FlowiseAI/Flowise · error · Error

Return output must be an object

Error message

Return output must be an object

What it means

Thrown on the code-sandbox branch of `getUpdateStateMemory` (`selectedTab === 'updateStateMemoryCode'`). User-supplied JS runs via `executeJavaScriptCode` in a sandbox; the response is merged into state memory with `Object.assign`-style semantics, so it must be a plain object. `typeof response !== 'object'` rejects strings, numbers, booleans, and undefined.

Source

Thrown at packages/components/nodes/sequentialagents/Agent/Agent.ts:945

                let value = sch.value as string
                if (value.startsWith('$flow')) {
                    value = customGet(flow, sch.value.replace('$flow.', ''))
                } else if (value.startsWith('$vars')) {
                    value = customGet(flow, sch.value.replace('$', ''))
                }
                obj[key] = value
            }
            return obj
        } catch (e) {
            throw new Error(e)
        }
    } else if (selectedTab === 'updateStateMemoryCode' && updateStateMemoryCode) {
        const sandbox = createCodeExecutionSandbox(input, variables, flow)

        try {
            const response = await executeJavaScriptCode(updateStateMemoryCode, sandbox)

            if (typeof response !== 'object') throw new Error('Return output must be an object')
            return response
        } catch (e) {
            throw new Error(e)
        }
    }

    return {}
}

const convertCustomMessagesToBaseMessages = (messages: string[], name: string, additional_kwargs: ICommonObject) => {
    return messages.map((message) => {
        return new HumanMessage({
            content: message,
            name,
            additional_kwargs: Object.keys(additional_kwargs).length ? additional_kwargs : undefined
        })
    })
}

View on GitHub (pinned to abe4a8601a)

Solutions

1. Make the sandbox code `return { ... }` an object literal keyed by the state fields you want to set.
2. Wrap any primitive in an object, e.g. `return { value: result }`.
3. Verify the return value with `console.log(typeof response)` while debugging.

Example fix

// before
updateStateMemoryCode = "const r = compute(); return r" // r is a string -> throws [288]

// after
updateStateMemoryCode = "const r = compute(); return { result: r }"

function assertStateMemoryCodeResult(response) {
  if (response === null || typeof response !== 'object' || Array.isArray(response)) {
    throw new Error('updateStateMemoryCode must return a plain object, e.g. { key: value }')
  }
  return response
}

// in your sandbox wrapper
const response = await executeJavaScriptCode(updateStateMemoryCode, sandbox)
assertStateMemoryCodeResult(response)

function isPlainObject(v): v is Record<string, unknown> {
  return v != null && typeof v === 'object' && !Array.isArray(v)
}

When it happens

Trigger: The custom updateStateMemory code returns a primitive (string, number, boolean), undefined, or an array instead of an object literal.

Common situations: User wrote `return result` where `result` is a string; forgot the return statement entirely (returns undefined); returned an array thinking it would be spread into state; returned null (typeof null === 'object' but downstream code throws on null access).

Related errors

• Condition function must return a string
• Condition function must return a string
• Model is required
• Model is required
• Scenarios are required

AI-assisted analysis of FlowiseAI/Flowise@abe4a8601a (2026-08-12). Data as JSON: /api/errors/0d220e0f50d8791d. Report an issue: GitHub.