diff --git a/Dockerfile b/Dockerfile
index 70a7726..d014f85 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -33,7 +33,11 @@ RUN apt-get update && apt-get install -y --no-install-recommends python3-venv \
   && /opt/tilion/bin/python -c "import tilion_fortress as t; tag = t._CHANNELS['latest']['tag']; t._download('linux-x64', t._host(tag), tag)"
 
 # Claude Code CLI must be on PATH: pi-claude-code-provider shells out to `claude`.
-RUN npm install -g @anthropic-ai/claude-code
+# Pinned to the version pi-claude-code-provider 0.4.0 is tested against (its
+# src/compatibility.ts). The provider rejects any stream-json record ahead of
+# system/init, so an unpinned newer CLI can break every turn with
+# "Claude emitted a record before initialization". Bump together with the provider.
+RUN npm install -g @anthropic-ai/claude-code@2.1.278
 
 COPY docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
 RUN chmod +x /usr/local/bin/docker-entrypoint.sh