Module compaction 

Compaction: summarize older context so a long session fits the model.

Port of packages/coding-agent/src/core/compaction/compaction.ts and compaction/utils.ts in pi v1.0.0. The functions here are pure apart from the summary request. The agent session decides when to compact and records the result.

Structs

CompactionSettings

When and how much to compact.

ContextEstimate

Estimated context size: the last valid usage plus estimates for what follows.

FileOperations

Files read and changed by tool calls, for the summary.

Preparation

What compaction will summarize and keep, serialized as pi’s CompactionPreparation.

RetryPolicy

Retry policy for summary requests, from settings.retry.

Summarizer

What summary requests need besides the messages.

Summary

A summary and the usage of the requests that made it.

Enums

BranchSummary

What summarizing a branch produced.

SummaryRetry

pi-ai’s RetryCallbacks: what a summarizer reports while it retries.

Constants

SUMMARIZATION_SYSTEM_PROMPT

System prompt of summary requests.

Functions

calculate_context_tokens

Tokens a response’s usage says the context held.

collect_branch_entries

Entries from old_leaf back to the deepest common ancestor with target, oldest first, and that ancestor.

estimate_context_tokens

Estimates context tokens from the last valid usage and the messages after it.

estimate_projected_context_tokens

Estimates projected context without trusting usage recorded before a later context edit or compaction.

estimate_tokens

Estimated tokens of one message: characters / 4, rounded up, where an image counts as 4800 characters.

format_file_operations

The file lists as tags appended to a summary.

prepare_branch_entries

Messages of the abandoned branch, newest first until token_budget (0 for none), and the files touched across all of it.

prepare_compaction

Plans a compaction of a branch, or None when there is nothing to summarize.

serialize_conversation

The conversation as plain text, so the summarizer does not continue it. Takes messages already converted for the model.

should_compact

Whether the context leaves less than the reserve free.