preview-build

name	preview-build
description	Use when you need to load a specific published preview/nightly extension build into the agent's MCP browser by run-number, branch name, or tag. Faster than rebuilding locally when you only want to exercise an existing artifact.

preview-build

Resolve a GitHub release published by CI (nightly or branch-preview), download its Chrome zip, expand to .tmp/, and install_extension it via the chrome-devtools-ext MCP. For active HMR development use browser-verify instead.

Prerequisites

• gh CLI authenticated against this repo
• chrome-devtools-ext MCP (see browser-verify for install)
• A shell with unzip (macOS/Linux/git-bash) or Expand-Archive (PowerShell)

If any are missing, stop and tell the human.

1. Resolve the release

By nightly run-number (the (<BUILD>) in the title):

gh release list --limit 50 --json tagName,name \
  --jq '.[] | select(.name | test("\\(<BUILD>\\)$")) | .tagName'

By branch:

gh release view preview-branch-<branch-slug> --json tagName,assets,name

Latest nightly:

gh release list --limit 5 --json tagName,name,createdAt \
  --jq 'map(select(.name | startswith("Preview Build nightly-"))) | sort_by(.createdAt) | last | .tagName'

Substitute <BUILD> / <branch-slug> at the call site.

2. Download + expand

Both shells end with an unpacked/ directory under .tmp/ (gitignored).

Unix / git-bash:

TAG=<tag from step 1>
ASSET=$(gh release view "$TAG" --json assets --jq '.assets[] | select(.name | endswith("-chrome.zip")) | .name')
DEST=.tmp/preview-$TAG
mkdir -p "$DEST"
gh release download "$TAG" --pattern "$ASSET" --dir "$DEST"
unzip -q "$DEST/$ASSET" -d "$DEST/unpacked"

PowerShell (parse the JSON in PowerShell rather than passing a jq filter through the native-command boundary, which mangles quotes):

$TAG = '<tag from step 1>'
$ASSET = ((gh release view $TAG --json assets | ConvertFrom-Json).assets | Where-Object { $_.name -like '*-chrome.zip' }).name
$DEST = ".tmp/preview-$TAG"
New-Item -ItemType Directory -Force -Path $DEST | Out-Null
gh release download $TAG --pattern $ASSET --dir $DEST
Expand-Archive -Path "$DEST/$ASSET" -DestinationPath "$DEST/unpacked" -Force

3. Load into the MCP browser

install_extension(<absolute path to the unpacked dir>)

Resolve the absolute path from the current working directory (pwd / Get-Location); don't embed a host-specific prefix.

The dev API (globalThis.__da) is NOT present in these builds; nightly tags ship prod, and attachDevApi is gated by !IS_DA_PROD. Seed state via chrome.storage.set directly.

4. Tear down

uninstall_extension(<id from list_extensions>)

Close lingering chrome-extension://<id>/... tabs first.

Gotchas

• Build numbers are not stable across forks. The parenthetical in the title is this repo's GitHub Actions run_number.
• Branch-preview release tags get overwritten by new pushes. Grab the asset immediately if bisecting; only nightly tags are stable.
• The Firefox zip is not loadable in Chromium. Pick the -chrome.zip asset.