diff --git a/analysis/values/slowstart.py b/analysis/values/slowstart.py
new file mode 100644
index 0000000..49219a6
--- /dev/null
+++ b/analysis/values/slowstart.py
@@ -0,0 +1,33 @@
+"""Initial ssthresh per (solution, qlen) from slowstart raw text files."""
+import os
+from pathlib import Path
+
+import numpy as np
+
+
+def _read(path: Path) -> dict[int, np.ndarray]:
+    out = {}
+    for line in path.read_text().splitlines():
+        line = line.strip()
+        if not line:
+            continue
+        qlen, vals = line.split(":", 1)
+        out[int(qlen)] = np.array([float(v) for v in vals.split()])
+    return out
+
+
+def compute(derived: Path) -> tuple[dict[str, str], list[Path]]:
+    raw_root = Path(os.environ.get("RAW_DATA_ROOT", derived.parent / "raw_data"))
+    raw = raw_root / "slowstart"
+    files = {"tso": raw / "tso.txt", "tso-pacing": raw / "tso_pacing.txt"}
+    if not all(p.exists() for p in files.values()):
+        return {}, []
+
+    out: dict[str, str] = {}
+    for sol, path in files.items():
+        for qlen, vals in _read(path).items():
+            base = f"slowstart/{sol}/qlen-{qlen}"
+            out[f"{base}/mean-pkts"] = f"{vals.mean():.0f}"
+            out[f"{base}/sd-pkts"]   = f"{vals.std(ddof=1):.0f}"
+            out[f"{base}/n-runs"]    = str(vals.size)
+    return out, list(files.values())
diff --git a/figures/fig_slowstart.R b/figures/fig_slowstart.R
new file mode 100644
index 0000000..be0796c
--- /dev/null
+++ b/figures/fig_slowstart.R
@@ -0,0 +1,46 @@
+#!/usr/bin/env Rscript
+source("common.R")
+
+parser <- fig_parser(description = "Initial ssthresh vs bottleneck queue")
+parser$add_argument("--ymin", type = "double")
+parser$add_argument("--ymax", type = "double")
+parser$add_argument("--ystep", type = "double")
+args <- parser$parse_args()
+
+read_runs <- function(path, label) {
+  lines <- readLines(path)
+  do.call(rbind, lapply(lines, function(ln) {
+    parts <- strsplit(ln, ":", fixed = TRUE)[[1]]
+    qlen  <- as.integer(trimws(parts[1]))
+    vals  <- as.numeric(strsplit(trimws(parts[2]), "\\s+")[[1]])
+    data.frame(solution = label, qlen = qlen, ssthresh = vals)
+  }))
+}
+
+runs <- rbind(
+  read_runs(file.path(args$data, "tso.txt"),        "tso"),
+  read_runs(file.path(args$data, "tso_pacing.txt"), "tso-pacing")
+) %>%
+  prepare_solution() %>%
+  group_by(solution, qlen) %>%
+  summarise(mean = mean(ssthresh),
+            sd   = sd(ssthresh), .groups = "drop")
+
+p <- ggplot(runs, aes(x = factor(qlen), y = mean, fill = solution)) +
+  geom_col(position = position_dodge(width = 0.75), width = 0.65, colour = "black") +
+  geom_errorbar(aes(ymin = mean - sd, ymax = mean + sd),
+                position = position_dodge(width = 0.75), width = 0.25) +
+  scale_fill_manual(values = LABEL_COLORS) +
+  labs(x = "Bottleneck queue limit (pkts)", y = "Max CWND (pkts)") +
+  theme_paper() +
+  theme_debug_margins(args)
+
+if (!is.null(args$ymax)) {
+  ymin <- if (is.null(args$ymin)) 0 else args$ymin
+  p <- p + coord_cartesian(ylim = c(ymin, args$ymax))
+  if (!is.null(args$ystep)) {
+    p <- p + scale_y_continuous(breaks = seq(ymin, args$ymax, args$ystep))
+  }
+}
+
+save_figure(p, args)