alibaba/spring-ai-alibaba · error · IllegalArgumentException

SubAgent name is required

Error message

SubAgent name is required

What it means

SubAgentSpec's builder requires a non-null, non-blank name before it can produce a spec. The framework uses the name to identify the sub-agent when the orchestrating agent delegates work to it, so building without one would yield an unusable spec. This IllegalArgumentException is thrown from build() as a fail-fast validation.

Source

Thrown at spring-ai-alibaba-agent-framework/src/main/java/com/alibaba/cloud/ai/graph/agent/extension/interceptor/SubAgentSpec.java:153

		}

		/**
		 * Set custom interceptors for this subagent.
		 * These will be applied after the default interceptors from SubAgentInterceptor.
		 */
		public Builder interceptors(List<ModelInterceptor> interceptors) {
			this.interceptors = interceptors;
			return this;
		}

		public Builder enableLoopingLog(boolean enableLoopingLog) {
			this.enableLoopingLog = enableLoopingLog;
			return this;
		}

		public SubAgentSpec build() {
			if (name == null || name.trim().isEmpty()) {
				throw new IllegalArgumentException("SubAgent name is required");
			}
			if (description == null || description.trim().isEmpty()) {
				throw new IllegalArgumentException("SubAgent description is required");
			}
			if (systemPrompt == null || systemPrompt.trim().isEmpty()) {
				throw new IllegalArgumentException("SubAgent system prompt is required");
			}
			return new SubAgentSpec(this);
		}
	}
}

View on GitHub (pinned to f82da0b50f)

Solutions

1. Add a name(...) call to the SubAgentSpec builder chain before build().
2. If the name comes from external config, validate it is non-blank before building and provide a default or fail with a clear message.
3. If the spec is optional in your flow, skip building it entirely rather than building with a blank name.

Example fix

// before
SubAgentSpec spec = SubAgentSpec.builder()
    .description("Handles billing questions")
    .systemPrompt("You are a billing agent")
    .build();
// after
SubAgentSpec spec = SubAgentSpec.builder()
    .name("billing-agent")
    .description("Handles billing questions")
    .systemPrompt("You are a billing agent")
    .build();

if (name == null || name.trim().isEmpty()) {
    throw new IllegalArgumentException("Cannot build SubAgentSpec: name is required");
}
SubAgentSpec spec = SubAgentSpec.builder().name(name)...build();

static boolean hasText(String s) { return s != null && !s.trim().isEmpty(); }

try {
    spec = SubAgentSpec.builder()...build();
} catch (IllegalArgumentException e) {
    log.error("Invalid SubAgentSpec: {}", e.getMessage());
}

When it happens

Trigger: Calling SubAgentSpec.builder()...build() without invoking name(String), or invoking it with null, "", or a whitespace-only string.

Common situations: Assembling sub-agents programmatically from config where the name field is optional/absent; forgetting the fluent name() call when copying an example; dynamically generated specs from a model or YAML mapping that omits 'name'.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• SubAgent description is required
• SubAgent system prompt is required
• ChatModel must be provided for LLM routing agent
• LoopAgent must have a loopStrategy.
• Sub-agents must be provided

AI-assisted analysis of alibaba/spring-ai-alibaba@f82da0b50f (2026-09-09). Data as JSON: /api/errors/ab63685f2329efae. Report an issue: GitHub.