github/copilot-sdk · error · IllegalArgumentException

setModel cannot combine an explicit autoTier with…

Error message

setModel cannot combine an explicit autoTier with resetAutoTier; choose one

What it means

CopilotSession.setModel rejects logically conflicting input: specifying an explicit autoTier while also requesting resetAutoTier=true is contradictory, so it throws IllegalArgumentException('setModel cannot combine an explicit autoTier with resetAutoTier; choose one'). You must choose either a concrete tier or a reset to automatic behavior, never both.

Solutions

Decide intent: keep the explicit autoTier and drop the resetAutoTier flag, or reset and clear autoTier.
Sanitize options at construction: if resetAutoTier is set, null out autoTier (or vice versa).
Fail fast in your own config loader when both fields are present so users get a clear message.

Example fix

// before
session.setModel(new SetModelOptions().setModel("gpt-5").setAutoTier("high").setResetAutoTier(true));
// after
var opts = new SetModelOptions().setModel("gpt-5");
if (resetRequested) {
    opts.setResetAutoTier(true);
} else {
    opts.setAutoTier("high");
}
session.setModel(opts);

Defensive patterns

Strategy: validation

Validate before calling

if (options.getAutoTier() != null && options.isResetAutoTier()) {
    throw new IllegalArgumentException("choose either autoTier or resetAutoTier, not both");
}

Type guard

boolean optionsConsistent(com.github.copilot.rpc.SetModelOptions o) { return !(o.getAutoTier() != null && o.isResetAutoTier()); }

Try / catch

try {
    session.setModel(options);
} catch (IllegalArgumentException e) {
    LOG.warning("conflicting auto-tier options: " + e.getMessage());
}

Prevention

Resolve config conflicts at merge time: if resetAutoTier is requested, clear autoTier.
Use a single builder function that enforces the mutual exclusion.
Surface conflicting settings to users at config load, not at call time.

When it happens

Trigger: Calling session.setModel with options where getAutoTier() != null and isResetAutoTier() is true simultaneously (CopilotSession.java:2243).

Common situations: Config merging bugs: one source sets autoTier (e.g. 'high') while another flag sets resetAutoTier, and both are copied into the same options object without conflict resolution.

Related errors

AI-assisted analysis of github/copilot-sdk@cd8cf15dc3 (2026-09-09). Data as JSON: /api/errors/77e46e0a3149dc62. Report an issue: GitHub.

Appendix: source

Thrown at java/sdk/src/main/java/com/github/copilot/CopilotSession.java:2243

     * @return a future that completes when the model switch is acknowledged
     * @throws IllegalArgumentException
     *             if {@code options} is {@code null}, if it carries no model ID, or
     *             if it requests both an explicit Auto tier and a return to
     *             provider-default Auto routing
     * @throws IllegalStateException
     *             if this session has been terminated
     * @since 1.6.0
     */
    public CompletableFuture<Void> setModel(com.github.copilot.rpc.SetModelOptions options) {
        ensureNotTerminated();
        if (options == null) {
            throw new IllegalArgumentException("options must not be null");
        }
        if (options.getModel() == null) {
            throw new IllegalArgumentException("options must specify a model");
        }
        if (options.getAutoTier() != null && options.isResetAutoTier()) {
            throw new IllegalArgumentException(
                    "setModel cannot combine an explicit autoTier with resetAutoTier; choose one");
        }
        var generatedReasoningSummary = options.getReasoningSummary() == null
                ? null
                : com.github.copilot.generated.rpc.ReasoningSummary.fromValue(options.getReasoningSummary());
        var params = new SessionModelSwitchToParams(sessionId, options.getModel(),
                toGeneratedAutoTier(options.getAutoTier()), options.getReasoningEffort(), generatedReasoningSummary,
                null, toGeneratedCapabilities(options.getModelCapabilities()), null, null, null, null, null, null, null,
                null, null);
        if (!options.isResetAutoTier()) {
            return getRpc().model.switchTo(params).thenApply(r -> null);
        }
        // The generated params record omits null properties, but returning to
        // provider-default Auto routing requires sending an explicit null tier, so
        // build the payload directly and reinstate the null.
        ObjectNode payload = MAPPER.valueToTree(params);
        payload.putNull("autoTier");
        return rpc.invoke("session.model.switchTo", payload, Void.class);

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