Prompt caching does not seem to be working

[dasupradyumna]

Issue

I have cache-prompts flag enabled in my settings.
For some reason, when I launch aider, it does not show this in the message and token cost output.

Configuration

##################################### AIDER CHAT CONFIGURATION #####################################

# Git settings
dirty-commits: false
watch-files: true
attribute-author: false
attribute-committer: false
attribute-co-authored-by: false

# Editor settings
vim: true
editor: nvim
input-history-file: /dev/null # Do not save input history
restore-chat-history: true

# Model settings
model: sonnet
editor-model: sonnet
weak-model: haiku
alias:
  - haiku:anthropic/claude-haiku-4-5
  - sonnet:anthropic/claude-sonnet-4-5
  - opus:anthropic/claude-opus-4-1
edit-format: diff
editor-edit-format: diff

# Cache prompt for better cost savings and lower latency
cache-prompts: true
cache-keepalive-pings: 3 # 5mins x 3 = 15 mins total

# Output settings
# BUG: this flag makes aider ignore color settings (#3163)
# dark-mode: true
stream: false # To display token usage

# Color settings
user-input-color: '#7ac098'
tool-output-color: '#9ac6e0'
tool-warning-color: '#ff9d57'
tool-error-color: '#fa4d56'
assistant-output-color: '#adb5bd'
completion-menu-color: '#878d96'
completion-menu-bg-color: '#212121'
completion-menu-current-color: '#c1c7cd'
completion-menu-current-bg-color: '#434343'
code-theme: lightbulb

Version and model info

Current behavior

Expected behavior

--- from aider documentation

[dasupradyumna]

Please let me know if I'm doing using some configuration wrong, or if this is indeed a bug.