Greptile Summary

This PR fixes an unrecoverable context overflow bug in screenshot-heavy sessions by allowing older image tool results to be pruned, instead of unconditionally protecting all of them. The change is surgical: a pre-pass collects the indexes of all image tool results, then protects only the 3 most recent; the main pruning loop skips only those protected entries — older image results fall through into prunableToolIndexes and become eligible for hard-clearing.

The logic is consistent and correct:

• Both the pre-pass and the main loop apply the same isToolPrunable guard, so non-prunable image results are untouched.
• softTrimToolResultMessage still returns null for all image-containing messages (soft-trimming a binary image is not meaningful), so unprotected image results bypass the soft-trim step but are still cleared in the hard-clear phase — which is the right outcome.
• totalChars accounting and prunableToolChars thresholds are unaffected by the change.

One finding: The module-level comment on lines 8–9 ("We currently skip pruning tool results that contain images") is now stale and should be updated to reflect the new partial-protection behaviour where only the most recent image results are shielded from pruning.

Confidence Score: 4/5

• Safe to merge — the fix correctly handles the overflow case with no observable regressions to recent-image protection, pending the minor documentation update.
• The logic change is small and well-scoped. The pre-pass and main loop share the same boundary conditions and guards, so the protected set is built from exactly the same population of messages that the main loop visits. The core fix is sound. The only finding is a stale module-level comment on lines 8–9, which is a minor documentation issue and not a correctness concern.
• src/agents/pi-extensions/context-pruning/pruner.ts — update the module-level comment on lines 8–9 to reflect the new partial-protection behaviour for image results.

_{Last reviewed commit: 0a1ebf1}