diff --git a/packages/opencode/src/tool/task.ts b/packages/opencode/src/tool/task.ts
index bc93f497a91..8d61bedd708 100644
--- a/packages/opencode/src/tool/task.ts
+++ b/packages/opencode/src/tool/task.ts
@@ -31,6 +31,22 @@ export const TaskTool = Tool.define("task", async () => {
     async execute(params, ctx) {
       const agent = await Agent.get(params.subagent_type)
       if (!agent) throw new Error(`Unknown agent type: ${params.subagent_type} is not a valid agent type`)
+
+      // Security: Inherit Plan mode restrictions to sub-agents
+      // When parent agent has edit="deny" (e.g., Plan mode), sub-agents must:
+      // 1. Run as Plan agent to inherit bash whitelist (read-only commands)
+      // 2. Have edit/write tools explicitly disabled
+      // This prevents bypass of Plan mode restrictions via Task tool
+      const parent = await Agent.get(ctx.agent)
+      const restricted = parent?.permission.edit === "deny"
+      const plan = restricted ? await Agent.get("plan") : null
+      if (restricted && !plan)
+        throw new Error(
+          `Cannot spawn sub-agent from restricted parent "${ctx.agent}": Plan agent is required but not available. ` +
+            `Ensure the Plan agent is not disabled in your configuration.`,
+        )
+      const target = restricted ? plan! : agent
+      const restrictions: Record<string, boolean> = restricted ? { edit: false, write: false } : {}
       const session = await iife(async () => {
         if (params.session_id) {
           const found = await Session.get(params.session_id).catch(() => {})
@@ -39,7 +55,7 @@ export const TaskTool = Tool.define("task", async () => {
 
         return await Session.create({
           parentID: ctx.sessionID,
-          title: params.description + ` (@${agent.name} subagent)`,
+          title: params.description + ` (@${target.name} subagent)`,
         })
       })
       const msg = await MessageV2.get({ sessionID: ctx.sessionID, messageID: ctx.messageID })
@@ -96,13 +112,14 @@ export const TaskTool = Tool.define("task", async () => {
           modelID: model.modelID,
           providerID: model.providerID,
         },
-        agent: agent.name,
+        agent: target.name,
         tools: {
           todowrite: false,
           todoread: false,
           task: false,
           ...Object.fromEntries((config.experimental?.primary_tools ?? []).map((t) => [t, false])),
           ...agent.tools,
+          ...restrictions,
         },
         parts: promptParts,
       })
diff --git a/packages/opencode/test/tool/task.test.ts b/packages/opencode/test/tool/task.test.ts
new file mode 100644
index 00000000000..22c6e1a91cc
--- /dev/null
+++ b/packages/opencode/test/tool/task.test.ts
@@ -0,0 +1,123 @@
+import { describe, expect, test } from "bun:test"
+import path from "path"
+import { Instance } from "../../src/project/instance"
+import { Agent } from "../../src/agent/agent"
+import { tmpdir } from "../fixture/fixture"
+
+describe("tool.task security", () => {
+  test("Plan agent has edit permission denied", async () => {
+    await using tmp = await tmpdir()
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const plan = await Agent.get("plan")
+        expect(plan).toBeDefined()
+        expect(plan?.permission.edit).toBe("deny")
+      },
+    })
+  })
+
+  test("Plan agent has bash whitelist with read-only commands", async () => {
+    await using tmp = await tmpdir()
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const plan = await Agent.get("plan")
+        expect(plan).toBeDefined()
+        // Verify read-only commands are allowed
+        expect(plan?.permission.bash["grep*"]).toBe("allow")
+        expect(plan?.permission.bash["ls*"]).toBe("allow")
+        expect(plan?.permission.bash["git status*"]).toBe("allow")
+        expect(plan?.permission.bash["git diff*"]).toBe("allow")
+        // Verify wildcard requires ask (not allow)
+        expect(plan?.permission.bash["*"]).toBe("ask")
+      },
+    })
+  })
+
+  test("Build agent has edit permission allowed", async () => {
+    await using tmp = await tmpdir()
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const build = await Agent.get("build")
+        expect(build).toBeDefined()
+        expect(build?.permission.edit).toBe("allow")
+      },
+    })
+  })
+
+  test("explore subagent exists and has edit disabled in tools", async () => {
+    await using tmp = await tmpdir()
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const explore = await Agent.get("explore")
+        expect(explore).toBeDefined()
+        expect(explore?.mode).toBe("subagent")
+        expect(explore?.tools.edit).toBe(false)
+        expect(explore?.tools.write).toBe(false)
+      },
+    })
+  })
+
+  test("general subagent exists without edit restrictions", async () => {
+    await using tmp = await tmpdir()
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const general = await Agent.get("general")
+        expect(general).toBeDefined()
+        expect(general?.mode).toBe("subagent")
+        // general agent doesn't have edit/write disabled by default
+        expect(general?.tools.edit).toBeUndefined()
+        expect(general?.tools.write).toBeUndefined()
+      },
+    })
+  })
+
+  test("Plan agent cannot be disabled when other restricted agents depend on it", async () => {
+    // This test verifies Plan agent exists by default
+    // The security fix requires Plan agent to be available for restricted parent agents
+    await using tmp = await tmpdir()
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const agents = await Agent.list()
+        const plan = agents.find((a) => a.name === "plan")
+        expect(plan).toBeDefined()
+        expect(plan?.native).toBe(true)
+      },
+    })
+  })
+
+  test("restricted parent detection uses permission.edit === deny", async () => {
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        // Create a custom restricted agent
+        await Bun.write(
+          path.join(dir, "opencode.json"),
+          JSON.stringify({
+            agent: {
+              "custom-restricted": {
+                mode: "primary",
+                permission: {
+                  edit: "deny",
+                },
+              },
+            },
+          }),
+        )
+      },
+    })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const custom = await Agent.get("custom-restricted")
+        expect(custom).toBeDefined()
+        expect(custom?.permission.edit).toBe("deny")
+        // This agent would trigger the restricted path in TaskTool
+      },
+    })
+  })
+})