fix(athena): address 9 council-audit findings — dead code, bugs, and hardening

Fixes from multi-model council audit (7 members, 19 findings, 9 selected):

- Use parseModelString() for cross-provider Anthropic thinking config (#3)
- Update stale AGENTS.md athena directory listing (#4)
- Replace prompt in appendMissingCouncilPrompt instead of appending (#5)
- Extract duplicated session cleanup logic in agent-switch hook (#6)
- Surface skipped council members when >=2 valid members exist (#9)
- Expand fallback handoff regex with negation guards (#11)
- Remove dead council-member agent from agentSources and tests (#12)
- Make runtime council member duplicate check case-insensitive (#14)
- Fix false-positive schema tests by adding required name field (#18)

src/agents/AGENTS.md

@@ -51,11 +51,10 @@ agents/
 ├── momus.ts               # Plan review
 ├── atlas/agent.ts         # Todo orchestrator
 ├── athena/                # Multi-model council orchestrator
-│   ├── agent.ts           # Athena agent factory
+│   ├── agent.ts           # Athena agent factory + system prompt
 │   ├── council-member-agent.ts  # Council member agent factory
-│   ├── model-parser.ts    # Model string parser
-│   ├── types.ts           # Council types
-│   └── index.ts           # Barrel exports
+│   ├── model-thinking-config.ts  # Per-provider thinking/reasoning config
+│   └── model-thinking-config.test.ts  # Tests for thinking config
 ├── types.ts               # AgentFactory, AgentMode
 ├── agent-builder.ts       # buildAgent() composition
 ├── utils.ts               # Agent utilities

src/agents/athena/model-thinking-config.test.ts

@@ -52,4 +52,30 @@ describe("applyModelThinkingConfig", () => {
       expect(result).toBe(BASE_CONFIG)
     })
   })
+
+  describe("given a Claude model through a non-Anthropic provider", () => {
+    it("returns thinking config for github-copilot/claude-opus-4-6", () => {
+      const result = applyModelThinkingConfig(BASE_CONFIG, "github-copilot/claude-opus-4-6")
+      expect(result).toEqual({
+        ...BASE_CONFIG,
+        thinking: { type: "enabled", budgetTokens: 32000 },
+      })
+    })
+
+    it("returns thinking config for opencode/claude-opus-4-6", () => {
+      const result = applyModelThinkingConfig(BASE_CONFIG, "opencode/claude-opus-4-6")
+      expect(result).toEqual({
+        ...BASE_CONFIG,
+        thinking: { type: "enabled", budgetTokens: 32000 },
+      })
+    })
+
+    it("returns thinking config for opencode/claude-sonnet-4-6", () => {
+      const result = applyModelThinkingConfig(BASE_CONFIG, "opencode/claude-sonnet-4-6")
+      expect(result).toEqual({
+        ...BASE_CONFIG,
+        thinking: { type: "enabled", budgetTokens: 32000 },
+      })
+    })
+  })
 })

src/agents/athena/model-thinking-config.ts

@@ -1,4 +1,5 @@
 import type { AgentConfig } from "@opencode-ai/sdk"
+import { parseModelString } from "../../tools/delegate-task/model-string-parser"
 import { isGptModel } from "../types"
 
 export function applyModelThinkingConfig(base: AgentConfig, model: string): AgentConfig {
@@ -6,10 +7,12 @@ export function applyModelThinkingConfig(base: AgentConfig, model: string): Agen
     return { ...base, reasoningEffort: "medium" }
   }
 
-  const slashIndex = model.indexOf("/")
-  const provider = slashIndex > 0 ? model.substring(0, slashIndex).toLowerCase() : ""
+  const parsed = parseModelString(model)
+  if (!parsed) {
+    return base
+  }
 
-  if (provider === "anthropic") {
+  if (parsed.providerID.toLowerCase() === "anthropic" || parsed.modelID.startsWith("claude")) {
     return { ...base, thinking: { type: "enabled", budgetTokens: 32000 } }
   }
 

src/agents/builtin-agents.ts

@@ -14,7 +14,6 @@ import { createMomusAgent, momusPromptMetadata } from "./momus"
 import { createHephaestusAgent } from "./hephaestus"
 import { createSisyphusJuniorAgentWithOverrides } from "./sisyphus-junior"
 import { createAthenaAgent, ATHENA_PROMPT_METADATA } from "./athena/agent"
-import { createCouncilMemberAgent } from "./athena/council-member-agent"
 import type { AvailableCategory } from "./dynamic-agent-prompt-builder"
 import {
   fetchAvailableModels,
@@ -45,7 +44,6 @@ const agentSources: Partial<Record<BuiltinAgentName, AgentSource>> = {
   metis: createMetisAgent,
   momus: createMomusAgent,
   athena: createAthenaAgent,
-  "council-member": createCouncilMemberAgent,
   // Note: Atlas is handled specially in createBuiltinAgents()
   // because it needs OrchestratorContext, not just a model string
   atlas: createAtlasAgent as AgentFactory,
@@ -196,7 +194,14 @@ export async function createBuiltinAgents(
 
     if (registeredKeys.length > 0) {
       const memberList = registeredKeys.map((key) => `- "${key}"`).join("\n")
-      const councilTaskInstructions = `\n\n## Registered Council Members\n\nUse these as subagent_type in task calls:\n\n${memberList}`
+      let councilTaskInstructions = `\n\n## Registered Council Members\n\nUse these as subagent_type in task calls:\n\n${memberList}`
+
+      if (skippedMembers.length > 0) {
+        const skipDetails = skippedMembers.map((m) => `- **${m.name}**: ${m.reason}`).join("\n")
+        councilTaskInstructions += `\n\n> **Note**: Some configured council members were skipped:\n${skipDetails}`
+        log("[builtin-agents] Some council members were skipped during registration", { skippedMembers })
+      }
+
       result["athena"] = {
         ...result["athena"],
         prompt: (result["athena"].prompt ?? "") + councilTaskInstructions,

src/agents/builtin-agents/athena-council-guard.ts

@@ -39,14 +39,15 @@ Each member requires \`model\` (\`"provider/model-id"\` format) and \`name\` (di
 After informing the user, **end your turn**. Do NOT try to work around this by using generic agents, the council-member agent, or any other fallback.`
 
 /**
- * Replaces Athena's prompt with a guard that tells the user to configure council members.
+ * Replaces Athena's orchestration prompt with a guard that tells the user to configure council members.
+ * The original prompt is discarded to avoid contradictory instructions.
  * Used when Athena is registered but no valid council config exists.
  */
 export function appendMissingCouncilPrompt(
   athenaConfig: AgentConfig,
   skippedMembers?: Array<{ name: string; reason: string }>,
 ): AgentConfig {
-  let prompt = (athenaConfig.prompt ?? "") + MISSING_COUNCIL_PROMPT
+  let prompt = MISSING_COUNCIL_PROMPT
 
   if (skippedMembers && skippedMembers.length > 0) {
     const skipDetails = skippedMembers.map((m) => `- **${m.name}**: ${m.reason}`).join("\n")

src/agents/builtin-agents/council-member-agents.ts

@@ -27,6 +27,7 @@ export function registerCouncilMemberAgents(
   const agents: Record<string, AgentConfig> = {}
   const registeredKeys: string[] = []
   const skippedMembers: SkippedMember[] = []
+  const registeredNamesLower = new Set<string>()
 
   for (const member of councilConfig.members) {
     const parsed = parseModelString(member.model)
@@ -40,16 +41,16 @@ export function registerCouncilMemberAgents(
     }
 
     const key = getCouncilMemberAgentKey(member)
+    const nameLower = member.name.toLowerCase()
 
-    if (agents[key]) {
+    if (registeredNamesLower.has(nameLower)) {
       skippedMembers.push({
         name: member.name,
-        reason: `Duplicate name: '${member.name}' already registered`,
+        reason: `Duplicate name: '${member.name}' already registered (case-insensitive match)`,
       })
       log("[council-member-agents] Skipping duplicate council member name", {
         name: member.name,
         model: member.model,
-        existingModel: agents[key].model ?? "unknown",
       })
       continue
     }
@@ -66,6 +67,7 @@ export function registerCouncilMemberAgents(
     }
 
     registeredKeys.push(key)
+    registeredNamesLower.add(nameLower)
 
     log("[council-member-agents] Registered council member agent", {
       key,