basecamp comment: multiline ANSI-C quoted content can post a literal leading $

[aaajiao]

Summary

basecamp comment appears to preserve a leading $ when multiline content is passed with shell ANSI-C quoting ($'...'). The posted Basecamp comment starts with a literal $, even though the expected content starts with the first character inside the quoted string.

This is easy to hit from agent/shell workflows when posting multiline comments with attachments.

Observed

Command shape used from bash:

basecamp comment 9802493119 $'海报 mockup 方向稿：\n\n<bc-attachment ...></bc-attachment>' --in 17525144 --json

The command succeeded, but the created comment content began with a literal $:

$海报 mockup 方向稿：\n\n<bc-attachment ...>...</bc-attachment>

The attachment uploaded and rendered correctly; only the leading $ was unexpected.

Expected

The comment body should begin with:

海报 mockup 方向稿：

not:

$海报 mockup 方向稿：

Notes

This may be a shell/argument parsing edge case rather than Basecamp API behavior, but from the CLI user perspective it is surprising because the help documents:

basecamp comment <id|url> <content> [flags]

and multiline content/Markdown is a common use case for comments.

Potential fixes or mitigations:

1. Add explicit support for --content-file / stdin content for basecamp comment, so agents can avoid fragile shell quoting for multiline rich text.
2. Document the recommended safe multiline pattern (temp file/stdin/here-doc) and warn against $'...' if unsupported.
3. If the CLI currently receives literal $'...' from some execution contexts, strip only the ANSI-C quote wrapper safely before posting.

Environment

• basecamp CLI: 0.7.2
• Command: basecamp comment
• Context: Linux sandbox shell invoked by an agent workflow