diff --git a/.github/workflows/marvin-dedupe-issues.yml b/.github/workflows/marvin-dedupe-issues.yml
index 5d83cbdf7..84a88f063 100644
--- a/.github/workflows/marvin-dedupe-issues.yml
+++ b/.github/workflows/marvin-dedupe-issues.yml
@@ -39,13 +39,13 @@ jobs:
 
           Follow these steps precisely:
 
-          1. Use the Task tool to check if the GitHub issue (a) is closed, (b) does not need to be deduped (eg. because it is broad product feedback without a specific solution, or positive feedback), or (c) already has a duplicates comment that you made earlier. If so, do not proceed.
+          1. Check if the GitHub issue (a) is closed, (b) does not need to be deduped (eg. because it is broad product feedback without a specific solution, or positive feedback), or (c) already has a duplicates comment that you made earlier. If so, do not proceed.
 
-          2. Use the Task tool to view the GitHub issue, and ask the agent to return a summary of the issue
+          2. View the GitHub issue and produce a summary of the issue
 
           3. Then, launch 3 parallel agents using the Task tool to search GitHub for duplicates of this issue, using diverse keywords and search approaches, using the summary from step 2
 
-          4. Next, feed the results from steps 2 and 3 into another agent using the Task tool, so that it can filter out false positives that are likely not actually duplicates of the original issue. If there are no duplicates remaining, do not proceed.
+          4. Next, consider the results from steps 2 and 3 and filter out false positives that are likely not actually duplicates of the original issue. If there are no duplicates remaining, do not proceed.
 
           5. Finally, comment back on the issue with a list of up to three duplicate issues (or zero, if there are no likely duplicates). If there are no duplicates, DO NOT COMMENT. Just exit.
 
@@ -81,6 +81,7 @@ jobs:
           prompt: ${{ steps.dedupe-prompt.outputs.PROMPT }}
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY_FOR_CI }}
           claude_args: |
+            --model claude-sonnet-4-5-20250929
             --allowedTools Bash(gh issue view:*),Bash(gh search:*),Bash(gh issue list:*),Bash(gh api:*),Bash(gh issue comment:*),Task
           settings: |
             {
diff --git a/.github/workflows/marvin-label-triage.yml b/.github/workflows/marvin-label-triage.yml
index 4264741fd..549bbe217 100644
--- a/.github/workflows/marvin-label-triage.yml
+++ b/.github/workflows/marvin-label-triage.yml
@@ -156,6 +156,7 @@ jobs:
           prompt: ${{ steps.triage-prompt.outputs.PROMPT }}
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY_FOR_CI }}
           claude_args: |
+            --model claude-sonnet-4-5-20250929
             --allowedTools Bash(gh label list),mcp__github__get_issue,mcp__github__get_issue_comments,mcp__github__update_issue,mcp__github__get_pull_request_files
             --mcp-config /tmp/mcp-config/mcp-servers.json
           settings: |
diff --git a/.github/workflows/marvin.yml b/.github/workflows/marvin.yml
index cd2fef58a..8b16e5928 100644
--- a/.github/workflows/marvin.yml
+++ b/.github/workflows/marvin.yml
@@ -66,6 +66,7 @@ jobs:
           trigger_phrase: "/marvin"
           allowed_bots: "*"
           claude_args: |
+            --model claude-sonnet-4-5-20250929
             --allowedTools WebSearch,WebFetch,Bash(uv:*),Bash(pre-commit:*),Bash(pytest:*),Bash(ruff:*),Bash(ty:*),Bash(git:*),Bash(gh:*),mcp__github__add_issue_comment,mcp__github__create_issue,mcp__github__get_issue,mcp__github__list_issues,mcp__github__search_issues,mcp__github__update_issue,mcp__github__update_issue_comment,mcp__github__create_pull_request,mcp__github__get_pull_request,mcp__github__get_pull_request_comments,mcp__github__get_pull_request_files,mcp__github__get_pull_request_reviews,mcp__github__get_pull_request_status,mcp__github__list_pull_requests,mcp__github__update_pull_request,mcp__github__update_pull_request_branch,mcp__github__update_pull_request_comment,mcp__github__merge_pull_request
           additional_permissions: |
             actions: read