What causes "Invalid user input request payload" in github/copilot-sdk?

Ensure params is an object containing both sessionId and question as non-empty strings before calling the method.

Invalid user input request payload

Error message

Invalid user input request payload

What it means

CopilotClient throws this when a user-input request handler receives a params object that is missing or whose sessionId/question fields are not strings. The library validates the payload shape before doing any work so it can fail fast instead of dispatching to a session with garbage data. It is a synchronous guard at the public API boundary.

Solutions

Ensure params is an object containing both sessionId and question as non-empty strings before calling the method.
Validate/coerce the payload where it is deserialized (e.g. after JSON.parse) rather than at call time.
Check that the caller passes fields individually and not a nested object (e.g. params.message.sessionId).

Example fix

// before
await client.handleUserInputRequest({ sessionId: msg.sid, question: undefined });
// after
if (typeof msg.sid !== "string" || typeof msg.question !== "string") return;
await client.handleUserInputRequest({ sessionId: msg.sid, question: msg.question });

Defensive patterns

Strategy: validation

Validate before calling

function canSendUserInput(p) {
  return !!p && typeof p.sessionId === "string" && typeof p.question === "string";
}

Type guard

function isUserInputParams(p): p is { sessionId: string; question: string; choices?: string[]; allowFreeform?: boolean } {
  return typeof p === "object" && p !== null &&
    typeof (p as any).sessionId === "string" && typeof (p as any).question === "string";
}

Try / catch

try {
  await client.handleUserInputRequest(params);
} catch (e) {
  if (e instanceof Error && e.message === "Invalid user input request payload") {
    // fix/serialize payload, do not retry blindly
  }
}

Prevention

Define a shared typed params interface and construct it via one factory function.
Validate payloads at the deserialization boundary (zod/ajv) before they reach client calls.
Never forward raw event objects; extract and check fields explicitly.

When it happens

Trigger: Calling the client's user-input request method (the handler at nodejs/src/client.ts:3169) with params=null/undefined, params.sessionId not a string (missing, number, object), or params.question not a string.

Common situations: Forwarding a deserialized JSON message where sessionId/question were absent or typed as numbers; building the params object dynamically and forgetting question; passing the raw event object instead of the extracted fields.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of github/copilot-sdk@cd8cf15dc3 (2026-09-09). Data as JSON: /api/errors/e7f8b42d8efec246. Report an issue: GitHub.

Appendix: source

Thrown at nodejs/src/client.ts:3169

                handler(event);
            } catch {
                // Ignore handler errors
            }
        }
    }

    private async handleUserInputRequest(params: {
        sessionId: string;
        question: string;
        choices?: string[];
        allowFreeform?: boolean;
    }): Promise<{ answer: string; wasFreeform: boolean }> {
        if (
            !params ||
            typeof params.sessionId !== "string" ||
            typeof params.question !== "string"
        ) {
            throw new Error("Invalid user input request payload");
        }

        const session = this.sessions.get(params.sessionId);
        if (!session) {
            throw new Error(`Session not found: ${params.sessionId}`);
        }

        const result = await session._handleUserInputRequest({
            question: params.question,
            choices: params.choices,
            allowFreeform: params.allowFreeform,
        });
        return result;
    }

    private async handleExitPlanModeRequest(
        params: ExitPlanModeRequest & { sessionId: string }
    ): Promise<ExitPlanModeResult> {

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