# Phase 153 — the document viewer carries its origin, and the path is copyable

**Source:** owner UX audit 2026-10-03 (live interactive-browser pass): "document.html's back link always says '← Sources' even when you arrived from Chat" + optimization "a 'copy path' affordance next to the path chip would speed up the copy-paste-to-terminal workflow."
**Story:** `.agents/user_stories/document-viewer.md` (phase 10, complete) + `.agents/user_stories/document-back-navigation.md` (phase 13, complete) — this phase extends both: the phase-13 `back` contract exists on the DIRECT chip link (`app.js::documentUrl`, L447–457) but the phase-26 same-page modal's "Full page" escape hatch (`document-modal.js::fullPageUrl`, L94–97) drops it, so a chat-originated document opened through the modal lands on "← Sources" in the standalone viewer.
**Context:** `openDocumentModal(source, path, trigger = null)` (document-modal.js L167) — called from the chat view (app.js L1700, L1762, L1804, L1825, L1908 — source chips, nearby-doc links, source-image figures) and from the RAG folder table (sources.js L2023). The "Full page" anchor (L202) and the no-skeleton `window.open` fallback (L172) both use `fullPageUrl`. The standalone back-link resolution (document.js, phase 13) honors a same-origin relative `back` param (`/` prefix, not `//`) and falls back to `/sources.html` otherwise; its label matches the resolved target (Chat / Sources) — already shipped, untouched by this phase. The clipboard idiom is established (app.js L216–221, L2375–2384; history.js L297–301): `navigator.clipboard.writeText` in a try — a non-secure (http) homelab origin rejects the clipboard, so the failure path renders an inline fallback field (an input-like node that selects its content on focus) + a status line.

## Objective
A document opened from the in-page modal carries its origin to the standalone viewer (chat → back to chat, Sources → back to Sources — the phase-13 resolution, finally fed on every path), and the owner can copy the document path (`source/path`) from both the modal's meta and the standalone titlebar with one click, with the established clipboard-fallback contract.

## Dependencies
- `13_document_back_navigation` (complete) — the `back` param + same-origin validation + label-match contract this phase feeds.
- `10_story_document_viewer` (complete) — the viewer's meta row (source/format chips, mono path) the Copy-path control joins.
- `144_modal_back_button` (complete) — the modal's history-entry model; this phase adds no navigation, only a URL param on the escape hatch.

## Design (shared by all tasks — the executor reads this, not the chat)
- **The origin param (task 01):** `openDocumentModal(source, path, trigger = null, back = null)` and `fullPageUrl(source, path, back = null)` — `back` is appended as `&back=` + `encodeURIComponent(back)` ONLY when truthy (a null/absent `back` keeps the URL byte-identical to pre-phase: the Sources path is unchanged). The modal remembers the `back` of the CURRENT open (a module-level variable set at each `openDocumentModal` — the modal is one-at-a-time by its own contract, so a single variable is sound). The five chat-view call sites (app.js) pass `"/"` — chat is the shell's home route, the same value `documentUrl` already uses; the sources.js L2023 call site omits it (null → no param → the viewer's `/sources.html` default). The no-skeleton fallback (L172) uses the same `back`. The app.js L447–457 comment ("this URL is also what the modal's 'Full page' link points at") becomes TRUE — update the comment where it cites the contract, do not restate it.
- **Copy path (task 02):** ONE control shape on both surfaces — an icon + "Copy path" text button (visible text, `aria-label` "Copy the document path" is redundant with the text so it carries the plain text; icon `aria-hidden`), placed in the standalone titlebar's meta row after the mono path and in the modal's meta block. The copied string is `source + "/" + path` (ASSUMPTION A1 — the exact `source/path` form the `read` tool, the chips, and the Sources table use; the paste target is the owner's own tooling). Clipboard contract (the share-link-fallback idiom, app.js L216–221): `navigator.clipboard.writeText` in a try → success: a transient status "Path copied." (visible near the control + the page's live region; auto-clears ~4 s, the toast idiom) → failure: an inline fallback field (input-like, prefilled with the path, selects its content on focus — the `.share-link-fallback` pattern) + the status line "Path ready — copy it from the field." (the owner-locked fallback wording, adapted for the path). Per-page duplication of the small helper is the established idiom (history.js L301) — document.js and document-modal.js each carry their own; no new shared module.
- **A11y (both tasks):** the standalone page already has the landmarks/label frame (phase 10/13); the new button is a labeled control (WCAG 1.3.1/4.1.2); the status line is `role="status"`; the fallback field is a labeled input-like node (the share-fallback precedent). No new color-alone state (B5).

## Tasks
1. `01_modal_back_context.md` — the `back` param through `openDocumentModal`/`fullPageUrl` + the six call-site updates + the comment correction.
2. `02_copy_path.md` — the Copy-path control on the standalone titlebar + the modal meta, clipboard idiom + fallback field + status line.
3. `03_unit_pins.md` — the URL-contract pins (with/without `back`), the modal param default, the copy-path strings + fallback contract.
4. `04_e2e_viewer_context.md` — the dedicated Playwright suite: chat→modal→Full page back-to-chat, Sources→modal→Full page back-to-Sources, Copy path success + fallback.

## Testing & Quality
- Unit: `tests/unit/` source-level pins — `fullPageUrl` byte-identical without `back`, `&back=%2F` appended with `back = "/"` (encoded); `openDocumentModal`'s default is null (the Sources path unchanged); the copy-path status strings pinned byte-for-byte (success + fallback); the phase-13 resolution pins (a garbage `back` still falls back to `/sources.html` — the regression guard).
- Integration: the `/api/documents/content` + `GET /document.html` contract is untouched (no new server surface — the phase is frontend-only; the server pins are regression guards only).
- Coverage: **>90%** on modified code (JS pinned by the source-level suites + the E2E).
- The phase is "Complete" only when the **entire** project test suite passes 100% (every test in the project, not just this phase's).
- E2E: `uv run pytest tests/e2e/test_document_viewer_context.py -v --no-cov` in isolation (DB up: `podman compose up -d db`; the deterministic `tests/e2e/mock_llm.py` — a citation-bearing answer renders the chips).

## Documentation & Consistency
- The final pass reviews `README.md` and `AGENTS.md` in full against the project as it stands after this phase — fixing every inconsistency found, **including pre-existing ones not caused by the phase**.
- Tasks update `README.md`/`AGENTS.md` immediately when their own changes are user-visible (the Copy-path affordance is a user-visible feature — name it where the viewer is described).

## Completion Criteria
- [ ] chat view → source chip → modal → "Full page": the standalone back link is `href="/"` with the "Chat" label; Sources table → modal → "Full page": `href="/sources.html"` with the "Sources" label (E2E)
- [ ] a direct Sources table chip (no `back` param) and the pre-phase URL are byte-identical — no regression on the phase-13/26 paths
- [ ] Copy path on both surfaces: clipboard success reads "Path copied."; a rejected clipboard renders the prefilled fallback field + "Path ready — copy it from the field." (E2E pins both branches)
- [ ] the copied string is exactly `source/path` (the `read`-tool form)
- [ ] `uv run pytest` green; the dedicated E2E green in isolation; `uv run ruff check . && uv run pyright` clean; `app/` coverage >90%
- [ ] one atomic commit per AGENTS.md rule 8 (`--no-gpg-sign`)