diff --git a/block/internal/da/fiber_client.go b/block/internal/da/fiber_client.go
index 3a4f9eb754..70902673e9 100644
--- a/block/internal/da/fiber_client.go
+++ b/block/internal/da/fiber_client.go
@@ -87,36 +87,65 @@ func (c *fiberDAClient) Submit(ctx context.Context, data [][]byte, _ float64, na
 		}
 	}
 
-	flat := flattenBlobs(data)
+	// Fibre's per-upload cap is ~128 MiB (hard server-side reject:
+	// "data size %d exceeds maximum 134217723"). flattenBlobs adds
+	// 4 bytes per blob + 4 prefix, so we target 120 MiB per chunk
+	// to leave overhead room and avoid borderline rejects.
+	chunks := chunkBlobsForFibre(data, fibreUploadChunkBudget)
 	nsID := namespace[len(namespace)-10:]
-	result, err := c.fiber.Upload(context.Background(), nsID, flat)
-	if err != nil {
-		code := datypes.StatusError
-		switch {
-		case errors.Is(err, context.Canceled):
-			code = datypes.StatusContextCanceled
-		case errors.Is(err, context.DeadlineExceeded):
-			code = datypes.StatusContextDeadline
-		}
-		c.logger.Error().Err(err).Msg("fiber upload failed")
-		return datypes.ResultSubmit{
-			BaseResult: datypes.BaseResult{
-				Code:           code,
-				Message:        fmt.Sprintf("fiber upload failed for blob: %v", err),
-				SubmittedCount: uint64(len(data) - 1),
-				BlobSize:       blobSize,
-				Timestamp:      time.Now(),
-			},
+
+	ids := make([][]byte, 0, len(chunks))
+	var submitted int
+	for chunkIdx, chunk := range chunks {
+		flat := flattenBlobs(chunk)
+		uploadStart := time.Now()
+		result, err := c.fiber.Upload(context.Background(), nsID, flat)
+		uploadDuration := time.Since(uploadStart)
+		if err != nil {
+			c.logger.Warn().
+				Dur("duration", uploadDuration).
+				Int("flat_size", len(flat)).
+				Int("blob_count", len(chunk)).
+				Int("chunk_idx", chunkIdx).
+				Int("chunk_total", len(chunks)).
+				Err(err).
+				Msg("fiber upload duration (failed)")
+			code := datypes.StatusError
+			switch {
+			case errors.Is(err, context.Canceled):
+				code = datypes.StatusContextCanceled
+			case errors.Is(err, context.DeadlineExceeded):
+				code = datypes.StatusContextDeadline
+			}
+			c.logger.Error().Err(err).Msg("fiber upload failed")
+			return datypes.ResultSubmit{
+				BaseResult: datypes.BaseResult{
+					Code:           code,
+					Message:        fmt.Sprintf("fiber upload failed for blob (chunk %d/%d): %v", chunkIdx+1, len(chunks), err),
+					SubmittedCount: uint64(submitted),
+					BlobSize:       blobSize,
+					Timestamp:      time.Now(),
+				},
+			}
 		}
+		c.logger.Info().
+			Dur("duration", uploadDuration).
+			Int("flat_size", len(flat)).
+			Int("blob_count", len(chunk)).
+			Int("chunk_idx", chunkIdx).
+			Int("chunk_total", len(chunks)).
+			Msg("fiber upload duration (ok)")
+		ids = append(ids, result.BlobID)
+		submitted += len(chunk)
 	}
 
-	c.logger.Debug().Int("num_ids", len(data)).Uint64("height", 0 /* TODO */).Msg("fiber DA submission successful")
+	c.logger.Debug().Int("num_ids", len(data)).Int("chunks", len(chunks)).Uint64("height", 0 /* TODO */).Msg("fiber DA submission successful")
 
 	return datypes.ResultSubmit{
 		BaseResult: datypes.BaseResult{
 			Code:           datypes.StatusSuccess,
-			IDs:            [][]byte{result.BlobID},
-			SubmittedCount: uint64(len(data)),
+			IDs:            ids,
+			SubmittedCount: uint64(submitted),
 			Height:         0, /* TODO */
 			BlobSize:       blobSize,
 			Timestamp:      time.Now(),
@@ -124,6 +153,40 @@ func (c *fiberDAClient) Submit(ctx context.Context, data [][]byte, _ float64, na
 	}
 }
 
+// fibreUploadChunkBudget is the target maximum flattened size of a single
+// Fibre Upload call. Fibre rejects payloads above ~128 MiB
+// ("data size N exceeds maximum 134217723"); 120 MiB leaves slack for
+// flattenBlobs's per-blob length prefixes and for any future overhead.
+const fibreUploadChunkBudget = 120 * 1024 * 1024
+
+// chunkBlobsForFibre groups data into chunks whose flattened size stays
+// below budget. Per-blob length-prefix overhead matches flattenBlobs.
+// A single oversized blob (already validated against DefaultMaxBlobSize
+// above) lands in its own chunk; the upload still fails server-side but
+// at least we don't drag healthy peers down with it.
+func chunkBlobsForFibre(data [][]byte, budget int) [][][]byte {
+	if len(data) == 0 {
+		return nil
+	}
+	chunks := make([][][]byte, 0, 1)
+	cur := make([][]byte, 0, len(data))
+	curSize := 4 // flattenBlobs's count prefix
+	for _, b := range data {
+		entry := 4 + len(b)
+		if len(cur) > 0 && curSize+entry > budget {
+			chunks = append(chunks, cur)
+			cur = make([][]byte, 0, len(data))
+			curSize = 4
+		}
+		cur = append(cur, b)
+		curSize += entry
+	}
+	if len(cur) > 0 {
+		chunks = append(chunks, cur)
+	}
+	return chunks
+}
+
 func (c *fiberDAClient) Retrieve(ctx context.Context, height uint64, namespace []byte) datypes.ResultRetrieve {
 	return c.retrieve(ctx, height, namespace, true)
 }
diff --git a/tools/celestia-node-fiber/cmd/evnode-fibre/main.go b/tools/celestia-node-fiber/cmd/evnode-fibre/main.go
index 7b8b73080f..77322116bd 100644
--- a/tools/celestia-node-fiber/cmd/evnode-fibre/main.go
+++ b/tools/celestia-node-fiber/cmd/evnode-fibre/main.go
@@ -302,7 +302,12 @@ func run(cli cliFlags) error {
 	// Fiber-tuned profile: BatchingStrategy=adaptive, BatchMaxDelay=1.5s,
 	// DA.BlockTime=1s, MaxPendingHeadersAndData=0, plus 120 MiB blob cap.
 	cfg.ApplyFiberDefaults()
-	block.SetMaxBlobSize(120 * 1024 * 1024)
+	// 100 MiB — bounded by Fibre's hard ~128 MiB per-upload cap (we
+	// hit `data size exceeds maximum 134217723` at 128 MiB - 5 B).
+	// Set the per-block data cap below that so each block_data item
+	// fits in a single Fibre upload after the submitter splits a
+	// multi-blob batch into ≤120 MiB chunks.
+	block.SetMaxBlobSize(100 * 1024 * 1024)
 	cfg.P2P.ListenAddress = cli.p2pListen
 	cfg.P2P.DisableConnectionGater = true
 	cfg.RPC.Address = cli.rpcListen