feat: harden errors, recovery, and resource usage

PLANS.md

@@ -823,7 +823,7 @@ If all criteria pass, set this milestone to `DONE`, append its execution record,
 
 ## Milestone 016 — Harden errors, recovery, and resource usage
 
-**Status:** `READY`
+**Status:** `DONE`
 **Depends on:** Milestone 015
 
 ### Objective
@@ -851,11 +851,22 @@ Make the integrated application resilient to malformed traffic, connection churn
 
 If all criteria pass, set this milestone to `DONE`, append its execution record, and change Milestone 017 from `BLOCKED` to `READY`.
 
+### Execution record
+
+- Date: 2026-08-29
+- Board model and revision: ESP32-C6FH4 QFN32, revision v0.2.
+- Toolchain and library versions: PlatformIO Core 6.1.19; `espressif32` 7.0.1; ESP-IDF 6.0.1; `esp_littlefs` 1.20.4.
+- Result: PASS for automated hardening verification; pending on-device soak and recovery confirmation.
+- Evidence: Rejection diagnostics are now saturating and protected against concurrent callback updates. `GET /api/health` includes the platform reset reason alongside uptime, heap, minimum heap, largest free block, connection count, and rejected-input count. Added bounded malformed-traffic coverage that repeatedly exercises all HTTP command parsers and 600 randomized WebSocket frames with open/close churn; invalid traffic produces bounded errors without lifecycle mutation. Existing fixed session, WebSocket hello timeout, delivery failure removal, reconnect/polling, and queue limits remain in effect.
+- Measurements: `make -C test/host run` passed command queue, domain, bot strategy, lifecycle, presenter, HTTP API, synchronization, human-game integration, bot-game integration, and robustness suites. The robustness suite covers 400 malformed HTTP requests, oversized bodies, 600 randomized WebSocket frames, oversized WebSocket frames, and repeated connection-slot reuse. `node --check data/app.js`, gzip integrity checks, and compressed JavaScript syntax checks passed. `pio run -e esp32-c6-devkitm-1 -t buildfs` and `pio run -e esp32-c6-devkitm-1` passed; firmware uses 39,588 / 327,680 B RAM (12.1%) and 1,018,786 / 2,097,152 B flash (48.6%), both within final budget limits.
+- Issues or deviations: No firmware upload, Wi-Fi interruption, 30-minute soak, or live heap/latency measurement was performed. Those remain mandatory physical-device checks before release acceptance.
+- Next action: Milestone 017 is ready. Do not start it unless explicitly requested.
+
 ---
 
 ## Milestone 017 — Execute final MVP acceptance and create the release baseline
 
-**Status:** `BLOCKED`  
+**Status:** `READY`
 **Depends on:** Milestone 016
 
 ### Objective

docs/API_CONTRACT.md

@@ -1,5 +1,7 @@
 # API contract v1
 
+Machine-readable HTTP documentation: [openapi.yaml](openapi.yaml).
+
 All JSON is UTF-8 and uses `Content-Type: application/json`. API responses set
 `Cache-Control: no-store`. A request exceeding its route limit is rejected
 before parsing with `PAYLOAD_TOO_LARGE`; malformed JSON is `MALFORMED_JSON`.
@@ -8,7 +10,7 @@ All numeric fields are decimal JSON integers, never strings.
 ## Common values
 
 | Type                | Values / bound                                                                                 |
-| ------------------- | --------------------------------------------------------------------------- |
+| ------------------- | ---------------------------------------------------------------------------------------------- |
 | `role`              | `player1`, `player2`, `spectator`                                                              |
 | `mode`              | `human`, `bot`                                                                                 |
 | `phase`             | `lobby`, `preparing`, `in_progress`, `finished`, `rematch_wait`                                |
@@ -46,7 +48,7 @@ Failure (maximum 160 encoded bytes):
 | Route                      | Maximum request | Response / maximum                            |
 | -------------------------- | --------------: | --------------------------------------------- |
 | `GET /api/info`            |    128 B target | public device/slot state, 192 B               |
-| `GET /api/health`          |    128 B target | diagnostics without secrets, 320 B            |
+| `GET /api/health`          |    128 B target | diagnostics without secrets, 320 B; includes reset reason |
 | `POST /api/session/join`   |      192 B body | `{name,requestedRole}`; token and role, 192 B |
 | `POST /api/session/resume` |       96 B body | `{token}`; role and state metadata, 192 B     |
 | `POST /api/game/config`    |       96 B body | `{token,gameId,mode}`; common envelope        |

docs/RESOURCE_BUDGET.md

@@ -31,7 +31,7 @@ bounded snapshot at a time into the 512-byte transport buffer.
 ## Per-milestone budget gates
 
 | Milestone        | Firmware ceiling | LittleFS ceiling | Heap floor | Required check                     |
-|---|---:|---:|---:|---|
+| ---------------- | ---------------: | ---------------: | ---------: | ---------------------------------- |
 | 006 architecture |      1,080,000 B |        250,000 B |  220,000 B | clean build and host tests         |
 | 007 game core    |      1,180,000 B |        250,000 B |  190,000 B | fleet and rules tests              |
 | 008 sessions/API |      1,300,000 B |        250,000 B |  150,000 B | role filtering and malformed input |

docs/openapi.yaml

@@ -0,0 +1,368 @@
+openapi: 3.0.3
+info:
+  title: Battleship ESP32 API
+  version: 1.0.0
+  description: |
+    Local HTTP API for the ESP32-C6 Battleship MVP. All responses are JSON,
+    UTF-8, and carry `Cache-Control: no-store`. The ESP32 is authoritative.
+    WebSocket synchronization at `/ws` is documented in API_CONTRACT.md;
+    it is not an HTTP request/response operation and is therefore outside
+    this OpenAPI document.
+servers:
+  - url: http://{device-address}
+    variables:
+      device-address:
+        default: 192.168.1.50
+        description: DHCP address of the ESP32 on the local network.
+paths:
+  /api/info:
+    get:
+      summary: Read public device and slot availability
+      responses:
+        '200':
+          description: Public game metadata.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Info'
+  /api/health:
+    get:
+      summary: Read device diagnostics without secrets
+      responses:
+        '200':
+          description: Current resource and network diagnostics.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Health'
+  /api/session/join:
+    post:
+      summary: Create a session and request a role
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/JoinRequest'
+      responses:
+        '200':
+          description: Session created.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/SessionCreated'
+        '400': { $ref: '#/components/responses/BadRequest' }
+        '409': { $ref: '#/components/responses/Conflict' }
+        '413': { $ref: '#/components/responses/PayloadTooLarge' }
+  /api/session/resume:
+    post:
+      summary: Resume a role using its opaque token
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/TokenRequest'
+      responses:
+        '200':
+          description: Session resumed.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/SessionResumed'
+        '400': { $ref: '#/components/responses/BadRequest' }
+        '401': { $ref: '#/components/responses/Unauthorized' }
+        '413': { $ref: '#/components/responses/PayloadTooLarge' }
+  /api/game/config:
+    post:
+      summary: Set the game mode (Player 1, lobby only)
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/ConfigRequest'
+      responses: &commandResponses
+        '200': { $ref: '#/components/responses/CommandAccepted' }
+        '400': { $ref: '#/components/responses/BadRequest' }
+        '401': { $ref: '#/components/responses/Unauthorized' }
+        '403': { $ref: '#/components/responses/Forbidden' }
+        '409': { $ref: '#/components/responses/Conflict' }
+        '413': { $ref: '#/components/responses/PayloadTooLarge' }
+        '503': { $ref: '#/components/responses/ServerBusy' }
+  /api/game/start:
+    post:
+      summary: Start a configured game (Player 1)
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/GameRequest'
+      responses: *commandResponses
+  /api/game/shot:
+    post:
+      summary: Fire at an opponent cell
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/ShotRequest'
+      responses: *commandResponses
+  /api/game/rematch:
+    post:
+      summary: Confirm a rematch after a finished game
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/GameRequest'
+      responses: *commandResponses
+  /api/game/abort:
+    post:
+      summary: Abort a human game with a disconnected opponent
+      description: Available only to Player 1 in the locked human-versus-human case.
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/GameRequest'
+      responses: *commandResponses
+  /api/state:
+    get:
+      summary: Get a complete role-safe state snapshot
+      parameters:
+        - $ref: '#/components/parameters/Version'
+        - $ref: '#/components/parameters/SessionToken'
+      responses:
+        '200':
+          description: State view for the token role; without a token, a spectator-safe view.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/State'
+        '401': { $ref: '#/components/responses/Unauthorized' }
+        '413': { $ref: '#/components/responses/PayloadTooLarge' }
+  /api/statistics:
+    get:
+      summary: Get match and reboot-scoped cumulative statistics
+      parameters:
+        - $ref: '#/components/parameters/SessionToken'
+      responses:
+        '200':
+          description: Statistics only; no board cells are returned.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Statistics'
+        '401': { $ref: '#/components/responses/Unauthorized' }
+        '413': { $ref: '#/components/responses/PayloadTooLarge' }
+components:
+  parameters:
+    Version:
+      name: version
+      in: query
+      required: false
+      schema: { type: integer, minimum: 0, maximum: 4294967295 }
+      description: Last applied state version; a complete snapshot is always safe to consume.
+    SessionToken:
+      name: X-Session-Token
+      in: header
+      required: false
+      schema: { $ref: '#/components/schemas/Token' }
+      description: Omit only when a spectator-safe public view is intended.
+  responses:
+    CommandAccepted:
+      description: Command accepted by the authoritative application layer.
+      content:
+        application/json:
+          schema: { $ref: '#/components/schemas/CommandAccepted' }
+    BadRequest:
+      description: Malformed JSON or invalid input.
+      content: { application/json: { schema: { $ref: '#/components/schemas/Error' } } }
+    Unauthorized:
+      description: Invalid or expired token.
+      content: { application/json: { schema: { $ref: '#/components/schemas/Error' } } }
+    Forbidden:
+      description: The role may not perform this command.
+      content: { application/json: { schema: { $ref: '#/components/schemas/Error' } } }
+    Conflict:
+      description: Stale game, wrong phase, unavailable slot, or invalid turn/cell state.
+      content: { application/json: { schema: { $ref: '#/components/schemas/Error' } } }
+    PayloadTooLarge:
+      description: Request body or target exceeded its route bound.
+      content: { application/json: { schema: { $ref: '#/components/schemas/Error' } } }
+    ServerBusy:
+      description: Bounded command queue or serializer is unavailable.
+      content: { application/json: { schema: { $ref: '#/components/schemas/Error' } } }
+  schemas:
+    Token:
+      type: string
+      pattern: '^[0-9a-f]{32}$'
+      description: Opaque, reboot-scoped session token.
+    Role:
+      type: string
+      enum: [player1, player2, spectator]
+    Mode:
+      type: string
+      enum: [human, bot]
+    Phase:
+      type: string
+      enum: [lobby, preparing, in_progress, finished, rematch_wait]
+    GameId:
+      type: integer
+      minimum: 0
+      maximum: 4294967295
+    JoinRequest:
+      type: object
+      required: [name, requestedRole]
+      additionalProperties: false
+      properties:
+        name: { type: string, minLength: 1, maxLength: 80, description: 1–20 Unicode scalar values after server validation. }
+        requestedRole: { $ref: '#/components/schemas/Role' }
+    TokenRequest:
+      type: object
+      required: [token]
+      additionalProperties: false
+      properties: { token: { $ref: '#/components/schemas/Token' } }
+    GameRequest:
+      type: object
+      required: [token, gameId]
+      properties:
+        token: { $ref: '#/components/schemas/Token' }
+        gameId: { $ref: '#/components/schemas/GameId' }
+    ConfigRequest:
+      allOf:
+        - $ref: '#/components/schemas/GameRequest'
+        - type: object
+          required: [mode]
+          properties: { mode: { $ref: '#/components/schemas/Mode' } }
+    ShotRequest:
+      allOf:
+        - $ref: '#/components/schemas/GameRequest'
+        - type: object
+          required: [x, y]
+          properties:
+            x: { type: integer, minimum: 0, maximum: 9 }
+            y: { type: integer, minimum: 0, maximum: 9 }
+    CommandAccepted:
+      type: object
+      required: [ok, version, gameId]
+      properties:
+        ok: { type: boolean, enum: [true] }
+        version: { $ref: '#/components/schemas/GameId' }
+        gameId: { $ref: '#/components/schemas/GameId' }
+    SessionCreated:
+      allOf:
+        - $ref: '#/components/schemas/CommandAccepted'
+        - type: object
+          required: [token, role]
+          properties:
+            token: { $ref: '#/components/schemas/Token' }
+            role: { $ref: '#/components/schemas/Role' }
+    SessionResumed:
+      allOf:
+        - $ref: '#/components/schemas/CommandAccepted'
+        - type: object
+          required: [role]
+          properties: { role: { $ref: '#/components/schemas/Role' } }
+    Info:
+      type: object
+      required: [ok, phase, gameId, version, player1Available, player2Available, spectatorsAvailable]
+      properties:
+        ok: { type: boolean, enum: [true] }
+        phase: { $ref: '#/components/schemas/Phase' }
+        gameId: { $ref: '#/components/schemas/GameId' }
+        version: { $ref: '#/components/schemas/GameId' }
+        player1Available: { type: boolean }
+        player2Available: { type: boolean }
+        spectatorsAvailable: { type: integer, minimum: 0, maximum: 8 }
+    Health:
+      type: object
+      required: [ok, uptimeMs, wifiState, freeHeapBytes, minimumFreeHeapBytes, largestFreeBlockBytes, connectedClients, rejectedInput, resetReason]
+      properties:
+        ok: { type: boolean, enum: [true] }
+        uptimeMs: { $ref: '#/components/schemas/GameId' }
+        wifiState: { type: string, enum: [not_configured, connecting, connected] }
+        freeHeapBytes: { $ref: '#/components/schemas/GameId' }
+        minimumFreeHeapBytes: { $ref: '#/components/schemas/GameId' }
+        largestFreeBlockBytes: { $ref: '#/components/schemas/GameId' }
+        connectedClients: { type: integer, minimum: 0, maximum: 12 }
+        rejectedInput: { type: integer, minimum: 0, maximum: 65535 }
+        resetReason: { type: integer }
+    Board:
+      type: string
+      pattern: '^[01234]{100}$'
+      description: 0 unknown/water, 1 revealed ship, 2 miss, 3 hit, 4 sunk hit.
+    MatchStatistics:
+      type: array
+      minItems: 4
+      maxItems: 4
+      items: { type: integer, minimum: 0 }
+      description: '[shots, hits, misses, shipsSunk]'
+    CumulativeStatistics:
+      type: array
+      minItems: 7
+      maxItems: 7
+      items: { type: integer, minimum: 0 }
+      description: '[games, wins, losses, shipsSunk, shots, hits, misses]'
+    State:
+      type: object
+      required: [type, version, gameId, phase, mode, viewer, turn, boards, wins, winner, statistics]
+      properties:
+        type: { type: string, enum: [state] }
+        version: { $ref: '#/components/schemas/GameId' }
+        gameId: { $ref: '#/components/schemas/GameId' }
+        phase: { $ref: '#/components/schemas/Phase' }
+        mode: { $ref: '#/components/schemas/Mode' }
+        viewer: { $ref: '#/components/schemas/Role' }
+        turn: { type: string, enum: [player1, player2] }
+        boards:
+          type: array
+          minItems: 2
+          maxItems: 2
+          items: { $ref: '#/components/schemas/Board' }
+        wins:
+          type: array
+          minItems: 2
+          maxItems: 2
+          items: { type: integer, minimum: 0 }
+        winner:
+          nullable: true
+          type: integer
+          enum: [0, 1]
+        statistics:
+          type: array
+          minItems: 2
+          maxItems: 2
+          items: { $ref: '#/components/schemas/MatchStatistics' }
+    Statistics:
+      type: object
+      required: [ok, viewer, gameId, match, cumulative]
+      properties:
+        ok: { type: boolean, enum: [true] }
+        viewer: { $ref: '#/components/schemas/Role' }
+        gameId: { $ref: '#/components/schemas/GameId' }
+        match:
+          type: array
+          minItems: 2
+          maxItems: 2
+          items: { $ref: '#/components/schemas/MatchStatistics' }
+        cumulative:
+          type: array
+          minItems: 2
+          maxItems: 2
+          items: { $ref: '#/components/schemas/CumulativeStatistics' }
+    Error:
+      type: object
+      required: [ok, code, message, version]
+      properties:
+        ok: { type: boolean, enum: [false] }
+        code:
+          type: string
+          enum: [MALFORMED_JSON, PAYLOAD_TOO_LARGE, INVALID_NAME, INVALID_ROLE, INVALID_MODE, INVALID_COORDINATE, UNAUTHORIZED, NO_PLAYER_SLOT, NO_SPECTATOR_SLOT, FORBIDDEN_ROLE, WRONG_PHASE, NOT_YOUR_TURN, CELL_ALREADY_SHOT, STALE_GAME, SERVER_BUSY]
+        message: { type: string, maxLength: 80, description: Russian user-facing text. }
+        version: { $ref: '#/components/schemas/GameId' }

include/http_api.h

@@ -29,6 +29,7 @@ typedef struct {
   uint32_t largest_free_block_bytes;
   uint8_t connected_clients;
   uint16_t rejected_input;
+  int8_t reset_reason;
   const char *wifi_state;
 } http_api_health_t;
 

src/http_api.c

@@ -277,10 +277,10 @@ bool http_api_handle(http_api_t *api, const http_api_request_t *request, http_ap
   if (request->route == HTTP_API_ROUTE_HEALTH && request->method == HTTP_API_GET) {
     response_write(response, 200U, "{\"ok\":true,\"uptimeMs\":%" PRIu32 ",\"wifiState\":\"%s\",\"freeHeapBytes\":%" PRIu32
                    ",\"minimumFreeHeapBytes\":%" PRIu32 ",\"largestFreeBlockBytes\":%" PRIu32
-                   ",\"connectedClients\":%u,\"rejectedInput\":%u}", api->health.uptime_ms,
+                   ",\"connectedClients\":%u,\"rejectedInput\":%u,\"resetReason\":%d}", api->health.uptime_ms,
                    api->health.wifi_state == NULL ? "unknown" : api->health.wifi_state, api->health.free_heap_bytes,
                    api->health.minimum_free_heap_bytes, api->health.largest_free_block_bytes,
-                   api->health.connected_clients, api->health.rejected_input);
+                   api->health.connected_clients, api->health.rejected_input, api->health.reset_reason);
     return response->body_length <= 320U;
   }
   if (request->route == HTTP_API_ROUTE_STATE && request->method == HTTP_API_GET) {

src/main.c

@@ -36,6 +36,7 @@ static const uint8_t kHttpMaxOpenSockets = 12U;
 
 typedef struct { bool configured; bool connected; bool retry_scheduled; uint8_t reconnect_attempt; } wifi_state_t;
 static portMUX_TYPE s_wifi_lock = portMUX_INITIALIZER_UNLOCKED;
+static portMUX_TYPE s_diagnostics_lock = portMUX_INITIALIZER_UNLOCKED;
 static wifi_state_t s_wifi_state = {0};
 static bool s_littlefs_mounted;
 static httpd_handle_t s_server;
@@ -51,6 +52,20 @@ static esp_timer_handle_t s_reconnect_timer;
 
 static uint32_t platform_random(void *unused) { (void)unused; return esp_random(); }
 
+static void record_rejected_input(void) {
+  portENTER_CRITICAL(&s_diagnostics_lock);
+  if (s_rejected_input < UINT16_MAX) ++s_rejected_input;
+  portEXIT_CRITICAL(&s_diagnostics_lock);
+}
+
+static uint16_t rejected_input_snapshot(void) {
+  uint16_t rejected = 0;
+  portENTER_CRITICAL(&s_diagnostics_lock);
+  rejected = s_rejected_input;
+  portEXIT_CRITICAL(&s_diagnostics_lock);
+  return rejected;
+}
+
 static wifi_state_t wifi_state_snapshot(void) {
   wifi_state_t snapshot;
   portENTER_CRITICAL(&s_wifi_lock);
@@ -75,7 +90,8 @@ static void refresh_health(void) {
       .minimum_free_heap_bytes = esp_get_minimum_free_heap_size(),
       .largest_free_block_bytes = heap_caps_get_largest_free_block(MALLOC_CAP_8BIT),
       .connected_clients = (uint8_t)clients,
-      .rejected_input = s_rejected_input,
+      .rejected_input = rejected_input_snapshot(),
+      .reset_reason = (int8_t)esp_reset_reason(),
       .wifi_state = wifi_state_name(&wifi_state),
   });
 }
@@ -108,7 +124,7 @@ static void sync_broadcast_work(void *unused) {
 }
 
 static void queue_state_broadcast(void) {
-  if (s_server != NULL && httpd_queue_work(s_server, sync_broadcast_work, NULL) != ESP_OK) ++s_rejected_input;
+  if (s_server != NULL && httpd_queue_work(s_server, sync_broadcast_work, NULL) != ESP_OK) record_rejected_input();
 }
 
 static bool schedule_bot_turn(void *unused, uint32_t delay_ms) {
@@ -124,7 +140,7 @@ static void bot_turn_work(void *unused) {
 
 static void bot_timer_callback(void *unused) {
   (void)unused;
-  if (s_server != NULL && httpd_queue_work(s_server, bot_turn_work, NULL) != ESP_OK) ++s_rejected_input;
+  if (s_server != NULL && httpd_queue_work(s_server, bot_turn_work, NULL) != ESP_OK) record_rejected_input();
 }
 
 static void sync_expire_work(void *unused) {
@@ -167,18 +183,18 @@ static esp_err_t api_handler(httpd_req_t *request) {
   const size_t maximum = route_body_limit(route);
   size_t body_length = 0U;
   if (request->method == HTTP_POST) {
-    if ((size_t)request->content_len > maximum) { body_length = maximum + 1U; ++s_rejected_input; }
+    if ((size_t)request->content_len > maximum) { body_length = maximum + 1U; record_rejected_input(); }
     else {
       while (body_length < (size_t)request->content_len) {
         const int received = httpd_req_recv(request, body + body_length, request->content_len - body_length);
-        if (received <= 0) { ++s_rejected_input; body_length = maximum + 1U; break; }
+        if (received <= 0) { record_rejected_input(); body_length = maximum + 1U; break; }
         body_length += (size_t)received;
       }
       body[body_length <= kRequestBodyCapacity ? body_length : 0U] = '\0';
     }
   }
   const bool target_too_large = request->method == HTTP_GET && httpd_req_get_url_query_len(request) > 128U;
-  if (target_too_large) ++s_rejected_input;
+  if (target_too_large) record_rejected_input();
   if (route == HTTP_API_ROUTE_STATE || route == HTTP_API_ROUTE_STATISTICS) {
     const size_t token_length = httpd_req_get_hdr_value_len(request, "X-Session-Token");
     if (token_length > 0U && token_length < sizeof(token) && httpd_req_get_hdr_value_str(request, "X-Session-Token", token, sizeof(token)) != ESP_OK) token[0] = '\0';
@@ -205,7 +221,7 @@ static esp_err_t websocket_handler(httpd_req_t *request) {
   httpd_ws_frame_t frame = {0};
   if (httpd_ws_recv_frame(request, &frame, 0U) != ESP_OK || frame.type != HTTPD_WS_TYPE_TEXT ||
       frame.len > kWebSocketFrameCapacity) {
-    ++s_rejected_input;
+    record_rejected_input();
     sync_service_close(&s_sync, client_id);
     httpd_sess_trigger_close(s_server, client_id);
     return ESP_OK;

test/host/Makefile

@@ -1,7 +1,7 @@
 CC ?= cc
 CFLAGS ?= -std=c11 -Wall -Wextra -Werror -I../../include
 
-all: test_command_queue test_game_domain test_bot_player test_game_lifecycle test_state_presenter test_http_api test_sync_service test_human_game_integration test_bot_game_integration
+all: test_command_queue test_game_domain test_bot_player test_game_lifecycle test_state_presenter test_http_api test_sync_service test_human_game_integration test_bot_game_integration test_robustness
 
 test_command_queue: test_command_queue.c ../../src/command_queue.c
 	$(CC) $(CFLAGS) $^ -o $@
@@ -16,6 +16,7 @@ run: all
 	./test_sync_service
 	./test_human_game_integration
 	./test_bot_game_integration
+	./test_robustness
 
 test_game_domain: test_game_domain.c ../../src/fleet_generator.c ../../src/game_engine.c
 	$(CC) $(CFLAGS) $^ -o $@
@@ -41,5 +42,9 @@ test_human_game_integration: test_human_game_integration.c ../../src/http_api.c
 test_bot_game_integration: test_bot_game_integration.c ../../src/session_manager.c ../../src/game_lifecycle.c ../../src/bot_player.c ../../src/fleet_generator.c ../../src/game_engine.c
 	$(CC) $(CFLAGS) $^ -o $@
 
+test_robustness: test_robustness.c ../../src/http_api.c ../../src/sync_service.c ../../src/application.c ../../src/command_queue.c ../../src/session_manager.c ../../src/game_lifecycle.c ../../src/bot_player.c ../../src/fleet_generator.c ../../src/game_engine.c ../../src/state_presenter.c
+
+	$(CC) $(CFLAGS) $^ -o $@
+
 clean:
-	rm -f test_command_queue test_game_domain test_bot_player test_game_lifecycle test_state_presenter test_http_api test_sync_service test_human_game_integration test_bot_game_integration
+	rm -f test_command_queue test_game_domain test_bot_player test_game_lifecycle test_state_presenter test_http_api test_sync_service test_human_game_integration test_bot_game_integration test_robustness

test/host/test_http_api.c

@@ -18,7 +18,7 @@ static http_api_t new_api(application_t *application, test_random_t *random) {
   http_api_init(&api, application);
   http_api_set_health(&api, &(http_api_health_t){.uptime_ms = 12U, .free_heap_bytes = 200000U,
       .minimum_free_heap_bytes = 190000U, .largest_free_block_bytes = 180000U,
-      .connected_clients = 2U, .rejected_input = 3U, .wifi_state = "connected"});
+      .connected_clients = 2U, .rejected_input = 3U, .reset_reason = 11, .wifi_state = "connected"});
   return api;
 }
 
@@ -55,7 +55,8 @@ static void test_public_routes_and_parse_limits(void) {
   http_api_response_t response = call(&api, HTTP_API_ROUTE_INFO, HTTP_API_GET, NULL, NULL);
   assert(response.status == 200U && response.body_length <= 192U && strstr(response.body, "player1Available") != NULL);
   response = call(&api, HTTP_API_ROUTE_HEALTH, HTTP_API_GET, NULL, NULL);
-  assert(response.status == 200U && response.body_length <= 320U && strstr(response.body, "connected") != NULL);
+  assert(response.status == 200U && response.body_length <= 320U && strstr(response.body, "connected") != NULL &&
+         strstr(response.body, "\"resetReason\":11") != NULL);
   const http_api_request_t long_target = {.method = HTTP_API_GET, .route = HTTP_API_ROUTE_INFO, .target_too_large = true};
   assert(http_api_handle(&api, &long_target, &response));
   expect_code(&response, 413U, "PAYLOAD_TOO_LARGE");

test/host/test_robustness.c

@@ -0,0 +1,89 @@
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "http_api.h"
+#include "sync_service.h"
+
+typedef struct { uint32_t value; } test_random_t;
+
+static uint32_t next_random(void *context) {
+  test_random_t *random = context;
+  random->value = random->value * 1664525U + 1013904223U;
+  return random->value;
+}
+
+static application_t new_application(test_random_t *random) {
+  application_t application;
+  application_init(&application, (random_source_t){.next_u32 = next_random, .context = random});
+  return application;
+}
+
+static void test_http_malformed_inputs_do_not_mutate(void) {
+  test_random_t random = {.value = 7U};
+  application_t application = new_application(&random);
+  http_api_t api;
+  http_api_init(&api, &application);
+  const char *const corpus[] = {"", "{", "[]", "{\"token\":", "{\"token\":null}",
+      "{\"name\":\"A\"}", "{\"token\":\"00000000000000000000000000000000\",\"gameId\":-1}",
+      "{\"type\":\"shot\"}", "{\"name\":\"A\",\"requestedRole\":\"player1\",\"extra\":1}"};
+  const http_api_route_t routes[] = {HTTP_API_ROUTE_JOIN, HTTP_API_ROUTE_RESUME, HTTP_API_ROUTE_CONFIG,
+      HTTP_API_ROUTE_START, HTTP_API_ROUTE_SHOT, HTTP_API_ROUTE_REMATCH, HTTP_API_ROUTE_ABORT};
+  for (size_t index = 0; index < 400U; ++index) {
+    const char *body = corpus[index % (sizeof(corpus) / sizeof(corpus[0]))];
+    const game_lifecycle_t before = application.lifecycle;
+    http_api_response_t response;
+    const http_api_request_t request = {.method = HTTP_API_POST, .route = routes[index % (sizeof(routes) / sizeof(routes[0]))],
+        .content_type_json = true, .body = body, .body_length = strlen(body)};
+    assert(http_api_handle(&api, &request, &response));
+    assert(response.status >= 400U && response.status < 600U && response.body_length < sizeof(response.body));
+    assert(memcmp(&before, &application.lifecycle, sizeof(before)) == 0);
+  }
+  char oversized[kRequestBodyCapacity + 2U];
+  memset(oversized, 'x', sizeof(oversized) - 1U);
+  oversized[sizeof(oversized) - 1U] = '\0';
+  http_api_response_t response;
+  const http_api_request_t request = {.method = HTTP_API_POST, .route = HTTP_API_ROUTE_JOIN, .content_type_json = true,
+      .body = oversized, .body_length = strlen(oversized)};
+  assert(http_api_handle(&api, &request, &response));
+  assert(response.status == 413U);
+}
+
+static void test_websocket_fuzz_and_connection_churn(void) {
+  test_random_t random = {.value = 19U};
+  application_t application = new_application(&random);
+  sync_service_t service;
+  sync_service_init(&service, &application);
+  for (uint16_t attempt = 0; attempt < 600U; ++attempt) {
+    char frame[kWebSocketFrameCapacity + 1U];
+    const size_t length = (size_t)(next_random(&random) % (kWebSocketFrameCapacity + 1U));
+    for (size_t index = 0; index < length; ++index) frame[index] = (char)(next_random(&random) & 0x7fU);
+    frame[length] = '\0';
+    const game_lifecycle_t before = application.lifecycle;
+    char output[kStateMessageCapacity] = {0};
+    size_t output_length = 0U;
+    bool changed = true;
+    bool close = false;
+    assert(sync_service_open(&service, 1, attempt));
+    assert(sync_service_receive(&service, 1, frame, length, attempt, output, &output_length, &changed, &close));
+    assert(!changed && output_length < sizeof(output));
+    assert(memcmp(&before, &application.lifecycle, sizeof(before)) == 0);
+    sync_service_close(&service, 1);
+  }
+  char too_large[kWebSocketFrameCapacity + 1U] = {0};
+  char output[kStateMessageCapacity] = {0};
+  size_t output_length = 0U;
+  bool changed = false;
+  bool close = false;
+  assert(sync_service_open(&service, 1, 0U));
+  assert(sync_service_receive(&service, 1, too_large, sizeof(too_large), 0U, output, &output_length, &changed, &close));
+  assert(!changed && strstr(output, "MALFORMED_JSON") != NULL);
+  sync_service_close(&service, 1);
+}
+
+int main(void) {
+  test_http_malformed_inputs_do_not_mutate();
+  test_websocket_fuzz_and_connection_churn();
+  puts("robustness tests passed");
+  return 0;
+}