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With 1.0, AG-UI now provides a stable, versioned protocol contract. The 1.0 specification will remain unchanged, while future protocol evolution will happen through new draft specifications and open community discussion before each release.
What changed since the draft
Many individuals and contributors helped shape AG-UI 1.0 during the review period, including people building on AG-UI at Anthropic, Google, Microsoft, Pydantic, and TanStack. Their feedback led directly to several improvements in the final release:
Tool results can carry content parts, including images and documents.
The protocol is prepared for content parts in messages as we move toward the same richer content model there.
Token usage accounting now has explicit semantics, including cached tokens.
Runs can explicitly end with outcome: "cancelled".
Successful runs can identify pending frontend tool calls that still need to be resolved.
The responsibility for resume coverage is now clearly specified.
A dedicated file upload type has been added.
Thank you to everyone who reviewed the draft, raised edge cases, and contributed to making the final specification more complete.
More in AG-UI 1.0
Beyond the changes that came out of the review period, 1.0 also introduces and formalizes several important protocol capabilities:
Metadata — a simple, defined way to send additional application- or provider-specific data to the frontend.
Subagents — first-class support for exposing delegated agent work, including attribution, nesting, parallel execution, and lifecycle events.
Run outcomes and token usage — explicit semantics for how runs finish and how model usage is reported.
Forward compatibility — clearly defined behavior that allows the protocol to evolve while remaining tolerant of older implementations.
Capabilities that have long been part of AG-UI — including streamed messages and tool calls, shared state, reasoning, and activity events — are now covered by the same formal specification as well.
A shared JSON Schema
AG-UI 1.0 comes with a machine-readable JSON Schema that defines the protocol structure, alongside the human-readable behavioral specification.
The official SDKs are generated from this shared schema, giving implementations across languages and frameworks the same structural foundation. The schema also provides a practical basis for code generation, validation, tooling, and automated compatibility testing.
For teams building AG-UI into production systems, this means the protocol is both precisely documented for humans and directly consumable by tooling.
Backwards compatibility
AG-UI 1.0 is designed to remain highly compatible with existing implementations.
For most users, moving to 1.0 should require little or no change. The specification gives new and existing implementers a precise contract to build against while preserving the flexibility needed for integrations already running in production.
With 1.0, teams can build on AG-UI with a stable specification, predictable versioning, and a clear path for future evolution.
Thank you to everyone who contributed to this release!
We’re excited to continue evolving AG-UI openly with the ecosystem beyond 1.0.
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AG-UI 1.0
Following the draft period and the feedback collected here, AG-UI 1.0 is now officially released and frozen.
→ https://docs.ag-ui.com/spec/1.0
With 1.0, AG-UI now provides a stable, versioned protocol contract. The 1.0 specification will remain unchanged, while future protocol evolution will happen through new draft specifications and open community discussion before each release.
What changed since the draft
Many individuals and contributors helped shape AG-UI 1.0 during the review period, including people building on AG-UI at Anthropic, Google, Microsoft, Pydantic, and TanStack. Their feedback led directly to several improvements in the final release:
outcome: "cancelled".Thank you to everyone who reviewed the draft, raised edge cases, and contributed to making the final specification more complete.
More in AG-UI 1.0
Beyond the changes that came out of the review period, 1.0 also introduces and formalizes several important protocol capabilities:
Capabilities that have long been part of AG-UI — including streamed messages and tool calls, shared state, reasoning, and activity events — are now covered by the same formal specification as well.
A shared JSON Schema
AG-UI 1.0 comes with a machine-readable JSON Schema that defines the protocol structure, alongside the human-readable behavioral specification.
The official SDKs are generated from this shared schema, giving implementations across languages and frameworks the same structural foundation. The schema also provides a practical basis for code generation, validation, tooling, and automated compatibility testing.
For teams building AG-UI into production systems, this means the protocol is both precisely documented for humans and directly consumable by tooling.
Backwards compatibility
AG-UI 1.0 is designed to remain highly compatible with existing implementations.
For most users, moving to 1.0 should require little or no change. The specification gives new and existing implementers a precise contract to build against while preserving the flexibility needed for integrations already running in production.
With 1.0, teams can build on AG-UI with a stable specification, predictable versioning, and a clear path for future evolution.
Thank you to everyone who contributed to this release!
We’re excited to continue evolving AG-UI openly with the ecosystem beyond 1.0.
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