feat(init): add --opencode flag for OpenCode plugin install

README.md

@@ -98,23 +98,33 @@ rtk gain        # Should show token savings stats
 
 ## Quick Start
 
+### Claude Code
+
 ```bash
-# 1. Install hook for Claude Code (recommended)
+# Install hook for Claude Code
 rtk init --global
 # Follow instructions to register in ~/.claude/settings.json
+# Restart Claude Code, then test
+git status  # Automatically rewritten to rtk git status
+```
 
-# 2. Restart Claude Code, then test
+### OpenCode
+
+```bash
+# Install plugin for OpenCode (opencode.ai)
+rtk init --opencode
+# Restart OpenCode, then test
 git status  # Automatically rewritten to rtk git status
 ```
 
-The hook transparently rewrites commands (e.g., `git status` -> `rtk git status`) before execution. Claude never sees the rewrite, it just gets compressed output.
+The hook/plugin transparently rewrites commands (e.g., `git status` -> `rtk git status`) before execution. The LLM never sees the rewrite, it just gets compressed output.
 
 ## How It Works
 
 ```
   Without rtk:                                    With rtk:
 
-  Claude  --git status-->  shell  -->  git         Claude  --git status-->  RTK  -->  git
+  Agent  --git status-->  shell  -->  git         Agent  --git status-->  RTK  -->  git
     ^                                   |            ^                      |          |
     |        ~2,000 tokens (raw)        |            |   ~200 tokens        | filter   |
     +-----------------------------------+            +------- (filtered) ---+----------+
@@ -268,7 +278,7 @@ The most effective way to use rtk. The hook transparently intercepts Bash comman
 
 **Result**: 100% rtk adoption across all conversations and subagents, zero token overhead.
 
-### Setup
+### Claude Code Setup
 
 ```bash
 rtk init -g                 # Install hook + RTK.md (recommended)
@@ -279,6 +289,14 @@ rtk init --show             # Verify installation
 
 After install, **restart Claude Code**.
 
+### OpenCode Setup
+
+```bash
+rtk init --opencode         # Install plugin to ~/.config/opencode/plugins/
+```
+
+After install, **restart OpenCode**. The plugin uses OpenCode's `tool.execute.before` hook to rewrite commands transparently.
+
 ### Commands Rewritten
 
 | Raw Command | Rewritten To |

hooks/opencode-rtk.js

@@ -0,0 +1,89 @@
+/**
+ * opencode-rtk — OpenCode plugin for rtk (Rust Token Killer)
+ *
+ * Transparently rewrites bash commands to use rtk equivalents,
+ * reducing LLM token consumption by 60-90% on common dev commands.
+ *
+ * Requires: rtk >= 0.23.0 (https://github.com/rtk-ai/rtk)
+ *
+ * Equivalent to rtk's Claude Code PreToolUse hook, adapted for
+ * OpenCode's plugin API (tool.execute.before hook).
+ */
+
+import { execFileSync, execSync } from "child_process";
+
+/**
+ * Check if rtk binary is available and meets minimum version.
+ * Returns true if available, null if unavailable.
+ */
+const checkRtk = () => {
+  try {
+    const version = execSync("rtk --version 2>/dev/null", {
+      encoding: "utf8",
+      timeout: 5000,
+    }).trim();
+
+    const match = version.match(/(\d+)\.(\d+)\.(\d+)/);
+    if (!match) return null;
+
+    const [, major, minor] = match.map(Number);
+    if (major === 0 && minor < 23) {
+      console.warn(
+        `[opencode-rtk] rtk ${match[0]} too old (need >= 0.23.0). Upgrade: brew upgrade rtk`,
+      );
+      return null;
+    }
+
+    return true;
+  } catch {
+    return null;
+  }
+};
+
+/**
+ * Call `rtk rewrite` on a command string.
+ * Returns the rewritten command, or null if no rewrite available.
+ */
+const rewriteCommand = (cmd) => {
+  try {
+    const rewritten = execFileSync("rtk", ["rewrite", cmd], {
+      encoding: "utf8",
+      timeout: 5000,
+      stdio: ["pipe", "pipe", "pipe"],
+    }).trim();
+
+    if (rewritten && rewritten !== cmd) {
+      return rewritten;
+    }
+    return null;
+  } catch {
+    return null;
+  }
+};
+
+export const RtkPlugin = async (_ctx) => {
+  const available = checkRtk();
+  if (!available) {
+    console.warn("[opencode-rtk] rtk binary not found or too old — plugin disabled");
+    return {};
+  }
+
+  const debug = process.env.RTK_DEBUG === "1";
+
+  return {
+    "tool.execute.before": async (input, output) => {
+      if (input.tool !== "bash") return;
+
+      const cmd = output.args?.command;
+      if (!cmd || typeof cmd !== "string") return;
+
+      const rewritten = rewriteCommand(cmd);
+      if (rewritten) {
+        output.args.command = rewritten;
+        if (debug) {
+          console.error(`[opencode-rtk] ${cmd} → ${rewritten}`);
+        }
+      }
+    },
+  };
+};

src/init.rs

@@ -43,6 +43,9 @@ schema_version = 1
 # max_lines = 40
 "#;
 
+// Embedded OpenCode plugin for tool.execute.before hook
+const OPENCODE_PLUGIN: &str = include_str!("../hooks/opencode-rtk.js");
+
 /// Control flow for settings.json patching
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub enum PatchMode {
@@ -858,6 +861,50 @@ fn run_hook_only_mode(global: bool, patch_mode: PatchMode, verbose: u8) -> Resul
     Ok(())
 }
 
+/// OpenCode mode: install plugin to ~/.config/opencode/plugins/
+pub fn run_opencode_mode(verbose: u8) -> Result<()> {
+    let opencode_dir = resolve_opencode_dir()?;
+    let plugins_dir = opencode_dir.join("plugins");
+    let plugin_path = plugins_dir.join("opencode-rtk.js");
+
+    // Check OpenCode is installed
+    if !opencode_dir.exists() {
+        anyhow::bail!(
+            "OpenCode config directory not found at {}\n\
+             Install OpenCode first: https://opencode.ai",
+            opencode_dir.display()
+        );
+    }
+
+    // Create plugins directory if needed
+    fs::create_dir_all(&plugins_dir).with_context(|| {
+        format!(
+            "Failed to create plugins directory: {}",
+            plugins_dir.display()
+        )
+    })?;
+
+    // Write plugin (idempotent)
+    let changed = write_if_changed(&plugin_path, OPENCODE_PLUGIN, "opencode-rtk.js", verbose)?;
+
+    let status = if changed {
+        "installed/updated"
+    } else {
+        "already up to date"
+    };
+
+    println!("\nRTK OpenCode plugin {} ✓\n", status);
+    println!("  Plugin: {}", plugin_path.display());
+    println!(
+        "  OpenCode auto-discovers plugins from {}/",
+        plugins_dir.display()
+    );
+    println!("\n  Restart OpenCode to activate. Test with: git status");
+    println!();
+
+    Ok(())
+}
+
 /// Legacy mode: full 137-line injection into CLAUDE.md
 fn run_claude_md_mode(global: bool, verbose: u8) -> Result<()> {
     let path = if global {
@@ -1091,6 +1138,13 @@ fn resolve_claude_dir() -> Result<PathBuf> {
         .context("Cannot determine home directory. Is $HOME set?")
 }
 
+/// Resolve OpenCode configuration directory
+fn resolve_opencode_dir() -> Result<PathBuf> {
+    dirs::home_dir()
+        .map(|h| h.join(".config").join("opencode"))
+        .context("Cannot determine home directory. Is $HOME set?")
+}
+
 /// Show current rtk configuration
 pub fn show_config() -> Result<()> {
     let claude_dir = resolve_claude_dir()?;

src/main.rs

@@ -325,6 +325,10 @@ enum Commands {
         #[arg(long = "hook-only", group = "mode")]
         hook_only: bool,
 
+        /// Install OpenCode plugin (auto-rewrite hook for opencode.ai)
+        #[arg(long, group = "mode")]
+        opencode: bool,
+
         /// Auto-patch settings.json without prompting
         #[arg(long = "auto-patch", group = "patch")]
         auto_patch: bool,
@@ -1486,6 +1490,7 @@ fn main() -> Result<()> {
             show,
             claude_md,
             hook_only,
+            opencode,
             auto_patch,
             no_patch,
             uninstall,
@@ -1494,6 +1499,8 @@ fn main() -> Result<()> {
                 init::show_config()?;
             } else if uninstall {
                 init::uninstall(global, cli.verbose)?;
+            } else if opencode {
+                init::run_opencode_mode(cli.verbose)?;
             } else {
                 let patch_mode = if auto_patch {
                     init::PatchMode::Auto