alibaba/spring-ai-alibaba · error · IllegalArgumentException

Invalid write mode: {item.writeMode()}

Error message

Invalid write mode: {item.writeMode()}

What it means

AssignerNode.apply throws this IllegalArgumentException when a write item's writeMode enum value hits the default branch of the switch, i.e. a write mode the node does not implement (typically a newly added or unknown enum constant). It indicates the assigner does not support that mode.

Source

Thrown at spring-boot-starters/spring-ai-alibaba-starter-builtin-nodes/src/main/java/com/alibaba/cloud/ai/graph/node/AssignerNode.java:124

				case CLEAR -> {
					if (targetValue instanceof List) {
						yield new ArrayList<>();
					}
					else if (targetValue instanceof Map) {
						yield new HashMap<>();
					}
					else if (targetValue instanceof String) {
						yield "";
					}
					else if (targetValue instanceof Number) {
						yield 0;
					}
					else {
						yield null;
					}
				}
				case INPUT_CONSTANT -> item.inputValue();
				default -> throw new IllegalArgumentException("Invalid write mode: " + item.writeMode());
			};
			updates.put(item.targetKey, result);
		}
		return updates;
	}

	// Builder pattern
	public static Builder builder() {
		return new Builder();
	}

	public static class Builder {

		private List<AssignItem> items = new ArrayList<>();

		public Builder setItems(List<AssignItem> items) {
			this.items = new ArrayList<>(items);
			return this;

View on GitHub (pinned to f82da0b50f)

Solutions

1. Use only write modes supported by your library version (check the WriteMode enum and apply's switch)
2. Align library versions so the runtime knows all write modes in your workflow definitions
3. Add the missing case to the switch if you maintain a fork/custom mode

Example fix

// before
Item.builder().targetKey("k").writeMode(SomeCustomMode.MERGE) // unsupported
// after
Item.builder().targetKey("k").writeMode(WriteMode.OVERWRITE)

Set<WriteMode> supported = Set.of(WriteMode.OVERWRITE, WriteMode.APPEND, WriteMode.CLEAR, WriteMode.INPUT_CONSTANT);
if (!supported.contains(item.writeMode())) throw new ConfigException("unsupported write mode: " + item.writeMode());

try {
    state = assignerNode.apply(state);
} catch (IllegalArgumentException e) {
    throw new WorkflowConfigException("Check WriteMode against library version: " + e.getMessage(), e);
}

When it happens

Trigger: Constructing an AssignerNode item with a WriteMode constant not covered by apply's switch (e.g. a mode added in a newer/older library version or INPUT_CONSTANT-adjacent custom modes), so the default case throws.

Common situations: Version mismatch between the workflow definition (serialized write modes) and the library runtime; typos or custom enum extensions; upgrading spring-ai-alibaba-starter-builtin-nodes adds modes your rules use but the pinned runtime lacks.

Related errors

• TOOL_PARAMS_INVALID
• INVALID_PARAMS
• Unknown vector store type:
• Unknown agent status code:
• Unknown agent type code:

AI-assisted analysis of alibaba/spring-ai-alibaba@f82da0b50f (2026-09-09). Data as JSON: /api/errors/895fbbd6fb9f129f. Report an issue: GitHub.