docs: Document Claude Code Provider CLAUDE.md injection behavior

- Add detailed documentation explaining CLAUDE.md auto-injection
- Update README with Known Issues section
- Clarify this is Claude CLI behavior, not Roo-Code
- Provide guidance for users about this feature

Fixes #6604

Author: roomote

README.md

@@ -122,6 +122,18 @@ Make Roo Code work your way with:
 
 ---
 
+## Known Issues
+
+### Claude Code Provider - CLAUDE.md Injection
+
+When using the Claude Code Provider, the Claude CLI tool (as of version 1.0.62) automatically injects content from `CLAUDE.md` files if they exist in your repository root. This is a behavior of the Claude CLI tool itself, not Roo Code.
+
+**Important:** If you have a `CLAUDE.md` file in your repository and are using the Claude Code Provider, its contents will be automatically included in the context sent to Claude, even without explicitly reading the file.
+
+For more details, see [docs/claude-code-provider-notes.md](docs/claude-code-provider-notes.md).
+
+---
+
 ## Local Setup & Development
 
 1. **Clone** the repo:

docs/claude-code-provider-notes.md

@@ -0,0 +1,37 @@
+# Claude Code Provider - CLAUDE.md Injection Notice
+
+## Overview
+
+When using the Claude Code Provider in Roo-Code, users may notice that the Claude CLI tool automatically injects content from `CLAUDE.md` files if they exist in the repository root. This is a behavior of the Claude CLI tool itself (as of version 1.0.62), not a feature implemented by Roo-Code.
+
+## How It Works
+
+1. Roo-Code integrates with the Claude CLI tool by executing it as a subprocess
+2. The system prompt is passed to the Claude CLI via:
+    - `--system-prompt` flag on non-Windows systems
+    - stdin on Windows systems (to avoid command length limitations)
+3. The Claude CLI tool independently checks for and injects `CLAUDE.md` content
+
+## Important Notes
+
+- This injection happens at the Claude CLI level, before Roo-Code receives any response
+- Roo-Code does not read or inject `CLAUDE.md` files - this is entirely handled by the Claude CLI
+- The behavior may change in future versions of the Claude CLI tool
+
+## Implications
+
+If you have a `CLAUDE.md` file in your repository root and are using the Claude Code Provider:
+
+- The contents will be automatically included in the context sent to Claude
+- This happens transparently without explicit indication in the Roo-Code interface
+- The AI will be aware of the `CLAUDE.md` contents even without using file reading tools
+
+## Recommendations
+
+- Be aware that `CLAUDE.md` files are automatically injected when using Claude Code Provider
+- If you don't want this behavior, avoid naming files `CLAUDE.md` in your repository root
+- This behavior is specific to the Claude Code Provider and does not affect other API providers
+
+## Reference
+
+This behavior was reported in [Issue #6604](https://github.com/RooCodeInc/Roo-Code/issues/6604).