Premiere Pro via the file bridge (verified Premiere 2026 / 26.5.2, Windows, CEP 12.0.1)

There is no Premiere MCP server here. panel/ is a CEP extension ("Claude Bridge"): while it is open, index.html calls ClaudeBridge.tick() in host.jsx about once a second. Each tick takes every *.jsx in <ROOT>/inbox, moves it to done/ first, runs it inside (function(){ ... })() (so a top-level return works) and writes <ROOT>/outbox/<name>.json = {file, ok, result | error+line, ms}. <ROOT>/status.json is rewritten every ~5 s: {state: listening|paused|running, time, file (while running), premiere, project, runs}. Default ROOT is D:/WORK/Claude/premiere-bridge (the ROOT line in host.jsx). $.global.ClaudeBridge exposes ROOT, stringify, readText, writeText, log (shown in the panel) and exportFrame (below).

Premiere has no scriptable undo groups: a bridge script is not one Ctrl+Z. Before anything destructive, work on a copy (app.project.saveAs, see Relinking) or have the user save first.

Installing (verified)

• scripts/install.ps1 sets HKCU\Software\Adobe\CSXS.12\PlayerDebugMode = "1" (string), self-signs the panel when D:\WORK\Claude\premiere-bridge-signing\ZXPSignCmd.exe exists, and copies it to %APPDATA%\Adobe\CEP\extensions\com.claude.premierebridge. Then Window › Extensions › Claude Bridge (with a project open; whether the Home screen offers it is unverified). Keep it docked so it stays open; whether it reopens by itself after a restart is unverified.
• CEP 12.0.1 ignores PlayerDebugMode. An unsigned panel just doesn't open: no window, no CEPHtmlEngine process. %TEMP%\CEP12-PPRO.log (needs LogLevel ≥ 1 under the same key) says Signature verification failed for extension com.claude.premierebridge.panel. Self-signing fixes it: ZXPSignCmd.exe 4.1.3 x64 from Adobe-CEP/CEP-Resources (ZXPSignCMD/4.1.3/x64, git blob f5df2ed8…; it has no Authenticode signature, so check the hash). The certificate and its password are created in the signing folder on first install. Never commit them.
• Premiere discovers new extensions only at start-up. After signing a panel Premiere had already discovered (and refused), clicking the menu item again loaded it without a restart.
• Every edit to a panel file breaks the signature: re-run install.ps1. A new host.jsx then loads via the panel's Reload host, or from a bridge script: $.evalFile(Folder.userData.fsName + "/Adobe/CEP/extensions/com.claude.premierebridge/host.jsx") (keeps the run count). A changed index.html needs the panel closed and reopened.

Sending scripts

• Never write straight into inbox/: scripts/send.sh NAME [timeout] stages $STAGE/NAME.jsx under a non-.jsx name, renames it, waits for the JSON (env BRIDGE = ROOT). Number scripts (023_snapshot.jsx) so done/ reads as a history.
• On a timeout send.sh reads status.json: running X (started N s ago) = Premiere is stuck in that script; a stale heartbeat = panel closed. A call that never returns (seen with QE exportFramePNG, below) leaves Premiere idle at 0 % CPU with a responsive UI, but the bridge is blocked until Premiere restarts. Scripts are claimed before they run, so the restart won't rerun it.
• err.line is the line in the script file. JSON exists in Premiere 26.5's ExtendScript.
• DOM objects stringify as "<Project>", "<Sequence>": copy the fields you need into plain objects.
• The regex literal /\\/g is a SyntaxError in ExtendScript; use s.split("\\").join(...) or new RegExp("\\\\", "g"). ExtendScript is ES3: a reserved word as an object key ({ in: … }) is a SyntaxError too ("Illegal use of reserved word"). Backslash paths written through sed/heredocs get mangled easily ("y:\bbc" is a backspace): build them with String.fromCharCode(92) or File.fsName.
• After only read-only scripts (plus enableQE, exportFramePNG, openSequence, setPlayerPosition) the title bar showed the project as modified (*); which call does it is unverified. Tell the user rather than letting them wonder about unsaved edits.

Inspecting (verified)

• Time: 254016000000 ticks per second. seq.timebase = ticks per frame (string); seq.end, seq.zeroPoint = tick strings. Clip start/end/inPoint/outPoint are Time objects (.seconds, .ticks string). seq.getInPoint()/getOutPoint() return seconds as strings, "-400000" = not set. seq.getSettings().videoFrameRate.seconds = frame duration; audioSampleRate is a Time (1/48000 s). seq.getPlayerPosition() → Time; seq.setPlayerPosition(ticksString).
• Tracks: seq.videoTracks[i].clips[j] (numTracks, numItems); clip.projectItem, clip.nodeId, clip.mediaType, track.isMuted(). Higher track index = on top.
• ProjectItemType: CLIP 1, BIN 2, ROOT 3, FILE 4. Sequences are CLIP items with isSequence(); map them via app.project.sequences[i].projectItem.nodeId. Walk bins via rootItem.children; item.treePath, item.getMediaPath(), item.isOffline().
• "Used in these timelines, including nested ones": recurse through clip.projectItem.nodeId → sequence. Subclips (X.mp4.Subclip01) are separate items sharing the master's media path, so count a media path as used when any used item has it. getInPoint()/getOutPoint() on a subclip project item returned the whole file (0 to full length), not the subclip's range: take used source ranges from the track items' inPoint/outPoint (master-media time, timecode-based).
• clip.getSpeed() (1, 2, 0.75…) and clip.isSpeedReversed() (0/1) work on track items. seq.getWorkAreaInPoint()/getWorkAreaOutPoint() return seconds as strings, like getInPoint.
• Timelines often park material after the edit. One 1-minute edit ran to 94 minutes, with two full 30-minute B-roll files laid end to end after its out point. Before calling anything "used", compare clip positions with the sequence's out point and look for a big gap, and ask which counts. In that project the master items and their subclips were both used, several of them at far-apart points. An item links to one file only, so cutting a source into separate pieces cannot serve such an item. (Unverified idea: re-encode at full length with unused stretches blacked out, which keeps timing and every link intact.)
• ProjectItem in 26.5 has no delete for clips (deleteBin only), plus moveBin, changeMediaPath, canChangeMediaPath, findItemsMatchingMediaPath, isMergedClip, isMulticamClip, setOffline, createSubClip, saveProjectSnapshot (list from item.reflect.methods).
• app.project.openSequence(sequenceID) activates a sequence (returns true); qe.project .getActiveSequence() follows it within the same script.

Exporting frames (verified)

• ClaudeBridge.exportFrame(timecode, name) → <ROOT>/frames/<name>.png at full sequence size, synchronously (4K ≈ 0.3–1 s), from the active sequence. Timecode as QE gives it ("00:00:26:11"). For an exact moment: openSequence(id), setPlayerPosition(ticks), then qe.project.getActiveSequence().CTI.timecode. The time argument is honoured.
• Why the helper exists: QE exportFramePNG(timecode, pathWithoutExtension) appends .png and escape-processes its path. After a backslash, a digit starts an octal escape (\009_cti cut the path, so …\frames\009_cti wrote …\frames.png; \123 became S). Lowercase a–e lose the backslash (…\frames\d2\abc_def wrote …\framesd2abc_def.png). \F hung Premiere for good. Forward slashes, a .png ending or doubled backslashes throw "Unknown error exception". Lowercase f–z and uppercase A–E survive. The helper allows names [f-z][a-z0-9_-]* only and refuses folders with an unsafe segment.
• Look at frames with Pillow (uv run --with pillow python -I …): before|after side by side plus a 1:1 centre crop shows both framing and fine detail.

Relinking media (verified on a 249-item, 17-sequence project)

• Work on a copy: app.project.saveAs(fsPath) saves the open state to the new file and switches the open project to it. The original file keeps its old save (mtime unchanged).
• item.changeMediaPath(newPath, false) relinked ProRes/MJPEG .mov → HEVC .mp4 and NAS → local paths for 225 items without the override flag. canChangeMediaPath() is false for Motion Graphics Template items (.aegraphic): they can't be relinked by script.
• Premiere keeps linked media open. To replace an .mp4 in place, relink the item elsewhere (e.g. back to the .mov), overwrite the file, then relink again.
• An image-sequence item (X.0001.png) relinks to a movie with changeMediaPath too. A 172-frame RGBA PNG sequence became a lossless PNG-in-MOV (ffmpeg -framerate 25 -start_number 1 -i X.%04d.png -c:v png -pix_fmt rgba -f mov, the same 102 MB as the frames). It kept its 25 fps interpretation, length and alpha settings, and the composite check frames were pixel-identical. Check alpha before choosing MP4: getFootageInterpretation() gives frameRate, alphaUsage, ignoreAlpha, and Pillow shows whether alpha really drops below 255.
• changeMediaPath also works on items that went offline (files removed outside Premiere). item.isOffline() finds them. Check isOffline after any file moves the user may make too.
• Prove nothing moved: before and after, snapshot every clip in the affected sequences (seq, track, index, name, start/end/in/out ticks) and export a check frame mid-clip for each changed medium. Ticks must be identical. Compare frames with numpy: PSNR plus mean level shift. Healthy HEVC re-encodes gave 35–48 dB with a shift of about −0.3. An edge-glow effect on a clip amplified the same compression to about 26 dB (identical framing). A levels problem shows as a steady shift (+9).

Transcoding for a relink (verified, ffmpeg 7.1.1, RTX 4090)

• HEVC 10-bit on NVENC: -map 0:v:0 -map 0:a? -map_metadata 0 -c:v hevc_nvenc -preset p7 -tune hq -rc vbr -multipass fullres -b:v 40M -maxrate 60M -bufsize 120M (HD: 20M/30M) -profile:v main10 -pix_fmt p010le -tag:v hvc1 -c:a aac -b:a 320k -movflags +faststart, plus -timecode <source tc> when the source has one. Write .part and rename on success. 17.7 GB of 4K ProRes LT (Topaz upscales) became 1.1 GB in about 2.5 min. Premiere read the timecode: in/out stayed identical, including sources starting at 01:40:00:00 and 21:55:31:16.
• Before relinking, check every output against its source with ffprobe: nb_frames, rate, size, timecode, audio streams.
• MJPEG sources (yuvj422p: full range, BT.601 matrix). A plain -pix_fmt p010le writes video-range pixels but keeps the pc flag, and Premiere showed lifted blacks. Use -vf scale=in_range=pc:out_range=tv:in_color_matrix=bt601:out_color_matrix=bt709,format=p010le,setparams=color_primaries=bt709:color_trc=bt709:colorspace=bt709:range=tv. The -color_trc/-color_primaries output options do not override tags carried by the frames; setparams does. A leftover sRGB transfer tag (iec61966-2-1) on the HEVC made Premiere 26 render it brighter than the MJPEG with the same tag; forcing bt709 matched.
• Leave alpha sources alone (ProRes 4444 yuva…, QuickTime RLE argb): MP4 drops the alpha. Re-encoding small or already-H.264 .mov files saves little and costs a generation.

Keeping this skill current

After a session that used the bridge, add only what was tested in a real project (mark the rest (unverified)), correct wrong entries instead of appending, keep this file under ~300 lines, and commit and push the skills repo. Project-specific facts (sequence names, paths, clients) go to that production's notes (see project-notes), never here.