sequenceDiagram
    participant Test as Test Suite
    participant Capture as capture.ts
    participant DomTree as domTree module
    participant A11yTree as a11yTree module
    participant Page as Page Mock
    participant Session as CDP Session
    
    Note over Test,Session: buildFrameContext Test
    Test->>Page: asProtocolFrameTree()
    Page-->>Test: frameTree structure
    Test->>Capture: buildFrameContext(page)
    Capture->>Page: mainFrameId(), listAllFrameIds()
    Capture-->>Test: FrameContext with parentByFrame map
    
    Note over Test,Session: buildSessionIndexes Test
    Test->>Capture: buildSessionIndexes(page, frames, pierce)
    loop for each unique session
        Capture->>Page: getSessionForFrame(frameId)
        Page-->>Capture: session
        Capture->>DomTree: buildSessionDomIndex(session, pierce)
        DomTree-->>Capture: SessionDomIndex
    end
    Capture-->>Test: Map<sessionId, SessionDomIndex>
    
    Note over Test,Session: collectPerFrameMaps Test
    Test->>Capture: collectPerFrameMaps(page, context, sessionToIndex, options, pierce)
    loop for each frame
        Capture->>Page: getSessionForFrame(frameId)
        Capture->>Session: send("DOM.getFrameOwner", {frameId})
        Session-->>Capture: {backendNodeId}
        Capture->>A11yTree: a11yForFrame(session, frameId, options)
        A11yTree-->>Capture: {outline, urlMap}
    end
    Capture-->>Test: {perFrameMaps, perFrameOutlines}
    
    Note over Test,Session: captureHybridSnapshot Test (scoped)
    Test->>Capture: captureHybridSnapshot(page, {focusSelector})
    Capture->>DomTree: domMapsForSession(session, frameId, pierce)
    DomTree-->>Capture: {tagNameMap, xpathMap, scrollableMap}
    Capture->>A11yTree: a11yForFrame(session, frameId, options)
    A11yTree-->>Capture: {outline, urlMap, scopeApplied: true}
    Capture-->>Test: HybridSnapshot (early return)
    
    Note over Test,Session: captureHybridSnapshot Test (full)
    Test->>Capture: captureHybridSnapshot(page)
    Capture->>Capture: buildFrameContext(page)
    Capture->>Capture: buildSessionIndexes(page, frames, pierce)
    Capture->>Capture: collectPerFrameMaps(...)
    Capture->>Capture: mergeFramesIntoSnapshot(...)
    Capture-->>Test: Complete HybridSnapshot with all frames