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>
+  }>
+}

tests/gemini-converter.test.ts

@@ -0,0 +1,342 @@
+import { describe, expect, test } from "bun:test"
+import { convertClaudeToGemini, toToml, transformContentForGemini } from "../src/converters/claude-to-gemini"
+import { parseFrontmatter } from "../src/utils/frontmatter"
+import type { ClaudePlugin } from "../src/types/claude"
+
+const fixturePlugin: ClaudePlugin = {
+  root: "/tmp/plugin",
+  manifest: { name: "fixture", version: "1.0.0" },
+  agents: [
+    {
+      name: "Security Reviewer",
+      description: "Security-focused agent",
+      capabilities: ["Threat modeling", "OWASP"],
+      model: "claude-sonnet-4-20250514",
+      body: "Focus on vulnerabilities.",
+      sourcePath: "/tmp/plugin/agents/security-reviewer.md",
+    },
+  ],
+  commands: [
+    {
+      name: "workflows:plan",
+      description: "Planning command",
+      argumentHint: "[FOCUS]",
+      model: "inherit",
+      allowedTools: ["Read"],
+      body: "Plan the work.",
+      sourcePath: "/tmp/plugin/commands/workflows/plan.md",
+    },
+  ],
+  skills: [
+    {
+      name: "existing-skill",
+      description: "Existing skill",
+      sourceDir: "/tmp/plugin/skills/existing-skill",
+      skillPath: "/tmp/plugin/skills/existing-skill/SKILL.md",
+    },
+  ],
+  hooks: undefined,
+  mcpServers: {
+    local: { command: "echo", args: ["hello"] },
+  },
+}
+
+describe("convertClaudeToGemini", () => {
+  test("converts agents to skills with SKILL.md frontmatter", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    const skill = bundle.generatedSkills.find((s) => s.name === "security-reviewer")
+    expect(skill).toBeDefined()
+    const parsed = parseFrontmatter(skill!.content)
+    expect(parsed.data.name).toBe("security-reviewer")
+    expect(parsed.data.description).toBe("Security-focused agent")
+    expect(parsed.body).toContain("Focus on vulnerabilities.")
+  })
+
+  test("agent with capabilities prepended to body", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    const skill = bundle.generatedSkills.find((s) => s.name === "security-reviewer")
+    expect(skill).toBeDefined()
+    const parsed = parseFrontmatter(skill!.content)
+    expect(parsed.body).toContain("## Capabilities")
+    expect(parsed.body).toContain("- Threat modeling")
+    expect(parsed.body).toContain("- OWASP")
+  })
+
+  test("agent with empty description gets default description", () => {
+    const plugin: ClaudePlugin = {
+      ...fixturePlugin,
+      agents: [
+        {
+          name: "my-agent",
+          body: "Do things.",
+          sourcePath: "/tmp/plugin/agents/my-agent.md",
+        },
+      ],
+      commands: [],
+      skills: [],
+    }
+
+    const bundle = convertClaudeToGemini(plugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    const parsed = parseFrontmatter(bundle.generatedSkills[0].content)
+    expect(parsed.data.description).toBe("Use this skill for my-agent tasks")
+  })
+
+  test("agent model field silently dropped", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    const skill = bundle.generatedSkills.find((s) => s.name === "security-reviewer")
+    const parsed = parseFrontmatter(skill!.content)
+    expect(parsed.data.model).toBeUndefined()
+  })
+
+  test("agent with empty body gets default body text", () => {
+    const plugin: ClaudePlugin = {
+      ...fixturePlugin,
+      agents: [
+        {
+          name: "Empty Agent",
+          description: "An empty agent",
+          body: "",
+          sourcePath: "/tmp/plugin/agents/empty.md",
+        },
+      ],
+      commands: [],
+      skills: [],
+    }
+
+    const bundle = convertClaudeToGemini(plugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    const parsed = parseFrontmatter(bundle.generatedSkills[0].content)
+    expect(parsed.body).toContain("Instructions converted from the Empty Agent agent.")
+  })
+
+  test("converts commands to TOML with prompt and description", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    expect(bundle.commands).toHaveLength(1)
+    const command = bundle.commands[0]
+    expect(command.name).toBe("workflows/plan")
+    expect(command.content).toContain('description = "Planning command"')
+    expect(command.content).toContain('prompt = """')
+    expect(command.content).toContain("Plan the work.")
+  })
+
+  test("namespaced command creates correct path", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    const command = bundle.commands.find((c) => c.name === "workflows/plan")
+    expect(command).toBeDefined()
+  })
+
+  test("command with argument-hint gets {{args}} placeholder", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    const command = bundle.commands[0]
+    expect(command.content).toContain("{{args}}")
+  })
+
+  test("command with disable-model-invocation is still included", () => {
+    const plugin: ClaudePlugin = {
+      ...fixturePlugin,
+      commands: [
+        {
+          name: "disabled-command",
+          description: "Disabled command",
+          disableModelInvocation: true,
+          body: "Disabled body.",
+          sourcePath: "/tmp/plugin/commands/disabled.md",
+        },
+      ],
+      agents: [],
+      skills: [],
+    }
+
+    const bundle = convertClaudeToGemini(plugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    // Gemini TOML commands are prompts, not code — always include
+    expect(bundle.commands).toHaveLength(1)
+    expect(bundle.commands[0].name).toBe("disabled-command")
+  })
+
+  test("command allowedTools silently dropped", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    const command = bundle.commands[0]
+    expect(command.content).not.toContain("allowedTools")
+    expect(command.content).not.toContain("Read")
+  })
+
+  test("skills pass through as directory references", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    expect(bundle.skillDirs).toHaveLength(1)
+    expect(bundle.skillDirs[0].name).toBe("existing-skill")
+    expect(bundle.skillDirs[0].sourceDir).toBe("/tmp/plugin/skills/existing-skill")
+  })
+
+  test("MCP servers convert to settings.json-compatible config", () => {
+    const bundle = convertClaudeToGemini(fixturePlugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    expect(bundle.mcpServers?.local?.command).toBe("echo")
+    expect(bundle.mcpServers?.local?.args).toEqual(["hello"])
+  })
+
+  test("plugin with zero agents produces empty generatedSkills", () => {
+    const plugin: ClaudePlugin = {
+      ...fixturePlugin,
+      agents: [],
+      commands: [],
+      skills: [],
+    }
+
+    const bundle = convertClaudeToGemini(plugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    expect(bundle.generatedSkills).toHaveLength(0)
+  })
+
+  test("plugin with only skills works correctly", () => {
+    const plugin: ClaudePlugin = {
+      ...fixturePlugin,
+      agents: [],
+      commands: [],
+    }
+
+    const bundle = convertClaudeToGemini(plugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    expect(bundle.generatedSkills).toHaveLength(0)
+    expect(bundle.skillDirs).toHaveLength(1)
+    expect(bundle.commands).toHaveLength(0)
+  })
+
+  test("hooks present emits console.warn", () => {
+    const warnings: string[] = []
+    const originalWarn = console.warn
+    console.warn = (msg: string) => warnings.push(msg)
+
+    const plugin: ClaudePlugin = {
+      ...fixturePlugin,
+      hooks: { hooks: { PreToolUse: [{ matcher: "*", body: "hook body" }] } },
+      agents: [],
+      commands: [],
+      skills: [],
+    }
+
+    convertClaudeToGemini(plugin, {
+      agentMode: "subagent",
+      inferTemperature: false,
+      permissions: "none",
+    })
+
+    console.warn = originalWarn
+    expect(warnings.some((w) => w.includes("Gemini"))).toBe(true)
+  })
+})
+
+describe("transformContentForGemini", () => {
+  test("transforms .claude/ paths to .gemini/", () => {
+    const result = transformContentForGemini("Read .claude/settings.json for config.")
+    expect(result).toContain(".gemini/settings.json")
+    expect(result).not.toContain(".claude/")
+  })
+
+  test("transforms ~/.claude/ paths to ~/.gemini/", () => {
+    const result = transformContentForGemini("Check ~/.claude/config for settings.")
+    expect(result).toContain("~/.gemini/config")
+    expect(result).not.toContain("~/.claude/")
+  })
+
+  test("transforms Task agent(args) to natural language skill reference", () => {
+    const input = `Run these:
+
+- Task repo-research-analyst(feature_description)
+- Task learnings-researcher(feature_description)
+
+Task best-practices-researcher(topic)`
+
+    const result = transformContentForGemini(input)
+    expect(result).toContain("Use the repo-research-analyst skill to: feature_description")
+    expect(result).toContain("Use the learnings-researcher skill to: feature_description")
+    expect(result).toContain("Use the best-practices-researcher skill to: topic")
+    expect(result).not.toContain("Task repo-research-analyst")
+  })
+
+  test("transforms @agent references to skill references", () => {
+    const result = transformContentForGemini("Ask @security-sentinel for a review.")
+    expect(result).toContain("the security-sentinel skill")
+    expect(result).not.toContain("@security-sentinel")
+  })
+})
+
+describe("toToml", () => {
+  test("produces valid TOML with description and prompt", () => {
+    const result = toToml("A description", "The prompt content")
+    expect(result).toContain('description = "A description"')
+    expect(result).toContain('prompt = """')
+    expect(result).toContain("The prompt content")
+    expect(result).toContain('"""')
+  })
+
+  test("escapes quotes in description", () => {
+    const result = toToml('Say "hello"', "Prompt")
+    expect(result).toContain('description = "Say \\"hello\\""')
+  })
+})

tests/gemini-writer.test.ts

@@ -0,0 +1,179 @@
+import { describe, expect, test } from "bun:test"
+import { promises as fs } from "fs"
+import path from "path"
+import os from "os"
+import { writeGeminiBundle } from "../src/targets/gemini"
+import type { GeminiBundle } from "../src/types/gemini"
+
+async function exists(filePath: string): Promise<boolean> {
+  try {
+    await fs.access(filePath)
+    return true
+  } catch {
+    return false
+  }
+}
+
+describe("writeGeminiBundle", () => {
+  test("writes skills, commands, and settings.json", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "gemini-test-"))
+    const bundle: GeminiBundle = {
+      generatedSkills: [
+        {
+          name: "security-reviewer",
+          content: "---\nname: security-reviewer\ndescription: Security\n---\n\nReview code.",
+        },
+      ],
+      skillDirs: [
+        {
+          name: "skill-one",
+          sourceDir: path.join(import.meta.dir, "fixtures", "sample-plugin", "skills", "skill-one"),
+        },
+      ],
+      commands: [
+        {
+          name: "plan",
+          content: 'description = "Plan"\nprompt = """\nPlan the work.\n"""',
+        },
+      ],
+      mcpServers: {
+        playwright: { command: "npx", args: ["-y", "@anthropic/mcp-playwright"] },
+      },
+    }
+
+    await writeGeminiBundle(tempRoot, bundle)
+
+    expect(await exists(path.join(tempRoot, ".gemini", "skills", "security-reviewer", "SKILL.md"))).toBe(true)
+    expect(await exists(path.join(tempRoot, ".gemini", "skills", "skill-one", "SKILL.md"))).toBe(true)
+    expect(await exists(path.join(tempRoot, ".gemini", "commands", "plan.toml"))).toBe(true)
+    expect(await exists(path.join(tempRoot, ".gemini", "settings.json"))).toBe(true)
+
+    const skillContent = await fs.readFile(
+      path.join(tempRoot, ".gemini", "skills", "security-reviewer", "SKILL.md"),
+      "utf8",
+    )
+    expect(skillContent).toContain("Review code.")
+
+    const commandContent = await fs.readFile(
+      path.join(tempRoot, ".gemini", "commands", "plan.toml"),
+      "utf8",
+    )
+    expect(commandContent).toContain("Plan the work.")
+
+    const settingsContent = JSON.parse(
+      await fs.readFile(path.join(tempRoot, ".gemini", "settings.json"), "utf8"),
+    )
+    expect(settingsContent.mcpServers.playwright.command).toBe("npx")
+  })
+
+  test("namespaced commands create subdirectories", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "gemini-ns-"))
+    const bundle: GeminiBundle = {
+      generatedSkills: [],
+      skillDirs: [],
+      commands: [
+        {
+          name: "workflows/plan",
+          content: 'description = "Plan"\nprompt = """\nPlan.\n"""',
+        },
+      ],
+    }
+
+    await writeGeminiBundle(tempRoot, bundle)
+
+    expect(await exists(path.join(tempRoot, ".gemini", "commands", "workflows", "plan.toml"))).toBe(true)
+  })
+
+  test("does not double-nest when output root is .gemini", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "gemini-home-"))
+    const geminiRoot = path.join(tempRoot, ".gemini")
+    const bundle: GeminiBundle = {
+      generatedSkills: [
+        { name: "reviewer", content: "Reviewer skill content" },
+      ],
+      skillDirs: [],
+      commands: [
+        { name: "plan", content: "Plan content" },
+      ],
+    }
+
+    await writeGeminiBundle(geminiRoot, bundle)
+
+    expect(await exists(path.join(geminiRoot, "skills", "reviewer", "SKILL.md"))).toBe(true)
+    expect(await exists(path.join(geminiRoot, "commands", "plan.toml"))).toBe(true)
+    // Should NOT double-nest under .gemini/.gemini
+    expect(await exists(path.join(geminiRoot, ".gemini"))).toBe(false)
+  })
+
+  test("handles empty bundles gracefully", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "gemini-empty-"))
+    const bundle: GeminiBundle = {
+      generatedSkills: [],
+      skillDirs: [],
+      commands: [],
+    }
+
+    await writeGeminiBundle(tempRoot, bundle)
+    expect(await exists(tempRoot)).toBe(true)
+  })
+
+  test("backs up existing settings.json before overwrite", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "gemini-backup-"))
+    const geminiRoot = path.join(tempRoot, ".gemini")
+    await fs.mkdir(geminiRoot, { recursive: true })
+
+    // Write existing settings.json
+    const settingsPath = path.join(geminiRoot, "settings.json")
+    await fs.writeFile(settingsPath, JSON.stringify({ mcpServers: { old: { command: "old-cmd" } } }))
+
+    const bundle: GeminiBundle = {
+      generatedSkills: [],
+      skillDirs: [],
+      commands: [],
+      mcpServers: {
+        newServer: { command: "new-cmd" },
+      },
+    }
+
+    await writeGeminiBundle(geminiRoot, bundle)
+
+    // New settings.json should have the new content
+    const newContent = JSON.parse(await fs.readFile(settingsPath, "utf8"))
+    expect(newContent.mcpServers.newServer.command).toBe("new-cmd")
+
+    // A backup file should exist
+    const files = await fs.readdir(geminiRoot)
+    const backupFiles = files.filter((f) => f.startsWith("settings.json.bak."))
+    expect(backupFiles.length).toBeGreaterThanOrEqual(1)
+  })
+
+  test("merges mcpServers into existing settings.json without clobbering other keys", async () => {
+    const tempRoot = await fs.mkdtemp(path.join(os.tmpdir(), "gemini-merge-"))
+    const geminiRoot = path.join(tempRoot, ".gemini")
+    await fs.mkdir(geminiRoot, { recursive: true })
+
+    // Write existing settings.json with other keys
+    const settingsPath = path.join(geminiRoot, "settings.json")
+    await fs.writeFile(settingsPath, JSON.stringify({
+      model: "gemini-2.5-pro",
+      mcpServers: { old: { command: "old-cmd" } },
+    }))
+
+    const bundle: GeminiBundle = {
+      generatedSkills: [],
+      skillDirs: [],
+      commands: [],
+      mcpServers: {
+        newServer: { command: "new-cmd" },
+      },
+    }
+
+    await writeGeminiBundle(geminiRoot, bundle)
+
+    const content = JSON.parse(await fs.readFile(settingsPath, "utf8"))
+    // Should preserve existing model key
+    expect(content.model).toBe("gemini-2.5-pro")
+    // mcpServers should be replaced (not merged) with new content
+    expect(content.mcpServers.newServer.command).toBe("new-cmd")
+  })
+})