Argtype descriptions name a literal parameter's cost, a phase's error is the phase's report, the ^-code table's grave-accent and dieresis rows (from dev ee86ca467512)

mac/machine.cpp

@@ -909,7 +909,9 @@ std::string Machine::run_phase_functions()
             // result text. The Eval is constructed per phase so a chained
             // phase sees its predecessor's result in K_result.
             Eval E(*this, Locator());
-            if (!f.empty() && f[0] != ':') {
+            const std::string spec = f;
+            const bool python_phase = !f.empty() && f[0] != ':';
+            if (python_phase) {
                 // K reaches a phase only as a parameter: the state's
                 // "class K" exists in the EVAL's globals (python_code()
                 // defines it), but a phase function's body resolves names in
@@ -929,7 +931,30 @@ std::string Machine::run_phase_functions()
             // Klammertext: take the raw result string.  Re-reading it as
             // Klammertext (Eval::eval) would misparse target characters --
             // e.g. a "@" from a quoted ^@ in justified txt output.
-            m_result = E.eval_command(katoms.begin(), katoms.end() - 2);
+            try {
+                m_result = E.eval_command(katoms.begin(), katoms.end() - 2);
+            } catch (const Parsing_error& e) {
+                // A Python phase's exception is the phase's report about the
+                // document, not a parsing error at "phase, line 1": a phase
+                // raises ValueError to say what is wrong (phases.
+                // check_section_links), and that message is what the user
+                // needs headlined, located nowhere -- the phase ran over the
+                // whole target text, so no line is the place.  Any other
+                // exception type is a fault in the phase itself and keeps
+                // its type name.  The traceback the Parsing_error carried is
+                // the trace, at -v 2.  (TODO 77, 2026-10-13)
+                if (!python_phase) throw;
+                (void)K::log(2, e.m_desc);
+                std::string what = last_python_exception_text();
+                const std::string type = last_python_exception_type();
+                if (what.empty()) throw;
+                if (type != "ValueError") what = type + ": " + what;
+                throw Target_error(
+                    what + "\n\n(Reported by the " + m_state.value("K_target")
+                    + " target's phase " + spec
+                    + "; -v 2 shows the Python traceback.)",
+                    Locator::none());
+            }
         }
     }
     return m_result;