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v0.2.9 Gemini model selects + fallback chain

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local
2026-05-12 00:45:41 -05:00
parent 05ebeb5d51
commit 8ffc3ffb73
5 changed files with 209 additions and 72 deletions
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server/backends/gemini.js
+142 -57
View File
@@ -27,6 +27,46 @@ const DEFAULT_TRANSCRIPTION_MODEL = "gemini-3-flash-preview";
const DEFAULT_ANALYSIS_MODEL = "gemini-3.1-pro-preview";
const EMPTY_RETRIES = 3;
// Per-pipeline fallback chains, ordered newest/most-expensive →
// older/cheaper. When the operator-selected primary model returns a
// retryable error (503 capacity, 429 rate limit, etc.) the relay
// walks DOWN this list — never up, since the operator's choice
// reflects their preferred price/quality point. The chain is sliced
// from the primary forward, so picking 2.5-flash falls back to only
// 2.0-flash, never back up to 3-flash.
const TRANSCRIPTION_FALLBACK_CHAIN = [
"gemini-3-flash-preview",
"gemini-2.5-flash",
"gemini-2.0-flash",
];
const ANALYSIS_FALLBACK_CHAIN = [
"gemini-3.1-pro-preview",
"gemini-3-pro-preview",
"gemini-3-flash-preview",
"gemini-2.5-flash",
];
// Slice the chain starting at the primary model. If the primary isn't
// in the chain (unknown / typo), return just the primary — no
// fallback possible. Returns a fresh array so callers can iterate
// safely.
function fallbackChain(chain, primary) {
const idx = chain.indexOf(primary);
if (idx < 0) return [primary];
return chain.slice(idx);
}
// Detect errors that warrant trying the next model in the chain.
// Capacity / rate-limit / network blips → yes. Auth failures / 400s
// → no, those would just keep failing with the same root cause.
function isFallbackEligibleError(err) {
const status = err?.status || err?.httpStatusCode || 0;
const msg = err?.message || String(err);
if (status === 503 || status === 429 || status === 529) return true;
if (/overloaded|unavailable|capacity|high demand|rate limit|fetch failed|ECONNRESET|ETIMEDOUT|socket hang up|network/i.test(msg)) return true;
return false;
}
const TRANSCRIPTION_SAFETY = [
{ category: "HARM_CATEGORY_HARASSMENT", threshold: "BLOCK_NONE" },
{ category: "HARM_CATEGORY_HATE_SPEECH", threshold: "BLOCK_NONE" },
@@ -47,10 +87,13 @@ export function createGeminiBackend({
apiKey,
httpOptions: { timeout: timeoutMs, headersTimeout: timeoutMs },
});
// Flash models accept `thinkingLevel: "minimal"`; Pro models reject
// it. Detect from the model id so the operator can flip flash <-> pro
// via the StartOS action without breaking the request.
const txIsFlash = /flash/i.test(transcriptionModel);
// Build the per-call fallback chains. The primary is whatever the
// operator selected via the StartOS action; subsequent entries are
// the lower-tier members of the chain (we never fall back UP). When
// the primary returns a 503/capacity/rate-limit error, the loops
// below try the next model.
const txChain = fallbackChain(TRANSCRIPTION_FALLBACK_CHAIN, transcriptionModel);
const anChain = fallbackChain(ANALYSIS_FALLBACK_CHAIN, analysisModel);
async function transcribeAudio({
audio,
@@ -84,67 +127,109 @@ export function createGeminiBackend({
}
const prompt = buildTranscriptionPrompt({ title, channel, description, chapters });
let result;
for (let attempt = 0; attempt < EMPTY_RETRIES; attempt++) {
result = await ai.models.generateContent({
model: transcriptionModel,
config: {
// thinkingLevel: "minimal" is only valid for Flash. Pro
// models reject it. Skip when the operator picks a Pro
// model for transcription (slower but valid).
...(txIsFlash ? { thinkingConfig: { thinkingLevel: "minimal" } } : {}),
safetySettings: TRANSCRIPTION_SAFETY,
},
contents: [
{
role: "user",
parts: [
{ fileData: { fileUri: f.uri, mimeType } },
{ text: prompt },
// Walk the fallback chain: try the primary model first; on a
// retryable error (capacity / 503 / rate-limit), try the next
// model in the chain. Non-retryable errors bubble up to the
// caller — they'd just fail the same way on every model.
let lastErr;
for (let modelIdx = 0; modelIdx < txChain.length; modelIdx++) {
const model = txChain[modelIdx];
const isFlash = /flash/i.test(model);
try {
let result;
// Empty-response retries: when the SDK returns 200 with no
// text (which happens periodically with audio inputs),
// retry up to N times with the SAME model before falling
// back.
for (let attempt = 0; attempt < EMPTY_RETRIES; attempt++) {
result = await ai.models.generateContent({
model,
config: {
// thinkingLevel: "minimal" is only valid for Flash.
// Pro models reject it. Skip when the chain hop
// landed on a Pro model.
...(isFlash ? { thinkingConfig: { thinkingLevel: "minimal" } } : {}),
safetySettings: TRANSCRIPTION_SAFETY,
},
contents: [
{
role: "user",
parts: [
{ fileData: { fileUri: f.uri, mimeType } },
{ text: prompt },
],
},
],
},
],
});
if (safeText(result)) break;
});
if (safeText(result)) break;
}
// Best-effort cleanup of the uploaded File API artifact.
try { await ai.files.delete({ name: f.name }); } catch {}
const text = safeText(result) || "";
return {
text,
segments: [],
duration_seconds: 0,
usage: result?.usageMetadata || null,
// Return the model that ACTUALLY served the request — so
// the audit log records what was used, not just what was
// requested. Lets the operator see "this call fell back
// from 3-flash to 2.5-flash" via the dashboard.
model,
};
} catch (err) {
lastErr = err;
const canFallback =
isFallbackEligibleError(err) && modelIdx < txChain.length - 1;
console.warn(
`[gemini] transcribe with ${model} failed (${err?.status || "?"}): ${err?.message || err}${canFallback ? ` — falling back to ${txChain[modelIdx + 1]}` : ""}`
);
if (!canFallback) {
try { await ai.files.delete({ name: f.name }); } catch {}
throw err;
}
// loop continues with next model
}
}
// Best-effort cleanup of the uploaded File API artifact.
try { await ai.files.delete({ name: f.name }); } catch {}
const text = safeText(result) || "";
return {
text,
// Gemini returns a single timestamped blob — segments are
// parsed client-side by the orchestration layer. We could
// pre-parse here but Recap already has parseTimestampedTranscript
// that handles this exact shape.
segments: [],
duration_seconds: 0,
// Pass usage + the model id back to the route so audit-log
// entries can include token counts + computed cost.
usage: result?.usageMetadata || null,
model: transcriptionModel,
};
throw lastErr || new Error("transcribe: all models in fallback chain failed");
} finally {
try { await fs.rm(tmpDir, { recursive: true, force: true }); } catch {}
}
}
async function analyzeText({ prompt }) {
const result = await ai.models.generateContent({
model: analysisModel,
contents: [
{
role: "user",
parts: [{ text: prompt }],
},
],
});
return {
text: safeText(result) || "",
usage: result?.usageMetadata || null,
model: analysisModel,
};
let lastErr;
for (let modelIdx = 0; modelIdx < anChain.length; modelIdx++) {
const model = anChain[modelIdx];
try {
const result = await ai.models.generateContent({
model,
contents: [
{
role: "user",
parts: [{ text: prompt }],
},
],
});
return {
text: safeText(result) || "",
usage: result?.usageMetadata || null,
model,
};
} catch (err) {
lastErr = err;
const canFallback =
isFallbackEligibleError(err) && modelIdx < anChain.length - 1;
console.warn(
`[gemini] analyze with ${model} failed (${err?.status || "?"}): ${err?.message || err}${canFallback ? ` — falling back to ${anChain[modelIdx + 1]}` : ""}`
);
if (!canFallback) throw err;
}
}
throw lastErr || new Error("analyze: all models in fallback chain failed");
}
return { transcribeAudio, analyzeText };
server/package.json
+1 -1
View File
@@ -1,6 +1,6 @@
{
"name": "recap-relay-server",
"version": "0.2.8",
"version": "0.2.9",
"type": "module",
"private": true,
"dependencies": {