[FIX] app: initialize session state at app level to prevent crashes on direct tab navigation

app.py

@@ -9,7 +9,8 @@ from tabs import (tab0_welcome, tab1_inputs, tab2_constraints,
                   tab3_coefficients, tab4_optimization, tab5_sensitivity,
                   tab6_scenarios)
 from utils.data_utils import load_slider_data, strip_unit_suffix
-from config.config import method_order, secondary_resources, hidden_resource_names
+from utils.state_utils import init_custom_resources
+from config.config import method_order, resource_order, secondary_resources
 
 # ── Auto-update: regenerate JSON files if inputs_aggregated.csv has changed ───
 # Uses a hash file to detect changes — works both locally and on Hugging Face.
@@ -104,6 +105,23 @@ with st.sidebar:
 
 cost_sliders = load_slider_data()
 
+# Initialise resource_caps / custom_resources / enabled_methods / auto_disabled_methods
+# here (not just in tab1) — the app's default landing tab is "Welcome", so a
+# user can reach any other tab (e.g. "Portfolio generation") without ever
+# rendering tab1 first. Several tabs access these via direct attribute
+# access (st.session_state.resource_caps, not .get()), which crashes with
+# an uninitialised-key AttributeError if tab1 hasn't run yet.
+if "resource_caps" not in st.session_state:
+    st.session_state.resource_caps = {}
+for r in resource_order:
+    if r not in st.session_state.resource_caps:
+        st.session_state.resource_caps[r] = 0.0
+init_custom_resources()
+# Same reasoning for "scenarios" — tab4's "Save scenario" button writes to it
+# directly, but it was previously only ever initialised inside tab6's render.
+if "scenarios" not in st.session_state:
+    st.session_state.scenarios = {}
+
 if "constraints" not in st.session_state:
     st.session_state.constraints = {}
 if "auto_disabled_methods" not in st.session_state:
@@ -130,6 +148,17 @@ if "costs" not in st.session_state or st.session_state.costs == {} or _expected_
         for m in cost_sliders
     }
 
+# Auto-activate/deactivate methods based on real resource availability on
+# EVERY render, not only when Tab 2 is the active tab — otherwise a user who
+# goes straight from Tab 1 to Tab 3/4/5 without visiting Tab 2 first would
+# find every method stuck "inactive" and the optimisation would fail with
+# "No active methods" despite correctly configured resources.
+_cost_sliders_norm = {
+    m: {strip_unit_suffix(name): conf for name, conf in resources.items()}
+    for m, resources in cost_sliders.items()
+}
+tab2_constraints.refresh_active_methods(_cost_sliders_norm)
+
 # When the user navigates TO "Method constraints" from any other tab, force a
 # full widget re-sync so toggle_M / slider_M keys always reflect the constraint
 # state.  Normal-mode setdefault can't recover keys that were externally set to

tabs/tab0_welcome.py

@@ -11,10 +11,10 @@ def render_tab():
     st.markdown('<h1 class="crra-heading">Welcome!</h1>', unsafe_allow_html=True)
     show_bar()
 
-    st.markdown(f"""
+    st.markdown("""
     <div class='custom-corps'>
     This tool helps you exploring how to optimize your carbon dioxide removal portfolios by adjusting resource usage and constraints.
-    </div>   
+    </div>
     <br>  
     """, unsafe_allow_html=True)