Add schema evolution guardrails and add_field MCP tool#8
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mgoldsborough merged 6 commits intomainfrom Mar 27, 2026
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- validate_schema_change(): pure function that detects unsafe schema changes (required-without-default, type changes, enum narrowing, field removal) - _check_required_without_defaults(): warns at validation time when required fields lack defaults (catches the footgun early) - UpjackApp.reload_schema(): hot-reloads entity schema from disk with manifest_dir tracking - add_field MCP tool: lets agents add fields to running apps with structural guardrails (default required, type validation, schema change validation before write) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
get_entity, list_entities, update_entity, and search_entities now accept an optional schema parameter. When provided, missing fields are filled with schema defaults before returning — enabling seamless schema evolution without backfill migrations. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
- deepcopy schema defaults so hydrated entities don't share mutable objects (lists, dicts) - Validate field names against [a-z][a-z0-9_]* pattern - Reject reserved base entity field names (id, type, status, etc.) - Block path traversal in schema paths - Reject adding a field that already exists, even with matching type
json.dumps doesn't include a trailing newline, causing "No newline at end of file" noise in git diffs.
Tests add_field + hydrate-on-read against real CRM, Todo, and Research Assistant schemas (allOf + $ref composition). Covers get, list, and search read paths after field addition.
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Summary
validate_schema_change()— pure function that compares two schema dicts and returns diagnostics for unsafe changes: required-without-default (error), type change (error), enum narrowing (error), field removal (warning)validate_entity()now logs a warning when required fields lack defaults, catching the footgun early without blockingUpjackApp.reload_schema()— hot-reloads an entity schema from disk via newmanifest_dirtracking on the app instanceadd_fieldMCP tool — lets agents add fields to a running app with structural guardrails: default is required, type is validated,validate_schema_change()gates the write, then schema is reloaded in-placeTest plan
TestValidateSchemaChange— 8 cases (no change, required+default ok, required no default, type change, enum narrow/widen, field removed, multiple issues)TestRequiredWithoutDefaultWarning— 3 cases via caplog (warns, no warn with default, no warn for base fields)TestReloadSchema— 3 cases (picks up file change, unknown entity, no manifest_dir)TestAddFieldTool— 7 cases (registered, writes schema, adds to required, reload+hydrate roundtrip, rejects invalid type, rejects bad default, rejects type conflict)add_fieldtool presence (tool count assertions)make checkpasses (format + lint + typecheck + 255 tests)