fix: make initial prompt preservation conditional on power-steering feature

[roomote]

Summary

This PR fixes issue #8093 by making the initial prompt preservation in context condensing conditional on the experimental power-steering feature being enabled.

Problem

Previously, context condensing always preserved the initial prompt/first message, which caused tasks to be restarted unnecessarily when the preserved initial prompt was reintroduced after condensing.

Solution

• Added a powerSteeringEnabled parameter to the summarizeConversation function
• The function now only preserves the first message when power steering is enabled
• Updated all callers to check the power steering experiment flag and pass the appropriate value
• Updated tests to handle the new parameter

Changes

• src/core/condense/index.ts: Added conditional logic for first message preservation
• src/core/task/Task.ts: Checks power steering flag before condensing
• src/core/sliding-window/index.ts: Propagates the flag through truncation logic
• Test files: Updated to explicitly pass the powerSteeringEnabled parameter

Testing

• All existing tests pass
• Tests verify both enabled and disabled states of the feature
• No breaking changes for existing functionality

Fixes #8093

---

Important

Make initial prompt preservation in context condensing conditional on the power-steering feature being enabled.

• Behavior:
  • summarizeConversation function now includes a powerSteeringEnabled parameter to conditionally preserve the first message.
  • Updates in Task.ts and sliding-window/index.ts to check the power steering flag before condensing.
• Tests:
  • Test cases in condense.spec.ts, index.spec.ts, and sliding-window.spec.ts updated to handle the powerSteeringEnabled parameter.
• Misc:
  • Propagates the power steering flag through truncation logic in sliding-window/index.ts.
  • Checks for power steering feature in Task.ts using experiments.isEnabled.

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[roomote]

Reviewing my own code because apparently I trust no one, not even myself.

[roomote]

Is this intentional? The parameter defaults to undefined but is used as a boolean. Consider explicitly defaulting to false for clarity:

Suggested change

	powerSteeringEnabled?: boolean,
	export async function summarizeConversation(
	messages: ApiMessage[],
	apiHandler: ApiHandler,
	systemPrompt: string,
	taskId: string,
	prevContextTokens: number,
	isAutomaticTrigger?: boolean,
	customCondensingPrompt?: string,
	condensingApiHandler?: ApiHandler,
	powerSteeringEnabled: boolean = false,
	): Promise<SummarizeResponse> {

[roomote]

Could we simplify this logic for better readability?

Suggested change

	const firstMessage = powerSteeringEnabled ? messages[0] : undefined
	// Conditionally preserve the first message based on power steering setting
	// When power steering is enabled, preserve the initial prompt to maintain task context
	// When disabled, don't preserve it to prevent task restarts after condensing
	const preserveFirstMessage = powerSteeringEnabled ?? false
	const firstMessage = preserveFirstMessage ? messages[0] : undefined
	const messagesToKeepFrom = preserveFirstMessage ? 1 : 0

This makes the boolean logic more explicit and easier to follow.

[roomote]

The JSDoc could be more explicit about the behavioral difference. Consider adding:

Suggested change

	* @param {boolean} powerSteeringEnabled - Whether power steering is enabled (controls initial prompt preservation)
	* @param {boolean} powerSteeringEnabled - Whether power steering is enabled (controls initial prompt preservation).
	* When true: preserves the first message to maintain task context.
	* When false: excludes first message to prevent task restarts after condensing.

[roomote]

Consider adding edge case tests:

1. Test behavior when powerSteeringEnabled is explicitly undefined
2. Test with empty message arrays to ensure no index errors
3. Test with single message to verify boundary conditions

These would help ensure robustness of the first message preservation logic.

[daniel-lxs]

#8093 (comment)