Runs on models without a registered tokenizer (e.g. 9router brand models)
ended with the generic "Agent couldn't generate a response" fallback even
though the real request used about 55% of the context window.
PruneStage counted history with TokenCounter, which falls back to a
chars/2 heuristic for unregistered models and overcounted about 1.8x.
Once over budget it ran memory flush (~35s, invisible in traces), then
mid-loop compaction, which cannot summarize a history made only of tool
call/result pairs. The callback reported the untouched history as
compacted, PruneStage still saw it over budget and returned AbortRun
before any LLM call, and FinalizeStage replaced the empty reply with the
fallback.
- PruneStage and ContextStage overhead count with the request guard's
BudgetCounter. PruneStage no longer controls loop flow; the final
request guard in ThinkStage decides.
- CompactMessages returns ErrNotCompacted when history is unchanged.
Callers stop counting it as a compaction and do not retry it in the
same run, while post-run summarization still sees the pressure.
- When the guard exhausts every reduction step, ThinkStage stops the run
with a localized chat.context_budget_exceeded notice instead of an
error, so the run's tool results are still persisted. The stop reason
marks the trace and agent span as error; team tasks, cron and
heartbeat treat it as a failure via RunOutcome.Failure().
- Memory flush and mid-loop compaction emit event spans.
- Web and desktop UIs treat an unset context_pruning as enabled (the
backend default since 7639a8c0), keep it unset when untouched, and can
re-enable pruning after it was turned off.
The v3 pipeline compacts session history mid-loop (prune_stage +
final-request guard) but only mutates the run's message buffer, never the
session store. Each turn reloads full history and re-compacts from scratch:
message_tokens climb 129k->156k across turns while every turn compacts back
down to ~60k. The lossy compaction differs per run, degrading the agent.
The same missing persistence stalls episodic memory: the cumulative
compaction count never advances, so the episodic worker's idempotency key
(sessionKey:count) is pinned and every cycle after the first is skipped.
Observed on live traffic: 8 run.completed since deploy, 0 new episodic.
Fixes, all reusing existing machinery (no new store methods, no migrations):
- Bug A: emitSessionCompleted reads cumulative GetCompactionCount (matching
the legacy v2 path) instead of the per-run counter that resets to 0.
- Bug B/anti-loop: finalize passes state.Prune.MidLoopCompacted into
maybeSummarize; under pressure it lowers the trigger to a unit-aligned
threshold (compactionInputCap - overhead, same MaxRequestShare the guard
uses) so the compaction is PERSISTED via the existing TruncateHistory +
IncrementCompaction path. Defensive floor prevents over-compaction on
pathological config; tool-result-only bloat still skips (history-only).
- Bug C: SourceID embeds the count (sessionKey:count) so the eventbus dedup
key advances per compaction cycle instead of swallowing rapid same-session
turns within the 5m TTL.
Tests: episodic compaction, maybe_summarize pressure, request budget.
go build (PG + sqliteonly), go vet, go test -race all green.
thotam