Phase 3 of 13

Phase 3: Tech Stack

Tech Stack complete — 4 languages, 4 build systems, 4 test frameworks, unified codegen pipeline.

1. Languages & Versions

TypeScript

ES2022

Target, strict mode

Python

>=3.11

Classifiers through 3.14

1.24

Standard toolchain

C# 14

.NET 8

SDK 10, LangVersion 14

Language	Version Constraint	Evidence
TypeScript	ES2022 target, strict mode	nodejs/tsconfig.json:3-4 — `"target": "ES2022", "module": "ES2022"`
Node.js	`>=20.0.0` (CI uses Node 22)	nodejs/package.json:69 — `"node": ">=20.0.0"`
Python	`>=3.11` (classifiers through 3.14)	python/pyproject.toml:10 — `requires-python = ">=3.11"`
Go	1.24	go/go.mod:3 — `go 1.24`
C#	Language version 14 (.NET 8 TFM, .NET SDK 10)	dotnet/Directory.Build.props:4-5 — `<TargetFramework>net8.0</TargetFramework>` / `<LangVersion>14</LangVersion>`

Language Distribution

TypeScript Primary SDK + Codegen scripts

Python SDK + Async support

Go SDK + Stdlib approach

C# SDK + AOT compatible

2. Runtime Dependencies (per SDK)

2.1 Node.js SDK

Source: nodejs/package.json:46-49

Package	Version	Purpose
`@github/copilot`	`^1.0.3-0`	GitHub Copilot CLI binary — the process the SDK drives over JSON-RPC
`vscode-jsonrpc`	`^8.2.1`	JSON-RPC 2.0 protocol implementation for bidirectional stdio communication
`zod`	`^4.3.6`	Runtime schema validation and type-safe parsing of JSON-RPC messages

2.2 Python SDK

Source: python/pyproject.toml:25-28

Package	Version	Purpose
`python-dateutil`	`>=2.9.0.post0`	Date/time parsing for protocol timestamps
`pydantic`	`>=2.0`	Data validation and settings management via dataclass-style models

2.3 Go SDK

Source: go/go.mod:5-10

Package	Version	Purpose
`github.com/google/jsonschema-go`	`v0.4.2`	JSON Schema generation from Go types (for tool parameter schemas)
`github.com/klauspost/compress`	`v1.18.3`	High-performance compression
`github.com/google/uuid`	`v1.6.0`	UUID generation for request IDs and correlation tokens

2.4 .NET SDK

Source: dotnet/src/GitHub.Copilot.SDK.csproj:33-38, dotnet/Directory.Packages.props:8-14

Package	Version	Purpose
`Microsoft.Extensions.AI.Abstractions`	`10.2.0`	AI model abstractions (IChatClient, etc.)
`Microsoft.Extensions.Logging.Abstractions`	`10.0.2`	Logging abstractions
`StreamJsonRpc`	`2.24.84`	Microsoft's JSON-RPC 2.0 over streams (stdio)
`System.Text.Json`	`10.0.2`	High-performance JSON serialization
`Microsoft.SourceLink.GitHub`	`10.0.102`	Source file links in PDB symbols

3. Dev Dependencies (per SDK)

3.1 Node.js SDK

Source: nodejs/package.json:51-67

Package	Version	Purpose
`esbuild`	`^0.27.2`	Ultra-fast JS/TS bundler
`eslint`	`^9.0.0`	Linting
`@typescript-eslint/*`	`^8.54.0`	TypeScript ESLint rules/parser
`prettier`	`^3.8.1`	Code formatter
`vitest`	`^4.0.18`	Test framework
`typescript`	`^5.0.0`	Compiler
`tsx`	`^4.20.6`	TypeScript execution engine
`json-schema-to-typescript`	`^15.0.4`	Codegen: JSON Schema → TS interfaces
`quicktype-core`	`^23.2.6`	Multi-language type generation
`rimraf`	`^6.1.2`	Cross-platform rm -rf
`semver`	`^7.7.3`	Version management

3.2 Python SDK

Source: python/pyproject.toml:34-42

Package	Version	Purpose
`ruff`	`>=0.1.0`	Fast linter + formatter
`ty`	`>=0.0.2`	Type checking
`pytest`	`>=7.0.0`	Test framework
`pytest-asyncio`	`>=0.21.0`	Async test support
`pytest-timeout`	`>=2.0.0`	Test timeouts
`httpx`	`>=0.24.0`	Async HTTP client (test infra)

3.3 .NET SDK (Test Project)

Source: dotnet/test/GitHub.Copilot.SDK.Test.csproj:17-29

Package	Version	Purpose
`xunit`	`2.9.3`	Test framework
`xunit.runner.visualstudio`	`3.1.5`	Test runner adapter
`Microsoft.NET.Test.Sdk`	`18.3.0`	Test SDK
`coverlet.collector`	`6.0.4`	Code coverage

4. Build Tools & Systems

4.1 Monorepo Task Runner — `just`

Source: justfile:1-230

just is the top-level task runner with unified recipes:

Recipe	Actions
`just format`	gofmt, ruff format, prettier, dotnet format
`just lint`	golangci-lint, ruff check + ty check, eslint + tsc --noEmit, dotnet format --verify-no-changes
`just test`	go test, pytest, vitest, dotnet test
`just install`	npm ci, uv pip install, go mod download, dotnet restore
`just scenario-build`	Compiles all cross-language scenario samples
`just validate-docs`	Extracts and validates documentation code examples

4.2 Node.js Build: esbuild + tsc

Source: nodejs/esbuild-copilotsdk-nodejs.ts:1-19

esbuild bundles src/**/*.ts → ESM JavaScript (ES2022, Node.js)
tsc generates .d.ts declaration files only (emitDeclarationOnly: true)

4.3 .NET Build: MSBuild/dotnet CLI

.NET SDK 10.0.100 with "rollForward": "major" (dotnet/global.json:3-4)
Target: net8.0, AOT-compatible (<IsAotCompatible>true</IsAotCompatible>)
Central package management enabled
Custom MSBuild target extracts Copilot CLI version from nodejs/package-lock.json

4.4 Python Build: setuptools + wheel

setuptools >=45 + wheel + setuptools_scm >=6.2 (python/pyproject.toml:2)
Platform wheels built by scripts/build-wheels.mjs

4.5 Go Build: standard toolchain

go build, go mod (Go 1.24)

5. Code Generation Pipeline

Source: scripts/codegen/package.json:1-18

Generates typed protocol bindings for all four SDKs from shared JSON Schema.

Tool	Purpose
`json-schema-to-typescript`	JSON Schema → TypeScript interfaces
`quicktype-core`	Multi-language type generation (C#, Python, Go)

Scripts execution order:

tsx typescript.ts && tsx csharp.ts && tsx python.ts && tsx go.ts

Generated Output Locations

SDK	Output Path	Files
Node.js	`nodejs/src/generated/`	rpc.ts, session-events.ts
Python	`python/copilot/generated/`	rpc.py, session_events.py
Go	`go/generated_*.go` and `go/rpc/`	generated_.go, rpc/
.NET	`dotnet/src/Generated/`	Rpc.cs, SessionEvents.cs

CI verification: codegen-check.yml re-runs codegen and checks git status --porcelain to ensure generated files are always up-to-date.

6. CI/CD Workflows

Workflow	Purpose	Trigger
`nodejs-sdk-tests.yml`	Lint + typecheck + test Node.js SDK (Linux/macOS/Windows)	push, PR, merge_group
`python-sdk-tests.yml`	Lint + type check + test Python SDK (3 OSes)	push, PR, merge_group
`go-sdk-tests.yml`	fmt + golangci-lint + test Go SDK (3 OSes)	push, PR, merge_group
`dotnet-sdk-tests.yml`	format + build + test .NET SDK (3 OSes)	push, PR, merge_group
`codegen-check.yml`	Verify generated files up-to-date	push, PR
`scenario-builds.yml`	Compile-check all scenario samples	push, PR, merge_group
`publish.yml`	Multi-SDK publish (npm, NuGet, PyPI) + GitHub Release	manual
`docs-validation.yml`	Validate docs code examples	PR

7. Linting & Formatting

SDK	Linter	Formatter	Config
Node.js	ESLint 9 (flat config)	Prettier 3.x	nodejs/eslint.config.js, .prettierrc.json
Python	Ruff (E/W/F/I/UP rules)	Ruff formatter	python/pyproject.toml:50-69
Go	golangci-lint (govet, ineffassign, staticcheck)	gofmt	go/.golangci.yml
.NET	dotnet format (AnalysisLevel 10.0-minimum)	dotnet format	dotnet/Directory.Build.props:8

8. Testing Frameworks

SDK	Framework	Config	Key Settings
Node.js	Vitest 4.x	nodejs/vitest.config.ts	30s timeout, forks pool, globals
Python	pytest 7+	python/pyproject.toml:81-86	async mode auto, pytest-timeout
Go	`go test` (stdlib)	go/test.sh	`-race` flag enabled
.NET	xUnit 2.9	dotnet/test/GitHub.Copilot.SDK.Test.csproj	coverlet for coverage

9. Package Managers

Ecosystem	Manager	Lock File
Node.js	npm	`package-lock.json`
Python	uv (Astral)	`uv.lock`
Go	Go Modules	`go.sum`
.NET	NuGet (central)	`Directory.Packages.props`

10. Protocol & Communication

JSON-RPC 2.0 over stdio to the Copilot CLI process:

IPC Communication Architecture

flowchart LR
    subgraph SDK["SDK Process"]
        direction TB
        Node["Node.js"]
        Py["Python"]
        Go["Go"]
        Net[".NET"]
    end
    subgraph CLI["Copilot CLI Process"]
        Binary["@github/copilot\nCLI binary\n(AI backend)"]
    end
    SDK -->|"stdin (JSON-RPC 2.0)"| CLI
    CLI -->|"stdout (responses)"| SDK
    CLI -->|"stderr (diagnostics)"| SDK

SDK	JSON-RPC Implementation	Schema Validation
Node.js	`vscode-jsonrpc ^8.2.1`	`zod ^4.3.6`
Python	Custom (pydantic-based)	`pydantic >=2.0`
Go	Custom (stdlib `encoding/json`)	`jsonschema-go v0.4.2`
.NET	`StreamJsonRpc 2.24.84`	`System.Text.Json 10.0.2` (AOT source-gen)

Summary Matrix

flowchart LR
    subgraph TS["<b>Node.js</b>"]
        direction TB
        TS1["Language: TypeScript #40;ES2022#41;<br/>Build: esbuild + tsc<br/>Test: Vitest 4.x<br/>Lint: ESLint 9 + Prettier 3<br/>JSON-RPC: vscode-jsonrpc<br/>Registry: npm<br/>Pkg Mgr: npm"]
    end
    subgraph PY["<b>Python</b>"]
        direction TB
        PY1["Language: Python 3.11+<br/>Build: setuptools<br/>Test: pytest 7+<br/>Lint: Ruff + ty<br/>JSON-RPC: custom / pydantic<br/>Registry: PyPI<br/>Pkg Mgr: uv"]
    end
    subgraph GO["<b>Go</b>"]
        direction TB
        GO1["Language: Go 1.24<br/>Build: go build<br/>Test: go test -race<br/>Lint: golangci-lint<br/>JSON-RPC: custom / stdlib<br/>Registry: Go modules<br/>Pkg Mgr: go mod"]
    end
    subgraph NET["<b>.NET</b>"]
        direction TB
        NET1["Language: C# 14 / .NET 8<br/>Build: MSBuild<br/>Test: xUnit 2.9<br/>Lint: dotnet format<br/>JSON-RPC: StreamJsonRpc<br/>Registry: NuGet<br/>Pkg Mgr: NuGet #40;central#41;"]
    end

Phase 3: Tech Stack

1. Languages & Versions

Language Distribution

2. Runtime Dependencies (per SDK)

2.1 Node.js SDK

2.2 Python SDK

2.3 Go SDK

2.4 .NET SDK

3. Dev Dependencies (per SDK)

3.1 Node.js SDK

3.2 Python SDK

3.3 .NET SDK (Test Project)

4. Build Tools & Systems

4.1 Monorepo Task Runner — just

4.2 Node.js Build: esbuild + tsc

4.3 .NET Build: MSBuild/dotnet CLI

4.4 Python Build: setuptools + wheel

4.5 Go Build: standard toolchain

5. Code Generation Pipeline

Generated Output Locations

6. CI/CD Workflows

7. Linting & Formatting

8. Testing Frameworks

9. Package Managers

10. Protocol & Communication

Summary Matrix

4.1 Monorepo Task Runner — `just`