diff --git a/bruno/neon-sprawl-server/ability-catalog/Health after ability catalog load.bru b/bruno/neon-sprawl-server/ability-catalog/Health after ability catalog load.bru
new file mode 100644
index 0000000..757385e
--- /dev/null
+++ b/bruno/neon-sprawl-server/ability-catalog/Health after ability catalog load.bru	
@@ -0,0 +1,25 @@
+meta {
+  name: GET health (ability catalog boot NEO-77)
+  type: http
+  seq: 1
+}
+
+get {
+  url: {{baseUrl}}/health
+  body: none
+  auth: none
+}
+
+docs {
+  NEO-77 loads content/abilities/*_abilities.json at startup (fail-fast). No ability HTTP API in this story — use this request to confirm the host started after catalog validation.
+}
+
+tests {
+  test("status 200", function () {
+    expect(res.getStatus()).to.equal(200);
+  });
+
+  test("service identity", function () {
+    expect(res.getBody().service).to.equal("NeonSprawl.Server");
+  });
+}
diff --git a/bruno/neon-sprawl-server/ability-catalog/folder.bru b/bruno/neon-sprawl-server/ability-catalog/folder.bru
new file mode 100644
index 0000000..b32d530
--- /dev/null
+++ b/bruno/neon-sprawl-server/ability-catalog/folder.bru
@@ -0,0 +1,3 @@
+meta {
+  name: ability-catalog
+}
diff --git a/docs/decomposition/modules/E5_M1_CombatRulesEngine.md b/docs/decomposition/modules/E5_M1_CombatRulesEngine.md
index 8c20037..bf7b722 100644
--- a/docs/decomposition/modules/E5_M1_CombatRulesEngine.md
+++ b/docs/decomposition/modules/E5_M1_CombatRulesEngine.md
@@ -7,7 +7,7 @@
 | **Module ID** | E5.M1 |
 | **Epic** | [Epic 5 — PvE Combat](../epics/epic_05_pve_combat.md) |
 | **Stage target** | Prototype |
-| **Status** | In Progress — Slice 1 backlog [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md): E5M1-01 [NEO-76](https://linear.app/neon-sprawl/issue/NEO-76) ability catalog + CI landed; E5M1-02+ pending (see [dependency register](module_dependency_register.md)) |
+| **Status** | In Progress — Slice 1 backlog [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md): E5M1-01 [NEO-76](https://linear.app/neon-sprawl/issue/NEO-76) ability catalog + CI landed; E5M1-02 [NEO-77](https://linear.app/neon-sprawl/issue/NEO-77) server load landed; E5M1-03+ pending (see [dependency register](module_dependency_register.md)) |
 | **Linear** | Label **`E5.M1`** · [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md) **E5M1-01** [NEO-76](https://linear.app/neon-sprawl/issue/NEO-76) → **E5M1-12** [NEO-86](https://linear.app/neon-sprawl/issue/NEO-86); gig XP **E5M1-10** [NEO-44](https://linear.app/neon-sprawl/issue/NEO-44) |
 
 ## Purpose
@@ -80,7 +80,7 @@ The **first shipped four-ability combat spine** under `content/abilities/*.json`
 | **`prototype_dash`** | Prototype Dash | 0 | 4.0 | `movement` |
 | **`prototype_burst`** | Prototype Burst | 40 | 5.0 | `attack` |
 
-**Rules:** Do **not** rename these `id` values—change **`displayName`** only, or add a new `id` in a follow-up issue. CI ([`scripts/validate_content.py`](../../../scripts/validate_content.py)) enforces **exactly** these four ids and duplicate-`id` rejection across all ability JSON files. Relaxing or changing that gate belongs in a new Linear issue once the catalog intentionally grows. **`prototype_pulse`** at 25 damage × 4 casts defeats a 100 HP prototype dummy (E5M1 backlog default). Server load: [NEO-77](https://linear.app/neon-sprawl/issue/NEO-77) (E5M1-02).
+**Rules:** Do **not** rename these `id` values—change **`displayName`** only, or add a new `id` in a follow-up issue. CI ([`scripts/validate_content.py`](../../../scripts/validate_content.py)) and server startup ([NEO-77](../../plans/NEO-77-implementation-plan.md)) enforce **exactly** these four ids and duplicate-`id` rejection across all ability JSON files. Relaxing or changing that gate belongs in a new Linear issue once the catalog intentionally grows. **`prototype_pulse`** at 25 damage × 4 casts defeats a 100 HP prototype dummy (E5M1 backlog default). **`IAbilityDefinitionRegistry`** + hotbar migration: [NEO-79](https://linear.app/neon-sprawl/issue/NEO-79) (E5M1-03).
 
 ## Prototype notes (NEO-28)
 
diff --git a/docs/decomposition/modules/documentation_and_implementation_alignment.md b/docs/decomposition/modules/documentation_and_implementation_alignment.md
index 5a228a2..5894324 100644
--- a/docs/decomposition/modules/documentation_and_implementation_alignment.md
+++ b/docs/decomposition/modules/documentation_and_implementation_alignment.md
@@ -56,7 +56,7 @@ Rows appear when work starts; default for unlisted modules is **Planned** / not
 | E3.M1 | Ready | **NEO-41 landed (prototype, superseded on interact by NEO-63):** inline XP on **`resource_node`** interact. **NEO-57–NEO-61** — content, registry, HTTP defs, depletion store (see prior alignment). **NEO-62 landed:** **`GatherOperations`** + **`GatherResult`**. **NEO-63 landed:** **`POST …/interact`** **`resource_node`** → gather engine; **four** **`PrototypeInteractableRegistry`** anchors; Bruno gather → inventory + depletion deny ([NEO-63](../../plans/NEO-63-implementation-plan.md), [`NEO-63` manual QA](../../manual-qa/NEO-63.md)); [server README — Gather via interact (NEO-63)](../../../server/README.md#gather-via-interact-neo-63). **NEO-64 landed:** comment-only **`resource_gathered`** / **`gather_node_depleted`** hook sites in **`GatherOperations.TryGather`** ([NEO-64](../../plans/NEO-64-implementation-plan.md), [`NEO-64` manual QA](../../manual-qa/NEO-64.md)); Epic 3 Slice 2 backlog **E3M1-01**–**E3M1-08** complete. **NEO-73 landed:** client gather feedback — **`skill_progression_client.gd`**, **`prototype_interactable_picker.gd`** (nearest in-range **R**), **`GatherFeedbackLabel`** + **`SkillProgressionLabel`**, auto inventory/skill refresh after successful gather ([NEO-73](../../plans/NEO-73-implementation-plan.md), [`NEO-73` manual QA](../../manual-qa/NEO-73.md)); `client/README.md` gather section. **NEO-75 landed:** capstone gather→refine→make loop in Godot — [`NEO-75` manual QA](../../manual-qa/NEO-75.md), `client/README.md` end-to-end section; Epic 3 Slice 5 client complete. | [NEO-41](../../plans/NEO-41-implementation-plan.md) … [NEO-64](../../plans/NEO-64-implementation-plan.md), [NEO-73](../../plans/NEO-73-implementation-plan.md), [NEO-75](../../plans/NEO-75-implementation-plan.md), [E3S5-client-prototype-backlog](../../plans/E3S5-client-prototype-backlog.md), [E3_M1](E3_M1_ResourceNodeAndGatherLoop.md); `server/NeonSprawl.Server/Game/Gathering/`, `Game/Interaction/`, `client/scripts/skill_progression_client.gd`, `client/scripts/prototype_interactable_picker.gd` |
 | E3.M3 | In Progress | **NEO-50 landed:** frozen prototype six-item catalog in [`content/items/prototype_items.json`](../../../content/items/prototype_items.json); [`item-def.schema.json`](../../../content/schemas/item-def.schema.json); PR gate + [`validate_content.py`](../../../scripts/validate_content.py). **NEO-51 landed:** fail-fast server load of `content/items/*_items.json` at startup — `server/NeonSprawl.Server/Game/Items/` ([NEO-51](../../plans/NEO-51-implementation-plan.md)); [server README — Item catalog](../../../server/README.md#item-catalog-contentitems-neo-51). **NEO-52 landed:** injectable **`IItemDefinitionRegistry`** + lookup tests ([NEO-52](../../plans/NEO-52-implementation-plan.md)). **NEO-53 landed:** **`GET /game/world/item-definitions`** — `ItemDefinitionsWorldApi` + DTOs in `Game/Items/` ([NEO-53](../../plans/NEO-53-implementation-plan.md), [`NEO-53` manual QA](../../manual-qa/NEO-53.md)); [server README — Item definitions (NEO-53)](../../../server/README.md#item-definitions-neo-53); Bruno `bruno/neon-sprawl-server/item-definitions/`. **NEO-54 landed:** **`IPlayerInventoryStore`** + **`PlayerInventoryOperations`** — 24 bag + 1 equipment slots, stack rules, `V005` migration ([NEO-54](../../plans/NEO-54-implementation-plan.md)). **NEO-55 landed:** **`GET`/`POST /game/players/{id}/inventory`** — `PlayerInventoryApi` + DTOs in `Game/Items/` ([NEO-55](../../plans/NEO-55-implementation-plan.md)); [server README — Player inventory (NEO-54 store, NEO-55 HTTP)](../../../server/README.md#player-inventory-neo-54-store-neo-55-http); Bruno `bruno/neon-sprawl-server/inventory/`. **NEO-56 landed:** comment-only **`item_created`** / **`inventory_transfer_denied`** telemetry hook sites in [`PlayerInventoryOperations`](../../../server/NeonSprawl.Server/Game/Items/PlayerInventoryOperations.cs) ([NEO-56](../../plans/NEO-56-implementation-plan.md), [`NEO-56` manual QA](../../manual-qa/NEO-56.md)); no E9.M1 ingest. **NEO-72 landed:** client inventory HUD — **`inventory_client.gd`**, **`item_definitions_client.gd`**, **`InventoryLabel`**, boot hydrate + **`I`** refresh ([NEO-72](../../plans/NEO-72-implementation-plan.md), [`NEO-72` manual QA](../../manual-qa/NEO-72.md)); `client/README.md` inventory HUD section. **NEO-75 landed:** **`prototype_economy_hud_section.gd`** collapse toggle + capstone manual QA ([NEO-75](../../plans/NEO-75-implementation-plan.md), [`NEO-75` manual QA](../../manual-qa/NEO-75.md)); Epic 3 Slice 5 client complete. | [NEO-50](../../plans/NEO-50-implementation-plan.md), [NEO-51](../../plans/NEO-51-implementation-plan.md), [NEO-52](../../plans/NEO-52-implementation-plan.md), [NEO-53](../../plans/NEO-53-implementation-plan.md), [NEO-54](../../plans/NEO-54-implementation-plan.md), [NEO-55](../../plans/NEO-55-implementation-plan.md), [NEO-56](../../plans/NEO-56-implementation-plan.md), [NEO-72](../../plans/NEO-72-implementation-plan.md), [NEO-75](../../plans/NEO-75-implementation-plan.md), [E3S5-client-prototype-backlog](../../plans/E3S5-client-prototype-backlog.md), [E3M3-prototype-backlog](../../plans/E3M3-prototype-backlog.md), [E3_M3](E3_M3_ItemizationAndInventorySchema.md) |
 | E3.M2 | Ready | **NEO-65 landed:** frozen prototype eight-recipe catalog in [`content/recipes/prototype_recipes.json`](../../../content/recipes/prototype_recipes.json); [`recipe-def.schema.json`](../../../content/schemas/recipe-def.schema.json) + [`recipe-io-row.schema.json`](../../../content/schemas/recipe-io-row.schema.json); PR gate + [`validate_content.py`](../../../scripts/validate_content.py) Slice 3 gates ([NEO-65](../../plans/NEO-65-implementation-plan.md)). **NEO-66 landed:** fail-fast server load of `content/recipes/*_recipes.json` at startup — `server/NeonSprawl.Server/Game/Crafting/` ([NEO-66](../../plans/NEO-66-implementation-plan.md)); [server README — Recipe catalog](../../../server/README.md#recipe-catalog-contentrecipes-neo-66). **NEO-67 landed:** injectable **`IRecipeDefinitionRegistry`** + lookup tests ([NEO-67](../../plans/NEO-67-implementation-plan.md)). **NEO-68 landed:** **`GET /game/world/recipe-definitions`** — `RecipeDefinitionsWorldApi` + DTOs in `Game/Crafting/` ([NEO-68](../../plans/NEO-68-implementation-plan.md), [`NEO-68` manual QA](../../manual-qa/NEO-68.md)); [server README — Recipe definitions (NEO-68)](../../../server/README.md#recipe-definitions-neo-68); Bruno `bruno/neon-sprawl-server/recipe-definitions/`. **NEO-69 landed:** **`CraftOperations.TryCraft`** + **`CraftResult`** — pre-flight inputs/outputs, inventory mutation, refine XP ([NEO-69](../../plans/NEO-69-implementation-plan.md)); [server README — Craft engine (NEO-69)](../../../server/README.md#craft-engine-neo-69-and-craft-http-neo-70). **NEO-70 landed:** **`POST /game/players/{id}/craft`** — `PlayerCraftApi` + wire **`CraftResponse`**; Bruno gather→refine→make spine ([NEO-70](../../plans/NEO-70-implementation-plan.md)); Bruno `bruno/neon-sprawl-server/craft/`. **NEO-71 landed:** comment-only **`item_crafted`** / **`craft_failed`** telemetry hook sites in **`CraftOperations.TryCraft`** ([NEO-71](../../plans/NEO-71-implementation-plan.md)); [server README — Craft telemetry hooks (NEO-71)](../../../server/README.md#craft-telemetry-hooks-neo-71). **NEO-42 landed (prep):** **`RefineActivitySkillXpGrant`** / **`RefineSkillXpConstants`** — wired from craft engine success path. Epic 3 Slice 3 server backlog **E3M2-01**–**E3M2-07** complete. Upstream: E3.M1 **Ready**, E3.M3 inventory landed. **NEO-74 landed:** client craft UI — **`recipe_definitions_client.gd`**, **`craft_client.gd`**, **`craft_recipe_panel.gd`**, **`CraftFeedbackLabel`**, **refine** skill row ([NEO-74](../../plans/NEO-74-implementation-plan.md), [`NEO-74` manual QA](../../manual-qa/NEO-74.md)); `client/README.md` craft section. **NEO-75 landed:** capstone playable gather→refine→make loop — [`NEO-75` manual QA](../../manual-qa/NEO-75.md), **`prototype_economy_hud_section.gd`**; Epic 3 Slice 5 client complete. | [NEO-42](../../plans/NEO-42-implementation-plan.md), [NEO-65](../../plans/NEO-65-implementation-plan.md), [NEO-66](../../plans/NEO-66-implementation-plan.md), [NEO-67](../../plans/NEO-67-implementation-plan.md), [NEO-68](../../plans/NEO-68-implementation-plan.md), [NEO-69](../../plans/NEO-69-implementation-plan.md), [NEO-70](../../plans/NEO-70-implementation-plan.md), [NEO-71](../../plans/NEO-71-implementation-plan.md), [NEO-74](../../plans/NEO-74-implementation-plan.md), [NEO-75](../../plans/NEO-75-implementation-plan.md), [E3M2-prototype-backlog](../../plans/E3M2-prototype-backlog.md), [E3S5-client-prototype-backlog](../../plans/E3S5-client-prototype-backlog.md), [E3_M2](E3_M2_RefinementAndRecipeExecution.md) |
-| E5.M1 | In Progress | **NEO-76 landed:** frozen prototype four-ability catalog in [`content/abilities/prototype_abilities.json`](../../../content/abilities/prototype_abilities.json); [`ability-def.schema.json`](../../../content/schemas/ability-def.schema.json); PR gate + [`validate_content.py`](../../../scripts/validate_content.py) E5M1 four-id gate ([NEO-76](../../plans/NEO-76-implementation-plan.md)). **Backlog decomposed:** Epic 5 Slice 1 — [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md) **E5M1-02** [NEO-77](https://linear.app/neon-sprawl/issue/NEO-77) through **E5M1-12** [NEO-86](https://linear.app/neon-sprawl/issue/NEO-86); gig XP **E5M1-10** [NEO-44](https://linear.app/neon-sprawl/issue/NEO-44). **Precursor landed:** E1.M4 cast funnel (NEO-28/31/32) — **`POST …/ability-cast`** accepts without **`CombatResolution`** yet. | [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md), [E5_M1](E5_M1_CombatRulesEngine.md), [E1M4-prototype-backlog.md](../../plans/E1M4-prototype-backlog.md) |
+| E5.M1 | In Progress | **NEO-76 landed:** frozen prototype four-ability catalog in [`content/abilities/prototype_abilities.json`](../../../content/abilities/prototype_abilities.json); [`ability-def.schema.json`](../../../content/schemas/ability-def.schema.json); PR gate + [`validate_content.py`](../../../scripts/validate_content.py) E5M1 four-id gate ([NEO-76](../../plans/NEO-76-implementation-plan.md)). **NEO-77 landed:** fail-fast server load of `content/abilities/*_abilities.json` at startup — `server/NeonSprawl.Server/Game/Combat/` ([NEO-77](../../plans/NEO-77-implementation-plan.md)); [server README — Ability catalog](../../../server/README.md#ability-catalog-contentabilities-neo-77). **Backlog decomposed:** Epic 5 Slice 1 — [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md) **E5M1-03** [NEO-79](https://linear.app/neon-sprawl/issue/NEO-79) through **E5M1-12** [NEO-86](https://linear.app/neon-sprawl/issue/NEO-86); gig XP **E5M1-10** [NEO-44](https://linear.app/neon-sprawl/issue/NEO-44). **Precursor landed:** E1.M4 cast funnel (NEO-28/31/32) — **`POST …/ability-cast`** accepts without **`CombatResolution`** yet. | [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md), [E5_M1](E5_M1_CombatRulesEngine.md), [NEO-77](../../plans/NEO-77-implementation-plan.md), [E1M4-prototype-backlog.md](../../plans/E1M4-prototype-backlog.md) |
 
 ---
 
diff --git a/docs/decomposition/modules/module_dependency_register.md b/docs/decomposition/modules/module_dependency_register.md
index 1a54104..d31efc4 100644
--- a/docs/decomposition/modules/module_dependency_register.md
+++ b/docs/decomposition/modules/module_dependency_register.md
@@ -76,7 +76,7 @@ Fleshed-out scope, contracts, and integration notes live in **per-module documen
 | E5.M3 | EncounterAndRewardTables | E5.M1, E3.M3, E7.M2 | EncounterDef, RewardTable, EncounterCompleteEvent | Prototype | Planned |
 | E5.M4 | GroupCombatScaling | E5.M3, E8.M1 | ScalingProfile, PartySizeModifier, CombatDifficultyBand | Pre-production | Planned |
 
-**E5.M1 note:** Epic 5 **Slice 1** backlog in Linear ([Epic 5 — PvE Combat and Encounter Content](https://linear.app/neon-sprawl/project/epic-5-pve-combat-and-encounter-content-cf3c94c3-5346-40e0-8aaf-281e846f2846)): [NEO-76](https://linear.app/neon-sprawl/issue/NEO-76) → [NEO-86](https://linear.app/neon-sprawl/issue/NEO-86); label **`E5.M1`**. Gig XP on defeat: **E5M1-10** [NEO-44](https://linear.app/neon-sprawl/issue/NEO-44). See [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md), [E5_M1_CombatRulesEngine.md](E5_M1_CombatRulesEngine.md). Builds on E1.M4 cast funnel (NEO-28/31/32); extends **`POST …/ability-cast`** with **`CombatResolution`**. **NEO-76 landed:** frozen four-ability catalog + CI ([NEO-76 plan](../../plans/NEO-76-implementation-plan.md)).
+**E5.M1 note:** Epic 5 **Slice 1** backlog in Linear ([Epic 5 — PvE Combat and Encounter Content](https://linear.app/neon-sprawl/project/epic-5-pve-combat-and-encounter-content-cf3c94c3-5346-40e0-8aaf-281e846f2846)): [NEO-76](https://linear.app/neon-sprawl/issue/NEO-76) → [NEO-86](https://linear.app/neon-sprawl/issue/NEO-86); label **`E5.M1`**. Gig XP on defeat: **E5M1-10** [NEO-44](https://linear.app/neon-sprawl/issue/NEO-44). See [E5M1-prototype-backlog.md](../../plans/E5M1-prototype-backlog.md), [E5_M1_CombatRulesEngine.md](E5_M1_CombatRulesEngine.md). Builds on E1.M4 cast funnel (NEO-28/31/32); extends **`POST …/ability-cast`** with **`CombatResolution`**. **NEO-76 landed:** frozen four-ability catalog + CI ([NEO-76 plan](../../plans/NEO-76-implementation-plan.md)). **NEO-77 landed:** fail-fast server load of `content/abilities/*_abilities.json` ([NEO-77 plan](../../plans/NEO-77-implementation-plan.md)).
 
 ### Epic 6 — PvP Security
 
diff --git a/docs/plans/E5M1-prototype-backlog.md b/docs/plans/E5M1-prototype-backlog.md
index 7e559a6..00795c1 100644
--- a/docs/plans/E5M1-prototype-backlog.md
+++ b/docs/plans/E5M1-prototype-backlog.md
@@ -115,8 +115,10 @@ Working backlog for **Epic 5 — Slice 1** ([combat rules MVP](../decomposition/
 
 **Acceptance criteria**
 
-- [ ] Host fails startup on invalid ability JSON (mirror CI rules).
-- [ ] Tests cover at least one happy path and one malformed catalog rejection.
+- [x] Host fails startup on invalid ability JSON (mirror CI rules).
+- [x] Tests cover at least one happy path and one malformed catalog rejection.
+
+**Landed ([NEO-77](https://linear.app/neon-sprawl/issue/NEO-77)):** fail-fast server load of `content/abilities/*_abilities.json` — `server/NeonSprawl.Server/Game/Combat/` ([NEO-77-implementation-plan.md](NEO-77-implementation-plan.md)); [server README — Ability catalog](../../server/README.md#ability-catalog-contentabilities-neo-77).
 
 ---
 
diff --git a/docs/plans/NEO-77-implementation-plan.md b/docs/plans/NEO-77-implementation-plan.md
new file mode 100644
index 0000000..99b7c6a
--- /dev/null
+++ b/docs/plans/NEO-77-implementation-plan.md
@@ -0,0 +1,139 @@
+# NEO-77 — Implementation plan
+
+## Story reference
+
+| Field | Value |
+|--------|--------|
+| **Key** | NEO-77 |
+| **Title** | E5M1-02: Server ability catalog load (fail-fast) |
+| **Linear** | https://linear.app/neon-sprawl/issue/NEO-77/e5m1-02-server-ability-catalog-load-fail-fast |
+| **Module** | [E5.M1 — CombatRulesEngine](../decomposition/modules/E5_M1_CombatRulesEngine.md) · Epic 5 Slice 1 · backlog **E5M1-02** |
+| **Branch** | `NEO-77-e5m1-server-ability-catalog-load` |
+| **Precursor** | [NEO-76](https://linear.app/neon-sprawl/issue/NEO-76) — frozen four-ability catalog + CI gates (**Done** on `main`) |
+| **Pattern** | [NEO-51](https://linear.app/neon-sprawl/issue/NEO-51) / [NEO-66](https://linear.app/neon-sprawl/issue/NEO-66) — fail-fast catalog loader + `ContentPathsOptions` + eager `Program.cs` resolve; strict split before registry ticket |
+| **Blocks** | [NEO-79](https://linear.app/neon-sprawl/issue/NEO-79) — `IAbilityDefinitionRegistry` + DI (E5M1-03) |
+
+## Kickoff clarifications
+
+| Topic | Question | Agent recommendation | Answer |
+|--------|----------|----------------------|--------|
+| **NEO-77 vs NEO-79 (DI scope)** | Ship `IAbilityDefinitionRegistry` on this story, or only load + `AbilityDefinitionCatalog`? | **Strict split** — NEO-77: loader + `AbilityDefinitionCatalog` + eager fail-fast boot; [NEO-79](https://linear.app/neon-sprawl/issue/NEO-79) adds injectable `IAbilityDefinitionRegistry` (E5M1-03). Rationale: E5M1 backlog separates E5M1-02/03; mirrors NEO-66/NEO-67. | **User:** `AbilityDefinitionCatalog` singleton only (kickoff). |
+| **Startup failure tests** | Loader unit tests only, or also `WebApplicationFactory` host boot failure? | **Both** — mirror `ItemDefinitionCatalogLoaderTests` / `RecipeDefinitionCatalogLoaderTests`. | **User:** loader AAA + host boot tests (kickoff). |
+| **`PrototypeAbilityRegistry`** | Migrate hotbar/cast allowlist reads this story? | **Leave unchanged** — E5M1-03 explicitly migrates call sites; NEO-77 is load-only. | **User:** unchanged (kickoff). |
+| **Runtime validation** | In-process C# vs subprocess `validate_content.py`? | **In-process C#** mirroring `scripts/validate_content.py` (Draft 2020-12 + E5M1 four-id gate). Rationale: NEO-51 / NEO-66 precedent; no cross-catalog refs in Slice 1. | **Adopted** — NEO-51 precedent; no separate question. |
+| **Lookup API on NEO-77** | How does “catalog resolves `AbilityDef` by `id`” land without NEO-79? | **`AbilityDefinitionCatalog.ById`** (read-only map) + `TryGetAbility(string id, out AbilityDefRow row)`; row carries damage + cooldown fields for NEO-79 consumers. | **Adopted** — NEO-66 `RecipeDefinitionCatalog` precedent. |
+
+## Goal, scope, and out-of-scope
+
+**Goal:** On host startup, load all `content/abilities/*_abilities.json` catalogs (validated in CI per [NEO-76](NEO-76-implementation-plan.md)), build an in-memory **`AbilityDefinitionCatalog`**, and **refuse to listen** when any file is missing, malformed, has duplicate `id`, or fails the prototype E5M1 four-id gate.
+
+**In scope (from Linear + [E5M1-02](E5M1-prototype-backlog.md#e5m1-02--server-ability-catalog-load-fail-fast)):**
+
+- Loader + catalog types under `server/NeonSprawl.Server/Game/Combat/`.
+- Configurable abilities directory and schema path (`ContentPathsOptions` extension).
+- CI-parity validation: `schemaVersion`, row schema (`ability-def`), duplicate `id`, E5M1 four-id allowlist gate.
+- DI registration of **`AbilityDefinitionCatalog`** singleton; eager resolve in `Program.cs`.
+- Unit + host startup tests (AAA).
+- `server/README.md` section.
+
+**Out of scope (from Linear):**
+
+- **`IAbilityDefinitionRegistry`** / hotbar-cast migration from **`PrototypeAbilityRegistry`** (**NEO-79**, E5M1-03).
+- HTTP projection (**NEO-78**, E5M1-04), combat resolution (**NEO-81+**).
+
+## Acceptance criteria checklist
+
+- [x] Server refuses boot when ability catalog invalid (missing dir, no `*_abilities.json`, bad JSON, `schemaVersion` ≠ 1, schema violation, duplicate `id`, E5M1 gate failure).
+- [x] `AbilityDefinitionCatalog` resolves prototype rows by ability `id` (e.g. `prototype_pulse`, `prototype_burst`) with `baseDamage`, `cooldownSeconds`, optional `abilityKind`.
+- [x] Unit tests (AAA): loader happy path + failure modes; host resolves catalog on success; host fails startup on invalid catalog directory.
+- [x] Success log includes **ability count**, **catalog directory**, and **file count** (Information).
+
+## Implementation reconciliation (shipped)
+
+- **Loader:** [`AbilityDefinitionCatalogLoader`](../../server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalogLoader.cs) — CI-parity validation via JsonSchema.Net + E5M1 gate.
+- **Catalog:** [`AbilityDefinitionCatalog`](../../server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalog.cs) + [`AbilityDefRow`](../../server/NeonSprawl.Server/Game/Combat/AbilityDefRow.cs) — `TryGetAbility` lookup by id.
+- **Gate rules:** [`PrototypeE5M1AbilityCatalogRules`](../../server/NeonSprawl.Server/Game/Combat/PrototypeE5M1AbilityCatalogRules.cs) — sync comment to `scripts/validate_content.py` `PROTOTYPE_E5M1_ABILITY_IDS`.
+- **DI / startup:** [`AbilityCatalogServiceCollectionExtensions`](../../server/NeonSprawl.Server/Game/Combat/AbilityCatalogServiceCollectionExtensions.cs) + eager resolve in [`Program.cs`](../../server/NeonSprawl.Server/Program.cs).
+- **Tests:** [`AbilityDefinitionCatalogLoaderTests`](../../server/NeonSprawl.Server.Tests/Game/Combat/AbilityDefinitionCatalogLoaderTests.cs) — 14 AAA cases (loader + host).
+- **Docs:** `server/README.md` ability catalog section; E5.M1 module doc + alignment register + E5M1 backlog E5M1-02 checkboxes.
+- **Unchanged:** [`PrototypeAbilityRegistry`](../../server/NeonSprawl.Server/Game/AbilityInput/PrototypeAbilityRegistry.cs) — migration deferred to NEO-79.
+
+## Technical approach
+
+1. **`Game/Combat/` row DTO** — `AbilityDefRow` (`Id`, `DisplayName`, `BaseDamage`, `CooldownSeconds`, optional `AbilityKind` enum or string).
+
+2. **`AbilityDefinitionCatalogLoader.Load(abilitiesDirectory, schemaPath, logger)`** — single-pass load mirroring `validate_content.py` `_validate_ability_catalogs` + `_prototype_e5m1_ability_gate`:
+   - Enumerate `*_abilities.json` (top-level only), ordered by path.
+   - Build **JsonSchema.Net** evaluator from `ability-def.schema.json`.
+   - Per file: parse JSON; require `schemaVersion == 1` and top-level `abilities` array.
+   - Per row: validate against schema; on clean rows track `id`; build `AbilityDefRow`; reject duplicate `id` across files.
+   - Run **`PrototypeE5M1AbilityCatalogRules.TryGetE5M1GateError`** (mirror `PROTOTYPE_E5M1_ABILITY_IDS` / `_prototype_e5m1_ability_gate` in `scripts/validate_content.py`).
+   - Throw **`InvalidOperationException`** with aggregated, sorted messages prefixed `Ability catalog validation failed:`.
+
+3. **`AbilityDefinitionCatalog`** — immutable snapshot: `AbilitiesDirectory`, `ById`, `DistinctAbilityCount`, `CatalogJsonFileCount`; `TryGetAbility(id, out AbilityDefRow?)` for lookups.
+
+4. **`AbilityCatalogPathResolution`** — `TryDiscoverAbilitiesDirectory`, `ResolveAbilitiesDirectory`, `ResolveAbilityDefSchemaPath` (parent `content/schemas/` layout when unset).
+
+5. **`PrototypeE5M1AbilityCatalogRules`** — frozen four ability ids; sync comment to `scripts/validate_content.py` `PROTOTYPE_E5M1_ABILITY_IDS` / `_prototype_e5m1_ability_gate`. Ids: `prototype_pulse`, `prototype_guard`, `prototype_dash`, `prototype_burst` (same set as [`PrototypeAbilityRegistry`](../../server/NeonSprawl.Server/Game/AbilityInput/PrototypeAbilityRegistry.cs) — unchanged this story).
+
+6. **`AbilityCatalogServiceCollectionExtensions.AddAbilityDefinitionCatalog`** — bind `ContentPathsOptions`; register **`AbilityDefinitionCatalog`** singleton factory that resolves paths and calls loader. No dependency on item/skill catalogs (Slice 1 abilities have no cross-ref fields).
+
+7. **`Program.cs`** — `AddAbilityDefinitionCatalog(configuration)` alongside existing catalog registrations; after `Build()`, `GetRequiredService<AbilityDefinitionCatalog>()` with other eager catalog resolves.
+
+8. **Tests** — temp-dir fixtures copying repo `ability-def.schema.json`; valid four-ability JSON matching [prototype_abilities.json](../../content/abilities/prototype_abilities.json); negative cases (duplicate id, wrong/missing E5M1 roster, bad `baseDamage` / `cooldownSeconds`, empty `displayName`, `schemaVersion` ≠ 1, missing dir/schema, no `*_abilities.json`, invalid JSON); `InMemoryWebApplicationFactory` host test + `WebApplicationFactory` with empty abilities dir fails startup.
+
+9. **Test factories** — pin `Content:AbilitiesDirectory` in `InMemoryWebApplicationFactory` and other `WebApplicationFactory` subclasses that already pin recipes/items (same pattern as NEO-66).
+
+## Files to add
+
+| Path | Purpose |
+|------|---------|
+| `server/NeonSprawl.Server/Game/Combat/AbilityDefRow.cs` | Load-time `AbilityDef` row DTO. |
+| `server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalog.cs` | In-memory catalog + `TryGetAbility`. |
+| `server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalogLoader.cs` | Disk I/O, schema validation, E5M1 gate. |
+| `server/NeonSprawl.Server/Game/Combat/AbilityCatalogPathResolution.cs` | Directory/schema discovery and config resolution. |
+| `server/NeonSprawl.Server/Game/Combat/PrototypeE5M1AbilityCatalogRules.cs` | Frozen four ids gate (sync comment to Python). |
+| `server/NeonSprawl.Server/Game/Combat/AbilityCatalogServiceCollectionExtensions.cs` | `AddAbilityDefinitionCatalog` DI registration. |
+| `server/NeonSprawl.Server.Tests/Game/Combat/AbilityCatalogTestPaths.cs` | Repo `content/abilities` + schema discovery for tests. |
+| `server/NeonSprawl.Server.Tests/Game/Combat/AbilityDefinitionCatalogLoaderTests.cs` | AAA loader + host startup tests. |
+| `docs/plans/NEO-77-implementation-plan.md` | This plan. |
+
+## Files to modify
+
+| Path | Rationale |
+|------|-----------|
+| `server/NeonSprawl.Server/Game/Skills/ContentPathsOptions.cs` | Add `AbilitiesDirectory`, `AbilityDefSchemaPath` under `Content` section. |
+| `server/NeonSprawl.Server/Program.cs` | Register and eagerly resolve `AbilityDefinitionCatalog` at startup. |
+| `server/NeonSprawl.Server/appsettings.json` | Optional empty `Content:AbilitiesDirectory` / schema path keys for override documentation (mirror other catalogs). |
+| `server/NeonSprawl.Server.Tests/InMemoryWebApplicationFactory.cs` | Pin `Content:AbilitiesDirectory` to discovered repo path so existing tests keep booting. |
+| `server/NeonSprawl.Server.Tests/Game/PositionState/PostgresWebApplicationFactory.cs` | Pin abilities directory (same as recipes/items). |
+| `server/NeonSprawl.Server.Tests/Game/Interaction/SalvageActivityDeniedRegistryWebApplicationFactory.cs` | Pin abilities directory. |
+| `server/NeonSprawl.Server.Tests/Game/Skills/RefineActivityDeniedRegistryWebApplicationFactory.cs` | Pin abilities directory. |
+| `server/NeonSprawl.Server.Tests/Game/Skills/MissionRewardDeniedRegistryWebApplicationFactory.cs` | Pin abilities directory. |
+| `server/README.md` | New **Ability catalog (`content/abilities`, NEO-77)** section (config keys, discovery, fail-fast, E5M1 parity with CI). |
+| `docs/decomposition/modules/documentation_and_implementation_alignment.md` | E5.M1 row — note NEO-77 server load when implementation completes. |
+| `docs/decomposition/modules/E5_M1_CombatRulesEngine.md` | Status line — E5M1-02 server load landed when complete. |
+| `docs/plans/E5M1-prototype-backlog.md` | E5M1-02 checkboxes when implementation completes. |
+
+## Tests
+
+| Test file | What it covers |
+|-----------|----------------|
+| `server/NeonSprawl.Server.Tests/Game/Combat/AbilityDefinitionCatalogLoaderTests.cs` | **Unit:** valid four-ability prototype catalog loads; `abilities` not array; schema violation (negative `baseDamage`, zero `cooldownSeconds`, empty `displayName`); duplicate `id` across files; E5M1 gate failure (missing id + extra/wrong id); `schemaVersion` ≠ 1; missing dir/schema; no `*_abilities.json` files; invalid JSON. **Host:** `InMemoryWebApplicationFactory` + `/health` + DI `AbilityDefinitionCatalog` count 4; `WebApplicationFactory` with empty abilities dir fails startup with actionable message. |
+
+**Manual QA:** Skipped — no player-visible HTTP; acceptance is fully covered by AAA loader/host tests above.
+
+## Open questions / risks
+
+| Question / risk | Agent recommendation | Status |
+|-----------------|----------------------|--------|
+| **Constants drift vs Python** | Comment on `PrototypeE5M1AbilityCatalogRules` pointing at `scripts/validate_content.py` `PROTOTYPE_E5M1_ABILITY_IDS` / `_prototype_e5m1_ability_gate`. | **adopted** |
+| **Test cwd** | `InMemoryWebApplicationFactory` must set `Content:AbilitiesDirectory` explicitly (do not rely on discovery alone in CI). | **adopted** |
+| **Registry consumers** | Hotbar/cast/combat use `IAbilityDefinitionRegistry` in NEO-79+; this story only exposes `AbilityDefinitionCatalog` for boot + direct test lookup. **`PrototypeAbilityRegistry` unchanged.** | **adopted** |
+| **Global cooldown still active** | Expected — catalog lands before E5M1-07 wires per-ability `cooldownSeconds`; load does not change runtime cast behavior. | **adopted** |
+
+## Decisions (kickoff)
+
+- **`AbilityDefinitionCatalog` singleton only** — defer `IAbilityDefinitionRegistry` and `PrototypeAbilityRegistry` migration to NEO-79 (user confirmed kickoff).
+- **In-process validation** + **loader and host boot tests** per NEO-51 / NEO-66 precedent.
+- **No cross-catalog checks** — ability rows have no item/skill refs in Slice 1; loader has no catalog dependencies.
diff --git a/docs/reviews/2026-05-24-NEO-77.md b/docs/reviews/2026-05-24-NEO-77.md
new file mode 100644
index 0000000..e31ccf2
--- /dev/null
+++ b/docs/reviews/2026-05-24-NEO-77.md
@@ -0,0 +1,66 @@
+# Code review — NEO-77 server ability catalog load (fail-fast)
+
+**Date:** 2026-05-24  
+**Scope:** Branch `NEO-77-e5m1-server-ability-catalog-load` · commits `07444e4`–`7c2697e` vs `origin/main`  
+**Base:** `origin/main`
+
+## Verdict
+
+**Approve with nits**
+
+## Summary
+
+NEO-77 delivers **E5M1-02**: fail-fast startup load of `content/abilities/*_abilities.json` under `server/NeonSprawl.Server/Game/Combat/`, mirroring the NEO-51 / NEO-66 catalog pattern. The loader validates Draft 2020-12 row schema, `schemaVersion`, duplicate `id`, and the frozen E5M1 four-id gate (`PrototypeE5M1AbilityCatalogRules`), registers `AbilityDefinitionCatalog` in DI, and eagerly resolves it in `Program.cs`. Fourteen AAA loader/host tests pass; full suite (354 tests) is green. Docs (plan, E5M1 backlog, E5.M1 module page, alignment register, `server/README.md`) are updated. `PrototypeAbilityRegistry` is correctly unchanged (NEO-79). Bruno adds a health smoke request consistent with other catalog stories. No client or ability HTTP API — appropriately deferred. Risk is low: infrastructure-only, CI already gates content.
+
+## Documentation checked
+
+| Document | Result |
+|----------|--------|
+| [`docs/plans/NEO-77-implementation-plan.md`](../plans/NEO-77-implementation-plan.md) | **Matches** — kickoff decisions, loader/catalog/DI scope, acceptance checklist, reconciliation section; `IAbilityDefinitionRegistry` correctly out of scope. |
+| [`docs/plans/E5M1-prototype-backlog.md`](../plans/E5M1-prototype-backlog.md) · **E5M1-02** | **Matches** — AC checkboxes + landed note. |
+| [`docs/decomposition/modules/E5_M1_CombatRulesEngine.md`](../decomposition/modules/E5_M1_CombatRulesEngine.md) | **Matches** — Status line and freeze rules reference NEO-77 server load + NEO-79 registry deferral. |
+| [`docs/decomposition/modules/documentation_and_implementation_alignment.md`](../decomposition/modules/documentation_and_implementation_alignment.md) | **Matches** — E5.M1 row updated with NEO-77 landed note; next backlog item NEO-79. |
+| [`docs/decomposition/modules/module_dependency_register.md`](../decomposition/modules/module_dependency_register.md) | **Matches** — E5.M1 table **Status** **In Progress** is correct; **E5.M1 note** cites NEO-76 + NEO-77 server load. |
+| [`docs/decomposition/modules/client_server_authority.md`](../decomposition/modules/client_server_authority.md) | **N/A** — server startup catalog only; no client mutation or combat resolution. |
+| [`scripts/validate_content.py`](../../scripts/validate_content.py) | **Matches** — C# loader mirrors `_validate_ability_catalogs` + `_prototype_e5m1_ability_gate`; sync comment on `PrototypeE5M1AbilityCatalogRules.ExpectedAbilityIds`. |
+| [`server/README.md`](../../server/README.md) | **Matches** — Ability catalog section (config keys, discovery, fail-fast, E5M1 parity). |
+| Full-stack epic decomposition | **Matches** — E5M1-02 is **server/content** only; client counterparts documented in backlog (NEO-85 / NEO-86); no false “prototype complete” claim. |
+| Manual QA | **N/A** — plan documents skip rationale: automated loader/host tests + Bruno health smoke. |
+
+Register/tracking: alignment table E5.M1 **In Progress** with NEO-77 note is correct.
+
+## Blocking issues
+
+None.
+
+## Suggestions
+
+1. ~~**Add `folder.bru` under `bruno/neon-sprawl-server/ability-catalog/`** — Other catalog smoke folders (`item-catalog`, `recipe-catalog`, `resource-node-catalog`, `mastery-catalog`) include a `folder.bru` meta file; ability-catalog currently has only the health request. Add for Bruno collection parity.~~ **Done.** Added `bruno/neon-sprawl-server/ability-catalog/folder.bru`.
+
+2. ~~**E5M1 gate test — extra/wrong id** — `Load_ShouldThrow_WhenE5M1GateFails` removes one ability (missing id). Plan test table also lists wrong roster; consider an AAA case that swaps in an unknown id (e.g. `prototype_extra`) to cover the “got […]” branch, not only “missing”.~~ **Done.** Renamed missing-id test to `Load_ShouldThrow_WhenE5M1GateFailsWithMissingId`; added `Load_ShouldThrow_WhenE5M1GateFailsWithExtraId`. Plan test table updated.
+
+## Nits
+
+- Nit: `ValidPrototypeCatalogJson` duplicates `content/abilities/prototype_abilities.json` inline — fine for isolated temp-dir fixtures (same pattern as NEO-66 recipe tests); optional future refactor to copy repo file.
+
+- Nit: E5M1 gate error string format differs slightly from Python (`'prototype_pulse', …` vs `sorted(...)!r`); behavior is equivalent and messages are actionable.
+
+- Nit: Repeated `services.AddOptions<ContentPathsOptions>().Bind(...)` in each catalog extension — established repo pattern (NEO-51/NEO-66); harmless duplicate binds.
+
+## Verification
+
+```bash
+cd /home/don/neon-sprawl/server
+dotnet test NeonSprawl.Server.Tests/NeonSprawl.Server.Tests.csproj --filter "FullyQualifiedName~AbilityDefinitionCatalogLoaderTests"
+dotnet test NeonSprawl.Server.Tests/NeonSprawl.Server.Tests.csproj
+
+# Content CI parity (repo root)
+python3 scripts/validate_content.py
+# Expect: 4 unique ability id(s)
+```
+
+Manual (optional):
+
+- Start server from repo root; confirm Information log: ability count **4**, catalog directory, file count **1**.
+- Bruno: `bruno/neon-sprawl-server/ability-catalog/Health after ability catalog load.bru` → 200 + `service: NeonSprawl.Server`.
+- Negative: set `Content__AbilitiesDirectory` to an empty temp dir → startup fails with `Ability catalog validation failed:`.
diff --git a/server/NeonSprawl.Server.Tests/Game/Combat/AbilityCatalogTestPaths.cs b/server/NeonSprawl.Server.Tests/Game/Combat/AbilityCatalogTestPaths.cs
new file mode 100644
index 0000000..1965b73
--- /dev/null
+++ b/server/NeonSprawl.Server.Tests/Game/Combat/AbilityCatalogTestPaths.cs
@@ -0,0 +1,17 @@
+using NeonSprawl.Server.Game.Combat;
+
+namespace NeonSprawl.Server.Tests.Game.Combat;
+
+internal static class AbilityCatalogTestPaths
+{
+    internal static string DiscoverRepoAbilitiesDirectory() =>
+        AbilityCatalogPathResolution.TryDiscoverAbilitiesDirectory(AppContext.BaseDirectory)
+        ?? throw new InvalidOperationException(
+            "Could not discover repo content/abilities from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+
+    internal static string DiscoverRepoAbilityDefSchemaPath() =>
+        AbilityCatalogPathResolution.ResolveAbilityDefSchemaPath(
+            DiscoverRepoAbilitiesDirectory(),
+            configuredSchemaPath: null,
+            contentRootPath: string.Empty);
+}
diff --git a/server/NeonSprawl.Server.Tests/Game/Combat/AbilityDefinitionCatalogLoaderTests.cs b/server/NeonSprawl.Server.Tests/Game/Combat/AbilityDefinitionCatalogLoaderTests.cs
new file mode 100644
index 0000000..74041ee
--- /dev/null
+++ b/server/NeonSprawl.Server.Tests/Game/Combat/AbilityDefinitionCatalogLoaderTests.cs
@@ -0,0 +1,350 @@
+using System.Net;
+using System.Text;
+using System.Text.Json.Nodes;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging.Abstractions;
+using NeonSprawl.Server.Game.Combat;
+using NeonSprawl.Server.Tests;
+using Xunit;
+
+namespace NeonSprawl.Server.Tests.Game.Combat;
+
+public class AbilityDefinitionCatalogLoaderTests
+{
+    private const string ValidPrototypeCatalogJson =
+        """
+        {
+          "schemaVersion": 1,
+          "abilities": [
+            {
+              "id": "prototype_pulse",
+              "displayName": "Prototype Pulse",
+              "baseDamage": 25,
+              "cooldownSeconds": 3.0,
+              "abilityKind": "attack"
+            },
+            {
+              "id": "prototype_guard",
+              "displayName": "Prototype Guard",
+              "baseDamage": 0,
+              "cooldownSeconds": 6.0,
+              "abilityKind": "utility"
+            },
+            {
+              "id": "prototype_dash",
+              "displayName": "Prototype Dash",
+              "baseDamage": 0,
+              "cooldownSeconds": 4.0,
+              "abilityKind": "movement"
+            },
+            {
+              "id": "prototype_burst",
+              "displayName": "Prototype Burst",
+              "baseDamage": 40,
+              "cooldownSeconds": 5.0,
+              "abilityKind": "attack"
+            }
+          ]
+        }
+        """;
+
+    private static (string Root, string AbilitiesDir, string SchemaPath) CreateTempContentLayout()
+    {
+        var root = Directory.CreateTempSubdirectory("neon-sprawl-abilitycat-");
+        var abilitiesDir = Path.Combine(root.FullName, "content", "abilities");
+        var schemaDir = Path.Combine(root.FullName, "content", "schemas");
+        Directory.CreateDirectory(abilitiesDir);
+        Directory.CreateDirectory(schemaDir);
+        var schemaPath = Path.Combine(schemaDir, "ability-def.schema.json");
+        File.Copy(AbilityCatalogTestPaths.DiscoverRepoAbilityDefSchemaPath(), schemaPath, overwrite: true);
+        return (root.FullName, abilitiesDir, schemaPath);
+    }
+
+    private static void WriteCatalog(string abilitiesDir, string catalogJson) =>
+        File.WriteAllText(Path.Combine(abilitiesDir, "prototype_abilities.json"), catalogJson, Encoding.UTF8);
+
+    private static JsonObject GetAbilityRow(JsonObject catalogRoot, string abilityId)
+    {
+        var abilities = catalogRoot["abilities"] as JsonArray
+                        ?? throw new InvalidOperationException("expected abilities array");
+        foreach (var node in abilities)
+        {
+            if (node is JsonObject row && row["id"]?.GetValue<string>() == abilityId)
+                return row;
+        }
+
+        throw new InvalidOperationException($"ability id not found: {abilityId}");
+    }
+
+    private static AbilityDefinitionCatalog LoadCatalog(string abilitiesDir, string schemaPath) =>
+        AbilityDefinitionCatalogLoader.Load(abilitiesDir, schemaPath, NullLogger.Instance);
+
+    [Fact]
+    public void Load_ShouldSucceed_WhenCatalogMatchesPrototypeContract()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        WriteCatalog(abilitiesDir, ValidPrototypeCatalogJson);
+        // Act
+        var catalog = LoadCatalog(abilitiesDir, schemaPath);
+        // Assert
+        Assert.Equal(4, catalog.DistinctAbilityCount);
+        Assert.Equal(1, catalog.CatalogJsonFileCount);
+        Assert.True(catalog.TryGetAbility("prototype_pulse", out var pulse));
+        Assert.NotNull(pulse);
+        Assert.Equal(25, pulse!.BaseDamage);
+        Assert.Equal(3.0, pulse.CooldownSeconds);
+        Assert.Equal("attack", pulse.AbilityKind);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenAbilitiesIsNotArray()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        File.WriteAllText(
+            Path.Combine(abilitiesDir, "bad_abilities.json"),
+            """{"schemaVersion": 1, "abilities": "nope"}""",
+            Encoding.UTF8);
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("bad_abilities.json", ioe.Message, StringComparison.Ordinal);
+        Assert.Contains("expected top-level 'abilities' array", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenSchemaVersionIsNotOne()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        File.WriteAllText(
+            Path.Combine(abilitiesDir, "bad_abilities.json"),
+            """{"schemaVersion": 2, "abilities": []}""",
+            Encoding.UTF8);
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("expected schemaVersion 1", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenDuplicateAbilityIdAcrossFiles()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        WriteCatalog(abilitiesDir, ValidPrototypeCatalogJson);
+        File.WriteAllText(
+            Path.Combine(abilitiesDir, "extra_abilities.json"),
+            """
+            {
+              "schemaVersion": 1,
+              "abilities": [
+                {
+                  "id": "prototype_pulse",
+                  "displayName": "Duplicate Pulse",
+                  "baseDamage": 1,
+                  "cooldownSeconds": 1.0
+                }
+              ]
+            }
+            """,
+            Encoding.UTF8);
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("duplicate ability id 'prototype_pulse'", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenE5M1GateFailsWithMissingId()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        var root = JsonNode.Parse(ValidPrototypeCatalogJson) as JsonObject
+                   ?? throw new InvalidOperationException("expected object root");
+        var abilities = root["abilities"] as JsonArray
+                        ?? throw new InvalidOperationException("expected abilities array");
+        abilities.RemoveAt(abilities.Count - 1);
+        WriteCatalog(abilitiesDir, root.ToJsonString());
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("prototype E5M1 expects exactly ability ids", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenE5M1GateFailsWithExtraId()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        var root = JsonNode.Parse(ValidPrototypeCatalogJson) as JsonObject
+                   ?? throw new InvalidOperationException("expected object root");
+        GetAbilityRow(root, "prototype_burst")["id"] = "prototype_extra";
+        WriteCatalog(abilitiesDir, root.ToJsonString());
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("prototype E5M1 expects exactly ability ids", ioe.Message, StringComparison.Ordinal);
+        Assert.Contains("prototype_extra", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenBaseDamageIsNegative()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        var root = JsonNode.Parse(ValidPrototypeCatalogJson) as JsonObject
+                   ?? throw new InvalidOperationException("expected object root");
+        GetAbilityRow(root, "prototype_pulse")["baseDamage"] = -1;
+        WriteCatalog(abilitiesDir, root.ToJsonString());
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("Ability catalog validation failed", ioe.Message, StringComparison.Ordinal);
+        Assert.Contains("baseDamage", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenCooldownSecondsIsZero()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        var root = JsonNode.Parse(ValidPrototypeCatalogJson) as JsonObject
+                   ?? throw new InvalidOperationException("expected object root");
+        GetAbilityRow(root, "prototype_pulse")["cooldownSeconds"] = 0;
+        WriteCatalog(abilitiesDir, root.ToJsonString());
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("Ability catalog validation failed", ioe.Message, StringComparison.Ordinal);
+        Assert.Contains("cooldownSeconds", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenDisplayNameIsEmpty()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        var root = JsonNode.Parse(ValidPrototypeCatalogJson) as JsonObject
+                   ?? throw new InvalidOperationException("expected object root");
+        GetAbilityRow(root, "prototype_pulse")["displayName"] = "";
+        WriteCatalog(abilitiesDir, root.ToJsonString());
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("Ability catalog validation failed", ioe.Message, StringComparison.Ordinal);
+        Assert.Contains("displayName", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenNoAbilityCatalogFiles()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("no *_abilities.json files", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenJsonIsInvalid()
+    {
+        // Arrange
+        var (_, abilitiesDir, schemaPath) = CreateTempContentLayout();
+        File.WriteAllText(
+            Path.Combine(abilitiesDir, "bad_abilities.json"),
+            "{not json",
+            Encoding.UTF8);
+        // Act
+        var ex = Record.Exception(() => LoadCatalog(abilitiesDir, schemaPath));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("bad_abilities.json", ioe.Message, StringComparison.Ordinal);
+        Assert.Contains("invalid JSON", ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenAbilitiesDirectoryMissing()
+    {
+        // Arrange
+        var missingDir = Path.Combine(Path.GetTempPath(), "neon-sprawl-no-abilities-" + Guid.NewGuid().ToString("n"));
+        var schemaPath = AbilityCatalogTestPaths.DiscoverRepoAbilityDefSchemaPath();
+        // Act
+        var ex = Record.Exception(() =>
+            AbilityDefinitionCatalogLoader.Load(missingDir, schemaPath, NullLogger.Instance));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("missing directory", ioe.Message, StringComparison.Ordinal);
+        Assert.Contains(missingDir, ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Load_ShouldThrow_WhenSchemaFileMissing()
+    {
+        // Arrange
+        var (_, abilitiesDir, _) = CreateTempContentLayout();
+        var missingSchema = Path.Combine(abilitiesDir, "missing-ability-def.schema.json");
+        // Act
+        var ex = Record.Exception(() =>
+            AbilityDefinitionCatalogLoader.Load(abilitiesDir, missingSchema, NullLogger.Instance));
+        // Assert
+        var ioe = Assert.IsType<InvalidOperationException>(ex);
+        Assert.Contains("missing schema file", ioe.Message, StringComparison.Ordinal);
+        Assert.Contains(missingSchema, ioe.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public async Task Host_ShouldResolveCatalogFromDi_WhenStartupSucceeds()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        using var client = factory.CreateClient();
+        // Act
+        var response = await client.GetAsync("/health");
+        // Assert
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var catalog = factory.Services.GetRequiredService<AbilityDefinitionCatalog>();
+        Assert.Equal(4, catalog.DistinctAbilityCount);
+        Assert.True(catalog.TryGetAbility("prototype_burst", out var burst));
+        Assert.Equal(40, burst!.BaseDamage);
+        Assert.Equal(5.0, burst.CooldownSeconds);
+    }
+
+    [Fact]
+    public void Host_ShouldFailStartup_WhenCatalogDirectoryInvalid()
+    {
+        // Arrange
+        var badDir = Path.Combine(Path.GetTempPath(), "neon-sprawl-empty-abilities-" + Guid.NewGuid().ToString("n"));
+        Directory.CreateDirectory(badDir);
+        try
+        {
+            // Act
+            var ex = Record.Exception(() =>
+            {
+                using var factory = new WebApplicationFactory<Program>().WithWebHostBuilder(b =>
+                    b.UseSetting("Content:AbilitiesDirectory", badDir));
+                factory.CreateClient();
+            });
+            // Assert
+            Assert.NotNull(ex);
+            Assert.Contains("Ability catalog validation failed", ex.ToString(), StringComparison.Ordinal);
+        }
+        finally
+        {
+            if (Directory.Exists(badDir))
+                Directory.Delete(badDir);
+        }
+    }
+}
diff --git a/server/NeonSprawl.Server.Tests/Game/Interaction/SalvageActivityDeniedRegistryWebApplicationFactory.cs b/server/NeonSprawl.Server.Tests/Game/Interaction/SalvageActivityDeniedRegistryWebApplicationFactory.cs
index f9efdbe..c1f96b7 100644
--- a/server/NeonSprawl.Server.Tests/Game/Interaction/SalvageActivityDeniedRegistryWebApplicationFactory.cs
+++ b/server/NeonSprawl.Server.Tests/Game/Interaction/SalvageActivityDeniedRegistryWebApplicationFactory.cs
@@ -6,6 +6,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Time.Testing;
 using NeonSprawl.Server.Game.AbilityInput;
+using NeonSprawl.Server.Game.Combat;
 using NeonSprawl.Server.Game.Crafting;
 using NeonSprawl.Server.Game.Gathering;
 using NeonSprawl.Server.Game.Items;
@@ -41,11 +42,15 @@ public sealed class SalvageActivityDeniedRegistryWebApplicationFactory : WebAppl
         var recipesDir = RecipeCatalogPathResolution.TryDiscoverRecipesDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/recipes from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+        var abilitiesDir = AbilityCatalogPathResolution.TryDiscoverAbilitiesDirectory(AppContext.BaseDirectory)
+            ?? throw new InvalidOperationException(
+                "Could not discover repo content/abilities from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
         builder.UseSetting("Content:SkillsDirectory", skillsDir);
         builder.UseSetting("Content:MasteryDirectory", masteryDir);
         builder.UseSetting("Content:ItemsDirectory", itemsDir);
         builder.UseSetting("Content:ResourceNodesDirectory", resourceNodesDir);
         builder.UseSetting("Content:RecipesDirectory", recipesDir);
+        builder.UseSetting("Content:AbilitiesDirectory", abilitiesDir);
         builder.UseSetting("Game:EnableMasteryFixtureApi", "true");
 
         builder.ConfigureTestServices(services =>
diff --git a/server/NeonSprawl.Server.Tests/Game/PositionState/PostgresWebApplicationFactory.cs b/server/NeonSprawl.Server.Tests/Game/PositionState/PostgresWebApplicationFactory.cs
index 0337336..dd6072b 100644
--- a/server/NeonSprawl.Server.Tests/Game/PositionState/PostgresWebApplicationFactory.cs
+++ b/server/NeonSprawl.Server.Tests/Game/PositionState/PostgresWebApplicationFactory.cs
@@ -1,6 +1,7 @@
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Testing;
 using Microsoft.Extensions.Configuration;
+using NeonSprawl.Server.Game.Combat;
 using NeonSprawl.Server.Game.Crafting;
 using NeonSprawl.Server.Game.Gathering;
 using NeonSprawl.Server.Game.Items;
@@ -39,11 +40,15 @@ public sealed class PostgresWebApplicationFactory : WebApplicationFactory<Progra
         var recipesDir = RecipeCatalogPathResolution.TryDiscoverRecipesDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/recipes from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+        var abilitiesDir = AbilityCatalogPathResolution.TryDiscoverAbilitiesDirectory(AppContext.BaseDirectory)
+            ?? throw new InvalidOperationException(
+                "Could not discover repo content/abilities from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
         builder.UseSetting("Content:SkillsDirectory", skillsDir);
         builder.UseSetting("Content:MasteryDirectory", masteryDir);
         builder.UseSetting("Content:ItemsDirectory", itemsDir);
         builder.UseSetting("Content:ResourceNodesDirectory", resourceNodesDir);
         builder.UseSetting("Content:RecipesDirectory", recipesDir);
+        builder.UseSetting("Content:AbilitiesDirectory", abilitiesDir);
 
         builder.ConfigureAppConfiguration((_, config) =>
         {
diff --git a/server/NeonSprawl.Server.Tests/Game/Skills/MissionRewardDeniedRegistryWebApplicationFactory.cs b/server/NeonSprawl.Server.Tests/Game/Skills/MissionRewardDeniedRegistryWebApplicationFactory.cs
index 1e29349..fb336d1 100644
--- a/server/NeonSprawl.Server.Tests/Game/Skills/MissionRewardDeniedRegistryWebApplicationFactory.cs
+++ b/server/NeonSprawl.Server.Tests/Game/Skills/MissionRewardDeniedRegistryWebApplicationFactory.cs
@@ -6,6 +6,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Time.Testing;
 using NeonSprawl.Server.Game.AbilityInput;
+using NeonSprawl.Server.Game.Combat;
 using NeonSprawl.Server.Game.Crafting;
 using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
@@ -33,9 +34,13 @@ public sealed class MissionRewardDeniedRegistryWebApplicationFactory : WebApplic
         var recipesDir = RecipeCatalogPathResolution.TryDiscoverRecipesDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/recipes from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+        var abilitiesDir = AbilityCatalogPathResolution.TryDiscoverAbilitiesDirectory(AppContext.BaseDirectory)
+            ?? throw new InvalidOperationException(
+                "Could not discover repo content/abilities from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
         builder.UseSetting("Content:SkillsDirectory", skillsDir);
         builder.UseSetting("Content:MasteryDirectory", masteryDir);
         builder.UseSetting("Content:RecipesDirectory", recipesDir);
+        builder.UseSetting("Content:AbilitiesDirectory", abilitiesDir);
 
         builder.ConfigureTestServices(services =>
         {
diff --git a/server/NeonSprawl.Server.Tests/Game/Skills/RefineActivityDeniedRegistryWebApplicationFactory.cs b/server/NeonSprawl.Server.Tests/Game/Skills/RefineActivityDeniedRegistryWebApplicationFactory.cs
index ea04cc8..b0b9a23 100644
--- a/server/NeonSprawl.Server.Tests/Game/Skills/RefineActivityDeniedRegistryWebApplicationFactory.cs
+++ b/server/NeonSprawl.Server.Tests/Game/Skills/RefineActivityDeniedRegistryWebApplicationFactory.cs
@@ -6,6 +6,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Time.Testing;
 using NeonSprawl.Server.Game.AbilityInput;
+using NeonSprawl.Server.Game.Combat;
 using NeonSprawl.Server.Game.Crafting;
 using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
@@ -33,9 +34,13 @@ public sealed class RefineActivityDeniedRegistryWebApplicationFactory : WebAppli
         var recipesDir = RecipeCatalogPathResolution.TryDiscoverRecipesDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/recipes from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+        var abilitiesDir = AbilityCatalogPathResolution.TryDiscoverAbilitiesDirectory(AppContext.BaseDirectory)
+            ?? throw new InvalidOperationException(
+                "Could not discover repo content/abilities from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
         builder.UseSetting("Content:SkillsDirectory", skillsDir);
         builder.UseSetting("Content:MasteryDirectory", masteryDir);
         builder.UseSetting("Content:RecipesDirectory", recipesDir);
+        builder.UseSetting("Content:AbilitiesDirectory", abilitiesDir);
 
         builder.ConfigureTestServices(services =>
         {
diff --git a/server/NeonSprawl.Server.Tests/InMemoryWebApplicationFactory.cs b/server/NeonSprawl.Server.Tests/InMemoryWebApplicationFactory.cs
index 0afbe68..dc283ad 100644
--- a/server/NeonSprawl.Server.Tests/InMemoryWebApplicationFactory.cs
+++ b/server/NeonSprawl.Server.Tests/InMemoryWebApplicationFactory.cs
@@ -5,6 +5,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Time.Testing;
 using NeonSprawl.Server.Game.AbilityInput;
+using NeonSprawl.Server.Game.Combat;
 using NeonSprawl.Server.Game.Crafting;
 using NeonSprawl.Server.Game.Gathering;
 using NeonSprawl.Server.Game.Items;
@@ -42,11 +43,15 @@ public sealed class InMemoryWebApplicationFactory : WebApplicationFactory<Progra
         var recipesDir = RecipeCatalogPathResolution.TryDiscoverRecipesDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/recipes from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+        var abilitiesDir = AbilityCatalogPathResolution.TryDiscoverAbilitiesDirectory(AppContext.BaseDirectory)
+            ?? throw new InvalidOperationException(
+                "Could not discover repo content/abilities from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
         builder.UseSetting("Content:SkillsDirectory", skillsDir);
         builder.UseSetting("Content:MasteryDirectory", masteryDir);
         builder.UseSetting("Content:ItemsDirectory", itemsDir);
         builder.UseSetting("Content:ResourceNodesDirectory", resourceNodesDir);
         builder.UseSetting("Content:RecipesDirectory", recipesDir);
+        builder.UseSetting("Content:AbilitiesDirectory", abilitiesDir);
         builder.UseSetting("Game:EnableMasteryFixtureApi", "true");
 
         builder.ConfigureTestServices(services =>
diff --git a/server/NeonSprawl.Server/Game/Combat/AbilityCatalogPathResolution.cs b/server/NeonSprawl.Server/Game/Combat/AbilityCatalogPathResolution.cs
new file mode 100644
index 0000000..cf75380
--- /dev/null
+++ b/server/NeonSprawl.Server/Game/Combat/AbilityCatalogPathResolution.cs
@@ -0,0 +1,60 @@
+namespace NeonSprawl.Server.Game.Combat;
+
+/// <summary>Resolves ability catalog paths for local dev, tests, and container layouts (NEO-77).</summary>
+public static class AbilityCatalogPathResolution
+{
+    /// <summary>Walks <paramref name="startDirectory"/> and parents for an existing <c>content/abilities</c> directory.</summary>
+    public static string? TryDiscoverAbilitiesDirectory(string startDirectory)
+    {
+        for (var dir = new DirectoryInfo(startDirectory); dir is not null; dir = dir.Parent)
+        {
+            var candidate = Path.Combine(dir.FullName, "content", "abilities");
+            if (Directory.Exists(candidate))
+                return Path.GetFullPath(candidate);
+        }
+
+        return null;
+    }
+
+    /// <summary>
+    /// Resolves the abilities catalog directory.
+    /// Empty <paramref name="configuredAbilitiesDirectory"/> triggers discovery from <see cref="AppContext.BaseDirectory"/>.
+    /// </summary>
+    public static string ResolveAbilitiesDirectory(string? configuredAbilitiesDirectory, string contentRootPath)
+    {
+        if (string.IsNullOrWhiteSpace(configuredAbilitiesDirectory))
+        {
+            var discovered = TryDiscoverAbilitiesDirectory(AppContext.BaseDirectory);
+            if (discovered is not null)
+                return discovered;
+
+            throw new InvalidOperationException(
+                "Content:AbilitiesDirectory is not set and auto-discovery failed (no ancestor of AppContext.BaseDirectory contains 'content/abilities'). " +
+                "Set Content:AbilitiesDirectory in configuration or environment (e.g. Content__AbilitiesDirectory).");
+        }
+
+        var trimmed = configuredAbilitiesDirectory.Trim();
+        if (Path.IsPathRooted(trimmed))
+            return Path.GetFullPath(trimmed);
+
+        return Path.GetFullPath(Path.Combine(contentRootPath, trimmed));
+    }
+
+    /// <summary>Resolves JSON Schema path for a single ability row (Draft 2020-12).</summary>
+    public static string ResolveAbilityDefSchemaPath(
+        string abilitiesDirectory,
+        string? configuredSchemaPath,
+        string contentRootPath)
+    {
+        if (!string.IsNullOrWhiteSpace(configuredSchemaPath))
+        {
+            var trimmed = configuredSchemaPath.Trim();
+            if (Path.IsPathRooted(trimmed))
+                return Path.GetFullPath(trimmed);
+
+            return Path.GetFullPath(Path.Combine(contentRootPath, trimmed));
+        }
+
+        return Path.GetFullPath(Path.Combine(abilitiesDirectory, "..", "schemas", "ability-def.schema.json"));
+    }
+}
diff --git a/server/NeonSprawl.Server/Game/Combat/AbilityCatalogServiceCollectionExtensions.cs b/server/NeonSprawl.Server/Game/Combat/AbilityCatalogServiceCollectionExtensions.cs
new file mode 100644
index 0000000..68e7c9f
--- /dev/null
+++ b/server/NeonSprawl.Server/Game/Combat/AbilityCatalogServiceCollectionExtensions.cs
@@ -0,0 +1,37 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Options;
+using NeonSprawl.Server.Game.Skills;
+
+namespace NeonSprawl.Server.Game.Combat;
+
+/// <summary>DI registration for the fail-fast ability catalog (NEO-77).</summary>
+public static class AbilityCatalogServiceCollectionExtensions
+{
+    /// <summary>Binds <see cref="ContentPathsOptions"/> and registers <see cref="AbilityDefinitionCatalog"/> as a singleton.</summary>
+    public static IServiceCollection AddAbilityDefinitionCatalog(this IServiceCollection services, IConfiguration configuration)
+    {
+        services.AddOptions<ContentPathsOptions>()
+            .Bind(configuration.GetSection(ContentPathsOptions.SectionName));
+
+        services.AddSingleton<AbilityDefinitionCatalog>(sp =>
+        {
+            var hostEnv = sp.GetRequiredService<IHostEnvironment>();
+            var opts = sp.GetRequiredService<IOptions<ContentPathsOptions>>().Value;
+            var logger = sp.GetRequiredService<ILoggerFactory>()
+                .CreateLogger("NeonSprawl.Server.Game.Combat.AbilityCatalog");
+
+            var abilitiesDir = AbilityCatalogPathResolution.ResolveAbilitiesDirectory(
+                opts.AbilitiesDirectory,
+                hostEnv.ContentRootPath);
+            var schemaPath = AbilityCatalogPathResolution.ResolveAbilityDefSchemaPath(
+                abilitiesDir,
+                opts.AbilityDefSchemaPath,
+                hostEnv.ContentRootPath);
+
+            return AbilityDefinitionCatalogLoader.Load(abilitiesDir, schemaPath, logger);
+        });
+
+        return services;
+    }
+}
diff --git a/server/NeonSprawl.Server/Game/Combat/AbilityDefRow.cs b/server/NeonSprawl.Server/Game/Combat/AbilityDefRow.cs
new file mode 100644
index 0000000..34ff4cb
--- /dev/null
+++ b/server/NeonSprawl.Server/Game/Combat/AbilityDefRow.cs
@@ -0,0 +1,9 @@
+namespace NeonSprawl.Server.Game.Combat;
+
+/// <summary>One validated <c>AbilityDef</c> row from <c>content/abilities/*_abilities.json</c> (NEO-77).</summary>
+public sealed record AbilityDefRow(
+    string Id,
+    string DisplayName,
+    int BaseDamage,
+    double CooldownSeconds,
+    string? AbilityKind);
diff --git a/server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalog.cs b/server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalog.cs
new file mode 100644
index 0000000..1c5b10f
--- /dev/null
+++ b/server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalog.cs
@@ -0,0 +1,24 @@
+using System.Collections.ObjectModel;
+
+namespace NeonSprawl.Server.Game.Combat;
+
+/// <summary>In-memory ability catalog loaded at startup (NEO-77). Game callers should use <c>IAbilityDefinitionRegistry</c> (NEO-79).</summary>
+public sealed class AbilityDefinitionCatalog(
+    string abilitiesDirectory,
+    IReadOnlyDictionary<string, AbilityDefRow> byId,
+    int catalogJsonFileCount)
+{
+    /// <summary>Absolute path to the directory that was enumerated for <c>*_abilities.json</c> catalogs.</summary>
+    public string AbilitiesDirectory { get; } = abilitiesDirectory;
+
+    public IReadOnlyDictionary<string, AbilityDefRow> ById { get; } = new ReadOnlyDictionary<string, AbilityDefRow>(new Dictionary<string, AbilityDefRow>(byId, StringComparer.Ordinal));
+
+    public int DistinctAbilityCount => ById.Count;
+
+    /// <summary>Number of <c>*_abilities.json</c> files under <see cref="AbilitiesDirectory"/>.</summary>
+    public int CatalogJsonFileCount { get; } = catalogJsonFileCount;
+
+    /// <summary>Resolves a catalog row by stable ability <paramref name="id"/>.</summary>
+    public bool TryGetAbility(string id, out AbilityDefRow? row) =>
+        ById.TryGetValue(id, out row);
+}
diff --git a/server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalogLoader.cs b/server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalogLoader.cs
new file mode 100644
index 0000000..5eb5e83
--- /dev/null
+++ b/server/NeonSprawl.Server/Game/Combat/AbilityDefinitionCatalogLoader.cs
@@ -0,0 +1,190 @@
+using System.Text;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using Json.Schema;
+using Microsoft.Extensions.Logging;
+
+namespace NeonSprawl.Server.Game.Combat;
+
+/// <summary>Loads and validates <c>content/abilities/*_abilities.json</c> using the same rules as <c>scripts/validate_content.py</c> (NEO-77).</summary>
+public static class AbilityDefinitionCatalogLoader
+{
+    /// <summary>Loads catalogs from disk or throws <see cref="InvalidOperationException"/> with actionable messages.</summary>
+    public static AbilityDefinitionCatalog Load(string abilitiesDirectory, string schemaPath, ILogger logger)
+    {
+        abilitiesDirectory = Path.GetFullPath(abilitiesDirectory);
+        schemaPath = Path.GetFullPath(schemaPath);
+
+        var errors = new List<string>();
+
+        if (!File.Exists(schemaPath))
+            errors.Add($"error: missing schema file {schemaPath}");
+
+        if (!Directory.Exists(abilitiesDirectory))
+            errors.Add($"error: missing directory {abilitiesDirectory}");
+
+        if (errors.Count > 0)
+            ThrowIfAny(errors);
+
+        var jsonFiles = Directory.GetFiles(abilitiesDirectory, "*_abilities.json", SearchOption.TopDirectoryOnly)
+            .OrderBy(p => p, StringComparer.Ordinal)
+            .ToArray();
+        if (jsonFiles.Length == 0)
+            errors.Add($"error: no *_abilities.json files under {abilitiesDirectory}");
+
+        if (errors.Count > 0)
+            ThrowIfAny(errors);
+
+        var schema = JsonSchema.FromText(File.ReadAllText(schemaPath));
+        var evalOptions = new EvaluationOptions { OutputFormat = OutputFormat.List };
+
+        var abilityIdToSourceFile = new Dictionary<string, string>(StringComparer.Ordinal);
+        var rows = new Dictionary<string, AbilityDefRow>(StringComparer.Ordinal);
+
+        foreach (var path in jsonFiles)
+        {
+            JsonNode? root;
+            try
+            {
+                root = JsonNode.Parse(File.ReadAllText(path));
+            }
+            catch (JsonException ex)
+            {
+                errors.Add($"error: {path}: invalid JSON: {ex.Message}");
+                continue;
+            }
+
+            if (root is not JsonObject rootObj)
+            {
+                errors.Add($"error: {path}: expected JSON object at root");
+                continue;
+            }
+
+            var schemaVersionNode = rootObj["schemaVersion"];
+            if (schemaVersionNode is not JsonValue schemaVersionValue ||
+                !schemaVersionValue.TryGetValue<int>(out var schemaVersion) ||
+                schemaVersion != 1)
+            {
+                var got = schemaVersionNode?.ToJsonString() ?? "null";
+                errors.Add($"error: {path}: expected schemaVersion 1, got {got}");
+                continue;
+            }
+
+            var abilitiesNode = rootObj["abilities"];
+            if (abilitiesNode is not JsonArray abilitiesArray)
+            {
+                errors.Add($"error: {path}: expected top-level 'abilities' array");
+                continue;
+            }
+
+            for (var i = 0; i < abilitiesArray.Count; i++)
+            {
+                var ability = abilitiesArray[i];
+                if (ability is not JsonObject rowObj)
+                {
+                    errors.Add($"error: {path}: abilities[{i}] must be an object");
+                    continue;
+                }
+
+                var eval = schema.Evaluate(rowObj, evalOptions);
+                var schemaMsgs = CollectSchemaMessages(eval, path, i).OrderBy(m => m, StringComparer.Ordinal).ToList();
+                if (!eval.IsValid)
+                {
+                    if (schemaMsgs.Count == 0)
+                        schemaMsgs.Add($"error: {path} abilities[{i}] (root): schema validation failed");
+
+                    errors.AddRange(schemaMsgs);
+                }
+
+                var rowSchemaErrors = schemaMsgs.Count;
+
+                var aid = (rowObj["id"] as JsonValue)?.GetValue<string>();
+                if (aid is not null && rowSchemaErrors == 0)
+                {
+                    if (abilityIdToSourceFile.TryGetValue(aid, out var prevPath))
+                    {
+                        errors.Add($"error: duplicate ability id '{aid}' in {prevPath} and {path}");
+                        continue;
+                    }
+
+                    abilityIdToSourceFile[aid] = path;
+                    rows[aid] = ParseRow(rowObj);
+                }
+            }
+        }
+
+        ThrowIfAny(errors);
+
+        var e5m1 = PrototypeE5M1AbilityCatalogRules.TryGetE5M1GateError(abilityIdToSourceFile);
+        if (e5m1 is not null)
+        {
+            errors.Add(e5m1);
+            ThrowIfAny(errors);
+        }
+
+        if (logger.IsEnabled(LogLevel.Information))
+        {
+            logger.LogInformation(
+                "Loaded ability catalog from {AbilitiesDirectory}: {AbilityCount} ability(s) across {CatalogFileCount} JSON catalog file(s).",
+                abilitiesDirectory,
+                rows.Count,
+                jsonFiles.Length);
+        }
+
+        return new AbilityDefinitionCatalog(abilitiesDirectory, rows, jsonFiles.Length);
+    }
+
+    private static AbilityDefRow ParseRow(JsonObject rowObj)
+    {
+        var id = (rowObj["id"] as JsonValue)!.GetValue<string>();
+        var displayName = (rowObj["displayName"] as JsonValue)!.GetValue<string>();
+        var baseDamage = (rowObj["baseDamage"] as JsonValue)!.GetValue<int>();
+        var cooldownSeconds = (rowObj["cooldownSeconds"] as JsonValue)!.GetValue<double>();
+        string? abilityKind = null;
+        if (rowObj["abilityKind"] is JsonValue abilityKindValue)
+            abilityKind = abilityKindValue.GetValue<string>();
+
+        return new AbilityDefRow(id, displayName, baseDamage, cooldownSeconds, abilityKind);
+    }
+
+    private static List<string> CollectSchemaMessages(EvaluationResults eval, string filePath, int index)
+    {
+        var sink = new List<string>();
+        AppendSchemaMessages(eval, filePath, index, sink);
+        return sink;
+    }
+
+    private static void AppendSchemaMessages(EvaluationResults r, string filePath, int index, List<string> sink)
+    {
+        if (r.HasDetails)
+        {
+            foreach (var d in r.Details!)
+                AppendSchemaMessages(d, filePath, index, sink);
+        }
+
+        if (!r.HasErrors)
+            return;
+
+        foreach (var kv in r.Errors!)
+        {
+            var loc = r.InstanceLocation?.ToString();
+            if (string.IsNullOrEmpty(loc) || loc == "#")
+                loc = "(root)";
+
+            sink.Add($"error: {filePath} abilities[{index}] {loc}: {kv.Key} — {kv.Value}");
+        }
+    }
+
+    private static void ThrowIfAny(List<string> errors)
+    {
+        if (errors.Count == 0)
+            return;
+
+        var sb = new StringBuilder();
+        sb.AppendLine("Ability catalog validation failed:");
+        foreach (var e in errors.OrderBy(x => x, StringComparer.Ordinal))
+            sb.AppendLine(e);
+
+        throw new InvalidOperationException(sb.ToString().TrimEnd());
+    }
+}
diff --git a/server/NeonSprawl.Server/Game/Combat/PrototypeE5M1AbilityCatalogRules.cs b/server/NeonSprawl.Server/Game/Combat/PrototypeE5M1AbilityCatalogRules.cs
new file mode 100644
index 0000000..30f8b89
--- /dev/null
+++ b/server/NeonSprawl.Server/Game/Combat/PrototypeE5M1AbilityCatalogRules.cs
@@ -0,0 +1,35 @@
+using System.Collections.Frozen;
+
+namespace NeonSprawl.Server.Game.Combat;
+
+/// <summary>
+/// Prototype E5M1 roster gate (NEO-76 / NEO-77), mirrored from <c>scripts/validate_content.py</c>
+/// <c>PROTOTYPE_E5M1_ABILITY_IDS</c> / <c>_prototype_e5m1_ability_gate</c>.
+/// </summary>
+public static class PrototypeE5M1AbilityCatalogRules
+{
+    /// <summary>Keep in sync with <c>scripts/validate_content.py</c> <c>PROTOTYPE_E5M1_ABILITY_IDS</c>.</summary>
+    public static readonly FrozenSet<string> ExpectedAbilityIds = FrozenSet.ToFrozenSet(
+        [
+            "prototype_pulse",
+            "prototype_guard",
+            "prototype_dash",
+            "prototype_burst",
+        ],
+        StringComparer.Ordinal);
+
+    /// <summary>Returns a human-readable error if the E5M1 ability contract fails, otherwise <see langword="null"/>.</summary>
+    public static string? TryGetE5M1GateError(IReadOnlyDictionary<string, string> abilityIdToSourceFile)
+    {
+        var ids = abilityIdToSourceFile.Keys.ToFrozenSet(StringComparer.Ordinal);
+        if (!ids.SetEquals(ExpectedAbilityIds))
+        {
+            return
+                "error: prototype E5M1 expects exactly ability ids " +
+                $"[{string.Join(", ", ExpectedAbilityIds.Order(StringComparer.Ordinal).Select(s => "'" + s + "'"))}], " +
+                $"got [{string.Join(", ", ids.Order(StringComparer.Ordinal).Select(s => "'" + s + "'"))}]";
+        }
+
+        return null;
+    }
+}
diff --git a/server/NeonSprawl.Server/Game/Skills/ContentPathsOptions.cs b/server/NeonSprawl.Server/Game/Skills/ContentPathsOptions.cs
index 4655375..93da821 100644
--- a/server/NeonSprawl.Server/Game/Skills/ContentPathsOptions.cs
+++ b/server/NeonSprawl.Server/Game/Skills/ContentPathsOptions.cs
@@ -76,4 +76,16 @@ public sealed class ContentPathsOptions
     /// When unset, resolved as <c>{parent of recipes directory}/schemas/recipe-io-row.schema.json</c>.
     /// </summary>
     public string? RecipeIoRowSchemaPath { get; set; }
+
+    /// <summary>
+    /// Optional. Absolute path, or path relative to <see cref="Microsoft.Extensions.Hosting.IHostEnvironment.ContentRootPath"/>.
+    /// When unset, the host walks ancestors of <see cref="AppContext.BaseDirectory"/> for a <c>content/abilities</c> directory.
+    /// </summary>
+    public string? AbilitiesDirectory { get; set; }
+
+    /// <summary>
+    /// Optional override for <c>ability-def.schema.json</c>.
+    /// When unset, resolved as <c>{parent of abilities directory}/schemas/ability-def.schema.json</c>.
+    /// </summary>
+    public string? AbilityDefSchemaPath { get; set; }
 }
diff --git a/server/NeonSprawl.Server/Program.cs b/server/NeonSprawl.Server/Program.cs
index 645dd15..87ae584 100644
--- a/server/NeonSprawl.Server/Program.cs
+++ b/server/NeonSprawl.Server/Program.cs
@@ -1,4 +1,5 @@
 using NeonSprawl.Server.Game.AbilityInput;
+using NeonSprawl.Server.Game.Combat;
 using NeonSprawl.Server.Game.Crafting;
 using NeonSprawl.Server.Game.Gathering;
 using NeonSprawl.Server.Game.Interaction;
@@ -19,6 +20,7 @@ builder.Services.AddSkillDefinitionCatalog(builder.Configuration);
 builder.Services.AddItemDefinitionCatalog(builder.Configuration);
 builder.Services.AddResourceNodeCatalog(builder.Configuration);
 builder.Services.AddRecipeDefinitionCatalog(builder.Configuration);
+builder.Services.AddAbilityDefinitionCatalog(builder.Configuration);
 builder.Services.AddMasteryCatalog(builder.Configuration);
 
 var app = builder.Build();
@@ -26,6 +28,7 @@ _ = app.Services.GetRequiredService<SkillDefinitionCatalog>();
 _ = app.Services.GetRequiredService<ItemDefinitionCatalog>();
 _ = app.Services.GetRequiredService<ResourceNodeCatalog>();
 _ = app.Services.GetRequiredService<RecipeDefinitionCatalog>();
+_ = app.Services.GetRequiredService<AbilityDefinitionCatalog>();
 _ = app.Services.GetRequiredService<MasteryCatalog>();
 _ = app.Services.GetRequiredService<ISkillLevelCurve>();
 
diff --git a/server/NeonSprawl.Server/appsettings.json b/server/NeonSprawl.Server/appsettings.json
index 3e9cd5a..b13ffb7 100644
--- a/server/NeonSprawl.Server/appsettings.json
+++ b/server/NeonSprawl.Server/appsettings.json
@@ -13,7 +13,9 @@
     "ItemDefSchemaPath": "",
     "RecipesDirectory": "",
     "RecipeDefSchemaPath": "",
-    "RecipeIoRowSchemaPath": ""
+    "RecipeIoRowSchemaPath": "",
+    "AbilitiesDirectory": "",
+    "AbilityDefSchemaPath": ""
   },
   "Game": {
     "DevPlayerId": "dev-local-1",
diff --git a/server/README.md b/server/README.md
index d8321d1..0277adf 100644
--- a/server/README.md
+++ b/server/README.md
@@ -80,6 +80,19 @@ On startup the host loads every **`*_recipes.json`** under the recipes directory
 
 On success, **Information** logs include the resolved recipes directory path, distinct recipe count, and catalog file count. Game code should use **`IRecipeDefinitionRegistry`** for lookups (NEO-67). The catalog singleton remains for fail-fast startup only; do not inject **`RecipeDefinitionCatalog`** in new game code.
 
+## Ability catalog (`content/abilities`, NEO-77)
+
+On startup the host loads every **`*_abilities.json`** under the abilities directory, validates each row against **`content/schemas/ability-def.schema.json`**, requires **`schemaVersion` 1** per file, rejects **duplicate `id`** values across files, and enforces the **prototype E5M1** four-id roster gate (same rules as **`scripts/validate_content.py`**). If anything is missing or invalid, the process **exits during startup** with an actionable error—there is no silent fallback.
+
+| Config | Meaning |
+|--------|---------|
+| **`Content:AbilitiesDirectory`** | Optional. Absolute path, or path relative to the server **content root**. When unset, walks **ancestors of `AppContext.BaseDirectory`** until it finds **`content/abilities`**. |
+| **`Content:AbilityDefSchemaPath`** | Optional override for **`ability-def.schema.json`**. When unset, **`{parent of abilities directory}/schemas/ability-def.schema.json`**. |
+
+**Docker / CI:** include **`content/abilities`** and **`content/schemas/ability-def.schema.json`** in the mounted **`content/`** tree; set **`Content__AbilitiesDirectory`** when layout differs.
+
+On success, **Information** logs include the resolved abilities directory path, distinct ability count, and catalog file count. Game code should use **`IAbilityDefinitionRegistry`** for lookups (NEO-79). The catalog singleton remains for fail-fast startup only; **`PrototypeAbilityRegistry`** hotbar/cast allowlist is unchanged until NEO-79.
+
 ## Recipe definitions (NEO-68)
 
 **`GET /game/world/recipe-definitions`** returns a versioned JSON body (`schemaVersion` **1**, **`recipes`**) backed by **`IRecipeDefinitionRegistry`** — the same prototype rows loaded at startup (no second source of truth). Each row includes **`id`**, **`displayName`**, **`recipeKind`**, **`requiredSkillId`**, and nested **`inputs`** / **`outputs`** (`itemId`, `quantity`). Plan: [NEO-68 implementation plan](../../docs/plans/NEO-68-implementation-plan.md); manual QA: [`docs/manual-qa/NEO-68.md`](../../docs/manual-qa/NEO-68.md); Bruno: `bruno/neon-sprawl-server/recipe-definitions/`.