a fresh automatic compaction id cannot be pre-canceled

Error message

a fresh automatic compaction id cannot be pre-canceled

What it means

When auto-compaction starts, a freshly generated compaction id is expected to never appear in the pre-canceled set, so the code asserts that a cancel-check on it is false. Firing would mean id generation collided or cancellation state leaked across turns — an internal logic bug.

Source

Thrown at crates/tui/src/core/engine/turn_loop.rs:724

                billed_input_tokens,
            ) {
                Some(self.prepare_compaction_envelope(auto_compaction_config))
            } else {
                None
            };

            if let Some(prepared) = prepared
                && crate::compaction::should_compact_with_billed(
                    &self.session.messages,
                    self.session.system_prompt.as_ref(),
                    &prepared,
                    billed_input_tokens,
                )
            {
                let compaction_id = format!("compact_{}", &uuid::Uuid::new_v4().to_string()[..8]);
                let compaction_cancel = self
                    .claim_compaction(&compaction_id)
                    .expect("a fresh automatic compaction id cannot be pre-canceled");
                self.emit_compaction_started(
                    compaction_id.clone(),
                    true,
                    "Auto context compaction started".to_string(),
                )
                .await;
                let auto_messages_before = self.session.messages.len();
                let auto_tokens_before = self.estimated_input_tokens();
                let turn_cancel = self.cancel_token.clone();
                let (compaction_result, turn_was_canceled) = tokio::select! {
                    biased;
                    _ = turn_cancel.cancelled() => (None, true),
                    _ = compaction_cancel.cancelled() => (None, false),
                    result = compact_messages_safe(
                        client.as_ref(),
                        &self.session.messages,
                        self.session.system_prompt.as_ref(),
                        &prepared,

View on GitHub (pinned to 0c42157ee5)

Solutions

Verify canceled-compaction ids are cleared per turn
Check for uuid collisions or reuse of a stale compaction id

Defensive patterns

Strategy: type-guard

When it happens

Trigger: Thrown at crates/tui/src/core/engine/turn_loop.rs:724 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Hmbown/CodeWhale@0c42157ee5 (2026-08-20). Data as JSON: /api/errors/a98f8274a67cf531. Report an issue: GitHub.