feat: add named profile support

[Mukil Loganathan (langchain-infra)]

Summary

• Adds langsmith profile subcommand group (create, list, show, delete, use) for managing named CLI profiles
• Profiles store API key, endpoint URL, and workspace ID in ~/.langsmith/config.toml (TOML format)
• New --profile flag and LANGSMITH_PROFILE env var for selecting active profile
• Resolution priority: CLI flags > env vars > named profile > default profile > hardcoded defaults
• client.New now accepts workspace ID as a parameter instead of reading env directly

Usage

# Create a profile
langsmith profile create prod --api-key lsv2_pt_... --api-url https://api.smith.langchain.com

# Create a second profile
langsmith profile create staging --api-key lsv2_pt_... --api-url https://staging.example.com

# List profiles (* marks active)
langsmith profile list
# [{"name":"prod","api_url":"https://api.smith.langchain.com","active":true},
#  {"name":"staging","api_url":"https://staging.example.com","active":false}]

# Switch active profile
langsmith profile use staging

# Show profile config (API key is masked)
langsmith profile show staging
# {"name":"staging","api_key":"lsv2_pt_...g456","api_url":"https://staging.example.com"}

# Use a profile for a single command
langsmith project list --profile prod

# Or via environment variable
LANGSMITH_PROFILE=staging langsmith project list

# Delete a profile
langsmith profile delete staging

Config file format (~/.langsmith/config.toml)

current_profile = "prod"

[prod]
api_key = "lsv2_pt_abc123..."
api_url = "https://api.smith.langchain.com"
workspace_id = "ws-optional"

[staging]
api_key = "lsv2_pt_def456..."
api_url = "https://staging.example.com"

Test plan

• Unit tests for config package (load, save, round-trip, permissions, resolution precedence, masking)
• Unit tests for all 5 profile subcommands (happy path + error cases)
• Unit tests for profile fallback in GetAPIKey/GetAPIURL/GetWorkspaceID
• E2E smoke test: create → list → show → use → delete flow
• All existing tests pass (go test ./...)
• Lint clean (golangci-lint run)

[devin-ai-integration]

Devin Review found 1 new potential issue.

View 6 additional findings in Devin Review.

[devin-ai-integration]

🟡 Test TestRawRequest_NoWorkspaceHeaderWhenUnset is environment-dependent after removing t.Setenv

The removal of t.Setenv("LANGSMITH_WORKSPACE_ID", "") from TestRawRequest_NoWorkspaceHeaderWhenUnset makes the test fail if the developer or CI environment has LANGSMITH_WORKSPACE_ID set to a non-empty value. The client.New() function (internal/client/client.go:50) and rawRequest() (internal/client/client.go:162) both read this env var and will set the x-tenant-id header, causing the assertion at line 243 to fail. The previous code explicitly cleared this variable, ensuring the test was self-contained regardless of the environment.

(Refers to lines 241-253)

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