feat(gemini): add Gemini CLI as sixth target provider

Add `--to gemini` support for both `convert` and `install` commands,
converting Claude Code plugins into Gemini CLI-compatible format.

- Agents convert to `.gemini/skills/*/SKILL.md` with description frontmatter
- Commands convert to `.gemini/commands/*.toml` with TOML prompt format
- Namespaced commands create directory structure (workflows:plan -> workflows/plan.toml)
- Skills pass through unchanged (identical SKILL.md standard)
- MCP servers written to `.gemini/settings.json` with merge support
- Content transforms: .claude/ paths, Task calls, @agent references
- Hooks emit warning (different format in Gemini)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/commands/convert.ts

@@ -23,7 +23,7 @@ export default defineCommand({
     to: {
       type: "string",
       default: "opencode",
-      description: "Target format (opencode | codex | droid | cursor | pi)",
+      description: "Target format (opencode | codex | droid | cursor | pi | gemini)",
     },
     output: {
       type: "string",
@@ -145,5 +145,6 @@ function resolveTargetOutputRoot(targetName: string, outputRoot: string, codexHo
   if (targetName === "pi") return piHome
   if (targetName === "droid") return path.join(os.homedir(), ".factory")
   if (targetName === "cursor") return path.join(outputRoot, ".cursor")
+  if (targetName === "gemini") return path.join(outputRoot, ".gemini")
   return outputRoot
 }

src/commands/install.ts

@@ -25,7 +25,7 @@ export default defineCommand({
     to: {
       type: "string",
       default: "opencode",
-      description: "Target format (opencode | codex | droid | cursor | pi)",
+      description: "Target format (opencode | codex | droid | cursor | pi | gemini)",
     },
     output: {
       type: "string",
@@ -183,6 +183,10 @@ function resolveTargetOutputRoot(
     const base = hasExplicitOutput ? outputRoot : process.cwd()
     return path.join(base, ".cursor")
   }
+  if (targetName === "gemini") {
+    const base = hasExplicitOutput ? outputRoot : process.cwd()
+    return path.join(base, ".gemini")
+  }
   return outputRoot
 }
 

src/converters/claude-to-gemini.ts

@@ -0,0 +1,193 @@
+import { formatFrontmatter } from "../utils/frontmatter"
+import type { ClaudeAgent, ClaudeCommand, ClaudeMcpServer, ClaudePlugin } from "../types/claude"
+import type { GeminiBundle, GeminiCommand, GeminiSkill } from "../types/gemini"
+import type { ClaudeToOpenCodeOptions } from "./claude-to-opencode"
+
+export type ClaudeToGeminiOptions = ClaudeToOpenCodeOptions
+
+const GEMINI_DESCRIPTION_MAX_LENGTH = 1024
+
+export function convertClaudeToGemini(
+  plugin: ClaudePlugin,
+  _options: ClaudeToGeminiOptions,
+): GeminiBundle {
+  const usedSkillNames = new Set<string>()
+  const usedCommandNames = new Set<string>()
+
+  const skillDirs = plugin.skills.map((skill) => ({
+    name: skill.name,
+    sourceDir: skill.sourceDir,
+  }))
+
+  // Reserve skill names from pass-through skills
+  for (const skill of skillDirs) {
+    usedSkillNames.add(normalizeName(skill.name))
+  }
+
+  const generatedSkills = plugin.agents.map((agent) => convertAgentToSkill(agent, usedSkillNames))
+
+  const commands = plugin.commands.map((command) => convertCommand(command, usedCommandNames))
+
+  const mcpServers = convertMcpServers(plugin.mcpServers)
+
+  if (plugin.hooks && Object.keys(plugin.hooks.hooks).length > 0) {
+    console.warn("Warning: Gemini CLI hooks use a different format (BeforeTool/AfterTool with matchers). Hooks were skipped during conversion.")
+  }
+
+  return { generatedSkills, skillDirs, commands, mcpServers }
+}
+
+function convertAgentToSkill(agent: ClaudeAgent, usedNames: Set<string>): GeminiSkill {
+  const name = uniqueName(normalizeName(agent.name), usedNames)
+  const description = sanitizeDescription(
+    agent.description ?? `Use this skill for ${agent.name} tasks`,
+  )
+
+  const frontmatter: Record<string, unknown> = { name, description }
+
+  let body = transformContentForGemini(agent.body.trim())
+  if (agent.capabilities && agent.capabilities.length > 0) {
+    const capabilities = agent.capabilities.map((c) => `- ${c}`).join("\n")
+    body = `## Capabilities\n${capabilities}\n\n${body}`.trim()
+  }
+  if (body.length === 0) {
+    body = `Instructions converted from the ${agent.name} agent.`
+  }
+
+  const content = formatFrontmatter(frontmatter, body)
+  return { name, content }
+}
+
+function convertCommand(command: ClaudeCommand, usedNames: Set<string>): GeminiCommand {
+  // Preserve namespace structure: workflows:plan -> workflows/plan
+  const commandPath = resolveCommandPath(command.name)
+  const pathKey = commandPath.join("/")
+  uniqueName(pathKey, usedNames) // Track for dedup
+
+  const description = command.description ?? `Converted from Claude command ${command.name}`
+  const transformedBody = transformContentForGemini(command.body.trim())
+
+  let prompt = transformedBody
+  if (command.argumentHint) {
+    prompt += `\n\nUser request: {{args}}`
+  }
+
+  const content = toToml(description, prompt)
+  return { name: pathKey, content }
+}
+
+/**
+ * Transform Claude Code content to Gemini-compatible content.
+ *
+ * 1. Task agent calls: Task agent-name(args) -> Use the agent-name skill to: args
+ * 2. Path rewriting: .claude/ -> .gemini/, ~/.claude/ -> ~/.gemini/
+ * 3. Agent references: @agent-name -> the agent-name skill
+ */
+export function transformContentForGemini(body: string): string {
+  let result = body
+
+  // 1. Transform Task agent calls
+  const taskPattern = /^(\s*-?\s*)Task\s+([a-z][a-z0-9-]*)\(([^)]+)\)/gm
+  result = result.replace(taskPattern, (_match, prefix: string, agentName: string, args: string) => {
+    const skillName = normalizeName(agentName)
+    return `${prefix}Use the ${skillName} skill to: ${args.trim()}`
+  })
+
+  // 2. Rewrite .claude/ paths to .gemini/
+  result = result
+    .replace(/~\/\.claude\//g, "~/.gemini/")
+    .replace(/\.claude\//g, ".gemini/")
+
+  // 3. Transform @agent-name references
+  const agentRefPattern = /@([a-z][a-z0-9-]*-(?:agent|reviewer|researcher|analyst|specialist|oracle|sentinel|guardian|strategist))/gi
+  result = result.replace(agentRefPattern, (_match, agentName: string) => {
+    return `the ${normalizeName(agentName)} skill`
+  })
+
+  return result
+}
+
+function convertMcpServers(
+  servers?: Record<string, ClaudeMcpServer>,
+): GeminiBundle["mcpServers"] | undefined {
+  if (!servers || Object.keys(servers).length === 0) return undefined
+
+  const result: NonNullable<GeminiBundle["mcpServers"]> = {}
+  for (const [name, server] of Object.entries(servers)) {
+    const entry: NonNullable<GeminiBundle["mcpServers"]>[string] = {}
+    if (server.command) {
+      entry.command = server.command
+      if (server.args && server.args.length > 0) entry.args = server.args
+      if (server.env && Object.keys(server.env).length > 0) entry.env = server.env
+    } else if (server.url) {
+      entry.url = server.url
+      if (server.headers && Object.keys(server.headers).length > 0) entry.headers = server.headers
+    }
+    result[name] = entry
+  }
+  return result
+}
+
+/**
+ * Resolve command name to path segments.
+ * workflows:plan -> ["workflows", "plan"]
+ * plan -> ["plan"]
+ */
+function resolveCommandPath(name: string): string[] {
+  return name.split(":").map((segment) => normalizeName(segment))
+}
+
+/**
+ * Serialize to TOML command format.
+ * Uses multi-line strings (""") for prompt field.
+ */
+export function toToml(description: string, prompt: string): string {
+  const lines: string[] = []
+  lines.push(`description = ${formatTomlString(description)}`)
+
+  // Use multi-line string for prompt
+  const escapedPrompt = prompt.replace(/\\/g, "\\\\").replace(/"""/g, '\\"\\"\\"')
+  lines.push(`prompt = """`)
+  lines.push(escapedPrompt)
+  lines.push(`"""`)
+
+  return lines.join("\n")
+}
+
+function formatTomlString(value: string): string {
+  return JSON.stringify(value)
+}
+
+function normalizeName(value: string): string {
+  const trimmed = value.trim()
+  if (!trimmed) return "item"
+  const normalized = trimmed
+    .toLowerCase()
+    .replace(/[\\/]+/g, "-")
+    .replace(/[:\s]+/g, "-")
+    .replace(/[^a-z0-9_-]+/g, "-")
+    .replace(/-+/g, "-")
+    .replace(/^-+|-+$/g, "")
+  return normalized || "item"
+}
+
+function sanitizeDescription(value: string, maxLength = GEMINI_DESCRIPTION_MAX_LENGTH): string {
+  const normalized = value.replace(/\s+/g, " ").trim()
+  if (normalized.length <= maxLength) return normalized
+  const ellipsis = "..."
+  return normalized.slice(0, Math.max(0, maxLength - ellipsis.length)).trimEnd() + ellipsis
+}
+
+function uniqueName(base: string, used: Set<string>): string {
+  if (!used.has(base)) {
+    used.add(base)
+    return base
+  }
+  let index = 2
+  while (used.has(`${base}-${index}`)) {
+    index += 1
+  }
+  const name = `${base}-${index}`
+  used.add(name)
+  return name
+}

src/targets/gemini.ts

@@ -0,0 +1,65 @@
+import path from "path"
+import { backupFile, copyDir, ensureDir, pathExists, readJson, writeJson, writeText } from "../utils/files"
+import type { GeminiBundle } from "../types/gemini"
+
+export async function writeGeminiBundle(outputRoot: string, bundle: GeminiBundle): Promise<void> {
+  const paths = resolveGeminiPaths(outputRoot)
+  await ensureDir(paths.geminiDir)
+
+  if (bundle.generatedSkills.length > 0) {
+    for (const skill of bundle.generatedSkills) {
+      await writeText(path.join(paths.skillsDir, skill.name, "SKILL.md"), skill.content + "\n")
+    }
+  }
+
+  if (bundle.skillDirs.length > 0) {
+    for (const skill of bundle.skillDirs) {
+      await copyDir(skill.sourceDir, path.join(paths.skillsDir, skill.name))
+    }
+  }
+
+  if (bundle.commands.length > 0) {
+    for (const command of bundle.commands) {
+      await writeText(path.join(paths.commandsDir, `${command.name}.toml`), command.content + "\n")
+    }
+  }
+
+  if (bundle.mcpServers && Object.keys(bundle.mcpServers).length > 0) {
+    const settingsPath = path.join(paths.geminiDir, "settings.json")
+    const backupPath = await backupFile(settingsPath)
+    if (backupPath) {
+      console.log(`Backed up existing settings.json to ${backupPath}`)
+    }
+
+    // Merge mcpServers into existing settings if present
+    let existingSettings: Record<string, unknown> = {}
+    if (await pathExists(settingsPath)) {
+      try {
+        existingSettings = await readJson<Record<string, unknown>>(settingsPath)
+      } catch {
+        // If existing file is invalid JSON, start fresh
+      }
+    }
+
+    const merged = { ...existingSettings, mcpServers: bundle.mcpServers }
+    await writeJson(settingsPath, merged)
+  }
+}
+
+function resolveGeminiPaths(outputRoot: string) {
+  const base = path.basename(outputRoot)
+  // If already pointing at .gemini, write directly into it
+  if (base === ".gemini") {
+    return {
+      geminiDir: outputRoot,
+      skillsDir: path.join(outputRoot, "skills"),
+      commandsDir: path.join(outputRoot, "commands"),
+    }
+  }
+  // Otherwise nest under .gemini
+  return {
+    geminiDir: path.join(outputRoot, ".gemini"),
+    skillsDir: path.join(outputRoot, ".gemini", "skills"),
+    commandsDir: path.join(outputRoot, ".gemini", "commands"),
+  }
+}

src/targets/index.ts

@@ -4,16 +4,19 @@ import type { CodexBundle } from "../types/codex"
 import type { DroidBundle } from "../types/droid"
 import type { CursorBundle } from "../types/cursor"
 import type { PiBundle } from "../types/pi"
+import type { GeminiBundle } from "../types/gemini"
 import { convertClaudeToOpenCode, type ClaudeToOpenCodeOptions } from "../converters/claude-to-opencode"
 import { convertClaudeToCodex } from "../converters/claude-to-codex"
 import { convertClaudeToDroid } from "../converters/claude-to-droid"
 import { convertClaudeToCursor } from "../converters/claude-to-cursor"
 import { convertClaudeToPi } from "../converters/claude-to-pi"
+import { convertClaudeToGemini } from "../converters/claude-to-gemini"
 import { writeOpenCodeBundle } from "./opencode"
 import { writeCodexBundle } from "./codex"
 import { writeDroidBundle } from "./droid"
 import { writeCursorBundle } from "./cursor"
 import { writePiBundle } from "./pi"
+import { writeGeminiBundle } from "./gemini"
 
 export type TargetHandler<TBundle = unknown> = {
   name: string
@@ -53,4 +56,10 @@ export const targets: Record<string, TargetHandler> = {
     convert: convertClaudeToPi as TargetHandler<PiBundle>["convert"],
     write: writePiBundle as TargetHandler<PiBundle>["write"],
   },
+  gemini: {
+    name: "gemini",
+    implemented: true,
+    convert: convertClaudeToGemini as TargetHandler<GeminiBundle>["convert"],
+    write: writeGeminiBundle as TargetHandler<GeminiBundle>["write"],
+  },
 }

src/types/gemini.ts

@@ -0,0 +1,27 @@
+export type GeminiSkill = {
+  name: string
+  content: string // Full SKILL.md with YAML frontmatter
+}
+
+export type GeminiSkillDir = {
+  name: string
+  sourceDir: string
+}
+
+export type GeminiCommand = {
+  name: string // e.g. "plan" or "workflows/plan"
+  content: string // Full TOML content
+}
+
+export type GeminiBundle = {
+  generatedSkills: GeminiSkill[] // From agents
+  skillDirs: GeminiSkillDir[] // From skills (pass-through)
+  commands: GeminiCommand[]
+  mcpServers?: Record<string, {
+    command?: string
+    args?: string[]
+    env?: Record<string, string>
+    url?: string
+    headers?: Record<string, string>
+  }>
+}