[Bug]: Compresses zero, creates summary.

[Trollgeir]

Bug Description

▣ ACP | Context 51.3K → 51.8K

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▣ Compression #43 → b45 -0 removed, +482 summary
→ Range: b45: m01309–m02150

The agent kept trying to compress some ranges, which didn't actually result in anything removed. It also got stuck in a loop for a while trying to compress the same range with no avail.

Some turns back I noticed that it had used some prune tools, but a direct followup compression after this worked as expected. I also occasionally revert the messages that have been compressed, so I don't know if this has side-effects.

Expected Behavior

Compressing messages should always compress -something-, and not create a summary out of nothing.

Debug Context Logs

...
2026-07-14T11:36:59.929Z INFO  index: Cached tool id: call_A7rWxCB8C3KfEWm6cQI69Iby (turn 848, 16 tokens)
2026-07-14T11:36:59.929Z INFO  index: Cached tool id: call_gPOPSZ4c57Vy4pnpd6t8jwcb (turn 848, 12 tokens)
2026-07-14T11:36:59.929Z INFO  index: Cached tool id: call_bjd6jZG8b4G6RGJ5Tvnqb112 (turn 1725, 747 tokens)
2026-07-14T11:36:59.929Z INFO  index: Cached tool id: call_a5JTjGBqVnL5baJdnl8EvPru (turn 1727, 495 tokens)
2026-07-14T11:36:59.929Z INFO  index: Synced cache - size: 2108, currentTurn: 1727
2026-07-14T11:36:59.929Z INFO  index: Major GC: deactivated aged-out blocks | agedOutCount=4 agedOutTokens=3000 maxBlockAge=15
2026-07-14T11:36:59.929Z INFO  index: Injected compress summary as tool-result recap | anchorMessageId=msg_f5d128d4f0023RuF1565PEvl7Z blockId=44 summaryLength=1649
2026-07-14T11:36:59.931Z INFO  index: Saved session state to disk | sessionId=ses_0a48a6899ffes31b2esPcmrQbY totalTokensSaved=2027214
2026-07-14T11:36:59.931Z INFO  index: Saved session state to disk | sessionId=ses_0a48a6899ffes31b2esPcmrQbY totalTokensSaved=2027214
2026-07-14T11:37:03.836Z DEBUG index: Recorded compression start | messageID=msg_f606a7e7a002lCyRRqHU1WiHCF callID=call_Ryv6YCyA6sVWLaPBBP56oCwX startedAt=1784029023835
2026-07-14T11:37:28.286Z WARN  index: compress summary omitted placeholders for required blocks: b44. They will be auto-attached as consumed blocks.
2026-07-14T11:37:28.335Z INFO  index: Saved session state to disk | sessionId=ses_0a48a6899ffes31b2esPcmrQbY totalTokensSaved=2027214
2026-07-14T11:37:28.351Z INFO  index: Saved session state to disk | sessionId=ses_0a48a6899ffes31b2esPcmrQbY totalTokensSaved=2027214
2026-07-14T11:37:28.351Z INFO  index: Attached compression time to blocks | messageID=msg_f606a7e7a002lCyRRqHU1WiHCF callID=call_Ryv6YCyA6sVWLaPBBP56oCwX blocks=1 durationMs=8024
2026-07-14T11:37:28.900Z INFO  index: Synced compress block state | missingOriginCount=0 deactivatedCount=0 reactivatedCount=4
2026-07-14T11:37:28.900Z INFO  index: Syncing tool parameters from OpenCode messages
2026-07-14T11:37:28.900Z INFO  index: Cached tool id: call_YdXTnBeHbFDhIIgqaKRczY80 (turn 1, 333 tokens)
2026-07-14T11:37:28.900Z INFO  index: Cached tool id: call_WAHiEzAv8h9GKpuqRl5plh29 (turn 2, 92 tokens)
2026-07-14T11:37:28.900Z INFO  index: Cached tool id: call_uAYv22MVEcNNtZpbsLZXur9q (turn 2, 64 tokens)
2026-07-14T11:37:28.900Z INFO  index: Cached tool id: call_zIO7G3x43JmfnOu5864byCoc (turn 2, 2889 tokens)
...

Tool Call Details

No response

DCP Version

3.1.9

Opencode Version

1.17.20

Model

Other (specify in description)

Additional Context

Using ChatGPT-5.6 Terra