Gemini CLI Hook Support (PR #131 Part 3)

Cargo.toml

@@ -26,6 +26,7 @@ rusqlite = { version = "0.31", features = ["bundled"] }
 toml = "0.8"
 chrono = "0.4"
 thiserror = "1.0"
+which = "7"
 tempfile = "3"
 
 [dev-dependencies]

INSTALL.md

@@ -67,6 +67,34 @@ rtk gain  # MUST show token savings, not "command not found"
 
 ⚠️ **WARNING**: `cargo install rtk` from crates.io might install the wrong package. Always verify with `rtk gain`.
 
+### Windows Installation
+
+RTK compiles natively for Windows. Download from GitHub Releases or:
+
+```bash
+cargo install --path .
+```
+
+Configure Claude Code `settings.json`:
+
+```json
+{
+  "hooks": {
+    "PreToolUse": [{
+      "matcher": "Bash",
+      "hooks": [{
+        "type": "command",
+        "command": "rtk hook claude"
+      }]
+    }]
+  }
+}
+```
+
+No bash, node, or bun required — `rtk hook claude` is a native Windows binary.
+The exec.rs shell selection (`cfg!(windows)`) automatically uses `cmd /C` on Windows
+and `sh -c` on Unix for passthrough commands.
+
 ## Project Initialization
 
 ### Recommended: Global Hook-First Setup
@@ -111,6 +139,37 @@ rtk init  # Creates ./CLAUDE.md with full RTK instructions (137 lines)
 
 **Token savings**: Instructions loaded only for this project
 
+### Gemini CLI Setup
+
+**Best for: Gemini CLI users wanting the same token optimization**
+
+```bash
+rtk init --gemini
+# → Registers "rtk hook gemini" in ~/.gemini/settings.json
+# → Prompts: "Patch settings.json? [y/N]"
+# → If yes: patches + creates backup (~/.gemini/settings.json.bak)
+
+# Automated alternatives:
+rtk init --gemini --auto-patch    # Patch without prompting
+rtk init --gemini --no-patch      # Print manual instructions instead
+
+# Verify installation
+rtk init --show  # Shows both Claude and Gemini hook status
+```
+
+**Manual setup** (if `rtk init --gemini` isn't available):
+```json
+// Add to ~/.gemini/settings.json
+{
+  "hooks": {
+    "BeforeTool": [{
+      "matcher": "run_shell_command",
+      "hooks": [{ "type": "command", "command": "rtk hook gemini" }]
+    }]
+  }
+}
+```
+
 ### Upgrading from Previous Version
 
 If you previously used `rtk init -g` with the old system (137-line injection):

README.md

@@ -6,7 +6,7 @@
 
 [Website](https://www.rtk-ai.app) | [GitHub](https://github.com/rtk-ai/rtk) | [Install](INSTALL.md)
 
-rtk filters and compresses command outputs before they reach your LLM context, saving 60-90% of tokens on common operations.
+rtk filters and compresses command outputs before they reach your LLM context, saving 60-90% of tokens on common operations. Works with **Claude Code** and **Gemini CLI**.
 
 ## ⚠️ Important: Name Collision Warning
 
@@ -624,19 +624,81 @@ chmod +x ~/.claude/hooks/rtk-suggest.sh
 
 The suggest hook detects the same commands as the rewrite hook but outputs a `systemMessage` instead of `updatedInput`, informing Claude Code that an rtk alternative exists.
 
+## Gemini CLI Integration
+
+RTK also supports [Gemini CLI](https://github.com/google-gemini/gemini-cli) via its **BeforeTool** hook protocol. The same safety engine that powers the Claude Code hook is used for Gemini, providing consistent command rewriting and blocking across both agents.
+
+### Quick Install (Automated)
+
+```bash
+rtk init --gemini
+# → Patches ~/.gemini/settings.json with BeforeTool hook
+# → Prompts: "Patch settings.json? [y/N]"
+# → Creates backup (~/.gemini/settings.json.bak) if file exists
+
+# Options:
+rtk init --gemini --auto-patch    # Patch without prompting (CI/CD)
+rtk init --gemini --no-patch      # Skip patching, print manual JSON snippet
+
+# Verify installation
+rtk init --show
+```
+
+### Manual Install
+
+Add the following to `~/.gemini/settings.json`:
+
+```json
+{
+  "hooks": {
+    "BeforeTool": [
+      {
+        "matcher": "run_shell_command",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "rtk hook gemini"
+          }
+        ]
+      }
+    ]
+  }
+}
+```
+
+### How It Works
+
+When Gemini CLI is about to execute a shell command, it sends a JSON payload to `rtk hook gemini` on stdin. RTK's safety engine evaluates the command and responds with:
+
+- **Allow + rewrite**: Rewrites the command to its `rtk run -c '...'` equivalent
+- **Block**: Returns `"deny"` with a reason explaining which native tool to use instead
+- **Passthrough**: Commands already using `rtk` pass through unchanged
+
+The `matcher` field (`run_shell_command`) identifies Gemini's shell execution tool (analogous to Claude Code's `Bash` matcher). Non-shell tool events pass through without inspection.
+
+### Uninstalling Gemini Hook
+
+```bash
+rtk init --gemini --uninstall
+# → Removes RTK hook entry from ~/.gemini/settings.json
+# → Preserves other hooks and settings
+```
+
+The global `rtk init -g --uninstall` also removes Gemini hooks alongside Claude Code hooks.
+
 ## Uninstalling RTK
 
 **Complete Removal (Global Only)**:
 ```bash
 rtk init -g --uninstall
 
 # Removes:
-#   - ~/.claude/hooks/rtk-rewrite.sh
+#   - RTK hook from ~/.claude/settings.json
+#   - RTK hook from ~/.gemini/settings.json
 #   - ~/.claude/RTK.md
 #   - @RTK.md reference from ~/.claude/CLAUDE.md
-#   - RTK hook entry from ~/.claude/settings.json
 
-# Restart Claude Code after uninstall
+# Restart Claude Code / Gemini CLI after uninstall
 ```
 
 **Restore from Backup** (if needed):