feat(coding-agent): add grok-4.6 prompt preset

[code-yeongyu]

Summary

Grok 4.6 shipped in four built-in catalogs (xai, opencode, openrouter, vercel-ai-gateway) with no prompt preset — the grok-4.5 matcher deliberately excludes it, so it fell back to the untuned dynamic prompt. This adds a grok-4.6 preset as a full-core rewrite tuned per the Grok 4.6 launch field guide (Eric Zakariasson, 2026-08-12). It is a direct-implementer core, deliberately NOT a clone of the grok-4.5 CEO/orchestrator preset, which is a fork experiment specific to that model.

Field-guide findings encoded in the core: exhortation phrasing ("work very hard") measurably changes nothing on this model while an explicit definition of "done" changes everything, so the routing line carries the binding declared-stop-condition contract and no intensity language; the single highest-leverage instruction is a real-surface verification loop (walk the user paths the change touches; for hard-to-inspect output: capture current state, list what is wrong, fix only those); its observed failure of repeating near-identical blocks across components gets one positive shared-piece rule; reporting is tuned information-dense (never restate the task, quiet through small changes, one short update at meaningful phase changes).

Changes

• prompt-preset/grok-4.6.ts — new corePrompt preset (precedent: kimi-k3.ts / gpt-5.6.ts). Reuses buildTestDisciplineSection(); no buildFileOperationsTuning() because apply_patch is gated to gpt-* ids and never activates on Grok.
• prompt-preset/presets.ts — hasGrok46Signal matcher (the 4.5 regex shape with a 4.6 minor version), checked before the 4.5 matcher; resolvePresetName branch + buildPreset case.
• prompt-preset/settings.ts — "grok-4.6" joins PromptPresetName / VALID_PRESETS.
• docs/settings.md — preset value list gains grok-4.6 and the previously missing grok-4.5; fork trackers (prompt-preset/changes.md) and [Unreleased] changelog updated.
• test/suite/prompt-presets-grok-4-6.test.ts — id-shape resolution (12 shapes incl. x-ai/, colon-separated, grok-4p6, grok46, trailing tags), non-routing of 4.5/4.3/4.20/3/build-0.1/4.60, 4.5-vs-4.6 distinctness, settings force, and a catalog sweep asserting every built-in Grok 4.6 entry resolves.

QA & Evidence

• What was tested: senpi-qa mock-loop channel — the REAL CLI driven from source in an isolated sandbox against a local fake model server, asserting on the recorded provider request bytes for model ids grok-4.6, grok-4.5, and grok-4.3.
• Observed result: 13/13 checks PASS — grok-4.6 turns carry the new implementer core ("running on Grok 4.6", declared stop condition, no CEO posture, no apply_patch reference); grok-4.5 keeps its CEO preset unchanged; grok-4.3 keeps the dynamic fallback; real ~/.senpi/agent/auth.json untouched.
• Artifact: local-ignore/qa-evidence/20260817-grok-4-6-preset/ (qa-run.log + per-model captured system prompts; local evidence dir, gitignored by design).
• Automated: new suite green (17 tests); prompt-presets-grok-4-5 and prompt-presets-extension suites green; root npm run check green. Full coding-agent suite: 7798 passed; 6 unrelated subprocess/timing tests failed under full-suite load and all pass in isolation.

Risks & Residuals

• Matcher collisions: the 4.6 regex requires a terminator after the 6 (grok-4.60 does not match) and the 4.5/4.3/4.20 families are covered by negative tests — mitigated.
• Prompt-content drift: coverage asserts structural sentinels and routing only (per the repo's prose-pinning prohibition), so wording can evolve without test churn — accepted.

Made with Cursor

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Summary by cubic

Routes Grok 4.6 models to a new grok-4.6 system-prompt preset instead of the untuned dynamic prompt. Grok 4.6 now uses a direct-implementer core; Grok 4.5 stays on its CEO/orchestrator preset.

• Adds grok-4.6.ts: full-core override via buildDynamicSystemPrompt with a binding declared stop condition, real-surface verification loop, shared-piece rule to avoid repeated blocks, and dense reporting; reuses buildTestDisciplineSection; no apply_patch references.
• Introduces hasGrok46Signal and routes it before 4.5; excludes 4.60 and other families; updates resolvePresetName/buildPreset.
• Extends PromptPresetName/VALID_PRESETS with "grok-4.6"; documents grok-4.5 and grok-4.6 in docs/settings.md; CHANGELOG and extension change log updated.
• Adds tests for id-shape resolution, non-routing of other Grok versions, 4.5 vs 4.6 distinctness, settings override, and a built-in catalog sweep across xai, opencode, openrouter, and vercel-ai-gateway.

^{Written for commit c2646d9. Summary will update on new commits.}