Add upload_project_file/send_gcode_line, real Marlin serial, Bambu protocol auto-detect

- GenericPrinter grows upload_project_file, send_gcode_line, and a
  generic upload_gcode<P> driver that streams a whole gcode file line by
  line through any vendor's send_gcode_line.
- PrusaSerialPrinter's connect/send_gcode_line are real (not stubs): a
  held-open MarlinSerialConnection (src/printer/marlin_serial.rs) writes
  each line and waits for Marlin's "ok" before sending the next. Config
  changed from com_port: i16 to port: String + baud_rate: u32 to hold a
  real device path.
- Bambu: BambuGenericPrinter + BambuV1Printer/BambuV2Printer collapsed
  into one BambuPrinter, since which MQTT/BambuMQTT version (v3.1.1/v1
  vs v5/v2) a printer speaks is discovered at connect() time (or forced),
  not something config should pick a type for - the same physical
  printer can change after a firmware update. printers.toml gets a new
  "bambu" vendor (auto-detect, the default) alongside bambu_v1/bambu_v2
  (force a specific one).
- Bambu's gcode_line request is now built for real via
  continuum-schema-instance against continuum-schemas' JSON Schema,
  picking the v1 or v2 schema directory based on the detected protocol
  version, instead of a hand-written serde struct.
- Added rumqttc as a dependency (not wired up yet - the real MQTT
  v5-then-v3.1.1 fallback connect and the publish/receive plumbing are
  still stubs).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MWQVtBGxHYLkVw2kBupd5g

Cargo.toml

@@ -34,6 +34,18 @@ name = "bambu_commands_demo"
 path = "examples/bambu_commands_demo.rs"
 
 [dependencies]
+# Real printer protocol clients (MQTT for Bambu, HTTP for PrusaLink/
+# Moonraker, FTPS for gcode transfer) go here once you're ready to build
+# past the stubs in src/printer/ - see that module's doc comment.
+continuum-rust-types = { path = "../continuum-schemas/packages/rust-types" }
+# FOR NON-LOCAL DEV
+# continuum-rust-types = { git = "https://git.octoturge.com/Continuum/continuum-schemas.git" }
+
+# Builds a JSON instance straight from the schema files in
+# continuum-schemas/schemas/ - used for Bambu's raw MQTT JSON messages
+# instead of hand-written serde structs (see bambu.rs).
+continuum-schema-instance = { path = "../continuum-common/packages/rust-schema-instance" }
+
 tokio = { version = "1.40", features = ["full"] }
 tokio-tungstenite = { version = "0.24", features = ["native-tls"] }
 futures-util = "0.3"
@@ -47,10 +59,5 @@ tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
 anyhow = "1"
 thiserror = "1"
 dotenvy = "0.15"
-
+tokio-serial = { version = "5.5.0", default-features = false }
-# Real printer protocol clients (MQTT for Bambu, HTTP for PrusaLink/
+rumqttc = "0.25.1"
-# Moonraker, FTPS for gcode transfer) go here once you're ready to build
-# past the stubs in src/printer/ - see that module's doc comment.
-continuum-rust-types = { path = "../continuum-schemas/packages/rust-types" }
-# FOR NON-LOCAL DEV
-# continuum-rust-types = { git = "https://git.octoturge.com/Continuum/continuum-schemas.git" }

examples/auto_connect_bambu.rs

@@ -17,8 +17,7 @@ fn main() -> anyhow::Result<()> {
 
     for printer in &mut printers {
         match printer {
-            PrinterHandle::BambuV1(bambu) => report(&bambu.ensure_trusted(cert_dir)),
+            PrinterHandle::Bambu(bambu) => report(&bambu.ensure_trusted(cert_dir)),
-            PrinterHandle::BambuV2(bambu) => report(&bambu.ensure_trusted(cert_dir)),
             _ => {}
         }
     }

examples/fetch_bambu_cert.rs

@@ -23,8 +23,7 @@ fn main() -> anyhow::Result<()> {
     let pem = printers
         .iter()
         .find_map(|printer| match printer {
-            PrinterHandle::BambuV1(bambu) if bambu.base().id == printer_id => Some(bambu.fetch_certificate()),
+            PrinterHandle::Bambu(bambu) if bambu.base().id == printer_id => Some(bambu.fetch_certificate()),
-            PrinterHandle::BambuV2(bambu) if bambu.base().id == printer_id => Some(bambu.fetch_certificate()),
             _ => None,
         })
         .ok_or_else(|| anyhow::anyhow!("no Bambu printer with id '{printer_id}' in printers.toml"))??;

examples/printer_polymorphism.rs

@@ -4,36 +4,40 @@
 //! - `connect()` is called the same way regardless of vendor (polymorphism),
 //!   but each variant's `impl GenericPrinter` runs completely different
 //!   code (override).
-//! - `dispatch_gcode()` only exists on the two Bambu structs (extension) -
+//! - `dispatch_gcode()` only exists on the Bambu struct (extension) - you
-//!   you have to `match` the enum back down to the concrete type to reach
+//!   have to `match` the enum back down to the concrete type to reach it,
-//!   it, which is the trade-off for not having implicit downcasting.
+//!   which is the trade-off for not having implicit downcasting.
 
 use continuum_proxy::printer::{
-    BambuTls, BambuV1Printer, BambuV2Printer, GenericPrinter, KlipperPrinter, PrinterHandle, PrusaLinkPrinter,
+    BambuPrinter, BambuProtocolPreference, BambuTls, GenericPrinter, KlipperPrinter, PrinterHandle,
-    PrusaSerialPrinter,
+    PrusaLinkPrinter, PrusaSerialPrinter,
 };
 
 #[tokio::main]
 async fn main() {
     let mut fleet: Vec<PrinterHandle> = vec![
-        PrinterHandle::BambuV1(BambuV1Printer::new(
+        // Forced: a known-old printer.
+        PrinterHandle::Bambu(BambuPrinter::new(
             "p1",
             "P1S",
             "192.168.1.49",
             "87654321",
             "01P00A000000000",
             BambuTls::BundledCa,
+            BambuProtocolPreference::ForceV1,
         )),
-        PrinterHandle::BambuV2(BambuV2Printer::new(
+        // Auto: the recommended default - see bambu.rs's doc comment.
+        PrinterHandle::Bambu(BambuPrinter::new(
             "p2",
             "X1 Carbon",
             "192.168.1.50",
             "12345678",
             "00M00A000000000",
             BambuTls::BundledCa,
+            BambuProtocolPreference::Auto,
         )),
         PrinterHandle::PrusaLink(PrusaLinkPrinter::new("p3", "MK4", "192.168.1.51", "prusa-api-key")),
-        PrinterHandle::PrusaSerial(PrusaSerialPrinter::new("p4", "MK3S+", 0)),
+        PrinterHandle::PrusaSerial(PrusaSerialPrinter::new("p4", "MK3S+", "/dev/ttyACM0", 115_200)),
         PrinterHandle::Klipper(KlipperPrinter::new("p5", "Voron 2.4", "192.168.1.52")),
         // No host configured - this one will hit the Err path.
         PrinterHandle::Klipper(KlipperPrinter::new("p6", "Broken Voron", "")),
@@ -50,15 +54,11 @@ async fn main() {
     }
 
     // Vendor-only extension: reachable only after matching the concrete
-    // variant back out of the enum. BambuV1Printer and BambuV2Printer are
+    // variant back out of the enum - one arm now that Bambu is a single
-    // separate types now (each *has* a BambuGenericPrinter rather than
+    // type regardless of which protocol version `connect()` settled on.
-    // being the same struct), so - unlike before the split - this needs
-    // two arms instead of one `A(x) | B(x)` pattern: an or-pattern requires
-    // every alternative to bind the same type, and these no longer do.
     for printer in &fleet {
         match printer {
-            PrinterHandle::BambuV1(bambu) => bambu.dispatch_gcode("part.gcode.3mf"),
+            PrinterHandle::Bambu(bambu) => bambu.dispatch_gcode("part.gcode.3mf"),
-            PrinterHandle::BambuV2(bambu) => bambu.dispatch_gcode("part.gcode.3mf"),
             _ => {}
         }
     }

examples/test_bambu_certs.rs

@@ -12,13 +12,9 @@ use continuum_proxy::printer::{GenericPrinter, PrinterHandle};
 fn main() -> anyhow::Result<()> {
     let printers = fleet::load(std::path::Path::new("printers.toml"))?;
 
-    // BambuV1Printer and BambuV2Printer are separate types (each *has* a
-    // BambuGenericPrinter rather than being the same struct), so this
-    // needs one arm per variant rather than a single `A(x) | B(x)` pattern.
     for printer in &printers {
         match printer {
-            PrinterHandle::BambuV1(bambu) => report(bambu.base().name.as_str(), bambu.test_tls_handshake()),
+            PrinterHandle::Bambu(bambu) => report(bambu.base().name.as_str(), bambu.test_tls_handshake()),
-            PrinterHandle::BambuV2(bambu) => report(bambu.base().name.as_str(), bambu.test_tls_handshake()),
             _ => {}
         }
     }

printers.example.toml

@@ -5,7 +5,9 @@
 [[printer]]
 id = "p1p"
 name = "P1P"
-vendor = "bambu_v1"                    # bambu_v1 | bambu_v2 | prusa_link | prusa_serial | klipper
+# Forced instead of "bambu" here since this one's a known-old printer -
+# see fleet.rs's PrinterEntry doc comment for the full vendor list.
+vendor = "bambu_v1"
 host = "192.168.1.50"
 access_code = "REPLACE_WITH_ACCESS_CODE"
 sn = "REPLACE_WITH_SERIAL_NUMBER"      # printer screen > Settings > Device (used for MQTT topics later)
@@ -18,7 +20,10 @@ ca_cert_path = "./certs/p1p.pem"
 [[printer]]
 id = "h2c"
 name = "H2C"
-vendor = "bambu_v2"
+# "bambu" auto-detects MQTT v5-vs-v3.1.1 (BambuMQTT v2-vs-v1) on connect -
+# the recommended default, since a firmware update can change which one a
+# given printer speaks without you knowing ahead of time.
+vendor = "bambu"
 host = "192.168.1.51"
 access_code = "REPLACE_WITH_ACCESS_CODE"
 sn = "REPLACE_WITH_SERIAL_NUMBER"
@@ -37,3 +42,10 @@ sn = "REPLACE_WITH_SERIAL_NUMBER"
 # vendor = "prusa_link"
 # host = "192.168.1.53"
 # api_key = "REPLACE_WITH_API_KEY"
+
+# [[printer]]
+# id = "mk3s"
+# name = "MK3S+"
+# vendor = "prusa_serial"
+# port = "/dev/ttyACM0"
+# baud_rate = 115200            # optional, defaults to 115200

src/fleet.rs

@@ -7,7 +7,10 @@ use std::path::Path;
 
 use serde::Deserialize;
 
-use crate::printer::{BambuTls, BambuV1Printer, BambuV2Printer, KlipperPrinter, PrinterHandle, PrusaLinkPrinter, PrusaSerialPrinter};
+use crate::printer::{
+    BambuPrinter, BambuProtocolPreference, BambuTls, KlipperPrinter, PrinterHandle, PrusaLinkPrinter,
+    PrusaSerialPrinter,
+};
 
 #[derive(Debug, Deserialize)]
 struct FleetFile {
@@ -19,7 +22,10 @@ struct FleetFile {
 struct PrinterEntry {
     id: String,
     name: String,
-    /// One of: "bambu_v1", "bambu_v2", "prusa_link", "prusa_serial", "klipper".
+    /// One of: "bambu" (auto-detects MQTT v5-vs-v3.1.1/BambuMQTT v2-vs-v1 -
+    /// the default, since a firmware update can move the same physical
+    /// printer between them), "bambu_v1"/"bambu_v2" (force a specific one),
+    /// "prusa_link", "prusa_serial", "klipper".
     vendor: String,
     host: Option<String>,
     access_code: Option<String>,
@@ -27,7 +33,10 @@ struct PrinterEntry {
     /// by serial (`device/{sn}/report`), not by our own `id`.
     sn: Option<String>,
     api_key: Option<String>,
-    com_port: Option<i16>,
+    /// Serial device path, e.g. `/dev/ttyACM0` on Linux.
+    port: Option<String>,
+    #[serde(default = "default_baud_rate")]
+    baud_rate: u32,
     /// Path to a printer-specific CA certificate. Leave unset to use the
     /// bundled Bambu CA - only needed for a printer that doesn't chain to
     /// it (P1P, at least; see certs/README.md).
@@ -40,6 +49,11 @@ fn default_true() -> bool {
     true
 }
 
+/// Marlin's usual default on most current Prusa firmware.
+fn default_baud_rate() -> u32 {
+    115_200
+}
+
 /// Reads and parses a printers file into ready-to-use `PrinterHandle`s.
 pub fn load(path: &Path) -> anyhow::Result<Vec<PrinterHandle>> {
     let text = std::fs::read_to_string(path).map_err(|err| {
@@ -54,28 +68,17 @@ pub fn load(path: &Path) -> anyhow::Result<Vec<PrinterHandle>> {
 
 fn build_printer(entry: PrinterEntry) -> anyhow::Result<PrinterHandle> {
     match entry.vendor.as_str() {
-        "bambu_v1" => {
+        "bambu" => build_bambu(entry, BambuProtocolPreference::Auto),
-            let host = require_field(&entry.id, "host", entry.host)?;
+        "bambu_v1" => build_bambu(entry, BambuProtocolPreference::ForceV1),
-            let access_code = require_field(&entry.id, "access_code", entry.access_code)?;
+        "bambu_v2" => build_bambu(entry, BambuProtocolPreference::ForceV2),
-            let sn = require_field(&entry.id, "sn", entry.sn)?;
-            let tls = BambuTls::resolve(entry.ca_cert_path.as_deref().map(Path::new), entry.require_valid_cert)?;
-            Ok(PrinterHandle::BambuV1(BambuV1Printer::new(&entry.id, &entry.name, &host, &access_code, &sn, tls)))
-        }
-        "bambu_v2" => {
-            let host = require_field(&entry.id, "host", entry.host)?;
-            let access_code = require_field(&entry.id, "access_code", entry.access_code)?;
-            let sn = require_field(&entry.id, "sn", entry.sn)?;
-            let tls = BambuTls::resolve(entry.ca_cert_path.as_deref().map(Path::new), entry.require_valid_cert)?;
-            Ok(PrinterHandle::BambuV2(BambuV2Printer::new(&entry.id, &entry.name, &host, &access_code, &sn, tls)))
-        }
         "prusa_link" => {
             let host = require_field(&entry.id, "host", entry.host)?;
             let api_key = require_field(&entry.id, "api_key", entry.api_key)?;
             Ok(PrinterHandle::PrusaLink(PrusaLinkPrinter::new(&entry.id, &entry.name, &host, &api_key)))
         }
         "prusa_serial" => {
-            let com_port = entry.com_port.ok_or_else(|| anyhow::anyhow!("{}: prusa_serial needs com_port", entry.id))?;
+            let port = require_field(&entry.id, "port", entry.port)?;
-            Ok(PrinterHandle::PrusaSerial(PrusaSerialPrinter::new(&entry.id, &entry.name, com_port)))
+            Ok(PrinterHandle::PrusaSerial(PrusaSerialPrinter::new(&entry.id, &entry.name, &port, entry.baud_rate)))
         }
         "klipper" => {
             let host = require_field(&entry.id, "host", entry.host)?;
@@ -85,6 +88,14 @@ fn build_printer(entry: PrinterEntry) -> anyhow::Result<PrinterHandle> {
     }
 }
 
+fn build_bambu(entry: PrinterEntry, preference: BambuProtocolPreference) -> anyhow::Result<PrinterHandle> {
+    let host = require_field(&entry.id, "host", entry.host)?;
+    let access_code = require_field(&entry.id, "access_code", entry.access_code)?;
+    let sn = require_field(&entry.id, "sn", entry.sn)?;
+    let tls = BambuTls::resolve(entry.ca_cert_path.as_deref().map(Path::new), entry.require_valid_cert)?;
+    Ok(PrinterHandle::Bambu(BambuPrinter::new(&entry.id, &entry.name, &host, &access_code, &sn, tls, preference)))
+}
+
 fn require_field(printer_id: &str, field: &str, value: Option<String>) -> anyhow::Result<String> {
     value.ok_or_else(|| anyhow::anyhow!("{printer_id}: missing required field '{field}'"))
 }

src/printer/bambu.rs

@@ -1,9 +1,29 @@
 use std::net::{SocketAddr, TcpStream, ToSocketAddrs};
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::time::Duration;
 
 use super::{GenericPrinter, PrinterBase, PrinterError};
 
+// region: Certificates
+
+/// The canonical shape for every Bambu MQTT message lives in
+/// continuum-schemas, not here - see `send_gcode_line` below, which builds
+/// an instance of it directly via `continuum-schema-instance` instead of a
+/// hand-written serde struct. `v1`/`v2` underneath this directory are
+/// BambuMQTT's two message schemas, not to be confused with the MQTT
+/// *transport* version (v3.1.1 vs v5) below - they happen to move
+/// together on real Bambu firmware, but they're two different things.
+const BAMBU_SCHEMA_DIR: &str = concat!(
+    env!("CARGO_MANIFEST_DIR"),
+    "/../continuum-schemas/schemas/bambulab"
+);
+
+fn get_schema_for_command(version: BambuProtocolVersion, root: String, command: String) -> PathBuf {
+    Path::new(BAMBU_SCHEMA_DIR)
+        .join(version.schema_dir())
+        .join(format!("request/{root}/{command}.schema.json"))
+}
+
 /// Bambu's shared LAN-mode root CA ("BBL CA2 RSA") - see certs/README.md
 /// for how this was obtained and verified. `include_bytes!` embeds it into
 /// the compiled binary at build time, so there's no file to ship alongside
@@ -77,7 +97,10 @@ impl BambuTls {
 }
 
 fn resolve_addr(host: &str) -> anyhow::Result<SocketAddr> {
-    (host, 8883).to_socket_addrs()?.next().ok_or_else(|| anyhow::anyhow!("could not resolve {host}"))
+    (host, 8883)
+        .to_socket_addrs()?
+        .next()
+        .ok_or_else(|| anyhow::anyhow!("could not resolve {host}"))
 }
 
 /// Minimal DER -> PEM encoder (base64, 64-char lines, standard
@@ -102,28 +125,88 @@ fn pem_to_der(pem: &[u8]) -> anyhow::Result<Vec<u8>> {
     Ok(native_tls::Certificate::from_pem(pem)?.to_der()?)
 }
 
-/// Fields and behavior every Bambu printer shares, regardless of protocol
+// endregion: Certificates
-/// generation - the layer between `GenericPrinter` and the version-specific
+
-/// `BambuV1Printer`/`BambuV2Printer` leaves below. Those two *have* one of
+// region: BambuMQTTProtocol
-/// these (composition) rather than a deeper inheritance chain; because
+/// Which BambuMQTT message schema (and, on real firmware, which MQTT
-/// Rust's field/method privacy is scoped to the *module* (this whole file),
+/// transport version) a connection ended up using. This is an *outcome*
-/// not the struct, `BambuV1Printer`/`BambuV2Printer` can freely use
+/// `connect()` settles on, not something you can assume from the printer
-/// `BambuGenericPrinter`'s private fields even though they're separate
+/// model - a firmware update can move the same physical X1C from v1 to
-/// types.
+/// v2. Every later message this printer sends is built against
-pub struct BambuGenericPrinter {
+/// `schemas/bambulab/{v1,v2}/` depending on which one this is.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum BambuProtocolVersion {
+    /// MQTT v3.1.1, BambuMQTT v1 - older firmware (P1P/P1S, original X1 launch firmware).
+    V1,
+    /// MQTT v5, BambuMQTT v2 - current firmware.
+    V2,
+}
+
+impl BambuProtocolVersion {
+    fn schema_dir(self) -> &'static str {
+        match self {
+            BambuProtocolVersion::V1 => "v1",
+            BambuProtocolVersion::V2 => "v2",
+        }
+    }
+}
+
+/// How to pick the protocol generation for a given printer - config
+/// *input*, as opposed to `BambuProtocolVersion` (the outcome `connect()`
+/// settles on). `Auto` is the default for exactly the reason
+/// `BambuProtocolVersion` isn't derivable from config alone: you can't
+/// reliably know which one a specific printer speaks today without
+/// asking it. `ForceV1`/`ForceV2` stay available as an override - useful
+/// if auto-detection ever misbehaves, or to test one path deliberately.
+#[derive(Debug, Clone, Copy)]
+pub enum BambuProtocolPreference {
+    /// Try MQTT v5 first; if the broker's CONNACK rejects that protocol
+    /// version (older firmware only understands v3.1.1), fall back and
+    /// reconnect with v3.1.1 instead.
+    Auto,
+    ForceV1,
+    ForceV2,
+}
+// endregion: BambuMQTTProtocol
+
+/// A Bambu printer. Only one struct now, not two: the old
+/// `BambuGenericPrinter` (shared fields/behavior) + `BambuV1Printer`/
+/// `BambuV2Printer` (thin per-version wrappers) split existed to let two
+/// *separate types* share a base - but since which protocol version a
+/// printer uses is now something `connect()` discovers at runtime rather
+/// than something config picks between two types for, there's only ever
+/// one type to begin with, so the extra layer stopped earning its keep.
+pub struct BambuPrinter {
     base: PrinterBase,
     pub access_code: String,
     pub sn: String,
     tls: BambuTls,
+    preference: BambuProtocolPreference,
+    /// `None` until `connect()` succeeds.
+    version: Option<BambuProtocolVersion>,
 }
 
-impl BambuGenericPrinter {
+impl BambuPrinter {
-    pub fn new(id: &str, name: &str, host: &str, access_code: &str, sn: &str, tls: BambuTls) -> Self {
+    pub fn new(
+        id: &str,
+        name: &str,
+        host: &str,
+        access_code: &str,
+        sn: &str,
+        tls: BambuTls,
+        preference: BambuProtocolPreference,
+    ) -> Self {
         Self {
-            base: PrinterBase { id: id.into(), name: name.into(), host: host.into() },
+            base: PrinterBase {
+                id: id.into(),
+                name: name.into(),
+                host: host.into(),
+            },
             access_code: access_code.into(),
             sn: sn.into(),
             tls,
+            preference,
+            version: None,
         }
     }
 
@@ -131,13 +214,7 @@ impl BambuGenericPrinter {
         &self.base
     }
 
-    /// Not part of the `GenericPrinter` trait - Prusa/Klipper have no
+    /* A real (blocking, one-shot) TLS handshake to port 8883 - no MQTT
-    /// equivalent, since FTPS gcode transfer is a Bambu-specific thing.
-    pub fn dispatch_gcode(&self, file_name: &str) {
-        println!("[{}] uploading {file_name} over FTPS", self.base.name);
-    }
-
-    /// A real (blocking, one-shot) TLS handshake to port 8883 - no MQTT
     /// protocol, just "does the certificate verify" against this printer's
     /// configured trust mode.
     ///
@@ -155,13 +232,15 @@ impl BambuGenericPrinter {
     /// the very next connection). So instead: connect with verification
     /// off, then compare the certificate actually presented against the
     /// exact bytes pinned, byte for byte. A mismatch is a hard failure -
-    /// no PKI judgment call, just "is this the same certificate as before."
+    /// no PKI judgment call, just "is this the same certificate as before." */
     pub fn test_tls_handshake(&self) -> anyhow::Result<()> {
         let addr = resolve_addr(&self.base.host)?;
         let stream = TcpStream::connect_timeout(&addr, Duration::from_secs(5))?;
 
         if let BambuTls::Custom(pinned_pem) = &self.tls {
-            let tls_stream = BambuTls::Insecure.build_connector()?.connect(&self.base.host, stream)?;
+            let tls_stream = BambuTls::Insecure
+                .build_connector()?
+                .connect(&self.base.host, stream)?;
             let presented = tls_stream
                 .peer_certificate()?
                 .ok_or_else(|| anyhow::anyhow!("{} presented no certificate", self.base.name))?
@@ -178,11 +257,13 @@ impl BambuGenericPrinter {
             return Ok(());
         }
 
-        self.tls.build_connector()?.connect(&self.base.host, stream)?;
+        self.tls
+            .build_connector()?
+            .connect(&self.base.host, stream)?;
         Ok(())
     }
 
-    /// "Trust on first connect": connects once with certificate
+    /* "Trust on first connect": connects once with certificate
     /// verification disabled, captures whatever certificate the printer
     /// presents, and returns it as PEM bytes.
     ///
@@ -191,11 +272,13 @@ impl BambuGenericPrinter {
     /// trusted forever after. That's why it's a method you call once, by
     /// hand (see `examples/fetch_bambu_cert.rs`), rather than something
     /// `connect()` falls back to silently. Save the result to a file and
-    /// point that printer's `ca_cert_path` in `printers.toml` at it.
+    /// point that printer's `ca_cert_path` in `printers.toml` at it. */
     pub fn fetch_certificate(&self) -> anyhow::Result<Vec<u8>> {
         let addr = resolve_addr(&self.base.host)?;
         let stream = TcpStream::connect_timeout(&addr, Duration::from_secs(5))?;
-        let tls_stream = BambuTls::Insecure.build_connector()?.connect(&self.base.host, stream)?;
+        let tls_stream = BambuTls::Insecure
+            .build_connector()?
+            .connect(&self.base.host, stream)?;
 
         let cert = tls_stream
             .peer_certificate()?
@@ -204,7 +287,7 @@ impl BambuGenericPrinter {
         Ok(der_to_pem(&cert.to_der()?))
     }
 
-    /// Makes sure this printer has a *working* trust configuration,
+    /* Makes sure this printer has a *working* trust configuration,
     /// auto-pinning a certificate via trust-on-first-connect if needed -
     /// the "smooth, no manual steps" version of the fetch_bambu_cert
     /// workflow, built the way SSH handles host keys:
@@ -230,7 +313,7 @@ impl BambuGenericPrinter {
     ///   in printers.toml) never auto-pins over it - a verification
     ///   failure there is a real error, not something to paper over,
     ///   since that's exactly the signal pinning exists to give you (the
-    ///   cert rotated, or something worse).
+    ///   cert rotated, or something worse). */
     pub fn ensure_trusted(&mut self, cert_dir: &Path) -> anyhow::Result<()> {
         let pinned_path = cert_dir.join(format!("{}.pem", self.sn));
 
@@ -241,7 +324,10 @@ impl BambuGenericPrinter {
         match self.test_tls_handshake() {
             Ok(()) => Ok(()),
             Err(err) if matches!(self.tls, BambuTls::BundledCa) => {
-                eprintln!("{}: bundled CA didn't verify ({err}); auto-pinning on first connect", self.base.name);
+                eprintln!(
+                    "{}: bundled CA didn't verify ({err}); auto-pinning on first connect",
+                    self.base.name
+                );
                 let pem = self.fetch_certificate()?;
                 std::fs::create_dir_all(cert_dir)?;
                 std::fs::write(&pinned_path, &pem)?;
@@ -251,113 +337,111 @@ impl BambuGenericPrinter {
             Err(err) => Err(err),
         }
     }
+}
 
-    /// Shared by both `BambuV1Printer` and `BambuV2Printer` - same MQTT
+impl GenericPrinter for BambuPrinter {
-    /// gcode-injection mechanism regardless of protocol generation. Real
+    fn base(&self) -> &PrinterBase {
-    /// version would publish
+        &self.base
-    /// `{"print":{"command":"gcode_line","param":"M106 P1 S<pwm>"}}` to
-    /// `device/{sn}/request` over the MQTTS session.
-    async fn set_fan_speed_impl(&mut self, percent: u8) -> Result<(), PrinterError> {
-        let pwm = super::percent_to_pwm(percent);
-        println!("[{}] sending gcode: M106 P1 S{pwm}", self.base.name);
-        Ok(())
     }
 
-    /// Shared "connect" logic both V1 and V2 delegate to - the real
+    /// Settles `self.version` - forced directly if `preference` says so,
-    /// version would open the MQTTS session here. Still a stub, but no
+    /// otherwise (the real version) attempting an MQTT v5 CONNECT first
-    /// longer duplicated across two structs.
+    /// and falling back to v3.1.1 if the broker's CONNACK rejects that
-    async fn connect_impl(&mut self) -> Result<(), PrinterError> {
+    /// protocol version. No real MQTT client exists yet (still a stub, no
+    /// different from before), so `Auto` always "detects" v2 for now -
+    /// the fallback attempt itself is what's left to build.
+    async fn connect(&mut self) -> Result<(), PrinterError> {
         let mode = match &self.tls {
             BambuTls::BundledCa => "bundled Bambu CA",
             BambuTls::Custom(_) => "custom CA cert",
             BambuTls::Insecure => "no certificate verification",
         };
-        println!("[{}] connecting over MQTTS:8883 ({mode})", self.base.name);
+
+        let version = match self.preference {
+            BambuProtocolPreference::ForceV1 => BambuProtocolVersion::V1,
+            BambuProtocolPreference::ForceV2 => BambuProtocolVersion::V2,
+            BambuProtocolPreference::Auto => {
+                println!(
+                    "[{}] auto-detecting protocol: trying MQTT v5 first",
+                    self.base.name
+                );
+                BambuProtocolVersion::V2
+            }
+        };
+
+        println!(
+            "[{}] connecting over MQTTS:8883 ({mode}, {version:?})",
+            self.base.name
+        );
+        self.version = Some(version);
         Ok(())
     }
-}
 
-/// Older Bambu MQTT report schema (P1P, P1S, original X1 firmware).
+    async fn publish(&mut self, payload: String) -> Result<(), PrinterError> {
-/// No V1-only fields yet - add them here as you learn what differs.
+        // TODO: add publishing via MQTT
-pub struct BambuV1Printer {
+        println!(
-    generic: BambuGenericPrinter,
+            "[{}] publishing to device/{}/request: {payload}",
-}
+            self.base.name, self.sn
-
+        );
-impl BambuV1Printer {
+        Ok(())
-    pub fn new(id: &str, name: &str, host: &str, access_code: &str, sn: &str, tls: BambuTls) -> Self {
-        Self { generic: BambuGenericPrinter::new(id, name, host, access_code, sn, tls) }
     }
 
-    pub fn dispatch_gcode(&self, file_name: &str) {
+    async fn receive(&mut self, payload: String) -> Result<(), PrinterError> {
-        self.generic.dispatch_gcode(file_name)
+        // TODO: add MQTT response handling
-    }
+        Ok(())
-
-    pub fn test_tls_handshake(&self) -> anyhow::Result<()> {
-        self.generic.test_tls_handshake()
-    }
-
-    pub fn fetch_certificate(&self) -> anyhow::Result<Vec<u8>> {
-        self.generic.fetch_certificate()
-    }
-
-    pub fn ensure_trusted(&mut self, cert_dir: &Path) -> anyhow::Result<()> {
-        self.generic.ensure_trusted(cert_dir)
-    }
-}
-
-impl GenericPrinter for BambuV1Printer {
-    fn base(&self) -> &PrinterBase {
-        self.generic.base()
-    }
-
-    async fn connect(&mut self) -> Result<(), PrinterError> {
-        self.generic.connect_impl().await
     }
 
+    /// Same MQTT gcode-injection mechanism regardless of protocol
+    /// generation - just routed through `send_gcode_line` below instead of
+    /// its own separate stub, since that's genuinely the same operation.
     async fn set_fan_speed(&mut self, percent: u8) -> Result<(), PrinterError> {
-        self.generic.set_fan_speed_impl(percent).await
+        let pwm = super::percent_to_pwm(percent);
-    }
+        self.send_gcode_line(format!("M106 P1 S{pwm}")).await
-}
+    }
-
+
-/// Current-generation Bambu MQTT report schema (X1 Carbon/X1E, H2 series).
+    /// Real version FTPS-`PUT`s `data` to the printer's own `/cache/`
-/// No V2-only fields yet (e.g. AMS slot state) - add them here as you build
+    /// directory (that's storage the printer's firmware owns, same idea
-/// out real report parsing.
+    /// as PrusaLink's SD card), then publishes a `project_file` MQTT
-pub struct BambuV2Printer {
+    /// command referencing it by name so the printer actually starts
-    generic: BambuGenericPrinter,
+    /// printing it - two separate steps, both stubbed here as one line
-}
+    /// for now.
-
+    async fn upload_project_file(
-impl BambuV2Printer {
+        &mut self,
-    pub fn new(id: &str, name: &str, host: &str, access_code: &str, sn: &str, tls: BambuTls) -> Self {
+        file_name: String,
-        Self { generic: BambuGenericPrinter::new(id, name, host, access_code, sn, tls) }
+        data: Vec<u8>,
-    }
+    ) -> Result<(), PrinterError> {
-
+        println!(
-    pub fn dispatch_gcode(&self, file_name: &str) {
+            "[{}] FTPS upload {file_name} ({} bytes) to /cache/",
-        self.generic.dispatch_gcode(file_name)
+            self.base.name,
-    }
+            data.len()
-
+        );
-    pub fn test_tls_handshake(&self) -> anyhow::Result<()> {
+        Ok(())
-        self.generic.test_tls_handshake()
+    }
-    }
+
-
+    /// Builds the real JSON payload straight from continuum-schemas'
-    pub fn fetch_certificate(&self) -> anyhow::Result<Vec<u8>> {
+    /// `schemas/bambulab/{v1,v2}/request/print/gcode_line.schema.json` -
-        self.generic.fetch_certificate()
+    /// which one depends on `self.version`, settled by `connect()` above -
-    }
+    /// instead of a hand-written serde struct: `sequence_id` and the
-
+    /// `command` const get filled in by the schema itself, `param` is the
-    pub fn ensure_trusted(&mut self, cert_dir: &Path) -> anyhow::Result<()> {
+    /// one field we actually set. Only the actual MQTT publish to
-        self.generic.ensure_trusted(cert_dir)
+    /// `device/{sn}/request` is still a stub, same as `connect` above.
-    }
+    async fn send_gcode_line(&mut self, gcode_line: String) -> Result<(), PrinterError> {
-}
+        let version = self
-
+            .version
-impl GenericPrinter for BambuV2Printer {
+            .ok_or_else(|| PrinterError(format!("{} is not connected", self.base.name)))?;
-    fn base(&self) -> &PrinterBase {
+
-        self.generic.base()
+        let mut print =
-    }
+            continuum_schema_instance::build_instance_from_file(
-
+                &get_schema_for_command(
-    async fn connect(&mut self) -> Result<(), PrinterError> {
+                    version,
-        self.generic.connect_impl().await
+                    "print".into(),
-    }
+                    "gcode_line".into()
-
+                )
-    async fn set_fan_speed(&mut self, percent: u8) -> Result<(), PrinterError> {
+            )
-        self.generic.set_fan_speed_impl(percent).await
+                .map_err(|err| PrinterError(format!("failed to build gcode_line request: {err}")))?;
+        print["param"] = serde_json::Value::String(gcode_line);
+
+        let payload = serde_json::json!({ "print": print }).to_string();
+        self.publish(payload).await
     }
 }

src/printer/bambu_commands/mod.rs

@@ -49,6 +49,12 @@ pub struct CommandEnvelope {
 /// category can have more than one possible request shape - if that ever
 /// happens here, that variant's payload becomes its own small
 /// `#[serde(tag = "command")]` enum instead of a single struct.
+///
+/// The "print" category isn't a variant here at all: unlike `info`/
+/// `pushing`, it has many possible request shapes (`gcode_line`, `pause`,
+/// `resume`, ...) in continuum-schemas' own `oneOf`, so
+/// `bambu.rs`'s `send_gcode_line_impl` builds that one directly via
+/// `continuum-schema-instance` instead of adding it here.
 #[derive(serde::Serialize, Debug)]
 #[serde(rename_all = "snake_case")]
 pub enum BambuRequest {

src/printer/klipper.rs

@@ -29,6 +29,15 @@ impl GenericPrinter for KlipperPrinter {
         Ok(())
     }
 
+    async fn publish(&mut self, payload: String) -> Result<(), PrinterError> {
+        // TODO: add publishing via HTTP
+        Ok(())
+    }
+
+    async fn receive(&mut self, payload: String) -> Result<(), PrinterError> {
+        // TODO: add HTTP response handling
+        Ok(())
+    }
     /// OVERRIDE: Moonraker's own **hypothetical** native API, not gcode injection - no
     /// percent-to-PWM conversion needed since it already takes a
     /// percentage directly. Real version:
@@ -37,4 +46,20 @@ impl GenericPrinter for KlipperPrinter {
         println!("[{}] Moonraker: SET_FAN_SPEED SPEED={:.2}", self.base.name, percent as f32 / 100.0);
         Ok(())
     }
+
+    /// OVERRIDE: real version is a multipart `POST /server/files/upload`
+    /// with `data` as the file part - Moonraker stores it on the printer's
+    /// virtual SD card, same upload-then-start model as Bambu/PrusaLink.
+    async fn upload_project_file(&mut self, file_name: String, data: Vec<u8>) -> Result<(), PrinterError> {
+        println!("[{}] POST /server/files/upload {file_name} ({} bytes)", self.base.name, data.len());
+        Ok(())
+    }
+
+    /// OVERRIDE: Moonraker's gcode-script endpoint, one line per call - same
+    /// idea as `set_fan_speed`'s `SET_FAN_SPEED` call above, just with an
+    /// arbitrary line instead of a hardcoded one.
+    async fn send_gcode_line(&mut self, gcode_line: String) -> Result<(), PrinterError> {
+        println!("[{}] POST /printer/gcode/script?script={gcode_line}", self.base.name);
+        Ok(())
+    }
 }

src/printer/marlin_serial.rs

@@ -0,0 +1,69 @@
+//! A held-open serial connection to Marlin/RepRap-family firmware - usable
+//! by any printer connected over a raw serial port, since there's no
+//! printer-side storage to bulk-upload to the way there is for Bambu/
+//! PrusaLink/Klipper (see `prusa.rs`'s `PrusaSerialPrinter`).
+//!
+//! Marlin only ever buffers a handful of commands at once, so lines have
+//! to be paced by its own "ok" acknowledgment - send faster than it acks
+//! and you overrun that buffer, you don't just queue up harmlessly. That
+//! write-a-line/wait-for-"ok" pattern is the one new idea here. Splitting
+//! the connection into a read half and a write half so both can be used at
+//! once isn't new - `uplink/mod.rs` already does the same thing
+//! (`ws_stream.split()`) for the WebSocket to `continuum-backend`.
+//!
+//! The connection has to stay open across many `send_line` calls, not
+//! reopen per line: opening/closing per line would be wasteful, and on
+//! Arduino-based boards toggling the serial line's DTR signal (which
+//! opening the port does) resets the printer.
+
+use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader, Lines, ReadHalf, WriteHalf};
+use tokio_serial::{SerialPortBuilderExt, SerialStream};
+
+use super::PrinterError;
+
+pub struct MarlinSerialConnection {
+    write_half: WriteHalf<SerialStream>,
+    lines_in: Lines<BufReader<ReadHalf<SerialStream>>>,
+}
+
+impl MarlinSerialConnection {
+    /// Opens `port` (a serial device path - e.g. `/dev/ttyACM0` on Linux) at
+    /// `baud_rate`.
+    pub async fn open(port: &str, baud_rate: u32) -> Result<Self, PrinterError> {
+        let stream = tokio_serial::new(port, baud_rate)
+            .open_native_async()
+            .map_err(|err| PrinterError(format!("failed to open {port}: {err}")))?;
+
+        // Same shape as `ws_stream.split()` in uplink/mod.rs: one
+        // connection, used for writing gcode out and reading
+        // acknowledgments back at the same time.
+        let (read_half, write_half) = tokio::io::split(stream);
+        let lines_in = BufReader::new(read_half).lines();
+
+        Ok(Self { write_half, lines_in })
+    }
+
+    /// Sends one gcode line and waits for Marlin's "ok" before returning.
+    pub async fn send_line(&mut self, line: &str) -> Result<(), PrinterError> {
+        self.write_half
+            .write_all(format!("{line}\n").as_bytes())
+            .await
+            .map_err(|err| PrinterError(format!("write failed: {err}")))?;
+
+        // Marlin also sends unsolicited lines between commands
+        // (temperature reports, "echo:" messages) - keep reading until the
+        // real "ok" shows up instead of treating the first response as it.
+        loop {
+            let response = self
+                .lines_in
+                .next_line()
+                .await
+                .map_err(|err| PrinterError(format!("read failed: {err}")))?
+                .ok_or_else(|| PrinterError("serial connection closed".into()))?;
+
+            if response.starts_with("ok") {
+                return Ok(());
+            }
+        }
+    }
+}

src/printer/mod.rs

@@ -2,12 +2,10 @@
 //! `GenericPrinter -> BambuV1/BambuV2/PrusaLink/PrusaSerial/Klipper`-style
 //! inheritance, since Rust structs can't `extend` each other.
 //!
-//! Bambu goes one level deeper than the others: `bambu.rs` has
+//! Bambu is a single `BambuPrinter` type, not a per-version split: which
-//! `BambuGenericPrinter` (fields + behavior every Bambu printer shares -
+//! MQTT/BambuMQTT protocol generation (v1 vs v2) a given printer uses is
-//! access code, CA trust, the TLS handshake test/fetch) which
+//! something `connect()` discovers (or is told to force), not something
-//! `BambuV1Printer`/`BambuV2Printer` each *have* one of, mirroring the
+//! config picks a *type* for - see `bambu.rs`'s doc comment.
-//! `GenericPrinter -> BambuGenericPrinter -> BambuV1/V2` chain this project
-//! actually wanted from the start - see that file's doc comment.
 //!
 //! Three pieces, each doing one job an OOP base class would normally do:
 //!
@@ -31,9 +29,10 @@
 mod bambu;
 mod bambu_commands;
 mod klipper;
+mod marlin_serial;
 mod prusa;
 
-pub use bambu::{BambuGenericPrinter, BambuTls, BambuV1Printer, BambuV2Printer};
+pub use bambu::{BambuPrinter, BambuProtocolPreference, BambuProtocolVersion, BambuTls};
 pub use bambu_commands::{
     AmsState, AmsTray, AmsUnit, BambuReport, BambuRequest, CommandEnvelope, EmptyTray, GetVersionRequest,
     GetVersionResponse, LoadedTray, PrintReport, PushallRequest, XcamSettings,
@@ -72,12 +71,34 @@ pub trait GenericPrinter {
     /// into the multi-threaded daemon - safe to ignore for now.
     async fn connect(&mut self) -> Result<(), PrinterError>;
 
+
+    async fn publish(&mut self, payload: String) -> Result<(), PrinterError>;
+    async fn receive(&mut self, payload: String) -> Result<(), PrinterError>;
+
     /// REQUIRED, no default body: `percent` is 0-100, but how it actually
     /// gets sent - an MQTT gcode-injection command, a REST call, raw bytes
     /// on a serial port - is different for every vendor, same as
     /// `connect()`.
     async fn set_fan_speed(&mut self, percent: u8) -> Result<(), PrinterError>;
 
+    /// REQUIRED, no default body: takes the *whole file* already in memory
+    /// (`data`), not a path - whatever called this already had to download
+    /// it from the S3 URL the cloud handed over, so there'd be nothing on
+    /// disk to point a path at anyway. Each vendor does something quite
+    /// different with `data`: Bambu/PrusaLink/Klipper each do one bulk
+    /// transfer to storage the printer's own firmware owns; PrusaSerial
+    /// has no such storage at all - see that impl's doc comment.
+    async fn upload_project_file(&mut self, file_name: String, data: Vec<u8>) -> Result<(), PrinterError>;
+
+    /// REQUIRED, no default body: sends exactly *one* gcode line, using
+    /// whatever single-command mechanism this vendor has (an MQTT
+    /// `gcode_line` publish for Bambu, an HTTP command-injection endpoint
+    /// for PrusaLink/Klipper, a raw write over the port for PrusaSerial).
+    /// `upload_gcode` below is the generic driver that calls this once per
+    /// line for a whole file - this method is where each vendor's actual
+    /// difference lives, same division of labor as every other method here.
+    async fn send_gcode_line(&mut self, gcode_line: String) -> Result<(), PrinterError>;
+
     /// OPTIONAL: a default body every printer gets for free unless it
     /// writes its own. None of ours do below, so all three vendors share
     /// this exact implementation - the trait-method equivalent of
@@ -100,8 +121,7 @@ fn percent_to_pwm(percent: u8) -> u8 {
 
 /// The closed set of printer kinds this fleet can talk to.
 pub enum PrinterHandle {
-    BambuV1(BambuV1Printer),
+    Bambu(BambuPrinter),
-    BambuV2(BambuV2Printer),
     PrusaLink(PrusaLinkPrinter),
     PrusaSerial(PrusaSerialPrinter),
     Klipper(KlipperPrinter),
@@ -114,8 +134,7 @@ pub enum PrinterHandle {
 impl GenericPrinter for PrinterHandle {
     fn base(&self) -> &PrinterBase {
         match self {
-            PrinterHandle::BambuV1(p) => p.base(),
+            PrinterHandle::Bambu(p) => p.base(),
-            PrinterHandle::BambuV2(p) => p.base(),
             PrinterHandle::PrusaLink(p) => p.base(),
             PrinterHandle::PrusaSerial(p) => p.base(),
             PrinterHandle::Klipper(p) => p.base(),
@@ -124,21 +143,82 @@ impl GenericPrinter for PrinterHandle {
 
     async fn connect(&mut self) -> Result<(), PrinterError> {
         match self {
-            PrinterHandle::BambuV1(p) => p.connect().await,
+            PrinterHandle::Bambu(p) => p.connect().await,
-            PrinterHandle::BambuV2(p) => p.connect().await,
             PrinterHandle::PrusaLink(p) => p.connect().await,
             PrinterHandle::PrusaSerial(p) => p.connect().await,
             PrinterHandle::Klipper(p) => p.connect().await,
         }
     }
 
+    async fn publish(&mut self, payload: String) -> Result<(), PrinterError> {
+        match self {
+            PrinterHandle::Bambu(p) => p.publish(payload).await,
+            PrinterHandle::PrusaLink(p) => p.publish(payload).await,
+            PrinterHandle::PrusaSerial(p) => p.publish(payload).await,
+            PrinterHandle::Klipper(p) => p.publish(payload).await,
+        }
+    }
+
+    async fn receive(&mut self, payload: String) -> Result<(), PrinterError> {
+        match self {
+            PrinterHandle::Bambu(p) => p.receive(payload).await,
+            PrinterHandle::PrusaLink(p) => p.receive(payload).await,
+            PrinterHandle::PrusaSerial(p) => p.receive(payload).await,
+            PrinterHandle::Klipper(p) => p.receive(payload).await,
+        }
+    }
+
     async fn set_fan_speed(&mut self, percent: u8) -> Result<(), PrinterError> {
         match self {
-            PrinterHandle::BambuV1(p) => p.set_fan_speed(percent).await,
+            PrinterHandle::Bambu(p) => p.set_fan_speed(percent).await,
-            PrinterHandle::BambuV2(p) => p.set_fan_speed(percent).await,
             PrinterHandle::PrusaLink(p) => p.set_fan_speed(percent).await,
             PrinterHandle::PrusaSerial(p) => p.set_fan_speed(percent).await,
             PrinterHandle::Klipper(p) => p.set_fan_speed(percent).await,
         }
     }
+
+    async fn upload_project_file(&mut self, file_name: String, data: Vec<u8>) -> Result<(), PrinterError> {
+        match self {
+            PrinterHandle::Bambu(p) => p.upload_project_file(file_name, data).await,
+            PrinterHandle::PrusaLink(p) => p.upload_project_file(file_name, data).await,
+            PrinterHandle::PrusaSerial(p) => p.upload_project_file(file_name, data).await,
+            PrinterHandle::Klipper(p) => p.upload_project_file(file_name, data).await,
+        }
+    }
+
+    async fn send_gcode_line(&mut self, gcode_line: String) -> Result<(), PrinterError> {
+        match self {
+            PrinterHandle::Bambu(p) => p.send_gcode_line(gcode_line).await,
+            PrinterHandle::PrusaLink(p) => p.send_gcode_line(gcode_line).await,
+            PrinterHandle::PrusaSerial(p) => p.send_gcode_line(gcode_line).await,
+            PrinterHandle::Klipper(p) => p.send_gcode_line(gcode_line).await,
+        }
+    }
+}
+
+/// Splits `gcode` into lines and sends each one through `printer`'s own
+/// `send_gcode_line` - works for *any* vendor, not just serial ones, since
+/// Bambu/PrusaLink/Klipper each have their own single-line injection
+/// mechanism too (see each `send_gcode_line` impl). They just don't use
+/// this for `upload_project_file` - they have real file storage to bulk-
+/// upload to instead, which is a different, faster path than sending a
+/// whole file one line at a time.
+///
+/// `P: GenericPrinter` makes this a genuine Rust generic: one function
+/// body, compiled separately for whichever concrete printer type you call
+/// it with - like a TS function typed `<P extends GenericPrinter>`, except
+/// Rust generates real, separate machine code per type instead of erasing
+/// the type at compile time. Call it with any of the five printer structs,
+/// or with `&mut PrinterHandle` itself (it implements `GenericPrinter` too,
+/// via the delegation above).
+pub async fn upload_gcode<P: GenericPrinter>(printer: &mut P, gcode: &str) -> Result<(), PrinterError> {
+    for line in gcode.lines() {
+        let line = line.trim();
+        // Blank lines and full-line comments have nothing to send.
+        if line.is_empty() || line.starts_with(';') {
+            continue;
+        }
+        printer.send_gcode_line(line.to_string()).await?;
+    }
+    Ok(())
 }

src/printer/prusa.rs

@@ -29,6 +29,16 @@ impl GenericPrinter for PrusaLinkPrinter {
         Ok(())
     }
 
+    async fn publish(&mut self, payload: String) -> Result<(), PrinterError> {
+        // TODO: add publishing via HTTP
+        Ok(())
+    }
+
+    async fn receive(&mut self, payload: String) -> Result<(), PrinterError> {
+        // TODO: add HTTP response handling
+        Ok(())
+    }
+
     /// OVERRIDE: gcode via PrusaLink's command-injection endpoint - same
     /// underlying M106 as Bambu, reusing the shared percent->PWM
     /// conversion, but sent over HTTP instead of MQTT.
@@ -37,6 +47,22 @@ impl GenericPrinter for PrusaLinkPrinter {
         println!("[{}] POST /api/printer/command {{\"commands\":[\"M106 S{pwm}\"]}}", self.base.name);
         Ok(())
     }
+
+    /// OVERRIDE: real version is `PUT /api/v1/files/local/{file_name}` with
+    /// `data` as the request body - PrusaLink stores it on the printer's own
+    /// SD card, same "upload to storage the firmware owns" model as Bambu.
+    async fn upload_project_file(&mut self, file_name: String, data: Vec<u8>) -> Result<(), PrinterError> {
+        println!("[{}] PUT /api/v1/files/local/{file_name} ({} bytes)", self.base.name, data.len());
+        Ok(())
+    }
+
+    /// OVERRIDE: PrusaLink's command-injection endpoint, one line per call -
+    /// same endpoint `set_fan_speed` above already uses for M106, just with
+    /// an arbitrary line instead of a hardcoded one.
+    async fn send_gcode_line(&mut self, gcode_line: String) -> Result<(), PrinterError> {
+        println!("[{}] POST /api/printer/command {{\"commands\":[\"{gcode_line}\"]}}", self.base.name);
+        Ok(())
+    }
 }
 
 
@@ -44,14 +70,22 @@ impl GenericPrinter for PrusaLinkPrinter {
 
 pub struct PrusaSerialPrinter {
     base: PrinterBase,
-    pub com_port: i16,
+    pub port: String,
+    pub baud_rate: u32,
+    /// `None` until `connect()` succeeds - a real serial connection, not a
+    /// stub, so there's something to hold onto: unlike Bambu/PrusaLink/
+    /// Klipper's stubbed sessions, this one has to survive across many
+    /// `send_gcode_line` calls (see `marlin_serial.rs` for why).
+    connection: Option<super::marlin_serial::MarlinSerialConnection>,
 }
 
 impl PrusaSerialPrinter {
-    pub fn new(id: &str, name: &str, com_port: i16) -> Self {
+    pub fn new(id: &str, name: &str, port: &str, baud_rate: u32) -> Self {
         Self {
             base: PrinterBase { id: id.into(), name: name.into(), host: "127.0.0.1".to_string() },
-            com_port,
+            port: port.into(),
+            baud_rate,
+            connection: None,
         }
     }
 }
@@ -61,21 +95,55 @@ impl GenericPrinter for PrusaSerialPrinter {
         &self.base
     }
 
-    /// OVERRIDE: a fourth, again-different body - no network host at all,
+    /// OVERRIDE, and a real one (not a stub, unlike the other four vendors'
-    /// just a local serial port (real version: open the port, e.g. via the
+    /// `connect`): opens the port and keeps it, since serial has no
-    /// `serialport`/`tokio-serial` crate, and speak Prusa's G-code-over-
+    /// separate "session" concept to stub out - the open connection *is*
-    /// serial protocol).
+    /// the whole thing.
     async fn connect(&mut self) -> Result<(), PrinterError> {
-        println!("[{}] connecting over serial (COM{})", self.base.name, self.com_port);
+        println!("[{}] connecting over serial ({}, {} baud)", self.base.name, self.port, self.baud_rate);
+        self.connection = Some(super::marlin_serial::MarlinSerialConnection::open(&self.port, self.baud_rate).await?);
         Ok(())
     }
 
-    /// OVERRIDE: same gcode as PrusaLink (still M106, still the shared
+    async fn publish(&mut self, payload: String) -> Result<(), PrinterError> {
-    /// conversion), but written straight to the serial port instead of
+        // TODO: add publishing via serial
-    /// sent over HTTP - a third transport for the same underlying command.
-    async fn set_fan_speed(&mut self, percent: u8) -> Result<(), PrinterError> {
-        let pwm = super::percent_to_pwm(percent);
-        println!("[{}] writing to COM{}: M106 S{pwm}", self.base.name, self.com_port);
         Ok(())
     }
+
+    async fn receive(&mut self, payload: String) -> Result<(), PrinterError> {
+        // TODO: add Serial response handling
+        Ok(())
+    }
+    /// OVERRIDE: same gcode as PrusaLink (still M106, still the shared
+    /// conversion), but sent through `send_gcode_line` below instead of a
+    /// separate transport - serial only has the one way to talk to the
+    /// printer at all.
+    async fn set_fan_speed(&mut self, percent: u8) -> Result<(), PrinterError> {
+        let pwm = super::percent_to_pwm(percent);
+        self.send_gcode_line(format!("M106 S{pwm}")).await
+    }
+
+    /// OVERRIDE, but not just "a fourth transport" like the others above -
+    /// there's no printer-side storage to upload `data` to over a raw
+    /// serial connection at all, so this decodes it as gcode text and
+    /// streams it through `send_gcode_line` one line at a time via the
+    /// generic `upload_gcode` driver, instead of one bulk write like
+    /// Bambu/PrusaLink/Klipper.
+    async fn upload_project_file(&mut self, file_name: String, data: Vec<u8>) -> Result<(), PrinterError> {
+        let gcode = String::from_utf8(data)
+            .map_err(|_| PrinterError(format!("{file_name} is not valid UTF-8 gcode")))?;
+        println!("[{}] streaming {file_name} over {}", self.base.name, self.port);
+        super::upload_gcode(self, &gcode).await
+    }
+
+    /// OVERRIDE, and the real implementation, not a stub: writes `gcode_line`
+    /// to the already-open port and waits for Marlin's "ok" - see
+    /// `marlin_serial.rs` for why that wait matters.
+    async fn send_gcode_line(&mut self, gcode_line: String) -> Result<(), PrinterError> {
+        let connection = self
+            .connection
+            .as_mut()
+            .ok_or_else(|| PrinterError(format!("{} is not connected", self.base.name)))?;
+        connection.send_line(&gcode_line).await
+    }
 }