Namespace keystone (§8 step 1): §13 unique-on-chain resolver in the executing v1 seed, default-off

[briansrls]

What

Lands namespace-resolution-design.md §8 step 1 in the executing v1 seed resolver — the §13 unique-on-chain semantics (operator-ratified 2026-07-21) behind a swappable NameResolutionPolicy gate, default OFF = ImportScoped, byte-for-byte today's behavior. No subtree is flipped; the flip (step 4) still gates on import→alias transmutation.

Mechanism

• Policy gate — name_resolution_policy_is_namespace_only thread-local builtin (runtime_rust.dag → v1_rt, mirroring the resolution_silent_pick_is_enabled precedent). Host-side setter only, no .dag surface can flip it, zero env plumbing (no TypeEnv/ResolvedFuncEnv field). Registered in 04_method.dag builtins + extdeps/languages/rust/emit.dag rt rows.
• Type/value path (04_env.dag) — under NamespaceOnlyY, a global_bare homonym resolves to the unique binder on the referencing module's ancestor chain: exactly-one resolves; zero-or-multiple refuses. The zero-on-chain whole-pool homonym is Ambiguous, never a fabricated bind — exact parity with the census containment walk (containment_resolve_fn_v1). Nearest-wins LCP preserved verbatim under the default arm.
• Fn path (04_sigs.dag / 04_lookup.dag) — the §13-named gap ("no refusal arm at all") closed by the return-type rewrite: lookup_resolved_sig / lookup_func_sig now return FuncSigLookup = FuncSigResolved | FuncSigUnresolved | FuncSigAmbiguous{candidates}, so a refusal finally has somewhere to go. FuncSigAmbiguous never falls through to the census fallback; the Absent-as-"keep looking" straddle is dead as a class. First-hit preserved verbatim under the default. Analysis-only consumers (provenance/descent, 8 sites) project through func_sig_if_resolved — conservative no-enrichment, never a fabricated bind; the semantic bind sites (04_infer.dag ExprVar/ExprCall) match the full outcome and refuse.
• Typed diagnostic — AmbiguousReference { name, candidates, span } minted in 00_core.dag (span-extractor + formatter arms), raised at the reference site with the full candidate fix-menu (§13: qualify / alias / rename). Emission sites: 04_resolve.dag bare-miss, 04_infer.dag type-annotation miss + record-lit presence, and both fn bind sites.

Proof (green-by-execution + RED)

• Discriminating witness src/v1/tests/src/namespace_unique_on_chain_policy_test.rs (6 tests, all green): the same homonym fixtures compile clean under ImportScoped and refuse — typed, located, full candidate list — under NamespaceOnlyY, on both paths (ancestor-chain type homonym; 2-parent-match fn homonym, the fn_parent_first_hit silent-pick class). Controls pin the boundary: exactly-one-on-chain still resolves under the strict policy; a genuinely-unbound name stays UnresolvedType (Ambiguous and Unresolved are distinct states); the zero-on-chain homonym discriminates the diagnostic label between the two policies.
• Regen fixed point: regen_stage0 (write) converged in two generations; regen_stage0 --verify green with regen_divergence_count=0.
• cross_representation_equality_test (4/4), func_env_scope_chain + func_env_semantic_equivalence (6 passed / 2 pre-existing opt-in ignores), flat_parents_* (3/3), all resolution_divergence_* fixture tests (4/4), and the corpus-scoped resolution_divergence_fn_parent_first_hit_subset_holds_on_closure_scoped_corpus (green, 113s). cargo fmt --all --check clean.

Census corroboration (Brief A verified-context, re-run fresh on this base)

resolution_divergence_census whole-tree (dag + src/v2, 1309 modules, 40,592 sites): diverge=0, containment_unresolved=0, owner_mismatch=0, containment_ambiguous=38, cost shape lexical_steps={1:17175, 2:1} — the §12.3 substitution-not-rewrite claim held. Raw rows checked in at docs/probes/resolution_divergence_census_2026-07-22.tsv; design doc §8/§12.3/§12.4/§13 updated to consume it (stale #6936 numbers annotated with the refresh).

Finding surfaced (pre-existing on main, not fixed here)

The census silent-pick gate exits 1 on main in both scopes (whole-tree and --closure-scoped): 1 genuine §13 fail-open — gunbc.falsifier_workflow's bare ci_repo_root_shell first-hits gunbc.ci_spec over the byte-identical duplicate decl in gunbc.merge_admission_produce (a real §3 fork). Recorded in §12.4; needs consolidation or qualification in its own change.

Bootstrap note

The committed stage0 .rs changes are the regen fixed point of the .dag edits (the fn-path outcome type changes emitted code even default-off, as briefed). The seed was bootstrapped through the standard maneuver: minimal hand-mirror of the three new-builtin surfaces (v1_rt, builtin map, rt rows) → regen → rebuild → regen → --verify green.

  

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