## What
Adds a **Context** tab to the stage detail view
(`/runs/:id/stages/:stageId`), beside the existing primary tab (Thread /
Logs / …) and Debug tab.
It surfaces a stage's *deliberate per-visit outputs* — the data the
workflow author makes a stage write into shared context, plus the
routing hints it emitted:
- **Routing** — `preferred_label` and `suggested_next_ids`
- **Context writes** — author-set `context_updates` keys
This data flow was previously invisible in the UI, which made it hard to
debug "why did the next stage get the wrong input / take the wrong
edge".
## Why no backend change
The per-visit `stage.completed` event already carries `context_updates`,
`preferred_label`, and `suggested_next_ids`, and the web UI already
fetches it via `useRunStageEvents`. The checkpoint's `node_outcomes` map
was rejected as a source: it is keyed by `node_id` only, so it is lossy
across visits (`implement@2` would overwrite `implement@1`).
## How
- `extractStageContext` (in `stage-renderers/helpers.ts`) reads the
`stage.completed` event and filters `context_updates` through an
engine-key denylist: `last_stage`, `last_response`, `response.*`,
`internal.*`, `current.*`, `command.output`, `human.gate.*`,
`parallel.*`. Those are bookkeeping or already shown in the stage's
primary tab.
- It returns `null` when nothing is left, so the tab stays
**conditional** — same pattern as Thread/Logs. It only appears when a
stage actually wrote something deliberate.
- New `stage-context.tsx` renders the result, reusing `CodeBlock` /
`JsonBlock`.
- `run-stages.tsx` gains a dynamic `availableTabs` list; `effectiveTab`
falls back to `primary` gracefully when the Context tab is absent.
## Verification
- `bun run typecheck` clean, `bun test` — 412 pass / 0 fail (4 new tests
for the denylist + routing extraction).
- Live run `01KS5WBZAE7K8321NHR7KFAHF9` (`context-demo` workflow): the
`emit@1` stage emitted `demo.greeting` / `demo.answer` / `demo.payload`
plus `preferred_label: "Done"` and `suggested_next_ids: ["exit"]`, and
the Context tab rendered them correctly.
## Notes
- The second commit adds a small `context-demo` workflow used for that
verification — kept separate so it can be dropped independently.
- Known limitations (acceptable for v1): data is read from
`stage.completed` only, so a stage ending in `stage.failed` shows no
tab; parallel stages write `parallel.*` directly to context
(denylisted), so they show no tab.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
