Sourced from modal's changelog.

1.3.1 (2026-01-22)

• We've improved our experimental support for Python 3.14t (free-threaded Python) inside Modal containers.
  • The container environment will now use the Python implementation of the Protobuf runtime rather than the incompatible upb implementation.
  • As 3.14t images are not being published to the official source for our prebuilt modal.Image.debian_slim() images, we recommend using modal.Image.from_registry to build a 3.14t Image:

    modal.Image.from_registry("debian:bookworm-slim", add_python="3.14t")
    

  • Note that 3.14t support is available only on the 2025.06 Image Builder Version.
  • Support is still experimental, so please share any issues that you encounter running 3.14t in Modal containers.
• It's now possible to provide a custom_domain for a modal.Sandbox:

  sb = modal.Sandbox.create(..., custom_domain="sandboxes.mydomain.com")
  

  Note that Sandbox custom domains work differently from Function custom domains and must currently be set up manually by Modal; please get in touch if this feature interests you.
• We added a new modal token info CLI command to retrieve information about the credentials that are currently in use.
• We added a --timestamps flag to a number of CLI entrypoints (modal run, modal serve, modal deploy, and modal container logs) to show timestamps in the logging output.
• The automatic CLI creation for modal run entrypoints now supports Literal type annotations, provided that the literal type contains either all str or all int values.
• We've fixed a bug that could cause App builds to fail with an uninformative CancelledError when the App was misconfigured.
• We've improved client resource management when running modal.Sandbox.exec, which avoids a rare thread race condition.

1.3.0 (2025-12-19)

Modal now supports Python 3.14. Python 3.14t (the free-threading build) support is currently a work in progress, because we are waiting for dependencies to be updated with free-threaded support. Additionally, Modal no longer supports Python 3.9, which has reached end-of-life.

We are adding experimental support for detecting cases where Modal's blocking APIs are used in async contexts (which can be a source of bugs or performance issues). You can opt into runtime warnings by setting MODAL_ASYNC_WARNINGS=1 as an environment variable or async_warnings = true as a config field. We will enable these warnings by default in the future; please report any apparent false positives or other issues while support is experimental.

This release also includes a small number of deprecations and behavioral changes:

• The Modal SDK will no longer propagate grpclib.GRPCError types out to the user; our own modal.Error subtypes will be used instead. To avoid disrupting user code that has relied on GRPCError exceptions for control flow, we are temporarily making some exception types inherit from GRPCError so that they will also be caught by except grpclib.GRPCError statements. Accessing the .status attribute of the exception will issue a deprecation warning, but warnings cannot be issued if the exception object is only caught and there is no other interaction with it. We advise proactively migrating any exception handling to use Modal types, as we will remove the dependency on grpclib types entirely in the future. See the modal.exception docs for the mapping from gRPC status codes to Modal exception types.
• The max_inputs parameter in the @app.function() and @app.cls decorators has been renamed to single_use_containers and now takes a boolean value rather than an integer. Note that only max_inputs=1 has been supported, so this has no functional implications. This change is being made to reduce confusion with @modal.concurrent(max_inputs=...) and so that Modal's autoscaler can provide better performance for Functions with single-use containers.
• The async (.aio) interface has been deprecated from modal.FunctionCall.from_id, modal.Image.from_id, and modal.SandboxSnapshot.from_id, because these methods do not perform I/O.
• The replace_bytes and delete_bytes methods have been removed from the modal.file_io filesystem interface.
• Images built with modal.Image.micromamba() using the 2023.12 Image Builder Version will now use a Python version that matches their local environment by default, rather than defaulting to Python 3.9.

1.2

1.2.6 (2025-12-16)

• Fixed bug where iterating on a modal.Sandbox.exec output stream could raise unauthenticated errors.

1.2.5 (2025-12-12)

• It is now possible to set a custom name= for a Function without using serialized=True. This can be useful when decorating a function multiple times, e.g. applying multiple Modal configurations to the same implementation.
• It is now possible to start modal shell with a Modal Image ID (modal shell im-abc123). Additionally, modal shell will now warn if you pass invalid combinations of arguments (like --cpu together with the ID of an already running Sandbox, etc.).
• Fixed a bug in modal shell that caused e.g. vi to fail with unicode decode errors.
• Fixed a thread-safety issue in modal.Sandbox resource cleanup.
• Improved performance when adding large local directories to an Image.
• Improved async Sandbox performance by not blocking the event loop while reading from stdout or stderr.

... (truncated)

• 2a31e94 Release v1.3.1 of the Python SDK (#32651)
• e35ff6d Release modal client 1.3.1.dev35 (#32612)
• f7c045c Update dependency astral-sh/uv to v0.9.26 (#32600)
• 8d44e82 Use local changelog for docs page (#32508)
• 99f3871 Update Modal client version (#32524)
• fa34c82 Update Modal client version (#32505)
• 0f980da Copybara configuration to push changes to public client repo (#32305)
• db254b3 Manually sync client on last time (#3904)
• 0f94603 Remove release workflow from this repo (#3903)
• 9689e5c [auto-commit] [skip ci] Bump the build number
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