Struct AutoCompactConfig 

pub struct AutoCompactConfig {
    pub token_threshold: usize,
    pub tool_output_max_chars: usize,
    pub keep_last: usize,
    pub compact_strategy: CompactStrategy,
    pub hard_limit_tokens: Option<usize>,
    pub hard_limit_strategy: CompactStrategy,
    pub custom_compactor: Option<VmValue>,
    pub mask_callback: Option<VmValue>,
    pub compress_callback: Option<VmValue>,
}

Configuration for automatic transcript compaction in agent loops.

Two-tier compaction: Tier 1 (token_threshold / compact_strategy): lightweight, deterministic observation masking that fires early. Masks verbose tool results while preserving assistant prose and error output. Tier 2 (hard_limit_tokens / hard_limit_strategy): aggressive LLM-powered summarization that fires when tier-1 alone isn’t enough, typically as the transcript approaches the model’s actual context window.

Fields

token_threshold: usize

Tier-1 threshold: estimated tokens before lightweight compaction.

tool_output_max_chars: usize

Maximum character length for a single tool result before microcompaction.

keep_last: usize

Number of recent messages to keep during compaction.

compact_strategy: CompactStrategy

Tier-1 strategy (default: ObservationMask).

hard_limit_tokens: Option<usize>

Tier-2 threshold: fires when tier-1 result still exceeds this. Typically set to ~75% of the model’s actual context window. When None, tier-2 is disabled.

hard_limit_strategy: CompactStrategy

Tier-2 strategy (default: Llm).

custom_compactor: Option<VmValue>

Optional Harn callback used when a strategy is custom.

mask_callback: Option<VmValue>

Optional callback for domain-specific per-message masking during observation mask compaction. Called with a list of archived messages, returns a list of Option<String> — Some(masked) to override the default mask for that message, None to use the default. This lets the host (e.g. burin-code) inject AST outlines, file summaries, etc. without putting language-specific logic in Harn.

compress_callback: Option<VmValue>

Optional callback for per-tool-result compression. Called with {tool_name, output, max_chars} and returns compressed output string. When set, used INSTEAD of the built-in microcompact_tool_output. This allows the pipeline to use LLM-based compression rather than keyword heuristics.

Trait Implementations

impl Clone for AutoCompactConfig

fn clone(&self) -> AutoCompactConfig

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for AutoCompactConfig

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for AutoCompactConfig

fn default() -> Self

Returns the “default value” for a type.