diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
index c0cd13a..23a0892 100644
--- a/.devcontainer/Dockerfile
+++ b/.devcontainer/Dockerfile
@@ -22,7 +22,7 @@ RUN apt-get update \
 
 # Build + install EigenScript at the pinned tag onto /usr/local (binary on
 # PATH, stdlib at /usr/local/lib/eigenscript — found relative to the binary).
-ARG EIGS_REF=v0.25.0
+ARG EIGS_REF=v0.26.0
 RUN git clone --depth 1 --branch "${EIGS_REF}" \
         https://github.com/InauguralSystems/EigenScript.git /tmp/eigs \
  && make -C /tmp/eigs install PREFIX=/usr/local CC=gcc \
diff --git a/CLAUDE.md b/CLAUDE.md
index dc4fb03..e9f046e 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -48,7 +48,7 @@ playground build).
 EigenScript is **not** vendored. Pin v0.13.0 minimum (strings
 needed `<`/`<=` comparison and `ord of s`, both of which shipped in
 v0.13.0 — see GAPS.md for the fix history). CI pins the runtime via
-`.devcontainer/Dockerfile`'s `EIGS_REF` (currently **v0.25.0**) and
+`.devcontainer/Dockerfile`'s `EIGS_REF` (currently **v0.26.0**) and
 builds it from source — bump that to move the tested runtime.
 
 ## Run / test