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StructuredOutput drops additionalProperties (map) fields on Gemini; Ajv accepts the lossy {} #139
Description
Context
In aictrl prod on 2026-10-10, all 5 PR Explanation runs on Gemini 3.8 Flash (Vertex) stored diagrams[*].elements as {}. In each run the model had written and linted a result file with populated elements ("lint: zero errors" right before the StructuredOutput call). GLM 5.2 runs were unaffected.
Root cause
@ai-sdk/google 2.0.54 convertJSONSchemaToOpenAPISchema keeps only type, description, required, properties, items, allOf/anyOf/oneOf, format, const, minLength and enum. It drops additionalProperties, so a map-typed field (elements: {type: object, additionalProperties: {...}}) reaches Gemini as a bare {type: object}, and constrained decoding emits {}. The CLI's Ajv check then accepts {} (valid against the original schema), and --output-result writes the lossy copy.
Expected
Map-typed fields survive the provider schema conversion, or the CLI fails fast when a schema uses a construct the provider path can't express. It must never silently empty a field.
Acceptance Criteria
- A test with a schema containing
additionalProperties(object map) round-trips non-empty data on the Google provider path, or the run fails with a clear config error. - Options to weigh: pass the full JSON Schema via Gemini's
parametersJsonSchema/responseJsonSchema; or skip provider-side schema constraints for StructuredOutput and rely on Ajv plus the corrective turn.
References
aictrl-dev/aictrl#6172 (symptom), aictrl run 2026-10-10 executions e9201d87, e6763c4b, 7b0e8945, 81c91038, 39ba301b. Related: #5958 / #129 (schema mode).
Activity
byapparov commentedon Oct 10, 2026
Reproduction on
aictrl run0.4.7 (the prod executor pin), 2026-10-10Confirmed: the map-typed field reaches Gemini without
additionalProperties, and Gemini returns{}.Files. Put
expected.jsonin an empty git dirws/.schema-nomin.json{ "type": "object", "required": [ "title", "elements" ], "properties": { "title": { "type": "string" }, "elements": { "type": "object", "additionalProperties": { "type": "object", "required": [ "label" ], "properties": { "label": { "type": "string" }, "lines": { "type": "array", "items": { "type": "integer" } } } } } } }expected.json{ "title": "Task lifecycle", "elements": { "queued->running": { "label": "dispatch", "lines": [12, 40] }, "[*]->queued": { "label": "create", "lines": [3] }, "TASKS.org_id": { "label": "org_id uuid FK", "lines": [88, 89, 90] }, "1": { "label": "first step", "lines": [] }, "A": { "label": "Actor A", "lines": [7] }, "done->[*]": { "label": "finish", "lines": [101] } } }prompt.txtCommand
Result:
ws/result.jsonis identical toexpected.json(all 6 keys), butout.jsonhas"elements": {}and the exit code is 0.On the wire (a pass-through proxy logged the Vertex request): the StructuredOutput function declaration carries
"elements":{"type":"object"}withtoolConfig.functionCallingConfig.mode: ANY. BothadditionalPropertiesandminPropertiesare gone. Offline,@ai-sdk/google2.0.54'sconvertJSONSchemaToOpenAPISchemaon the same schema gives:{"required":["title","elements"],"type":"object","properties":{"title":{"type":"string"},"elements":{"type":"object"}}}The 0.4.7 bundle contains two copies of that converter, and neither handles
additionalProperties.Matrix
elements{}2/2{}minProperties: 1{}5/5zai-coding-plan/glm-5.2), mapelementsas an array of{id,label,lines}In every run the file the model wrote matched
expected.jsonexactly. The loss is only in the schema-constrained StructuredOutput call.Workaround evidence: array-shaped collections survive the converter (full
itemskept; onlyminItemsis dropped).byapparov commentedon Oct 10, 2026
Upstream status: fixed in
@ai-sdk/google4.0.70 (vercel/ai#20757), which preserves the JSON Schema viaparametersJsonSchema/responseJsonSchema. That is the AI SDK v7 line only; the v6 line (google 3.0.131) still converts, and upstream OpenCodedev(ai 6.0.168, google 3.0.73) has this bug too. Decision: fix via the SDK migration, tracked in #141.byapparov commentedon Oct 10, 2026
Blocked by #141 (AI SDK v7 migration). Keep this open until #141 merges and the reproduction above passes on Gemini (5/5, all keys published). #140 (publish the validated file) would stop PR Explanations from hitting this, but any inline map-typed
--output-schemastays affected until #141.byapparov commentedon Oct 10, 2026
Update: on AI SDK v7 (probe in #141), the map field is no longer emptied, but Gemini rewrites non-identifier keys in its function-call response (
queued->running→queued__running,1→_1,TASKS.org_id→TASKS_org_id), and that still passes Ajv silently. So the acceptance criterion "all 6 keys published" fails on v7 alone. #140 (path form) avoids it for file-based results; for inline schema results, map keys with non-identifier characters are unsafe on Gemini.byapparov commentedon Oct 11, 2026
Resolved for StructuredOutput by #142 (0.4.8): in schema mode the tool's only argument is
{path}, so no map-typed result schema reaches the Google converter. Verified in prod on 2026-10-10: Talentrix (Gemini) PR Explanations store all diagram elements. The underlying converter limitation in @ai-sdk/google 2.x/3.x still applies to any other map-typed tool schema sent to Gemini (e.g. an MCP tool). If that shows up, reopen this together with #141.