feat(charts): render_chart tool and artifact delivery - #29
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Takes a spec — a read-only SELECT plus how to encode it — runs the query through analyticsRepository, and returns a two-part result: a short receipt for the model, the resolved rows as an artifact for the renderer. Refuses rather than draws when the result would mislead: a column the query does not return (naming the real ones), a truncated or oversized result, or an empty one that may be a misspelling rather than missing data. Adds callToolWithArtifact, since a plain invoke returns only the content and silently drops the artifact half. Not registered with the agent yet — that is the next commit. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Binds the tool to the agent and carries its artifact through the stream, so a chart request now renders end to end. The artifact is not on the toolCalls stream — `call.output` resolves to the content string alone — so it is collected from the ToolMessages in `run.values`, keyed by call id, with a fallback to the final state for the case where the snapshot has not arrived by the time the call resolves. A chart renders above the collapsed tool disclosure rather than inside it: it is the answer, not a detail of it. The receipt stays collapsed below. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This was referenced Sep 12, 2026
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Slices B1 and B2 of v3 phase 2: the tool that produces chart payloads, and the wiring that gets them to the renderer merged in #28. A chart request now works end to end.
The tool
The agent sends a spec — a read-only SELECT plus how to encode it — and never sees a row.
render_chartruns the query throughanalyticsRepository(the one sanctioned raw-SQL site) and returns two payloads to two consumers viaresponseFormat: "content_and_artifact":content{"ok":true,"chartType":"bar","points":5,"x":"category","y":"total"}— 69 bytesartifactgeneratedAtThat is why there is no truncation machinery here:
query_transactionscaps and warns because the agent must reason over the rows, but a chart of any size costs the agent the same handful of tokens.It refuses rather than draws when the result would mislead: a column the query does not return (naming the real ones back), a truncated or oversized result, or an empty one — which is byte-identical whether a category is missing or misspelled.
Getting the artifact to the client
pumpToolCallsonly ever forwardedcontent. The plan assumed the artifact sat beside it on the tool-call stream; a probe against a real agent run showedcall.outputresolves to the content string alone, so a field access there would have silently forwarded nothing.The artifact lives on the
ToolMessages inrun.values. A third pump collects them by call id, with a fallback to the final state for when the snapshot has not landed by the time the call resolves — the two iterables are independent, so leaving that to ordering would be a race.Presentation
A chart renders above the collapsed tool disclosure rather than inside it — it is the answer, not a detail of it. The receipt stays collapsed below for inspection.
Verified
A real turn against seeded dev data:
load_skill→describe_finance_schema→run_sql→render_chart, zero errors, chart rendered./api/agent/historyreturns the artifact forrender_chartand omits it for the other three tools — the frozen snapshot replaying from the checkpointer, with no query re-run185 tests,
tscclean.🤖 Generated with Claude Code