Subagents (Task tool) fail 100% on all BYOK models — "No output received" / "Task failed"

[HaydenLundin]

Summary

The Task tool fails to execute any subagent when using BYOK custom models. Tested across 5 different models, 2 different providers, and 2 different provider types — all produce the same ⚠ Task failed with no output. The simplest possible task ("respond with the word hello") fails every time.

The default worker droid (shipped by Factory) fails on every BYOK model. This is not a droid configuration issue.

This appears related to closed FAC-12629 (same symptoms). The underlying issue persists.

---

Environment

• OS: Windows (PowerShell)
• Droid CLI version: [run droid --version and fill in]
• Plan: Free (BYOK only, no Factory-hosted models available)
• Droid files: Factory defaults (worker.md, scrutiny-feature-reviewer.md)
• Custom Droids: Enabled in /settings

---

Reproduction

Prompt used (identical for all 5 tests)

Run the Task tool with subagent worker with prompt "respond with the word hello"

Results

#	Model	Provider	API Type	Result
1	Kimi K2.5	NVIDIA NIM	generic-chat-completion-api	⚠ No output received
2	MiniMax M2.5	NVIDIA NIM	generic-chat-completion-api	⚠ Task failed
3	Qwen 3.5	NVIDIA NIM	generic-chat-completion-api	⚠ Task failed
4	GLM5	NVIDIA NIM	generic-chat-completion-api	⚠ Task failed
5	Arcee Trinity Large	OpenRouter	openai	⚠ Task failed

5 out of 5 BYOK models fail. The failure is identical regardless of:

• Model (tested 5 different models from 5 different labs)
• Hosting provider (NVIDIA NIM vs OpenRouter)
• Provider type (generic-chat-completion-api vs openai)

All 5 models work perfectly as the parent model for normal tasks (file reading, code editing, git commands, etc.). Only subagent delegation via the Task tool fails.

---

BYOK Configuration

{
  "customModels": [
    {
      "name": "minimax-m2.5",
      "displayName": "MiniMax M2.5 (NVIDIA Free)",
      "model": "minimaxai/minimax-m2.5",
      "baseUrl": "https://integrate.api.nvidia.com/v1",
      "apiKey": "REDACTED",
      "provider": "generic-chat-completion-api"
    },
    {
      "name": "kimi-k2.5",
      "displayName": "Kimi K2.5 (NVIDIA Free)",
      "model": "moonshotai/kimi-k2.5",
      "baseUrl": "https://integrate.api.nvidia.com/v1",
      "apiKey": "REDACTED",
      "provider": "generic-chat-completion-api"
    },
    {
      "name": "glm5",
      "displayName": "GLM5 (NVIDIA Free)",
      "model": "z-ai/glm5",
      "baseUrl": "https://integrate.api.nvidia.com/v1",
      "apiKey": "REDACTED",
      "provider": "generic-chat-completion-api"
    },
    {
      "name": "qwen3.5-397b-a17b",
      "displayName": "Qwen 3.5 (NVIDIA Free)",
      "model": "qwen/qwen3.5-397b-a17b",
      "baseUrl": "https://integrate.api.nvidia.com/v1",
      "apiKey": "REDACTED",
      "provider": "generic-chat-completion-api"
    },
    {
      "name": "trinity-large",
      "displayName": "Arcee Trinity Large (OpenRouter Free)",
      "model": "arcee-ai/trinity-large-preview:free",
      "baseUrl": "https://openrouter.ai/api/v1",
      "apiKey": "REDACTED",
      "provider": "openai"
    }
  ]
}

---

Droid File (Factory default)

~/.factory/droids/worker.md:

---
name: worker
description: >-
  General-purpose worker droid for delegating tasks. Use for non-trivial tasks
  that benefit from parallel execution, such as code exploration, Q&A, research,
  analysis.
model: inherit
---
# Worker Droid

Complete the requested task and report back concisely. In your response, include your chain of
thought and a paper trail of relevant resources (e.g. files, code, git commits, web searches, etc)
following the order and logic through which you discovered them.

---

What I Cannot Test

I am on the free tier with BYOK only — I have no access to Factory built-in models. This means:

• I cannot do a control test to confirm subagents work on built-in models
• I have no workaround for this issue
• If subagents require Factory-hosted tokens, free BYOK users are completely blocked with no error message explaining why

---

Documentation Gap

The [BYOK docs](https://docs.factory.ai/cli/byok/overview) state all features work with BYOK. The [Custom Droids docs](https://docs.factory.ai/cli/configuration/custom-droids) show model: inherit as the standard pattern with no caveats about BYOK compatibility.

If subagents require a paid subscription, this should be documented clearly on both pages.

---

Expected Behavior

• Subagent spawns using the parent session's BYOK model and credentials
• Subagent executes and returns output
• model: inherit propagates the BYOK configuration to the subagent

Actual Behavior

• Task tool invokes subagent
• Subagent produces no output (or returns 402)
• Parent model silently falls back to doing the work itself
• User has no clarity on what went wrong

---

Request

1. Confirm or deny: Do subagents work with BYOK models on the free plan?
2. If yes (bug): Fix credential propagation to subagent processes
3. If no (by design): Update BYOK and Custom Droids docs to state this limitation, and replace the silent "No output received" error with a clear message like "Subagents require a Factory subscription"
4. Either way: Improve error reporting — silent failures waste significant user debugging time

---

Related Issues

• FAC-12629 — Specialist Droid hangs on requests (closed, same symptoms)
• FAC-12288 — Droid Exec headless mode doesn't support custom models
• FAC-12403 — Feature request for custom models in droid exec

[wbisschoff13]

Having the same issue trying to use MiniMax coding plan. Works fine on the main agent, but all subtasks fail with "Invalid model: custom:MiniMax-M2.5"

[wbisschoff13]

Also affects droid exec with custom models when using the --model override. Somehow that works fine if the default model is a custom one though, ad opposed to the subagents.

[stepan-factory]

as per our byok docs, you need to use "provider": "generic-chat-completion-api for all non-openai hosted models. "openai" provider only works with Responses API specification

[wbisschoff13]

Yessir, just confirmed that is what mine is set to.

~/.factory/settings.json

{
  "customModels": [
    {
      "model": "glm-4.7",
      "id": "custom:glm",
      "index": 1,
      "baseUrl": "https://api.z.ai/api/coding/paas/v4",
      "apiKey": "${ZAI_API_KEY}",
      "displayName": "GLM-4.7 [Z.AI Coding Plan]",
      "maxOutputTokens": 131072,
      "noImageSupport": false,
      "provider": "generic-chat-completion-api"
    }
  ],
  "autonomyLevel": "auto-medium",
  "sessionDefaultSettings": {
    "model": "custom:glm",
    "reasoningEffort": "none",
    "autonomyMode": "auto-medium",
    "interactionMode": "auto",
    "autonomyLevel": "medium"
  },
  "logoAnimation": "off"
}

❯ droid exec --auto medium -o json --model custom:glm "this is a test"                    7s 08:03
Invalid model: custom:glm

Available built-in models:
  claude-opus-4-5-20251101, claude-opus-4-6, claude-opus-4-6-fast, claude-sonnet-4-5-20250929, claude-sonnet-4-6, claude-haiku-4-5-20251001, gpt-5.1, gpt-5.1-codex, gpt-5.1-codex-max, gpt-5.2, gpt-5.2-codex, gpt-5.3-codex, gemini-3-pro-preview, gemini-3.1-pro-preview, gemini-3-flash-preview, glm-4.7, glm-5, kimi-k2.5, minimax-m2.5

Available custom models:
  GLM-4.7 [Z.AI Coding Plan]

Note: Custom models are loaded from ~/.factory/settings.json
Invalid model: custom:glm

Available built-in models:
  claude-opus-4-5-20251101, claude-opus-4-6, claude-opus-4-6-fast, claude-sonnet-4-5-20250929, claude-sonnet-4-6, claude-haiku-4-5-20251001, gpt-5.1, gpt-5.1-codex, gpt-5.1-codex-max, gpt-5.2, gpt-5.2-codex, gpt-5.3-codex, gemini-3-pro-preview, gemini-3.1-pro-preview, gemini-3-flash-preview, glm-4.7, glm-5, kimi-k2.5, minimax-m2.5

Available custom models:
  GLM-4.7 [Z.AI Coding Plan]

Note: Custom models are loaded from ~/.factory/settings.json

❯ droid exec --auto medium -o json --model "GLM-4.7 [Z.AI Coding Plan]" "this is a test"  3s 08:04
Invalid model: GLM-4.7 [Z.AI Coding Plan]

Available built-in models:
  claude-opus-4-5-20251101, claude-opus-4-6, claude-opus-4-6-fast, claude-sonnet-4-5-20250929, claude-sonnet-4-6, claude-haiku-4-5-20251001, gpt-5.1, gpt-5.1-codex, gpt-5.1-codex-max, gpt-5.2, gpt-5.2-codex, gpt-5.3-codex, gemini-3-pro-preview, gemini-3.1-pro-preview, gemini-3-flash-preview, glm-4.7, glm-5, kimi-k2.5, minimax-m2.5

Available custom models:
  GLM-4.7 [Z.AI Coding Plan]

Note: Custom models are loaded from ~/.factory/settings.json
Invalid model: GLM-4.7 [Z.AI Coding Plan]

Available built-in models:
  claude-opus-4-5-20251101, claude-opus-4-6, claude-opus-4-6-fast, claude-sonnet-4-5-20250929, claude-sonnet-4-6, claude-haiku-4-5-20251001, gpt-5.1, gpt-5.1-codex, gpt-5.1-codex-max, gpt-5.2, gpt-5.2-codex, gpt-5.3-codex, gemini-3-pro-preview, gemini-3.1-pro-preview, gemini-3-flash-preview, glm-4.7, glm-5, kimi-k2.5, minimax-m2.5

Available custom models:
  GLM-4.7 [Z.AI Coding Plan]

Note: Custom models are loaded from ~/.factory/settings.json

Works normal on the main droid, just droid exec and subagents where it breaks.

[bnp8]

i think i have the same issue but just a little different.

The bug was that when those validators tried to spawn sub-subagents (via the Task tool), the model: inherit in your droid configs resolved to glm-5 instead of inheriting the parent's gpt-5.3-codex. It's a Factory platform bug in the Task tool's model inheritance chain.

[mkulariya]

Getting this for the last week, the main agent gives this. It was working fine earlier, tested with both minimax and z ai, looks like issue is with antrhpic style api calls in BYOK mode.

BYOK Error: Streaming is required for operations that may take longer than 10 minutes. See
https://github.com/anthropics/anthropic-sdk-typescript#long-requests for more details

[HaydenLundin]

@stepan-factory

Follow-up: Root cause identified through additional testing
After further investigation, I've narrowed this down to two distinct bugs. Posting findings so others hitting this issue have a clear path forward.

Bug 1: Factory-shipped droid files are silently overwritten on startup
worker.md, scrutiny-feature-reviewer.md, and user-testing-flow-validator.md are reset to model: inherit every time a Droid session starts. User edits do not survive a restart — no warning, no log entry, no validation error. This is what causes the 100% failure rate on BYOK models: the explicit model ID you set gets wiped before the session even begins, and inherit then fails to resolve BYOK credentials in the Task tool.
Verified on Windows (PowerShell):

Edit worker.md to model: claude-haiku-4-5-20251001 (a valid built-in)

Start Droid session, run no prompts

Get-Content ~/.factory/droids/worker.md

→ model: inherit ← already reset

This happens with both BYOK model IDs and valid built-in model IDs — the reset is unconditional, not validator-triggered.
The docs state validation issues appear in CLI logs when a file fails to load — a silent overwrite is not documented behavior.

Bug 2: model: inherit does not resolve BYOK credentials in the Task tool
Even when inherit is intentional, subagents fail 100% of the time when the parent session is running a BYOK model. The Task tool does not propagate the parent's baseUrl / apiKey to the subagent process. This is what the original issue reported and what other commenters are hitting independently.

Workaround (confirmed working)
Create a user-owned droid file instead of editing Factory's defaults. Factory does not overwrite files it didn't ship:

---

name: worker-byok
description: >-
General-purpose worker droid for delegating tasks.
model: custom:minimaxai/minimax-m2.5

Worker Droid

Complete the requested task and report back concisely...

Using worker-byok as the subagent type instead of worker succeeds consistently and fast:

Subagent	Model config	Result	Time
worker (Factory default)	Overwritten to inherit	⚠ Task failed	~180s
worker-byok (user-created)	custom:minimaxai/minimax-m2.5	✅ Success	34s

Note: per the docs, the correct BYOK syntax for droid files is custom: where matches the model field in your settings.json — not the displayName.

Requests

1. Stop overwriting user edits to default droid files on startup — or at minimum log a warning when a managed file is being reset
2. Fix model: inherit credential propagation in the Task tool for BYOK sessions
3. Add a note to the BYOK docs and the Custom Droids docs that worker.md is a managed file and will be reset, so users should create their own droid files for custom model configurations

[fernandodamaso]

Same bug here... really hard using the CLI without sub agents in byok

[stepan-factory]

@fernandodamaso sorry about the delay

We are looking into this issue

[tristanwagner]

I'm also experiencing this issue, it seems to me that model: inherit while using a custom model is broken.

[fernandodamaso]

@tristanwagner is right, when i've changed the model to custom:kimi-for-coding then it worked