FCPXML MCP

Scenario	How FCPXML MCP Helps
QC before delivery	Detect flash frames, gaps, duplicate clips, and generate a health score automatically.
Chapter creation	Convert a transcript or SRT file into perfectly timed YouTube chapter markers.
Rough‑cut assembly	Build a 60‑second rough cut from clips tagged `Interview` with pacing presets, then push directly to FCP.
Bulk metadata extraction	Export an EDL or CSV of all clips with timecodes for downstream tools or asset management.
Automated montage	Generate a beat‑synced montage using audio analysis, then export to Resolve.
Template‑driven projects	Apply pre‑built intro/outro or lower‑third templates across multiple timelines.

The bridge between Final Cut Pro and AI. 7 grouped tools (62 underlying operations) that turn timeline XML into structured data Claude can read, edit, and generate.

Hardened for real libraries: 134 adversarial-input security tests, defusedxml everywhere, sandboxed writes, no patched binaries, no private APIs — plus a private disclosure channel with externally reported fixes already credited and merged.

FCPXML MCP demo — transcript-based editing

Real v0.13.0 output: local Whisper transcription, filler-word removal, and phrase-based cutting on a podcast timeline.

Why This Exists

After directing 350+ music videos (Chief Keef, Migos, Masicka), I noticed the same editing bottlenecks on every project: counting cuts manually, extracting chapter markers one by one, hunting flash frames by scrubbing, building rough cuts clip by clip.

These are batch operations that don't need visual feedback. Export the XML, let Claude handle the tedium, import the result. That's the entire philosophy.

See It In Action

You:    "Run a health check on my wedding edit"

Claude: ✓ Analyzed WeddingFinal.fcpxml
        ├─ 247 clips · 42:18 total · 24fps · 1920×1080
        ├─ 3 flash frames detected (clips 44, 112, 198)
        ├─ 2 unintentional gaps at 12:04 and 31:47
        ├─ 14 duplicate source clips
        └─ Health score: 72/100

You:    "Fix the flash frames and gaps, then add chapter markers from
         this transcript"

Claude: ✓ Extended adjacent clips to cover 3 flash frames
        ✓ Filled 2 gaps by extending previous clips
        ✓ Added 18 chapter markers from transcript
        → Saved: WeddingFinal_modified.fcpxml

Import the modified XML back into Final Cut Pro. Every change is non-destructive — your original file is never touched.

What Claude Actually Sees

This is the magic trick. When you export XML from Final Cut Pro, your timeline becomes structured data that Claude can reason about:

<!-- What FCP exports -->
<asset-clip ref="r2" offset="342/24s" name="Interview_A"
            start="120s" duration="720/24s" format="r1">
    <marker start="48/24s" duration="1/24s" value="Key quote"/>
    <keyword start="0s" duration="720/24s" value="Interview"/>
</asset-clip>

# What Claude works with (after parsing)
Clip(
    name="Interview_A",
    offset=TimeValue(342, 24),   # timeline position: 14.25s
    start=TimeValue(120, 1),     # source in-point: 2:00
    duration=TimeValue(720, 24), # 30 seconds
    markers=[Marker(value="Key quote", start=TimeValue(48, 24))],
    keywords=["Interview"]
)

Every time value stays as a rational fraction — 720/24s, not 30.0 — so trim, split, and speed operations have zero rounding error across any frame rate. Comparisons use cross-multiplication (a/b < c/d → a*d < c*b) to stay in integer-land end to end. Denominators are always normalized to positive values at construction, so sign lives on the numerator and cross-multiplication is always correct. Addition and subtraction share a single _binop() code path that handles same-denominator fast paths and LCM alignment in one place.

How It Works

  ┌──────────┐      ┌──────────────────────────────┐      ┌──────────┐
  │ Final Cut│      │  parser.py   → Python objects │      │ Final Cut│
  │   Pro    │─XML─>│  writer.py   → Modify & save  │─XML─>│   Pro    │
  │          │      │  rough_cut.py→ Generate new   │      │          │
  └──────────┘      │  diff.py     → Compare        │      └──────────┘
                    │  export.py   → Resolve / FCP7 │
                    └──────────────────────────────┘
                              ▲
                     Claude Desktop / MCP client

Export from FCP — File → Export XML...
Ask Claude — analyze, edit, generate, QC, export
Import back — File → Import → XML

What This Is NOT

Not a plugin — it doesn't run inside Final Cut Pro
Not for creative calls — color, framing, motion still need your eyes

New in v0.9 — Live Mode. The server can now push an FCPXML straight into the running Final Cut Pro with zero clicks, using Apple's official Open Document event — no XML re-import step. See Live Mode below.

Live Mode (macOS)

XML mode is offline and portable; Live mode drives a running Final Cut Pro through Apple's sanctioned surfaces — no patched binary, no private APIs, no accessibility scripting. Two tools, both verified end-to-end against FCP 12.2:

Tool	What it does
`push_to_fcp`	Sends an FCPXML file into FCP with zero clicks (Open Document Apple event). Injects `<import-options>` (library location, copy/link assets, suppress warnings), launches FCP if needed, and never mutates your original — flat files get an options-injected copy.
`list_fcp_libraries`	Enumerates FCP's open libraries → events → projects via the read-only AppleScript dictionary.

You:    "Build a rough cut from my Interview clips and push it into Final Cut"

Claude: ✓ Generated RoughCut.fcpxml (8 clips, 0:54)
        ✓ Pushed into Final Cut Pro → library "ProjectX", event 2026-06-11
        → Open Final Cut Pro to keep editing

The asymmetry you must know: Apple makes import scriptable but offers no programmatic export — to pull your current timeline back out for further AI work, you still run File > Export XML yourself. Live mode pushes; round-trips come back through the XML tools.

Notes (all live-verified): pass a library_location ending in .fcpbundle for a true zero-click import (a new path is auto-created); omitting it makes FCP show a modal library picker that blocks until you answer. First use triggers a one-time macOS Automation permission prompt for your terminal/MCP host. The capability audit maps the full surface and the optional SpliceKit/CommandPost bridges planned for v1.0.

Quick Start

Claude Code (fastest)

claude mcp add fcpxml -e FCP_PROJECTS_DIR=~/Movies -- uvx fcp-mcp-server

Or project-scoped — commit a .mcp.json so your whole team gets it:

{
  "mcpServers": {
    "fcpxml": {
      "command": "uvx",
      "args": ["fcp-mcp-server"],
      "env": { "FCP_PROJECTS_DIR": "/Users/you/Movies" }
    }
  }
}

With media intelligence (beat detection) and transcript editing (local Whisper):

claude mcp add fcpxml -e FCP_PROJECTS_DIR=~/Movies -- uvx --from "fcp-mcp-server[intelligence,transcribe]" fcp-mcp-server

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "fcpxml": {
      "command": "uvx",
      "args": ["fcp-mcp-server"],
      "env": { "FCP_PROJECTS_DIR": "/Users/you/Movies" }
    }
  }
}

From source (contributors)

git clone https://github.com/DareDev256/fcp-mcp-server.git
cd fcp-mcp-server
pip install -e .
# then point your MCP client at: python /path/to/fcp-mcp-server/server.py

Use It

Export XML from Final Cut Pro (File → Export XML…), open your MCP client, and ask it to work with your timeline.

When To Use This

Good For	Not Ideal For
Batch marker insertion (100 chapters from a transcript)	Creative editing decisions (no visual feedback)
QC before delivery (flash frames, gaps, duplicates)	Real-time adjustments (export/import cycle)
Data extraction (EDL, CSV, chapter markers)	Fine-tuning cuts (faster directly in FCP)
Template generation (rough cuts from tagged clips)	Anything visual (color, framing, motion)
Automated assembly (montages from keywords + pacing)
Timeline health checks (validation, stats, scoring)

How It Compares

Three projects have connected AI agents to Final Cut Pro. They make different trade-offs:

	FCPXML MCP (this)	SpliceKit	CommandPost
Approach	Parses/writes FCPXML + official Apple events only	Patches FCP's binary to expose internal APIs	Accessibility scripting + Lua
Raw live control	Push-to-FCP, library inspection	Deepest (full internal API)	Deep (UI-level)
Survives FCP updates	Yes — no patching	Re-patch per FCP version	Mostly
Works on managed/corporate Macs	Yes	No (requires binary patching)	Varies (Accessibility perms)
Works without FCP installed	Yes (pure XML mode)	No	No
MCP server	Yes, active (this repo)	Yes (last release Apr 2026)	Planned, PR unmerged
Requires	Python 3.10+	Patched FCP binary	CommandPost app

SpliceKit's runtime depth is genuinely impressive — if you're on your own Mac and comfortable patching FCP, it can do things XML never will. This project stays on the no-patch side so it runs anywhere, survives every FCP update, and can be trusted with client libraries. Full ecosystem analysis: capability audit.

Prompt Cookbook

Copy-paste these into Claude Desktop. Each one maps to a real tool chain under the hood.

Analysis

"Give me a full breakdown of ProjectX.fcpxml — clips, duration, frame rate, markers, everything"
"Show me pacing analysis for my timeline — where are the slow sections?"
"Export an EDL and CSV of all clips with timecodes"

QC & Fixes

"Run a health check on my timeline and fix anything under 2 frames"
"Find all gaps and flash frames, then auto-fix them"
"Are there any duplicate source clips I can consolidate?"

Markers & Chapters

"Add chapter markers from this transcript: [paste transcript]"
"Import markers from my-subtitles.srt onto the timeline"
"List all markers and export them as YouTube chapter timestamps"

Generation

"Build a 60-second rough cut from clips tagged 'Interview' — medium pacing"
"Generate a montage from all B-roll clips with accelerating pacing"
"Create an A/B roll: Interview_A as primary, B-roll cuts every 8 seconds"

Cross-NLE & Reformat

"Export this timeline for DaVinci Resolve"
"Convert to FCP7 XML so I can open it in Premiere"
"Reformat my 16:9 timeline to 9:16 for Instagram Reels"

Under the Hood

When you say "Run a health check on my wedding edit", Claude chains these tools:

analyze_timeline  →  stats, frame rate, resolution
detect_flash_frames  →  clips under threshold duration
detect_gaps  →  unintentional silence/black
detect_duplicates  →  repeated source media
validate_timeline  →  structural health score (0-100)

Each tool returns structured text that Claude synthesizes into the summary you see. No magic — just batch XML queries that would take 20 minutes by hand.

Pre-Built Prompts

Select these from Claude's prompt menu (⌘/) — they chain multiple tools automatically.

Prompt	What It Does	Grouped calls it drives
qc-check	Full quality control — flash frames, gaps, duplicates, health score	`diagnose` → `validate_timeline`, `detect_flash_frames`, `detect_gaps`, `detect_duplicates`; then `edit` → `fix_flash_frames`, `fill_gaps`
youtube-chapters	Extract chapter markers formatted for YouTube descriptions	`inspect` → `list_markers`, `analyze_pacing`
rough-cut	Guided rough cut — shows clips, suggests structure, generates	`inspect` → `list_library_clips`, `list_keywords`; then `generate` → `auto_rough_cut`
timeline-summary	Quick overview — stats, pacing, keywords, markers, assessment	`inspect` → `analyze_timeline`, `analyze_pacing`, `list_keywords`, `list_markers`
cleanup	Find and auto-fix flash frames and gaps	`diagnose` → `validate_timeline`; then `edit` → `fix_flash_frames`, `fill_gaps`

Every call takes the grouped form — the tool name is the group, and the operation goes in action:

{ "action": "validate_timeline", "args": { "filepath": "/path/to/project.fcpxml" } }

Tools

As of v0.14.0, the MCP tool list Claude sees by default is 7 grouped verbs, not 62 flat tool names:

Group	Covers
`inspect`	Read-only understanding — stats, clips, markers, keywords, EDL/CSV, pacing
`diagnose`	Finding problems — flash frames, gaps, duplicates, health score
`edit`	Changing clips — markers, trim, reorder, transitions, speed, split, silence removal
`mark`	Markers and chapters — batch add, SRT/VTT import, beat import
`generate`	Building new structure — rough cuts, montages, A/B roll, templates
`transcript`	Local Whisper transcription and transcript-driven cuts
`deliver`	Getting the timeline out — NLE export, reformat, relink, push-to-FCP

Each call has the same shape: {"action": "trim_clip", "args": {...}}. The action is one of the 62 original tool names below; args is whatever that tool always took. The group dispatches straight into the same handler — the behavior is identical, only the schema Claude sees up front is smaller. An unknown or cross-group action returns an error listing the valid actions for that group, so a wrong guess is recoverable in one turn.

Grouping is what's advertised, not what's callable. call_tool resolves every one of the 62 flat names from a handler registry that doesn't care what list_tools chose to show — an existing MCP config that calls trim_clip directly keeps working with no changes. If you'd rather see all 62 flat tools (e.g. for debugging, or a client that doesn't like the grouped shape), set:

FCP_MCP_LEGACY_TOOLS=1

This advertises the original 62 alongside the 7 groups. They will not be removed before a 1.0 release.

See the timeline before you touch it

Reading the preview://<path> MCP resource (any FCPXML path the server can already reach) returns a self-contained HTML render of the timeline: clip blocks sized proportionally to duration, connected clips on their own lane rows above/below the primary storyline, and marker ticks — all values HTML-escaped, served as text/html. Point your MCP client's resource viewer at it, or fetch it directly, to see a cut without opening Final Cut Pro.

Claude Code skill

A final-cut-pro skill ships in skill/, wrapping this server with the workflow order (inspect → diagnose → read preview:// → edit) and the FCPXML gotchas that don't fit in a tool description. Install it alongside the MCP server:

git clone https://github.com/DareDev256/fcp-mcp-server
ln -s "$PWD/fcp-mcp-server/skill" ~/.claude/skills/final-cut-pro

All 62 Tools

The 62 tools below are the operations behind the 7 groups in Tools — every action value the groups accept, unchanged from prior releases and still callable directly with FCP_MCP_LEGACY_TOOLS=1.

Category	Tools	What It Does
Analysis	11	Stats, clips, markers, keywords, EDL/CSV, pacing
Multi-Track	3	Connected clips, compound clips, secondary lanes
Roles	4	List, assign, filter, export stems
QC & Validation	4	Flash frames, duplicates, gaps, health score
Editing	9	Markers, trim, reorder, transitions, speed, split
Batch Fixes	3	Auto-fix flash frames, rapid trim, fill gaps
Comparison	1	Diff two timelines — added/removed/moved/trimmed
Reformat	1	Aspect ratio conversion (9:16, 1:1, 4:5, custom)
Silence	2	Detect and remove silence candidates (XML heuristics)
Media Intelligence	3	Real silence detection + auto-removal (ffmpeg), musical beat detection (librosa)
NLE Export	2	DaVinci Resolve v1.9, FCP7 XMEML v5
Generation	3	Rough cuts, montages, A/B roll
Beat Sync	2	Import beat markers, snap cuts to beats
Import	2	SRT/VTT subtitles, YouTube chapters → markers
Audio	1	Add audio clips, music beds at any lane
Compound	2	Create/flatten compound clips
Templates	2	Pre-built timeline structures (intro/outro, lower thirds, music video)
Effects	1	List FCP transition effects with UUIDs
Media	1	Bulk relink moved/renamed media (rewrite `media-rep` src paths)
Transcript Intelligence	3	Local Whisper transcription, transcript-driven cuts, filler-word removal
Live (macOS)	2	Push FCPXML into the running FCP (zero-click Apple-event import); list open libraries
	62

Analysis — 11 tools

list_projects · analyze_timeline · list_clips · list_library_clips · list_markers · find_short_cuts · find_long_clips · list_keywords · export_edl · export_csv · analyze_pacing

Multi-Track — 3 tools

list_connected_clips · add_connected_clip · list_compound_clips

Roles — 4 tools

list_roles · assign_role · filter_by_role · export_role_stems

QC & Validation — 4 tools

detect_flash_frames · detect_duplicates · detect_gaps · validate_timeline

Editing — 9 tools

add_marker · batch_add_markers · insert_clip · trim_clip · reorder_clips · add_transition · change_speed · delete_clips · split_clip

Batch Fixes — 3 tools

fix_flash_frames · rapid_trim · fill_gaps

Comparison · Reformat · Silence

diff_timelines · reformat_timeline · detect_silence_candidates · remove_silence_candidates

NLE Export — 2 tools

export_resolve_xml (DaVinci Resolve FCPXML v1.9) · export_fcp7_xml (Premiere Pro / Resolve / Avid XMEML v5)

Generation — 3 tools

auto_rough_cut · generate_montage · generate_ab_roll

Beat Sync — 2 tools

import_beat_markers · snap_to_beats

Import — 2 tools

import_srt_markers · import_transcript_markers (supports SMPTE HH:MM:SS:FF with frame-accurate placement)

v0.6.0 — Audio, Compound, Templates, Effects — 6 tools

list_effects · add_audio · create_compound_clip · flatten_compound_clip · list_templates · apply_template

v0.8.0 — Media — 1 tool

relink_media (bulk-rewrite asset/media-rep src paths with dry_run preview — relink a moved drive without opening FCP)

v0.10–0.12 — Media Intelligence — 3 tools

detect_media_silence (analyzes each clip's real source audio with ffmpeg silencedetect and maps silence spans into timeline time) · remove_media_silence (cuts detected silence out of the timeline with ripple — clips split around silence, padding keeps edits breathing, non-destructive output) — both require ffmpeg, degrade gracefully without it · detect_beats (musical beat + tempo detection via librosa, writes a beats JSON that chains into import_beat_markers + snap_to_beats; needs the optional [intelligence] extra)

v0.13.0 — Transcript Intelligence — 3 tools

transcribe_media · edit_by_transcript · remove_filler_words

v0.9.0 — Live Mode (macOS + Final Cut Pro) — 2 tools

push_to_fcp (zero-click FCPXML import into the running FCP via Apple event) · list_fcp_libraries (enumerate open libraries/events/projects)

Environment Variables

Variable	Required	Default	Description
`FCP_PROJECTS_DIR`	No	`~/Movies`	Root directory for FCPXML file discovery via `list_projects`
`FCPXML_DTD_DIR`	No	FCP app bundle	Directory of Apple `FCPXMLv_.dtd` files for DTD validation (auto-detected from the installed Final Cut Pro)
`FCP_MCP_LEGACY_TOOLS`	No	unset	Set to `1` to advertise the original 62 flat tools alongside the 7 grouped tools

Compatibility

Component	Supported Versions
FCPXML format	reads v1.8 – v1.14 · writes v1.13 (modified files keep their source version)
Final Cut Pro	10.4+ through 12.x · flat `.fcpxml` and `.fcpxmld` bundles (sidecars preserved)
Python	3.10, 3.11, 3.12
MCP protocol	1.0
Export targets
→ DaVinci Resolve	FCPXML v1.9
→ Premiere Pro / Avid	FCP7 XMEML v5

Architecture

fcp-mcp-server/           ~9.4k lines Python
├── server.py              MCP entry point — 7 grouped tools advertised by default
│                          (TOOL_GROUPS), dispatching into 62 flat handlers
│                          (TOOL_HANDLERS); 5 prompts, resource discovery.
│                          FCP_MCP_LEGACY_TOOLS=1 re-advertises the 62 flat tools.
│                          _resolve_io_paths() / _setup_modifier() / _setup_generator()
│                          _format_clip_table() / _markdown_table() / _format_batch_result()
│                          _raw_markers_to_batch()
│                          _detect_flash_frames() / _detect_gaps() / _detect_duplicate_groups()
│                          consolidate path validation, QC detection, rendering, handler boilerplate
├── fcpxml/
│   ├── models.py          TimeValue, Timecode, Clip, ConnectedClip, MarkerType, Timeline
│   ├── parser.py          FCPXML → Python (spine, connected clips, roles, markers)
│   ├── writer.py          Modify & write (markers, trim, gaps, transitions, silence)
│   │                       FCPXMLModifier: index-based editing (clips/resources/formats dicts)
│   │                       FCPXMLWriter: generate new FCPXML from Python objects
│   │                       Helpers: _resolve_asset, _absorb_into_neighbor, _ripple_from_index
│   ├── rough_cut.py       Generate timelines (rough cuts, montages, A/B roll)
│   ├── diff.py            Timeline comparison engine (identity matching, threshold docs)
│   ├── export.py          DaVinci Resolve v1.9 + FCP7 XMEML v5 export
│   ├── media_intel.py     Real media analysis — audio silence detection via bounded ffmpeg subprocess
│   ├── preview.py         Standalone HTML timeline render, served as preview://<path>
│   ├── safe_xml.py        Centralized defusedxml wrappers (XXE/entity-bomb protection) + serialize_xml()
│   ├── dtd.py             Validate output against Apple's official DTDs (located in the FCP app bundle)
│   └── templates.py       Template system (intro/outro, lower thirds, music video)
├── skill/                 final-cut-pro Claude Code skill wrapping this server
├── tests/                 1093 tests across 27 suites (1089 pass, 4 skip without ffmpeg/FCP)
│   ├── test_models.py     TimeValue math, Timecode formatting, MarkerType contracts
│   ├── test_parser.py     FCPXML parsing, connected clips, edge cases
│   ├── test_writer.py     Clip editing, marker writing, speed changes
│   ├── test_fcpxml_writer.py  FCPXMLWriter generation from Python objects
│   ├── test_server.py     MCP tool handlers, dispatch, path validation
│   ├── test_rough_cut.py  Rough cut generation, montage, A/B roll
│   ├── test_diff.py       Moved clips, transitions, markers, clip identity
│   ├── test_export.py     Attribute stripping, compound flattening, audio tracks
│   ├── test_features_v05.py  Multi-track, roles, diff, reformat, export
│   ├── test_features_v06.py  Audio, compound clips, templates, effects, validation
│   ├── test_marker_pipeline.py  Marker builder, batch modes, output format
│   ├── test_speed_cutting.py  Speed cutting, montage config, pacing curves
│   ├── test_security.py   Input validation, XML sanitization, XXE protection
│   ├── test_edge_cases.py Boundary arithmetic, clip collisions, split/diff edges
│   ├── test_diversity.py  Boundary conditions across diff, models, validation
│   ├── test_refactored_helpers.py  _index_elements, _iter_spine_clips, serialize_xml edges
│   ├── test_targeted_gaps.py  Targeted branch coverage for diff, export, models
│   ├── test_bundles.py    .fcpxmld bundles, sidecar preservation, FCPXML 1.13/1.14 tolerance
│   ├── test_relink.py     Bulk media relink (URL + plain paths, dry run, segment matching)
│   ├── test_media_intel.py  silencedetect parsing, timeline mapping, real-WAV integration, handler
│   ├── test_transcribe.py Phrase/filler span matching, range merge/invert algebra, Whisper handlers
│   ├── test_validation.py Pydantic input validation models
│   ├── test_live.py       push_to_fcp / list_fcp_libraries (Apple events, mocked + live-gated)
│   ├── test_tool_groups.py  7 TOOL_GROUPS dispatch to the 62 TOOL_HANDLERS, legacy flag, schema size
│   ├── test_preview.py    preview:// HTML timeline render
│   ├── test_skill.py      final-cut-pro skill structure
│   └── test_dtd_validation.py  Output validated against Apple's shipped DTDs (skips without FCP)
├── docs/
│   ├── WORKFLOWS.md       8 production workflow recipes
│   └── CAPABILITY-AUDIT-2026-06.md  Ecosystem audit + dual-mode (XML + Live) roadmap
└── examples/
    └── sample.fcpxml      9 clips, 24fps — test fixture

Security

Every tool handler is hardened against adversarial input — critical for MCP servers where prompts may be LLM-generated, not human-typed.

Found a vulnerability? Report it privately via the repo's Security → Report a vulnerability tab — see SECURITY.md.

Layer	Protection
File I/O	Path traversal blocked, null bytes rejected, symlinks resolved, 100 MB size limit
Output sandbox	All generation, write, export, beat sync, subtitle, and reformat handlers enforce `_validate_output_path(anchor_dir=...)` — restricts writes to descendants of the source file's directory, blocking LLM-generated path escapes
Subprocess bounds	`_ensure_video_asset()` bounds-checks duration (0 < d ≤ 3600s), fps (1–240), width/height (even, ≤ 7680×4320) before `subprocess.run()` — blocks `inf`/`NaN`, negative values, odd dimensions, string injection, and oversized resolutions that could hang or exhaust ffmpeg
Speed validation	`handle_change_speed` validates speed is positive and ≤100 before any math — prevents ZeroDivisionError crash and nonsensical results
Directory listing	Confined to `FCP_PROJECTS_DIR` when set — `find_fcpxml_files` globs `.fcpxml` / `.fcpxmld` under that root and every discovered path is re-validated through `_validate_filepath` before it is opened; when `FCP_PROJECTS_DIR` is unset, the caller may name any directory to list
XML parsing	`defusedxml` with explicit `forbid_entities/external=True` blocks XXE, billion laughs, entity expansion, remote DTD attacks at all 4 entry points (parser, writer, exporter, rough cut) — minidom pretty-print path also hardened via `defusedxml.minidom`. Ruff `S314`/`S320` rules enforce safe parsing in CI
JSON depth limit	Iterative BFS depth checker rejects payloads nested beyond 50 levels — immune to RecursionError even at ~1000 nesting
Symlink resolution	`_validate_filepath` calls `Path.resolve()` before the extension whitelist runs, so a symlink named `innocent.fcpxml` that points at `/etc/passwd` is rejected on its resolved suffix — a symlink cannot smuggle a disallowed target past the file gate
Marker strings	Sanitized via `_sanitize_xml_value()` — null bytes, control chars stripped before write
Role values	Stripped of control characters before XML attribute assignment
Resource URI parsing	`file://` and `preview://` URIs have their scheme removed with `str.removeprefix()` (leading match only, so a path containing the scheme string is not mangled) and are then `urllib.parse.unquote()`d before validation — so percent-encoded traversal, percent-encoded null bytes, and ordinary spaces in filenames are all decoded first and then run through the same `_validate_filepath` gate as every other path
Output suffixes	Path separators and special characters stripped — no traversal via suffix injection
Marker types	`completed` attribute strict-matched (`'0'`/`'1'` only) — rejects `"true"`, `"1 OR 1=1"`, whitespace-padded values

134 security-specific tests across test_security.py covering XXE, path traversal, sandbox boundaries, output path anchoring, input validation, subprocess bounds, minidom hardening, JSON depth limits, role sanitization, ffmpeg parameter bounds, symlink resolution, resource-URI decoding, preview:// rejection paths, and write-handler sandbox enforcement. Ruff S (bandit) rules enforced in CI — S314/S320 block unsafe XML parsing, S105 catches hardcoded passwords, S108 flags insecure temp paths. Security events (null bytes, sandbox escapes, unhandled exceptions) are logged via Python logging for audit trails.

Timestamp Parsing — How Import Tools Place Markers

All subtitle and transcript import tools (import_srt_markers, import_transcript_markers) funnel through a single internal function: _parse_timestamp_parts() in server.py. Understanding it matters when timestamps don't land where you expect.

Supported Formats

Format	Example	Parts	Result
Minutes:Seconds	`1:30`	2	90.0s
H:MM:SS	`1:05:30`	3	3930.0s
HH:MM:SS.ms	`00:02:15.500`	3	135.5s
SMPTE (HH:MM:SS:FF)	`01:00:10:12`	4	3610.5s @ 24fps

The SMPTE 4-part format converts the frame component to fractional seconds: frames / frame_rate. The default rate is 24fps — pass frame_rate= to override for 25fps (PAL) or 30fps (NTSC) projects.

The Import Pipeline

SRT / VTT / YouTube chapters / plain transcript
        │
        ▼
  parse_srt()  /  parse_vtt()  /  parse_transcript_timestamps()
        │                │                      │
        └────────────────┴──────────────────────┘
                         │
                    split on ':'
                         │
                         ▼
             _parse_timestamp_parts(parts, frame_rate=24.0)
                         │
                         ▼
                   total seconds (float)
                         │
                         ▼
               marker placed on timeline

Edge Cases

Unrecognized part counts (1 part, 5+ parts) return None — the marker is silently skipped, not placed incorrectly
Zero frame rate — falls back to base seconds (frames ignored) rather than dividing by zero
Milliseconds — only carried in 3-part format via float() on the seconds component ("15.500" → 15.5)
Frame rounding — SMPTE frames are divided exactly (12/24 = 0.5), not rounded to the nearest frame boundary. The resulting float is converted to FCPXML's rational TimeValue downstream, preserving precision

Why This Matters

Before v0.6.20, the 4-part SMPTE parser silently dropped frames — 01:00:10:12 became 3610.0s instead of 3610.5s. At 24fps, that's up to ~0.96 seconds of drift per marker. If you imported a subtitle file with SMPTE timecodes, every marker was slightly off. This was subtle enough to pass QC but visible when scrubbing.

Design Principles

Principle	Implementation
Rational time, never floats	All durations are fractions (`600/2400s`) matching FCPXML's native format — zero rounding errors across trim, split, speed
Non-destructive by default	Modified files get `_modified`, `_chapters` suffixes. Originals are never overwritten
Single source of truth	`MarkerType` enum owns serialization: `from_string()` for input, `from_xml_element()` for parsing, `xml_attrs` for writing. `INCOMPLETE` is canonical; `TODO` is a backward-compat alias (same object)
Security-first	13-layer defense-in-depth across all 62 handlers — see Security for the full matrix
Dispatch, not conditionals	`TOOL_HANDLERS` dict maps names → async handlers. No 1000-line if/elif

Documentation

Guide	What's Inside
WORKFLOWS.md	8 production recipes — QC pipelines, beat-synced assembly, cross-NLE handoffs, documentary A/B roll
MCP_ECOSYSTEM.md	How this server composes with GitNexus, filesystem, and memory MCP servers
CHANGELOG.md	Full version history from v0.1.0 to present

Testing

uv run --extra dev pytest tests/ -v    # or: python3 -m pytest tests/ -v
ruff check . --exclude docs/           # lint — must pass before committing

1093 tests across 27 suites (1089 pass, 4 skip without ffmpeg or Final Cut Pro present) covering models, parser, writer, FCPXMLWriter generation, server handlers, rough cut generation, speed cutting & pacing curves, marker pipeline, refactored helper functions, regression fixes, security hardening (XXE, entity expansion, path traversal, sandbox boundaries, minidom defense-in-depth, JSON depth limits, input validation, ffmpeg bounds, write-handler sandboxing), connected clips, roles, diff, export, compound clip flattening, audio track generation, templates, effects, .fcpxmld bundles with sidecar preservation, bulk media relink, real media silence detection (parser, timeline mapping, real-WAV ffmpeg integration), transcript-driven editing, the 7 grouped tools dispatching to the 62 flat handlers, the preview:// HTML render and its traversal/extension/null-byte/symlink rejection paths, the final-cut-pro skill, and DTD validation against Apple's official DTDs (auto-skipped on machines without Final Cut Pro).

Requirements

Python 3.10+ · Final Cut Pro 10.4+ (FCPXML 1.8+) · Claude Desktop or any MCP client
Dependencies (auto-installed): mcp, defusedxml
ffmpeg (optional) — needed for silence analysis (detect_media_silence, remove_media_silence)
[intelligence] extra (optional) — adds librosa for detect_beats; everything else works without it. Install via uvx --from "fcp-mcp-server[intelligence]" fcp-mcp-server or pip install "fcp-mcp-server[intelligence]" (from source: pip install -e '.[intelligence]').
See Compatibility for full version matrix

Ecosystem — XML Mode Today, Live Mode Next

This server is the safe, offline layer of FCP automation: no patched binaries, no private APIs, runs on managed Macs, works without Final Cut Pro installed. It composes with the live-control side of the ecosystem rather than competing with it:

SpliceKit by @elliotttate with @latenitefilms — live in-process control of a patched FCP copy with its own ~200-tool MCP server. The deep edit engine here and the live hands there are complementary by design; an optional bridge to SpliceKit's local JSON-RPC endpoint is on this project's roadmap (see below).
CommandPost by @latenitefilms — nine years of accessibility-layer FCP automation with a built-in WebSocket control surface; another candidate live backend.

The full ecosystem analysis and the dual-mode architecture plan live in docs/CAPABILITY-AUDIT-2026-06.md.

Roadmap

Known Issues

Issue	Impact	Workaround
Still images crash FCP	PNG/JPEG assets referenced directly in FCPXML crash Final Cut Pro on import (`addAssetClip` null pointer). Confirmed across multiple format configurations, dimension matching, and element types.	Convert stills to short MOVs before referencing: `ffmpeg -loop 1 -i image.png -c:v libx264 -t 2 -pix_fmt yuv420p -r 24 output.mov`. This is an FCP limitation, not an FCPXML spec issue.
Non-standard timebases	FCP rejects time values with denominators outside its standard set (e.g. `100800/57600s`). Cross-denominator arithmetic previously produced these.	Fixed in v0.5.29 — TimeValue arithmetic now uses LCM, and speed changes snap to frame boundaries in 2400-tick timebase.
Malformed frameDuration crash	A `frameDuration` with zero or negative denominator (e.g. `"0/0s"`) in the writer's `_detect_fps` would silently produce 0.0 fps, causing downstream ZeroDivisionError in speed/trim operations. The parser already validated this correctly.	Fixed in v0.6.23 — writer now validates both numerator and denominator, falling back to 30.0 fps.
Duplicate clip names corrupt edits	When multiple spine clips share the same name (e.g. `Interview_A` ×4), operations using the name-indexed dict silently target the wrong clip (last-indexed instead of first). Affected: `delete_clip`, `add_marker_at_timeline`, `trim_clip`, `change_speed`, `split_clip`, `add_transition`, `reorder_clips`.	Fixed in v0.6.37–0.6.39 — all methods now resolve clips via `_resolve_clip()` which walks the spine directly, returning the first match.

Status & Contributing

Actively maintained — live-verified against FCP 12.2, with external contributions already merged and credited: @mikegrant25 (sandbox security fix, #6) and @jardelapp (audio duration probing, #7).

PRs welcome. If you're a video editor who codes (or a coder who edits), let's build this together.

Credits

Built by @DareDev256 — former music video director (350+ videos), now building AI tools for creators.

License

MIT — see LICENSE.

mcp-name: io.github.DareDev256/fcpxml-mcp-server

FCPXML MCP

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Analysis — 11 tools

Multi-Track — 3 tools

Roles — 4 tools

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Editing — 9 tools

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Comparison · Reformat · Silence

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Generation — 3 tools

Beat Sync — 2 tools

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v0.6.0 — Audio, Compound, Templates, Effects — 6 tools

v0.8.0 — Media — 1 tool

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v0.13.0 — Transcript Intelligence — 3 tools

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