[SaladDay]

Change

Default to the system instruction role for thinking-enabled custom OpenAI Chat Completions connections to the exact api.mistral.ai host. Preserve reasoning, explicit compatibility overrides, all other request fields, other hosts, and the native Mistral transport.

Scope excludes authentication, thinking switches, token-limit fields, provider redesign, and a global default change. Kimi (#206), DashScope (#207), and SiliconFlow (#209) are inherited unchanged. The preceding provider PRs are merged; this PR now targets main.

Stack

main -> #210

#206, #207, and #209 are already merged. This final layer is rebased onto main as one commit, preserving the previous PR's file contents. There are no remaining downstream branches.

Evidence

• Official Mistral Chat Completions contract: the request message union contains System, User, Assistant, and Tool messages, with no Developer variant.
• OpenClaw's current compatibility code disables developer role on Mistral public endpoints; regressions cover custom providers on that host.
• OpenCode's current compatible request construction retains system instructions.

Validation

• Focused resolver suite: 101 tests passed; the Mistral endpoint case failed before the source fix.
• npx --yes pnpm@9.12.0 verify: all 14 full-profile gates passed on macOS arm64 / Node 26.7.0 at abc17a4.
• Fresh independent blind review of the rebased changes found no actionable issues; git diff --check passed.

Publication and maintainer handoff

• Existing licenses and notices are preserved; publication scope is unchanged.
• No credentials, account data, real user content, private review material, or internal history is included.
• No files were added or removed; regressions extend a registered test file. Documentation impact is limited to the vendor patch ledger.
• Shared-source port: pending.

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