diff --git a/docs/specs/2026-05-21-schema-camelcase-fix.md b/docs/specs/2026-05-21-schema-camelcase-fix.md
index 8f2db68..0cd369b 100644
--- a/docs/specs/2026-05-21-schema-camelcase-fix.md
+++ b/docs/specs/2026-05-21-schema-camelcase-fix.md
@@ -17,7 +17,7 @@ the canonical JSON layer.
 
 ## Architecture
 
-This is a schema-only milestone. Three layers are affected:
+This is a schema-only milestone. Four layers are affected:
 
 1. **Canonical JSON tag layer.** Two `#[serde(rename = "...")]`
    attributes on `Term::Lam` in `crates/ailang-core/src/ast.rs:492,494`
@@ -41,7 +41,42 @@ This is a schema-only milestone. Three layers are affected:
    - `experiments/2026-05-12-cross-model-authoring/master/examples/fn_with_lambda.ail.json`
    - `crates/ailang-core/src/workspace.rs:1925-1926`
    (Verified via `grep -rn '"paramTypes"\|"retType"' --include="*.rs"
-   --include="*.json"` — exhaustive list.)
+   --include="*.json"` — exhaustive list. Each fixture carries
+   exactly two occurrences of the two tags combined, one per line.)
+
+4. **Canonical-schema contract + rustdoc layer.** Three rustdoc
+   strings in production source describe the present-state schema
+   (rather than implementation history); per the Honesty Rule
+   (`design/contracts/honesty-rule.md`) they must read truthfully
+   after the rename:
+   - `crates/ailang-core/src/ast.rs:8` — module-level `//!` enumerating
+     example field renames.
+   - `crates/ailang-surface/src/parse.rs:81` — module-level `//!`
+     mentioning `lam`'s `paramTypes` carry.
+   - `crates/ailang-check/src/lib.rs:1707` — rustdoc on the InstanceMethod
+     routing helper.
+
+   Plus the canonical data-model contract document itself, which
+   ships fenced JSON blocks describing the schema verbatim:
+   - `design/contracts/data-model.md:142-147` — the `Term::Lam`
+     fenced-JSON schema block.
+
+   The data-model contract IS the canonical schema documentation
+   (linked from `design/INDEX.md` row `data-model`, with ratifying
+   test `crates/ailang-core/tests/design_schema_drift.rs`). Leaving
+   it on the old tags after `ast.rs` ships kebab would be a direct
+   Honesty-Rule violation.
+
+The experiment-tree under
+`experiments/2026-05-12-cross-model-authoring/` (master spec,
+renderings, run transcripts) carries the old tags in multiple
+places. These are frozen historical artefacts of the 2026-05-12
+cross-model-authoring experiment — analogous to `docs/plans/*.md`
+under the Honesty Rule — and are NOT migrated by this milestone.
+The experiment's `master/examples/fn_with_lambda.ail.json` IS
+migrated (it is a checked-in JSON fixture the workspace loader
+could deserialise); the surrounding prose documents and run
+transcripts are not.
 
 **Hash blast radius is zero on pinned modules.** None of the
 `.ail` modules pinned in `crates/ailang-core/tests/hash_pin.rs`
@@ -180,20 +215,27 @@ the surrounding fixture content is untouched.
 | Component | Change |
 |-----------|--------|
 | `crates/ailang-core/src/ast.rs:492,494` | Two `#[serde(rename)]` strings: `"paramTypes" → "param-types"`, `"retType" → "ret-type"`. |
-| `crates/ailang-core/src/workspace.rs:1925-1926` | In-source JSON-literal in a test: same two key renames. |
-| `examples/test_loop_binder_captured_by_lambda.ail.json` | Same two key renames (verified 3 occurrences combined of the two tags via `grep -c`). |
-| `experiments/2026-05-12-cross-model-authoring/master/examples/fn_with_lambda.ail.json` | Same two key renames (verified 3 occurrences combined). |
-| `crates/ailang-surface/src/{print,parse}.rs` | **No change.** Form-A never used these tag names. |
+| `crates/ailang-core/src/ast.rs:8` | Module-level `//!` rustdoc — substitute the new tag spellings in the example list. |
+| `crates/ailang-surface/src/parse.rs:81` | Module-level `//!` rustdoc — substitute the new tag spelling. |
+| `crates/ailang-check/src/lib.rs:1707` | `///` rustdoc — substitute the new tag spellings. |
+| `crates/ailang-core/src/workspace.rs:1925-1926` | In-source JSON-literal in `ct1_validator_walks_lam_embedded_types` (function at L1911): same two key renames. |
+| `design/contracts/data-model.md:142-147` | Fenced JSON-block in the canonical data-model contract: same two key renames. |
+| `examples/test_loop_binder_captured_by_lambda.ail.json` | Same two key renames (2 occurrences total of the two tags, one per line). |
+| `experiments/2026-05-12-cross-model-authoring/master/examples/fn_with_lambda.ail.json` | Same two key renames (2 occurrences total). |
+| `crates/ailang-surface/src/{print,parse}.rs` (code) | **No change.** Form-A never used these tag names — only `parse.rs:81` rustdoc above. |
 | `crates/ailang-core/tests/hash_pin.rs` | **No change.** No pinned `.ail` module contains `(lam ...)` (verified per-file). |
 
-Historic documents (`docs/plans/2026-05-10-23.3-...`,
-`docs/plans/2026-05-09-22b3-monomorphisation.md`,
-`docs/plans/2026-05-09-22c-user-class-e2e.md`,
-`docs/plans/24.2.md`) embed the old tag names inside example JSON
-blocks. Per the Honesty Rule
-(`design/contracts/honesty-rule.md`), historic plan documents
-describe the state at the time of writing — not the present state —
-and are NOT migrated.
+Historic / frozen documents NOT migrated (per Honesty Rule
+analogue: these describe state at the time of writing, not the
+present state):
+- `docs/plans/2026-05-10-23.3-...md`,
+  `docs/plans/2026-05-09-22b3-monomorphisation.md`,
+  `docs/plans/2026-05-09-22c-user-class-e2e.md`, `docs/plans/24.2.md`
+  — embed old tag names in example JSON blocks.
+- `experiments/2026-05-12-cross-model-authoring/master/spec.md`,
+  `experiments/2026-05-12-cross-model-authoring/rendered/*.md`,
+  and any `experiments/2026-05-12-cross-model-authoring/runs/**`
+  transcripts — frozen artefacts of the 2026-05-12 experiment.
 
 ## Data flow
 
@@ -257,12 +299,20 @@ The milestone is GREEN if:
 - `cargo test -p ailang-surface --test round_trip` passes — confirms
   Form-A is untouched.
 - A single targeted assertion is added: a fresh test in
-  `crates/ailang-core/tests/schema_coverage.rs` (or equivalent
-  existing schema-shape test) verifies that
+  `crates/ailang-core/tests/design_schema_drift.rs` verifies that
   `serde_json::to_value(&Term::Lam{...})` emits the keys
-  `"param-types"` and `"ret-type"` (and NOT the old camelCase). The
-  test pins the new schema layer concretely so a future regression
-  cannot silently flip the rename string back.
+  `"param-types"` and `"ret-type"` (and NOT the old camelCase),
+  AND extends the existing fenced-block anchor sweep to assert
+  that `design/contracts/data-model.md` contains the new tag
+  spellings inside the `Term::Lam` fenced JSON block. The home
+  is `design_schema_drift.rs` (not `schema_coverage.rs`, which is
+  a corpus-coverage walker) because that file already operates as
+  the data-model contract's ratifying test, already builds
+  `Term::Lam` exemplars (L121-129), and already pins the
+  `data-model.md` ↔ schema pairing via the
+  `anchor_in_jsonc_block` helper. The two assertions pin the
+  schema layer and the contract document together so a future
+  regression cannot silently flip the rename string back.
 - `cargo build --workspace` produces no new clippy warnings.
 
 No bench-regression check is required: the rename is a string
@@ -272,15 +322,19 @@ literal swap at compile time with no runtime cost path.
 
 1. Tag-rename change in `crates/ailang-core/src/ast.rs:492,494` is
    landed and observable in serialisation output.
-2. Three call-sites (`workspace.rs` + two `.ail.json` fixtures)
-   carry the new tag names verbatim.
-3. `cargo test --workspace` is GREEN.
-4. `cargo test -p ailang-surface --test round_trip` is GREEN
+2. All four code call-sites (`workspace.rs` JSON-literal + two
+   `.ail.json` fixtures + `design/contracts/data-model.md` fenced
+   JSON block) carry the new tag names verbatim.
+3. All three rustdoc strings (`ast.rs:8`, `parse.rs:81`,
+   `check/lib.rs:1707`) describe the new tag spellings.
+4. `cargo test --workspace` is GREEN.
+5. `cargo test -p ailang-surface --test round_trip` is GREEN
    (Form-A unchanged invariant).
-5. A new schema-shape assertion test fires GREEN with the new tag
-   names and would fire RED with the old ones.
-6. The commit body references `closes #30`. No `docs/plans/*.md`
-   files are mutated.
+6. The new `design_schema_drift.rs` assertion(s) fire GREEN with
+   the new tag names and would fire RED with the old ones.
+7. The commit body references `closes #30`. No `docs/plans/*.md`,
+   `experiments/.../master/spec.md`, `experiments/.../rendered/*`,
+   or `experiments/.../runs/*` files are mutated.
 
 ## Feature-acceptance gate