diff --git a/Arm/Memory/Common.lean b/Arm/Memory/Common.lean
index 8ba58452..0a354bfc 100644
--- a/Arm/Memory/Common.lean
+++ b/Arm/Memory/Common.lean
@@ -281,17 +281,8 @@ def TacticM.traceLargeMsg
 
 
 /-- TacticM's omega invoker -/
-def omega (bvToNatSimpCtx : Simp.Context) (bvToNatSimprocs : Array Simp.Simprocs) : TacticM Unit := do
-  withMainContext do
-    -- https://leanprover.zulipchat.com/#narrow/stream/326056-ICERM22-after-party/topic/Regression.20tests/near/290131280
-    let .some goal ← LNSymSimpAtStar (← getMainGoal) bvToNatSimpCtx bvToNatSimprocs
-      | trace[simp_mem.info] "simp [bv_toNat] at * managed to close goal."
-    replaceMainGoal [goal]
-    TacticM.withTraceNode' m!"goal post `bv_toNat` reductions (Note: can be large)" do
-      trace[simp_mem.info] "{goal}"
-    -- @bollu: TODO: understand what precisely we are recovering from.
-    withoutRecover do
-      evalTactic (← `(tactic| bv_omega_bench))
+def omega (g : MVarId) (bvToNatSimpCtx : Simp.Context) (bvToNatSimprocs : Array Simp.Simprocs) : MetaM Unit := do
+    BvOmegaBench.run g bvToNatSimpCtx bvToNatSimprocs
 
 /-
 Introduce a new definition into the local context, simplify it using `simp`,
@@ -326,6 +317,33 @@ def simpAndIntroDef (name : String) (hdefVal : Expr) : TacticM FVarId  := do
     replaceMainGoal [goal]
     return fvar
 
+def simpAndIntroDef' (g : MVarId) (name : String) (hdefVal : Expr) : MetaM (FVarId × MVarId)  := do
+  g.withContext do
+    let name ← mkFreshUserName <| .mkSimple name
+    let hdefTy ← inferType hdefVal
+
+    /- Simp to gain some more juice out of the defn.. -/
+    let mut simpTheorems : Array SimpTheorems := #[]
+    for a in #[`minimal_theory, `bitvec_rules, `bv_toNat] do
+      let some ext ← (getSimpExtension? a)
+        | throwError m!"[simp_mem] Internal error: simp attribute {a} not found!"
+      simpTheorems := simpTheorems.push (← ext.getTheorems)
+
+    -- unfold `state_value.
+    simpTheorems := simpTheorems.push <| ← ({} : SimpTheorems).addDeclToUnfold `state_value
+    let simpCtx : Simp.Context := {
+      simpTheorems,
+      config := { decide := true, failIfUnchanged := false },
+      congrTheorems := (← Meta.getSimpCongrTheorems)
+    }
+    let (simpResult, _stats) ← simp hdefTy simpCtx (simprocs := #[])
+    let hdefVal ← simpResult.mkCast hdefVal
+    let hdefTy ← inferType hdefVal
+
+    let g ← g.assert name hdefTy hdefVal
+    let (fvar, g) ← g.intro1P
+    return (fvar, g)
+
 section Hypotheses
 
 /--
@@ -467,12 +485,11 @@ def MemLegalProof.omega_def (h : MemLegalProof e) : Expr :=
   mkAppN (Expr.const ``mem_legal'.omega_def []) #[e.span.base, e.span.n, h.h]
 
 /-- Add the omega fact from `mem_legal'.def`. -/
-def MemLegalProof.addOmegaFacts (h : MemLegalProof e) (args : Array Expr) :
-    TacticM (Array Expr) := do
-  withMainContext do
-    let fvar ← simpAndIntroDef "hmemLegal_omega" h.omega_def
-    trace[simp_mem.info]  "{h}: added omega fact ({h.omega_def})"
-    return args.push (Expr.fvar fvar)
+def MemLegalProof.addOmegaFacts (h : MemLegalProof e) (g : MVarId) (args : Array Expr) :
+    MetaM (Array Expr × MVarId) := do
+  let (fvar, g) ← simpAndIntroDef' g "hmemLegal_omega" h.omega_def
+  trace[simp_mem.info]  "{h}: added omega fact ({h.omega_def})"
+  return (args.push (Expr.fvar fvar), g)
 
 /--
 info: mem_subset'.omega_def {a : BitVec 64} {an : Nat} {b : BitVec 64} {bn : Nat} (h : mem_subset' a an b bn) :
@@ -489,12 +506,11 @@ def MemSubsetProof.omega_def (h : MemSubsetProof e) : Expr :=
     #[e.sa.base, e.sa.n, e.sb.base, e.sb.n, h.h]
 
 /-- Add the omega fact from `mem_legal'.omega_def` into the main goal. -/
-def MemSubsetProof.addOmegaFacts (h : MemSubsetProof e) (args : Array Expr) :
-    TacticM (Array Expr) := do
-  withMainContext do
-    let fvar ← simpAndIntroDef "hmemSubset_omega" h.omega_def
-    trace[simp_mem.info]  "{h}: added omega fact ({h.omega_def})"
-    return args.push (Expr.fvar fvar)
+def MemSubsetProof.addOmegaFacts (h : MemSubsetProof e) (g : MVarId) (args : Array Expr) :
+    MetaM (Array Expr × MVarId) := do
+  let (fvar, g) ← simpAndIntroDef' g "hmemSubset_omega" h.omega_def
+  trace[simp_mem.info]  "{h}: added omega fact ({h.omega_def})"
+  return (args.push (Expr.fvar fvar), g)
 
 /--
 Build a term corresponding to `mem_separate'.omega_def` which has facts written
@@ -505,13 +521,11 @@ def MemSeparateProof.omega_def (h : MemSeparateProof e) : Expr :=
     #[e.sa.base, e.sa.n, e.sb.base, e.sb.n, h.h]
 
 /-- Add the omega fact from `mem_legal'.omega_def`. -/
-def MemSeparateProof.addOmegaFacts (h : MemSeparateProof e) (args : Array Expr) :
-    TacticM (Array Expr) := do
-  withMainContext do
-    -- simp only [bitvec_rules] (failIfUnchanged := false)
-    let fvar ← simpAndIntroDef "hmemSeparate_omega" h.omega_def
-    trace[simp_mem.info]  "{h}: added omega fact ({h.omega_def})"
-    return args.push (Expr.fvar fvar)
+def MemSeparateProof.addOmegaFacts (h : MemSeparateProof e) (g : MVarId) (args : Array Expr) :
+    MetaM (Array Expr × MVarId) := do
+  let (fvar, g) ← simpAndIntroDef' g "hmemSeparate_omega" h.omega_def
+  trace[simp_mem.info]  "{h}: added omega fact ({h.omega_def})"
+  return (args.push (Expr.fvar fvar), g)
 
 
 
@@ -537,7 +551,7 @@ info: Memory.Region.separate'_of_pairwiseSeprate_of_mem_of_mem {mems : List Memo
 /-- make `Memory.Region.separate'_of_pairwiseSeprate_of_mem_of_mem i j (by decide) a b rfl rfl`. -/
 def MemPairwiseSeparateProof.mem_separate'_of_pairwiseSeparate_of_mem_of_mem
     (self : MemPairwiseSeparateProof mems) (i j : Nat) (a b : MemSpanExpr)  :
-    TacticM <| MemSeparateProof ⟨a, b⟩ := do
+    MetaM <| MemSeparateProof ⟨a, b⟩ := do
   let iexpr := mkNatLit i
   let jexpr := mkNatLit j
     -- i ≠ j
@@ -562,41 +576,44 @@ Currently, if the list is syntacticaly of the form [x1, ..., xn],
  we create hypotheses of the form `mem_separate' xi xj` for all i, j..
 This can be generalized to pairwise separation given hypotheses x ∈ xs, x' ∈ xs.
 -/
-def MemPairwiseSeparateProof.addOmegaFacts (h : MemPairwiseSeparateProof e) (args : Array Expr) :
-    TacticM (Array Expr) := do
+def MemPairwiseSeparateProof.addOmegaFacts (h : MemPairwiseSeparateProof e) (g : MVarId) (args : Array Expr) :
+    MetaM (Array Expr × MVarId) := do
   -- We need to loop over i, j where i < j and extract hypotheses.
   -- We need to find the length of the list, and return an `Array MemRegion`.
   let mut args := args
+  let mut g := g
   for i in [0:e.xs.size] do
     for j in [i+1:e.xs.size] do
       let a := e.xs[i]!
       let b := e.xs[j]!
-      args ← TacticM.withTraceNode' m!"Exploiting ({i}, {j}) : {a} ⟂ {b}" do
+      (args, g) ← TacticM.withTraceNode' m!"Exploiting ({i}, {j}) : {a} ⟂ {b}" do
         let proof ← h.mem_separate'_of_pairwiseSeparate_of_mem_of_mem i j a b
         TacticM.traceLargeMsg m!"added {← inferType proof.h}" m!"{proof.h}"
-        proof.addOmegaFacts args
-  return args
+        proof.addOmegaFacts g args
+  return (args, g)
 /--
 Given a hypothesis, add declarations that would be useful for omega-blasting
 -/
-def Hypothesis.addOmegaFactsOfHyp (h : Hypothesis) (args : Array Expr) : TacticM (Array Expr) :=
+def Hypothesis.addOmegaFactsOfHyp (g : MVarId) (h : Hypothesis) (args : Array Expr) : 
+    MetaM (Array Expr × MVarId) :=
   match h with
-  | Hypothesis.legal h => h.addOmegaFacts args
-  | Hypothesis.subset h => h.addOmegaFacts args
-  | Hypothesis.separate h => h.addOmegaFacts args
-  | Hypothesis.pairwiseSeparate h => h.addOmegaFacts args
-  | Hypothesis.read_eq _h => return args -- read has no extra `omega` facts.
+  | Hypothesis.legal h => h.addOmegaFacts g args
+  | Hypothesis.subset h => h.addOmegaFacts g args
+  | Hypothesis.separate h => h.addOmegaFacts g args
+  | Hypothesis.pairwiseSeparate h => h.addOmegaFacts g args
+  | Hypothesis.read_eq _h => return (args, g) -- read has no extra `omega` facts.
 
 /--
 Accumulate all omega defs in `args`.
 -/
-def Hypothesis.addOmegaFactsOfHyps (hs : List Hypothesis) (args : Array Expr)
-    : TacticM (Array Expr) := do
+def Hypothesis.addOmegaFactsOfHyps (g : MVarId) (hs : List Hypothesis) (args : Array Expr)
+    : MetaM (Array Expr × MVarId) := do
   TacticM.withTraceNode' m!"Adding omega facts from hypotheses" do
     let mut args := args
+    let mut g := g
     for h in hs do
-      args ← h.addOmegaFactsOfHyp args
-    return args
+      (args, g) ← h.addOmegaFactsOfHyp g args
+    return (args, g)
 
 end Hypotheses
 
@@ -741,7 +758,7 @@ An example is `mem_lega'.of_omega n a`, which has type:
 -/
 def proveWithOmega?  {α : Type} [ToMessageData α] [OmegaReducible α] (e : α)
     (bvToNatSimpCtx : Simp.Context) (bvToNatSimprocs : Array Simp.Simprocs)
-    (hyps : Array Memory.Hypothesis) : TacticM (Option (Proof α e)) := do
+    (hyps : Array Memory.Hypothesis) : MetaM (Option (Proof α e)) := do
   let proofFromOmegaVal := (OmegaReducible.reduceToOmega e)
   -- (h : a.toNat + n ≤ 2 ^ 64) → mem_legal' a n
   let proofFromOmegaTy ← inferType (OmegaReducible.reduceToOmega e)
@@ -753,19 +770,16 @@ def proveWithOmega?  {α : Type} [ToMessageData α] [OmegaReducible α] (e : α)
   trace[simp_mem.info] "omega obligation '{omegaObligationTy}'"
   let omegaObligationVal ← mkFreshExprMVar (type? := omegaObligationTy)
   let factProof := mkAppN proofFromOmegaVal #[omegaObligationVal]
-  let oldGoals := (← getGoals)
-
+  let g := omegaObligationVal.mvarId!
+  g.withContext do
   try
-    setGoals (omegaObligationVal.mvarId! :: (← getGoals))
-    withMainContext do
-    let _ ← Hypothesis.addOmegaFactsOfHyps hyps.toList #[]
+    let (_, g) ← Hypothesis.addOmegaFactsOfHyps g hyps.toList #[]
     trace[simp_mem.info] m!"Executing `omega` to close {e}"
-    omega bvToNatSimpCtx bvToNatSimprocs
+    omega g bvToNatSimpCtx bvToNatSimprocs
     trace[simp_mem.info] "{checkEmoji} `omega` succeeded."
     return (.some <| Proof.mk (← instantiateMVars factProof))
   catch e =>
     trace[simp_mem.info]  "{crossEmoji} `omega` failed with error:\n{e.toMessageData}"
-    setGoals oldGoals
     return none
   end ReductionToOmega
 
@@ -775,7 +789,7 @@ and simplifying all other expressions. return `true` if goal has been closed, an
 -/
 partial def closeMemSideCondition (g : MVarId)
     (bvToNatSimpCtx : Simp.Context) (bvToNatSimprocs : Array Simp.Simprocs)
-    (hyps : Array Memory.Hypothesis) : TacticM Bool := do
+    (hyps : Array Memory.Hypothesis) : MetaM Bool := do
   g.withContext do
     trace[simp_mem.info] "{processingEmoji} Matching on ⊢ {← g.getType}"
     let gt ← g.getType
diff --git a/Arm/Memory/MemOmega.lean b/Arm/Memory/MemOmega.lean
index 48c60ae7..50044854 100644
--- a/Arm/Memory/MemOmega.lean
+++ b/Arm/Memory/MemOmega.lean
@@ -62,16 +62,13 @@ def init (cfg : Config) : MetaM Context := do
   return {cfg, bvToNatSimpCtx, bvToNatSimprocs}
 end Context
 
-abbrev MemOmegaM := (ReaderT Context TacticM)
+abbrev MemOmegaM := (ReaderT Context MetaM)
 
 namespace MemOmegaM
-
-  def run (ctx : Context) (x : MemOmegaM α) : TacticM α := ReaderT.run x ctx
-
+  def run (ctx : Context) (x : MemOmegaM α) : MetaM α := ReaderT.run x ctx
 end MemOmegaM
 
-def memOmegaTac : MemOmegaM Unit := do
-  let g ← getMainGoal
+def memOmega (g : MVarId) : MemOmegaM Unit := do
   g.withContext do
     /- We need to explode all pairwise separate hyps -/
     let rawHyps ← getLocalHyps
@@ -85,22 +82,20 @@ def memOmegaTac : MemOmegaM Unit := do
     hyps := hyps.filter (!·.isPairwiseSeparate || isPairwiseEnabled)
 
     -- used specialized procedure that doesn't unfold everything for the easy case.
-    if ← closeMemSideCondition (← getMainGoal) (← readThe Context).bvToNatSimpCtx (← readThe Context).bvToNatSimprocs hyps then
+    if ← closeMemSideCondition g (← readThe Context).bvToNatSimpCtx (← readThe Context).bvToNatSimprocs hyps then
       return ()
     else
       -- in the bad case, just rip through everything.
-      -- let _ ← Hypothesis.addOmegaFactsOfHyps (hyps.toList.filter (fun h => h.isPairwiseSeparate)) #[]
-      let _ ← Hypothesis.addOmegaFactsOfHyps hyps.toList #[]
+      let (_, g) ← Hypothesis.addOmegaFactsOfHyps g hyps.toList #[]
 
       TacticM.withTraceNode' m!"Reducion to omega" do
         try
-          TacticM.traceLargeMsg m!"goal (Note: can be large)"  m!"{← getMainGoal}"
-          omega (← readThe Context).bvToNatSimpCtx (← readThe Context).bvToNatSimprocs
+          TacticM.traceLargeMsg m!"goal (Note: can be large)"  m!"{g}"
+          omega g (← readThe Context).bvToNatSimpCtx (← readThe Context).bvToNatSimprocs
           trace[simp_mem.info] "{checkEmoji} `omega` succeeded."
         catch e =>
           trace[simp_mem.info]  "{crossEmoji} `omega` failed with error:\n{e.toMessageData}"
 
-
 /--
 Allow elaboration of `MemOmegaConfig` arguments to tactics.
 -/
@@ -124,14 +119,16 @@ syntax (name := mem_omega_bang) "mem_omega!" (Lean.Parser.Tactic.config)? : tact
 def evalMemOmega : Tactic := fun
   | `(tactic| mem_omega $[$cfg]?) => do
     let cfg ← elabMemOmegaConfig (mkOptionalNode cfg)
-    memOmegaTac.run (← Context.init cfg)
+    liftMetaFinishingTactic fun g => do
+      memOmega g |>.run (← Context.init cfg)
   | _ => throwUnsupportedSyntax
 
 @[tactic mem_omega_bang]
 def evalMemOmegaBang : Tactic := fun
   | `(tactic| mem_omega! $[$cfg]?) => do
     let cfg ← elabMemOmegaConfig (mkOptionalNode cfg)
-    memOmegaTac.run (← Context.init cfg.mkBang)
+    liftMetaFinishingTactic fun g => do
+      memOmega g |>.run (← Context.init cfg.mkBang)
   | _ => throwUnsupportedSyntax
 
 end MemOmega
diff --git a/Tactics/BvOmegaBench.lean b/Tactics/BvOmegaBench.lean
index 8a159eab..4224998f 100644
--- a/Tactics/BvOmegaBench.lean
+++ b/Tactics/BvOmegaBench.lean
@@ -18,9 +18,11 @@ open Lean Elab Meta Tactic Omega
 
 namespace BvOmegaBench
 
-
--- Adapted mkSimpContext:
--- from https://github.com/leanprover/lean4/blob/master/src/Lean/Elab/Tactic/Simp.lean#L287
+/-
+Make the `SimpContext` that corresponds to using `bv_toNat` 
+Adapted mkSimpContext:
+from https://github.com/leanprover/lean4/blob/master/src/Lean/Elab/Tactic/Simp.lean#L287
+-/
 def bvOmegaSimpCtx : MetaM (Simp.Context ×  Array Simp.Simprocs) := do
   let mut simprocs := #[]
   let mut simpTheorems := #[]
@@ -47,14 +49,13 @@ Code adapted from:
 - https://github.com/leanprover/lean4/blob/master/src/Lean/Elab/Tactic/Simp.lean#L406
 - https://github.com/leanprover/lean4/blob/master/src/Lean/Elab/Tactic/Omega/Frontend.lean#L685
 -/
-def run (g : MVarId) : MetaM Unit := do
+def run (g : MVarId)  (bvToNatSimpCtx : Simp.Context) (bvToNatSimprocs : Array Simp.Simprocs) : MetaM Unit := do
   let minMs ← getBvOmegaBenchMinMs
   let goalStr ← ppGoal g
   let startTime ← IO.monoMsNow
   let filePath ← getBvOmegaBenchFilePath
   try
       g.withContext do
-        let (bvToNatSimpCtx, bvToNatSimprocs) ← bvOmegaSimpCtx
         let nonDepHyps ← g.getNondepPropHyps
         let mut g := g
 
@@ -101,6 +102,11 @@ def run (g : MVarId) : MetaM Unit := do
           h.putStrLn s!"enderror"
     throw e
 
+/-- Build the default simp context (bv_toNat) and run omega -/
+def runWithDefaultSimpContext (g : MVarId) : MetaM Unit := do
+  let (bvToNatSimpCtx, bvToNatSimprocs) ← bvOmegaSimpCtx
+  run g bvToNatSimpCtx bvToNatSimprocs
+
 end BvOmegaBench
 
 syntax (name := bvOmegaBenchTac) "bv_omega_bench" : tactic
@@ -109,5 +115,5 @@ syntax (name := bvOmegaBenchTac) "bv_omega_bench" : tactic
 def bvOmegaBenchImpl : Tactic
 | `(tactic| bv_omega_bench) =>
     liftMetaFinishingTactic fun g => do
-      BvOmegaBench.run g
+      BvOmegaBench.runWithDefaultSimpContext g
 | _ => throwUnsupportedSyntax