diff --git a/src/Cthulhu.jl b/src/Cthulhu.jl
index 2a9a9f18..93281183 100644
--- a/src/Cthulhu.jl
+++ b/src/Cthulhu.jl
@@ -295,7 +295,7 @@ end
 # src/ui.jl provides the user facing interface to which _descend responds
 ##
 function _descend(term::AbstractTerminal, interp::CthulhuInterpreter, mi::MethodInstance;
-    override::Union{Nothing,InferenceResult}=nothing, debuginfo::Union{Symbol,DebugInfo}=DInfo.compact, # default is compact debuginfo
+    override::Union{Nothing,InferenceResult,SemiConcreteCallInfo}=nothing, debuginfo::Union{Symbol,DebugInfo}=DInfo.compact, # default is compact debuginfo
     optimize::Bool=true, interruptexc::Bool=true,
     iswarn::Bool=false, hide_type_stable::Union{Nothing,Bool}=nothing, verbose::Union{Nothing,Bool}=nothing,
     remarks::Bool=false, with_effects::Bool=false, inline_cost::Bool=false, type_annotations::Bool=true)
@@ -327,7 +327,14 @@ function _descend(term::AbstractTerminal, interp::CthulhuInterpreter, mi::Method
             callsites = Callsite[]
         else
             if override !== nothing
-                if optimize
+                if isa(override, SemiConcreteCallInfo)
+                    src = Compiler.copy(override.ir)
+                    rt = get_rt(override)
+                    infos = src.stmts.info
+                    slottypes = src.argtypes
+                    effects = get_effects(override)
+                    (;codeinf) = lookup(interp, mi, optimize)
+                elseif optimize
                     opt = override.src
                     rt = override.result
                     if isa(opt, Compiler.OptimizationState)
@@ -367,7 +374,7 @@ function _descend(term::AbstractTerminal, interp::CthulhuInterpreter, mi::Method
                 (; src, rt, infos, slottypes, codeinf, effects) = lookup(interp, mi, optimize)
             end
             src = preprocess_ci!(src, mi, optimize, CONFIG)
-            if optimize # optimization might have deleted some statements
+            if optimize || isa(src, IRCode) # optimization might have deleted some statements
                 infos = src.stmts.info
             else
                 @assert length(src.code) == length(infos)
@@ -472,8 +479,14 @@ function _descend(term::AbstractTerminal, interp::CthulhuInterpreter, mi::Method
                 continue
             end
 
+            doverride = nothing
+            if isa(info, ConstPropCallInfo)
+                doverride = info.result
+            elseif isa(info, SemiConcreteCallInfo)
+                doverride = info
+            end
             _descend(term, interp, next_mi;
-                     override = isa(info, ConstPropCallInfo) ? info.result : nothing, debuginfo,
+                     override = doverride, debuginfo,
                      optimize, interruptexc,
                      iswarn, hide_type_stable,
                      remarks, with_effects, inline_cost, type_annotations)
@@ -656,7 +669,7 @@ with the option to `descend` into intermediate calls. `kwargs` are passed to [`d
 """
 ascend
 
-if ccall(:jl_generating_output, Cint, ()) == 1
+if false && ccall(:jl_generating_output, Cint, ()) == 1
     input = Pipe()
     Base.link_pipe!(input, reader_supports_async=true, writer_supports_async=true)
     term = REPL.Terminals.TTYTerminal("dumb", input.out, IOBuffer(), IOBuffer())
diff --git a/src/callsite.jl b/src/callsite.jl
index 5c83c31b..3ec39f1f 100644
--- a/src/callsite.jl
+++ b/src/callsite.jl
@@ -136,6 +136,15 @@ get_mi(ceci::ConstEvalCallInfo) = get_mi(ceci.mi)
 get_rt(ceci::ConstEvalCallInfo) = get_rt(ceci.mi)
 get_effects(ceci::ConstEvalCallInfo) = get_effects(ceci.mi)
 
+struct SemiConcreteCallInfo <: CallInfo
+    mi::CallInfo
+    argtypes::ArgTypes
+    ir::IRCode
+end
+get_mi(scci::SemiConcreteCallInfo) = get_mi(scci.mi)
+get_rt(scci::SemiConcreteCallInfo) = get_rt(scci.mi)
+get_effects(scci::SemiConcreteCallInfo) = get_effects(scci.mi)
+
 # CUDA callsite
 struct CuCallInfo <: CallInfo
      cumi::MICallInfo
@@ -303,6 +312,13 @@ function show_callinfo(limiter, ci::ConstEvalCallInfo)
     __show_limited(limiter, name, tt, get_rt(ci))
 end
 
+function show_callinfo(limiter, ci::SemiConcreteCallInfo)
+    # XXX: The first argument could be const-overriden too
+    name = get_mi(ci).def.name
+    tt = ci.argtypes[2:end]
+    __show_limited(limiter, name, tt, get_rt(ci))
+end
+
 function show_callinfo(limiter, (; vmi)::ReturnTypeCallInfo)
     if isa(vmi, FailedCallInfo)
         ft = Base.tuple_type_head(vmi.sig)
@@ -373,6 +389,9 @@ function Base.show(io::IO, c::Callsite)
     elseif isa(info, ConstEvalCallInfo)
         print(limiter, " = < consteval > ")
         show_callinfo(limiter, info)
+    elseif isa(info, SemiConcreteCallInfo)
+        print(limiter, " = < semi-consteval > ")
+        show_callinfo(limiter, info)
     elseif isa(info, OCCallInfo)
         print(limiter, " = < opaque closure call > ")
         show_callinfo(limiter, info.ci)
diff --git a/src/interpreter.jl b/src/interpreter.jl
index caa8e9ff..0966bd1f 100644
--- a/src/interpreter.jl
+++ b/src/interpreter.jl
@@ -96,7 +96,7 @@ function Compiler.finish(state::InferenceState, interp::CthulhuInterpreter)
 end
 
 function Compiler.transform_result_for_cache(interp::CthulhuInterpreter, linfo::MethodInstance,
-        valid_worlds::WorldRange, @nospecialize(inferred_result), ipo_effects::Effects = Effects())
+    valid_worlds::WorldRange, @nospecialize(inferred_result), ipo_effects::Effects = Effects())
     return maybe_create_optsource(inferred_result, ipo_effects)
 end
 
@@ -127,6 +127,11 @@ function Compiler.inlining_policy(interp::CthulhuInterpreter)
 end
 end # @static if isdefined(Compiler, :is_stmt_inline)
 
+function Compiler.codeinst_to_ir(interp::CthulhuInterpreter, code::CodeInstance)
+     isa(code.inferred, Nothing) && return nothing
+     return Compiler.copy((code.inferred::OptimizedSource).ir)
+end
+
 function Compiler.finish!(interp::CthulhuInterpreter, caller::InferenceResult)
     effects = EFFECTS_ENABLED ? caller.ipo_effects : nothing
     caller.src = maybe_create_optsource(caller.src, effects)
diff --git a/src/reflection.jl b/src/reflection.jl
index ecdf0a62..61b0d998 100644
--- a/src/reflection.jl
+++ b/src/reflection.jl
@@ -145,6 +145,11 @@ function process_info(interp, @nospecialize(info), argtypes::ArgTypes, @nospecia
                 effects = get_effects(interp.unopt, linfo)
                 mici = MICallInfo(linfo, rt, effects)
                 ConstEvalCallInfo(mici, argtypes)
+            elseif (@static isdefined(Compiler, :SemiConcreteResult) && true) && isa(result, Compiler.SemiConcreteResult)
+                linfo = result.mi
+                effects = result.effects
+                mici = MICallInfo(linfo, rt, effects)
+                SemiConcreteCallInfo(mici, argtypes, result.ir)
             else
                 @assert isa(result, Compiler.InferenceResult)
                 linfo = result.linfo