LAM-2006: read agent outputs from separate trace_outputs_v0 view

[dinmukhamedm]

Summary

Ports the agent-IO work on this branch to the split read-path: agent_output is removed from the default trace schema (traces_v0 / traces_agg_v0) — the dict-resolving output join was too expensive inside the hot traces view (why is a separate investigation) — and is now read from the dedicated trace_outputs_v0 view, which returns the winning LLM span's entire output-message array (one raw message JSON per element, hashes resolved through deduped_content_dict).

Changes

ClickHouse (migration 55)

• Recreates traces_agg_v0 without the trace_agent_output join and repoints traces_v0 at traces_agg; both expose agent_input only. trace_outputs_v0 (created in migration 54) is project-parameterized only, not time-parameterized.

Query engine / SQL surface

• trace_outputs registered as an allowlisted table (validator.rs TableRegistry, schema.rs prompt, frontend tableSchemas, MCP joins hint trace_outputs.trace_id = traces.id); agent_output removed from the traces allowlist and editor schema. Validator test added for the rewrite.

Shared extraction (frontend/lib/traces/agent-output.ts)

• extractAgentOutput pulls the valuable bits out of each output message: non-empty thinking/reasoning, non-empty text (or GenAI content), and tool calls rendered as name(payload) (message-level tool_calls, Anthropic tool_use, AI SDK tool-call, OpenAI Responses items, etc.). Deliberately permissive — unknown parts are stringified rather than dropped, so it degrades to extracting more instead of nothing. Pinned by tests/test-agent-output-extraction.test.ts (16 cases).

Read path

• getAgentOutputsBatch (frontend/lib/actions/traces/outputs.ts) reads trace_outputs via the query engine, extracts text with the shared helper, and falls back to the legacy last-main-agent-LLM-span preview for traces without a trace_agent_output row.
• Trace view: getTrace / getSharedTrace resolve agentOutput in parallel with the trace row; the transcript renders it as a trailing OutputItem row.
• Session + debugger views: collapsed trace cards lazily fetch outputs for rows in view via the batched POST /api/projects/:id/traces/output route (store-level batching/debounce/dedupe, key agentOutputs).
• Traces table: Output column + filter removed (agent_output no longer exists on the trace row).

Testing

• cargo test --bin app-server query_engine — 112 passed.
• pnpm test extraction suite — 16/16 passed; tsc --noEmit clean (two pre-existing unrelated test failures also fail on dev).
• End-to-end against the staging stack: applied migrations 54+55, seeded a trace_agent_output row from real deduped_content hashes, and verified in the browser that (1) the trace-view transcript shows the extracted Output row, (2) the session view's collapsed trace card populates output via POST /traces/output, (3) SELECT agent_output FROM traces is now rejected while SELECT ... FROM trace_outputs and the traces ⋈ trace_outputs join work through the query engine. No console errors.

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