Module: TurnKit::Compaction

Defined in:
lib/turnkit/compaction.rb

Constant Summary collapse

DEFAULTS = 
{
  "enabled" => true,
  "threshold" => 0.75,
  "context_limit" => 128_000,
  "reserved_tokens" => 20_000,
  "head_messages" => 0,
  "tail_messages" => 12,
  "tail_tokens" => 8_000,
  "summary_ratio" => 0.20,
  "min_summary_tokens" => 1_000,
  "max_summary_tokens" => 12_000,
  "tool_output_max_chars" => 2_000,
  "model" => nil,
  "client" => nil
}.freeze
KNOWN_KEYS = 
DEFAULTS.keys.freeze
COMPACTION_SYSTEM_PROMPT = 
<<~TEXT.strip
  You are an anchored context summarization assistant for TurnKit conversations.

  Summarize only the conversation history you are given. Recent turns may be kept verbatim outside your summary, so focus on older context that still matters for continuing the work.

  If a previous summary is provided, update it by preserving still-true details, removing stale details, and merging in new facts.

  Produce only the requested Markdown summary. Do not answer the conversation itself. Do not mention that you are summarizing, compacting, or merging context.

  Write in the same language the user was using.

  Never include API keys, tokens, passwords, secrets, credentials, or connection strings. Replace secret values with [REDACTED].
TEXT
SUMMARY_TEMPLATE = 
<<~TEXT.strip
  Use this exact structure:

  ## Active Task
  - [latest unfulfilled user request, preferably verbatim]

  ## Goal
  - [what the user is trying to accomplish overall]

  ## Constraints & Preferences
  - [user/developer preferences, specs, constraints, important choices]

  ## Completed Actions
  - [completed work and outcomes]

  ## Active State
  - [current state, records/files touched, test status, running tool/turn state]

  ## In Progress
  - [work underway, or "(none)"]

  ## Blocked
  - [blockers, exact errors, missing information, or "(none)"]

  ## Key Decisions
  - [important decisions and why]

  ## Resolved Questions
  - [questions already answered]

  ## Pending User Asks
  - [unanswered or unfulfilled asks]

  ## Relevant Files
  - [file/path/resource and why it matters, or "(none)"]

  ## Tool Results To Remember
  - [important tool output summaries, or "(none)"]

  ## Remaining Work
  - [likely next work, framed as context, not instructions]

  ## Critical Context
  - [specific values, IDs, commands, errors, constraints; redact secrets]

  Rules:
  - Keep every section.
  - Use terse bullets.
  - Preserve exact file paths, commands, error strings, IDs, and important values.
  - Do not invent facts.
  - Do not include secrets.
  - Do not include a greeting or preamble.
TEXT

Class Method Summary collapse

Class Method Details

.active_summaries(messages) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 306

def active_summaries(messages)
  summaries = Array(messages).select(&:context_summary?).sort_by { |summary| summary.sequence.to_i }
  active = []

  summaries.reverse_each do |summary|
    next if active.any? { |newer| (range_for(newer)&.cover?(summary.sequence.to_i)) }

    active << summary
  end

  active.reverse
end

.append_summary(conversation, turn:, summary:, selected:, policy:, focus:, auto:, input_tokens:) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 382

def append_summary(conversation, turn:, summary:, selected:, policy:, focus:, auto:, input_tokens:)
  model = policy["model"] || turn&.model || conversation.model || conversation.agent.effective_model
  conversation.append_message(
    role: "assistant",
    kind: "context_summary",
    text: summary,
    turn_id: turn&.id,
    metadata: {
      "compaction" => {
        "auto" => auto,
        "focus" => focus,
        "replaces_from_sequence" => selected.fetch("replaces_from_sequence"),
        "replaces_through_sequence" => selected.fetch("replaces_through_sequence"),
        "tail_start_sequence" => selected["tail_start_sequence"],
        "summary_model" => model,
        "input_tokens" => input_tokens,
        "summary_tokens" => estimate_text_tokens(summary),
        "created_for_turn_id" => turn&.id,
        "created_at" => Clock.now.iso8601
      }.compact
    }
  )
end

.build_prompt(previous_summary:, focus:, target_tokens:) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 247

def build_prompt(previous_summary:, focus:, target_tokens:)
  parts = []
  if previous_summary && !previous_summary.empty?
    parts << <<~TEXT.strip
      Update the anchored summary below using the conversation history above.

      Preserve still-true details, remove stale details, and merge in new facts. Remove stale details that are no longer relevant or have been superseded.

      <previous-summary>
      #{previous_summary}
      </previous-summary>
    TEXT
  else
    parts << <<~TEXT.strip
      Create a structured context checkpoint for the conversation history above.

      This summary will replace older TurnKit messages in future model prompts while the original messages remain stored durably.
    TEXT
  end

  if focus && !focus.to_s.strip.empty?
    parts << <<~TEXT.strip
      Focus topic: "#{focus}"

      Preserve extra detail related to this focus topic. Summarize unrelated context more aggressively, but do not omit constraints or active blockers that affect the current task.
    TEXT
  end

  parts << "Target length: approximately #{target_tokens} tokens."
  parts << SUMMARY_TEMPLATE
  parts.join("\n\n")
end

.compact!(conversation, agent:, turn: nil, focus: nil, auto: false, overrides: {}, force: true) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 125

def compact!(conversation, agent:, turn: nil, focus: nil, auto: false, overrides: {}, force: true)
  policy = policy_for(agent, overrides)
  raise CompactionError, "compaction is disabled" unless policy["enabled"]

  messages = turn ? conversation.messages_for_turn(turn) : conversation.messages
  projected = project(messages)
  selected = select_messages(projected, policy)
  return nil if selected.nil? && auto
  raise CompactionError, "not enough messages to compact" unless selected

  selected_tokens = estimate_messages_tokens(selected.fetch("middle"))
  return nil if auto && !force && !over_threshold?(projected, policy)

  summary = generate_summary(
    agent: agent,
    policy: policy,
    messages: selected.fetch("middle"),
    previous_summary: selected["previous_summary"]&.text,
    focus: focus,
    target_tokens: summary_budget(selected_tokens, policy),
    fallback_model: turn&.model || conversation.model || agent.effective_model,
    conversation_id: conversation.id,
    turn_id: turn&.id
  )

  append_summary(conversation, turn: turn, summary: summary, selected: selected, policy: policy, focus: focus, auto: auto, input_tokens: selected_tokens)
rescue CompactionError
  raise
rescue StandardError => error
  raise CompactionError, "#{error.class}: #{error.message}"
end

.enabled_for?(agent, overrides = {}) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/turnkit/compaction.rb', line 93

def enabled_for?(agent, overrides = {})
  policy_for(agent, overrides)["enabled"]
end

.estimate_messages_tokens(messages) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 197

def estimate_messages_tokens(messages)
  Array(messages).sum { |message| estimate_text_tokens(message.text) + 8 }
end

.estimate_text_tokens(text) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 201

def estimate_text_tokens(text)
  (text.to_s.length / 4.0).ceil
end

.expand_tail_start_for_tool_pairs(messages, tail_start) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 339

def expand_tail_start_for_tool_pairs(messages, tail_start)
  index = tail_start
  while index.positive? && messages[index]&.tool_result?
    call_id = messages[index].metadata["tool_call_id"]
    call_index = (index - 1).downto(0).find do |i|
      messages[i].tool_call? && Array(messages[i].metadata["tool_calls"]).any? { |call| call["id"] == call_id || call[:id] == call_id }
    end
    break unless call_index

    index = call_index
  end
  index
end

.generate_summary(agent:, policy:, messages:, previous_summary:, focus:, target_tokens:, fallback_model:, conversation_id:, turn_id:) ⇒ Object

Raises:



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# File 'lib/turnkit/compaction.rb', line 353

def generate_summary(agent:, policy:, messages:, previous_summary:, focus:, target_tokens:, fallback_model:, conversation_id:, turn_id:)
  client = policy["client"] || agent.effective_client
  model = policy["model"] || fallback_model
  safe_messages = messages.map { |message| sanitize_message(message, policy) }
  prompt = build_prompt(previous_summary: previous_summary, focus: focus, target_tokens: target_tokens)
  result = client.chat(
    model: model,
    messages: MessageProjection.for(safe_messages) + [ { role: :user, content: prompt } ],
    tools: [],
    instructions: COMPACTION_SYSTEM_PROMPT,
    metadata: { compaction: true, conversation_id: conversation_id, turn_id: turn_id }
  )
  text = result.text.to_s.strip
  raise CompactionError, "compaction model returned an empty summary" if text.empty?

  text
end

.maybe_compact!(turn, force: nil, focus: nil) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 109

def maybe_compact!(turn, force: nil, focus: nil)
  return if turn.compact == false

  force = turn.compact == true if force.nil?
  policy = policy_for(turn.agent)
  return unless policy["enabled"]

  messages = project(turn.conversation.messages_for_turn(turn))
  return unless force || over_threshold?(messages, policy)

  compact!(turn.conversation, agent: turn.agent, turn: turn, focus: focus, auto: true, overrides: policy, force: true)
rescue StandardError => error
  TurnKit.logger&.warn("TurnKit compaction failed: #{error.class}: #{error.message}")
  nil
end

.normalize_config(value) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 280

def normalize_config(value)
  case value
  when nil, true
    nil
  when false
    false
  when Hash
    attrs = value.transform_keys(&:to_s)
    unknown = attrs.keys - KNOWN_KEYS
    raise ConfigError, "unknown compaction options: #{unknown.join(", ")}" if unknown.any?

    attrs
  else
    raise ConfigError, "compaction must be true, false, nil, or a Hash"
  end
end

.over_threshold?(messages, policy) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/turnkit/compaction.rb', line 211

def over_threshold?(messages, policy)
  usable = [ policy["context_limit"].to_i - policy["reserved_tokens"].to_i, 1 ].max
  estimate_messages_tokens(messages) >= (usable * policy["threshold"].to_f)
end

.policy_for(agent, overrides = {}) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 97

def policy_for(agent, overrides = {})
  global = normalize_config(TurnKit.compaction)
  local = normalize_config(agent.compaction)
  override = normalize_config(overrides)

  return DEFAULTS.merge("enabled" => false) if global == false
  return DEFAULTS.merge("enabled" => false) if local == false
  return DEFAULTS.merge("enabled" => false) if override == false

  DEFAULTS.merge(global || {}).merge(local || {}).merge(override || {})
end

.project(messages) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 157

def project(messages)
  rows = Array(messages).sort_by { |message| [ message.sequence.to_i, message.id ] }
  summaries = active_summaries(rows)
  ranges = summaries.filter_map { |summary| range_for(summary) }
  summaries_by_id = summaries.to_h { |summary| [ summary.id, summary ] }
  inserted = {}
  projected = []

  rows.each do |message|
    summaries.each do |summary|
      range = range_for(summary)
      next unless range
      next if inserted[summary.id]
      next unless range.begin <= message.sequence.to_i

      projected << summary
      inserted[summary.id] = true
    end

    if message.context_summary?
      projected << message if summaries_by_id[message.id] && !inserted[message.id] && !range_for(message)
      inserted[message.id] = true if summaries_by_id[message.id]
      next
    end

    next if ranges.any? { |range| range.cover?(message.sequence.to_i) }

    projected << message
  end

  summaries.each do |summary|
    next if inserted[summary.id]

    projected << summary
    inserted[summary.id] = true
  end

  projected
end

.range_for(summary) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 297

def range_for(summary)
  metadata = summary.compaction_metadata
  from = metadata["replaces_from_sequence"]
  through = metadata["replaces_through_sequence"]
  return nil unless from && through

  (from.to_i..through.to_i)
end

.sanitize_message(message, policy) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 371

def sanitize_message(message, policy)
  return message unless message.tool_result?

  max = policy["tool_output_max_chars"].to_i
  return message if max <= 0 || message.text.length <= max

  attrs = message.to_h
  text = "#{message.text[0, max]}\n\n[Tool result truncated for compaction]"
  Message.new(attrs.merge("text" => text, "content" => [ { "type" => "text", "text" => text } ]))
end

.select_messages(messages, policy) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 216

def select_messages(messages, policy)
  rows = Array(messages)
  return nil if rows.length <= policy["head_messages"].to_i + 1

  previous_summary = rows.reverse.find(&:context_summary?)
  candidates = rows.reject(&:context_summary?)
  return nil if candidates.length <= policy["head_messages"].to_i + 1

  head_count = policy["head_messages"].to_i
  tail_start = tail_start_index(candidates, policy)
  tail_start = [ tail_start, head_count ].max
  tail_start = expand_tail_start_for_tool_pairs(candidates, tail_start)
  middle = candidates[head_count...tail_start]
  return nil if middle.nil? || middle.empty?

  from_sequence = middle.first.sequence.to_i
  through_sequence = middle.last.sequence.to_i
  if previous_summary
    from_sequence = [ from_sequence, previous_summary.sequence.to_i ].min
    through_sequence = [ through_sequence, previous_summary.sequence.to_i ].max
  end

  {
    "middle" => middle,
    "previous_summary" => previous_summary,
    "replaces_from_sequence" => from_sequence,
    "replaces_through_sequence" => through_sequence,
    "tail_start_sequence" => candidates[tail_start]&.sequence
  }
end

.summary_budget(input_tokens, policy) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 205

def summary_budget(input_tokens, policy)
  budget = (input_tokens.to_i * policy["summary_ratio"].to_f).ceil
  budget = [ budget, policy["min_summary_tokens"].to_i ].max
  [ budget, policy["max_summary_tokens"].to_i ].min
end

.tail_start_index(messages, policy) ⇒ Object 



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# File 'lib/turnkit/compaction.rb', line 319

def tail_start_index(messages, policy)
  max_messages = policy["tail_messages"].to_i
  max_tokens = policy["tail_tokens"].to_i
  count = 0
  tokens = 0
  index = messages.length

  (messages.length - 1).downto(0) do |i|
    message_tokens = estimate_text_tokens(messages[i].text) + 8
    break if count >= max_messages
    break if count.positive? && tokens + message_tokens > max_tokens

    count += 1
    tokens += message_tokens
    index = i
  end

  index
end