What does this PR do?

When the user explicitly sets model.context_length in config.yaml, the minimum 64K context check is now bypassed. Previously the check rejected models below 64K even when the user had already configured the override that the error message itself recommended.

Why: Users of smaller models (e.g. Qwen3-235B-A22B with 32K context) were blocked from using Hermes Agent even after following the error message's instructions to set model.context_length in config.

How:

• Extracted validate_minimum_context() function from AIAgent.__init__ so the validation logic is testable
• Added config_context_length is None guard so explicit overrides bypass the check
• 5 regression tests covering: reject without override, accept with override, boundary conditions, zero context

Related Issue

Closes #8430

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• Extracted validate_minimum_context() function from AIAgent.__init__ so the validation logic is testable
• Added config_context_length is None guard so explicit overrides bypass the check
• tests/run_agent/test_minimum_context_length.py — 5 regression tests (reject without override, accept with override, boundary conditions, zero context)

How to Test

1. pytest tests/run_agent/test_minimum_context_length.py -v — 5 tests pass
2. pytest tests/run_agent/test_switch_model_context.py -v — related tests pass (no regression)

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS 15 (Darwin 24.6.0)

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

Screenshots / Logs

$ pytest tests/run_agent/test_minimum_context_length.py -v
5 tests pass