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@ai-sdk/anthropic 3.0.71 rejects usage.iterations[].type: "fallback_message" — turn fails with AI_TypeValidationError #31579
Description
Description
The bundled @ai-sdk/anthropic@3.0.71 validates usage.iterations[].type as "compaction" | "message". Anthropic now emits "fallback_message" when a response is served by a fallback model (new fallbacks API parameter, e.g. claude-fable-5 → opus). The whole message_delta fails validation and the turn errors out — the assistant can't continue while fallbacks occur.
AI_TypeValidationError: Type validation failed
path: ["usage","iterations",1,"type"]
expected "compaction" | "message", received "fallback_message"
"iterations": [
{ "type": "message", "model": "claude-fable-5", ... },
{ "type": "fallback_message", "model": "claude-opus-4-8", ... }
]Fixed upstream in vercel/ai#15928, released in @ai-sdk/anthropic@3.0.82 — bumping the pin resolves it.
OpenCode version
1.16.2
Steps to reproduce
- Use the Anthropic provider with a model where the API serves a fallback (
claude-fable-5with opus fallback) - Response
usage.iterationscontains an entry withtype: "fallback_message" - Stream fails validation; error repeats on retry while the fallback persists
Operating System
Ubuntu 24.04 (WSL2)
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moynzzz commentedon Jun 10, 2026
A few findings for whoever picks this up:
bunfig.tomlsetsminimumReleaseAge = 259200(3 days) and@ai-sdk/anthropicis not inminimumReleaseAgeExcludes. 3.0.82 was published 2026-06-09 17:24 UTC, so it can't resolve before 2026-06-12 ~17:25 UTC. Verified locally that the gate also fires with an already-updated lockfile, so a bump PR before that date failsbun install.packages/opencode(3.0.71),packages/core(3.0.71),packages/console/function(3.0.64). Bothpackages/opencode/src/provider/provider.tsandpackages/core/src/plugin/provider/anthropic.tsimport the provider, so the CLI path needs at least those two bumped.packages/opencodeto 3.0.82 regenerates the lockfile cleanly andtsgo --noEmitpasses.Happy to send the bump PR once the release-age window opens on the 12th.
kagura-chen commentedon Jun 10, 2026
I can take this — straightforward bump of
@ai-sdk/anthropicfrom 3.0.71 to 3.0.82 which includes thefallback_messageiteration type fix (vercel/ai#15928).