AI tab unification

Between Stage 0c Pillar 1 and Stage 2d-ui, the repository top-tab strip grew four AI-adjacent tabs — Prompts, Sessions, Activity, and Prompt context — that are all views of the same underlying agent runs. This plan collapses them into a single "AI" umbrella entry with sub-sections, so the four slices of one run live under one navigation home.

Status: drafted — phase 1 (the umbrella shell) in flight.

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The problem

Between Stage 0c Pillar 1 (just shipped) and Stage 2d-ui (shipped 2026-06-03), the repository top-tab strip grew four AI-adjacent tabs:

These are four views of the same underlying agent runs. A single prompt-PR submission ends up represented in all four (Prompts as the job row, Sessions as a session entry, Activity as a graph_event, Prompt context as the input layer). Users have to remember which tab to open for which slice of the same story.

The "holy trinity" thesis in gitoku-product-direction memory implies a single coherent per-run view: the sellable/forkable unit is (git ref, fs snapshot, trace subgraph). That implication never landed as an explicit UI plan — this doc fixes that.

Goal

One top-strip entry — "AI" — that absorbs the four current tabs as sub-sections. The sub-sections preserve the existing slices but live under one navigation umbrella.

Pillar 2 surfaces (runner kind / provider / cost) will land as chips and columns inside this umbrella rather than as a fifth top tab.

Phased delivery

Phase 1 — umbrella shell (this PR, v0.1.15)

• New RepositoryAiTab enum value in Application/PageTabs.hs.
• New route /<org>/<repo>/ai + slug-and-id variants registered in Web/Routes.hs + Web/Types.hs + Application/RepositoryUrls.hs.
• New view Web/View/Repositories/Ai.hs with a sub-nav (Submit / Sessions / Trace / Context). For phase 1, each sub-nav entry links to the existing standalone URL — we don't compose yet.
• The four current top tabs (Prompts / Sessions / Activity / Prompt context) are removed from renderRepositoryTopTabs. Their URLs stay fully functional for bookmarks, deep-links, and rgh / API consumers. Tab enums stay in PageTabs.hs so parsing doesn't break.
• doc/README.md stage table gets a new row for this work.

Acceptance for phase 1:

1. Top strip shows one "AI" entry where four used to be.
2. /<org>/<repo>/ai renders the umbrella shell with sub-nav.
3. Clicking each sub-nav entry navigates to the existing standalone page.
4. Old URLs still resolve (no 404s on /prompts, /sessions, /activity, /prompt-context).
5. Nix-build green; deploy clean.

Phase 2 — composed sections (later PRs)

Progressively absorb each old view into the umbrella as an actual rendered section rather than a link out. Order of absorption (smallest first):

1. Prompt context — already a pure read-only render; trivial to fold in.
2. Sessions — render the index inline, drill-down still navigates to the per-session timeline.
3. Activity — the graph_events table inline; sticky filter bar.
4. Prompts — the submission form + recent-jobs list inline.

Each phase-2 PR also deletes the corresponding old tab's standalone view if no external system relies on its URL. URLs we know external systems depend on (rgh / API):

• /<org>/<repo>/prompts — used by rgh's submit flow (verify before removing).
• /<org>/<repo>/sessions/<id> — likely referenced in commit-context payloads.

Keep the *BySlug*Action constructors in Web/Types.hs for as long as any external system might link to them.

Phase 3 — (git, fs, trace) triple per run

Pillar 2 (CLI runners / HTTP providers) + Stage 4b ZFS-snapshot UI eventually let one agent-run row inside Sessions surface its three legs together: the commit it produced, the filesystem snapshot it ran inside, the trace subgraph it generated. That's the "holy trinity" UI manifestation. Out of scope for this plan but the umbrella established here is the home for that surfacing.

Non-goals

• Settings consolidation. The plan-doc reference to a "single AI providers tab" (continuity-completion §"Stage 0c", line 560) is about the account settings UI for credentials — out of scope here; that lands with Pillar 2.
• Renaming or migrating data. No schema changes. No data movement. Pure UI shell.
• Adding new functionality. Sub-sections render exactly what their old standalone views rendered, just under the umbrella.

Risks

• Bookmarks. Mitigated by keeping old URLs functional.
• External consumers (rgh, MCP). Audit before removing any old URL. Phase 2 PRs must verify.
• Test fixtures referencing the old tab IDs. Keep RepositoryPromptsTab etc. in PageTabs.hs enum so parsing stays backward-compatible.

Done (whole plan)

A single "AI" entry in the repo top strip. Clicking it lands on /ai with sub-nav. Every AI-adjacent view in the repo (Submit prompt, Sessions, Trace, Context preview, and eventually per-run triple) is reachable through that umbrella. The four old tabs are gone from the top strip; their URLs may still respond, but only as compatibility shims for external consumers.