[qduc]

What leaked

When a model has no catalogue capacity, @qduc/agent-core scheduled automatic compaction at DEFAULT_ASSUMED_CONTEXT_WINDOW × compactThreshold, where DEFAULT_ASSUMED_CONTEXT_WINDOW (128_000) was a constant owned and exported by the core. Which window to assume for an unknown model is the consumer's policy, not the harness's. (#7 raised that constant to a consumer's figure; #10 reverted it. This PR removes the core-side number instead of changing it.)

What the host now supplies

The host already sets a required Model.contextWindow on every model: catalogue capacity when known, otherwise its own fallback. The compaction planner now receives that value as a separate field, assumedContextWindow, distinct from the existing contextWindow field that carries real capacity only.

• packages/core/src/engine/recovery-compaction.ts: DirectCompactionInput gains required assumedContextWindow: number; the unknown-capacity softTrigger uses it where the constant was. Nothing else reads it. When it would be used (automatic compaction, unknown capacity), a non-positive or non-integer value throws a RangeError, like the existing contextWindow validation, so a bad host value cannot silently compact on every boundary.
• packages/core/src/engine/turn-model-compaction.ts: the only call site of compactDirectHistory passes assumedContextWindow: model.contextWindow (the resolved model). The real-capacity argument is unchanged (deps.compaction.contextWindow ?? model.catalogContextWindow).
• packages/core/src/model/index.ts: constant and its export removed; Model.contextWindow documented as a host-supplied window that only schedules maintenance when capacity is unknown.
• packages/core/README.md (public-interface doc): new section on capacity versus the host's assumption, plus the migration note.

Unchanged: known catalogue capacities, explicit maxRequestInputTokens ceilings, raw compactThresholdTokens, manual compaction (ignores the assumption), and admission (enforceDirectInputLimit still only sees real capacity or the explicit ceiling, so the assumption is never a hard limit).

Breaking change

DEFAULT_ASSUMED_CONTEXT_WINDOW is no longer exported. The package is a prerelease and its one consumer is Term2, so this is a deliberate breaking removal. Consumers that imported it must define their own fallback and set it as Model.contextWindow for uncatalogued models. package.json version is unchanged; packages/wire is untouched.

Verification

Ran on Node 24.22.1 / pnpm 11.7.0 at the head commit: pnpm install --frozen-lockfile, pnpm build, pnpm typecheck, pnpm test (8/8), node scripts/agent-package-smoke.mjs, and pnpm smoke:checkout after committing. All passed.

A temporary probe (not committed) called compactDirectHistory from the built dist of this branch and of origin/main, ratio 0.8, local mode. "Needed" means the planner went past the trigger into an attempt (the probe history has nothing to summarise, so it ends blocked:no_complete_cold_turn); "not needed" is not_needed.

Case	This branch	origin/main
unknown capacity, host window 500,000, measured 399,999 / 400,000	not needed / needed	needed / needed (core 128k governed)
unknown capacity, host window 128,000, measured 102,399 / 102,400	not needed / needed	same
unknown, host 128k, compactThresholdTokens 50,000: 49,999 / 50,000	not needed / needed	same
unknown, host 128k, maxRequestInputTokens 60,000: 44,999 / 45,000	not needed / needed	same
catalogue 200,000 (host window 500k or 128k): 159,999 / 160,000	not needed / needed	same

End to end through startTurn, a model with no catalogue capacity and host window 128,000 received a request of roughly a million estimated tokens: the turn completed and the model saw the large request on both builds (admitted, not rejected). Control: with maxRequestInputTokens 200,000 the same turn failed before dispatch on both builds.

Not verified

• Term2 against this change. It still imports the removed export and needs a follow-up after this is published.
• The probe exercises the planner and a fake-model turn, not a real provider.
• Native-compaction mode was not probed separately; the trigger code path is shared.

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Generated by Claude Code