search subagent -> fine-tuned model flighting#3864
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bhavyaus merged 12 commits intomicrosoft:mainfrom Feb 20, 2026
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Pull request overview
Updates the search subagent’s model selection/flighting so proxy and non-proxy paths use a single model setting, and improves the subagent’s initial prompt context to help it generate correct absolute paths.
Changes:
- Consolidates search subagent model configuration into
SearchSubagentModel, and passes the chosen model intoProxyAgenticSearchEndpoint. - Switches
SearchSubagentUseAgenticProxyto experiment-based config access and adds a default proxy model (agentic-search-v3). - Adds workspace “current working directory” context to the search subagent prompt and changes
EnableReadFileV2default tofalse.
Reviewed changes
Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| src/platform/endpoint/node/proxyAgenticSearchEndpoint.ts | Accepts model name via constructor parameter instead of reading a separate config key. |
| src/platform/configuration/common/configurationService.ts | Removes the old proxy-model config key, updates search subagent configs, and changes EnableReadFileV2 default to false. |
| src/extension/tools/node/searchSubagentTool.ts | Adds workspace-root “cwd” context into the first user prompt for the subagent. |
| src/extension/prompt/node/searchSubagentToolCallingLoop.ts | Uses experiment-based config for proxy enablement and selects the proxy model from SearchSubagentModel with a default. |
| package.nls.json | Removes deprecated setting description and updates SearchSubagentModel description to reflect new defaulting behavior. |
| package.json | Removes the deprecated agenticProxySearchModelName contributed setting. |
bhavyaus
approved these changes
Feb 20, 2026
TylerLeonhardt
approved these changes
Feb 20, 2026
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Improves the search subagent configuration by consolidating model settings, fixing experiment-based config usage, and enhancing the search subagent prompt with current working directory.
Changes
Consolidated Search Subagent Model Configuration:
Removed the separate AgenticProxySearchModelName config in favor of using SearchSubagentModel for both proxy and non-proxy modes. Also updated ProxyAgenticSearchEndpoint to accept model name as a constructor parameter.
When useAgenticProxy is enabled:
uses SearchSubagentModel if specified
Defaults to 'agentic-search-v3' if not specified
When useAgenticProxy is disabled:
Uses SearchSubagentModel if specified
Falls back to the main agent model if not specified
Fixed Experiment-Based Config Usage
Changed
SearchSubagentUseAgenticProxyto usegetExperimentBasedConfiginstead ofgetConfigto prepare for upcoming custom model flightEnhanced Search Subagent Context
Added current working directory to the search subagent's first user prompt, since the search subagent needs to provide absolute paths for tool calls & its final answer
Disabled ReadFile V2 by Default
Changed EnableReadFileV2 default from isPreRelease to false
This means the readFile tool uses startLine/endLine parameters instead of offset/limit by default
Note: this change was okayed by @connor4312. We needed to change it so that our experiment uses a consistent read file tool between insiders and public