feat: add GitHub Copilot platform support

.trellis/scripts/common/cli_adapter.py

@@ -1,7 +1,7 @@
 """
 CLI Adapter for Multi-Platform Support.
 
-Abstracts differences between Claude Code, OpenCode, Cursor, iFlow, Codex, Kilo, Kiro Code, Gemini CLI, Antigravity, Qoder, and CodeBuddy interfaces.
+Abstracts differences between Claude Code, OpenCode, Cursor, iFlow, Codex, Kilo, Kiro Code, Gemini CLI, Antigravity, Qoder, CodeBuddy, and GitHub Copilot interfaces.
 
 Supported platforms:
 - claude: Claude Code (default)
@@ -15,6 +15,7 @@
 - antigravity: Antigravity (workflow-based)
 - qoder: Qoder
 - codebuddy: CodeBuddy
+- copilot: GitHub Copilot (VS Code)
 
 Usage:
     from common.cli_adapter import CLIAdapter
@@ -45,6 +46,7 @@
     "antigravity",
     "qoder",
     "codebuddy",
+    "copilot",
 ]
 
 
@@ -111,6 +113,8 @@ def config_dir_name(self) -> str:
             return ".qoder"
         elif self.platform == "codebuddy":
             return ".codebuddy"
+        elif self.platform == "copilot":
+            return ".github/copilot"
         else:
             return ".claude"
 
@@ -508,9 +512,10 @@ def get_cli_adapter(platform: str = "claude") -> CLIAdapter:
         "antigravity",
         "qoder",
         "codebuddy",
+        "copilot",
     ):
         raise ValueError(
-            f"Unsupported platform: {platform} (must be 'claude', 'opencode', 'cursor', 'iflow', 'codex', 'kilo', 'kiro', 'gemini', 'antigravity', 'qoder', or 'codebuddy')"
+            f"Unsupported platform: {platform} (must be 'claude', 'opencode', 'cursor', 'iflow', 'codex', 'kilo', 'kiro', 'gemini', 'antigravity', 'qoder', 'codebuddy', or 'copilot')"
         )
 
     return CLIAdapter(platform=platform)  # type: ignore
@@ -529,6 +534,7 @@ def get_cli_adapter(platform: str = "claude") -> CLIAdapter:
     ".agent",
     ".qoder",
     ".codebuddy",
+    ".github/copilot",
 )
 """All platform config directory names (used by detect_platform exclusion checks)."""
 
@@ -581,6 +587,7 @@ def detect_platform(project_root: Path) -> Platform:
         "antigravity",
         "qoder",
         "codebuddy",
+        "copilot",
     ):
         return env_platform  # type: ignore
 
@@ -634,6 +641,10 @@ def detect_platform(project_root: Path) -> Platform:
     if (project_root / ".qoder").is_dir():
         return "qoder"
 
+    # Check for .github/copilot directory (GitHub Copilot-specific)
+    if (project_root / ".github" / "copilot").is_dir():
+        return "copilot"
+
     return "claude"
 
 

packages/cli/src/cli/index.ts

@@ -72,6 +72,7 @@ program
   .option("--windsurf", "Include Windsurf workflows")
   .option("--qoder", "Include Qoder commands")
   .option("--codebuddy", "Include CodeBuddy commands")
+  .option("--copilot", "Include GitHub Copilot hooks")
   .option("-y, --yes", "Skip prompts and use defaults")
   .option(
     "-u, --user <name>",

packages/cli/src/commands/init.ts

@@ -362,6 +362,7 @@ interface InitOptions {
   windsurf?: boolean;
   qoder?: boolean;
   codebuddy?: boolean;
+  copilot?: boolean;
   yes?: boolean;
   user?: string;
   force?: boolean;

packages/cli/src/configurators/copilot.ts

@@ -0,0 +1,31 @@
+import path from "node:path";
+import { getAllHooks, getHooksConfig } from "../templates/copilot/index.js";
+import { ensureDir, writeFile } from "../utils/file-writer.js";
+import { resolvePlaceholders } from "./shared.js";
+
+/**
+ * Configure GitHub Copilot by writing:
+ * - .github/copilot/hooks/session-start.py   (hook scripts)
+ * - .github/copilot/hooks.json               (hooks config, tracked by trellis update)
+ * - .github/hooks/trellis.json               (hooks config for VS Code Copilot discovery)
+ */
+export async function configureCopilot(cwd: string): Promise<void> {
+  const copilotRoot = path.join(cwd, ".github", "copilot");
+
+  // Hook scripts → .github/copilot/hooks/
+  const hooksDir = path.join(copilotRoot, "hooks");
+  ensureDir(hooksDir);
+
+  for (const hook of getAllHooks()) {
+    await writeFile(path.join(hooksDir, hook.name), hook.content);
+  }
+
+  // Hooks config → .github/copilot/hooks.json (tracked copy)
+  const resolvedConfig = resolvePlaceholders(getHooksConfig());
+  await writeFile(path.join(copilotRoot, "hooks.json"), resolvedConfig);
+
+  // Hooks config → .github/hooks/trellis.json (VS Code Copilot discovery)
+  const githubHooksDir = path.join(cwd, ".github", "hooks");
+  ensureDir(githubHooksDir);
+  await writeFile(path.join(githubHooksDir, "trellis.json"), resolvedConfig);
+}

packages/cli/src/configurators/index.ts

@@ -30,6 +30,7 @@ import { configureAntigravity } from "./antigravity.js";
 import { configureWindsurf } from "./windsurf.js";
 import { configureQoder } from "./qoder.js";
 import { configureCodebuddy } from "./codebuddy.js";
+import { configureCopilot } from "./copilot.js";
 
 // Shared utilities
 import { resolvePlaceholders } from "./shared.js";
@@ -63,6 +64,10 @@ import { getAllWorkflows as getAntigravityWorkflows } from "../templates/antigra
 import { getAllWorkflows as getAllWindsurfWorkflows } from "../templates/windsurf/index.js";
 import { getAllSkills as getQoderSkills } from "../templates/qoder/index.js";
 import { getAllCommands as getCodebuddyCommands } from "../templates/codebuddy/index.js";
+import {
+  getAllHooks as getCopilotHooks,
+  getHooksConfig as getCopilotHooksConfig,
+} from "../templates/copilot/index.js";
 
 // =============================================================================
 // Platform Functions Registry
@@ -241,6 +246,22 @@ const PLATFORM_FUNCTIONS: Record<AITool, PlatformFunctions> = {
       return files;
     },
   },
+  copilot: {
+    configure: configureCopilot,
+    collectTemplates: () => {
+      const files = new Map<string, string>();
+      for (const hook of getCopilotHooks()) {
+        files.set(`.github/copilot/hooks/${hook.name}`, hook.content);
+      }
+      // Note: .github/hooks/trellis.json is also written by configureCopilot
+      // for VS Code Copilot discovery, but tracked here under configDir
+      files.set(
+        ".github/copilot/hooks.json",
+        resolvePlaceholders(getCopilotHooksConfig()),
+      );
+      return files;
+    },
+  },
 };
 
 // =============================================================================

packages/cli/src/templates/copilot/hooks.json

@@ -0,0 +1,11 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "type": "command",
+        "command": "{{PYTHON_CMD}} .github/copilot/hooks/session-start.py",
+        "timeout": 10
+      }
+    ]
+  }
+}

packages/cli/src/templates/copilot/hooks/session-start.py

@@ -0,0 +1,218 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Copilot Session Start Hook - Inject Trellis context into VS Code Copilot sessions.
+
+Output format follows Copilot hook protocol:
+  stdout JSON → { hookSpecificOutput: { hookEventName: "SessionStart", additionalContext: "..." } }
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import subprocess
+import sys
+import warnings
+from io import StringIO
+from pathlib import Path
+
+warnings.filterwarnings("ignore")
+
+
+def should_skip_injection() -> bool:
+    return os.environ.get("COPILOT_NON_INTERACTIVE") == "1"
+
+
+def read_file(path: Path, fallback: str = "") -> str:
+    try:
+        return path.read_text(encoding="utf-8")
+    except (FileNotFoundError, PermissionError):
+        return fallback
+
+
+def run_script(script_path: Path) -> str:
+    try:
+        env = os.environ.copy()
+        env["PYTHONIOENCODING"] = "utf-8"
+        cmd = [sys.executable, "-W", "ignore", str(script_path)]
+        result = subprocess.run(
+            cmd,
+            capture_output=True,
+            text=True,
+            encoding="utf-8",
+            errors="replace",
+            timeout=5,
+            cwd=str(script_path.parent.parent.parent),
+            env=env,
+        )
+        return result.stdout if result.returncode == 0 else "No context available"
+    except (subprocess.TimeoutExpired, FileNotFoundError, PermissionError):
+        return "No context available"
+
+
+def _normalize_task_ref(task_ref: str) -> str:
+    normalized = task_ref.strip()
+    if not normalized:
+        return ""
+
+    path_obj = Path(normalized)
+    if path_obj.is_absolute():
+        return str(path_obj)
+
+    normalized = normalized.replace("\\", "/")
+    while normalized.startswith("./"):
+        normalized = normalized[2:]
+
+    if normalized.startswith("tasks/"):
+        return f".trellis/{normalized}"
+
+    return normalized
+
+
+def _resolve_task_dir(trellis_dir: Path, task_ref: str) -> Path:
+    normalized = _normalize_task_ref(task_ref)
+    path_obj = Path(normalized)
+    if path_obj.is_absolute():
+        return path_obj
+    if normalized.startswith(".trellis/"):
+        return trellis_dir.parent / path_obj
+    return trellis_dir / "tasks" / path_obj
+
+
+def _get_task_status(trellis_dir: Path) -> str:
+    current_task_file = trellis_dir / ".current-task"
+    if not current_task_file.is_file():
+        return "Status: NO ACTIVE TASK\nNext: Describe what you want to work on"
+
+    task_ref = _normalize_task_ref(current_task_file.read_text(encoding="utf-8").strip())
+    if not task_ref:
+        return "Status: NO ACTIVE TASK\nNext: Describe what you want to work on"
+
+    task_dir = _resolve_task_dir(trellis_dir, task_ref)
+    if not task_dir.is_dir():
+        return f"Status: STALE POINTER\nTask: {task_ref}\nNext: Task directory not found. Run: python3 ./.trellis/scripts/task.py finish"
+
+    task_json_path = task_dir / "task.json"
+    task_data: dict = {}
+    if task_json_path.is_file():
+        try:
+            task_data = json.loads(task_json_path.read_text(encoding="utf-8"))
+        except (json.JSONDecodeError, PermissionError):
+            pass
+
+    task_title = task_data.get("title", task_ref)
+    task_status = task_data.get("status", "unknown")
+
+    if task_status == "completed":
+        return f"Status: COMPLETED\nTask: {task_title}\nNext: Archive with `python3 ./.trellis/scripts/task.py archive {task_dir.name}` or start a new task"
+
+    has_context = False
+    for jsonl_name in ("implement.jsonl", "check.jsonl", "spec.jsonl"):
+        jsonl_path = task_dir / jsonl_name
+        if jsonl_path.is_file() and jsonl_path.stat().st_size > 0:
+            has_context = True
+            break
+
+    has_prd = (task_dir / "prd.md").is_file()
+
+    if not has_prd:
+        return f"Status: NOT READY\nTask: {task_title}\nMissing: prd.md not created\nNext: Write PRD, then research → init-context → start"
+
+    if not has_context:
+        return f"Status: NOT READY\nTask: {task_title}\nMissing: Context not configured (no jsonl files)\nNext: Complete Phase 2 (research → init-context → start) before implementing"
+
+    return f"Status: READY\nTask: {task_title}\nNext: Continue with implement or check"
+
+
+def main() -> None:
+    if should_skip_injection():
+        sys.exit(0)
+
+    # Read hook input from stdin
+    try:
+        hook_input = json.loads(sys.stdin.read())
+        project_dir = Path(hook_input.get("cwd", ".")).resolve()
+    except (json.JSONDecodeError, KeyError):
+        project_dir = Path(".").resolve()
+
+    trellis_dir = project_dir / ".trellis"
+
+    output = StringIO()
+
+    output.write("""<session-context>
+You are starting a new session in a Trellis-managed project.
+Read and follow all instructions below carefully.
+</session-context>
+
+""")
+
+    output.write("<current-state>\n")
+    context_script = trellis_dir / "scripts" / "get_context.py"
+    output.write(run_script(context_script))
+    output.write("\n</current-state>\n\n")
+
+    output.write("<workflow>\n")
+    workflow_content = read_file(trellis_dir / "workflow.md", "No workflow.md found")
+    output.write(workflow_content)
+    output.write("\n</workflow>\n\n")
+
+    output.write("<guidelines>\n")
+    output.write("**Note**: The guidelines below are index files — they list available guideline documents and their locations.\n")
+    output.write("During actual development, you MUST read the specific guideline files listed in each index's Pre-Development Checklist.\n\n")
+
+    spec_dir = trellis_dir / "spec"
+    if spec_dir.is_dir():
+        for sub in sorted(spec_dir.iterdir()):
+            if not sub.is_dir() or sub.name.startswith("."):
+                continue
+
+            if sub.name == "guides":
+                index_file = sub / "index.md"
+                if index_file.is_file():
+                    output.write(f"## {sub.name}\n")
+                    output.write(read_file(index_file))
+                    output.write("\n\n")
+                continue
+
+            index_file = sub / "index.md"
+            if index_file.is_file():
+                output.write(f"## {sub.name}\n")
+                output.write(read_file(index_file))
+                output.write("\n\n")
+            else:
+                for nested in sorted(sub.iterdir()):
+                    if not nested.is_dir():
+                        continue
+                    nested_index = nested / "index.md"
+                    if nested_index.is_file():
+                        output.write(f"## {sub.name}/{nested.name}\n")
+                        output.write(read_file(nested_index))
+                        output.write("\n\n")
+
+    output.write("</guidelines>\n\n")
+
+    task_status = _get_task_status(trellis_dir)
+    output.write(f"<task-status>\n{task_status}\n</task-status>\n\n")
+
+    output.write("""<ready>
+Context loaded. Steps 1-3 (workflow, context, guidelines) are already injected above — do NOT re-read them.
+Start from Step 4. Wait for user's first message, then follow the workflow to handle their request.
+If there is an active task, ask whether to continue it.
+</ready>""")
+
+    context = output.getvalue()
+    result = {
+        "suppressOutput": True,
+        "systemMessage": f"Trellis context injected ({len(context)} chars)",
+        "hookSpecificOutput": {
+            "hookEventName": "SessionStart",
+            "additionalContext": context,
+        },
+    }
+
+    print(json.dumps(result, ensure_ascii=False), flush=True)
+
+
+if __name__ == "__main__":
+    main()