Limits

Studio bounds source inspection, provider processes, build snapshots, browser artifacts, projection requests, and validation waits. Limits apply before publication or mutation commit unless the table names a browser boundary.

Names and Source documents

Boundary	Limit	Failure or diagnostic
View name	238 UTF-8 bytes	configuration-error or an inline creation error
Source document	64 MiB	source-too-large
Source encoding	UTF-8	invalid-source-encoding
Source documents returned by one provider inspection	256	Provider conformance error
Provider path, title, summary, message, or hint field	64 KiB UTF-8	Provider conformance error

View names also follow the syntax and reserved-name rules in View projects. Source paths follow Source documents and build inputs.

Build inputs and artifacts

Boundary	Files	Per file	Total
Declared project build inputs	4,096	64 MiB	512 MiB
Published artifact	4,096	128 MiB	1 GiB

Studio rejects symlinks and path collisions that violate the contained project or artifact contract. Artifact validation also rejects reserved routes, a missing entry document, and a document without one head, one body, and one #app-shell.

Static export combines the artifact with Studio runtime assets and notebook public files. Prepared export adds verified output assets within marimo-export's 64 MiB asset and 512 MiB export limits. Browser export adds notebook source. Studio checks each copied tree against the artifact file budget before the staged directory replaces the destination.

Projection declarations

Boundary	Limit
Projection sites returned by provider inspection	512
Encoded projection sites	1 MiB
Finite cell targets on one site	256
Finite output targets on one site	100
Finite value targets on one site	100
Projection target	4,096 UTF-8 bytes
Value selector path	64 steps
Media types in one output accept list	32

Value selectors and accept lists follow marimo-export's values module, which a Prepared export also uses. A "*" target marks a dynamic site, so inspection skips enumerating its targets. Runtime policy still applies to active instances and unique targets. Prepared export requires finite targets on every site.

Renders

Boundary	Limit	Failure
Renders declared by one view	32	Provider conformance error
Encoded render values for one render	8 MiB	render-values-too-large
Outputs and cells read by one render	16 MiB	render-outputs-too-large
Files returned by one render	1,024	Provider conformance error
One rendered file	512 MiB	render-too-large
All files returned by one render	1 GiB	render-too-large
Provider commands during one render	300 s	render-failed
Renders across one static export's states	256	render-states-exceeded
Regions kept from one render	4,096	render-regions-limited warning
Reads kept by one region	64	Later reads left out
UTF-16 code units in one region label	256	Label shortened

Active presentation projections

Boundary	Limit	Browser diagnostic
Active projection instances	512	projection-instance-limit
Unique cell targets	256	projection-cell-target-limit
Unique output targets	100	projection-output-target-limit
Unique value targets	100	projection-value-target-limit
Projection instance ID	256 UTF-8 bytes	Projection resolution error
Projection target	4,096 UTF-8 bytes	Projection resolution error
Value selector path	64 steps	Projection resolution error

A complete cell or rendered output target accepts one host, and duplicate hosts enter an error state. Several mo-value hosts may share one value target.

Runtime payloads

Boundary	Limit	Failure
Encoded browser runtime configuration	16 MiB	runtime-config-too-large
One projected JSON value	1,000,000 bytes	value-too-large
Values and keys in one projected JSON value	100,000 values	value-too-large
JSON values in one value read	1,000,000 bytes	response-too-large
One projected Arrow value	64 MiB	value-too-large
Arrow values in one value read	128 MiB	response-too-large
Arrow values in one Browser runtime value read	64 MiB	response-too-large
One rendered output, and the outputs of a request	5,000,000 bytes	output-too-large or response-too-large
One rendered output request set	100 selectors	Capability or protocol error
Browser client response	5,000,000 bytes	Live request failure

The Python and Browser runtimes enforce the value limits. A value read carries the values that a view projects from one producer cell, and marimo-studio validate --level runtime reads them the same way. Eager pandas, Polars, and PyArrow tables travel as Arrow IPC, a columnar binary format. Collect lazy dataframes in the notebook before projecting them. Other values travel as JSON, so return a table to project more than 1,000,000 bytes.

The Python runtime publishes Arrow values through marimo's shared memory. A container's default 64 MiB /dev/shm holds about one large value, so start containers with a larger --shm-size. A value that does not fit travels inline and takes longer to load.

The Browser runtime passes Arrow values from its worker as base64 text, which caps a value read there at 64 MiB of Arrow. marimo-studio validate --level runtime applies the Python runtime budgets.

The Prepared runtime stores each value as a marimo-export asset. One asset holds at most 64 MiB, and one export holds at most 512 MiB of unique assets across its prepared states.

Browser runtime configuration contains saved notebook source, projection declarations, runtime bindings, and presentation settings. Prepared runtime configuration contains the publication identity and manifest URL. When a Browser record reaches 16 MiB, use finite projection targets and reduce notebook source.

Provider records

Boundary	Limit
Starters per provider	256
Source documents per starter	256
Options in one view project	256
Cell targets consumed by one starter plan	256
Provider inspection diagnostics	512 records and 1 MiB encoded
Provider build diagnostics	512 records and 1 MiB encoded
Encoded third-party operation request	128 MiB
Encoded third-party operation result	16 MiB

Provider titles, summaries, option values, paths, diagnostics, starter files, and notebook context also pass structural and byte validation. The View provider API defines the record responsibilities.

Timeouts

Operation	Default	Accepted range or budget
Runtime inspection and validation	60 seconds	Greater than 0, up to 300 seconds
Prepared export	30 seconds	Positive duration
Provider runner command	120 seconds	Finite positive duration within the request's shared 120-second command budget
Third-party provider metadata, availability, and starter discovery	10 seconds	Fixed extension-operation deadline

Runtime workers get an additional 10-second shutdown allowance after the requested runtime timeout. A timeout bounds waiting and cleanup ownership. It does not restrict the operating-system authority of notebook or provider code.

Browser message bounds

Navigation and public query synchronization accept at most 16 KiB of query text and 8 KiB of URL fragment text. Studio validates messages between the trusted presentation shell and the opaque-origin authored frame before changing history or runtime state.