A rundown of 23 habits that waste usage limits or degrade output quality on the newest Claude models, drawn from Anthropic's own guides, engineer comments, and power-user tips. The core themes: keep sessions scoped to one task, stop paying to re-read bloated conversations, stop defaulting to the biggest model and highest effort, and put guardrails around file edits, plugins, and MCP connectors. It ends with advanced fixes like cache-warming loops, session retention settings, manual compaction instructions, and automated model routing.
- Long multi-topic "kitchen sink" sessions get re-read on every prompt — even with the prompt cache dropping that cost to about 5% on the newest models, it still drains limits and dilutes answers, so start a new chat or use /clear per task.
- Switching models mid-chat wipes the cache and forces a full-price re-read; Anthropic's engineer says flipping from Opus to Haiku 100k tokens in costs more than just letting Opus answer, while changing effort level mid-chat no longer wipes the cache (still in beta).
- Max effort shows diminishing returns and overthinking — on Artificial Analysis tests, Opus at max scores roughly four points higher than high but costs over three times as much per task, so medium or high is the sensible default.
- On a subscription the prompt cache goes cold after about an hour; one ~400k-word session cost 15 cents to continue warm versus nearly $12 cold, so use /clear, compact while warm, or have Claude ping itself every 30 minutes to keep the cache alive.
- Vague prompts and "make it not look like AI" instructions just swap one default style for another — name the exact patterns to avoid, or supply a design system or skill so the model starts from your standards.
- Keep CLAUDE.md under about 200 lines and treat it as a router pointing to skills, docs, and folders; it loads on every message and Claude starts ignoring parts of it when it gets too long.
- Skipping permissions is genuinely dangerous — someone reported Claude deleting their entire C drive in that mode, with at least four similar Windows reports since September; use auto mode plus a destructive command guard and dated backups or git.
- Use a model routing system instead of defaulting to the biggest model: the speaker's router sent 9 out of 10 prompts to Sonnet or Haiku over three weeks at a total routing cost of 13 cents, and Haiku costs roughly 40 times less than Opus.
Max effort costs 3x for four points
4:41–5:35
A concrete benchmark number that directly contradicts the instinct to max out effort on every task.
For Opus 5.5, max scores about four points higher than high, so only a bit, but costs over three times as much per task.
15 cents warm, $12 cold
11:02–11:49
The single most dramatic cost figure in the video, with three practical fixes attached.
In one example, in a big session where the conversation was already about 400,000 words long, it only cost 15 cents to continue the conversation warm with a cache — almost 12 dollars if it's cold.
Anthropic's own rule is after two failed corrections, that is when you should stop and just use the rewind feature.
If you ask it for a design without a direction, it falls back on a few default styles — which, if you think about it, is where most AI slop comes from.
The model is actually at its least intelligent point when it's compacting, so the details usually get dropped.