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Gemma / Nano Banana compat: skip tools, hint on billing-required quotas #12

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Merged
aciderix merged 1 commit into from
Apr 22, 2026
Merged

Gemma / Nano Banana compat: skip tools, hint on billing-required quotas #12

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47 changes: 41 additions & 6 deletions core-bridge/src/main/kotlin/com/gemini/bridge/RestGeminiCore.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -591,11 +591,17 @@ class RestGeminiCore(
private fun buildRequestBody(): String {
val contents = JSONArray()
turns.forEach { contents.put(it) }
val body = JSONObject()
.put("systemInstruction", buildSystemInstruction())
.put("contents", contents)
.put("tools", buildToolsJson())
if (modelEmitsImages(model)) {
val body = JSONObject().put("contents", contents)
val emitsImages = modelEmitsImages(model)
val supportsTools = modelSupportsFunctionCalling(model)
// Gemma + image-only models reject systemInstruction on the generateContent
// endpoint ("400: system_instruction is not supported"). Gemini 2.5+ is
// fine and benefits from the workspace/tool preamble.
if (supportsTools) {
body.put("systemInstruction", buildSystemInstruction())
body.put("tools", buildToolsJson())
}
if (emitsImages) {
body.put(
"generationConfig",
JSONObject().put(
Expand Down Expand Up @@ -737,9 +743,23 @@ class RestGeminiCore(
}

private fun tryExtractError(body: String): String? = runCatching {
JSONObject(body).optJSONObject("error")?.optString("message")
val raw = JSONObject(body).optJSONObject("error")?.optString("message") ?: return@runCatching null
if (looksLikeImageFreeTierQuota(raw)) {
raw + "\n\n" +
"Image generation models (Imagen, Nano Banana / *-image) are " +
"not included in the Gemini free tier (limit 0). Enable " +
"billing on the Google Cloud project linked to your API key: " +
"https://console.cloud.google.com/billing — then retry."
} else raw
}.getOrNull()

private fun looksLikeImageFreeTierQuota(message: String): Boolean {
val m = message.lowercase()
return m.contains("quota") &&
m.contains("limit: 0") &&
(m.contains("-image") || m.contains("imagen"))
}

private fun mapToJson(map: Map<String, Any?>): JSONObject {
val obj = JSONObject()
map.forEach { (k, v) -> obj.put(k, toJson(v)) }
Expand Down Expand Up @@ -808,5 +828,20 @@ class RestGeminiCore(
*/
fun modelEmitsImages(modelName: String): Boolean =
modelName.contains("-image", ignoreCase = true)

/**
* True when the model accepts `tools` + `systemInstruction` in the
* request body. Gemma models and image-only models do not (the API
* returns 400). Gemini text/multimodal models do.
*/
fun modelSupportsFunctionCalling(modelName: String): Boolean {
val lower = modelName.lowercase()
if (lower.startsWith("gemma")) return false
if (lower.startsWith("imagen")) return false
// `*-image*` chat models (Nano Banana etc.) reject tools today —
// they only produce images + short captions.
if (lower.contains("-image")) return false
return true
}
}
}
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