chore(models): add fable tier and refresh Zen alias maps

[moabualruz]

What

• Adds fable to the logical tier vocabulary (frontier tier above opus; Claude Fable 5 in Claude Code, GA 2026-06-09). No core code change needed: model-policy.ts is alias-generic.
• Refreshes approvedModelAliasMaps + approvedPiFallbackModels in scripts/headless-smoke.ts against the live OpenCode Zen catalog (2026-06-09):
  • deepseek-v4-pro was removed from Zen: opencode-go/kimi-k2.6 takes fable, opencode-go/glm-5.1 takes opus
  • contract test now also guards deepseek-v4-pro and claude-fable from reappearing in the maps
• README Model Alias Policy: fable examples + a recommended per-harness alias map table (Claude Code, Codex, Gemini CLI, OpenCode, Pi, Grok Build, Antigravity), with catalog-churn caveats.

Evidence

bun test: 217 pass / 0 fail (903 expect() calls, 19 files)

Summary by CodeRabbit

• Documentation

  • Updated model aliasing docs to add the new "fable" tier, expand alias policy and usage examples, and show environment/config guidance.

• Updates

  • Refreshed model alias mappings to include the "fable" tier and updated catalog references to current model variants.

• Tests

  • Adjusted headless smoke tests to validate the revised alias mappings and updated fallback model order.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 44cc842f-bfa7-4b9d-84ac-c4c688be5f91

📥 Commits

Reviewing files that changed from the base of the PR and between da2ea92 and 5496e24.

📒 Files selected for processing (2)

• README.md
• scripts/headless-smoke.ts

---

📝 Walkthrough

Walkthrough

Adds a fable frontier tier to README model-alias docs, updates OpenCode alias maps and approved fallback models in the headless smoke script, and updates smoke tests to assert the new mappings and that deprecated models (e.g., deepseek-v4-pro) are absent.

Changes

Model Tier System and Catalog Updates

Layer / File(s)	Summary
Model alias policy documentation README.md	Documentation expanded to define tier vocabulary (`fable
Model catalog configuration and test validation scripts/headless-smoke.ts, tests/headless-smoke-contract.test.ts	approvedModelAliasMaps updated to add fable and change opus to opencode-go/glm-5.1; approvedPiFallbackModels updated to begin with opencode-go/kimi-k2.6, opencode-go/glm-5.1 (removed deepseek-v4-pro); tests adjusted to match mappings and assert absence of claude-fable and deepseek-v4-pro.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

I’m a rabbit in the code-lined glade,
A new frontier tier called "fable" made—
Old names retire, new mappings spring,
Tests and docs now dance and sing.
Hop on, the catalog’s freshly laid. 🐇✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main changes: adding the 'fable' tier to the model vocabulary and refreshing the OpenCode Zen alias maps with updated model mappings.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/model-alias-fable-refresh

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@README.md`:
- Around line 279-291: Update the per-harness alias table in README to match
validated identifiers: ensure OpenCode/Pi rows exactly match
approvedModelAliasMaps used in scripts/headless-smoke.ts (including removal of
deepseek-v4-pro and replacing nemotron-3-super-free with nemotron-3-ultra-free),
annotate that Codex "effort xhigh/high" is a host-only reasoning-effort (move it
to a footnote or separate column so it’s not part of the model id), and add a
short caveat for unverified harness rows (Grok/Antigravity) noting they may
drift and require external validation of tokens like grok-build vs
grok-build-0.1 and antigravity-preview-05-2026.

In `@scripts/headless-smoke.ts`:
- Around line 57-63: Update the comment and any tests referencing the OpenCode
Zen catalog to use the catalog's raw id + owned_by values rather than the
constructed config prefixes: adjust wording around approvedModelAliasMaps (the
opencode map entries for fable and opus) to state that catalog ids are
kimi-k2.6, glm-5.1, qwen3.6-plus, and deepseek-v4-flash-free and that
deepseek-v4-pro is not present; clarify that the opencode-go/... strings in
approvedModelAliasMaps are our internal/constructed names and not the catalog id
field, and ensure any assertions or comments compare owned_by + id (e.g.,
owned_by: "opencode" with id: "kimi-k2.6") rather than expecting the prefixed
form.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 307a3b35-ed32-444d-b9b1-69ef55913096

📥 Commits

Reviewing files that changed from the base of the PR and between bbac66d and da2ea92.

📒 Files selected for processing (3)

• README.md
• scripts/headless-smoke.ts
• tests/headless-smoke-contract.test.ts