function query(queryId, filters, view = "events", extra = {}) {
+  const res = await fetch(
+    `https://api.cloudflare.com/client/v4/accounts/${account}/workers/observability/telemetry/query`,
+    {
+      method: "POST",
+      headers: { authorization: `Bearer ${token}`, "content-type": "application/json" },
+      body: JSON.stringify({
+        queryId,
+        timeframe,
+        parameters: {
+          datasets: ["cloudflare-workers"],
+          filters: [service, ...filters],
+          limit: LIMIT,
+          ...extra,
+        },
+        view,
+      }),
+    },
+  );
+  const body = await res.json();
+  if (!body.success) throw new Error(`telemetry query failed: ${JSON.stringify(body.errors)}`);
+  return body.result;
+}
+
+const shadow = await query("shadow", [
+  { key: "component", operation: "eq", value: "attachment-index", type: "string" },
+  { key: "event", operation: "eq", value: "shadow", type: "string" },
+]);
+const lines = (shadow.events?.events ?? []).map((e) => e.source ?? {});
+
+const errors = {};
+for (const message of [
+  "attachment index: shadow read failed",
+  "attachment index: shadow read timed out",
+]) {
+  const r = await query("err", [
+    { key: "$metadata.message", operation: "eq", value: message, type: "string" },
+  ]);
+  errors[message] = (r.events?.events ?? []).length;
+}
+
+const withAttachments = lines.filter((l) => l.fanout > 0 || l.index > 0);
+const matched = lines.filter((l) => l.match === true);
+const matchedWithAttachments = withAttachments.filter((l) => l.match === true);
+const tally = (field) => {
+  const counts = new Map();
+  for (const l of lines)
+    for (const key of l[field] ?? []) counts.set(key, (counts.get(key) ?? 0) + 1);
+  return [...counts.entries()].sort((a, b) => b[1] - a[1]).slice(0, 10);
+};
+const byRepo = new Map();
+for (const l of withAttachments) {
+  const r = byRepo.get(l.repo) ?? { syncs: 0, matched: 0, missing: 0, extra: 0 };
+  r.syncs += 1;
+  if (l.match) r.matched += 1;
+  r.missing += l.missingCount ?? 0;
+  r.extra += l.extraCount ?? 0;
+  byRepo.set(l.repo, r);
+}
+
+const report = {
+  hours,
+  truncated: lines.length >= LIMIT,
+  syncs: lines.length,
+  matched: matched.length,
+  syncsWithAttachments: withAttachments.length,
+  matchedWithAttachments: matchedWithAttachments.length,
+  missingTotal: lines.reduce((n, l) => n + (l.missingCount ?? 0), 0),
+  extraTotal: lines.reduce((n, l) => n + (l.extraCount ?? 0), 0),
+  topMissing: tally("missing"),
+  topExtra: tally("extra"),
+  byRepo: [...byRepo.entries()].sort((a, b) => b[1].syncs - a[1].syncs),
+  errors,
+};
+
+if (asJson) {
+  console.log(JSON.stringify(report, null, 2));
+} else {
+  const pct = (a, b) => (b === 0 ? "n/a" : `${((100 * a) / b).toFixed(1)}%`);
+  console.log(
+    `attachment-index shadow, last ${hours}h${report.truncated ? " (truncated at " + LIMIT + " lines)" : ""}`,
+  );
+  console.log(
+    `  syncs shadowed:          ${report.syncs}  (match ${pct(report.matched, report.syncs)})`,
+  );
+  console.log(
+    `  with real attachments:   ${report.syncsWithAttachments}  (match ${pct(report.matchedWithAttachments, report.syncsWithAttachments)})`,
+  );
+  console.log(`  missing from index:      ${report.missingTotal}`);
+  console.log(`  extra in index:          ${report.extraTotal}`);
+  console.log(
+    `  read failed / timed out: ${errors["attachment index: shadow read failed"]} / ${errors["attachment index: shadow read timed out"]}`,
+  );
+  if (report.byRepo.length) {
+    console.log("  by repo (syncs with attachments):");
+    for (const [repo, r] of report.byRepo)
+      console.log(
+        `    ${repo}: ${r.syncs} syncs, ${r.matched} matched, ${r.missing} missing, ${r.extra} extra`,
+      );
+  }
+  if (report.topMissing.length) {
+    console.log("  top missing keys:");
+    for (const [key, n] of report.topMissing) console.log(`    ${n}x ${key}`);
+  }
+  if (report.topExtra.length) {
+    console.log("  top extra keys:");
+    for (const [key, n] of report.topExtra) console.log(`    ${n}x ${key}`);
+  }
+  if (report.syncs === 0)
+    console.log(
+      "  (no shadow lines: flag off, no comment syncs in the window, or the deploy is not live)",
+    );
+}