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Deterministic fallback

Lens shows no error code on screen for this message; E-DETERMINISTIC-FALLBACK is this documentation's name for it. Quote it when you contact the Lens team.

What happened

A Digital Soul card carries the Deterministic fallback badge, with a ⚠. An amber ⚠ line on the card explains why.

The action ran deterministically, so the card holds Lens's deterministic output instead of a narrative written by Claude. Without an API key, an amber banner also explains how to turn explanations back on.

Likely cause

The LLM was unavailable, for example because no API key is set, or the call to it failed. Claude (Anthropic) is the only provider Lens implements.

Fix

  1. Open Settings > LLM Configuration.
  2. Turn on Enable LLM-powered explanations.
  3. Paste your API key into API Key.
  4. Select Test Connection. It verifies the key and a round trip to the model.

The key is one you create in your own Anthropic account; Lens sends your requests straight to Anthropic with it, and the usage is billed to that account. MachAI does not issue keys.

There is no Save button. The key is stored the moment the API Key field loses focus (click or tab elsewhere), and the other settings on the screen store as you change them. If the field is blank, Lens falls back to the ANTHROPIC_API_KEY environment variable of the terminal you started it from; the hint under the field tells you which one is in use (Field is blank — currently using ANTHROPIC_API_KEY from your terminal, or No key found). A key typed into Settings always wins over the environment variable.

A card that already carries the badge is not rewritten when the key starts working. Run the action again and the new card comes from Claude.

Lens sends Claude curated evidence summaries only. Raw SDC and report text is never sent to it.

If that does not work

Lens still works without a key. Deterministic analysis is always available, and many actions never call Claude at all.

When Test Connection fails, the status line beside the button turns to Connection failed and a dialog shows Connection failed. followed by the reason from the provider, typically an invalid or expired key, no network, or a model name that your account cannot use. Fix what the reason names (re-paste the key, check your connection, pick another model in the dropdown) and test again; until it succeeds, actions keep running deterministically.

If none of this helps, contact the Lens team through the channel you were given with your access to Lens, quote E-DETERMINISTIC-FALLBACK, and include what the screen said.

Still have a question?

Updated 19 October 2026