chroma-core/chroma · error · ChromaValueError

Task cannot be updated

Error message

Task cannot be updated

What it means

Thrown as a ChromaValueError by ChromaCloudQwenEmbeddingFunction.validateConfigUpdate() when an update payload contains the key "task". The task (e.g. nl_to_code) selects the instruction used when generating embeddings; changing it after data is indexed would embed new documents under a different instruction than existing ones, so it is immutable.

Source

Thrown at clients/new-js/packages/ai-embeddings/chroma-cloud-qwen/src/index.ts:254

        serializedInstructions[taskKey][targetKey] = instruction;
      }
    }

    return {
      model: this.model,
      task: this.task,
      instructions: serializedInstructions as any,
      api_key_env_var: this.apiKeyEnvVar,
    };
  }

  public validateConfigUpdate(newConfig: Record<string, any>): void {
    if ("model" in newConfig) {
      throw new ChromaValueError("Model cannot be updated");
    }

    if ("task" in newConfig) {
      throw new ChromaValueError("Task cannot be updated");
    }

    if ("instructions" in newConfig) {
      throw new ChromaValueError("Instructions cannot be updated");
    }
  }

  public static validateConfig(config: ChromaCloudQwenConfig): void {
    validateConfigSchema(config, NAME);
  }
}

registerEmbeddingFunction(NAME, ChromaCloudQwenEmbeddingFunction);

View on GitHub (pinned to aecdd12c8a)

Solutions

1. Drop "task" from the update payload.
2. If a different task/instruction setup is needed, create a fresh collection and re-embed.
3. Choose task at construction time (new ChromaCloudQwenEmbeddingFunction({ task: ... })).

Example fix

// before
await collection.modify({
  embedding_function: { name: "chroma-cloud-qwen", config: { task: "nl_to_code" } },
});

// after
const ef = new ChromaCloudQwenEmbeddingFunction({
  model: ChromaCloudQwenEmbeddingModel.QWEN3_EMBEDDING_0p6B,
  task: "nl_to_code",
});
const col = await client.createCollection({ name: "docs-task", embeddingFunction: ef });

const patch = { ...desiredUpdate };
delete patch.task;
if (Object.keys(desiredUpdate).includes("task")) {
  console.warn("'task' is immutable and was stripped; recreate the collection to change it");
}

When it happens

Trigger: Updating the EF config with { task: "nl_to_code" } or any payload containing "task"; round-tripping a full config snapshot into an update call.

Common situations: Deciding later that a collection should use a task-specific instruction; porting creation-time config into modify-time calls.

Related errors

• Model cannot be updated
• Instructions cannot be updated
• Config is missing a required field
• The model name cannot be changed after initialization.
• The task type cannot be changed after initialization.

AI-assisted analysis of chroma-core/chroma@aecdd12c8a (2026-08-16). Data as JSON: /api/errors/b8401ad107694612. Report an issue: GitHub.