@@ -269,6 +269,10 @@ typedef struct {
                                         // pass_lsp_cross.c. Default false.
     bool requires_lsp_resolution;       // synthetic semantic candidate (for example an implicit
                                         // C++ operator). Never fall back to textual resolution.
+    bool callee_is_locally_bound;       // bare call foo() whose callee identifier is bound as a
+                                        // parameter of an enclosing function, so it cannot be the
+                                        // module-level foo. Python only today. Read by the
+                                        // weak-local-binding guard. Default false.
 } CBMCall;
 
 typedef struct {
 
@@ -2973,6 +2973,41 @@ static bool python_receiver_is_exempt(CBMExtractCtx *ctx, TSNode receiver) {
     return false;
 }
 
+/* Name bound by one Python parameter node, or NULL when the shape binds none.
+ * Covers every binding form a `parameters` / `lambda_parameters` list produces:
+ * a bare `identifier`, the `name` field of default/typed parameters, and the
+ * identifier under a `*args` / `**kwargs` splat. A shape with no identifier (the
+ * bare `*` keyword separator) yields NULL and simply matches nothing. */
+/* True when the callee of a BARE Python call `foo()` is bound as a parameter of
+ * an enclosing function or lambda -- the bare-call counterpart of
+ * python_receiver_is_exempt above.
+ *
+ * A parameter binding shadows any module-level `foo` for the whole body, so
+ * resolving such a call to a project Function/Method by short name alone
+ * fabricates the edge BY CONSTRUCTION: `def _run_with_heavy_slot(run): run()`
+ * must not bind an unrelated `SatoriLive.run`. Unlike a receiver type this is
+ * decidable from the AST outright, with no flow analysis and no list of
+ * "generic-looking" callee names -- Python forbids `global` on a parameter, and
+ * a parameter is in scope for the entire body regardless of position.
+ *
+ * The answer is CARRIED BY THE WALK rather than recomputed here. The unified
+ * walk binds a def's or lambda's parameters when it opens that scope and
+ * unwinds them when it closes it, so this is an O(1) map lookup. Deciding it
+ * by ascending the tree instead -- with ts_node_parent() or with a copied walk
+ * cursor -- costs O(depth) per call, and since every level of f(f(f(...))) is
+ * itself a bare call, that is quadratic across the file: the 30,000-deep
+ * fixture in tests/test_stack_overflow.c turned it into a hang rather than a
+ * slowdown. An O(1) lookup needs no hop cap, so unlike a capped walk this can
+ * no longer fail open on deep-but-ordinary code.
+ *
+ * It still answers false if the walk's own tracking hit an allocation failure,
+ * which costs a suppression and never a true edge. */
+static bool python_callee_is_bound_parameter(CBMExtractCtx *ctx, WalkState *state,
+                                             TSNode callee_ident) {
+    const char *callee_name = cbm_node_text(ctx->arena, callee_ident, ctx->source);
+    return cbm_walk_python_param_is_bound(state, callee_name);
+}
+
 static bool is_objectscript_language(CBMLanguage language) {
     return language == CBM_LANG_OBJECTSCRIPT_UDL || language == CBM_LANG_OBJECTSCRIPT_ROUTINE;
 }
@@ -3597,11 +3632,18 @@ CBMInvocationDescriptor handle_calls(CBMExtractCtx *ctx, TSNode node, const CBML
             // (`accelerator.print()` must not bind MockAccelerator.print).
             // Imported receivers stay unflagged: module.function() is Python's
             // canonical cross-file call and the import map resolves it.
+            // A BARE Python call foo() whose callee is bound as a parameter of an
+            // enclosing scope cannot be the module-level foo, so short-name
+            // resolution would fabricate the edge (`def f(run): run()` must not
+            // bind SatoriLive.run). Distinct from is_method: there is no receiver
+            // here, so the weak-member guard cannot see this class at all.
             if (ctx->language == CBM_LANG_PYTHON && strcmp(ts_node_type(node), "call") == 0) {
                 TSNode fn = ts_node_child_by_field_name(node, TS_FIELD("function"));
                 if (!ts_node_is_null(fn) && strcmp(ts_node_type(fn), "attribute") == 0) {
                     TSNode obj = ts_node_child_by_field_name(fn, TS_FIELD("object"));
                     call.is_method = !python_receiver_is_exempt(ctx, obj);
+                } else if (!ts_node_is_null(fn) && strcmp(ts_node_type(fn), "identifier") == 0) {
+                    call.callee_is_locally_bound = python_callee_is_bound_parameter(ctx, state, fn);
                 }
             }
             // TS/JS/TSX receiver-aware guard (#592/#606 direction; same intent
 
@@ -119,11 +119,196 @@ static uint32_t add_lexical_scope(WalkState *state, TSNode node, CBMLexicalScope
     return scope->id;
 }
 
+/* ── #1912: Python parameter bindings held live by the walk ───────────────────
+ *
+ * A bare Python call `run()` cannot honestly resolve to a project function by
+ * short name when `run` is bound as a parameter of an enclosing def or lambda:
+ * the parameter shadows any module-level `run` for the whole body, so the match
+ * is fabricated by construction.
+ *
+ * Deciding that per call by ASCENDING the tree is the trap this replaces. Both
+ * ts_node_parent() (O(depth) per hop) and a walk-cursor ascent (O(1) per hop,
+ * O(depth) per call) are per-call costs, and every level of f(f(f(...))) is
+ * itself a bare call, so the file-wide cost is quadratic or worse -- exactly
+ * what CBMWalkScope's comment records for the state it replaced. Scanning the
+ * frame stack has the same shape.
+ *
+ * So the walk carries the answer instead: a name -> active-count map, pushed
+ * when a Python function or lambda scope opens and unwound when it closes.
+ * Lookup is O(1), which is what removes the need for a hop cap.
+ *
+ * A COUNT, not a flag: `def outer(run): def inner(run):` binds one name twice,
+ * and leaving the inner scope must not unbind the outer one.
+ *
+ * Every failure path answers "not bound", which can only ever cost a
+ * suppression -- never a true edge. */
+
+static uint32_t py_param_hash(const char *s) {
+    uint32_t h = 2166136261u; /* FNV-1a */
+    for (const unsigned char *p = (const unsigned char *)s; *p; p++) {
+        h = (h ^ *p) * 16777619u;
+    }
+    return h ? h : 1u; /* 0 marks an empty slot */
+}
+
+static CBMParamSlot *py_param_slot(WalkState *state, const char *name, uint32_t hash) {
+    int mask = state->py_param_slot_capacity - 1;
+    int i = (int)(hash & (uint32_t)mask);
+    for (;;) {
+        CBMParamSlot *slot = &state->py_param_slots[i];
+        if (slot->hash == 0) {
+            return slot; /* free slot -- caller decides whether to claim it */
+        }
+        if (slot->hash == hash && strcmp(slot->name, name) == 0) {
+            return slot;
+        }
+        i = (i + 1) & mask;
+    }
+}
+
+static bool py_param_grow(WalkState *state) {
+    int new_capacity = state->py_param_slot_capacity * PAIR_LEN;
+    if (new_capacity <= state->py_param_slot_capacity) {
+        return false;
+    }
+    CBMParamSlot *grown =
+        (CBMParamSlot *)cbm_arena_alloc(state->arena, (size_t)new_capacity * sizeof(*grown));
+    if (!grown) {
+        return false;
+    }
+    memset(grown, 0, (size_t)new_capacity * sizeof(*grown));
+    CBMParamSlot *old = state->py_param_slots;
+    int old_capacity = state->py_param_slot_capacity;
+    state->py_param_slots = grown;
+    state->py_param_slot_capacity = new_capacity;
+    for (int i = 0; i < old_capacity; i++) {
+        if (old[i].hash != 0) {
+            *py_param_slot(state, old[i].name, old[i].hash) = old[i];
+        }
+    }
+    return true;
+}
+
+static bool py_param_stack_reserve(WalkState *state) {
+    if (state->py_param_stack_count < state->py_param_stack_capacity) {
+        return true;
+    }
+    int new_capacity = state->py_param_stack_capacity * PAIR_LEN;
+    if (new_capacity <= state->py_param_stack_capacity) {
+        return false;
+    }
+    const char **grown =
+        (const char **)cbm_arena_alloc(state->arena, (size_t)new_capacity * sizeof(*grown));
+    if (!grown) {
+        return false;
+    }
+    memcpy(grown, state->py_param_stack, (size_t)state->py_param_stack_count * sizeof(*grown));
+    state->py_param_stack = grown;
+    state->py_param_stack_capacity = new_capacity;
+    return true;
+}
+
+/* Bind one parameter name for the lifetime of the frame currently on top. */
+static void py_param_bind(WalkState *state, const char *name) {
+    if (state->py_param_tracking_failed || !name || !name[0]) {
+        return;
+    }
+    /* Grow before inserting: the probe below must always find a free slot, and
+     * a table above ~70% load degrades toward linear probing. */
+    if ((state->py_param_slot_used + 1) * 10 >= state->py_param_slot_capacity * 7) {
+        if (!py_param_grow(state)) {
+            state->py_param_tracking_failed = true;
+            return;
+        }
+    }
+    if (!py_param_stack_reserve(state)) {
+        state->py_param_tracking_failed = true;
+        return;
+    }
+    uint32_t hash = py_param_hash(name);
+    CBMParamSlot *slot = py_param_slot(state, name, hash);
+    if (slot->hash == 0) {
+        slot->hash = hash;
+        slot->name = name;
+        slot->count = 0;
+        state->py_param_slot_used++;
+    }
+    slot->count++;
+    state->py_param_stack[state->py_param_stack_count++] = name;
+}
+
+/* Unwind to a frame's entry height, undoing exactly what that frame bound. */
+static void py_param_unwind_to(WalkState *state, int base) {
+    if (state->py_param_tracking_failed) {
+        return;
+    }
+    while (state->py_param_stack_count > base) {
+        const char *name = state->py_param_stack[--state->py_param_stack_count];
+        CBMParamSlot *slot = py_param_slot(state, name, py_param_hash(name));
+        if (slot->hash != 0 && slot->count > 0) {
+            slot->count--;
+        }
+    }
+}
+
+bool cbm_walk_python_param_is_bound(const WalkState *state, const char *name) {
+    if (!state || !name || !name[0] || state->py_param_tracking_failed ||
+        state->py_param_slot_used == 0) {
+        return false;
+    }
+    const CBMParamSlot *slot = py_param_slot((WalkState *)state, name, py_param_hash(name));
+    return slot->hash != 0 && slot->count > 0;
+}
+
+/* The identifier a Python parameter node binds. Handles the bare, typed,
+ * defaulted, keyword-only, *args and **kwargs shapes. */
+static const char *py_parameter_name(CBMExtractCtx *ctx, TSNode param) {
+    if (ts_node_is_null(param)) {
+        return NULL;
+    }
+    if (strcmp(ts_node_type(param), "identifier") == 0) {
+        return cbm_node_text(ctx->arena, param, ctx->source);
+    }
+    TSNode name = ts_node_child_by_field_name(param, TS_FIELD("name"));
+    if (!ts_node_is_null(name) && strcmp(ts_node_type(name), "identifier") == 0) {
+        return cbm_node_text(ctx->arena, name, ctx->source);
+    }
+    /* `*args` / `**kwargs`, and any typed shape without a `name` field: the
+     * bound identifier is the first named child. */
+    TSNode first = ts_node_named_child(param, 0);
+    if (!ts_node_is_null(first) && strcmp(ts_node_type(first), "identifier") == 0) {
+        return cbm_node_text(ctx->arena, first, ctx->source);
+    }
+    return NULL;
+}
+
+/* Bind this node's parameters into the frame just pushed for it. Called after
+ * every push in push_boundary_scopes, so the top frame is this node's own and
+ * pop_expired_scopes unwinds them at exactly the right depth. */
+static void py_bind_scope_parameters(CBMExtractCtx *ctx, TSNode node, WalkState *state) {
+    if (ctx->language != CBM_LANG_PYTHON || state->scope_top == 0) {
+        return;
+    }
+    const char *kind = ts_node_type(node);
+    if (strcmp(kind, "function_definition") != 0 && strcmp(kind, "lambda") != 0) {
+        return;
+    }
+    TSNode params = ts_node_child_by_field_name(node, TS_FIELD("parameters"));
+    if (ts_node_is_null(params)) {
+        return;
+    }
+    uint32_t count = ts_node_named_child_count(params);
+    for (uint32_t i = 0; i < count; i++) {
+        py_param_bind(state, py_parameter_name(ctx, ts_node_named_child(params, i)));
+    }
+}
+
 static bool push_scope(WalkState *state, uint8_t kind, uint32_t depth, const char *qn) {
     if (!ensure_scope_capacity(state)) {
         return false;
     }
     CBMWalkScope *f = &state->scopes[state->scope_top];
+    f->prev_py_param_stack_count = state->py_param_stack_count;
     f->kind = kind;
     f->depth = depth;
     f->qn = qn;
@@ -260,6 +445,7 @@ static void pop_expired_scopes(WalkState *state, uint32_t cur_depth) {
         state->inside_import = f->prev_inside_import;
         state->loop_depth = f->prev_loop_depth;
         state->branch_depth = f->prev_branch_depth;
+        py_param_unwind_to(state, f->prev_py_param_stack_count);
     }
 }
 
@@ -2354,6 +2540,7 @@ static void push_boundary_scopes(CBMExtractCtx *ctx, TSNode node, const CBMLangS
     }
 
     push_lexical_boundary(node, state, depth);
+    py_bind_scope_parameters(ctx, node, state);
     push_call_scope(state, depth, invocation);
     if (is_actual_import_boundary(ctx, node, spec) && !is_export_of_declaration(node)) {
         push_scope(state, SCOPE_IMPORT, depth, NULL);
@@ -2387,6 +2574,14 @@ void cbm_extract_unified(CBMExtractCtx *ctx) {
     state.scope_capacity = MAX_SCOPES;
     state.lexical_scopes = state.inline_lexical_scopes;
     state.lexical_scope_capacity = INLINE_LEXICAL_SCOPES;
+    state.py_param_slots = state.inline_py_param_slots;
+    state.py_param_slot_capacity = INLINE_PY_PARAM_SLOTS;
+    state.py_param_slot_used = 0;
+    memset(state.inline_py_param_slots, 0, sizeof(state.inline_py_param_slots));
+    state.py_param_stack = state.inline_py_param_stack;
+    state.py_param_stack_capacity = INLINE_PY_PARAM_STACK;
+    state.py_param_stack_count = 0;
+    state.py_param_tracking_failed = false;
     state.usage_start_index = ctx->result->usages.count;
     state.root_lexical_scope_id = add_lexical_scope(&state, ctx->root, CBM_LEXICAL_SCOPE_MODULE);
     /* Base walk-state tuple (previously established by the first
 
@@ -18,6 +18,8 @@
 #define INLINE_LEXICAL_SCOPES 64
 #define INLINE_LEXICAL_BINDINGS 64
 #define INLINE_PYTHON_DIRECTIVES 16
+#define INLINE_PY_PARAM_SLOTS 64
+#define INLINE_PY_PARAM_STACK 64
 
 // ObjectScript type map: variable name → class name (for instance_method_call
 // resolution). Stack-allocated, per-method scope. Overflow is silent (no crash).
@@ -51,6 +53,15 @@ typedef struct {
     bool raw_call_emitted;
 } CBMInvocationDescriptor;
 
+/* One name bound as a function/lambda parameter by a scope currently OPEN on
+ * the walk stack. A count, not a flag: `def outer(run): def inner(run):` binds
+ * the same name twice and the inner pop must not unbind the outer. */
+typedef struct {
+    const char *name;
+    uint32_t hash;
+    int count;
+} CBMParamSlot;
+
 typedef struct {
     const char *qn;
     uint32_t depth;
@@ -73,6 +84,9 @@ typedef struct {
     bool prev_inside_import;
     int prev_loop_depth;
     int prev_branch_depth;
+    /* #1912: py_param_stack height on entry. Pop unwinds back to it, so a
+     * frame unbinds exactly the parameters it bound and nothing else. */
+    int prev_py_param_stack_count;
 } CBMWalkScope;
 
 typedef enum {
@@ -158,11 +172,43 @@ typedef struct {
     CBMPythonDirective inline_python_directives[INLINE_PYTHON_DIRECTIVES];
     int python_directive_capacity;
     int python_directive_count;
+    /* #1912 -- Python bare-call shadowing. A name bound as a parameter by ANY
+     * enclosing function or lambda shadows every project function, so a bare
+     * `run()` under `def outer(run)` cannot honestly resolve by short name.
+     *
+     * Maintained as a live name->count map pushed and popped BY THE WALK, not
+     * recomputed per call. Walking ancestors (either ts_node_parent or a
+     * cursor) and scanning the frame stack are both O(depth) per call, and
+     * since every level of f(f(f(...))) is itself a bare call that is
+     * quadratic across the file -- the same trap CBMWalkScope records above.
+     * Lookup here is O(1), so no hop cap and no fail-open cap are needed.
+     *
+     * The other binding table (CBMLexicalBinding) cannot serve this: it is
+     * qsort-ed in cbm_finalize_lexical_usages AFTER the walk and its
+     * active_end stays 0 until then, so its binary search is invalid from
+     * handle_calls, which runs mid-walk and before handle_usages. */
+    CBMParamSlot *py_param_slots;
+    CBMParamSlot inline_py_param_slots[INLINE_PY_PARAM_SLOTS];
+    int py_param_slot_capacity;
+    int py_param_slot_used;
+    const char **py_param_stack;
+    const char *inline_py_param_stack[INLINE_PY_PARAM_STACK];
+    int py_param_stack_capacity;
+    int py_param_stack_count;
+    /* Allocation failure: stop tracking and answer "not bound" forever after,
+     * which can only cost a suppression, never a true edge. */
+    bool py_param_tracking_failed;
+
     CBMLanguage language;
 
     os_type_map_t os_type_map; // ObjectScript variable → type mapping
 } WalkState;
 
+/* #1912: is `name` bound as a parameter by a Python function or lambda scope
+ * currently open on the walk stack? O(1). Answers false on any failure, so a
+ * caller can only ever lose a suppression, never a true edge. */
+bool cbm_walk_python_param_is_bound(const WalkState *state, const char *name);
+
 // Per-node handler prototypes. Each is called once per node during the
 // unified cursor walk, replacing the old recursive walk_* functions.
 CBMInvocationDescriptor handle_calls(CBMExtractCtx *ctx, TSNode node, const CBMLangSpec *spec,
 
@@ -627,8 +627,16 @@ static int resolve_single_call(cbm_pipeline_ctx_t *ctx, CBMCall *call,
     bool suppress_weak_member = lang == CBM_LANG_PYTHON || lang == CBM_LANG_JAVASCRIPT ||
                                 lang == CBM_LANG_TYPESCRIPT || lang == CBM_LANG_TSX ||
                                 lang == CBM_LANG_ARKTS;
+    /* Bare-call local-binding suppression. A member call has a receiver the
+     * guard above can reason about; a bare `run()` has none, so that guard
+     * cannot see this class at all. Python-only today because the extraction
+     * flag is set only for Python — this gate MUST match pass_parallel.c's
+     * exactly, for the same divergence reason noted above. */
+    bool suppress_weak_local_binding = lang == CBM_LANG_PYTHON;
     bool drop_plain_call =
-        cbm_suppress_weak_member_match(suppress_weak_member, call->is_method, res.strategy);
+        cbm_suppress_weak_member_match(suppress_weak_member, call->is_method, res.strategy) ||
+        cbm_suppress_weak_local_binding_call(suppress_weak_local_binding,
+                                             call->callee_is_locally_bound, res.strategy);
 
     /* Service-pattern HTTP/ASYNC calls to an EXTERNAL client library (e.g.
      * `requests.get("/api/orders/{id}")`) resolve to a QN containing the library