What causes "Internal server error" in SillyTavern/SillyTavern?

Check the server console for the specific `console.error` output to identify the real exception.

Internal server error

Error message

Internal server error

What it means

Generic HTTP 500 returned by the Anthropic captioning route's top-level `catch (error)`. Any unhandled exception inside the handler — a thrown fetch error, a JSON parse failure on the upstream body, or a missing `content[0]` — lands here and is logged via `console.error` while the client receives a generic message.

Source

Thrown at src/endpoints/anthropic.js:64

        if (!result.ok) {
            const text = await result.text();
            console.warn(`Claude API returned error: ${result.status} ${result.statusText}`, text);
            return response.status(result.status).send({ error: true });
        }

        /** @type {any} */
        const generateResponseJson = await result.json();
        const caption = generateResponseJson.content[0].text;
        console.debug('Claude response:', generateResponseJson);

        if (!caption) {
            return response.status(500).send('No caption found');
        }

        return response.json({ caption });
    } catch (error) {
        console.error(error);
        response.status(500).send('Internal server error');
    }
});

View on GitHub (pinned to 8172dcd0ee)

Solutions

Check the server console for the specific `console.error` output to identify the real exception.
Confirm the Anthropic API key is configured and valid.
Verify network connectivity to the Anthropic API from the server.
If the upstream shape changed, harden access to `content[0].text` with optional chaining.

Example fix

// before
const caption = generateResponseJson.content[0].text;

// after
const caption = generateResponseJson?.content?.[0]?.text;

Defensive patterns

Strategy: try-catch

Validate before calling

// preflight before the request
if (!process.env.ANTHROPIC_API_KEY) {
    return response.status(503).send('Anthropic API key not configured.');
}

Type guard

null

Try / catch

try {
    // ... captioning logic with hardened access
} catch (error) {
    console.error('Caption route failed:', error);
    const status = error?.status || 500;
    response.status(status).send(error?.message?.includes('API key') ? 'Caption service unavailable' : 'Internal server error');
}

Prevention

Always read nested upstream fields with optional chaining (`json?.content?.[0]?.text`).
Garden-wall the route: validate config (API key), input image, and network before calling upstream.
Log the real error server-side while returning a generic message to the client.
Pre-flight the API key and return 503 instead of a 500 stack-trace path.

When it happens

Trigger: Any unexpected throw in the route: upstream network failure, `result.json()` body not valid JSON, `generateResponseJson.content` being undefined so `[0].text` throws, or a missing API key causing the initial fetch to reject.

Common situations: Anthropic API key unset/invalid; network egress blocked; response schema change where `content` is absent; transient upstream 5xx that wasn't `result.ok`-gated cleanly.

Understand the failure class

HTTP status errors: handling 4xx and 5xx responses — how to handle 4xx and 5xx responses properly.

Related errors

AI-assisted analysis of SillyTavern/SillyTavern@8172dcd0ee (2026-08-13). Data as JSON: /api/errors/19c59fdfe97271af. Report an issue: GitHub.