Add gRPC reflection-based discovery and h2c support

AGENTS.md

@@ -4,7 +4,7 @@ This file provides guidance to AI agents when working with code in this reposito
 
 ## Project Overview
 
-`fetch` is a modern HTTP(S) client CLI written in Go. It features automatic response formatting (JSON, XML, YAML, HTML, CSS, CSV, protobuf, msgpack), image rendering in terminals, gRPC support with JSON-to-protobuf conversion, and authentication (Basic, Bearer, AWS SigV4).
+`fetch` is a modern HTTP(S) client CLI written in Go. It features automatic response formatting (JSON, XML, YAML, HTML, CSS, CSV, protobuf, msgpack), image rendering in terminals, gRPC support with reflection/discovery and JSON-to-protobuf conversion, and authentication (Basic, Bearer, AWS SigV4).
 
 The repository currently targets Go 1.26.1 in `go.mod` and GitHub Actions.
 
@@ -52,7 +52,7 @@ prettier -w .
 - **internal/config** - INI-format config file parsing with host-specific overrides.
 - **internal/core** - Shared types (`Printer`, `Color`, `Format`, `HTTPVersion`) and utilities.
 - **internal/curl** - Curl command parser for `--from-curl` flag. Tokenizes and parses curl command strings into an intermediate `Result` struct.
-- **internal/fetch** - Core HTTP request execution. `fetch.go:Fetch()` is the main entry point that builds requests, handles gRPC framing, and routes to formatters.
+- **internal/fetch** - Core HTTP request execution. `fetch.go:Fetch()` is the main entry point that builds requests, handles gRPC framing/reflection/discovery, and routes to formatters.
 - **internal/fileutil** - Shared file helpers, including cross-platform atomic replacement for temp-file write flows.
 - **internal/format** - Response body formatters (JSON, XML, YAML, HTML, CSS, CSV, msgpack, protobuf, SSE, NDJSON). Each formatter writes colored output to a `Printer`.
 - **internal/grpc** - gRPC framing, headers, and status code handling.
@@ -68,7 +68,13 @@ prettier -w .
 1. CLI args parsed (`cli.Parse`) → `App` struct
 2. Config file merged (`config.GetFile`)
 3. `fetch.Request` built from merged config
-4. If gRPC: load proto schema, setup descriptors, convert JSON→protobuf, frame message
+4. If gRPC: load local proto schema or resolve it via reflection, setup descriptors, convert JSON→protobuf, frame message
+
+## Recent Notes
+
+- `--grpc-list` and `--grpc-describe` provide grpcurl-style discovery using reflection or local descriptor files.
+- `--grpc` now automatically tries gRPC reflection when no local schema is supplied.
+- Plaintext loopback gRPC servers are supported via `h2c` for both calls and discovery.
 5. HTTP client executes request
 6. Response formatted based on Content-Type and output to stdout (optionally via pager)
 

README.md

@@ -9,7 +9,7 @@ A modern HTTP(S) client for the command line.
 - **Response formatting** - Automatic formatting and syntax highlighting for JSON, XML, YAML, HTML, CSS, CSV, Markdown, MessagePack, Protocol Buffers, and more
 - **Image rendering** - Display images directly in your terminal
 - **WebSocket support** - Bidirectional WebSocket connections with automatic JSON formatting
-- **gRPC support** - Make gRPC calls with automatic JSON-to-protobuf conversion
+- **gRPC support** - Make gRPC calls with automatic reflection, discovery, and JSON-to-protobuf conversion
 - **Authentication** - Built-in support for Basic Auth, Bearer Token, AWS Signature V4, and mTLS
 - **Compression** - Automatic gzip and zstd response body decompression
 - **TLS inspection** - Inspect TLS certificate chains, expiry, SANs, and OCSP status

docs/advanced-features.md

@@ -151,6 +151,7 @@ fetch --http 2 example.com
 - Multiplexed streams
 - Header compression (HPACK)
 - Required for gRPC
+- Automatically uses h2c (HTTP/2 over cleartext) for gRPC requests with `http://` URLs, enabling plaintext HTTP/2 connections to local development servers without TLS
 
 ### HTTP/3 (QUIC)
 

docs/cli-reference.md

@@ -407,9 +407,12 @@ Force specific HTTP version. Values: `1`, `2`, `3`.
 - `2` - HTTP/2 (default preference)
 - `3` - HTTP/3 (QUIC)
 
+When `--http 2` is used with an `http://` URL for gRPC requests, `fetch` automatically uses h2c (HTTP/2 over cleartext) to connect without TLS.
+
 ```sh
 fetch --http 1 example.com
 fetch --http 3 example.com
+fetch --grpc --http 2 http://localhost:50051/pkg.Svc/Method  # uses h2c
 ```
 
 ## Compression
@@ -489,23 +492,41 @@ See [WebSocket documentation](websocket.md) for details.
 
 ### `--grpc`
 
-Enable gRPC mode. Automatically sets HTTP/2, POST method, and gRPC headers.
+Enable gRPC mode. Automatically sets HTTP/2, POST method, and gRPC headers. When no local proto schema is provided, `fetch` automatically tries gRPC reflection before falling back to generic protobuf handling.
 
 ```sh
 fetch --grpc https://localhost:50051/package.Service/Method
 ```
 
+### `--grpc-list`
+
+List available gRPC services. Uses reflection when a URL is provided, or runs offline when `--proto-file` / `--proto-desc` is provided.
+
+```sh
+fetch --grpc-list https://localhost:50051
+fetch --grpc-list --proto-desc service.pb
+```
+
+### `--grpc-describe NAME`
+
+Describe a gRPC service, method, or message. Accepts `package.Service`, `package.Service/Method`, `package.Service.Method`, and full message names.
+
+```sh
+fetch --grpc-describe grpc.health.v1.Health https://localhost:50051
+fetch --grpc-describe grpc.health.v1.Health/Check --proto-desc service.pb
+```
+
 ### `--proto-file PATH`
 
-Compile `.proto` file(s) for JSON-to-protobuf conversion. Requires `protoc`. Can specify multiple comma-separated paths.
+Compile `.proto` file(s) for gRPC requests or offline discovery. Requires `protoc`. Can specify multiple comma-separated paths.
 
 ```sh
 fetch --grpc --proto-file service.proto -j '{"field": "value"}' localhost:50051/pkg.Svc/Method
 ```
 
 ### `--proto-desc PATH`
 
-Use pre-compiled descriptor set file instead of `--proto-file`.
+Use a pre-compiled descriptor set file instead of `--proto-file`.
 
 ```sh
 # Generate descriptor:
@@ -523,6 +544,8 @@ Add import paths for proto compilation. Use with `--proto-file`.
 fetch --grpc --proto-file service.proto --proto-import ./proto localhost:50051/pkg.Svc/Method
 ```
 
+Plaintext servers are supported via `h2c` (HTTP/2 over cleartext) when using an `http://` URL with HTTP/2. This works for `--grpc` and reflection-based discovery (`--grpc-list`, `--grpc-describe`).
+
 ## Configuration
 
 ### `-c, --config PATH`

docs/grpc.md

@@ -1,6 +1,6 @@
 # gRPC Support
 
-`fetch` supports making gRPC calls with automatic protocol handling, JSON-to-protobuf conversion, and formatted responses.
+`fetch` supports making gRPC calls with automatic protocol handling, reflection-backed schema discovery, JSON-to-protobuf conversion, and formatted responses.
 
 ## Overview
 
@@ -22,6 +22,41 @@ Enable gRPC mode. This flag:
 fetch --grpc https://localhost:50051/package.Service/Method
 ```
 
+When `--proto-file` or `--proto-desc` is not provided, `fetch` automatically tries gRPC reflection for schema-aware request conversion and response formatting.
+
+## Reflection and Discovery
+
+### `--grpc-list`
+
+List available services from a reflection-enabled server:
+
+```sh
+fetch --grpc-list https://localhost:50051
+```
+
+Or run the same lookup offline with a local descriptor set:
+
+```sh
+fetch --grpc-list --proto-desc service.pb
+```
+
+### `--grpc-describe NAME`
+
+Describe a service, method, or message:
+
+```sh
+fetch --grpc-describe grpc.health.v1.Health https://localhost:50051
+fetch --grpc-describe grpc.health.v1.Health/Check https://localhost:50051
+fetch --grpc-describe grpc.health.v1.HealthCheckRequest --proto-desc service.pb
+```
+
+`NAME` accepts:
+
+- `package.Service`
+- `package.Service/Method`
+- `package.Service.Method`
+- full message names
+
 ### URL Format
 
 The service and method are specified in the URL path:
@@ -39,7 +74,7 @@ fetch --grpc https://localhost:50051/echo.EchoService/Echo
 
 ## Proto Schema Options
 
-To enable JSON-to-protobuf conversion and rich response formatting, provide a proto schema.
+To enable offline discovery, guaranteed JSON-to-protobuf conversion, or to bypass reflection entirely, provide a local proto schema.
 
 ### `--proto-file PATH`
 
@@ -106,11 +141,14 @@ fetch --grpc \
 
 ### Without Proto Schema
 
-When no schema is provided:
+When no local schema is provided:
 
-- Request bodies must be raw protobuf (not JSON)
-- Responses are formatted using generic protobuf parsing
-- Field numbers are shown instead of names
+- `fetch` first tries gRPC reflection
+- If reflection is available, request/response descriptors are resolved automatically
+- If reflection is unavailable, schema-less requests still work for raw/empty protobuf bodies and responses fall back to generic protobuf formatting
+- JSON request bodies fail with an actionable error because descriptors are required for conversion
+
+If reflection is unavailable and you need schema-aware behavior, pass `--proto-file` or `--proto-desc`.
 
 ## Request Bodies
 
@@ -217,6 +255,15 @@ fetch --grpc --insecure \
   https://localhost:50051/pkg.Service/Method
 ```
 
+### Plaintext Local Servers (`h2c`)
+
+For local development servers that use plaintext HTTP/2, use an `http://` URL:
+
+```sh
+fetch --grpc -j '{"service":""}' http://127.0.0.1:50051/grpc.health.v1.Health/Check
+fetch --grpc-list http://127.0.0.1:50051
+```
+
 ### Custom CA Certificate
 
 ```sh