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+# Observatoire Link from Search & Tableau Results — Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Let users jump from search/tableau results to the observatoire page, pre-filtered for a given organization, via a 📊 link in the `_nom` columns.
+
+**Architecture:** Modify `add_links()` in `src/utils.py` to append an observatoire link to `_nom` columns. Add two callbacks to `src/pages/observatoire.py` for bidirectional URL ↔ filter sync using the existing `dcc.Location(id="dashboard_url")`. Add a share URL input and clipboard button to the observatoire layout.
+
+**Tech Stack:** Dash 3.4, Polars, `urllib.parse`, `dcc.Location`, `dcc.Clipboard`
+
+**Spec:** `docs/superpowers/specs/2026-03-18-observatoire-link-from-search-design.md`
+
+---
+
+### Task 1: Add observatoire link to `acheteur_nom` in `add_links()`
+
+**Files:**
+
+- Modify: `src/utils.py:82-91` (the `acheteur_` block inside `add_links()`)
+- Test: `tests/test_main.py`
+
+**Context:** The `add_links()` function loops over column names. The `if col.startswith("acheteur_")` block (lines 82-91) currently wraps both `acheteur_nom` and `acheteur_id` in a detail page link. We must only append the observatoire link when `col == "acheteur_nom"`.
+
+- [ ] **Step 1: Write a unit test for the observatoire link in acheteur_nom**
+
+In `tests/test_main.py`, add a test that calls `add_links()` on a minimal DataFrame and checks the `acheteur_nom` column contains both the detail link and the observatoire link, while `acheteur_id` does NOT contain the observatoire link.
+
+```python
+def test_004_add_links_observatoire_acheteur():
+    import polars as pl
+
+    from src.utils import add_links
+
+    dff = pl.DataFrame(
+        {
+            "acheteur_id": ["a1"],
+            "acheteur_nom": ["ACHETEUR 1"],
+        }
+    )
+    result = add_links(dff)
+    nom_value = result["acheteur_nom"][0]
+    id_value = result["acheteur_id"][0]
+
+    # acheteur_nom should contain detail link + observatoire link
+    assert "/acheteurs/a1" in nom_value
+    assert "ACHETEUR 1" in nom_value
+    assert '/observatoire?acheteur_id=a1' in nom_value
+    assert "📊" in nom_value
+
+    # acheteur_id should NOT contain observatoire link
+    assert "/observatoire" not in id_value
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_004_add_links_observatoire_acheteur -v`
+Expected: FAIL — `'/observatoire?acheteur_id=a1'` not found in the output string.
+
+- [ ] **Step 3: Implement the observatoire link for acheteur_nom**
+
+In `src/utils.py`, modify the `if col.startswith("acheteur_")` block (lines 82-91). Gate the observatoire link append on `col == "acheteur_nom"`:
+
+```python
+            if col.startswith("acheteur_"):
+                detail_link = (
+                    '<a href = "/acheteurs/'
+                    + pl.col("acheteur_id")
+                    + '">'
+                    + pl.col(col)
+                    + "</a>"
+                )
+                if col == "acheteur_nom":
+                    detail_link = (
+                        detail_link
+                        + ' <a href="/observatoire?acheteur_id='
+                        + pl.col("acheteur_id")
+                        + '" title="Voir dans l\'observatoire">📊</a>'
+                    )
+                dff = dff.with_columns(detail_link.alias(col))
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_004_add_links_observatoire_acheteur -v`
+Expected: PASS
+
+- [ ] **Step 5: Update `test_001` to account for the new emoji in cell text**
+
+The existing `test_001` asserts `result_table.find_element(...).text == name` for `acheteur_nom`. The cell text now includes "📊" from the observatoire link. Update the assertion in `tests/test_main.py` to use `startswith` instead of exact match:
+
+```python
+        assert result_table.find_element(
+            by=By.CSS_SELECTOR, value=f'td[data-dash-column="{org_type}_nom"]'
+        ).text.startswith(
+            name
+        ), f"The search result should have the right {org_type} name"
+```
+
+- [ ] **Step 6: Run `test_001` to verify it still passes**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_001_logo_and_search -v`
+Expected: PASS
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add src/utils.py tests/test_main.py
+git commit -m "Ajout du lien observatoire dans acheteur_nom via add_links() #65"
+```
+
+---
+
+### Task 2: Add observatoire link to `titulaire_nom` in `add_links()`
+
+**Files:**
+
+- Modify: `src/utils.py:64-81` (the `titulaire_` block inside `add_links()`)
+- Test: `tests/test_main.py`
+
+**Context:** The `titulaire_` block (lines 64-81) uses a `pl.when().then().otherwise()` pattern because it guards on `titulaire_typeIdentifiant` being SIRET or null. The observatoire link must be appended inside the `.then()` branch, and only when `col == "titulaire_nom"`. Note: this block requires `titulaire_typeIdentifiant` to be present in the DataFrame.
+
+- [ ] **Step 1: Write a unit test for the observatoire link in titulaire_nom**
+
+```python
+def test_005_add_links_observatoire_titulaire():
+    import polars as pl
+
+    from src.utils import add_links
+
+    dff = pl.DataFrame(
+        {
+            "titulaire_id": ["t1"],
+            "titulaire_nom": ["TITULAIRE 1"],
+            "titulaire_typeIdentifiant": ["SIRET"],
+        }
+    )
+    result = add_links(dff)
+    nom_value = result["titulaire_nom"][0]
+    id_value = result["titulaire_id"][0]
+
+    # titulaire_nom should contain detail link + observatoire link
+    assert "/titulaires/t1" in nom_value
+    assert "TITULAIRE 1" in nom_value
+    assert '/observatoire?titulaire_id=t1' in nom_value
+    assert "📊" in nom_value
+
+    # titulaire_id should NOT contain observatoire link
+    assert "/observatoire" not in id_value
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_005_add_links_observatoire_titulaire -v`
+Expected: FAIL — `'/observatoire?titulaire_id=t1'` not found.
+
+- [ ] **Step 3: Implement the observatoire link for titulaire_nom**
+
+In `src/utils.py`, modify the `if col.startswith("titulaire_")` block (lines 64-81). The `.then()` branch must build the link differently when `col == "titulaire_nom"`:
+
+```python
+            if col.startswith("titulaire_"):
+                detail_link = (
+                    '<a href = "/titulaires/'
+                    + pl.col("titulaire_id")
+                    + '">'
+                    + pl.col(col)
+                    + "</a>"
+                )
+                if col == "titulaire_nom":
+                    detail_link = (
+                        detail_link
+                        + ' <a href="/observatoire?titulaire_id='
+                        + pl.col("titulaire_id")
+                        + '" title="Voir dans l\'observatoire">📊</a>'
+                    )
+                dff = dff.with_columns(
+                    pl.when(
+                        pl.Expr.or_(
+                            pl.col("titulaire_typeIdentifiant").is_null(),
+                            pl.col("titulaire_typeIdentifiant") == "SIRET",
+                        )
+                    )
+                    .then(detail_link)
+                    .otherwise(pl.col(col))
+                    .alias(col)
+                )
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_005_add_links_observatoire_titulaire -v`
+Expected: PASS
+
+- [ ] **Step 5: Run all tests so far to check for regressions**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_004_add_links_observatoire_acheteur tests/test_main.py::test_005_add_links_observatoire_titulaire -v`
+Expected: both PASS
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add src/utils.py tests/test_main.py
+git commit -m "Ajout du lien observatoire dans titulaire_nom via add_links() #65"
+```
+
+---
+
+### Task 3: Observatoire Callback A — URL → Inputs (page load)
+
+**Files:**
+
+- Modify: `src/pages/observatoire.py` (add import + new callback after line 281)
+- Test: `tests/test_main.py`
+
+**Context:** The existing `dcc.Location(id="dashboard_url")` is in the observatoire layout. A new callback reads `dashboard_url.search` on page load, parses query params, and sets `dashboard_acheteur_id.value` and/or `dashboard_titulaire_id.value`. It also clears `dashboard_url.search` to `""` to prevent re-triggering. Two imports must be added: `import urllib.parse` at the top of the file, and `no_update` to the existing `from dash import ...` line (currently: `from dash import ALL, Input, Output, State, callback, ctx, dcc, html, register_page` — add `no_update` to this).
+
+- [ ] **Step 1: Write a Selenium test for URL → Input sync**
+
+This test navigates to `/observatoire?acheteur_id=a1` and verifies the SIRET input gets populated.
+
+```python
+def test_006_observatoire_url_to_input(dash_duo: DashComposite):
+    from src.app import app
+
+    dash_duo.start_server(app)
+    dash_duo.wait_for_text_to_equal(".logo > h1", "decp.info", timeout=4)
+
+    # Navigate to observatoire with acheteur_id query param
+    dash_duo.wait_for_page(f"{dash_duo.server_url}/observatoire?acheteur_id=a1")
+    dash_duo.wait_for_element("#dashboard_acheteur_id", timeout=4)
+
+    acheteur_input = dash_duo.find_element("#dashboard_acheteur_id")
+    dash_duo.wait_for_text_to_equal(
+        "#dashboard_acheteur_id", "", timeout=4
+    )  # Wait for callback
+    import time
+    time.sleep(1)  # Allow callback chain to complete
+
+    assert acheteur_input.get_attribute("value") == "a1", (
+        "acheteur_id input should be populated from URL param"
+    )
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_006_observatoire_url_to_input -v`
+Expected: FAIL — the input value is empty because no callback reads URL params yet.
+
+- [ ] **Step 3: Implement Callback A**
+
+Add `import urllib.parse` to the imports at the top of `src/pages/observatoire.py` (after line 1). Also add `no_update` to the existing dash import line:
+
+```python
+from dash import ALL, Input, Output, State, callback, ctx, dcc, html, no_update, register_page
+```
+
+Add the callback after the `layout` list ends, before existing callbacks:
+
+```python
+@callback(
+    Output("dashboard_acheteur_id", "value"),
+    Output("dashboard_titulaire_id", "value"),
+    Output("dashboard_url", "search"),
+    Input("dashboard_url", "search"),
+)
+def restore_filters_from_url(search):
+    if not search:
+        return no_update, no_update, no_update
+
+    params = urllib.parse.parse_qs(search.lstrip("?"))
+
+    acheteur_id = params.get("acheteur_id", [None])[0] or no_update
+    titulaire_id = params.get("titulaire_id", [None])[0] or no_update
+
+    return acheteur_id, titulaire_id, ""
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_006_observatoire_url_to_input -v`
+Expected: PASS
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add src/pages/observatoire.py tests/test_main.py
+git commit -m "Callback URL → filtres sur la page observatoire #65"
+```
+
+---
+
+### Task 4: Observatoire Callback B — Inputs → shareable URL + layout
+
+**Files:**
+
+- Modify: `src/pages/observatoire.py` (add layout components + new callback)
+- Test: `tests/test_main.py`
+
+**Context:** Following the tableau.py pattern (lines 237-238 for layout, lines 399-450 for callback), add a hidden `share-url` input and a `copy-container` div to the observatoire layout. The callback listens to the ID inputs and builds a shareable URL. Component IDs must be unique across the app, so use `observatoire-share-url` and `observatoire-copy-container` to avoid collisions with tableau's `share-url` and `copy-container`.
+
+- [ ] **Step 1: Write a test for the shareable URL generation**
+
+```python
+def test_007_observatoire_share_url(dash_duo: DashComposite):
+    from src.app import app
+
+    dash_duo.start_server(app)
+    dash_duo.wait_for_text_to_equal(".logo > h1", "decp.info", timeout=4)
+
+    # Navigate to observatoire with acheteur_id query param
+    dash_duo.wait_for_page(f"{dash_duo.server_url}/observatoire?acheteur_id=a1")
+    dash_duo.wait_for_element("#observatoire-share-url", timeout=4)
+
+    import time
+    time.sleep(1)  # Allow callback chain to complete
+
+    share_url_input = dash_duo.find_element("#observatoire-share-url")
+    share_url_value = share_url_input.get_attribute("value")
+
+    assert "acheteur_id=a1" in share_url_value, (
+        f"Share URL should contain acheteur_id param, got: {share_url_value}"
+    )
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_007_observatoire_share_url -v`
+Expected: FAIL — `#observatoire-share-url` element does not exist yet.
+
+- [ ] **Step 3: Add layout components to observatoire**
+
+In `src/pages/observatoire.py`, add the share URL input and copy container inside the filters column (after the download button, before the closing `]` of the `id="filters"` children list, around line 264):
+
+```python
+                                    dcc.Input(
+                                        id="observatoire-share-url",
+                                        readOnly=True,
+                                        style={"display": "none"},
+                                    ),
+                                    html.Div(id="observatoire-copy-container"),
+```
+
+- [ ] **Step 4: Implement Callback B**
+
+Add after Callback A in `src/pages/observatoire.py`:
+
+```python
+@callback(
+    Output("observatoire-share-url", "value"),
+    Output("observatoire-copy-container", "children"),
+    Input("dashboard_acheteur_id", "value"),
+    Input("dashboard_titulaire_id", "value"),
+    State("dashboard_url", "href"),
+    prevent_initial_call=True,
+)
+def sync_observatoire_share_url(acheteur_id, titulaire_id, href):
+    if not href:
+        return no_update, no_update
+
+    base_url = href.split("?")[0]
+
+    params = {}
+    if acheteur_id:
+        params["acheteur_id"] = acheteur_id
+    if titulaire_id:
+        params["titulaire_id"] = titulaire_id
+
+    query_string = urllib.parse.urlencode(params)
+    full_url = f"{base_url}?{query_string}" if query_string else base_url
+
+    copy_button = dcc.Clipboard(
+        id="btn-copy-observatoire-url",
+        target_id="observatoire-share-url",
+        title="Copier l'URL de cette vue",
+        style={
+            "display": "inline-block",
+            "fontSize": 20,
+            "verticalAlign": "top",
+            "cursor": "pointer",
+        },
+        className="fa fa-link",
+        children=[
+            dbc.Button(
+                "Partager",
+                className="btn btn-primary mt-2",
+                title="Copier l'adresse de cette vue filtrée pour la partager.",
+            )
+        ],
+    )
+
+    return full_url, copy_button
+```
+
+- [ ] **Step 5: Run test to verify it passes**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_007_observatoire_share_url -v`
+Expected: PASS
+
+- [ ] **Step 6: Run all tests to check for regressions**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py -v`
+Expected: all tests PASS
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add src/pages/observatoire.py tests/test_main.py
+git commit -m "URL partageable pour la page observatoire #65"
+```
+
+---
+
+### Task 5: End-to-end integration test
+
+**Files:**
+
+- Test: `tests/test_main.py`
+
+**Context:** Verify the full flow: search for an organization on the homepage, see the 📊 link in results, click it, arrive on the observatoire with the correct input populated.
+
+- [ ] **Step 1: Write end-to-end test**
+
+```python
+def test_008_search_to_observatoire(dash_duo: DashComposite):
+    from src.app import app
+
+    dash_duo.start_server(app)
+    dash_duo.wait_for_text_to_equal(".logo > h1", "decp.info", timeout=4)
+
+    # Search for an acheteur
+    search_bar = dash_duo.find_element("#search")
+    search_bar.send_keys("ACHETEUR 1")
+    search_bar.send_keys(Keys.ENTER)
+
+    dash_duo.wait_for_element("#results_acheteur_datatable", timeout=2)
+
+    # Find the observatoire link in acheteur_nom column
+    observatoire_link = dash_duo.find_element(
+        '#results_acheteur_datatable td[data-dash-column="acheteur_nom"] a[href*="observatoire"]'
+    )
+    assert "📊" in observatoire_link.text
+
+    # Click the observatoire link
+    observatoire_link.click()
+
+    # Wait for observatoire page to load
+    dash_duo.wait_for_element("#dashboard_acheteur_id", timeout=4)
+
+    import time
+    time.sleep(1)  # Allow callback chain to complete
+
+    acheteur_input = dash_duo.find_element("#dashboard_acheteur_id")
+    assert acheteur_input.get_attribute("value") == "a1", (
+        "acheteur_id input should be populated after navigating from search"
+    )
+```
+
+- [ ] **Step 2: Run end-to-end test**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py::test_008_search_to_observatoire -v`
+Expected: PASS
+
+- [ ] **Step 3: Run the full test suite**
+
+Run: `source .venv/bin/activate && pytest tests/test_main.py -v`
+Expected: all tests PASS
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add tests/test_main.py
+git commit -m "Test e2e : recherche → observatoire #65"
+```