create_schema enum fields silently discarded: prose teaches core_values, serde expects coreValues #1809

Overview

Every agent-driven create_schema call with an enum field fails, and the error message misdirects the reader. The cause is a casing contradiction between two instruction channels, made silent by missing deny_unknown_fields.

Problem Statement

packages/agent/src/agent_guidance.rs:27 instructs the model to emit "core_values". SchemaField (packages/nodespace-types/src/schema.rs:30) is #[serde(rename_all = "camelCase")], so deserialization expects coreValues. Neither struct in the path sets deny_unknown_fields, so the key is dropped without error and validation later fails with "enum has no values" — describing a symptom two layers from the cause.

The create_schema tool schema already says coreValues correctly (packages/agent/src/local_agent/tools.rs:630, :698). The model therefore receives both spellings in the same prompt and follows the prose.

That makes this more than a typo. It is a single-variable natural experiment with a known-correct control, showing resident prose overriding a correct tool schema — the strongest evidence behind ADR-064.

Evidence

• packages/agent/src/agent_guidance.rs:27 — teaches "core_values"
• packages/nodespace-types/src/schema.rs:30-38 — rename_all = "camelCase", field core_values → wire key coreValues
• packages/core/src/schema/mod.rs:139 — CreateSchemaParams, no deny_unknown_fields
• packages/agent/src/local_agent/tools.rs:630, :698 — tool schema correctly declares coreValues
• Verified present in the live assembled system prompt
• Channel-authority measurement: a rule in the tool schema produced 100% compliance, the same rule absent produced 62.5%, the same rule in prose produced 87.5%

Acceptance Criteria

• deny_unknown_fields added to SchemaField — this is where the discard occurs. Adding it only to CreateSchemaParams does not fix the bug
• deny_unknown_fields also added to CreateSchemaParams
• The ENUM FIELDS line is deleted from agent_guidance.rs, not corrected. Argument shape belongs to the tool schema, which already carries it — correcting the prose would leave two sources to drift again
• A test asserts a SchemaField payload using core_values is rejected with an error naming the unknown field
• An agent-level test asserts create_schema with an enum field succeeds end to end

Architecture Impact

First application of ADR-064 rule 1 (tool schemas own argument shape). Note packages/agent/src/local_agent/tools.rs is also touched by the create_schema description-inference removal — coordinate if both are in flight.