Describe the bug

qwen3.6-plus is missing from agent/model_metadata.py → DEFAULT_CONTEXT_LENGTHS. The model name does not match any specific entry, so it falls back to the generic qwen 131072 entry.

Actual context: 1,048,576 tokens (1M)
Effective context in Hermes: 131,072 tokens (128K)

Impact

• Compression threshold auto-lowered from 524,288 to 131,072 tokens
• Unnecessary context compression triggers in long sessions
• Degraded reasoning quality due to premature compression
• Misleading warnings about context mismatch

Reproduction

Configure qwen3.6-plus as the main model via Alibaba/DashScope provider. Start a session, Hermes warns that compression model context 131K is lower than the threshold derived from main model.

Root cause

agent/model_metadata.py has qwen: 131072 as a catch-all, but qwen3.6-plus does not match this key. All new Qwen API models without explicit entries silently inherit wrong context limit.

Proposed fix

Add explicit entry in DEFAULT_CONTEXT_LENGTHS before the generic qwen fallback:

qwen3.6-plus: 1048576,  # 1M context

Affected versions

v2026.5.16 current release