CLAUDE_CODE_MESSAGES_PROMPT_CACHE_TTL

Updated October 14, 2026 by Alex Sorokoletov

CLAUDE_CODE_MESSAGES_PROMPT_CACHE_TTL is a Claude Code environment variable: Set to 5m to force the messages prompt cache to a five-minute lifetime. It sits beside the existing CLAUDE_CODE_PROMPT_CACHE_TTL and CLAUDE_CODE_SUBAGENT_PROMPT_CACHE_TTL controls and pairs with the new 5m/1h cache-write split in telemetry. Added in v2.1.300 and still present in v2.1.300. It is not in the official reference.

Status	Present in v2.1.300
Added	Added in v2.1.300
Category	Other
Official docs	Not listed

How to set it

For one session, export it in the shell that starts Claude Code:

export CLAUDE_CODE_MESSAGES_PROMPT_CACHE_TTL=<value>
claude

To apply it to every session, add it to the env object of a settings file:

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_MESSAGES_PROMPT_CACHE_TTL": "<value>"
  }
}

Release notes that mention it

Related variables

CLAUDE_CODE_PROMPT_CACHE_TTL
CLAUDE_CODE_INCLUDE_PARTIAL_MESSAGES: Include partial/streaming messages in output.
CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT: Switches to a reduced system prompt, stripping out the non-essential guidance sections that bulk up the default prompt.
CLAUDE_CODE_SYSTEM_PROMPT_GB_FEATURE: Names a GrowthBook feature flag whose value overrides the system prompt — but only when CLAUDE_CODE_REMOTE is set.
CLAUDE_CODE_VERIFY_PROMPT: The verify flow was reworked; the standalone prompt override no longer maps to how verification runs.
CLAUDE_CODE_APPEND_PROMPT_HEAD
CLAUDE_CODE_FEDERATION_CACHE_DIR
CLAUDE_CODE_GROWTHBOOK_KICK_ON_WARM_CACHE

Frequently asked questions

What does CLAUDE_CODE_MESSAGES_PROMPT_CACHE_TTL do?

Set to 5m to force the messages prompt cache to a five-minute lifetime. It sits beside the existing CLAUDE_CODE_PROMPT_CACHE_TTL and CLAUDE_CODE_SUBAGENT_PROMPT_CACHE_TTL controls and pairs with the new 5m/1h cache-write split in telemetry.

Which Claude Code version has CLAUDE_CODE_MESSAGES_PROMPT_CACHE_TTL?

Added in v2.1.300 and still present in v2.1.300.

How do I set CLAUDE_CODE_MESSAGES_PROMPT_CACHE_TTL?

Export it before starting Claude Code (export CLAUDE_CODE_MESSAGES_PROMPT_CACHE_TTL=value), or add it to the "env" object in ~/.claude/settings.json to apply it to every session.

All variables, searchable: Claude Code environment variables.