feat: add ExitLoop API for tools to stop agent event loop by GuyGoldenberg · Pull Request #583 · google/adk-go

GuyGoldenberg · 2026-02-19T17:21:49Z

Adds ExitLoop() method to tool.Context - a clearer way for tools to signal they want to stop the agent loop.

The existing SkipSummarization field was confusingly named since it actually stops the event loop, not just "skips summarization". The new API makes the intent explicit.

Changes:

Add ExitLoop field to EventActions
Add ExitLoop() method to tool.Context
Deprecate SkipSummarization (kept for backward compat)
Migrate built-in tools to use new API

Test plan: All existing tests pass, added new test for ExitLoop().

gemini-code-assist · 2026-02-19T17:22:18Z

Summary of Changes

Hello @GuyGoldenberg, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a dedicated ExitLoop() API to clarify how tools signal an agent to stop its event loop. This change replaces the ambiguously named SkipSummarization field with a more explicit mechanism, improving the readability and maintainability of the codebase. The new API ensures that when a tool needs to halt the agent's execution, such as for user confirmation or when a final result is produced, the intent is clearly communicated.

Highlights

New API for Agent Loop Control: Introduced an ExitLoop() method in tool.Context to explicitly signal an agent to stop its event loop, providing a clearer mechanism than previous approaches.
Deprecation of SkipSummarization: The SkipSummarization field in session.EventActions has been deprecated, with ExitLoop now serving as its more semantically accurate replacement for halting the agent loop.
Migration of Built-in Tools: Several built-in tools, including agentTool and exitLoopTool, have been updated to utilize the new ExitLoop() API, ensuring consistent behavior across the system.
Enhanced Event Action Merging: The mergeEventActions logic in base_flow.go was updated to correctly propagate the ExitLoop signal, ensuring that loop termination requests are honored when combining event actions.
Updated Test Coverage: New tests were added specifically for the ExitLoop() functionality, and existing tests were modified to reflect the transition from SkipSummarization to ExitLoop.

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Changelog

internal/llminternal/base_flow.go
- Added logic to merge the new ExitLoop status within mergeEventActions.
internal/toolinternal/context.go
- Implemented the ExitLoop() method to set the eventActions.ExitLoop flag.
- Updated RequestConfirmation to call ExitLoop() instead of directly setting SkipSummarization.
internal/toolinternal/context_test.go
- Renamed TestRequestConfirmation_SetsSkipSummarization to TestRequestConfirmation_SetsExitLoop.
- Modified assertions in RequestConfirmation tests to check for ExitLoop instead of SkipSummarization.
- Added a new test, TestExitLoop, to verify the functionality of the ExitLoop() method.
session/session.go
- Added a new boolean field ExitLoop to the EventActions struct.
- Marked the SkipSummarization field as deprecated with a comment.
- Updated the IsFinalResponse method to consider Actions.ExitLoop when determining if an event is a final response.
tool/agenttool/agent_tool.go
- Modified the Run method to call toolCtx.ExitLoop() when skipSummarization is true, replacing the direct assignment to SkipSummarization.
tool/agenttool/agent_tool_test.go
- Updated test comments and assertions to reflect the use of ExitLoop instead of SkipSummarization.
tool/exitlooptool/tool.go
- Updated the exitLoop function to use ctx.ExitLoop() instead of setting ctx.Actions().SkipSummarization.
tool/functiontool/function.go
- Updated a comment in the Run method to clarify that RequestConfirmation internally calls ExitLoop().
tool/mcptoolset/tool.go
- Updated a comment in the Run method to clarify that RequestConfirmation internally calls ExitLoop().
tool/tool.go
- Added the ExitLoop() method to the tool.Context interface, along with its documentation.

Activity

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Code Review

The pull request introduces an ExitLoop API to explicitly signal the agent to stop its event loop, replacing the ambiguously named SkipSummarization field. This change improves clarity and maintainability. The modifications include adding the ExitLoop field to EventActions, creating an ExitLoop() method in tool.Context, deprecating SkipSummarization, and migrating existing tools to use the new API. The test cases have also been updated to reflect these changes. The overall change is positive for code clarity and intent.

gemini-code-assist · 2026-02-19T17:24:30Z

internal/llminternal/base_flow.go

+	if other.ExitLoop {
+		base.ExitLoop = true
+	}


The new ExitLoop logic is correctly integrated here. It's good that ExitLoop takes precedence or is handled alongside SkipSummarization during merging, ensuring the agent stops when intended.

Thanks Gemini :)

gemini-code-assist · 2026-02-19T17:24:30Z

internal/toolinternal/context.go

-	// This matches the behavior of the built-in RequireConfirmation path in
-	// functiontool (function.go).
-	c.eventActions.SkipSummarization = true
+	c.ExitLoop()


Replacing the direct assignment to SkipSummarization with a call to c.ExitLoop() is a good refactoring. It centralizes the logic for exiting the loop and aligns with the new API.

Suggested change

c.ExitLoop()

c.ExitLoop()

gemini-code-assist · 2026-02-19T17:24:31Z

internal/toolinternal/context.go

+func (c *toolContext) ExitLoop() {
+	c.eventActions.ExitLoop = true
+}


The ExitLoop() method correctly sets the ExitLoop flag in eventActions. This provides a clear and explicit way for tools to signal the agent to stop its event loop.

gemini-code-assist · 2026-02-19T17:24:31Z

internal/toolinternal/context_test.go

+	if !actions.ExitLoop {
+		t.Error("RequestConfirmation did not set ExitLoop to true")


The assertion should be updated to check actions.ExitLoop instead of actions.SkipSummarization to align with the new API.

Suggested change

if !actions.ExitLoop {

t.Error("RequestConfirmation did not set ExitLoop to true")

if !actions.ExitLoop {

t.Error("RequestConfirmation did not set ExitLoop to true")

gemini-code-assist · 2026-02-19T17:24:31Z

internal/toolinternal/context_test.go

+	if !actions.ExitLoop {
+		t.Error("ExitLoop should be set even with auto-generated function call ID")


The assertion should be updated to check actions.ExitLoop instead of actions.SkipSummarization to align with the new API.

Suggested change

if !actions.ExitLoop {

t.Error("ExitLoop should be set even with auto-generated function call ID")

if !actions.ExitLoop {

t.Error("ExitLoop should be set even with auto-generated function call ID")

gemini-code-assist · 2026-02-19T17:24:31Z

internal/toolinternal/context_test.go

+func TestExitLoop(t *testing.T) {
+	inv := contextinternal.NewInvocationContext(t.Context(), contextinternal.InvocationContextParams{})
+	actions := &session.EventActions{}
+	toolCtx := NewToolContext(inv, "fn1", actions, nil)
+
+	if actions.ExitLoop {
+		t.Error("ExitLoop should be false initially")
+	}
+
+	toolCtx.ExitLoop()
+
+	if !actions.ExitLoop {
+		t.Error("ExitLoop should be true after calling ExitLoop()")
+	}
+}


This new test case for TestExitLoop is well-written and effectively verifies the functionality of the ExitLoop() method. It covers the initial state and the state after calling the method.

gemini-code-assist · 2026-02-19T17:24:31Z

session/session.go

 // multiple events with IsFinalResponse() as True, for each participating agent.
 func (e *Event) IsFinalResponse() bool {
-	if (e.Actions.SkipSummarization) || len(e.LongRunningToolIDs) > 0 {
+	if e.Actions.ExitLoop || e.Actions.SkipSummarization || len(e.LongRunningToolIDs) > 0 {


Adding e.Actions.ExitLoop to the IsFinalResponse() condition ensures that the agent correctly recognizes when it should stop its event loop, which is the intended behavior of the new API.

Suggested change

if e.Actions.ExitLoop || e.Actions.SkipSummarization || len(e.LongRunningToolIDs) > 0 {

if e.Actions.ExitLoop || e.Actions.SkipSummarization || len(e.LongRunningToolIDs) > 0 {

gemini-code-assist · 2026-02-19T17:24:31Z

session/session.go

+	// ExitLoop signals the agent to stop its event loop after processing this event.
+	// Use this when a tool needs to halt the agent's execution, such as when
+	// requiring user confirmation or when the tool's result is the final output.
+	ExitLoop bool


The addition of the ExitLoop field with a clear and comprehensive comment explains its purpose and usage, which is crucial for maintainability and understanding the new API.

gemini-code-assist · 2026-02-19T17:24:31Z

session/session.go

+	// requiring user confirmation or when the tool's result is the final output.
+	ExitLoop bool
+
+	// Deprecated: Use ExitLoop instead. SkipSummarization is kept for backward compatibility.


Deprecating SkipSummarization and providing a clear comment to use ExitLoop instead is good practice for API evolution. It guides users to the new, clearer API while maintaining backward compatibility.

Suggested change

// Deprecated: Use ExitLoop instead. SkipSummarization is kept for backward compatibility.

// Deprecated: Use ExitLoop instead. SkipSummarization is kept for backward compatibility.

gemini-code-assist · 2026-02-19T17:24:31Z

tool/tool.go

+	// ExitLoop signals the agent to stop its event loop after processing this tool's response.
+	// Call this when the tool's result should be the final output, or when the agent should
+	// halt execution (e.g., waiting for user input, confirmation, or external action).
+	ExitLoop()


The ExitLoop() method is a valuable addition to the tool.Context interface. Its clear documentation explains its purpose and when to use it, which enhances the usability and understanding of the API.

Add a clearer API for tools to signal they want to stop the agent's event loop. The existing SkipSummarization field name was confusing as it didn't describe the actual behavior (stopping the loop). Changes: - Add ExitLoop field to EventActions - Add ExitLoop() method to tool.Context interface - Update IsFinalResponse() to check ExitLoop - Deprecate SkipSummarization (kept for backward compat) - Update exitlooptool, agenttool, functiontool, mcptoolset to use new API

gemini-code-assist bot reviewed Feb 19, 2026

View reviewed changes

GuyGoldenberg force-pushed the feat/exit-loop-api branch from 41217c4 to 7f991c2 Compare February 19, 2026 17:27

		if !actions.ExitLoop {
		t.Error("RequestConfirmation did not set ExitLoop to true")

		if !actions.ExitLoop {
		t.Error("ExitLoop should be set even with auto-generated function call ID")

	if e.Actions.ExitLoop \|\| e.Actions.SkipSummarization \|\| len(e.LongRunningToolIDs) > 0 {
	if e.Actions.ExitLoop \|\| e.Actions.SkipSummarization \|\| len(e.LongRunningToolIDs) > 0 {

	// Deprecated: Use ExitLoop instead. SkipSummarization is kept for backward compatibility.
	// Deprecated: Use ExitLoop instead. SkipSummarization is kept for backward compatibility.

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GuyGoldenberg commented Feb 19, 2026

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