fix(agents): substitute prompt placeholders in a single pass

[ritsth]

Description

AgentExecutor._format_prompt (lib/crewai/src/crewai/experimental/agent_executor.py) substituted the template placeholders sequentially:

prompt = prompt.replace("{input}", inputs["input"])
prompt = prompt.replace("{tool_names}", inputs["tool_names"])
return prompt.replace("{tools}", inputs["tools"])

Because {input} is substituted first, any value inserted earlier that itself contains a later placeholder token gets clobbered by the subsequent replace. So when a task's input legitimately mentions the literal {tools} or {tool_names} (for example an agent working on prompt-engineering or template docs), those tokens in the user's text are overwritten with the tool list/names before reaching the LLM:

inputs = {"input": "explain the {tools} placeholder", "tool_names": "search", "tools": "search: web search"}
_format_prompt("Task: {input}", inputs)
# -> "Task: explain the search: web search placeholder"   (user text corrupted)

This switches to a single re.sub pass that matches only the three known tokens, so substituted values are not re-scanned and user text is preserved. Behavior is unchanged for templates that don't contain this collision, and other {...} content in the template is left untouched exactly as before.

The now-deprecated CrewAgentExecutor has an identical copy of this method; I left it untouched since it is slated for removal, but happy to mirror the fix there if you'd prefer.

Type of Change

• Bug fix (non-breaking change which fixes an issue)

Testing

Extended test_agent_executor.py::TestAgentExecutor with test_format_prompt_preserves_placeholder_tokens_in_values. It fails on main (the token is clobbered) and passes with this change; the existing test_format_prompt still passes, and the full tests/agents/test_agent_executor.py file is green (92 passed). ruff check, ruff format --check, and mypy on the changed files are clean.

This bug was found and the patch drafted with AI assistance (Claude Code); I reviewed the change, ran the reproduction above, and validated the tests before and after the fix.

[ritsth]

Per CONTRIBUTING, flagging that this PR was drafted with AI assistance (Claude Code) and should carry the llm-generated label. I don't have label permissions as an external contributor, so could a maintainer please apply it? The change itself was human-reviewed and validated with the reproduction and tests described above.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: b7c5d4ec-921a-4130-9f43-332f415ae678

📥 Commits

Reviewing files that changed from the base of the PR and between 2b90117 and d1f168a.

📒 Files selected for processing (2)

• lib/crewai/src/crewai/experimental/agent_executor.py
• lib/crewai/tests/agents/test_agent_executor.py

---

📝 Walkthrough

Walkthrough

The AgentExecutor._format_prompt method now uses a single regex-based re.sub pass to substitute {input}, {tool_names}, and {tools} placeholders, replacing sequential str.replace calls that could clobber placeholder-like tokens within substituted values. A regression test was added to verify this behavior.

Changes

Prompt Placeholder Fix

Layer / File(s)	Summary
Single-pass regex substitution lib/crewai/src/crewai/experimental/agent_executor.py	Adds import re and replaces sequential str.replace calls in _format_prompt with a single-pass re.sub using a match-to-inputs[...] mapping, preventing later substitutions from altering placeholder-like tokens introduced by earlier ones.
Regression test lib/crewai/tests/agents/test_agent_executor.py	Adds test_format_prompt_preserves_placeholder_tokens_in_values, asserting literal {tools} and {tool_names} tokens inside input values remain unchanged after formatting.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main fix: single-pass substitution for prompt placeholders.
Description check	✅ Passed	The description accurately explains the bug, the fix, and the added regression test.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}