chat: lazy-load final tool input

[roblourens]

Summary

• make partial arguments and invocation-message updates independently optional on chat/toolCallDelta, so hosts may send either or both
• let hosts choose inline strings or ContentRef values for final toolInput
• keep edited input action-only: reducers replace inline input, while referenced input is updated by the host before echoing confirmation
• regenerate schemas and all five clients, with cross-language reducer fixtures

Validation

• npm run test (354 tests, 100% reducer coverage)
• TypeScript client typecheck and tests (65 tests)
• Rust formatting, Clippy, workspace tests, and doc tests
• Swift package tests (115 tests)
• Kotlin Gradle tests
• Go tests
• second npm run generate pass and git diff --check

(Written by Copilot)

[Copilot]

Pull request overview

Note

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Updates the chat tool-call protocol to avoid streaming raw tool parameters via deltas and instead expose the final tool input as a lazy-loaded ContentRef, while keeping streaming invocation-message updates available to subscribers.

Changes:

• Replace chat/toolCallDelta parameter chunk streaming with invocation-message-only updates.
• Change tool input from inline string to ContentRef across state/actions/schemas and regenerate all clients.
• Update reducer fixtures and docs to reflect the new lazy-load + edited-input host-rewrite model.

Show a summary per file

File	Description
types/test-cases/reducers/260-edited-tool-input-survives-reconfirmation.json	Adds fixture ensuring tool input ref persists across re-confirmation after edited confirmation.
types/test-cases/reducers/255-toolcallcomplete-ignores-requiresresultconfirmation-when-cancelling-auth-required.json	Updates fixtures to use ContentRef for tool input and formatting adjustments.
types/test-cases/reducers/254-toolcallcomplete-ignores-successful-result-from-auth-required.json	Updates fixtures to use ContentRef for tool input and formatting adjustments.
types/test-cases/reducers/253-toolcallcomplete-cancels-auth-required-tool-call.json	Updates fixtures to use ContentRef for tool input and formatting adjustments.
types/test-cases/reducers/252-session-inputneededremoved-removes-tool-authentication.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/251-session-inputneededset-appends-tool-authentication.json	Updates fixture tool input to ContentRef and reformats nested JSON arrays/objects.
types/test-cases/reducers/250-turncomplete-force-cancels-auth-required-tool-call.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/249-toolcallauthresolved-preserves-fields-and-clears-input-needed.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/248-toolcallauthrequired-sets-input-needed-status-and-preserves-metadata.json	Updates fixture tool input to ContentRef and formatting adjustments.
types/test-cases/reducers/247-toolcallauthresolved-noop-when-not-auth-required.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/243-toolcallauthrequired-full-lifecycle-running-authrequired-running-completed.json	Updates fixture tool input to ContentRef and formatting adjustments.
types/test-cases/reducers/242-toolcallready-completes-risk-assessment.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/220-toolcall-actions-update-meta.json	Removes delta content/partialInput expectations and updates tool input to ContentRef.
types/test-cases/reducers/163-toolcallstart-carries-mcp-contributor-through-lifecycle.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/158-toolcallconfirmed-approved-with-editedtoolinput-overrides-original.json	Adjusts fixture semantics for host-handled edited input; tool input becomes ContentRef.
types/test-cases/reducers/111-toolcall-pending-confirmation-sets-input-needed-status.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/101-toolcalldelta-without-invocationmessage.json	Updates delta fixture to invocation-message-only behavior.
types/test-cases/reducers/100-delta-targeting-toolcall-partid-is-no-op.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/099-endturn-force-cancels-running-tool-call.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/098-toolcallresultconfirmed-wrong-status-is-no-op.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/097-toolcallcomplete-wrong-status-is-no-op.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/096-toolcallconfirmed-wrong-status-is-no-op.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/095-toolcalldelta-wrong-status-is-no-op.json	Updates delta fixture to invocation-message-only behavior and tool input to ContentRef.
types/test-cases/reducers/090-toolcalldelta-wrong-turnid-is-no-op.json	Updates delta fixture to invocation-message-only behavior.
types/test-cases/reducers/086-toolcall-contentchanged-replaces-existing.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/085-toolcall-contentchanged-noop-non-running.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/084-toolcall-contentchanged-updates-running.json	Updates fixture tool input to ContentRef.
types/test-cases/reducers/025-tool-call-actions-for-unknown-toolcallid-are-no-op.json	Updates delta fixture to invocation-message-only behavior.
types/test-cases/reducers/019-tool-call-full-lifecycle-start-delta-ready-confirmed-complete.json	Removes delta content streaming and uses ContentRef for ready/final input.
types/channels-chat/state.ts	Switches tool input to ContentRef and removes partialInput from streaming state.
types/channels-chat/reducer.ts	Updates reducer logic for invocation-message-only deltas and preserves tool input ref across confirmation.
types/channels-chat/actions.ts	Changes delta action shape (remove content, require invocationMessage) and updates tool input type to ContentRef.
scripts/generate-swift.ts	Updates generated SnapshotState doc string to include content state.
scripts/generate-rust.ts	Updates generated SnapshotState doc string and adds ContentRef to generated action imports.
scripts/generate-markdown.ts	Formatting-only whitespace adjustments in markdown generator.
scripts/generate-kotlin.ts	Updates generated SnapshotState doc string to include content state.
scripts/generate-go.ts	Updates generated SnapshotState doc string to include content state.
schema/state.schema.json	Updates tool input schema to ContentRef and removes partialInput from streaming tool-call state.
schema/notifications.schema.json	Mirrors state schema changes for notifications (tool input as ContentRef, remove partialInput).
schema/errors.schema.json	Mirrors action/state schema changes for errors (delta requires invocationMessage, tool input ContentRef).
schema/commands.schema.json	Mirrors action/state schema changes for commands (delta requires invocationMessage, tool input ContentRef).
schema/actions.schema.json	Updates action schema for tool-call delta (remove content, require invocationMessage) and tool input to ContentRef.
docs/guide/state-model.md	Documents lazy ContentRef tool input and invocation-message-only deltas; updates editable-input flow.
docs/guide/customizations.md	Updates customizations guide sequence to reflect invocation-message deltas and tool input refs.
docs/guide/actions.md	Updates tool-call delta description to reflect invocation-message-only semantics.
docs/.changes/20260730-tool-input-content-ref.json	Adds changelog entry describing tool input ref and new delta semantics.
clients/typescript/test/hosts.test.ts	Formatting-only whitespace adjustment.
clients/typescript/src/client/state-mirror.ts	Formatting-only whitespace adjustment.
clients/typescript/src/client/hosts/state-mirror.ts	Formatting-only whitespace adjustment.
clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/ToolCallStateExtensions.swift	Extends base-field extraction to include toolInput: ContentRef?.
clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Reducers.swift	Updates Swift reducer for invocation-message-only deltas and ContentRef tool input.
clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift	Regenerates Swift state types (remove partialInput, tool input as ContentRef).
clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/Actions.generated.swift	Regenerates Swift action types (delta invocationMessage required, tool input as ContentRef).
clients/swift/AHPApp/AHPApp/Views/ResponsePartView.swift	Updates Swift UI to display tool input via ContentRef.uri and removes partialInput use.
clients/swift/AHPApp/AHPApp/Views/ChatView.swift	Updates preview/sample tool calls to use ContentRef.
clients/rust/crates/ahp/src/reducers.rs	Updates Rust reducer to remove partial input accumulation and propagate ContentRef tool input.
clients/rust/crates/ahp-types/src/state.rs	Regenerates Rust state types (remove partial_input, tool input as ContentRef).
clients/rust/crates/ahp-types/src/actions.rs	Regenerates Rust action types (delta invocation_message required, tool_input as ContentRef).
clients/kotlin/src/test/kotlin/com/microsoft/agenthostprotocol/FixtureDrivenReducerTest.kt	Formatting-only whitespace adjustment.
clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt	Regenerates Kotlin state types (remove partialInput, tool input as ContentRef).
clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/Actions.generated.kt	Regenerates Kotlin action types (delta invocationMessage required, tool input as ContentRef).
clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/Reducers.kt	Updates Kotlin reducer to remove partial input accumulation and propagate ContentRef tool input.
clients/go/ahptypes/state.generated.go	Regenerates Go state types (remove PartialInput, tool input as *ContentRef).
clients/go/ahptypes/actions.generated.go	Regenerates Go action types (delta InvocationMessage required, tool input as *ContentRef).
clients/go/ahp/reducers.go	Updates Go reducer to remove partial input accumulation and propagate *ContentRef tool input.

Review details

• Files reviewed: 61/65 changed files
• Comments generated: 2
• Review effort level: Lite

[connor4312]

Thoughts on allowing this to be a string | ContentRef and leaving it to the host to decide?

[roblourens]

How would a host decide one way or another?

[roblourens]

It seems like it would be the client that cares- based on whether it wants to render raw tool args, or whether it is very bandwidth-sensitive

[roblourens]

Updated this to string | ContentRef, with the host choosing the representation. I also restored optional partial argument chunks on chat/toolCallDelta; invocationMessage remains required. (Written by Copilot)

[connor4312]

@roblourens streaming tool input is used for MCP apps to progressive rendering (e.g. in Claude https://claude.com/blog/claude-builds-visuals at 0:30 in their video; FastMCP supports this too) so I'm not sure we should just remove the ability.

[roblourens]

Ah, so for some types of tools it's unavoidable and we want the host to decide that? Makes sense