[dotnet-code] Cache agent mode display internals

[github-actions]

Summary

Cache the agent-mode provider's supported-mode display string during construction instead of rebuilding it each time tools are created. This mirrors the .NET provider's stored mode-name display field and keeps future .NET-to-Go ports structurally easier to compare without changing public APIs or behavior.

.NET Reference

• dotnet/src/Microsoft.Agents.AI/Harness/AgentMode/AgentModeProvider.cs - stores _modeNamesDisplay during provider construction and reuses it in tool descriptions and validation errors.

Public API and Behavior

No public Go API changed. No intentional behavior change was made.

Tests

• go test ./agent/harness/agentmode

Notes

Rejected candidates:

• dotnet/src/Microsoft.Agents.AI.Abstractions/AgentSessionStateBagValue.cs overlapped with the existing open PR [dotnet-code] Consolidate portable value delayed decode helper #900.
• dotnet/src/Microsoft.Agents.AI.Workflows/HandoffToolCallFilteringBehavior.cs has no matching Go implementation; adding it would be a feature.
• dotnet/src/Microsoft.Agents.AI.Workflows/Configured.cs did not expose a similarly small, behavior-preserving Go cleanup after comparison with workflow executor internals.

Generated by .NET-to-Go Code Portability Refactoring Agent · gpt55 · 78.8 AIC · ⌖ 15.8 AIC · ⊞ 23.2K · ◷

---

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The changes have been pushed to branch dotnet-code-agentmode-display-1787697166-0d28664376ddac17.

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Show patch preview (90 of 90 lines)

From 37f098b92bf12b8171b81271b0a0da6878022e6c Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Tue, 25 Aug 2026 22:32:46 +0000
Subject: [PATCH] Cache agent mode display internals

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 agent/harness/agentmode/agentmode.go | 32 +++++++++++++---------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/agent/harness/agentmode/agentmode.go b/agent/harness/agentmode/agentmode.go
index cfad5f890..46de188be 100644
--- a/agent/harness/agentmode/agentmode.go
+++ b/agent/harness/agentmode/agentmode.go
@@ -130,6 +130,7 @@ func New(cfg Config) *Provider {
 
 	// Validate modes: no empty names, no duplicates.
 	validModes := make(map[string]struct{}, len(modes))
+	modeNames := make([]string, 0, len(modes))
 	for i, m := range modes {
 		if strings.TrimSpace(m.Name) == "" {
 			panic(fmt.Sprintf("agentmode: mode at index %d has an empty name", i))
@@ -138,16 +139,18 @@ func New(cfg Config) *Provider {
 			panic(fmt.Sprintf("agentmode: duplicate mode name %q", m.Name))
 		}
 		validModes[m.Name] = struct{}{}
+		modeNames = append(modeNames, m.Name)
 	}
 	if _, ok := validModes[defaultMode]; !ok {
 		panic(fmt.Sprintf("agentmode: default mode %q is not in the configured modes list", defaultMode))
 	}
 
 	p := &Provider{
-		modes:        modes,
-		defaultMode:  defaultMode,
-		instructions: instructions,
-		validModes:   validModes,
+		modes:            modes,
+		defaultMode:      defaultMode,
+		instructions:     instructions,
+		validModes:       validModes,
+		modeNamesDisplay: strings.Join(modeNames, "\", \""),
 	}
 
 	p.provider = agent.NewContextProvider(agent.ContextProviderConfig{
@@ -160,11 +163,12 @@ func New(cfg Config) *Provider {
 // Provider is an agent mode context provider.
 // Use [New] to create. Provider can be used directly in agent configuration.
 type Provider struct {
-	provider     agent.ContextProvider
-	modes     
... (truncated)

[michelle-clayton-work]

Pull request #927 is linked to this issue and will close it when merged.