Bug

When using mcp__github_comment__update_claude_comment to post a comment containing an HTML comment marker like <!-- claude-code-review -->, the ! character gets escaped to \!, resulting in <\!-- claude-code-review --> being stored in the comment body.

Since <\!-- is not valid HTML comment syntax, GitHub renders it as visible text instead of hiding it.

Reproduction

1. Configure a workflow that uses claude-code-action with a prompt instructing Claude to include <!-- some-marker --> in a comment body via mcp__github_comment__update_claude_comment
2. Trigger the workflow
3. Observe the posted comment contains <\!-- some-marker --> (with \!)

Expected behavior

The HTML comment <!-- some-marker --> should be posted verbatim, so GitHub hides it as intended.

Actual behavior

The ! is escaped to \!, producing <\!-- some-marker --> which renders as visible text.

Root cause

This is likely bash history expansion escaping the ! character when the comment body passes through a shell context with double quotes. In bash, ! triggers history expansion inside double-quoted strings and gets escaped to \!.

Example

• PR: chore: add error logging to down migrations and password round-trip test shellhub-io/shellhub#5868
• Comment with the issue: chore: add error logging to down migrations and password round-trip test shellhub-io/shellhub#5868 (comment)

Environment

• anthropics/claude-code-action@v1
• --model claude-opus-4-6
• Using track_progress and mcp__github_comment__update_claude_comment