Bug Description

When a user changes skills.disabled in config.yaml while the gateway is running, disabled skills continue to appear in the system prompt's <available_skills> index until the gateway is restarted.

Root Cause

The in-process LRU cache in build_skills_system_prompt() (agent/prompt_builder.py) is keyed on:

• skills_dir
• external_dirs
• available_tools
• available_toolsets
• platform_hint

The disabled skills set is NOT part of the cache key. The disabled set is loaded after the cache check, so a cache hit returns the stale prompt without ever checking the current disabled list.

Impact

• Users pay unnecessary tokens per turn for disabled skill descriptions
• Config changes to skills.disabled silently have no effect until restart
• On a typical setup (92 skills, 17 disabled), this wastes ~1,700 tokens per turn

Steps to Reproduce

1. Start gateway with default config
2. Add a skill to skills.disabled in config.yaml
3. Send a message — disabled skill still appears in the agent's available_skills

Fix

Move get_disabled_skill_names() before the cache check and include the sorted disabled tuple in the cache key. This way any config change automatically invalidates the cache.

PR: fix/skills-cache-includes-disabled