feat: add fable model tier and refresh per-harness model aliases

Add Claude Fable 5 (model: fable) as the tier above opus across the
adapter framework - native passthrough in Claude Code, mapped to each
harness's top model elsewhere. No agents are promoted yet; tier criteria
and cost guidance are documented in docs/agents.md and docs/authoring.md.

Refresh MODEL_ALIASES against current harness catalogs (June 2026):
- Codex: gpt-5 family -> gpt-5.5 / gpt-5.4-mini (per Codex model docs)
- Copilot: GPT-5 stand-ins -> native Claude models (claude-opus-4.8,
  claude-sonnet-4.6, claude-haiku-4.5) now that Copilot CLI serves them
- OpenCode: opus -> anthropic/claude-opus-4-8; haiku dated pin ->
  latest-tracking anthropic/claude-haiku-4-5
- Gemini: intentionally stays on GA gemini-2.5-* (3.x is preview-gated)
- plugin-eval judge opus tier -> claude-opus-4-8

Gates: generate-all (no committed drift), validate STRICT=1, garden,
test (442 passed), smoke-test all green.

AGENTS.md

@@ -66,7 +66,7 @@ Top-level `skills/` is Gemini output; do not use it for OpenCode installs.
 
 192 subagents under `plugins/*/agents/<name>.md`. Per-harness transpilation:
 
-- **Codex**: `.codex/agents/<plugin>__<agent>.toml` (drop `tools:`, map model alias to GPT-5 family, infer `sandbox_mode`)
+- **Codex**: `.codex/agents/<plugin>__<agent>.toml` (drop `tools:`, map model alias to the GPT-5.x family, infer `sandbox_mode`)
 - **OpenCode**: `.opencode/agents/<plugin>__<agent>.md` with `mode: subagent` + `permission:` block (locked agents — those with source `tools: []` — get deny-everything except base `skill`/`task`)
 - **Gemini**: `agents/<plugin>__<agent>.md` (April 2026 subagent spec)
 - **Cursor**: reads `.claude/agents/` directly

ARCHITECTURE.md

@@ -61,7 +61,7 @@ Each adapter consumes the canonical `plugins/` source and emits harness-native a
 | `codex.py` | committed `.agents/plugins/marketplace.json` + `plugins/*/.codex-plugin/plugin.json`; gitignored `.codex/skills/`, `.codex/agents/*.toml` | Marketplace + per-plugin manifests (point at source `plugins/`); Markdown → TOML transform, 8 KB body cap with `references/` overflow, sandbox_mode heuristic, collision detection |
 | `cursor.py` | `.cursor-plugin/`, `.cursor/rules/*.mdc` | Marketplace manifests + hand-curated rules. Cursor reads `.claude/` directly for skills/agents |
 | `opencode.py` | `.opencode/agents/`, `.opencode/commands/`, `.opencode/skills/` | Permission block from `tools:` allowlist (locked agents preserve intent); strict lowercase tool names; OpenCode-safe skill names |
-| `copilot.py` | `.copilot/agents/`, `.copilot/skills/`, `.copilot/commands/` | Markdown agent profiles + SKILL.md skills + commands-as-skills; model maps to GPT-5 family |
+| `copilot.py` | `.copilot/agents/`, `.copilot/skills/`, `.copilot/commands/` | Markdown agent profiles + SKILL.md skills + commands-as-skills; model maps to native Claude models |
 | `gemini.py` | `skills/`, `agents/`, `commands/*.toml` at extension root | Native skills + April-2026 subagents; `@{path}` injection for large command bodies |
 
 Detail in [`docs/harnesses.md`](docs/harnesses.md) (capability matrix per harness) and [`docs/architecture.md`](docs/architecture.md) (full design rationale).

README.md

@@ -69,11 +69,12 @@ plugins/python-development/
 └── skills/             # 16 specialized skills (async, testing, packaging, …)
 ```
 
-Three-tier model strategy:
+Tiered model strategy:
 
 | Tier | Model | Use |
 |---|---|---|
-| 1 | Opus 4.7 | Architecture, security, code review, production-critical |
+| 0 | Fable 5  | Longest-horizon autonomous work — large migrations, multi-hour runs (opt-in, premium cost) |
+| 1 | Opus     | Architecture, security, code review, production-critical |
 | 2 | inherit  | User-chosen — backend, frontend, AI/ML, specialized |
 | 3 | Sonnet   | Docs, testing, debugging, API references |
 | 4 | Haiku    | Fast operational tasks, SEO, deployment, content |
@@ -92,7 +93,7 @@ emits harness-native artifacts (not lowest-common-denominator translations):
 | **Cursor** | `.cursor-plugin/`, `.cursor/rules/` | Thin marketplace + curated rules; reuses `.claude/` |
 | **OpenCode** | `.opencode/agents/`, `.opencode/commands/`, `.opencode/skills/` | `permission:` block from `tools:` allowlist; OpenCode-safe skill names |
 | **Gemini CLI** | `skills/`, `agents/`, `commands/` (TOML) | Native skills + subagents (April 2026 spec) |
-| **Copilot** | `.copilot/agents/`, `.copilot/skills/`, `.copilot/commands/` | Markdown agent profiles + SKILL.md skills + commands-as-skills; model maps to GPT-5 family |
+| **Copilot** | `.copilot/agents/`, `.copilot/skills/`, `.copilot/commands/` | Markdown agent profiles + SKILL.md skills + commands-as-skills; model maps to native Claude models |
 
 ```bash
 make generate-all                        # all five

docs/agents.md

@@ -230,6 +230,7 @@ Agents are assigned to specific Claude models based on task complexity and compu
 
 | Model   | Agent Count | Use Case                                                        |
 | ------- | ----------- | --------------------------------------------------------------- |
+| Fable   | 0           | Longest-horizon autonomous work (tier above Opus; see criteria) |
 | Opus    | 54          | Critical architecture, security, code review, production coding |
 | Sonnet  | 62          | Complex tasks, support with intelligence                        |
 | Haiku   | 20          | Fast operational tasks                                          |
@@ -263,6 +264,30 @@ Agents are assigned to specific Claude models based on task complexity and compu
 - Orchestrating multi-agent workflows
 - Handling business-critical legal/HR matters
 
+#### Fable - Longest-Horizon Autonomous Work
+
+Claude Fable 5 (`model: fable`) is the tier above Opus. It is opt-in in Claude Code
+(v2.1.170+, never the default) and carries roughly 2.6× the effective cost of Opus
+($10/$50 per MTok plus a ~30% heavier tokenizer), so reserve it for agents where Opus
+demonstrably needs multiple attempts.
+
+**Use when:**
+
+- Running multi-hour autonomous sessions (large codebase migrations, overnight refactors)
+- Executing end-to-end work from a single well-specified goal
+- Coordinating long-lived parallel sub-agent workstreams
+
+**Avoid for:**
+
+- Security-analysis agents — Fable 5's cyber/bio safety classifiers fall back to
+  Opus 4.8 on that content anyway
+- Anything Sonnet or Opus already completes in one pass
+
+Other harnesses map `fable` to their top available model (see
+[authoring.md](authoring.md#model-aliases)). Fable-tier agent bodies should state goals
+and constraints rather than step-by-step scaffolding, and must not ask the model to echo
+its internal reasoning.
+
 ### Hybrid Orchestration Patterns
 
 The plugin ecosystem leverages Sonnet + Haiku orchestration for optimal performance and cost efficiency:

docs/authoring.md

@@ -41,7 +41,7 @@ to invoke your skill/agent.
 
 ### Talk about actions, not tools
 
-Codex's underlying GPT-5 doesn't have a `Read`/`Edit`/`Bash` vocabulary — the model picks
+Codex's underlying GPT-5.x models don't have a `Read`/`Edit`/`Bash` vocabulary — the model picks
 the native tool from the action you describe. OpenCode is strict about lowercase
 (`read`, `bash`). Cursor's agent has its own vocabulary.
 
@@ -112,14 +112,29 @@ clean naming — pick distinct names for skill/command pairs within a plugin.
 
 | Source field | Codex | Cursor | OpenCode | Gemini | Copilot |
 |---|---|---|---|---|---|---|
-| `model: opus` | `gpt-5` | `inherit` | `anthropic/claude-opus-4-7` | `gemini-2.5-pro` | `gpt-5` |
-| `model: sonnet` | `gpt-5-mini` | `inherit` | `anthropic/claude-sonnet-4-6` | `gemini-2.5-pro` | `gpt-5-mini` |
-| `model: haiku` | `gpt-5-nano` | `inherit` | `anthropic/claude-haiku-4-5-20251001` | `gemini-2.5-flash` | `gpt-5-nano` |
-| `model: inherit` | `gpt-5` | `inherit` | `anthropic/claude-sonnet-4-6` | `gemini-2.5-pro` | `gpt-5` |
+| `model: fable` | `gpt-5.5` | `inherit` | `anthropic/claude-fable-5` | `gemini-2.5-pro` | `claude-opus-4.8` |
+| `model: opus` | `gpt-5.5` | `inherit` | `anthropic/claude-opus-4-8` | `gemini-2.5-pro` | `claude-opus-4.8` |
+| `model: sonnet` | `gpt-5.4-mini` | `inherit` | `anthropic/claude-sonnet-4-6` | `gemini-2.5-pro` | `claude-sonnet-4.6` |
+| `model: haiku` | `gpt-5.4-mini` | `inherit` | `anthropic/claude-haiku-4-5` | `gemini-2.5-flash` | `claude-haiku-4.5` |
+| `model: inherit` | `gpt-5.5` | `inherit` | `anthropic/claude-sonnet-4-6` | `gemini-2.5-pro` | `claude-sonnet-4.6` |
 
 The adapter handles mapping. The `BARE_MODEL_ALIAS` lint is informational — it just notes
 that the mapping is implicit. If you want explicit, use `inherit`.
 
+Mapping targets live in `tools/adapters/capabilities.py` (`MODEL_ALIASES`) and track each
+harness's published catalog (last verified June 2026). Copilot CLI serves Claude models
+natively, so its aliases map Claude → Claude using Copilot's dotted IDs. Gemini stays on
+the GA `gemini-2.5-*` family because Gemini 3.x ships only access-gated `-preview` IDs.
+
+`fable` (Claude Fable 5) is the tier above `opus`, reserved for the longest-horizon
+autonomous work. It is native in Claude Code (v2.1.170+, opt-in, ~2.6× Opus effective
+cost); other harnesses map it to their top available model. Tag an agent `fable` only
+when Opus demonstrably needs multiple attempts at the task. Avoid it for
+security-analysis agents — Fable 5's cyber/bio classifiers fall back to Opus there
+anyway. Prefer stating goals over step-by-step scaffolding in fable-tier agent bodies,
+and never instruct the model to echo its reasoning (triggers `reasoning_extraction`
+refusals).
+
 ## Skills layout for progressive disclosure
 
 The OpenAI harness-engineering post argues that "agents start with a small, stable entry

docs/harnesses.md

@@ -34,7 +34,7 @@ as Claude Code markdown. Per-harness artifacts are generated by adapters under `
 | Context file recommended cap | 150 lines / 500 tokens | 150 lines / 500 tokens | 150 lines / 500 tokens | 150 lines / 500 tokens | 150 lines / 500 tokens |
 | Skill body hard cap | none | **8 KB** | none | none | none |
 | Tool name case | CamelCase (`Read`) | action verbs (no tool vocab) | lowercase | lowercase (strict) | lowercase (Gemini names) |
-| Bare model aliases | ✅ (`opus`/`sonnet`/`haiku`) | mapped to GPT-5 family | use `inherit` | full provider/model-id | mapped to `gemini-2.5-*` |
+| Bare model aliases | ✅ (`fable`/`opus`/`sonnet`/`haiku`) | mapped to GPT-5.x family | use `inherit` | full provider/model-id | mapped to `gemini-2.5-*` |
 
 ## Claude Code native features
 
@@ -60,7 +60,8 @@ rules to write portable content.
 |---|---|---|---|---|
 | `tools: Read, Grep` (agent allowlist) | dropped; `sandbox_mode = "read-only"` heuristic | dropped (Cursor doesn't honor) | converted to `permission:` deny block | passed through |
 | `color: blue` (agent) | dropped | dropped | dropped | dropped |
-| `model: opus` (agent) | mapped to `gpt-5` | rewritten to `inherit` | rewritten to `anthropic/claude-opus-4-7` | mapped to `gemini-2.5-pro` |
+| `model: opus` (agent) | mapped to `gpt-5.5` | rewritten to `inherit` | rewritten to `anthropic/claude-opus-4-8` | mapped to `gemini-2.5-pro` |
+| `model: fable` (agent) | mapped to `gpt-5.5` | rewritten to `inherit` | rewritten to `anthropic/claude-fable-5` | mapped to `gemini-2.5-pro` |
 | `TodoWrite` in body | no equivalent — leave as-is | no equivalent — leave as-is | works as-is | no equivalent |
 | Skill body > 8 KB | split into `references/details.md` | passed through | passed through | passed through |
 | Agent named `worker` | namespaced to `<plugin>__worker` | passed through | passed through | passed through |

plugins/plugin-eval/src/plugin_eval/layers/harness_portability.py

@@ -54,7 +54,7 @@ _CAMEL_TOOL_PATTERN = re.compile(
 _TOOL_PROSE_PATTERN = re.compile(rf"(?i:\bthe)\s+(?:`)?({_TOOL_ALTERNATION})(?:`)?\s+tool\b")
 
 # Bare model aliases that don't map cleanly (Cursor/OpenCode/Gemini need full IDs)
-_BARE_MODEL_ALIAS_PATTERN = re.compile(r"^(opus|sonnet|haiku)$")
+_BARE_MODEL_ALIAS_PATTERN = re.compile(r"^(fable|opus|sonnet|haiku)$")
 
 # Context file line cap (per harness-engineering principle)
 _CONTEXT_FILE_LINE_CAP = 150

plugins/plugin-eval/src/plugin_eval/layers/judge.py

@@ -38,7 +38,7 @@ Score 1.0 — Perfectly calibrated: Minimal surface area, maximum cohesion, idea
 _MODEL_MAP: dict[str, str] = {
     "haiku": "claude-haiku-4-5-20251001",
     "sonnet": "claude-sonnet-4-6",
-    "opus": "claude-opus-4-7",
+    "opus": "claude-opus-4-8",
 }
 
 

tools/adapters/capabilities.py

@@ -244,39 +244,51 @@ TOOL_NAME_MAPS: dict[str, dict[str, str]] = {
 }
 
 
-# Model alias map: bare Claude alias -> full provider-prefixed ID per harness
+# Model alias map: bare Claude alias -> full provider-prefixed ID per harness.
+# Targets verified against each harness's published model catalog 2026-06:
+# Codex recommends gpt-5.5 (top) / gpt-5.4-mini (light tasks, subagents);
+# Copilot CLI serves Claude models natively, so aliases map Claude -> Claude
+# (no Fable in Copilot — top available Claude is Opus 4.8, dotted-ID format);
+# Gemini CLI's GA models remain gemini-2.5-* (3.x is preview-gated and its
+# IDs churn), so the gemini column intentionally stays on the 2.5 family.
 MODEL_ALIASES: dict[str, dict[str, str]] = {
     "claude-code": {
+        "fable": "fable",
         "opus": "opus",
         "sonnet": "sonnet",
         "haiku": "haiku",
         "inherit": "inherit",
     },
     "codex": {
-        "opus": "gpt-5",
-        "sonnet": "gpt-5-mini",
-        "haiku": "gpt-5-nano",
-        "inherit": "gpt-5",
+        "fable": "gpt-5.5",
+        "opus": "gpt-5.5",
+        "sonnet": "gpt-5.4-mini",
+        "haiku": "gpt-5.4-mini",
+        "inherit": "gpt-5.5",
     },
     "copilot": {
-        "opus": "gpt-5",
-        "sonnet": "gpt-5-mini",
-        "haiku": "gpt-5-nano",
-        "inherit": "gpt-5",
+        "fable": "claude-opus-4.8",
+        "opus": "claude-opus-4.8",
+        "sonnet": "claude-sonnet-4.6",
+        "haiku": "claude-haiku-4.5",
+        "inherit": "claude-sonnet-4.6",
     },
     "cursor": {
+        "fable": "inherit",
         "opus": "inherit",
         "sonnet": "inherit",
         "haiku": "inherit",
         "inherit": "inherit",
     },
     "opencode": {
-        "opus": "anthropic/claude-opus-4-7",
+        "fable": "anthropic/claude-fable-5",
+        "opus": "anthropic/claude-opus-4-8",
         "sonnet": "anthropic/claude-sonnet-4-6",
-        "haiku": "anthropic/claude-haiku-4-5-20251001",
+        "haiku": "anthropic/claude-haiku-4-5",
         "inherit": "anthropic/claude-sonnet-4-6",
     },
     "gemini": {
+        "fable": "gemini-2.5-pro",
         "opus": "gemini-2.5-pro",
         "sonnet": "gemini-2.5-pro",
         "haiku": "gemini-2.5-flash",

tools/tests/test_adapters.py

@@ -76,8 +76,8 @@ class TestCodexAdapter:
 
         parsed = tomllib.loads(content)
         assert parsed["name"] == "demo__greeter"
-        # opus is mapped to gpt-5
-        assert parsed["model"] == "gpt-5"
+        # opus is mapped to gpt-5.5
+        assert parsed["model"] == "gpt-5.5"
         # tools: Read, Grep -> read-only-ish set -> sandbox_mode = read-only
         assert parsed["sandbox_mode"] == "read-only"
         # color: blue should NOT be present
@@ -561,7 +561,7 @@ class TestOpenCodeAdapter:
         assert fm["name"] == "demo__greeter"
         assert fm["mode"] == "subagent"
         # opus -> full provider/model-id
-        assert fm["model"] == "anthropic/claude-opus-4-7"
+        assert fm["model"] == "anthropic/claude-opus-4-8"
 
     def test_permission_block_denies_unlisted_tools(
         self, synthetic_plugin: PluginSource, output_root: Path
@@ -945,7 +945,7 @@ class TestCopilotAdapter:
         fm, body = parse_frontmatter(agent_path.read_text())
         assert fm["name"] == "demo__greeter"
         assert fm["description"] == "Use when delegating greetings."
-        assert fm["model"] == "gpt-5"
+        assert fm["model"] == "claude-opus-4.8"
         assert fm["tools"] == ["read", "search"]
         assert "color" not in fm
 
@@ -1014,10 +1014,10 @@ class TestCopilotAdapter:
         CopilotAdapter(output_root=output_root).emit_plugin(plugin)
 
         expected = {
-            "sonnet-agent": "gpt-5-mini",
-            "haiku-agent": "gpt-5-nano",
-            "inherit-agent": "gpt-5",
-            "default-model": "gpt-5",
+            "sonnet-agent": "claude-sonnet-4.6",
+            "haiku-agent": "claude-haiku-4.5",
+            "inherit-agent": "claude-sonnet-4.6",
+            "default-model": "claude-sonnet-4.6",
         }
         for name, exp_model in expected.items():
             fm, _ = parse_frontmatter(
@@ -1099,7 +1099,7 @@ class TestCopilotAdapter:
         fm, body = parse_frontmatter(content)
         assert fm["name"] == "demo__advisory"
         assert fm["description"] == "Use when advising."
-        assert fm["model"] == "gpt-5-mini"
+        assert fm["model"] == "claude-sonnet-4.6"
         assert "tools:" in content
 
     def test_no_tools_field(self, tmp_path: Path, output_root: Path):
@@ -1124,7 +1124,7 @@ class TestCopilotAdapter:
         fm, body = parse_frontmatter(content)
         assert fm["name"] == "demo__unrestricted"
         assert fm["description"] == "Use when unrestricted."
-        assert fm["model"] == "gpt-5"
+        assert fm["model"] == "claude-opus-4.8"
         assert "tools" not in fm
 
 
@@ -1200,5 +1200,5 @@ class TestCapabilities:
         from tools.adapters.capabilities import MODEL_ALIASES, supported_harnesses
 
         for harness in supported_harnesses():
-            for alias in ("opus", "sonnet", "haiku", "inherit"):
+            for alias in ("fable", "opus", "sonnet", "haiku", "inherit"):
                 assert alias in MODEL_ALIASES[harness], f"{harness} missing {alias}"