Claude Code v2.1.239｜Bedrock で API 課金が 2 倍になっていた｜毎日Changelog解説Claude Code v2.1.239 fixes a bug where streaming requests blocked by a Bedrock…

Anthropic has shipped Claude Code v2.1.239, a maintenance release whose most consequential change is a fix for a billing bug that affected users running the tool through Amazon Bedrock. According to the official changelog, the update resolves a scenario in which streaming requests blocked by a Bedrock proxy were silently retried as non-streaming calls, causing billable API usage to double on every turn. For teams that route Claude Code traffic through Bedrock, the fix is worth applying promptly, because the underlying defect had a direct and easily overlooked cost impact.

The problem stemmed from how Claude Code handled a failed streaming connection. Claude Code, Anthropic's command-line agent for software development tasks, normally requests model output as a stream, receiving tokens incrementally as they are generated. In some Bedrock deployments a proxy sitting between the client and the service would block that streaming connection. Rather than surfacing the failure, the client appears to have fallen back to a non-streaming request for the same turn. The result was that a single interaction generated two billable API calls instead of one, and because this happened on each turn, the extra charges accumulated across a session without any obvious signal to the user.

The reason this matters specifically for Bedrock users comes down to how the platform is billed and deployed. Amazon Bedrock is AWS's managed service for foundation models, and it offers Anthropic's Claude family among its available models. Organizations often choose Bedrock so that model traffic stays inside their AWS account and existing governance boundaries, and enterprise networks frequently enforce outbound traffic through proxies for security and monitoring. Those same proxies can interfere with long-lived streaming connections, which typically rely on server-sent events or similar mechanisms that some proxy configurations do not pass through cleanly. That combination is exactly the condition under which this bug would trigger, so it was likely most visible in corporate or regulated environments rather than in simple direct-to-API setups.

Doubling billable usage is a meaningful issue because token-based pricing scales with every request. When each turn quietly produced a redundant non-streaming call, the affected accounts would have paid roughly twice the expected amount for those interactions. The behavior was also easy to miss: the tool continued to work, output still appeared, and the only symptom was a higher-than-anticipated bill. Cost anomalies of this kind can be difficult to trace back to a specific client behavior, which is part of why a changelog entry calling it out explicitly is useful for anyone reconciling recent Bedrock spend.

For context, Claude Code has been iterating rapidly, and the granular version number here reflects a fast release cadence in which small fixes and refinements ship frequently. That pace is common for developer tooling, but it also means users benefit from watching the changelog, since fixes like this one can carry real financial or operational significance even when a release is otherwise routine. The Qiita source that surfaced this item is one of several community efforts that translate and annotate Anthropic's official changelog shortly after publication, which helps non-English-speaking developers keep up with changes that might otherwise be buried in terse release notes.

It is also worth noting that Bedrock is not the only way to run Claude Code against a managed backend. Anthropic supports its own direct API, and Claude models are additionally available through Google Cloud's Vertex AI, giving teams a choice of hosting and billing arrangements depending on their existing cloud commitments. The proxy-related failure described here is tied to the Bedrock path, so users on other backends are unlikely to have been affected in the same way, though the general lesson about how streaming fallbacks can inflate usage applies broadly.

Practically, users on Bedrock should update to v2.1.239 or later to ensure that a blocked stream no longer triggers a duplicate non-streaming request. Teams that suspect they were affected may want to review their recent Bedrock invoices for unexplained increases that align with periods of heavy Claude Code activity. As always with a single changelog entry, the precise internal mechanics are described only briefly, so the summary above reflects the behavior as reported rather than a full technical postmortem.