[Brian Krabach (bkrabach)]

Dense recent history can leave a request over budget even after the last compaction level, because historical machine reminders still receive percentage-based recency protection. A synthetic retained request fails at 17,123 estimated tokens against a 10,000-token budget on the previous source.

After the normal ladder, add one budget-fit pass that relaxes only the recent-message fraction. The existing protection logic continues to preserve current required injections, first/latest human prompts, loaded-tool metadata, and protected tool-result groups. Requests already within budget do not take this pass. Required content that cannot fit still fails, with failed-retention state rolled back and canonical history unchanged.

Validation in owned DTU dtu-unified-public-readiness-20261008, using synthetic state and no credentials:

• New regression: 1 failed / 3 passed before the change; all 4 pass after it.
• Complete context-module suite: 231 passed, 1 existing expected failure.
• Tests cover dense historical reminders, byte-preserved requirements, tool-pair integrity, loaded-tool state, stable subsequent views, and rollback on an oversized required floor.

This addresses a reproduced defect discovered while investigating a spark-1 local context failure. The production event reported 854,567 estimated tokens after compaction against an 853,104 effective budget; its saved diagnostics do not provide an exact retained-content breakdown. This PR is not a claim of end-to-end recovery of that conversation. Live state has not been edited or retried; integrated runtime qualification is complete as described below; actual-session recovery remains separate.

Integrated qualification in the same owned DTU:

• 29 request-retention, measured-compaction, and real OpenAI-provider/context/streaming-loop tests passed with no skips.
• Joint dense-history regression: old context source fails before dispatch; candidate passes and sends exactly one request. Required content and the canonical history prefix remain intact.
• Impossible required-content case remains blocked with zero transport calls. Both joint tests pass on the candidate.
• Streaming source dd916499344671e0209d4951bc025777e3e891fd; OpenAI provider main 89ad2ee72e3e1d5ffdd30eb940d8608a68c99b26; Core 2.0.1, OpenAI SDK 3.28.0. In-memory transport only, no provider credentials or network generation.