SetStatusAgentHook never resets _cost on retry attempts, double-counting the previous attempt's spend in the batch status line #1567

Describe the bug

SetStatusAgentHook (which renders the per-instance status line in the batch progress UI) never resets self._cost when a new attempt starts. On a retry attempt, the status line therefore shows the previous attempt's spend twice — roughly 2x the actual spend — until the new attempt's first step completes.

Root cause in sweagent/agent/hooks/status.py:16-20:

def on_setup_attempt(self):
    self._i_attempt += 1
    self._i_step = 0
    # Costs will be reset for the next attempt
    self._previous_cost += self._cost

The comment says "Costs will be reset for the next attempt", but self._cost is never reset. on_step_start then displays self._previous_cost + self._cost (status.py:28), double-counting the previous attempt's spend until on_step_done (status.py:31) overwrites _cost with the new attempt's instance_cost.

This is reachable in normal batch runs: sweagent/run/run_batch.py:347 registers SetStatusAgentHook for every agent, and with a type: retry agent, RetryAgent._next_attempt (sweagent/agent/agents.py:321) re-attaches the same hook objects to a fresh DefaultAgent (agents.py:312-318), whose setup calls self._chook.on_setup_attempt() (agents.py:594) at the start of every retry attempt.

Expected behaviour: after attempt 1 ends having spent $1.00 in total, the first status line of attempt 2 should read Attempt 2 Step 1 ($1.00). The basis is the code itself: the comment at status.py:19 ("Costs will be reset for the next attempt") and the display formula (${self._previous_cost + self._cost:.2f}) at status.py:28 — the previous+current split only yields the true total spend if _cost is zeroed at the attempt boundary.

Steps/commands/code to Reproduce

Setup from source (no docker needed; plain pip install -e . in a venv), at commit 3ea751c087f32b16e039a2233dd6eefecef325d5 (current main HEAD):

git clone https://github.com/SWE-agent/SWE-agent && cd SWE-agent
python3.12 -m venv .venv && . .venv/bin/activate
pip install -e .
python /tmp/repro_status_hook_cost.py

/tmp/repro_status_hook_cost.py:

"""Repro: SetStatusAgentHook double-counts the previous attempt's cost in the
status line during a retry attempt (comment says "Costs will be reset for the
next attempt", but `self._cost` is never reset in on_setup_attempt).
"""
from sweagent.agent.hooks.status import SetStatusAgentHook
from sweagent.types import AgentInfo, StepOutput

statuses = []
hook = SetStatusAgentHook("inst-1", lambda _id, msg: statuses.append(msg))

# --- Attempt 1: two steps, each costing 0.50 -> total 1.00 ---
hook.on_setup_attempt()
for i in range(2):
    hook.on_step_start()
    hook.on_step_done(step=StepOutput(), info=AgentInfo(model_stats={"instance_cost": 0.5 * (i + 1)}))

print("attempt 1 statuses:")
for s in statuses:
    print("   ", s)

# --- Attempt 2 starts (retry) ---
hook.on_setup_attempt()
statuses.clear()
hook.on_step_start()  # first step of attempt 2, no new cost yet

print("attempt 2, step 1 status:", statuses[-1])
# Actual money spent so far is still $1.00 (attempt 2 has not completed a step).
# Expected: "Attempt 2 Step 1 ($1.00)" -- instead _previous_cost($1.00) + stale _cost($1.00)
assert "($1.00)" in statuses[-1], f"double counted: {statuses[-1]}"
print("PASS: no double counting")

Error message/results

Verbatim output of python /tmp/repro_status_hook_cost.py — attempt 2's first status line shows ($2.00) although only $1.00 has been spent so far:

👋 INFO     This is SWE-agent version 1.1.0
            (hash='3ea751c087f32b16e039a2233dd6eefecef325d5') with SWE-ReX
            version 1.4.0 (rex_hash='unavailable').
attempt 1 statuses:
    Step   1 ($0.00)
    Step   2 ($0.50)
attempt 2, step 1 status: Attempt 2 Step   1 ($2.00)
Traceback (most recent call last):
  File "/tmp/repro_status_hook_cost.py", line 29, in <module>
    assert "($1.00)" in statuses[-1], f"double counted: {statuses[-1]}"
           ^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: double counted: Attempt 2 Step   1 ($2.00)

Expected: attempt 2, step 1 status: Attempt 2 Step 1 ($1.00) and PASS: no double counting (resetting self._cost = 0.0 in on_setup_attempt after the accumulation produces exactly that).

System Information

• SWE-agent 1.1.0, commit 3ea751c087f32b16e039a2233dd6eefecef325d5 (current main HEAD), installed from source via pip install -e . (no docker)
• Python 3.12.14
• macOS 15, arm64 (Apple Silicon)

Checklist

• I'm running with the latest docker container/on the latest development version (i.e., I ran git pull)
• I have copied the full command/code that I ran (as text, not as screenshot!)
• If applicable: I have copied the full log file/error message that was the result (as text, not as screenshot!)
• I have enclosed code/log messages in triple backticks (docs) and clicked "Preview" to make sure it's displayed correctly.

Related: I searched the tracker and found no existing report of the status line double-counting spend across retry attempts. #1492 is related in theme (cost accounting around retries) but is a different mechanism — actual re-billing of API calls by the tenacity retry in sweagent/agent/models.py — not the status-line display in sweagent/agent/hooks/status.py.

Happy to open a PR with the approach above (reset self._cost = 0.0 in on_setup_attempt after accumulating it into _previous_cost) — I have verified locally that it makes the repro pass.