Subagents are using the task tool

Description

Although the subagents do not have the task tool but they sometimes delegate to other agents. I have noticed this happening after v1.0.68, but I can't tell which version it was.

Unfortunately the sub-agent got stuck somewhere, and I can't navigate to the sub-sub-agents either to see what is happening.

OpenCode version

v1.0.72

Steps to reproduce

Unfortunately I can't reliably produce a step for this. This is quite random. In the same session.

Screenshot and/or share link

Shared session:

Primary agent: https://opencode.ai/s/1LiETc7T
Sub-agent: https://opencode.ai/s/Lyh1uNbY

Operating System

Arch Linux

Terminal

foot

Interesting find: https://opencode.ai/s/j0eMtkw1

This shows me some instructions that are only accessible by the primary agents

I can confirm my subagent is set to "mode": "subagent". Here is a part of my config:

    "agent": {
        "build": {
            "mode": "primary",
            "color": "#c864af",
            "prompt": "{file:~/.config/opencode/config/primary/primary-role.md}{file:./config/primary/non-robin-constraints.md}",
        },

        "research:smart": {
            "mode": "subagent",
            "description": "Deep research specialist [preferred:research,reasoning,readonly] | Capabilities: Read-only file access | Smart model (sonnet) | Extended reasoning | Deep analysis | Selection criteria: Task requires understanding complex code, architecture, or patterns without modification | Use cases: Codebase exploration | Architectural review | Dependency analysis | Pattern identification | Impact assessment | Design investigation | Anti-patterns: Code implementation | File modifications | Quick lookups | Straightforward fact-finding",
            "prompt": "{file:./config/subagent/_directives.md}",
            "model": "anthropic/claude-sonnet-4-5-medium",
       }
    }

ill check it out

the issue here is in the new agent loop it tries to resolve the tools from the last user message
but it's possible to insert a user message without any tools, need to think about how to resolve this/if this is even a good pattern i introduced

@thdxr

I asked Claude to help investigate this and here's what it found. I'm not sure if this holds any truth to it, but I'm hoping this helps pinpointing the problem.

What Claude Found

The issue seems to trace back to the agent loop refactor in commit a1214ff. @thdxr you're right about it being tool resolution from user messages, but there's a specific execution path that causes it.

The Problem

File: packages/opencode/src/session/prompt.ts

The refactor extracted loop() as a separately callable function (line 229). The server can now call it directly from packages/opencode/src/server/server.ts:801:

await SessionPrompt.loop(id)

This bypasses the tool restrictions that were set up in the original prompt() call.

How It Happens

Primary agent delegates via TaskTool with restricted tools: {task: false, todoread: false, todowrite: false}
SessionPrompt.prompt() creates the user message with these restrictions
loop(sessionID) gets called-works fine initially
Later, the server calls SessionPrompt.loop(sessionID) directly for session continuation
loop() tries to resolve tools from lastUser.tools (line 465), but if that message doesn't have complete tool restrictions, it falls back to agent defaults
Subagent ends up with task tool access

Before vs After

Before refactor: The loop was internal to prompt(), so the tool context was consistent.

After refactor: Loop is exported and can be called independently, which breaks the guarantee that tool restrictions stick around.

Code Locations

Tool resolution in the loop (prompt.ts:461-467):

const tools = await resolveTools({
  agent,
  sessionID,
  model: lastUser.model,
  tools: lastUser.tools,  // Can be undefined/incomplete
  processor,
})

This would explain why it's random-it depends on the message history state when the server decides to continue the session.

Interesting Finding

With current implementation one issue we have is that when the sub-agent delegates, there is no way of navigating to the sub-sub-agent view/session to see what it is doing. However with the following change it is actually possible to navigate. It doesn't fix the issue in this conversation, but I thought it would be interesting to know:

M packages/opencode/src/server/server.ts
@@ -798,7 +798,7 @@ export namespace Server {
               modelID: body.modelID,
             },
           })
-          await SessionPrompt.loop(id)
+          await SessionPrompt.prompt({ sessionID: id, parts: [] })
           return c.json(true)
         },
       )

@rekram1-node

@rekram1-node I did a bit of digging and I found some interesting lines in the code, some defaults might be the issue. I've applied this patch locally and I haven't seen the issue yet.

TLDR; there is something weird going on, but the default subagent can't be the build agent, it should have been the general agent.

diff --git a/packages/opencode/src/session/index.ts b/packages/opencode/src/session/index.ts
index 0936f530b..9f5005352 100644
--- a/packages/opencode/src/session/index.ts
+++ b/packages/opencode/src/session/index.ts
@@ -39,6 +39,7 @@ export namespace Session {
       id: Identifier.schema("session"),
       projectID: z.string(),
       directory: z.string(),
+      agent: z.string(),
       parentID: Identifier.schema("session").optional(),
       summary: z
         .object({
@@ -124,6 +125,7 @@ export namespace Session {
       .object({
         parentID: Identifier.schema("session").optional(),
         title: z.string().optional(),
+        agent: z.string().optional(),
       })
       .optional(),
     async (input) => {
@@ -131,6 +133,7 @@ export namespace Session {
         parentID: input?.parentID,
         directory: Instance.directory,
         title: input?.title,
+        agent: input?.agent,
       })
     },
   )
@@ -172,12 +175,19 @@ export namespace Session {
     })
   })
 
-  export async function createNext(input: { id?: string; title?: string; parentID?: string; directory: string }) {
+  export async function createNext(input: {
+    id?: string
+    title?: string
+    parentID?: string
+    directory: string
+    agent?: string
+  }) {
     const result: Info = {
       id: Identifier.descending("session", input.id),
       version: Installation.VERSION,
       projectID: Instance.project.id,
       directory: input.directory,
+      agent: input.agent ?? "build",
       parentID: input.parentID,
       title: input.title ?? createDefaultTitle(!!input.parentID),
       time: {
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index 9611b5289..c32b94811 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -827,7 +827,10 @@ export namespace SessionPrompt {
   }
 
   async function createUserMessage(input: PromptInput) {
-    const agent = await Agent.get(input.agent ?? "build")
+    const session = await Session.get(input.sessionID)
+    const agent =
+      (await Agent.get(input.agent ?? "")) || (await Agent.get(session.agent ?? "")) || (await Agent.get("general"))
+    if (!agent) throw new Error(`Agent not found: ${input.agent ?? session.agent ?? "general"}`)
     const info: MessageV2.Info = {
       id: input.messageID ?? Identifier.ascending("message"),
       role: "user",
diff --git a/packages/opencode/src/tool/task.ts b/packages/opencode/src/tool/task.ts
index c4444f1b6..cd75ae2fc 100644
--- a/packages/opencode/src/tool/task.ts
+++ b/packages/opencode/src/tool/task.ts
@@ -61,6 +61,7 @@ export const TaskTool = Tool.define("task", async () => {
         return await Session.create({
           parentID: ctx.sessionID,
           title: params.description + ` (@${agent.name} subagent)`,
+          agent: agent.name,
         })
       })
       const msg = await MessageV2.get({ sessionID: ctx.sessionID, messageID: ctx.messageID })

I am not happy about this though, this looks like a band-aid to me. A proper fix would be figuring out why sometimes the agent is not set properly.

ill take a looksie

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Subagents are using the task tool #4439

Description

OpenCode version

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Operating System

Terminal

What Claude Found

The Problem

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Before vs After

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Interesting Finding

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Subagents are using the task tool #4439

Description

Description

OpenCode version

Steps to reproduce

Screenshot and/or share link

Operating System

Terminal

Activity

arsham commented on Nov 18, 2025

rekram1-node commented on Nov 18, 2025

thdxr commented on Nov 19, 2025

arsham commented on Nov 20, 2025

What Claude Found

The Problem

How It Happens

Before vs After

Code Locations

Interesting Finding

arsham commented on Nov 28, 2025

rekram1-node commented on Nov 29, 2025

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