SpliceKit: Instructions file for Codex

SpliceKit - Programmatic Final Cut Pro Control

SpliceKit is an ObjC dylib injected into FCP's process. It exposes all 78,000+ ObjC classes via a JSON-RPC server on TCP 127.0.0.1:9876. Everything is fully programmatic -- no AppleScript, no UI automation, no menu clicks.

NEVER Use Keyboard Simulation or AppleScript

All FCP actions MUST go through direct ObjC calls. Never use any of these:

• SpliceKit_simulateKeyPress() or synthetic NSEvent key events
• CGEvent keyboard/mouse posting
• osascript / NSAppleScript / AppleScript tell application
• Accessibility APIs (AXUIElement) for clicking or typing
• Frame-stepping loops (nextFrame x N) when seekToTime exists

Instead, always use one of these patterns (in priority order):

1. Direct method call on the timeline/sequence/clip object via objc_msgSend
2. Responder chain via [NSApp sendAction:NSSelectorFromString(@"selector:") to:nil from:nil]
3. Batch bridge endpoint (e.g. timeline.addMarkers) for operations on multiple items
4. Menu execute via menu.execute for actions only accessible through menus

If an action doesn't have a direct ObjC selector yet, find one using explore_class / search_methods on the relevant class (FFAnchoredTimelineModule, FFAnchoredSequence, etc.) rather than simulating the keyboard shortcut.

Quick Start

1. bridge_status()                    -- verify connection
2. get_timeline_clips()               -- see timeline contents
3. timeline_action("blade")           -- edit
4. verify_action("after blade")       -- confirm

CRITICAL: Must Know Before Editing

Opening a Project

If get_timeline_clips() returns an error about "no sequence", load a project:

# Navigate: library -> sequences -> find one with content -> load it
libs = call_method_with_args("FFLibraryDocument", "copyActiveLibraries", "[]", true, true)
libs_handle = json.loads(libs)["handle"]
lib = call_method_with_args(libs_handle, "objectAtIndex:", '[{"type":"int","value":0}]', false, true)
lib_handle = json.loads(lib)["handle"]
seqs = call_method_with_args(lib_handle, "_deepLoadedSequences", "[]", false, true)
seqs_handle = json.loads(seqs)["handle"]
allSeqs = call_method_with_args(seqs_handle, "allObjects", "[]", false, true)
# For each sequence result, extract its "handle" before calling hasContainedItems
# Example: seq_handle = json.loads(seq)["handle"]
# Check each: call_method_with_args(seq_handle, "hasContainedItems", "[]", false)
# Load: get NSApp -> delegate -> activeEditorContainer -> loadEditorForSequence: