diff --git a/src/debug.jl b/src/debug.jl
index 881bad94..382865a2 100644
--- a/src/debug.jl
+++ b/src/debug.jl
@@ -21,7 +21,9 @@ function backtrace(inst::LLVM.Instruction, bt = StackTraces.StackFrame[])
                 name = replace(something(scope.name, ""), r";$"=>"")
                 isempty(name) && (name = "unknown")
                 file = scope.file
-                path = file === nothing ? "unknown" : joinpath(file.directory, file.filename)
+                path = file === nothing ? "unknown" :
+                       joinpath(file.directory::Union{Nothing,String},
+                                file.filename::Union{Nothing,String})
                 line = loc.line
                 push!(bt, StackTraces.StackFrame(name, path, line))
             end
diff --git a/src/determinism.jl b/src/determinism.jl
index 893e4307..cf39af62 100644
--- a/src/determinism.jl
+++ b/src/determinism.jl
@@ -78,12 +78,12 @@ function dedup_compile_units!(mod::LLVM.Module)
     cus = mds["llvm.dbg.cu"].operands
     length(cus) <= 1 && return false
 
-    canonical = Dict{Tuple,LLVM.Metadata}()
+    canonical = Dict{Vector{Union{Nothing,LLVM.Metadata}},LLVM.Metadata}()
     canonical_cus = LLVM.Metadata[]
     replacement = Dict{LLVM.Metadata,LLVM.Metadata}()
     for cu in cus
         cu === nothing && continue
-        key = Tuple(cu.operands)
+        key = Union{Nothing,LLVM.Metadata}[cu.operands...]
         canon = get!(canonical, key, cu)
         if canon == cu
             push!(canonical_cus, cu)
diff --git a/src/driver.jl b/src/driver.jl
index 13c3f81d..1065ca3c 100644
--- a/src/driver.jl
+++ b/src/driver.jl
@@ -282,7 +282,13 @@ const __llvm_initialized = Ref(false)
                     # which was loaded in a newer world.
                     dyn_ir, dyn_meta = @invokelatest deferred_codegen(dyn_job, job)
                     dyn_entry_fn = dyn_meta.entry.name
-                    merge!(compiled, dyn_meta.compiled)
+                    # the sibling compiler's result isn't inferred
+                    dyn_compiled = dyn_meta.compiled
+                    if dyn_compiled isa Dict{Any,Any}
+                        merge!(compiled, dyn_compiled)
+                    else
+                        Base.inferencebarrier(merge!)(compiled, dyn_compiled)
+                    end
                     @assert dyn_ir.context == ir.context
                     link_relocatable!(ir, relocations, dyn_ir,
                                       dyn_meta.relocations)
diff --git a/src/interface.jl b/src/interface.jl
index 1b656eaf..0ada05fe 100644
--- a/src/interface.jl
+++ b/src/interface.jl
@@ -61,7 +61,7 @@ llvm_targetinfo(@nospecialize(target::AbstractCompilerTarget)) = nothing
 # the target's datalayout, with Julia's non-integral address spaces added to it, as a
 # `DataLayout` the caller owns (or `nothing`)
 function julia_datalayout(@nospecialize(target::AbstractCompilerTarget))
-    dl = llvm_datalayout(target)
+    dl = llvm_datalayout(target)::Union{Nothing,String}
     dl === nothing && return nothing
     LLVM.DataLayout(dl * "-ni:10:11:12:13")
 end
diff --git a/src/irgen.jl b/src/irgen.jl
index c40f508c..7ded0af6 100644
--- a/src/irgen.jl
+++ b/src/irgen.jl
@@ -565,7 +565,7 @@ end
 #          is not passed at the LLVM level.
 function classify_arguments(@nospecialize(job::CompilerJob), codegen_ft::LLVM.FunctionType;
                             post_optimization::Bool=false)
-    source_sig = job.source.specTypes
+    source_sig = job.source.specTypes::DataType
     source_types = collect(Any, source_sig.parameters)
 
     source_argnames = Base.method_argnames(job.source.def)
@@ -979,7 +979,7 @@ function (self::AddKernelState)(mod::LLVM.Module)
                     position!(builder, LLVM.before(val))
                     state_arg = call!(builder, state_intr_ft, state_intr, Value[], "state")
                     new_val = if val isa LLVM.CallInst
-                        call!(builder, ft, f, [state_arg, val.arguments...],
+                        call!(builder, ft, f, Value[state_arg, val.arguments...],
                               val.operand_bundles)
                     else
                         # TODO: invoke and callbr
@@ -997,13 +997,10 @@ function (self::AddKernelState)(mod::LLVM.Module)
                     # XXX: we won't have to do this with opaque pointers.
                     position!(builder, LLVM.before(val))
                     target_ft = val.called_type
-                    new_args = map(zip(target_ft.parameters,
-                                       val.arguments)) do (param_typ, arg)
-                        if arg.value_type != param_typ
-                            const_bitcast(arg, param_typ)
-                        else
-                            arg
-                        end
+                    new_args = Value[]
+                    for (param_typ, arg) in zip(target_ft.parameters, val.arguments)
+                        push!(new_args, arg.value_type != param_typ ?
+                                        const_bitcast(arg, param_typ) : arg)
                     end
                     new_val = call!(builder, val.called_type, val.called_operand, new_args,
                                     val.operand_bundles)
@@ -1460,7 +1457,7 @@ function add_input_arguments!(@nospecialize(job::CompilerJob), mod::LLVM.Module,
                     position!(builder, LLVM.before(val))
                     new_val = if val isa LLVM.CallInst
                         call!(builder, new_f.function_type, new_f,
-                              [val.arguments..., callee_f.parameters[end-nargs+1:end]...],
+                              Value[val.arguments..., callee_f.parameters[end-nargs+1:end]...],
                               val.operand_bundles)
                     else
                         # TODO: invoke and callbr
diff --git a/src/mangling.jl b/src/mangling.jl
index 9272f05a..5f58e7a0 100644
--- a/src/mangling.jl
+++ b/src/mangling.jl
@@ -71,7 +71,7 @@ function mangle_param(@nospecialize(t), substitutions = Any[], top = false)
         # check if we already know this base type
         str = find_substitution(t.name.wrapper)
         if str === nothing
-            tn = safe_name(t)
+            tn = safe_name(t)::String
             str = "$(length(tn))$tn"
             push!(substitutions, t.name.wrapper)
         end
@@ -82,7 +82,7 @@ function mangle_param(@nospecialize(t), substitutions = Any[], top = false)
         else
             # encode typevars as template parameters
             if isempty(t.parameters)
-                w_types = t.name.wrapper.types
+                w_types = (t.name.wrapper::DataType).types
                 if !isempty(w_types) && !isempty(w_types[end] isa Core.TypeofVararg)
                     # If the type accepts a variable amount of parameters,
                     # e.g. `Tuple{}`, then we mark it as empty: "Tuple<>"
@@ -123,7 +123,7 @@ function mangle_param(@nospecialize(t), substitutions = Any[], top = false)
         # `N` is a `TypeVar` when the length is still parametric, which is what unwrapping a
         # `UnionAll` such as `NTuple{N,Int}` leaves behind. There is no count to repeat then,
         # so the type is mangled like the unbounded `Vararg{T}` it is equal to.
-        N = isdefined(t, :N) && isa(t.N, Integer) ? t.N : nothing
+        N = isdefined(t, :N) && isa(t.N, Int) ? t.N::Int : nothing
         if N !== nothing
             # For NTuple, repeat the type as needed
             str = ""
@@ -171,7 +171,7 @@ function mangle_param(@nospecialize(t), substitutions = Any[], top = false)
         bits = string(reinterpret(UInt64, t); base=16)
         "Ld$(bits)E"
     else
-        tn = safe_name(t)   # TODO: actually does support digits...
+        tn = safe_name(t)::String   # TODO: actually does support digits...
         if startswith(tn, r"\d")
             # C++ classes cannot start with a digit, so mangling doesn't support it
             tn = "_$(tn)"
diff --git a/src/metal.jl b/src/metal.jl
index 649f4bc1..aeff57dc 100644
--- a/src/metal.jl
+++ b/src/metal.jl
@@ -2271,18 +2271,19 @@ function msl_identifier(@nospecialize(T))
     str = String(strip(replace(julia_type_words(T), r"[^A-Za-z0-9_]+" => "_"), '_'))
     return isempty(str) || isdigit(str[1]) ? "_" * str : str
 end
-function julia_type_words(@nospecialize(x))
+# (recursive, so the result type is declared for inference)
+function julia_type_words(@nospecialize(x))::String
     if x isa DataType
-        join([String(nameof(x)); map(julia_type_words, x.parameters)], "_")
+        join([String(nameof(x)); String[julia_type_words(p) for p in x.parameters]], "_")
     elseif x isa Union
         # (sorted, as Julia orders union members by module name, which can be generated)
-        join(["Union"; sort!(map(julia_type_words, Base.uniontypes(x)))], "_")
+        join(["Union"; sort!(String[julia_type_words(T) for T in Base.uniontypes(x)])], "_")
     elseif x isa UnionAll
         julia_type_words(Base.unwrap_unionall(x))
     elseif x isa TypeVar
         String(x.name)
     elseif x isa Tuple
-        join(map(julia_type_words, x), "_")
+        join(String[julia_type_words(y) for y in x], "_")
     elseif x isa Union{Number,Symbol,AbstractChar,AbstractString}
         string(x)
     else
diff --git a/src/relocation.jl b/src/relocation.jl
index 59da580f..31bfab2a 100644
--- a/src/relocation.jl
+++ b/src/relocation.jl
@@ -83,7 +83,7 @@ end
 function resolve_relocation_target(target::CGlobalRef)
     if target.library === nothing
         # `jl_cglobal` accepts the symbol directly and does the process-wide `jl_dlfind`.
-        address = ccall(:jl_cglobal, Any, (Any, Any), target.symbol, UInt)
+        address = ccall(:jl_cglobal, Any, (Any, Any), target.symbol, UInt)::Ptr{UInt}
         return unsafe_load(address + target.offset)
     end
     handle = Libdl.dlopen(target.library)
diff --git a/src/rtlib.jl b/src/rtlib.jl
index 6c2d16a5..e38bd00c 100644
--- a/src/rtlib.jl
+++ b/src/rtlib.jl
@@ -37,7 +37,7 @@ function LLVM.call!(builder, rt::Runtime.RuntimeMethodInstance, args=LLVM.Value[
             runtime_function_type(job, rt)
         end
         LLVM.Function(mod, rt.llvm_name, ft)
-    end
+    end::LLVM.Function
     ft = f.function_type
     if !isdeclaration(f) && (rt.name !== :gc_pool_alloc && rt.name !== :report_exception)
         # XXX: uses of the gc_pool_alloc intrinsic can be introduced _after_ the runtime
diff --git a/src/runtime.jl b/src/runtime.jl
index 52168924..205092bc 100644
--- a/src/runtime.jl
+++ b/src/runtime.jl
@@ -13,6 +13,11 @@ using ..GPUCompiler
 using LLVM, LLVM.IR, LLVM.Build
 using LLVM.Interop
 
+# imported explicitly, so that the binding exists before the generated functions below
+# first use it. Julia 1.13 reports edges to a binding that a downstream package's
+# precompilation created as invalidations (JuliaLang/julia#59135).
+import Base: |
+
 
 ## representation of a runtime method instance
 
@@ -202,7 +207,7 @@ const gc_bits = 0x3 # FIXME
     T_pjlvalue = convert(LLVMType, Any; allow_boxed=true)
 
     # this isn't really a function, but we abuse it to get the JIT to resolve the address
-    typ = LLVM.Function(current_module(builder), "jl_" * String(type_name) * "_type",
+    typ = LLVM.Function(current_module(builder), "jl_" * String(type_name::Symbol) * "_type",
                         LLVM.FunctionType(T_pjlvalue))
 
     typ_var = bitcast!(builder, typ, T_ptag)
diff --git a/src/utils.jl b/src/utils.jl
index 3fc15d79..02758d79 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -72,6 +72,9 @@ end
 struct ExternalBackend
     library::String     # path to the shared library, as exported by its JLL
     prefix::String      # e.g. "NVPTX" for `NVPTXCompile`
+
+    # JLLs are loaded lazily, so the type of their library paths isn't inferred
+    ExternalBackend(library, prefix) = new(library::String, prefix::String)
 end
 
 function api(backend::ExternalBackend, name::String)
diff --git a/src/validation.jl b/src/validation.jl
index 2fef286a..2b0ea8d9 100644
--- a/src/validation.jl
+++ b/src/validation.jl
@@ -73,7 +73,7 @@ function explain_nonisbits(@nospecialize(dt), depth=1; maxdepth=10)
 end
 
 function check_invocation(@nospecialize(job::CompilerJob))
-    sig = job.source.specTypes
+    sig = job.source.specTypes::DataType
     ft = sig.parameters[1]
     tt = Tuple{sig.parameters[2:end]...}
 
@@ -656,6 +656,7 @@ function emitted_functions(mod::LLVM.Module, compiled)
     for entry in values(compiled)
         for name in (entry.func, entry.specfunc)
             name === nothing && continue
+            name = name::String     # `compiled` holds entries of any type
             emitted[name] = entry
             # functions may have been renamed since, but not their debug information
             f = get(functions, name, nothing)
@@ -795,7 +796,9 @@ end
 function describe_call(src::CodeInfo, mi::MethodInstance, pc::Int, @nospecialize(callee),
                        world::UInt; strict::Bool=false)
     stmt = src.code[pc]
-    (stmt isa Expr && stmt.head === :call) || return nothing
+    # separate checks, so that inference narrows `stmt` to an `Expr`
+    stmt isa Expr || return nothing
+    stmt.head === :call || return nothing
     f = constant_value(stmt.args[1], world)
     if callee !== nothing
         f === nothing && strict && return nothing