diff --git a/src/internal/ingest/ingest.zig b/src/internal/ingest/ingest.zig
index e9ee978..c5a532d 100644
--- a/src/internal/ingest/ingest.zig
+++ b/src/internal/ingest/ingest.zig
@@ -959,11 +959,9 @@ test "repair hot tail skips an undecodable archived record without failing inges
     defer consumer.deinit();
 
     // A complete repository can contain opaque record bytes outside
-    // DAG-CBOR. A float decoder error killed the experiment while a verifier
-    // repair was filling the hot tail from its fetched repository. zat 0.4.2
-    // accepts finite 64-bit floats, so this uses a 32-bit float, which
-    // DAG-CBOR still forbids.
-    const float_record = "\xa1\x61x\xfa\x3f\x80\x00\x00";
+    // DAG-CBOR. This exact float decoder error killed the experiment while a
+    // verifier repair was filling the hot tail from its fetched repository.
+    const float_record = "\xa1\x61x\xfb\x3f\xf0\x00\x00\x00\x00\x00\x00";
     try appendArchivedTailRow(&consumer, .{
         .seq = 42,
         .witnessed_at = 100,
diff --git a/src/internal/serve/wire.zig b/src/internal/serve/wire.zig
index 6b94341..0842ee7 100644
--- a/src/internal/serve/wire.zig
+++ b/src/internal/serve/wire.zig
@@ -194,7 +194,9 @@ fn writeCborValue(s: *std.json.Stringify, value: cbor.Value) !void {
     switch (value) {
         .unsigned => |v| try s.write(v),
         .negative => |v| try s.write(v),
-        .float => |v| try s.write(v),
+        // upstream's cbor.ToJSON rejects floats as outside the atproto data
+        // model (atmos cbor/json.go), so the record is unencodable, not emitted
+        .float => return error.WriteFailed,
         // record text can be any bytes a PDS chose to write; the same
         // array-instead-of-string hazard applies to it as to the envelope
         .text => |v| try writeString(s, v),
@@ -356,6 +358,29 @@ test "record with cid link and bytes" {
     try testing.expect(std.mem.indexOf(u8, json, "\"blob\":{\"$bytes\":\"AQID\"}") != null);
 }
 
+// Mirrors upstream: atmos decodes a finite float64 but cbor.ToJSON rejects it
+// as outside the atproto data model, so the subscribe encoder errors instead
+// of emitting a JSON number.
+test "record with a float is unencodable" {
+    var out: std.Io.Writer.Allocating = .init(testing.allocator);
+    defer out.deinit();
+    const cid = try cbor.Cid.forDagCbor(testing.allocator, "x");
+    defer testing.allocator.free(cid.raw);
+    var arena = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena.deinit();
+    const record = try cbor.decodeAll(arena.allocator(), "\xa1\x61x\xfb\x3f\xf0\x00\x00\x00\x00\x00\x00");
+    try testing.expectError(error.WriteFailed, encodeCommit(testing.allocator, &out.writer, .{
+        .did = "did:plc:abc",
+        .time_us = 1,
+        .rev = "3l3qo2vutsw2b",
+        .operation = "create",
+        .collection = "app.bsky.feed.post",
+        .rkey = "k",
+        .record = record,
+        .cid = cid,
+    }));
+}
+
 // === network.bsky.jetstream.subscribeEvents: proposal-0015 wire ===
 // One xrpc.v1.json message frame per event:
 //   {"$type":"message","payload":{"$type":"network.bsky.jetstream.subscribeEvents#<kind>", ...}}