Claude Code returns blank thinking blocks, but reasoning still costs you
Anthropic's Claude Code appears to be having trouble displaying summaries of its "thinking," according to several bug reports, while the underlying reasoning tokens still cost money.
According to complaints, the API has been returning empty thinking blocks for Opus 4.8 and Sonnet 5 even when users explicitly request summarized thinking.
Models from several sources can display their "thinking," a process that gives models additional tokens to reason through complex problems before producing a response.
Software with this capability delivers a summary that explains how it tackled a task.
Some can also indulge in "extended thinking," though this capability is now deprecated.
Developers often enable "thinking" in the hope that it produces better results, at the cost of additional tokens and latency.
Developer Michael Hood has noticed that some of Anthropic's models are currently not always good at sharing their thinking.
"As of 2026-07-16 ~15:00Z, the API returns empty thinking blocks (thinking: '', signature only) for Claude Opus 4.8 and Sonnet 5, even when display: 'summarized' is explicitly requested — including when injected directly into the raw request body," Hood recently observed.
We're told this issue is under investigation but doesn't appear to be a broad, ongoing concern.
It may simply be an artefact of tests that change how Anthripic displays summaries.
Similar behavior involving missing thinking blocks has been reported in Claude Code for VS Code.
Another bug report claims thinking block summaries are being truncated while token bills are not adjusted accordingly.
"The thinking is generated (and billed) in full; a portion of the summary stream is silently dropped," the anonymous author claims.
This particular claim, that customers are being billed for text not delivered, may follow from a misunderstanding of Anthropic's terms: "You are charged for all thinking tokens generated, even when collapsed or redacted," the company's documentation explains.
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