go-integration

name	go-integration
description	This skill is for writing integrations to the Go SDK. Claude acts as the engineer implementing LLM provider integrations. Use when adding support for OpenAI-like providers, Anthropic-like providers, or other LLM frameworks. Covers TDD workflow, comprehensive testing (streaming/non-streaming/tokens), VCR cassettes, orchestrion auto-instrumentation, and golangci-lint compliance.

Writing Go SDK Integrations

This skill is for writing integrations. Claude acts as the Braintrust engineer implementing new integrations to the Go SDK.

Reference Integrations

Study existing integrations as examples. Choose the pattern that matches your provider SDK's design:

Pattern	Reference Implementation	Use When
Middleware	trace/contrib/openai/	SDK supports option.WithMiddleware()
Middleware	trace/contrib/anthropic/	SDK supports option.WithMiddleware()
Middleware	trace/contrib/genkit/	Framework exposes a ModelMiddleware / ai.WithMiddleware hook
HTTP Wrapper	trace/contrib/genai/	SDK accepts custom *http.Client
HTTP Wrapper	trace/contrib/github.com/sashabaranov/go-openai/	SDK accepts custom *http.Client
Callback	trace/contrib/langchaingo/	SDK has callback/handler interface
Callback	trace/contrib/cloudwego/eino/	Framework has a global callbacks.Handler + per-invocation hook
Callback	trace/contrib/adk/	Framework wires per-agent / per-tool callbacks on a config struct

Before starting: Examine the provider library's documentation and source to identify ALL methods that call LLM APIs.

Integration Patterns

Pattern 1: Middleware-Based

• Reference: trace/contrib/openai/traceopenai.go, trace/contrib/anthropic/traceanthropic.go
• Key components: NewMiddleware() function, middlewareConfig struct, URL router
• Uses: trace/internal.Middleware() helper with a router function
• Endpoint tracers: Separate files per endpoint (e.g., chatcompletions.go, responses.go, messages.go)
• Framework-level variant: trace/contrib/genkit/tracegenkit.go — wraps ai.ModelFunc instead of an HTTP middleware, but the shape (NewMiddleware() + config struct + options) is the same.

Pattern 2: HTTP Client Wrapper

• Reference: trace/contrib/genai/tracegenai.go, trace/contrib/github.com/sashabaranov/go-openai/traceopenai.go
• Key components: WrapClient() / Client() function, custom roundTripper implementing http.RoundTripper
• Intercepts: Request/response at transport level

Pattern 3: Callback-Based

• Reference: trace/contrib/langchaingo/tracelangchaingo.go (chain → llm → tool span stack)
• Reference: trace/contrib/cloudwego/eino/traceeino.go (global callbacks.Handler + per-invocation registration, streaming wg)
• Reference: trace/contrib/adk/traceadk.go (per-agent / per-model / per-tool callbacks keyed by session + invocation id)
• Key components: Handler / Callbacks struct implementing the framework's callback interface
• Manages: Span stack or session-keyed span map for nested calls (chain/agent → llm → tools)

Endpoint-Specific Tracers

Follow the internal.MiddlewareTracer interface pattern:

• Reference: trace/internal/middleware.go
• Example implementation: trace/contrib/anthropic/messages.go

Key methods:

• StartSpan() - Parse request, start span, set input/metadata attributes
• TagSpan() - Parse response, set output/metrics attributes

Streaming

For streaming responses, aggregate chunks and capture final usage:

• Reference: trace/contrib/anthropic/messages.go (streaming handling)
• Reference: trace/contrib/openai/chatcompletions.go (tool call aggregation)

Required Components

Each integration lives in its own Go module under trace/contrib/. Do in this order:

• Go module: trace/contrib/yourprovider/go.mod (see Module Setup below)
• Register module: Add to scripts/nested_modules.txt and go.work
• Core tracer: trace/contrib/yourprovider/traceyourprovider.go
• Endpoint parsers: trace/contrib/yourprovider/messages.go (etc.)
• Tests: trace/contrib/yourprovider/traceyourprovider_test.go
• VCR cassettes: trace/contrib/yourprovider/testdata/cassettes/
• Orchestrion config: trace/contrib/yourprovider/orchestrion.yml — mandatory
• Orchestrion deps: trace/contrib/yourprovider/orchestrion.go — mandatory, even if the YAML template's imports appear already satisfied. Every integration ships both files; use blank imports (see trace/contrib/openai/orchestrion.go and trace/contrib/anthropic/orchestrion.go) to pull the packages referenced by orchestrion.yml into the module graph.
• Update all package: Add blank import to trace/contrib/all/all.go + add require and replace directives in trace/contrib/all/go.mod
• Run generate: make generate to regenerate trace/contrib/all/orchestrion.yml from the per-integration YAML files
• Tidy all modules: make mod-verify to ensure all go.mod/go.sum are consistent and the manifest matches
• : (nested paths are fine, e.g. )

Module Setup

Every integration is its own Go module. This keeps the root SDK dependency-free of provider SDKs — users only pull in what they need.

Reference: trace/contrib/anthropic/go.mod, trace/contrib/openai/go.mod

1. Create go.mod

module github.com/braintrustdata/braintrust-sdk-go/trace/contrib/yourprovider

go 1.24.4

toolchain go1.26.1

require (
    github.com/braintrustdata/braintrust-sdk-go v0.0.0
    github.com/yourprovider/sdk-go vX.Y.Z
    // ... other deps
)

// Required: point to repo root so local development works in go.work mode.
// The release pipeline pins v0.0.0 to the real version (e.g. v0.5.0) before
// tagging via `go mod edit` + `GOWORK=off go mod tidy`; do NOT hand-edit it.
replace github.com/braintrustdata/braintrust-sdk-go => ../../..

• Use v0.0.0 when first creating the module. After the next release, the merged go.mod on main will carry the real pinned version — that is expected (see docs/PUBLISHING.md).
• The replace directive depth depends on nesting: ../../.. for trace/contrib/yourprovider/, ../../../.. for trace/contrib/cloudwego/eino/, etc.

2. Register the module

Add the repo-relative path to both:

• scripts/nested_modules.txt — one path per line (this drives the release pipeline)
• go.work — add a use entry so the workspace resolves the module locally

3. Update trace/contrib/all

Add a blank import in trace/contrib/all/all.go and update trace/contrib/all/go.mod:

// In all.go
_ "github.com/braintrustdata/braintrust-sdk-go/trace/contrib/yourprovider"

// In trace/contrib/all/go.mod — add to the existing require() and replace() blocks.
// all/go.mod already lists every nested integration's require + replace; add yours
// in the same style. For nested paths, keep the full import path intact.
require github.com/braintrustdata/braintrust-sdk-go/trace/contrib/yourprovider v0.0.0
replace github.com/braintrustdata/braintrust-sdk-go/trace/contrib/yourprovider => ../yourprovider
// Nested example (see the existing cloudwego/eino entry):
// replace github.com/braintrustdata/braintrust-sdk-go/trace/contrib/cloudwego/eino => ../cloudwego/eino

4. Run make mod-verify

This tidies all modules (with GOWORK=off for nested ones) and runs scripts/check_nested_modules.sh to verify the manifest matches actual go.mod files.

Test Coverage

1. Non-streaming requests (basic + attributes + metrics)
2. Streaming requests (full consumption)
3. Early stream termination (close without reading)
4. Error handling (network errors, API errors)
5. All critical features:
   • Tool/function calling (if supported) — verify span_attributes.type = "tool", input args, output result
   • Agentic spans — if the SDK has a callback/handler system, implement span capture for tool calls and subagent invocations in addition to LLM calls
   • Images/vision (if supported)
   • System messages (if supported)
   • Multiple messages/chat history
   • Any provider-specific features (reasoning, caching, etc.)
6. Token usage edge cases (cached tokens, reasoning tokens)
7. Multiple APIs (if provider has multiple endpoints)

Agentic Spans

Many LLM frameworks support multi-step agents with tool calling, subagent delegation, or graph-based orchestration. When the SDK has an event/callback system, capture all of these as spans:

• Tool calls: span_attributes.type = "tool". Set input to the tool arguments, output to the result, and metadata.name to the tool name.
• Subagents / nested agents: If the framework emits a callback when one agent calls another, capture it as a child span. Use a descriptive span type ("function" or "task") and include the subagent name.
• Graph nodes / chains: If the SDK wraps components (retrievers, embedders, rerankers) in a graph and fires per-node callbacks, capture them too using the appropriate span type.

Key pattern: Dispatch on the SDK's callback input/output type to determine what kind of span to create. Ignore types that don't map to a recognizable span type. See trace/contrib/cloudwego/eino/traceeino.go (uses model.ConvCallbackInput / tool.ConvCallbackInput and falls through to return ctx for unknown types) and trace/contrib/adk/traceadk.go (session + invocation-id keyed span map across BeforeAgent/AfterAgent/BeforeModel/AfterModel/BeforeTool/AfterTool).

Internal example must cover: at minimum one full agentic turn — model call → tool execution → model incorporating result — to verify the full span chain appears correctly in Braintrust. See examples/internal/adk-parallel/main.go and examples/internal/cloudwego/eino/main.go.

VCR Testing

Prefer real tests over mocks. All integration tests must use real API requests recorded via VCR — actual HTTP against the live provider, captured into a cassette that later runs in replay mode. Mocks, fake HTTP handlers, httptest.NewServer with canned JSON, stub SDK clients, hand-crafted eventstream frames, and similar test doubles are a last resort. They are only acceptable when:

• the real API cannot be recorded (e.g. a non-deterministic binary protocol that go-vcr can't round-trip), or
• the provider has no accessible test account for this repo

When you reach for a mock, document in a comment on the test why VCR wasn't viable. Do not default to mocks because they're faster to write — cassettes catch real bugs (wire-format changes, header scrubbing, streaming framing) that mocks will not.

Use internal/vcr and internal/oteltest packages for HTTP recording/replay and span verification.

References:

• VCR package: internal/vcr/vcr.go
• OTel test helpers: internal/oteltest/oteltest.go
• Test setup pattern: trace/contrib/openai/traceopenai_test.go (setUpTest function)
• Test assertions: trace/contrib/anthropic/traceanthropic_test.go

Key patterns:

1. Create setUpTest(t) helper that returns client + exporter
2. Use oteltest.Setup(t) for tracer provider
3. Use vcr.NewHTTPClient(t) for VCR-wrapped HTTP client (cassette auto-named from t.Name())
4. Use dummy API key in replay mode, require real key in record/off modes
5. Use oteltest.NewTimer() and timer.Tick() for timing assertions
6. Use exporter.FlushOne() or exporter.Flush() to get spans
7. Use span helper methods: AssertNameIs(), AssertInTimeRange(), Metadata(), Metrics(), Input(), Output()

VCR Modes:

• VCR_MODE=replay (default): Use recorded cassettes
• VCR_MODE=record: Record new cassettes (requires API keys)
• VCR_MODE=off: Live API calls (requires API keys)

Cassette location: testdata/cassettes/<TestFunctionName>.yaml

Orchestrion Auto-Instrumentation

Orchestrion provides compile-time tracing injection with zero code changes. Every integration must ship both orchestrion.yml and orchestrion.go. There are no exceptions.

References:

• Middleware pattern (SDK option): trace/contrib/openai/orchestrion.yml, trace/contrib/anthropic/orchestrion.yml
• Middleware pattern (framework option append): trace/contrib/genkit/orchestrion.yml
• HTTP wrapper pattern: trace/contrib/genai/orchestrion.yml, trace/contrib/github.com/sashabaranov/go-openai/orchestrion.yml
• Callback pattern (append to AppendGlobalHandlers): trace/contrib/cloudwego/eino/orchestrion.yml
• Callback pattern (struct-literal wrap): trace/contrib/adk/orchestrion.yml
• Callback pattern (function-call arg append): trace/contrib/langchaingo/orchestrion.yml
• Dependency file: trace/contrib/openai/orchestrion.go, trace/contrib/anthropic/orchestrion.go
• Combined config: trace/contrib/all/orchestrion.yml (auto-generated — do not hand-edit)
• Generator source: internal/genorchestrion/ (run via make generate)

Required files (all mandatory):

1. orchestrion.yml — Define join-points and advice. Pick the closest reference above.
2. orchestrion.go — Blank imports pulling every package referenced by orchestrion.yml templates into the module graph (e.g. _ "github.com/openai/openai-go/option"). Required even when those packages are already imported elsewhere in the integration — the contract is uniform across integrations.
3. Blank import in trace/contrib/all/all.go.
4. Corresponding require + replace in trace/contrib/all/go.mod.
5. Run make generate to update the combined trace/contrib/all/orchestrion.yml, then make mod-verify to tidy go.mod/go.sum everywhere.

Examples

References:

• Customer example pattern: examples/openai/main.go, examples/anthropic/main.go, examples/genkit/main.go, examples/cloudwego/eino/main.go, examples/adk/main.go
• Internal example pattern: examples/internal/autoinstrumentation/main.go (orchestrion end-to-end), examples/internal/kitchensink/main.go (multi-provider coverage), examples/internal/genkit/main.go, examples/internal/cloudwego/eino/main.go, examples/internal/adk-parallel/main.go
• Internal examples README: examples/internal/README.md — shows the "kitchen sink" convention per provider

Customer example (examples/yourprovider/main.go):

• Concise, shows basic usage with manual middleware
• Creates root span, makes API call, prints permalink
• MUST use real model SDK — no mocks, stubs, or fake responses

Internal example (examples/internal/yourprovider/main.go):

• Comprehensive feature coverage for CI validation
• Must cover: non-streaming, streaming, tool calling (agentic turn), and multiple providers where available
• Skip sections gracefully when optional API keys are not set (e.g. if key := os.Getenv("ANTHROPIC_API_KEY"); key != "")
• MUST use real model SDK — no mocks, stubs, or fake responses
• Read API keys from environment variables

Rule: Examples must always use real provider SDKs with real API keys. Never use mock models, stub implementations, or hardcoded fake responses. For callback-based integrations, use the real model implementation from the provider's extension library rather than a hand-rolled callback invoker.

TDD Workflow

After EVERY major change: test -> lint -> fix -> commit cycle

1. Write one failing test
2. Implement minimal code to pass
3. Run tests for your module: VCR_MODE=replay go test -C trace/contrib/yourprovider ./...
4. Record cassettes (when needed): VCR_MODE=record go test -C trace/contrib/yourprovider -v -run=TestName ./...
5. Run all tests: make test (runs root + all nested modules)
6. Lint: make lint (fix issues before committing)
7. Run CI: make ci before committing
8. Repeat cycle for: basic -> streaming -> errors -> tools -> tokens

Note: Integration modules are separate Go modules, so use -C <module-dir> to run tests in the correct module context. make test handles this automatically for all modules.

Defensive Coding

• Nil checks before accessing nested fields
• Type assertions with ok checks: if v, ok := m["key"].(string); ok { ... }
• Error handling with proper span status
• JSON serialization safety (handle marshal errors)
• Graceful handling of missing/unexpected response fields

Token Normalization

Normalize provider-specific token fields to standard Braintrust metric names.

References:

• OpenAI token parsing: trace/contrib/openai/chatcompletions.go (parseUsageTokens)
• Anthropic token parsing: trace/contrib/anthropic/messages.go (parseUsageTokens)
• Token parsing tests: trace/contrib/openai/traceopenai_test.go (TestParseUsageTokens)

Standard metric names:

• prompt_tokens - Input tokens (from input_tokens or prompt_tokens)
• completion_tokens - Output tokens (from output_tokens or completion_tokens)
• tokens - Total tokens
• prompt_cached_tokens - Cache read tokens
• prompt_cache_creation_tokens - Cache write tokens
• completion_reasoning_tokens - Reasoning tokens
• time_to_first_token - Streaming latency (seconds)

Span Attributes

Set these standard Braintrust attributes:

Attribute	Description
braintrust.input_json	Request input (messages array)
braintrust.output_json	Response output (content)
braintrust.metadata	Provider, model, parameters
braintrust.metrics	Token counts, timing
braintrust.span_attributes	Span type info

Linting & CI

make lint         # Run golangci-lint
make fmt          # Format code
make test         # Run tests for root + all nested modules (VCR replay)
make mod-verify   # Tidy all go.mod files and verify manifest
make ci           # Full CI: lint + mod-verify + test + build

# Test a single nested module:
VCR_MODE=replay go test -C trace/contrib/yourprovider ./...

# Record cassettes for a single nested module:
VCR_MODE=record go test -C trace/contrib/yourprovider -v -run=TestName ./...

Reference Files

• Integrations (one Go module each): trace/contrib/{openai,anthropic,genai,genkit,langchaingo,adk,cloudwego/eino,github.com/sashabaranov/go-openai}/
• Module manifests: trace/contrib/*/go.mod
• Tests: trace/contrib/*/trace*_test.go (also context_test.go, nested_test.go, integration_test.go, golden_test.go in some integrations)
• Shared middleware helper: trace/internal/middleware.go, trace/internal/utils.go
• Test helpers: internal/oteltest/oteltest.go, internal/vcr/vcr.go
• Examples: examples/{openai,anthropic,genai,genkit,langchaingo,adk,sashabaranov-openai}/main.go, examples/cloudwego/eino/main.go
• Internal examples: examples/internal/*/main.go (see examples/internal/README.md)
• Orchestrion per-integration: trace/contrib/*/orchestrion.yml + trace/contrib/*/orchestrion.go
• Orchestrion combined (generated): trace/contrib/all/orchestrion.yml
• Orchestrion generator: internal/genorchestrion/ (invoked by make generate)
• All-integrations meta-module: trace/contrib/all/all.go, trace/contrib/all/go.mod
• Workspace: go.work
• Nested module registry: scripts/nested_modules.txt, verified by scripts/check_nested_modules.sh
• Manual-instrumentation guide (user-facing): trace/contrib/README.md
• Release docs: docs/PUBLISHING.md (explains the v0.0.0 → real-version pin flow)