RTK (Rust Token Killer)

The Mistral Vibe hook is implemented as a subcommand of the RTK Rust binary (rtk hook vibe). It operates by intercepting Vibe's stdin JSON payload and performing transparent command rewrites.

Hook Configuration

The hook is declared in ~/.vibe/hooks.toml with the following requirements:

• match = "bash"
• strict = false

Data Flow

1. Input: The hook reads a JSON payload from stdin containing tool_name, tool_input.command, hook_event_name, and session_id.
2. Processing: The rtk hook vibe binary processes the command.
3. Output: The hook returns hook_specific_output.tool_input.command to perform the rewrite and a system_message to provide visibility in the UI.

Error Handling and Passthrough

• Passthrough: If the tool is not bash, the command is empty, the JSON is malformed, or the command is unknown to RTK, the hook exits with code 0 and empty stdout (allowing the original command to proceed).
• Permission Denied: If RTK denies a command, the hook returns: {"decision":"deny","reason":"..."}.

Fallback Mechanism

By default, a system prompt is installed at ~/.vibe/prompts/rtk.md to act as a fallback. You can skip this prompt installation by using the --hook-only flag during setup.

RTK uses a sophisticated pipeline to ensure shell commands are rewritten safely without breaking syntax:

1. Tokenization

A lexer (lexer.rs) converts raw strings into typed tokens. This prevents errors caused by naive string splitting, such as breaking on quoted content like git commit -m "fix && update".

2. Compound Splitting

The engine splits commands on operators (&&, ||, ;) and pipes (|, |&).

• Safety Rule: For standard pipelines, only the final stage marked pipeline_final_safe is rewritten.
• Exclusions: Stderr pipelines (|&) and pipelines containing opaque shell groups remain raw to prevent corruption.

3. Per-segment Rewriting

Each command segment undergoes these steps:

• Strip Redirects: Trailing redirects like 2>&1 or >/dev/null are stripped and re-appended after the rewrite.
• Short-circuit Special Cases: Specific patterns like head -20 file are converted to rtk read file --max-lines 20 rather than using generic prefix replacement.
• Classification: The command is normalized (stripping sudo, environment variables, and absolute paths) and matched against 60+ regex patterns.
• Application: The matching prefix is replaced with rtk <cmd>, and the original environment prefixes and redirects are re-applied.

4. Rewrite Guards (When rewriting is skipped)

Rewriting is automatically skipped if:

• RTK_DISABLED=1 is present in the environment prefix.
• The command is gh with structured output flags (--json, --jq, --template).
• The command is cat with flags other than -n.
• The command involves write operations (e.g., cat or head with > or >>).
• The command is explicitly listed in the hooks.exclude_commands configuration.

RTK provides specialized wrappers for common PHP CLI tools to improve developer experience by cleaning up noise and focusing on actionable errors.

Key behaviors include:

• Syntax Checks: php -l syntax checks are summarized via php_cmd.rs.
• Laravel Artisan: php artisan* commands are routed to specialized helpers. artisan_cmd.rs cleans the output and applies runner-aware filtering specifically for php artisan test.
• Testing Frameworks:
  • phpunit_cmd.rs strips progress and header noise, preserving only failure details and the final summary.
  • pest_cmd.rs and paratest_cmd.rs suppress compact progress to provide test-focused output.
  • test_output.rs provides the shared filtering logic used by PHPUnit, Pest, and ParaTest.
• Static Analysis & Linting:
  • phpstan_cmd.rs injects JSON output by default and emits compact file/line error summaries.
  • ecs_cmd.rs (EasyCodingStandard) condenses output while preserving file paths and error lines.

Tool Resolution Strategy: RTK uses a specific resolution order for all PHP tools: it first attempts to resolve binaries from the local vendor/bin/* directory, falling back to global binaries if no local version is found.

RTK follows a least-privilege permission precedence: Deny > Ask > Allow (explicit) > Default (ask). It extracts Bash(...) rules from Claude Code settings.json files (project, global, and .local variants) to determine if a command should be rewritten.

Permission Verdicts and Behavior

Per-tool Support Details