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add html_head parameter to create_asgi_app()#8302

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nojaf:create_asgi_app-html-head
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add html_head parameter to create_asgi_app()#8302
nojaf wants to merge 3 commits intomarimo-team:mainfrom
nojaf:create_asgi_app-html-head

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@nojaf nojaf commented Feb 13, 2026

📝 Summary

Adds an html_head parameter to marimo.create_asgi_app() that injects custom HTML into the <head> of every notebook served through the ASGI app, without requiring per-notebook configuration.

🔍 Description of Changes

ASGI deployers often need to inject global snippets (analytics, custom fonts, meta tags) into every notebook page. Previously this was only possible per-notebook via App(html_head_file="..."). This PR adds an html_head string parameter to create_asgi_app() for global injection.

Usage:

app = (
    create_asgi_app(
        html_head='<script src="https://analytics.example.com/tracker.js"></script>',
    )
    .with_app(path="/", root="app.py")
    .build()
)

How it works:

  • create_asgi_app(html_head=...) stores the string and sets it on each sub-app's app.state.html_head.
  • AppStateBase.html_head property exposes it (with hasattr fallback for non-ASGI contexts).
  • The index() handler passes it to notebook_page_template().
  • notebook_page_template() injects it before </head>, before any per-notebook html_head_file content. This means both are additive and per-notebook content takes priority on conflicts.

Files changed:

File Change
marimo/_server/asgi.py New html_head param, docstring, app.state.html_head
marimo/_server/api/deps.py html_head property on AppStateBase
marimo/_server/api/endpoints/assets.py Pass html_head to template
marimo/_server/templates/templates.py Inject global html_head before per-notebook content
tests/_server/templates/test_templates.py 2 new tests (global-only, global + per-notebook ordering)
tests/_server/test_asgi.py 3 new tests (state propagation, default, end-to-end)

📋 Checklist

  • I have read the contributor guidelines.
  • For large changes, or changes that affect the public API: this change was discussed or approved through an issue, on Discord, or the community discussions (Please provide a link if applicable).
  • Tests have been added for the changes made.
  • Documentation has been updated where applicable, including docstrings for API changes.
  • Pull request title is a good summary of the changes - it will be used in the release notes.

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@mscolnick mscolnick requested a review from Copilot February 13, 2026 17:29
Copilot AI reviewed Feb 13, 2026
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Pull request overview

Adds a new html_head parameter to marimo.create_asgi_app() to support injecting a global HTML snippet into the <head> of every notebook page served via the ASGI builder, without requiring per-notebook configuration.

Changes:

  • Add html_head: Optional[str] to create_asgi_app() and propagate it via app.state.html_head to sub-apps.
  • Expose html_head via AppStateBase.html_head and pass it through the index handler into notebook_page_template().
  • Inject global html_head into the HTML template before per-notebook html_head_file content; add tests covering propagation and ordering.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file
File Description
marimo/_server/asgi.py Adds the html_head builder parameter and stores it on each created sub-app’s app.state.
marimo/_server/api/deps.py Adds AppStateBase.html_head accessor with a safe fallback for states without the attribute.
marimo/_server/api/endpoints/assets.py Passes app_state.html_head into the notebook page template rendering path.
marimo/_server/templates/templates.py Adds html_head param to notebook_page_template() and injects it into <head> before per-notebook head file content.
tests/_server/templates/test_templates.py Adds tests for global-only injection and ordering vs per-notebook html_head_file.
tests/_server/test_asgi.py Adds tests for state propagation, default None, and end-to-end HTML injection in responses.

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