[tfon23]

Closes #57

Adds configurable trace tags, settable from two sources (per @bezbac in #57; no LANGFUSE_TAGS env var):

• an optional tags array in ~/.config/opencode/opencode-langfuse.json
• an optional plugin option in the OpenCode config, which takes precedence over the config file

Tags are applied to every exported span via the langfuse.trace.tags attribute (an array of strings), matching the official Langfuse JS SDK, so Langfuse maps them to trace tags.

Usage

Config file (~/.config/opencode/opencode-langfuse.json):

{
  "publicKey": "pk-lf-...",
  "secretKey": "sk-lf-...",
  "tags": ["app:opencode-sdx"]
}

Plugin option (OpenCode 2):

{
  "plugins": [["@langfuse/opencode-observability-plugin", { "tags": ["app:opencode-sdx"] }]]
}

Plugin option (OpenCode 1):

{
  "plugin": [["@langfuse/opencode-observability-plugin", { "tags": ["app:opencode-sdx"] }]]
}

When both are set, the plugin option wins (mirroring how environment variables override the config file for the other settings). A malformed tags value is ignored with a warning rather than disabling tracing.

Tests

• v1 + v2 integration tests assert the tag lands on exported spans via the plugin option, and that no langfuse.trace.tags attribute is emitted when no tags are configured.
• runtime tests cover config-file tags, plugin-option precedence, and decodePluginTags handling of absent/malformed/unknown-key input.

All checks pass: format, build, lint, knip, and the integration suite.

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All committers have signed the CLA.

[tfon23]

@bezbac Hello can you help me by approving ?