Preserve tracker tags when an execution completes

[symphony-stream]

Defect

Instrumentation#build_running_execution_data injects the active tracker's request_id and tags (via inject_tracker_data) into the execution's metadata when the "running" row is created. But when the run completes, build_completion_data rebuilds metadata from agent metadata + context metadata and never carries the tracker fields over. So whenever the completion rebuild produces any metadata at all — which it does on essentially every successful LLM run, since request timing/count land in context metadata — the update! replaces the whole metadata column and the tags correlation written at start is gone.

Error runs keep their tags only by accident: their rebuild usually produces no metadata, so the column is left untouched.

Reproduction

middleware = RubyLLM::Agents::Pipeline::Middleware::Instrumentation.new(app, MyAgent)

RubyLLM::Agents.track(tags: {feature: "voice-chat", session_id: "sess_1"}) do
  middleware.call(context) # successful run that records llm_request_count in metadata
end

execution = RubyLLM::Agents::Execution.last
execution.metadata["llm_request_count"] # => 1
execution.metadata["tags"]              # => nil (expected: {"feature" => "voice-chat", "session_id" => "sess_1"})

Fix

At the end of build_completion_data, call the existing inject_tracker_data(context, data) — the same helper build_running_execution_data uses — but only when the rebuild actually produced metadata (if data[:metadata]). The guard keeps the no-metadata case on the previous behavior: data carries no metadata key, the update! leaves the column alone, and the running record's metadata (tags included) is preserved. This also avoids replacing the column with a tags-only hash, so other keys written at start (e.g. replay_source_id) can never be clobbered by the completion.

Tests

New tracker tags on completion examples in spec/lib/pipeline/middleware/instrumentation_spec.rb:

• successful run keeps tracker tags alongside rebuilt metadata (fails on main — tags are dropped)
• failed executions keep tracker tags (pins the existing behavior)
• no tags are added when no tracker was active
• an empty rebuild leaves completion metadata unset, preserving the running record's metadata

Full suite: 4900 examples, 0 failures (Ruby 3.3.6). standardrb clean on changed files.