fix(skill): enforce agent restriction in createSkillTool (#1018)

* fix(skill): enforce agent restriction in createSkillTool

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* fix(skill): block restricted skills when agent context missing

Addresses cubic review feedback: previously agent-restricted skills
could be invoked when ctx or ctx.agent was undefined because the
guard only ran when ctx?.agent was truthy.

Changed condition from:
  skill.definition.agent && ctx?.agent && skill.definition.agent !== ctx.agent
To:
  skill.definition.agent && (!ctx?.agent || skill.definition.agent !== ctx.agent)

This ensures restricted skills are blocked unless the exact matching
agent is present in the context.

---------

Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/skill/tools.test.ts

@@ -20,6 +20,21 @@ Test skill body content`
   },
 }))
 
+function createMockSkill(name: string, options: { agent?: string } = {}): LoadedSkill {
+  return {
+    name,
+    path: `/test/skills/${name}/SKILL.md`,
+    resolvedPath: `/test/skills/${name}`,
+    definition: {
+      name,
+      description: `Test skill ${name}`,
+      template: "Test template",
+      agent: options.agent,
+    },
+    scope: "opencode-project",
+  }
+}
+
 function createMockSkillWithMcp(name: string, mcpServers: Record<string, unknown>): LoadedSkill {
   return {
     name,
@@ -42,6 +57,59 @@ const mockContext = {
   abort: new AbortController().signal,
 }
 
+describe("skill tool - agent restriction", () => {
+  it("allows skill without agent restriction to any agent", async () => {
+    // #given
+    const loadedSkills = [createMockSkill("public-skill")]
+    const tool = createSkillTool({ skills: loadedSkills })
+    const context = { ...mockContext, agent: "any-agent" }
+
+    // #when
+    const result = await tool.execute({ name: "public-skill" }, context)
+
+    // #then
+    expect(result).toContain("public-skill")
+  })
+
+  it("allows skill when agent matches restriction", async () => {
+    // #given
+    const loadedSkills = [createMockSkill("restricted-skill", { agent: "sisyphus" })]
+    const tool = createSkillTool({ skills: loadedSkills })
+    const context = { ...mockContext, agent: "sisyphus" }
+
+    // #when
+    const result = await tool.execute({ name: "restricted-skill" }, context)
+
+    // #then
+    expect(result).toContain("restricted-skill")
+  })
+
+  it("throws error when agent does not match restriction", async () => {
+    // #given
+    const loadedSkills = [createMockSkill("sisyphus-only-skill", { agent: "sisyphus" })]
+    const tool = createSkillTool({ skills: loadedSkills })
+    const context = { ...mockContext, agent: "oracle" }
+
+    // #when / #then
+    await expect(tool.execute({ name: "sisyphus-only-skill" }, context)).rejects.toThrow(
+      'Skill "sisyphus-only-skill" is restricted to agent "sisyphus"'
+    )
+  })
+
+  it("throws error when context agent is undefined for restricted skill", async () => {
+    // #given
+    const loadedSkills = [createMockSkill("sisyphus-only-skill", { agent: "sisyphus" })]
+    const tool = createSkillTool({ skills: loadedSkills })
+    const contextWithoutAgent = { ...mockContext, agent: undefined as unknown as string }
+
+    // #when / #then
+    await expect(tool.execute({ name: "sisyphus-only-skill" }, contextWithoutAgent)).rejects.toThrow(
+      'Skill "sisyphus-only-skill" is restricted to agent "sisyphus"'
+    )
+  })
+
+})
+
 describe("skill tool - MCP schema display", () => {
   let manager: SkillMcpManager
   let loadedSkills: LoadedSkill[]

src/tools/skill/tools.ts

@@ -156,7 +156,7 @@ export function createSkillTool(options: SkillLoadOptions = {}): ToolDefinition
     args: {
       name: tool.schema.string().describe("The skill identifier from available_skills (e.g., 'code-review')"),
     },
-    async execute(args: SkillArgs) {
+    async execute(args: SkillArgs, ctx?: { agent?: string }) {
       const skills = await getSkills()
       const skill = skills.find(s => s.name === args.name)
 
@@ -165,6 +165,10 @@ export function createSkillTool(options: SkillLoadOptions = {}): ToolDefinition
         throw new Error(`Skill "${args.name}" not found. Available skills: ${available || "none"}`)
       }
 
+      if (skill.definition.agent && (!ctx?.agent || skill.definition.agent !== ctx.agent)) {
+        throw new Error(`Skill "${args.name}" is restricted to agent "${skill.definition.agent}"`)
+      }
+
       let body = await extractSkillBody(skill)
 
       if (args.name === "git-master") {