# Contextual typing at deep source occurrences This experimental checker reconstructs a lexical context along an original source path, then asks the pinned Lean kernel to type the selected expression in that context. Domains and let values are instantiated only when needed; the traversal keeps the original source expression. It does not repeatedly instantiate the complete remaining proof body. Each context entry retains its depth along the one original query path. Its complete original route is that path's prefix, rather than a copied path stored at every binder. Names do not identify binders: fresh local identifiers distinguish shadowed declarations. Binder domains use the prior context; lambda/forall bodies use an extended context; let types and values precede the new let declaration. Domains must be types and let values must check against their declared type before the context is extended. The finite controls serialize and decode the exact source DAG, including all constructor payloads and ordered fields, before checking its type/value pair. Typed identity application asks the kernel to check the value against its expected type. A query checks its selected term and abstracts the inferred type over the original ordered context; reopening it must reproduce the native type structurally. That type has a **computed-native-type** namespace, not an invented original source occurrence. This is executable native replay evidence, not a quoted kernel certificate for the query algorithm. The role is **proof** if the checked type has kernel-normalized type `Prop`, **type** if the checked type itself normalizes to a sort, and **value** otherwise. These labels use the native context, not the selected constructor or node name. Eight self-contained controls cover a deep equality proof, a deep shadowed context, shared variables with different binders, dependent binder domains, let values before their new binder, forall scope, Boolean metadata and a structure projection. Eight native rejection cases cover invalid fields, ill-formed contexts, loose indices, missing constants, a wrong root type and an unresolved metavariable. The independent reader recomputes source paths, binding targets, scope requirements and counts, compares observations and passes the original selections through the existing occurrence geometry. The underlying source cut stays structural. An optional reader layer attaches a native record only to its exact source hash and original packed route. Every other position remains without recorded typing. Computed type navigation uses the same constructor glyphs and ordered fields, with separate type-local binders and links back to the original source Γ. Moving inside a type does not move the source selection or infer additional type judgments. Explicit Γ jumps return to the original source binder. The compact type cut retains at most thirteen term occurrences, depth three and three nodes per layer, plus displayed context references. It stores no copied ancestor path per context entry; only displayed references materialize their original packed prefix. A type-node number selects a representative occurrence; other uses of that shared node can have different bindings. The existing 512-entry renderer and native transport are unchanged. The new reader overlay consumes the finite core-only records through its own explicit attachment format. The producer's immutable `browserTypingAttached: false` records its earlier extraction scope; the separate attachment checks establish the current reader correspondence. This does not certify the JavaScript or browser, type the project/AI corpora, recover source syntax, establish semantic abstraction or measure comprehension. The full research program remains active. No blog result is published for this prototype. The attachment audit checks all 27 records and 60 type cuts, including both type-local binding and original Γ links. Twelve invalid attachment, scope, identity, mutation or limit cases are refused. The browser suite selects all 27 recorded source positions, tests type and source binder jumps, and exercises deep representative navigation, shared-node contexts, let scope, missing code, corrupt evidence and late loads. These checks establish finite correspondence; they do not turn type descendants into additional native queries. [Context control](/projects/proof-atlas/library/?view=occurrence&control=checked-context&case=dependent-domain) · [Deep equality control](/projects/proof-atlas/library/?view=occurrence&control=checked-context&case=deep-reflexivity) The driver also replays the existing public `AtlasLargeCutControl.deepSucc` packet in core Lean. Its source bytes, hash and original `not-claimed` producer metadata remain unchanged. A separate record checks the type/value pair and three selected positions, including the variable at depth 10,001. Missing baseline constants and admitted dependencies cannot acquire a checked record. This adds evidence for that fixed synthetic packet; it does not replay the project snapshots or the Goedel corpus. ## Bounds and reproduction The frozen decoder accepts at most 131,072 stored nodes. Queries have an explicit 262,144-slot path limit; this control generator accepts depths 1–20,000. The default test uses depth 10,000. Native processes have the existing 8 GiB RSS, 120-second and 64 MiB output-file limits. The local free-space reserve defaults to 30 GiB; CI explicitly uses its existing 5 GiB reserve. These are runtime guards and finite tests, not arbitrary-size or whole-browser memory guarantees. ```sh python3 research/proof-atlas/deep-typing/verify.py \ --lean /absolute/path/to/lean-4.33.1 \ --workdir /tmp/atlas-deep-typing node scripts/test-proof-atlas-deep-typing.cjs /tmp/atlas-deep-typing python3 research/proof-atlas/deep-typing/pack.py /tmp/atlas-deep-typing node scripts/test-proof-atlas-deep-typing.cjs node scripts/test-proof-atlas-deep-context.cjs # Build and serve the production site; set ATLAS_ORIGIN/ATLAS_CHROMIUM_PATH if needed. node scripts/test-proof-atlas-deep-context-browser.cjs ``` The packaged evidence retains nine fixed packets, 27 contextual judgments and 54 source cuts, with depth 10,002 and a context of 10,000 binders. Eight native rejections and nine altered-correspondence rejections are finite controls. The compiled-data commands check the hash-bound artifact without invoking Lean. `verify.py --compare` reruns Lean and requires exact agreement of its emitted terms and judgments with that artifact; platform-specific compiler descriptions and resource observations are outside that byte comparison. Only Lean's core library and this repository's own extraction tooling are used. Original mathematical projects and their dependencies are not rebuilt. Raw compiler output and resource records remain in the private work directory. No live reader typing or deployment follows from running these commands.