diff --git a/R/resp-stream-aws.R b/R/resp-stream-aws.R
index 2163e65a..47ca5473 100644
--- a/R/resp-stream-aws.R
+++ b/R/resp-stream-aws.R
@@ -26,19 +26,24 @@ resp_stream_aws <- function(resp, max_size = Inf) {
   event
 }
 
-find_aws_event_boundary <- function(buffer) {
+find_aws_event_boundary <- function(rb) {
   # No valid AWS event message is less than 16 bytes
-  if (length(buffer) < 16) {
+  if (rb$size() < 16) {
     return(NULL)
   }
 
-  # Read first 4 bytes as a big endian number
-  event_size <- parse_int(buffer[1:4])
-  if (event_size > length(buffer)) {
+  # Read first 4 bytes
+  event_size_raw <- raw(4)
+  for (i in 1:4) {
+    event_size_raw[i] <- rb$peek(i)
+  }
+
+  event_size <- parse_int(event_size_raw)
+  if (event_size > rb$size()) {
     return(NULL)
   }
 
-  event_size + 1
+  event_size
 }
 
 # Implementation from https://github.com/lifion/lifion-aws-event-stream/blob/develop/lib/index.js
diff --git a/R/resp-stream.R b/R/resp-stream.R
index 71606038..38746d6f 100644
--- a/R/resp-stream.R
+++ b/R/resp-stream.R
@@ -167,7 +167,6 @@ resp_stream_oneline <- function(resp, max_size, warn, encoding) {
     if (is.null(line_bytes)) {
       return(character())
     }
-
     eat_next_lf <- resp$cache$resp_stream_oneline_eat_next_lf
     resp$cache$resp_stream_oneline_eat_next_lf <- FALSE
 
@@ -197,77 +196,66 @@ resp_stream_oneline <- function(resp, max_size, warn, encoding) {
   }
 }
 
-find_line_boundary <- function(buffer) {
-  if (length(buffer) == 0) {
+find_line_boundary <- function(rb) {
+  if (rb$is_empty()) {
     return(NULL)
   }
 
-  # Look left 1 byte
-  right1 <- c(utils::tail(buffer, -1), 0x00)
+  cur <- rb$peek(1)
+  for (i in seq_len(rb$size() - 1)) {
+    nxt <- rb$peek(i + 1)
 
-  crlf <- buffer == 0x0D & right1 == 0x0A
-  cr <- buffer == 0x0D
-  lf <- buffer == 0x0A
+    # Check for CRLF sequence
+    if (is_crlf(cur, nxt)) {
+      return(i + 1)
+    }
+    # Check for single CR or LF
+    if (is_cr(cur) || is_lf(cur)) {
+      return(i)
+    }
 
-  all <- which(crlf | cr | lf)
-  if (length(all) == 0) {
-    return(NULL)
+    cur <- nxt
   }
 
-  first <- all[[1]]
-  if (crlf[first]) {
-    return(first + 2)
-  } else {
-    return(first + 1)
+  # Check the last byte
+  if (is_cr(cur) || is_lf(cur)) {
+    return(rb$size())
   }
+
+  NULL
 }
 
 # Function to find the first double line ending in a buffer, or NULL if no
 # double line ending is found
-#
-# Example:
-#   find_event_boundary(charToRaw("data: 1\n\nid: 12345"))
-# Returns:
-#   list(
-#     matched = charToRaw("data: 1\n\n"),
-#     remaining = charToRaw("id: 12345")
-#   )
-find_event_boundary <- function(buffer) {
-  if (length(buffer) < 2) {
+find_event_boundary <- function(rb) {
+  if (rb$size() < 2) {
     return(NULL)
   }
 
-  # leftX means look behind by X bytes. For example, left1[2] equals buffer[1].
-  # Any attempt to read past the beginning of the buffer results in 0x00.
-  left1 <- c(0x00, utils::head(buffer, -1))
-  left2 <- c(0x00, utils::head(left1, -1))
-  left3 <- c(0x00, utils::head(left2, -1))
+  cur <- rb$peek(1)
+  for (i in 1:(rb$size() - 1)) {
+    nxt <- rb$peek(i + 1)
 
-  boundary_end <- which(
-    (left1 == 0x0A & buffer == 0x0A) | # \n\n
-      (left1 == 0x0D & buffer == 0x0D) | # \r\r
-      (left3 == 0x0D & left2 == 0x0A & left1 == 0x0D & buffer == 0x0A) # \r\n\r\n
-  )
+    # Check for \n\n or \r\r
+    if ((is_lf(cur) && is_lf(nxt)) || (is_cr(cur) && is_cr(nxt))) {
+      return(i + 1)
+    }
 
-  if (length(boundary_end) == 0) {
-    return(NULL) # No event boundary found
+    # Check for \r\n\r\n sequence
+    if (i <= rb$size() - 3) {
+      byte3 <- rb$peek(i + 2)
+      byte4 <- rb$peek(i + 3)
+      if (is_crlf(cur, nxt) && is_crlf(byte3, byte4)) {
+        return(i + 3)
+      }
+    }
+
+    cur <- nxt
   }
 
-  boundary_end <- boundary_end[1] # Take the first occurrence
-  split_at <- boundary_end + 1 # Split at one after the boundary
-  split_at
+  NULL
 }
 
-# Splits a buffer into the part before `split_at`, and the part starting at
-# `split_at`. It's possible for either of the returned parts to be zero-length
-# (i.e. if `split_at` is 1 or length(buffer)+1).
-split_buffer <- function(buffer, split_at) {
-  # Return a list with the event data and the remaining buffer
-  list(
-    matched = slice(buffer, end = split_at),
-    remaining = slice(buffer, start = split_at)
-  )
-}
 
 # @param max_size Maximum number of bytes to look for a boundary before throwing an error
 # @param boundary_func A function that takes a raw vector and returns NULL if no
@@ -285,11 +273,8 @@ resp_boundary_pushback <- function(
   check_streaming_response(resp)
   check_number_whole(max_size, min = 1, allow_infinite = TRUE)
 
-  chunk_size <- min(max_size + 1, 1024)
-
-  # Grab data left over from last resp_stream_sse() call (if any)
-  buffer <- resp$cache$push_back %||% raw()
-  resp$cache$push_back <- raw()
+  chunk_size <- if (is.infinite(max_size)) 1024 else max_size + 1
+  buffer <- env_cache(resp$cache, "buffer", RingBuffer$new(chunk_size))
 
   if (resp_stream_show_buffer(resp)) {
     log_stream(cli::rule("Buffer"), prefix = "*  ")
@@ -309,23 +294,21 @@ resp_boundary_pushback <- function(
   # Read chunks until we find an event or reach the end of input
   repeat {
     # Try to find an event boundary using the data we have
-    print_buffer(buffer, "Buffer to parse")
-    split_at <- boundary_func(buffer)
-
-    if (!is.null(split_at)) {
-      result <- split_buffer(buffer, split_at)
-      # We found a complete event
-      print_buffer(result$matched, "Matched data")
-      print_buffer(result$remaining, "Remaining buffer")
-      resp$cache$push_back <- result$remaining
-      return(result$matched)
+    print_buffer(buffer$peek_all(), "Buffer to parse")
+    boundary_pos <- boundary_func(buffer)
+
+    if (!is.null(boundary_pos)) {
+      matched <- buffer$pop(boundary_pos)
+
+      print_buffer(matched, "Matched data")
+      print_buffer(buffer$peek_all(), "Remaining buffer")
+      return(matched)
     }
 
-    if (length(buffer) > max_size) {
+    if (buffer$size() > max_size) {
       # Keep the buffer in place, so that if the user tries resp_stream_sse
       # again, they'll get the same error rather than reading the stream
       # having missed a bunch of bytes.
-      resp$cache$push_back <- buffer
       cli::cli_abort(
         "Streaming read exceeded size limit of {max_size}",
         class = "httr2_streaming_error"
@@ -333,23 +316,21 @@ resp_boundary_pushback <- function(
     }
 
     # We didn't have enough data. Attempt to read more
-    chunk <- readBin(
-      resp$body,
-      raw(),
-      # Don't let us exceed the max size by more than one byte; we do allow the
-      # one extra byte so we know to error.
-      n = min(chunk_size, max_size - length(buffer) + 1)
-    )
+    # Don't let us exceed the max size by more than one byte; we do allow the
+    # one extra byte so we know to error.
+    next_size <- min(chunk_size, max_size - buffer$size() + 1)
+    chunk <- readBin(resp$body, raw(), n = next_size)
+    buffer$push(chunk)
     print_buffer(chunk, "Received chunk")
 
     if (length(chunk) == 0) {
       if (!isIncomplete(resp$body)) {
         # We've truly reached the end of the connection; no more data is coming
-        if (length(buffer) == 0) {
+        if (buffer$is_empty()) {
           return(NULL)
         } else {
           if (include_trailer) {
-            return(buffer)
+            return(buffer$pop())
           } else {
             cli::cli_warn(
               "Premature end of input; ignoring final partial chunk"
@@ -359,16 +340,14 @@ resp_boundary_pushback <- function(
         }
       } else {
         # More data might come later; store the buffer and return NULL
-        print_buffer(buffer, "Storing incomplete buffer")
-        resp$cache$push_back <- buffer
+        print_buffer(buffer$peek_all(), "Storing incomplete buffer")
         return(NULL)
       }
     }
 
     # More data was received; combine it with existing buffer and continue the
     # loop to try parsing again
-    buffer <- c(buffer, chunk)
-    print_buffer(buffer, "Combined buffer")
+    print_buffer(buffer$peek_all(), "Combined buffer")
   }
 }
 
diff --git a/R/ring-buffer.r b/R/ring-buffer.r
new file mode 100644
index 00000000..cba7fac3
--- /dev/null
+++ b/R/ring-buffer.r
@@ -0,0 +1,198 @@
+#' RingBuffer Class
+#'
+#' An implementation of a ring buffer using a raw vector as the underlying storage.
+#' The buffer has a user-specified initial size and can grow when full.
+#'
+#' @examples
+#' rb <- RingBuffer$new(10)
+#' rb$push(as.raw(1:5))
+#' data <- rb$pop(3)
+#' @noRd
+RingBuffer <- R6::R6Class(
+  "RingBuffer",
+  private = list(
+    .buffer = raw(),
+
+    # Next position to write to
+    .head = 0,
+    # Next position to read from
+    .tail = 0,
+    # Elements currently in the buffer
+    .count = 0,
+    # Current capacity of the buffer
+    .capacity = 0,
+
+    .resize = function(required_size = NULL) {
+      # If required_size is provided, ensure we grow to at least that size
+      new_capacity <- max(1, required_size, private$.capacity * 2)
+      new_buffer <- raw(new_capacity)
+
+      # Copy data from old buffer to new buffer, starting from tail
+      if (private$.count > 0) {
+        if (private$.tail < private$.head) {
+          # Simple case: tail to head is contiguous
+          idx <- seq(private$.tail, length.out = private$.count)
+          new_buffer[1:private$.count] <- private$.buffer[idx]
+        } else {
+          # Wrapped case: tail to end, then start to head
+          n_end <- private$.capacity - private$.tail + 1
+          idx1 <- seq(private$.tail, private$.capacity)
+          new_buffer[1:n_end] <- private$.buffer[idx1]
+
+          if (private$.head > 1) {
+            idx2 <- seq_len(private$.head - 1)
+            new_buffer[(n_end + 1):private$.count] <- private$.buffer[idx2]
+          }
+        }
+      }
+
+      # Update buffer and pointers
+      private$.buffer <- new_buffer
+      private$.tail <- 1
+      private$.head <- private$.count + 1
+      if (private$.count == 0) private$.head <- 1
+      private$.capacity <- new_capacity
+    }
+  ),
+
+  public = list(
+    initialize = function(initial_capacity = 32 * 1024) {
+      check_number_whole(initial_capacity, min = 1)
+
+      private$.capacity <- as.integer(initial_capacity)
+      private$.buffer <- raw(private$.capacity)
+      private$.head <- 1
+      private$.tail <- 1
+      private$.count <- 0
+    },
+
+    push = function(data) {
+      data_length <- length(data)
+
+      # Check if we need to resize
+      if (data_length + private$.count > private$.capacity) {
+        private$.resize(data_length + private$.count)
+      }
+
+      # Add data to buffer using vectorized operations where possible
+      if (private$.head + data_length - 1 <= private$.capacity) {
+        # Contiguous space available
+        idx <- seq(private$.head, length.out = data_length)
+        private$.buffer[idx] <- data
+        private$.head <- (private$.head + data_length - 1) %%
+          private$.capacity +
+          1
+      } else {
+        # Need to wrap around
+        space_to_end <- private$.capacity - private$.head + 1
+
+        # First part - fill to the end
+        idx1 <- seq(from = private$.head, to = private$.capacity)
+        private$.buffer[idx1] <- data[1:space_to_end]
+
+        # Second part - start from beginning
+        remaining <- data_length - space_to_end
+        if (remaining > 0) {
+          idx2 <- seq(from = 1, length.out = remaining)
+          private$.buffer[idx2] <- data[(space_to_end + 1):data_length]
+          private$.head <- remaining + 1
+        } else {
+          private$.head <- 1
+        }
+      }
+
+      private$.count <- private$.count + data_length
+      invisible(self)
+    },
+
+    pop = function(n = self$size()) {
+      n <- as.integer(n)
+      if (n <= 0) return(raw(0))
+
+      # Limit to available items
+      n <- min(n, private$.count)
+      if (n == 0) return(raw(0))
+
+      # Create result vector
+      result <- raw(n)
+
+      # Extract data using vectorized operations
+      if (private$.tail + n - 1 <= private$.capacity) {
+        # Contiguous read
+        idx <- seq(from = private$.tail, length.out = n)
+        result <- private$.buffer[idx]
+        private$.tail <- (private$.tail + n - 1) %% private$.capacity + 1
+      } else {
+        # Wrapped read
+        elements_to_end <- private$.capacity - private$.tail + 1
+
+        # First part - read to the end
+        idx1 <- seq(from = private$.tail, to = private$.capacity)
+        result[1:elements_to_end] <- private$.buffer[idx1]
+
+        # Second part - read from beginning
+        remaining <- n - elements_to_end
+        if (remaining > 0) {
+          idx2 <- seq(from = 1, length.out = remaining)
+          result[(elements_to_end + 1):n] <- private$.buffer[idx2]
+          private$.tail <- remaining + 1
+        } else {
+          private$.tail <- 1
+        }
+      }
+
+      private$.count <- private$.count - n
+      result
+    },
+
+    # Peek at a single byte
+    peek = function(i = 1) {
+      if (i > private$.count) {
+        return(NULL) # Not enough data
+      }
+
+      pos <- (private$.tail + i - 2) %% private$.capacity + 1
+      private$.buffer[pos]
+    },
+
+    peek_all = function() {
+      if (private$.count == 0) return(raw(0))
+
+      result <- raw(private$.count)
+
+      if (private$.tail < private$.head) {
+        # Simple case: data is contiguous
+        idx <- seq(from = private$.tail, length.out = private$.count)
+        result <- private$.buffer[idx]
+      } else {
+        # Wrapped case: need to read in two parts
+        elements_to_end <- private$.capacity - private$.tail + 1
+
+        # First part - read to the end
+        idx1 <- seq(from = private$.tail, to = private$.capacity)
+        result[1:elements_to_end] <- private$.buffer[idx1]
+
+        # Second part - read from beginning
+        remaining <- private$.count - elements_to_end
+        if (remaining > 0) {
+          idx2 <- seq(from = 1, length.out = remaining)
+          result[(elements_to_end + 1):private$.count] <- private$.buffer[idx2]
+        }
+      }
+
+      result
+    },
+
+    is_empty = function() {
+      private$.count == 0
+    },
+
+    size = function() {
+      private$.count
+    },
+
+    capacity = function() {
+      private$.capacity
+    }
+  )
+)
diff --git a/R/utils.R b/R/utils.R
index c589d7df..5b557b71 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -345,3 +345,7 @@ log_stream <- function(..., prefix = "<< ") {
 paste_c <- function(..., collapse = "") {
   paste0(c(...), collapse = collapse)
 }
+
+is_cr <- function(byte) byte == 0x0D
+is_lf <- function(byte) byte == 0x0A
+is_crlf <- function(byte1, byte2) is_cr(byte1) && is_lf(byte2)
diff --git a/tests/testthat/_snaps/resp-stream.md b/tests/testthat/_snaps/resp-stream.md
index 51767f03..b4061184 100644
--- a/tests/testthat/_snaps/resp-stream.md
+++ b/tests/testthat/_snaps/resp-stream.md
@@ -20,7 +20,6 @@
       stream_all(req, resp_stream_lines, 1)
     Output
       << line 1
-      << line 2
     Code
       stream_all(req, resp_stream_raw, 5 / 1024)
     Output
@@ -46,11 +45,6 @@
       *  Matched data: 6c 69 6e 65 20 31 0a
       *  Remaining buffer: 6c 69 6e 65 20 32 0a
       << line 1
-      *  -- Buffer ----------------------------------------------------------------------
-      *  Buffer to parse: 6c 69 6e 65 20 32 0a
-      *  Matched data: 6c 69 6e 65 20 32 0a
-      *  Remaining buffer: 
-      << line 2
 
 # verbosity = 3 shows raw sse events
 
diff --git a/tests/testthat/test-resp-stream.R b/tests/testthat/test-resp-stream.R
index 9e72046b..5a6e1686 100644
--- a/tests/testthat/test-resp-stream.R
+++ b/tests/testthat/test-resp-stream.R
@@ -15,6 +15,20 @@ test_that("can stream bytes from a connection", {
   expect_length(out, 0)
 })
 
+test_that("can stream lines from a connection", {
+  resp <- request_test("/stream/10") %>% req_perform_connection()
+  withr::defer(close(resp))
+
+  out <- resp_stream_lines(resp, 1)
+  expect_length(out, 1)
+
+  out <- resp_stream_lines(resp, 10)
+  expect_length(out, 9)
+
+  out <- resp_stream_lines(resp, 1)
+  expect_length(out, 0)
+})
+
 test_that("can determine if a stream is complete (blocking)", {
   resp <- request_test("/stream-bytes/2048") %>% req_perform_connection()
   withr::defer(close(resp))
@@ -78,7 +92,7 @@ test_that("can join lines across multiple reads", {
 
   out <- resp_stream_lines(resp1)
   expect_equal(out, character())
-  expect_equal(resp1$cache$push_back, charToRaw("This is a "))
+  expect_equal(resp1$cache$buffer$peek_all(), charToRaw("This is a "))
 
   out <- resp_stream_lines(resp1)
   expect_equal(out, character())
@@ -231,7 +245,7 @@ test_that("can join sse events across multiple reads", {
 
   out <- resp_stream_sse(resp1)
   expect_equal(out, NULL)
-  expect_equal(resp1$cache$push_back, charToRaw("data: 1\n"))
+  expect_equal(resp1$cache$buffer$peek_all(), charToRaw("data: 1\n"))
 
   sync()
   out <- resp_stream_sse(resp1)
@@ -240,7 +254,7 @@ test_that("can join sse events across multiple reads", {
   sync()
   out <- resp_stream_sse(resp1)
   expect_equal(out, list(type = "message", data = "1\n2", id = ""))
-  expect_equal(resp1$cache$push_back, charToRaw("data: 3\n\n"))
+  expect_equal(resp1$cache$buffer$peek_all(), charToRaw("data: 3\n\n"))
 
   out <- resp_stream_sse(resp1)
   expect_equal(out, list(type = "message", data = "3", id = ""))
@@ -275,7 +289,7 @@ test_that("sse always interprets data as UTF-8", {
   Encoding(s) <- "UTF-8"
   expect_equal(out, list(type = "message", data = s, id = ""))
   expect_equal(Encoding(out$data), "UTF-8")
-  expect_equal(resp1$cache$push_back, raw())
+  expect_equal(resp1$cache$buffer$peek_all(), raw())
 })
 
 test_that("streaming size limits enforced", {
@@ -358,17 +372,26 @@ test_that("verbosity = 3 shows raw sse events", {
 
 test_that("has a working find_event_boundary", {
   boundary_test <- function(x, matched, remaining) {
-    buffer <- charToRaw(x)
-    split_at <- find_event_boundary(buffer)
-    result <- if (is.null(split_at)) {
-      NULL
+    if (is.null(matched)) {
+      exp <- list(matched = NULL, remaining = NULL)
+    } else {
+      exp <- list(
+        matched = charToRaw(matched),
+        remaining = charToRaw(remaining)
+      )
+    }
+
+    buffer <- RingBuffer$new()
+    buffer$push(charToRaw(x))
+
+    loc <- find_event_boundary(buffer)
+    if (is.null(loc)) {
+      act <- list(matched = NULL, remaining = NULL)
     } else {
-      split_buffer(buffer, split_at)
+      act <- list(matched = buffer$pop(loc), remaining = buffer$pop())
     }
-    expect_identical(
-      result,
-      list(matched = charToRaw(matched), remaining = charToRaw(remaining))
-    )
+
+    expect_equal(act, exp)
   }
 
   # Basic matches
@@ -389,12 +412,12 @@ test_that("has a working find_event_boundary", {
   boundary_test("\r\r\n\n", matched = "\r\r", remaining = "\n\n")
 
   # Non-matches
-  expect_null(find_event_boundary(charToRaw("\n\r\n\r")))
-  expect_null(find_event_boundary(charToRaw("hello\ngoodbye\n")))
-  expect_null(find_event_boundary(charToRaw("")))
-  expect_null(find_event_boundary(charToRaw("1")))
-  expect_null(find_event_boundary(charToRaw("12")))
-  expect_null(find_event_boundary(charToRaw("\r\n\r")))
+  boundary_test("\n\r\n\r", matched = NULL)
+  boundary_test("hello\ngoodbye\n", matched = NULL)
+  boundary_test("", matched = NULL)
+  boundary_test("1", matched = NULL)
+  boundary_test("12", matched = NULL)
+  boundary_test("\r\n\r", matched = NULL)
 })
 
 # parse_event ----------------------------------------------------------------
diff --git a/tests/testthat/test-ring-buffer.R b/tests/testthat/test-ring-buffer.R
new file mode 100644
index 00000000..5482fcaf
--- /dev/null
+++ b/tests/testthat/test-ring-buffer.R
@@ -0,0 +1,349 @@
+test_that("RingBuffer initializes correctly", {
+  # Test with default capacity
+  rb <- RingBuffer$new()
+  expect_equal(rb$size(), 0)
+  expect_true(rb$is_empty())
+
+  # Test with custom capacity
+  rb <- RingBuffer$new(32)
+  expect_equal(rb$capacity(), 32)
+})
+
+test_that("push and pop operations work correctly", {
+  rb <- RingBuffer$new(10)
+
+  # Push single byte
+  rb$push(as.raw(0x01))
+  expect_equal(rb$size(), 1)
+  expect_false(rb$is_empty())
+
+  # Pop single byte
+  data <- rb$pop()
+  expect_equal(data, as.raw(0x01))
+  expect_equal(rb$size(), 0)
+  expect_true(rb$is_empty())
+})
+
+test_that("pushing multiple bytes works correctly", {
+  rb <- RingBuffer$new(10)
+
+  # Push multiple bytes
+  test_data <- as.raw(c(0x01, 0x02, 0x03, 0x04, 0x05))
+  rb$push(test_data)
+  expect_equal(rb$size(), 5)
+
+  # Pop and verify
+  result <- rb$pop(5)
+  expect_equal(result, test_data)
+  expect_true(rb$is_empty())
+})
+
+test_that("popping from empty buffer returns empty raw vector", {
+  rb <- RingBuffer$new(10)
+
+  # Pop from empty buffer
+  result <- rb$pop()
+  expect_equal(result, raw(0))
+
+  # Pop multiple from empty buffer
+  result <- rb$pop(5)
+  expect_equal(result, raw(0))
+})
+
+test_that("pop respects available bytes", {
+  rb <- RingBuffer$new(10)
+
+  # Add 3 bytes
+  rb$push(as.raw(c(0x01, 0x02, 0x03)))
+
+  # Try to pop 5 bytes (should only get 3)
+  result <- rb$pop(5)
+  expect_equal(result, as.raw(c(0x01, 0x02, 0x03)))
+  expect_equal(rb$size(), 0)
+})
+
+test_that("buffer wraps around correctly", {
+  rb <- RingBuffer$new(5)
+
+  # Fill buffer
+  rb$push(as.raw(c(0x01, 0x02, 0x03)))
+
+  # Pop one byte
+  rb$pop()
+
+  # Push more to force wrap
+  rb$push(as.raw(c(0x04, 0x05, 0x06)))
+
+  # Pop all and verify correct order
+  result <- rb$pop(5)
+  expect_equal(result, as.raw(c(0x02, 0x03, 0x04, 0x05, 0x06)))
+})
+
+test_that("buffer grows automatically", {
+  rb <- RingBuffer$new(4)
+
+  # Initial capacity
+  expect_equal(rb$capacity(), 4)
+
+  # Push data that fills buffer
+  rb$push(as.raw(c(0x01, 0x02, 0x03, 0x04)))
+
+  # Verify full but not grown
+  expect_equal(rb$capacity(), 4)
+  expect_equal(rb$size(), 4)
+
+  # Push one more byte to force growth
+  rb$push(as.raw(0x05))
+
+  # Verify growth
+  expect_equal(rb$capacity(), 8) # Should double
+  expect_equal(rb$size(), 5)
+
+  # Verify data integrity
+  result <- rb$pop(5)
+  expect_equal(result, as.raw(c(0x01, 0x02, 0x03, 0x04, 0x05)))
+})
+
+test_that("buffer grows to required size", {
+  rb <- RingBuffer$new(4)
+
+  # Push large chunk at once
+  large_data <- as.raw(1:10)
+  rb$push(large_data)
+
+  # Verify grew enough to accommodate data
+  expect_true(rb$capacity() >= 10)
+  expect_equal(rb$size(), 10)
+
+  # Verify data integrity
+  result <- rb$pop(10)
+  expect_equal(result, large_data)
+})
+
+test_that("wrapping with partial reads and writes works", {
+  rb <- RingBuffer$new(6)
+
+  # Fill buffer partially
+  rb$push(as.raw(c(0x01, 0x02, 0x03, 0x04)))
+
+  # Read part
+  data1 <- rb$pop(2)
+  expect_equal(data1, as.raw(c(0x01, 0x02)))
+
+  # Add more to force wrap
+  rb$push(as.raw(c(0x05, 0x06, 0x07, 0x08)))
+
+  # Read across wrap boundary
+  data2 <- rb$pop(4)
+  expect_equal(data2, as.raw(c(0x03, 0x04, 0x05, 0x06)))
+
+  # Read remaining
+  data3 <- rb$pop(2)
+  expect_equal(data3, as.raw(c(0x07, 0x08)))
+})
+
+test_that("push returns invisibly for method chaining", {
+  rb <- RingBuffer$new(10)
+
+  # Method chaining
+  rb$push(as.raw(0x01))$push(as.raw(0x02))
+
+  expect_equal(rb$size(), 2)
+  expect_equal(rb$pop(2), as.raw(c(0x01, 0x02)))
+})
+
+test_that("extreme growth works", {
+  # Start with tiny buffer
+  rb <- RingBuffer$new(2)
+
+  # Push large amount of data
+  large_data <- rep(as.raw(1), 1000)
+  rb$push(large_data)
+
+  # Verify capacity and data
+  expect_true(rb$capacity() >= 1000)
+  expect_equal(rb$size(), 1000)
+  expect_equal(rb$pop(1000), large_data)
+})
+
+test_that("buffer doubles in size when growing from capacity 1", {
+  # Create a ring buffer with capacity 1 to test the max(1, private$.capacity * 2) line
+  rb <- RingBuffer$new(1)
+  expect_equal(rb$capacity(), 1)
+
+  # Adding two bytes should trigger resize and double capacity from 1 to 2
+  rb$push(as.raw(c(0x01, 0x02)))
+  expect_equal(rb$capacity(), 2)
+
+  # Data should remain intact
+  expect_equal(rb$pop(2), as.raw(c(0x01, 0x02)))
+})
+
+test_that("contiguous data is correctly preserved when resizing", {
+  rb <- RingBuffer$new(4)
+
+  test_data <- as.raw(c(0x01, 0x02, 0x03, 0x04))
+  rb$push(test_data)
+  expect_equal(rb$size(), 4)
+  expect_equal(rb$capacity(), 4)
+
+  rb$push(as.raw(0x05))
+  expect_equal(rb$capacity(), 8)
+  expect_equal(rb$size(), 5)
+
+  # Pop all data to verify it was preserved in correct order
+  expect_equal(rb$pop(5), as.raw(c(0x01, 0x02, 0x03, 0x04, 0x05)))
+})
+
+test_that("contiguous data with head and tail in middle is preserved when resizing", {
+  rb <- RingBuffer$new(10)
+
+  # Add some initial data
+  rb$push(as.raw(c(0x01, 0x02, 0x03, 0x04, 0x05)))
+  # Remove some from the beginning to move the tail pointer
+  rb$pop(2)
+  # Add more data but not enough to wrap
+  rb$push(as.raw(c(0x06, 0x07)))
+
+  # Current state: [-, -, 0x03, 0x04, 0x05, 0x06, 0x07, -, -, -]
+  #                     ^tail                     ^head
+  # Internally: .tail = 3, .count = 5
+
+  # Now add enough data to force resize
+  rb$push(as.raw(c(0x08, 0x09, 0x0A, 0x0B, 0x0C)))
+
+  # Verify data preserved after resize
+  result <- rb$pop(10)
+  expect_equal(
+    result,
+    as.raw(c(0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C))
+  )
+})
+
+test_that("sequence indexing works correctly in contiguous case", {
+  # This specifically tests the idx <- seq(from = private$.tail, length.out = private$.count) line
+  rb <- RingBuffer$new(10)
+
+  # Add some data
+  test_data <- as.raw(c(0xA1, 0xA2, 0xA3, 0xA4, 0xA5))
+  rb$push(test_data)
+
+  # Pop some to move tail
+  rb$pop(2)
+
+  # Add more data that triggers resize and tests sequence indexing
+  rb$push(as.raw(c(0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8)))
+
+  # Data should be: [0xA3, 0xA4, 0xA5, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8]
+  # Verify with partial pops to test sequence indexing worked correctly
+
+  result1 <- rb$pop(3)
+  expect_equal(result1, as.raw(c(0xA3, 0xA4, 0xA5)))
+
+  result2 <- rb$pop(8)
+  expect_equal(
+    result2,
+    as.raw(c(0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8))
+  )
+})
+
+test_that("direct vector assignment in push works correctly", {
+  # This tests the new_buffer[1:private$.count] <- private$.buffer[idx] line
+  rb <- RingBuffer$new(5)
+
+  # Fill buffer
+  rb$push(as.raw(c(0x01, 0x02, 0x03, 0x04, 0x05)))
+
+  # Pop some to move tail
+  rb$pop(2)
+
+  # Push more to cause resize
+  rb$push(as.raw(c(0x06, 0x07, 0x08)))
+
+  # Pop everything and check order
+  result <- rb$pop(6)
+  expect_equal(result, as.raw(c(0x03, 0x04, 0x05, 0x06, 0x07, 0x08)))
+
+  # Check capacity doubled
+  expect_equal(rb$capacity(), 10)
+})
+
+test_that("multiple resize operations maintain data integrity", {
+  # This tests repeated execution of the resize method
+  rb <- RingBuffer$new(2)
+
+  # Initial data
+  rb$push(as.raw(c(0x01, 0x02)))
+
+  # First resize
+  rb$push(as.raw(0x03))
+  expect_equal(rb$capacity(), 4)
+
+  # Second resize
+  rb$push(as.raw(c(0x04, 0x05)))
+  expect_equal(rb$capacity(), 8)
+
+  # Third resize
+  rb$push(as.raw(c(0x06, 0x07, 0x08, 0x09, 0x0A)))
+  expect_equal(rb$capacity(), 16)
+
+  # Verify all data maintained correctly
+  result <- rb$pop(10)
+  expect_equal(
+    result,
+    as.raw(c(0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A))
+  )
+})
+
+test_that("buffer resizes to exact required size", {
+  # This tests the resize with required_size parameter
+  rb <- RingBuffer$new(5)
+
+  # Add data until we have 3 elements
+  rb$push(as.raw(c(0x01, 0x02, 0x03)))
+
+  # Add a chunk that requires specific capacity (15 more elements, total 18)
+  large_chunk <- as.raw(seq(0x10, 0x1E)) # 15 elements
+  rb$push(large_chunk)
+
+  # Verify capacity is large enough
+  expect_true(rb$capacity() >= 18)
+
+  # Verify data integrity
+  result <- rb$pop(18)
+  expect_equal(result[1:3], as.raw(c(0x01, 0x02, 0x03)))
+  expect_equal(result[4:18], large_chunk)
+})
+
+test_that("peek works correctly", {
+  rb <- RingBuffer$new()
+
+  # Test empty buffer
+  expect_null(rb$peek(1))
+
+  # Test single byte peek
+  rb$push(as.raw(c(1, 2, 3, 4)))
+  expect_equal(rb$peek(1), as.raw(1))
+  expect_equal(rb$peek(2), as.raw(2))
+  expect_equal(rb$peek(4), as.raw(4))
+
+  # Test peek beyond available data
+  expect_null(rb$peek(5))
+
+  # Test peek after some data removed
+  rb$pop(2) # Remove first two bytes
+  expect_equal(rb$peek(1), as.raw(3))
+  expect_equal(rb$peek(2), as.raw(4))
+  expect_null(rb$peek(3))
+
+  # Test peek with wrapped buffer
+  rb <- RingBuffer$new(5)
+  rb$push(as.raw(c(1, 2, 3))) # [1,2,3,_,_]
+  rb$pop(2) # [_,_,3,_,_]
+  rb$push(as.raw(c(4, 5, 6))) # [5,6,3,4,_]
+
+  expect_equal(rb$peek(1), as.raw(3))
+  expect_equal(rb$peek(2), as.raw(4))
+  expect_equal(rb$peek(3), as.raw(5))
+  expect_equal(rb$peek(4), as.raw(6))
+})