Cursor users report agents switching to costly Claude Opus, Sonnet, Fable, or API calls

• Cursor users reported selected Grok 4.5, Auto, or Fable settings while sub-runs hit API usage or other models; the Grok/API usage report cites Opus and Sonnet high calls, and the 22.6M-token Opus report says an implementation sub-instance ran Opus 4.8.
• Cursor’s billing split explains part of the blast radius: first-party usage covers Auto, Composer 2.5, and Grok 4.5, while specific models draw from an API pool, the distinction behind mario61752's dashboard confusion post.
• Subagents are the clearest sharp edge: the Composer subagent post matches a Cursor forum explanation that the Explore Subagent Model setting only applies to Explore, while regular Task subagents can be model-picked by the parent agent.
• Fable adds a separate routing path because Cursor’s Fable docs say guardrail trips route to Opus automatically, matching the Opus switch screenshot and haider1's Fable post.
• The burn can get huge fast: dzhng's loop logged 50,645,608 tokens over roughly 2 days and 20 hours, while doodlestein's FrankenSim thread shows five parallel Explore agents spending six-figure token counts each.

Cursor’s models and pricing docs split Cursor into a first-party pool and an API pool; its Fable 5 docs add that guardrailed Fable requests route to Opus automatically. In Cursor’s forum thread, the subagent bug report became a UI semantics story: “Explore Subagent Model” does not mean “all subagents.” The screenshots were not subtle: a 22.6M-token Opus burn, a €200 alleged Fable charge, and a 50M-token goal loop.

According to Cursor’s models and pricing docs, individual plans have two monthly pools:

• First-party models: Auto, Composer 2.5, and Grok 4.5.
• API: provider-priced model usage, with at least $20 included each month on individual plans.

Cursor’s usage limits docs list Pro at $20 of API agent usage, Pro Plus at $70, and Ultra at $400, each with a separate first-party models pool.

That split matches the confusion in the Grok/API usage report, where a user selected Grok max but saw API usage falling and calls from Opus and Sonnet high. In mario61752's dashboard post, a $20 Pro user asked whether the account would stop at $20 total spend or at 100% first-party/API usage.

The model table puts the expensive paths in plain numbers:

• Claude Fable 5: $10 per 1M input tokens, $50 per 1M output tokens.
• Claude Opus 4.8: $5 input, $25 output.
• Claude Sonnet 5: $3 input, $15 output list price, with a launch promo through August 31.
• Max Mode: billed at the model’s API rate on current individual plans.

Subagent model choice was the cleanest reproducible mechanism in the reports. The 22.6M-token Opus report says the user set “Cursor Grok 4.5 High,” switched into Agent mode, and later found a separate implementation task running Opus 4.8.

In the Cursor forum, Congzhi said the Composer 2.5 setting applied only to the Explore subagent. Dean Rie added that regular Task subagents are picked by the parent agent, with no separate UI setting to hard-lock their model and no warning before a premium model starts.

That lines up with the Reddit subagent complaint, where a user could no longer find a way to stop Cursor from choosing Composer 2.5 Fast for subagents. A separate pvncher reply said usage goes up with subagents, which are “much easier to trigger now.”

Cursor’s Fable 5 docs say Fable runs with tight security guardrails and routes guardrailed requests to Claude Opus automatically so work continues without an error.

The Opus switch screenshot shows that behavior on a biology prompt: “Fable’s safeguards flagged this message,” followed by a switch to Opus 4.8 High. The dialog says the safeguards are intentionally broad and may flag safe coding, cybersecurity, or biology work.

Fable also has its own limit dynamics. HamelHusain's limit screenshot showed the current session at 100% while weekly “All models” sat at 26% and “Fable” at 41%, and HamelHusain said Fable can saturate the current session limit and block other subscription models.

haider1's Fable post said practical work was better on GPT-5.6 Sol because Fable had “randomly switched to Opus 4.8” several times. One separate chetaslua EAP post claimed a brief “claude honeycomb EAP” sighting in Cursor and said a jailbreak test fell back to Opus 4.8.

The reports moved from routing confusion to payment anxiety.

• The €200 Fable charge report said a German user saw a 200€ charge for alleged Fable 5 usage despite a 20€ subscription and said there was no warning.
• The hard-stop report said a Pro user previously continued after included usage ran out, but the July cycle showed “Total usage limit reached” after cloud agents on Auto did “max” work.
• The free-plan stop report said a college free Pro user could not enter prompts for two days and believed tokens were exhausted.
• The Ultra charge report said a user was charged $226 for Ultra after canceling Pro, with the dashboard showing an upgraded account.

Cursor’s usage docs say that when limits are reached, the editor shows a notification and users can enable usage-based pricing or upgrade. The same docs say on-demand usage is billed monthly at the same API rates.

Reports also went the other direction. YuriYurchenko's Grok switch report said Cursor 3.11.19 switched to Grok 4.5 even after Fable 5 was specified and explicitly prohibited.

Status signals were fragmented. On X, davidgomes's revert reply said “This has been reverted” and that a window reload might be needed, while deredleritt3r's reply described “stealth-rerouting to Opus” as “now fixed” and criticized the earlier decision.

The multi-model version of this problem has a more technical name: handoff.

zeeg's handoff reply said swapping models with a 200K-token session feeds those tokens into a new, more expensive model and also hurts caching. His Junior screenshot shows a handoff event moving from grok-4.5 to gpt-5.6-sol; he said Junior summarizes, “basically compaction,” before swapping models.

Cost accounting was already part of zeeg's post. In a reply, zeeg said most Sentry usage pays per token, while his own setup makes it hard to swap between subscription and per-token modes zeeg's per-token reply.

Fully agentic runs make the token drain visible. dzhng's loop logged 50,645,608 tokens over roughly 2 days and 20 hours.

doodlestein's FrankenSim thread shows the other pattern: parallel investigation. One screenshot lists five Explore agents at 111.6k, 140.3k, 73.8k, 166.6k, and 151.2k tokens, followed by fresh-eyes reviews, red-team passes, and a final 2,969-line plan with 48 external references checked.

Some users were deliberately routing work by task. One Cursor Reddit workflow used Opus for the first hour of system understanding and Minimax M3 for routine implementation, while a Grok 4.5 benchmark post said Grok matched Claude Opus in a small internal agentic marketing benchmark at lower cost.