feat(cbuffer): add rdc cbuffer command and cbuffer_raw export (#224)

docs-astro/src/data/commands.json

@@ -201,6 +201,12 @@
           "help": "Export buffer raw data.",
           "usage": "rdc buffer <ID> [-o PATH] [--raw]"
         },
+        {
+          "name": "cbuffer",
+          "id": "cbuffer",
+          "help": "Decode a constant buffer to JSON or export its raw bytes.",
+          "usage": "rdc cbuffer [EID] [--stage CHOICE] [--set INTEGER] [--binding INTEGER] [--json] [--raw] [-o PATH]"
+        },
         {
           "name": "rt",
           "id": "rt",

openspec/changes/2026-05-15-issue-224-cbuffer-export/proposal.md

@@ -0,0 +1,95 @@
+# OpenSpec: issue-224-cbuffer-export
+
+## Summary
+
+Expose `rdc cbuffer` as a first-class CLI command with decoded JSON output and optional
+raw binary export (`--raw`).
+
+## Context and Motivation
+
+OpenSpec phase2-buffer-decode (archived 2026-02-19) originally planned three CLI commands:
+`rdc cbuffer`, `rdc vbuffer`, and `rdc ibuffer`. The daemon handler `cbuffer_decode` and its
+VFS route shipped in that phase. The CLI half — `rdc cbuffer` — was never implemented.
+This change completes that unshipped work.
+
+GitHub issue #224 (part 2) tracks the gap. Users who rely on `rdc buffer --raw` for raw bytes
+have no ergonomic path to decoded constant-buffer variables without constructing VFS paths
+manually.
+
+**Scope note:** The archived phase2-buffer-decode plan envisioned `rdc cbuffer` as a thin VFS
+`cat` wrapper; this change implements a richer direct command with decoded JSON output, a new
+`cbuffer_raw` handler, and a new VFS `leaf_bin` route — reviewers should not expect a pure VFS
+wrapper.
+
+## Design
+
+### New command: `rdc cbuffer`
+
+```
+rdc cbuffer [EID] --stage [vs|hs|ds|gs|ps|cs] --set N --binding N [--json] [--raw -o file.bin]
+```
+
+- `EID`: optional; resolved via `complete_eid` if omitted (matches existing `rdc buffer` pattern).
+- `--stage`: default `ps`.
+- `--set`: default `0`.
+- `--binding`: default `0`.
+- `--json`: emit decoded variables as JSON (default output mode).
+- `--raw -o file.bin`: export the raw constant-buffer bytes to a file.
+
+### Decoded path
+
+Calls the existing `cbuffer_decode` daemon handler unchanged.  Returns
+`{"eid", "set", "binding", "variables": [{name, type, value}, ...]}` and writes it via
+`write_json`.  No daemon changes required for this path.
+
+### Raw path
+
+Adds a new `cbuffer_raw` daemon handler in `handlers/buffer.py`.  The handler repeats the
+reflection lookup (`fixedBindSetOrSpace` / `fixedBindNumber`), obtains
+`GetConstantBlock(...).descriptor`, calls `controller.GetBufferData(resource, byteOffset,
+byteSize)`, writes the bytes to `state.temp_dir/cbuffer_<eid>_<set>_<binding>.bin`, and
+returns `{"path", "size"}`.
+
+The handler is exposed as a VFS `leaf_bin` route at
+`/draws/<eid>/cbuffer/<set>/<binding>/data` in `vfs/router.py`, mirroring the way `buf_raw`
+is wired at `/buffers/<id>/data`.  The CLI calls
+`_export_vfs_path(f"/draws/{eid}/cbuffer/{set}/{binding}/data", output, raw)` (from
+`commands/export.py`), which follows the same `vfs_ls` + `resolve_path` → `_deliver_binary`
+flow used by `rdc buffer --raw`.  `_deliver_binary` (vfs.py:216) is the final delivery
+step — it calls `call(match.handler, match.args)` through the VFS resolve layer; it is NOT
+a standalone "call handler, get path, write bytes" helper invoked directly.
+
+The `hasattr(pipe_state, "GetConstantBlock")` guard present in `cbuffer_decode` is preserved
+in `cbuffer_raw` for RenderDoc version drift safety.
+
+### New source file
+
+`src/rdc/commands/cbuffer.py` — registered in `src/rdc/cli.py` adjacent to `buffer_cmd`
+(~line 138).
+
+## Risks
+
+### Non-buffer-backed constant buffers
+
+`ConstantBlock.bufferBacked == False` for push constants (Vulkan) and D3D12 root constants.
+These have no backing buffer resource; `GetBufferData` would operate on a null resource.
+
+Defined behavior: `--raw` MUST return a JSON-RPC error with a descriptive message
+(e.g. `"cbuffer is not buffer-backed (push constant or root constant)"`) rather than crash
+or silently return zero bytes.  Decoded `--json` output is unaffected and continues to work
+via `GetCBufferVariableContents`.
+
+### D3D12 root constants / register spaces
+
+The `fixedBindSetOrSpace` / `fixedBindNumber` mapping for D3D12 root constants cannot be
+verified on this Linux development machine.  The Vulkan (vkcube) integration test exercises
+the buffer-backed path only.  Behavior on D3D12 root-constant captures is verified by
+reporter @Misaka-Mikoto-Tech on real D3D12 hardware after the PR ships.
+
+### `_extract_value` type coverage (optional improvement)
+
+The existing `_extract_value` helper (`buffer.py:163-173`) handles only `f32v` members;
+integer and unsigned-integer shader variables degrade silently.  `_flatten_shader_var`
+in `handlers/_helpers.py` already handles `u32v`/`s32v` and is used by `shader_constants`.
+Switching `cbuffer_decode` to use `_flatten_shader_var` is an optional polish step; it does
+not block this change but is tracked as a separate optional task.

openspec/changes/2026-05-15-issue-224-cbuffer-export/specs/daemon/spec.md

@@ -0,0 +1,40 @@
+## ADDED Requirements
+
+### Requirement: Constant Buffer Raw Export
+The daemon SHALL expose a handler to export raw constant-buffer bytes to a temporary file.
+
+#### Scenario: Export buffer-backed constant buffer
+- **WHEN** client requests `cbuffer_raw` with `eid`, `set`, `binding`, and `stage`
+- **THEN** daemon resolves the constant block via `fixedBindSetOrSpace` / `fixedBindNumber`,
+  calls `GetBufferData(resource, byteOffset, byteSize)`, writes bytes to
+  `state.temp_dir/cbuffer_<eid>_<set>_<binding>.bin`, and returns `{"path", "size"}`.
+- **IF** `state.adapter` is None, return error -32002.
+- **IF** `eid` is not a valid draw event, return error.
+
+#### Scenario: Reject non-buffer-backed constant buffer
+- **WHEN** client requests `cbuffer_raw` and `ConstantBlock.bufferBacked == False`
+- **THEN** daemon returns a JSON-RPC error with a message indicating the cbuffer is not
+  buffer-backed (push constant or root constant) and does not write any file.
+
+#### Scenario: RenderDoc version guard
+- **WHEN** `GetConstantBlock` is not present on the pipeline state object
+- **THEN** daemon returns an error indicating the API is unavailable on this RenderDoc version.
+
+### Requirement: Constant Buffer CLI Command
+The CLI SHALL expose `rdc cbuffer` as a first-class command for decoded and raw export.
+
+#### Scenario: Decoded JSON output
+- **WHEN** user runs `rdc cbuffer [EID] --stage STAGE --set N --binding N`
+- **THEN** CLI calls `cbuffer_decode` handler and writes the JSON response to stdout.
+- **IF** `EID` is omitted, CLI resolves it via `complete_eid`.
+
+#### Scenario: Raw binary export
+- **WHEN** user runs `rdc cbuffer [EID] --raw -o FILE`
+- **THEN** CLI resolves the VFS path `/draws/<eid>/cbuffer/<set>/<binding>/data` via
+  `_export_vfs_path` (vfs_ls + resolve_path → _deliver_binary), exactly mirroring how
+  `rdc buffer --raw` uses `/buffers/<id>/data`, and writes bytes to `FILE`.
+- **IF** `-o` is not specified alongside `--raw`, CLI exits with a usage error.
+
+#### Scenario: No active session
+- **WHEN** user runs `rdc cbuffer` and no daemon session is active
+- **THEN** CLI exits with code 1 and prints an error message to stderr.

openspec/changes/2026-05-15-issue-224-cbuffer-export/tasks.md

@@ -0,0 +1,47 @@
+# Tasks: issue-224-cbuffer-export
+
+## Phase A: Mock API additions
+
+- [ ] Add `GetBufferData` stub to `mock_renderdoc.py` (anchor: ~line 1356 `GetConstantBlock`).
+  The happy-path test must give the mock `Descriptor` (returned via
+  `GetConstantBlock(...).descriptor`) a non-null `resource`, `byteOffset`, and `byteSize` —
+  these are the fields the raw-path handler keys off (`buffer.py:143-147`).
+- [ ] Add `bufferBacked=False` variant to the mock `ConstantBlock` for the push-constant
+  clean-error test; this stubs the reflection-level field used to reject non-buffer-backed
+  cbuffers before `GetBufferData` is called.
+
+## Phase B: `cbuffer_raw` daemon handler (tests first)
+
+- [ ] Extend `tests/unit/test_buffer_decode.py` with `cbuffer_raw` cases (happy path,
+  `bufferBacked=False` error, no-adapter guard)
+- [ ] Implement `cbuffer_raw` handler in `src/rdc/handlers/buffer.py` (~line 370,
+  adjacent to `HANDLERS` dict)
+- [ ] Register `cbuffer_raw` in `HANDLERS`
+- [ ] Add VFS `leaf_bin` route for `/draws/<eid>/cbuffer/<set>/<binding>/data` →
+  `cbuffer_raw` in `src/rdc/vfs/router.py`, mirroring
+  `/buffers/<id>/data` → `buf_raw` (router.py:184)
+- [ ] Verify handler unit tests pass
+
+## Phase C: `rdc cbuffer` CLI command (tests first)
+
+- [ ] Write `tests/unit/test_cbuffer_commands.py` (JSON mode, `--raw -o`, no-session error,
+  `complete_eid` fallback, `--raw` without `-o` usage error)
+- [ ] Implement `src/rdc/commands/cbuffer.py`; raw path calls
+  `_export_vfs_path(f"/draws/{eid}/cbuffer/{set}/{binding}/data", output, raw)` from
+  `commands/export.py` — no direct handler dispatch
+- [ ] Register `cbuffer_cmd` in `src/rdc/cli.py` (~line 138, adjacent to `buffer_cmd`)
+- [ ] Verify CLI unit tests pass
+
+## Phase D: Integration + verification
+
+- [ ] Extend `tests/integration/test_daemon_handlers_real.py` with `@pytest.mark.gpu`
+  tests for `cbuffer_raw` (Vulkan vkcube capture)
+- [ ] Run `pixi run lint && pixi run test` — all pass, coverage ≥ 80% for new paths
+- [ ] Run GPU integration tests against real capture — pass
+- [ ] Code review
+
+## Phase E: Optional polish (non-blocking)
+
+- [ ] Switch `cbuffer_decode` to use `_flatten_shader_var` from `handlers/_helpers.py`
+  instead of `_extract_value` to fix int/uint member degradation
+- [ ] Extend `test_buffer_decode.py` with int/uint value assertions

openspec/changes/2026-05-15-issue-224-cbuffer-export/test-plan.md

@@ -0,0 +1,78 @@
+# Test Plan: issue-224-cbuffer-export
+
+## Scope
+
+### In scope
+- New daemon handler `cbuffer_raw` (unit + integration)
+- New CLI command `rdc cbuffer` (unit: JSON mode, raw mode, error paths)
+- `bufferBacked == False` error path for `cbuffer_raw`
+- Optional: `_extract_value` int/uint coverage in `test_buffer_decode.py`
+
+### Out of scope
+- Existing `cbuffer_decode` handler correctness (covered by prior test suite)
+- `rdc vbuffer` / `rdc ibuffer` (separate issue)
+- D3D12 root-constant register-space mapping (cannot run on this Linux box; deferred to reporter verification)
+
+## Test Matrix
+
+| Layer | Test Type | File |
+|-------|-----------|------|
+| Unit | `cbuffer_raw` handler (mock) | `tests/unit/test_buffer_decode.py` (extend) |
+| Unit | `rdc cbuffer` CLI command | `tests/unit/test_cbuffer_commands.py` (new) |
+| Integration | real capture decoded + raw | `tests/integration/test_daemon_handlers_real.py` (extend) |
+
+## Cases
+
+### `cbuffer_raw` handler (extend `test_buffer_decode.py`)
+
+- **Happy path**: mock `GetConstantBlock` returns a buffer-backed descriptor (`bufferBacked=True`,
+  known `byteOffset`/`byteSize`); mock `GetBufferData` returns 16 known bytes.
+  Assert response contains `{"path": "...", "size": 16}` and the temp file exists with the
+  expected bytes.
+- **bufferBacked=False**: mock `GetConstantBlock` returns `bufferBacked=False`.
+  Assert the handler returns a JSON-RPC error (code -32602 or equivalent) with a message
+  containing `"not buffer-backed"`.  Assert no temp file is created.
+- **No adapter**: `state.adapter is None` → assert error -32002 (standard no-adapter guard).
+- **Missing eid**: invalid `eid` → assert error from `SetFrameEvent`.
+
+Mock anchor: `mock_renderdoc.py` `GetConstantBlock` (~line 1356), `GetBufferData`.
+
+### `rdc cbuffer` CLI command (new `test_cbuffer_commands.py`)
+
+Mirror structure of `tests/unit/test_mesh_commands.py` (monkeypatch `rdc.commands.cbuffer.call`).
+
+- **JSON mode (default)**: monkeypatch `call("cbuffer_decode", ...)` returns
+  `{"eid": 10, "set": 0, "binding": 0, "variables": [{"name": "mvp", "type": "mat4", "value": [...]}]}`.
+  Invoke `rdc cbuffer 10 --stage ps --set 0 --binding 0`.
+  Assert exit code 0, stdout is valid JSON matching the payload.
+- **`--json` explicit flag**: same as above with `--json` flag; assert identical output.
+- **`--raw -o file.bin`**: monkeypatch `call("cbuffer_raw", ...)` returns `{"path": "/tmp/cbuffer_10_0_0.bin", "size": 16}`;
+  monkeypatch binary delivery (`_deliver_binary` / `fetch_remote_file`).
+  Assert exit code 0, output file contains the expected bytes.
+- **No session**: `call` raises connection error → assert exit code 1, message on stderr.
+- **`--raw` without `-o`**: assert exit code non-zero with usage error on stderr.
+- **EID omitted**: monkeypatch `complete_eid` returns `42`; assert the handler is called with `eid=42`.
+
+### Integration (`test_daemon_handlers_real.py`, `@pytest.mark.gpu`)
+
+Extend analogous to `test_cbuffer_decode_returns_data` (~line 1965), using a vkcube/Vulkan
+capture with a known draw EID that has a buffer-backed cbuffer.
+
+- **`cbuffer_raw` returns file**: call `cbuffer_raw` with valid `eid`/`set`/`binding`.
+  Assert response contains `path` and `size > 0`; assert temp file exists and `size` matches
+  `os.path.getsize(path)`.
+- **`cbuffer_decode` + `cbuffer_raw` size agreement**: decoded `variables` total byte footprint
+  is consistent with the raw `size`.
+
+## Assertions (all tests)
+
+- Exit code 0 on success, non-zero on error.
+- JSON output: valid JSON, `variables` array present for decoded mode.
+- Raw output: file written at `-o` path, byte count matches `size` from handler.
+- Error messages go to stderr; stdout is empty on error.
+- `bufferBacked=False` produces an error message containing `"not buffer-backed"` (case-insensitive).
+
+## Coverage Gate
+
+CI enforces ≥ 80% line coverage for `src/rdc/commands/cbuffer.py` and the new
+`cbuffer_raw` code path in `src/rdc/handlers/buffer.py`.

scripts/gen-commands.py

@@ -35,7 +35,7 @@
         "search", "passes", "pass", "unused-targets",
     ]),
     ("Export", "export", None, [
-        "texture", "buffer", "rt", "mesh", "snapshot",
+        "texture", "buffer", "cbuffer", "rt", "mesh", "snapshot",
     ]),
     ("Pixel & Debug", "pixel-debug", None, [
         "pixel", "pick-pixel", "tex-stats",

src/rdc/_skills/references/commands-quick-ref.md

@@ -282,6 +282,27 @@ Output VFS leaf node content.
 | `--raw` | Force raw output even on TTY | flag |  |
 | `-o, --output` | Write binary output to file | path |  |
 
+## `rdc cbuffer`
+
+Decode a constant buffer to JSON or export its raw bytes.
+
+**Arguments:**
+
+| Name | Type | Required |
+|------|------|----------|
+| `eid` | integer | no |
+
+**Options:**
+
+| Flag | Help | Type | Default |
+|------|------|------|---------|
+| `--stage` | Shader stage (default: ps) | choice | ps |
+| `--set` | Vulkan: descriptor set. D3D12: register space. | integer | 0 |
+| `--binding` | Vulkan: binding. D3D12: shader register (bN). | integer | 0 |
+| `--json` | JSON output (default) | flag |  |
+| `--raw` | Export raw constant-buffer bytes | flag |  |
+| `-o, --output` | Write raw bytes to file | path |  |
+
 ## `rdc close`
 
 Close daemon-backed session.

src/rdc/cli.py

@@ -28,6 +28,7 @@
     sections_cmd,
     thumbnail_cmd,
 )
+from rdc.commands.cbuffer import cbuffer_cmd
 from rdc.commands.completion import completion_cmd
 from rdc.commands.counters import counters_cmd
 from rdc.commands.debug import debug_group
@@ -136,6 +137,7 @@ def entry() -> None:
 main.add_command(texture_cmd, name="texture")
 main.add_command(rt_cmd, name="rt")
 main.add_command(buffer_cmd, name="buffer")
+main.add_command(cbuffer_cmd, name="cbuffer")
 main.add_command(mesh_cmd, name="mesh")
 main.add_command(search_cmd, name="search")
 main.add_command(usage_cmd, name="usage")

src/rdc/commands/cbuffer.py

@@ -0,0 +1,61 @@
+"""rdc cbuffer -- decoded or raw constant-buffer export."""
+
+from __future__ import annotations
+
+from typing import Any
+
+import click
+
+from rdc.commands._helpers import call, complete_eid
+from rdc.commands.export import _export_vfs_path
+from rdc.formatters.json_fmt import write_json
+
+
+@click.command("cbuffer")
+@click.argument("eid", type=int, required=False, default=None, shell_complete=complete_eid)
+@click.option(
+    "--stage",
+    type=click.Choice(["vs", "hs", "ds", "gs", "ps", "cs"]),
+    default="ps",
+    help="Shader stage (default: ps)",
+)
+@click.option(
+    "--set",
+    "cb_set",
+    type=int,
+    default=0,
+    help="Vulkan: descriptor set. D3D12: register space.",
+)
+@click.option(
+    "--binding",
+    type=int,
+    default=0,
+    help="Vulkan: binding. D3D12: shader register (bN).",
+)
+@click.option("--json", "use_json", is_flag=True, help="JSON output (default)")
+@click.option("--raw", is_flag=True, help="Export raw constant-buffer bytes")
+@click.option("-o", "--output", type=click.Path(), default=None, help="Write raw bytes to file")
+def cbuffer_cmd(
+    eid: int | None,
+    stage: str,
+    cb_set: int,
+    binding: int,
+    use_json: bool,
+    raw: bool,
+    output: str | None,
+) -> None:
+    """Decode a constant buffer to JSON or export its raw bytes."""
+    if raw:
+        if output is None:
+            raise click.UsageError("-o/--output is required with --raw")
+        if eid is None:
+            raise click.UsageError("EID is required with --raw")
+        _export_vfs_path(f"/draws/{eid}/cbuffer/{cb_set}/{binding}/data", output, raw)
+        return
+
+    del use_json
+    params: dict[str, Any] = {"stage": stage, "set": cb_set, "binding": binding}
+    if eid is not None:
+        params["eid"] = eid
+    result = call("cbuffer_decode", params)
+    write_json(result)