feat: Integrate GitHub Copilot as a first-class provider

- Added GitHub Copilot integration with canonical ID `copilot` using ACP stdio mode.
- Implemented provider identity and contracts in the contracts module.
- Created a new action plan for GitHub Copilot integration detailing phases for implementation.
- Added tests for Copilot provider settings and model selection in server settings.
- Established binary probing and provider registration for Copilot.
- Developed ACP runtime generalization to support Copilot-specific authentication and environment restrictions.
- Implemented Copilot-specific parsing and normalization for tool identity and permissions.
- Updated web integration for provider model/config UI and provider selection.

Author: ronak-guliani

apps/server/scripts/acp-mock-agent.ts

@@ -17,9 +17,14 @@ const emitInterleavedAssistantToolCalls =
   process.env.T3_ACP_EMIT_INTERLEAVED_ASSISTANT_TOOL_CALLS === "1";
 const emitGenericToolPlaceholders = process.env.T3_ACP_EMIT_GENERIC_TOOL_PLACEHOLDERS === "1";
 const emitAskQuestion = process.env.T3_ACP_EMIT_ASK_QUESTION === "1";
+const emitElicitation = process.env.T3_ACP_EMIT_ELICITATION === "1";
 const failSetConfigOption = process.env.T3_ACP_FAIL_SET_CONFIG_OPTION === "1";
 const exitOnSetConfigOption = process.env.T3_ACP_EXIT_ON_SET_CONFIG_OPTION === "1";
 const promptResponseText = process.env.T3_ACP_PROMPT_RESPONSE_TEXT;
+const authMethods = (process.env.T3_ACP_AUTH_METHODS ?? "")
+  .split(",")
+  .map((method) => method.trim())
+  .filter((method) => method.length > 0);
 const sessionId = "mock-session-1";
 
 let currentModeId = "ask";
@@ -217,6 +222,14 @@ const program = Effect.gen(function* () {
       return {
         protocolVersion: 1,
         agentCapabilities: { loadSession: true },
+        ...(authMethods.length > 0
+          ? {
+              authMethods: authMethods.map((id) => ({
+                id,
+                name: id,
+              })),
+            }
+          : {}),
       };
     }),
   );
@@ -285,6 +298,20 @@ const program = Effect.gen(function* () {
     }),
   );
 
+  yield* agent.handleSetSessionMode((request) =>
+    Effect.gen(function* () {
+      currentModeId = request.modeId;
+      yield* agent.client.sessionUpdate({
+        sessionId: String(request.sessionId ?? sessionId),
+        update: {
+          sessionUpdate: "current_mode_update",
+          currentModeId,
+        },
+      });
+      return {};
+    }),
+  );
+
   yield* agent.handleCancel(({ sessionId }) =>
     Effect.sync(() => {
       cancelledSessions.add(String(sessionId ?? "mock-session-1"));
@@ -484,6 +511,35 @@ const program = Effect.gen(function* () {
         return { stopReason: "end_turn" };
       }
 
+      if (emitElicitation) {
+        yield* agent.client.elicit({
+          sessionId: requestedSessionId,
+          mode: "form",
+          message: "Choose deployment options",
+          requestedSchema: {
+            type: "object",
+            title: "Deployment",
+            properties: {
+              environment: {
+                type: "string",
+                title: "Environment",
+                description: "Which environment should Copilot use?",
+                enum: ["staging", "production"],
+              },
+              runChecks: {
+                type: "boolean",
+                title: "Run checks",
+                description: "Run validation before deploy?",
+                default: true,
+              },
+            },
+            required: ["environment"],
+          },
+        });
+
+        return { stopReason: "end_turn" };
+      }
+
       yield* agent.client.sessionUpdate({
         sessionId: requestedSessionId,
         update: {

apps/server/src/git/Services/TextGeneration.ts

@@ -13,7 +13,7 @@ import type { ChatAttachment, ModelSelection } from "@t3tools/contracts";
 import type { TextGenerationError } from "@t3tools/contracts";
 
 /** Providers that support git text generation (commit messages, PR content, branch names). */
-export type TextGenerationProvider = "codex" | "claudeAgent" | "cursor" | "opencode";
+export type TextGenerationProvider = "codex" | "claudeAgent" | "cursor" | "copilot" | "opencode";
 
 export interface CommitMessageGenerationInput {
   cwd: string;

apps/server/src/orchestration/Layers/ProviderCommandReactor.ts

@@ -309,6 +309,9 @@ const make = Effect.gen(function* () {
         ...(preferredProvider ? { provider: preferredProvider } : {}),
         ...(effectiveCwd ? { cwd: effectiveCwd } : {}),
         modelSelection: desiredModelSelection,
+        ...(thread.interactionMode !== undefined
+          ? { interactionMode: thread.interactionMode }
+          : {}),
         ...(input?.resumeCursor !== undefined ? { resumeCursor: input.resumeCursor } : {}),
         runtimeMode: desiredRuntimeMode,
       });