chore(core): remove unreachable AI SDK providers

[opencode-agent]

Summary

• remove direct dependencies on the Amazon Bedrock, Anthropic, Azure, and OpenAI-compatible AI SDK providers now covered by native routing
• delete unreachable AI SDK provider hooks while retaining catalog and integration transforms still used by native routes
• reject OpenAI-compatible configurations without an endpoint before the generic AI SDK fallback
• remove the now-unused AWS credential-chain and Google auth dependencies from Core

Checks

• bun typecheck (packages/core)
• bun test test/model-resolver.test.ts test/aisdk-native.test.ts test/plugin/provider-amazon-bedrock.test.ts test/plugin/provider-anthropic.test.ts test/plugin/provider-azure.test.ts test/plugin/provider-cloudflare-workers-ai.test.ts test/plugin/provider-google-vertex.test.ts (74 pass)
• bun test test/aisdk.test.ts test/plugin/provider-factory.test.ts (30 pass)

Requested by: @rekram1-node (Aiden Cline via Slack)

[Enough1122]

AI code review — automated review for reference; please use your judgment.

• packages/opencode/src/provider/provider.ts (and core plugins generally) — This removes real user-facing behaviors along with the dead code: Snowflake Cortex loses its protocol shims (max_tokens→max_completion_tokens rewriting, role:"" stream repair, conversation-complete 400→stop translation), Bedrock loses cross-region inference-prefix resolution plus the default AWS credential chain, and Azure loses its missing-resourceName validation — none of these have generic equivalents in the diff — please add a changeset/migration note stating these configurations are no longer supported and what users should move to, so removal isn't discovered as a runtime breakage.
• packages/core/src/plugin/provider/amazon-bedrock.ts — Even granting "unreachable", the deletion leaves the remaining catalog/auth-form hooks advertising a provider whose SDK wiring no longer exists anywhere in this package; either strip the plugin files down consistently (as done for openai-compatible/snowflake-cortex) or keep a pointer comment naming what now owns SDK creation for @ai-sdk/amazon-bedrock, otherwise the half-empty files mislead the next reader.
• packages/core/src/plugin/provider/google-vertex.ts:41 — Dropping authFetch means OpenAI-compatible Vertex endpoints no longer receive ADC bearer-token injection; if the generic loader does not replicate Google-auth for that endpoint shape, Vertex-via-openai-compatible breaks silently at request time — worth an explicit test or doc line confirming the supported path for Vertex non-native endpoints post-change.
• packages/core/src/model-resolver.ts:188 — The two consecutive isAISDK(package) && packageName === "@ai-sdk/openai-compatible" checks read as separate rules but are really one guard plus its body; folding into a single if/else would make the new unsupported-rejection obviously exhaustive and avoid re-evaluating the same predicate twice.
• packages/core/test/model-resolver.test.ts:418 — Good rejection test with the loader-must-not-run assertion; consider one companion case proving openai-compatible WITH baseURL still resolves through OpenAICompatibleChat, since this PR narrows the accepted input space and both edges deserve pinning.

— AI code review (automated)

[Enough1122]

AI code review - automated review for reference; please use your judgment.

• packages/core/package.json - @ai-sdk/google-vertex remains in dependencies even though plugin/provider/google-vertex.ts and its test are deleted here; if nothing else imports it, this looks like an incomplete cleanup (its transitive google-auth-library was removed, so a lingering import would break anyway). Worth grepping once more or removing it too.
• packages/core/src/model-resolver.ts:188-196 - the two consecutive openai-compatible branches read awkwardly: first rejects missing baseURL, then handles present baseURL. A single branch with early-return inside would be clearer; behavior itself is fine and the new test locking "loader must not be called" is a good guard.
• Deletion scope (bedrock/anthropic/azure/cloudflare/snowflake/openai-compatible plugins) matches "unreachable" claim since none are imported from provider.ts; ~2k lines of tests removed with them - acceptable given they tested dead code, but note users pinning e.g. snowflake cortex via config will now get unsupported-package errors instead of silent no-ops.

[Enough1122]

AI code review — automated review for reference; please use your judgment.

• Coordination flag: this deletes packages/core/src/plugin/provider/amazon-bedrock.ts and azure.ts as "unreachable," while two other open PRs in flight actively extend exactly those files (feat: support Claude models on the Bedrock Mantle endpoint #43231 Bedrock Mantle support, refactor(ai): move credential lowering into providers #43515/fix(provider): select Azure DeepSeek adapter #43135 Azure DeepSeek adapter). Please reconcile with those authors before merging — either they're building on dead code (they should retarget), or these paths aren't actually unreachable.
• packages/core/src/model-resolver.ts:188 — behavior change worth a release note: @ai-sdk/openai-compatible without a baseURL is now hard-unsupported instead of falling through to the (removed) plugin's defaults. Configs that relied on implicit defaults will start erroring.
• The inlined OpenAI-compatible handling in the resolver keeps the Auth.none/bearer distinction; the new resolver tests cover it — good replacement coverage for the deleted plugin tests.
• Large test deletions (~1500 lines) match the removed surface 1:1 from what I can see; no blocking issues beyond the coordination question above.