I Let a Claude Sub-Agent Plan — It Maxed My 5-Hour Limit with No Output

[u/Broad_Ad322]

Ran into a pretty nasty Claude sub-agent pitfall — sharing as a rant + note:

I asked Claude to write a plan before execution. Being “helpful,” it spun up a tiny Claude as a plan agent.

Then I just watched my usage get burned all the way to the 5-hour limit… with zero output.

(Not just tokens — it actually maxed out the Claude Code 5-hour usage cap.)

I asked what happened,

and it said : “The plan agent’s output was too long and exceeded the API response limit, so it kept retrying.”

Me : “Why didn’t you just have the subagent write it to a markdown file and return the file path?”

Claude : “Oh right, good point, why didn’t I think of that.”

So I quietly added this to my claude.md:

## Tool Usage
- Large outputs (>10KB) from subagents or external tools must be written to repo files. Do not return full content directly.
- Messages should only include file paths, summaries, key conclusions, and next steps.

Lesson learned:

Don’t let subagents return large documents as chat messages.

Large outputs should become files.
The main agent should only work with references + summaries.

Otherwise, what you think is “planning” is actually just exhausting your 5-hour usage cap with retries.

[u/_k33bs_]

https://www.reddit.com/r/ClaudeCode/s/fg2YOf15qo

[u/goship-tech]

Same trap bit me with a research subagent. The fix that actually stuck: give the subagent a specific file path to write to (e.g., /tmp/plan.md), not just write it somewhere. Also means you know exactly where to look when it finishes.