github/copilot-sdk · error · RuntimeException

session.create response did not include a sessionId

Error message

session.create response did not include a sessionId

What it means

CopilotClient.createSession sends a session.create RPC and requires the server response to carry a sessionId. If the response's sessionId field is null or empty, the client cannot register or look up the session, so it throws immediately rather than returning a broken CopilotSession.

Solutions

1. Upgrade the Copilot agent/server to a version matching the SDK's expected session.create response schema
2. Verify no proxy or interceptor is stripping the sessionId field from RPC responses
3. Log the raw session.create response (enable FINE logging via LoggingHelpers) to confirm what the server returned
4. If using a stub server, make it return a non-empty sessionId

Example fix

// before (stub server)
server.on("session.create", (req, resp) -> resp.send(Map.of()));
// after
server.on("session.create", (req, resp) -> resp.send(Map.of("sessionId", UUID.randomUUID().toString())));

try {
    CopilotSession s = client.createSession(options);
} catch (RuntimeException e) {
    if (e.getMessage().contains("did not include a sessionId")) {
        // check server/agent version compatibility; retry with a fresh server
    }
}

When it happens

Trigger: The session.create RPC completes but response.sessionId() returns null or "" — e.g. a misbehaving or incompatible Copilot server/extension version that omits the sessionId field, or a proxy mangling the response payload.

Common situations: Running against an outdated or third-party Copilot agent binary whose session.create response schema differs; network middleware stripping fields; testing against a mock/stub RPC server that returns an incomplete response.

Understand the failure class

Background: "invalid response format", "malformed payload", "missing data field": when an API returns 200 but the response shape is wrong — this error's family across 23 libraries.

Related errors

• session.create returned sessionId
• No session found for sessionId
• session.create returned sessionId
• Failed to delete session
• Failed to set foreground session

AI-assisted analysis of github/copilot-sdk@cd8cf15dc3 (2026-09-09). Data as JSON: /api/errors/425803ed537eb7f0. Report an issue: GitHub.

Appendix: source

Thrown at java/sdk/src/main/java/com/github/copilot/CopilotClient.java:1015

                    ? null
                    : gitHubTokenProviders.register(config.getGitHubTokenProvider());
            if (tokenRegistration != null) {
                request.setGitHubTokenProviderRegistrationId(tokenRegistration.id());
                if (preRegisteredSessionHolder[0] != null) {
                    preRegisteredSessionHolder[0].setGitHubTokenProviderRegistration(tokenRegistration);
                }
            }

            long rpcNanos = System.nanoTime();
            return connection.rpc.invoke("session.create", request, CreateSessionResponse.class)
                    .thenCompose(response -> {
                        String returnedId = response.sessionId();
                        LoggingHelpers.logTiming(LOG, Level.FINE,
                                "CopilotClient.createSession session creation request completed. Elapsed={Elapsed}, SessionId="
                                        + (returnedId != null ? returnedId : localSessionId),
                                rpcNanos);
                        if (returnedId == null || returnedId.isEmpty()) {
                            throw new RuntimeException("session.create response did not include a sessionId");
                        }
                        if (localSessionId != null && !localSessionId.equals(returnedId)) {
                            throw new RuntimeException("session.create returned sessionId " + returnedId
                                    + " but the caller requested " + localSessionId);
                        }
                        CopilotSession session = preRegisteredSessionHolder[0] != null
                                ? preRegisteredSessionHolder[0]
                                : initializeSession.apply(returnedId);
                        preRegisteredSessionHolder[0] = session;
                        if (tokenRegistration != null) {
                            session.setGitHubTokenProviderRegistration(tokenRegistration);
                        }
                        registeredIdHolder[0] = returnedId;
                        CompletableFuture<?> interest = config.getOnMcpAuthRequest() != null
                                ? session.getRpc().eventLog.registerInterest(
                                        new SessionEventLogRegisterInterestParams(returnedId, "mcp.oauth_required"))
                                : CompletableFuture.completedFuture(null);
                        session.setWorkspacePath(response.workspacePath());

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