tui: /compact fails with "Compaction produced no summary" (deepseek flash)

Summary

Running /compact in the TUI consistently fails: the compaction step is marked as failed (red x Compaction) and reports "Compaction produced no summary". No session summary is produced, so context compaction does not work.

Environment

• opencode version: 1.18.16 (opencode --version)
• OS: macOS Darwin arm64
• Terminal: TERM=xterm-256color
• Shell: /bin/zsh
• Install/channel: release (1.18.16)
• Active plugins: none found (no opencode.json/opencode.jsonc in cwd or ~/.config/opencode/)

Reproduction

1. Open a session in the TUI (active model: deepseek flash).
2. Run /compact.
3. Observe the red x Compaction entry and the message Compaction produced no summary.

Expected Behavior

Compaction runs and produces a summary of the session that is applied, so the context is compacted and the conversation can continue normally.

Actual Behavior

Consistent failure: no summary is produced. The compaction step is marked as failed (red x Compaction) with the message Compaction produced no summary.

Additional Context

• Consistently reproducible, not intermittent.
• Active model: deepseek flash. Hypothesis: compaction uses the active model, and deepseek flash returns empty/unsupported content for the summary step (or the summary request fails). Worth checking whether compaction succeeds with other models, and surfacing the underlying model response/error instead of the generic "produced no summary" message.
• No workarounds found.