diff --git a/README.md b/README.md
index 42e9a75..1a00531 100644
--- a/README.md
+++ b/README.md
@@ -193,6 +193,7 @@ without knowing any precedence rules.
 | `ollama` | Ollama | `ollama_api_key`, `ollama_base_url` | `ollama_base_url` |
 | `openai` | OpenAI | `openai_api_key`, `openai_base_url` | `openai_api_key` or `openai_base_url` |
 | `openrouter` | OpenRouter | `openrouter_api_key` | `openrouter_api_key` |
+| `opper` | Opper | `opper_api_key` | `opper_api_key` |
 | `orcarouter` | OrcaRouter | `orcarouter_api_key` | `orcarouter_api_key` |
 | `requesty` | Requesty | `requesty_api_key`, `requesty_base_url` | `requesty_api_key` |
 | `vercel` | Vercel AI Gateway | `vercel_api_key`, `vercel_base_url` | `vercel_api_key` or `vercel_base_url` |
@@ -349,7 +350,7 @@ The first sync after the merge creates `codeboarding/baseline`, catching up from
 
 `target_branch` and `sync_strategy` are deprecated, and read as the `codeboarding_analysis_location` they stand for, with a warning: `sync_strategy: push` as `in_place`, `sync_strategy: pull_request` as `codeboarding_branch`. `target_branch` is accepted only when it names the branch the run is on: the push trigger picks the branch. `force_full: true` is ignored with a warning. Anything the new input cannot express fails, linking to [moving an existing setup](#moving-an-existing-setup).
 
-The `/codeboarding` command, comment heading, Mermaid direction (`LR`), hosted webview URL, commit message, and CodeBoarding 0.15.1 version are intentionally fixed rather than exposed as configuration.
+The `/codeboarding` command, comment heading, Mermaid direction (`LR`), hosted webview URL, commit message, and CodeBoarding 0.15.3 version are intentionally fixed rather than exposed as configuration.
 
 Review mode needs no sync job or committed `.codeboarding` directory. If no
 usable merge-base analysis exists, it runs full analysis there directly, then
@@ -406,7 +407,7 @@ Run the local analysis pipeline:
 
 ```bash
 export OPENROUTER_API_KEY=sk-or-...
-python -m pip install codeboarding==0.15.1
+python -m pip install codeboarding==0.15.3
 tests/run_local.sh --repo /path/to/repo --base main --head feature
 ```
 
diff --git a/action.yml b/action.yml
index ee958d8..7547260 100644
--- a/action.yml
+++ b/action.yml
@@ -10,7 +10,7 @@ inputs:
     required: false
     default: 'review'
   llm:
-    description: 'Required. Where analysis credentials come from: hosted, license, or a provider name (anthropic, aws_bedrock, cerebras, deepseek, glm, google, kimi, litellm, ollama, openai, openrouter, orcarouter, requesty, vercel).'
+    description: 'Required. Where analysis credentials come from: hosted, license, or a provider name (anthropic, aws_bedrock, cerebras, deepseek, glm, google, kimi, litellm, ollama, openai, openrouter, opper, orcarouter, requesty, vercel).'
     required: true
   license_key:
     description: 'CodeBoarding license key. Required by llm: license; optional alongside a provider key.'
@@ -99,6 +99,11 @@ inputs:
     description: 'OpenRouter API key, used when llm is openrouter. Sets OPENROUTER_API_KEY.'
     required: false
     default: ''
+  # Opper - selected by llm: opper
+  opper_api_key:
+    description: 'Opper API key, used when llm is opper. Sets OPPER_API_KEY.'
+    required: false
+    default: ''
   # OrcaRouter - selected by llm: orcarouter
   orcarouter_api_key:
     description: 'OrcaRouter API key, used when llm is orcarouter. Sets ORCAROUTER_API_KEY.'
@@ -306,6 +311,7 @@ runs:
         CB_IN_OPENAI_API_KEY: ${{ inputs.openai_api_key }}
         CB_IN_OPENAI_BASE_URL: ${{ inputs.openai_base_url }}
         CB_IN_OPENROUTER_API_KEY: ${{ inputs.openrouter_api_key }}
+        CB_IN_OPPER_API_KEY: ${{ inputs.opper_api_key }}
         CB_IN_ORCAROUTER_API_KEY: ${{ inputs.orcarouter_api_key }}
         CB_IN_REQUESTY_API_KEY: ${{ inputs.requesty_api_key }}
         CB_IN_REQUESTY_BASE_URL: ${{ inputs.requesty_base_url }}
@@ -404,7 +410,7 @@ runs:
       if: steps.guard.outputs.skip != 'true'
       shell: bash
       run: |
-        python -m pip install --disable-pip-version-check 'codeboarding==0.15.2'
+        python -m pip install --disable-pip-version-check 'codeboarding==0.15.3'
         # Fail here, with the reason, rather than mid-analysis with a traceback:
         # pinning a release does not pin what its dependencies resolve to. Run
         # the console script, not `python -c`, which would put the analyzed
diff --git a/scripts/action/supported-providers.json b/scripts/action/supported-providers.json
index 59bf34f..3cfc163 100644
--- a/scripts/action/supported-providers.json
+++ b/scripts/action/supported-providers.json
@@ -18,7 +18,7 @@
     "a selection env (AWS_DEFAULT_REGION, OLLAMA_API_KEY) therefore cannot select a provider",
     "on its own, which is why ollama and litellm need their base URL and not just a key."
   ],
-  "engine": "0.15.2",
+  "engine": "0.15.3",
   "hosted_provider": "openrouter",
   "providers": {
     "openrouter": {
@@ -30,6 +30,15 @@
         "openrouter_api_key": "OPENROUTER_API_KEY"
       }
     },
+    "opper": {
+      "label": "Opper",
+      "selection_envs": [
+        "OPPER_API_KEY"
+      ],
+      "inputs": {
+        "opper_api_key": "OPPER_API_KEY"
+      }
+    },
     "orcarouter": {
       "label": "OrcaRouter",
       "selection_envs": [