diff --git a/README.md b/README.md
index 79285d3..a76a753 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,7 @@ Works with Claude Code, Cursor, Cline, GitHub Copilot, and other compatible agen
 | [skill-creator](plugins/sentry-skills/skills/skill-creator/SKILL.md) | Create new agent skills for this repository |
 | [skill-scanner](plugins/sentry-skills/skills/skill-scanner/SKILL.md) | Scan agent skills for security issues before adoption |
 | [local-repo](plugins/sentry-skills/skills/local-repo/SKILL.md) | Investigate, compare, and modify files in other local git repositories |
+| [similar-sdks](plugins/sentry-skills/skills/similar-sdks/SKILL.md) | Investigate how other Sentry SDKs in the same category implement a concept |
 
 ## Available Subagents
 
diff --git a/plugins/sentry-skills/skills/claude-settings-audit/SKILL.md b/plugins/sentry-skills/skills/claude-settings-audit/SKILL.md
index b17232b..a95d8b9 100644
--- a/plugins/sentry-skills/skills/claude-settings-audit/SKILL.md
+++ b/plugins/sentry-skills/skills/claude-settings-audit/SKILL.md
@@ -157,6 +157,7 @@ If this is a Sentry project (or sentry-skills plugin is installed), include:
   "Skill(sentry-skills:skill-creator)",
   "Skill(sentry-skills:skill-scanner)",
   "Skill(sentry-skills:local-repo)",
+  "Skill(sentry-skills:similar-sdks)"
 ]
 ```
 
diff --git a/plugins/sentry-skills/skills/similar-sdks/SKILL.md b/plugins/sentry-skills/skills/similar-sdks/SKILL.md
new file mode 100644
index 0000000..a21730d
--- /dev/null
+++ b/plugins/sentry-skills/skills/similar-sdks/SKILL.md
@@ -0,0 +1,142 @@
+---
+name: similar-sdks
+description: Investigate how other Sentry SDKs in the same category implement a concept. Use when asked to "check other SDKs", "how do other SDKs do X", "similar SDKs", "cross-sdk comparison", "compare SDK implementations", "what do sibling SDKs do", or investigate a feature across backend, mobile, or frontend SDK groups.
+argument-hint: "[category:] <query>"
+allowed-tools: Read, Bash, Task, Skill
+---
+
+# Similar SDKs
+
+Investigate how other Sentry SDKs in the same category implement a concept, then compile a cross-SDK comparison.
+
+## Arguments
+
+- `query` — a question or topic to investigate across sibling SDKs (e.g., "what are typical options for metrics")
+- `category` (optional prefix) — one of `backend`, `mobile`, `frontend`, `uses`, or `used-by`; restricts the search to that category only
+
+## Examples
+
+```
+/similar-sdks what are typical options for metrics
+/similar-sdks how is session replay implemented
+/similar-sdks backend: how are breadcrumbs captured
+/similar-sdks frontend: how is error boundary handled
+/similar-sdks uses: how is the native layer initialized
+/similar-sdks used-by: how is the Java SDK integrated
+```
+
+## Step 1: Detect the Current Repo
+
+Run this command via Bash to get the repo root path:
+
+```bash
+git rev-parse --show-toplevel
+```
+
+Extract the repo name from the last path component of the output (e.g., `/Users/me/repos/sentry-java` → `sentry-java`).
+
+## Step 2: Load Reference Files
+
+Read both reference files:
+1. `${CLAUDE_SKILL_ROOT}/references/sdk-groups.md` — predefined category-to-SDK mapping
+2. `${CLAUDE_SKILL_ROOT}/references/sdk-dependencies.md` — dependency graph between SDKs
+
+## Step 3: Parse the Argument
+
+Check if the argument starts with a category prefix:
+
+| Pattern | Category | Query |
+|---------|----------|-------|
+| `backend: how are breadcrumbs captured` | `backend` | `how are breadcrumbs captured` |
+| `mobile: scope management` | `mobile` | `scope management` |
+| `uses: how is the native layer initialized` | `uses` | `how is the native layer initialized` |
+| `used-by: how is the Java SDK integrated` | `used-by` | `how is the Java SDK integrated` |
+| `how is replay implemented` | _(none)_ | `how is replay implemented` |
+
+The category must be one of: `backend`, `mobile`, `frontend`, `uses`, `used-by`.
+
+## Step 4: Determine Target SDKs
+
+### Static categories (`backend`, `mobile`, `frontend`, or no prefix)
+
+**If a static category was specified:**
+1. Use only the SDKs listed under that category in `sdk-groups.md`
+2. Remove the current repo from the list
+
+**If no category was specified:**
+1. Find ALL categories in `sdk-groups.md` that contain the current repo
+2. Collect all SDKs from those categories into a single list
+3. Deduplicate — each SDK appears only once
+4. Remove the current repo from the list
+
+**Examples (from `sentry-java`, which is in `backend` + `mobile`):**
+- No prefix → targets: `sentry-python`, `sentry-ruby`, `sentry-go`, `sentry-dotnet`, `sentry-php`, `sentry-elixir`, `sentry-cocoa`, `sentry-dart`, `sentry-react-native`
+- `backend:` prefix → targets: `sentry-python`, `sentry-ruby`, `sentry-go`, `sentry-dotnet`, `sentry-php`, `sentry-elixir`
+
+### Dynamic category: `uses`
+
+Collect all SDKs that the current repo transitively **depends on** by traversing the dependency graph from `sdk-dependencies.md`:
+
+1. Initialize a `visited` set (empty) and a `queue` containing only the current repo
+2. While `queue` is not empty:
+   a. Pop a repo from `queue`
+   b. If already in `visited`, skip it (prevents infinite loops from circular dependencies)
+   c. Add it to `visited`
+   d. Look up its dependencies in `sdk-dependencies.md`
+   e. For each dependency not yet in `visited`, add it to `queue`
+3. The target list is `visited` minus the current repo
+
+**Example (from `sentry-dotnet`):**
+- `sentry-dotnet` depends on: `sentry-native`, `sentry-cocoa`, `sentry-java`
+- `sentry-java` depends on: `sentry-native`
+- `sentry-native` depends on: (none)
+- `sentry-cocoa` depends on: (none)
+- `uses` targets: `sentry-native`, `sentry-cocoa`, `sentry-java`
+
+### Dynamic category: `used-by`
+
+Collect all SDKs that transitively **depend on** the current repo by traversing the reverse dependency graph from `sdk-dependencies.md`:
+
+1. Build a reverse mapping: for each SDK in `sdk-dependencies.md`, record which other SDKs list it as a dependency (i.e., "dependents")
+2. Initialize a `visited` set (empty) and a `queue` containing only the current repo
+3. While `queue` is not empty:
+   a. Pop a repo from `queue`
+   b. If already in `visited`, skip it (prevents infinite loops from circular dependencies)
+   c. Add it to `visited`
+   d. Look up its dependents from the reverse mapping
+   e. For each dependent not yet in `visited`, add it to `queue`
+4. The target list is `visited` minus the current repo
+
+**Example (from `sentry-java`):**
+- Direct dependents of `sentry-java`: `sentry-kotlin-multiplatform`, `sentry-react-native`, `sentry-dotnet`, `sentry-godot`, `sentry-unity`, `sentry-unreal`, `sentry-dart`
+- Direct dependents of `sentry-dotnet`: `sentry-powershell`, `sentry-unity`
+- (Continue until no new repos are found)
+- `used-by` targets: `sentry-kotlin-multiplatform`, `sentry-react-native`, `sentry-dotnet`, `sentry-godot`, `sentry-unity`, `sentry-unreal`, `sentry-dart`, `sentry-powershell`
+
+## Step 5: Investigate Each Target SDK
+
+For each SDK in the target list, invoke `/local-repo` using the Skill tool:
+
+```
+/local-repo <sdk-name> <query>
+```
+
+- Launch all invocations in parallel using the Task tool (one Task per SDK, `subagent_type` of `general-purpose`)
+- Each Task should use the Skill tool to call `/local-repo <sdk-name> <query>`
+- Never invoke `/local-repo` for the same SDK more than once
+- If `/local-repo` reports that a repo is not available locally, do NOT fall back to GitHub or any remote queries. Instead, report "`<sdk-name>` is not cloned locally — skipped." in the final summary.
+- **Relay warnings:** `/local-repo` may report that a repo is not on its default branch, is behind the remote, or has local changes. Each Task MUST include these warnings in its result so they can be surfaced in the final summary.
+
+## Step 6: Compile Cross-SDK Comparison
+
+After all investigations complete, present a structured summary:
+
+1. **Repo notices** — list any warnings from `/local-repo` about repos that were skipped (not cloned locally), not on their default branch, behind the remote, or having local changes. Omit this section if there are no notices.
+2. **Overview** — one-paragraph summary of how the concept is handled across SDKs
+3. **Per-SDK findings** — for each SDK investigated:
+   - What it does (brief description)
+   - Key file paths
+   - Notable implementation details
+4. **Common patterns** — what most SDKs share
+5. **Notable differences** — where SDKs diverge and why (language idioms, platform constraints, etc.)
+6. **Recommendations** (if applicable) — insights relevant to the current repo based on what sibling SDKs do
diff --git a/plugins/sentry-skills/skills/similar-sdks/references/sdk-dependencies.md b/plugins/sentry-skills/skills/similar-sdks/references/sdk-dependencies.md
new file mode 100644
index 0000000..18cc395
--- /dev/null
+++ b/plugins/sentry-skills/skills/similar-sdks/references/sdk-dependencies.md
@@ -0,0 +1,80 @@
+# Sentry SDK Dependencies
+
+## sentry-java
+- sentry-native
+
+## sentry-kotlin-multiplatform
+- sentry-java
+- sentry-cocoa
+
+## sentry-react-native
+- sentry-javascript
+- sentry-java
+- sentry-cocoa
+
+## sentry-dotnet
+- sentry-native
+- sentry-cocoa
+- sentry-java
+
+## sentry-php
+- (none)
+
+## sentry-laravel
+- sentry-php
+
+## sentry-symfony
+- sentry-php
+
+## sentry-elixir
+- (none)
+
+## sentry-go
+- (none)
+
+## sentry-ruby
+- (none)
+
+## sentry-python
+- (none)
+
+## sentry-javascript
+- (none)
+
+## sentry-native
+- (none)
+
+## sentry-godot
+- sentry-native
+- sentry-cocoa
+- sentry-javascript
+- sentry-java
+
+## sentry-powershell
+- sentry-dotnet
+
+## sentry-unity
+- sentry-dotnet
+- sentry-java
+- sentry-native
+- sentry-cocoa
+
+## sentry-unreal
+- sentry-native
+- sentry-cocoa
+- sentry-java
+
+## sentry-rust
+- (none)
+
+## sentry-cocoa
+- (none)
+
+## sentry-dart
+- sentry-java
+- sentry-cocoa
+- sentry-native
+- sentry-javascript
+
+## sentry-electron
+- sentry-javascript
diff --git a/plugins/sentry-skills/skills/similar-sdks/references/sdk-groups.md b/plugins/sentry-skills/skills/similar-sdks/references/sdk-groups.md
new file mode 100644
index 0000000..2d8ed06
--- /dev/null
+++ b/plugins/sentry-skills/skills/similar-sdks/references/sdk-groups.md
@@ -0,0 +1,38 @@
+# SDK Groups
+
+Predefined categories of Sentry SDK repositories. Each entry is the repository folder name as it appears in the `repoDirs` from `repos.local.json`.
+
+## backend
+
+- `sentry-python`
+- `sentry-java`
+- `sentry-ruby`
+- `sentry-go`
+- `sentry-dotnet`
+- `sentry-php`
+- `sentry-rust`
+- `sentry-elixir`
+
+## mobile
+
+- `sentry-capacitor`
+- `sentry-cocoa`
+- `sentry-cordova`
+- `sentry-dart`
+- `sentry-dart-plugin`
+- `sentry-java`
+- `sentry-kotlin-multiplatform`
+- `sentry-react-native`
+
+## gdx
+
+- `sentry-dotnet`
+- `sentry-godot`
+- `sentry-native`
+- `sentry-powershell`
+- `sentry-unity`
+- `sentry-unreal`
+
+## frontend
+
+- `sentry-javascript`