fix(claude-code): patch playwright MCP on every session start (#98)

.github/workflows/build-claude-code.yml

@@ -6,6 +6,7 @@ on:
     paths:
       - "claude-code/.devcontainer/Dockerfile"
       - "claude-code/.devcontainer/*.sh"
+      - "claude-code/.devcontainer/managed-settings.json"
   schedule:
     - cron: '13 11 * * *'
   workflow_dispatch:
@@ -76,19 +77,19 @@ jobs:
       matrix:
         include:
           - image-suffix: claude-code
-            verify-command: "bun --version || true && claude --version && mise --version && fish --version && rtk --version && ralphex --version && test -x /usr/local/bin/patch-playwright-mcp && printenv AGENT_BROWSER_EXECUTABLE_PATH | grep -qx /usr/bin/chromium"
+            verify-command: "bun --version || true && claude --version && mise --version && fish --version && rtk --version && ralphex --version && test -x /usr/local/bin/patch-playwright-mcp && jq -e '.hooks.SessionStart[0].hooks[0].command == \"/usr/local/bin/patch-playwright-mcp\"' /etc/claude-code/managed-settings.json >/dev/null && printenv AGENT_BROWSER_EXECUTABLE_PATH | grep -qx /usr/bin/chromium"
             runner: ubuntu-24.04
             arch: amd64
           - image-suffix: claude-code
-            verify-command: "bun --version || true && claude --version && mise --version && fish --version && rtk --version && ralphex --version && test -x /usr/local/bin/patch-playwright-mcp && printenv AGENT_BROWSER_EXECUTABLE_PATH | grep -qx /usr/bin/chromium"
+            verify-command: "bun --version || true && claude --version && mise --version && fish --version && rtk --version && ralphex --version && test -x /usr/local/bin/patch-playwright-mcp && jq -e '.hooks.SessionStart[0].hooks[0].command == \"/usr/local/bin/patch-playwright-mcp\"' /etc/claude-code/managed-settings.json >/dev/null && printenv AGENT_BROWSER_EXECUTABLE_PATH | grep -qx /usr/bin/chromium"
             runner: ubuntu-24.04-arm
             arch: arm64
           - image-suffix: claude-code-sandbox
-            verify-command: "claude --version && mise --version && fish --version && which iptables && rtk --version && ralphex --version && test -x /usr/local/bin/patch-playwright-mcp"
+            verify-command: "claude --version && mise --version && fish --version && which iptables && rtk --version && ralphex --version && test -x /usr/local/bin/patch-playwright-mcp && jq -e '.hooks.SessionStart[0].hooks[0].command == \"/usr/local/bin/patch-playwright-mcp\"' /etc/claude-code/managed-settings.json >/dev/null"
             runner: ubuntu-24.04
             arch: amd64
           - image-suffix: claude-code-sandbox
-            verify-command: "claude --version && mise --version && fish --version && which iptables && rtk --version && ralphex --version && test -x /usr/local/bin/patch-playwright-mcp"
+            verify-command: "claude --version && mise --version && fish --version && which iptables && rtk --version && ralphex --version && test -x /usr/local/bin/patch-playwright-mcp && jq -e '.hooks.SessionStart[0].hooks[0].command == \"/usr/local/bin/patch-playwright-mcp\"' /etc/claude-code/managed-settings.json >/dev/null"
             runner: ubuntu-24.04-arm
             arch: arm64
     runs-on: ${{ matrix.runner }}

claude-code/.devcontainer/Dockerfile

@@ -140,10 +140,18 @@ COPY --from=ralphex-download /usr/local/bin/ralphex /usr/local/bin/ralphex
 # ── Playwright MCP patch script ──────────────────────────────────────────────
 # Universal logic with no project-specific config — bake into the image so
 # consumer projects don't carry a copy. Invoked from postCreateCommand
-# (init-plugins.sh) and postStartCommand (devcontainer.json) to re-patch
-# plugin auto-updates between sessions. See issue #87.
+# (init-plugins.sh), postStartCommand (devcontainer.json), and the Claude Code
+# SessionStart hook (managed-settings.json below) — the hook closes the gap
+# where the plugin auto-updates mid-container-run. See issues #87, #98.
 COPY --chmod=0755 patch-playwright-mcp.sh /usr/local/bin/patch-playwright-mcp
 
+# ── Claude Code managed settings ─────────────────────────────────────────────
+# Image-policy settings at the Linux managed location (highest precedence,
+# outside any volume mount). Wires patch-playwright-mcp as a SessionStart hook
+# so cache dirs created by mid-session plugin auto-updates get patched before
+# the next session reads them. See issue #98.
+COPY --chmod=0644 managed-settings.json /etc/claude-code/managed-settings.json
+
 # ── Claude Code CLI ───────────────────────────────────────────────────────────
 # Using npm instead of the native installer (curl claude.ai/install.sh | bash).
 # The native installer is recommended for interactive use, but rate-limits (429)

claude-code/.devcontainer/claude-sandbox/devcontainer.json

@@ -124,9 +124,9 @@
   // Chromium is baked into the sandbox image (firewall blocks runtime install).
   "postCreateCommand": "sudo find /workspace -maxdepth 4 -name node_modules -type d -exec chown node {} + && sudo chown -R node /home/node/.claude && mise install && bun install",
   // Firewall init (bind-mounted from project) + re-patch the Playwright MCP
-  // plugin's .mcp.json. The patch runs on every start so plugin auto-updates
-  // between sessions don't leave MCP pointing at the missing chrome channel.
-  // See issues #85, #87.
+  // plugin's .mcp.json. The patch is defense in depth alongside the SessionStart
+  // hook in /etc/claude-code/managed-settings.json, which handles the case where
+  // the plugin auto-updates mid-container-run. See issues #85, #87, #98.
   "postStartCommand": "sudo /usr/local/bin/init-firewall.sh && /usr/local/bin/patch-playwright-mcp",
   "waitFor": "postStartCommand"
 }

claude-code/.devcontainer/devcontainer.json

@@ -111,10 +111,10 @@
   // Chromium is baked into the image via apt — no playwright install step needed.
   // Projects' playwright.config.ts should use process.env.PLAYWRIGHT_CHROMIUM_EXECUTABLE_PATH.
   "updateContentCommand": "sudo find /workspace -maxdepth 4 -name node_modules -type d -exec chown node {} + && sudo chown -R node /home/node/.claude && mise install && bun install",
-  // Re-patch the Playwright MCP plugin's .mcp.json on every start.
-  // Plugin auto-updates between sessions create new cache dirs whose .mcp.json
-  // points at /opt/google/chrome/chrome (which we don't ship). Without this,
-  // MCP silently breaks until the next image rebuild. See issues #85, #87.
+  // Re-patch the Playwright MCP plugin's .mcp.json on every start. Defense in
+  // depth alongside the SessionStart hook in /etc/claude-code/managed-settings.json,
+  // which handles the case where the plugin auto-updates mid-container-run.
+  // See issues #85, #87, #98.
   "postStartCommand": "/usr/local/bin/patch-playwright-mcp",
   "waitFor": "postCreateCommand"
 }

claude-code/.devcontainer/init-plugins.sh

@@ -59,7 +59,8 @@ done
 # ── Playwright MCP: route every cached .mcp.json to system chromium ─────────
 # Universal across arches (no Chrome stable binary in either default or sandbox).
 # The patch binary is baked into the image (see Dockerfile #87) and also runs
-# from postStartCommand to catch plugin auto-updates between sessions (#85).
+# from postStartCommand (#85) and a Claude Code SessionStart hook (#98) — the
+# hook is what closes the gap when the plugin auto-updates mid-container-run.
 /usr/local/bin/patch-playwright-mcp
 
 # ── rtk init (token-optimized CLI proxy) ────────────────────────────────────

claude-code/.devcontainer/managed-settings.json

@@ -0,0 +1,14 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "/usr/local/bin/patch-playwright-mcp"
+          }
+        ]
+      }
+    ]
+  }
+}