Summary Validation

Summary validation has a typed input/output boundary before the replacement can be committed. Identity checks happen before content checks, and all rejection reasons are bounded.

Input and output types

// package loop
type CompactionInput struct {
	Basis              event.ContextBasis
	Model              model.ModelKey
	RequestFingerprint [32]byte
	Transcript         content.AgenticMessages
	MaxSummaryTokens   content.TokenCount
}

type CompactionOutput struct {
	Basis              event.ContextBasis
	Model              model.ModelKey
	RequestFingerprint [32]byte
	Summary            *content.UserMessage
}

func (CompactionInput) Validate() error
func (CompactionOutput) Validate() error

Input requires a nonzero basis revision and ThroughEventID, valid model key, nonzero fingerprint, nonempty supported transcript, and positive summary token budget. Output must match identity fields and contain exactly one nonempty user text block.

Proof: compaction input/output contracts and contract tests.

Transcript validation

Supported messages are User, AI, System, and ToolResult with matching roles. Supported leaf blocks are Text, Image, Audio, Document, Thinking, and ToolUse; ToolResult content may nest to a maximum depth of 128. Typed nil messages or blocks, unsupported block types, malformed JSON, and an empty transcript are rejected before adapter serialization.

Proof: transcript validator and fuzz/contract tests.

Summary XML grammar

The internal parser accepts exactly one unnamespaced root <conversation_summary> with no attributes, comments, directives, processing instructions, CDATA, or extra text. Its child order is exactly:

<conversation_summary>
  <goal>...</goal>
  <constraints>...</constraints>
  <decisions>...</decisions>
  <state>...</state>
  <open_items>...</open_items>
</conversation_summary>

goal and state must contain nonblank text. The parser preserves the raw escaped XML in one content.TextBlock; it does not turn XML sections into separate conversation blocks.

Proof: strict summary parser and parser tests.

Typed invalid-summary reasons

loop.InvalidSummaryError.Reason is one of InvalidSummaryWire, InvalidSummaryIdentity, InvalidSummaryOutputShape, InvalidSummaryByteLimit, InvalidSummaryTokenUsage, InvalidSummaryTokenLimit, InvalidSummaryXMLSyntax, InvalidSummaryXMLRoot, InvalidSummaryXMLStructure, or InvalidSummaryXMLContent. A post-replacement complete-request count that exceeds its limit is *loop.SummaryTooLargeError.

Proof: invalid summary errors and adapter validation tests.

Source and proof

• Compaction domain types
• XML parser
• Validation proof