[BUG] ENABLE_PROMPT_CACHING_1H is not working (API key user)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The ENABLE_PROMPT_CACHING_1H environment variable (which opts into 1-hour prompt cache TTL) has no effect. Cache entries are always created with 5-minute TTL regardless of the setting.

By intercepting the raw HTTP traffic between Claude Code and the Anthropic API, I confirmed that:

• The client correctly sends cache_control: {"type":"ephemeral","ttl":"1h","scope":"global"} on system blocks and cache_control: {"type":"ephemeral","ttl":"1h"} on message blocks
• The anthropic-beta header includes prompt-caching-scope-2026-01-05
• The server responds with ephemeral_5m_input_tokens: 7025, ephemeral_1h_input_tokens: 0 — all cache creation goes into the 5-minute bucket, none into the 1-hour bucket

This is reproducible on both an enterprise/organization API key and a personal API key.

What Should Happen?

When ENABLE_PROMPT_CACHING_1H=1 is set, cache entries should be created with a 1-hour TTL. The server response should show ephemeral_1h_input_tokens > 0 and ephemeral_5m_input_tokens: 0 for the cache creation.

Error Messages/Logs

**Request (client → server):**

POST https://api.anthropic.com/v1/messages?beta=true
anthropic-beta: claude-code-20250219,context-1m-2025-08-07,interleaved-thinking-2025-05-14,context-management-2025-06-27,prompt-caching-scope-2026-01-05,advisor-tool-2026-03-01,advanced-tool-use-2025-11-20,effort-2025-11-24,afk-mode-2026-01-31

System block cache_control: {"type":"ephemeral","ttl":"1h","scope":"global"}
Message block cache_control: {"type":"ephemeral","ttl":"1h"}


**Response (server → client):**

{
  "input_tokens": 3,
  "cache_creation_input_tokens": 7025,
  "cache_read_input_tokens": 12112,
  "cache_creation": {
    "ephemeral_5m_input_tokens": 7025,
    "ephemeral_1h_input_tokens": 0
  }
}

The server creates cache entries (7025 tokens) but places them all in the 5-minute bucket despite the client requesting 1-hour TTL.

Steps to Reproduce

1. Set ENABLE_PROMPT_CACHING_1H=1 (either as environment variable or in settings.json under env)
2. Start Claude Code
3. Send a message
4. Observe usage stats — ephemeral_1h_input_tokens is always 0

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.110 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

_No response_