diff --git a/bin/soongdbg b/bin/soongdbg
new file mode 100755
index 0000000..132a0f0
--- /dev/null
+++ b/bin/soongdbg
@@ -0,0 +1,313 @@
+#!/usr/bin/env python3
+
+import argparse
+import fnmatch
+import json
+import os
+import pathlib
+import types
+import sys
+
+
+class Graph:
+    def __init__(self, modules):
+        def get_or_make_node(dictionary, id, module):
+            node = dictionary.get(id)
+            if node:
+                if module and not node.module:
+                    node.module = module
+                return node
+            node = Node(id, module)
+            dictionary[id] = node
+            return node
+        self.nodes = dict()
+        for module in modules.values():
+            node = get_or_make_node(self.nodes, module.id, module)
+            for d in module.deps:
+                dep = get_or_make_node(self.nodes, d.id, None)
+                node.deps.add(dep)
+                dep.rdeps.add(node)
+
+    def find_paths(self, id1, id2):
+        # Throws KeyError if one of the names isn't found
+        def recurse(node1, node2, visited):
+            result = set()
+            for dep in node1.rdeps:
+                if dep == node2:
+                    result.add(node2)
+                if dep not in visited:
+                    visited.add(dep)
+                    found = recurse(dep, node2, visited)
+                    if found:
+                        result |= found
+                        result.add(dep)
+            return result
+        node1 = self.nodes[id1]
+        node2 = self.nodes[id2]
+        # Take either direction
+        p = recurse(node1, node2, set())
+        if p:
+            p.add(node1)
+            return p
+        p = recurse(node2, node1, set())
+        p.add(node2)
+        return p
+
+
+class Node:
+    def __init__(self, id, module):
+        self.id = id
+        self.module = module
+        self.deps = set()
+        self.rdeps = set()
+
+
+PROVIDERS = [
+    "android/soong/java.JarJarProviderData",
+    "android/soong/java.BaseJarJarProviderData",
+]
+
+
+def format_node_label(node):
+    if not node.module:
+        return node.id
+    if node.module.debug:
+        module_debug = f"<tr><td>{node.module.debug}</td></tr>"
+    else:
+        module_debug = ""
+
+    result = (f"<<table border=\"0\" cellborder=\"0\" cellspacing=\"0\" cellpadding=\"0\">"
+            + f"<tr><td><b>{node.module.name}</b></td></tr>"
+            + module_debug
+            + f"<tr><td>{node.module.type}</td></tr>")
+    for p in node.module.providers:
+        if p.type in PROVIDERS:
+            result += "<tr><td><font color=\"#666666\">" + format_provider(p) + "</font></td></tr>"
+    result += "</table>>"
+    return result
+
+
+def format_source_pos(file, lineno):
+    result = file
+    if lineno:
+        result += f":{lineno}"
+    return result
+
+
+STRIP_TYPE_PREFIXES = [
+    "android/soong/",
+    "github.com/google/",
+]
+
+
+def format_provider(provider):
+    result = ""
+    for prefix in STRIP_TYPE_PREFIXES:
+        if provider.type.startswith(prefix):
+            result = provider.type[len(prefix):]
+            break
+    if not result:
+        result = provider.type
+    if True and provider.debug:
+        result += " (" + provider.debug + ")"
+    return result
+
+
+def load_soong_debug():
+    # Read the json
+    try:
+        with open(SOONG_DEBUG_DATA_FILENAME) as f:
+            info = json.load(f, object_hook=lambda d: types.SimpleNamespace(**d))
+    except IOError:
+        sys.stderr.write(f"error: Unable to open {SOONG_DEBUG_DATA_FILENAME}. Make sure you have"
+                         + " built with GENERATE_SOONG_DEBUG.\n")
+        sys.exit(1)
+
+    # Construct IDs, which are name + variant if the
+    name_counts = dict()
+    for m in info.modules:
+        name_counts[m.name] = name_counts.get(m.name, 0) + 1
+    def get_id(m):
+        result = m.name
+        if name_counts[m.name] > 1 and m.variant:
+            result += "@@" + m.variant
+        return result
+    for m in info.modules:
+        m.id = get_id(m)
+        for dep in m.deps:
+            dep.id = get_id(dep)
+
+    return info
+
+
+def load_modules():
+    info = load_soong_debug()
+
+    # Filter out unnamed modules
+    modules = dict()
+    for m in info.modules:
+        if not m.name:
+            continue
+        modules[m.id] = m
+
+    return modules
+
+
+def load_graph():
+    modules=load_modules()
+    return Graph(modules)
+
+
+def module_selection_args(parser):
+    parser.add_argument("modules", nargs="*",
+                        help="Modules to match. Can be glob-style wildcards.")
+    parser.add_argument("--provider", nargs="+",
+                        help="Match the given providers.")
+    parser.add_argument("--dep", nargs="+",
+                        help="Match the given providers.")
+
+
+def load_and_filter_modules(args):
+    # Which modules are printed
+    matchers = []
+    if args.modules:
+        matchers.append(lambda m: [True for pattern in args.modules
+                                   if fnmatch.fnmatchcase(m.name, pattern)])
+    if args.provider:
+        matchers.append(lambda m: [True for pattern in args.provider
+                                   if [True for p in m.providers if p.type.endswith(pattern)]])
+    if args.dep:
+        matchers.append(lambda m: [True for pattern in args.dep
+                                   if [True for d in m.deps if d.id == pattern]])
+
+    if not matchers:
+        sys.stderr.write("error: At least one module matcher must be supplied\n")
+        sys.exit(1)
+
+    info = load_soong_debug()
+    for m in sorted(info.modules, key=lambda m: (m.name, m.variant)):
+        if len([matcher for matcher in matchers if matcher(m)]) == len(matchers):
+            yield m
+
+
+def print_nodes(nodes):
+    print("digraph {")
+    for node in nodes:
+        print(f"\"{node.id}\"[label={format_node_label(node)}];")
+        for dep in node.deps:
+            if dep in nodes:
+                print(f"\"{node.id}\" -> \"{dep.id}\";")
+    print("}")
+
+
+def get_deps(nodes, root):
+    if root in nodes:
+        return
+    nodes.add(root)
+    for dep in root.deps:
+        get_deps(nodes, dep)
+
+
+class BetweenCommand:
+    help = "Print the module graph between two nodes."
+
+    def args(self, parser):
+        parser.add_argument("module", nargs=2,
+                            help="The two modules")
+
+    def run(self, args):
+        graph = load_graph()
+        print_nodes(graph.find_paths(args.module[0], args.module[1]))
+
+
+class DepsCommand:
+    help = "Print the module graph of dependencies of one or more modules"
+
+    def args(self, parser):
+        parser.add_argument("module", nargs="+",
+                            help="Module to print dependencies of")
+
+    def run(self, args):
+        graph = load_graph()
+        nodes = set()
+        err = False
+        for id in sys.argv[3:]:
+            root = graph.nodes.get(id)
+            if not root:
+                sys.stderr.write(f"error: Can't find root: {id}\n")
+                err = True
+                continue
+            get_deps(nodes, root)
+        if err:
+            sys.exit(1)
+        print_nodes(nodes)
+
+
+class IdCommand:
+    help = "Print the id (name + variant) of matching modules"
+
+    def args(self, parser):
+        module_selection_args(parser)
+
+    def run(self, args):
+        for m in load_and_filter_modules(args):
+            print(m.id)
+
+
+class QueryCommand:
+    help = "Query details about modules"
+
+    def args(self, parser):
+        module_selection_args(parser)
+
+    def run(self, args):
+        for m in load_and_filter_modules(args):
+            print(m.id)
+            print(f"    type:     {m.type}")
+            print(f"    location: {format_source_pos(m.source_file, m.source_line)}")
+            for p in m.providers:
+                print(f"    provider: {format_provider(p)}")
+            for d in m.deps:
+                print(f"    dep:      {d.id}")
+
+
+COMMANDS = {
+    "between": BetweenCommand(),
+    "deps": DepsCommand(),
+    "id": IdCommand(),
+    "query": QueryCommand(),
+}
+
+
+def assert_env(name):
+    val = os.getenv(name)
+    if not val:
+        sys.stderr.write(f"{name} not set. please make sure you've run lunch.")
+    return val
+
+ANDROID_BUILD_TOP = assert_env("ANDROID_BUILD_TOP")
+
+TARGET_PRODUCT = assert_env("TARGET_PRODUCT")
+OUT_DIR = os.getenv("OUT_DIR")
+if not OUT_DIR:
+    OUT_DIR = "out"
+if OUT_DIR[0] != "/":
+    OUT_DIR = pathlib.Path(ANDROID_BUILD_TOP).joinpath(OUT_DIR)
+SOONG_DEBUG_DATA_FILENAME = pathlib.Path(OUT_DIR).joinpath("soong/soong-debug-info.json")
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    subparsers = parser.add_subparsers(required=True, dest="command")
+    for name in sorted(COMMANDS.keys()):
+        command = COMMANDS[name]
+        subparser = subparsers.add_parser(name, help=command.help)
+        command.args(subparser)
+    args = parser.parse_args()
+    COMMANDS[args.command].run(args)
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    main()
+
diff --git a/cmd/soong_build/main.go b/cmd/soong_build/main.go
index 4727566..673f305 100644
--- a/cmd/soong_build/main.go
+++ b/cmd/soong_build/main.go
@@ -79,6 +79,7 @@
 	flag.BoolVar(&cmdlineArgs.MultitreeBuild, "multitree-build", false, "this is a multitree build")
 	flag.BoolVar(&cmdlineArgs.BuildFromSourceStub, "build-from-source-stub", false, "build Java stubs from source files instead of API text files")
 	flag.BoolVar(&cmdlineArgs.EnsureAllowlistIntegrity, "ensure-allowlist-integrity", false, "verify that allowlisted modules are mixed-built")
+	flag.StringVar(&cmdlineArgs.ModuleDebugFile, "soong_module_debug", "", "soong module debug info file to write")
 	// Flags that probably shouldn't be flags of soong_build, but we haven't found
 	// the time to remove them yet
 	flag.BoolVar(&cmdlineArgs.RunGoTests, "t", false, "build and run go tests during bootstrap")
diff --git a/ui/build/config.go b/ui/build/config.go
index 5085c68..e29d239 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -115,6 +115,11 @@
 
 	// Data source to write ninja weight list
 	ninjaWeightListSource NinjaWeightListSource
+
+	// This file is a detailed dump of all soong-defined modules for debugging purposes.
+	// There's quite a bit of overlap with module-info.json and soong module graph. We
+	// could consider merging them.
+	moduleDebugFile string
 }
 
 type NinjaWeightListSource uint
@@ -273,6 +278,10 @@
 		ret.sandboxConfig.SetSrcDirIsRO(srcDirIsWritable == "false")
 	}
 
+	if os.Getenv("GENERATE_SOONG_DEBUG") == "true" {
+		ret.moduleDebugFile, _ = filepath.Abs(shared.JoinPath(ret.SoongOutDir(), "soong-debug-info.json"))
+	}
+
 	ret.environ.Unset(
 		// We're already using it
 		"USE_SOONG_UI",
@@ -325,6 +334,9 @@
 		"ANDROID_DEV_SCRIPTS",
 		"ANDROID_EMULATOR_PREBUILTS",
 		"ANDROID_PRE_BUILD_PATHS",
+
+		// We read it here already, don't let others share in the fun
+		"GENERATE_SOONG_DEBUG",
 	)
 
 	if ret.UseGoma() || ret.ForceUseGoma() {
diff --git a/ui/build/soong.go b/ui/build/soong.go
index 90c3bfc..a201ac5 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -204,6 +204,11 @@
 		commonArgs = append(commonArgs, "--build-from-source-stub")
 	}
 
+	if pb.config.moduleDebugFile != "" {
+		commonArgs = append(commonArgs, "--soong_module_debug")
+		commonArgs = append(commonArgs, pb.config.moduleDebugFile)
+	}
+
 	commonArgs = append(commonArgs, "-l", filepath.Join(pb.config.FileListDir(), "Android.bp.list"))
 	invocationEnv := make(map[string]string)
 	if pb.debugPort != "" {