Enum SessionEvent 

pub enum SessionEvent {
    User(UserEvent),
    Assistant(AssistantEvent),
    Progress(ProgressEvent),
    System(SystemEvent),
    FileSnapshot(FileHistorySnapshot),
    QueueOperation(QueueOperation),
    Summary(SessionSummary),
    Attachment(RootAttachmentEvent),
    CustomTitle(CustomTitleEvent),
    AiTitle(AiTitleEvent),
    LastPrompt(LastPromptEvent),
    BridgeSession(BridgeSessionEvent),
    AtisLatch(AtisLatchEvent),
    Mode(ModeEvent),
    PermissionMode(PermissionModeEvent),
    AgentName(AgentNameEvent),
    FileHistoryDelta(FileHistoryDeltaEvent),
    Unknown,
}

Top-level session event discriminator

All events in a Claude Code session JSONL file parse into one of these variants. Uses serde’s tagged enum feature to automatically select variant based on type field.

Frequency Distribution (per large session)

1. Progress: ~82,200 (51%)
2. Assistant: ~49,426 (31%)
3. User: ~29,913 (19%)
4. FileSnapshot: ~65 (<0.1%)
5. QueueOperation: ~58 (<0.1%)
6. System: ~6 (<0.1%)
7. Summary: ~1 (<0.1%)

Links and Relationships

Events form a conversation graph via:

• uuid: Unique identifier for this event
• parent_uuid: Links to previous message in conversation chain
• tool_use_id: Links progress to tool invocation
• source_tool_assistant_uuid: Links tool result back to assistant

Variants

User(UserEvent)

User message event

Represents messages from:

• Human users (userType = “external”)
• Tool results (has tool_use_result field)

Links

• parent_uuid → previous message
• source_tool_assistant_uuid → assistant that invoked tool
• Contains .message.content[] with text/tool_result types

Frequency

~29,913 events per large session (~19%)

Assistant(AssistantEvent)

Assistant message event

Represents responses from Claude, including:

• Text responses
• Tool use invocations
• Token usage statistics

Links

• parent_uuid → user message being responded to
• Contains .message.content[] with text/tool_use types
• Tool uses link to user tool results via id

Frequency

~49,426 events per large session (~31%)

Progress(ProgressEvent)

Progress event

Real-time updates during tool execution. Contains full conversation context in .data.normalizedMessages[].

Links

• tool_use_id → tool invocation that triggered this
• parent_uuid → parent message
• Contains full conversation history (HUGE!)

Frequency

~82,200 events per large session (~51% - MOST FREQUENT!)

System(SystemEvent)

System event

System-level events:

• Compact boundaries (conversation compaction)
• API errors
• System reminders

Links

• logical_parent_uuid → last message before compaction

Frequency

~6 events per large session (rare but important!)

FileSnapshot(FileHistorySnapshot)

File history snapshot

Tracks file state at message boundaries for undo/redo.

Links

• message_id → message where snapshot was taken

Frequency

~65 events per large session

QueueOperation(QueueOperation)

Queue operation event

Tracks session queue management (enqueue/dequeue).

Frequency

~58 events per large session

Summary(SessionSummary)

Session summary

Summary of entire session (typically at end).

Frequency

~1 event per session

Attachment(RootAttachmentEvent)

Root-level attachment event

A hook result, todo reminder, or similar side-channel notice — the same payload shape as the nested attachment field found inside progress normalizedMessages, but emitted directly at the root. The dominant root event type on real transcripts (v2.1.2xx): dwarfs every other type combined in raw line count, though it carries no conversational text relevant to a restore digest.

CustomTitle(CustomTitleEvent)

Custom session title

The session title Claude Code’s own UI shows, set by the user or the model. Repeats verbatim through the file as it is re-affirmed; the last occurrence is authoritative. This is the provider’s own title/topic — prefer it over any inferred label.

AiTitle(AiTitleEvent)

Model-generated session title

A model-authored title, distinct from custom-title (which reflects an explicit/user-affirmed title). Used as the topic fallback when no custom-title is present.

LastPrompt(LastPromptEvent)

Latest verbatim user prompt

Tracks the most recent human prompt text as the session progresses; updates repeatedly. Falls back to this for the topic when neither title event is present.

BridgeSession(BridgeSessionEvent)

Bridge session correlation (cloud sync identity) — not conversational content, tracked only so it does not fall into the generic unknown bucket.

AtisLatch(AtisLatchEvent)

ATIS latch state — harness-internal signal, not conversational content.

Mode(ModeEvent)

Conversation mode marker (e.g. “normal”) — harness-internal signal.

PermissionMode(PermissionModeEvent)

Permission-mode marker (e.g. “auto”) — harness-internal signal.

AgentName(AgentNameEvent)

Agent/session display-name marker — harness-internal signal.

FileHistoryDelta(FileHistoryDeltaEvent)

Incremental file-history delta (undo/redo tracking), the incremental counterpart to file-history-snapshot.

Unknown

Unknown event type (forward compatibility)

Anything not matched above lands here. This is normal on a continuously-evolving transcript format and must never be treated as a parse failure — the whole point of tolerant parsing is that one unrecognized root type never drops the rest of the line’s siblings.

Implementations

impl SessionEvent

pub fn metadata(&self) -> Option<EventMetadata>

Extract common metadata present in most events

pub fn uuid(&self) -> Option<&str>

Get UUID of this event

pub fn parent_uuid(&self) -> Option<&str>

Get parent UUID for conversation graph traversal

pub fn timestamp(&self) -> DateTime<Utc>

Get event timestamp

Several harness-internal marker events (custom-title, ai-title, last-prompt, bridge-session, atis-latch, mode, permission-mode, agent-name) carry no timestamp field on disk; these fall back to the current time, matching the existing Unknown fallback, since ordering by them is never meaningful.

pub fn extract_text_content(&self) -> Option<String>

Extract all text content from this event (for FTS indexing)

pub fn extract_file_paths(&self) -> Vec<String>

Extract file paths mentioned in this event

pub fn extract_tool_names(&self) -> Vec<String>

Extract tool names used in this event

impl SessionEvent

pub fn extract_tags(&self) -> Vec<String>

Extract tags for indexing (legacy method)

Tags enable fast filtering of events without parsing full content.

pub fn is_context_relevant(&self) -> bool

Check if this event is important for context extraction

Trait Implementations

impl Clone for SessionEvent

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SessionEvent

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for SessionEvent

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for SessionEvent

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

Formats the value using the given formatter.

impl Serialize for SessionEvent

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.