feat: add named profile support

Add profile management to the CLI, allowing users to store and switch
between multiple LangSmith configurations (API key, endpoint, workspace)
via ~/.langsmith/config.toml.

New subcommands:
  langsmith profile create/list/show/delete/use

New flags:
  --profile, LANGSMITH_PROFILE env var

Resolution priority: flags > env vars > named profile > default profile.

Includes internal/config package for TOML config read/write and
comprehensive test coverage across config, profile commands, and
resolution logic.

Author: langchain-infra

docs/superpowers/specs/2026-04-03-profiles-design.md

@@ -0,0 +1,132 @@
+# Profiles Feature Design
+
+## Overview
+
+Add named profile support to the langsmith CLI, allowing users to store and switch between multiple LangSmith configurations (API endpoint, credentials, workspace). Profiles are stored in a TOML config file and selected via CLI flag, environment variable, or a persistent `current_profile` setting.
+
+## Config File
+
+- **Location:** `~/.langsmith/config.toml`
+- **Format:** TOML with a top-level `current_profile` key and one `[section]` per profile
+
+```toml
+current_profile = "default"
+
+[default]
+api_url = "https://api.smith.langchain.com"
+api_key = "lsv2_pt_abc123..."
+workspace_id = "optional-uuid"
+
+[staging]
+api_url = "https://staging.api.smith.langchain.com"
+api_key = "lsv2_pt_def456..."
+```
+
+### Profile Fields
+
+| Field          | Required | Default                                |
+|----------------|----------|----------------------------------------|
+| `api_key`      | yes      | —                                      |
+| `api_url`      | no       | `https://api.smith.langchain.com`      |
+| `workspace_id` | no       | —                                      |
+
+## Resolution Priority
+
+Credential and endpoint resolution follows AWS-style precedence (highest wins):
+
+1. `--api-key` / `--api-url` CLI flags
+2. `LANGSMITH_API_KEY` / `LANGSMITH_ENDPOINT` / `LANGSMITH_WORKSPACE_ID` env vars
+3. Named profile selected via `--profile` flag or `LANGSMITH_PROFILE` env var
+4. `current_profile` value from config file
+5. `[default]` profile in config file
+6. Hardcoded default URL (`https://api.smith.langchain.com`)
+
+If no config file exists and no env vars or flags are set, the CLI behaves exactly as it does today (requires `LANGSMITH_API_KEY`).
+
+## Subcommands
+
+All under `langsmith profile`:
+
+### `langsmith profile list`
+
+Lists all profiles. Marks the active profile with `*`.
+
+- JSON output: array of objects with `name`, `api_url`, `active` fields (key never shown)
+- Pretty output: table with name, URL, active marker
+
+### `langsmith profile show <name>`
+
+Shows a single profile's configuration. The API key is masked (e.g., `lsv2_pt_...c123`).
+
+- JSON output: object with `name`, `api_url`, `api_key` (masked), `workspace_id`
+- Pretty output: key-value display
+
+### `langsmith profile create <name>`
+
+Creates a new profile. Accepts flags for scripting; prompts interactively for missing required fields.
+
+**Flags:**
+- `--api-key` (required, or prompted)
+- `--api-url` (optional, defaults to `https://api.smith.langchain.com`)
+- `--workspace-id` (optional)
+
+If `~/.langsmith/config.toml` does not exist, it is created. If this is the first profile and no `current_profile` is set, it becomes the current profile automatically.
+
+Errors if a profile with that name already exists.
+
+### `langsmith profile delete <name>`
+
+Removes a profile from the config file.
+
+Errors if the profile does not exist. If the deleted profile was the `current_profile`, clears `current_profile` (the user must `profile use` another one or rely on env vars).
+
+### `langsmith profile use <name>`
+
+Sets `current_profile` in the config file to the given profile name.
+
+Errors if the profile does not exist.
+
+## Root Command Changes
+
+- New `--profile` persistent flag on the root command
+- `GetAPIKey()`, `GetAPIURL()` updated to consult profile config as a fallback after checking flags and env vars
+- New helper to resolve workspace ID from profile
+
+## New Package: `internal/config`
+
+Handles reading, writing, and querying the TOML config file.
+
+### Key types and functions:
+
+```go
+// Profile represents a single named profile.
+type Profile struct {
+    APIKey      string `toml:"api_key"`
+    APIURL      string `toml:"api_url,omitempty"`
+    WorkspaceID string `toml:"workspace_id,omitempty"`
+}
+
+// Config represents the full config file.
+type Config struct {
+    CurrentProfile string             `toml:"current_profile,omitempty"`
+    Profiles       map[string]Profile // each TOML section is a profile
+}
+
+func Load() (*Config, error)           // reads ~/.langsmith/config.toml, returns empty Config if missing
+func (c *Config) Save() error          // writes back to ~/.langsmith/config.toml
+func (c *Config) ActiveProfileName(flagProfile, envProfile string) string
+func (c *Config) ResolveProfile(flagProfile, envProfile string) *Profile
+```
+
+## Behavioral Notes
+
+- The config file is only created on first `profile create`, never eagerly.
+- All existing behavior is preserved when no config file exists.
+- `profile delete` of the active profile clears `current_profile` rather than picking a new one automatically.
+- API key masking shows first 8 and last 4 characters (e.g., `lsv2_pt_...c123`).
+
+## Out of Scope
+
+- `langsmith login` (OAuth/browser-based auth flow) — future work
+- Config file locking for concurrent access — single-user CLI
+- Profile import/export

go.mod

@@ -3,6 +3,7 @@ module github.com/langchain-ai/langsmith-cli
 go 1.25.0
 
 require (
+	github.com/BurntSushi/toml v1.6.0
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/websocket v1.5.3
 	github.com/hashicorp/yamux v0.1.2

go.sum

@@ -1,3 +1,5 @@
+github.com/BurntSushi/toml v1.6.0 h1:dRaEfpa2VI55EwlIW72hMRHdWouJeRF7TPYhI+AUQjk=
+github.com/BurntSushi/toml v1.6.0/go.mod h1:ukJfTF/6rtPPRCnwkur4qwRxa8vTRFBF0uk2lLoLwho=
 github.com/cenkalti/backoff/v5 v5.0.3 h1:ZN+IMa753KfX5hd8vVaMixjnqRZ3y8CuJKRKj1xcsSM=
 github.com/cenkalti/backoff/v5 v5.0.3/go.mod h1:rkhZdG3JZukswDf7f0cwqPNk4K0sa+F97BxZthm/crw=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=

internal/client/client.go

@@ -7,7 +7,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"os"
 	"strings"
 	"time"
 
@@ -17,9 +16,10 @@ import (
 
 // Client wraps the LangSmith Go SDK and provides helpers for raw HTTP calls.
 type Client struct {
-	SDK    *langsmith.Client
-	apiKey string
-	apiURL string
+	SDK         *langsmith.Client
+	apiKey      string
+	apiURL      string
+	workspaceID string
 
 	// Cached session name → ID mappings (per invocation).
 	sessionCache map[string]string
@@ -34,7 +34,7 @@ func NormalizeURL(apiURL string) string {
 }
 
 // New creates a new Client.
-func New(apiKey, apiURL string) *Client {
+func New(apiKey, apiURL, workspaceID string) *Client {
 	normalized := NormalizeURL(apiURL)
 
 	opts := []option.RequestOption{
@@ -44,17 +44,18 @@ func New(apiKey, apiURL string) *Client {
 	if normalized != "" {
 		opts = append(opts, option.WithBaseURL(normalized))
 	}
-	// Forward LANGSMITH_WORKSPACE_ID to the SDK as the tenant ID.
+	// Forward workspaceID to the SDK as the tenant ID.
 	// The SDK already reads LANGSMITH_TENANT_ID, but LANGSMITH_WORKSPACE_ID
 	// is the documented env var for the CLI and MCP server.
-	if wsID := os.Getenv("LANGSMITH_WORKSPACE_ID"); wsID != "" {
-		opts = append(opts, option.WithTenantID(wsID))
+	if workspaceID != "" {
+		opts = append(opts, option.WithTenantID(workspaceID))
 	}
 
 	return &Client{
 		SDK:          langsmith.NewClient(opts...),
 		apiKey:       apiKey,
 		apiURL:       normalized,
+		workspaceID:  workspaceID,
 		sessionCache: make(map[string]string),
 	}
 }
@@ -110,8 +111,8 @@ func (c *Client) RawDo(ctx context.Context, method, path string, body io.Reader,
 
 	req.Header.Set("x-api-key", c.apiKey)
 	req.Header.Set("Content-Type", "application/json")
-	if wsID := os.Getenv("LANGSMITH_WORKSPACE_ID"); wsID != "" {
-		req.Header.Set("x-tenant-id", wsID)
+	if c.workspaceID != "" {
+		req.Header.Set("x-tenant-id", c.workspaceID)
 	}
 	for k, vals := range extraHeaders {
 		for _, v := range vals {
@@ -159,8 +160,8 @@ func (c *Client) rawRequest(ctx context.Context, method, path string, body any,
 
 	req.Header.Set("x-api-key", c.apiKey)
 	req.Header.Set("Content-Type", "application/json")
-	if wsID := os.Getenv("LANGSMITH_WORKSPACE_ID"); wsID != "" {
-		req.Header.Set("x-tenant-id", wsID)
+	if c.workspaceID != "" {
+		req.Header.Set("x-tenant-id", c.workspaceID)
 	}
 
 	httpClient := &http.Client{Timeout: 30 * time.Second}