Opencode pattern (session/overflow.ts): fire compaction at 85% of
ctx_max, replacing the v1.11.0-era `ctx_max - 20_000` formula.
Old formula: usable = ctx_max - 20_000
- ctx=262144 → trigger at 242144 (92.4%) — only 7.6% headroom
- ctx=100000 → trigger at 80000 (80.0%)
- ctx= 32000 → trigger at 12000 (37.5%) — over-eager
- ctx<=20000 → trigger at 0 — never fires
New formula: usable = floor(0.85 * ctx_max)
- ctx=262144 → trigger at 222822 (85.0%) — 15% headroom for summarizer
- ctx=100000 → trigger at 85000 (85.0%)
- ctx= 32000 → trigger at 27200 (85.0%)
- ctx= 8192 → trigger at 6963 (85.0%)
Ratio gives consistent headroom at any context scale. The qwen3.6
daily driver gets ~19k tokens more breathing room before overflow;
small-ctx models no longer degenerate to never-triggering.
usable() is the only consumer of COMPACTION_BUFFER → constant deleted.
New EARLY_TRIGGER_RATIO constant takes its place.
isOverflow() and the maybeFlagForCompaction() call site at
payload.ts:184 are unchanged — formula swap is internal to compaction.ts.
payload.ts comment touched only to drop the stale COMPACTION_BUFFER
reference (PRUNE_TRIGGER_TOKENS stays at 20k as the prune-freed
threshold; independent of the overflow formula).
Tests: 4 new usable() corner cases (262k/100k/8k/zero+negative), plus
5 isOverflow() numbers shifted to match the 85k budget at ctx=100k.
195/195 server tests pass (was 194).
Smoke: ratio math verified by unit tests at all four corners. Live
cap-hit verification deferred — requires accumulating >222k tokens
in a session under qwen3.6-35b-a3b-mxfp4 (was >242k pre-fix); will
surface organically in extended use.
Audit traced compaction's summary path post-v1.13.1-B read flip:
- Q1: reads from messages_with_parts (view) — clean
- Q2: parts shape correctly threaded through buildHeadPayload — clean
- Q3: reasoning omitted from summary input — FIX NEEDED
v1.13.1-C wired reasoning end-to-end into inference/payload.ts but
missed this read site. Summarizer model couldn't see the reasoning
trail for tool-bearing turns, quietly degrading summary quality for
reasoning-channel models (qwen3.6).
Fix:
- CompactionMessage extended with reasoning_parts field
- SELECT pulls reasoning_parts from messages_with_parts
- buildHeadPayload (now exported for tests) prefixes assistant content
with <reasoning>...</reasoning>\n\n<content>... when reasoning is
present; standalone <reasoning>...</reasoning> for tool-call-only
turns; omits the tag when reasoning is null or empty
4 new render branch tests (190 total).
Smoke deferred: forcing real compaction requires either threshold
pollution or building up a >40k-token chat with reasoning_parts.
Render branches are unit-covered; integration would only re-prove
structural correctness.
