feat(modem): Add enhanced URC observer API

components/esp_modem/examples/modem_console/main/modem_console_main.cpp

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Unlicense OR CC0-1.0
  */
@@ -97,10 +97,21 @@ void wakeup_modem(void)
 }
 
 #ifdef CONFIG_ESP_MODEM_URC_HANDLER
-command_result handle_urc(uint8_t *data, size_t len)
+esp_modem::DTE::UrcConsumeInfo handle_enhanced_urc(const esp_modem::DTE::UrcBufferInfo &info)
 {
-    ESP_LOG_BUFFER_HEXDUMP("on_read", data, len, ESP_LOG_INFO);
+    // Log buffer information for debugging
-    return command_result::TIMEOUT;
+    ESP_LOGI(TAG, "URC Buffer Info: total_size=%zu, processed_offset=%zu, new_data_size=%zu, command_active=%s",
+             info.buffer_total_size, info.processed_offset, info.new_data_size,
+             info.is_command_active ? "true" : "false");
+
+    // Log the new data content
+    if (info.new_data_size > 0) {
+        ESP_LOG_BUFFER_HEXDUMP("on_read", info.new_data_start, info.new_data_size, ESP_LOG_INFO);
+    }
+
+    // For console example, we just log and don't consume anything
+    // This allows the data to be processed by command handlers
+    return {esp_modem::DTE::UrcConsumeResult::CONSUME_NONE, 0};
 }
 #endif
 
@@ -381,14 +392,14 @@ extern "C" void app_main(void)
         CHECK_ERR(dce->reset(), ESP_LOGI(TAG, "OK"));
     });
 #ifdef CONFIG_ESP_MODEM_URC_HANDLER
-    const ConsoleCommand HandleURC("urc", "toggle urc handling", no_args, [&](ConsoleCommand * c) {
+    const ConsoleCommand HandleURC("urc", "toggle enhanced urc handling", no_args, [&](ConsoleCommand * c) {
         static int cnt = 0;
         if (++cnt % 2) {
-            ESP_LOGI(TAG, "Adding URC handler");
+            ESP_LOGI(TAG, "Adding enhanced URC handler");
-            dce->set_urc(handle_urc);
+            dce->set_enhanced_urc(handle_enhanced_urc);
         } else {
-            ESP_LOGI(TAG, "URC removed");
+            ESP_LOGI(TAG, "Enhanced URC removed");
-            dce->set_urc(nullptr);
+            dce->set_enhanced_urc(nullptr);
         }
         return 0;
     });

components/esp_modem/include/cxx_include/esp_modem_dce_template.hpp

@@ -103,6 +103,11 @@ public:
     {
         dte->set_urc_cb(on_read_cb);
     }
+
+    void set_enhanced_urc(esp_modem::DTE::enhanced_urc_cb enhanced_cb)
+    {
+        dte->set_enhanced_urc_cb(enhanced_cb);
+    }
 #endif
 
     /**

components/esp_modem/include/cxx_include/esp_modem_dte.hpp

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2021-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -115,6 +115,42 @@ public:
     {
         command_cb.urc_handler = std::move(line_cb);
     }
+
+    /**
+     * @brief Enhanced URC handler with buffer consumption control
+     * @param buffer_info Information about the current buffer state
+     * @return Information about how much of the buffer to consume
+     */
+    struct UrcBufferInfo {
+        const uint8_t* buffer_start;        // Start of entire buffer
+        size_t buffer_total_size;           // Total buffer size
+        size_t processed_offset;            // Offset of already processed data
+        size_t new_data_size;               // Size of new data since last call
+        const uint8_t* new_data_start;      // Pointer to start of new data
+        bool is_command_active;             // Whether a command is currently waiting for response
+    };
+
+    enum class UrcConsumeResult {
+        CONSUME_NONE,           // Don't consume anything, continue waiting
+        CONSUME_PARTIAL,        // Consume only part of the buffer
+        CONSUME_ALL             // Consume entire buffer
+    };
+
+    struct UrcConsumeInfo {
+        UrcConsumeResult result;
+        size_t consume_size;    // How many bytes to consume (0 = none, SIZE_MAX = all)
+    };
+
+    typedef std::function<UrcConsumeInfo(const UrcBufferInfo &)> enhanced_urc_cb;
+
+    /**
+     * @brief Set enhanced URC callback with buffer consumption control
+     * @param enhanced_cb Enhanced callback that can control buffer consumption
+     */
+    void set_enhanced_urc_cb(enhanced_urc_cb enhanced_cb)
+    {
+        command_cb.enhanced_urc_handler = std::move(enhanced_cb);
+    }
 #endif
 
     /**
@@ -171,6 +207,33 @@ private:
     [[nodiscard]] bool exit_cmux();                         /*!< Exit of CMUX mode and cleanup  */
     void exit_cmux_internal();                              /*!< Cleanup CMUX */
 
+#ifdef CONFIG_ESP_MODEM_URC_HANDLER
+    /**
+     * @brief Buffer state tracking for enhanced URC processing
+     */
+    struct BufferState {
+        size_t total_processed = 0;         /*!< Total bytes processed by URC handlers */
+        size_t last_urc_processed = 0;      /*!< Last offset processed by URC */
+        bool command_waiting = false;       /*!< Whether command is waiting for response */
+        size_t command_start_offset = 0;    /*!< Where current command response started */
+    } buffer_state;
+
+    /**
+     * @brief Update buffer state when new data arrives
+     * @param new_data_size Size of new data added to buffer
+     */
+    void update_buffer_state(size_t new_data_size);
+
+    /**
+     * @brief Create URC buffer information for enhanced handlers
+     * @param data Buffer data pointer
+     * @param consumed Already consumed bytes
+     * @param len New data length
+     * @return UrcBufferInfo structure with complete buffer context
+     */
+    UrcBufferInfo create_urc_info(uint8_t* data, size_t consumed, size_t len);
+#endif
+
     Lock internal_lock{};                                   /*!< Locks DTE operations */
     unique_buffer buffer;                                   /*!< DTE buffer */
     std::shared_ptr<CMux> cmux_term;                        /*!< Primary terminal for this DTE */
@@ -216,6 +279,7 @@ private:
     struct command_cb {
 #ifdef CONFIG_ESP_MODEM_URC_HANDLER
         got_line_cb urc_handler {};                             /*!< URC callback if enabled */
+        enhanced_urc_cb enhanced_urc_handler {};                /*!< Enhanced URC callback with consumption control */
 #endif
         static const size_t GOT_LINE = SignalGroup::bit0;       /*!< Bit indicating response available */
         got_line_cb got_line;                                   /*!< Supplied command callback */
@@ -223,7 +287,7 @@ private:
         char separator{};                                       /*!< Command reply separator (end of line/processing unit) */
         command_result result{};                                /*!< Command return code */
         SignalGroup signal;                                     /*!< Event group used to signal request-response operations */
-        bool process_line(uint8_t *data, size_t consumed, size_t len);  /*!< Lets the processing callback handle one line (processing unit) */
+        bool process_line(uint8_t *data, size_t consumed, size_t len, DTE* dte = nullptr);  /*!< Lets the processing callback handle one line (processing unit) */
         bool wait_for_line(uint32_t time_ms)                    /*!< Waiting for command processing */
         {
             return signal.wait_any(command_cb::GOT_LINE, time_ms);

components/esp_modem/src/esp_modem_dte.cpp

@@ -65,6 +65,10 @@ void DTE::set_command_callbacks()
 {
     primary_term->set_read_cb([this](uint8_t *data, size_t len) {
         Scoped<Lock> l(command_cb.line_lock);
+#ifdef CONFIG_ESP_MODEM_URC_HANDLER
+        // Update buffer state when new data arrives
+        update_buffer_state(len);
+#endif
 #ifndef CONFIG_ESP_MODEM_URC_HANDLER
         if (command_cb.got_line == nullptr || command_cb.result != command_result::TIMEOUT) {
             return false;   // this line has been processed already (got OK or FAIL previously)
@@ -80,7 +84,7 @@ void DTE::set_command_callbacks()
                 std::memcpy(inflatable.current(), data, len);
                 data = inflatable.begin();
             }
-            if (command_cb.process_line(data, inflatable.consumed, len)) {
+            if (command_cb.process_line(data, inflatable.consumed, len, this)) {
                 return true;
             }
             // at this point we're sure that the data processing hasn't finished,
@@ -92,7 +96,7 @@ void DTE::set_command_callbacks()
             inflatable.consumed += len;
             return false;
 #else
-            if (command_cb.process_line(data, 0, len)) {
+            if (command_cb.process_line(data, 0, len, this)) {
                 return true;
             }
             // cannot inflate and the processing hasn't finishes in the first iteration, but continue
@@ -105,7 +109,7 @@ void DTE::set_command_callbacks()
         if (buffer.size > buffer.consumed) {
             data = buffer.get();
             len = primary_term->read(data + buffer.consumed, buffer.size - buffer.consumed);
-            if (command_cb.process_line(data, buffer.consumed, len)) {
+            if (command_cb.process_line(data, buffer.consumed, len, this)) {
                 return true;
             }
             buffer.consumed += len;
@@ -121,7 +125,7 @@ void DTE::set_command_callbacks()
             inflatable.grow(inflatable.consumed + len);
         }
         len = primary_term->read(inflatable.current(), len);
-        if (command_cb.process_line(inflatable.begin(), inflatable.consumed, len)) {
+        if (command_cb.process_line(inflatable.begin(), inflatable.consumed, len, this)) {
             return true;
         }
         inflatable.consumed += len;
@@ -150,10 +154,19 @@ void DTE::set_command_callbacks()
 command_result DTE::command(const std::string &command, got_line_cb got_line, uint32_t time_ms, const char separator)
 {
     Scoped<Lock> l1(internal_lock);
+#ifdef CONFIG_ESP_MODEM_URC_HANDLER
+    // Track command start
+    buffer_state.command_waiting = true;
+    buffer_state.command_start_offset = buffer_state.total_processed;
+#endif
     command_cb.set(got_line, separator);
     primary_term->write((uint8_t *)command.c_str(), command.length());
     command_cb.wait_for_line(time_ms);
     command_cb.set(nullptr);
+#ifdef CONFIG_ESP_MODEM_URC_HANDLER
+    // Track command end
+    buffer_state.command_waiting = false;
+#endif
     buffer.consumed = 0;
 #ifdef CONFIG_ESP_MODEM_USE_INFLATABLE_BUFFER_IF_NEEDED
     inflatable.deflate();
@@ -365,18 +378,54 @@ void DTE::on_read(got_line_cb on_read_cb)
     });
 }
 
-bool DTE::command_cb::process_line(uint8_t *data, size_t consumed, size_t len)
+bool DTE::command_cb::process_line(uint8_t *data, size_t consumed, size_t len, DTE* dte)
 {
     // returning true indicates that the processing finished and lower layers can destroy the accumulated buffer
 #ifdef CONFIG_ESP_MODEM_URC_HANDLER
-    bool consume_buffer = false;
+    // Call enhanced URC handler if registered
-    if (urc_handler) {
+    if (enhanced_urc_handler && dte) {
-        consume_buffer = urc_handler(data, consumed + len) != command_result::TIMEOUT;
+        // Create buffer info for enhanced URC handler
+        UrcBufferInfo buffer_info = dte->create_urc_info(data, consumed, len);
+
+        // Call enhanced URC handler
+        UrcConsumeInfo consume_info = enhanced_urc_handler(buffer_info);
+
+        // Handle consumption control
+        switch (consume_info.result) {
+        case UrcConsumeResult::CONSUME_NONE:
+            // Don't consume anything, continue with command processing
+            break;
+
+        case UrcConsumeResult::CONSUME_PARTIAL:
+            // Consume only specified amount
+            dte->buffer_state.last_urc_processed += consume_info.consume_size;
+            // Adjust data pointers for command processing
+            data += consume_info.consume_size;
+            consumed = (consumed + len) - consume_info.consume_size;
+            len = 0;
+            break;
+
+        case UrcConsumeResult::CONSUME_ALL:
+            // Consume entire buffer
+            dte->buffer_state.last_urc_processed = consumed + len;
+            return true;  // Signal buffer consumption
+        }
     }
-    if (result != command_result::TIMEOUT || got_line == nullptr) {
+
-        return consume_buffer;   // this line has been processed already (got OK or FAIL previously)
+    // Fallback to legacy URC handler if enhanced handler not set
+    if (urc_handler) {
+        bool consume_buffer = urc_handler(data, consumed + len) != command_result::TIMEOUT;
+        if (result != command_result::TIMEOUT || got_line == nullptr) {
+            return consume_buffer;   // this line has been processed already (got OK or FAIL previously)
+        }
     }
 #endif
+
+    // Continue with normal command processing
+    if (result != command_result::TIMEOUT || got_line == nullptr) {
+        return false;  // Command processing continues
+    }
+
     if (memchr(data + consumed, separator, len)) {
         result = got_line(data, consumed + len);
         if (result == command_result::OK || result == command_result::FAIL) {
@@ -423,3 +472,22 @@ void DTE::extra_buffer::grow(size_t need_size)
  */
 unique_buffer::unique_buffer(size_t size):
     data(std::make_unique<uint8_t[]>(size)), size(size), consumed(0) {}
+
+#ifdef CONFIG_ESP_MODEM_URC_HANDLER
+void DTE::update_buffer_state(size_t new_data_size)
+{
+    buffer_state.total_processed += new_data_size;
+}
+
+DTE::UrcBufferInfo DTE::create_urc_info(uint8_t* data, size_t consumed, size_t len)
+{
+    return {
+        .buffer_start = data,
+        .buffer_total_size = consumed + len,
+        .processed_offset = buffer_state.last_urc_processed,
+        .new_data_size = (consumed + len) - buffer_state.last_urc_processed,
+        .new_data_start = data + buffer_state.last_urc_processed,
+        .is_command_active = buffer_state.command_waiting
+    };
+}
+#endif

components/esp_modem/test/target_urc/README.md

@@ -0,0 +1,152 @@
+# ESP Modem Enhanced URC Test
+
+## Overview
+
+This test validates the enhanced URC (Unsolicited Result Code) interface with buffer consumption control. It demonstrates the new `set_enhanced_urc()` API that provides granular control over buffer consumption and complete buffer visibility.
+
+## Test Configuration
+
+- **Target**: ESP-AT device with HTTP server
+- **UART**: 115200 baud, 8N1, TX=17, RX=18
+- **Buffer Size**: 1024 bytes
+- **Timeout**: 15 seconds
+
+## Test Cases
+
+### 1. Enhanced URC Handler Registration
+- **Objective**: Verify enhanced URC handler can be registered
+- **Method**: Call `set_enhanced_urc()` with custom handler
+- **Expected**: Handler receives `UrcBufferInfo` with complete buffer context
+
+### 2. Buffer Visibility
+- **Objective**: Verify URC handler receives complete buffer information
+- **Method**: Log buffer state information in handler
+- **Expected**: Handler receives `buffer_start`, `buffer_total_size`, `processed_offset`, `new_data_size`, `is_command_active`
+
+### 3. Granular Consumption Control
+- **Objective**: Verify handler can consume partial buffer data
+- **Method**: Process HTTP URCs line-by-line using `CONSUME_PARTIAL`
+- **Expected**: Each complete line is consumed individually, remaining data preserved
+
+### 4. Multi-part Response Handling
+- **Objective**: Verify handling of chunked HTTP responses
+- **Method**: Process 9 HTTP chunks from ESP-AT server
+- **Expected**: All chunks processed correctly with proper offset tracking
+
+### 5. Transfer Completion Detection
+- **Objective**: Verify detection of transfer completion message
+- **Method**: Search for "Transfer completed" in buffer
+- **Expected**: Completion detected and event group signaled
+
+### 6. Command State Awareness
+- **Objective**: Verify handler knows command state
+- **Method**: Check `is_command_active` flag during processing
+- **Expected**: Flag correctly reflects command state
+
+## Test Implementation
+
+The test uses an ESP-AT device running an HTTP server that sends chunked responses. The enhanced URC handler processes each HTTP URC line individually and detects completion.
+
+### Key Components
+
+```cpp
+// Enhanced URC handler registration
+set_enhanced_urc(handle_enhanced_urc);
+
+// Handler implementation
+static esp_modem::DTE::UrcConsumeInfo handle_enhanced_urc(const esp_modem::DTE::UrcBufferInfo& info)
+{
+    // Process HTTP URCs with granular consumption control
+    if (line.starts_with("+HTTPCGET:")) {
+        // Consume this line only
+        return {esp_modem::DTE::UrcConsumeResult::CONSUME_PARTIAL, line_end + 1};
+    }
+
+    // Check for completion
+    if (buffer.find("Transfer completed") != std::string_view::npos) {
+        xEventGroupSetBits(s_event_group, transfer_completed);
+        return {esp_modem::DTE::UrcConsumeResult::CONSUME_ALL, 0};
+    }
+
+    return {esp_modem::DTE::UrcConsumeResult::CONSUME_NONE, 0};
+}
+```
+
+## Example Output
+
+### Successful Test Run
+```
+I (908) urc_test: Starting Enhanced URC Test
+I (938) urc_test: Start HTTP server...(0)
+I (948) urc_test: HTTP GET...(43)
+I (1228) urc_test: HTTP URC: +HTTPCGET:27,=== Async Response #4 ===
+I (2778) urc_test: HTTP URC: +HTTPCGET:61,[1/9] [633135 ms] This is a simulated slow server response.
+I (4288) urc_test: HTTP URC: +HTTPCGET:71,[2/9] [634639 ms] Chunk 1: The ESP-AT HTTP server is demonstrating...
+I (5788) urc_test: HTTP URC: +HTTPCGET:73,[3/9] [636143 ms] Chunk 2: ...asynchronous chunked transfer encoding...
+I (7288) urc_test: HTTP URC: +HTTPCGET:72,[4/9] [637647 ms] Chunk 3: ...with artificial delays between chunks...
+I (8788) urc_test: HTTP URC: +HTTPCGET:74,[5/9] [639151 ms] Chunk 4: ...to simulate real-world network conditions.
+I (10288) urc_test: HTTP URC: +HTTPCGET:62,[6/9] [640655 ms] Chunk 5: Processing data... please wait...
+I (11788) urc_test: HTTP URC: +HTTPCGET:63,[7/9] [642159 ms] Chunk 6: Still processing... almost done...
+I (13288) urc_test: HTTP URC: +HTTPCGET:61,[8/9] [643663 ms] Chunk 7: Final chunk - transfer complete!
+I (14758) urc_test: HTTP URC: +HTTPCGET:43,[9/9] [645168 ms] === END OF RESPONSE ===
+I (15258) urc_test: Transfer completed detected in buffer!
+I (15298) urc_test: Enhanced URC test completed successfully!
+I (15308) urc_test: The enhanced URC handler successfully processed all HTTP chunks
+I (15308) urc_test: with granular buffer consumption control
+```
+
+### Debug Output (with ESP_LOG_LEVEL_DEBUG)
+```
+D (958) urc_test: URC Buffer Info: total_size=43, processed_offset=0, new_data_size=43, command_active=false
+D (958) urc_test: Buffer content (first 43 chars): AT+HTTPCGET="http://127.0.0.1:8080/async"
+D (968) urc_test: Other data: AT+HTTPCGET="http://127.0.0.1:8080/async"
+D (1218) urc_test: URC Buffer Info: total_size=85, processed_offset=43, new_data_size=42, command_active=false
+D (1228) urc_test: Consuming 40 bytes (line_end=82, processed_offset=43)
+D (2778) urc_test: Consuming 76 bytes (line_end=158, processed_offset=83)
+```
+
+### Failed Test (Timeout)
+```
+I (908) urc_test: Starting Enhanced URC Test
+I (948) urc_test: HTTP GET...(43)
+E (15385) urc_test: Enhanced URC test timed out
+I (15385) urc_test: Enhanced URC test done
+```
+
+## Test Validation
+
+### Success Criteria
+- All 9 HTTP chunks processed successfully
+- Transfer completion detected within 15 seconds
+- No buffer arithmetic errors (no negative `new_data_size`)
+- Proper consumption control (line-by-line processing)
+
+### Failure Indicators
+- Test timeout (15 seconds)
+- Buffer arithmetic errors (negative `new_data_size`)
+- Missing HTTP chunks
+- Transfer completion not detected
+
+## Dependencies
+
+- ESP-AT device with HTTP server capability
+- UART connection configured
+- `CONFIG_ESP_MODEM_URC_HANDLER=y`
+- FreeRTOS event groups
+
+## Build and Run
+
+```bash
+idf.py build
+idf.py flash monitor
+```
+
+## Comparison with Legacy URC
+
+| Feature | Legacy URC | Enhanced URC |
+|---------|------------|--------------|
+| Buffer Consumption | All or nothing | Granular (partial) |
+| Buffer Visibility | None | Complete context |
+| Command State | Unknown | Known (`is_command_active`) |
+| Processing State | Unknown | Tracked (`processed_offset`) |
+| Multi-part Support | Limited | Full support |

components/esp_modem/test/target_urc/main/urc_test.cpp

@@ -3,7 +3,26 @@
  *
  * SPDX-License-Identifier: Unlicense OR CC0-1.0
  */
+
+/**
+ * @file urc_test.cpp
+ * @brief Enhanced URC (Unsolicited Result Code) Test
+ *
+ * This test demonstrates the new enhanced URC interface with buffer consumption control.
+ * It tests the following features:
+ *
+ * 1. Enhanced URC Handler Registration: Uses set_enhanced_urc() instead of set_urc()
+ * 2. Buffer Visibility: URC handler receives complete buffer information
+ * 3. Granular Consumption Control: Handler can consume none, partial, or all buffer data
+ * 4. Processing State Awareness: Handler knows what data is new vs. already processed
+ * 5. Command State Awareness: Handler knows if a command is currently active
+ *
+ * The test works with ESP-AT HTTP server that sends chunked responses, demonstrating
+ * how the enhanced URC handler can process multi-part responses with precise control
+ * over buffer consumption.
+ */
 #include <cstring>
+#include <algorithm>
 #include "freertos/FreeRTOS.h"
 #include "freertos/event_groups.h"
 #include "esp_netif.h"
@@ -67,7 +86,7 @@ public:
     bool http_get(const std::string &url)
     {
         std::string command = "AT+HTTPCGET=\"" + url + "\"\r\n";
-        set_urc(handle_urc);
+        set_enhanced_urc(handle_enhanced_urc);
         auto ret = dte->write(esp_modem::DTE_Command(command));
         ESP_LOGI(TAG, "HTTP GET...(%d)", static_cast<int>(ret));
         return ret > 0;
@@ -82,25 +101,88 @@ public:
 
     static constexpr int transfer_completed = 1;
 private:
-    static esp_modem::command_result handle_urc(uint8_t *data, size_t len)
+    static esp_modem::DTE::UrcConsumeInfo handle_enhanced_urc(const esp_modem::DTE::UrcBufferInfo &info)
     {
-        static int start_chunk = 0;
+        // Log buffer information for debugging
-        static int end_chunk = 0;
+        ESP_LOGD(TAG, "URC Buffer Info: total_size=%zu, processed_offset=%zu, new_data_size=%zu, command_active=%s",
-        std::string_view chunk((const char*)data + start_chunk, len - start_chunk);
+                 info.buffer_total_size, info.processed_offset, info.new_data_size,
-        int newline = chunk.find('\n');
+                 info.is_command_active ? "true" : "false");
-        if (newline == std::string_view::npos) {
+
-            end_chunk = len;    // careful, this grows buffer usage
+        // Debug: Show buffer content (first 200 chars)
-            printf(".");
+        if (info.buffer_total_size > 0) {
-            return esp_modem::command_result::TIMEOUT;
+            size_t debug_len = std::min(info.buffer_total_size, (size_t)200);
+            ESP_LOGD(TAG, "Buffer content (first %zu chars): %.*s",
+                     debug_len, (int)debug_len, (const char*)info.buffer_start);
         }
-        printf("%.*s\n", newline, (char*)data + start_chunk);
+
-        start_chunk = end_chunk;
+        // Create string view of the entire buffer for processing
-        // check for the last one
+        std::string_view buffer((const char*)info.buffer_start, info.buffer_total_size);
-        constexpr char last_chunk[] = "Transfer completed";
+
-        if (memmem(data, len, last_chunk, sizeof(last_chunk) - 1) != nullptr) {
+        // First, check if we have the completion message anywhere in the buffer
+        if (buffer.find("Transfer completed") != std::string_view::npos) {
+            ESP_LOGI(TAG, "Transfer completed detected in buffer!");
             xEventGroupSetBits(s_event_group, transfer_completed);
+            // Consume everything
+            return {esp_modem::DTE::UrcConsumeResult::CONSUME_ALL, 0};
         }
-        return esp_modem::command_result::OK;
+
+        // Process from the last processed offset
+        size_t search_start = info.processed_offset;
+
+        // Look for complete lines starting from the processed offset
+        while (search_start < info.buffer_total_size) {
+            size_t line_end = buffer.find('\n', search_start);
+
+            if (line_end == std::string_view::npos) {
+                // No complete line found, wait for more data
+                ESP_LOGD(TAG, "Waiting for more data... (search_start=%zu, total_size=%zu)",
+                         search_start, info.buffer_total_size);
+                return {esp_modem::DTE::UrcConsumeResult::CONSUME_NONE, 0};
+            }
+
+            // Found a complete line, process it
+            std::string_view line = buffer.substr(search_start, line_end - search_start);
+
+            // Remove carriage return if present
+            if (!line.empty() && line.back() == '\r') {
+                line.remove_suffix(1);
+            }
+
+            // Check if this is an HTTP URC
+            if (line.starts_with("+HTTPCGET:")) {
+                ESP_LOGI(TAG, "HTTP URC: %.*s", (int)line.length(), line.data());
+
+                // Check for transfer completion - look for "Transfer completed" anywhere in the line
+                if (line.find("Transfer completed") != std::string_view::npos) {
+                    ESP_LOGI(TAG, "Transfer completed detected!");
+                    xEventGroupSetBits(s_event_group, transfer_completed);
+                }
+
+                // Consume this line (including the newline)
+                size_t consume_size = line_end + 1 - info.processed_offset;
+                ESP_LOGD(TAG, "Consuming %zu bytes (line_end=%zu, processed_offset=%zu)",
+                         consume_size, line_end, info.processed_offset);
+                return {esp_modem::DTE::UrcConsumeResult::CONSUME_PARTIAL, consume_size};
+
+            } else if (line.starts_with("+HTTPCGET")) {
+                // Partial HTTP URC, don't consume yet
+                ESP_LOGD(TAG, "Partial HTTP URC: %.*s", (int)line.length(), line.data());
+                return {esp_modem::DTE::UrcConsumeResult::CONSUME_NONE, 0};
+
+            } else if (!line.empty()) {
+                // Other data, log and consume
+                ESP_LOGD(TAG, "Other data: %.*s", (int)line.length(), line.data());
+                size_t consume_size = line_end + 1 - info.processed_offset;
+                return {esp_modem::DTE::UrcConsumeResult::CONSUME_PARTIAL, consume_size};
+            }
+
+            // Move to next line
+            search_start = line_end + 1;
+        }
+
+        // Processed all available data
+        ESP_LOGD(TAG, "Processed all available data");
+        return {esp_modem::DTE::UrcConsumeResult::CONSUME_NONE, 0};
     }
 };
 
@@ -131,8 +213,8 @@ extern "C" void app_main(void)
 
     esp_modem_dte_config_t dte_config = ESP_MODEM_DTE_DEFAULT_CONFIG();
     dte_config.dte_buffer_size = 1024;
-    dte_config.uart_config.tx_io_num = 18;
+    dte_config.uart_config.tx_io_num = 17;
-    dte_config.uart_config.rx_io_num = 17;
+    dte_config.uart_config.rx_io_num = 18;
     auto uart_dte = esp_modem::create_uart_dte(&dte_config);
     if (uart_dte == nullptr) {
         ESP_LOGE(TAG, "Failed to create UART DTE");
@@ -144,15 +226,24 @@ extern "C" void app_main(void)
         return;
     }
 
+    ESP_LOGI(TAG, "Starting Enhanced URC Test");
+    ESP_LOGI(TAG, "This test demonstrates the new enhanced URC interface with buffer consumption control");
+
     dce->start_http_server();
 
+    ESP_LOGI(TAG, "Sending HTTP GET request with enhanced URC handler");
     dce->http_get("http://127.0.0.1:8080/async");
 
     EventBits_t bits = xEventGroupWaitBits(s_event_group, 1, pdTRUE, pdFALSE, pdMS_TO_TICKS(15000));
     if (bits & DCE::transfer_completed) {
-        ESP_LOGI(TAG, "Request finished!");
+        ESP_LOGI(TAG, "Enhanced URC test completed successfully!");
+        ESP_LOGI(TAG, "The enhanced URC handler successfully processed all HTTP chunks");
+        ESP_LOGI(TAG, "with granular buffer consumption control");
+    } else {
+        ESP_LOGE(TAG, "Enhanced URC test timed out");
     }
+
     dce->sync();
     vEventGroupDelete(s_event_group);
-    ESP_LOGI(TAG, "Done");
+    ESP_LOGI(TAG, "Enhanced URC test done");
 }

docs/esp_modem/en/advanced_api.rst

@@ -38,6 +38,15 @@ work with commands differently. This might be useful to add some custom preproce
 Please check the ``modem_console`` example with ``CONFIG_EXAMPLE_MODEM_DEVICE_SHINY=y`` configuration which demonstrates
 overriding default ``command()`` method to implement URC processing in user space.
 
+Enhanced URC (Unsolicited Result Code) Handling
+------------------------------------------------
+
+The ESP modem library provides two interfaces for handling URCs: a legacy callback-based interface and an enhanced interface with granular buffer consumption control. The enhanced interface, available through :cpp:func:`esp_modem::DCE_T::set_enhanced_urc`, provides complete buffer visibility and allows URC handlers to make precise decisions about buffer consumption. This is particularly useful for processing multi-part responses or when you need to consume only specific portions of the buffer while preserving other data for command processing.
+
+The enhanced URC handler receives a :cpp:struct:`esp_modem::DTE::UrcBufferInfo` structure containing the complete buffer context, including what data has been processed, what's new, and whether a command is currently active. The handler returns a :cpp:struct:`esp_modem::DTE::UrcConsumeInfo` structure specifying how much of the buffer to consume: none (wait for more data), partial (consume specific amount), or all (consume entire buffer). This granular control enables sophisticated URC processing scenarios such as line-by-line parsing of chunked HTTP responses or selective processing based on command state.
+
+For applications migrating from the legacy URC interface, the enhanced interface maintains backward compatibility while providing significantly more control over buffer management. The legacy :cpp:func:`esp_modem::DCE_T::set_urc` method continues to work as before, but new applications should consider using the enhanced interface for better buffer control and processing flexibility.
+
 Create new communication interface
 ----------------------------------