Sequence Builder

A single-file, zero-dependency UML sequence diagram builder.
Runs entirely in the browser. No build step. npm install only for Playwright render tests.

Live demo  |  Download v0.9.109  |  All releases

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Quick start

git clone https://github.com/MeatPopSci1972/sequence-builder
cd sequence-builder
node launcher.js        # dev server with hot-reload at http://localhost:3799

Open http://localhost:3799 in your browser.

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What it does

Capabilities pinned by the contract test suites:

• ADD_ACTOR
• DELETE_ACTOR cascade
• UPDATE_MESSAGE
• meta.undoable
• UNDO
• REDO
• _parseUML
• end-to-end
• bounding boxes + selection
• message label + inline edit
• canvas pan + nudge
• schema + properties
• regex contracts
• BOM contract
• ULID ID contract
• ActorElement contract
• MessageElement contract
• NoteElement contract
• FragmentElement contract

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Repository structure

File	Notes
COWORK_HELLO.md
LICENSE
README.md
build.js
demo/auth-flow.json
demo/cybersec-zones.json
demo/index.json
demo/scada-control-flow.json
demo/transit-tap-to-ride.json
endpoints.js
launcher.js
lint.js
log.html
logview-test.html
logview.html
logview.sf.config.json
package.json
preflight.ps1
readme-gen.js
sequence-builder.html
sequence-builder.store.js
sequence-builder.test-runner.js
sequence-builder.test.js
server.js
src/elements/ActorElement.js
src/elements/ElementFactory.js
src/elements/FragmentElement.js
src/elements/MessageElement.js
src/elements/NoteElement.js
src/elements/SequenceElement.js
sync-labels.sh
themes.json

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Dev server API

Served by server.js via launcher.js on port 3799.

Method	Path	Description
GET	/status	Session bootstrap — version, git, demos
GET	/HANDOFF.md	Session handoff doc
GET	/api	Endpoint reference JSON (this)
GET	/usage	AI usage guide plain text
GET	/log	Server event log JSON
GET	/git-log	git log --oneline JSON. Default n=20
GET	/test	Run build+tests — returns HTML report
GET	/test-render	Playwright render gate — 3 demos x 5 SVG layers
GET	/validate-readme	Check README link+label for vX.Y.Z. Returns {ok,hasLink,hasLabel}
GET	/check-pages?v=X.Y.Z	Fetch live GitHub Pages URL for vX.Y.Z. Returns {ok,status,url,ms}
GET	/slice	Return named sentinel section of a file. No section = manifest
POST	/generate-readme	Generate README.md from live sources — git, test suites, endpoints, version
POST	/build	Run build.js — sync store.js into HTML
POST	/lint	Run lint.js — button count, SVG balance, sentinels
POST	/patch	Find-replace in file. Body:{file,anchor,replace}. Flex whitespace matching. Returns {ok,replaced,length}
POST	/git	git add -A && commit. Body:{message}
POST	/git-restore	Restore tracked file to HEAD. Body:{file}
POST	/tag	Create annotated git tag. Body:{tag,message}
POST	/changelog	Auto-gen CHANGELOG.md from git log since last tag. Body:{version}
POST	/update-handoff	Populate live fields in HANDOFF.md from status+test+test-render
POST	/snapshot?v=X.Y.Z	Copy build+HANDOFF to releases/vX.Y.Z/
GET	/<file>	Read any file in repo root
PUT	/<file>	Write any file in repo root. ?verify=1 returns {ok,wrote,status}

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Running the tests

node build.js && node sequence-builder.test-runner.js
# Expected: 175 passed | 0 failed | 175 total

Or via the dev server: GET http://localhost:3799/test

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Tech stack

Vanilla JS, SVG, HTML5 Canvas. No frameworks, no bundler, no runtime dependencies.

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License

MIT