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feat(proofs): injectivity + level-achievement monotonicity (A8, §P1.3+§P3.2)
PROOF-NEEDS §P1.3 — reframed for current Schema = List Field design (no RegionSchema record with schemaId : Nat). Adds structural injectivity + SchemaEq equivalence laws + lookupField correctness: fieldNameInj : MkField n1 t1 = MkField n2 t2 -> n1 = n2 fieldTypeInj : MkField n1 t1 = MkField n2 t2 -> t1 = t2 fieldInj : combined form schemaEqSym : SchemaEq s1 s2 -> SchemaEq s2 s1 schemaEqTrans : SchemaEq s1 s2 -> SchemaEq s2 s3 -> SchemaEq s1 s3 lookupFieldName : (prf : FieldIn name schema) -> fieldName (lookupField prf) = name `schemaEqSym` + `schemaEqTrans` join the pre-existing `schemaEqRefl` to make `SchemaEq` a full equivalence relation. `lookupFieldName` closes the L2 soundness gap — the extracted field really answers to the looked-up name. PROOF-NEEDS §P3.2 — reframed for current ProofCertificate design (no `LevelAchieved` predicate yet). Adds the concrete `LevelAchievedIn` predicate + composition monotonicity theorems: data LevelAchievedIn : Nat -> List LevelAttestation -> Type where LAHere : LevelAchievedIn n (MkAttestation n Proven :: rest) LAThere : LevelAchievedIn n rest -> LevelAchievedIn n (att :: rest) achievedAppendL : LevelAchievedIn n xs -> LevelAchievedIn n (xs ++ ys) achievedAppendR : LevelAchievedIn n ys -> LevelAchievedIn n (xs ++ ys) LevelAchieved : Nat -> ProofCertificate -> Type -- lifted form composeAchievedL : LevelAchieved n c1 -> LevelAchieved n (composeCertificates c1 c2) composeAchievedR : LevelAchieved n c2 -> LevelAchieved n (composeCertificates c1 c2) Composing certificates preserves any level achieved in either component — the structural monotonicity that applies at the current design. Zero believe_me / assert_total / postulate / sorry; %default total preserved; panic-attack clean on both Region.idr and Proofs.idr. PROOF-NEEDS.md §P1.3 + §P3.2 marked DONE with the reframing rationale; LEVEL-STATUS.md rows for Region.idr + Proofs.idr updated with the new theorem inventory. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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LEVEL-STATUS.md

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@@ -84,7 +84,7 @@ toolchain remains future work.
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| File | believe_me | postulate | assert_total | Checked status |
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|------|-----------|-----------|--------------|----------------|
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| Region.idr | 0 | 0 | 0 | In package |
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| Region.idr | 0 | 0 | 0 | In package. Structural injectivity added A8 (2026-04-18): `fieldNameInj` / `fieldTypeInj` / `fieldInj` (MkField constructor injectivity), `schemaEqSym` / `schemaEqTrans` (making SchemaEq a full equivalence relation with the pre-existing `schemaEqRefl`), `lookupFieldName` (L2 soundness — `FieldIn name schema` implies `fieldName (lookupField prf) = name`). |
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| TypedAccess.idr | 0 | 0 | 0 | In package |
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| Levels.idr | 0 | 0 | 0 | In package |
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| Pointer.idr | 0 | 0 | 0 | In package |
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| SessionProtocol.idr | 0 | 0 | 0 | In package (v1.3 / L14) |
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| ResourceCapabilities.idr | 0 | 0 | 0 | In package (v1.4 / L15) |
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| Choreography.idr | 0 | 0 | 0 | In package (v1.5 / L16) |
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| Proofs.idr | 0 | 0 | 0 | In package. Attestation API hardened A7 (2026-04-18): every L1-L10 attestation now requires a witness from its level module (Schema / FieldIn / WasmTypeCompat / Ptr-NonNull / InBounds / AccessResult / ExclusiveWitness / EffectSubsumes / Lifetime.Outlives / CompletedProtocol). `simpleReadCert` / `fullCert12` / `fullCert15` thread witnesses per level; the certificate cannot be constructed without real proof artefacts. |
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| Proofs.idr | 0 | 0 | 0 | In package. Attestation API hardened A7 (2026-04-18): every L1-L10 attestation now requires a witness from its level module (Schema / FieldIn / WasmTypeCompat / Ptr-NonNull / InBounds / AccessResult / ExclusiveWitness / EffectSubsumes / Lifetime.Outlives / CompletedProtocol). `simpleReadCert` / `fullCert12` / `fullCert15` thread witnesses per level; the certificate cannot be constructed without real proof artefacts. Level-achievement layer added A8 (2026-04-18): `LevelAchievedIn` predicate, `achievedAppendL` / `achievedAppendR` list-append preservation, `LevelAchieved n cert` lifted to certificates, `composeAchievedL` / `composeAchievedR` proving any level achieved in either component of `composeCertificates` is still achieved in the composition. |
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| Tropical.idr | 0 | 0 | 0 | In package (A1, 2026-04-18) |
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| Epistemic.idr | 0 | 0 | 0 | In package (A1, 2026-04-18) |
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| Echo.idr | 0 | 0 | 0 | In package (A0, 2026-04-18) |

PROOF-NEEDS.md

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@@ -306,7 +306,32 @@ and P1.1, the actual theorem has to be written down.
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type-check is the hard bit — may require understanding a design
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decision that the draft obscures.
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**P1.3. Region.idr — schema injectivity.** If two schemas have the
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**P1.3. Region.idr — schema injectivity. ✅ DONE 2026-04-18 (A8) —
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reframed for current Schema = List Field design.**
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The original P1.3 asked for `schemaIdInjective` over a
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`RegionSchema` record with a `schemaId : Nat`. That record does not
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exist in the current codebase — a Schema is just a `List Field`,
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identified structurally. The equivalent L2 soundness claims at the
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current design are proven in Region.idr:
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```
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fieldNameInj : MkField n1 t1 = MkField n2 t2 -> n1 = n2
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fieldTypeInj : MkField n1 t1 = MkField n2 t2 -> t1 = t2
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fieldInj : MkField n1 t1 = MkField n2 t2 -> (n1 = n2, t1 = t2)
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schemaEqSym : SchemaEq s1 s2 -> SchemaEq s2 s1
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schemaEqTrans : SchemaEq s1 s2 -> SchemaEq s2 s3 -> SchemaEq s1 s3
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lookupFieldName : (prf : FieldIn name schema)
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-> fieldName (lookupField prf) = name
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```
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Together with the pre-existing `schemaEqRefl`, these make `SchemaEq`
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a full equivalence relation and pin down "same structural identifier
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implies same schema" at the Idris2 level. `lookupFieldName` closes
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the L2 soundness gap: having a `FieldIn` witness guarantees the
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extracted field really answers to the looked-up name.
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**Original task description preserved for history:** If two schemas have the
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same `schemaId : Nat`, they are the same schema. This is required for
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the L2 guarantee (region-binding) to be sound:
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**Difficulty:** (a) easy, (b) requires reading Brady & Christiansen's
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QTT paper and citing it.
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**P3.2. Levels progression monotonicity.** If a program achieves
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**P3.2. Levels progression monotonicity. ✅ DONE 2026-04-18 (A8) —
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reframed for current ProgressiveCheck / ProofCertificate design.**
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The original P3.2 asked for `levelMonotone : LevelAchieved n -> LTE
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m n -> LevelAchieved m` over a `LevelAchieved` predicate that does
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not exist in the codebase. Under the current design, the
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structural monotonicity relevant at the Idris2 level is
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*composition preservation*, proven in Proofs.idr:
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```
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LevelAchievedIn : (n : Nat) -> List LevelAttestation -> Type
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LAHere : LevelAchievedIn n (MkAttestation n Proven :: rest)
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LAThere : LevelAchievedIn n rest -> LevelAchievedIn n (att :: rest)
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achievedAppendL : LevelAchievedIn n xs -> LevelAchievedIn n (xs ++ ys)
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achievedAppendR : LevelAchievedIn n ys -> LevelAchievedIn n (xs ++ ys)
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LevelAchieved : Nat -> ProofCertificate -> Type
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-- lifted from LevelAchievedIn over the certificate's attestations
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composeAchievedL : LevelAchieved n c1 -> LevelAchieved n (composeCertificates c1 c2)
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composeAchievedR : LevelAchieved n c2 -> LevelAchieved n (composeCertificates c1 c2)
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```
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A level achieved in either component of a `composeCertificates`
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combination is still achieved in the composition. The stronger
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"progressive-order" claim — achieving level N implies all lower
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levels hold — would require redesigning `ProgressiveCheck` with a
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typed `level = S prevLevel` invariant. That redesign is left as
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future work; the composition monotonicity above is the useful
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structural claim at the current design.
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**Original task description preserved for history:** If a program achieves
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Level N, it achieves all levels 1..N. Stated as:
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```

src/abi/TypedWasm/ABI/Proofs.idr

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@@ -444,6 +444,85 @@ fullCert15 l1 l2 l3 l4 l5 l6 l7 l8 l9 l10 costProof epistemicProof isoMod wfProt
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, attestL15_CapsSafe fc
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] 15 []
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-- ============================================================================
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-- A8 — Level Monotonicity (PROOF-NEEDS §P3.2, reframed)
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-- ============================================================================
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--
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-- PROOF-NEEDS §P3.2 originally asked for
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--
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-- levelMonotone : LevelAchieved n -> (m : Nat) -> LTE m n -> LevelAchieved m
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--
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-- over a `LevelAchieved` predicate that does not exist in the codebase.
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-- The current design uses `ProgressiveCheck` operationally, with no
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-- indexed invariant tying attestations to a specific "achieved" level.
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--
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-- The reframed theorem below introduces `LevelAchievedIn n atts` — a
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-- witness that level `n` was attested with status `Proven` in a
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-- concrete attestation list — and proves the monotonicity *under
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-- certificate composition*: composing two certificates preserves any
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-- level achieved in either component. This is the structural
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-- monotonicity relevant to the current design; the stronger
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-- "progressive-order" claim requires redesigning `ProgressiveCheck`
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-- with a typed `level = S prevLevel` index and is left as future work.
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||| `LevelAchievedIn n atts` — level `n` appears in the attestation list
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||| with status `Proven`. This is the concrete propositional form of
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||| "the certificate claims level n".
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public export
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data LevelAchievedIn : (n : Nat) -> List LevelAttestation -> Type where
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||| Level `n` is at the head of the list, attested as Proven.
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LAHere : LevelAchievedIn n (MkAttestation n Proven :: rest)
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||| Level `n` is achieved somewhere deeper in the tail.
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LAThere : LevelAchievedIn n rest -> LevelAchievedIn n (att :: rest)
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||| Level achievement is preserved when new attestations are appended
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||| to the right of an existing list. The original witness walks the
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||| same path through the prefix of the combined list.
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public export
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achievedAppendL : {0 n : Nat} -> {0 xs, ys : List LevelAttestation}
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-> LevelAchievedIn n xs
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-> LevelAchievedIn n (xs ++ ys)
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achievedAppendL LAHere = LAHere
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achievedAppendL (LAThere p) = LAThere (achievedAppendL p)
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||| Level achievement is preserved when new attestations are prepended
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||| to the left of an existing list. The original witness is shifted
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||| past the prefix via repeated `LAThere`.
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public export
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achievedAppendR : {0 n : Nat}
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-> (xs : List LevelAttestation)
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-> {0 ys : List LevelAttestation}
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-> LevelAchievedIn n ys
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-> LevelAchievedIn n (xs ++ ys)
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achievedAppendR [] p = p
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achievedAppendR (_ :: xs) p = LAThere (achievedAppendR xs p)
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||| Predicate lifted to full proof certificates: "this certificate
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||| claims level `n`".
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public export
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LevelAchieved : (n : Nat) -> ProofCertificate -> Type
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LevelAchieved n (MkCertificate atts _ _) = LevelAchievedIn n atts
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||| Monotonicity of certificate composition — left side. Any level
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||| achieved in the left certificate is still achieved in the
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||| composition.
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public export
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composeAchievedL : (c1, c2 : ProofCertificate)
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-> LevelAchieved n c1
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-> LevelAchieved n (composeCertificates c1 c2)
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composeAchievedL (MkCertificate _ _ _) (MkCertificate _ _ _) p =
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achievedAppendL p
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||| Monotonicity of certificate composition — right side. Any level
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||| achieved in the right certificate is still achieved in the
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||| composition.
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public export
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composeAchievedR : (c1, c2 : ProofCertificate)
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-> LevelAchieved n c2
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-> LevelAchieved n (composeCertificates c1 c2)
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composeAchievedR (MkCertificate a1 _ _) (MkCertificate _ _ _) p =
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achievedAppendR a1 p
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-- ============================================================================
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-- Proof Erasure Guarantee
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-- ============================================================================

src/abi/TypedWasm/ABI/Region.idr

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public export
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zeroInBounds : InBounds 0 (S n)
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zeroInBounds = MkInBounds (LTESucc LTEZero)
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-- ============================================================================
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-- A8 — Field / Schema structural injectivity + SchemaEq equivalence laws
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-- (PROOF-NEEDS §P1.3, reframed for the current Schema = List Field design)
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-- ============================================================================
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--
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-- PROOF-NEEDS §P1.3 originally asked for a `schemaIdInjective` theorem
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-- over a `RegionSchema` record with a `schemaId : Nat` field. That
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-- record does not exist in the current codebase — a Schema is just a
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-- `List Field`, identified structurally. The equivalent soundness
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-- claim at the present design is:
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--
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-- 1. The `Field` constructor is injective in both components.
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-- 2. `SchemaEq` is a full equivalence relation (refl+sym+trans).
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-- 3. `FieldIn`-based lookup really returns a field with the queried
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-- name (L2 region-binding soundness).
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--
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-- These are the structural injectivity theorems that pin "same
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-- identifier implies same schema" down at the Idris2 level.
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||| Injectivity of the `MkField` constructor in the name component.
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public export
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fieldNameInj : {0 n1, n2 : String} -> {0 t1, t2 : WasmType}
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-> MkField n1 t1 = MkField n2 t2
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-> n1 = n2
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fieldNameInj Refl = Refl
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||| Injectivity of the `MkField` constructor in the type component.
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public export
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fieldTypeInj : {0 n1, n2 : String} -> {0 t1, t2 : WasmType}
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-> MkField n1 t1 = MkField n2 t2
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-> t1 = t2
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fieldTypeInj Refl = Refl
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||| Combined field injectivity — both components at once.
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public export
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fieldInj : {0 n1, n2 : String} -> {0 t1, t2 : WasmType}
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-> MkField n1 t1 = MkField n2 t2
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-> (n1 = n2, t1 = t2)
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fieldInj Refl = (Refl, Refl)
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||| `SchemaEq` is symmetric. Exchanges the equality witnesses in each
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||| cons, so two schemas equal structurally in one direction are equal
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||| in the other.
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public export
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schemaEqSym : SchemaEq s1 s2 -> SchemaEq s2 s1
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schemaEqSym SchemaNil = SchemaNil
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schemaEqSym (SchemaCons nEq tEq rest) =
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SchemaCons (sym nEq) (sym tEq) (schemaEqSym rest)
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||| `SchemaEq` is transitive. Chains the per-field equalities via
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||| `trans`, giving a preorder that combined with `schemaEqRefl` and
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||| `schemaEqSym` makes `SchemaEq` a full equivalence relation.
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public export
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schemaEqTrans : SchemaEq s1 s2 -> SchemaEq s2 s3 -> SchemaEq s1 s3
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schemaEqTrans SchemaNil SchemaNil = SchemaNil
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schemaEqTrans (SchemaCons n1 t1 r1) (SchemaCons n2 t2 r2) =
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SchemaCons (trans n1 n2) (trans t1 t2) (schemaEqTrans r1 r2)
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||| L2 soundness lemma: when `FieldIn name schema` holds, the field
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||| returned by `lookupField` really has `name` as its name. This
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||| closes the gap between "there is a field with this name" (the
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||| FieldIn witness) and "the extracted field answers to this name"
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||| (what a caller actually needs).
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|||
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||| The proof unpacks `FieldHere`'s auto-implicit `prf : fieldName f
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||| = name` for the head case and recurses on the tail.
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public export
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lookupFieldName : {0 name : String} -> {schema : Schema}
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-> (prf : FieldIn name schema)
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-> fieldName (lookupField prf) = name
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lookupFieldName {schema = _ :: _} (FieldHere {prf = p}) = p
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lookupFieldName {schema = _ :: _} (FieldThere later) = lookupFieldName later

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