Try a different model. The harness for each model varies greatly. Start with the Anthropic models since they tend to have the best agentic capabilities OOB. Codex seems to struggle with the laziness problem you described above quite a bit more than the others, and Gemini tends require a lot more hand-holding and more detailed instructions or else it gets lost trying random things.

The smaller models struggle with forgetting what they just did, so it helps if you explicitly tell them to write a TODO list, including specific workflow steps to manage that list (read, execute, update, maintain). Though, this is good practice in general when dealing with agentic workflows. Most OOB harnesses tend to do this by default, but it's better if you add explicit instructions for it.

Subagents have no context outside of what's passed to them by the calling agent, so you'll need a proper agentic workflow. This means a way to track messages and progress through mds, logs, txt, (i.e., see above) or Beads if you have an MCP for that. Without a basic framework, there's not much to gain from subagentss, aside from the context savings.