diff --git a/src/runtime/c/pgf/lookup.c b/src/runtime/c/pgf/lookup.c
index 700991222..fc5b0d367 100644
--- a/src/runtime/c/pgf/lookup.c
+++ b/src/runtime/c/pgf/lookup.c
@@ -354,6 +354,7 @@ typedef struct {
 	GuChoice* choice;
 	GuBuf* expr_tokens;
 	GuBuf* ctrees;
+	int max_fid;
 	PgfAbsFun** curr_absfun;
 	GuPool* pool;
 } PgfLookupState;
@@ -366,75 +367,6 @@ typedef struct {
 	GuPool* out_pool;
 } PgfLookupEnum;
 
-static PgfCncTree
-pgf_lookup_extract(PgfLookupState* st, PgfMetaId meta_id, PgfCCat *ccat);
-
-static PgfCncTree
-pgf_lookup_extract_app(PgfLookupState* st,
-                       PgfCCat* ccat, GuBuf* buf,
-                       size_t n_args, PgfMetaId* args)
-{
-	GuChoiceMark mark = gu_choice_mark(st->choice);
-
-	PgfCncTree ret = gu_null_variant;
-	PgfCncTreeApp* capp =
-		gu_new_flex_variant(PGF_CNC_TREE_APP,
-							PgfCncTreeApp,
-							args, n_args, &ret, st->pool);
-	capp->ccat    = ccat;
-	capp->n_vars  = 0;
-	capp->context = NULL;
-
-redo:;
-	int index = gu_choice_next(st->choice, gu_buf_length(buf));
-	if (index < 0) {
-		return gu_null_variant;
-	}
-
-	PgfProductionApply* papply =
-		gu_buf_get(buf, PgfProductionApply*, index);
-	gu_assert(n_args == gu_seq_length(papply->args));
-
-	capp->fun = papply->fun;
-	capp->fid = 0;
-	capp->n_args = n_args;
-
-	for (size_t i = 0; i < n_args; i++) {
-		PgfPArg* parg     = gu_seq_index(papply->args, PgfPArg, i);
-		PgfMetaId meta_id = args[i];
-		
-		PgfCCat* ccat = NULL;
-		GuBuf* coercions =
-			gu_map_get(st->concr->coerce_idx, parg->ccat, GuBuf*);
-		if (coercions == NULL) {
-			ccat = parg->ccat;
-		} else {
-			int index = gu_choice_next(st->choice, gu_buf_length(coercions));
-			if (index < 0) {
-				gu_choice_reset(st->choice, mark);
-				if (!gu_choice_advance(st->choice))
-					return gu_null_variant;
-				goto redo;
-			}
-
-			PgfProductionCoerce* pcoerce =
-				gu_buf_get(coercions, PgfProductionCoerce*, index);
-			ccat = pcoerce->coerce;
-		}
-
-		capp->args[i] =
-			pgf_lookup_extract(st, meta_id, ccat);
-		if (gu_variant_is_null(capp->args[i])) {
-			gu_choice_reset(st->choice, mark);
-			if (!gu_choice_advance(st->choice))
-				return gu_null_variant;
-			goto redo;
-		}
-	}
-
-	return ret;
-}
-
 static bool
 pgf_lookup_filter(GuBuf* join, PgfMetaId meta_id, GuSeq* counts, GuBuf* stack)
 {
@@ -492,57 +424,222 @@ pgf_lookup_filter(GuBuf* join, PgfMetaId meta_id, GuSeq* counts, GuBuf* stack)
 	return true;
 }
 
-typedef struct {
-	GuMapItor fn;
-	int index;
-	PgfCCat* ccat;
-	GuBuf* buf;
-} PgfCncItor;
-
 static void
-pgf_cnc_cat_resolve_itor(GuMapItor* fn, const void* key, void* value, GuExn* err)
+gu_ccat_fini(GuFinalizer* fin)
 {
-	PgfCncItor* clo = (PgfCncItor*) fn;
-	PgfCCat* ccat = (PgfCCat*) key;
-	GuBuf* buf = *((GuBuf**) value);
-
-	if (clo->index == 0) {
-		clo->ccat = ccat;
-		clo->buf = buf;
-	}
-
-	clo->index--;
+	PgfCCat* cat = gu_container(fin, PgfCCat, fin);
+	if (cat->prods != NULL)
+		gu_seq_free(cat->prods);
 }
 
-static PgfCncTree
-pgf_lookup_extract(PgfLookupState* st, PgfMetaId meta_id, PgfCCat *ccat)
+static PgfCCat*
+pgf_lookup_new_ccat(PgfLookupState* st, PgfCCat* ccat)
 {
-	PgfCncTree ret = gu_null_variant;
+	PgfCCat* new_ccat = gu_new_flex(st->pool, PgfCCat, fin, 1);
+	new_ccat->cnccat = ccat->cnccat;
+	new_ccat->lindefs = ccat->lindefs;
+	new_ccat->linrefs = ccat->linrefs;
+	new_ccat->viterbi_prob = 0;
+	new_ccat->fid = st->max_fid++;
+	new_ccat->conts = NULL;
+	new_ccat->answers = NULL;
+	new_ccat->prods = NULL;
+	new_ccat->n_synprods = 0;
+
+	new_ccat->fin[0].fn = gu_ccat_fini;
+	gu_pool_finally(st->pool, new_ccat->fin);
+
+	return new_ccat;
+}
+
+static PgfCCat*
+pgf_lookup_concretize(PgfLookupState* st, GuMap* cache, PgfMetaId meta_id, PgfCCat *ccat);
+
+static PgfCCat*
+pgf_lookup_concretize_coercions(PgfLookupState* st, GuMap* cache,
+                                PgfMetaId meta_id, PgfCCat* ccat,
+                                GuBuf* coercions)
+{
+	PgfPair pair;
+	pair[0] = meta_id;
+	pair[1] = ccat->fid;
+	PgfCCat** pnew_ccat = gu_map_find(cache, &pair);
+	if (pnew_ccat != NULL)
+		return *pnew_ccat;
+
+	PgfCCat* new_ccat = NULL;
+
+	size_t n_coercions = gu_buf_length(coercions);
+	for (size_t i = 0; i < n_coercions; i++) {
+		PgfProductionCoerce* pcoerce =
+			gu_buf_get(coercions, PgfProductionCoerce*, i);
+
+		PgfCCat* new_coerce =
+			pgf_lookup_concretize(st, cache, meta_id, pcoerce->coerce);
+		if (new_coerce == NULL)
+			continue;
+
+		if (new_ccat == NULL) {
+			new_ccat = pgf_lookup_new_ccat(st, ccat);
+		}
+
+		PgfProduction cnc_prod;
+		PgfProductionCoerce* new_pcoerce =
+			gu_new_variant(PGF_PRODUCTION_COERCE,
+			               PgfProductionCoerce,
+			               &cnc_prod, st->pool);
+		new_pcoerce->coerce = new_coerce;
+
+		if (new_ccat->prods == NULL || new_ccat->n_synprods >= gu_seq_length(new_ccat->prods)) {
+			new_ccat->prods = gu_realloc_seq(new_ccat->prods, PgfProduction, new_ccat->n_synprods+(n_coercions-i));
+		}
+		gu_seq_set(new_ccat->prods, PgfProduction, new_ccat->n_synprods++, cnc_prod);
+
+#ifdef PGF_LOOKUP_DEBUG
+		{
+			GuPool* tmp_pool = gu_new_pool();
+			GuOut* out = gu_file_out(stderr, tmp_pool);
+			GuExn* err = gu_exn(tmp_pool);
+			gu_printf(out,err,"C%d -> _[C%d]\n",new_ccat->fid,new_pcoerce->coerce->fid);
+			gu_pool_free(tmp_pool);
+		}
+#endif
+	}
+
+	gu_map_put(cache, &pair, PgfCCat*, new_ccat);
+
+	return new_ccat;
+}
+
+static PgfCCat*
+pgf_lookup_concretize(PgfLookupState* st, GuMap* cache, PgfMetaId meta_id, PgfCCat *ccat)
+{
+	if (meta_id == 0) {
+		if (ccat->lindefs == NULL || gu_seq_length(ccat->lindefs) == 0)
+			return NULL;
+		return ccat;
+	}
+
+	PgfPair pair;
+	pair[0] = meta_id;
+	pair[1] = ccat->fid;
+	PgfCCat** pnew_ccat = gu_map_find(cache, &pair);
+	if (pnew_ccat != NULL)
+		return *pnew_ccat;
+
+	PgfCCat* new_ccat = NULL;
 
 	GuBuf* id_prods = gu_buf_get(st->join, GuBuf*, meta_id);
 
-	if (id_prods == NULL || gu_buf_length(id_prods) == 0) {
-		PgfCncTree chunks_tree;
-		PgfCncTreeChunks* chunks =
-			gu_new_flex_variant(PGF_CNC_TREE_CHUNKS,
-			                    PgfCncTreeChunks,
-			                    args, 0, &chunks_tree, st->pool);
-		chunks->n_vars  = 0;
-		chunks->context = NULL;
-		chunks->n_args  = 0;
+	size_t n_id_prods = gu_buf_length(id_prods);
+	for (size_t i = 0; i < n_id_prods; i++) {
+		PgfAbsProduction* prod =
+			gu_buf_get(id_prods, PgfAbsProduction*, i);
 
-		if (ccat == NULL) {
-			return chunks_tree;
-		}
-		if (ccat->lindefs == NULL) {
-			return ret;
-		}
+		PgfCncOverloadMap* overl_table =
+			gu_map_get(st->concr->fun_indices, prod->fun->name, PgfCncOverloadMap*);
+		if (overl_table == NULL)
+			continue;
 
+		GuBuf* buf =
+			gu_map_get(overl_table, ccat, GuBuf*);
+		if (buf == NULL)
+			continue;
+
+		size_t n_prods = gu_buf_length(buf);
+		for (size_t j = 0; j < n_prods; j++) {
+			PgfProductionApply* papply =
+				gu_buf_get(buf, PgfProductionApply*, j);
+
+			size_t n_args   = gu_seq_length(papply->args);
+			GuSeq* new_args = gu_new_seq(PgfPArg, n_args, st->pool);
+			for (size_t k = 0; k < n_args; k++) {
+				PgfPArg* parg     = gu_seq_index(papply->args, PgfPArg, k);
+				PgfPArg* new_parg = gu_seq_index(new_args, PgfPArg, k);
+
+				new_parg->hypos = parg->hypos;
+
+				GuBuf* coercions =
+					gu_map_get(st->concr->coerce_idx, parg->ccat, GuBuf*);
+				if (coercions == NULL) {
+					new_parg->ccat =
+						pgf_lookup_concretize(st, cache, prod->args[k], parg->ccat);
+				} else {
+					new_parg->ccat =
+						pgf_lookup_concretize_coercions(st, cache, prod->args[k], parg->ccat, coercions);
+				}
+
+				if (new_parg->ccat == NULL)
+					goto skip;
+			}
+
+			if (new_ccat == NULL) {
+				new_ccat = pgf_lookup_new_ccat(st, ccat);
+			}
+
+			PgfProduction cnc_prod;
+			PgfProductionApply* new_papp = 
+				gu_new_variant(PGF_PRODUCTION_APPLY,
+				               PgfProductionApply,
+				               &cnc_prod, st->pool);
+			new_papp->fun  = papply->fun;
+			new_papp->args = new_args;
+
+			if (new_ccat->prods == NULL || new_ccat->n_synprods >= gu_seq_length(new_ccat->prods)) {
+				new_ccat->prods = gu_realloc_seq(new_ccat->prods, PgfProduction, new_ccat->n_synprods+(n_prods-j));
+			}
+			gu_seq_set(new_ccat->prods, PgfProduction, new_ccat->n_synprods++, cnc_prod);
+
+#ifdef PGF_LOOKUP_DEBUG
+			{
+				GuPool* tmp_pool = gu_new_pool();
+				GuOut* out = gu_file_out(stderr, tmp_pool);
+				GuExn* err = gu_exn(tmp_pool);
+
+				gu_printf(out,err,"C%d -> F%d[",new_ccat->fid,new_papp->fun->funid);
+
+				size_t n_args = gu_seq_length(new_papp->args);
+				for (size_t l = 0; l < n_args; l++) {
+					if (l > 0)
+						gu_putc(',',out,err);
+
+					PgfPArg arg = gu_seq_get(new_papp->args, PgfPArg, l);
+
+					if (arg.hypos != NULL) {
+						size_t n_hypos = gu_seq_length(arg.hypos);
+						for (size_t r = 0; r < n_hypos; r++) {
+							if (r > 0)
+								gu_putc(' ',out,err);
+							PgfCCat *hypo = gu_seq_get(arg.hypos, PgfCCat*, r);
+							gu_printf(out,err,"C%d",hypo->fid);
+						}
+					}
+
+					gu_printf(out,err,"C%d",arg.ccat->fid);
+				}
+				gu_printf(out,err,"]\n");
+				gu_pool_free(tmp_pool);
+			}
+#endif
+
+skip:;
+		}
+	}
+
+	gu_map_put(cache, &pair, PgfCCat*, new_ccat);
+
+	return new_ccat;
+}
+
+static PgfCncTree
+pgf_lookup_extract(PgfLookupState* st, PgfCCat* ccat)
+{
+	PgfCncTree ret;
+
+	if (ccat->fid < st->concr->total_cats) {
 		int index =
 			gu_choice_next(st->choice, gu_seq_length(ccat->lindefs));
-		if (index < 0) {
-			return ret;
-		}
+
 		PgfCncTreeApp* capp =
 			gu_new_flex_variant(PGF_CNC_TREE_APP,
 			                    PgfCncTreeApp,
@@ -553,55 +650,53 @@ pgf_lookup_extract(PgfLookupState* st, PgfMetaId meta_id, PgfCCat *ccat)
 		capp->n_vars = 0;
 		capp->context = NULL;
 		capp->n_args = 1;
-		capp->args[0] = chunks_tree;
 
-		return ret;
-	}
-
-	size_t n_id_prods = gu_buf_length(id_prods);
-
-	size_t i = gu_choice_next(st->choice, n_id_prods);
-	PgfAbsProduction* prod =
-		gu_buf_get(id_prods, PgfAbsProduction*, i);
-
-	size_t n_args = gu_seq_length(prod->fun->type->hypos);
-
-	PgfCncOverloadMap* overl_table =
-		gu_map_get(st->concr->fun_indices, prod->fun->name, PgfCncOverloadMap*);
-	if (overl_table == NULL) {
-		return gu_null_variant;
-	}
-
-	if (ccat == NULL) {
-		size_t n_count = gu_map_count(overl_table);
-		GuChoiceMark mark = gu_choice_mark(st->choice);
-
-redo:;
-		int index = gu_choice_next(st->choice, n_count);
-		if (index < 0) {
-			goto done;
-		}
-
-		PgfCncItor clo = { { pgf_cnc_cat_resolve_itor }, index, NULL, NULL };
-		gu_map_iter(overl_table, &clo.fn, NULL);
-		assert(clo.ccat != NULL && clo.buf != NULL);
-
-		ret = pgf_lookup_extract_app(st, clo.ccat, clo.buf, n_args, prod->args);
-		if (gu_variant_is_null(ret)) {
-			gu_choice_reset(st->choice, mark);
-			if (gu_choice_advance(st->choice))
-				goto redo;
-		}
+		PgfCncTreeChunks* chunks =
+			gu_new_flex_variant(PGF_CNC_TREE_CHUNKS,
+			                    PgfCncTreeChunks,
+			                    args, 0, &capp->args[0], st->pool);
+		chunks->n_vars  = 0;
+		chunks->context = NULL;
+		chunks->n_args  = 0;
 	} else {
-		GuBuf* buf =
-			gu_map_get(overl_table, ccat, GuBuf*);
-		if (buf == NULL) {
-			goto done;
-		}
+		int index =
+			gu_choice_next(st->choice, ccat->n_synprods);
 
-		ret = pgf_lookup_extract_app(st, ccat, buf, n_args, prod->args);
+		PgfProduction prod = 
+			gu_seq_get(ccat->prods, PgfProduction, index);
+
+		GuVariantInfo i = gu_variant_open(prod);
+		switch (i.tag) {
+		case PGF_PRODUCTION_APPLY: {
+			PgfProductionApply* papply = i.data;
+
+			size_t n_args = gu_seq_length(papply->args);
+			PgfCncTreeApp* capp =
+				gu_new_flex_variant(PGF_CNC_TREE_APP,
+				                    PgfCncTreeApp,
+				                    args, n_args, &ret, st->pool);
+			capp->ccat = ccat;
+			capp->fun = papply->fun;
+			capp->fid = 0;
+			capp->n_vars = 0;
+			capp->context = NULL;
+			capp->n_args = n_args;
+
+			for (size_t i = 0; i < n_args; i++) {
+				PgfPArg* arg = gu_seq_index(papply->args, PgfPArg, i);
+				capp->args[i] = pgf_lookup_extract(st, arg->ccat);
+			}
+			break;
+		}
+		case PGF_PRODUCTION_COERCE: {
+			PgfProductionCoerce* pcoerce = i.data;
+			ret = pgf_lookup_extract(st, pcoerce->coerce);
+			break;
+		}
+		default:
+			gu_impossible();
+		}
 	}
-done:
 
 	return ret;
 }
@@ -911,20 +1006,32 @@ pgf_lookup_sentence(PgfConcr* concr, PgfType* typ, GuString sentence, GuPool* po
 	st.expr_tokens=gu_new_buf(PgfInputToken, work_pool);
 	st.ctrees  = gu_new_buf(PgfCncTreeScore, pool);
 	st.curr_absfun= NULL;
+	st.max_fid = concr->total_cats;
 	st.pool    = pool;
 
-	GuChoiceMark mark = gu_choice_mark(st.choice);
-	
+	GuMap* cache = gu_new_map(PgfPair, pgf_pair_hasher, PgfCCat*, &gu_null_struct, pool);
+
 	double sentence_value =
 		pgf_lookup_compute_kernel(sentence_tokens, sentence_tokens);
 
 	double max = 0;
-	PgfCncTreeScore* cts = gu_buf_extend(st.ctrees);
-	for (;;) {
-		cts->ctree =
-			pgf_lookup_extract(&st, st.start_id, NULL);
 
-		if (!gu_variant_is_null(cts->ctree)) {
+	PgfCncCat* cnccat =
+		gu_map_get(concr->cnccats, typ->cid, PgfCncCat*);
+	size_t n_ccats = gu_seq_length(cnccat->cats);
+	for (size_t i = 0; i < n_ccats; i++) {
+		PgfCCat* ccat = gu_seq_get(cnccat->cats, PgfCCat*, i);
+		PgfCCat* new_ccat = pgf_lookup_concretize(&st, cache, st.start_id, ccat);
+		if (new_ccat == NULL)
+			continue;
+
+		GuChoiceMark mark = gu_choice_mark(st.choice);
+
+		for (;;) {
+			PgfCncTreeScore* cts = gu_buf_extend(st.ctrees);
+			cts->ctree =
+				pgf_lookup_extract(&st, new_ccat);
+
 			cts->ctree = pgf_lzr_wrap_linref(cts->ctree, st.pool);
 			pgf_lzr_linearize(concr, cts->ctree, 0, &st.funcs, st.pool);
 
@@ -953,18 +1060,16 @@ pgf_lookup_sentence(PgfConcr* concr, PgfType* typ, GuString sentence, GuPool* po
 				max = cts->score;
 			}
 
-			cts = gu_buf_extend(st.ctrees);
-		}
-		
-		gu_choice_reset(st.choice, mark);
+			gu_choice_reset(st.choice, mark);
 
-		if (!gu_choice_advance(st.choice))
-			break;
+			if (!gu_choice_advance(st.choice))
+				break;
+		}
 	}
-	gu_buf_trim(st.ctrees);
 
 	gu_pool_free(work_pool);
 
+
 	PgfLookupEnum* lenum = gu_new(PgfLookupEnum, pool);
 	lenum->en.next = pgf_lookup_enum_next;
 	lenum->max     = max;