feat: promptconduit collect — local-first OTLP receiver + dashboard

[scotthavird]

Summary

Scaffolds the open-source half of an agent-tracing stack so we can start dogfooding today without any cloud backend.

• New promptconduit collect command starts an OTLP/HTTP+JSON receiver on 127.0.0.1:4318 (/v1/traces, /v1/logs; /v1/metrics accepted-and-discarded).
• Append-only NDJSON store at ~/.config/promptconduit/collect/ with 50MB rotation.
• Embedded read-only dashboard at 127.0.0.1:4319 — single HTML/JS file served from go:embed, lists traces grouped by trace_id with parent/child indentation, 2s auto-refresh, dark mode.
• Zero new go.mod dependencies — stdlib only.

This is the public, open-source side of the open-core split. The cloud-side OTLP receiver lives in promptconduit/platform (companion PR) and accepts the same wire format, so the same agent can ship traces to either endpoint by swapping OTEL_EXPORTER_OTLP_ENDPOINT.

Dogfood path

make build && ./promptconduit collect

# in another shell
export CLAUDE_CODE_ENABLE_TELEMETRY=1
export OTEL_EXPORTER_OTLP_PROTOCOL=http/json
export OTEL_EXPORTER_OTLP_ENDPOINT=http://127.0.0.1:4318

# use Claude Code, then open http://127.0.0.1:4319

Files

• cmd/collect.go — cobra command
• cmd/root.go — register collectCmd, add it to the update-check skip list
• internal/collect/server.go — orchestrates OTLP receiver + dashboard + store
• internal/collect/otlp.go — minimal OTLP/HTTP+JSON parser + normalization
• internal/collect/store.go — NDJSON append store, span/log read & trace summaries
• internal/collect/dashboard.go — /, /api/traces, /api/spans
• internal/collect/ui/index.html — embedded single-file dashboard
• internal/collect/otlp_test.go — round-trip + 415 + 405 tests

Test plan

• make test passes (3 new tests in internal/collect)
• make build produces a binary that links cleanly (no new deps)
• ./promptconduit collect starts both servers, prints addresses, exits cleanly on Ctrl-C
• Send a sample OTLP/JSON POST via curl and confirm the dashboard shows it
• Point Claude Code at the local endpoint and watch real traces accumulate
• Sending Content-Type: application/x-protobuf returns 415 with the documented hint
• Hitting /v1/metrics returns 200 (accept-and-discard)
• After 50MB of spans, rotation produces spans.ndjson.1

Out of scope (follow-ups)

• Protobuf support (only JSON for now).
• Optional upstream forwarding to the cloud platform.
• MCP server for in-IDE query of local traces.
• promptconduit run <agent> wrapper that auto-sets OTEL env vars.

https://claude.ai/code/session_01ECtvFtsTx4QMVWKttzMQW2

---

Generated by Claude Code