[nixpt]

Why

Two producer blindspots made the ledger unusable beyond the "does the consumer compile" fallback (found while gating zorro's 13-crate decomposition, ZORRA-1 step 4):

1. pub use chains vanished — every shimmed path (zorro::io, zorro::kv_cache, zorro::pipeline::sampling, …) was reported as Removed even though it existed.
2. rustdoc ids leaked into signatures — ids renumber on every rebuild and across a split, so structurally identical items showed up as SignatureChanged (“id-noise”).

What

Re-export materialization (producer.rs):

• named item re-exports emit <parent>::<name>;
• module aliases expand public contents, with a duplicate-segment collapse so pub use zorro_io as io maps to zorro::io::X, not zorro::io::io::X;
• globs expand into the parent, including globs of private local modules (walked through the index tree, which paths cannot express);
• local use chains resolve to the ultimate target;
• aliases carry snapshot::RE_EXPORT_ATTR and a stable signature (target payload for in-crate targets, re-export of <path> for external ones).

Signature normalization:

• resolved_path drops ids and uses the canonical defining path;
• impls / implementations / items / fields / variants / links id lists become sorted stable labels (paths, local names, impl descriptors);
• generic params become local:<name>;
• after alias discovery, signature type paths prefer the shortest local re-export spelling (zorro_nn::backend::ComputeBackend → zorro::backend::ComputeBackend).

Classification / ledger:

• signature changes on re-export-backed items are Warning (the defining crate owns the shape), not Breaking;
• API_DRIFT_UPDATE=1 now rewrites an existing snapshot (it previously only handled the first record, so the documented recording command silently did nothing after init). Demo ledger regenerated.

Validation

• cargo test --workspace --all-features green; new synthetic tests for named/module/glob/private-module/chain materialization and id churn (same shape + different ids → no diff).
• cargo clippy --workspace --all-features --all-targets clean.
• Validated against zorro: its current surface went 61 → 202 items, consumer compile stayed green, and the 15 remaining breaking signature changes are real cross-crate type-provenance moves (TensorIndex etc.), not ids.

Known limits (documented in the ticket)

rustdoc JSON's paths is a reference table, not a dependency index, so a dependency's flattened re-exports (zorro_io's pub use io::*) are only materialized where referenced. Full reconstruction needs ingesting dependency rustdoc JSON (filed as a follow-on).

Compatibility note

diff::Changed gains old_attrs/new_attrs (struct literal construction is affected; only internal call sites in this repo). New public items: snapshot::RE_EXPORT_ATTR, producer behavior. No crate version bump yet — this is for the next release.

Ticket: .jagent/planning/tickets/APIDRIFT-21-reexport-materialization.md.