AppendHandler Reference¶

AppendHandler writes agent output to timestamped files on disk. It is the persistence layer used by post-session hooks and batch recipe runs to capture results for later inspection.

Contents¶

Overview
AppendResult
Filename Format
Usage Examples
Error Handling
API

Overview¶

from amplihack.append_handler import AppendHandler, AppendResult

AppendHandler writes one file per append call. Files are created atomically using os.open() with O_CREAT | O_WRONLY | O_EXCL to prevent overwriting existing output. The caller receives an AppendResult describing the outcome.

AppendResult¶

AppendResult is a dataclass describing a single append operation:

@dataclass
class AppendResult:
    success: bool
    file_path: str | None        # Absolute path of the file written, or None on failure
    bytes_written: int           # 0 on failure
    error: str | None            # Error message string, or None on success

Attributes

Attribute	Type	Description
`success`	`bool`	`True` if the file was written without error.
`file_path`	`str \\| None`	Absolute path of the written file. `None` if `success` is `False`.
`bytes_written`	`int`	Number of bytes written. `0` on failure.
`error`	`str \\| None`	Human-readable error description. `None` on success.

Checking the result:

from amplihack.append_handler import AppendHandler

handler = AppendHandler(output_dir="~/.amplihack/.claude/runtime/output")
result = handler.append("Agent completed task successfully.\n\nSummary: 3 files modified.")

if result.success:
    print(f"Saved {result.bytes_written} bytes to {result.file_path}")
else:
    print(f"Failed to save: {result.error}")

Filename Format¶

Each file is named with a timestamp derived from the moment append() is called:

YYYYMMDD_HHMMSS_ffffff.txt

Where ffffff is microseconds (6 digits), providing sub-second uniqueness even under rapid sequential calls.

Examples:

20260312_143022_483921.txt
20260312_143022_501847.txt   # same second, different microsecond

This format sorts lexicographically in chronological order, which simplifies log browsing with standard shell tools:

ls ~/.amplihack/.claude/runtime/output/ | tail -5
# 20260312_140011_002341.txt
# 20260312_143022_483921.txt
# 20260312_143022_501847.txt
# 20260312_151300_119204.txt
# 20260312_162500_883412.txt

Note: Prior to v0.9.2, timestamps used %Y%m%d_%H%M%S (no microseconds). Files from old runs keep their original names; the new format is used only for files written by v0.9.2 and later.

Usage Examples¶

Write a session summary¶

from amplihack.append_handler import AppendHandler

handler = AppendHandler(output_dir="~/.amplihack/.claude/runtime/output")

summary = """
Session complete.

Tasks completed: 3
Files modified: auth.py, tests/test_auth.py, README.md
""".strip()

result = handler.append(summary)
print(f"Written to: {result.file_path}")
# Written to: /home/user/.amplihack/.claude/runtime/output/20260312_143022_483921.txt

Persist all recipe step outputs¶

from amplihack.append_handler import AppendHandler
from amplihack.recipes.runner import RecipeRunner

runner = RecipeRunner()
handler = AppendHandler(output_dir="./run-logs")
recipe_result = runner.run("default-workflow", {"task_description": "add caching layer"})

for step in recipe_result.step_results:
    if step.output:
        result = handler.append(f"# {step.step_name}\n\n{step.output}")
        print(f"Step {step.step_id} saved: {result.file_path}")

Handle permission errors¶

handler = AppendHandler(output_dir="/root/protected")
result = handler.append("some content")

if not result.success:
    # result.error contains the OS error string, e.g. "Permission denied: '/root/protected/...'"
    import logging
    logging.error("Could not write output: %s", result.error)

Error Handling¶

append() never raises. All errors are captured in the returned AppendResult:

Condition	`result.success`	`result.error`
Write succeeded	`True`	`None`
Output directory does not exist	`False`	`"[Errno 2] No such file or directory: '…'"`
Permission denied	`False`	`"[Errno 13] Permission denied: '…'"`
Disk full	`False`	`"[Errno 28] No space left on device"`

API¶

`AppendHandler(output_dir: str)`¶

Constructs a handler that writes files to output_dir. The directory is expanded (supports ~) but not created — callers must ensure it exists before the first append() call.

`handler.append(content: str) -> AppendResult`¶

Writes content to a new timestamped file in output_dir. Uses os.open() with O_CREAT | O_WRONLY | O_EXCL to guarantee each call creates a unique file.

Parameters

Name	Type	Description
`content`	`str`	Text to write. Encoded as UTF-8.

Returns AppendResult — always. Never raises.