feat: add Jcode prompt overlay integration

docs/guide/getting-started/supported-agents.md

@@ -1,6 +1,6 @@
 ---
 title: Supported Agents
-description: How to integrate RTK with Claude Code, Cursor, Copilot, Cline, Windsurf, Codex, OpenCode, Hermes, Kilo Code, and Antigravity
+description: How to integrate RTK with Claude Code, Cursor, Copilot, Cline, Windsurf, Codex, Jcode, OpenCode, Hermes, Kilo Code, and Antigravity
 sidebar:
   order: 3
 ---
@@ -42,6 +42,7 @@ Agent runs "cargo test"
 | Codex CLI | AGENTS.md instructions | N/A |
 | Kilo Code | Rules file (prompt-level) | N/A |
 | Google Antigravity | Rules file (prompt-level) | N/A |
+| Jcode | Prompt overlay (prompt-level) | N/A |
 | Mistral Vibe | Planned ([#800](https://github.com/rtk-ai/rtk/issues/800)) | Pending upstream |
 
 ## Installation by agent
@@ -161,6 +162,15 @@ rtk init --agent antigravity    # creates .agents/rules/antigravity-rtk-rules.md
 
 Antigravity reads `.agents/rules/` as custom instructions. RTK adds guidance telling Antigravity to prefer `rtk <cmd>` over raw commands.
 
+### Jcode
+
+```bash
+rtk init --agent jcode       # creates .jcode/prompt-overlay.md in current project
+rtk init -g --agent jcode    # creates $JCODE_HOME/prompt-overlay.md or ~/.jcode/prompt-overlay.md
+```
+
+Jcode reads `prompt-overlay.md` as custom instructions. RTK adds guidance telling Jcode to prefer `rtk <cmd>` when using its `bash` / `shell_exec` tool. This is prompt-level guidance until Jcode exposes a before-tool hook that can mutate `command`.
+
 ### Mistral Vibe (planned)
 
 Support is blocked on upstream `BeforeToolCallback` ([mistral-vibe#531](https://github.com/mistralai/mistral-vibe/issues/531)). Tracked in [#800](https://github.com/rtk-ai/rtk/issues/800).
@@ -173,7 +183,7 @@ Support is blocked on upstream `BeforeToolCallback` ([mistral-vibe#531](https://
 | **Plugin** | TypeScript, JavaScript, or Python in agent's plugin system | Transparent, in-place mutation when the agent allows it |
 | **Rules file** | Prompt-level instructions | Guidance only — agent is told to prefer `rtk <cmd>` |
 
-Rules file integrations (Cline, Windsurf, Codex, Kilo Code, Antigravity) rely on the model following instructions. Full hook integrations (Claude Code, Cursor, Gemini) are guaranteed — the command is rewritten before the agent sees it. Plugin integrations (OpenCode, Pi) use in-place mutation via the agent's TypeScript extension API.
+Rules file integrations (Cline, Windsurf, Codex, Kilo Code, Antigravity, Jcode) rely on the model following instructions. Full hook integrations (Claude Code, Cursor, Gemini) are guaranteed — the command is rewritten before the agent sees it. Plugin integrations (OpenCode, Pi) use in-place mutation via the agent's TypeScript extension API.
 
 ## Windows support
 

hooks/README.md

@@ -4,7 +4,7 @@
 
 **Deployed hook artifacts** — the actual files installed on user machines by `rtk init`. These are shell scripts, TypeScript plugins, and rules files that run outside the Rust binary. They are **thin delegates**: parse agent-specific JSON, call `rtk rewrite` as a subprocess, format agent-specific response. Zero filtering logic lives here.
 
-Owns: per-agent hook scripts and configuration files for 9 supported agents (Claude Code, Copilot, Cursor, Cline, Windsurf, Codex, OpenCode, Hermes, Pi).
+Owns: per-agent hook scripts and configuration files for 10 supported agents (Claude Code, Copilot, Cursor, Cline, Windsurf, Codex, OpenCode, Hermes, Pi, Jcode).
 
 Does **not** own: hook installation/uninstallation (that's `src/hooks/init.rs`), the rewrite pattern registry (that's `discover/registry`), or integrity verification (that's `src/hooks/integrity.rs`).
 
@@ -42,6 +42,7 @@ Each agent subdirectory has its own README with hook-specific details:
 - **[`opencode/`](opencode/README.md)** — TypeScript plugin, `zx` library, `tool.execute.before` event, in-place mutation
 - **[`pi/`](pi/README.md)** — TypeScript extension, `tool_call` event, `isToolCallEventType` guard, in-place mutation, `~/.pi/agent/extensions/`
 - **[`hermes/`](hermes/README.md)** — Python plugin, `pre_tool_call` hook, in-place terminal command mutation
+- **[`jcode/`](jcode/README.md)** — Prompt overlay, `.jcode/prompt-overlay.md` project-local or `$JCODE_HOME/prompt-overlay.md` global
 
 ## Supported Agents
 
@@ -58,6 +59,7 @@ Each agent subdirectory has its own README with hook-specific details:
 | OpenCode | TypeScript plugin (`tool.execute.before`) | In-place mutation | Yes |
 | Pi | TypeScript extension (`tool_call` event) | In-place mutation | Yes |
 | Hermes | Python plugin (`pre_tool_call`) | In-place mutation | Yes |
+| Jcode | Prompt overlay (`prompt-overlay.md`) | Prompt-level guidance | N/A |
 
 ## JSON Formats by Agent
 

hooks/jcode/README.md

@@ -0,0 +1,45 @@
+# RTK for Jcode
+
+Jcode currently supports prompt-level RTK integration through `prompt-overlay.md`.
+
+## Installation
+
+Project-scoped:
+
+```bash
+rtk init --agent jcode
+```
+
+Creates or updates:
+
+```text
+.jcode/prompt-overlay.md
+```
+
+Global:
+
+```bash
+rtk init -g --agent jcode
+```
+
+Creates or updates:
+
+```text
+$JCODE_HOME/prompt-overlay.md
+```
+
+If `JCODE_HOME` is unset, RTK uses:
+
+```text
+~/.jcode/prompt-overlay.md
+```
+
+## How it works
+
+Jcode reads prompt overlay files and incorporates them into the agent instructions. RTK adds a marked instruction block telling Jcode to prefer `rtk <command>` when using its `bash` or `shell_exec` tool.
+
+This is a prompt-level integration. It does not transparently rewrite commands before execution because current Jcode builds do not expose a before-tool hook with `updated_input.command` support.
+
+## Future transparent rewrite support
+
+If Jcode adds a `BeforeToolCall` hook that can mutate the `command` field, RTK can add `rtk hook jcode` and upgrade this integration to transparent command rewriting.

hooks/jcode/rules.md

@@ -0,0 +1,23 @@
+<!-- rtk-instructions jcode v1 -->
+# RTK command usage for Jcode
+
+When using Jcode's `bash` or `shell_exec` tool, prefer RTK-wrapped commands for supported developer workflows. RTK filters noisy command output before it reaches the model context.
+
+Use RTK for common commands such as:
+
+- `rtk git status` instead of `git status`
+- `rtk git diff` instead of `git diff`
+- `rtk git log` instead of `git log`
+- `rtk cargo test` instead of `cargo test`
+- `rtk cargo build` instead of `cargo build`
+- `rtk npm install` instead of `npm install`
+- `rtk pytest` instead of `pytest`
+- `rtk grep <pattern> <path>` instead of raw `grep` when compact output is acceptable
+
+Rules:
+
+- If a command already starts with `rtk`, do not add another `rtk`.
+- Use raw commands only when RTK is unavailable, unsuitable, or exact raw output is required.
+- For chained commands, prefix each supported command separately when practical, for example `rtk cargo fmt && rtk cargo test`.
+- RTK is safe for unsupported commands because it passes through when no filter applies.
+<!-- /rtk-instructions -->

integration-docs/README.md

@@ -0,0 +1,9 @@
+# Integration Analysis Documents
+
+This directory stores exploratory integration analysis and design notes for agent support work.
+
+These files are intentionally kept outside RTK's product documentation under `docs/` so experimental or implementation-planning material does not pollute user-facing docs.
+
+## Current analyses
+
+- [`jcode/agent-requirements.zh.md`](jcode/agent-requirements.zh.md) — Jcode capabilities and RTK integration requirements.