Compaction request exceeds context window on high-output models (v2)

Description

A V2 session using a custom OpenAI-compatible model reached about 236k of its 299,964-token context window (79%). Automatic compaction did not run, and /compact failed because the provider reported that the prompt plus requested output exceeded the context limit.

The model advertises a 131,072-token output limit. SessionCompaction.required() caps its reserved output budget at 32,000, but the compaction LLM.request() does not set generation.maxTokens. OpenAI-compatible lowering therefore leaves max_tokens unset, allowing the provider to use 131,072 instead.

Expected: the compaction request should use the same bounded output budget used to calculate the automatic-compaction threshold.

Before /compact, the model also returned finish=stop with no text or tool calls several times, leaving the TUI with no visible response. This may be a separate empty-response issue.

Plugins

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OpenCode version

0.0.0-next-17403

Steps to reproduce

1. Configure a custom OpenAI-compatible model with context limit 299964 and output limit 131072.
2. Grow a V2 session to approximately 236k tokens, displayed as 79% context usage.
3. Observe that automatic compaction does not run.
4. Run /compact.
5. Observe that the provider rejects the request because the prompt plus requested output exceeds the context window.

Screenshot and/or share link

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Operating System

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Terminal

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