diff --git a/src/config/schema/agent-definitions.ts b/src/config/schema/agent-definitions.ts
new file mode 100644
index 000000000..508bfde0b
--- /dev/null
+++ b/src/config/schema/agent-definitions.ts
@@ -0,0 +1,5 @@
+import { z } from "zod"
+
+export const AgentDefinitionPathSchema = z.string()
+
+export const AgentDefinitionsConfigSchema = z.array(AgentDefinitionPathSchema).optional()
diff --git a/src/config/schema/oh-my-opencode-config.ts b/src/config/schema/oh-my-opencode-config.ts
index eb9299769..e62413d26 100644
--- a/src/config/schema/oh-my-opencode-config.ts
+++ b/src/config/schema/oh-my-opencode-config.ts
@@ -1,6 +1,7 @@
 import { z } from "zod"
 import { AnyMcpNameSchema } from "../../mcp/types"
 import { BuiltinSkillNameSchema } from "./agent-names"
+import { AgentDefinitionsConfigSchema } from "./agent-definitions"
 import { AgentOverridesSchema } from "./agent-overrides"
 import { BabysittingConfigSchema } from "./babysitting"
 import { BackgroundTaskConfigSchema } from "./background-task"
@@ -29,6 +30,8 @@ export const OhMyOpenCodeConfigSchema = z.object({
   new_task_system_enabled: z.boolean().optional(),
   /** Default agent name for `oh-my-opencode run` (env: OPENCODE_DEFAULT_AGENT) */
   default_run_agent: z.string().optional(),
+  /** Paths to external agent definition files (.md or .json) */
+  agent_definitions: AgentDefinitionsConfigSchema,
   disabled_mcps: z.array(AnyMcpNameSchema).optional(),
   disabled_agents: z.array(z.string()).optional(),
   disabled_skills: z.array(BuiltinSkillNameSchema).optional(),
diff --git a/src/features/claude-code-agent-loader/json-agent-loader.test.ts b/src/features/claude-code-agent-loader/json-agent-loader.test.ts
new file mode 100644
index 000000000..b3f6a4f5c
--- /dev/null
+++ b/src/features/claude-code-agent-loader/json-agent-loader.test.ts
@@ -0,0 +1,139 @@
+import { describe, test, expect, afterEach } from "bun:test"
+import { mkdtempSync, writeFileSync, rmSync } from "fs"
+import { join } from "path"
+import { tmpdir } from "os"
+import { parseJsonAgentFile } from "./json-agent-loader"
+
+describe("json-agent-loader", () => {
+  const dirs: string[] = []
+
+  afterEach(() => {
+    for (const dir of dirs) {
+      rmSync(dir, { recursive: true, force: true })
+    }
+    dirs.length = 0
+  })
+
+  function trackDir(dir: string): string {
+    dirs.push(dir)
+    return dir
+  }
+
+  test("parses valid JSON agent file", () => {
+    const dir = trackDir(mkdtempSync(join(tmpdir(), "json-agent-loader-test-")))
+    const filePath = join(dir, "agent.json")
+
+    writeFileSync(filePath, JSON.stringify({
+      name: "test-agent",
+      description: "A test agent",
+      prompt: "You are a test agent.",
+      tools: ["Bash", "Read"],
+      model: "claude-3-5-sonnet-20241022",
+      mode: "subagent",
+    }), "utf-8")
+
+    const result = parseJsonAgentFile(filePath, "definition-file")
+
+    expect(result).not.toBeNull()
+    expect(result?.name).toBe("test-agent")
+    expect(result?.path).toBe(filePath)
+    expect(result?.scope).toBe("definition-file")
+    expect(result?.config.description).toBe("(definition-file) A test agent")
+    expect(result?.config.prompt).toBe("You are a test agent.")
+    expect(result?.config.mode).toBe("subagent")
+    expect(result?.config.tools).toEqual({ bash: true, read: true })
+  })
+
+  test("parses JSONC with comments", () => {
+    const dir = trackDir(mkdtempSync(join(tmpdir(), "json-agent-loader-test-")))
+    const filePath = join(dir, "agent.jsonc")
+
+    writeFileSync(filePath, `{
+  // Agent name
+  "name": "commented-agent",
+  "description": "Agent with comments",
+  "prompt": "Do something.",
+  "tools": ["Bash"], // Tools for the agent
+  // Model specification
+  "model": "claude-3-5-sonnet-20241022"
+}`, "utf-8")
+
+    const result = parseJsonAgentFile(filePath, "definition-file")
+
+    expect(result).not.toBeNull()
+    expect(result?.name).toBe("commented-agent")
+    expect(result?.config.tools).toEqual({ bash: true })
+  })
+
+  test("returns null when required fields are missing (name)", () => {
+    const dir = trackDir(mkdtempSync(join(tmpdir(), "json-agent-loader-test-")))
+    const filePath = join(dir, "agent.json")
+
+    writeFileSync(filePath, JSON.stringify({
+      description: "Missing name",
+      prompt: "You are an agent.",
+    }), "utf-8")
+
+    const result = parseJsonAgentFile(filePath, "definition-file")
+    expect(result).toBeNull()
+  })
+
+  test("returns null when required fields are missing (prompt)", () => {
+    const dir = trackDir(mkdtempSync(join(tmpdir(), "json-agent-loader-test-")))
+    const filePath = join(dir, "agent.json")
+
+    writeFileSync(filePath, JSON.stringify({
+      name: "missing-prompt",
+      description: "Missing prompt",
+    }), "utf-8")
+
+    const result = parseJsonAgentFile(filePath, "definition-file")
+    expect(result).toBeNull()
+  })
+
+  test("defaults optional fields correctly", () => {
+    const dir = trackDir(mkdtempSync(join(tmpdir(), "json-agent-loader-test-")))
+    const filePath = join(dir, "agent.json")
+
+    writeFileSync(filePath, JSON.stringify({
+      name: "minimal-agent",
+      prompt: "You are minimal.",
+    }), "utf-8")
+
+    const result = parseJsonAgentFile(filePath, "definition-file")
+
+    expect(result).not.toBeNull()
+    expect(result?.config.description).toBe("(definition-file) ")
+    expect(result?.config.mode).toBe("subagent")
+    expect(result?.config.tools).toBeUndefined()
+    expect(result?.config.model).toBeUndefined()
+  })
+
+  test("handles tools as string comma-separated list", () => {
+    const dir = trackDir(mkdtempSync(join(tmpdir(), "json-agent-loader-test-")))
+    const filePath = join(dir, "agent.json")
+
+    writeFileSync(filePath, JSON.stringify({
+      name: "string-tools-agent",
+      prompt: "You are an agent.",
+      tools: "Bash, Read, Grep",
+    }), "utf-8")
+
+    const result = parseJsonAgentFile(filePath, "definition-file")
+
+    expect(result?.config.tools).toEqual({ bash: true, read: true, grep: true })
+  })
+
+  test("returns null for malformed JSON", () => {
+    const dir = trackDir(mkdtempSync(join(tmpdir(), "json-agent-loader-test-")))
+    const filePath = join(dir, "agent.json")
+
+    writeFileSync(filePath, `{
+  "name": "broken",
+  "prompt": "incomplete json`,
+      "utf-8")
+
+    const result = parseJsonAgentFile(filePath, "definition-file")
+    expect(result).toBeNull()
+  })
+})
diff --git a/src/features/claude-code-agent-loader/json-agent-loader.ts b/src/features/claude-code-agent-loader/json-agent-loader.ts
new file mode 100644
index 000000000..394d2a25c
--- /dev/null
+++ b/src/features/claude-code-agent-loader/json-agent-loader.ts
@@ -0,0 +1,67 @@
+import { existsSync, readFileSync } from "fs"
+import { parseJsoncSafe } from "../../shared/jsonc-parser"
+import { mapClaudeModelToOpenCode } from "./claude-model-mapper"
+import type { AgentScope, AgentJsonDefinition, ClaudeCodeAgentConfig, LoadedAgent } from "./types"
+
+function parseToolsConfig(tools?: string | string[]): Record<string, boolean> | undefined {
+  if (!tools) return undefined
+
+  const toolsArray = Array.isArray(tools) ? tools : tools.split(",").map((t) => t.trim())
+  const filtered = toolsArray.filter((t) => typeof t === "string" && t.length > 0)
+
+  if (filtered.length === 0) return undefined
+
+  const result: Record<string, boolean> = {}
+  for (const tool of filtered) {
+    result[tool.toLowerCase()] = true
+  }
+  return result
+}
+
+export function parseJsonAgentFile(filePath: string, scope: AgentScope): LoadedAgent | null {
+  try {
+    if (!existsSync(filePath)) {
+      return null
+    }
+
+    const content = readFileSync(filePath, "utf-8")
+    const { data } = parseJsoncSafe<AgentJsonDefinition>(content)
+
+    if (!data) {
+      return null
+    }
+
+    if (!data.name || !data.prompt) {
+      return null
+    }
+
+    const originalDescription = data.description ?? ""
+    const formattedDescription = `(${scope}) ${originalDescription}`
+
+    const mappedModelOverride = mapClaudeModelToOpenCode(data.model)
+    const modelString = mappedModelOverride
+      ? `${mappedModelOverride.providerID}/${mappedModelOverride.modelID}`
+      : undefined
+
+    const config: ClaudeCodeAgentConfig = {
+      description: formattedDescription,
+      mode: data.mode ?? "subagent",
+      prompt: data.prompt.trim(),
+      ...(modelString ? { model: modelString } : {}),
+    }
+
+    const toolsConfig = parseToolsConfig(data.tools)
+    if (toolsConfig) {
+      config.tools = toolsConfig
+    }
+
+    return {
+      name: data.name,
+      path: filePath,
+      config,
+      scope,
+    }
+  } catch {
+    return null
+  }
+}
diff --git a/src/features/claude-code-agent-loader/types.ts b/src/features/claude-code-agent-loader/types.ts
index 90a236828..db5287243 100644
--- a/src/features/claude-code-agent-loader/types.ts
+++ b/src/features/claude-code-agent-loader/types.ts
@@ -1,6 +1,6 @@
 import type { AgentConfig } from "@opencode-ai/sdk"
 
-export type AgentScope = "user" | "project" | "opencode" | "opencode-project"
+export type AgentScope = "user" | "project" | "opencode" | "opencode-project" | "definition-file" | "opencode-config"
 
 export type ClaudeCodeAgentConfig = Omit<AgentConfig, "model"> & {
   model?: string | { providerID: string; modelID: string }
@@ -14,6 +14,15 @@ export interface AgentFrontmatter {
   mode?: "subagent" | "primary" | "all"
 }
 
+export interface AgentJsonDefinition {
+  name: string
+  description?: string
+  model?: string
+  tools?: string | string[]
+  mode?: "subagent" | "primary" | "all"
+  prompt: string
+}
+
 export interface LoadedAgent {
   name: string
   path: string
diff --git a/src/plugin-config.ts b/src/plugin-config.ts
index 0b79e96d3..9cbe0030b 100644
--- a/src/plugin-config.ts
+++ b/src/plugin-config.ts
@@ -9,6 +9,7 @@ import {
   parseJsonc,
   detectPluginConfigFile,
   migrateConfigFile,
+  resolveAgentDefinitionPaths,
 } from "./shared";
 import { migrateLegacyConfigFile } from "./shared/migrate-legacy-config-file";
 import { CONFIG_BASENAME, LEGACY_CONFIG_BASENAME } from "./shared/plugin-identity";
@@ -41,6 +42,7 @@ const PARTIAL_STRING_ARRAY_KEYS = new Set([
   "disabled_commands",
   "disabled_tools",
   "mcp_env_allowlist",
+  "agent_definitions",
 ]);
 
 export function parseConfigPartially(
@@ -139,6 +141,12 @@ export function mergeConfigs(
     ...override,
     agents: deepMerge(base.agents, override.agents),
     categories: deepMerge(base.categories, override.categories),
+    agent_definitions: [
+      ...new Set([
+        ...(base.agent_definitions ?? []),
+        ...(override.agent_definitions ?? []),
+      ]),
+    ],
     disabled_agents: [
       ...new Set([
         ...(base.disabled_agents ?? []),
@@ -250,6 +258,15 @@ export function loadPluginConfig(
   // Load user config first (base). Parse empty config through Zod to apply field defaults.
   const userConfig = loadConfigFromPath(userConfigPath, ctx)
   const userGitMasterOverrides = loadExplicitGitMasterOverrides(userConfigPath)
+
+  if (userConfig?.agent_definitions) {
+    userConfig.agent_definitions = resolveAgentDefinitionPaths(
+      userConfig.agent_definitions,
+      configDir,
+      null
+    )
+  }
+
   let config: OhMyOpenCodeConfig =
     userConfig ?? OhMyOpenCodeConfigSchema.parse({});
 
@@ -257,6 +274,15 @@ export function loadPluginConfig(
   const defaultGitMaster = OhMyOpenCodeConfigSchema.parse({}).git_master
   const projectConfig = loadConfigFromPath(projectConfigPath, ctx);
   const projectGitMasterOverrides = loadExplicitGitMasterOverrides(projectConfigPath)
+
+  if (projectConfig?.agent_definitions) {
+    projectConfig.agent_definitions = resolveAgentDefinitionPaths(
+      projectConfig.agent_definitions,
+      directory,
+      directory
+    )
+  }
+
   if (projectConfig) {
     config = mergeConfigs(config, projectConfig);
   }
diff --git a/src/shared/index.ts b/src/shared/index.ts
index 485926bfd..cf9792361 100644
--- a/src/shared/index.ts
+++ b/src/shared/index.ts
@@ -17,6 +17,7 @@ export * from "./claude-config-dir"
 export * from "./jsonc-parser"
 export * from "./migration"
 export * from "./opencode-config-dir"
+export * from "./resolve-agent-definition-paths"
 export type {
   OpenCodeBinaryType,
   OpenCodeConfigDirOptions,
diff --git a/src/shared/resolve-agent-definition-paths.ts b/src/shared/resolve-agent-definition-paths.ts
new file mode 100644
index 000000000..c7334e4b7
--- /dev/null
+++ b/src/shared/resolve-agent-definition-paths.ts
@@ -0,0 +1,22 @@
+import { homedir } from "os"
+import { isAbsolute, resolve } from "path"
+import { isWithinProject } from "./contains-path"
+import { log } from "./logger"
+
+export function resolveAgentDefinitionPaths(
+  paths: string[],
+  baseDir: string,
+  containmentDir: string | null
+): string[] {
+  return paths.flatMap((p) => {
+    const expanded = p.startsWith("~/") ? p.replace(/^~\//, `${homedir()}/`) : p
+    const resolved = isAbsolute(expanded) ? expanded : resolve(baseDir, expanded)
+
+    if (containmentDir !== null && !isWithinProject(resolved, containmentDir)) {
+      log(`agent_definitions path rejected (outside project boundary): ${p} -> ${resolved}`)
+      return []
+    }
+
+    return [resolved]
+  })
+}