Bound automatic compaction input to model capacity #1160
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,6 +1,6 @@ | ||
| //! Durable explicit context-compaction command and call lifecycle. | ||
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| use std::{collections::BTreeMap, error::Error, fmt, num::NonZeroU64}; | ||
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| use rust_decimal::Decimal; | ||
| use signalbox_application::{ClassifyOperatorFailure, OperatorFailureClass}; | ||
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@@ -34,6 +34,8 @@ pub struct PrepareContextCompactionRequest { | |
| pub requested_through_position: Option<u64>, | ||
| /// Queued turn whose context guard owns this automatic attempt. | ||
| pub automatic_for_turn: Option<TurnId>, | ||
| /// Model-derived content-byte target for an automatic summary prefix. | ||
| pub automatic_content_byte_target: Option<NonZeroU64>, | ||
| /// Current defaults epoch observed before entering the transaction. | ||
| pub defaults_version: SessionConfigurationDefaultsVersion, | ||
| /// Current direct model selection after freezing any alias. | ||
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@@ -777,6 +779,11 @@ async fn prepare_in_transaction( | |
| transaction: &mut sqlx::Transaction<'_, sqlx::Postgres>, | ||
| request: &PrepareContextCompactionRequest, | ||
| ) -> Result<(bool, PrepareContextCompactionOutcome), ContextCompactionRepositoryError> { | ||
| if request.automatic_for_turn.is_some() != request.automatic_content_byte_target.is_some() | ||
| || request.automatic_for_turn.is_some() && request.requested_through_position.is_some() | ||
| { | ||
| return Ok((false, PrepareContextCompactionOutcome::InvalidBoundary)); | ||
| } | ||
| match lookup_command_on_connection( | ||
| transaction, | ||
| request.command, | ||
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@@ -1010,8 +1017,10 @@ async fn prepare_in_transaction( | |
| Some(position) => visible | ||
| .iter() | ||
| .position(|member| member.position == position), | ||
| None => match request.automatic_content_byte_target { | ||
| Some(target) => bounded_safe_boundary(&visible, target.get()), | ||
| None => latest_safe_boundary(&visible), | ||
| }, | ||
| }; | ||
| let Some(through_index) = through_index else { | ||
| return Ok((false, PrepareContextCompactionOutcome::InvalidBoundary)); | ||
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@@ -1395,11 +1404,14 @@ fn latest_safe_boundary(members: &[ProjectedFrontierMember]) -> Option<usize> { | |
| latest | ||
| } | ||
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| fn bounded_safe_boundary( | ||
| members: &[ProjectedFrontierMember], | ||
| content_byte_target: u64, | ||
| ) -> Option<usize> { | ||
| let total_weight = members.iter().fold(0_u64, |total, member| { | ||
| total.saturating_add(member.content_bytes.max(1)) | ||
| }); | ||
| let target_weight = total_weight.div_ceil(2).min(content_byte_target); | ||
|
There was a problem hiding this comment.
When a session history is sufficiently larger than twice the model's input capacity, capping the summarized prefix at AGENTS.md reference: AGENTS.md:L252-L257 Useful? React with 👍 / 👎. |
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| let mut through_weight = 0_u64; | ||
| let mut open_requests = 0_usize; | ||
| for (index, member) in members.iter().enumerate() { | ||
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@@ -1411,7 +1423,7 @@ fn bounded_safe_boundary(members: &[ProjectedFrontierMember]) -> Option<usize> { | |
| } | ||
| _ => {} | ||
| } | ||
| if through_weight >= target_weight && open_requests == 0 { | ||
| return Some(index); | ||
| } | ||
| } | ||
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@@ -1662,7 +1674,7 @@ mod tests { | |
| ordinary(4, entry(0x7024)), | ||
| ]; | ||
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| assert_eq!(bounded_safe_boundary(&visible, u64::MAX), Some(1)); | ||
| } | ||
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| #[test] | ||
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@@ -1700,7 +1712,7 @@ mod tests { | |
| ordinary(6, entry(0x7036)), | ||
| ]; | ||
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| assert_eq!(bounded_safe_boundary(&visible, u64::MAX), Some(3)); | ||
| } | ||
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| #[test] | ||
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@@ -1712,6 +1724,44 @@ mod tests { | |
| weighted_ordinary(4, entry(0x7044), 100), | ||
| ]; | ||
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| assert_eq!(bounded_safe_boundary(&visible, u64::MAX), Some(2)); | ||
| } | ||
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| #[test] | ||
| fn automatic_boundary_stops_at_the_model_derived_content_budget() { | ||
| let visible = vec![ | ||
| weighted_ordinary(1, entry(0x7051), 100), | ||
| weighted_ordinary(2, entry(0x7052), 100), | ||
| weighted_ordinary(3, entry(0x7053), 100), | ||
| weighted_ordinary(4, entry(0x7054), 100), | ||
| weighted_ordinary(5, entry(0x7055), 100), | ||
| weighted_ordinary(6, entry(0x7056), 100), | ||
| ]; | ||
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| assert_eq!(bounded_safe_boundary(&visible, 200), Some(1)); | ||
| } | ||
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| #[test] | ||
| fn automatic_boundary_closes_a_tool_exchange_crossing_the_model_budget() { | ||
| let visible = vec![ | ||
| weighted_ordinary(1, entry(0x7061), 100), | ||
| ProjectedFrontierMember { | ||
| position: 2, | ||
| reference: entry(0x7062), | ||
| payload_kind: "assistant_tool_use".to_owned(), | ||
| content_bytes: 100, | ||
| summary_range: None, | ||
| }, | ||
| ProjectedFrontierMember { | ||
| position: 3, | ||
| reference: entry(0x7063), | ||
| payload_kind: "tool_execution_result".to_owned(), | ||
| content_bytes: 100, | ||
| summary_range: None, | ||
| }, | ||
| weighted_ordinary(4, entry(0x7064), 100), | ||
| ]; | ||
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| assert_eq!(bounded_safe_boundary(&visible, 150), Some(2)); | ||
| } | ||
| } | ||
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When a frontier contains many small entries—or content requiring JSON escaping—this target does not actually bound the model input:
bounded_safe_boundarycounts only stored payload bytes, whileload_context_compaction_rangeserializes every selected entry with IDs, type metadata, field names, delimiters, and escaping, and the request also adds the nonempty compaction system prompt. The selected prefix can therefore render far beyondcontext_window_tokens - max_output_tokens, causing the provider to reject the sole automatic compaction attempt and leaving the oversized queued turn unrecoverable. Compute the boundary from the rendered/token-counted request or reserve all serialization and prompt overhead.AGENTS.md reference: AGENTS.md:L116-L120
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