diff --git a/src/agents/builtin-agents/atlas-agent.ts b/src/agents/builtin-agents/atlas-agent.ts
index 50cfc2cf3..d44c50d60 100644
--- a/src/agents/builtin-agents/atlas-agent.ts
+++ b/src/agents/builtin-agents/atlas-agent.ts
@@ -3,6 +3,7 @@ import type { AgentOverrides } from "../types"
 import type { CategoriesConfig, CategoryConfig } from "../../config/schema"
 import type { AvailableAgent, AvailableSkill } from "../dynamic-agent-prompt-builder"
 import { AGENT_MODEL_REQUIREMENTS } from "../../shared"
+import { log } from "../../shared/logger"
 import { applyOverrides } from "./agent-overrides"
 import { applyModelResolution } from "./model-resolution"
 import { createAtlasAgent } from "../atlas"
@@ -52,7 +53,13 @@ export function maybeCreateAtlasConfig(input: {
     atlasResolution = { model: orchestratorOverride.model, provenance: "override" as const }
   }
 
-  if (!atlasResolution) return undefined
+  if (!atlasResolution) {
+    log("[agent-registration] Agent skipped: model resolution returned no result", {
+      agent: "atlas",
+      configuredModel: orchestratorOverride?.model,
+    })
+    return undefined
+  }
   const { model: atlasModel, variant: atlasResolvedVariant } = atlasResolution
 
   let orchestratorConfig = createAtlasAgent({
diff --git a/src/agents/builtin-agents/general-agents.ts b/src/agents/builtin-agents/general-agents.ts
index 065e26831..aefcb0f87 100644
--- a/src/agents/builtin-agents/general-agents.ts
+++ b/src/agents/builtin-agents/general-agents.ts
@@ -66,6 +66,10 @@ export function collectPendingBuiltinAgents(input: {
     // Check if agent requires a specific model
     if (requirement?.requiresModel && availableModels) {
       if (!isModelAvailable(requirement.requiresModel, availableModels)) {
+        log("[agent-registration] Agent skipped: required model not available", {
+          agent: agentName,
+          requiredModel: requirement.requiresModel,
+        })
         continue
       }
     }
@@ -92,7 +96,13 @@ export function collectPendingBuiltinAgents(input: {
         resolution = getFirstFallbackModel(requirement)
       }
     }
-    if (!resolution) continue
+    if (!resolution) {
+      log("[agent-registration] Agent skipped: model resolution returned no result", {
+        agent: agentName,
+        configuredModel: override?.model,
+      })
+      continue
+    }
     const { model, variant: resolvedVariant } = resolution
 
     let config = buildAgent(source, model, mergedCategories)
diff --git a/src/agents/builtin-agents/hephaestus-agent.ts b/src/agents/builtin-agents/hephaestus-agent.ts
index c05b1fa71..0b42913f2 100644
--- a/src/agents/builtin-agents/hephaestus-agent.ts
+++ b/src/agents/builtin-agents/hephaestus-agent.ts
@@ -3,6 +3,7 @@ import type { AgentOverrides } from "../types"
 import type { CategoryConfig } from "../../config/schema"
 import type { AvailableAgent, AvailableCategory, AvailableSkill } from "../dynamic-agent-prompt-builder"
 import { AGENT_MODEL_REQUIREMENTS, isAnyProviderConnected } from "../../shared"
+import { log } from "../../shared/logger"
 import { createHephaestusAgent } from "../hephaestus"
 import { applyEnvironmentContext } from "./environment-context"
 import { applyCategoryOverride, mergeAgentConfig } from "./agent-overrides"
@@ -51,7 +52,13 @@ export function maybeCreateHephaestusConfig(input: {
     isFirstRunNoCache ||
     isAnyProviderConnected(hephaestusRequirement.requiresProvider, availableModels)
 
-  if (!hasRequiredProvider) return undefined
+  if (!hasRequiredProvider) {
+    log("[agent-registration] Agent skipped: required provider not connected", {
+      agent: "hephaestus",
+      requiredProvider: hephaestusRequirement?.requiresProvider,
+    })
+    return undefined
+  }
 
   let hephaestusResolution = applyModelResolution({
     userModel: hephaestusOverride?.model,
@@ -64,7 +71,13 @@ export function maybeCreateHephaestusConfig(input: {
     hephaestusResolution = getFirstFallbackModel(hephaestusRequirement)
   }
 
-  if (!hephaestusResolution) return undefined
+  if (!hephaestusResolution) {
+    log("[agent-registration] Agent skipped: model resolution returned no result", {
+      agent: "hephaestus",
+      configuredModel: hephaestusOverride?.model,
+    })
+    return undefined
+  }
   const { model: hephaestusModel, variant: hephaestusResolvedVariant } = hephaestusResolution
 
   let hephaestusConfig = createHephaestusAgent(
diff --git a/src/agents/builtin-agents/sisyphus-agent.ts b/src/agents/builtin-agents/sisyphus-agent.ts
index 6cb91370f..6a8d0dc1c 100644
--- a/src/agents/builtin-agents/sisyphus-agent.ts
+++ b/src/agents/builtin-agents/sisyphus-agent.ts
@@ -3,6 +3,7 @@ import type { AgentOverrides } from "../types"
 import type { CategoriesConfig, CategoryConfig } from "../../config/schema"
 import type { AvailableAgent, AvailableCategory, AvailableSkill } from "../dynamic-agent-prompt-builder"
 import { AGENT_MODEL_REQUIREMENTS, isAnyFallbackModelAvailable } from "../../shared"
+import { log } from "../../shared/logger"
 import { applyEnvironmentContext } from "./environment-context"
 import { applyOverrides } from "./agent-overrides"
 import { applyModelResolution, getFirstFallbackModel } from "./model-resolution"
@@ -51,6 +52,11 @@ export function maybeCreateSisyphusConfig(input: {
     isFirstRunNoCache ||
     isAnyFallbackModelAvailable(sisyphusRequirement.fallbackChain, availableModels)
 
+  if (!disabledAgents.includes("sisyphus") && !meetsSisyphusAnyModelRequirement) {
+    log("[agent-registration] Agent skipped: no model in fallback chain is available", {
+      agent: "sisyphus",
+    })
+  }
   if (disabledAgents.includes("sisyphus") || !meetsSisyphusAnyModelRequirement) return undefined
 
   let sisyphusResolution = applyModelResolution({
@@ -65,7 +71,13 @@ export function maybeCreateSisyphusConfig(input: {
     sisyphusResolution = getFirstFallbackModel(sisyphusRequirement)
   }
 
-  if (!sisyphusResolution) return undefined
+  if (!sisyphusResolution) {
+    log("[agent-registration] Agent skipped: model resolution returned no result", {
+      agent: "sisyphus",
+      configuredModel: sisyphusOverride?.model,
+    })
+    return undefined
+  }
   const { model: sisyphusModel, variant: sisyphusResolvedVariant } = sisyphusResolution
 
   let sisyphusConfig = createSisyphusAgent(